The International Journal of Oral & Maxillofacial Implants, 04/2010

Purpose: The purpose of this study was to investigate and compare bone formation on titanium implant surfaces coated with biomimetically deposited calcium phosphate (BDCaP) or electrochemically deposited hydroxyapatite (EDHA). Materials and Methods: The implants were separated into three groups: a control group, a BDCaP group, and an EDHA group. Surface analysis was performed by field-emission scanning electron microscopy, x-ray diffractometry, and Fourier transform infrared spectroscopy. Implants were inserted in a randomized arrangement into rabbit tibiae. After 2, 4, and 8 weeks, the tibiae were retrieved and prepared for histomorphometric evaluation. Results: Field-emission scanning electron microscopy showed that the BDCaP crystals were flakelike and the EDHA crystals were rodlike with a hexagonal cross section. X-ray diffractometric patterns and Fourier transform infrared spectroscopy spectra showed that the BDCaP coating consisted of HA and octacalcium phosphate, whereas the EDHA coating consisted of HA. Histologic observation showed that new bone on the EDHA-coated implant became mature after 4 weeks, while new bone on the control and BDCaP-coated implants was mature after 8 weeks. The EDHA implant showed significantly greater BIC and bone area compared to the control and BDCaP implants during 4 to 8 weeks. The BDCaP coating failed to show increased bone formation during the test period. Conclusion: The present EDHA coating has good bone formation properties, while the BDCaP coating has weaker bone formation properties. Keywords: biomimetic deposition, bone formation, dissolution, electrochemical deposition, hydroxy-apatite coating

Purpose: The aim of the present study was to evaluate the validity of a new experimental microthreaded scalloped (MTS) implant design in comparison to a conventional flat-top (FT) implant by measuring the proximal bone loss at different interimplant distances in a canine model. Materials and Methods: MTS implants were placed in one side of the posterior mandible and conventional flat-top (FT) implants were placed in the other side of the mandible in 10 beagle dogs. In five dogs, four each of the MTS and FT implants were placed with an interimplant distance of 2 mm. In another five dogs, three each of the MTS and FT implants were placed at an interimplant distance of 5 mm. All 70 implants (35 MTS and 35 FT implants) were placed in a nonsubmerged (one-stage) manner. The animals were sacrificed 4 months after implant placement, and the crestal bone levels around the MTS and FT implants were measured and compared on radiographs and histologic sections. Results: The experimental MTS im-plants showed significantly less crestal bone loss (0.81 ± 0.34 mm) than the FT implants (1.60 ± 0.42 mm) on radiographs (P .001). Histologic measurement also demonstrated that there was significantly less (P .001) marginal bone loss around the MTS implants (0.74 ± 0.41 mm) than around the FT implants (1.53 ± 0.52 mm). There was no statistically significant difference in bone loss between the 2-mm and 5-mm interimplant distances for either MTS or FT implants (P > .05). Conclusion: The experimental MTS implant was more effective in preserving the proximal bone than the conventional FT external-hex implant with the same surface. In this canine model, placement of the implants at either a 2-mm and or a 5-mm interimplant distance did not result in significant differences in marginal bone loss for both MTS and FT implants. This experiment demonstrated a potential benefit of the microthread design on a scalloped implant. Keywords: interimplant distance, microthreaded scalloped implant, proximal bone healing

Purpose: To characterize the normal bacterial flora and evaluate the presence of periodontopathogenic bacteria around dental implants and to correlate them with the periodontal flora or, in completely edentulous patients, the alveolar gingival flora. Materials and Methods: Clinical and radiographic parameters were recorded to exclude peri-implantitis in 34 partially edentulous and 19 completely edentulous patients. Partially edentulous patients were subdivided into two subgroups based on the depth of the periodontal pocket: = 4 mm (n = 19) and > 4 mm (n = 15). Microbial samples were collected from peri-implant sulci, the deepest periodontal sulci, and, for completely edentulous patients, from the alveolar gingiva. Predominant aerobic bacteria were determined by microbiologic culturing, and multiplex polymerase chain reaction was used to detect five periodontopathogenic bacteria: Porphyromonas gingivalis, Tannerella forsythensis, Treponema denticola, Prevotella intermedia, and Actinobacillus actinomycetemcomitans. Results: In all the examined patients, oral streptococci were the most frequent aerobic peri-implant bacteria. The frequency of four periodontopathogenic bacteria in tooth sulci (A actino-mycetemcomitans, P gingivalis, T forsythensis, T denticola) was significantly higher around natural teeth with deeper periodontal pockets, but there was no significant difference in the frequency of the same bacteria in peri-implant sulci in the two partially edentulous subgroups. In contrast, there were no such bacteria in the peri-implant sulci or the alveolar gingiva of completely edentulous patients. Conclusions: In healthy peri-implant sulci, oral streptococci constitute the predominant bacterial flora. In partially edentulous patients four periodontopathogenic bacteria were detected around implants, and none of these bacteria were found around implants in completely edentulous patients. Keywords: complete edentulism, partial edentulism, peri-implant bacteria

Purpose: Bone tissue engineering is a promising approach for bone reconstruction in oral and maxillofacial surgery. The aim of this study was to investigate the microstructure and biocompatibility of a novel albumin scaffold developed from human serum on human alveolar osteoblasts. Materials and Methods: Samples of mandibular bone were obtained during routine oral surgery. Osteoblast cells were cultured and plated in a spongy, noncalcified protein scaffold prepared with plasmatic albumin crossed with a glutaraldehyde-type agent (study group) and in a large-particle mineralized cancellous allograft (control group). Measurement of the differentiation marker alkaline phosphatase and histologic examination were performed after 30 days of incubation. The cultures were examined for cell growth patterns and morphology by scanning electron microscopy and histomorphometry. Results: Cultured osteoblasts showed comparable phenotypic profiles and expressed alkaline phosphatase in albumin scaffold. Hematoxylin-eosin staining revealed a bonelike extracellular matrix in study scaffold and mineralization of osteoblasts cultured in the albumin scaffold was confirmed by von Kossa staining. Conclusion: Osteoblasts were able to proliferate in vitro and synthesize a bonelike extracellular matrix and mineralized tissue. The results indicate that this novel albumin scaffold is a favorable substrate for the growth and differentiation of osteoblasts and a promising material for bone tissue engineering and repair of bone defects. Keywords: bone culture, osteoblasts, scaffold, tissue engineering

Purpose: The aim of this study was to evaluate the effects of cortical bone thickness and implant length on strain in the surrounding bone and micromotion at the bone-implant interface in single immediately loaded implants. Materials and Methods: Experiments with rapid prototyping technique and finite element simulations were performed to evaluate bone strain and micromotion at the bone-implant interface. Implants (13-mm long) were embedded into models with three thicknesses of cortical bone (0.5, 1.7, and 3.4 mm), and implants with different lengths (11.5 and 15.0 mm) were inserted into models with 1.7 mm of thickness of cortical bone. Vertical and lateral loads of 130 N were applied to the models. Results: On lateral loading, the strains were highly concentrated on one side of the mandible in both experimental and finite element models. Sliding and gap distances were reduced when the cortical bone was thicker and when the implant was longer. Conclusion: Placement of a longer implant into thicker cortical bone will result in reduced sliding and gap distances. However, bone strain is influenced more by the cortical bone thickness than by the implant length for single immediately loaded implants. Keywords: cortical bone thickness, dental implants, finite element analysis, immediate loading, implant length

Purpose: This in vitro study compared the dimensional accuracy of a stone index and of two impression techniques (squared impression copings and modified squared impression copings) for implant-supported prostheses. Materials and Methods: A master cast with four parallel implant-abutment analogs and a passive framework were fabricated. Vinyl polysiloxane impression material was used for all impressions with a metal stock tray. Three groups of impressions were tested (n = 5): index (I), squared (S), and modified squared (MS). The measurement method employed was just one titanium screw tightened to the framework. The measurements (60 gap values) were analyzed using software that received the images from a video camera coupled to a stereomicroscope at 3100 magnification. The results were evaluated statistically (analysis of variance, Holm-Sidak method, a = .05). Results: The mean abutment/framework interface gaps were: master cast = 31.63 µm; group I = 45.25 µm; group S = 96.14 µm; group MS = 51.20 µm. No significant difference was detected among the index and modified squared techniques (P = .05). Conclusion: Under the limitations of this study, the techniques modified squared and index generated more accurate casts than the squared technique. Keywords: dental implants, dental impression technique, dental models

Purpose: The purpose of this study was to determine whether osseous tissues engineered in three-dimensional (3D) environments preserved their mineralizing capacity and retained biologic characteristics when cultured on dental implant surfaces. Materials and Methods: Human preosteoblast cells were cultured in both 3D rotary wall vessels and on 2D tissue culture plastic plates for 3 days. Aggregates from the 3D chambers and cells from the 2D plates were collected and transferred to commercially pure titanium disks with either 600-grit polished or sandblasted surfaces. These were cultured for an additional 7 days. The aggregates and cells from the disks were collected and prepared for scanning electron microscopy for microscopic evaluation and atomic adsorption assays for mineral content analysis. Additionally, staining with Alizarin red S was performed to compare the mineralization amount and pattern in each group. Polymerase chain reaction analysis was performed to evaluate expression of osteogenic genes, including Runx2, FAK, bone morphogenetic protein 2, and osteocalcin. Results: Cells from 3D rotary wall vessel cultures attached to implant surfaces and presented cell attachment and growth patterns similar to those of standard 2D cultured cells, showing evidence of radial and random growth, yet they formed multiple focal niches on implant surfaces out of which cells proliferated. The 3D cultured cells and osseous tissues retained higher amounts of mineral formed during the initial culture and showed a higher tendency toward mineralization on implant surfaces compared to standard cultured cells. The 3D cultured cells and osseous tissues on implant surfaces at 1 week showed higher key gene protein expression. RNA expression at 1 week was equivalent to that of standard cultured cells. Conclusion: Culture of human osteogenic cells and tissues in 3D rotary wall vessels may expedite the osseointegration process on dental implant surfaces, thus reducing the overall treatment time. Keywords: dental implant, osseointegration, osteoblast, tissue engineering

Purpose: It has been proposed that increased crown heights lead to greater crestal stresses on dental implants, crestal bone loss, and other complications. The purpose of this study was to evaluate the effect of increased crown-to-implant ratio (C/IR) on single-tooth implants. Materials and Methods: A retrospective cohort study was conducted between July 2001 and August 2003. The cohort was composed of patients who had at least one single-tooth Bicon implant restored with a cementless restoration and attended recall examinations in 2004, 2005, and 2007, during which several clinical and radiographic variables were documented. Descriptive statistics and univariate and multivariate mixed-effects regression models, adjusted for multiple implants in the same patient, were used. Results: The cohort was composed of 81 subjects who received 326 Bicon implants. The mean duration of follow-up was 70.7 months. Mean change in the mesiodistal crestal bone levels was -0.33 mm. The mean C/IR was 1.6 (range, 0.79 to 4.95). Forty implant restorations (16%) had a C/IR >= 2. Implant restorations with increased C/IR were significantly more likely to have increased mesiodistal crown width, larger implant diameter, larger distance to mesial and distal adjacent structures, and deeper sulcular probings. Increased C/IR had a statistically significant effect in the loosening of maxillary anterior Integrated Abutment Crowns (Bicon) as well as a significant effect in the fracture of 2-mm-wide titanium abutment posts used to restore posterior areas. A C/IR up to 4.95 did not lead to an increased risk of crestal bone loss or to an increase in implant failures, crown failures, or crown fractures. Conclusion: Larger C/IR was associated with a significant increase in prosthetic complications but had no significant effect on crestal bone levels on single-tooth locking-taper implants. Keywords: cementless restorations, crown-to-implant ratio, plateau design dental implants, resin crowns, stress

Purpose: Critical bending moment (CBM), defined as the bending moment at which the external nonaxial load applied overcomes screw joint preload and causes loss of contact between the mating surfaces of the implant screw joint components, was measured for four different implants and their single-tooth replacement abutments. Materials and Methods: CBM at the implant-abutment screw joint for four implant-abutment test groups was measured in vitro at 80%, 100%, and 120% of the manufacturers' recommended torque levels. Regular-platform implants with their corresponding single-tooth abutments were used. Microstrain was measured while known loads were applied to the abutment at known distances from the implant-abutment interface. Strain instrumentation was used to record the strain data dynamically to determine the point of gap opening. All torque applications and strain measurements were repeated five times for the five samples in each group. Results: For the Brånemark/CeraOne assemblies, the mean CBMs were 72.14 Ncm, 102.21 Ncm, and 119.13 Ncm, respectively, at 80%, 100%, and 120% of the manufacturer's recommended torque. For the Replace/Easy assemblies, mean CBMs were 86.20 Ncm, 109.92 Ncm, and 120.93 Ncm; for the Biomet 3i/STA assemblies, they were 67.97 Ncm, 83.14 Ncm, and 91.81 Ncm; and for the Lifecore/COC assemblies, they were 58.32 Ncm, 76.79 Ncm, and 78.93 Ncm. Two-way analysis of variance revealed significant effects for the test groups and torque levels. Subsequent tests confirmed that significant differences existed between test groups and torque levels. Conclusion: The results appear to confirm the primary role of the compressive preload imparted by the abutment screw in maintaining screw joint integrity. CBM was found to differ among implant systems and torque levels. Torque levels recommended by the manufacturer should be followed to ensure screw joint integrity. Keywords: abutment screw, bending moment, dental implant, implant-abutment screw joint, strain gauge, tightening torque

Purpose: Rotational freedom of various implant positional index designs has been previously calculated. To investigate its clinical relevance, a three-dimensional simulation was performed to demonstrate the influence of rotational displacements of the abutment on the marginal fit of prosthetic superstructures. Materials and Methods: Idealized abutments with different angulations (0, 5, 10, 15, and 20 degrees) were virtually constructed (SolidWorks Office Premium 2007). Then, rotational displacement was simulated with various degrees of rotational freedom (0.7, 0.95, 1.5, 1.65, and 1.85 degrees). The resulting horizontal displacement of the abutment from the original position was quantified in microns, followed by a simulated pressure-less positioning of superstructures with defined internal gaps (5 µm, 60 µm, and 100 µm). The resulting marginal gap between the abutment and the superstructure was measured vertically with the SolidWorks measurement tool. Results: Rotation resulted in a displacement of the abutment of up to 157 µm at maximum rotation and angulation. Interference of a superstructure with a defined internal gap of 5 µm placed on the abutment resulted in marginal gaps up to 2.33 mm at maximum rotation and angulation; with a 60-µm internal gap, the marginal gaps reached a maximum of 802 µm. Simulation using a superstructure with an internal gap of 100 µm revealed a marginal gap of 162 µm at abutment angulation of 20 degrees and rotation of 1.85 degrees. The marginal gaps increased with the degree of abutment angulation and the extent of rotational freedom. Conclusions: Rotational displacement of the abutment influenced prosthesis misfit. The marginal gaps between the abutment and the superstructure increased with the rotational freedom of the index and the angulation of the abutment. Keywords: abutment rotation, marginal gap, prosthesis misfit, three-dimensional simulation

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: Ideally, implants for dental prostheses should be placed parallel to each other. However, anatomic limitations sometimes make nonparallel implants necessary. The purpose of this study was to determine the bone stresses on implants tilted at various angles and to determine what arrangements might carry a higher risk of failure. Materials and Methods: Three-dimensional finite element models were constructed using the mean values measured for the Asian mandible in the first and second molar areas. Eight implants were divided into three tilting types: parallel implants (P1PP, P2MM, and P3DD), convergent implant apices (C1PD and C2MP), and divergent implant apices (D1DP, D2DM, and D3PM). A biting load of 200 N was applied vertically and obliquely on the occlusal central fossa of the splinted crowns. The main effects of each level of the three investigated factors (loading type, relationship of implant apices, and distal tilting of one or both implants) in terms of the stress values were computed for all models. Results: The loading type was the main factor affecting the stress in bone when comparing implant apices and distal tilting of the implant body. When loading was combined with distal tilting, the stress values were significantly increased, especially in models P3DD and C1PD. Conclusion: The loading type is the main factor affecting the stress distribution for different implantation arrangement. Moreover, placement of the implants with distal tilting should be avoided in the posterior mandible. Keywords: convergent implant apices, divergent implant apices, finite element analysis, implant axis, implant loading

Purpose: To investigate, in vitro, the dimensional accuracy of two impression techniques (squared impression copings and squared impression copings sandblasted and coated with impression adhesive) made of vinyl polysiloxane and polyether impression materials. Materials and Methods: A master cast (control group) with four parallel implant abutment analogs, a passive framework, and a custom aluminum tray was fabricated. Four groups (n = 5 each group) were tested: squared Impregum (SI), squared Express (SE), sandblasted adhesive squared Impregum (ASI), and sandblasted adhesive squared Express (ASE). The measurement method employed was just one titanium screw tightened to the framework. A stereomicroscope was used to evaluate the fit of the framework by measuring the size of the gap between the abutment and the framework. The results were analyzed statistically. Results: The mean values for the abutment/framework interface gaps were: master cast, 31.63 µm (SD 2.16); SI, 38.03 µm (SD 9.29); ASI, 46.80 µm (SD 8.47); SE, 151.21 µm (SD 22.79); and ASE, 136.59 µm (SD 29.80). No significant difference was detected between the SI or ASI techniques and the master cast. No significant difference was detected between the SE and ASE techniques. Conclusion: Within the limitations of this study, it can be concluded that Impregum Soft medium consistency was the best impression material and the impression technique did not influence the accuracy of the stone casts. Keywords: dental implant, implant impression technique, impression material

Purpose: This study compared the insertion and removal torque of tapered and cylindric orthodontic miniscrews. Materials and Methods: Ninety-six miniscrews were placed into the buccal alveolar bone of the mandible in six male beagle dogs. Maximum insertion torque was measured during placement of 48 miniscrews, and the maximum removal torque was recorded after 3 and 12 weeks of loading. After 4 months of healing, 48 additional miniscrews were implanted in almost the same place as the first set of implants; insertion torque was again measured. Histologic analysis was performed after 3 and 12 weeks of loading. Bone-implant contact and bone volume/total volume were compared during each period and in each group. Results: The tapered miniscrews showed a higher mean maximum insertion torque (22.3 ± 3.2 Ncm) than the cylindric miniscrews (13.6 ± 2.0 Ncm) (P .001). The mean maximum removal torque of the tapered miniscrews (9.1 ± 2.3 Ncm) was significantly higher than that of the cylindric miniscrews (5.7 ± 2.2 Ncm) at 3 weeks after placement (P .05), but there was no significant difference in the mean maximum removal torque value between the tapered (4.2 ± 1.4 Ncm) and cylindric (3.0 ± 1.1 Ncm) implants after 12 weeks of loading. The percentage of bone-implant contact was similar between the groups after 3 weeks of loading and increased later. The percentage of bone volume/total volume was higher in the tapered miniscrews than in the cylindric miniscrews after 3 weeks of loading (P .05), but there was no significant difference between the groups after 12 weeks of loading. Conclusions: In this dog model, the tapered miniscrew design increased initial stability until 3 weeks of loading but had no additional effect on the secondary stability (ie, after 12 weeks of loading) versus a cylindric miniscrew design. Keywords: cylindric implant design, insertion torque, orthodontic miniscrew, removal torque, tapered implant design

Purpose: The aim of this 1-year pilot prospective study was to evaluate the implant success rate, peri-implant tissue response, and complications associated with the immediate loading of two freestanding implants retaining mandibular overdentures. Materials and Methods: Ten adults with a mean age of 59.7 years (range, 43 to 78 years) underwent treatment that included a maxillary removable complete denture opposing a mandibular removable overdenture retained by two freestanding, threaded, titanium oxide-surface implants with a 3-mm machined collar (n = 20 implants). The success of each implant was evaluated clinically and radiographically. Marginal bone levels and changes were evaluated using sequential standardized periapical radiographs. Surgical and prosthetic complications were recorded. Results: Two patients, one with one failed implant, dropped out prior to completion of the study. The failed implants were included in the evaluation of cumulative implant success. The cumulative implant success rate at 1 year was 94% (16/17). The mean marginal bone loss was 1.12 ± 1.10 mm at 12 months. However, if the expected bone loss of 0.39 mm above the smooth-rough implant surface junction was considered, the mean marginal bone loss was only 0.73 mm. Mean Periotest values of -4.25 ± 0.93 at 1 year implied that osseointegration had been achieved for all successful implants. Modified Plaque Index scores of 0 and 1 were recorded throughout the duration of the study. No irreversible surgical and/or prosthetic complications were observed. Conclusions: In this 1-year pilot prospective study, two immediately loaded unsplinted mandibular symphyseal implants retaining an overdenture resulted in favorable implant success and peri-implant tissue response. Keywords: ball-attachment, immediate loading, implant-supported prosthesis, mandibular overdenture, prospective, two freestanding implants

Purpose: To assess and compare patient satisfaction and oral health-related quality of life (OHQOL) in patients treated with implant-supported overdentures and complete implant fixed prostheses. Materials and Methods: From a database of patients who had undergone implant treatment over a 6-year period, a study population of 62 patients was identified; every patient had at least four implants placed in one edentulous arch and was restored with either an overdenture or a fixed prosthesis. Patients were examined and a self-administered, structured multiple-response questionnaire, including the Oral Health Impact Profile-14 measurement tool and a patient satisfaction survey, was used to evaluate patient-centered treatment outcomes. Results: Generally, patient satisfaction was very high in both the implant overdenture and fixed prosthesis groups, although the subjects in the overdenture group, who had mostly maxillary prostheses, reported significantly lower overall satisfaction and lower satisfaction with chewing capacity and esthetics. In just three categories-cost, satisfaction with treating doctor, and ability to perform oral hygiene measures-the fixed prosthesis group was less satisfied than the removable overdenture group, but the difference was not significant. Similarly, the overall OHQOL was high, although patients receiving a fixed prosthesis demonstrated significantly lower psychologic discomfort and psychological disability compared to the overdenture group. Conclusions: Among all patients who had similar numbers of implants placed, those who received an implant overdenture were less satisfied and had lower OHQOL than the patients who had a fixed prosthesis. Since patient and dentist preferences influenced the type of prosthesis provided, it is likely that subjective, patient-related factors are major determinants of satisfaction and treatment outcomes. Keywords: dental implants, patient satisfaction, quality of life, treatment outcomes

Purpose: To compare the efficacy of two different techniques for vertical bone regeneration at implant placement with particulated autogenous bone at 3 years after loading: resorbable collagen barriers supported by osteosynthesis plates and nonresorbable titanium-reinforced expanded polytetrafluoro-ethylene barriers. Materials and Methods: Twenty-two partially edentulous patients requiring vertical bone augmentation were randomly allocated to two treatment groups, each composed of 11 patients. Prosthetic and implant failures, complications, the amount of vertically regenerated bone, and peri-implant marginal bone levels were recorded by independent and blinded assessors. The implant site requiring the most vertical bone regeneration was selected in each patient for bone level assessment. The follow-up time ranged from provisional loading to 3 years after loading. Analysis of covariance and paired t tests were conducted to compare means at the .05 level of significance. Results: No patient dropped out or was excluded at the 3-year follow-up. No prosthetic failures and no implant failures or complications occurred after loading. There was no statistically significant difference in bone loss between the two groups at either 1 year or 3 years. Both groups had gradually lost a statistically significant amount of peri-implant bone at 1 and 3 years (P .05). After 3 years, patients treated with resorbable barriers had lost a mean of 0.55 mm of bone; patients who had received nonresorbable barriers showed a mean of 0.53 mm of bone loss. Conclusions: Up to 3 years after implant loading, no failures or complications occurred and peri-implant marginal bone loss was minimal. Vertically regenerated bone can be successfully maintained after functional loading. Keywords: dental implants, guided bone regeneration, peri-implant bone levels, vertical augmentation

Restoration of a nasal defect after ablative surgery for squamous cell carcinoma necessitates replacing the missing volume and anchoring a prosthesis to the patient's face. This report describes the failure of plastic reconstructive surgery after ablation of a squamous cell cancer of the nose and the esthetic and functional restoration of the patient with a nasal prosthesis. The process of making an implant-supported prosthesis using digital technology, including digitized anatomic models from a "nose library," and the rapid prototyping of the mesiostructure for bar anchorage and of the mold for silicone processing are presented. Keywords: computer-aided design, computer-assisted manufacture, maxillofacial prosthesis, nasal prosthesis, rapid prototyping

Purpose: To evaluate an alternative treatment for rehabilitation of the atrophic maxilla with palatal and tilted implants and to assess patient satisfaction with the results. Materials and Methods: A retrospective case study was made of completely edentulous subjects with tilted, palatally positioned implants in the anterior maxillary buttress placed and loaded between January 2005 and January 2007. Patients with severely resorbed edentulous maxillae (Class V according to Cawood and Howell) who requested overdentures and were followed for 12 months after implant loading were included. Mesial and distal implant bone loss was measured on panoramic radiographs. Subjects indicated satisfaction with the new prosthesis after 12 months on a visual analog scale. Results: Twelve patients treated with tilted and palatal implants in the anterior maxillary buttress were included in the study; 48 implants were placed (4 implants in each patient) to support 12 overdentures with bars. One implant failed, resulting in a survival rate of 97.9%. The mean peri-implant bone loss of implants with palatal anchorage after 1 year of loading was 0.78 ± 0.5 mm. All patients had stable prostheses at the end of the observation period. Patients were satisfied with comfort and stability, ability to speak, ease of cleaning, esthetics, and function of the prosthesis. Conclusion: Placement of implants slightly to the palatal and tilted in the anterior maxillary buttress to support an overdenture with bars may be a viable treatment alternative for the rehabilitation of the atrophic maxilla, providing a high level of satisfaction with the prosthesis and reducing patient morbidity and costs. Keywords: anterior maxillary buttress, maxillary atrophy, overdenture, palatal position, tilted implants, visual analog scale

Purpose: After the loss of natural teeth, bone changes in the jaws begin to take place immediately. Because the alveolar bone no longer responds to stresses placed in this area by teeth and periodontal ligaments, the bone begins to resorb. In such cases, alveolar bone reconstruction followed by implant-prosthetic treatment must be considered to reestablish esthetics and function. The present study was designed to compare and evaluate the effectiveness of titanium screws and absorbable fixation systems for the fixation of autogenous onlay bone grafts in maxillary reconstruction. Materials and Methods: A total of 10 consecutive patients with severely resorbed maxillae were referred to the Oral and Maxillofacial Surgery Department at Piracicaba Dental School, Campinas State University (São Paulo, Brazil), for oral rehabilitation through implant placement. The bone defects were treated by autologous bone grafting from the iliac crest, which was fixed with absorbable screws. The patients were followed for a minimum of 6 months after prosthodontic work was concluded. Results: The average age of the patients in this study was 46.9 years. Two dental implants were lost during the healing period. Four absorbable screws showed an unusual tissue reaction and were lost, and 90% of patients received the planned fixed prostheses. The implant success rate was 97% at 1 year after prosthesis placement. Conclusion: Fixation with absorbable screws has been shown to be safe and predictable. The absorbable screws did not interfere with bone graft healing and dental implant osseointegration. Keywords: biodegradable screws, bone grafting, dental implants, maxillary reconstruction

Implant placement in orbital sites is challenging because of limited bone volume and poor bone quality. Preoperative optimal implant planning and intraoperative guides are important to ensure success. This article describes the use of computer simulation for implant insertion and fabrication of a surgical template as a drilling guide for orbital implant placement. A 29-year-old woman with a right orbital defect underwent computerized tomographic scanning, and the data were processed with interactive software to simulate orbital implant placement. A surgical template that served as a drilling guide was designed and fabricated to transfer orbital recipient site information from the three-dimensional computer model into the actual orbital implant sites. Three craniofacial implants were placed in the 7:00, 8:00, and 11:00 positions. No unexpected complications or injuries were encountered during the surgery. Magnetic abutments were attached to the implants 2 weeks later. The definitive facial prosthesis was fitted 6 months later, with excellent esthetic results. The surgical template contributed to the success of this treatment. Keywords: computer-aided design, computer-assisted manufacture, craniofacial implant, orbital defect, surgical template

The following report presents the treatment of a 53-year-old man that developed a radiolucency around the apex of the implant in the mandibular incisor region after placement and immediate provisionalization (nonfunctional loading). The radiolucency was detected during the final impression phase, 4 months after placement. A cone-beam computed tomographic scan revealed extensive involvement of the apical one third of the implant. The patient was placed on a course of antibiotics and monitored periodically over the next 12 months. The radiographic lesion gradually resolved over the following 9 months without further treatment. The patient remained asymptomatic throughout the course of final restorative therapy. Keywords: dental implant, radiolucency, retrograde peri-implantitis