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Purpose: To evaluate the effect of misfit at implant-level fixed partial dentures (ILFPDs) and marginal bone support on the generation of implant cracks., Materials and Methods: This in vitro study included a mechanical fatigue test and finite element analysis. A mechanical cycling loading test was performed using 16 experimental models, each consisting of two parallel implants subdivided into four groups based on the misfit and the supporting bone condition. The framework, firmly seated at implants, was dynamically loaded vertically with a force of 1,600/160 N and 15 Hz for 1 × 10 6 cycles. Optical microscope, scanning electron microscope (SEM), and computed tomography three-dimensional (CT-3D) analyses were performed to detect impairments. Finite element models, representing the setups in the mechanical fatigue test, were used to represent the fatigue life., Results: None of the mechanical components presented distortion or fracture at the macroscopic level during the test. In a microscopy evaluation, the fatigue test revealed scratches visible in the inner part of the conical portion of the implants regardless of the groups. SEM and CT-3D analysis revealed one implant from the misfit/no bone loss group with a microfracture in the inner part of the conical interface. The simulated effective stress levels in the coronal body were higher in the misfit groups compared with the no misfit groups. The misfit groups presented effective stress levels, above 375 MPa, that penetrated the entire wall thickness. The no bone loss group presented an effective stress level above 375 MPa along its axial direction. In the no misfit group, the area presenting effective stress levels above 375 MPa in the conical connection was larger for the bone loss group compared with the no bone loss group., Conclusion: This study confirmed that implant fracture is an unlikely adverse event. A clear pattern of effective distribution greater than fatigue limit stresses could be noticed when the misfit was present. The dynamic load simulation demonstrated that the crack is more likely to occur when implants are fully supported by marginal bone compared with a bone loss scenario. Within the limitations of this study, it is speculated that marginal bone loss might follow the appearance of an undetected crack. Further research is needed to develop safe clinical protocols with regard to ILFPD.

Purpose: The objective of this study was to assess whether long-term implant survival rates and bone loss in patients with moderately controlled type 2 diabetes is similar to the rates reported in the nondiabetic population., Materials and Methods: This retrospective observational study utilized patient medical records from a general practitioner's dental office. The records of patients who had moderately controlled type 2 diabetes with hemoglobin A1C (HbA1c) up to 8% and glucose level below 150 mg/dL were reviewed, as patients with HbA1c up to 7% are considered to be well-controlled type 2 diabetes. Follow-up data were recorded and analyzed. Inclusion criteria were as follows: partially edentulous patients with missing teeth who were subsequently treated with implant-supported prosthetic restorations; patients were at least 18 years of age and demonstrated the ability to maintain oral hygiene. Exclusion criteria were as follows: patients did not present for annual follow-up visits; patients presented with a neglected periodontal status; patient records had incomplete surgical or restorative data or nondiagnostic radiographs; implants with external hexagonal and machined surfaces. All the restorations were cement-retained. Three different implant insertion/placement methods were used: (1) implants immediately inserted following tooth extraction; (2) implants inserted 6 to 8 weeks after tooth extraction to allow for primary healing; and (3) implants inserted 4 to 6 months after tooth extraction., Results: After review of more than 3,256 medical records, 169 patients were identified (with 1,112 implants) who met the inclusion criteria. The mean follow-up time was 8.7 years, with a minimum of 4.9 years. Sixty-seven implants failed, yielding a 94% overall implant survival rate. The overall mean bone loss around the implants was 1.98 (± 1.81) mm. Comparable to data published earlier, no statistical significance in survival rate was found between the nondiabetic and diabetic population. The delayed insertion protocol presented the least bone loss, compared with immediate insertion (P = .06), and compared with early insertion (P = .046)., Conclusion: The results show that implant survival and bone loss levels were comparable to reported outcomes in the nondiabetic population. The delayed insertion protocol presented less bone loss compared with other insertion methods. Likewise, less bone loss was found in implants placed in the posterior region.

Purpose: The purpose of this study was to evaluate the stress distribution during application of occlusal loads to maxillary anterior single external- and internal-connection implant-supported restorations with different amounts of bone loss and with the use of different metal alloys for restorations and fixation screws., Materials and Methods: Models of external- and internal-connection implants, corresponding abutments/crowns, and fixation screws were developed. These models were then imported into finite element analysis software to study the impact of forces on different implant connections and materials. Each prosthesis was subjected to a 200-N compressive shear force applied at 130 degrees relative to the long axis of the implant. The materials were considered linear, isotropic, and homogenous. The parameters changed for each connection type included: bone resorption in relation to the prosthetic platform (no, 2 mm, or 4 mm of resorption); alloys of the restorations (nonprecious vs precious); and alloys of the abutment screws (titanium vs gold). Von Mises stresses were used to display the stress in five models: implant, restoration, screw, cancellous bone, and cortical bone., Results: Statistically significant differences in the stresses of all involved structures occurred when the bone level decreased by 2 mm and by 4 mm. The connection type contributed to statistically significant differences in the stresses in both the restoration and the screw. The alloy type resulted in statistically significant differences in the implant, the superstructure, and the cortical bone stresses., Conclusion: As bone resorbed, the stresses generated within the internal-connection implant were greater than those generated in the external-connection implant. The same findings applied for the restoration and for cancellous and cortical bone. The stresses generated in the fixation screw were greater in the external-connection implant than in the internal-connection implant for all bone resorption scenarios.

Purpose: Although the risks of using a cantilever to treat missing teeth have been described, the mechanisms remain unclear. This study aimed to reveal these mechanisms from a biomechanical perspective. The effects of various implant sites, number of implants, and superstructural connections on stress distribution in the marginal bone were analyzed with three-dimensional finite element models based on mandibular computed tomography data. Forces from the masseter, temporalis, and internal pterygoid were applied as vectors., Materials and Methods: Two three-dimensional finite element models were created with the edentulous mandible showing severe and relatively modest residual ridge resorption. Cantilevers of the premolar and molar were simulated in the superstructures in the models. The following conditions were also included as factors in the models to investigate changes: poor bone quality, shortened dental arch, posterior occlusion, lateral occlusion, double force of the masseter, and short implant. Multiple linear regression analysis with a forced-entry method was performed with stress values as the objective variable and the factors as the explanatory variable., Results: When bone mass was high, stress around the implant caused by differences in implantation sites was reduced. When bone mass was low, the presence of a cantilever was a possible risk factor. The stress around the implant increased significantly if bone quality was poor or if increased force (eg, bruxism) was applied., Conclusion: The addition of a cantilever to the superstructure increased stress around implants. When large muscle forces were applied to a superstructure with cantilevers or if bone quality was poor, stress around the implants increased.

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.

Purpose: The aims of this study were (1) to evaluate long-term changes in bone height beneath mandibular screw-retained implant-supported prostheses with distal cantilevers and (2) to determine whether the reversal of residual ridge resorption in the posterior mandible is temporary or continues over the long term., Materials and Methods: Panoramic radiographs, obtained at surgery and at two follow-up visits, of 81 patients rehabilitated with mandibular screw-retained implant-supported prostheses with distal cantilevers supported by four, five, or six implants were followed for 5 to 19 years (overall mean follow-up, 9.00 years. Changes and trends in bone height adjacent to the most distal implant were evaluated between each follow up visit as well as from time of surgery (baseline) to the final visit using two-way analysis of variance, a two-sample t test, and piecewise linear regression., Results: Average bone height distal to the distal most implant at placement was 10.34 ± 6.87 mm. From baseline to the first follow-up exam, a mean bone gain of 0.68 mm was noticed, and a mean gain of 0.26 mm was observed from baseline to the second follow-up exam. A statistically significant bone gain (0.92 mm) was noticed in women (n = 49) between the first and second exams, compared to 0.33 mm in men (n = 32). Individuals experienced both bone gain and loss during the study, with an overall gain. Patients with lower initial bone height experienced greater growth, but this was not statistically significant., Conclusion: Bone growth is associated with mandibular screw-retained implant-supported prostheses with distal cantilevers, and both bone loss and bone growth may occur in the same patient over time. Within the diverse population of this study, women experienced 2.5 times more gain in bone height than men. No correlation could be established between initial bone height and overall bone height changes.

Purpose: The crestal bone level around a dental implant may influence its strength characteristics by offering protection against mechanical failures. Therefore, the present study investigated the effect of simulated bone loss on modes, loads, and cycles to failure in an in vitro model., Materials and Methods: Different amounts of bone loss were simulated: 0, 1.5, 3.0, and 4.5 mm from the implant head. Forty narrow-diameter (3.0-mm) implant-abutment assemblies were tested using compressive bending and cyclic fatigue testing. Weibull and accelerated life testing analysis were used to assess reliability and functional life. Statistical analyses were performed using the Fisher-Exact test and the Spearman ranked correlation., Results: Compressive bending tests showed that the level of bone loss influenced the load-bearing capacity of implant-abutment assemblies. Fatigue testing showed that the modes, loads, and cycles to failure had a statistically significant relationship with the level of bone loss. All 16 samples with bone loss of 3.0 mm or more experienced horizontal implant body fractures. In contrast, 14 of 16 samples with 0 and 1.5 mm of bone loss showed abutment and screw fractures. Weibull and accelerated life testing analysis indicated a two-group distribution: the 0- and 1.5-mm bone loss samples had better functional life and reliability than the 3.0- and 4.5-mm samples., Conclusion: Progressive bone loss had a significant effect on modes, loads, and cycles to failure. In addition, bone loss influenced the functional life and reliability of the implant-abutment assemblies. Maintaining crestal bone levels is important in ensuring biomechanical sustainability and predictable long-term function of dental implant assemblies.

Purpose: This study is a retrospective assessment of the long-term efficacy of dental implant therapy in periodontally susceptible patients., Materials and Methods: A private-practice chart review was conducted to identify partially dentate subjects treated with implant-supported restorations that had been monitored annually for at least 9.5 years. Subjects were assigned to either a periodontal group or a control group according to their health histories. Data were entered into spreadsheets on a personal computer and analyzed statistically with dedicated software., Results: Thirty periodontal subjects were treated with 138 implants and 45 prostheses, and 16 control subjects were treated with 35 implants and 21 prostheses. The mean follow-up was 130 months. One implant failed before loading in the periodontal group. Cumulative 10-year survival rates were 99.3% (n = 137/138) for periodontal implants and 100% (n = 35/35) for control implants. Most surviving implants had no bone loss (n = 109/172, 63.4%). Most of the surviving implants with bone loss (n = 63/172, 36.6%) were concentrated in the periodontal cohort (90%, n = 57/63) and among women (60%, n = 15/25) regardless of cohort. Prosthesis failure was 25.2% (n = 16/66), with 12 porcelain fractures, 2 cement failures, and 2 framework fractures. In all cases, failed prostheses were immediately replaced and patients continued to function., Conclusions: Periodontal susceptibility resulted in increased bone loss but did not affect implant survival. The cause of greater bone loss in women could not be determined from the data but may have been related to the postmenopausal status of the subject population (mean age = 54 years).

Purpose: The long-term neuromuscular status of edentulous patients with severe mandibular atrophy who wore complete dentures (CDs) or implant-supported overdentures (ISOs) was investigated in the present study., Materials and Methods: Eleven CD patients and 11 patients with ISOs supported by two implants took part in the study. All patients had used their dentures for more than a decade. All patients (average age, 76 years) suffered from severe mandibular atrophy, which was to be quantified using panoramic radiographs and computer software. Kinesiographic parameters such as opening and extension movements as well as opening and closing velocities were recorded by means of a sirognathograph during test food chewing on the left and right sides. Simultaneously, electromyographic recording of masseter and temporalis activities was performed using surface electrodes., Results: The kinesiographic values obtained from ISO patients were higher than those for CD patients: 12.65 mm for vertical opening (CD, 11.79 mm) and 5.66 mm for horizontal extension (CD, 5.11 mm). Opening velocity values were 100.93 mm/s and 91.74 mm/s, respectively. Closing velocity of 78.16 mm/s in ISO patients was significantly different from that measured in CD patients (58.45 mm/s). With regard to electromyographic activities, the increase was significant for the masseter during chewing on the working side (ISO: 189.79 μV, CD: 78.05 μV) and on the nonworking side (ISO: 130.53 μV, CD: 47.25 μV). For the temporalis, values of 194.11 μV and 119.02 μV in the ISO and CD patients, respectively, were observed for working side chewing. Nonworking side values reached 155.48 μV for ISO subjects and 78.35 μV for CD subjects, which was significantly different. The degree of atrophy in both groups did not differ statistically., Conclusions: The use of two interforaminal implants with an overdenture can provide long-term neuromuscular benefits for edentulous patients.

Purpose: This 3-year study evaluated the implant survival rate, peri-implant tissue response, prosthetic maintenance, and prosthetic complications in a series of patients who received two immediately loaded unsplinted threaded implants to retain a mandibular overdenture., Materials and Methods: Eight completely edentulous patients were evaluated clinically and radiographically immediately after implant placement, at 3 months, and at 1, 2, and 3 years after implant placement. Data were analyzed using repeated-measures one-way analysis of variance and the Wilcoxon signed rank test at a significance level of α = .05., Results: At 3 years, all implants remained osseointegrated (16/16), with an overall mean marginal bone change of -0.58 ± 0.39 mm and a mean Periotest value of -7.19 ± 0.54. The modified Plaque Index scores showed marked improvement in oral hygiene during the first year, but some relapse was observed thereafter. Prosthetic maintenance and complications included replacement of the attachment inserts, abutment loosening, dislodgement of the attachment housing, overdenture reline, denture tooth fracture, and overdenture base fracture., Conclusions: This 3-year study suggests that, despite less than ideal oral hygiene and a high incidence of complete/partial fracture of overdentures, favorable implant survival rate and peri-implant tissue responses can be achieved in mandibular overdentures retained with two immediately loaded unsplinted threaded implants.

Purpose: The success of zygomatic implants following the two-stage, as well as the immediate loading, concept has been well documented. This graftless approach for the treatment of the completely edentulous resorbed maxilla allows for rehabilitation with an implant-supported fixed prosthesis. The purpose of this prospective study is to report on the 7-year follow-up of patients treated with zygomatic implants in conjunction with two to four anterior maxillary implants placed into immediate function and restored with a definitive fixed prosthesis., Materials and Methods: This prospective study involved 36 patients treated with 74 zygomatic implants and 98 anterior maxillary implants supporting fixed prostheses between 2003 and 2005., Results: Two zygomatic implants in two patients were identified as mobile at stage-two surgery; replacement implants resulted in successful osseointegration. All anterior maxillary implants were determined as osseointegrated at stage two. Three patients experienced unilateral maxillary sinus infections that were refractory to oral antibiotics and were treated with functional endoscopic sinus surgery, which resolved the infections. All patients treated with the immediate loading concept were restored with definitive fixed profile prostheses as planned., Conclusion: The high survival rate, reduced morbidity, and high rate of patient acceptance for the zygomatic implant concept allowed the rehabilitation of the resorbed edentulous maxilla with fixed implant-supported prosthesis, rendering this procedure a viable and a predictable treatment option.

Purpose: The aim of this study was to describe the stress and strain fields around orthodontically loaded dental implants using the finite element method and to evaluate the relationship between the generated strain and the biologic reaction expressed through histomorphometric parameters. Finally, this study aimed to evaluate the interaction between the orthodontic loading and the deformation generated by normal occlusal function., Materials and Methods: Sixteen titanium dental implants were inserted in extraction sockets after the removal of the second premolars and first molars of 4 adult Macaca fascicularis monkeys. After 17 weeks of healing, the implants were loaded by a pair of Sentalloy springs (50 cN) for 16 weeks. After sacrifice, tissue blocks including the implants and surrounding bone were excised. Five tissue blocks were scanned with a synchrotron radiation-based microtomography (microCT) scanner and sample-specific finite element models were generated. Subsequently all samples were prepared for histomorphometric analysis., Results: All implants were osseointegrated, although the surrounding alveolar bone differed from sample to sample. As a consequence the finite element analyses showed that the stresses and strains in the peri-implant alveolar bone greatly varied among the samples. A high level of remodeling activity was found close to the implants., Discussion: Individual differences between the receptors (in this case, the monkeys) have a large effect on both the biologic and morphologic parameters. These variations were indeed found to have a substantial impact on the (re)modeling dynamics and the load transfer mechanisms around the implants., Conclusions: By integrating different analysis techniques to evaluate bone (re)modeling around orthodontically loaded implants, this study has demonstrated the complexity and case-specific character of alveolar adaptation to orthodontic loading. Furthermore, stresses generated by combined functional and orthodontic forces should not be neglected.

Purpose: A 3-dimensional finite element model was developed to investigate the cause of different crestal bone loss patterns observed around sintered porous-surfaced and machined (turned) threaded dental implants used for orthodontic anchorage in a previously reported animal study., Materials and Methods: Twenty-noded structural solid elements with parabolic interpolation between nodes were used for modeling the bone-implant interface zone. A 3-N traction force acting between either 2 porous-surfaced or 2 machined threaded implants placed in canine premolar mandibular sites and bone profiles observed at initiation and 22 weeks of orthodontic loading were modeled., Results: Higher maximum stresses in peri-implant bone next to the coronal region of the implants were predicted with the machined threaded implants at both the initial and final time points, with the values 20% greater than those predicted after the 22-week loading period. These values were approximately 200% greater than those predicted for the porous-surfaced implants, for which a more uniform stress distribution was predicted., Discussion: The finite element model results indicated that the observed greater retention of crestal bone next to the porous-surfaced implants was attributable to lower peak stresses developing in crestal peri-implant bone with this design, which decreased the probability of bone loss related to local overstressing and bone microfracture., Conclusion: The predicted lower stresses were a result of the more uniform transfer of force from implant to bone with the porous-surfaced implants, which was a consequence of the interlocking of bone and implant possible with this design.

Purpose: The authors' aim was to perform a histomorphometric study of the healing of bone defects created adjacent to titanium and hydroxyapatite (HA) -coated implants and covered with either a resorbable or a nonresorbable membrane in combination with different filler materials and to evaluate to what degree coating, membrane, and/or filler influenced the healing of the defects., Materials and Methods: Posterior teeth were extracted from the mandibles of 10 baboons, and 12 implants were placed in each animal in the edentulous areas. The implants were either titanium or HA-coated, the membranes were either Vicryl, Gore-Tex, or Resolut, and the filler was either demineralized freeze-dried bone (DFDB), autogenous bone, or Biocoral. The implants were observed for either 3, 6, 9, 12, or 18 months. The volume of newly generated tissue and the relative contribution of bone, marrow, and filler were evaluated, as was relative extension of resorption, formation, and quiescent surface., Results: The results indicated that autogenous bone is still the gold standard, but both the DFDB and Biocoral compared favorably to it. Both filler materials were being gradually replaced by bone; this process was not yet finished at 18 months postsurgery., Discussion: Since even the sterilization of DFDB cannot exclude the possibility of a disease transmission, it is important to find an appropriate substitute. Both filler and membranes contributed to the re-establishment of the original volume; better results were achieved with the Vicryl and Gore-Tex membranes than with the Resolut. Biocoral can be considered an effective material., Conclusion: A bony defect is not necessarily a contraindication for the placement of an implant. (More than 50 references.)

Purpose: The aim of this study was to compare bone healing and crestal bone changes following immediate (Im) versus delayed (De) placement of titanium dental implants with acid-etched surfaces (Osseotite) in extraction sockets., Materials and Methods: Forty-six patients were randomly allocated to the Im or De group (n = 23 per group) and received 1 implant at the incisor, canine, or premolar region of the maxilla or the mandible. The implants were placed an average of 10 days following tooth extraction in the Im group and approximately 3 months after extraction in the De group. The widths (parallel and perpendicular to the implant) and the depth of marginal bone defects around the implants were measured clinically just after placement and 3 months later at the abutment surgery. The crestal bone changes mesially and distally to the implants were evaluated radiographically by linear measurements., Results: The survival rates were 91% in the Im group and 96% in the De group. In the Im group, the mean reductions in parallel width, perpendicular width, and depth of the largest defect of each implant amounted to 48% (from 4.4 to 2.3 mm), 59% (from 2.2 to 0.9 mm), and 48% (from 6.9 to 3.6 mm), respectively. The corresponding mean reductions in the De group amounted to 39% (from 3.1 to 1.9 mm), 77% (from 1.3 to 0.3 mm), and 34% (from 4.4 to 2.9 mm). The reduction over time was statistically significant in both groups (P < .04). For both groups, a higher degree of bone healing was achieved in the infrabony defects (> 60% for depth) than in dehiscence-type defects (approximately 25%). Furthermore, 70% of the 3-wall infrabony defects with a parallel width of up to 5 mm, a depth of maximum 4 mm, and a perpendicular width of maximum 2 mm had a capacity of spontaneous healing within a period of 3 months., Discussion and Conclusion: New bone formation occurs in infrabony defects associated with immediately placed implants in extraction sockets.

Animal studies have shown that a periodontal ligament may be produced around a titanium implant when it is in contact with fractured and retained roots. Formation of cementum and attachment connective tissue around titanium implants confirms that cementum progenitor cells are located in the periodontal ligament, since cementum and periodontal ligament are present at the implant-root interface, whereas the remainder of the implant, which is not in contact with the root, shows osseointegration. The aim was to evaluate histologically the characteristics of the tissue present between a titanium implant and a retained root, which were subsequently extracted as a result of peri-implantitis. The histologic examination revealed a continuous layer of cementum and numerous cementocytes on the implant surface. No blood vessel or collagen fibers were detected in the periodontal space. In contrast to experimental studies carried out on animals, the lack of connective tissue fibers and the presence of hypercementosis in this specimen could have been caused by the inflammatory process. Furthermore, the extrusive movement of the root might explain the presence of cementum hypertrophy. Further studies are required to establish whether the neoformation of cementum and collagen fibers on an implant in the presence of root residues occurs only in animal models or whether it may also occur in humans.

Purpose: A 3-dimensional finite element model consisting of a bone block and 2 simulated premolar crowns supported by 2 adjacent cylindric implants without immediately surrounding cortical bone was generated and used to investigate the effects of prosthesis materials and prosthesis splinting on the peri-implant bone stress under static loads., Materials and Methods: The peri-implant maximum equivalent bone stress (von Mises [VM] stress) was evaluated when a vertical or a horizontal load of 1 N was applied to the center of a single resin, gold alloy, or porcelain crown, nonsplinted or splinted to the adjacent crown., Results: The numeric results indicated that: (1) in a single crown, no significant difference could be found in the maximum VM stress between different materials for both vertical and horizontal loading; (2) splinting the crowns reduced the maximum VM stress induced by the horizontal load, and the maximum VM stress increased about 14% for the horizontal loading when the restorative material was changed from gold alloy or porcelain to resin., Discussion: Under the condition of this study's analysis, prosthesis materials of a single crown have insignificant effects on the peri-implant bone stress. Splinting the crowns reduced the peri-implant bone stress under horizontal load, and gold alloy and porcelain each demonstrated less peri-implant bone stress than resin in the splinted crown situation under static horizontal load., Conclusion: Splinting the crowns of adjacent implants with relatively stiff restorative materials is recommended for implants surrounded by poor-quality bone.

This multicenter study was conducted to determine the predictability for implants placed into immediate extraction sockets and augmented with e-PTFE barrier membranes. Forty-nine implants were placed in immediate extraction sockets. Initial and final defect measurements and the number of threads exposed were compared. Patients were followed up to 1 year after implant loading. Three implants were lost at the abutment connection surgery. The 1-year survival rate was 93.9%. Twenty barrier membranes became exposed and were removed prior to stage 2 surgery, while the remaining barriers were removed at abutment connection. The average defect bone formation for membrane-retained sites was 4.8 mm, while the average bone formation for sites in which the membranes were prematurely removed was 4.0 mm (P < .0001). At stage 2 surgery there was an average of 0.6 threads exposed (P < .001) for the membrane-retained sites and 2.6 threads for the early removal sites (NS). Forty-five pairs of nonstandardized radiographs were evaluated for bone loss after implant loading (average 7.5 months). The mesiodistal bone loss averaged 0.72 mm. Within the limits of this study, e-PTFE membranes will promote clinically and statistically significant amounts of bone around immediately placed implants. Retention of e-PTFE barriers until stage 2 surgery improves the amount of bone promoted around the implants.

This study evaluated the treatment of ligature-induced peri-implantitis using guided tissue regeneration (GTR) around submerged and nonsubmerged implants in beagle dogs. Two titanium implants were placed bilaterally in the premolar regions of the mandible in each of 10 beagle dogs. Cotton floss ligatures were placed around the implant necks and no oral hygiene procedures were performed for 5 months. Periodontal surgery was performed, and in five dogs (submerged group) the abutments were removed and an e-PTFE barrier was placed to cover the test implants and their adjacent osseous defects, while the control implants received no barriers. In the other five dogs (nonsubmerged group), flap surgery was performed without removing the abutments. In the test sites, an e-PTFE barrier was placed around the abutment and adjacent defects, while on the control sites no barrier was placed. Nondecalcified specimens were prepared using standard histologic methods and analyzed. No differences were found between any of the clinical parameters in both the control and experimental sites from the submerged and nonsubmerged groups. Histologic and histomorphometric analyses also revealed no significant differences between groups with regard to new bone formation. In the experimental (GTR) groups, however, the amount of regenerated connective tissue was significantly greater than on the control groups. Under the conditions of this study, the treatment of peri-implantitis using GTR did not enhance clinical parameters or bone formation around "diseased" implants.

An engineering model of maxillary single anterior implants was developed to calculate the force-moment systems resulting from occlusal contacts. Analysis of a clinical example showed that flattening the incisal guidance and/or placing the implant in a more upright position reduced the moment and the labial component of the force but increased the intrusive component. The calculations are applicable to the design of implants and may help in the long-term evaluation of clinical success.

This case report demonstrates that severe disuse atrophy of an edentulous mandible can be changed to reparative bone growth through restoration of function and masticatory ability using an osseointegrated implant-supported fixed prosthesis. In 8 years, bone height in the retroforaminal area nearly doubled and a new bony layer remodeled the cranial roof of the mandibular canal.