Marc Quirynen Bilal Al-Nawas Henny J.A. Meijer Amir Razavi Torsten E. Reichert Martin Schimmel Stefano Storelli Eugenio Romeo On behalf of the Roxolid Study Group
Small-diameter titanium Grade IV and titanium–zirconium implants in edentulous mandibles: three-year results from a double-blind, randomized controlled trial
Authors’ affiliations: Marc Quirynen, Catholic University Leuven, Leuven, Belgium Bilal Al-Nawas, Johannes-Gutenberg University, Mainz, Germany Henny J.A. Meijer, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands Amir Razavi, Cantonal Hospital Lucerne, Lucerne, Switzerland Torsten E. Reichert, University of Regensburg Clinic, Regensburg, Germany Martin Schimmel, University of Geneva, Geneva, Switzerland Stefano Storelli, Eugenio Romeo, University of Milan Dental Clinic, San Paolo Hospital, Milan, Italy
Key words: edentulous, Roxolid, SLActive surface, Titanium/zirconium
Corresponding author: Marc Quirynen Department of Periodontology Faculty of Medicine Catholic University Leuven Capucijnenvoer 7 B-3000 Leuven Belgium Tel.: +32 16 332407 Fax: +32 16 332484 e-mail: [email protected]
Results: Of 91 treated patients, 75 completed the three-year follow-up. Three implants were lost
Date: Accepted 10 February 2014 To cite this article: Quirynen M, Al-Nawas B, Meijer HJA, Razavi A, Reichert TE, Schimmel M, Storelli S, Romeo E. Small-diameter titanium Grade IV and titanium–zirconium implants in edentulous mandibles: three-year results from a double-blind, randomized controlled trial. Clin. Oral Impl. Res. 26, 2015, 831–840 doi: 10.1111/clr.12367
Abstract Objective: The aim of this study was to compare crestal bone-level changes, soft tissue parameters and implant success and survival between small-diameter implants made of titanium/zirconium (TiZr) alloy or of Grade IV titanium (Ti) in edentulous mandibles restored with removable overdentures. Materials and Methods: This was a randomized, controlled, double-blind, split-mouth multicenter clinical trial. Patients with edentulous mandibles received two Straumann bone-level implants (diameter 3.3 mm), one of Ti Grade IV (control) and one of TiZr (test), in the interforaminal region. Implants were loaded after 6–8 weeks and removable Locator-retained overdentures were placed within 2 weeks of loading. Modified plaque and sulcus bleeding indices, radiographic bone level, and implant survival and success were evaluated up to 36 months. (two control and one test implant). The survival rates were 98.7% and 97.3%, and the mean marginal bone level change was
0.78 0.75 and
0.60 0.71 mm for TiZr and Ti Grade IV
implants. Most patients had a plaque score of 0 or 1 (54% for test and 51.7% for control), and a sulcus bleeding score of 0 (46.1% for test and 44.9% for control). No significant differences were found between the two implant types for bone-level change, soft tissue parameters, survival and success. Conclusions: After 36 months, similar outcomes were found between Ti Grade IV and TiZr implants. The results confirm that the results seen at 12 months continue over time.
Edentulism is a major health concern and, although the prevalence has decreased, it remains a substantial problem in a large part of the population, especially among elderly individuals (M€ uller et al. 2007; Polzer et al. 2010). Historically, full dentures have been used to restore oro-facial function in edentulous patients, but they have certain disadvantages including: incompletely restored masticatory function, poor nutrition because of the difficulty in chewing certain foods, adverse effects on self-esteem because of physical appearance or difficulties in speaking, and technical complications (Berg 1984; Burns 2004; Carpentieri 2004; Heydecke et al. 2008; Hyland et al. 2009).
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
The use of dental implants in patients with edentulous jaws was first described over 30 years ago (Br anemark et al. 1977; Adell et al. 1981). In recent years, prostheses supported by dental implants have become a widely accepted treatment option for edentulous patients in the maxilla as well as the mandible, particularly for early or conventional loading, and for implants placed in non-augmented native bone (Att et al. 2009; Gallucci et al. 2009). Several clinical studies have demonstrated increased patient satisfaction and positive impact on quality of life with implant-retained overdentures compared with conventional dentures in the mandible (Boerrigter et al. 1995a,b; Wismeijer et al.
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1997; Awad et al. 2003; Thomason et al. 2003; Thomason 2010; Mellili et al. 2011; Rashid et al. 2011; Geckili et al. 2012). Others have reported an improvement in chewing ability (Bakke et al. 2002; Meijer et al. 2003), and in nutritional aspects (Ellis et al. 2010; Moynihan et al. 2012), including anthropometric parameters (e.g. skin-fold thickness, waist-hip ratio and body mass index; Morais et al. 2003), with implantretained overdentures. These advantages have proven to be stable over time (Al-Zubeidi et al. 2011; Jabbour et al. 2012). Comparable patient satisfaction has been reported with either a mandibular long-bar implant overdenture or a fixed full-dental prosthesis (Feine et al. 1994a,b; de Grandmont et al. 1994). Therefore, an overdenture supported by two implants is considered “the standard of care” for edentulous mandibles in some countries (Feine et al. 2002; Thomason et al. 2009, 2012; Melascanu Imre et al. 2011), except for patients where a removable denture is considered a foreign body (Feine et al. 1994a). While many studies are available about patient satisfaction for implantsupported mandibular overdentures, much less information can be found for the maxilla (Visser et al. 2009). A recent study revealed significant short-term improvements in patient satisfaction for maxillary overdentures retained by two implants compared to conventional dentures (Zembic & Wismeijer 2014). Survival data for implants supporting an overdenture have shown some inconsistency. A systematic review on implants loaded for at least 5 years reported higher implant failure when supporting an overdenture (2.5% early loss, 5.9% late failures) than when supporting a full fixed (2.2% and 2.7%) or partial prosthesis (2.7% and 2.4%), respectively (Berglundh et al. 2002). The higher percentage of late failures found for overdentures is predominantly due to implant losses in the maxilla. More recent papers, however, reported much better survival rates with minimal marginal bone loss for mandibular overdenture cases (Ma & Payne 2010; Ma et al. 2010; Vercruyssen & Quirynen 2010; Vercruyssen et al. 2010). Implants with a smaller diameter (e.g. ≤3.5 mm) may have advantages in certain clinical situations where standard implants may be less suitable due to greater risk of complications or failure (Geckili et al. 2011; Bourael et al. 2012), such as narrow interdental spaces (Froum et al. 2007; Reddy et al. 2008; Lee et al. 2013), reduced alveolar ridge width (Veltri et al. 2008; Lee et al. 2013), and
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severe maxillary resorption (Hallman 2001). It may also be possible to avoid the need for extensive grafting procedures when using a small-diameter implant and therefore may be a solution for patients who are reluctant to undergo such a procedure (Geckili et al. 2011; Sohrabi et al. 2012). Some evidence, however, suggests that reduced diameter implants may be at greater risk of fatigue failure after a long period in function (Zinsli et al. 2004; Allum et al. 2008; Artzi et al. 2010; Yaltirik et al. 2011). This may be due to a lower amount of surface area available for osseointegration, potentially making the implant more susceptible to adverse loading forces (Ivanoff et al. 1997; Winkler et al. 2000). Some papers have also suggested that narrow implants may have a less favorable stress distribution (Petrie & Williams 2005; Qian et al. 2009). Reduced diameter implants need to have high mechanical stability and be able to withstand high stress and loading forces. The material the implant is made of is therefore of crucial importance. Titanium has been the material of choice for dental implants, but titanium alloys such as titanium/aluminum/ vanadium (TiAlV), have greater mechanical strength. However, the biocompatibility and corrosion resistance properties of these alloys tend to be less than that of titanium (Ikarashi et al. 2005). In addition, the presence of ionized Al or V in the tissues may inhibit the differentiation of osteoblasts and hence the development of new bone (Thompson & Puleo 1996; Hallab et al. 2002). For many common Ti alloys, because of their biphasic metal structure, it may also be difficult to make some surface modifications to enhance the osseointegration (Wong et al. 1995; Oates et al. 2007). An alloy of titanium and zirconium (Ti–Zr), however, could be considered, as both are highly biocompatible (Kobayashi et al. 1995; Steinemann 1998). Ti–Zr alloys demonstrate greater chondrogenic differentiation compared with pure Ti (Tsuchiya et al. 1998), and a lesser inflammatory and tissue response than Ti (Ikarashi et al. 2005). Such an alloy of Ti–Zr, with increased fatigue strength, has recently been developed (Roxolidâ; Institut Straumann AG, Basel, Switzerland). It has shown equally good osseointegration as pure Ti (Gottlow et al. 2012; Thoma et al. 2011), and it allows further modification of the SLActiveâ Institut Straumann AG, Basel, Switzerland surface, which has been shown to enhance osseointegration in the early healing stages (Buser et al. 2004; Oates et al. 2007; Bornstein et al. 2008; Schwarz et al. 2008) .
The aim of the current study was to evaluate whether outcomes (in terms of change in crestal bone level, soft tissue parameters and implant survival and success) with reduced diameter (3.3 mm) implants made of Ti–Zr were significantly different to those with implants of the same diameter, the same macro- and micro-design and sandblasted acid etched hydrophilic surface (SLActiveâ) made of Ti Grade IV supporting removable mandibular overdentures in edentulous patients.
Materials and methods The materials and methods for this study have previously been published (Al-Nawas et al. 2012) and are briefly outlined here. This study was designed as a randomized, controlled, double-blind, split-mouth, noninferiority, multicenter clinical trial involving eight centers in five countries (Belgium, Germany, Italy, the Netherlands and Switzerland). The study was conducted in accordance with the Declaration of Helsinki (1964 and all subsequent amendments) and Good Clinical Practice (ISO 14155:2003). It was approved by the Independent Ethics Committee of the Principal Investigator (No. 837.190.07(5725)) and subsequent centers if considered applicable before the start of the study. Written informed consent was obtained from all patients. The study was registered at www.clinicaltrials.gov (registration no. NCT00905840). Patients and implants
Patients were selected according to predefined inclusion and exclusion criteria. The most important inclusion criteria were as follows: edentulous mandible, age ≥18 years, last tooth extraction >8 weeks prior to surgery, and sufficient bone height of at least 9 mm above vital structures and bone width for placement of a 3.3 mm diameter implant without concurrent bone augmentation. No maximum dimensions of the bone ridge were defined. Important exclusion criteria were as follows: smoking >10 cigarettes or cigarette equivalents per day, bisphosphonate medication, various metabolic disorders, irradiation, inflammation, infection and bruxism. The full list of inclusion and exclusion criteria can be found in the previous publication (Al-Nawas et al. 2012). All patients received two Straumann bonelevel implants (Institut Straumann AG), one of Ti Grade IV (control) and one of Ti–Zr alloy (test). All implants were 3.3 mm in
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Quirynen et al RCT on implants made from Ti–Zr and Ti Grade IV
diameter, had a similar macro- and microstructure, and had the chemically modified SLActiveâ surface. The test and control implants were placed in the interforaminal region of the mandible (one implant in each side). Implant placement (i.e. which implant at which side) was double-blinded (coded A or B), as the implants are visually identical, and the study was unblinded after 12 months for the first analysis. The randomization sequence was created by means of computergenerated randomization codes and concealed in sealed non-transparent consecutively numbered envelopes. The randomization envelopes were opened after preparation of the osteotomy sites by a designated study nurse in the presence of a witness (the surgeon). The sealed master randomization list, provided by an external data management company, was kept by the sponsor until study unblinding. Surgical procedure
Implant surgery was performed under local anesthesia following standard surgical techniques described by the manufacturer. Implants of lengths of 8, 10, 12 and 14 mm were available. After a flap elevation, the implant bed was prepared by using titanium drills with increasing diameter followed by the use of a profile drill. Flattening of a knife ridge edge up to 1 mm was allowed. Implants were placed in healed sites at the level of the crestal bone either by a hand ratchet or by a motor device. Healing abutments were inserted to allow transmucosal healing. Sutures were removed after 1–2 weeks, and Locatorâ abutments (Zest Anchors LLC, Escondido, CA, USA) were connected 6–8 weeks after surgery. An implant-supported removable overdenture, relined (existing denture) or remade (new denture) to incorporate the Locatorâ parts was then placed within 2 weeks. Patients were recalled at 6, 12, 24 and 36 months after surgery for an evaluation of the peri-implant tissues and the dentures. If necessary, oral hygiene was reinforced and the occlusion of the denture was adjusted.
defined as a stable prosthesis in good function with absence of abutment mobility, corrective measures to the prosthesis or repairs to either prosthesis or abutments. Bone-level changes
Panoramic radiographs (Fig. 1) with standardized settings were taken at implant surgery (baseline), abutment connection and after 6, 12, 24 and 36 months. Digital images were analyzed using ImageJ 1.33 open software (National Institutes of Health, Bethesda, MD, USA), and film-based images were digitized via a video camera, light box and an image analysis program, as described by Br€agger (1998; Br€agger et al. 2004). All images were analyzed by an independent investigator who was blind to the implant material. The implant length was used as a reference measurement, and the implant chamfer 0.2 mm above the implant shoulder was used as the reference line for the bone-level measurement. Bone level was, therefore, defined
Fig. 1. Panoramic radiograph 3 years after implant placement.
Survival and success
Surviving implants were those still in place after 36 months. Implant success was defined according to the definition by Buser et al. (1990), i.e., the absence of persistent subjective complaints (e.g., pain, foreign body sensation, dysesthesia), the absence of periimplant infection with suppuration, the absence of mobility, the absence of continuous peri-implant radiolucency, and possibility for restoration. Prosthetic success was
as the distance from the reference point to the first bone-to-implant contact (BIC); mesial and distal bone-level changes in this region were considered as remodeling. Mesial and distal measurements were recorded and the mean of these two values was used (Fig. 2). Soft tissue and safety assessments
Modified Plaque Index (mPI) and modified Sulcus Bleeding Index (mSBI), according to Mombelli et al. (1987), were assessed at four sites per implant (lingual, buccal, mesial and distal) at prosthesis placement and after 6, 12, 24 and 36 months. Safety evaluations included recording of all complications, adverse events (AEs), and serious adverse events (SAEs). Each AE and SAE was assessed for severity and its potential relationship to the study device. Statistical analyses
The analysis of the primary outcome variable, which was the bone-level change 12 months after implant placement (Al-Nawas et al. 2012), was based on a confirmatory non-inferiority test with a one-sided 97.5% confidence interval. The non-inferiority margin (D) for a clinically relevant difference was set at 0.1 (0.3) mm. For a sample size of at least 73, a paired ttest with a 0.025 one-sided significant level was calculated to have 80% power to reject the hypothesis that the test is inferior to the standard. To ensure robustness against deviations and to allow for possible dropouts, the calculated sample size for the primary endpoint was increased by 20% (15 patients) to give a total of 88 (73 + 15). Secondary efficacy variables included bone-level change, implant survival and success, prosthetic success, and soft tissue assessments up to 36 months. Bone-level change at 24 and 36 months was analyzed by means of the Student’s t-test, plaque and bleeding indices by means of the Wilcoxon signed rank test, while implant success and survival were analyzed by means of the McNemar’s test. Continuous data are presented in the form of means (standard deviations [SDs]). Hypothesis tests were performed at a two-sided significance level a of 5%. The intent-to-treat (ITT) population consisted of all randomized patients who received implants and who underwent at least one efficacy assessment.
Results Patients Fig. 2. X-ray measurement. (1) Chamfer to first mesial implant-to-bone contact, (2) chamfer to first distal implant-to-bone contact, (3) length of implant.
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Ninety-two patients were screened, of whom 91 were randomized and received implants (one patient was a screening failure). The ITT
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Quirynen et al RCT on implants made from Ti–Zr and Ti Grade IV
Table 1. Patient demographic data (intent-totreat population, 89 patients) N Gender Male 40 Female 49 Ethnicity Caucasian 89 Smoking status Non-smoker 67 Past smoker 17 Occasional smoker 1 Smoker 4 Current clinically relevant disease Yes 35 No 54
% 44.9 55.1 100.0 75.3 19.1 1.1 4.5 39.3 60.7
the 36-month follow-up (six were lost to follow-up, one had an AE unrelated to the study treatment, and one died). Recruitment began in October 2007 and the last 36-month follow-up occurred in September 2011. No methodological changes were made after commencement of the trial. The primary endpoint of the study was change in periimplant bone level after 12 months (previously reported; Al-Nawas et al. 2012), but the study was designed to assess secondary parameters for up to 36 months, after which the study ended. Implant survival and success
population included 89 patients (one patient had no efficacy data, and one patient had unknown treatment allocation). The mean age at implant surgery was 65.8 8.4 years. Patient demographic data are shown in Table 1. Of the 91 patients who received implants, 75 patients completed the 36-month follow-up (Fig. 3). Three patients dropped out before the 12-month follow-up (one withdrew consent after implant loss, one was lost to follow-up, and one died), five patients dropped out before the 24-month follow-up (four lost to follow-up, and one died), and another eight patients dropped out before
Three implants were lost between baseline and 12 months (all before Locator abutment connection), one in the Ti–Zr group and two in the Ti Grade IV group. No further implant losses occurred up to 36 months. The cumulative survival rates were 98.7% for Ti–Zr and 97.3% for Ti Grade IV, respectively, after 36 months (Table 2). There were no significant differences between the two implant types at any time point. One patient presented with peri-implant infection and suppuration after 12 months along both test and control implants; both implants were therefore considered unsuccessful at this time. At 24 months, no signs
of infection were apparent at the Ti Grade IV implant; the Ti–Zr implant however continued to show peri-implant infection and suppuration and was again considered unsuccessful. After 36 months, neither implant in this patient showed detectable peri-implant infection with suppuration; both implants were therefore considered successful at this stage. The cumulative success rates (Table 2) after 36 months were 98.7% for Ti–Zr and 97.3% for Ti Grade IV, respectively. Bone-level changes
The mean change in marginal bone level in the Ti–Zr group was 0.58 0.60 at 24 months, and 0.78 0.75 mm at 36 months. In the Ti Grade IV group, the mean change in marginal bone level was 0.57 0.63 at 24 months, and 0.60 0.71 mm at 36 months. There were no significant differences between the two implant types at any time point (Table 3). The strong overlapping of the 95% confidence intervals for the test and the control group at 24 months ( 0.72 to 0.45 and 0.72 to 0.42) and 36 months ( 0.96 to 0.60 and 0.77 to 0.43) confirm the results that no difference can be seen for both groups at the two time points. The crestal bone-level change after 36 months ranged from 3.6 to +0.1 mm in the Ti–Zr group, and from 2.7 to +0.6 mm in the Ti Grade IV group (Fig. 4). Soft tissue and safety assessments
Fig. 3. Patient flow diagram. One patient was a screening failure and was therefore not eligible for treatment.
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After 36 months, most patients had a mPI score of 0 or 1; there were no significant differences between the implant types at any time point (Table 4). Similarly, most patients showed a mSBI score of 0 at 36 months after surgery, with no significant differences between the groups at any time point (Table 4). Forty-seven patients (51.6%) experienced a total of 92 AEs within 3 years. The most frequent AEs were prosthesis fracture (nine cases), minor inflammation during the healing process at the implant site (five cases), moderate peri-implant infection (five cases), tactile horizontal or vertical implant mobility (five cases), loosening of a prosthetic component (three cases), prosthesis maintenance, i.e., repair of broken or lost matrix (three cases) and wisdom tooth removal (three cases). Of these 92 AEs in total, 28 (30.4%) were judged to be related to the study device. A total of 14 patients experienced 19 SAEs (four coronary/circulatory, four orthopedic, three oncologic, three systemic infection, two cognitive/psychological and three resulting in death); none of the SAEs were judged to be related to the study device.
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Quirynen et al RCT on implants made from Ti–Zr and Ti Grade IV
Table 2. Survival and success rates at 12, 24 and 36 months (intent-to-treat population, 89 titanium–zirconium (TiZr) and Ti Grade IV implants)
Up to 12 months Missing data (excluding failures)* Failed implants (0–12 months) Unsuccessful implants (excluding failures) Successful implants Survival (success) (%) P-value† survival (success) Up to 24 months Missing data (excluding failures)* Failed implants (0–24 months) Unsuccessful implants (excluding failures) Successful implants Survival (success) (%) P-value† survival (success) Up to 36 months Missing data (excluding failures)* Failed implants (0–36 months) Unsuccessful implants (excluding failures) Successful implants Survival (success) (%) P-value† survival (success) * †
Ti–Zr
Ti Grade IV
1 1 1 86 98.9 (97.7)
2 2 1 84 97.7 (96.6) 0.1573 (0.1573)
7 1 1 80 98.8 (97.6)
8 2 0 79 97.5 (97.5) 0.1573 (0.5637)
14 1 0 74 98.7 (98.7)
14 2 0 73 97.3 (97.3) 0.3173 (0.3173)
Missing data excluded from analysis. Results from McNemar’s test.
Table 3. Change in crestal bone level after 12, 24 and 36 months (intent-to-treat population; N and mean SD in mm) Ti–Zr 12 months N Mean SD P-value* 24 months N Mean SD 95% CI P-value* 36 months N Mean SD 95% CI P-value*
82 0.34 0.54
Ti Grade IV
N/A†
76 0.58 0.60 0.72 to 0.45
78 0.31
0.56
72 0.57 0.63 0.72 to 0.42 0.8627
69 0.78 0.75 0.96 to 0.60
67 0.60 0.71 0.77 to 0.43 0.1584
CI, confidence interval; Ti–Zr, titanium–zirconium. Some radiographs could not be evaluated, hence the differences in sample numbers. * Results from Student’s t-test. † The respective one-sided 97.5% confidence interval for the treatment difference was [ ∞, 0.0867] which confirmed the non-inferiority of Ti–Zr compared with Ti Grade IV after 12 months as the noninferiority margin of 0.1 is not part of the confidence interval (Al-Nawas et al. 2012).
Discussion This was a prospective, randomized, doubleblind, split-mouth study in which dental implants made of Ti–Zr alloy were compared to implants made of Ti Grade IV, both with the SLActiveâ surface. After 36 months, no significant differences in change in crestal bone level, clinical parameters or survival and success rates were evident between the groups, and the outcomes seen at 12 months continued over time, indicating that Ti–Zr in this clinical setting was similar to Ti Grade IV.
Reduced diameter implants can be an effective alternative to standard diameter implants in certain cases, and can expand the range of treatment options for both the clinician and the patient. Although most commonly used in cases where there is limited interdental space (e.g. narrow singletooth gaps) or edentulous ridges that are too narrow for standard diameter implants (Hallman 2001; Froum et al. 2007), the outcomes shown with these implants are promising. This may increase the acceptance of implant treatment by avoiding augmentation procedures (Pommer et al. 2011; Hof et al.
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
2014). However, some evidence indicates that implants with a smaller than standard diameter (e.g. 2 mm shown by only 4.8% of the implants (Hallman 2001). Very limited data is available for the usage of implants to support overdentures in the maxilla. While two implants are sufficient to support a mandibular overdenture, this could not be confirmed in the edentulous maxilla (Weng & Richter 2007) with a survival rate of 48.9%. More than two implants are recommended to support a maxillar overdenture, regardless of the loading protocol (Gallucci et al. 2009). The results of the current study support the one-year findings (Al-Nawas et al. 2012), which showed mean peri-implant bone loss of 0.34 0.54 and 0.31 0.56 mm for Ti–Zr and Ti Grade IV implants, respectively and demonstrated that Ti–Zr implants perform non-inferior to Ti Grade IV implants in regards of bone loss 12 months after implant placement. Another clinical study confirmed similar survival and success between Ti–Zr and Ti Grade IV implants. Similar bone loss was again observed 2 years after loading (overall mean bone loss 0.33 0.54 mm). Healthy peri-implant tissues were also noted (Barter et al. 2011). A more recent clinical trial evaluated 51 Ti–Zr implants in horizontally deficient edentulous ridges in 18 patients. In this study, the implants were loaded either immediately or delayed with either fixed or removable prostheses. The peri-implant bone resorption ranged from 0 to 1 mm after 2 years, survival and success was 100%, and no prosthetic complications occurred. The outcomes obtained in this challenging indication, i.e., occlusal loading in the lateral-posterior region, suggested that the new Ti–Zr implants can withstand high mechanical stresses (Chiapasco et al. 2012). Radiographic evaluations can provide evidence in peri-implant bone changes over time, either by intraoral periapical films (Lau-
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Quirynen et al RCT on implants made from Ti–Zr and Ti Grade IV
rell & Lundgren 2011) which has already become a standard method in dental implantology, or extraoral panoramic scans (Spiekermann et al. 1995). One limitation of both techniques is that marginal bone-level changes are only mesially and distally measurable. Panoramic radiographs were found to be a useful alternative to intraoral periapical films in the atrophic mandible for the evaluation of the marginal bone loss around implants as no difference was found between the two methods (Zechner et al. 2003). Therefore, in the present study, panoramic radiographs were used. Due to the multicentric nature of the study, the standardization of the panoramic x-rays was limited to the same settings at the baseline and follow-up visits. An important aspect of this study is the trial design. The trial utilizes a split-mouth design, which has been successfully used in implant dentistry (van Steenberghe et al. 2000; Roccuzzo et al. 2008; Fung et al. 2011; Cannizzaro et al. 2012) and which can reduce the risk of bias when appropriate statistical and scientific assumptions are met (AntczakBouckoms et al. 1990; Koch & Paquette 1997). In addition, the trial may potentially
be, to the authors’ knowledge, the only double-blind trial evaluating two implants. This was possible because the Ti–Zr and Ti Grade IV implants used in the study are visually identical, so that neither the patient nor the surgeon knew which implants were placed in which positions; this is normally not possible in clinical trials with different implants because of different implant designs, surface appearance or storage requirements. The key characteristics for high quality randomized controlled trials are blinding, concealment of treatment allocation, randomization and follow-up of the patients (Montenegro et al. 2002), all of which were a part of this study. The study was unblinded only after 12 months so that the primary endpoint outcomes could be analyzed. A recent review of the quality of reporting of RCTs in implant dentistry indicated that the overall quality is poor and that the risk of bias was higher with statistically significantly reported outcomes (Cairo et al. 2012). The Eighth European Workshop on Periodontology recommended that researchers performing clinical trials in implant dentistry should pay special attention to limiting potential bias in trial design (Tonetti & Palmer 2012). The authors believe
that the risk of treatment or clinician bias in this study was therefore minimized in comparison to other similar studies. In summary, this double-blind randomized controlled clinical trial confirmed that the similar outcomes with Ti–Zr and and the well-established Ti Grade IV 3.3 mm diameter SLActiveâ surface implants continue over time. Existing biomechanical and biocompatibility evidence showing greater fatigue strength and excellent osseointegration, together with the clinical outcomes, suggest that the narrow Ti–Zr implants may allow implant therapy in more challenging indications. Further clinical studies are recommended.
Acknowledgements: The trial was sponsored by Institut Straumann AG, Basel, Switzerland.
Conflict of interest The authors have no conflicts of interest to declare.
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Appendix The Roxolid Study Group Bilal Al-Nawas (Johannes-Gutenberg University, Mainz, Germany); Isabel Br€auer (University of Regensburg Clinic, Regensburg, Germany); Jose Castro-Laza (University of Regensburg Clinic, Regensburg, Germany); Henny JA Meijer (University Medical Center Groningen, University of Groningen, Groningen, the Netherlands); Frauke M€ uller (University of Geneva, Geneva, Switzerland); Ignace Naert (Catholic University Leuven, Leuven, Belgium); Alessandro Perrucchi (Cantonal Hospital Lucerne, Lucerne, Switzerland); Marc Quirynen (Catholic University Leuven, Leuven, Belgium); Gerry M Raghoebar (University Medical Center Groningen, University of Groningen, Groningen, the Netherlands); Amir Razavi (Cantonal Hospital Lucerne, Lucerne, Switzerland); Torsten Reichert (University of Regensburg Clinic, Regensburg, Germany); Eugenio Romeo (University of Milan Dental Clinic, Milan, Italy); Eric Santing (University Medical Center Groningen, University of Groningen, Groningen, the Netherlands); Martin Schimmel (University of Geneva, Geneva, Switzerland); Stefano Storelli (University of Milan Dental Clinic, Milan, Italy); Christiaan ten Bruggenkate (Academic Center for Dentistry Amsterdam, Amsterdam, the Netherlands); Betty Vandekerckhove (Catholic University Leuven, Leuven, Belgium); Wilfried Wagner (Johannes-Gutenberg University, Mainz, Germany); Daniel Wismeijer (Academic Center for Dentistry Amsterdam, Amsterdam, the Netherlands).
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Small-diameter titanium Grade IV and titanium–zirconium implants in edentulous mandibles: three-year results from a double-blind, randomized controlled trial
Authors’ affiliations: Marc Quirynen, Catholic University Leuven, Leuven, Belgium Bilal Al-Nawas, Johannes-Gutenberg University, Mainz, Germany Henny J.A. Meijer, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands Amir Razavi, Cantonal Hospital Lucerne, Lucerne, Switzerland Torsten E. Reichert, University of Regensburg Clinic, Regensburg, Germany Martin Schimmel, University of Geneva, Geneva, Switzerland Stefano Storelli, Eugenio Romeo, University of Milan Dental Clinic, San Paolo Hospital, Milan, Italy
Key words: edentulous, Roxolid, SLActive surface, Titanium/zirconium
Corresponding author: Marc Quirynen Department of Periodontology Faculty of Medicine Catholic University Leuven Capucijnenvoer 7 B-3000 Leuven Belgium Tel.: +32 16 332407 Fax: +32 16 332484 e-mail: [email protected]
Results: Of 91 treated patients, 75 completed the three-year follow-up. Three implants were lost
Date: Accepted 10 February 2014 To cite this article: Quirynen M, Al-Nawas B, Meijer HJA, Razavi A, Reichert TE, Schimmel M, Storelli S, Romeo E. Small-diameter titanium Grade IV and titanium–zirconium implants in edentulous mandibles: three-year results from a double-blind, randomized controlled trial. Clin. Oral Impl. Res. 26, 2015, 831–840 doi: 10.1111/clr.12367
Abstract Objective: The aim of this study was to compare crestal bone-level changes, soft tissue parameters and implant success and survival between small-diameter implants made of titanium/zirconium (TiZr) alloy or of Grade IV titanium (Ti) in edentulous mandibles restored with removable overdentures. Materials and Methods: This was a randomized, controlled, double-blind, split-mouth multicenter clinical trial. Patients with edentulous mandibles received two Straumann bone-level implants (diameter 3.3 mm), one of Ti Grade IV (control) and one of TiZr (test), in the interforaminal region. Implants were loaded after 6–8 weeks and removable Locator-retained overdentures were placed within 2 weeks of loading. Modified plaque and sulcus bleeding indices, radiographic bone level, and implant survival and success were evaluated up to 36 months. (two control and one test implant). The survival rates were 98.7% and 97.3%, and the mean marginal bone level change was
0.78 0.75 and
0.60 0.71 mm for TiZr and Ti Grade IV
implants. Most patients had a plaque score of 0 or 1 (54% for test and 51.7% for control), and a sulcus bleeding score of 0 (46.1% for test and 44.9% for control). No significant differences were found between the two implant types for bone-level change, soft tissue parameters, survival and success. Conclusions: After 36 months, similar outcomes were found between Ti Grade IV and TiZr implants. The results confirm that the results seen at 12 months continue over time.
Edentulism is a major health concern and, although the prevalence has decreased, it remains a substantial problem in a large part of the population, especially among elderly individuals (M€ uller et al. 2007; Polzer et al. 2010). Historically, full dentures have been used to restore oro-facial function in edentulous patients, but they have certain disadvantages including: incompletely restored masticatory function, poor nutrition because of the difficulty in chewing certain foods, adverse effects on self-esteem because of physical appearance or difficulties in speaking, and technical complications (Berg 1984; Burns 2004; Carpentieri 2004; Heydecke et al. 2008; Hyland et al. 2009).
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
The use of dental implants in patients with edentulous jaws was first described over 30 years ago (Br anemark et al. 1977; Adell et al. 1981). In recent years, prostheses supported by dental implants have become a widely accepted treatment option for edentulous patients in the maxilla as well as the mandible, particularly for early or conventional loading, and for implants placed in non-augmented native bone (Att et al. 2009; Gallucci et al. 2009). Several clinical studies have demonstrated increased patient satisfaction and positive impact on quality of life with implant-retained overdentures compared with conventional dentures in the mandible (Boerrigter et al. 1995a,b; Wismeijer et al.
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1997; Awad et al. 2003; Thomason et al. 2003; Thomason 2010; Mellili et al. 2011; Rashid et al. 2011; Geckili et al. 2012). Others have reported an improvement in chewing ability (Bakke et al. 2002; Meijer et al. 2003), and in nutritional aspects (Ellis et al. 2010; Moynihan et al. 2012), including anthropometric parameters (e.g. skin-fold thickness, waist-hip ratio and body mass index; Morais et al. 2003), with implantretained overdentures. These advantages have proven to be stable over time (Al-Zubeidi et al. 2011; Jabbour et al. 2012). Comparable patient satisfaction has been reported with either a mandibular long-bar implant overdenture or a fixed full-dental prosthesis (Feine et al. 1994a,b; de Grandmont et al. 1994). Therefore, an overdenture supported by two implants is considered “the standard of care” for edentulous mandibles in some countries (Feine et al. 2002; Thomason et al. 2009, 2012; Melascanu Imre et al. 2011), except for patients where a removable denture is considered a foreign body (Feine et al. 1994a). While many studies are available about patient satisfaction for implantsupported mandibular overdentures, much less information can be found for the maxilla (Visser et al. 2009). A recent study revealed significant short-term improvements in patient satisfaction for maxillary overdentures retained by two implants compared to conventional dentures (Zembic & Wismeijer 2014). Survival data for implants supporting an overdenture have shown some inconsistency. A systematic review on implants loaded for at least 5 years reported higher implant failure when supporting an overdenture (2.5% early loss, 5.9% late failures) than when supporting a full fixed (2.2% and 2.7%) or partial prosthesis (2.7% and 2.4%), respectively (Berglundh et al. 2002). The higher percentage of late failures found for overdentures is predominantly due to implant losses in the maxilla. More recent papers, however, reported much better survival rates with minimal marginal bone loss for mandibular overdenture cases (Ma & Payne 2010; Ma et al. 2010; Vercruyssen & Quirynen 2010; Vercruyssen et al. 2010). Implants with a smaller diameter (e.g. ≤3.5 mm) may have advantages in certain clinical situations where standard implants may be less suitable due to greater risk of complications or failure (Geckili et al. 2011; Bourael et al. 2012), such as narrow interdental spaces (Froum et al. 2007; Reddy et al. 2008; Lee et al. 2013), reduced alveolar ridge width (Veltri et al. 2008; Lee et al. 2013), and
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severe maxillary resorption (Hallman 2001). It may also be possible to avoid the need for extensive grafting procedures when using a small-diameter implant and therefore may be a solution for patients who are reluctant to undergo such a procedure (Geckili et al. 2011; Sohrabi et al. 2012). Some evidence, however, suggests that reduced diameter implants may be at greater risk of fatigue failure after a long period in function (Zinsli et al. 2004; Allum et al. 2008; Artzi et al. 2010; Yaltirik et al. 2011). This may be due to a lower amount of surface area available for osseointegration, potentially making the implant more susceptible to adverse loading forces (Ivanoff et al. 1997; Winkler et al. 2000). Some papers have also suggested that narrow implants may have a less favorable stress distribution (Petrie & Williams 2005; Qian et al. 2009). Reduced diameter implants need to have high mechanical stability and be able to withstand high stress and loading forces. The material the implant is made of is therefore of crucial importance. Titanium has been the material of choice for dental implants, but titanium alloys such as titanium/aluminum/ vanadium (TiAlV), have greater mechanical strength. However, the biocompatibility and corrosion resistance properties of these alloys tend to be less than that of titanium (Ikarashi et al. 2005). In addition, the presence of ionized Al or V in the tissues may inhibit the differentiation of osteoblasts and hence the development of new bone (Thompson & Puleo 1996; Hallab et al. 2002). For many common Ti alloys, because of their biphasic metal structure, it may also be difficult to make some surface modifications to enhance the osseointegration (Wong et al. 1995; Oates et al. 2007). An alloy of titanium and zirconium (Ti–Zr), however, could be considered, as both are highly biocompatible (Kobayashi et al. 1995; Steinemann 1998). Ti–Zr alloys demonstrate greater chondrogenic differentiation compared with pure Ti (Tsuchiya et al. 1998), and a lesser inflammatory and tissue response than Ti (Ikarashi et al. 2005). Such an alloy of Ti–Zr, with increased fatigue strength, has recently been developed (Roxolidâ; Institut Straumann AG, Basel, Switzerland). It has shown equally good osseointegration as pure Ti (Gottlow et al. 2012; Thoma et al. 2011), and it allows further modification of the SLActiveâ Institut Straumann AG, Basel, Switzerland surface, which has been shown to enhance osseointegration in the early healing stages (Buser et al. 2004; Oates et al. 2007; Bornstein et al. 2008; Schwarz et al. 2008) .
The aim of the current study was to evaluate whether outcomes (in terms of change in crestal bone level, soft tissue parameters and implant survival and success) with reduced diameter (3.3 mm) implants made of Ti–Zr were significantly different to those with implants of the same diameter, the same macro- and micro-design and sandblasted acid etched hydrophilic surface (SLActiveâ) made of Ti Grade IV supporting removable mandibular overdentures in edentulous patients.
Materials and methods The materials and methods for this study have previously been published (Al-Nawas et al. 2012) and are briefly outlined here. This study was designed as a randomized, controlled, double-blind, split-mouth, noninferiority, multicenter clinical trial involving eight centers in five countries (Belgium, Germany, Italy, the Netherlands and Switzerland). The study was conducted in accordance with the Declaration of Helsinki (1964 and all subsequent amendments) and Good Clinical Practice (ISO 14155:2003). It was approved by the Independent Ethics Committee of the Principal Investigator (No. 837.190.07(5725)) and subsequent centers if considered applicable before the start of the study. Written informed consent was obtained from all patients. The study was registered at www.clinicaltrials.gov (registration no. NCT00905840). Patients and implants
Patients were selected according to predefined inclusion and exclusion criteria. The most important inclusion criteria were as follows: edentulous mandible, age ≥18 years, last tooth extraction >8 weeks prior to surgery, and sufficient bone height of at least 9 mm above vital structures and bone width for placement of a 3.3 mm diameter implant without concurrent bone augmentation. No maximum dimensions of the bone ridge were defined. Important exclusion criteria were as follows: smoking >10 cigarettes or cigarette equivalents per day, bisphosphonate medication, various metabolic disorders, irradiation, inflammation, infection and bruxism. The full list of inclusion and exclusion criteria can be found in the previous publication (Al-Nawas et al. 2012). All patients received two Straumann bonelevel implants (Institut Straumann AG), one of Ti Grade IV (control) and one of Ti–Zr alloy (test). All implants were 3.3 mm in
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Quirynen et al RCT on implants made from Ti–Zr and Ti Grade IV
diameter, had a similar macro- and microstructure, and had the chemically modified SLActiveâ surface. The test and control implants were placed in the interforaminal region of the mandible (one implant in each side). Implant placement (i.e. which implant at which side) was double-blinded (coded A or B), as the implants are visually identical, and the study was unblinded after 12 months for the first analysis. The randomization sequence was created by means of computergenerated randomization codes and concealed in sealed non-transparent consecutively numbered envelopes. The randomization envelopes were opened after preparation of the osteotomy sites by a designated study nurse in the presence of a witness (the surgeon). The sealed master randomization list, provided by an external data management company, was kept by the sponsor until study unblinding. Surgical procedure
Implant surgery was performed under local anesthesia following standard surgical techniques described by the manufacturer. Implants of lengths of 8, 10, 12 and 14 mm were available. After a flap elevation, the implant bed was prepared by using titanium drills with increasing diameter followed by the use of a profile drill. Flattening of a knife ridge edge up to 1 mm was allowed. Implants were placed in healed sites at the level of the crestal bone either by a hand ratchet or by a motor device. Healing abutments were inserted to allow transmucosal healing. Sutures were removed after 1–2 weeks, and Locatorâ abutments (Zest Anchors LLC, Escondido, CA, USA) were connected 6–8 weeks after surgery. An implant-supported removable overdenture, relined (existing denture) or remade (new denture) to incorporate the Locatorâ parts was then placed within 2 weeks. Patients were recalled at 6, 12, 24 and 36 months after surgery for an evaluation of the peri-implant tissues and the dentures. If necessary, oral hygiene was reinforced and the occlusion of the denture was adjusted.
defined as a stable prosthesis in good function with absence of abutment mobility, corrective measures to the prosthesis or repairs to either prosthesis or abutments. Bone-level changes
Panoramic radiographs (Fig. 1) with standardized settings were taken at implant surgery (baseline), abutment connection and after 6, 12, 24 and 36 months. Digital images were analyzed using ImageJ 1.33 open software (National Institutes of Health, Bethesda, MD, USA), and film-based images were digitized via a video camera, light box and an image analysis program, as described by Br€agger (1998; Br€agger et al. 2004). All images were analyzed by an independent investigator who was blind to the implant material. The implant length was used as a reference measurement, and the implant chamfer 0.2 mm above the implant shoulder was used as the reference line for the bone-level measurement. Bone level was, therefore, defined
Fig. 1. Panoramic radiograph 3 years after implant placement.
Survival and success
Surviving implants were those still in place after 36 months. Implant success was defined according to the definition by Buser et al. (1990), i.e., the absence of persistent subjective complaints (e.g., pain, foreign body sensation, dysesthesia), the absence of periimplant infection with suppuration, the absence of mobility, the absence of continuous peri-implant radiolucency, and possibility for restoration. Prosthetic success was
as the distance from the reference point to the first bone-to-implant contact (BIC); mesial and distal bone-level changes in this region were considered as remodeling. Mesial and distal measurements were recorded and the mean of these two values was used (Fig. 2). Soft tissue and safety assessments
Modified Plaque Index (mPI) and modified Sulcus Bleeding Index (mSBI), according to Mombelli et al. (1987), were assessed at four sites per implant (lingual, buccal, mesial and distal) at prosthesis placement and after 6, 12, 24 and 36 months. Safety evaluations included recording of all complications, adverse events (AEs), and serious adverse events (SAEs). Each AE and SAE was assessed for severity and its potential relationship to the study device. Statistical analyses
The analysis of the primary outcome variable, which was the bone-level change 12 months after implant placement (Al-Nawas et al. 2012), was based on a confirmatory non-inferiority test with a one-sided 97.5% confidence interval. The non-inferiority margin (D) for a clinically relevant difference was set at 0.1 (0.3) mm. For a sample size of at least 73, a paired ttest with a 0.025 one-sided significant level was calculated to have 80% power to reject the hypothesis that the test is inferior to the standard. To ensure robustness against deviations and to allow for possible dropouts, the calculated sample size for the primary endpoint was increased by 20% (15 patients) to give a total of 88 (73 + 15). Secondary efficacy variables included bone-level change, implant survival and success, prosthetic success, and soft tissue assessments up to 36 months. Bone-level change at 24 and 36 months was analyzed by means of the Student’s t-test, plaque and bleeding indices by means of the Wilcoxon signed rank test, while implant success and survival were analyzed by means of the McNemar’s test. Continuous data are presented in the form of means (standard deviations [SDs]). Hypothesis tests were performed at a two-sided significance level a of 5%. The intent-to-treat (ITT) population consisted of all randomized patients who received implants and who underwent at least one efficacy assessment.
Results Patients Fig. 2. X-ray measurement. (1) Chamfer to first mesial implant-to-bone contact, (2) chamfer to first distal implant-to-bone contact, (3) length of implant.
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Ninety-two patients were screened, of whom 91 were randomized and received implants (one patient was a screening failure). The ITT
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Quirynen et al RCT on implants made from Ti–Zr and Ti Grade IV
Table 1. Patient demographic data (intent-totreat population, 89 patients) N Gender Male 40 Female 49 Ethnicity Caucasian 89 Smoking status Non-smoker 67 Past smoker 17 Occasional smoker 1 Smoker 4 Current clinically relevant disease Yes 35 No 54
% 44.9 55.1 100.0 75.3 19.1 1.1 4.5 39.3 60.7
the 36-month follow-up (six were lost to follow-up, one had an AE unrelated to the study treatment, and one died). Recruitment began in October 2007 and the last 36-month follow-up occurred in September 2011. No methodological changes were made after commencement of the trial. The primary endpoint of the study was change in periimplant bone level after 12 months (previously reported; Al-Nawas et al. 2012), but the study was designed to assess secondary parameters for up to 36 months, after which the study ended. Implant survival and success
population included 89 patients (one patient had no efficacy data, and one patient had unknown treatment allocation). The mean age at implant surgery was 65.8 8.4 years. Patient demographic data are shown in Table 1. Of the 91 patients who received implants, 75 patients completed the 36-month follow-up (Fig. 3). Three patients dropped out before the 12-month follow-up (one withdrew consent after implant loss, one was lost to follow-up, and one died), five patients dropped out before the 24-month follow-up (four lost to follow-up, and one died), and another eight patients dropped out before
Three implants were lost between baseline and 12 months (all before Locator abutment connection), one in the Ti–Zr group and two in the Ti Grade IV group. No further implant losses occurred up to 36 months. The cumulative survival rates were 98.7% for Ti–Zr and 97.3% for Ti Grade IV, respectively, after 36 months (Table 2). There were no significant differences between the two implant types at any time point. One patient presented with peri-implant infection and suppuration after 12 months along both test and control implants; both implants were therefore considered unsuccessful at this time. At 24 months, no signs
of infection were apparent at the Ti Grade IV implant; the Ti–Zr implant however continued to show peri-implant infection and suppuration and was again considered unsuccessful. After 36 months, neither implant in this patient showed detectable peri-implant infection with suppuration; both implants were therefore considered successful at this stage. The cumulative success rates (Table 2) after 36 months were 98.7% for Ti–Zr and 97.3% for Ti Grade IV, respectively. Bone-level changes
The mean change in marginal bone level in the Ti–Zr group was 0.58 0.60 at 24 months, and 0.78 0.75 mm at 36 months. In the Ti Grade IV group, the mean change in marginal bone level was 0.57 0.63 at 24 months, and 0.60 0.71 mm at 36 months. There were no significant differences between the two implant types at any time point (Table 3). The strong overlapping of the 95% confidence intervals for the test and the control group at 24 months ( 0.72 to 0.45 and 0.72 to 0.42) and 36 months ( 0.96 to 0.60 and 0.77 to 0.43) confirm the results that no difference can be seen for both groups at the two time points. The crestal bone-level change after 36 months ranged from 3.6 to +0.1 mm in the Ti–Zr group, and from 2.7 to +0.6 mm in the Ti Grade IV group (Fig. 4). Soft tissue and safety assessments
Fig. 3. Patient flow diagram. One patient was a screening failure and was therefore not eligible for treatment.
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After 36 months, most patients had a mPI score of 0 or 1; there were no significant differences between the implant types at any time point (Table 4). Similarly, most patients showed a mSBI score of 0 at 36 months after surgery, with no significant differences between the groups at any time point (Table 4). Forty-seven patients (51.6%) experienced a total of 92 AEs within 3 years. The most frequent AEs were prosthesis fracture (nine cases), minor inflammation during the healing process at the implant site (five cases), moderate peri-implant infection (five cases), tactile horizontal or vertical implant mobility (five cases), loosening of a prosthetic component (three cases), prosthesis maintenance, i.e., repair of broken or lost matrix (three cases) and wisdom tooth removal (three cases). Of these 92 AEs in total, 28 (30.4%) were judged to be related to the study device. A total of 14 patients experienced 19 SAEs (four coronary/circulatory, four orthopedic, three oncologic, three systemic infection, two cognitive/psychological and three resulting in death); none of the SAEs were judged to be related to the study device.
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Quirynen et al RCT on implants made from Ti–Zr and Ti Grade IV
Table 2. Survival and success rates at 12, 24 and 36 months (intent-to-treat population, 89 titanium–zirconium (TiZr) and Ti Grade IV implants)
Up to 12 months Missing data (excluding failures)* Failed implants (0–12 months) Unsuccessful implants (excluding failures) Successful implants Survival (success) (%) P-value† survival (success) Up to 24 months Missing data (excluding failures)* Failed implants (0–24 months) Unsuccessful implants (excluding failures) Successful implants Survival (success) (%) P-value† survival (success) Up to 36 months Missing data (excluding failures)* Failed implants (0–36 months) Unsuccessful implants (excluding failures) Successful implants Survival (success) (%) P-value† survival (success) * †
Ti–Zr
Ti Grade IV
1 1 1 86 98.9 (97.7)
2 2 1 84 97.7 (96.6) 0.1573 (0.1573)
7 1 1 80 98.8 (97.6)
8 2 0 79 97.5 (97.5) 0.1573 (0.5637)
14 1 0 74 98.7 (98.7)
14 2 0 73 97.3 (97.3) 0.3173 (0.3173)
Missing data excluded from analysis. Results from McNemar’s test.
Table 3. Change in crestal bone level after 12, 24 and 36 months (intent-to-treat population; N and mean SD in mm) Ti–Zr 12 months N Mean SD P-value* 24 months N Mean SD 95% CI P-value* 36 months N Mean SD 95% CI P-value*
82 0.34 0.54
Ti Grade IV
N/A†
76 0.58 0.60 0.72 to 0.45
78 0.31
0.56
72 0.57 0.63 0.72 to 0.42 0.8627
69 0.78 0.75 0.96 to 0.60
67 0.60 0.71 0.77 to 0.43 0.1584
CI, confidence interval; Ti–Zr, titanium–zirconium. Some radiographs could not be evaluated, hence the differences in sample numbers. * Results from Student’s t-test. † The respective one-sided 97.5% confidence interval for the treatment difference was [ ∞, 0.0867] which confirmed the non-inferiority of Ti–Zr compared with Ti Grade IV after 12 months as the noninferiority margin of 0.1 is not part of the confidence interval (Al-Nawas et al. 2012).
Discussion This was a prospective, randomized, doubleblind, split-mouth study in which dental implants made of Ti–Zr alloy were compared to implants made of Ti Grade IV, both with the SLActiveâ surface. After 36 months, no significant differences in change in crestal bone level, clinical parameters or survival and success rates were evident between the groups, and the outcomes seen at 12 months continued over time, indicating that Ti–Zr in this clinical setting was similar to Ti Grade IV.
Reduced diameter implants can be an effective alternative to standard diameter implants in certain cases, and can expand the range of treatment options for both the clinician and the patient. Although most commonly used in cases where there is limited interdental space (e.g. narrow singletooth gaps) or edentulous ridges that are too narrow for standard diameter implants (Hallman 2001; Froum et al. 2007), the outcomes shown with these implants are promising. This may increase the acceptance of implant treatment by avoiding augmentation procedures (Pommer et al. 2011; Hof et al.
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
2014). However, some evidence indicates that implants with a smaller than standard diameter (e.g. 2 mm shown by only 4.8% of the implants (Hallman 2001). Very limited data is available for the usage of implants to support overdentures in the maxilla. While two implants are sufficient to support a mandibular overdenture, this could not be confirmed in the edentulous maxilla (Weng & Richter 2007) with a survival rate of 48.9%. More than two implants are recommended to support a maxillar overdenture, regardless of the loading protocol (Gallucci et al. 2009). The results of the current study support the one-year findings (Al-Nawas et al. 2012), which showed mean peri-implant bone loss of 0.34 0.54 and 0.31 0.56 mm for Ti–Zr and Ti Grade IV implants, respectively and demonstrated that Ti–Zr implants perform non-inferior to Ti Grade IV implants in regards of bone loss 12 months after implant placement. Another clinical study confirmed similar survival and success between Ti–Zr and Ti Grade IV implants. Similar bone loss was again observed 2 years after loading (overall mean bone loss 0.33 0.54 mm). Healthy peri-implant tissues were also noted (Barter et al. 2011). A more recent clinical trial evaluated 51 Ti–Zr implants in horizontally deficient edentulous ridges in 18 patients. In this study, the implants were loaded either immediately or delayed with either fixed or removable prostheses. The peri-implant bone resorption ranged from 0 to 1 mm after 2 years, survival and success was 100%, and no prosthetic complications occurred. The outcomes obtained in this challenging indication, i.e., occlusal loading in the lateral-posterior region, suggested that the new Ti–Zr implants can withstand high mechanical stresses (Chiapasco et al. 2012). Radiographic evaluations can provide evidence in peri-implant bone changes over time, either by intraoral periapical films (Lau-
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Quirynen et al RCT on implants made from Ti–Zr and Ti Grade IV
rell & Lundgren 2011) which has already become a standard method in dental implantology, or extraoral panoramic scans (Spiekermann et al. 1995). One limitation of both techniques is that marginal bone-level changes are only mesially and distally measurable. Panoramic radiographs were found to be a useful alternative to intraoral periapical films in the atrophic mandible for the evaluation of the marginal bone loss around implants as no difference was found between the two methods (Zechner et al. 2003). Therefore, in the present study, panoramic radiographs were used. Due to the multicentric nature of the study, the standardization of the panoramic x-rays was limited to the same settings at the baseline and follow-up visits. An important aspect of this study is the trial design. The trial utilizes a split-mouth design, which has been successfully used in implant dentistry (van Steenberghe et al. 2000; Roccuzzo et al. 2008; Fung et al. 2011; Cannizzaro et al. 2012) and which can reduce the risk of bias when appropriate statistical and scientific assumptions are met (AntczakBouckoms et al. 1990; Koch & Paquette 1997). In addition, the trial may potentially
be, to the authors’ knowledge, the only double-blind trial evaluating two implants. This was possible because the Ti–Zr and Ti Grade IV implants used in the study are visually identical, so that neither the patient nor the surgeon knew which implants were placed in which positions; this is normally not possible in clinical trials with different implants because of different implant designs, surface appearance or storage requirements. The key characteristics for high quality randomized controlled trials are blinding, concealment of treatment allocation, randomization and follow-up of the patients (Montenegro et al. 2002), all of which were a part of this study. The study was unblinded only after 12 months so that the primary endpoint outcomes could be analyzed. A recent review of the quality of reporting of RCTs in implant dentistry indicated that the overall quality is poor and that the risk of bias was higher with statistically significantly reported outcomes (Cairo et al. 2012). The Eighth European Workshop on Periodontology recommended that researchers performing clinical trials in implant dentistry should pay special attention to limiting potential bias in trial design (Tonetti & Palmer 2012). The authors believe
that the risk of treatment or clinician bias in this study was therefore minimized in comparison to other similar studies. In summary, this double-blind randomized controlled clinical trial confirmed that the similar outcomes with Ti–Zr and and the well-established Ti Grade IV 3.3 mm diameter SLActiveâ surface implants continue over time. Existing biomechanical and biocompatibility evidence showing greater fatigue strength and excellent osseointegration, together with the clinical outcomes, suggest that the narrow Ti–Zr implants may allow implant therapy in more challenging indications. Further clinical studies are recommended.
Acknowledgements: The trial was sponsored by Institut Straumann AG, Basel, Switzerland.
Conflict of interest The authors have no conflicts of interest to declare.
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Appendix The Roxolid Study Group Bilal Al-Nawas (Johannes-Gutenberg University, Mainz, Germany); Isabel Br€auer (University of Regensburg Clinic, Regensburg, Germany); Jose Castro-Laza (University of Regensburg Clinic, Regensburg, Germany); Henny JA Meijer (University Medical Center Groningen, University of Groningen, Groningen, the Netherlands); Frauke M€ uller (University of Geneva, Geneva, Switzerland); Ignace Naert (Catholic University Leuven, Leuven, Belgium); Alessandro Perrucchi (Cantonal Hospital Lucerne, Lucerne, Switzerland); Marc Quirynen (Catholic University Leuven, Leuven, Belgium); Gerry M Raghoebar (University Medical Center Groningen, University of Groningen, Groningen, the Netherlands); Amir Razavi (Cantonal Hospital Lucerne, Lucerne, Switzerland); Torsten Reichert (University of Regensburg Clinic, Regensburg, Germany); Eugenio Romeo (University of Milan Dental Clinic, Milan, Italy); Eric Santing (University Medical Center Groningen, University of Groningen, Groningen, the Netherlands); Martin Schimmel (University of Geneva, Geneva, Switzerland); Stefano Storelli (University of Milan Dental Clinic, Milan, Italy); Christiaan ten Bruggenkate (Academic Center for Dentistry Amsterdam, Amsterdam, the Netherlands); Betty Vandekerckhove (Catholic University Leuven, Leuven, Belgium); Wilfried Wagner (Johannes-Gutenberg University, Mainz, Germany); Daniel Wismeijer (Academic Center for Dentistry Amsterdam, Amsterdam, the Netherlands).
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