The International Journal of Oral & Maxillofacial Implants, 06/2009

Purpose: To investigate the method and conditions of isolation and proliferation of multipotent mesenchymal stem cells (MSCs) from human maxillary sinus membrane in vitro and to induce osteogenic differentiation directly for identification. Materials and Methods: A human maxillary sinus membrane specimen was collected in aseptic conditions from an orthognathic surgery patient and cultured. The cells at passage three were sorted by flow cytometry and treated with osteogenic differentiation media. To determine the osteogenic potential of these cells, the authors analyzed alkaline phosphatase (ALP) expression, mineralization of extracellular matrix, and osteocalcin expression; staining with alizarin red and von Kossa and reverse-transcriptase polymerase chain reaction were also performed. Results: Maxillary sinus membrane-derived cells were positive for STRO-1 and CD105 and negative for CD34. After 7 days, ALP began to be expressed. After 21 and 28 days, most cells showed expression of ALP. Mineralization of the extracelluar matrix was observed and, after 21 and 28 days, most of the cells showed mineralization. After 7 days, the osteocalcin gene was expressed; this expression was strongest on the 28th day. Conclusions: The results suggest that there are MSCs in human maxillary sinus membrane tissue, which can be differentiated into osteoblasts under osteogenic induction. This indicates that maxillary sinus membrane may be a useful source of MSCs for cell therapy. Keywords: adult stem cells, maxillary sinus membrane, osteogenic differentiation

Purpose: Following resection of malignant tumors from the mandible, immediate reconstruction of the discontinuous jaw is commonly performed. The present study aims to define the risks associated with dynamic loading of the reconstructed mandible. Materials and Methods: Computer-aided design simulations of eight mandibles were produced and termed normal models. The normal models were then modified by removing part of the right body and restoring the defects with bone from the rib or fibula. These modified models were termed reconstructed models. Thereafter, an implant was embedded in the first molar region of the left side for all models. Using finite element analysis, the stresses occurring at the implant-bone interface with simulated mastication were calculated. The Wilcoxon signed rank test was applied to compare the magnitudes of stresses in both models. Results: In terms of the stress exerted at the implant-bone interface during mastication, the normal models and the reconstructed models showed no significant differences (P > .05). Conclusion: Placement of an implant on the nonreconstructed side following partial resection and mandibular reconstruction presents no significant risk. Keywords: fibula, implant, mandible, reconstruction, rib, stress

Purpose: Resonance frequency analysis (RFA) offers the opportunity to monitor the osseointegration of an implant in a simple, noninvasive way. A better comprehension of the relationship between RFA and parameters related to bone quality would therefore help clinicians improve diagnoses. In this study, a bone analog made from polyurethane foam was used to isolate the influences of bone density and cortical thickness in RFA. Materials and Methods: Straumann standard implants were inserted in polyurethane foam blocks, and primary implant stability was measured with RFA. The blocks were composed of two superimposed layers with different densities. The top layer was dense to mimic cortical bone, whereas the bottom layer had a lower density to represent trabecular bone. Different densities for both layers and different thicknesses for the simulated cortical layer were tested, resulting in eight different block combinations. RFA was compared with two other mechanical evaluations of primary stability: removal torque and axial loading response. Results: The primary stability measured with RFA did not correlate with the two other methods, but there was a significant correlation between removal torque and the axial loading response (P .005). Statistical analysis revealed that each method was sensitive to different aspects of bone quality. RFA was the only method able to detect changes in both bone density and cortical thickness. However, changes in trabecular bone density were easier to distinguish with removal torque and axial loading than with RFA. Conclusions: This study shows that RFA, removal torque, and axial loading are sensitive to different aspects of the bone-implant interface. This explains the absence of correlation among the methods and proves that no standard procedure exists for the evaluation of primary stability. Keywords: artificial bone, axial loading, bone quality, removal torque, resonance frequency analysis

Purpose: To evaluate correlations between Periotest, cutting torque or insertion torque, and/or the reverse torque test with resonance frequency analysis measurements. Materials and Methods: The combined search terms dental implant, primary stability, resonance frequency analysis, removal torque, vibration analysis, torque, Periotest, cutting torque, and insertion torque and specific inclusion and exclusion criteria were used to retrieve eligible articles published between 1998 and 2008 (up to April 1) from PubMed, EMBASE, OVID, The Cochrane Library databases, and 10 journals by hand-searching. The pooled P value was calculated with the Fisher method. The correlation coefficients (r) were combined using fixed and random effect models. Heterogeneity of the studies was tested by performing the homogeneity test. Results: Fifty articles were identified, but 3 studies were excluded because of limitations in study design. Studies that fulfilled the inclusion criteria fell into a variety of categories (11 human cadaver, 16 clinical, 15 animal, and 5 in vitro studies). Assessment of P values revealed that correlation between cutting torque or insertion torque and resonance frequency analysis was significant (6 studies; P = .0022). Correlation between Periotest and cutting torque or insertion torque was significant (1 study; P = .015), and correlations between resonance frequency analysis and reverse torque test values (1 study; P = .319; r = 0.405) and Periotest and resonance frequency analysis (P = .28) were insignificant. Nine articles provided r values, and cutting torque or insertion torque and resonance frequency analysis showed a statistically significant and direct relationship of 55.4% (P = .000). One study provided an r value of -0.149. A statistically significant and direct relationship of 87.6% was found between cutting torque or insertion torque and reverse torque (2 studies; P = .000). Conclusion: This meta-analysis of 47 studies showed a statistically significant correlation between cutting torque or insertion torque and resonance frequency analysis. Keywords: cutting-torque, implant stability, insertion torque, meta-analysis, periotest, removal torque, resonance frequency analysis

Purpose: To evaluate implant angulations and alignments with neighboring teeth/implants and compare them to angulations and alignments measured with preinsertion surgical gauges. Materials and Methods: Two hundred implants placed freehand were included. For each site, two panoramic radio-graphs were obtained, one with a gauge and one with an implant. The mesiodistal angular relationships between gauge and subsequently placed implant, gauge and gauge (for neighboring implants), gauge and neighboring teeth, implant and neighboring teeth, and gauge and the inferior border of the mandible were measured. Results: The mean gauge-implant discrepancy was -0.72 degrees. The gauge to teeth angulation was -3.95 degrees, the implant-teeth angulation was -4.67 degrees, the gauge-gauge angulation was 0.49 degrees, and the angulation between the gauge and the inferior border of the mandible was 86.86 degrees. Maxillary implants were more divergent than mandibular implants (-9.89 degrees versus -2.14 degrees). Likewise, implants placed away from (opposite) the clinician's side had smaller gauge-implant discrepancies than those placed in the ipsilateral side (-0.94 degrees versus -1.66 degrees). Implant location (incisor, premolar, molar) also affected this angular relationship; implants placed in the anterior region diverged more (-3.96 degrees) than implants placed in premolar (-1.02 degrees) and molar regions (0.06 degrees). Implants that were placed adjacent to teeth had greater divergence than implants placed in an edentulous region (-1.66 degrees versus 0.09 degrees). Likewise, gauges placed in conjunction with shorter implants (10 mm or shorter) were more divergent than those placed in conjunction with longer implants (-8.29 degrees versus -3.259 degrees, respectively). Conclusion: Placement of dental implants, even without the use of a surgical guide, can result in adequate dental implant angular relationships. An implant's location (arch, side, or site) and the presence of adjacent teeth might affect these relationships. Keywords: clinical study, dental implants, implant angulation, presurgical planning, radiography, surgical gauge

Purpose: This study aimed to evaluate the influence of implants with or without threads representation on the outcome of a two-dimensional finite element (FE) analysis. Materials and Methods: Two-dimensional FE models that reproduced a frontal section of edentulous mandibular posterior bone were constructed using a standard crown/implant/screw system representation. To evaluate the effect of implant threads, two models were created: a model in which the implant threads were accurately simulated (precise model) and a model in which implants with a smooth surface (press-fit implant) were used (simplified model). An evaluation was performed on ANSYS software, in which a load of 133 N was applied at a 30-degree angulation and 2 mm off-axis from the long axis of the implant on the models. The Von Mises stresses were measured. Results: The precise model (1.45 MPa) showed higher maximum stress values than the simplified model (1.2 MPa). Whereas in the cortical bone, the stress values differed by about 36% (292.95 MPa for the precise model and 401.14 MPa for the simplified model), in trabecular bone (19.35 MPa and 20.35 MPa, respectively), the stress distribution and stress values were similar. Stress concentrations occurred around the implant neck and the implant apex. Conclusions: Considering implant and cortical bone analysis, remarkable differences in stress values were found between the models. Although the models showed different absolute stress values, the stress distribution was similar. Keywords: biomechanics, dental implants, finite element analysis, threads

Purpose: This study evaluated the effect of different screw-tightening sequences, forces, and methods on the stresses generated on a well-fitting internal-connection implant (Astra Tech) superstructure. Materials and Methods: A metal framework directly connected to four parallel implants was fabricated on a fully edentulous mandibular resin model. Six stone casts with four implant replicas were made from a pickup impression of the superstructure to represent a "well-fitting" situation. Stresses generated by four screw-tightening sequences (1-2-3-4, 4-3-2-1, 2-4-3-1, and 2-3-1-4), two forces (10 and 20 Ncm), and two methods (one-step and two-step) were evaluated. In the two-step method, screws were tightened to the initial torque (10 Ncm) in a predetermined screw-tightening sequence and then to the final torque (20 Ncm) in the same sequence. Stresses were recorded twice by three strain gauges attached to the framework (superior face midway between abutments). Deformation data were analyzed using multiple analysis of variance at a .05 level of statistical significance. Results: In all stone casts, stresses were produced by the superstructure connection, regardless of screw-tightening sequence, force, and method. No statistically significant differences for superstructure preload stresses were found based on screw-tightening sequences (-180.0 to -181.6 µm/m) or forces (-163.4 and -169.2 µm/m) (P > .05). However, different screw-tightening methods induced different stresses on the superstructure. The two-step screw-tightening method (-180.1 µm/m) produced significantly higher stress than the one-step method (-169.2 µm/m) (P = .0457). Conclusions: Within the limitations of this in vitro study, screw-tightening sequence and force were not critical factors in the stress generated on a well-fitting internal-connection implant superstructure. The stress caused by the two-step method was greater than that produced using the one-step method. Further studies are needed to evaluate the effect of screw-tightening techniques on preload stress in various different clinical situations. Keywords: internal-connection dental implant, preload stress, screw-tightening sequence, tightening force, tightening method

Purpose: The influence of bone marrow in the osteogenic potential of bone has not been evaluated in the rabbit tibia model. Previous studies employed this model extensively to test the osteogenic capabilities of bone grafts. The primary aim of the present study was to assess the role of bone marrow in the healing of experimental defects in the rabbit tibia model. Materials and Methods: Ten New Zealand rabbits were divided into two groups of five each. In the first experimental test group (PoP), the marrow cavity was emptied completely under a 6-mm defect in the rabbit tibia metaphysis; the marrow was replaced by plaster of Paris, and a round piece of lyophilized collagen membrane was placed in contact with the endosteum and rested on the plaster. In the second experimental group (control), similar artificial defects were made, but the marrow was left intact. After 8 weeks, the animals were sacrificed and prepared for histologic and histomorphometric analysis. Results: There was a statistically significant difference (P = .016) in newly formed bone area between the control group (mean, 68.08% ± 12.09%) and the PoP group (mean, 54.02% ± 13.93%). Similarly, there was a statistically significant difference in new bone density (P .001) between the control group (mean, 95.99% ± 1.74%) and the PoP group (mean, 75.37% ± 13.27%). Conclusions: The current study confirms the significant effect that bone marrow has in bone regeneration and also the true regenerative capabilities of the osseous walls of the defects. The proposed experimental model may be a more reliable method of investigating and comparing the potential of different graft materials and methods. Keywords: bone marrow, bone regeneration, plaster of Paris, rabbit tibia

Purpose: The purpose of this study was to evaluate the clinical efficacy of implant prostheses retained by screws and cement (SCPs) by examining the reverse torque values (RTVs) of the abutment screws and the marginal openings of the implant prostheses. Materials and Methods: Two implants (3.8 3 13 mm; Camlog Biotechnologies) were embedded in an acrylic resin block 5 mm apart. Eighteen copies of this resin specimen were fabricated and randomly divided into two groups. Two-unit implant prostheses with two different designs-purely cement-retained implant prostheses (group 1) and SCPs (group 2)-were made out of type IV gold alloy and placed on the implants. After tightening to about 30 Ncm, the preloading RTVs of the abutment screws were measured. After retightening the abutment screws or cementing the prostheses, followed by cyclic loading, the postloading RTVs of the abutment screws were examined. Also, the marginal openings of the prostheses in the two groups were measured under a stereomicroscope. These measurements were compared statistically. Results: The postloading RTVs and their differences from the preloading RTVs of the abutment screws demonstrated no significant differences between groups (P > .05). Group 2 prostheses showed significantly smaller marginal openings than group 1 prostheses (P .05). Conclusion: The forces generated when torquing the abutment screw of the SCP did not cause more loosening of the abutment screws than the purely cement-retained implant prosthesis. The SCP showed better marginal adaptation of the cement-retained part than the purely cement-retained implant prosthesis, possibly as a result of the screw-retained abutment seating the restoration. Within the limitations of this in vitro test, the SCP showed no significant difference in RTV of the abutment screw and a smaller marginal gap compared to a purely cement-retained implant prosthesis. Keywords: dental cement, dental screw, implant-supported prosthesis, marginal opening

Purpose: The aim of this study was to evaluate the effect of the topical application of growth hormone on the osseointegration of dental implants in beagle dogs 14 days after placement. Materials and Methods: Maxillary and mandibular premolars and molars were extracted from 12 beagle dogs. Two months later, each mandible received cylindric screw-type implants of 3.25 mm in diameter and 10 mm in length. The implants were randomly assigned to the mesial and distal sites on each side of the mandible. Prior to implantation, lyophilized powdered growth hormone was applied to one osteotomy on each side of the mandible. No growth hormone was applied at the control sites. Eight histologic sections per implant were obtained for histomorphometric analysis. Results: After a 2-week treatment period, the growth hormone-treated sites showed significant (P .0001) increases in the perimeter of bone that was in direct contact with the treated implants (40.19% ± 2.51%), total peri-implant area (P .001) (69.57% ± 3.53%), and new bone formation (P .0001) (35.18% ± 0.31%), in comparison to control implants (25.05% ± 2.43%, 53.40% ± 4.58%, and 28.65% ± 1.92%, respectively). There was no significant increase in interthread bone in growth hormone-treated implants (27.92% ± 3.31%) in comparison to control implants (25.08% ± 3.47%) (P > .05). Conclusion: Topical application of growth hormone may act as a bone stimulant in the placement of endosseous dental implants. Keywords: bone remodeling, dental implants, dogs, growth hormone, oral cavity

Purpose: The aim of this study was to quantitatively evaluate and qualitatively describe autogenous bone graft healing with or without an expanded polytetrafluoroethylene (e-PTFE) membrane in ovariectomized rats. Materials and Methods: Eighty Wistar rats, weighing approximately 300 g each, were used. A graft was obtained from the parietal bone and fixed to the sidewall of each animal's left mandibular ramus. The animals were randomly divided into four experimental groups (n = 20 in each group): group 1, sham operated and autogenous bone graft only; group 2, sham operated and autogenous bone graft covered by e-PTFE membrane; group 3, ovariectomized (OVX) and autogenous bone graft only; group 4, OVX and autogenous bone graft covered by e-PTFE membrane. The animals were sacrificed at five different time points: immediately after grafting or at 7, 21, 45, or 60 days after grafting. Histologic examination and morphometric measurement of the sections were performed, and values were submitted to statistical analyses. Results: Both groups (sham and OVX) experienced loss of the original graft volume when it was not covered by the membrane, whereas use of the membrane resulted in additional bone formation beyond the edges of the graft and under the membrane. Histologic analysis showed integration of the grafts in all animals, although a larger number of marrow spaces was found in OVX groups. Conclusions: Association of bone graft with an e-PTFE membrane resulted in maintenance of its original volume as well as formation of new bone that filled the space under the membrane. Osteopenia did not influence bone graft repair, regardless of whether or not it was associated with e-PTFE membrane, but descriptive histologic analysis showed larger numbers of marrow spaces in the bone graft and receptor bed and formation of new bone in the OVX animals. Keywords: bone regeneration, bone transplantation, metabolic bone diseases

Purpose: Immediate loading is among the most innovative techniques in implant therapy today. This pilot study investigates the biomechanical outcome of various designs and surfaces that claim to shorten implant treatment. Materials and Methods: In each quadrant of two mongrel dogs, four different implants were used for immediate loading. The following implants were placed 3 months after tooth extraction: screw with low thread profile and anodic oxidized surface (LPAOS), solid screw with wide thread profile and titanium plasma spray coating (WPTPS), screw with low profile and hybrid design of double-etched and machined surface (LPHES), and screw with two thread profiles and a sandblasted and acid-etched surface (DTSAE). The insertion torque of each implant was above 35 Ncm. Resonance frequency analysis was performed after implant placement and again after sacrifice. Additionally, the removal torque and the amount of embedded titanium particles in the peri-implant bone were measured. Results: All 16 prostheses were functional after a 5-month loading period. The highest mean removal torque values were recorded with WPTPS implants (24.4 Ncm/mm), followed by DTSAE implants (22.3 Ncm/mm) and LPAOS implants (18.7 Ncm/mm); the lowest score was obtained by LPHES (12.0 Ncm/mm). The ISQ values increased between the time of surgery and recall for all systems on average, but a significant positive correlation was found for DTSAE only. Significantly higher amounts of titanium were found in the surrounding bone with WPTPS (0.76%) and LPAOS (0.41%) in comparison with DTSAE (0.10%) and LPHES (0.03%). Conclusion: Immediate loading is possible with various designs and surfaces if high primary stability can be achieved during implant placement. Keywords: immediate loading, implant design, implant surface, removal torque, titanium wear

Purpose: This randomized, controlled study was designed to compare bone formation around microimplants with a sandblasted, acid-etched surface placed at the time of maxillary sinus floor augmentation with a synthetic biphasic calcium phosphate (BCP) or deproteinized bovine bone (DBB). Materials and Methods: Nine completely edentulous patients and two partially edentulous patients (six women, five men) with a mean age of 67 years (range, 50 to 79 years) requiring bilateral sinus augmentation were included in the study. The patients were randomized for augmentation with BCP (test) in one side and DBB (control) in the contralateral side. At the time of augmentation, one microimplant on each side was placed vertically from the top of the alveolar crest, penetrating the residual bone and the grafting material. After 8 months of graft healing, at the time of ordinary implant placement, all 22 microimplants were retrieved with a surrounding bone core for histologic analyses. Results: The bone-to-implant contact in the BCP group was 64.6% ± 9.0%, versus 55.0% ± 16.0% for the DBB group. The difference was not significant. The corresponding values for the area of newly formed bone in the biopsies were 41.1% ± 9.8% and 41.6% ± 14.0% for BCP and DBB, respectively. There were significantly more DBB particles in contact with newly formed bone than BCP particles (87.9 ± 18.2% versus 53.9 ± 26.1%; Wilcoxon rank sum test; P = .007). Conclusion: In this randomized, controlled clinical trial, new bone formation and bone-to-implant contact around microimplants with a sandblasted, acid-etched surface was found to be equivalent between sinuses augmented with BCP or DBB. Significantly more DBB particles than BCP particles were in contact with newly formed bone, but the clinical relevance of this has yet to be established. Keywords: biphasic calcium phosphate, bone substitutes, deproteinized bovine bone, histology, microimplants, sinus floor augmentation

Purpose: Tumor necrosis factor-alpha (TNFa) is a proinflammatory cytokine, which promotes bone resorption and mediates the inflammatory response to infection. Because implant failures appear to cluster in subsets of individuals, this phenomenon may be related to gene polymorphisms. Therefore, the aim of this study was to investigate the relationship between a specific polymorphism in the TNFa gene (allele 2 of TNFa-308) and peri-implantitis. Materials and Methods: This case-control study included Caucasian nonsmoking Brazilian patients with implant-supported restorations. Oral epithelial cells were taken from patients with and without peri-implantitis to evaluate the frequencies of different alleles of the TNFa-308 gene by polymerase chain reaction. Results: Ninety patients (49 with peri-implantitis and 41 with healthy implants) were enrolled in this study. Polymorphism in allele 2 of TNFa-308 was not associated with an increased risk for peri-implantitis (P = .8171), although 14.63% of the subjects in the control group carried allele 2 and 19.39% in the peri-implantitis group carried allele 2 (chi-squared = 0.708; P = .5202). Conclusion: Polymorphism of the TNFa-308 gene was not associated with an increased risk of peri-implantitis in the population evaluated in this study. Keywords: bone loss, dental implants, gene polymorphisms, peri-implantitis, tumor necrosis factor-alpha

Purpose: Immediate loading in the maxilla is not a routinely recommended treatment concept; however, some clinical series have shown a high survival rate for nonfunctionally loaded implants. The purpose of this study was to demonstrate the prognosis for immediately loaded implants with a progressive thread design and platform switching placed in the maxilla with or without simultaneous augmentations using autogenous bone. Materials and Methods: Ninety implants were placed (six in each maxillary arch) in 15 patients. Immediately after surgery, the implants were loaded with a provisional acrylic resin prosthesis (immediate occlusal loading). Splinting of the implants with the provisional remained for 6 to 8 weeks of healing. In patients with augmented sites, a 3-month period of provisionalization was necessary to ensure implant stability; a soft/liquid diet was recommended for this intermediate transitional period. Definitive fixed restorations were then fabricated and delivered. Clinical and radiologic examinations of the implants were performed at various times. Results: After a mean loading period of 42.4 (± 19.15) months, only three failures were reported. This represented a survival rate of 96.66%. No complications, including inflammation or bone loss, were reported during the study period. Conclusions: Based on these results, the immediate loading protocol in the maxilla can be used successfully when implant primary stability, cross-arch stabilization, and a soft diet for the initial stages of healing are considered. Keywords: dental implants, immediate loading, maxilla

Purpose: To compare the time-dependent cumulative survival rates of smooth- and rough-surface dental implants. Materials and Methods: A retrospective chart review was conducted for two time periods: January 1, 1991, through December 31, 1996, during which smooth-surface implants were used, and January 1, 2001, through December 31, 2005, during which rough-surface implants were used. This study included all implants placed and restored in one institution during the two time frames. Data were collected relative to patient age, gender, implant diameter, implant length, and anatomic location of implants. To facilitate the comparison, implants from the first and second time periods were followed through mid-1998 and mid-2007, respectively. Associations of patient/implant characteristics with implant survival were evaluated using marginal Cox proportional hazards models (adjusted for age and gender) and summarized with hazard ratios and corresponding 95% confidence intervals. Results: A total of 593 patients (322 women and 271 men; mean age, 51.3 ± 18.5 years) received 2,182 smooth-surface implants between 1991 and 1996, while 905 patients (539 women and 366 men; mean age, 48.2 ± 17.8 years) received 2,425 rough-surface implants between 2001 and 2005. At 5 years after implant placement, survival rates were 94.0% and 94.5%, respectively, for smooth- and rough-surface implants (difference not significant). Among the smooth implants, implant length = 10 mm and anatomic location were identified as significantly associated with implant failure. In contrast, among the rough implants, implant length = 10 mm and anatomic location were not identified as risk factors for implant failure. Conclusions: Based on this retrospective study of two groups of patients with different implant surfaces and more than 2,000 implants in each group, there was no significant difference in the survival rates of smooth- and rough-surface dental implants. Anatomic location and implant length = 10 mm were associated with failures of the smooth-surface implants only. Keywords: dental implants, implant surface, retrospective study, survival rates

Purpose: The purpose of this retrospective longitudinal study was to evaluate the survival and success rates of 56 implants consecutively placed in alveolar ridges following a one- or two-stage augmentative procedure, using autogenous bone and titanium micromeshes. Materials and Methods: This study included 24 consecutive patients treated with 27 micromeshes and mandibular particulated bone. In 13 patients, 20 implants were placed at the time of the reconstructive procedure. In the remaining 11 patients, 36 implants were positioned in a second surgery 8 to 9 months after grafting. Follow-up data (implant survival, success rate, marginal bone resorption) were collected after 3 to 8 years of prosthetic loading. Results: Four of the 27 micromeshes (complication rate, 14.8%) were exposed prematurely and were removed before the intended time. The mean vertical bone augmentation obtained was 5.4 ± 1.81 mm for implants placed in simultaneous procedures and 4.5 ± 1.16 mm in delayed procedures. None of the 56 implants was lost during the observation period (cumulative implant survival rate, 100%). Radiographic analysis showed stable marginal bone levels, with a mean bone resorption of 1.58 ± 0.48 mm after 3 to 8 years. Only two implants demonstrated increased bone loss (3.12 and 3.37 mm) over the follow-up period, whereas the remaining 54 implants were considered clinically successful, resulting in a cumulative success rate of 96.4%. Conclusions: This study revealed that implant placement in augmented ridges using micromeshes and autogenous bone provided satisfactory long-term survival and success rates, with minimal bone resorption. Keywords: alveolar ridge augmentation, autogenous bone graft, dental implants, follow-up study, titanium mesh

Purpose: This retrospective study reports the clinical outcome following placement of extraoral implants in severely resorbed posterior ridges to support distal-extension removable dentures. Material and Methods: Consecutively treated patients with partially or completely edentulous ridges, with available bone height in the posterior region of 6 mm or less, were included in the study. Implants originally intended for extraoral use (Straumann) were placed in second molar regions and allowed to heal for 4 to 6 months before abutment connection. At recall appointments, the peri-implant hard and soft tissues were evaluated. Complications with implant components, as well as mechanical and structural failures of the prostheses, were recorded. Two-year survival rates were calculated and life table analyses undertaken. Results: Twenty-nine patients (19 women and 10 men; average age 61.2 years, range, 44 to 75 years) were included in the study. Forty-seven extraoral implants in 26 patients were placed in the second molar site of the mandible. Two extraoral implants in 2 patients failed during the osseointegration phase, yielding an 8-year cumulative success rate of 91.8%. The mean distance from the extraoral implants to the most distal tooth/implant was 28.1 mm (range, 16.7 to 39.2 mm). Twenty-three extraoral implants were restored with magnets, 18 with ball anchors, and 4 with conical cylinders. Replacement of abutments and retention elements was necessary in 2 patients. Four abutments in 2 patients were disconnected from the restorations. Conclusions: Within the limits of the employed research design, extraoral implants may be used successfully to provide support for distal-extension removable dentures in severely resorbed posterior alveolar ridges. Keywords: alveolar atrophy, extraoral implant, life table analysis, posterior alveolar ridge, submerged implants

Purpose: Inadvertent perforation of the sinus membrane is a frequent complication encountered during sinus floor elevation (SFE). Different strategies have been described for the prevention or treatment of perforations, with varying results. This paper reports the findings of a preliminary study into the application of a novel nasal suction technique in which negative antral air pressure was used to facilitate the raising of the sinus lining and to reduce the risk of perforations occurring during SFE. Materials and Methods: In 24 consecutive patients, nasal suction was applied through the ipsilateral nostril during SFE. The suction device was attached to a high-flow vacuum regulator that incorporated a suction canister connected to a -10-kPA medical vacuum (-75 mm Hg). Fifteen subjects received unilateral SFE, and six subjects had bilateral staged lateral wall sinus elevation; the remaining three subjects had osteotome sinus floor elevation (three unilateral and one bilateral) with simultaneous implant placement. Results: During SFE, the use of nasal suction facilitated the inversion of the sinus lining around the edges of the lateral access window. This made the sinus lifting easier, as the need for extensive instrumentation was significantly reduced. In three subjects, elevation of the sinus lining occurred spontaneously from the lateral, medial, and inferior surfaces of the antrum when nasal suction was applied. Conclusion: Sinus lifting was facilitated by nasal suction. No perforation of the sinus lining occurred in this series. Controlled clinical trials are being designed to further demonstrate the clinical efficacy of the nasal suction technique in SFE. Keywords: nasal suction, sinus grafting, sinus lift, sinus membrane elevation, sinus membrane perforation

The present report describes the oral rehabilitation of a female patient suffering from type III osteogenesis imperfecta. Agenesis of the mandibular anterior teeth and malocclusion caused partly by heavily worn teeth made dental rehabilitation necessary. Before a decision to use implants following a grafting procedure, the osseointegration of microimplants was tested. After 4 and 12 months, bone plugs containing two microimplants were retrieved from the patient. Histologic evaluation showed very sparse/poor osseointegration, and the healing time seemed to be much longer than normal. A decision was made to use the "tent-pole" procedure described by Marx et al, followed by prolonged healing. Surgery was uneventful, and the patient was provided with four implants that were partly covered with bone obtained from the iliac crest. Platelet-rich plasma was used to accelerate bone healing. After 9 months, the implants were uncovered and the prosthetic construction was completed. The implant-supported metal-ceramic restoration was serving well at the 1-year and 3-year follow-ups. Minimal resorption of marginal bone was detected during the first year. Keywords: autogenous bone graft, dental implants, osseointegration, osteogenesis imperfecta, platelet-rich plasma

In a sinus lift procedure, bone grafting is usually performed concomitantly. The mandibular coronoid process is an advantageous donor site for autogenous bone grafts. A clinical case of sinus bone grafting using the coronoid process of the mandible is presented here, along with the surgical technique to accomplish this procedure. A successful outcome was obtained in the patient, who experienced no functional problems. Keywords: autogenous bone graft, coronoid process, sinus lift procedure

The peripheral giant cell granuloma is a benign reactive exophytic lesion of unknown etiology occurring on the gingiva and alveolar ridge. Different local causal factors have been associated with this type of lesion. Although peripheral giant cell granuloma is the most common giant cell lesion of the jaws, it is rarely seen in association with implants. This report discusses the etiology and management of a peripheral giant cell granuloma around dental implants in a 60-year-old woman. A new implant-supported prosthesis with adequate marginal adaptation between the restoration and abutments was made. There were no complications during 1 year of clinical and radiologic follow-up. Keywords: bone loss, dental implant, etiology, giant cell, granuloma