Two-Year Clinical Performance of Dimethacrylatebased Composite Restorations Repaired with a Silorane-based Composite Daniela Araújo Veloso Popoffa / Cláudia Silami de Magalhãesb / Wallace de Freitas Oliveirac / Luíza Anjos Soaresd / Thalita Thyrza de Almeida Santa Rosae / Raquel Conceição Ferreiraf / Allyson Nogueira Moreirag / Ivar Andreas Mjörh
Purpose: To investigate the clinical performance of a silorane-based composite resin used for repairing dimethacrylate-based composite restorations. Materials and Methods: One operator repaired defective dimethacrylate-based resin restorations that were randomly assigned to one of two treatment groups: control (n = 50), repaired with Adper SE Plus and Filtek P60 Posterior Restorative (3M ESPE); or test (n = 50), repaired with P90 System Adhesive Self-Etch Primer and Bond and Filtek P90 Low Shrink Posterior Restorative (3M ESPE). After 1 week, restorations were finished and polished. Two calibrated examiners (weighted Kappa ≥ 0.78) evaluated the repaired restorations, blindly and independently, at baseline, after 6 months, 1 and 2 years. The parameters examined were marginal adaptation, anatomic form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries. The restorations were classified as Alfa, Bravo, or Charlie, according to modified US Public Health Service criteria. Variation in the levels of clinical parameters over time was evaluated by Friedman’s ANOVA (α = 0.05). The Mann-Whitney test assessed the differences between the materials for all clinical criteria at baseline, 6-month, 1- and 2-year recalls (α = 0.05). The Wilcoxon test compared each composite resin for all clinical criteria at the same recalls (α = 0.05). Results: After two years, 79 repaired restorations were re-examined. No statistically significant differences were found between the materials at baseline or at the 2-year recall (p > 0.05). Comparing baseline and 2-year recall, there was a statistically significant difference for marginal discoloration (p = 0.029) in silorane-based composite restorations. Conclusion: After two years, the clinical performance of the silorane-based composite was similar to that of the dimethacrylate-based composite when used to make repairs. Keywords: low-shrinkage silorane-based composite, dimethacrylate-based composite, resin-based restoration, repair. J Adhes Dent 2014; 16: 575–583. doi: 10.3290/j.jad.a33196
Submitted for publication: 26.07.13; accepted for publication: 14.08.14
a
Assistant Professor, School of Dentistry, University of Montes Claros, Montes Claros, Minas Gerais, Brazil. Idea, hypothesis, performed the experiments in partial fulfillment of requirements for a PhD degree, wrote manuscript, contributed substantially to discussion.
f
Assistant Professor, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. Co-wrote and proofread manuscript, consulted on and performed statistical evaluation, contributed substantially to discussion.
b
Associate Professor, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. Idea, hypothesis, experimental design, co-wrote and proofread manuscript, contributed substantially to discussion.
g
Associate Professor, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. Idea, hypothesis, experimental design, co-wrote and proofread manuscript, contributed substantially to discussion.
c
Graduate Student, School of Dentistry, University of Montes Claros, Montes Claros, Minas Gerais, Brazil. Co-wrote manuscript, contributed substantially to discussion.
h
Dr.odont Inactive, ad hoc reviewer, College of Dentistry, University of Florida, Gainesville, FL, USA. Co-wrote and proofread manuscript, contributed substantially to discussion.
d
Graduate Student, School of Dentistry, United Colleges of North Minas Gerais, Montes Claros, Minas Gerais, Brazil. Co-wrote manuscript, contributed substantially to discussion.
e
Assistant Professor, School of Dentistry, University of Montes Claros, Montes Claros, Minas Gerais, Brazil. Co-wrote and proofread manuscript, contributed substantially to discussion.
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Correspondence: Claudia Silami de Magalhães, Av. Antônio Carlos, 6627, Pampulha, CEP 31270-901, Belo Horizonte, Minas Gerais, Brazil. Tel: +55-319971-3747, Fax: +55-31-3409-2405. e-mail: [email protected]
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D
ue to the growing demand for esthetic restorations and the evident enhancement of the properties of restorative dental composites, these materials have become the best choice for performing direct restorations.8,28,33,37 Such improvements, along with a minimally invasive approach to caries treatment, have made these restorative materials very popular for direct posterior restorations. Nevertheless, the longevity of these restorations is still affected by the consequences of their polymerization shrinkage.1,4,43 Clinically, incremental insertion and control of polymerization rate are the main strategies used to control polymerization shrinkage. These techniques are widely recommended in order to reduce the C-factor and the composite volume being polymerized at each stage of the restoration procedure.33,39 Nonetheless, the composites’ intrinsic contraction remains a challenge, and changes in the monomer composition seem to hold promise for minimizing the effects of shrinkage.5,21,41 An innovative monomer system termed “silorane” was introduced to the dental market for clinical use. The silorane-based resin takes its name from the combination of its chemical blocks, siloxanes and oxiranes.1,41 The silorane molecule has a siloxane core with four attached oxirane rings that open upon polymerization to bond to other monomers. This mechanism results in a volumetric shrinkage of less than 1%, which may reduce the deleterious effects of shrinkage stress at the tooth/restoration interface. This characteristic has also been validated by in vivo studies in which silorane-based resin restorations exhibited satisfactory clinical performance.1,4,11,33 In vitro studies suggest that bonding of silorane-based composites to old dimethacrylate-based composites may be a viable clinical procedure19,22,23 and previous findings have shown viable clinical performance for the silorane systems after one year.33 As clinical studies evaluating the long-term clinical performance of restorations repaired by silorane-based composite resin are lacking, it would be desirable to keep evaluating the clinical performance of this system for making repairs. In this context, keeping in mind the current trends toward minimally invasive techniques that allow preservation of sound tooth structure,25,27,32 the purpose of the present study was to investigate the clinical performance of a lowshrinkage silorane-based composite resin when used for repairing conventional dimethacrylate-based composite restorations. The hypothesis tested in this randomized controlled clinical trial was that low-shrinkage siloranebased composites exhibit performance similar to that of conventional dimethacrylate-based composites when repairing composite resin restorations.
MATERIALS AND METHODS Study Design The observation unit of this prospective randomized clinical trial was the restoration, and the dependent variable was qualitative categorical ordinal. Patients aged 18 to 56 years with 100 defective composite resin res576
torations participated in this study. They were routinely assigned for treatment at the operative dentistry clinic, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. The fillings to be repaired were class I or class II methacrylate-based composite resin restorations (small, medium, or large size) on premolars and molars. The fillings had to present defects on the occlusal but not on the proximal surfaces and had to be scored Bravo according to the Modified United States Public Health Service (USPHS) clinical criteria (Table 1). The exclusion criteria were: contraindications for regular dental treatment according to the patient’s medical history; xerostomia, including consumption of medications proven to significantly reduce salivary flow; visible plaque index (VPI) > 30%; and defective restorations not indicated for repairs that scored Charlie (modified USPHS clinical criteria). Teeth with clinical and radiographic diagnosis of caries and teeth without their respective antagonist were excluded from the sample. This study was approved by the Institutional Ethics Committee (ETIC 0546.0.203.000-09). Written informed consent was obtained from all patients. Study Methods The restorations were examined one week after they were repaired for baseline assessment, then at 6 months and 1 and 2 years. Two examiners independently evaluated all repaired restorations by direct observation using a plane buccal mirror and a WHO model explorer. A calibration exercise revealed an interexaminer agreement ratio ≥ 0.78. If there was disagreement on the rating, the clinicians re-examined the repaired restoration together and arrived at a joint final decision. The parameters examined were marginal adaptation, anatomic form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries. The examiners classified all restorations as Alfa, Bravo, or Charlie, according to modified USPHS clinical criteria (Table 1). Treatment Groups To minimize preparation variability, the same operator repaired all defective composite resin restorations. The defective surfaces of the restorations were explored using a high-speed round diamond bur (#1010, #1011, #1012, #1013 or #1014, KG Sorensen; São Paulo, SP, Brazil) compatible with the defect size, in a handpiece with air-water cooling. The removal of the restorative material started in the area of the defect and included any stained and soft tooth tissues. The operator randomly assigned the restorations to one of two treatment groups: 1. control (n = 50), repaired with a self-etching primer (Adper SE Plus, 3M ESPE, St Paul, MN, USA) and a dimethcrylate-based composite (Filtek P60 Posterior Restorative, 3M ESPE), or 2. test (n = 50), repaired with a self-etching primer (P90 System Adhesive Self-Etch Primer and Bond, 3M ESPE) and a low-shrinkage silorane-based composite (Filtek P90 Low Shrink Posterior Restorative, 3M ESPE (Table 2). Rubber-dam isolation was used during the restorative procedures. The surfaces of restorations and enamel marThe Journal of Adhesive Dentistry
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Table 1
Modified United States Public Health Service clinical criteria
Marginal adaptation
Anatomic form
Marginal discoloration
Surface roughness
Post-operative sensitivity
Secondary caries
Table 2
Alfa
(A)
Restoration adapts closely to the tooth structure; there is no visible crevice
Bravo
(B)
There is a visible crevice, the explorer will penetrate, without dentin exposure
Charlie (C)
The explorer penetrates into crevice in which dentin or the base is exposed
Alfa
(A)
Anatomic form ideal
Bravo
(B)
Restoration is undercontoured, without dentin or base exposure
Charlie (C)
Restoration is undercontoured, with dentin or base exposure; anatomic form is unsatisfactory; restoration needs replacement
Alfa
(A)
No marginal discoloration
Bravo
(B)
Minor marginal discoloration without staining toward pulp, only visible using mirror and operating light
Charlie (C)
Deep discoloration with staining toward pulp, visible at a speaking distance of 60 to 100 cm
Alfa
(A)
As smooth as the surrounding enamel
Bravo
(B)
Rougher than surrounding enamel; improvement by finishing is feasible
Charlie (C)
Very rough, could become antiesthetic and/or retain biofilm; improvement by finishing is not feasible
Alfa
(A)
No postoperative sensitivity
Bravo
(B)
Short-term and tolerable postoperative sensitivity
Charlie (C)
Long-term or intolerable postoperative sensitivity; restoration replacement is necessary
Alfa
(A)
No active caries present
Bravo
(B)
Active caries is present in contact with the restoration
Chemical composition and manufacturers of the materials evaluated
Material (batch number)
Chemical composition
Manufacturer
Magic Acid Gel
37% phosphoric acid
Vigodent/Coltene
Adper SE Plus Self-Etch Adhesive – Liquid A (8BH)
Water, HEMA, surfactant, pink colorant
3M ESPE
Adper SE Plus Self-Etch Adhesive – Liquid B (9BN)
UDMA, TEGMA, TMPTMA, HEMA, MHP, bonded zirconia nanofiller, initiator system based on camphorquinone
3M ESPE
Filtek P60 Posterior Restorative (N126307)
Matrix: UDMA (urethane dimethacrylate), TEG-DMA, bis-EMA; filler: silica/zirconia; initiator system: camphorquinone
3M ESPE
P90 System Adhesive Self-Etch Primer (N107465)
Phosphorylated methacrylates, Vitrebond copolymer, bis-GMA, HEMA, water and ethanol, silane-treated silica, initiators and stabilizers
3M ESPE
P90 System Adhesive Bond (N098714)
Hydrophobic bifunctional monomer, acidic monomers, silane-treated sılica, initiators and stabilizers
3M ESPE
Filtek P90 Low Shrink Posterior Restorative (N130928)
Matrix: silorane; filler: quartz, yttrium fluoride; initiator system: camphorquinone, iodonium salts and electron donors; stabilizers and pigments
3M ESPE
gins were etched with 37% phosphoric acid (Magic Acid Gel, Vigodent/Coltene; Rio de Janeiro, Brazil) before adhesive procedures. Materials were used according to the manufacturer’s recommendations (Table 3).
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Outcome Measurements and Statistical Analysis At baseline, 6-month, 1- and 2-year recalls, all restorations received a clinical rating of Alfa, Bravo, or Charlie. The dependent variable was the percentage of Alfa, Bravo, or Charlie ratings. 577
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Table 3 Clinical sequence of repair procedures using methacrylate or silorane-based restorative materials Repair procedure
Silorane-based restorative system (Filtek P90 / P90 system adhesive)
Methacrylatebased restorative system (Filtek P60 / Adper SE Plus)
Rubber-dam
X
X
Etch enamel with 37% phosphoric acid for 15 s
X
X
Rinse the acid with water and air dry
X
X
Remove excess water with absorbent paper
X
X
Apply self-etching primer for 15 s
X
Apply Liquid A (Adper SE Plus) for 10 s
X
Light cure for 10 s
X
Apply adhesive with disposable brush
X
Apply Liquid B (Adper SE Plus) for 20 s
X
Application of hydrophobic layer
X
Light cure for 10 s
X
X
Insert horizontal increments 2 mm thick (max) and sculpt resin
X
Insert oblique increments 2 mm thick (max) and sculpt resin
X
Light cure (600mW/cm2)
40 s
20 s
Remove excess restorative material with a scalpel blade #15
X
X
Finish with #9714FF bur (KG Sorensen)
X
X
Polish with Enhance System (Dentsply; Petrópolis, RJ, Brazil)
X
X
Statistical analysis of data was done with SPSS 15.0.1 for Windows (SPSS; Chicago, IL, USA). Variation in the levels of clinical parameters over time was evaluated by Friedman’s ANOVA for each composite material independently (α = 0.05). The Mann-Whitney test was used to assess differences between the materials tested and for all clinical criteria, at baseline, 6-month, 1 and 2-year recalls (α = 0.05). The Wilcoxon test was used to compare each composite resin for all clinical criteria at baseline examinations, 6-month, 1- and 2-year recalls (α = 0.05).
578
Patients assessed for elegibility (n = 56)
Excluded patients (n = 22)
Patients (n = 34) Randomized teeth (n = 100)
Allocated to control group – Filtek P60 Teeth (n = 50)
Allocated to test group – Filtek P90 Teeth (n = 50)
Teeth lost to baseline = 0
Teeth lost to baseline = 7
(n = 50)
(n = 43)
Teeth lost to sixmonth recall = 2
Teeth lost to sixmonth recall = 0
(n = 48)
(n = 43)
Teeth lost to oneyear recall = 8
Teeth lost to oneyear recall = 2
(n = 42)
(n = 41)
Teeth lost to twoyear recall = 4
Teeth lost to twoyear recall = 0
(n = 38)
(n = 41)
Fig 1 Flowchart of patients and number of restorations through each stage of the study.
RESULTS In the present study, the main reasons for restorations being repaired were marginal defects (81%) and loss of anatomic form (19%). Of the 100 repaired restorations, 93 (50 methacrylate-based restorations; 43 silorane-based restorations) were examined at baseline. Of those, 79 were reexamined at the 2-year recall (38 methacrylate-based restorations; 41 silorane-based restorations). The flow of participants and the total number of restorations evaluated at each recall are presented in Fig 1. The dropout rate in this study was about 15% from baseline to the 2-year recall. The Journal of Adhesive Dentistry
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Table 4 Frequency of Alfa, Bravo and Charlie ratings according to the materials tested at baseline and at 6-month, 1- and 2-year recalls Dimethacrylate-based composite
Silorane-based composite
Baseline (50)
6-month (48)
12-month (42)
24-month (38)
Baseline (43)
6-month (43)
12-month (41)
24-month (41)
Marginal adaptation
Alfa Bravo Charlie
94 6 0
95.8 4.2 0
95.2 4.8 0
89.5 7.9 2.6
100 0 0
100 0 0
97.6 2.4 0
97.6 0 2.4
Anatomic form
Alfa Bravo
98 2
97.9 2.1
95.2 4.8
94.7 5.3
88.4 11.6
88.4 11.6
87.8 12.2
92.7 7.3
Surface roughness
Alfa Bravo
80 20
75 25
71.4 28.6
71.1 28.9
65.1 34.9
69.8 30.2
63.4 36.6
73.2 26.8
Marginal discoloration
Alfa Bravo
98 2
100 0
100 0
92.1 7.9
100 0
100 0
92.7 7.3
90.2 9.8
Postoperative sensitivity
Alfa Bravo
100 0
100 0
100 0
100 0
95.3 4.7
100 0
100 0
100 0
Secondary caries
Alfa Bravo
100 0
100 0
100 0
100 0
100 0
100 0
100 0
100 0
Table 5
Comparisons among baseline, 6-month, 1- and 2-year recalls for each material independently Restorations rated Alfa (%) Marginal adaptation
DBC
Baseline 6-month 12-month 24-month
Anatomic form
Surface roughness
Marginal discoloration
Postoperative sensitivity
Secondary caries
94.0 95.8 95.2 89.5
98.0 97.9 95.2 94.7
80.0 75.0 71.4 71.1
98.0 100.0 100.0 92.1
100.0 100.0 100.0 100.0
100.0 100.0 100.0 100.0
X2*, p-value
6; 0.112
3; 0.392
3.6; 0.308
6; 0.112
-; 1.0
-; 1.0
SBC
100.0 100.0 97.6 97.6
88.4 88.4 87.8 92.7
65.1 69.8 63.4 73.2
100.0 100.0 92.7 90.2
95.3 100.0 100.0 100.0
100.0 100.0 100.0 100.0
2; 0.572
6; 0.112
9; 0.029
3; 0.392
Baseline 6-month 12-month 24 month
X2, p-value
3.39; 0.336
-; 1.0
*Chi-square test for 3 degrees of freedom; DBC: dimethacrylate-based composite; SBC: silorane-based composite.
Table 4 shows the frequencies of Alfa, Bravo, and Charlie ratings according to the materials tested at baseline and all recalls. Table 5 summarizes the comparisons among baseline and all recalls for each material independently, for all clinical parameters. Comparing baseline and the 2-year recall, there was statistically significant difference for marginal discoloration in the test group (p = 0.029). No statistically significant difference was found for the other criteria and follow-up periods (p > 0.05). At the 2-year recall, 2.6% of the restorations from the control group and 2.4% of the restorations from the test group were classified as Charlie. Despite this, no statistically significant difference between the materials was found (p > 0.05) (Table 6). Vol 16, No 6, 2014
DISCUSSION A silorane-based resin was the first non-methacrylatebased resin composite marketed for use in dentistry.3 Based on an innovative resin matrix, this epoxy-based resin contains an oxygen-containing ring molecule – oxiranes – and a siloxane molecule. It cures via a cationic ring-opening reaction rather than the linear chain reaction associated with conventional methacrylates.4 Developed with the primary purpose of overcoming some drawbacks related to polymerization of dimethacrylatebased composites, such as radical oxygen inhibition, polymerization shrinkage, polymerization stress, water 579
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Table 6
Comparison between the materials tested for all clinical criteria at each recall Restorations rated Alfa (%) Baseline
6 -month
12-month
24-month
DBC
SBC
p-value
DBC
SBC
p-value
DBC
SBC
p-value
DBC
SBC
p-value
Marginal adaptation
94.0
100
0.104
95.8
100
0.178
95.2
97.6
0.573
89.5
97.6
0.153
Anatomic form
98.0
88.4
0.061
97.9
88.4
0.069
95.2
87.8
0.226
94.7
92.7
0.710
Surface roughness
80.0
65.1
0.108
75.0
65.1
0.579
71.4
63.4
0.439
71.1
73.2
0.835
Marginal discoloration
98.0
100
0.354
100
100
1.00
100
92.7
0.076
92.1
90.2
0.773
Postoperative sensitivity
100.0
95.3
0.125
100
100
1.00
100
100
1.00
100
100
1.00
Secondary caries
100.0
100
1.00
100
100
1.00
100
100
1.00
100
100
1.00
DBC: dimethacrylate-based composite; SBC: silorane-based composite.
sorption, and instability of conventional monomers in aqueous systems,33 its mechanism involves a slight reduction of the initial distance between monomers, which results in a volumetric shrinkage around 1%, which might generate less stress on the adhesive interface.5,18,41 Silorane-based composites have been thoroughly investigated by in vitro tests, and promising results have been obtained regarding biocompatibility and mechanical characteristics, including reduced polymerization shrinkage.6,17,41 However, as in vitro studies are limited in terms of simulating clinical conditions, early results of clinical studies are important to evaluate innovative products. The dropout rates remain one of the problems associated with long-term clinical studies and having multiple restorations in one patient.36 In the current study, dropout was about 15% after two years. Because this rate was expected by the authors, the number of sample units was increased (n = 50) compared to sample size estimate (n = 25). Nevertheless, this was in accordance with other similar clinical studies that had dropout rates of 0% to 15% for early recalls.10,12,13,27,36 Although it is generally acknowledged that the USPHS criteria may provide information that is too general and has limited sensitivity in short-term clinical investigations,10,12 it is the most widely used method for clinical evaluations of restorations worldwide. In the present study, six modified USPHS criteria – marginal adaptation, anatomic form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries – were used to verify the clinical performance of repairs. The main reasons for adopting it here were that it enables comparison with previous studies, and involves a simple visual inspection as well as the use of a dental explorer.10 580
The age of restorations selected for repair could not be retrieved from the dental records in this study. Moreover, the patients did not provide this information accurately, but they were all certain that the restoration to be repaired was older than 12 months. This represents the typical clinical situation and seems to be common in similar studies.13,27 Thus, the development of accurate methods to retrieve this type of information should be encouraged in future studies, since when dimethacrylate-based composites have undergone aging, the number of available vinyl groups for cross polymerization decreases,19 which certainly influences the clinical performance of repairs. When repair is the appropriate procedure, the clinician is faced with a dilemma: composite monomers other than dimethacrylates (eg, siloranes) may have been used, requiring compatibility between different matrix compositions. However, only patients with dimethacrylate-based restoration were found to participate of the present study, since the beginning of the commercialization of silorane composites in Brazil was almost coincident with the beginning of the patients’ recruitment. The current study found no statistically significant differences between the materials tested for marginal adaptation at the 2-year follow-up. Although there are no results from clinical trials that have tested silorane-based composite as a repair material, one study investigated the marginal integrity of restorations performed by a lowshrinkage silorane-based composite across the same time interval.4 That study refers to completely replaced restorations, but their results are consistent with the results of this clinical study, finding 84% of the restorations to be optimal. On the other hand, two other studies10,36 on restorations completely replaced 1 to 1.5 years after insertion disagree with the findings of the present study, since a better performance was found for the dimethThe Journal of Adhesive Dentistry
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acrylate-based composite material. Thus, while laboratory studies have shown lower values of polymerization shrinkage related to silorane-based composites, it is difficult to show the effects in clinical studies, where many different factors influence the final result.18,35,41 As secondary caries is usually associated with loss of marginal integrity and marginal adaptation, favorable results are expected for a low-shrinkage resin-based composite.41 The current study confirmed this, but no statistically significant difference between the materials tested was found for secondary caries. This could be partly explained by the insufficient time for the development of caries, as well as the fact that patients with inadequate oral hygiene (VPI > 30%) and decreased salivary flow were excluded. Regarding anatomic form and sculptability criteria, general practitioners in five European countries were asked to rate several handling criteria of the silorane-based composite resin on a five-point scale, in which a score of 1 was given for excellent performance and a score of 5 for poor performance (3M ESPE, Filtek P90 Technical Profile). The best score given for the silorane-based composite was 3. This was also observed in the current study and could explain the percentage of Bravo ratings recorded for anatomic form in the test group, with a difference of 10% in the baseline results between the two materials tested. The fact that these findings were not observed again at the 2-year recall, with some restorations scoring better at follow-up than at baseline, may reflect the difficulty of assessing some criteria clinically, even though the interexaminer agreement ratio was ≥ 0.78. Moreover, if a study requires recording of minute detail, calibration becomes difficult with the concomitant risk of recording differences in clinical judgment between evaluators rather than between experimental and control groups.16 At the 2-year follow-up, no statistically significant difference was found when each composite resin was evaluated independently or when the two of them were compared. These findings are in agreement with the results of studies that have analyzed the longevity of minimally invasive dimethacrylatebased restorations, in which the restorations examined were considered acceptable for anatomic form, remaining stable and unchanged over the 2-year observation period.13,26,27 The composite surface roughness can be influenced by different factors related to the material itself, such as the filler (type, shape, size, and distribution of the particles), the type of resinous matrix, the ultimate degree of cure reached, and the bond efficacy at the filler/matrix interface.20,30 A direct correlation was found between the hardness and surface roughness, indicating that a composite with a higher hardness value is usually associated with a higher surface roughness.20,24 In the current study, no statistically significant difference between the materials was found for surface roughness at any recall examination. At baseline, however, a 15% difference in surface roughness between the materials was found, indicating better performance of the methacrylate-based composite resin. A previous study15 found a higher Knoop hardness for silorane-based than Vol 16, No 6, 2014
for dimethacrylate-based composites, due to the former’s organic matrix being mainly composed of silorane resin and inorganic particles, such as quartz and yttrium fluoride (76% by weight), which could explain the baseline findings for surface roughness in the test group here. Furthermore, the percentages of Bravo ratings found for both materials could be explained by the fact that an Alfa rating is given to a surface as smooth as the surrounding enamel; perhaps the evaluators were very critical in their evaluation, since it is known that no dental material can replace all the qualities of enamel, and this especially applies to its smooth, polished surface.40 Moreover, as occurred with the anatomic form parameter, the baseline findings for surface roughness did not remain after two years, again reflecting the difficulty in assessing certain clinical criteria, highlighting the risk of recording differences in clinical judgment between evaluators rather than between experimental and control groups. At the 2-year recall, a statistically significant difference vs baseline was observed for marginal discoloration when the restorations were repaired by the silorane-based composite. In the present study, we did not use a silane agent before the silorane adhesive system, as their combined effect on repair bond strength has not been completely elucidated. Although Ivanovas et al19 have considered silane application as a decisive factor for adhesion of methacrylate-based adhesives on silorane surfaces, another study showed that silane application is not mandatory when silorane composite and silorane adhesive system are used for repair.42 However, since the silane agent did not adversely affect the bond strength of the silorane adhesive system, the routine application of silane for repair of composite fillings with unknown composite matrix could be recommended.42 Thus, it is appropriate to emphasize that early marginal staining is usually a clinical sign that a restoration will be prone to failure or the adhesive interface will undergo degradation with time.40 The main reasons for marginal discoloration include the presence of excess filling materials, a deficient restoration around the margin, and the formation of gaps.38 Marginal discoloration has also been associated with poor etching ability of self-etching adhesives at the enamel margins.7,9,31 Consequently, stable adhesion to enamel with self-etching adhesives is still a challenge.1 This may explain our findings, since the silorane-based composite resin requires using a selfetching adhesive, as does the adhesive system used on the control group. Both materials presented Charlie ratings for marginal discolorations, and there was no statistically significant difference between them. Another factor that may have influenced our findings is the use of burs to roughen the composite surface. Although a previous study showed that micromechanical retention by bur abrasion is less effective than sandblasting or silica coating,34 it was assumed that the type of mechanical treatment is of minor relevance for silorane repair.42 Clinical trials with resin-based composites restorations have observed initial postoperative sensitivity, which generally decreases during the first weeks after placement of restorations.2,36 At baseline examination, the low in581
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cidence of restorations that received a Bravo rating can be explained by the use of a self-etching bonding system in both treatment groups. These systems incorporate the smear layer into the hybrid layer, providing better penetration of the monomers to the collagen fibers of the demineralized dentin. At the 2-year follow-up, the same good performance was observed for all composites, possibly because resin-based agents may provide pulp protection as long as the dentin is sealed by hydrophilic resins.2,36 Thus, since the frequency of ratings that remained constant from baseline to the 2-year recall was much higher than the frequency of ratings that worsened, the null hypothesis tested in this study was confirmed: the clinical performance of low-shrinkage silorane-based composites was similar to that of the dimethacrylate-based composites when repairing dimethacrylate-based composite restorations after a two-year observation period. Although one- and two-year evaluations have been considered to provide timely information on the performance of restorations, particularly for newly introduced materials such as that used in the present study, longer observation periods are necessary to confirm these findings.
6. 7.
8.
9.
10.
11.
12.
13.
14.
15.
CONCLUSIONS This clinical trial showed that, after two years, siloranebased composites are clinically acceptable to repair failed conventional dimethacrylate-based composites restorations, but they did not demonstrate any advantage over dimethacrylate-based composites. Repairs with resin chemically different than the original restoration were successful as long as the bonding agent chemically resembled the repair resin. After two years, the reduced polymerization shrinkage attributed to silorane-based composites did not establish better clinical performance, indicating that laboratory findings should be substantiated by clinical investigations. Clinical studies with longer recall periods are necessary.
16.
17.
18. 19. 20. 21. 22.
ACKNOWLEDGMENTS
23.
Our thanks go to FAPEMIG, which supported the present study.
24.
REFERENCES
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3.
4.
5.
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Eick JD, Smith RE, Pinzino CS, Kostoryz EL. Stability of silorane dental monomers in aqueous systems J Dent 2006;34:405-410. Ermis RB, Temel UB, Cellik EU, Kam O. Clinical performance of a twostep self-etch adhesive with additional enamel etching in Class III cavities. Oper Dent 2010;35:147-155. Frankenberger R, Roth S, Krämer N, Pelka M, Petschelt A. Effect of preparation mode on class II resin composite repair J Oral Rehabil 2003;30:559-564. Fron H, Vergnes JN, Moussally C, Cazier S, Simon AL, Chieze JB, Savard G, Tirlet G, Attal JP. Effectiveness of a new one-step self-etch adhesive in the restoration of non-carious cervical lesions: 2-year results of a randomized controlled practice-based study Dent Mater 2011;27:304-312. Gonçalves FS, Leal CD, Bueno AC, Freitas ABDA, Moreira AN, Magalhães CS. A double-blind randomized clinical trial of a silorane-based resin composite in class 2 restorations: 18-month follow-up. Am J Dent 2013;26:93-98. Gonçalves FS, Castro CD, Bueno AC, de Freitas ABDA, Moreira AN, Magalhães CS. The short-term clinical performance of a silorane-based resin composite in the proximal contacts of class II restorations. J Contemp Dent Pract 2012;13:251-256. Gordan VV, Mondragon E, Watson RE, Garvan C, Mjör IA. A clinical evaluation of a self-etching primer and giomer restorative material. J Am Dent Assoc 2007;138:621-627. Gordan VV, Shen C, Riley J, Mjör IA. Two-year clinical evaluation of repair versus replacement of composite restorations. J Esthet Dent 2006;18:144-154. Gordan VV, Shen C, Watson RE, Mjör IA. Four-year clinical evaluation of self-etching primer and resin-based restorative material. Am J Dent 2005;18:45-49. Guiraldo RD, Consani S, Consani RLX, Berger SB, Mendes WB, Sinhoreti MAC, Correr-Sobrinho L. Comparison of silorane and methacrylatebased composite resins on the curing light transmission. Brazil Dent J 2010;21:538-542. Hickel R, Roulet JF, Bayne S, Heintze SD, Mjör IA, Peters M, Rousson V, Randall R, Schmalz G, Tyas M, Vanherle G. Recommendations for conducting controlled clinical studies of dental restorative materials. Science Committee Project 2/98—FDI World Dent Federation study design (Part I) and criteria for evaluation (Part II) of direct and indirect restorations including onlays and partial crowns J Adhes Dent 2007;9:121-147. Ilie N, Hickel R. Macro-, micro- and nano-mechanical investigations of silorane and methacrylate-based composites Dent Mater 2009;25: 810-819. Ilie N, Jelen E, Clementino-Luedemann T, Hickel R. Low-shrinkage composite for dental application Dent Mater J 2007;26:149-155. Ivanovas S, Hickel R, Ilie N. How to repair fillings made by siloranebased composites. Clin Oral Invest 2011;15:915-922. Jefferies SR. The art and science of abrasive finishing and polishing in restorative dentistry. Dent Clin North Am 1998;42:613-627. Kishikawa R, Koiwa A, Chikawa H, Cho E, Inai N, Tagami J. Effect of cavity form on adhesion to cavity floor. Am J Dent 2005;18:311-314. Lührs AK, Görmann B, Jaker-Guhr S, Geurtsen W. Repairability of dental siloranes in vitro. Dent Mater 2011;27:144-149. Mannenut C, Sakoolnamarka R, Tyas MJ. The repair potential of resin composite materials Dent Mater 2011;27:20-27. Marghalani HY. Effect of finishing/polishing systems on the surface roughness of novel posterior composites. J Esthet Restor Dent 2010;22:127-138. Mjör IA, Reep RL, Kubilis PS, Mondragon BE. Change in size of replaced amalgam restorations: a methodological study Oper Dent 1998;23: 272-277. Moncada G, Fernández E, Martin J, Arancibia C, Mjör I, Gordan VV. Increasing longevity of restorations by minimal intervention: a two-year clinical trial Oper Dent 2008;33:258-264. Moncada G, Martin J, Fernández E, Hampel MC, Mjör IA, Gordan VV. Sealing, refurbishment and repair of class I and class II defective restorations: a three-year clinical trial. J Am Dent Assoc 2009;140:425-432. Papacchini F, Magni E, Radovic I, Mazzitelli C, Monticelli F, Goracci C, Polimeni A, Ferrari M. Effect of intermediate agents and pre-heating of repairing resin on composite-repair bonds. Oper Dent 2007;32: 363-371. Papadogiannis D, Kakaboura A, Palaghias G, Eliades G. Setting characteristics and cavity adaptation of low-shrinking resin composites. Dent Mater 2010;25:1509-1516. Park J, Chang J, Ferracane J, Lee IB. How should composite be layered to reduce shrinkage stress: incremental or bulk filling? Dent Mater 2008;24:1501-1505.
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Popoff et al 31. Perdigão J, Dutra-Correa M, Anauate-Netto C, Castilhos N, Carmo APR, Lewgoy HR, Amore R, Cordeiro HJ. Two-year clinical evaluation of self-etch adhesives in posterior restorations. J Adhes Dent 2009;11: 149-159. 32. Popoff DAV, Gonçalves FS, Ferreira RC, Magalhães CS, Moreira AN, Mjör IA. Repair of amalgam restorations with conventional and bonded amalgam: an in vitro study. J Dent Sci 2010;25:154-158. 33. Popoff DAV, Santa Rosa TTA, Ferreira RC, Magalhães CS, Moreira AN, Mjör IA. Repair of dimethacrylate-based composite restorations by a silorane-based composite: a one-year randomized clinical trial. Oper Dent 2012;37:E1-E10. 34. Rodrigues Jr SA, Ferracane JL, Della Bona A. Influence of surface treatments on the bond strength of repaired resin composite restorative materials. Dent Mater 2009;25:442–451. 35. Ruttermann S, Kruger S, Raab WH, Janda R. Polymerization shrinkage and hygroscopic expansion of contemporary posterior resin-based filling materials—a comparative study. J Dent 2007;35:806-813. 36. Schmidt M, Kirkevang LL, Hǿrsted-Bindslev P, Poulsen S. Marginal adaptation of a low-shrinkage silorane-based composite: 1-year randomized clinical trial. Clin Oral Invest 2011;15:291-295. 37. Tesvergil A, Lassila LVJ, Vallittu PK. Composite-composite repair bond strength: effect of different adhesion primers J Dent 2003;31:521-525. 38. Turkun LS. The clinical performance of one- and two-step self-etching adhesive systems at one year. J Am Dent Assoc 2003;136:656-664. 39. Van Ende A, Mine A, De Munck J, Poitevin A, Van Meerbeek B. Bonding of low-shrinking composites in high C-factor cavities. J Dent 2012;40:295-303.
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40. Vangelov L, Markova K, Miteva T. Application of Filtek silorane – initial observations and prospective clinical trial for 12 months. J Int Med Assoc Bulgaria (IMAB) 2010;16:58-62. 41. Weinmann W, Thalacker C, Guggenberger R. Siloranes in dental composites. Dent Mater 2005;21:68-74. 42. Wiegand A, Stawarczyk B, Buchalla W, Tauböck TT, Özcan M, Attin T. Repair of silorane composite using the same substrate or a methacrylate-based composite? Dent Mater 2012;28:19-25. 43. Zakir M, Kheraif AA, Asif M, Rehman IU. A comparison of the mechanical properties of a modified silorane based dental composite with those of commercially available composite material. Dent Mater 2013;29: 53-59.
Clinical relevance: This two-year clinical trial showed that using a silorane-based composite for repairing composite resin restorations may be a viable clinical procedure, since restorations repaired by this novel composite exhibited similar clinical performance to that of conventional composites.
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Purpose: To investigate the clinical performance of a silorane-based composite resin used for repairing dimethacrylate-based composite restorations. Materials and Methods: One operator repaired defective dimethacrylate-based resin restorations that were randomly assigned to one of two treatment groups: control (n = 50), repaired with Adper SE Plus and Filtek P60 Posterior Restorative (3M ESPE); or test (n = 50), repaired with P90 System Adhesive Self-Etch Primer and Bond and Filtek P90 Low Shrink Posterior Restorative (3M ESPE). After 1 week, restorations were finished and polished. Two calibrated examiners (weighted Kappa ≥ 0.78) evaluated the repaired restorations, blindly and independently, at baseline, after 6 months, 1 and 2 years. The parameters examined were marginal adaptation, anatomic form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries. The restorations were classified as Alfa, Bravo, or Charlie, according to modified US Public Health Service criteria. Variation in the levels of clinical parameters over time was evaluated by Friedman’s ANOVA (α = 0.05). The Mann-Whitney test assessed the differences between the materials for all clinical criteria at baseline, 6-month, 1- and 2-year recalls (α = 0.05). The Wilcoxon test compared each composite resin for all clinical criteria at the same recalls (α = 0.05). Results: After two years, 79 repaired restorations were re-examined. No statistically significant differences were found between the materials at baseline or at the 2-year recall (p > 0.05). Comparing baseline and 2-year recall, there was a statistically significant difference for marginal discoloration (p = 0.029) in silorane-based composite restorations. Conclusion: After two years, the clinical performance of the silorane-based composite was similar to that of the dimethacrylate-based composite when used to make repairs. Keywords: low-shrinkage silorane-based composite, dimethacrylate-based composite, resin-based restoration, repair. J Adhes Dent 2014; 16: 575–583. doi: 10.3290/j.jad.a33196
Submitted for publication: 26.07.13; accepted for publication: 14.08.14
a
Assistant Professor, School of Dentistry, University of Montes Claros, Montes Claros, Minas Gerais, Brazil. Idea, hypothesis, performed the experiments in partial fulfillment of requirements for a PhD degree, wrote manuscript, contributed substantially to discussion.
f
Assistant Professor, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. Co-wrote and proofread manuscript, consulted on and performed statistical evaluation, contributed substantially to discussion.
b
Associate Professor, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. Idea, hypothesis, experimental design, co-wrote and proofread manuscript, contributed substantially to discussion.
g
Associate Professor, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. Idea, hypothesis, experimental design, co-wrote and proofread manuscript, contributed substantially to discussion.
c
Graduate Student, School of Dentistry, University of Montes Claros, Montes Claros, Minas Gerais, Brazil. Co-wrote manuscript, contributed substantially to discussion.
h
Dr.odont Inactive, ad hoc reviewer, College of Dentistry, University of Florida, Gainesville, FL, USA. Co-wrote and proofread manuscript, contributed substantially to discussion.
d
Graduate Student, School of Dentistry, United Colleges of North Minas Gerais, Montes Claros, Minas Gerais, Brazil. Co-wrote manuscript, contributed substantially to discussion.
e
Assistant Professor, School of Dentistry, University of Montes Claros, Montes Claros, Minas Gerais, Brazil. Co-wrote and proofread manuscript, contributed substantially to discussion.
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Correspondence: Claudia Silami de Magalhães, Av. Antônio Carlos, 6627, Pampulha, CEP 31270-901, Belo Horizonte, Minas Gerais, Brazil. Tel: +55-319971-3747, Fax: +55-31-3409-2405. e-mail: [email protected]
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D
ue to the growing demand for esthetic restorations and the evident enhancement of the properties of restorative dental composites, these materials have become the best choice for performing direct restorations.8,28,33,37 Such improvements, along with a minimally invasive approach to caries treatment, have made these restorative materials very popular for direct posterior restorations. Nevertheless, the longevity of these restorations is still affected by the consequences of their polymerization shrinkage.1,4,43 Clinically, incremental insertion and control of polymerization rate are the main strategies used to control polymerization shrinkage. These techniques are widely recommended in order to reduce the C-factor and the composite volume being polymerized at each stage of the restoration procedure.33,39 Nonetheless, the composites’ intrinsic contraction remains a challenge, and changes in the monomer composition seem to hold promise for minimizing the effects of shrinkage.5,21,41 An innovative monomer system termed “silorane” was introduced to the dental market for clinical use. The silorane-based resin takes its name from the combination of its chemical blocks, siloxanes and oxiranes.1,41 The silorane molecule has a siloxane core with four attached oxirane rings that open upon polymerization to bond to other monomers. This mechanism results in a volumetric shrinkage of less than 1%, which may reduce the deleterious effects of shrinkage stress at the tooth/restoration interface. This characteristic has also been validated by in vivo studies in which silorane-based resin restorations exhibited satisfactory clinical performance.1,4,11,33 In vitro studies suggest that bonding of silorane-based composites to old dimethacrylate-based composites may be a viable clinical procedure19,22,23 and previous findings have shown viable clinical performance for the silorane systems after one year.33 As clinical studies evaluating the long-term clinical performance of restorations repaired by silorane-based composite resin are lacking, it would be desirable to keep evaluating the clinical performance of this system for making repairs. In this context, keeping in mind the current trends toward minimally invasive techniques that allow preservation of sound tooth structure,25,27,32 the purpose of the present study was to investigate the clinical performance of a lowshrinkage silorane-based composite resin when used for repairing conventional dimethacrylate-based composite restorations. The hypothesis tested in this randomized controlled clinical trial was that low-shrinkage siloranebased composites exhibit performance similar to that of conventional dimethacrylate-based composites when repairing composite resin restorations.
MATERIALS AND METHODS Study Design The observation unit of this prospective randomized clinical trial was the restoration, and the dependent variable was qualitative categorical ordinal. Patients aged 18 to 56 years with 100 defective composite resin res576
torations participated in this study. They were routinely assigned for treatment at the operative dentistry clinic, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. The fillings to be repaired were class I or class II methacrylate-based composite resin restorations (small, medium, or large size) on premolars and molars. The fillings had to present defects on the occlusal but not on the proximal surfaces and had to be scored Bravo according to the Modified United States Public Health Service (USPHS) clinical criteria (Table 1). The exclusion criteria were: contraindications for regular dental treatment according to the patient’s medical history; xerostomia, including consumption of medications proven to significantly reduce salivary flow; visible plaque index (VPI) > 30%; and defective restorations not indicated for repairs that scored Charlie (modified USPHS clinical criteria). Teeth with clinical and radiographic diagnosis of caries and teeth without their respective antagonist were excluded from the sample. This study was approved by the Institutional Ethics Committee (ETIC 0546.0.203.000-09). Written informed consent was obtained from all patients. Study Methods The restorations were examined one week after they were repaired for baseline assessment, then at 6 months and 1 and 2 years. Two examiners independently evaluated all repaired restorations by direct observation using a plane buccal mirror and a WHO model explorer. A calibration exercise revealed an interexaminer agreement ratio ≥ 0.78. If there was disagreement on the rating, the clinicians re-examined the repaired restoration together and arrived at a joint final decision. The parameters examined were marginal adaptation, anatomic form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries. The examiners classified all restorations as Alfa, Bravo, or Charlie, according to modified USPHS clinical criteria (Table 1). Treatment Groups To minimize preparation variability, the same operator repaired all defective composite resin restorations. The defective surfaces of the restorations were explored using a high-speed round diamond bur (#1010, #1011, #1012, #1013 or #1014, KG Sorensen; São Paulo, SP, Brazil) compatible with the defect size, in a handpiece with air-water cooling. The removal of the restorative material started in the area of the defect and included any stained and soft tooth tissues. The operator randomly assigned the restorations to one of two treatment groups: 1. control (n = 50), repaired with a self-etching primer (Adper SE Plus, 3M ESPE, St Paul, MN, USA) and a dimethcrylate-based composite (Filtek P60 Posterior Restorative, 3M ESPE), or 2. test (n = 50), repaired with a self-etching primer (P90 System Adhesive Self-Etch Primer and Bond, 3M ESPE) and a low-shrinkage silorane-based composite (Filtek P90 Low Shrink Posterior Restorative, 3M ESPE (Table 2). Rubber-dam isolation was used during the restorative procedures. The surfaces of restorations and enamel marThe Journal of Adhesive Dentistry
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Table 1
Modified United States Public Health Service clinical criteria
Marginal adaptation
Anatomic form
Marginal discoloration
Surface roughness
Post-operative sensitivity
Secondary caries
Table 2
Alfa
(A)
Restoration adapts closely to the tooth structure; there is no visible crevice
Bravo
(B)
There is a visible crevice, the explorer will penetrate, without dentin exposure
Charlie (C)
The explorer penetrates into crevice in which dentin or the base is exposed
Alfa
(A)
Anatomic form ideal
Bravo
(B)
Restoration is undercontoured, without dentin or base exposure
Charlie (C)
Restoration is undercontoured, with dentin or base exposure; anatomic form is unsatisfactory; restoration needs replacement
Alfa
(A)
No marginal discoloration
Bravo
(B)
Minor marginal discoloration without staining toward pulp, only visible using mirror and operating light
Charlie (C)
Deep discoloration with staining toward pulp, visible at a speaking distance of 60 to 100 cm
Alfa
(A)
As smooth as the surrounding enamel
Bravo
(B)
Rougher than surrounding enamel; improvement by finishing is feasible
Charlie (C)
Very rough, could become antiesthetic and/or retain biofilm; improvement by finishing is not feasible
Alfa
(A)
No postoperative sensitivity
Bravo
(B)
Short-term and tolerable postoperative sensitivity
Charlie (C)
Long-term or intolerable postoperative sensitivity; restoration replacement is necessary
Alfa
(A)
No active caries present
Bravo
(B)
Active caries is present in contact with the restoration
Chemical composition and manufacturers of the materials evaluated
Material (batch number)
Chemical composition
Manufacturer
Magic Acid Gel
37% phosphoric acid
Vigodent/Coltene
Adper SE Plus Self-Etch Adhesive – Liquid A (8BH)
Water, HEMA, surfactant, pink colorant
3M ESPE
Adper SE Plus Self-Etch Adhesive – Liquid B (9BN)
UDMA, TEGMA, TMPTMA, HEMA, MHP, bonded zirconia nanofiller, initiator system based on camphorquinone
3M ESPE
Filtek P60 Posterior Restorative (N126307)
Matrix: UDMA (urethane dimethacrylate), TEG-DMA, bis-EMA; filler: silica/zirconia; initiator system: camphorquinone
3M ESPE
P90 System Adhesive Self-Etch Primer (N107465)
Phosphorylated methacrylates, Vitrebond copolymer, bis-GMA, HEMA, water and ethanol, silane-treated silica, initiators and stabilizers
3M ESPE
P90 System Adhesive Bond (N098714)
Hydrophobic bifunctional monomer, acidic monomers, silane-treated sılica, initiators and stabilizers
3M ESPE
Filtek P90 Low Shrink Posterior Restorative (N130928)
Matrix: silorane; filler: quartz, yttrium fluoride; initiator system: camphorquinone, iodonium salts and electron donors; stabilizers and pigments
3M ESPE
gins were etched with 37% phosphoric acid (Magic Acid Gel, Vigodent/Coltene; Rio de Janeiro, Brazil) before adhesive procedures. Materials were used according to the manufacturer’s recommendations (Table 3).
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Outcome Measurements and Statistical Analysis At baseline, 6-month, 1- and 2-year recalls, all restorations received a clinical rating of Alfa, Bravo, or Charlie. The dependent variable was the percentage of Alfa, Bravo, or Charlie ratings. 577
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Table 3 Clinical sequence of repair procedures using methacrylate or silorane-based restorative materials Repair procedure
Silorane-based restorative system (Filtek P90 / P90 system adhesive)
Methacrylatebased restorative system (Filtek P60 / Adper SE Plus)
Rubber-dam
X
X
Etch enamel with 37% phosphoric acid for 15 s
X
X
Rinse the acid with water and air dry
X
X
Remove excess water with absorbent paper
X
X
Apply self-etching primer for 15 s
X
Apply Liquid A (Adper SE Plus) for 10 s
X
Light cure for 10 s
X
Apply adhesive with disposable brush
X
Apply Liquid B (Adper SE Plus) for 20 s
X
Application of hydrophobic layer
X
Light cure for 10 s
X
X
Insert horizontal increments 2 mm thick (max) and sculpt resin
X
Insert oblique increments 2 mm thick (max) and sculpt resin
X
Light cure (600mW/cm2)
40 s
20 s
Remove excess restorative material with a scalpel blade #15
X
X
Finish with #9714FF bur (KG Sorensen)
X
X
Polish with Enhance System (Dentsply; Petrópolis, RJ, Brazil)
X
X
Statistical analysis of data was done with SPSS 15.0.1 for Windows (SPSS; Chicago, IL, USA). Variation in the levels of clinical parameters over time was evaluated by Friedman’s ANOVA for each composite material independently (α = 0.05). The Mann-Whitney test was used to assess differences between the materials tested and for all clinical criteria, at baseline, 6-month, 1 and 2-year recalls (α = 0.05). The Wilcoxon test was used to compare each composite resin for all clinical criteria at baseline examinations, 6-month, 1- and 2-year recalls (α = 0.05).
578
Patients assessed for elegibility (n = 56)
Excluded patients (n = 22)
Patients (n = 34) Randomized teeth (n = 100)
Allocated to control group – Filtek P60 Teeth (n = 50)
Allocated to test group – Filtek P90 Teeth (n = 50)
Teeth lost to baseline = 0
Teeth lost to baseline = 7
(n = 50)
(n = 43)
Teeth lost to sixmonth recall = 2
Teeth lost to sixmonth recall = 0
(n = 48)
(n = 43)
Teeth lost to oneyear recall = 8
Teeth lost to oneyear recall = 2
(n = 42)
(n = 41)
Teeth lost to twoyear recall = 4
Teeth lost to twoyear recall = 0
(n = 38)
(n = 41)
Fig 1 Flowchart of patients and number of restorations through each stage of the study.
RESULTS In the present study, the main reasons for restorations being repaired were marginal defects (81%) and loss of anatomic form (19%). Of the 100 repaired restorations, 93 (50 methacrylate-based restorations; 43 silorane-based restorations) were examined at baseline. Of those, 79 were reexamined at the 2-year recall (38 methacrylate-based restorations; 41 silorane-based restorations). The flow of participants and the total number of restorations evaluated at each recall are presented in Fig 1. The dropout rate in this study was about 15% from baseline to the 2-year recall. The Journal of Adhesive Dentistry
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Table 4 Frequency of Alfa, Bravo and Charlie ratings according to the materials tested at baseline and at 6-month, 1- and 2-year recalls Dimethacrylate-based composite
Silorane-based composite
Baseline (50)
6-month (48)
12-month (42)
24-month (38)
Baseline (43)
6-month (43)
12-month (41)
24-month (41)
Marginal adaptation
Alfa Bravo Charlie
94 6 0
95.8 4.2 0
95.2 4.8 0
89.5 7.9 2.6
100 0 0
100 0 0
97.6 2.4 0
97.6 0 2.4
Anatomic form
Alfa Bravo
98 2
97.9 2.1
95.2 4.8
94.7 5.3
88.4 11.6
88.4 11.6
87.8 12.2
92.7 7.3
Surface roughness
Alfa Bravo
80 20
75 25
71.4 28.6
71.1 28.9
65.1 34.9
69.8 30.2
63.4 36.6
73.2 26.8
Marginal discoloration
Alfa Bravo
98 2
100 0
100 0
92.1 7.9
100 0
100 0
92.7 7.3
90.2 9.8
Postoperative sensitivity
Alfa Bravo
100 0
100 0
100 0
100 0
95.3 4.7
100 0
100 0
100 0
Secondary caries
Alfa Bravo
100 0
100 0
100 0
100 0
100 0
100 0
100 0
100 0
Table 5
Comparisons among baseline, 6-month, 1- and 2-year recalls for each material independently Restorations rated Alfa (%) Marginal adaptation
DBC
Baseline 6-month 12-month 24-month
Anatomic form
Surface roughness
Marginal discoloration
Postoperative sensitivity
Secondary caries
94.0 95.8 95.2 89.5
98.0 97.9 95.2 94.7
80.0 75.0 71.4 71.1
98.0 100.0 100.0 92.1
100.0 100.0 100.0 100.0
100.0 100.0 100.0 100.0
X2*, p-value
6; 0.112
3; 0.392
3.6; 0.308
6; 0.112
-; 1.0
-; 1.0
SBC
100.0 100.0 97.6 97.6
88.4 88.4 87.8 92.7
65.1 69.8 63.4 73.2
100.0 100.0 92.7 90.2
95.3 100.0 100.0 100.0
100.0 100.0 100.0 100.0
2; 0.572
6; 0.112
9; 0.029
3; 0.392
Baseline 6-month 12-month 24 month
X2, p-value
3.39; 0.336
-; 1.0
*Chi-square test for 3 degrees of freedom; DBC: dimethacrylate-based composite; SBC: silorane-based composite.
Table 4 shows the frequencies of Alfa, Bravo, and Charlie ratings according to the materials tested at baseline and all recalls. Table 5 summarizes the comparisons among baseline and all recalls for each material independently, for all clinical parameters. Comparing baseline and the 2-year recall, there was statistically significant difference for marginal discoloration in the test group (p = 0.029). No statistically significant difference was found for the other criteria and follow-up periods (p > 0.05). At the 2-year recall, 2.6% of the restorations from the control group and 2.4% of the restorations from the test group were classified as Charlie. Despite this, no statistically significant difference between the materials was found (p > 0.05) (Table 6). Vol 16, No 6, 2014
DISCUSSION A silorane-based resin was the first non-methacrylatebased resin composite marketed for use in dentistry.3 Based on an innovative resin matrix, this epoxy-based resin contains an oxygen-containing ring molecule – oxiranes – and a siloxane molecule. It cures via a cationic ring-opening reaction rather than the linear chain reaction associated with conventional methacrylates.4 Developed with the primary purpose of overcoming some drawbacks related to polymerization of dimethacrylatebased composites, such as radical oxygen inhibition, polymerization shrinkage, polymerization stress, water 579
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Table 6
Comparison between the materials tested for all clinical criteria at each recall Restorations rated Alfa (%) Baseline
6 -month
12-month
24-month
DBC
SBC
p-value
DBC
SBC
p-value
DBC
SBC
p-value
DBC
SBC
p-value
Marginal adaptation
94.0
100
0.104
95.8
100
0.178
95.2
97.6
0.573
89.5
97.6
0.153
Anatomic form
98.0
88.4
0.061
97.9
88.4
0.069
95.2
87.8
0.226
94.7
92.7
0.710
Surface roughness
80.0
65.1
0.108
75.0
65.1
0.579
71.4
63.4
0.439
71.1
73.2
0.835
Marginal discoloration
98.0
100
0.354
100
100
1.00
100
92.7
0.076
92.1
90.2
0.773
Postoperative sensitivity
100.0
95.3
0.125
100
100
1.00
100
100
1.00
100
100
1.00
Secondary caries
100.0
100
1.00
100
100
1.00
100
100
1.00
100
100
1.00
DBC: dimethacrylate-based composite; SBC: silorane-based composite.
sorption, and instability of conventional monomers in aqueous systems,33 its mechanism involves a slight reduction of the initial distance between monomers, which results in a volumetric shrinkage around 1%, which might generate less stress on the adhesive interface.5,18,41 Silorane-based composites have been thoroughly investigated by in vitro tests, and promising results have been obtained regarding biocompatibility and mechanical characteristics, including reduced polymerization shrinkage.6,17,41 However, as in vitro studies are limited in terms of simulating clinical conditions, early results of clinical studies are important to evaluate innovative products. The dropout rates remain one of the problems associated with long-term clinical studies and having multiple restorations in one patient.36 In the current study, dropout was about 15% after two years. Because this rate was expected by the authors, the number of sample units was increased (n = 50) compared to sample size estimate (n = 25). Nevertheless, this was in accordance with other similar clinical studies that had dropout rates of 0% to 15% for early recalls.10,12,13,27,36 Although it is generally acknowledged that the USPHS criteria may provide information that is too general and has limited sensitivity in short-term clinical investigations,10,12 it is the most widely used method for clinical evaluations of restorations worldwide. In the present study, six modified USPHS criteria – marginal adaptation, anatomic form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries – were used to verify the clinical performance of repairs. The main reasons for adopting it here were that it enables comparison with previous studies, and involves a simple visual inspection as well as the use of a dental explorer.10 580
The age of restorations selected for repair could not be retrieved from the dental records in this study. Moreover, the patients did not provide this information accurately, but they were all certain that the restoration to be repaired was older than 12 months. This represents the typical clinical situation and seems to be common in similar studies.13,27 Thus, the development of accurate methods to retrieve this type of information should be encouraged in future studies, since when dimethacrylate-based composites have undergone aging, the number of available vinyl groups for cross polymerization decreases,19 which certainly influences the clinical performance of repairs. When repair is the appropriate procedure, the clinician is faced with a dilemma: composite monomers other than dimethacrylates (eg, siloranes) may have been used, requiring compatibility between different matrix compositions. However, only patients with dimethacrylate-based restoration were found to participate of the present study, since the beginning of the commercialization of silorane composites in Brazil was almost coincident with the beginning of the patients’ recruitment. The current study found no statistically significant differences between the materials tested for marginal adaptation at the 2-year follow-up. Although there are no results from clinical trials that have tested silorane-based composite as a repair material, one study investigated the marginal integrity of restorations performed by a lowshrinkage silorane-based composite across the same time interval.4 That study refers to completely replaced restorations, but their results are consistent with the results of this clinical study, finding 84% of the restorations to be optimal. On the other hand, two other studies10,36 on restorations completely replaced 1 to 1.5 years after insertion disagree with the findings of the present study, since a better performance was found for the dimethThe Journal of Adhesive Dentistry
Popoff et al
acrylate-based composite material. Thus, while laboratory studies have shown lower values of polymerization shrinkage related to silorane-based composites, it is difficult to show the effects in clinical studies, where many different factors influence the final result.18,35,41 As secondary caries is usually associated with loss of marginal integrity and marginal adaptation, favorable results are expected for a low-shrinkage resin-based composite.41 The current study confirmed this, but no statistically significant difference between the materials tested was found for secondary caries. This could be partly explained by the insufficient time for the development of caries, as well as the fact that patients with inadequate oral hygiene (VPI > 30%) and decreased salivary flow were excluded. Regarding anatomic form and sculptability criteria, general practitioners in five European countries were asked to rate several handling criteria of the silorane-based composite resin on a five-point scale, in which a score of 1 was given for excellent performance and a score of 5 for poor performance (3M ESPE, Filtek P90 Technical Profile). The best score given for the silorane-based composite was 3. This was also observed in the current study and could explain the percentage of Bravo ratings recorded for anatomic form in the test group, with a difference of 10% in the baseline results between the two materials tested. The fact that these findings were not observed again at the 2-year recall, with some restorations scoring better at follow-up than at baseline, may reflect the difficulty of assessing some criteria clinically, even though the interexaminer agreement ratio was ≥ 0.78. Moreover, if a study requires recording of minute detail, calibration becomes difficult with the concomitant risk of recording differences in clinical judgment between evaluators rather than between experimental and control groups.16 At the 2-year follow-up, no statistically significant difference was found when each composite resin was evaluated independently or when the two of them were compared. These findings are in agreement with the results of studies that have analyzed the longevity of minimally invasive dimethacrylatebased restorations, in which the restorations examined were considered acceptable for anatomic form, remaining stable and unchanged over the 2-year observation period.13,26,27 The composite surface roughness can be influenced by different factors related to the material itself, such as the filler (type, shape, size, and distribution of the particles), the type of resinous matrix, the ultimate degree of cure reached, and the bond efficacy at the filler/matrix interface.20,30 A direct correlation was found between the hardness and surface roughness, indicating that a composite with a higher hardness value is usually associated with a higher surface roughness.20,24 In the current study, no statistically significant difference between the materials was found for surface roughness at any recall examination. At baseline, however, a 15% difference in surface roughness between the materials was found, indicating better performance of the methacrylate-based composite resin. A previous study15 found a higher Knoop hardness for silorane-based than Vol 16, No 6, 2014
for dimethacrylate-based composites, due to the former’s organic matrix being mainly composed of silorane resin and inorganic particles, such as quartz and yttrium fluoride (76% by weight), which could explain the baseline findings for surface roughness in the test group here. Furthermore, the percentages of Bravo ratings found for both materials could be explained by the fact that an Alfa rating is given to a surface as smooth as the surrounding enamel; perhaps the evaluators were very critical in their evaluation, since it is known that no dental material can replace all the qualities of enamel, and this especially applies to its smooth, polished surface.40 Moreover, as occurred with the anatomic form parameter, the baseline findings for surface roughness did not remain after two years, again reflecting the difficulty in assessing certain clinical criteria, highlighting the risk of recording differences in clinical judgment between evaluators rather than between experimental and control groups. At the 2-year recall, a statistically significant difference vs baseline was observed for marginal discoloration when the restorations were repaired by the silorane-based composite. In the present study, we did not use a silane agent before the silorane adhesive system, as their combined effect on repair bond strength has not been completely elucidated. Although Ivanovas et al19 have considered silane application as a decisive factor for adhesion of methacrylate-based adhesives on silorane surfaces, another study showed that silane application is not mandatory when silorane composite and silorane adhesive system are used for repair.42 However, since the silane agent did not adversely affect the bond strength of the silorane adhesive system, the routine application of silane for repair of composite fillings with unknown composite matrix could be recommended.42 Thus, it is appropriate to emphasize that early marginal staining is usually a clinical sign that a restoration will be prone to failure or the adhesive interface will undergo degradation with time.40 The main reasons for marginal discoloration include the presence of excess filling materials, a deficient restoration around the margin, and the formation of gaps.38 Marginal discoloration has also been associated with poor etching ability of self-etching adhesives at the enamel margins.7,9,31 Consequently, stable adhesion to enamel with self-etching adhesives is still a challenge.1 This may explain our findings, since the silorane-based composite resin requires using a selfetching adhesive, as does the adhesive system used on the control group. Both materials presented Charlie ratings for marginal discolorations, and there was no statistically significant difference between them. Another factor that may have influenced our findings is the use of burs to roughen the composite surface. Although a previous study showed that micromechanical retention by bur abrasion is less effective than sandblasting or silica coating,34 it was assumed that the type of mechanical treatment is of minor relevance for silorane repair.42 Clinical trials with resin-based composites restorations have observed initial postoperative sensitivity, which generally decreases during the first weeks after placement of restorations.2,36 At baseline examination, the low in581
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cidence of restorations that received a Bravo rating can be explained by the use of a self-etching bonding system in both treatment groups. These systems incorporate the smear layer into the hybrid layer, providing better penetration of the monomers to the collagen fibers of the demineralized dentin. At the 2-year follow-up, the same good performance was observed for all composites, possibly because resin-based agents may provide pulp protection as long as the dentin is sealed by hydrophilic resins.2,36 Thus, since the frequency of ratings that remained constant from baseline to the 2-year recall was much higher than the frequency of ratings that worsened, the null hypothesis tested in this study was confirmed: the clinical performance of low-shrinkage silorane-based composites was similar to that of the dimethacrylate-based composites when repairing dimethacrylate-based composite restorations after a two-year observation period. Although one- and two-year evaluations have been considered to provide timely information on the performance of restorations, particularly for newly introduced materials such as that used in the present study, longer observation periods are necessary to confirm these findings.
6. 7.
8.
9.
10.
11.
12.
13.
14.
15.
CONCLUSIONS This clinical trial showed that, after two years, siloranebased composites are clinically acceptable to repair failed conventional dimethacrylate-based composites restorations, but they did not demonstrate any advantage over dimethacrylate-based composites. Repairs with resin chemically different than the original restoration were successful as long as the bonding agent chemically resembled the repair resin. After two years, the reduced polymerization shrinkage attributed to silorane-based composites did not establish better clinical performance, indicating that laboratory findings should be substantiated by clinical investigations. Clinical studies with longer recall periods are necessary.
16.
17.
18. 19. 20. 21. 22.
ACKNOWLEDGMENTS
23.
Our thanks go to FAPEMIG, which supported the present study.
24.
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40. Vangelov L, Markova K, Miteva T. Application of Filtek silorane – initial observations and prospective clinical trial for 12 months. J Int Med Assoc Bulgaria (IMAB) 2010;16:58-62. 41. Weinmann W, Thalacker C, Guggenberger R. Siloranes in dental composites. Dent Mater 2005;21:68-74. 42. Wiegand A, Stawarczyk B, Buchalla W, Tauböck TT, Özcan M, Attin T. Repair of silorane composite using the same substrate or a methacrylate-based composite? Dent Mater 2012;28:19-25. 43. Zakir M, Kheraif AA, Asif M, Rehman IU. A comparison of the mechanical properties of a modified silorane based dental composite with those of commercially available composite material. Dent Mater 2013;29: 53-59.
Clinical relevance: This two-year clinical trial showed that using a silorane-based composite for repairing composite resin restorations may be a viable clinical procedure, since restorations repaired by this novel composite exhibited similar clinical performance to that of conventional composites.
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