The International Journal of Oral & Maxillofacial Implants, 02/2017

Purpose: The purpose of this study was to evaluate stress distribution around two craniofacial implants in an auricular prosthesis according to the removal forces. Three attachment combinations were used to evaluate the stress distribution under removal forces of 45 and 90 degrees. Materials and Methods: Three attachment designs were examined: (1) a Hader bar with three clips; (2) a Hader bar with one clip and two extracoronal resilient attachments (ERAs); and (3) a Hader bar with one clip and two Locators. The removal force was determined by means of an Instron universal testing machine with a crosshead speed of 10 mm/ minute. All three designs were created in three dimensions using SolidWorks. The applied removal force and the models were then introduced to finite element software to analyze the stress distribution. Results: The angle of removal force greatly affected the magnitude and direction of stress distribution on the implants. The magnitude of stress under the 45-degree removal force was higher than the stress at 90 degrees. The combination of the 1,000-g retention clip and 2,268-g retention Locator exhibited the highest stress on the implant flange when the removal force was applied at 45 degrees. Conclusion: The removal angle greatly influences the amount of force and stress on the implants. Prosthodontists are encouraged to inform patients to remove the prosthesis at 90 degrees and, if possible, use a low-retentive attachment to reduce stress. Keywords: finite element method, implant-retained auricular prostheses, removal force, stress

Purpose: To examine the effect of different torque application techniques (torqued, retorqued once, and retorqued twice) on the removal torque of implant-supported fixed complete dental prostheses. Materials and Methods: Four Nobel Biocare implants (4.3 × 13 + 3; 13-mm thread height + 3-mm collar height) were stabilized temporarily inside four holes made in an acrylic mandibular master model. A metal framework was constructed, casted, and finished using a standardized technique. A passively fitting framework was achieved by removing the implants from the acrylic master model and hand-screwing them to the metal framework. Then, the whole assembly was restabilized in the acrylic master model. The torque experiment consisted of three protocols: (1) torquing screws to 35 Ncm a single time; (2) torquing the screws to 35 Ncm and then immediately retorquing the same screws to the same value; and (3) torquing the same screws to 35 Ncm three consecutive times. Removal torque was recorded for each implant using a digital torque meter. Results: The highest torque value was recorded for the retorqued-once application technique (29.5 ± 1.5 Ncm); next was the torqued technique (27.9 ± 0.7 Ncm); and, last was the retorqued-twice technique (27.2 ± 1.6 Ncm). The Games- Howell post hoc test showed that the retorqued-once application technique resulted in significantly higher torque values than the torqued and retorqued-twice torque application techniques (P ≤ .05). Conclusion: Retightening abutment screws once after the initial torquing could enhance the removal torque of the screw. Care must be taken when retorquing the screws more than once, as this may inversely affect the removal torque. Keywords: dental implant, preload, removal torque, screw loosening, torquing technique

Purpose: The aim of this study was to evaluate the influence of implant macrodesign when using different types of collar and thread designs on stress/strain distributions in a maxillary bone site. Materials and Methods: Six groups were obtained from the combination of two collar designs (smooth and microthread) and three thread shapes (square, trapezoidal, and triangular) in external hexagon implants (4 × 10 mm) supporting a single zirconia crown in the maxillary first molar region. A 200-N axial occlusal load was applied to the crown, and measurements were made of the von Mises stress (σ_vM) for the implant, and tensile stress (σ_max), shear stress (τ_max), and strain (ε_max) for the surrounding bone using tridimensional finite element analysis. The main effects of each level of the two factors investigated (collar and thread designs) were evaluated by one-way analysis of variance (ANOVA) at a 5% significance level. Results: Collar design was the main factor of influence on von Mises stress in the implant and stresses/strain in the cortical bone, while thread design was the main factor of influence on stresses in the trabecular bone (P .05). The optimal collar design able to produce more favorable stress/strain distribution was the microthreaded design for the cortical bone. For the trabecular bone, the triangular thread shape had the lowest stresses and strain values among the square and trapezoidal implants. Conclusion: Stress/strain distribution patterns were influenced by collar design in the implant and cortical bone, and by thread design in the trabecular bone. Microthreads and triangular thread-shape designs presented improved biomechanical behavior in posterior maxillary bone when compared with the smooth collar design and trapezoidal and square-shaped threads.

Purpose: The use of biologic agents is emerging in bone regeneration procedures due to their ability to increase cellular events in wound healing and therefore to obtain more predictable outcomes. Hence, the aim of the present study was to critically evaluate the methodology of systematic reviews investigating biologic agents in promoting bone formation and implant site development. Materials and Methods: A literature search for systematic reviews with and without meta-analyses was performed in Medline, Embase, and the Cochrane database, as well as in journals with high impact factors in periodontics and implant dentistry. Titles, abstracts, and full-text articles were analyzed for potential inclusion. Three guidelines-AMSTAR, R-AMSTAR, and the checklist proposed by Glenny et al-were utilized to analyze their methodologic quality. Two calibrated reviewers performed all data extraction and appraisal. Cohen's kappa coefficients were calculated to appraise the interexaminer agreement. Results: A total of 12 systematic reviews, 3 with meta-analyses, were evaluated. Platelet-rich derivatives and BMP-2 were the most widely studied biologic agents and sinus augmentation was the most common procedure evaluated. The R-AMSTAR mean score was 28 (range 14-38) and none of the systematic reviews analyzed met all of the items. In the AMSTAR checklist, the mean score was 5.75 (range 2-9) and the only item met by all the systematic reviews was the a priori design. The Glenny et al checklist mean score was 8.6 (range 4-13) and two items, "focused question" and "to identify all relevant studies," were met by all systematic reviews. Conclusion: Systematic reviews on biologic agents to promote bone formation at implant site development demonstrate substantial methodologic variability. Therefore, caution must be exercised when interpreting their findings. Keywords: alveolar bone loss, bias, bone regeneration, dental implants, evidence-based dentistry, literature review

Purpose: To investigate the effect of coating a titanium implant surface with a phosphorylated exopolysaccharide, pullulan, on the peri-implant bone formation and implant osseointegration. Materials and Methods: Implants were placed in the skull bone of 12 domestic pigs and healed for 1 or 3 months. Osseointegration of (un)coated implants was evaluated by quantitative histology (peri-implant bone fraction [BF] and bone-to-implant-contact [BIC]). The Wilcoxon-Mann-Whitney test with α = .05 was used to statistically compare BF and BIC of the coated and uncoated implants. Results: Significantly more BF was observed surrounding pullulan-coated implants compared with uncoated implants (P .05) and for both healing periods (P .05). BIC was positively affected by the exopolysaccharide coating, with significantly more BIC after the 3-month healing period compared with the uncoated implant (P .05). Furthermore, BIC remained stable over time for the coated implants, while it significantly decreased for the uncoated ones (P .05). Conclusion: These findings reveal the capacity of functionalizing the titanium implant surface with phosphorylated pullulan to improve the mineralization of the implant-bone interface. Keywords: bone, organic coating, osseointegration, pullulan, titanium implant

Purpose: To systematically appraise the effectiveness/reliability of vertical ridge augmentation (VRA) in the atrophic mandible. Articles that addressed any one of the following four areas were included in this study: amount of VRA, implant survival (ISR) and success rates (SSR) in the area of newly regenerated bone, complication rate during the bone augmentation procedure, and bone resorption. Materials and Methods: An electronic literature search was conducted by two independent reviewers in several databases, including MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Cochrane Oral Health Group Trials Register databases for articles reporting VRA in the atrophic mandible via distraction osteogenesis (DO), inlay block grafting (IBG), onlay block grafting (OBG), and guided bone regeneration (GBR). For meta-analysis, two primary (VRA and ISR [%]) and two secondary outcomes were studied (SSR [%] and vertical bone resorption [VBR] [%}). Additionally, for qualitative assessment, complications (ie, causes of failure) were further extracted and comprehensively described. Results: Overall, 73 full-text papers were evaluated. Of these, 52 articles fulfilled the inclusion criteria. The weight mean (WM) of VRA (± SD) was 4.49 ± 0.33 mm (95% CI: 3.85 to 5.14 mm). It was most notable that DO involved greater VRA than IBG, and thus, significantly higher than GBR and OBG. The technique significantly influenced the mean VRA obtained (P .001). Nonetheless, no technique showed superiority in terms of ISR or SSR. VBR and complications were shown to be minimized for GBR. Conclusion: If ~ 4 mm of VRA is needed, any technique in optimum local and systemic conditions should be equally reliable in the atrophic mandible. However, when greater VRA is needed, DO and IBG have demonstrated accuracy. By means of complication and VBR rates, GBR was shown to have the lowest. For ISR and SSR, no statistical differences existed among all techniques. Controlled studies are needed to examine the long-term peri-implant bone fate and the frequency of biologic complications in each technique applied for the vertical augmentation of the atrophied mandible. Keywords: alveolar bone, bone, dental implant, endosseous implant, evidence-based dentistry, trabecular

Purpose: To compare the three-dimensional (3D) accuracy of conventional impressions (CIs) with digital scans (DSs) using an intraoral scanner (IOS) with intraoral scan bodies (SBs) and varying buccolingual interimplant angulations. A secondary aim was to measure the SB machining tolerance and height with and without application of torque. Materials and Methods: Three master models (MMs) with two implants simulating an implant-supported three-unit fixed partial denture for bone-level implants were used. The implants had buccolingual interimplant angulations of 0, 10, and 20 degrees. Test models for the CI test groups were made with impression copings and polyether impressions. SBs were attached to the MMs, tightened to 15-Ncm torque, and scanned by an IOS for the DS test groups (six test groups, n = 5). A coordinate measuring machine measured linear distortions (dx, dy, dz), 3D distortions (dR), angular distortions (dϴx, dϴy), and absolute angular distortions (Absdϴx, Absdϴy) of the physical CI test models and STL files of the DS virtual models relative to the MMs. Metrology software allowed both physical and virtual measurement of geometric targets that were comparable and allowed computation of relative displacements of implant centroids and axes. Results: Mean dR ranged from 31 ± 14.2 to 45 ± 3.4 μm for DS and 18 ± 8.4 to 36 ± 6.5 μm for the CI test groups. Mean Absdϴx ranged from 0.041 ± 0.0318 to 0.794 ± 0.2739 degrees for DS and 0.073 ± 0.0618 to 0.545 ± 0.0615 degrees for the CI test groups. Mean Absdϴy ranged from 0.075 ± 0.0615 to 0.111 ± 0.0639 degrees for DS and 0.106 ± 0.0773 to 0.195 ± 0.1317 degrees for the CI test groups. Two-way analysis of variance showed that the impression technique (P = .012) and implant angulations (P = .007) had a significant effect on dR. Distortions were mostly in the negative direction for DS test groups. Perfect coaxiality of the SB with the implant was never achieved. For SB to implant machining tolerances, the mean absolute horizontal displacement ranged from 4 ± 1.2 to 7 ± 2.3 μm. The SB dz was -5 ± 3.2 μm, which increased in the negative direction to -11 ± 4.9 μm with torque application (P = .002). Conclusion: Distortions were found for both DS and CI test groups. The best accuracy was obtained with CIs for parallel implants. With angulated implants, conventional and DSs were not significantly different. Excessive torque application that causes negative dz for SB fit would position the virtual implant at a deeper location compared with reality, resulting in possible framework misfit.

Purpose: The prevalence of peri-implant infection in patients with dental implants has been shown to range from 28% to 56%. A nanotube-modified implant surface can deliver antibiotics locally and suppress periodontal pathogenic bacterial growth. The aim of this study was to evaluate the deliverability of antibiotics via a nanotube-modified implant. Materials and Methods: Dental implants with a nanotube surface were fabricated and loaded with doxycycline. Afterward, each dental implant with a nanotube surface was placed into 2-mL tubes, removed from solution, and placed in a fresh solution daily for 28 days. Experimental samples from 1, 2, 4, 16, 24, and 28 days were used for this evaluation. The concentration of doxycycline was measured using spectrophotometric analysis at 273-nm absorbance. The antibacterial effect of doxycycline was evaluated by supplementing Porphyromonas gingivalis (P gingivalis) growth media with the solution collected from the dental implants at the aforementioned time intervals for a period of 48 hours under anaerobic conditions. A bacterial viability assay was used to evaluate P gingivalis growth at 550-nm absorbance. Results: Doxycycline concentration varied from 0.33 to 1.22 μg/mL from day 1 to day 28, respectively. A bacterial viability assay showed the highest P gingivalis growth at day 1 (2 nm) and the lowest at day 4 (0.17 nm), with a gradual reduction from day 1 to day 4 of approximately 87.5%. The subsequent growth pattern was maintained and slightly increased from baseline in approximately 48.3% from day 1 to day 24. The final P gingivalis growth measured at day 28 was 29.4% less than the baseline growth. Conclusion: P gingivalis growth was suppressed in media supplemented with solution collected from dental implants with a nanotube surface loaded with doxycycline during a 28-day time interval. Keywords: decontamination, dental implants, doxycycline, nanotube surface, Porphyromonas gingivalis

Purpose: This study evaluated whether simplified drilling protocols would provide comparable histologic and histomorphometric results to conventional drilling protocols at a low rotational speed. Materials and Methods: A total of 48 alumina-blasted and acid-etched Ti-6Al-4V implants with two diameters (3.75 and 4.2 mm, n = 24 per group) were bilaterally placed in the tibiae of 12 dogs, under a low-speed protocol (400 rpm). Within the same diameter group, half of the implants were inserted after a simplified drilling procedure (pilot drill + final diameter drill), and the other half were placed using the conventional drilling procedure. After 3 and 5 weeks, the animals were euthanized, and the retrieved bone-implant samples were subjected to nondecalcified histologic sectioning. Histomorphology, bone-to-implant contact (BIC), and bone area fraction occupancy (BAFO) analysis were performed. Results: Histology showed that new bone was formed around implants, and inflammation or bone resorption was not evident for both groups. Histomorphometrically, when all independent variables were collapsed over drilling technique, no differences were detected for BIC and BAFO; when drilling technique was analyzed as a function of time, the conventional groups reached statistically higher BIC and BAFO at 3 weeks, but comparable values between techniques were observed at 5 weeks; 4.2-mm implants obtained statistically higher BAFO relative to 3.75-mm implants. Conclusion: Based on the present methodology, the conventional technique improved bone formation at 3 weeks, and narrower implants were associated with less bone formation. Keywords: bone, dental implant, histology, osseointegration, surgical technique

Purpose: It was hypothesized that calcium phosphate (CaP) deposition onto Ti surfaces using biomimetic deposition contributed to not only improving osteogenesis but also suppressing osteoclastogenesis in terms of high surface hydrophilicity. Materials and Methods: Ti discs with two different surfaces were prepared: machined and anodic oxidized surfaces. The specimens of two different surfaces were soaked in modified simulated body fluid solution for 14 days at physiologic condition. Murine RAW 264.7 cells were utilized as osteoclast precursor cells. To evaluate osteoclast differentiation activity on Ti surfaces, tartrate-resistant acid phosphatase activity assay was conducted, and cells on Ti discs were investigated with a field emissionscanning electron microscope (FE-SEM). The expression of nuclear factor of activated T cells 1 (NFATc1) and c-Fos, two critical transcriptional factors involved in osteoclastogenesis, were also assessed in terms of mRNA and protein levels by real-time reverse transcriptase-polymerase chain reaction and western blot, respectively. Results: Tartrate-resistant acid phosphatase activities on both machined and anodic oxidized Ti surfaces soaked in modified simulated body fluid were significantly lower compared with nonimmersed ones. FE-SEM observation showed that the number of differentiated osteoclasts was lower on anodic oxidized surfaces immersed in modified simulated body fluid compared with nonimmersed Ti surfaces. Protein and mRNA expression of NFATc1 and c-Fos were significantly decreased on anodic oxidized Ti surfaces immersed in modified simulated body fluid compared with those on nonimmersed ones. The effects of immersion of Ti discs in modified simulated body fluid on osteoclastogenesis were higher on anodic oxidized surfaces than on machined surfaces. Conclusion: It can be concluded that osteoclastogenesis was inhibited by biomimetic deposition using modified simulated body fluid, especially on anodic oxidized Ti surfaces. Keywords: anodic oxidation, biomimetic deposition, osteoclast, simulated body fluid, surface energy

Purpose: The purpose of this study was to evaluate the influence of placement angle and force direction on the initial stability of orthodontic miniscrews using a three-dimensional finite element model that approximates the real interface between the screw and surrounding bone. Materials and Methods: Three-dimensional finite element models with 6-mm-long and 1.4-mm-diameter titanium miniscrews were used. Four insertion angles, ranging from 0 degrees (perpendicular to the bone surface) to 45 degrees, were examined. A load of 2 N was applied to the center of the screw head in four directions (upward, downward, and on the right and left sides). Results: At the same insertion angle, the stresses on the miniscrews were highest in downward force applications, while they were the lowest in upward force applications. This means that with upward traction, stresses are more evenly distributed on the surface of the miniscrew. An analysis of the principal stress distribution in surrounding bone showed that compressive and tensile stresses increased with the angle of insertion up to 30 degrees. For larger insertion angles, the increase almost vanished. Conclusion: An obliquely inserted miniscrew and its surrounding tissues generally provide sufficient anchorage for 2 N of orthodontic loading, but care must be taken to avoid screw failure during placement and removal of obliquely placed miniscrews. Keywords: finite element model, initial stability, miniscrew, oblique insertion

Purpose: The aim of this study was to compare the loosening of interchangeable one-piece abutments connected to internal-connection-type implants after cyclic loading. Materials and Methods: Four implant abutment groups (n = 7 in each group) with Straumann tissue-level implants were assessed: Straumann solid abutment (group S), Southern Implants solid abutment (group SI), Implant Direct straight abutment (group ID), and Blue Sky Bio regular platform abutment (group BSB). The implant was firmly held in a special jig to ensure fixation. Abutment screws were tightened to manufacturers' recommended torque with a digital torque gauge. The hemispherical loading members were fabricated for the load cell of a universal testing machine to evenly distribute the force on the specimens and to fulfill the ISO 14801:2007 standard. A cyclic loading of 25 N at 30 degrees to the implant's long axis was applied for a duty of a half million cycles. Tightening torques were measured prior to the loading. Removal torques were measured after cyclic loading. The data were analyzed with one-way analysis of variance (ANOVA), and the significance level was set at P .05. Results: The mean removal torques after cyclic loading were 34.0 ± 1.1 Ncm (group S), 25.0 ± 1.5 Ncm (group SI), 23.9 ± 2.1 Ncm (group ID), and 27.9 ± 1.3 Ncm (group BSB). Removal torques of each group were statistically different in the order of group S > group BSB > groups SI and ID (P .05). The mean reduction rates were -2.9% ± 3.2% (group S), -21.9% ± 4.8% (group SI), -20.2% ± 7.2% (group ID), and -6.9% ± 4.3% (group BSB) after a half million cycles, respectively. Reduction rates of groups S and BSB were statistically lower than those of groups SI and ID (P .01). The standard deviation of group S was lower than group BSB. Conclusion: The removal torque of the original Straumann abutment was significantly higher than those of the copy abutments. The reduction rate of the groups S and BSB abutments was lower than those of the other copy abutments. Keywords: cyclic loading, implant abutment, implant-abutment stability, internal-connection-type implant, removal torque, screw loosening

Purpose: The success of nonsurgical or surgical treatments of peri-implantitis is unpredictable, often without a clear reason. The aim of this study was to investigate the efficacy of nonsurgical and surgical cleaning, focusing on the impact of implant design, defect size, type of superstructure, and experience of the operator. Materials and Methods: Conical and straight implants were coated with a biofilm-like material and placed in shallow/deep defects in an artificial jaw model. Treatment was done by three operators and included either healing abutments or crowns as superstructures. Analysis was done using stereomicroscopy and ImageJ software. Results: Nonsurgical treatment of peri-implantitis defects was inefficient in removing all biofilm areas, regardless of the depth of the defect. The type of implant, experience of the operator, or type of superstructure did not have a significant impact. Surgical treatment was more efficient than a nonsurgical approach with regard to biofilm residues. However, the surgical approach failed to clean the apical portion of the exposed part of the implants. Conclusion: Nonsurgical and surgical treatment were found to be ineffective in cleaning the exposed portion of implants with peri-implantitis. Treatment of periimplantitis should therefore also include other approaches, such as chemical or biological modalities. Keywords: cleaning, nonsurgical treatment, peri-implantitis, surgical treatment

Purpose: Implant-retained overdentures are the first choice of rehabilitation for edentulous mandibles. Bone morphology and anatomical landmarks may be influenced by the location and angulation of implants and distances between the implants. The purpose of this study was to investigate stress distribution characteristics and to compare stress levels of three different attachment designs of three-implant-retained mandibular overdentures with three different interimplant distances. Materials and Methods: Three photoelastic mandibular models with three implants were fabricated using an edentulous mandible cast with moderate residual ridge resorption. The center implants were embedded parallel to the midline, and the distal implants were aligned at a 20-degree angulation corresponding to the center implants. Distances between the center and distal implants were set at 11, 18, and 25 mm at the photoelastic models. Bar, bar-ball, and Locator attachment-retained overdentures were prepared for the models. Vertical loads were applied to the overdentures, and stress levels and distribution were evaluated by a circular polariscope. Results: The greatest observed stress level was moderate for the tested overdenture designs. The Locator attachment system showed the lowest stress level for the 11-mm and 25-mm photoelastic models. The bar attachment design transmitted less stress compared with the other tested designs for the 18-mm photoelastic model. Conclusion: Stresses were observed on the loaded side of the photoelastic models. The lowest stress was found with the Locator and bar attachments for the 11-mm photoelastic model, which transmitted little or no discernible stress around the implants. Keywords: implant-retained overdenture, photoelastic stress analysis, precision attachment

Purpose: The aim of this study was to compare the biomechanical performance of splinted or nonsplinted prostheses over short- or regular-length Morse taper implants (5 mm and 11 mm, respectively) in the posterior area of the mandible using finite element analysis. Materials and Methods: Three-dimensional geometric models of regular implants (Ø 4 × 11 mm) and short implants (Ø 4 × 5 mm) were placed into a simulated model of the left posterior mandible that included the first premolar tooth; all teeth posterior to this tooth had been removed. The four experimental groups were as follows: regular group SP (three regular implants were rehabilitated with splinted prostheses), regular group NSP (three regular implants were rehabilitated with nonsplinted prostheses), short group SP (three short implants were rehabilitated with splinted prostheses), and short group NSP (three short implants were rehabilitated with nonsplinted prostheses). Oblique forces were simulated in molars (365 N) and premolars (200 N). Qualitative and quantitative analyses of the minimum principal stress in bone were performed using ANSYS Workbench software, version 10.0. Results: The use of splinting in the short group reduced the stress to the bone surrounding the implants and tooth. The use of NSP or SP in the regular group resulted in similar stresses. Conclusions: The best indication when there are short implants is to use SP. Use of NSP is feasible only when regular implants are present. Keywords: ceramics, dental implantation, dental prosthesis implant-supported, finite element analysis

Purpose: To report on the clinical outcome of 129 zygomatic implants placed in 37 patients with severely resorbed partially or completely edentulous maxillae. Materials and Methods: Patients who received zygomatic implants between 2007 and 2014 were included in this retrospective analysis. All patients were treated using the same surgical protocol, the sinus slot technique. The following data were recorded: sex, age, race, medical history, etiology, addictions, degree of bone atrophy, type and size of zygomatic implants, number of implants placed, type of prosthesis, survival rate, and success of implants and complications. Follow-up included standardized clinical and tomography examinations. Results: Thirty-seven consecutive patients (25 women, 12 men; mean age 55.64 years [range 40 to 77 years]) were treated. All were in need of oral reconstruction and had maxillary atrophy that warranted zygomatic implant placement. One hundred twenty nine zygomatic implants were placed in these 37 patients. Two of the implants failed, resulting in a cumulative survival rate of 98.44%. Maxillary sinusitis was the most common complication found (21.62%); however, neither of the implant failures was related to sinusitis or smoking. Conclusion: The zygomatic implant is a reliable option for treatment of the severely resorbed maxilla. Keywords: atrophic maxilla, dental implants, maxillary sinus, sinusitis, zygomatic implants

Purpose: The aim of this study was to evaluate the success and survival rates of extraoral implants for the fixation of facial prostheses in three anatomical regions. Materials and Methods: Subjects were consecutive patients with facial defects who underwent implant placement by the same surgeon in the orbital, nasal, and auricular regions between 2003 and 2012. After a minimum of 4 months of osseointegration, prostheses were anchored to the implants, and the patients were monitored for 11 to 111 months. Success rate, implant survival time, and occurrence of previous radiotherapy were evaluated. Rate of implant survival was estimated as a function of the anatomical region of the three groups (orbital, nasal, or auricular), and confidence intervals were calculated using Kaplan-Meier analysis with α = .05. Results: In the 68 patients' 138 fixed implants, 48 showed defects in the orbital, 9 in the nasal, and 11 in the auricular region. The success rates and survival times were 95.9% and 8.6 years for the orbital, 92.9% and 2.8 years for the nasal, and 92% and 9.0 years for the auricular region, respectively. The success rate of implants in previously irradiated regions was 90.3% for the orbital and 100% for the auricular region. None of the patients was irradiated in the nasal region. Conclusion: No significant differences in implant success or survival were observed with regard to anatomical region or previous irradiation. Keywords: extraoral implants, facial defects, facial prosthesis, osseointegration, survival rate

Purpose: Zirconia (ZrO2) and titanium nitride (TiN) implant abutments were introduced mainly for esthetic purposes, as titanium's gray color can be visible through mucosal tissues. This study was aimed at assessing whether ZrO2 and TiN abutments could achieve better esthetics in comparison with titanium (Ti) abutments, regarding the appearance of soft tissues. Materials and Methods: Ninety patients were included in the study. Each patient was provided with an implant (OsseoSpeed, Dentsply Implant System). A two-stage surgical technique was performed. Six months later, surgical reentry was performed. After 1 week, provisional restorations were screwed onto the implants. After 8 weeks, implant-level impressions were taken and soft tissue thickness was recorded, ranking thin (≤ 2 mm) or thick (> 2 mm). Patients were randomly allocated to three experimental groups, based on abutment type: (1) Ti, (2) TiN, and (3) ZrO2. After 15 weeks, the final restorations were delivered. The mucosal area referring to each abutment was measured for color using a clinical spectrophotometer (Easyshade, VITA); color measurements of the contralateral areas referring to natural teeth were performed at the same time. The data were collected using the Commission Internationale de l'Eclairage (CIE) L*a*b* color system, and ΔE was calculated between peri-implant and contralateral soft tissues. A critical threshold of ΔE = 3.7 was selected. The chi-square test was used to identify statistically significant differences in ΔE between thin and thick mucosal tissues and among the abutment types. Results: Three patients were lost at follow-up. No statistically significant differences were noticed as to the abutment type (P = .966). Statistically significant differences in ΔE were recorded between thick and thin peri-implant soft tissues (P .001). Only 2 out of 64 patients with thick soft tissues showed a ΔE higher than 3.7: 1 in the TiN group and 1 in the ZrO2 group. All the patients with thin soft tissues reported color changes that exceeded the critical threshold. Conclusion: The different abutment materials showed comparable results in terms of influence on soft tissue color. Regarding peri-implant soft tissue thickness, the influence of the tested abutments on soft tissue color became clinically relevant for values ≤ 2 mm. Keywords: customized abutment, gingival color, implant biotype, titanium, titanium nitride, zirconia

Purpose: The aim of this retrospective study was to evaluate implant survival rates (ISRs) for implants placed in grafted sinuses where a membrane perforation occurred during augmentation using exclusively anorganic bovine bone (ABB) by means of clinical and radiographic examinations. Histologic information of five biopsy specimens taken from large membrane perforations is also presented. Materials and Methods: Consecutive patients who underwent sinus augmentation procedures at a private practice Dental Institute between 2004 and 2013 were collected from a computer database. The following profiles were selected for data analysis: computed tomography prior to treatment; perforated membrane information according to size: not perforated, small (≤ 5 mm), medium (> 5 and 10 mm), or large (≥ 10 mm); sinuses grafted exclusively with ABB and lateral window covered with a collagen membrane (CM); and implant survival after at least 2 years of functional loading placed in augmented sinuses. Implants were considered survivals in the absence of infection, mobility, or pain. Results: The sample in this retrospective study comprised 531 patients; 214 required bilateral sinus augmentation, and 317 required unilateral sinus augmentation (total = 745 sinuses). A total of 1,588 implants were placed. From 745 augmented sinuses, 237 (31.8%; 523 implants) were perforated during the procedure. Among these, 48 perforations were large (20.2%; 107 implants), 67 (28.3%; 150 implants) were medium, and 122 were small (51.5%; 266 implants). Of 523 implants placed in perforated sinuses, 15 were lost (ISR = 97.1%). Comparison of the ISRs for small (97.7%), medium (97.3%), and large (95.3%) perforations with 1,065 implants placed in nonperforated sinuses (ISR = 97.7%) was not statistically significant. The histomorphometric analysis of the five biopsy specimens showed 24.52% ± 6.99% of new bone, 24.32% ± 6.42% of marrow space, and 51.2% ± 3.75% of the remaining ABB. Conclusion: The difference in ISR for implants placed in perforated and nonperforated sinuses was not statistically significant. Within the limits of the histologic data, histomorphometric results with 24.52% ± 6.99% of new bone formation in sinuses with large perforations showed similar bone formation compatible with nonperforated sinuses described in the literature. The authors attributed the high ISR shown in perforated sinuses in this study to the proper management of the perforations. Keywords: bone substitutes, intraoperative complications, maxillary sinus, osseointegration, sinus floor augmentation, sinus membrane

Purpose: When failing front teeth are replaced by implants, vestibular bone deficiencies frequently require augmentation, even though the amount of missing alveolar volume may vary. The objective of this study was to analyze the horizontal alveolar ridge dimension after implant placement and simultaneous augmentation, and to compare it to the condition at the contralateral natural site. Materials and Methods: Forty-eight patients with a failing maxillary incisor received an immediate or early implant (Straumann Bone Level), according to a randomized study protocol. The vestibular wall of the implant site was reconstructed and moderately overcontoured with bovine hydroxyapatite and a collagen membrane (BioOss, BioGide, Geistlich). Provisional restoration followed either immediately, or after a 6-week healing period. To investigate the vestibular volume 6 months after surgery, a plaster model of the maxilla was scanned with cone beam computed tomography (CBCT; Morita 3D) and evaluated using coDiagnostiX software (Dental Wings). Statistical analysis comprised one- and two-sample t tests. Results: The ridge volume was not significantly influenced by the treatment schedule. The vestibular segments had a mean ± SD volume of 207.9 ± 102.5 mm3 for the implant sites, and 202.1 ± 101.5 mm3 for the corresponding natural sites (P = .28). The difference in vestibular volume between implant sites and natural tooth sites was 10.4 ± 36.2 mm3 for immediate implantation, and 0.00 ± 31.1 mm3 for early implantation (P = .32). Comparing immediate and early restoration, a difference of 0.4 mm3 and 12.5 mm3 between the implant and contralateral site was found (P = .23). Conclusion: Six months after treatment, no significant differences between the alveolar volumes at augmented implant sites and natural sites were found. Moderate buccal overcontouring may have been beneficial to achieve a symmetrical contour. Long-term follow-up investigation will document if the restored volume remains stable over time. Keywords: alveolar ridge augmentation, cone beam computed tomography, dental implants, hydroxyapatite, single tooth

Purpose: To describe the survival rate and peri-implant bone loss in very old patients dependent for their activities of daily living (ADL), treated with mandibular two-implant overdentures (IODs) in the context of a previously reported randomized controlled trial. Materials and Methods: A total of 19 patients received two interforaminal Straumann implants (Regular Neck, 4.1 mm diameter, 8 mm length) that were subsequently loaded with Locator attachments, transforming their preexisting inferior conventional denture into an IOD. The primary outcome measures were implant survival rate and radiographically assessed peri-implant bone loss. Secondary outcome measures included peri-implant probing depth and Plaque Index scores, as well as implant mobility. Nutritional state (body mass index and blood markers) and cognitive state (Mini- Mental State Examination) were also analyzed. Results: The patient cohort comprised eight men and 11 women with a mean age of 85.7 ± 6.6 years. The implant survival rate up to 5 years was 94.7%, with one early and one late implant failure. The mean loss of peri-implant bone height was 0.17 mm per year (95% confidence interval: 0.09 to 0.24; P .001). Peri-implant probing depth and Plaque Index scores were low and stable during the first 2 years, and thereafter increased continuously. Correlation analysis suggests that a reduced cognitive function and nutritional state are not a particular risk factor for accelerated peri-implant bone loss. Conclusion: The high implant survival and acceptable peri-implant health suggest that neither age nor dependency for the ADLs is a contraindication for the placement of implants. Nevertheless, close monitoring of the patients concerning a potential further functional decline precluding denture management and performing oral hygiene measures is advised. Keywords: dental care for aged, dental implants, geriatric dentistry, peri-implant bone loss, peri-implantitis

Purpose: The aim of this study was to investigate the influence of posterior mandibular dimensions (height and width at various levels) on alveolar bone microarchitecture using microcomputed tomography (micro- CT). Materials and Methods: Partially edentulous subjects with one missing molar were included in the study. A bone core biopsy was performed at the site of planned implant surgery. For each patient, alveolar morphologic and architectural characteristics were analyzed using cone beam computed tomography (CBCT) and micro-CT imaging. Two parameters for height (apicocoronal residual height [RH] and residual ridge from inferior alveolar canal [RHN]) and three for buccolingual width (residual width at 5 mm [RW1], at 10 mm [RW2], and at 15 mm [RW3]) were determined using CBCT. Additionally, 10 parameters were obtained from micro-CT to determine microarchitecture. Pearson product-moment correlation coefficients were calculated to examine the correlation between the morphologic and microarchitectural variables. Results: Significant positive correlations (P .05) were found between RH and bone volumetric fraction (BV/TV) (r_s = 0.34) and trabecular thickness (Tb.Th) (r_s = 0.45). A significant negative correlation was found between RH and the bone-specific surface (BS/BV) (r_s = -0.34). A strong significant negative correlation was found between trabecular spacing (Tb.Sp) and RW1 (r_s = -0.42). None of the other variables reached statistical significance. Conclusion: Posterior mandibular dimensions may affect bony architectural characteristics. Keywords: alveolar bone, bone, dental implant, endosseous implant, evidence-based dentistry, trabecular

Purpose: To profile human β-globin gene fragment lengths from cell-free DNA in peri-implant skin exudate of craniofacial implants with various degrees of soft tissue inflammation. Materials and Methods: Fifteen participants (30 implants) were recruited for this study. All participants were recalled for three consecutive visits at days 0, 14, and 28. During each visit, the soft tissue condition at the skin-abutment interface of each craniofacial implant was graded by Holgers score, and the implant stability quotient (ISQ) values of the implants were also measured. Peri-implant skin exudate specimens were collected and centrifuged to obtain cell-free DNA. Conventional polymerase chain reaction was used to assess DNA fragment lengths by amplifying five polymerase chain reaction amplicon sizes from 110-base pairs (bp) to 2-kilobase pairs (kbp) of human β-globin gene. The longest polymerase chain reaction amplicon size found in each specimen was then recorded. Results: No significant differences in the ISQ values of the implants (P > .05) were noted during the study period. In each recall visit, a correlation was observed between Holgers score and polymerase chain reaction amplicon sizes (P .001). A gradual decrease in both parameters was also noted following the treatment protocol (P .05). From the 90 exudate specimens obtained from all the observation visits, 1-kbp amplicon sizes were usually found in the group with Holgers score 1 (47 of 52 specimens); 2-kbp amplicon sizes were often found in the group with Holgers score 2 (22 of 32 specimens) and predominantly found in the group with Holgers score 3 (5 of 6 specimens). Conclusion: The 1-kbp amplicon sizes can serve as a marker for mild clinical inflammation of peri-implant skin. Similarly, 2-kbp amplicon sizes may be used as a prognostic marker for denoting greater cell destruction and inflammation, which indicate a greater risk of severe inflammation. However, further studies are required to support these findings. Keywords: cell-free DNA, craniofacial implant, DNA fragment lengths, Holgers score, peri-implant skin exudate

Purpose: To report on a cohort of patients referred to a tertiary center because of neuropathic pain after dental implant placement. Materials and Methods: This retrospective study of pain after dental implant placement involved a minimum follow-up of 12 months after the initial diagnosis of neuropathic pain or persistent, uncontrolled postoperative pain at the Department of Oral and Maxillofacial Surgery, Leuven University, Leuven, Belgium, from January 2013 to June 2014. Results: Following clinical and radiologic examination, the cause of pain was established in 17 of 26 patients, while the cause was unknown in 9 of 26 patients. Regular implants were placed in the mandibles of 18 patients; in the remaining 8 patients, 6 received regular implants and 2 received a zygoma implant in the maxilla. Surgical management alone brought relief to 2 patients, surgical and pharmacologic management did so for 12 patients, and pharmacologic management alone brought relief for 10 patients. Conclusions: Early removal of an at-risk implant seems justified, preferably within 48 hours after placement. No treatment, either surgical or medical, seems to cure neuropathic pain, but amitriptyline appears to be associated with consistent improvement in symptoms. Keywords: antidepressant, dental implant, inferior alveolar nerve, nerve pain, nerve regeneration, neuropathic pain

Complications in medicine and dentistry are usually analyzed from a purely technical point of view. Rarely is the role of human behavior or judgment considered as a reason for adverse outcomes. When the role of human factors is considered, these are usually described in general terms rather than specifically identifying the factors responsible for an adverse event. The impact of cognitive and behavioral factors in the explanation of adverse events has been studied in other high-stakes areas such as aviation and nuclear power. Specific protocols have been developed to reduce rates of human error, and, where human error is unavoidable, to lessen its impact. This approach has dramatically reduced the incidence of accidents in these fields. This article aims to review how a similar approach may prove valuable in the reduction of complications in implant dentistry. Keywords: attitude, human behaviors, human factors, medical errors, stress

Digital technology has been widely used in the field of implant dentistry. From a surgical standpoint, computer-guided surgery can be utilized to enhance primary implant stability and to improve the precision of implant placement. From a prosthetic standpoint, computer-aided design/computer-assisted manufacture (CAD/CAM) technology has brought about various restorative options, including the fabrication of customized abutments through a virtual design based on computer-guided surgical planning. This case report describes a novel technique combining the use of a three-dimensional (3D) printed surgical template for the immediate placement of an implant, with CAD/CAM technology to optimize hard and soft tissue healing after bone grafting with the use of a socket sealing abutment. Keywords: bone graft, CAD/CAM healing abutment, computer-guided surgery, immediate placement, soft tissue healing

Purpose: This human case series presents the clinical and histologic results of five cases of peri-implantitis with subsequent sinus graft infections. Complications may follow maxillary sinus augmentation procedures. It is possible to have an inflammatory reaction, movement of the implant inside the sinus, formation of an insufficient quantity of osseous tissue, and the production of an oroantral fistula. Complications following maxillary subantral augmentation procedures are relatively rare; however, the risks and benefits of any surgery must be carefully evaluated at the onset. Materials and Methods: In this case series, bacterial proliferation from infected implants into the grafted biomaterial in sinus cavities was examined. In five cases, removal of infected implants from augmented sinuses did not result in resolution of the infection, but rather in persistence of the infection in the area of the sinus augmentation procedure. Intraoral examination revealed edema/redness in two cases and edema and sinus tract formation in another case. In all cases, surgical curettage of the affected maxillary sinuses was performed. The inserted biomaterials and the accompanying inflammatory tissue infiltrate were totally removed with curettes. The sample was sent for a histopathologic examination. The maxillary sinuses were filled with an autologous platelet gel. Results: Necrotic bone was found lining the different biomaterial grafts. Macrophages were observed around the grafted particles. No blood vessels were observed. Conclusion: This case series is the first to document the spread of infection from an implant surface to the entirety of the graft in the maxillary antrum. Complete removal of all infected bone graft material is the treatment of choice in such cases. Keywords: implant failure, peri-implantitis, sinus failure, sinus graft infection, sinusitis

This technical protocol outlines the use of computer-assisted image-guided technology for the preoperative planning and intraoperative procedures involved in implant-retained facial prosthetic treatment. A contributing factor for a successful prosthetic restoration is accurate preoperative planning to identify prosthetically driven implant locations that maximize bone contact and enhance cosmetic outcomes. Navigational systems virtually transfer precise digital planning into the operative field for placing implants to support prosthetic restorations. In this protocol, there is no need to construct a physical, and sometimes inaccurate, surgical guide. The report addresses treatment workflow, radiologic data specifications, and special considerations in data acquisition, virtual preoperative planning, and intraoperative navigation for the prosthetic reconstruction of unilateral, bilateral, and midface defects. Utilization of this protocol for the planning and surgical placement of craniofacial bone-anchored implants allows positioning of implants to be prosthetically driven, accurate, precise, and efficient, and leads to a more predictable treatment outcome. Keywords: anaplastology, computer-assisted image-guided surgery, craniofacial bone-anchored implant, facial prostheses, navigation, preoperative planning

Purpose: Commercially pure titanium (CpTi) and its alloys possess favorable mechanical and biologic properties for use as implants in orthopedics and dentistry. However, failures in osseointegration still exist and are common in select individuals with risk factors such as smoking. Therefore, in this study, a proposal was made to enhance the potential for osseointegration of CpTi discs by coating their surfaces with nanoplexes comprising polyethylenimine (PEI) and plasmid DNA (pDNA) encoding bone morphogenetic protein-2 (pBMP- 2). Materials and Methods: The nanoplexes were characterized for size and surface charge with a range of N/P ratios (the molar ratio of amine groups of PEI to phosphate groups in pDNA backbone). CpTi discs were surface characterized for morphology and composition before and after nanoplex coating using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD). The cytotoxicity and transfection ability of CpTi discs coated with nanoplexes of varying N/P ratios in human bone marrow-derived mesenchymal stem cells (BMSCs) was measured via MTS assays and flow cytometry, respectively. Results: The CpTi discs coated with nanoplexes prepared at an N/P ratio of 10 (N/P-10) were considered optimal, resulting in 75% cell viability and 14% transfection efficiency. Enzyme-linked immunosorbent assay results demonstrated a significant enhancement in BMP-2 protein secretion by BMSCs 7 days posttreatment with PEI/pBMP-2 nanoplexes (N/P-10) compared to the controls, and real-time PCR data demonstrated that the BMSCs treated with PEI/pBMP-2 nanoplex-coated CpTi discs resulted in an enhancement of Runx-2, alkaline phosphatase, and osteocalcin gene expressions on day 7 posttreatment. In addition, these BMSCs demonstrated enhanced calcium deposition on day 30 posttreatment as determined by qualitative (alizarin red staining) and quantitative (atomic absorption spectroscopy) assays. Conclusion: It can be concluded that PEI/pBMP-2 nanoplex (N/P-10)-coated CpTi discs have the potential to induce osteogenesis and enhance osseointegration. Keywords: BMP-2, gene therapy, implant surface, non-viral, titanium

Purpose: To determine the bone regeneration potential of a ceramic biomaterial coated with fibronectin and adipose-derived stem cells covered in three-wall critical-size defects associated with dental implants. Materials and Methods: In a total of 18 dogs, four dehiscence-type and critical-size defects were created surgically in the edentulous alveolar ridge with the simultaneous placement of dental implants. Defects were randomly regenerated using biomaterials coated with particulate ß-tricalcium phosphate (ß-TCP), ß-TCP with fibronectin (Fn) (ß-TCP-Fn), and ß-TCP with a combination of Fn and autologous adipose-derived stem cells (ADSCs) (ß-TCP-Fn-ADSCs), leaving one defect as the control. The animals were divided into three groups according to the time of euthanasia (1, 2, or 3 months). Results: Statistically significant differences between the three study groups (ß-TCP, ß-TCP-Fn, ß-TCP-Fn-ADSCs) and the control group in the total area of bone regeneration and mineralized and nonmineralized tissue at 1, 2, and 3 months of healing were not observed. At 2 months, defects treated with ß-TCP-Fn-ADSCs showed a significant decrease in the percentage of bone-to-implant contact (BIC) as compared with the ß-TCP-Fn (P = .041) and control (P = .012) groups. At 3 months of healing, however, significant differences in BIC between the three study groups and controls were not found (P = .388). Conclusion: The use of ADSCs in the bone regeneration processes of dehiscencetype defects associated with simultaneous implant insertion does not seem to improve the area of bone regeneration or the percentage of BIC compared with other biomaterials or the control alveolar defect. Keywords: adipose-derived stem cells, dehiscence-type defects, dental implants, stem cells