Eloana Thom e Hyung Joo Lee Ivete Aparecida de Mattias Sartori Roseli Latenek Trevisan Jaques Luiz Rodrigo Tiossi

A randomized controlled trial comparing interim acrylic prostheses with and without cast metal base for immediate loading of dental implants in the edentulous mandible

Authors’ affiliations: Eloana Thom e, Roseli Latenek Trevisan, Jaques Luiz, Department of Implantology, Latin American Institute of Dental Research and Education, Curitiba, PR, Brazil Hyung Joo Lee, Ivete Aparecida de Mattias Sartori, Department of Prosthodontics, Latin American Institute of Dental Research and Education, Curitiba, PR, Brazil Rodrigo Tiossi, Department of Prosthodontics (MOT), Fluminense Federal University, School of Dentistry, Niter oi, RJ, Brazil

Key words: edentulous mandible, immediate dental implant loading, implant stability,

Corresponding author: Ivete Aparecida de Mattias Sartori Latin American Institute of Dental Research and Education – ILAPEO, Rua Jacarezinho, 656 – Merc^es, Curitiba, Paran a 80710-150, Brazil Tel.: +55 41 3595 6000 Fax: +55 41 3597 6000 e-mail: [email protected]

implant-supported dental prosthesis, osseointegration Abstract Objectives: This randomized controlled trial used resonance frequency analysis (RFA) to assess the effects of the presence or absence of a cast rigid bar splinting multiple implants in the stability of immediately loaded implants. Material and Methods: Twenty-nine edentulous patients were randomly divided into two groups: G1 with full-arch implant-fixed prostheses and G2 with multiple implant splinting via acrylic resin denture bases. All implants were immediately loaded. RFA measurements assessed implant stability at three different times (T0 – at baseline, T1 – 4 months, and T2 – 8 months. Wilcoxon and Friedman tests and a multivariate model with repeated measures for longitudinal data were used for statistical comparison (a = 0.05). Results: Twenty-nine patients were assessed (G1 = 15 and G2 = 14). Implant and prostheses survival rates were 100% for both groups after the 8-month observation period and no significant differences in the mean ISQ values were found at the different implant stability assessment times (P > 0.05). Conclusions: The different splinting protocols did not appear to affect implant stability during the 8-month observation period.

Date: Accepted 24 July 2014 To cite this article: Thome E, Lee HJ, Sartori IAM, Trevisan RL, Luiz J, Tiossi R. A randomized controlled trial comparing interim acrylic prostheses with and without cast metal base for immediate loading of dental implants in the edentulous mandible. Clin. Oral Impl. Res. 00, 2014; 1–7. doi: 10.1111/clr.12470

A successful oral implant treatment depends on the combination between patient factors, treatment planning, surgical factors, type of prosthesis, and technical aspects of the implant restoration (Van de Velde et al. 2010). The immediate loading of dental implants placed in the edentulous mandible and maxilla, restored by a full-arch splinted fixed prosthesis, has shown successful outcomes (Malo et al. 2007; Meloni et al. 2010, 2012). Less morbidity associated with fewer surgical interventions and a simplified functional rehabilitation account for the selection of the immediate loading protocol (Cooper et al. 2002; Degidi & Piattelli 2005). Primary stability is considered one of the most important parameters to immediately load an implant and is an important requirement for the long-term success of dental implants (Degidi & Piattelli 2005; Esposito et al. 2009; Makary et al. 2011). Other important factors include bone quality, macro- and

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

micro-interlock properties of the implant, bicortical initial stabilization, number and optimal distribution of implants, and careful use of cantilevers (Sertgoz & Guvener 1996; Degidi & Piattelli 2005). Several methods are available to assess primary stability, such as the cutting resistance of the implant during its insertion and percussion tests. However, these methods can only yield poor qualitative information at best (Sennerby & Meredith 2008). Measurement of the insertion torque during implant installation using manual torque ratchets can also be used to determine primary implant stability (Sennerby & Meredith 2008). Resonance frequency analysis (RFA) is a noninvasive test, extensively used in both clinical and experimental research for the last 15 years (Meredith 1998; Aparicio et al. 2006; Sennerby & Meredith 2008). Initially, it used kilohertz in a range from 3500 to 8500 kHz as units of measurement; soon after, the

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implant stability quotient (ISQ) was developed, converting kHz units to ISQ values on a scale of 1–100 (Quesada-Garcia et al. 2009). Higher values indicate higher stability and are considered a reliable indication to immediately load an implant (Quesada-Garcia et al. 2009; Markovic et al. 2011). The prosthetic restoration and the transmission of the masticatory loads to the supporting structures also are important factors when deciding to immediately load the implants (Skalak 1983). Splinting multiple implants together with a passive fitting prosthesis can limit the micromotion at the bone-implant interface. Stabilizing the implants at initial placement and limiting micromovement to no more than 100 lm can contribute to successful osseointegration (Cameron et al. 1973; Brunski 1992; Tarnow et al. 1997). The rigid splinting of the implants by a cast metal bar to support a fullarch implant-fixed prosthesis has shown successful outcomes (Degidi et al. 2009; Melo et al. 2009; Borges et al. 2010). The temporary initial semi-rigid splinting of mandibular implants without the presence of cast rigid bars (via the acrylic resin denture base) was proposed with the attempt to simplify the immediate loading protocol and found promising results (Lazzara et al. 2004; Lee et al. 2012). Immediate implant loading with a provisional restoration has been proposed as a simpler, more predictable, less expensive, and less time-consuming method (Crespi et al. 2012). The use of prefabricated components allows easy prosthetic procedures for prosthesis conversion shortly after implant surgery (Misch 2004; Lee et al. 2012). An earlier study found that the semi-rigid splinting promotes better passivity to the implant restoration because of the absence of a cast metal framework, with the resulting stresses in the implant-surrounding bone within acceptable thresholds to avoid bone resorption (Teixeira et al. 2010; Lee et al. 2012). Also, beneficial small accommodations of the implant position can occur due to small movements allowed by the absence of a rigid cast framework (Gapski et al. 2003). This randomized controlled trial used RFA to assess the effects of the presence or absence of a rigid bar splinting multiple implants in the stability of immediately loaded implant fixtures. The ISQ values were assessed immediately, 4-, and 8-months after implant placement. The tested null hypothesis was that there would be no significant differences in the ISQ values with or without the presence of a cast rigid bar supporting a full-arch implant-fixed prosthesis.

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Material and methods The trial protocol for this study was approved by the ethics committee of the Pontifıcia Universidade Cat olica do Paran a (CONEP protocol numbers 04890084-08 and 000339409). This study includes data from an initial study that evaluated the same parameters in 15 patients (Lee et al. 2012). This article reports the results from a randomized trial with two parallel arms that compared the rigid and semi-rigid splinting of immediately loaded implants in fully edentulous mandible. All patients included in this study were fully edentulous. The trial participants were enrolled from October 2008 to January 2010. The criteria for inclusion in the study were: good overall health, adequate thickness in the anterior region of the mandible for implant placement, and an interforaminal distance to allow the placement of five implants to support a distal extension of the cantilever beyond the mental foramina with a minimum of 14 mm and a maximum of 18 mm in length (Sertgoz & Guvener 1996; Fazi et al. 2011; Lee et al. 2012). Noncompensated diabetic patients, patients with immunodeficiencies, patients who had used bisphosphonate drugs or received any radiation treatment in the last 5 years, and smokers were excluded from the study. The patients were informed about the evidence-based, positive outcome of implant treatment, the experimental approach of immediate loading (Van de Velde et al. 2010), and semi-rigid splinting of the implants (Lee et al. 2012). All patients gave their informed and written consent. All patients underwent clinical and radiographic examination (panoramic and cephalometry of the facial profile). All patients were rehabilitated with full-arch implant-fixed prostheses (FPs) and were randomly divided in 2 groups. Group 1 had a conventional cast rigid bar framework splinting the implants and group 2 had a semi-rigid cantilever extension system with titanium bars placed at the two distal abutment cylinders (Fig. 1) (Lee et al. 2012). Treatment allocation is summarized in Fig. 2 in accordance with the Consolidated Standards of Reporting Trials (CONSORT) criteria (Appendix S1). The patients were treated at the Latin American Institute of Dental Research and Education (ILAPEO) and were randomly assigned to receive interim acrylic prostheses with or without a cast metal base. The groups were further divided according to design parameters (Fig. 2). A computer-generated random number table was created to

Fig. 1. Hybrid prosthesis fabricated for the patients from group 1 with a cast rigid bar splinting the implants.

facilitate patient allocation. A researcher not involved with other parts of the trial prepared and secured the random numbers that were placed in sealed, opaque envelopes. The surgical procedures for implant placement and the fabrication and prostheses placement were standardized for all patients in both groups. Threaded implants (Titamax, Neodent, Curitiba, PR, Brazil) were placed from 3.5 to 5 mm anterior to the foramen mentalis and 1–2 mm subcrestal. Two implant diameters (3.75 and 4.0 mm) were used based on the availability of local bone. An insertion torque of at least 45 Ncm was checked before immediately loading the implants (Szmukler-Moncler et al. 2000; Drago & Lazzara 2006). Singlepiece prosthetic abutments for screw-retained prostheses were later tightened to the implants (Mini conical abutments, Neodent). The patients were randomly assigned after implant placement and after the implant position transfer impression to ensure similar surgical and impression procedures for both groups. The implants were loaded within 72 h according to the immediate loading protocol. RFA measurements assessed the implant stability according to recommendations from the manufacturer of the RFA device (OsstellTM, Osstell, Gothenburg, Sweden). A transducer (SmartPeg, Osstell) was attached to the prosthetic abutments, and a probe connected to the frequency response analyzer was used to measure implant stability. The measurements were performed at 3 different times (T0 – at baseline, T1 – 4 months after implant placement, and T2 – 8 months after implant placement) on the buccal and proximal surfaces of the prosthetic abutments installed on the implants. The RFA measurements were performed by a blinded researcher after prosthesis removal by a different researcher. A previously published technique (Borges et al. 2010) was used to fabricate the FPs in

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Thome et al  Interim acrylic prostheses for immediate implant loading

Fig. 2. Patient screening, recruitment, and allocation chart according to the Consolidated Standards of Reporting Trials (CONSORT) criteria.

group 1. The cast framework was waxed over a dimensionally larger brass cylinder and cast. The cast framework was then cemented to a smaller titanium cylinder using resin cement (Panavia F, Kuraray Co., Ltd, Tokyo, Japan). The titanium cylinders with smaller dimensions than the brass cylinders are used to compensate for the shrinkage of the alloy after casting, aiming to provide frameworks with better passive fit (Borges et al. 2010). An example of the restoration that was fabricated for group 1 is presented in Figs 1, 3, and 4. The semi-rigid splinting of the implants in group 2 used a distal cantilever extension system with a titanium bar located at the 2 most distal implants (implant #s 1 and 5) (Fig. 5). The remaining titanium

cylinders were connected between each other and to the distal cylinders by the acrylic resin denture base (Fig. 6; Lee et al. 2012). Titanium excesses from the cylinders were sawed off using ultra-thin carborundum separating disks (Dentorium Products Co. Inc., Farmingdale, NY, USA). Patients from both groups received hybrid prostheses fabricated with a combination of each mentioned techniques and acrylic resin denture base and teeth (Testori et al. 2003). The FPs were extended to the lower first molar and the antagonist maxillary complete dentures (CDs) CDs were extended to the upper second molar. To avoid using different acrylic resin for each group in the study, an impression of the abutments was made for the

Fig. 3. Final aspect of a patient treated for group 1.

Fig. 4. Panoramic X-ray of a patient from the group with the cast metal bar splinting the implants.

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

patients from group 2, and the cylinders were connected at the laboratory. Panoramic and intraoral radiographs were taken after prosthesis placement to check the prosthesis fit with the abutments (Fig. 7). Occlusal adjustments were performed after the installation of the FPs, and all patients were instructed for adequate hygiene. All patients presented removable maxillary CDs that were all renewed. Most of the maxillary CDs presented worn acrylic teeth and inadequate occlusal relation because of the long time elapsed since their fabrication. Two patients complained about the esthetic appearance of their CDs and were also provided with new CDs. The mean ISQ values at the different measured times were calculated and used for the comparison between groups. The Shapiro– Wilk test was used to check for normal distribution of data. A multivariate model with repeated measures for longitudinal data was used to analyze each implant within the same patient and through each time point. Nonparametric tests were performed for the other comparisons. Wilcoxon test was performed for the same implant comparison between different groups and within same stability measurement times. Friedman test was performed for the comparison between different implants within the same group and same measurement time (a = 0.05). The mean ISQ value found in the pilot study for group 1 at T0 was 70.67 (SD = 3.96; Lee et al. 2012). It is not recommended to immediately load the implant when a mean ISQ value lower than 60 is present (Sennerby & Meredith 2008). This clinically relevant difference was considered for sample size calculation. The necessary sample size to obtain a power of 95% with a significance level of 5% was therefore 10 patients for each group (Effect size f = 1.78).

Results To account for possible exclusions or voluntary dropouts, this study selected a total of 29 patients (22 females and 7 males), aged between 42 and 80 years. Each patient had 5 implants installed in the anterior interforaminal region of the mandible to a total of 145 implants (Titamax, Neodent) that were placed and immediately loaded. The results for the 2 groups in the different measurement times are presented in Tables 1 and 2. Wilcoxon statistical test found no significant differences in the mean ISQ values for each implant between the different groups

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loosen or fractured screws, prosthesis detachment, and fractured abutments or implants were found in this study. No biological complications (peri-implant mucositis or peri-implantitis) were found during maintenance.

Discussion Fig. 5. Titanium cylinders used for the semi-rigid splinting technique.

Fig. 6. Final aspect of a patient treated for the group with acrylic resin splinting the implants.

Fig. 7. Panoramic X-ray of a patient from the group with acrylic resin splinting the implants.

and stability assessment times (P > 0.05) (Table 1). When each implant position within the same group and measurement time was compared, implant #1 was significantly different from implant #4 in group 1 at baseline (T0) (Friedman test; P = 0.0059) (Table 1). No significant differences were found between the other implant positions for the other groups and measurement times (P > 0.05) (Table 1). A multivariate model with repeated measures for longitudinal data was used to analyze each implant within the same patient and through each time point – again, no significant differences were found (P > 0.05) (Table 2). The implant success rate at the 4- and 8-month follow-up was 100%. No implant mobility was found for both groups. None of the 29 FPs were lost at the 4- nor at the 8-months follow-up. No technical or mechanical complications such as fracture of the acrylic teeth or denture base,

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The results found in this study support acceptance of the tested null hypothesis as no significant differences in the mean ISQ values were found in the groups that were tested. The presence or absence of a cast rigid bar to support a full-arch implant-fixed prosthesis had no influence in the mean ISQ values 4- and 8-months after immediately loading the implants. This is in agreement with previous studies that used full-arch fixed provisional acrylic resin prostheses for immediately loading dental implants and found reliable outcomes in the short- and midterm (Antoun et al. 2012; Crespi et al. 2012; Lee et al. 2012). A previous systematic review and meta-analysis on the effect of immediate implant loading with fixed prosthesis (Papaspyridakos et al. 2014) also reported that when carefully selected cases associated with rough surface implants are immediately loaded, the implant and prosthesis survival and failure rates are similar with early and conventionally loaded implants. The same systematic review found a recommended minimum insertion torque of 30 Ncm and an estimated 1-year implant survival above 99% for all 3 loading protocols (immediate, early, and conventional) (Papaspyridakos et al. 2014). The primary stability of a dental implant is considered an important parameter when deciding for immediate loading (Ericsson et al. 2000; Horiuchi et al. 2000; Hruska et al. 2002; Degidi & Piattelli 2005). The surgical technique used in this study was controlled to achieve the recommended implant insertion torque for immediate loading (Fanuscu et al. 2007; Akca et al. 2010). The insertion torque was checked, and the implants were loaded when at least 45 Ncm insertion torque was present – when lower than 45 Ncm, the 3.75-mm diameter implant was replaced by a 4.0-mm diameter implant (Szmukler-Moncler et al. 2000; Drago & Lazzara 2006). RFA was also performed after implant placement to decide whether or not immediately load the implant. It is indicated to immediately load an implant when an ISQ higher than 60 is present (Sennerby & Meredith 2008). All implants placed for this study presented an insertion torque higher than

45 Ncm and an ISQ higher than 60 and were all subjected to immediate loading. Resonance frequency analysis is a noninvasive method capable of predicting and preventing implant loss (Glauser et al. 2004; Atsumi et al. 2007). It can detect changes at the bone-implant interface during the healing period (Pattijn et al. 2006), indicate the failure risk of an implant (Friberg et al. 1999; Sjostrom et al. 2007), and it seems feasible to monitor the stability of an implant in the initial healing period (Bornstein et al. 2009). A previous study suggested that an ISQ higher than 65 indicates a successful implant whereas an ISQ lower than 50 indicates a potential risk of implant failure (Bornstein et al. 2009). Other studies (Balleri et al. 2002; Sjostrom et al. 2007; Sennerby & Meredith 2008) stated that an ISQ between 55 and 85 characterizes the stability of a fully osseointegrated implant. The mean ISQ values for the groups in this study ranged from 66.89 to 70.08. This indicates that immediately loading the implants placed for this study was recommended and that all implants presented ISQ values of fully osseointegrated implants at the 4- and 8-month follow-ups. Longitudinal studies found that ISQ values remain stable after osseointegration (Friberg et al. 1999; Balshi et al. 2005). The rigid splinting of multiple implants together by hybrid prosthesis with a cast metal framework to stabilize the implants can contribute to successful osseointegration by minimizing implant micromotion (Cameron et al. 1973; Brunski 1992; Tarnow et al. 1997; Degidi & Piattelli 2005). A passive fitting prosthesis is recommended to limit implant micromotion within 100 lm for successful outcomes (Tarnow et al. 1997). Recent studies evaluated the splinting of multiple implants using acrylic resin, and the results suggested that it would not interfere with the 3- to 4-month healing period for implant osseointegration (Misch 2004; Antoun et al. 2012; Crespi et al. 2012; Lee et al. 2012). The conversion of the patient’s satisfactory existing denture to a screw-retained implantfixed prosthesis was described to splint implants together using acrylic resin denture base and enables the clinician to deliver the prosthesis in a few hours (Misch 2004). Another advantage of the provisional acrylic prosthesis is that the laboratory technician is not able to dedicate time to only 1 case over the course of 1 or 2 days (Misch 2004). Also, the patient can wear and evaluate the appearance, speech, and comfort of the prosthesis and ask for changes in the final prosthesis to

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Thome et al  Interim acrylic prostheses for immediate implant loading

Table 1. ISQ median results, standard deviation (SD), and statistical comparison between groups, implants, and measurement times Groups (Time) Group 1 (T0)

Group 2 (T0)

Group 1 (T4)

Group 2 (T4)

Group 1 (T8)

Group 2 (T8)

Implant #1 Median  SD

Implant #2 Median  SD

Implant #3 Median  SD

Implant #4 Median  SD

Implant #5 Median  SD

68  3.41 A (P = 0.7421) a (P = 0.0059) 68  3.62 A (P = 0.7421) a (P = 0.0592) 68  3.14 A (P = 0.1955) a (P = 0.7482) 70  6.41 A (P = 0.1955) a (P = 0.7843) 69  2.64 A (P = 0.3931) a (P = 0.9783) 70  5.66 A (P = 0.3931) a (P = 0.0817)

69.50  3.98 A (P = 0.8784) ab (P = 0.0059) 68.25  4.92 A (P = 0.8784) a (P = 0.0592) 69  4.08 A (P = 0.1552) a (P = 0.7482) 71.50  3.92 A (P = 0.1552) a (P = 0.7843) 69  4.06 A (P = 0.0217) a (P = 0.9783) 72  4.11 A (P = 0.0217) a (P = 0.0817)

70  3.92 A (P = 0.6935) ab (P = 0.0059) 69.75  5.86 A (P = 0.6935) a (P = 0.0592) 70  2.93 A (P = 0.7253) a (P = 0.7482) 70.25  2.67 A (P = 0.7253) a (P = 0.7843) 69.50  3.36 A (P = 0.7261) a (P = 0.9783) 69.75  4.29 A (P = 0.7261) a (P = 0.0817)

71.50  2.70 A (P = 0.3238) b (P = 0.0059) 70.25  7.43 A (P = 0.3238) a (P = 0.0592) 70  2.95 A (P = 0.6141) a (P = 0.7482) 72.25  3.34 A (P = 0.6141) a (P = 0.7843) 69.60  3.90 A (P = 0.2745) a (P = 0.9783) 71  3.41 A (P = 0.2745) a (P = 0.0817)

69.50  4.54 A (P = 0.3643) ab (P = 0.0059) 71  5.06 A (P = 0.3643) a (P = 0.0592) 69  3.62 A (P = 0.0602) a (P = 0.7482) 71.75  4.61 A (P = 0.0602) a (P = 0.7843) 69  4.13 A (P = 0.4937) a (P = 0.9783) 70.50  2.81 A (P = 0.4937) a (P = 0.0817)

Upper case letters indicate Wilcoxon test results for the same implant comparison between different groups within same stability measurement times; lower case letters indicate Friedman test results for the comparison between different implants and within the same group and same measurement time. Different letters indicate significant differences between comparisons (P < 0.05).

Table 2. ISQ mean results, standard deviation (SD), and statistical comparison between each implant in the different measurement times Groups (Time) Group 1 (T0) Group 1 (T4) Group 1 (T8) Group 2 (T0) Group 2 (T4) Group 2 (T8)

Implant #1 Mean  SD

Implant #2 Mean  SD

Implant #3 Mean  SD

Implant #4 Mean  SD

Implant #5 Mean  SD

67.88  3.41 A (P = 0.9705) 68.14  3.14 A (P = 0.9705) 68.69  2.64 A (P = 0.9705) 67.72  3.62 A (P = 0.9705) 68.29  6.41 A (P = 0.9705) 68.84  5.66 A (P = 0.9705)

69.27  3.98 A (P = 0.1633) 69.00  4.08 A (P = 0.1633) 68.40  4.06 A (P = 0.1633) 69.29  4.92 A (P = 0.1633) 70.75  3.92 A (P = 0.1633) 71.82  4.11 A (P = 0.1633)

69.43  3.92 A (P = 0.5254) 70.20  2.93 A (P = 0.5254) 69.73  3.36 A (P = 0.5254) 70.89  5.86 A (P = 0.5254) 70.79  2.67 A (P = 0.5254) 69.82  4.29 A (P = 0.5254)

72.00  2.70 A (P = 0.8540) 70.57  2.95 A (P = 0.8540) 68.84  3.91 A (P = 0.8540) 69.32  7.43 A (P = 0.8540) 71.07  3.34 A (P = 0.8540) 70.36  3.41 A (P = 0.8540)

69.90  4.54 A (P = 0.2373) 68.87  3.62 A (P = 0.2373) 69.77  4.13 A (P = 0.2373) 71.64  5.06 A (P = 0.2373) 71.07  4.61 A (P = 0.2373) 70.29  2.81 A (P = 0.2373)

Within columns, upper case letters indicate multivariate model with repeated measures for longitudinal data test results for the comparison of each implant in the different implant stability assessment times for each group. Matching letters indicate nonsignificant differences between comparisons.

be placed after the healing period (Misch 2004). The conversion of the patient’s denture can be performed chair-side or the clinician can choose to make an impression of the abutments and have the laboratory convert the denture on a master cast (Becker et al. 2003; Misch 2004). In the present study, the patients from group 1 received new hybrid full-arch fixed prosthesis with a cast metal bar, and the patients from group 2 received new screw-retained full-arch implant-fixed prosthesis without the cast metal bar. The acrylic resin denture base therefore splinted the implants on patients from group 2. However, despite acrylic resin being considered a semi-rigid material, the prostheses without the cast metal bar still were rigid enough to not have a negative effect on the implant stability, which is supported by the results found in this study.

The implants placed for this study were 3.75 or 4.0 mm wide and varied from 8 to 15 mm in length. The bone quality and patient’s gender also varied among the patients selected for the present study. Implant size, bone quality, patient’s gender, and age could influence the stability of an implant (Balshi et al. 2005). However, with the exception of group 1 at baseline, this study found no significant differences between the different implant positions when the groups and stability assessment times were compared. This is in agreement with a previous study (Yamaguchi et al. 2008) that found no significant differences in the stability of implants placed in different mandibular sites. The implants that were significantly different between each other at baseline (G1, implant #s 1 and 4), presented similar ISQ mean results at the other stability assessment times

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(after 4- and 8-months). It has been previously found that mandibular implants present statistically higher stability values compared to maxillary implants (Liaje et al. 2012). No correlation between the size and the stability of the implants was reported (Balleri et al. 2002; Liaje et al. 2012). It can be speculated that as bone-implant contact is established at the marginal level, composed mainly of dense bone, with implant firmly in place, a 2-mm distinction in length in the apical portion of the implant would not result in a significant change in support (Valderrama et al. 2007; Liaje et al. 2012), therefore resulting in similar implant stability. This is in agreement with the results found in this study. The size of the implants and bone quality are considered important factors for the initial implant stability, but the ISQ values are comparable after 1 year (Friberg et al. 1999).

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After a 10-year follow-up, no significant differences in implant stability among mandibular sides, sites, and gender were found for the stability of 328 implants (Yamaguchi et al. 2008). A previous report (Wagenberg et al. 2013) found that patients below the age of 50 experience significantly more bone loss compared to older patients. Postmenopausal women were found to present lower ISQ values compared to men of the same age. This

could have affected the outcome of this study and could be considered in future studies. Different genders were previously found to not significantly influence implant stability (Liaje et al. 2012) nor were identified as a risk factor for implant longevity (Snauwaert et al. 2000). In conclusion, the results suggest that the different splinting protocols did not appear to affect implant stability during the healing

Acknowledgements: The authors wish to thank Neodent (Curitiba, PR, Brazil) for supplying the implants and implant components.

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Supporting Information Additional Supporting Information may be found in the online version of this article: Appendix S1. CONSORT 2010 checklist of information to include when reporting a randomised trial.

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A randomized controlled trial comparing interim acrylic prostheses with and without cast metal base for immediate loading of dental implants in the edentulous mandible.

This randomized controlled trial used resonance frequency analysis (RFA) to assess the effects of the presence or absence of a cast rigid bar splintin...
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