The International Journal of Oral & Maxillofacial Implants, 02/2014

Purpose: The aim of this study was to investigate the influence of interimplant distance of internal connection implants with platform switching on crestal bone loss using radiographic evaluation. Materials and Methods: The present study included patients missing two consecutive teeth in the posterior quadrant and receiving internal connection implants. Digital periapical radiographs were taken at the time of superstructure connection and at the time of more than 1 year of loading. Bone level change was measured on the modified image using a digital subtraction program. The crestal bone loss between implants and the horizontal and vertical loss of peri-implant marginal bone were evaluated, and the influence of interimplant distance on crestal bone loss was analyzed at α = .05. Results: A total of 10 pairs of implants having ≤ 3 mm of interimplant distance was included in this study (group 1). The other 15 pairs of implants having > 3 mm of interimplant distance were selected as a control group (group 2). After the mean 19.3 months of observation, the mean crestal bone loss between implants was -0.26 ± 0.14 mm in group 1 and -0.23 ± 0.29 mm in group 2 (P > .05). There was no significant difference between the interimplant distance and the crestal bone loss according to the regression analysis (P = .765). The mean horizontal and vertical marginal bone loss was -0.18 ± 0.25 mm and -0.15 ± 0.18 mm, respectively, in group 1 and -0.17 ± 0.31 mm and -0.11 ± 0.33 mm, respectively, in group 2. There were no significant differences between outside and inside bone loss of implants in horizontal and vertical change (P > .05). Conclusions: Within the limitations of the shortterm study, the interimplant distance did not affect the crestal bone loss with internal connection implants with platform switching. The horizontal and vertical marginal bone loss was found to be too small to result in overlapping loss of the interimplant crestal bone. Keywords: crestal bone loss, digital subtraction, internal connection, interimplant distance, platform switching, tissue thickness

Purpose: Dental implants generally provide good results as replacements for missing teeth, but a few patients experience implant failure. The aim of this retrospective study was to analyze the characteristics and causes of implant failures in hopes of reducing future failures. Materials and Methods: Patients who received one or more implants at the Dental Hospital of Yonsei University College of Dentistry between February 1991 and May 2009 were included in this study. Data including age, sex, medical history, habits (eg, smoking and drinking), bone quality, primary stability, implant size, implant surface, additional surgical procedures, prosthetic type, clinical symptoms, implant failure date, and causes of implant failure were obtained through a chart review. Follow-up radiographs were compared to those obtained at baseline. The Pearson chi-square test and Fisher exact test were used to evaluate the correlations between risk factors and implant failure. Results: In total, 879 patients received 2,796 implants; 150 implants in 91 patients had failed. Early and late implant failures occurred with 86 (57.3%) and 64 (42.7%) implants, respectively. The main causes of early and late implant failures were inflammation (47%) and overloading (53%), respectively. When the cause of early implant failure was inflammation, the failure rate was significantly higher for implants in the anterior maxilla; implants with poor primary stability, a machined surface, or a length exceeding 15 mm; and implants placed with a reconstructive procedure and two-stage surgery. When late implant failure was caused by overloading, the failure rate was significantly higher for implants with a machined surface, placed with a reconstructive procedure and/or two-stage surgery, and supporting telescopic dentures. Conclusion: Within the limitations of this study, the major causes of implant failure are inflammation and overloading, and they differ between early and late implant failures. Keywords: causes of implant failure, early implant failure, inflammation, late implant failure, overloading

Purpose: This study aimed to compare the values of removal torque (RT) and bone-implant contact (BIC) reported in different animal studies for zirconia and titanium implants. Materials and Methods: A systematic review of the literature was performed to analyze BIC and RT of animal studies in which both zirconia and titanium dental implants were used. To identify the studies to include in this systematic review, an exhaustive search of PubMed was performed of animal studies published in English with reports on the quantification of the osseointegration of both titanium and zirconia implants by means of BIC and/or RT. The results were aggregated and analyzed within each of the animal models (pig, rabbit, rat, monkey, dog, and sheep). Results: The selection process resulted in a final sample of 16 studies. In general, no significant differences were found between titanium and zirconia. The significant differences in terms of BIC and RT reported by the authors were attributable to the different surface treatments and microporosities of the implant surfaces studied, not to the materials themselves. Only two articles reported significantly lower BIC for modified zirconia implants as compared to modified titanium implants. Four authors described statistically significant differences in terms of RT between zirconia and titanium implants in the different animal models, regardless of the surface treatment received by the implants. Conclusions: Within the limitations of this study, the values for the BIC and RT of zirconia implants in most of the studies analyzed did not show statistical differences compared with titanium implants. Modified-surface zirconia may have potential as a candidate for a successful implant material, although further clinical studies are necessary. Keywords: dental implants, titanium, zirconia

Purpose: The objective of this study was to describe bone healing around self-drilling orthodontic miniimplants (MIs), sterilized in an office with an autoclave, with or without immediate orthodontic loading. Materials and Methods: One hundred forty-four self-drilling MIs (TOMAS, Dentaurum) were inserted into the tibiae of 18 white rabbits, with full-thickness flaps elevated under general anesthesia. An immediate load (50 cN) was applied to 50% of the MIs. Two rabbits were sacrificed soon after the surgery and served as a control group. Four rabbits each were sacrificed at 15, 21, 30, or 60 days after the surgeries. Digital radiographs were obtained to measure the cortical bone thickness (CBT) around and between the implants. Sections were obtained and stained for histologic and histomorphometric analysis. Bone quantity (BQ), boneto- implant contact (BIC), and CBT were evaluated statistically. Results: At day 0, fractures were visible in the cortical area around the MIs. At days 15 and 21, intense proliferation of woven bone followed by formation of lamellar bone was seen. After 30 days, primary bone was visible, with less proliferation activity. At day 60, primary bone in the process of remodeling into secondary bone was apparent. BQ was better with loading after 15 days and increased throughout the healing period in the loaded and unloaded groups. Loading did not influence the BIC values, which increased with healing time for loaded and unloaded implants. CBT increased in all regions, and CBT was greater around the MIs than between them except for unloaded MIs in the 15-day group. Conclusion: An immediate, light orthodontic load did not affect the bone healing process around orthodontic MIs. Osseointegration and CBT increased and were time-related. Keywords: bone, dental implants, histology, orthodontic anchorage, orthodontics, radiography

Purpose: The aim of this study was to evaluate the cleaning effectiveness of implant prophylaxis instruments on polished and acid-etched implant surfaces. Materials and Methods: Biofilm layers of Streptococcus mutans were grown on a total of 80 titanium disks; 40 disks were polished and 40 were acid-etched. Five disks of each surface were cleaned using each of seven implant prophylaxis instruments: (1) manual plastic curette, (2) manual carbon fiber-reinforced plastic (CFRP) curette, (3) sonic-driven prophylaxis brush, (4) rotating rubber cup with prophylaxis paste, (5) sonic-driven polyether ether ketone (PEEK) plastic tip, (6) ultrasonic-driven PEEK plastic tip, and (7) air polishing with amino acid (glycine) powder. Ten disks (five of each surface type) served as controls. After cleaning, the surfaces with remaining bacteria were assessed by light microscopy. Statistical analyses of the results were performed with one-way and two-way analyses of variance with Bonferroni-Dunn multiple comparisons post hoc analysis (α = .05). Results: The cleaning effectiveness of the plastic curette was significantly lower than those of all machine-driven instruments on the polished surface. Significantly lower cleaning effectiveness occurred with the CFRP curette compared to the prophylaxis brush and to both oscillating PEEK plastic tips on the polished surface. The rubber cup provided less cleaning effectiveness compared to the ultrasonic PEEK plastic tip and air polishing on the acid-etched surface. Superior results, with less than 4% of the biofilm remaining, were obtained for both oscillating PEEK plastic tips and air polishing on both implant surfaces. The cleaning ability of the prophylaxis brush, rubber cup, and ultrasonic PEEK plastic tip differed significantly between both surface structures. Conclusions: Cleaning effectiveness, ie, less than 4% of the biofilm remaining, was not observed with all tested implant prophylaxis instruments. The cleaning ability of the devices depended on the implant surface structure. Keywords: air polishing, implant cleaning, implant scaler, implant supportive therapy, implant surfaces, prophylaxis instruments

Purpose: To compare the interfaces of loaded and unloaded zirconium and titanium abutments with titanium implants using scanning electron microscopy (SEM). Materials and Methods: Zirconium and titanium abutments (n = 5 per group; four test and one control) were torque-tightened into titanium implants secured into metal blocks, and computer-aided design/computer-assisted manufacture- based zirconium oxide copings were fabricated and cemented to the abutments with temporary resinbased cement. Specimens of each restoration were subjected to cyclic axial and lateral loading of 30 N at 2 Hz for 500,000 cycles using a servohydraulic test system; control specimens were left unloaded. Then, the abutment/implant assemblies were embedded in acrylic resin, sectioned longitudinally along the midline, and inspected under SEM with x-ray microanalysis. Results: Loosening or fracture of the copings and implant components was not observed after dynamic loading in both groups. SEM and x-ray microanalysis revealed unexpected microleakage of acrylic resin at the interface. Acrylic resin in the implants tightened to the titanium abutments was limited to the cervical part, and the components displayed scratched and smashed regions, suggesting slight deformation of the implant neck. Microleakage and pooling of acrylic resin were observed approaching the screw joint in loaded implants tightened to zirconia abutments, and the amount of microleakage was greater than in the unloaded control specimens, which had a larger microgap than the titanium abutment/titanium implant interface. Loaded zirconia abutments were associated with wear, scratches, and, in one sample, chipping. Conclusions: Zirconium abutment/titanium implant interface may be susceptible to wear of the abutment coupled with deformation of the implant neck greater than that associated with the conventional titanium abutment/titanium implant interface under dynamic loading. Keywords: abutment, dynamic loading, implant-abutment interface, dynamic loading, scanning electron microscopy, titanium, zirconia

Purpose: To systematically evaluate implant success rates with different loading protocols. Materials and Methods: A search was conducted of electronic databases, including The Cochrane Oral Health Group's Trials Register, PubMed, SciSearch, Medline, and EMBASE, for all randomized controlled trials published between 1997 and 2011 to compare implant success rates among different loading methods. The quality of randomized controlled trials was critically appraised, and the data were extracted by two independent reviewers. Meta-analyses were conducted of the eligible randomized controlled trials. Results: A total of 26 randomized controlled trials met the criteria for meta-analysis. The quality of these articles was moderate. Eight trials compared immediate and early loading (relative risk [RR] = 0.90, 95% confidence interval [CI] 0.42-1.93, P = .79), 7 compared early with delayed loading (RR = 1.19, 95% CI 0.52-2.72, P = .69), and 11 compared immediate and delayed loading (RR = 1.19, 95% CI 0.52-2.72, P = .69). Conclusions: The limited evidence shows that there is no significant difference in implant success rates with different loading protocols. Keywords: delayed loading, dental implants, early loading, immediate loading, meta-analysis

Purpose: Physical attachment of connective tissue fibers to a laser-microtextured (8- and 12-μm grooves) surface on the collar of an implant has been demonstrated using human histology. Related clinical research has suggested that this microtextured surface may help to decrease initial bone loss after implant placement. The aim of this retrospective study was to compare crestal bone heights and clinical parameters between implants with laser-microtextured and machined collars placed and loaded with different protocols. Materials and Methods: This study evaluated 300 single implants in 300 patients (155 men, 145 women; mean age: 49.3 years; range: 45 to 75 years). One hundred sixty implants with laser-microtextured collars (L) and 140 with machined collars (M) were used. Implants were grouped into the treatment categories of immediate placement, delayed placement, immediate nonocclusal loading, and delayed loading. For all groups, crestal bone level, attachment level (CAL), Plaque Index, and bleeding on probing were recorded at baseline and 6, 12, and 24 months after loading with the definitive restoration. Results: Nine implants were lost (four L and five M). The type of implant and timing of placement and loading showed no significant influence on survival rates. A mean CAL loss of 1.12 mm was observed during the first 2 years in the M group, while the mean CAL loss observed in the L group was 0.55 mm. Radiographically, L group implants showed a mean crestal bone loss of 0.58 mm, compared to 1.09 mm for the M group. Conclusion: A laser-microtextured surface on the implant collar may mitigate the negative sequelae associated with peri-implant bone loss, regardless of the placement and loading protocols used. Keywords: delayed loading, delayed placement, immediate nonocclusal loading, immediate placement, laser microtexturing

Purpose: To evaluate the fatigue resistance and failure mode of composite resin and porcelain onlays and crowns bonded to premolar custom metal-composite resin premolar implant abutments. Materials and Methods: Sixty composite resin mesostructures were fabricated with computer assistance with two preparation designs (crown vs onlay) and bonded to a metal implant abutment. Following insertion into an implant with a tapered abutment interface (Titamax CM), each metal-composite resin abutment was restored with either composite resin (Paradigm MZ100) or ceramic (Paradigm C) (n = 15) and attached with adhesive resin (Optibond FL) and a preheated light-curing composite resin (Filtek Z100). Cyclic isometric chewing (5 Hz) was then simulated, starting with 5,000 cycles at a load of 50 N, followed by stages of 200, 400, 600, 800, 1,000, 1,200, and 1,400 N (25,000 cycles each). Samples were loaded until fracture or to a maximum of 180,000 cycles. The four groups were compared using life table survival analysis (log-rank test). Previously published data using zirconia abutments of the same design were included for comparison. Results: Paradigm C and MZ100 specimens fractured at average loads of 1,133 N and 1,266 N, respectively. Survival rates ranged from 20% to 33.3% (ceramic crowns and onlays) to 60% (composite resin crowns and onlays) and were significantly different (pooled data for restorative material). There were no restoration failures, but there were adhesive failures at the connection between the abutment and the mesostructure. The survival of the metal-composite resin premolar abutments was inferior to that of identical zirconia abutments from a previous study (pooled data for abutment material). Conclusions: Composite resin onlays/ crowns bonded to metal-composite resin premolar implant abutments presented higher survival rates than comparable ceramic onlays/crowns. Zirconia abutments outperformed the metal-composite resin premolar abutments. Keywords: adhesion, ceramic, composite resin, computer-aided design/computer-assisted manufacture, fatigue resistance, implant abutment, premolar

Purpose: This study aims to compare and evaluate the accuracy of surgical templates fabricated using coordinate synchronization processing with five-axis milling and design-related processing with rapid prototyping (RP). Materials and Methods: Master phantoms with 10 embedded gutta-percha cylinders hidden under artificial gingiva were fabricated and imaged using cone beam computed tomography. Vectors of the hidden cylinders were extracted and transferred to those of the planned implants through reverse engineering using virtual planning software. An RP-produced template was fabricated by stereolithography in photopolymer at the RP center according to planned data. Metal sleeves were bonded after holes were bored (group RP). For the milled template, milling coordinates were synchronized using the conversion process for the coordinate synchronization platform located on the model's bottom. Metal bushings were set on holes milled on the five-axis milling machine, on which the model was fixed through the coordinate synchronization plate, and the framework was constructed on the model using orthodontic resin (group CS). A computed tomography image was taken with templates firmly fixed on models using anchor pins (RP) or anchor screws (CS). The accuracy was analyzed via reverse engineering. Differences between the two groups were compared by repeated measures two-factor analysis. Results: From the reverse-engineered image of the template on the experimental model, RP-produced templates showed significantly larger deviations than did milled surgical guides. Maximum deviations of the group RP were 1.58 mm (horizontal), 1.68 mm (vertical), and 8.51 degrees (angular); those of the group CS were 0.68 mm (horizontal), 0.41 mm (vertical), and 3.23 degrees (angular). Conclusions: A comparison of milling and RP template production methods showed that a vector-milled surgical guide had significantly smaller deviations than did an RP-produced template. The accuracy of computer-guided milled surgical templates was within the safety margin of previous studies. Keywords: computer-guided surgery, coordinate synchronization, implant surgical template, milling machine, rapid prototyping, reverse engineering

Purpose: Missing teeth are a major problem in cleft patients, who require specialized prosthetic management, including dental implants. The aim of this review was to investigate the optimal date for implant insertion in patients born with cleft lip and palate after bone grafting and to assess the long-term prognosis of the inserted dental implants. Materials and Methods: A systematic review of the current literature electronically in several databases and additional hand searching were performed. Relevant publications were assessed with regard to their evidence according to the guidelines of the Oxford Centre for Evidence-Based Medicine. Results: Forty-nine publications (prospective and retrospective clinical studies, case series, and case reports) were included for analysis, but only 18 clinical papers reported survival rates for dental implants (in all, 670 implants in 460 cleft patients). Most studies were evidence level 3b (case-control studies) or 4 (case series, case reports). Reported 5-year survival rates for dental implants in cleft patients ranged from 80% to 96% (mean, 88.6%). Implant placement is favored after growth is complete and is generally recommended within 4 to 6 months after bone grafting. Conclusions: Dental implants in patients with cleft lip and palate show high success rates and allow for sufficient oral rehabilitation. However, because of a lack of sufficient prospective clinical studies on dental implants in cleft patients, the available evidence is poor and insufficient. Keywords: bone grafting, cleft lip and palate, dental implants, implant survival, osteoplasty, review

Purpose: To evaluate changes in the general and oral health-related quality of life (using the European Quality of Life indicator and the Oral Health Impact Profile-49 [OHIP-49], respectively) of patients treated with conventionally or immediately loaded implants. Materials and Methods: This clinical trial consisted of a clinical oral examination and a questionnaire-based interview carried out before and after both surgery and definitive prosthetic rehabilitation in a consecutive sample of patients requiring dental implants. According to the clinical diagnosis and patient preference, patients were assigned to the immediate loading group (IL group; n = 29) or the conventional loading group (CL group; n = 75). The change summary scores and effect sizes were calculated in the intermediate stage and at the final follow-up, taking baseline scores as reference. Results: The oral health-related quality of life and oral satisfaction after implant therapy were significantly better than at baseline, with an even greater benefit when the implants were loaded immediately than when prosthetic rehabilitation was delayed. However, there were no significant differences in between-group comparisons in the ratings of general health status. The effect size for the OHIP-49 exceeded the threshold value of 0.8 for the domains functional limitation, pain/discomfort, and psychological discomfort in both groups and also for physical disability and psychological disability in the IL group. Conclusions: A gradual improvement in oral well-being scores, but not in those of general well-being, were observed for both groups from the intermediate stage to the final evaluation. This benefit was markedly greater for the IL group. Keywords: general health-related quality of life, oral health-related quality of life, satisfaction, dental implant, immediate loading

Purpose: The purpose of this study was to investigate the impact of graft bone particle size on autogenous bone graft augmentation in a vertical augmentation chamber model. Materials and Methods: A total of 12 rabbits were used in this study. The donor bone particles were of different sizes: small (150 to 400 μm), large (1.0 to 2.0 mm), and a mixture comprising equal weights of both large and small bone particles. One type of bone graft material was placed into each of two polytetrafluoroethylene chambers that were implanted in the parietal bone of each rabbit's cranium. Animals were sacrificed 4 or 8 weeks after the grafting procedure. The recovered samples were analyzed by microcomputed tomography (micro-CT) for quantitative analysis. Total bone volume, bone height, and the distribution of bone structure were calculated by micro-CT. Results: Micro-CT evaluations revealed that the bone grafts performed with large bone particles provided, statistically, the best outcome. Total bone volume and bone height decreased in a time-dependent manner, and there was a statistically significant reduction in total bone volume between 4 and 8 weeks in the group with the mixed bone particle sizes. Conclusion: Within the limitations of the present study, large bone graft particles provided the best preservation of total bone volume and bone height up to 8 weeks after grafting in an animal vertical augmentation model. Keywords: animal study, autogenous bone particle size, micro-CT, vertical augmentation graft

Purpose: This retrospective study investigated the predictability of the osteotome technique for sinus floor elevation in the presence of antral pseudocysts. Materials and Methods: A retrospective study was carried out in patients treated with the osteotome technique for sinus floor elevation in the presence of antral pseudocysts and simultaneous implant placement between 2005 and 2009. Pseudocyst cases were collected from the patient population during that period based on faint dome-shaped radiographic findings in the elevated sinus floor. Data were recorded and evaluated in terms of bone gain and alterations in the sinus floor and peri-implant parameters. Results: Twenty-one patients were diagnosed with antral pseudocysts in the sinus floor, with 21 implants placed underneath. All implants osseointegrated uneventfully, and all but one implant radiographically appeared to gain bone around the apex. Mean residual bone height was 6.85 ± 1.22 mm and the mean length of implants protruding into the sinus was 2.96 ± 1.16 mm. The mean endosinus bone gain after the healing period was 3.40 ± 1.78 mm, with an average crestal bone loss of 0.85 ± 0.42 mm. Thirteen implants showed healed bone graft extending all around the apices, three implants had major bony coverage (50% to 100%) of the apically protruding portion, and four implants showed less coverage ( 50%). The survival rate of implants was 100% (mean follow-up, 27.26 ± 15.22 months), and at that time, mean crestal bone loss was 0.50 ± 0.33 mm, modified Plaque Index was 1.30 ± 0.67, modified Bleeding Index was 0.60 ± 0.70, and mean probing depth was 3.35 ± 0.74 mm. Conclusion: Based upon a retrospective study of 21 implants placed beneath pseudocysts for a mean time of 27 months, it appears that implants that extend into the maxillary sinus can remain functionally stable after osteotome sinus elevation in the presence of antral pseudocysts. Keywords: antral pseudocyst, dental implants, osteotome technique, sinus floor elevation

Purpose: The objective of this study was to assess the antral balloon technique for sinus elevation followed by bone graft and implant placement. Materials and Methods: A total of 34 patients with atrophic edentulous posterior maxillary ridges underwent antral balloon sinus elevation followed by bone grafting (autogenous bone retrieved from the chin mixed with platelet-rich plasma) and implant placement. Results: The population consisted of 26 male and 8 female patients with a mean age of 42 years (range, 33 to 56 years). Successful sinus membrane balloon elevation was performed in all 34 patients, and 62 implants were placed. A membrane tear in one patient was managed intraoperatively by placement of a collagen membrane. Two implants failed within 6 months, and the survival rate of the other 60 implants was 100% after 3 years of follow-up. The mean inflated balloon volume was 1.96 mL and the mean elevated sinus height by balloon was 11.6 mm. An average bone gain of 7.5 mm (range, 5.2 to 10.5 mm) was observed. Conclusions: This case series demonstrates the feasibility of antral balloon sinus membrane elevation followed by bone augmentation and implant placement. This technique offers optimal assurance for membrane safety, and it is less invasive than the routine lateral window technique, safe, and associated with less postoperative bleeding and discomfort. This method is predictable, easy to learn, and associated with low complication rates. However, large comparative studies with other techniques are required. Keywords: antral balloon sinus elevation, dental implants, direct sinus elevation, lateral window sinus elevation

Purpose: (1) To determine whether immediate loading of orthodontic bone anchors (OBAs) generates more failures than delayed loading and (2) to evaluate the impact of different variables on the success rate of the use of OBAs as temporary anchorage devices in orthodontic treatment. Materials and Methods: In a prospective registry, consecutive patients were treated with OBAs by one experienced maxillofacial surgeon. An independent evaluator compared and analyzed different prospectively determined parameters: gender, age (young [ 16 years] versus mature [≥ 16 years]), time of loading (delayed versus immediate), jaw, location, fixation screw length, complications, and orthodontic indications. Success with the OBA was defined as the capacity to maintain anchorage throughout treatment. Premature removal of an OBA because of infection, serious mobility, or persistent pain was considered a failure. Fisher exact tests for analysis of associations between the categorical variables, with the patient as independent variable, were performed. Success and complications were evaluated using multivariate logistic regression. Results: Sixty-one patients (37 male, 24 female) were treated with 106 OBAs over a 5-year period (2001 to 2006). The reported success rate in this study was 88.3%. In seven patients (11.7%) an OBA was removed prematurely. Age, gender, time of loading, jaw, and location did not influence the failure rate. In 25% of patients, at least one screw failure was noted. A statistically higher screw failure rate was noted in female patients, and the younger group presented more complications than the mature group. Conclusion: According to the results of this study, OBAs are a reliable means to obtain absolute orthodontic anchorage. Immediate loading of an OBA did not generate more failures than delayed loading. Age, jaw, and position did not seem to play important roles in success. Age and gender were important parameters in fixation screw failure rate. Keywords: delayed loading, immediate loading, longitudinal study, orthodontic anchorage procedures, orthodontic bone anchor, prospective study

Purpose: The purpose of this study was to analyze and evaluate the clinical success of distal cantilevers of fixed full-arch prostheses for the rehabilitation of edentulous arches in conjunction with immediate loading. Materials and Methods: Twenty-seven patients (15 men and 12 women) with a mean age of 59 years received 203 implants (Ankylos, Dentsply), either in edentulous jaws or after extraction and immediate implant placement. All implants were splinted together with provisional restorations and loaded immediately after surgery. After an average of 60 days, the definitive prostheses were fabricated and cemented provisionally. Thirty-one prostheses were delivered. A total of 92 units on distal cantilevers were incorporated into the prostheses. Implant stability was recorded (via percussion testing) after prostheses were removed and crestal bone levels were measured with radiographs. Results: Average crestal bone loss was 0.33 mm. After a follow-up of 5 years, only one prosthesis broke (at the connection between the main part of the denture and the distal extension). A total of five implants were lost because of overloading or peri-implantitis (during early healing). The success rate of implants was 94.5%, the survival rate was 97.5%, and the survival rate of the prostheses was 96.7% after a loading period of 79.30 ± 35.31 months. Conclusions: Based on the long-term clinical data, distal cantilevers on a full-arch prosthesis can be a successful treatment modality and can be employed in patient treatment planning when posterior support is indicated. Keywords: cantilever, complications, crestal bone loss, implant-retained prostheses

Purpose: This 1-year randomized controlled prospective study evaluated the implant success rate and periimplant tissue response following single immediate implant placement and provisionalization (IIPP) with and without subepithelial connective tissue graft (SCTG) in the esthetic zone. Materials and Methods: Implants were placed either IIPP with SCTG (test group) or IIPP without SCTG (control group). The implants were evaluated both clinically and radiographically before surgery, immediately after implant placement, and 3, 6, and 12 months after implant placement. Data were analyzed using Friedman, Wilcoxon signed-rank, and Mann-Whitney U tests at the significance level of α = .05. Results: Twenty implants (10 test, 10 control) were placed in 20 patients (7 men, 13 women) between the ages of 27 and 87 (mean age, 52.6 years). At 1 year, all implants remained osseointegrated, with overall mean marginal bone changes of -0.01 mm and -0.14 mm for the test and control groups, respectively. Mean facial gingival level change was significantly more pronounced in the control group (-0.70 mm) than in the test group (-0.25 mm). The modified Plaque Index scores showed that patients were able to maintain a good level of hygiene throughout the study. At 1 year, the Papilla Index indicated that more than 50% papilla fill was observed in 75% of the test sites and 80% of the control sites. Conclusions: Within the limitations of this study, SCTG was shown to be beneficial in maintaining facial gingival level when performed in conjunction with IIPP procedures. Keywords: esthetics, esthetic zone, gingival biotype, gingival recession, immediate loading, immediate provisionalization, immediate tooth replacement, papilla

Purpose: The aim of this study was to evaluate the radiographic bone level changes after delayed implant placement at medium-term follow-up, with three elements kept constant: keratinized gingiva thickness, implant axes perpendicular to the opposing occlusal surface, and implants with a collar of 2 mm. Materials and Methods: Patients treated in a private practice setting were retrospectively enrolled in the study. They underwent delayed placement (4 to 8 weeks after extraction) of dental implants in edentulous premolar or molar regions. Implants followed a delayed loading protocol. Crestal bone levels were measured at baseline; at provisional prosthesis placement; at 1, 3, and 5 years; and at medium-term follow-up of healing from implant placement. Results: One hundred twenty patients received 135 implants (one or two implants per patient); 3 implants were lost. After a mean follow-up period of 9.71 ± 4.88 years, a survival rate of 97.76% was reported. At 1 year after implant placement, mean bone loss of -1.5 ± 0.62 mm was found. At almost 3 years post-implant placement, a mean bone gain of +1.20 ± 0.49 mm was seen, which was statistically significantly different compared with 1 year. After this point, the bone levels remained stable; similar values were reported over time, with no significant differences. Conclusions: The mean vertical bone gain of +1.20 ± 0.49 mm seen at almost 3 years after implant placement in this study may be supported by both clinical parameters as presence of sufficiently thick keratinized gingiva (3 mm), implants with a 2-mm collar, and the axis of implant insertion perpendicular to the opposing occlusal surface. Keywords: crestal bone, delayed loading, dental implants, osseointegration

Purpose: To evaluate the outcome of narrow-diameter (3.3-mm) locking-taper implants used in the rehabilitation of partially and fully edentulous patients over a 10-year period. Materials and Methods: Between January 2002 and December 2011, all patients referred to a private dental clinic for treatment with narrow-diameter implants were enrolled in this study. At each annual follow-up session, clinical and radiographic parameters were assessed; the outcome measurements were implant failure, peri-implant marginal bone loss (distance between the implant shoulder and the first visible bone-to-implant contact [DIB]), and biologic and technical complications. The cumulative survival rate (CSR) was assessed using the Kaplan-Meier survival estimator; Tarone-Ware and chi-square analyses were used to evaluate correlations between the study variables. The statistical analysis was performed at the patient- and implant-level. Results: A total of 324 narrow-diameter implants were placed in 279 patients (159 men, 120 women; age: 25 to 73 years). Four implants failed, for an overall CSR of 98.5% (patient-based) and 98.7% (implant-based) at the 10-year follow-up. The survival rate did not differ significantly with respect to patients' sex, age, smoking or parafunctional habits, bone type, prosthetic restoration, or implant location, position, or length. Among the surviving implants, a mean DIB of 0.31 ± 0.23 mm, 0.45 ± 0.27 mm, and 0.69 ± 0.28 mm was observed at the 1-, 5-, and 10-year follow-up examinations, respectively. A few biologic (1.2%) and technical complications (7.5%) were reported. Conclusions: Within the limitations of this study, it can be concluded that narrow-diameter locking-taper implants represent a good treatment option for the prosthetic rehabilitation of partially and totally edentulous patients. Keywords: narrow-diameter implants, locking-taper implants, implant survival, complications

Purpose: The aim of this study was to test the sensitivity of the resonance frequency analysis for detecting early implant failure. Materials and Methods: In all, 3,786 implants placed from June 2007 to January 2013 were retrospectively evaluated. A total of 20 implants (in 20 patients) placed in pristine bone were found to have failed before loading. The implant stability quotient (ISQ) values were extracted from these 20 implants at baseline (immediate) and 4 months after placement (delayed). Simple linear regression, logistic regression, and two-way contingency tables were used to test for the relationships between ISQ values and early implant failure. Results: Immediate ISQ values were significantly related to failure (odds ratio [OR] = 4.27). Furthermore, the results of the second regression showed a significant relationship between ISQ at delayed measurement and implant failure (OR = 9.20). For immediate ISQ, it seems that the 73.7% correct classifications were obtained at the cost of an incorrect classification of 55% of the implant failures. However, for the delayed ISQ, 86.2% correct classifications were obtained at the cost of assuming that all implants will survive. Conclusion: The present study showed that ISQ values are not reliable in predicting early implant failure. In addition, the real cutoff ISQ value to differentiate between success and early implant failure remains to be determined. Keywords: early failure, implant failure, implant stability, ISQ, primary stability, resonance frequency analysis

Purpose: The purpose of this study was to investigate the influence of cortical perforation on angiogenesis and osteogenesis following guided bone regeneration using synthetic bone substitutes in rabbit cranial defects. Materials and Methods: The right and left sides of the calvaria were exposed in 11 rabbits. In each rabbit, two custom-made titanium domes were placed on either side of the midline. In experimental sites, the cortical surface inside the boundary of one of the two circular slits was then mechanically perforated five times with a round bur; in control sites, this was left intact. All sites received beta-tricalcium phosphate. The animals were sacrificed at 2, 4, and 8 weeks. Biopsy samples were examined histomorphometrically by light microscopy, and the expression of vascular endothelial growth factor (VEGF) and osteocalcin (OC) was determined immunohistochemically. Results: The percent area of newly formed bone was significantly higher in the experimental group than in the control group 2 weeks after surgery. Marrow cells reached the normal rabbit calvarial bone more rapidly in experimental sites than in control sites. Immunostaining intensity and the percentage of positively stained cells for VEGF were greater in the experimental group than in the control group at 2 weeks after surgery. At 4 weeks, immunostaining intensity and the percentage of positively stained cells for OC were greater in the experimental group than in the control group. However, there were no significant differences between the experimental and control groups in immunohistochemical findings for VEGF and OC. Conclusions: The results of this study suggest that cortical perforation of the receptor bone may improve angiogenesis in bone grafts and increase the amount of newly formed bone in grafted areas, especially in the early bony healing phase. Further studies in larger samples are needed to confirm these results. Keywords: beta-tricalcium phosphate, cortical perforation, osteocalcin, vascular endothelial growth factor

Purpose: Titanium (Ti) is frequently used in dental implants because of its excellent corrosion resistance, mechanical properties, and biocompatibility. However, Ti ions may be slowly released as a result of corrosion, contributing to peri-implantitis, a major cause of dental implant failure. This study examined the influence of Ti ions on cytokine levels in murine splenocytes, an immunocompetent cell type, stimulated with Aggregatibacter actinomycetemcomitans lipopolysaccharide (LPS) and the influence of Ti ions on splenocyte viability. Materials and Methods: Splenocytes were prepared from 5- to 10-week-old male C57BL/6 mice and BALB/c mice. Cytokine levels in culture supernatants from murine splenocytes stimulated with A actinomycetemcomitans LPS were determined with enzyme-linked immunosorbent assay. A tetrazolium salt assay was carried out to evaluate the cytotoxicity of Ti ions against murine splenocytes. Results: The present study demonstrated that Ti ions influence cytokine levels in LPS-stimulated splenocytes. Significantly higher values (P .05) were observed for interleukins 1β, 6, and 10; interferon-γ; tumor necrosis factor alpha; and granulocyte macrophage colony-stimulating factor in the culture supernatants of LPS-stimulated splenocytes of both mouse strains in the presence of Ti ions, as compared to the absence of Ti ions. Tetrazolium salt assay confirmed that the Ti ions used in this study did not affect the viability of murine splenocytes. Conclusion: This study suggests that Ti ions enhanced cytokine production induced by periodontopathic bacterial LPS. Keywords: cytokine, lipopolysaccharide, murine splenocyte, titanium ion

Purpose: Coating prostheses with calcium phosphate (CaP) can boost ossification and provide an appropriate vehicle for drug delivery. In this study, CaP coating was performed using a biomimetic method, and zoledronate (ZOL) was incorporated to promote peri-implant bone formation in an osteoporotic environment. Materials and Methods: Twenty female 8-week-old rats were ovariectomized to induce osteoporosis. Twelve weeks later, the animals were randomly separated into four groups representing different ZOL concentrations in the immersion solution: 0 (control), 8, 80, and 800 μg/mL. Surface-treated implants were inserted in both tibiae, and the rats were sacrificed 8 weeks after implantation. Specimens were retrieved for histomorphometric and microcomputed tomographic analyses. Results: A thin CaP coating was formed on the surface of the titanium implants, and ZOL was successfully incorporated into the structure of the biomimetic CaP coating. There were significant differences between the groups with regard to bone volume, whereas bone-implant contact comparisons did not yield any significant differences. The microstructural results clearly illustrated the positive effect of ZOL loading on the implants, as compared to the controls. Conclusions: The data suggest that biomimetic CaP coating followed by bisphosphonate immobilization is effective in improving bone quality and preserving bone volume around dental implants; therefore, this technique may be beneficial for osteoporosis patients. Keywords: biomimetic, calcium phosphate, bisphosphonate, osteoporosis, dental implant

Purpose: Ridge preservation protocols reduce crestal remodeling after tooth extraction. There is insufficient evidence on bone grafting in combination with platelet-rich plasma (PRP) or recombinant human plateletderived growth factor (rhPDGF-BB). The aim of this study is to evaluate healing of grafted and nongrafted sockets and the effect of PRP and rhPDGF-BB on early remodeling. Materials and Methods: Forty-one patients whose treatment plan included extraction of anterior or premolar teeth were randomized into four groups. Group 1: collagen plug (control). Group 2: mineralized freeze-dried bone allograft (FDBA)/β-tricalcium phosphate (β-TCP)/collagen plug. Group 3: FDBA/β-TCP/PRP/collagen plug. Group 4: FDBA/β-TCP/rhPDGFBB/ collagen plug. At 8 weeks, a core was harvested from the center of 41 sockets. Histomorphometric analysis took place. Differences were analyzed using one-way analysis of variance (ANOVA) or chi-square tests for continuous and categorical data. Pairwise comparisons were tested using least squares means. Spearman correlation coefficients were used to evaluate the relationship of bone growth with potential confounders. A P value .05 was considered statistically significant. Results: ANOVA did not indicate statistical significance in age, gender, smoking, ethnicity, or race distribution. Significant differences in tissue distribution were identified between groups and between different thirds of harvested core. More new bone and amorphous organic matrix was noted in the control group. In sites where bone graft was combined with growth factors, the amount of residual particles was less than in sites where bone graft was used alone. Conclusions: Inclusion of bone replacement graft suppressed new bone formation during early healing. Inclusion of PRP and rhPDGF-BB produced less residual bone graft material, indicating more rapid turnover of bone graft. All treatment modalities achieved a significant amount of new vital bone at 8 weeks postextraction. Keywords: extraction socket, freeze-dried bone allograft (FDBA), platelet-derived growth factor (rhPDGF-BB), platelet-rich plasma (PRP), ridge preservation

Purpose: Elevated bite forces and reduced bone densities and dimensions associated with posterior regions of the maxilla cause relatively high failure rates when short dental implants are placed to substitute missing teeth. This study uses the finite element method to evaluate four distinctly different short implant designs (Bicon, Neodent, Nobel Biocare, and Straumann) for their influences on the von Mises stress characteristics within the posterior maxilla. Materials and Methods: Finite element models of the supporting bone and tooth crowns are developed based on computed tomography data, and implant geometries are obtained from manufacturers' catalogs. The finite element models are meshed using three-dimensional hexahedral and wedge-shaped brick elements. Assumptions made in the analyses are: linear elastic material properties for bone, 50% osseointegration between bone and implant, and crown height-implant length ratio of 2:1. Results: Bicon's neck indentation produced reduced stress in the cortical bone when compared with the Nobel Biocare and Straumann systems. The increased taper of the Neodent design decreased the stress level in cancellous bone. Nobel Biocare's rounded thread crest and reduced thread pitch produced a smoother stress profile. Straumann's increased thread pitch produced elevated stress in the cancellous bone. Generally, stresses were concentrated in the crestal bone region around the implant neck, attributable to the inclined nature of the masticatory force. Conclusion: Nobel Biocare and Bicon systems are recommended for use in type 4 cancellous and cortical bone, respectively. Keywords: finite element analysis, posterior maxilla, short dental implant, stress characteristics

Purpose: This study evaluated the biomechanical behavior of short dental implants with different heights of residual bone and compared it with that of standard dental implants in 13 mm or less of residual bone by means of finite element analysis. Materials and Methods: It was assumed that the maxillary first and second molars had been replaced with splinted cast gold crowns supported by two implants. A total of five posterior edentulous maxilla models were fabricated with various residual bone heights (13 mm, 7 mm, 6 mm, 5 mm, and 4 mm). Residual bone height was 13 mm in the group 1 model (control) and 7, 6, 5, and 4 mm in group 2-1, group 2-2, group 2-3, and group 2-4 models, respectively. In the group 1 model, two identical implants (4.5 × 11 mm) and abutments (6 × 2.5 mm) were placed. In the group 2 models, two identical wide/short implants (6 × 5.7 mm) and abutments (6 × 5 mm) were placed. Off-axis (30 degrees) loading of 187 N was applied to the central fossae of the two implant-supported crowns. Results: Maximum von Mises stresses in crestal cortical bone were lower in group 2 models than in the group 1 model. Conclusion: This numeric simulation confirmed that, without maxillary sinus bone graft, more effective stress distribution could be obtained in 4, 5, 6, or 7 mm of residual bone with short dental implants than in 13 mm of residual bone with standard dental implants. Keywords: atrophic maxilla, bone graft, finite element analysis, short implant

Purpose: Different forms of dentin, including untreated, undemineralized, demineralized, boiled, or mixed with other materials, have been evaluated for efficacy as bone substitutes. However, the effects of application of liquid nitrogen-treated dentin for bone grafting remain unknown. The objective of this study was to chronologically evaluate bone healing following grafting with liquid nitrogen-treated dentin in a rabbit model. Materials and Methods: Autogenous dentin treated with liquid nitrogen at -196°C for 20 minutes was used. In 16 New Zealand White rabbits, a bone defect (5 mm in diameter) was created in each femur and randomly grafted with either autogenous dentin (experimental group) or autogenous bone grafts (positive control). In another four rabbits (negative control), a similar defect in each femur was left empty. The rabbits were sacrificed at 2, 4, 8, and 12 weeks. Explants of grafted sites were harvested for histologic and histomorphometric analysis. Results: At 2 and 4 weeks in both the experimental and positive control groups, accelerated formation of new bone was observed, which was undergoing remodeling at 8 and 12 weeks. The mean new bone score was higher in the experimental than in the negative control groups, but this was not statistically significant. Conclusion: The present results demonstrated that liquid nitrogen-treated autogenous dentin has both osteoconductive and osteoinductive properties and therefore has potential as a bone substitute. Keywords: autogenous bone graft, autogenous dentin graft, bone regeneration, bone substitute, liquid nitrogen

This paper presents the results of a structured review of the literature concerning in vitro molecular assessment of osseointegration at the level of cell-surface topography interactions. A search of the electronic databases was performed up to and including November 2010, with 320 articles meeting the inclusion criteria. Characteristics of the included in vitro reports were model systems used, genes examined, techniques used for molecular assessment of the osseointegration process, and wide gene expression profiling studies. There exists a growing body of in vitro evidence to support a role for surface topography in the direct influence of cellular phenotypes as related to the process of osseointegration. Most recently, functional or mechanistic studies have provided evidence that particular topographic cues can be specifically integrated among the many extracellular signals received by the cell in its signal transduction network. Such investigations begin to define linkages between the character of the implant surface and adherent cellular responses, including cells from extravasated blood (eg, platelets) and of the immune system (eg, monocytes). In vitro studies involving cell culture on endosseous implant- related biomaterials offer important and beneficial insight into the clinical control of the implantbone interface. Keywords: cell culture, gene profiling, molecular regulation, osseointegration

Purpose: This study investigated the role of the bone marrow-derived CD34+ cell in a milieu of osteoprogenitor cells, bone marrow plasma cell adhesion molecules, recombinant human bone morphogenetic protein (rhBMP), and a matrix of crushed cancellous allogeneic bone in the clinical regeneration of functionally useful bone in craniomandibular reconstructions. The history and current concepts of bone marrow hematopoietic stem cells and mesenchymal stem cells are reviewed as they relate to bone regeneration in large continuity defects of the mandible. Materials and Methods: Patients with 6- to 8-cm continuity defects of the mandible with retained proximal and distal segments were randomized into two groups. Group A received an in situ tissue-engineered graft containing 54 ± 38 CD34+ cells/mL along with 54 ± 38 CD44+, CD90+, and CD105+ cells/mL together with rhBMP-2 in an absorbable collagen sponge (1 mg/cm of defect) and crushed cancellous allogeneic bone. Group B received the same graft, except the CD34+ cell concentration was 1,012 ± 752 cells/mL. The results were analyzed clinically, radiographic bone density was measured in Hounsfield units (HU), and specimens were analyzed histomorphometrically. Results: Forty patients participated (22 men and 12 women; mean age, 57 years). Eight of 20 group A patients (40%) achieved the primary endpoint of mature bone regeneration, whereas all 20 group B patients (100%) achieved the primary endpoint. CD34+ cell counts above 200/mL were associated with achievement of the primary endpoint. Bone density was lower in group A (424 ± 115 HU) than in group B (731 ± 98 HU). Group A bone showed a mean trabecular bone area of 36% ± 10%, versus 67% ± 13% for group B. Conclusions: The CD34+ cell functions as a central signaling cell to mesenchymal stem cells and osteoprogenitor cells in bone regeneration. The mechanism of bone marrow-supported grafts requires a complete milieu to regenerate large quantities of functionally useful bone. CD34+ cell counts in a concentration of at least 200/mL in composite grafts are directly correlated to clinically successful bone regeneration. Keywords: bone regeneration, hematopoietic stem cells, mesenchymal stem cells, recombinant human bone morphogenetic protein

In the face of extraordinary advances in the prevention, diagnosis, and treatment of human diseases, the inability of most tissues and organs to repair and regenerate after damage is a problem that needs to be solved. Stem cell research is being pursued in the hope of achieving major medical breakthroughs. Scientists are striving to create therapies that rebuild or replace damaged cells with tissues grown from stem cells that will offer hope to people suffering from various ailments. Regeneration of damaged periodontal tissue, bone, pulp, and dentin is a problem that dentists face today. Stem cells present in dental pulp, periodontal ligament, and alveolar bone marrow have the potential to repair and regenerate teeth and periodontal structures. These stem cells can be harvested from dental pulp, periodontal ligament, and/or alveolar bone marrow; expanded; embedded in an appropriate scaffold; and transplanted back into a defect to regenerate bone and tooth structures. These cells have the potential to regenerate dentin, periodontal ligament, and cementum and can also be used to restore bone defects. The kind of scaffold, the source of cells, the type of in vitro culturing, and the type of surgical procedure to be used all require careful consideration. The endeavor is clearly multidisciplinary in nature, and the practicing dental surgeon has a critical role in it. Playing this role in the most effective way requires awareness of the huge potential associated with the use of stem cells in a clinical setting, as well as a proper understanding of the related problems. Keywords: dental pulp stem cells, dentistry, human cementum-derived cells, periodontal ligament stem cells, stem cells from human exfoliated deciduous teeth, stem cells from root apical papilla

Purpose: Atrophic ridges usually have both hard and soft tissue shortages, and bone augmentation can make soft tissue closure difficult. The aim of this case series is to present a new method utilizing transfer of free fat tissue grafts (FFG) from the buccal fat bad (BFP) during bone augmentation to enhance immediate primary soft tissue closure and improve long-term soft tissue thickness and quality at the recipient site. Materials and Methods: Patients with moderate to severe ridge atrophy in different regions of the jaws were treated over a 4-year period with bone augmentation and FFG. The BFP was the donor site for the FFG. Patients were examined clinically and radiographically (periapical) every 2 weeks. At 4 months, computed tomography was performed to evaluate the bone gain. Reentry was performed after 4 to 5 months to evaluate the soft tissue, obtain specimens for histologic examination, and insert implants. Results: Twenty patients (18 women, 2 men; mean age 43 years) were followed for 4 to 42 months and received 92 implants in the augmented sites. The healing process was uneventful, with minimal morbidity. Bone volume increased by 4 to 8 mm horizontally and 3 to 6 mm vertically. Thick soft tissue was obtained at the recipient sites and around the dental implants, and histologic specimens showed that the FFG was replaced by fibrous tissue. Conclusions: Harvesting of the FFG from the BFP is a simple procedure with minor complications, and manipulation and handling of the graft are easy. The FFG enhances primary soft tissue closure of augmented bone, prevents dehiscences, improves long-term soft tissue thickness, and mimics the attached gingiva in its fibrous healing. Keywords: autologous fat transfer, bone augmentation, buccal fat pad, fibrous healing, soft tissue grafts, soft tissue management

Purpose: Primary stability of dental implants, particularly when they are placed into immediate function in the maxilla, has been thought to be required. An alternative to primary stability is secondary stabilization, which can be obtained by a four-implant distribution pattern using 30-degree angulations for all four implants in the so-called "M-4" treatment scheme in combination with cross-arch stabilization from a prosthesis. If successful, the use of these two measures brings into question whether or not primary stability is required for immediate function in the maxilla. Materials and Methods: Patients were treated with the M-4 implant scheme with immediate function, despite the instability of at least one of the four implants. Instability was defined as less than 15 Ncm of insertion torque and palpable mobility, and an average anteroposterior spread of 15 mm between each implant was sought. The patients were followed for 1 year. Results: Ten patients were treated with a total of 40 implants. Composite insertion torque of the four implants was less than 100 Ncm in half of the patients; the average anteroposterior spread was 15.6 mm. After 1 year, no implants had been lost, and bone levels around all implants were at or near operative levels. There were no failures of provisional or definitive prostheses. Conclusions: M-4 distribution of implants with an average of 15 mm of anteroposterior spread and cross-arch stabilization did not require that all four implants had high insertion torque; in fact, all mobile implants stabilized and osseointegrated under these conditions. Keywords: All-on-Four, anteroposterior spread, composite insertion torque, cross-arch stabilization, immediate function maxilla, insertion torque, M-4, primary stability, secondary stabilization

Purpose: It is hypothesized that local application of statins positively affects bone formation. The aim of this study was to evaluate the potential effect of topical slow-release simvastatin as a bone substitute on the healing of bone defects in rat tibia. Materials and Methods: Granules of slow-releasing hydroxypropyl methylcellulose, with or without simvastatin, were inserted into critical-size defects in the tibiae of 16 rats (8 in the study group, 8 in the control group). Bone static and dynamic histomorphometric variables were examined at 2, 4, 6, and 8 weeks postsurgery. Results: All indices examined in the study group indicated improved healing relative to the control group, although statistical significance was not demonstrated for all variables. In the static histomorphometric analysis, osteoid thickness and volume were significantly higher in the study group, but the fraction of trabecular surface covered with active osteoblasts, the fraction of trabecular surface covered with osteoid, and total calcified bone volume were not significantly higher in the experimental group. In the dynamic histomorphometric analysis, the mineral apposition rate, determined by time-repeated calcein labeling, was significantly higher in the study group than in the control group. Experimental time and dosage effects were observed for most bone values in the study group. Conclusion: The findings indicate that topical application of simvastatin for the treatment of bone defects enhances the process of healing. Dosage and the methodology of administration require further calibration. Keywords: animal study, bone healing, bone substitutes, simvastatin, statins

While the AIDS epidemic of the 1980s taught the medical and dental professions much about immune cells and the immune system's cellular relationships, the bisphosphonate-induced osteonecrosis epidemic of the past decade has taught these same professions much about bone turnover, bone cell cross talk, the response and functional relationship of bone cells to loading, and drug effects on cellular dynamic relationships. The present article explores the literature as well as both evidence- and experience-based data to discuss known bone pathologies and physiologic mechanisms as well as uncover new findings: (1) bone remodeling is the mechanism by which bone adapts to loading stresses, termed either bone modeling or Wolff's law, and it is also the mechanism for bone renewal; (2) osteoclastic bone resorption triggers bone renewal at a rate of about 0.7%/ day by its release of growth factors; (3) bisphosphonates prevent the renewal of old and injured bone, thus making it brittle and more likely to fracture over time; (4) bisphosphonates have a halflife in bone of 11 years because of their irreversible binding to bone via their central carbon atom; (5) when administered intravenously, bisphosphonate loads bone and accumulates in bone 142.8 times faster than when administered orally; (6) osteoclastic resorption of bisphosphonate-loaded bone results in osteoclast death in which the cell bursts, releasing the bisphosphonate molecules to reenter the local bone or bone marrow in a re-dosing effect; (7) endosteal osteoblasts are dependent on the osteoclastic resorption/growth factor release/new bone formation mechanism of bone renewal, whereas periosteal osteoblasts are not; and (8) it is likely that endosteal osteoblasts and periosteal osteoblasts have different cell membrane receptors and arise from separate embryologic niches. Keywords: bisphosphonates, bisphosphonate-induced osteonecrosis of the jaw, bone modeling, bone remodeling, bone resorption, osteoblasts, osteoclasts, osteoporosis

Reconstruction of complex maxillofacial defects where the use of bone morphogenetic protein-2 composite grafts may be preferred can be done using perforated titanium shells or forms that confine the graft material and simultaneously establish the desired shape of the augmentation without resorting to autogenous block bone grafting. Reported here is a method for creation of rapid-prototype titanium bone forms, which was developed from a software program, to reproduce bone morphology precisely. The technique and treatment planning objectives are elucidated, especially with regard to complex vertical augmentations. Keywords: bone forms, bone morphogenetic protein-2, rapid-prototype titanium, titanium shells, treatment planning, vertical augmentation

Purpose: This study used finite element analysis and a clinical case example to test the hypothesis that a wing-thread placed 4 mm below the top of an implant would decrease crestal bone loss in function. Materials and Methods: Finite element analysis was used to compare standard and wingthread implants subjected to axial and off-axis forces based on the hypothesis that decreasing bone strain at the alveolar crestal margin improves peri-implant bone stability. A clinical case example of the wing-thread implant was followed for 30 months. Results: Stress concentration was diminished at the crest when a wing-thread was used compared to a standard implant body. Ninety-degree lateral forces were diminished by a factor of 10 in the wing-thread implant. A patient followed for 30 months showed stable bone levels around the wing-thread implants. Conclusion: The wing-thread hypothesis appears to have some support for increasing bone stability based on finite element analysis and early clinical results. Keywords: biomechanics, bone loss, bone strain, mechanostat, peri-implantitis, wing-thread