The International Journal of Oral & Maxillofacial Implants, 03/2016

Purpose: The aim of this study was to evaluate the effect of off-axis implant placement in relation to the prosthetic crown on abutment screw loosening under different directions of twisting moments. Materials and Methods: Twenty-one implant assemblies were divided equally into three groups (n = 7). Each assembly consisted of an internal-octagon implant measuring 4.1 × 12 mm (standard plus implants) with corresponding 5.5-mm synocta abutments (Straumann) mounted in an epoxy resin-glass fiber composite. Group A had a straight implant configuration in relation to the prosthetic crown and was subjected to clockwise twisting moment (control). The other two groups, B and C, with off-axis implant placement were subjected to clockwise and counterclockwise moments, respectively. A lateral load of 80 N was applied to the specimens for 1 × 106 cycles at 90 degrees to the long axis of the implant. The loading point was 4 mm from the center of the implant in group A and 6 mm in groups B and C. The reverse torque value (RTV) of the abutment screw was measured before and after loading. Data were analyzed using a paired samples t test and one-way analysis of variance (ANOVA) at a significance level of α = .05. Results: An increase in postloading RTV was found relative to preloading RTV in all groups, but was only significant in group A (P .05). The mean reverse torque difference (RTD) was higher in group A (3.17 ± 1.04 Ncm), followed by groups B (1.03 ± 1.41 Ncm) and C (0.43 ± 1.09 Ncm). A significant difference in RTD was noted between group A and the remaining groups (P .05). However, no significant difference was found between groups B and C (P > .05). Conclusion: Placement of an implant in an off-axis relation to the prosthetic crown resulted in significantly lower reverse torque values compared with straight implant configuration. However, the extent of reduction in Ncm is small and is considered clinically insignificant in the studied implant system. Furthermore, no significant difference was found in RTV between clockwise and counterclockwise twisting moments. Keywords: implant cantilevers, lateral loading, off-axial loading, screw loosening

Purpose: Cone beam computed tomography (CBCT) is increasingly overtaking multislice computed tomography (MSCT) for implant planning and computer-aided design/computer-assisted manufacturing (CAD/CAM) surgical guide fabrication. The purpose of this study was to evaluate whether the image modality has a significant influence on the accuracy of image-fusion stereolithographic guides. Materials and Methods: A total of 240 implants were placed in 30 polymer models using surgical guides fabricated using CBCT or MSCT and optical scanning of dental casts and diagnostic wax-up. Postsurgical image data were fused with the planning data for evaluation of the following errors: total error (Euclidean error), mesiodistal and buccolingual error, depth error, and angular error. The CBCT and MSCT results were statistically compared using a t test (P = .05). Results: CBCT showed a statistically significantly higher total error with mean (± SD) of 0.36 ± 0.13 mm vs 0.27 ± 0.13 mm (P = .000), mesiodistal error with 0.20 ± 0.14 mm vs 0.16 ± 0.11 mm (P = .018), and depth error with 0.17 ± 0.12 mm vs 0.07 ± 0.07 mm (P = .000). Buccolingual and angular errors did not statistically significantly differ with 0.16 ± 0.11 mm vs 0.15 ± 0.12 mm (P = .613), and 0.96 ± 0.47 degrees vs 0.85 ± 0.59 degrees (P = .111). Conclusion: Using CBCT for image-fusion stereolithographic guides may provide lower accuracy than MSCT. The results should be confirmed on alternative CBCT scanners. Due to the total volume of tissues, image artifacts, and patient movements, the advantages seen using MSCT on models could be nonexistent or exacerbated on patients. Patient studies are required to demonstrate clinical relevance. Keywords: 3D optical scanning, accuracy, cone beam computed tomography, multislice computed tomography, stereolithography, surgical guides

Purpose: To assess the clinical outcomes of replaced implants after removal of failed ones. In addition, associated risk factors that might affect the final outcome of these procedures were also explored. Materials and Methods: An electronic literature search was conducted by two reviewers in several databases for articles written in English up to November 2014. Human clinical trials with a minimum of 10 subjects enrolled that reported clinical outcomes with a mean follow-up period of at least 12 months after implant replacement were included. Implant survival and nonmodifiable/modifiable factors at second and third implant placement attempts were studied. Hence, the PICO question that was aimed to be addressed was: Do patients undergoing implant replacement (second and third attempts) in previous failed sites have comparable clinical outcomes by means of implant survival/failure rate to implants placed at the first attempt? Results: Five retrospective clinical cohort studies and two case series satisfied the selection criteria and thus were included in this review. In total, 396 patients were studied due to implant replacement in previous failed sites. The survival rate for implant replacement at the second attempt was 88.84% (390/439; range, 71% to 94.6%) with a mean follow-up of 41.59 ± 16.77 months. Thirty-one implants were replaced for a third attempt with a mean survival rate of 74.19% (23/31) at the follow-up of 29.66 ± 14.71 months. Major risk indicators were generally divided into patient-related factors (health status, smoking habits, and oral hygiene maintenance), implant characteristics (dimensions, coating, and loading), and site characteristics (bone quality and density, vertical and horizontal dimensions, soft tissue around the implant). Conclusion: Implant replacement is a reasonably feasible option for scenarios of early and late implant failure. However, modifiable risk factors must be controlled before proceeding for implant replacement. Keywords: endosseous implant, evidence-based dentistry, implant replacement, reimplantation, risk factors, survival rate

Purpose: To evaluate the mechanical properties and biologic response of single-phase Ti-Zr alloys cast in higher-purity casting conditions, with comprehensive compositions (from 10 to 90 mol% of Zr). Materials and Methods: The mechanical properties and in vitro biologic response with proportional increase of Zr to Ti-Zr alloy composition were assessed. Tensile strength, surface hardness, and Young's modulus were examined. The in vitro cell response of the alloys was also tested with mouse osteoblast cells. Results: Analyses of mechanical tests demonstrated improved strength and reduced Young's modulus on this binary alloy system. In vitro cell culture studies with osteogenic MCT3T-E1 cells exhibited the highest attachment rate with the largest and more mature cells on Ti10Zr, instead of commercially pure Ti, whereas a significantly lower cell attachment rate and delayed alkaline phosphatase-specific activity (ALP) differentiation were detected on Ti50Zr. Conclusion: The results revealed that the composition did have an impact on the in vitro biologic response. Ti-Zr alloys with 50-50 mol% composition had a decreased biologic response, although the mechanical properties improved. The overall highest strength was Ti with 30 mol% Zr without significant decrease of biologic response. Keywords: alloy composition, biologic response, dental implant material, mechanical property, titaniumzirconium alloy

Purpose: This in vitro study was designed to compare the effects of oxygen plasma and sandblasting treatment of the surface of titanium implant abutments on retention of implant-supported fixed prostheses using eugenol-free provisional cement and surface topography. Cement failure mode and elemental composition were surveyed. Materials and Methods: Thirty implant abutments were used. They were divided into three groups (n = 10 implants) according to the surface treatment made (no treatment, sandblasting with 50 μm Al2O3, and oxygen plasma). Thirty metal copings were fabricated with an occlusal metal O-ring and cemented using eugenol-free cement. The tensile bond strength was recorded using a universal testing machine, cement failure was recorded, surface topography was determined using the optical method, and elemental composition was determined using energy-dispersive x-ray spectroscopy. Data from all the groups were compared with a one-way analysis of variance (ANOVA; P .05) and Tukey test. Results: The mean values of tensile bond strength of metal copings bonded to three implant-abutment surface groups with either control, sandblasting, or oxygen plasma were 138.8 ± 10.2, 261.3 ± 20.6, and 264.7 ± 12.8 N, respectively. The cements failed adhesively in the control and oxygen plasma groups and cohesively for sandblasting. The mean values of surface roughness were 1.1 ± 0.2, 2.3 ± 0.5, and 1.0 ± 0.1, respectively. The oxygen plasma-treated group evidenced a decreased level of C and increased levels of O2. Conclusion: The retention of cast crown copings to titanium implant abutments using eugenol-free provisional cement in the sandblasting and oxygen plasma groups was more improved than in the control group. Keywords: abutment surface modification, implant-abutment surface, plasma-surface modification, provisional cement retention

Purpose: Bacterial colonization of the inner part of dental implants has been reported in numerous studies. The aim of this in vitro study was to analyze the bacterial colonization of the implant lumen of two implant systems that were partly subjected to a thermal cycling regimen after three different approaches to reducing bacterial load: filling of the hollow parts with either a disinfectant agent, a setting sealing compound, or a nonsetting sealing compound. Materials and Methods: Two implant systems with internal connections (the Bego Semados RI implant, Bego, and the Xive S Plus Screw Implant, Dentsply) were used in this study. Before the corresponding abutments were fixed, the internal cavities were pretreated in four different ways (application of a 0.2% chlorhexidine gel, a special silicone, or a sealing grease, or no pretreatment). Half of the specimens were subjected to thermocycling. After incubation of the assemblies in a bacterial suspension of Escherichia coli for 1 week, the abutments were removed, and microbial samples of the internal aspects were collected; contamination was evaluated with quantitative realtime polymerase chain reaction (PCR). Results: No pretreatment could hinder bacterial leakage in all cases, but all applied agents could reduce bacterial burden significantly (P .05). There was less bacterial colonization after thermocycling (P .05), and the Xive implants showed better resistance against microbial contamination (P .05). Conclusion: The application of products to reduce bacterial invasion can help reduce bacterial load to a minimum and therefore can be helpful in minimizing the cofactors that contribute to the development of peri-implantitis. Keywords: bacterial contamination, bacterial leakage, implant-abutment connection, implant-abutment interface, in vitro, real-time PCR

Purpose: To evaluate supracortical bone neoformation with the use of hydroxyapatite (HA) hollow domes specially manufactured for osteogenesis promotion. Materials and Methods: Nine New Zealand rabbits were selected and 18 domes were placed, divided into three groups according to the filler: control (blood clot), vitamin complex, and particulate β-tricalcium phosphate (β-TCP). The healing period was 8 weeks, hence fluorescent markers were applied. After healing, the samples were embedded in resin to prepare slides for light and fluorescence microscopic evaluation of the amount of neoformed bone tissue. Energy dispersive spectroscopy was also used for chemical analysis of the material inside the domes. Results: The quality of neoformed bone tissue with active bone remodeling areas was observed. As a filler, β-TCP showed higher bone formation (14.1%), better quality of neoformed bone tissue with organized structures, and an area of mineralized tissue in the dome. Bone neoformation inside the dome filled with blood clot confirmed the osteoconductive property of HA, as indicated by the migration of osteogenic cells from the blood clot, without the action of another biomaterial (mean area of bone formation for blood clot filler = 7.5%). Bone neoformation was not favored in samples filled with vitamin complex because of the difficulty of blood penetration through the material. Conclusion: HA domes performed well as a scaffold for bone neoformation over the cortical bone of rabbits, and this is based on maintenance of good stability and good integration with bone tissue. β-TCP presented higher values of neoformed bone area compared with the blood clot. HA domes have osteoconductive properties, especially when filled with blood clot, because of the migration of osteogenic cells without action of any other biomaterial. In domes filled with vitamin complex, no bone formation was noted because of the absence of resorption. Keywords: bone neoformation, dome barrier, hydroxyapatite, osteoconduction

Purpose: The objectives of this study were to evaluate bioactivity of a titanium membrane with anodization, cyclic precalcification, and heat (APH) treatment (APHTM), and to compare APHTM and nontreated titanium membrane (NTTM) in guided bone regeneration using histologic analysis and microcomputed tomography (micro-CT). Materials and Methods: APHTM samples were prepared and immersed in simulated body fluid for 2 days, then observed using field-emission scanning electron microscopy, followed by an analysis of calcium and phosphate precipitation using an energy dispersive x-ray spectroscopy. For the in vivo experiment, critical-size defects were created in rat calvaria (diameter, 8 mm) and treated with either APHTM or NTTM (n = 14 each). Biopsies were performed at 2 and 4 weeks for histologic analysis (n = 3 per group each time). Fluorochrome bone markers were injected in three rats in each group at 3 (alizarin red) and 5 weeks (calcein green), followed by histologic examination at 7 weeks. Micro-CT was performed at 8 weeks (n = 5 per group). Results: APHTM exhibited high bioactivity, characterized by dense nano-sized flakelike crystals throughout the membrane and an increase in the calcium-phosphate concentrations after 2-day immersion in simulated body fluid. At 2 and 4 weeks, APHTM samples showed an intimate bone formation onto the membrane, whereas NTTM samples demonstrated interposition of connective tissue between the membrane and newly formed bone. The same pattern was found in the fluorescent study. The micro-CT analysis revealed significantly lower bone volume but higher bone mineral density in the APHTM samples than in the NTTM samples (P .05). Conclusion: The results suggest that APH treatment on titanium membrane promotes intimate bone formation toward the membrane, thus increasing structural durability for bone regeneration. Further research is warranted to confirm the results found in these in vitro and in vivo experiments. Keywords: calcium-phosphate coating, fluorochrome labeling, guided bone regeneration, rat calvarial model, titanium membrane

Purpose: To evaluate the survival rates of titanium dental implants placed using split crest procedures for alveolar ridge expansion. Materials and Methods: The MEDLINE, CENTRAL, and OpenGrey databases were searched up to January 2015 for studies assessing implants that had been placed in areas submitted to split crest procedures. Two methodologic quality-assessment tools were used based on the type of study. For randomized controlled trials (RCTs), the Cochrane Collaboration tool was used to assess the risk of bias. For the observational studies, an adapted version of the Newcastle-Ottawa scale was used. Results: A total of 1,178 patients received 3,033 implants with ridge expansion. On average, the success rate was 96.6% and the survival rate was 96.8%, with a mean follow-up of 58.3 months. Six of the nine included studies used a bone substitute associated or not with a membrane, and seven studies used an implant in both the maxilla and mandible. In addition, half of the observational studies were considered to be of medium quality, whereas the others were considered to be of low quality; the sole RCT included was classified as having a high risk of bias. Conclusion: The use of split crest techniques appears to provide predictable alveolar ridge augmentation as well as high survival rates in the short and long term for implants placed in the maxilla or mandible. Patients must be selected with caution. Keywords: alveolar process, alveolar ridge augmentation, bone substitutes, dental implants, systematic review

Purpose: Zirconia is being widely used, at times apparently by simply copying a metal design into ceramic. Structurally, ceramics are sensitive to both design and processing (fabrication) details. The aim of this work was to examine four computer-aided design/computer-assisted manufacture (CAD/CAM) abutments using a modified International Standards Organization (ISO) implant fatigue protocol to determine performance as a function of design and processing. Materials and Methods: Two full zirconia and two hybrid (Ti-based) abutments (n = 12 each) were tested wet at 15 Hz at a variety of loads to failure. Failure probability distributions were examined at each load, and when found to be the same, data from all loads were combined for lifetime analysis from accelerated to clinical conditions. Results: Two distinctly different failure modes were found for both full zirconia and Ti-based abutments. One of these for zirconia has been reported clinically in the literature, and one for the Ti-based abutments has been reported anecdotally. The ISO protocol modification in this study forced failures in the abutments; no implant bodies failed. Extrapolated cycles for 10% failure at 70 N were: full zirconia, Atlantis 2 × 107 and Straumann 3 × 107; and Ti-based, Glidewell 1 × 106 and Nobel 1 × 1021. Under accelerated conditions (200 N), performance differed significantly: Straumann clearly outperformed Astra (t test, P = .013), and the Glidewell Ti-base abutment also outperformed Atlantis zirconia at 200 N (Nobel ran-out; t test, P = .035). Conclusion: The modified ISO protocol in this study produced failures that were seen clinically. The manufacture matters; differences in design and fabrication that influence performance cannot be discerned clinically. Keywords: CAD/CAM abutments, fatigue, implant abutments, titanium, zirconia

Purpose: The purpose of this study was to evaluate a reverse-tapered design on the osseointegration of narrow-diameter implants in comparison with a conventional tapered design in beagle dogs. Materials and Methods: All mandibular premolars and first molars were extracted bilaterally in four beagle dogs. Three months later, three kinds of implants were placed in both quadrants of the mandible: tapered narrow-diameter implants processed by cold working (TNC; n = 8), reverse-tapered narrow-diameter implants (RTN; n = 8), and reverse-tapered narrow-diameter implants processed by cold working (RTNC; n = 8). The animals were sacrificed at 4 weeks. Implant stability quotient (ISQ) values were measured at the time of implant placement and sacrifice. Histomorphometric analysis was performed. Results: The baseline ISQ values were significantly lower in the RTN (56.0 ± 11.6) and RTNC (57.2 ± 9.8) than in the TNC (68.0 ± 5.4; P = .021). At 4 weeks, the TNC (69.9 ± 5.1) exhibited significantly higher ISQ values compared with the RTNC (61.6 ± 4.1; P = .024). Histologic analysis in the RTN and RTNC revealed osseointegration without any signs of inflammation; however, unresolved coronal gap or dehiscence was also observed. The total bone-to-implant contact ratios (BIC) in TNC, RTN, and RTNC were 55.1% ± 11.5%, 47.8% ± 19.1%, and 60.2% ± 15.3%, respectively, and no significant differences were shown among them. The BIC for the coronal part in each group was 51.1% ± 29.4%, 28.8% ± 33.8%, and 23.9% ± 23.3%, respectively, and the differences were not significant. In the threaded part, TNC, RTN, and RTNC showed a BIC of 56.3% ± 9.6%, 50.7% ± 18.3%, and 65.3% ± 15.6%, respectively. There was no significant difference among them. Conclusion: The reverse-tapered design on narrow-diameter implants showed a lower initial stability than the conventional tapered design; however, there was equivalent osseointegration in an early healing phase. Keywords: animal, dental implant, histology, osseointegration, titanium

Purpose: This prospective longitudinal study reports on the results in patients given autologous tooth material for augmentation in a sinus elevation procedure. Materials and Methods: Six patients with inadequate bone supply for augmentation in the maxillary posterior tooth region and at least one impacted maxillary third molar underwent sinus elevation surgery with lateral access using the particulate tooth material. One of the patients received four implants during the same session, while the other patients had a total of 15 implants placed after a healing phase of an average 5.5 months. Drill cylinders collected from the implant bed during the procedure were subjected to histologic/immunohistochemical evaluation. Results: All six patients showed normal and unobtrusive postoperative healing, having undergone prosthetic restoration up to 5 years before. The average peri-implant probing pocket depth after a period of up to 5 years ranged between 1.86 mm (mesial and lingual) and 2.07 mm (distal and buccal). No bleeding could be triggered with any of the peri-implant probes. The average peri-implant bone resorption measured during the first year was up to 0.63 mm, with the lowest being 0 mm and the maximum 2.9 mm. Peri-implant bone remained stable for the follow-up time of up to 5 years. Histologically, six biopsy specimens collected from five patients showed osteoconductive osteogenesis with encapsulation of tooth enamel and dentin portions and partial resorption of the tooth components. Cementum shares were no longer discernible. Immunohistochemical assessment showed intense new vessel formation that could be observed in the area of loose stroma of reorganized tissue in the augmented area. Conclusion: Within the limits of these preliminary results and with adequate consideration of the small number of patients included, the use of autogenous crushed tooth material from impacted third molars may represent an alternative augmentation material for use in sinus elevation procedures. Keywords: augmentation, bone substitute, dental implant, dentin, enamel, sinus elevation

Purpose: To evaluate the soft tissue response in posterior teeth adjacent to interdental single implants comparing intrasulcular and trapezoidal incision, and to study their evolution over time. Materials and Methods: A controlled randomized clinical trial was carried out in the Oral Surgery and Implantology Unit of a University Clinic. All the included patients received an interdental single implant (Frontier 2.45, Ilerimplant; Global Medical Implants). The incision type was randomized by sealed envelopes into two groups using the SPSS statistical package (SPSS): (1) intrasulcular or (2) trapezoidal incision. Probing depth and gingival recession at the mesial and distal teeth adjacent to the implant were measured before implant placement, 1 month after surgery, the day of the abutment connection, and at 6 months and 1 year postloading. Scar formation and papilla index were measured 1 month after surgery, and at 6 months and 1 year postloading. Results: Forty patients with one implant per patient were included: 20 in the intrasulcular and 20 in the trapezoidal group. No statistical differences were found between incision types in the measured parameters (probing depth, recession, and interproximal papilla). When analyzing periodontal changes of the total sample, significant differences were found between implant placement and the 1-year follow-up in recession, scar formation, and papilla index. Conclusion: The incision type used to place a single interdental implant did not significantly influence the periodontal parameters of the adjacent teeth. Considering the whole sample, the values between implant placement and 1 year postloading showed significant differences in recession, scar formation, and papilla index over time. Keywords: dental papilla, gingival recession, incision, mucoperiosteal flap, scar, single-tooth implant

Purpose: To longitudinally evaluate marginal bone remodeling around tapered, platform-shifted implants placed for total arch rehabilitation with fixed hybrid prostheses. Materials and Methods: A retrospective cohort study was designed that evaluated radiographic data from patients undergoing implant surgical procedures with an immediately loaded four-implant-supported fixed prosthetic concept in a single clinic setting during a 36-month period. The primary outcome variable was the change in marginal bone levels during a 12- to 36-month follow-up postloading with the definitive prosthesis. All measurements were performed on matched and calibrated periapical radiographs obtained at: (1) the time of placement of the definitive prosthesis (baseline) versus (2) 12 to 36 months following definitive loading (follow-up). Other study variables, including duration of follow-up, implant position, maximum insertion torque, implant angulation, and implant diameter, were assessed for their association with changes in marginal bone levels. Results: One hundred sixty-nine patients (n = 856 implants) with a mean age of 59.5 ± 10.5 years were included in this study. Two implants failed, resulting in a 99.8% overall survival rate (mean follow-up: 15.2 ± 4.8 months, range: 12 to 36 months). The radiographic mean bone levels at baseline and follow-up were 1.16 ± 0.71 mm (n = 805) and 1.31 ± 0.93 mm (n = 805), respectively. The mean marginal bone loss from baseline to follow-up was 0.14 ± 0.59 mm (n = 805). The duration of follow-up had no effect on the extent of marginal bone loss (P = .154). Conclusion: Within the limitations of this large-scale retrospective cohort study, it was concluded that the use of tapered, platform-shifted implants for total arch rehabilitation with the use of the All-on-Four protocol yields very favorable radiographic outcomes, at least after a minimum of 12 months in function. Keywords: All-on-4, bone level, dental implants, edentulism, immediate loading

Purpose: Failing residual dentition gives rise to patient concerns about the surgical and prosthodontic management of immediate implant rehabilitation. The purpose of this study was to assess subjective patient experiences of full-arch immediate implant loading. Materials and Methods: Patients made a transition from poor dentition in the maxilla (25 patients) or mandible (25 patients) to full-arch rehabilitation on the day of extraction using four interantral or interforaminal implants. Provisional restoration was performed, and postoperative pain, swelling, and patient-perceived impairment in the first week was recorded. Results: Absence of pain was reported by 40%, 52%, and 66% of patients, on the day of surgery, on the first day after surgery, and on the second day after surgery, respectively; pain levels decreased significantly (from 1.8 to 0.9, P .001) and patient-reported swelling decreased from 1.5 to 1.3 (P = .058) on a 10-point scale. Postoperative impairment of everyday life and work (mean score = 1.1) was significantly less pronounced than impairment of food intake (mean score = 2.2; P = .004) or speech (mean score = 1.9; P = .002). Of these patients, 88% would again undergo the procedure without doubt. Conclusion: Although patient-perceived morbidity after immediate full-arch implant rehabilitation is low in general, minor masticatory and phonetic impairment should be taken into account. Keywords: complications, dental implants, immediate dental implant loading, implant-supported dental prosthesis, patient satisfaction, quality of life

Purpose: The purpose of this prospective study was to assess the change of marginal bone level around three different types of external-hex implants after 5 years using radiography. Materials and Methods: Included in this study were 54 patients randomly put into three different groups; rough-surface implants (Brånemark), machined coronal aspect implants (Restore), and microthreaded coronal aspect implants (Hexplant). Clinical and radiographic assessments were performed contemporaneously with implant loading (baseline) and at 1, 3, and 5 years post-functional loading. A mixed-model analysis was employed to examine mean marginal bone change significance in the three treatment groups. Results: In a total of 31 out of 54 patients, 81 of 135 implants remained to the end of the study. At 5 years, the microthreaded coronal aspect implants had 0.61 ± 0.32 mm mean crestal bone loss; the rough-surface implants without microthread, 0.99 ± 0.38 mm; and the machined coronal aspect implants, 1.06 ± 0.39 mm. The rough-surface implants and the machined coronal aspect implants did not exhibit statistically significantly different marginal bone loss, whereas the microthreaded coronal aspect implants exhibited significantly less marginal bone loss (P = .0015). Conclusion: In this research, rough-surface implants with microthreads showed positive long-term effects in preserving peri-implant bone level against functional loads when compared with implants lacking these aspects at the coronal part. Most of the bone loss was shown within 1 year of loading, and all types of implants stabilized after 1 year. Keywords: dental implant, marginal bone level, microthread, radiographic evaluation

Purpose: The aim of this study was to evaluate the volumetric stability of deproteinized bovine bone after sinus augmentation, using cone beam computed tomography (CBCT) and three-dimensional (3D) analysis. Materials and Methods: Using a specific selection tool and 3D reconstruction from InVesalius 3.0, volumetric analysis of CBCT scans was performed in patients undergoing a sinus elevation technique in critical defects, using deproteinized bovine bone. The first scan was performed immediately after graft surgery (T1), and the second was performed 8 months after graft surgery (T2). Results: A total of 13 patients met the inclusion criteria of this retrospective study; 26 postoperative CBCT scans were analyzed for these patients. All patients exhibited an increase in bone volume (9.10%). The mean bone volume increase from T1 to T2 was 0.137 cm3 (SD: ± 0.104 cm3). There was a statistically significant correlation between bone volume and time (P .0001). The mean bone volume was 1.506 cm3 (SD: ± 0.473 cm3) for T1 and 1.644 cm3 (SD: ± 0.506 cm3) for T2. Conclusion: Within the limited sample, the study demonstrated an increase in graft volume after sinus elevation with deproteinized bovine bone in critical defects. Keywords: Bio-Oss, bone grafting, cone beam CT scan, dental implants, maxillary sinus

Purpose: High crown-implant ratios might affect the biologic and technical performance of a reconstruction. The aim of this study was to assess whether a higher crown-implant ratio of single restorations on 6-mm implants resulted in more peri-implant bone loss and more prosthetic complications during a 1-year followup period. Materials and Methods: A group of 37 patients were provided with 47 single-implant-supported restorations on 6-mm implants. Implants were placed in the posterior mandible or maxilla, where limited bone height was available. The clinical crown-implant ratio was determined on digitized casts. Peri-implant bone changes were analyzed on intraoral radiographs. Prosthetic complications were scored throughout the evaluation period. Results: The mean crown-implant ratio was 2.14 ± 0.42. The mean peri-implant bone loss was 0.13 ± 0.36 mm. No complications occurred. Conclusion: High crown-implant ratios are not accompanied by increased peri-implant bone changes or prosthetic complications during a 1-year follow-up period. Keywords: alveolar bone loss, crown-implant ratio, dental implants, fixed dental prosthesis, prospective study, single-tooth

Purpose: The objective of this study was to compare the rate of implant stability development of as-received and photofunctionalized dental implants in regular and complex cases. Materials and Methods: Forty-nine implants (24 as-received and 25 photofunctionalized) placed in regular or complex cases (simultaneous guided bone regeneration, sinus elevation, or fresh extraction sockets) were studied. Photofunctionalization was performed by ultraviolet (UV) treatment of implants for 15 minutes using a photo device immediately prior to placement, and the generation of superhydrophilicity was confirmed. Implant stability was evaluated by measuring the implant stability quotient (ISQ) at placement (ISQ1) and at stage-two surgery (ISQ2). The rate of implant stability development was evaluated by calculating the osseointegration speed index (OSI), defined as the ISQ increase per month ([ISQ2-ISQ1]/healing time in months). The percentage of innate bone support at placement was evaluated clinically and radiographically. Results: The average OSI was considerably greater for photofunctionalized implants (3.7 ± 2.9) than for as-received implants (0.0 ± 1.0). The OSI in complex cases was 4.2 ± 3.2 for photofunctionalized implants and 0.2 ± 0.9 for as-received implants. The OSI in cases with simultaneous sinus elevation was 5.5 ± 3.5 for photofunctionalized implants and 0.2 ± 1.1 for as-received implants. Photofunctionalized implants showed significantly higher ISQ2 values than as-received implants. Photofunctionalized implant ISQ2 values were greater than 60, regardless of primary stability and innate bone support at placement. In multivariate analysis including the effects of photofunctionalization, age and sex of patients, and diameter and length of implants, photofunctionalization showed the strongest influence on the OSI for both regular and complex cases, while other factors influenced the OSI only in certain conditions. Conclusion: Photofunctionalization accelerated the rate and enhanced the final level of implant stability development compared with as-received implants, particularly for implants placed into poor-quality bone and other complex cases. Photofunctionalization was a stronger determinant of implant stability than all the other tested implant- and host-related factors. Keywords: hydrophilic, implant stability quotient (ISQ), photofunctionalization, primary stability, superosseointegration, ultraviolet (UV)

Purpose: The purpose of this study was to evaluate the efficacy of the ridge-splitting technique in the anterior maxilla, using piezoelectric surgery for immediate implant placement. Study outcomes were compared with those of implant placement in the same patients using the conventional drilling technique. Materials and Methods: Ten patients received a total of 22 implants in the anterior maxilla, 11 of which were placed using a ridge-splitting procedure (test group) and the other 11 using the conventional drilling procedure (control group). Ridge width (RW), crestal bone level (BL), and implant stability quotient (ISQ) were measured at different points in time. Data were analyzed and compared between the groups using analysis of variance (ANOVA) and paired-sample t tests at a significance level of 5%. Results: For the test group, the gain in RW was not stable in time because at 6 months postoperatively, the RW lost some of the initial gain; however, the net gain was still significant. At 6 months postoperatively, BL was similar for both groups. The net bone loss on the mesial aspect and the average of the mesial and the distal measures did not differ significantly between both groups. ISQ values sharply increased at 3 months postoperatively in the test group. All implants met the modified Albrektsson criteria (1989) for success. Conclusion: The results from this study support the efficacy and safety of ridge expansion using piezoelectric surgery for implant insertion in the anterior maxilla. The modest net gain in bone width suggests that additional hard and soft tissue augmentation may be necessary, especially in the esthetic zone. ISQ values suggest a minimum healing time of 3 months before loading the implants that have been inserted using this ridge-splitting protocol. Keywords: bone expansion, dental implant, piezoelectric surgery, ridge splitting

Purpose: As dental implants have become routine therapy, clinicians are more frequently being faced with treating peri-implantitis. To date, no single treatment protocol has been shown to be the preferred means to treat peri-implantitis. The aim of this retrospective case series is to present a novel approach utilizing porcine collagen-coated bovine bone (CBB) to treat peri-implantitis. Materials and Methods: Eleven patients, with no history of periodontitis, presenting with peri-implantitis around a single restored dental implant, were included in the study. At initial and follow-up examinations, bleeding on probing (BOP), probing depth (PD), and gingival margin location (GM) were recorded. Following surgical debridement of the peri-implant defect and treatment of the implant surface with a 0.12% chlorhexidine gluconate solution, bony defects were grafted with CBB. All patients had 12 months of follow-up. Results: Upon presentation, average PD at the deepest site (DS) was 7.6 ± 1.9 mm. At the time of surgery, excess cement was found around nine implants (81%). All patients healed uneventfully without postoperative complications. At 6 and 12 months, all implants showed favorable results with average DS PD reduction of 3.9 ± 1.5 mm and 4.1 ± 1.6 mm, respectively. All implants showed radiographic signs of bone fill, while GM showed no changes from preoperative measurements at either 6 (0.1 ± 0.5 mm) or 12 (0.0 ± 0.6 mm) months. Conclusion: The use of a porcine collagen-coated bovine bone graft to treat peri-implantitis represents a potentially predictable therapeutic modality. Randomized controlled trials are necessary to substantiate the treatment outcomes. Keywords: alveolar bone loss, bone regeneration, bone substitutes, dental implants, peri-implantitis

Purpose: This study was conducted to characterize clinically and radiographically the effect of using platelet-rich fibrin (PRF) autologous graft on the augmentation results of autogenous palatal bone blocks. Materials and Methods: Patients who suffered from horizontal alveolar bone defects in the anterior maxillary ridge (≤ 4.5 mm) with one or two missing teeth were augmented with autogenous palatal bone blocks 4 months prior to implant placement. PRF was used to cover the block in the test group, while only the block was used in the control. Bone width was measured with a manual caliper preaugmentation (t0), and at 0 (t1) and 4 months (t2). Cone beam computed tomography (CBCT) scans were performed at t0 and t2. Nonparametric tests (Mann-Whitney, Friedman's, and Wilcoxon signed-rank tests) were used for the comparisons. The significance level was set at P ≤ .05. Results: In the 14 sites (12 patients), all but one autograft (from the control group) integrated successfully after 4 months. No statistically significant difference was found between demographic data in the two groups. There was a statistically significant increase in the buccopalatal bone width in both groups by time as measured by CBCT as well as the manual caliper. The test group showed statistically significantly lower mean graft resorption than the control group (test, 0.8 ± 0.6 mm; control, 1.6 ± 0.9 mm; P = .006). Conclusion: Autogenous palatal bone block surface resorption is significantly decreased by the use of PRF coverage. Keywords: alveolar resorption, alveolar ridge augmentation, hard palate, maxillary bone, platelet-rich fibrin

Purpose: Since bacterial leakage along the implant-abutment interface may be responsible for peri-implant infections, a realistic estimation of the interface gap width during function is important for risk assessment. The purpose of this study was to compare two methods for investigating microgap formation in a loaded dental implant, namely, microcomputed tomography (micro-CT) and three-dimensional (3D) nonlinear finite element analysis (FEA); additionally, stresses to be expected during loading were also evaluated by FEA. Materials and Methods: An implant-abutment complex was inspected for microgaps between the abutment and implant in a micro-CT scanner under an oblique load of 200 N. A numerical model of the situation was constructed; boundary conditions and external load were defined according to the experiment. The model was refined stepwise until its load-displacement behavior corresponded sufficiently to data from previous load experiments. FEA of the final, validated model was used to determine microgap widths. These were compared with the widths as measured in micro-CT inspection. Finally, stress distributions were evaluated in selected regions. Results: No microgaps wider than 13 μm could be detected by micro-CT for the loaded implant. FEA revealed gap widths up to 10 μm between the implant and abutment at the side of load application. Furthermore, FEA predicted plastic deformation in a limited area at the implant collar. Conclusion: FEA proved to be an adequate method for studying microgap formation in dental implant-abutment complexes. FEA is not limited in gap width resolution as are radiologic techniques and can also provide insight into stress distributions within the loaded complex. Keywords: dental implant, finite element analysis, microcomputed tomography, microgap formation, preload, tightening torque

Purpose: As maxillary implant overdentures are being increasingly used in clinical practice, prosthodontic complications related to these dentures are also reported more often. The purpose of this study was to examine the influence of palatal coverage and implant distribution on the shear strain of maxillary implant overdentures. Materials and Methods: A maxillary edentulous model with implants inserted in the anterior, premolar, and molar areas was fabricated. Two kinds of experimental overdentures, with and without palatal coverage, were also fabricated, and two strain gauges were attached at the midline of the labial and palatal sides. A vertical occlusal load of 98 N was applied through a mandibular complete denture, and the shear strain in each denture was compared by analysis of variance (P = .05). Results: In all situations, the shear strain in palateless dentures was significantly higher than in dentures with palate on both sides (P .05). In dentures with palate, the shear strain was lower when anterior implants were present. Conclusion: Palateless maxillary implant overdentures exhibited much higher strain than overdentures with palate regardless of the implant distribution; this may cause more prosthodontic and implant complications. The most favorable configuration to prevent complications in maxillary implant overdentures was palatal coverage that was supported by more than four widely distributed implants. Keywords: implant, load, maxillary implant overdenture, palateless denture, strain

Purpose: This study aimed to evaluate peri-implant bone reactions to dynamic and static loads in a rat model. Materials and Methods: Two cylindrical titanium implants were placed in the left tibia diaphysis of 39 rats, which were divided into three groups: static load for 4 weeks (S4), static load for 8 weeks (S8), and static load for 4 weeks followed by dynamic load for 4 weeks (S4D4). All implants received a mechanical lateral load. After the experiment, the implants were extracted to determine the attachment strength around the bone and implant. The new bone formation and bone-to-implant contact were measured using plain and polarized light microscopy. Results: Histologic tissue analysis revealed good contact between the bone and implant, and new bone formation around all implants. The S4D4 group had the greatest attachment strength, new bone formation, and complex collagen fiber orientation in the new bone tissue, compared with the other groups. No statistically significant differences in bone-to-implant contact were observed among the three groups. Conclusions: Applying dynamic and static loads to osseointegrated implants increased the amplification of new bone. The attachment strength was significantly improved when dynamic load was used for 4 weeks, compared with when static load was used. Keywords: animal experiment, dynamic load, implant attachment strength test, peri-implant bone, static load

Purpose: Fracture of orthodontic mini-implants during insertion is a limiting factor for their clinical success. The purpose of this study was to determine the fracture potential of commonly used self-drilling orthodontic mini-implants when placed into simulated thick, dense mandibular bone. Materials and Methods: Six mini-implant systems were assessed for the potential for fracture (Aarhus, Medicon; Dual-Top, Jeil Medical; OrthoEasy, Forestadent; tomas-pin, Dentaurum; Unitek, 3M; and VectorTAS, Ormco). First, mini-implants were inserted manually, without predrilling, into bone substitutes (Sawbones) with a 3-mm-thick, dense (1.64 g/cm3) cortical layer. A custom-made insertion device was used for placement of mini-implants. A sixaxis force/torque transducer was secured at the base of the bone blocks to measure the maximum torque experienced during insertion. Measured insertion torques were compared with previously reported fracture torques, yielding a torque ratio (insertion torque as a percentage of fracture torque), which was used as an indicator of the potential for mini-implant fracture. Mini-implants that experienced torque ratios ≥ 75% upon insertion underwent further testing, following the manufacturer's recommendations for predrilling in thick, dense bone conditions. Results: Significant differences in torque ratios were found among all mini-implants, except between OrthoEasy and Dual-Top, and OrthoEasy and VectorTAS. Overall, Aarhus had the highest torque ratio (91% ± 3%), with Unitek showing the lowest ratio (37% ± 3%). Aarhus and tomas-pin mini-implants displayed torque ratios ≥ 75% and experienced fracture upon insertion. When the manufacturer's specific predrilling recommendations were followed, no changes in torque ratio were found for Aarhus and tomas-pin. However, while Aarhus continued to fracture upon insertion, all tomas-pin mini-implants were inserted fully without fracture following predrilling. Conclusion: These findings support the safe use of Unitek, VectorTAS, Dual-Top, and OrthoEasy self-drilling mini-implants in areas of 3-mm-thick, 1.64 g/cm3 dense cortical bone without predrilling. Following predrilling, fractures did not occur with tomas-pin. For implants that continued to fracture after predrilling, other strategies may be required, such as the use of larger-diameter mini-implants in thick, dense bone conditions. Keywords: fracture potential, insertion torque, mandibular bone, orthodontic mini-implants, predrilling, self-drilling

Purpose: The aim of this in vitro study was to assess the resistance to static fatigue of implants with different connections before and after implantoplasty. Materials and Methods: Sixty conical implants and 60 abutments were used; 4-mm-diameter versions were available for each model. Three groups (n = 20) were established based on the following implant connections: external hexagon (group 1), internal hexagon (group 2), and Morse taper (group 3). The implants of each group were submitted to a compressive load before (n = 10) and after the implantoplasty (n = 10). The wear was performed in a mechanical lathe machine using a carbide bur, and the final dimensions of each sample were measured. All groups were subjected to quasi-static loading at a 30-degree angle to the implant axis in a universal testing machine and 5 mm out of the implant support. Results: After the implantoplasty, the mean final diameter was 3.13 ± 0.033 mm for group 1, 3.23 ± 0.023 mm for group 2, and 3.25 ± 0.03 mm for group 3. The mean fracture strengths for the groups before and after the implantoplasty were, respectively, 773.1 ± 13.16 N and 487.1 ± 93.72 N in group 1; 829.4 ± 14.12 N and 495.7 ± 85.24 N in group 2; and 898.1 ± 19.25 N and 717.6 ± 77.25 N in group 3. Conclusion: Resistance to loading decreased significantly after implantoplasty, and varied among the three implant connection designs. Keywords: dental implant, fracture mode, fracture strength, implant connection, implantoplasty

Purpose: Peri-implantitis is a common complication of dental implants. The first step of treatment is elimination of bacterial biofilm and disinfection of the implant surface. This study sought to compare the effects of an erbium-doped yttrium aluminum garnet (Er:YAG) laser, photodynamic therapy using an indocyanin green-based photosensitizer (ICG-based PS) and diode laser, toluidine blue O (TBO) photosensitizer and light-emitting diode (LED) light source, and 2% chlorhexidine (CHX) on biofilm of Aggregatibacter actinomycetemcomitans to sandblasted, large-grit, acid-etched (SLA) implant surfaces. Materials and Methods: Fifty SLA implants were divided into five groups and were incubated with A actinomycetemcomitans bacteria to form bacterial biofilm. Group 1 underwent Er:YAG laser radiation (with 10-Hz frequency, 100-mJ energy, and 1-W power); group 2 was subjected to LED (with 630-nm wavelength and maximum output intensity of 2.000 to 4.000 mW/cm2) and TBO as a photosensitizer; group 3 was exposed to diode laser radiation (with 810-nm wavelength and 300-mW power) and ICG-based PS; and group 4 was immersed in 2% CHX. Group 5 was the control group, and the samples were rinsed with normal saline. The number of colony-forming units (CFU) per implant was then calculated. Data were analyzed using one-way analysis of variance (ANOVA), and the five groups were compared. Results: Significant differences was found between the control group and the other groups (P .01). The lowest mean of CFU per implant count was in group 4 (P .01), and the highest mean belonged to the control group. Photodynamic therapy by TBO + LED and ICG-based PS + diode laser was more effective than Er:YAG laser irradiation in suppression of this organism (P .01). There was no significant difference between groups 2 and 3. Conclusion: The antibacterial effect of 2% CHX was greater than that of other understudy methods. Keywords: diode laser, Er:YAG laser, implant, implant surface decontamination, laser, photodynamic therapy

This study reports a case of peri-implantitis correlated with floss fibers trapped by the implant-prosthetic macrostructure. Discrepancy between the radiographic feature and probing depth was the starting point for a correct evaluation. The minimally invasive removal of the trapped material with the aid of a periodontal endoscope resulted in a complete resolution of the peri-implantitis with a stable long-term result (6 years). This case report argues for some reconsiderations in hygienic, diagnostic, and therapeutic approaches in oral implantology. Keywords: diagnosis, endoscopy, floss, nonsurgical therapy, peri-implantitis