A Three-year Prospective Randomized Study of Silorane- and Methacrylate-based Composite Restorative Systems in Class II Restorations Salah Hasab Mahmouda / Abeer Khairy Alib / Hanan Abd-El Razak Hegazic Purpose: To evaluate and compare the 3-year clinical performance of a silorane-based composite with that of a methacrylate-based composite in Class II restorations. Materials and Methods: Seventy-eight patients, each with two class II restorations under occlusion, were enrolled in this study. One hundred fifty-six restorations were placed, 50% for each material: a silorane-based composite, Filtek P90/ P90 System Adhesive and a methacrylate-based resin composite, Quixfil/ Prime &Bond NT. A single operator placed all restorations according to the manufacturers’ instructions. Immediately after placement, the restorations were finished/polished. Clinical evaluation was performed at baseline and at yearly intervals after placement by two other independent examiners using slightly modified USPHS criteria. The changes in the USPHS parameters during the three-year period were analyzed with the Friedman test. The baseline scores were compared with those at the recall visits using the Wilcoxon signed rank test. The level of significance was set at p < 0.05. Results: All restorations were evaluated at 3 years. Post-operative sensitivity was observed in 6 patients (2 Filtek P90, 4 Quixfil) between 1 and 3 weeks. Seven failed restorations (4.5%) were observed during the follow up: 4 in the Filtek P90 (5.1%) and 3 in the Quixfil group (3.8%). This resulted in non-significantly different annual failure rates of 1.7% and 1.2%, respectively. Fracture of restoration was the main reason for failure. Conclusion: After 3 years, no significant difference was seen in overall clinical effectiveness between the silorane-based and methacrylate-based composite restorative systems. Keywords: silorane composite, methacrylate composite, posterior restorations, clinical performance. J Adhes Dent 2014; 16: 285–292. doi: 10.3290/j.jad.a31939
D
ue to their esthetic properties and good clinical service, resin composites (RC) have become the preferred material for direct posterior restorations.11,12,21,25,30,31,39 Apart from the development of a minimally invasive preparation technique as well as improved adhesion to tooth structures, these materials exhibit predictable long-term stability with annual failure rates that are comparable to
a
Professor and Chair, Department of Conservative Dentistry, Faculty of Dentistry, Mansoura University, Mansoura, Egypt. Idea, hypothesis, experimental design, wrote manuscript.
b
Assistant Professor, Department of Conservative Dentistry, Faculty of Dentistry, Mansoura University, Mansoura, Egypt. Performed the clinical procedures.
c
Professor, Department of Conservative Dentistry, Faculty of Dentistry, Mansoura University, Mansoura, Egypt. Co-wrote manuscript, contributed substantially to discussion.
Correspondence: Professor Salah Hasab Mahmoud, Department of Conservative Dentistry, Faculty of Dentistry, Mansoura University, El Gomhoreya St, PO Box 35516, Mansoura, Egypt. Tel: +20-050-228-512, Fax: +20-050-226-0173. e-mail: [email protected]
Vol 16, No 3, 2014
Submitted for publication: 08.06.13; accepted for publication: 28.02.14
amalgam in stress-bearing class I and class II cavities.25 Due to polymerization shrinkage of composite materials which leads to shrinkage stress at the adhesive interface, possible consequences such as cusp deflection and loss of marginal integrity occur, resulting in fractures at the interface, marginal staining, microleakage, and gap formation.7,16 Advances in material formulation may improve the shortcomings of RC, and recent reviews8,10 have summarized significant developments, including improved filler morphology, progress with existing dimethacrylate chemistry, and novel monomer technologies. Current changes are more focused on the polymeric matrix of the material, principally to develop systems with reduced polymerization shrinkage in order to overcome these drawbacks. Silorane composite consisting of a new organic matrix (ie, monomers with a ring-opening oxirane) was marketed in 2007.42 The goal of developing silorane was to create a material with reduced polymerization shrinkage and less polymerization stress.14,42 So far, reduction of polymerization shrinkage could only be achieved if, for example, high molecular monomers or larger amounts of filler par285
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ticles were added to the organic matrix. Siloranes reveal shrinkage of approximately 1 vol%.42 Silorane has been found to have no mutagenic effects when analyzed for the formation of chromosomal aberrations and the induction of gene mutations in mammalian cells.37 Papadogiannis et al32 evaluated the setting characteristics of low-shrinkage resin composites and examined the possible interactions with curing efficiency and marginal adaptation in dentin cavities. The results indicated that silorane material performed better than the dimethacrylate materials in terms of setting shrinkage and marginal adaptation. A recent laboratory study24 tested the marginal adaptation of ormocer-, silorane-, and methacrylate-based composite restorative systems bonded to dentin cavities after water storage. That study found silorane-based restorative systems to possess the best marginal adaptation at all aging times. According to Burke et al,6 “the setting shrinkage characteristics of resin composites affects their marginal adaptation with dentin and [the] shrinkage strain rate and time at maximum strain rate were found to be more important than total volumetric shrinkage in predicting the adaptation in dentin cavities”. The results of in vitro cusp deflection and microleakage of maxillary premolars restored with novel low-shrinkage dental composites indicated reduced cusp deflection when compared with two conventional materials.29 These results concur with those obtained by Bouillaguet et al,5 who showed that cusp movement during polymerization of silorane induced the lowest tooth deformation when tested against four conventional resin composite materials. Microleakage was also found to be reduced when a low-shrinkage silorane resin prototype (Hermes, 3M ESPE) was used.43 The physical properties of silorane have also been tested by Ilie and Hickel,23 whose results indicated that these were comparable to other clinically successful methacrylate-based composite materials. Those authors also noted that there was no difference in degree of cure at depths of 2 mm and 6 mm. Ernst et al14 found the shrinkage stress of silorane to be less than that of ten conventional RC materials. Claro-Pereira et al9 compared initial in situ dental plaque formation on a silorane-based RC (Filtek Silorane) and a methacrylate-based RC (Synergy D6). The results found no significant differences with respect to bacterial adhesion between Filtek Silorane and Synergy D6, despite the differences found for surface free energy and hydrophobicity. Silorane-based materials have not yet been investigated widely in vivo3,36 due to their relatively recent appearance on the dental market. Ferracane15 reported that conducting clinical trials to evaluate the performance of new dental composite formulations is expensive and time consuming, and it would be ideal to be able to predict clinical outcomes based on a single or multiple laboratory tests. However, although certain correlations exist, the overall clinical success of dental composites is multifactorial and therefore unlikely to be predicted accurately even by a battery of in vitro test methods. Accordingly, the aim of this study was to evaluate the 3-year clinical performance of a silorane-based RC restorative system 286
(Filtek P90 / P90 system adhesive) in class II cavities and to compare it to an established methacrylate-based RC restorative system (Quixfil / Prime & Bond NT) in a split-mouth design. The reference RC (Quixfil) is widely used and has been evaluated in several earlier trials, which enables a noninferiority/equivalence design of the trial.1,26 The null hypothesis tested was that the siloranebased RC showed different durability compared to the methacrylate-based RC. The alternative hypothesis was that they were equally effective.
MATERIALS AND METHODS Restorative Materials Two light-activated RC restorative materials with their respective bonding systems were used in the current study. These materials were a silorane-based composite (Filtek P90/Filtek P90 System Adhesive, 3M ESPE; St Paul, MN, USA), and a methacrylate-based composite (Quixfil/Prime & Bond NT, Dentsply DeTrey; York, PA, USA). A full description of these restorative systems is listed in Table 1. They were used in accordance with the manufacturers’ instructions. A well-controlled LED lightcuring unit (Elipar S10, 3M ESPE; Seefeld, Germany) was used for light polymerization with a light intensity of 1200 mW/cm2 as measured by the built-in light meter. Experimental Design Adult patients attending the Dental Clinic at the Faculty of Dentistry, Mansoura University who needed two similar class II restorations were asked to participate in the follow-up. Female patients who were pregnant or nursing were excluded. All patients were informed of the background of the study, which was approved by the Ethics Committee of the University of Mansoura. The enrolled patients were required to have complete and normal occlusion as well as good oral hygiene. Reasons for placement of the RC restorations were primary carious lesions. Seventy-eight patients participated, 32 men and 46 women, with a mean age of 39.7 years (range 27–58). One hundred fifty-six restorations were placed in 52 premolars and 104 molars. Each patient received one pair of Class II restorations, a silorane and a conventional hybrid RC restoration, in order to make intraindividual comparison possible. The cavities within the pair were chosen to match each other concerning size and localization. The two RCs tested were placed in the two cavities of each pair (78 pairs) at random, as determined by flipping a coin. The distribution and size of the restorations are given in Table 2. Clinical Procedures One operator, well trained in adhesive restorations, prepared, restored, and finished 78 class II Filtek P90 composite restorations in combination with the self-etching adhesive Filtek P90 System Adhesive, and 78 class II Quixfil composite restorations bonded with the etchand-rinse adhesive Prime & Bond NT. Before restorative procedures, periapical radiographs of the teeth to be The Journal of Adhesive Dentistry
Table 1
Materials used in the study
Restorative system
Type
Composition
Batch no.
Manufacture
Filtek P 90
Silorane-based composite
Matrix: 3,4-epoxycyclohexylethylcyclopoly-methylsiloxane, bis-3,4-epoxycyclohexylethyl-phenylmethylsilane Filler: silanized quartz, yttrium fluoride, 76 wt%
183458
3M/ESPE, St Paul; MN, USA
Filtek P 90 System Adhesive
Siloranebased, twostep self-etch adhesive
Primer: phosphorylated methacrylates, Vitrebond copolymer, bis-GMA, HEMA, water, ethanol, silane-treated silica filler, initiators, stabilizers Bond: hydrophobic dimethacrylate, phosphorylated methacrylates, TEG-DMA, silane-treated silica filler, initiators, stabilizers
9BH
3M/ESPE; Seefeld, Germany
Quixfil
Methacrylatebased composite
Matrix: bis-EMA, UDMA, TEG-DMA, TMPTMA, small amount of butane-1,2,3,4-tetracarboxylic acid, bis-2-hydroxyethyl methacrylate, camphor quinone (photoinitiator), dimethylaminobenzoic acid ethyl ester (accelerator) Filler: Silanated strontium aluminum sodium fluoride phosphate silicate glass, 86 wt%
0910001530
Dentsply DeTrey; York, PA, USA
Prime & Bond NT
Methacrylatebased, 2-step etch-and-rinse adhesive
Etchant: 36% phosphoric acid Adhesive: di- and trimethacrylate resins, functionalized amorphous silica, PENTA, stabilizers, cetylamine hydrofluoride, acetone
0806002408
Dentsply DeTrey
Bis-GMA: bisphenol glycidyl methacrylate; HEMA: hydroxyethyl methacrylate; TEG-DMA: triethylene glycol dimethacrylate; bis-EMA: ethoxylated bisphenol-Adimethacrylate; UDMA: urethane dimethacrylate; TMPTMA: trimethylolpropane trimethacrylate.
restored were taken. Vitality scores of the teeth were recorded with a vitality tester (Parkell Pulp Vitality Tester, Parkell Electronics; Farmingdale, NY, USA). For cavity preparation, local anesthesia was applied to prevent patient discomfort during the restorative procedures. The cavities were prepared using round diamond and fissure burs (Komet, Brasseler; Lemgo, Germany) at high speed with water cooling. Hand instruments and slow-speed tungsten carbide burs were used to remove the caries. Control of the excavated preparation floor was mainly conducted by probing with a sharp explorer and by visual inspection of the color of the underlying dentin. The adhesive preparation design was employed according to the principles of minimally invasive dentistry. The common characteristics of this preparation design were the following: 1) none of the cavity preparations involved one or more cusps; 2) all of the gingival margins included sound enamel and were placed above the gingival sulcus; and 3) preparation walls and margins were not bevelled. The buccolingual width of the preparations did not exceed one-third of the intercuspal distance. After cavity preparation and shade selection, the operative field was moisture isolated with cotton rolls and suctioning. Calcium hydroxide-based material (Dycal, Dentsply/Caulk; Milford, DE, USA) was only used in deep preparations and was applied directly over the deepest site and then sealed with a glass-ionomer cement lining (Vivaglass Liner, Ivoclar Vivadent; Schaan, Liechtenstein). For all class II cavities, a thin metallic matrix was used and carefully wedged with wooden wedges (KerrHawe Neos; Bioggio, Switzerland). The cavities were cleaned by a thorough rinsing with water. In order to make intraindividual comparison possible, all patients received two Vol 16, No 3, 2014
Table 2
Distribution of the experimental restorations
Surfaces
Mandible
Maxilla
Premolar
Molar
Premolar
Molar
2
22
45
15
28
3
10
21
5
10
Total
32
66
20
38
restorations. Cavities were randomly distributed to be restored with either the experimental RC Filtek P90 or the control RC Quixfil. For silorane-based composite (Filtek P90) restorations, the Filtek P90 System Adhesive (two-step self-etching adhesive) was applied in two steps. In the first step, System Adhesive self-etching primer was applied to the cavity for 15 s with the black applicator, followed by gentle air dispersion and 10 s of light curing. In the second step, System Adhesive Bond was then applied with the green applicator, followed by gentle air dispersion and 10 s light curing. Where the methacrylate-based composite (Quixfil) was used, Prime & Bond NT (two-step etch-and-rinse adhesive) was applied. The preparation was etched with 36% phosphoric acid gel (Conditioner; Dentsply DeTrey). The acid gel was first placed on enamel, and then the dentin was conditioned during the last 15 s of the 30 s etching time. The cavity was then thoroughly rinsed with water for 10 s and dried with air, keeping the dentin surface moist. Prime 287
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Table 3
Criteria for direct clinical evaluation (modified Ryge criteria; van Dijken et al40)
Category
Score Acceptable
Anatomical form
Criteria
Unacceptable
0 1 2 3
Marginal adaptation
3 4
• Restoration is contiguous with existing anatomic form, explorer does not catch • Explorer catches, no crevice is visible into which explorer will penetrate • Crevice at margin, enamel exposed • Obvious crevice at margin, dentin or base exposed • Restoration mobile, fractured or missing
3 4
• • • • •
Very good color match Good color match; crevice at margin, enamel exposed Slight mismatch in color, shade or translucency Obvious mismatch, outside the normal range Gross mismatch
3
• • • •
No discoloration evident Slight staining, can be polished away Obvious staining cannot be polished away Gross staining
3
• • • •
Smooth surface Slightly rough or pitted Rough, cannot be refinished Surface deeply pitted, irregular grooves
0 1 2
Color match
Marginal discoloration
Surface roughness
Secondary caries
0 1 2
0 1 2 0 1 2 0 1
• The restoration is contiguous with tooth anatomy • Slightly under- or overcontoured restoration; marginal ridges slightly undercontoured; contact slightly open (may be self-correcting); occlusal height reduced locally • Restoration is undercontoured, dentin or base exposed; contact is faulty, not self-correcting; occlusal height reduced; occlusion affected • Restoration is missing partially or totally; fracture of tooth structure; shows traumatic occlusion; restoration causes pain in tooth or adjacent tissue
• No evidence of caries contiguous with the margin of the restoration • Caries is evident contiguous with the margin of the restoration
& Bond NT adhesive was applied generously to thoroughly wet the entire cavity. After 20 s, excess solvent was removed with 5 s of gentle air drying, and then light curing was performed for 10 s. The RC was then applied in layers of 2 to 3 mm maximum, if possible with an oblique layering technique using selected composite instruments (Optra Contact & Optra Sculpt, Ivoclar Vivadent). Every increment was light cured for at least 10 s. Following removal of the matrix band, the proximal regions of the restorations were additionally polymerized buccally and lingually/palatally for 10 s. Contouring and finishing of the restorations was performed at the same appointment using a watercooled, fine-grit diamond finishing instrument (Komet). Articulating paper (Bausch; Nashua, NH, USA) was used to establish appropriate occlusal morphology and contact. Flexible points impregnated with silicone dioxide were used to obtain smooth surfaces (Astropol; Ivoclar Vivadent). For finishing and polishing of the proximal surfaces, finishing strips (GC; Tokyo, Japan) were used. The quality of the interproximal contacts was checked with dental floss.
288
Evaluation Procedures Each restoration was evaluated according to slightly modified USPHS criteria for the following characteristics: anatomical form, marginal adaptation, color match, marginal discoloration, surface roughness, and secondary caries (Table 3).40 The restorations were evaluated at baseline, and then blindly every year for 3 years by two independent examiners. The Cohen Kappa index was used as a measure of interexaminer agreement. Examiners were not involved in the restorative procedures. Disagreement occurred only once during evaluations; this restoration was reevaluated by both examiners and a consensus was obtained. To detect secondary caries, the presence of softness, opacity, etching, or white spots is considered evidence of undermining or demineralization in areas where the explorer catches or resists removal after insertion. Furthermore, bitewing radiographs (Kodak; Rochester, NY, USA) were taken at each follow-up appointment. A magnifying aid was used for examination of marginal adaptation. Retention loss, severe marginal defects, discoloration that needed repair or replacement, and the occurrence of caries along the restoration margins were considered clinical failures. The Journal of Adhesive Dentistry
Table 4
Nonacceptable class II restorations and reasons for failure during the 3-year follow-up 1 year
2 years
3 years
F P90
Quixfil
F P90
Quixfil
F P90
Quixfil
Fracture
1
0
1
1
1
1
Fracture and caries
0
0
0
0
0
0
Caries
0
0
0
0
0
0
Cusp fracture
0
0
0
1
0
0
Endodontic reasons
0
0
0
0
1
0
Cumulative absolute failure frequencies
1
0
2
2
4
3
1.2
0
2.4
2.7
5.1
3.8
Cumulative relative failure frequencies (%)
Statistical Analysis Statistical analysis was performed using the statistical package for the Social Sciences, version 19 (SPSS; Chicago, IL, USA). Since the assessment of the restorations yielded clearly ordinally structural data, only nonparametric procedures were used. The changes in the parameters during the 3-year period were analyzed using the Friedman test, which is a nonparametric ANOVA. The baseline scores were compared with those at the recall visits using the Wilcoxon signed rank test. The level of significance was set at p < 0.05.
RESULTS All patients attended the 3-year recall visit. Cohen Kappa statistics (Kappa = 0.90) showed strong examiner agreement, and no statistical difference was observed in their answers (p > 0.05). Postoperative sensitivity was reported for 6 teeth in 6 participants between 1 and 3 weeks after baseline. Two Filtek P90 restorations showed postoperative sensitivity during biting forces, as did four Quixfil restorations during biting forces or cold stimuli. Postoperative sensitivity disappeared by the 1-year evaluation. Seven failed restorations (4.5%) were observed during the follow-up, four Filtek P90 (5.1%; 1 premolar and 3 molars) and three Quixfil (3.8%; 3 molars). This resulted in annual failure rates of 1.7% for Filtek P90 group and 1.2% for the Quixfil group. Reasons and year of failure for the nonacceptable restorations are shown in Table 4. The main reason for failure was RC fracture. Small chip fractures were observed in 3 restorations, which were treated by polishing. Relative frequencies of the scores (%) for the evaluated variables are given in Table 5. A significant decrease in color match was observed between baseline and 3 years. The color changes observed were within the acceptable score range and no significant differences were seen between the two groups. Slight marginal discoloration was observed in 21% of silorane and in 20% of Quixfil restorations. The surface characteristics of the Filtek P90 and Quixfil Vol 16, No 3, 2014
resin composites showed no clinical change from smooth characteristics at baseline to the end of the follow-up. In the overall intra-individual comparisons between the Filtek Silorane and Quixfil composite restoratives, no significant differences were observed at the recalls (p > 0.05).
DISCUSSION This study evaluated the 3-year clinical effectiveness of a silorane-based composite (Filtek P90), launched on the dental market as a low-shrinkage material, compared to a well-established methacrylate-based RC (Quixfil). Laboratory investigations served as a screening model before human clinical trials were initiated. Comprehensive laboratory studies19,14,23,32 of silorane RC were carried out, finding that silorane RC exhibited properties at least as good as methacrylate RC. In this regard, the results of the present study may be considered to indicate good performance of the silorane composite under evaluation. The tested silorane-based RC showed good clinical efficacy, confirming results observed in earlier 1- and 2-year trials.3,6,36 In the present study, the annual failure rates of 1.7% for the Filtek P90/P90 System Adhesive group and 1.2% for the Quixfil/Prime & Bond NT group were not significantly different. The null hypothesis was therefore rejected, the alternative hypothesis was accepted. No significant differences in any of the clinical criteria listed in Table 5 were found between the two RC restorative systems tested. For both of the tested RC, there was a significant decrease in color match observed between baseline and 3 years. The color changes observed were within the acceptable scoring range. Both tested materials exhibited a significant color change during follow-up, which may be related to surface roughness, surface integrity, and polishing technique.17,35 However, it must be mentioned that the changes were within scores of 0 to 2, meaning that they were still clinically acceptable. To ensure excellent esthetics, it is necessary for tooth-colored restorative materials to maintain their intrinsic color and be resistant to surface staining. A number of both intrinsic and extrinsic 289
Mahmoud et al
Table 5 Scores for the evaluated class II restorations of Filtek P90 and Quixfil given as relative frequencies for baseline and the yearly recalls (%) Evaluation criteria
Score
Baseline
1 year
2 years
3 years
FP 90
Quixfil
FP 90
Quixfil
FP 90
Quixfil
FP 90
Quixfil
Anatomical form
0 1 2 3
91.3 8.7 0 0
89.0 11.0 0 0
94.5 3.3 2.2 0
4.4 5.6 0 0
87.3 9.2 2.3 1.2
93.9 3.1 1.5 1.5
89.6 5.7 1.2 3.5
92.9 2.9 1.4 2.9
Marginal adaptation
0 1 2 3 4
97.9 2.1 0 0 0
97.3 2.7 0 0 0
87.5 11.4 1.1 0 0
9.1 0.0 0 0 0
86.9 9.6 0 0 3.5
9.4 6.1 1.5 0 3
80.5 16.1 0 0 3.4
84.3 11.4 1.4 0 2.9
Color match
0 1 2 3 4
47.8 51.1 1.1 0 0
48.3 0.3 1.4 0 0
29.7 62.6 7.7 0 0
8.0 9.2 2.8 0 0
19.4 74.6 6.0 0 0
0.6 75.2 4.2 0 0
21.8 70.1 8.1 0 0
1.4 0.0 8.6 0 0
Marginal discoloration
0 1 2 3
100 0 0 0
100 0 0 0
94.5 4.4 1.1 0
97.2 2.8 0 0
90.8 8.0 1.2 0
93.9 6.1 0 0
79.3 16.1 4.6 0
82.9 15.7 1.4 0
Surface roughness
0 1 2 3
100 0 0 0
100 0 0 0
100 0 0 0
100 0 0 0
100 0 0 0
97.0 3.0 0 0
100 0 0 0
97.1 2.9 0 0
Secondary caries
0 1
100 0
100 0
100 0
100 0
100 0
100 0
100 0
100 0
factors affect the degree of color change, such as degree of polymerization, water sorption, diet, oral hygiene, and surface smoothness of restorations. Barutcigi and Yıldız4 evaluated the intrinsic and extrinsic color change of dimethacrylate and silorane-based composites. They reported that the tested restorative materials were susceptible to staining by commonly consumed beverages. In vitro, the surface roughness in terms of Ra and bacterial adhesion of silorane-based composite was similar to that of the methacrylate-based composite.36 Regarding the cavosurface marginal discoloration criterion, the majority of scores were 0. Scores of 1 were only recorded at the 1-year examination in 4.4% Filtek P90 and 2.8% Quixfil restorations and increased during the 3-year period, but they remained under 20% in both groups. After 3 years of clinical use, insignificant differences were found in the marginal adaptation of both composites over the course of time (baseline, 1 year, 2 years and 3 years). Except for seven failed restorations (4 Filtek P90, 3 Quixfil), all the other restorations received scores of 0 (80.5% to 84.3%) or 1 (16% to 11.4%) for marginal adaptation. Hickel et al21 found that this phenomenon usually appeared in the medium term following placement of the restorations. One clinical trial that examined a methacrylate-based composite resin and a silorane in class II cavities revealed that the marginal adaptation of 290
the silorane was inferior to that of a methacrylate-based material, both occlusally and approximally.36 Alteration in marginal adaptation and marginal discoloration over the course of time could also stem from degradation of the resin/bond interface as a result of slow hydrolysis. Most of the monomers in adhesive materials can absorb water and chemicals from the environment, and this absorbed water weakens the resin/dentin bond over time. Thus, both water sorption and solubility could lead to a variety of chemical and physical processes that may result in deleterious effects on marginal adaptation, discoloration, and color match of adhesive restorations over time.2,18,24 Alteration in marginal quality could also be attributed to fracture of a slight overlapping marginal excess.38 Shrinkage stress, the effects of cavity geometry on C-factor, butt-joint occlusal margin and self-etching adhesives may also be involved.28 Filtek silorane composite demonstrated clinically smooth surface characteristics during the whole followup, indicating a good wear pattern similar to that of Quixfil methacrylate composite. No case of inacceptable clinical wear was observed. Our results are supported by laboratory investigations which reported that mechanical properties of silorane-based composite are comparable to those of both dimethacrylate-based materials and methacrylate composites.13,22,23 The Journal of Adhesive Dentistry
Postoperative sensitivity after placing posterior RC restorations has been a problem experienced in general practice for many years.19 It has been attributed to several factors, such as effects of shrinkage stress on the marginal integrity, etching of dentin, cusp deformation, and interfacial bacterial penetration. A low frequency of postoperative sensitivity was reported in the present study, which is in accordance with other clinical evaluations.4,6,36 In the current study, postoperative sensitivity was reported for 2 silorane composite restorations during biting forces and 4 methacrylate composite restorations during biting forces or cold stimuli. By the 1-year evaluation, postoperative sensitivity disappeared for both materials. Both silorane and methacrylate composites were used with their proprietary adhesive system according to the manufacturers’ recommendations. The silorane composite was bonded with a two-step self-etching adhesive, but the methacrylate composite was bonded with a two-step etchand-rinse adhesive. Although the bonding systems used were different in application strategy and bonding mechanism, no significant difference was reported between the test and the control restorative systems regarding postoperative sensitivity. Santini and Miletic34 found bonding to dentin using the silorane adhesive system to produce a hybrid layer of similar thickness to that of a methacrylate-based adhesive (Excite, Ivoclar Vivadent) and thicker than that of the onestep adhesives (G Bond, GC; AdheSE, Ivoclar Vivadent). This presence of an interaction zone has also been confirmed by the work of Mine et al,27 who also found that the two bottles in the silorane adhesive system, Primer and Bond, were distinguishable as two distinct layers. In this respect, it has been postulated that the high-viscosity second layer of adhesive might act as an elastic buffer.41 In addition, Van Ende et al41 examined the stress at the adhesive interface with different configuration factors. Their results indicated that cavity configuration affected the microtensile bond strength of the silorane adhesive system and noted that an incremental layering technique was still required for placement of silorane restorations. Indeed, Perdigao et al33 suggested that the clinical technique may be more relevant for the development of postoperative sensitivity than is the type of adhesive itself. The low level of postoperative sensitivity could be considered to be a substantial clinical advantage, especially if found to be associated with a high expectation of clinical success. In one clinical study, the marginal quality of the silorane composite was shown to be somewhat inferior to that of a nanohybrid composite.36 For Quixfil resin composite, the results of the current study were confirmed by the results of previous clinical trials,1,26 which reported that posterior restorations of Quixfil and other composites exhibited good clinical results, predominantly with scores of zero. Concerning Filtek silorane composite, there are few published clinical studies that can be used for comparison, bearing in mind that the design and follow-up periods of these studies differ from those of the current study. Despite the excellent performance reported by the manufacturer of the silorane-based composite, its clinVol 16, No 3, 2014
ical performance was not superior to that of the control group, which was restored with Quixfil, a methacrylatebased composite that has been on the dental market for a longer period. The results of the present work thus document favorable medium-term performance of silorane restorations when compared with Quixfil composite and previously published work on “conventional” resin composite restorations in posterior teeth.
CONCLUSION On the basis of the results of the current study, it seems reasonable to conclude that there is no proof that silorane composite (Filtek P90) performs better than normal hybrid methacrylate composite (Quixfil). Both restorative materials exhibited acceptable clinical performance in class II restorations over an evaluation period of 3 years and the null hypothesis was therefore not accepted. Longer term clinical evaluations are required to fully assess the performance of this novel material.
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Arhun N, Celik C, Yamanel K. Clinical evaluation of resin-based composites in posterior restorations: two-year results. Oper Dent 2010;35: 397-404. Armstrong SR, Vargas MA, Chung I, Pashley DH, Campbell JA, Laffoon JE, Qian F. Resin-dentin interfacial ultrastructure and microtensile dentin bond strength after five-year water storage. Oper Dent 2004;29: 705–712. Baracco B, Perdigão J, Cabrera E, Giráldez I, Ceballos L. Clinical evaluation of a low-shrinkage composite in posterior restorations: one-year results. Oper Dent 2012;37:117-129. Barutcigil C, Yıldız M. Intrinsic and extrinsic discoloration of dimethacrylate and silorane based composites. J Dent 2012;40:e57-e63. Bouillaguet S, Gamba J, Forchelet J, Krejci I, Wataha C. Dynamics of composite polymerization mediates the development of cuspal strain. Dent Mater 2006;22:896-902. Burke FJ, Crisp RJ, James A, Mackenzie L, Pal A, Sands P, Thompson O, Palin WM. Two year clinical evaluation of a low-shrink resin composite material in UK general dental practices. Dent Mater 2011;27:622-630. Calheiros FC, Sadek FT, Braga RR, Cardoso PE. Polymerization contraction stress of low-shrinkage composites and its correlation with microleakage in class V restorations. J Dent 2004;32:407-412. Chen MH. Update on dental nanocomposites. J Dent Res 2010;89: 549-560. Claro-Pereira D, Sampaio-Maia B, Ferreira C, Rodrigues A, Melo LF, Vasconcelos MR. In situ evaluation of a new silorane-based composite resin’s bioadhesion properties. Dent Mater 2011;27:1238-1245. Cramer NB, Stansbury JW, Bowman CN. Recent advances and developments in composite dental restorative materials. J Dent Res 2011; 90:402-416. Da Rosa Rodolpho PA, Donassollo TA, Cenci MS, Loguércio AD, Moraes RR, Bronkhorst EM, Opdam NJ, Demarco FF. 22-year clinical evaluation of the performance of two posterior composites with different filler characteristics. Dent Mater 2011;27:955-963. Demarco, FF, Corrêa MB, Cenci MS, Moraes RR, Opdam NJ. Longevity of posterior composite restorations: not only a matter of materials. Dent Mater 2012;28:87-101. Duarte Jr S, Botta AC, Phark JH, Sadan A. Selected mechanical and physical properties and clinical application of a new low-shrinkage composite restoration. Quintessence Int 2009;40:631–638. Ernst CP, Meyer GR, Klocker K, Willershausen B. Determination of polymerization shrinkage stress by means of a photoelastic investigation. Dent Mater 2004;20:313-321. Ferracane JL. Resin-based composite performance: are there some things we can’t predict? Dent Mater 2013;29:51-58.
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Mahmoud et al 16. Gonzalez-Lopez S, Vilchez Diaz MA, de Haro-Gasquet F, Ceballos L, de Haro-Munoz C. Cuspal flexure of teeth with composite restorations subjected to occlusal loading. J Adhes Dent 2007;9:11-15. 17. Guler AU, Kurt S, Kulunk T. Effects of various finishing procedures on the staining of provisional restorative materials. J Prosthet Dent 2005;93: 453-458. 18. Hashimoto M, Ohno H, Kaga M, Endo K, Sano H, Oguchi H. In vivo degradation of resin-dentin bonds in humans over 1 to 3 years. J Dent Res 2000;79:1385-1391. 19. Hayashi M, Wilson NHF. Failure risk of posterior composites with postoperative sensitivity. Oper Dent 2003;28:681-688. 20. Heintze SD, Rousson V. Clinical effectiveness of direct class II restorations – a meta-analysis. J Adhes Dent 2012;14:407-431. 21. Hickel R, Roulet JF, Bayne S, Heintze SD, Mjor 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 Dental 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(suppl 1):121–147. 22. Ilie N, Hickel R. Macro-, micro- and nano-mechanical investigations on silorane and methacrylate-based composites. Dent Mater 2009; 25:810-819. 23. Ilie N, Hickel R. Silorane-based dental composite: behavior and abilities. Dent Mater 2006;25:445-454. 24. Mahmoud SH, Al-Wakeel E. Marginal adaptation of ormocer-, silorane-, and methacrylate-based composite restorative systems bonded to dentin cavities after water storage. Quintessence Int 2011;42:e131-e139. 25. Manhart J, Chen HY, Hamm G, Hickel R. Buonocore Memorial Lecture. Review of the clinical survival of direct and indirect restorations in posterior teeth of the permanent dentition. Oper Dent 2004;29:481-508. 26. Manhart J, Chen HY, Hickel R. Clinical evaluation of the posterior composite Quixfil in class I and II cavities: 4-year follow-up of a randomized controlled trial. J Adhes Dent 2010;12:237-243. 27. Mine A, De Munck J, Van Landuyt P, Lambrechts P, Van Meerbeck B. TEM interface characterization of a low shrinking composite bonded to enamel/dentin [abstract 0252]. J Dent Res 2008;87(special issue C). 28. Palaniappan S, Bharadwaj D, Mattar DL, Peumans M, Van Meerbeek B, Lambrecht P. Three-year randomized clinical trial to evaluate the clinical performance and wear of a nanocomposite versus a hybrid composite. Dent Mater 2009;25:1302–1314. 29. Palin WM, Fleming GJ, Nathwani H, Burke FJ. In vitro cusp deflection and microleakage of maxillary premolars restored with novel low-shrink dental composites. Dent Mater 2005;21:324-335. 30. Pallesen U, van Dijken JW, Halken J, Hallonsten AL, Höigaard R. A prospective 8-year follow-up of posterior resin composite restorations in permanent teeth of children and adolescents in Public Dental Health Service: reasons for replacement. Clin Oral Investig 2014;18:819-827.
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31. Pallesen U, van Dijken JW, Halken J, Hallonsten AL, Höigaard R. Longevity of posterior resin composite restorations in permanent teeth in Public Dental Health Service: a prospective 8-year follow up. J Dent 2013;41:297-306. 32. Papadogiannis D, Kakaboura A, Palaghias G, Eliades G. Setting characteristics and cavity adaptation of low-shrinking resin composites. Dent Mater 2009;25:1509-1518. 33. Perdigao J, Geraldeli S, Hodges JS. Total-etch versus self-etch adhesive: effect on postoperative sensitivity. J Am Dent Assoc 2003;134: 1621-1629. 34. Santini A, Miletic V. Comparison of hybrid layer formed by silorane adhesive, one step self-etch and etch and rinse using confocal micro-Raman spectroscopy and SEM. J Dent 2008;36:683-692. 35. Sarac D, Sarac YS, Kulunk S, Ural C, Kulunk T. The effect of polishing techniques on the surface roughness and color change of composite resins. J Prosthet Dent 2006;96:33-40. 36. Schmidt M, Kirkevang LL, Hørsted-Bindslev P, Poulsen S. Marginal adaptation of a low-shrinkage silorane-based composite: 1-year randomized clinical trial. Clin Oral Investig 2011;15:291-295. 37. Schweikl G, Schmalz G, Weinmann W. Mutagenic activity of structurally related oxiranes and siloranes in salmonella typhimurium. Mut Res 2002;521:19-27. 38. Turkun LS, Aktener BO. Twenty-four-month clinical evaluation of different posterior composite resin materials. J Am Dent Assoc 2001;132: 196–203. 39. van de Sande FH, Opdam NJ, Da Rosa Rodolpho PA, Correa MB, Demarco FF, Cenci MS. Patient risk factors’ influence on survival of posterior composites. J Dent Res 2013;92:S78-83. 40. Van Dijken JW, Sunnegardh-Gronberg K, Sorensson E. Clinical bonding of a single-step self-etching adhesive in noncarious cervical lesions. J Adhes Dent 2007;9(suppl 2):241-243. 41. Van Ende A, De Munck J, Mine A, Lambrechts P, Van Meerbeck B. Does a low shrinking composite induce less stress at the adhesive interface? Dent Mater 2010;26:215-222. 42. Weinmann W, Thalacker C, Guggenberger R. Siloranes in dental composites. Dent Mater 2005;21:68-74. 43. Yamazaki PC, Bedran-Russo AK, Pereira PN, Swift EJ Jr. Microleakage evaluation of a new low-shrinkage composite restorative material. Oper Dent 2006;31:670-676.
Clinical relevance: Silorane-based composite exhibited clinical performance similar to conventional methacrylate-based composite in class II restorations.
The Journal of Adhesive Dentistry
D
ue to their esthetic properties and good clinical service, resin composites (RC) have become the preferred material for direct posterior restorations.11,12,21,25,30,31,39 Apart from the development of a minimally invasive preparation technique as well as improved adhesion to tooth structures, these materials exhibit predictable long-term stability with annual failure rates that are comparable to
a
Professor and Chair, Department of Conservative Dentistry, Faculty of Dentistry, Mansoura University, Mansoura, Egypt. Idea, hypothesis, experimental design, wrote manuscript.
b
Assistant Professor, Department of Conservative Dentistry, Faculty of Dentistry, Mansoura University, Mansoura, Egypt. Performed the clinical procedures.
c
Professor, Department of Conservative Dentistry, Faculty of Dentistry, Mansoura University, Mansoura, Egypt. Co-wrote manuscript, contributed substantially to discussion.
Correspondence: Professor Salah Hasab Mahmoud, Department of Conservative Dentistry, Faculty of Dentistry, Mansoura University, El Gomhoreya St, PO Box 35516, Mansoura, Egypt. Tel: +20-050-228-512, Fax: +20-050-226-0173. e-mail: [email protected]
Vol 16, No 3, 2014
Submitted for publication: 08.06.13; accepted for publication: 28.02.14
amalgam in stress-bearing class I and class II cavities.25 Due to polymerization shrinkage of composite materials which leads to shrinkage stress at the adhesive interface, possible consequences such as cusp deflection and loss of marginal integrity occur, resulting in fractures at the interface, marginal staining, microleakage, and gap formation.7,16 Advances in material formulation may improve the shortcomings of RC, and recent reviews8,10 have summarized significant developments, including improved filler morphology, progress with existing dimethacrylate chemistry, and novel monomer technologies. Current changes are more focused on the polymeric matrix of the material, principally to develop systems with reduced polymerization shrinkage in order to overcome these drawbacks. Silorane composite consisting of a new organic matrix (ie, monomers with a ring-opening oxirane) was marketed in 2007.42 The goal of developing silorane was to create a material with reduced polymerization shrinkage and less polymerization stress.14,42 So far, reduction of polymerization shrinkage could only be achieved if, for example, high molecular monomers or larger amounts of filler par285
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ticles were added to the organic matrix. Siloranes reveal shrinkage of approximately 1 vol%.42 Silorane has been found to have no mutagenic effects when analyzed for the formation of chromosomal aberrations and the induction of gene mutations in mammalian cells.37 Papadogiannis et al32 evaluated the setting characteristics of low-shrinkage resin composites and examined the possible interactions with curing efficiency and marginal adaptation in dentin cavities. The results indicated that silorane material performed better than the dimethacrylate materials in terms of setting shrinkage and marginal adaptation. A recent laboratory study24 tested the marginal adaptation of ormocer-, silorane-, and methacrylate-based composite restorative systems bonded to dentin cavities after water storage. That study found silorane-based restorative systems to possess the best marginal adaptation at all aging times. According to Burke et al,6 “the setting shrinkage characteristics of resin composites affects their marginal adaptation with dentin and [the] shrinkage strain rate and time at maximum strain rate were found to be more important than total volumetric shrinkage in predicting the adaptation in dentin cavities”. The results of in vitro cusp deflection and microleakage of maxillary premolars restored with novel low-shrinkage dental composites indicated reduced cusp deflection when compared with two conventional materials.29 These results concur with those obtained by Bouillaguet et al,5 who showed that cusp movement during polymerization of silorane induced the lowest tooth deformation when tested against four conventional resin composite materials. Microleakage was also found to be reduced when a low-shrinkage silorane resin prototype (Hermes, 3M ESPE) was used.43 The physical properties of silorane have also been tested by Ilie and Hickel,23 whose results indicated that these were comparable to other clinically successful methacrylate-based composite materials. Those authors also noted that there was no difference in degree of cure at depths of 2 mm and 6 mm. Ernst et al14 found the shrinkage stress of silorane to be less than that of ten conventional RC materials. Claro-Pereira et al9 compared initial in situ dental plaque formation on a silorane-based RC (Filtek Silorane) and a methacrylate-based RC (Synergy D6). The results found no significant differences with respect to bacterial adhesion between Filtek Silorane and Synergy D6, despite the differences found for surface free energy and hydrophobicity. Silorane-based materials have not yet been investigated widely in vivo3,36 due to their relatively recent appearance on the dental market. Ferracane15 reported that conducting clinical trials to evaluate the performance of new dental composite formulations is expensive and time consuming, and it would be ideal to be able to predict clinical outcomes based on a single or multiple laboratory tests. However, although certain correlations exist, the overall clinical success of dental composites is multifactorial and therefore unlikely to be predicted accurately even by a battery of in vitro test methods. Accordingly, the aim of this study was to evaluate the 3-year clinical performance of a silorane-based RC restorative system 286
(Filtek P90 / P90 system adhesive) in class II cavities and to compare it to an established methacrylate-based RC restorative system (Quixfil / Prime & Bond NT) in a split-mouth design. The reference RC (Quixfil) is widely used and has been evaluated in several earlier trials, which enables a noninferiority/equivalence design of the trial.1,26 The null hypothesis tested was that the siloranebased RC showed different durability compared to the methacrylate-based RC. The alternative hypothesis was that they were equally effective.
MATERIALS AND METHODS Restorative Materials Two light-activated RC restorative materials with their respective bonding systems were used in the current study. These materials were a silorane-based composite (Filtek P90/Filtek P90 System Adhesive, 3M ESPE; St Paul, MN, USA), and a methacrylate-based composite (Quixfil/Prime & Bond NT, Dentsply DeTrey; York, PA, USA). A full description of these restorative systems is listed in Table 1. They were used in accordance with the manufacturers’ instructions. A well-controlled LED lightcuring unit (Elipar S10, 3M ESPE; Seefeld, Germany) was used for light polymerization with a light intensity of 1200 mW/cm2 as measured by the built-in light meter. Experimental Design Adult patients attending the Dental Clinic at the Faculty of Dentistry, Mansoura University who needed two similar class II restorations were asked to participate in the follow-up. Female patients who were pregnant or nursing were excluded. All patients were informed of the background of the study, which was approved by the Ethics Committee of the University of Mansoura. The enrolled patients were required to have complete and normal occlusion as well as good oral hygiene. Reasons for placement of the RC restorations were primary carious lesions. Seventy-eight patients participated, 32 men and 46 women, with a mean age of 39.7 years (range 27–58). One hundred fifty-six restorations were placed in 52 premolars and 104 molars. Each patient received one pair of Class II restorations, a silorane and a conventional hybrid RC restoration, in order to make intraindividual comparison possible. The cavities within the pair were chosen to match each other concerning size and localization. The two RCs tested were placed in the two cavities of each pair (78 pairs) at random, as determined by flipping a coin. The distribution and size of the restorations are given in Table 2. Clinical Procedures One operator, well trained in adhesive restorations, prepared, restored, and finished 78 class II Filtek P90 composite restorations in combination with the self-etching adhesive Filtek P90 System Adhesive, and 78 class II Quixfil composite restorations bonded with the etchand-rinse adhesive Prime & Bond NT. Before restorative procedures, periapical radiographs of the teeth to be The Journal of Adhesive Dentistry
Table 1
Materials used in the study
Restorative system
Type
Composition
Batch no.
Manufacture
Filtek P 90
Silorane-based composite
Matrix: 3,4-epoxycyclohexylethylcyclopoly-methylsiloxane, bis-3,4-epoxycyclohexylethyl-phenylmethylsilane Filler: silanized quartz, yttrium fluoride, 76 wt%
183458
3M/ESPE, St Paul; MN, USA
Filtek P 90 System Adhesive
Siloranebased, twostep self-etch adhesive
Primer: phosphorylated methacrylates, Vitrebond copolymer, bis-GMA, HEMA, water, ethanol, silane-treated silica filler, initiators, stabilizers Bond: hydrophobic dimethacrylate, phosphorylated methacrylates, TEG-DMA, silane-treated silica filler, initiators, stabilizers
9BH
3M/ESPE; Seefeld, Germany
Quixfil
Methacrylatebased composite
Matrix: bis-EMA, UDMA, TEG-DMA, TMPTMA, small amount of butane-1,2,3,4-tetracarboxylic acid, bis-2-hydroxyethyl methacrylate, camphor quinone (photoinitiator), dimethylaminobenzoic acid ethyl ester (accelerator) Filler: Silanated strontium aluminum sodium fluoride phosphate silicate glass, 86 wt%
0910001530
Dentsply DeTrey; York, PA, USA
Prime & Bond NT
Methacrylatebased, 2-step etch-and-rinse adhesive
Etchant: 36% phosphoric acid Adhesive: di- and trimethacrylate resins, functionalized amorphous silica, PENTA, stabilizers, cetylamine hydrofluoride, acetone
0806002408
Dentsply DeTrey
Bis-GMA: bisphenol glycidyl methacrylate; HEMA: hydroxyethyl methacrylate; TEG-DMA: triethylene glycol dimethacrylate; bis-EMA: ethoxylated bisphenol-Adimethacrylate; UDMA: urethane dimethacrylate; TMPTMA: trimethylolpropane trimethacrylate.
restored were taken. Vitality scores of the teeth were recorded with a vitality tester (Parkell Pulp Vitality Tester, Parkell Electronics; Farmingdale, NY, USA). For cavity preparation, local anesthesia was applied to prevent patient discomfort during the restorative procedures. The cavities were prepared using round diamond and fissure burs (Komet, Brasseler; Lemgo, Germany) at high speed with water cooling. Hand instruments and slow-speed tungsten carbide burs were used to remove the caries. Control of the excavated preparation floor was mainly conducted by probing with a sharp explorer and by visual inspection of the color of the underlying dentin. The adhesive preparation design was employed according to the principles of minimally invasive dentistry. The common characteristics of this preparation design were the following: 1) none of the cavity preparations involved one or more cusps; 2) all of the gingival margins included sound enamel and were placed above the gingival sulcus; and 3) preparation walls and margins were not bevelled. The buccolingual width of the preparations did not exceed one-third of the intercuspal distance. After cavity preparation and shade selection, the operative field was moisture isolated with cotton rolls and suctioning. Calcium hydroxide-based material (Dycal, Dentsply/Caulk; Milford, DE, USA) was only used in deep preparations and was applied directly over the deepest site and then sealed with a glass-ionomer cement lining (Vivaglass Liner, Ivoclar Vivadent; Schaan, Liechtenstein). For all class II cavities, a thin metallic matrix was used and carefully wedged with wooden wedges (KerrHawe Neos; Bioggio, Switzerland). The cavities were cleaned by a thorough rinsing with water. In order to make intraindividual comparison possible, all patients received two Vol 16, No 3, 2014
Table 2
Distribution of the experimental restorations
Surfaces
Mandible
Maxilla
Premolar
Molar
Premolar
Molar
2
22
45
15
28
3
10
21
5
10
Total
32
66
20
38
restorations. Cavities were randomly distributed to be restored with either the experimental RC Filtek P90 or the control RC Quixfil. For silorane-based composite (Filtek P90) restorations, the Filtek P90 System Adhesive (two-step self-etching adhesive) was applied in two steps. In the first step, System Adhesive self-etching primer was applied to the cavity for 15 s with the black applicator, followed by gentle air dispersion and 10 s of light curing. In the second step, System Adhesive Bond was then applied with the green applicator, followed by gentle air dispersion and 10 s light curing. Where the methacrylate-based composite (Quixfil) was used, Prime & Bond NT (two-step etch-and-rinse adhesive) was applied. The preparation was etched with 36% phosphoric acid gel (Conditioner; Dentsply DeTrey). The acid gel was first placed on enamel, and then the dentin was conditioned during the last 15 s of the 30 s etching time. The cavity was then thoroughly rinsed with water for 10 s and dried with air, keeping the dentin surface moist. Prime 287
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Table 3
Criteria for direct clinical evaluation (modified Ryge criteria; van Dijken et al40)
Category
Score Acceptable
Anatomical form
Criteria
Unacceptable
0 1 2 3
Marginal adaptation
3 4
• Restoration is contiguous with existing anatomic form, explorer does not catch • Explorer catches, no crevice is visible into which explorer will penetrate • Crevice at margin, enamel exposed • Obvious crevice at margin, dentin or base exposed • Restoration mobile, fractured or missing
3 4
• • • • •
Very good color match Good color match; crevice at margin, enamel exposed Slight mismatch in color, shade or translucency Obvious mismatch, outside the normal range Gross mismatch
3
• • • •
No discoloration evident Slight staining, can be polished away Obvious staining cannot be polished away Gross staining
3
• • • •
Smooth surface Slightly rough or pitted Rough, cannot be refinished Surface deeply pitted, irregular grooves
0 1 2
Color match
Marginal discoloration
Surface roughness
Secondary caries
0 1 2
0 1 2 0 1 2 0 1
• The restoration is contiguous with tooth anatomy • Slightly under- or overcontoured restoration; marginal ridges slightly undercontoured; contact slightly open (may be self-correcting); occlusal height reduced locally • Restoration is undercontoured, dentin or base exposed; contact is faulty, not self-correcting; occlusal height reduced; occlusion affected • Restoration is missing partially or totally; fracture of tooth structure; shows traumatic occlusion; restoration causes pain in tooth or adjacent tissue
• No evidence of caries contiguous with the margin of the restoration • Caries is evident contiguous with the margin of the restoration
& Bond NT adhesive was applied generously to thoroughly wet the entire cavity. After 20 s, excess solvent was removed with 5 s of gentle air drying, and then light curing was performed for 10 s. The RC was then applied in layers of 2 to 3 mm maximum, if possible with an oblique layering technique using selected composite instruments (Optra Contact & Optra Sculpt, Ivoclar Vivadent). Every increment was light cured for at least 10 s. Following removal of the matrix band, the proximal regions of the restorations were additionally polymerized buccally and lingually/palatally for 10 s. Contouring and finishing of the restorations was performed at the same appointment using a watercooled, fine-grit diamond finishing instrument (Komet). Articulating paper (Bausch; Nashua, NH, USA) was used to establish appropriate occlusal morphology and contact. Flexible points impregnated with silicone dioxide were used to obtain smooth surfaces (Astropol; Ivoclar Vivadent). For finishing and polishing of the proximal surfaces, finishing strips (GC; Tokyo, Japan) were used. The quality of the interproximal contacts was checked with dental floss.
288
Evaluation Procedures Each restoration was evaluated according to slightly modified USPHS criteria for the following characteristics: anatomical form, marginal adaptation, color match, marginal discoloration, surface roughness, and secondary caries (Table 3).40 The restorations were evaluated at baseline, and then blindly every year for 3 years by two independent examiners. The Cohen Kappa index was used as a measure of interexaminer agreement. Examiners were not involved in the restorative procedures. Disagreement occurred only once during evaluations; this restoration was reevaluated by both examiners and a consensus was obtained. To detect secondary caries, the presence of softness, opacity, etching, or white spots is considered evidence of undermining or demineralization in areas where the explorer catches or resists removal after insertion. Furthermore, bitewing radiographs (Kodak; Rochester, NY, USA) were taken at each follow-up appointment. A magnifying aid was used for examination of marginal adaptation. Retention loss, severe marginal defects, discoloration that needed repair or replacement, and the occurrence of caries along the restoration margins were considered clinical failures. The Journal of Adhesive Dentistry
Table 4
Nonacceptable class II restorations and reasons for failure during the 3-year follow-up 1 year
2 years
3 years
F P90
Quixfil
F P90
Quixfil
F P90
Quixfil
Fracture
1
0
1
1
1
1
Fracture and caries
0
0
0
0
0
0
Caries
0
0
0
0
0
0
Cusp fracture
0
0
0
1
0
0
Endodontic reasons
0
0
0
0
1
0
Cumulative absolute failure frequencies
1
0
2
2
4
3
1.2
0
2.4
2.7
5.1
3.8
Cumulative relative failure frequencies (%)
Statistical Analysis Statistical analysis was performed using the statistical package for the Social Sciences, version 19 (SPSS; Chicago, IL, USA). Since the assessment of the restorations yielded clearly ordinally structural data, only nonparametric procedures were used. The changes in the parameters during the 3-year period were analyzed using the Friedman test, which is a nonparametric ANOVA. The baseline scores were compared with those at the recall visits using the Wilcoxon signed rank test. The level of significance was set at p < 0.05.
RESULTS All patients attended the 3-year recall visit. Cohen Kappa statistics (Kappa = 0.90) showed strong examiner agreement, and no statistical difference was observed in their answers (p > 0.05). Postoperative sensitivity was reported for 6 teeth in 6 participants between 1 and 3 weeks after baseline. Two Filtek P90 restorations showed postoperative sensitivity during biting forces, as did four Quixfil restorations during biting forces or cold stimuli. Postoperative sensitivity disappeared by the 1-year evaluation. Seven failed restorations (4.5%) were observed during the follow-up, four Filtek P90 (5.1%; 1 premolar and 3 molars) and three Quixfil (3.8%; 3 molars). This resulted in annual failure rates of 1.7% for Filtek P90 group and 1.2% for the Quixfil group. Reasons and year of failure for the nonacceptable restorations are shown in Table 4. The main reason for failure was RC fracture. Small chip fractures were observed in 3 restorations, which were treated by polishing. Relative frequencies of the scores (%) for the evaluated variables are given in Table 5. A significant decrease in color match was observed between baseline and 3 years. The color changes observed were within the acceptable score range and no significant differences were seen between the two groups. Slight marginal discoloration was observed in 21% of silorane and in 20% of Quixfil restorations. The surface characteristics of the Filtek P90 and Quixfil Vol 16, No 3, 2014
resin composites showed no clinical change from smooth characteristics at baseline to the end of the follow-up. In the overall intra-individual comparisons between the Filtek Silorane and Quixfil composite restoratives, no significant differences were observed at the recalls (p > 0.05).
DISCUSSION This study evaluated the 3-year clinical effectiveness of a silorane-based composite (Filtek P90), launched on the dental market as a low-shrinkage material, compared to a well-established methacrylate-based RC (Quixfil). Laboratory investigations served as a screening model before human clinical trials were initiated. Comprehensive laboratory studies19,14,23,32 of silorane RC were carried out, finding that silorane RC exhibited properties at least as good as methacrylate RC. In this regard, the results of the present study may be considered to indicate good performance of the silorane composite under evaluation. The tested silorane-based RC showed good clinical efficacy, confirming results observed in earlier 1- and 2-year trials.3,6,36 In the present study, the annual failure rates of 1.7% for the Filtek P90/P90 System Adhesive group and 1.2% for the Quixfil/Prime & Bond NT group were not significantly different. The null hypothesis was therefore rejected, the alternative hypothesis was accepted. No significant differences in any of the clinical criteria listed in Table 5 were found between the two RC restorative systems tested. For both of the tested RC, there was a significant decrease in color match observed between baseline and 3 years. The color changes observed were within the acceptable scoring range. Both tested materials exhibited a significant color change during follow-up, which may be related to surface roughness, surface integrity, and polishing technique.17,35 However, it must be mentioned that the changes were within scores of 0 to 2, meaning that they were still clinically acceptable. To ensure excellent esthetics, it is necessary for tooth-colored restorative materials to maintain their intrinsic color and be resistant to surface staining. A number of both intrinsic and extrinsic 289
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Table 5 Scores for the evaluated class II restorations of Filtek P90 and Quixfil given as relative frequencies for baseline and the yearly recalls (%) Evaluation criteria
Score
Baseline
1 year
2 years
3 years
FP 90
Quixfil
FP 90
Quixfil
FP 90
Quixfil
FP 90
Quixfil
Anatomical form
0 1 2 3
91.3 8.7 0 0
89.0 11.0 0 0
94.5 3.3 2.2 0
4.4 5.6 0 0
87.3 9.2 2.3 1.2
93.9 3.1 1.5 1.5
89.6 5.7 1.2 3.5
92.9 2.9 1.4 2.9
Marginal adaptation
0 1 2 3 4
97.9 2.1 0 0 0
97.3 2.7 0 0 0
87.5 11.4 1.1 0 0
9.1 0.0 0 0 0
86.9 9.6 0 0 3.5
9.4 6.1 1.5 0 3
80.5 16.1 0 0 3.4
84.3 11.4 1.4 0 2.9
Color match
0 1 2 3 4
47.8 51.1 1.1 0 0
48.3 0.3 1.4 0 0
29.7 62.6 7.7 0 0
8.0 9.2 2.8 0 0
19.4 74.6 6.0 0 0
0.6 75.2 4.2 0 0
21.8 70.1 8.1 0 0
1.4 0.0 8.6 0 0
Marginal discoloration
0 1 2 3
100 0 0 0
100 0 0 0
94.5 4.4 1.1 0
97.2 2.8 0 0
90.8 8.0 1.2 0
93.9 6.1 0 0
79.3 16.1 4.6 0
82.9 15.7 1.4 0
Surface roughness
0 1 2 3
100 0 0 0
100 0 0 0
100 0 0 0
100 0 0 0
100 0 0 0
97.0 3.0 0 0
100 0 0 0
97.1 2.9 0 0
Secondary caries
0 1
100 0
100 0
100 0
100 0
100 0
100 0
100 0
100 0
factors affect the degree of color change, such as degree of polymerization, water sorption, diet, oral hygiene, and surface smoothness of restorations. Barutcigi and Yıldız4 evaluated the intrinsic and extrinsic color change of dimethacrylate and silorane-based composites. They reported that the tested restorative materials were susceptible to staining by commonly consumed beverages. In vitro, the surface roughness in terms of Ra and bacterial adhesion of silorane-based composite was similar to that of the methacrylate-based composite.36 Regarding the cavosurface marginal discoloration criterion, the majority of scores were 0. Scores of 1 were only recorded at the 1-year examination in 4.4% Filtek P90 and 2.8% Quixfil restorations and increased during the 3-year period, but they remained under 20% in both groups. After 3 years of clinical use, insignificant differences were found in the marginal adaptation of both composites over the course of time (baseline, 1 year, 2 years and 3 years). Except for seven failed restorations (4 Filtek P90, 3 Quixfil), all the other restorations received scores of 0 (80.5% to 84.3%) or 1 (16% to 11.4%) for marginal adaptation. Hickel et al21 found that this phenomenon usually appeared in the medium term following placement of the restorations. One clinical trial that examined a methacrylate-based composite resin and a silorane in class II cavities revealed that the marginal adaptation of 290
the silorane was inferior to that of a methacrylate-based material, both occlusally and approximally.36 Alteration in marginal adaptation and marginal discoloration over the course of time could also stem from degradation of the resin/bond interface as a result of slow hydrolysis. Most of the monomers in adhesive materials can absorb water and chemicals from the environment, and this absorbed water weakens the resin/dentin bond over time. Thus, both water sorption and solubility could lead to a variety of chemical and physical processes that may result in deleterious effects on marginal adaptation, discoloration, and color match of adhesive restorations over time.2,18,24 Alteration in marginal quality could also be attributed to fracture of a slight overlapping marginal excess.38 Shrinkage stress, the effects of cavity geometry on C-factor, butt-joint occlusal margin and self-etching adhesives may also be involved.28 Filtek silorane composite demonstrated clinically smooth surface characteristics during the whole followup, indicating a good wear pattern similar to that of Quixfil methacrylate composite. No case of inacceptable clinical wear was observed. Our results are supported by laboratory investigations which reported that mechanical properties of silorane-based composite are comparable to those of both dimethacrylate-based materials and methacrylate composites.13,22,23 The Journal of Adhesive Dentistry
Postoperative sensitivity after placing posterior RC restorations has been a problem experienced in general practice for many years.19 It has been attributed to several factors, such as effects of shrinkage stress on the marginal integrity, etching of dentin, cusp deformation, and interfacial bacterial penetration. A low frequency of postoperative sensitivity was reported in the present study, which is in accordance with other clinical evaluations.4,6,36 In the current study, postoperative sensitivity was reported for 2 silorane composite restorations during biting forces and 4 methacrylate composite restorations during biting forces or cold stimuli. By the 1-year evaluation, postoperative sensitivity disappeared for both materials. Both silorane and methacrylate composites were used with their proprietary adhesive system according to the manufacturers’ recommendations. The silorane composite was bonded with a two-step self-etching adhesive, but the methacrylate composite was bonded with a two-step etchand-rinse adhesive. Although the bonding systems used were different in application strategy and bonding mechanism, no significant difference was reported between the test and the control restorative systems regarding postoperative sensitivity. Santini and Miletic34 found bonding to dentin using the silorane adhesive system to produce a hybrid layer of similar thickness to that of a methacrylate-based adhesive (Excite, Ivoclar Vivadent) and thicker than that of the onestep adhesives (G Bond, GC; AdheSE, Ivoclar Vivadent). This presence of an interaction zone has also been confirmed by the work of Mine et al,27 who also found that the two bottles in the silorane adhesive system, Primer and Bond, were distinguishable as two distinct layers. In this respect, it has been postulated that the high-viscosity second layer of adhesive might act as an elastic buffer.41 In addition, Van Ende et al41 examined the stress at the adhesive interface with different configuration factors. Their results indicated that cavity configuration affected the microtensile bond strength of the silorane adhesive system and noted that an incremental layering technique was still required for placement of silorane restorations. Indeed, Perdigao et al33 suggested that the clinical technique may be more relevant for the development of postoperative sensitivity than is the type of adhesive itself. The low level of postoperative sensitivity could be considered to be a substantial clinical advantage, especially if found to be associated with a high expectation of clinical success. In one clinical study, the marginal quality of the silorane composite was shown to be somewhat inferior to that of a nanohybrid composite.36 For Quixfil resin composite, the results of the current study were confirmed by the results of previous clinical trials,1,26 which reported that posterior restorations of Quixfil and other composites exhibited good clinical results, predominantly with scores of zero. Concerning Filtek silorane composite, there are few published clinical studies that can be used for comparison, bearing in mind that the design and follow-up periods of these studies differ from those of the current study. Despite the excellent performance reported by the manufacturer of the silorane-based composite, its clinVol 16, No 3, 2014
ical performance was not superior to that of the control group, which was restored with Quixfil, a methacrylatebased composite that has been on the dental market for a longer period. The results of the present work thus document favorable medium-term performance of silorane restorations when compared with Quixfil composite and previously published work on “conventional” resin composite restorations in posterior teeth.
CONCLUSION On the basis of the results of the current study, it seems reasonable to conclude that there is no proof that silorane composite (Filtek P90) performs better than normal hybrid methacrylate composite (Quixfil). Both restorative materials exhibited acceptable clinical performance in class II restorations over an evaluation period of 3 years and the null hypothesis was therefore not accepted. Longer term clinical evaluations are required to fully assess the performance of this novel material.
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Clinical relevance: Silorane-based composite exhibited clinical performance similar to conventional methacrylate-based composite in class II restorations.
The Journal of Adhesive Dentistry
