The International Journal of Oral & Maxillofacial Implants, 05/2010

Purpose: Orthopedic surgeons use different types of screws for bone fixation. Whereas hard cortical bone requires a screw with a fine pitch, in softer cancellous bone a wider pitch might help prevent micromotion and eventually lead to greater implant stability. The aim of this study was to validate the assumption that fine-pitch implants are appropriate for cortical bone and wide-pitch implants are appropriate for cancellous bone. Materials and Methods: Wide-pitch and fine-pitch implants were inserted in both hard (D1 and D2) bone and soft (D3 and D4) bone, which was simulated by separate experimental blocks of cellular rigid polyurethane foam. A series of insertion sites in D1-D2 and D3-D4 experimental blocks were prepared using 1.5-mm and 2.5-mm drills. The final torque required to insert each implant was recorded. Results: Wide-pitch implants displayed greater insertion torque (20% more than the fine-pitch implants) in cancellous bone and were therefore more suitable than fine-pitch implants. Conclusion: It is more appropriate to use a fine pitch design for implants, in conjunction with a 2.5-mm osteotomy site, in dense cortical bone (D1 or D2), whereas it is recommended to choose a wide-pitch design for implants, in conjunction with a 1.5-mm osteotomy site, in softer bone (D3 or D4). Keywords: cancellous bone, cortical bone, implant stability, insertion torque, screw pitch

Purpose: This study evaluated the bone-regeneration properties of titanium fiber web (TW) that had been coated with a thin hydroxyapatite (HA) layer using the molecular precursor method. Materials and Methods: TW disks with or without the thin HA coating were implanted into rat cranial bone defects. The rats were sacrificed after 3 or 6 weeks. New bone formation into the TW was evaluated. Results: The porous structure of TW was clearly maintained after the HA coating was applied. In the HA-coated TW group, new woven bone was observed in the majority of the disks after 6 weeks, whereas the control (uncoated TW) group showed limited new bone formation in the interior. The bone formation ratio in the HA-coated group was significantly higher than in the control group (20.6% and 59.1% after 3 and 6 weeks, respectively, versus 2.0% and 15.5%, respectively; P .05). Conclusions: The molecular precursor method of applying a thin HA coating to TW appeared to effectively enhance new bone formation through maintenance of TW porosity and promotion of osteoconductivity in the TW three-dimensional scaffold. Keywords: bone scaffold, hydroxyapatite coating, molecular precursor method, porosity, titanium fiber web

Purpose: To study bone healing at implant sites in simulated extraction sockets with 1-mm marginal defects and compare healing around a turned surface (T) to that around a porous oxide surface prepared by anodic oxidation (AO) with or without the use of an autogenous bone graft. Materials and Methods: All mandibular premolars and first molars were extracted from 10 mongrel dogs. After 9 weeks, four sites were prepared on both sides of all mandibles. Each osteotomy was widened in the coronal 5 mm to create a marginal defect of 1 mm around the implants. Autogenous bone was collected during the drilling procedure. The sites were randomized to receive implants with a T or an AO surface, with or without bone grafting. The animals were sacrificed 4 months after implant placement for histologic analysis. Results: Clinically, all sites healed with complete bone fill. The combination of an AO implant and a bone graft resulted in a significantly greater percentage of bone-to-implant contact (BIC) (P .05) versus all other groups. The highest point of BIC was achieved with the AO group, which was significantly greater than the lowest group (T). No significant differences between groups were found when the apical 4 mm (nongap areas) were compared (P = .65). Conclusions: Studies have demonstrated that bone can fill in a marginal defect around a titanium implant with varied histologic BIC, depending on implant surface type and defect dimensions. Based upon this animal study using 10 mongrel dogs, marginal circumferential defects of 1 mm showed significantly higher BIC values for implants that were prepared by AO compared to implants with a turned surface. The addition of autogenous bone grafts further enhanced the degree of BIC. Keywords: anodic oxidation, autogenous, bone graft, histomorphometry, osseointegration

Purpose: To evaluate the influence of implant collar geometry on the distribution of stress and strain in the crestal compact bone contiguous to an implant collar for four types of bone under axial and oblique loads. Materials and Methods: Finite element models of threaded implants with three kinds of implant collar designs (divergent, straight, and convergent) with their corresponding suprastructures embedded in the posterior mandible were created with ANSYS software. Eight different test conditions incorporating four types of bone (orthotropic and effectively isotropic in part 1 and high and low densities in part 2) under separate 100-N axial and 35.6-degree oblique forces were created to investigate the stress and strain distributions in the crestal compact bone around the implant collars. Results: In all eight conditions, the divergent collar demonstrated the lowest maximum von Mises and principal stresses and strains in the crestal compact bone contiguous to the implant collar, followed by the straight and convergent collars. The oblique load induced higher peak values than the axial load. The orthotropic design amplified and increased the pathologic microstrains and tensile stresses in the crestal compact bone compared to the effectively isotropic design, especially in models with a convergent collar design. In part 2 of the study, the maximum von Mises stresses and strains increased with a decrease in the cancellous bone density. Under oblique loading, the convergent and straight collars showed pathologic microstrain values as well as excessive ultimate tensile stresses in the orthotropic bone model with low-density cancellous bone. Conclusions: Within the limitations, it was concluded that stress and strain distributions in the adjacent compact bone are influenced by the implant collar design. The divergent implant collar design was associated with the lowest stress and strain concentrations in the crestal compact bone. Keywords: biomechanics, bone density, finite element analysis, implant collar, orthotropy

Purpose: To evaluate the influence of platform switching on the biomechanical environment of implants in different placement and loading protocols. Materials and Methods: A computed tomography-based finite element model of a maxillary central incisor extraction socket was constructed containing a conical 13-mm external-hex implant with a 4.3-mm-diameter shoulder. Abutment models that were 4.3 mm and 3.8 mm in diameter were then imported and aligned to the implant. The 4.3-mm abutment edge matched perfectly the edge of the implant shoulder, while the 3.8-mm abutment assumed a platform-switching configuration. Then, immediately placed, immediately loaded, and osseointegrated (ie, conventional delayed loaded) protocols were simulated. Analysis of variance was used to interpret the data for peak equivalent strain (EQV strain) in the bone, bone-to-implant relative displacement, peak von Mises stress (EQV stress) in the abutment screw, and implant-abutment gap. Results: In the same clinical situation, the differences in the values of the assessed results were minor for abutments of different diameters. In addition, no statistically significant influence of the abutment diameter was seen on any of the evaluated biomechanical parameters, except for the bone-to-implant displacement, although this was observed in a rather low percentage. Nevertheless, a slightly higher EQV stress in the abutment screw was seen in all cases for the 3.8-mm-diameter abutment, although this was not statistically significant. Conclusion: Within the limitation of this finite element analysis, it can be concluded that a circumferential horizontal mismatch of 0.5 mm does not make an important contribution to the biomechanical environment of implants. Also, there seems to be no significant biomechanical drawback to the design rationale of reducing the abutment diameter to move the implant-abutment gap area away from the implant-bone interface. Keywords: finite element analysis, immediate implant loading, immediate implant placement, platform switching

Purpose: The purposes of this study were (1) to evaluate the fit between implant frameworks and implants fabricated with two types of implant framework fabrication techniques: computer-aided design/computer-assisted machining (CAD/CAM) and conventional casting with the lost wax technique; and (2) to describe a digital measurement system consisting of tactile scanning and computer software programs that measured the volumetric differences between implant-supported frameworks and implant restorative platforms fabricated with these technologies. Materials and Methods: This laboratory study used acrylic resin models with five interforaminal implants. The models were scanned; implant-level impressions and verification indexes were then made to construct master casts. First, a cast gold alloy framework and a titanium milled bar fabricated with CAD/CAM technology were made to clarify the construction processes of each. After this pilot study was completed, five cast and five CAD/CAM frameworks were made at each of three dental schools (15 milled and 15 cast bars). Each framework was made on a master cast from individual impressions. The implant restorative interfaces of the frameworks were scanned, and the data were entered into a computer software program. The virtual representations of the frameworks were fit onto digitized scans of the implant restorative platforms and used for virtual one-screw tests on both sides of the arch. Volumetric differences between the implant restorative platforms of the implant-supported frameworks and the model implants were measured to determine the amount of misfit between the frameworks and the model implants. Results: Implant-supported frameworks made with the CAD/CAM technology fit significantly better onto the implants than the cast implant frameworks. There was a significant difference between the right and left one-screw tests; there were no significant differences among the three university sites. Conclusions: The CAD/CAM frameworks featured in this study were significantly more accurate than cast frameworks made with the lost-wax technique. Keywords: computer-aided design, gold, implant-supported frameworks, precision of fit, volumetric assessment

Purpose: Although many studies have analyzed the suitability of different grafting materials for maxillary sinus augmentation by means of histomorphometry in conventional histologic strains, the three-dimensional (3D) structure and remodeling of these grafts after healing beneath the sinus membrane remain unclear. The aim of the present study was to determine whether microcomputed tomography is a suitable method to evaluate the 3D structure and remodeling of grafts after sinus floor augmentation. Materials and Methods: Sinus floor augmentation was performed in five patients using autogenous bone (AB) alone, AB and beta-tricalcium phosphate (b-TCP, Cerasorb), AB and b TCP/hydroxyapatite (HA) (BoneCeramic), AB and calcium carbonate (Algipore), and AB and HA (PepGen). Specimens from the grafted sites were harvested by means of a trephine bur 5 to 16 months after maxillary sinus augmentation. Microcomputed tomography of these specimens was performed with a nominal isotropic resolution of 6 3 6 3 6 µm2 voxel size. After segmentation, 3D images were reconstructed, and the distribution of bone and substitute material was evaluated by means of volumetric and density measurements. Results: In all images, both bone and substitute material could clearly be identified. The connectivity of trabeculae surrounding the substitute material was visible in the 3D reconstructions. Volumetric evaluation such as total bone volume, volume of substitute material, and trabecular thickness and spacing revealed differences between the different grafting materials. Conclusion: Microcomputed tomography is a promising method to evaluate the 3D structure of grafts after sinus floor augmentation with autogenous bone and bone substitute materials. Keywords: bone grafting, maxillary sinus augmentation, microcomputed tomography

Purpose: The objectives of this in vitro study were to determine whether the commercial collagen material used in bone augmentation procedures induces oxidative stress-mediated adverse effects on the viability and function of osteoblasts and to determine whether N-acetyl cysteine (NAC), an antioxidant amino acid derivative, can alleviate these effects. Materials and Methods: Commercial collagen sponge (Collaplug) and membrane (BioGide) were treated with NAC. Rat calvaria-derived osteoblasts were directly seeded on these materials with or without NAC pretreatment. Cytotoxic evaluation was performed by flowcytometric cell viability assay, confocal laser microscopic analysis of attached cell morphology and reactive oxygen species (ROS) localization, and alkaline phosphatase staining. Results: Cell viability was less than 40% on both collagen sponge and membrane 24 hours after seeding and increased to 50% with NAC pretreatment. Cell death was characterized by apoptosis. Colonization of attached cells was sparse on the untreated sponge and membrane on day 1, and the cells were round, small, and filled with intense and closely packed intracellular ROS. In contrast, NAC-pretreated material had dense cell colonies consisting of well-spread osteoblasts and fully developing cytoskeleton and cellular processes with little ROS generation. On day 7 of culture, NAC-pretreated collagen sponge and membrane yielded an expanded alkaline phosphatase-positive area occupying 60% and 80% of the surface area, respectively, whereas the untreated collagen materials had limited alkaline phosphatase activity (7% or less). Conclusions: Commercial collagen sponge and membrane induced considerable cell death, impaired initial function, and generated extraordinary intracellular ROS in attached osteoblasts, whereas NAC pretreatment substantially ameliorated these effects. The potential benefits of NAC's detoxifying capacity on bone regeneration using collagen matrix materials in an animal model should be confirmed with further study. Keywords: antioxidant, biocompatibility, guided bone regeneration, oxidative stress, socket preservation

Purpose: To show, by comparison of horizontal, vertical, and angular misfit in a three-dimensional finite element model, that clinical methods for the evaluation of implant framework fit cannot provide objective results. Materials and Methods: Two three-dimensional finite element models were designed for the simulation of experimentally determined strain values of three-unit fixed dental prostheses supported by two implants. Horizontal, vertical, and angular misfits between implants and restorations were used to create predetermined strain levels. The magnitudes of misfit and resulting bone loading were recorded as von Mises equivalent stresses for the different types of misfit. Results: A horizontal misfit of 36 µm and a vertical misfit of 79 µm had to be modeled to simulate the experimentally determined strain values. An angular misfit of 0.083 degree (equivalent to a gap of 3 µm on one aspect of the implant) resulted in comparable strain levels. Bone loading in the cortical area around both implants ranged from 50 to 90 MPa for horizontal and vertical misfit. In trabecular bone, loading of 2 to 5 MPa was found. For the angular misfit, bone loading up to 20 MPa in the cortical layer and 1 MPa in the cervical part of the trabecular bone occurred at the implant where the misfit had been introduced. Horizontal and vertical misfits led to comparable loading patterns around both supporting implants. Under angular misfit, bone loading mainly occurred around the implant where the misfit had been introduced. Almost no loading was observed in the circumference of the contralateral implant. Conclusions: Minimal angular misfits between implant abutments and restorations, which cannot be detected clinically, may lead to substantial bone loading. Keywords: bone loading, finite element analysis, implant-supported restoration, misfit, passive fit

Purpose: This study aimed to analyze and compare strain distribution patterns for splinted and nonsplinted restorations for dental implants with an internal conical connection. Materials and Methods: Two stereolithic acrylic resin models were created using computed tomographic scan data from a patient missing all mandibular molar teeth. Two implants were placed in the right side of two mandibular models using a computer-generated surgical guide and appropriate protocol. The first model received 5 3 13-mm implants, and the second received 5 3 11-mm implants. Three splinted and three nonsplinted sets of gold screw-retained prostheses were created to fit the implants on each of the two stereolithic models. The 3D image correlation technique was used for full-field measurement of strains using commercial image correlation software and a pair of high-resolution digital cameras, which provided a synchronized stereo view of the models during the experiment. Static loads of up to 203 N were applied in vertical and oblique directions. Strain distribution data were compared for major and minor strains. A mixed-models analysis of variance was done to evaluate all main effect and two-way interactions for each strain, and P values were corrected for multiple comparisons using the step-down Bonferroni adjustment. Results: Evidence of increased load sharing for the splinted prostheses compared to the nonsplinted prostheses was shown. Strain distribution data represented by the ratio of anterior and posterior peak strains were not statistically different for the splinted and nonsplinted prostheses for either implant length. Conclusions: Splinted prostheses generated more uniform strain distributions; however, the strain distribution data were not statistically different from that seen for the nonsplinted prostheses. This suggests that splinting may not be significant for internally connected implants when the crown-to-implant ratio is less than 1. However, clinical corroboration of these findings is required. Keywords: crowns, dental implants, splinting, strains

Purpose: The number of clinicians performing dental implant treatment has increased in recent years. Evidence-based information is necessary to support dentists' decision making. This study was undertaken to present a strategy for searching, selecting, and appraising scientific literature and applying the information in the clinical setting. Materials and Methods: A focused question in the PICO format (patient, intervention, comparison, and outcome) was developed to optimize the literature search process. Systematic reviews (SRs) of randomized controlled trials (RCTs) on the treatment of peri-implantitis were retrieved from the PubMed and Cochrane electronic databases on January 1, 2009. The methodologic quality of the two SRs selected was assessed by two referees using three checklists (CASP, QUOROM, and AMSTAR). The level of agreement between the referees was determined by use of the intraclass correlation coefficient. The evidence retrieved served as the basis for development of a treatment algorithm. Results: The selected SRs reported that subgingival debridement, subgingival debridement plus use of antibiotics, and regenerative procedures can be effective treatments for peri-implantitis. Although the RCTs included in both SRs had several limitations, the checklists demonstrated that the SRs were methodologically rigorous. Intraclass correlation coefficients ranged from substantial to good, indicating that reviewers agreed in their assessment. The evidence-based algorithm visually illustrated the options for the management of peri-implantitis of different severity. Conclusions: This scheme may help clinicians to understand research evidence and to apply it directly in a clinical setting. Keywords: decision making, dental implants, evidence-based dentistry, model, peri-implantitis

Purpose: This pilot study aimed to determine the tissue (both soft and hard) clinical criteria of extraction sockets that are needed to develop ideal implant esthetics following immediate or delayed implant placement. Materials and Methods: Twenty-five maxillary anterior teeth from 25 patients (15 men and 10 women; age 18 to 51 years, mean age 32.4 ± 9.1 years) were extracted. Soft and hard tissue assessments of the sockets were performed immediately after extraction. Therapeutic approaches were made according to a proposed classification. The esthetic outcomes of the implants were evaluated at the time of prosthesis placement and 1 year after function. Results: A treatment decision tree for immediate and delayed implant placement was proposed based on the soft and hard tissue morphology of the extraction sockets. Five extraction sockets were categorized as adequate, 12 as compromised, and 8 as deficient. Type I sockets achieved "adequate" esthetic results regardless of the treatment modalities used. All type II sockets treated with immediate implantation achieved an "adequate" esthetic result at prosthesis placement, but after 1 year, 50% of these sockets were downgraded to the "compromised" category. Type II sockets treated with immediate-delayed implantation (ie, implant placed at 6 weeks after tooth extraction) showed better results: 87.5% of the cases were rated "adequate" at prosthesis placement and 62.5% were rated "adequate" after 1 year of function. Seventy-five percent of type III sockets treated with delayed implantation after soft and hard tissue surgery scored "adequate" at both evaluation periods. Conclusions: Treatment of extraction sockets based on soft and hard tissue morphology promotes the ability to achieve predictable implant esthetics. Keywords: esthetic outcomes, esthetics, guided bone regeneration, immediate implants, single-tooth replacement

Purpose: Excessive stretching of the overlying soft tissue often occurs during the attempt at primary closure after bone augmentation. Preliminary soft tissue expansion may prevent such perfusion disturbances caused by stretching. The purpose of this study was to investigate the effects of using self-inflating expanders at different rates to expand overlying soft tissue prior to the bone grafting procedure. Materials and Methods: Two different hydrogel expanders with different inflation curves were used. For the experiments, 48 Lewis rats were divided into six groups of eight animals each. In four groups, the different expanders were implanted subperiosteally on the calvarium. In two of these groups, an observation window was implanted for intravital microscopy. In the other two groups, histologic analysis of the covering skin was performed. Intravital microscopy of the unexpanded periosteum and histologic analyses of unoperated rats served as control groups. Results: Following implantation of the expanders, intravital microscopic examinations showed that, irrespective of the expansion curve, periosteal microcirculation had stopped completely without reperfusion within 14 days. Histologic analyses of the soft tissues, however, showed a well-vascularized connective tissue layer clinging to the expander. The microvessel density measured was significantly higher above slowly inflating expanders (91.2 ± 8.8 vessels/mm2) than above rapidly inflating expanders (48.4 ± 2.7 vessels/mm2) or unoperated periosteum (60.4 ± 4.8 vessels/mm2). Conclusions: Subperiosteal implantation of self-inflating expanders leads to complete ischemia of the periosteum. However, replacement of the periosteum by connective tissue takes place within 14 days; as a result of subcutaneous angiogenesis, this tissue may have a significantly higher microvessel density than healthy periosteum. Keywords: expander, microcirculation, periosteum, surgery

Purpose: To evaluate the initial stability parameters (insertion torque value [ITV], implant stability quotient [ISQ], and Periotest value [PTV]) of implants inserted just after tooth extraction in human fresh cadavers and to examine the relationship between initial stability parameters and bone-to-implant contact ratio (BICR). Materials and Methods: This study was undertaken in three fresh human cadavers, which were divided into six groups. A total of 48 sites (four maxillary sites and four mandibular sites in each of the six groups) were selected for the experiment. Extractions were performed under minimal surgical trauma and each manufacturer's recommended formal surgical procedure was followed to place implants. Initial stability parameters (ITV, ISQ via two different instruments, PTV) were measured. Specimens were prepared to analyze histologic findings and BICR. Results: A total of 44 implants were included in this study. Statistically significant correlations were found between ITV and ISQ1 (r = 0.555, P .001), ITV and ISQ2 (r = 0.398, P .007), ITV and PTV (r = -0.452, P .002), ISQ1 and ISQ2 (r = 0.603, P .001), ISQ1 and PTV (r = -0.576, P .001), and ISQ2 and PTV (r = -0.423, P .004). No statically significant correlations were found between BICR and the initial stability parameters. Conclusion: The initial stability parameters have statistically significant correlations to each other. However, the initial stability parameters do not seem to present a reliable parameter to predict the area of bone-to-implant contact. Keywords: bone-to-implant contact, immediate implantation, initial stability, insertion torque, Periotest values, resonance frequency analysis

Purpose: The aim of the study was to evaluate the influence of artificial aging on the fracture behavior of straight and angulated zirconia implant abutments used in ZirDesign (Astra Tech) implant/tooth-supported fixed partial dentures (FPDs) in the maxilla. Materials and Methods: Four different test groups (n = 8) representing anterior implant/tooth-supported FPDs were prepared. Groups 1 and 2 simulated a clinical situation with an ideal implant position (maxillary left central incisor) from a prosthetic point of view, which allowed for the use of a straight, prefabricated zirconia abutment. Groups 3 and 4 simulated a situation with a compromised implant position that required an angulated (20-degree) abutment. OsseoSpeed implants (4.5 3 13 mm, Astra Tech) as well as metal tooth analogs (maxillary right lateral incisor) with simulated periodontal mobility were mounted in polymethyl methacrylate. The FPDs (chromium-cobalt alloy) were cemented with glass ionomer. Groups 2 and 4 were thermomechanically loaded and subjected to static loading until failure. Statistical analysis of force data at the fracture site was performed using nonparametric tests. Results: All samples survived thermomechanical loading. Artificial aging did not lead to a significant decrease in load-bearing capacity in either the straight abutments or the angulated abutments. The restorations that used angulated abutments exhibited higher fracture loads than the restorations with straight abutments (group 1: 209.13 ± 39.11 N; group 2: 233.63 ± 30.68 N; group 3: 324.62 ± 108.07 N; group 4: 361.75 ± 73.82 N). This difference in load-bearing performance was statistically significant, both with and without artificial aging. All abutment fractures occurred below the implant shoulder. Conclusions: Compensation for angulated implant positions with an angulated zirconia abutment is possible without reducing the load-bearing capacity of implant/tooth-supported anterior FPDs. Keywords: fatigue testing, fracture resistance, implant abutments, load-bearing capability, zirconia, zirconium dioxide

Purpose: The objective of this study was to assess the accuracy of the model-based NobelGuide method in transferring preoperative planning and estimation of bone volume to the surgical situation. Materials and Methods: Thirteen implant replicas were placed in bounded edentulous spaces in nine human cadavers. Highly restrictive guides were fabricated using preoperative bone mapping data. A stone cast was modified to represent the bone contours at the implant site. Postoperative impressions were taken for comparison with the planning cast that had been used to generate the guides. Mucoperiosteal flaps were raised over each implant site, and the areas were inspected for fenestrations, thread exposures, or dehiscences. A coordinate measuring device was used to obtain positional and angular information from each implant placed in the planned and postsurgical casts. These were compared and analyzed for clinical and statistical significance. Results: The median value for linear accuracy in three dimensions for the model-based NobelGuide was 0.48 mm and the median angular deviation was 2.88 degrees. The greatest measured errors were still within clinically acceptable limits. The bone mapping was of sufficient diagnostic value for implant placement in sites with sufficient bone volume (greater than 5 mm buccolingually). In sites with insufficient bone volume, dehiscences were seen, but the accuracy was independent of bone volume. Conclusion: The use of the model-based NobelGuide encourages adherence to the restorative-driven approach. The accuracy of the method is within acceptable limits for guided surgery described in the literature, and the use of the bone mapping is satisfactory in cases with adequate bone volume. The technique can also be used in sites with insufficient bone volume, but a mucoperiosteal flap procedure is recommended. Keywords: bone mapping, computed tomography, dental implant placement, model-based planning

Recently, implant surgery has been introduced into postdoctoral prosthodontic programs; however, efficient training models to teach this have not been described to date. For training models to be effective and acceptable to all parties, a mutually beneficial situation must be created, and guidelines that can be followed easily need to be described. The purpose of this report is to suggest immediate loading of dental implants as an example for an interdisciplinary training model that integrates both the surgical aspects of implant therapy into the education of prosthodontic graduate students and the prosthodontic aspects of implant therapy into the training of periodontal graduate students. A flow chart of training steps is described for a patient treated with an immediately loaded mandibular fixed full-arch prosthesis on five interforaminal implants. Both the prosthodontic and the periodontal residents were involved in all phases of treatment. These postdoctoral students were in the final year of their program. Therefore, individual treatment steps could be taught interchangeably and accomplished by the student of the other specialty under the supervision of a clinical instructor. The unique characteristic of the immediate loading procedure, which includes surgical implant placement as well as immediate conversion of an existing denture into a fixed implant-supported provisional prosthesis, allows each postgraduate student to experience detailed surgical and prosthodontic treatment in a controlled environment on the day of surgery. Keywords: dental implant, guidelines, immediate loading, interdisciplinary, postdoctoral training

Purpose: The purpose of this prospective clinical trial was to evaluate over a 5-year period the treatment outcomes for immediately loaded full-arch fixed prostheses supported by two axially inclined and two tilted implants used to rehabilitate edentulous arches. This report presents preliminary 1-year results. Materials and Methods: Thirty-seven patients were recruited for treatment with either mandibular or maxillary full-arch fixed prostheses supported by four implants. Within 24 hours, the implants were immediately loaded with screw-retained full-arch acrylic resin provisional restorations. Definitive reconstructions were delivered 6 months later. Complete full-arch prostheses were supported by metal frameworks combined with high-density acrylic resin. Follow-up visits were scheduled for 6 and 12 months after initial prosthetic loading and then annually for up to 5 years. Digital radiographs were obtained immediately, 6 months after surgery, and at each annual follow-up visit. Marginal peri-implant bone levels were assessed using digital image analysis. Results: The 1-year implant survival rates were 96.0% for axially positioned implants and 94.6% for tilted implants. The survival rates were 96.6% for maxillary implants and 98.7% for mandibular implants. The prosthetic survival rate was 100%. No significant differences were found in the results for tilted versus axially positioned implants. One year after loading, the mean marginal bone loss was 0.82 ± 0.31 mm around the axially oriented implants and 0.76 ± 0.49 mm around the tilted implants (P = .05). Conclusions: Preliminary data from this clinical trial show high implant survival rates for immediately loaded full-arch prostheses supported by four implants. Immediate loading of tilted implants may be considered a viable treatment option for the rehabilitation of edentulous patients. Keywords: dental implants, edentulous jaw, immediate loading, tilted implants

Purpose: This retrospective study sought to demonstrate the outcome of maxillary sinus elevation surgery in a series of 177 procedures performed over 12 years and to determine the existence of variables that could independently predict implant survival. Materials and Methods: A retrospective descriptive and analytic study of a series of maxillary sinus elevation procedures performed between 1996 and 2007 was undertaken. The sample was composed of patients with severe atrophy of the posterior maxilla who had been rehabilitated with osseointegrated implants placed in grafted maxillary sinuses. Several features of the patients (smoking habit, presence of comorbidities, and previous oral carcinoma) and of the surgical procedure (grafting material, associated procedures, associated materials, simultaneous/delayed implant placement, and complications) related to implant survival or failure were monitored during the follow-up period. Implant survival and the existence of variables that could predict implant survival independently were analyzed statistically. Results: One hundred seventy-seven sinus augmentation procedures were performed in 119 consecutive patients (mean age 50.02 years; SD 11.5). Of the 272 implants placed in sinus-augmented regions, 19 were lost. The mean follow-up period was 60.7 months (SD 36.5). The overall cumulative implant survival rate was 93% after 5 years. The multivariate analysis showed that the presence of complications related to the sinus augmentation procedure (membrane perforation and sinusitis) and peri-implantitis were factors in predicting implant failure. Conclusions: On the basis of this retrospective analysis, it might be concluded that sinus augmentation is a very versatile procedure. Its efficacy and predictability in terms of implant survival rate is extremely high and independent of the graft material, surgical technique, associated comorbidities, smoking habits, and timing of implant placement. Complications such as membrane perforation, sinusitis, and peri-implantitis appeared to influence implant failure. Keywords: implant survival rate, multivariate analysis, sinus augmentation, univariate analysis

Purpose: This case series evaluated the implant success rate and peri-implant tissue response of immediately loaded unsplinted implants retaining a mandibular overdenture. Materials and Methods: Eight completely edentulous patients (five men, three women) with a mean age of 69.1 years were included in the study. All participants received new maxillary and mandibular complete dentures prior to implant placement. Two 4.0- 3 13-mm threaded implants with a fluoride-modified microrough titanium surface were placed mesial to the mandibular canine position bilaterally. Individual stud attachments were connected and torqued to 25 Ncm and the overdenture was immediately attached. The patients were evaluated clinically and radiographically at implant placement and at 3, 6, and 12 months after implant placement. The data were analyzed using the paired-samples t test and the Wilcoxon signed-ranks test at a significance level of a = .05. Results: At 12 months, all implants remained osseointegrated and showed an overall mean marginal bone change of -0.36 ± 0.29 mm and a mean Periotest value of -6.94 ± 0.73. The modified Plaque Index scores indicated improvements in oral hygiene over time. Surgical complications involved two episodes of implant rotational instability. Prosthetic complications were attributed to abutment loosening, the patients' inability to insert the prosthesis correctly, and soft tissue shrinkage. Conclusions: The results of this study suggest that favorable implant success rates and peri-implant tissue responses can be achieved with mandibular overdentures retained with two immediately loaded unsplinted threaded implants with a fluoride-modified microrough titanium surface. Keywords: immediate loading, implant-retained prosthesis, locator abutment, mandibular overdenture, unsplinted

Purpose: The aim of this 1-year prospective study was to evaluate, in patients with severe periodontitis, the clinical performance of implants placed immediately after extraction of remaining teeth or in healed sockets and immediately loaded for prosthetic oral rehabilitation, and to compare the clinical outcomes for implants placed in fresh extraction sockets versus healed sites. Materials and Methods: All patients in this study had received periodontal treatment; however, the teeth were eventually deemed hopeless. The remaining teeth were extracted, the periodontally compromised sites were débrided, implants were inserted guided by a surgical template, and a provisional restoration was delivered immediately. The opposing arch was restored with a complete denture. Definitive prostheses were inserted after 6 months. Initial implant and prosthesis stability and the inflammatory response were evaluated. Clinical and radiographic analyses were performed. Results: A total of 84 rough-surfaced implants were placed (50 in the maxilla and 34 in the mandible). Of these, 32 were placed in fresh extraction sockets. Four implants in three patients failed within the first 6 months, resulting in an implant survival rate of 95.2%. All of the failed implants had been placed in fresh maxillary extraction sockets. The survival rates were 92% (46/50) in the maxilla and 100% (34/34) in the mandible. Prosthetic success was 100%. The mean bone level change (± SE) between baseline and 12 months was -1.12 ± 0.18 mm. There were no statistically significant differences in insertion torque and alveolar bone loss between postextraction sites and healed sites. Conclusions: The implant failure rate was higher in maxillary postextraction sites. This indicates a heightened risk of failure for immediate implants placed in periodontally compromised maxillae. Nevertheless, a satisfactory prosthetic success was achieved after 1 year. Keywords: dental implants, full-arch reconstruction, immediate loading, immediate placement, periodontal disease

A fungus ball is one of the fungal diseases that can affect the paranasal sinuses. It requires surgical treatment. Because there is only one previously reported case of dental implant placement after treatment of a maxillary sinus fungus ball, the authors here report on a case of a maxillary sinus fungus ball with bone erosion that was treated surgically with a combined endoscopic endonasal and endoral (Caldwell-Luc) approach. One year later, a graft from the ilium was obtained and a sinus elevation was performed to allow the placement of dental implants. Three months later, the dental implants were placed, and they were all osseointegrated at the 9-month follow-up. Keywords: bone graft, dental implants, fungus ball, maxillary sinus, sinus lift