The International Journal of Oral & Maxillofacial Implants, 05/2005

Purpose: The purpose of this study was to radiographically evaluate the effect of a machined titanium coronal collar on the marginal bone around 1-part endosseous dental implants placed at different heights relative to the bone crest. Materials and Methods: Sixty dental implants were placed in edentulous spaces bilaterally in 5 foxhounds. Thirty test implants had a sandblasted, large-grit, dual acid-etched surface (SLA) over the entire length of the implant. The other 30 implants (control) had a machined collar around the most coronal 1.8 mm of the implant; an SLA surface covered the remainder of the implant. Both control and test implants were placed at 3 distinct levels relative to the bone crest. Six implants (3 control and 3 test) were randomly placed side by side in each hemimandible. Radiographs were taken at placement (baseline) and monthly for 6 months postplacement using a standardized radiographic template. Results: Fifty-eight of the implants integrated and were analyzed on each proximal surface. Bone loss occurred around all implants over the 6 months of the study. In general, implants placed with the top of the SLA surface above the bone crest had significantly less bone loss than implants with the top of the SLA surface placed flush with the bone level. Apically placed implants had greater bone loss than coronally placed implants. The magnitude of bone loss around paired control and test implants was approximately the same. Discussion and Conclusion: The least bone loss with each implant type was observed when the top of the implant was placed above the alveolar crest. When there was no machined collar, the least distance from the implant top to the bone crest (not, however, the least bone loss) was observed when the top of the implant was level with the bone crest.

Purpose: The purpose of this study was to determine the clinical parameters associated with long-term success and failure of single-tooth titanium plasma-sprayed (TPS) cylindric implants. Materials and Methods: Thirty-nine implants in 39 subjects were followed for 5 years. The following data were collected: subject age and gender, implant length, implant location, bone density, and implant position in relation to crestal bone. Assessments made at recall intervals included: Gingival Index (GI), probing depth, relative attachment level, and standardized radiographs. Failure was defined as a mean annual attachment loss rate (ALR) of >= 0.25 mm after the first year of implant function. Between-group differences were assessed nonparametrically using the Mann-Whitney and chi-square tests. Results: Nineteen implants were considered successes and 20 were considered failures with respective mean ALRs of 0.12 ¡À 0.07 mm and 0.42 ¡À 0.19 mm. The following factors were associated with success: longer implants (P .001), lower GI (P .001), higher bone density (P .0001), and implant position at the crest or supracrestally (P .0001). Age, gender, probing depth, and implant location were not related to outcome. Conclusions: A model using attachment loss as a parameter for success and failure has not been previously utilized. Longer implants, lower GI, higher bone density, and implant position at the crest or supracrestally were clinical factors associated with long-term success of single-tooth TPS cylindric implants in this patient population. Keywords: alveolar bone loss, attached gingiva, dental implants

Purpose: The primary goal of this study was to compare bone-to-implant contact (BIC) in alveolar bone augmented by distraction osteogenesis with BIC in alveolar bone augmented by onlay iliac crest grafting. Materials and Methods: Alveolar bone defects were created bilaterally in 5 American foxhounds, and after healing, bone augmentation was accomplished using distraction osteogenesis on 1 side of the jaw and onlay grafting on the other. Twelve weeks after consolidation, implants were placed in augmented and control sites. The animals were sacrificed and the jaws harvested for histologic analysis after an additional 8 weeks. Results: The mean BIC was 54.7% ± 14.6% for implants placed in distracted sites, 53.8% ± 11.8% for sites where an onlay graft was used, and 51.2% ± 14.4% for control sites. Significant differences in BIC were noted between experimental and control sites only at the apical third of the implant (19.8 ± 1.8 for distracted sites; 15.5 ± 1.5 for grafted sites; 8.0 ± 0.5 for control sites; P .05). Discussion: The data showed that both distraction osteogenesis and onlay grafting produce sufficient bone for implant placement. There were no differences between procedures in regard to BIC after 8 weeks. Conclusion: These data suggest that both onlay grafting and vertical distraction are appropriate methods for bone augmentation prior to implant placement. Keywords: bone augmentation, distraction osteogenesis, implants, onlay grafts

Purpose: To evaluate the effect of the addition of platelet concentrate (PC) to autografts or bone substitutes on bone regeneration in standardized bone defects. Materials and Methods: Three standardized bone defects were prepared in both mandibular angles of 12 adult minipigs. The defects were grafted with autograft, anorganic bovine bone, or synthetic b-tricalcium phosphate (b-TCP). PC was added to only 1 side. The animals were divided into 4 groups, which were sacrificed at 4 different time points (1, 2, 4, and 8 weeks) for histologic and histomorphometric analysis. The concentrations of platelets and growth factors were measured to identify correlation to the histologic and histomorphometric results. Results: No correlation was found between platelet count in whole blood and platelet count in PC (rp = 0.36). Furthermore, no correlation could be demonstrated between the platelet count of the PC and the concentrations of PDGF-AB (rp = -0.27) and TGF-b (rp = 0.34). There were no signs of a stimulating effect of PC on bone formation in combination with autografts or bone substitutes at any time point (P = .89). Addition of PC did not alter the pattern of graft degradation. Discussion: The present study underlines the need for further investigation to identify the optimal concentrations of platelets and combinations of growth factors to achieve a predictable stimulatory effect on bone regeneration. One of the first steps to achieve this goal will be the development of a reliable method for the procurement of PC. Conclusion: PC had no impact on bone formation and graft degradation in standardized bone defects in the mandibles of minipigs. Keywords: autogenous bone grafting, bone regeneration, bone substitutes, growth factors, platelet concentrates, platelet-rich plasma

Purpose: This study tested the hypothesis that interruption of cigarette smoke inhalation (CSI) would reverse its impact on bone quality around implants. Materials and Methods: Sixty-nine rats were assigned to 1 of 4 groups. Group 1 (n = 16) was the control group; group 2 experienced CSI for the duration of the study (150 days); group 3 experienced CSI for 83 days prior to implant placement, until 7 days prior to implant placement, when CSI ceased; and for group 4, CSI exposure was temporarily halted from 7 days before implantation to 21 days afterward. Bone density (the proportion of mineralized bone in a 500-µm-wide zone lateral to the implant) was calculated for each specimen (mean ± SD). Results: In the cortical bone, a slight difference in bone density was noted between the groups (97.66% ± 3.69% for group 1, 98.30% ± 0.95% for group 2, 98.83% ± 0.73% for group 3, and 98.11% ± 1.14 for group 4; P > .05). In contrast, continuous exposure to cigarette smoke (group 2) significantly decreased density in the cancellous bone in comparison to the other groups (25.69% ± 9.41% for group 1, 18.08% ± 6.0% for group 2, 25.46% ± 5.42 for group 3, and 26.20% ± 6.77% for group 4; P .05), with no significant differences between groups 1, 3, and 4 (P > .05). Discussion: The results support the concept that the effects of cigarette consumption on dental implants may be reversible, and therefore suggest that smokers may realize satisfactory outcomes if they cease smoking, even temporarily. Conclusion: In conclusion, smoking may affect bone quality around titanium implants in cancellous bone, and cessation could result in a return toward to the levels of the control group. Keywords: dental implants, osseointegration, smoking, smoking cessation

Purpose: To compare the dimensional accuracy of implant framework castings from an argon vacuum casting machine with those from a centrifugal casting machine. Materials and Methods: Three 4 3 10-mm external hex-type implants (3i/Implant Innovations) were embedded in an acrylic resin block 7 mm apart, with a 2 mm offset of the middle implant. Eight reference points were marked on the implant collars. Twenty implant bar frameworks were waxed with UCLA abutments, invested with a ringless system, and subjected to the same thermal cycle. Ten wax patterns were cast in gold alloy using an oxygen-propane torch and centrifugal casting system; 10 were cast using an argon vacuum casting machine (KDF; Denken). The White 1-screw technique was applied after sequentially tightening the mesial and distal abutment screws to 10 Ncm. Fit of the implant framework castings was evaluated by measuring the marginal opening between the casting and implant at the reference points. These measurements were averaged and statistically compared for differences. Results: The mean marginal openings at the most distant measuring locations from the tightened retaining screw at location 1 was between 44 to 48 µm for the centrifugal system compared to between 28 to 32 mm for KDF (P .01). For screws tightened at location 3, the mean marginal openings at the most distant measuring locations were between 40 to 51 mm for the centrifugal system compared to between 27 to 29 µm for KDF (P .01). Discussion: In comparison with the centrifugal casting and oxygen-propane system, the argon vacuum system was more accurate and user friendly and less technique-sensitive. Conclusion: The argon vacuum casting machine tested produced more accurate, better fitting implant-supported prosthesis frameworks than a conventional centrifugal casting system. The "1-screw" method of evaluating casting fit was most effective when either of the prostheses' end screws were tightened. Keywords: argon vacuum casting machine, centrifugal casting machine, implant frameworks, implant-prosthesis fit

Purpose: The influence of calcium phosphate (CaP) and hydroxyapatite (HA) crystallinity on bone-implant osseointegration is not well established. In this study, the effect of HA crystallinity and coating method on bone-implant osseointegration was investigated using a rat tibia model. Materials and Methods: HA coatings 1 to 5 µm thick were produced using a supersonic particle acceleration (SPA) technology. The HA crystallinities used for this study were weight ratios of 30%, 50%, 70%, and 90%. A total of 128 HA-coated implants were placed into the tibiae of 64 male Sprague-Dawley rats. Bone-implant interfaces were evaluated using histology and push-out strength testing at 3 and 9 weeks after implantation. Results: The 70% crystalline coatings exhibited significantly greater interfacial strength (5 implants/time point/treatment) than the 30%, 50%, and 90% crystalline coatings at 3 and 9 weeks following implantation. The implants with coatings of 70% crystallinity also had the greatest bone contact length. In addition, the HA coatings produced with SPA demonstrated greater interfacial strength and bone contact length than plasma-sprayed HA coatings (except for the HA coating with 30% crystallinity). Discussion: HA coatings of different crystallinities exhibited different dissolution and re-precipitation properties which may enhance early bone formation and bone bonding. Conclusions: This study suggested that coating crystallinity and coating methods can influence the bone-implant interface. Keywords: animal models, crystallinity, hydroxyapatite, interfacial strength, supersonic particle acceleration

Purpose: To test in vitro whether the seal provided by the locking taper used in the implant-abutment connection was capable of preventing the invasion of oral microorganisms. Materials and Methods: Twenty-five wide-body implants (5 3 11 mm) and 25 abutments were divided into 2 groups for a 2-phase experiment. The first phase tested the ability of the seal to shield the implant well from outside bacteria; the second phase tested the ability of the seal to prevent bacteria present in the implant well from seeping out. For phase 1, 10 implant-abutment units were immersed in a bacterial broth for 24 hours. The abutments were then separated from the implants and bacterial presence was evaluated using scanning electron microscopy. In phase 2, the tested abutments were inoculated with a droplet of soft agar bacterial gel and assembled with the implant. These units were incubated in a sterile nutrient broth for 72 hours, sampled, and plated to assess bacterial presence. Results: In phase 1, no bacteria were detected in any of the implant wells. In phase 2, no bacteria were detected in the nutrient broth or on the agar plates at 72 hours. Discussion: In implants where a microgap is present, microbial leakage could lead to inflammation and bone loss; thus, it is important to minimize bacterial presence in and around the the implant-abutment junction. Conclusion: The seal provided by the locking taper design has been demonstrated to be hermetic with regard to bacterial invasion in vitro. Keywords: bacterial seal, implant-abutment connection

Purpose: This study aimed to estimate the cumulative survival rates (CSRs) of implants placed in reconstructed mandibles and to identify prognostic factors that may influence implant survival. Materials and Methods: The charts of 24 patients (10 male, 14 female) who had undergone mandibular resection and reconstruction with fibula free-flaps treated with implant-supported prostheses from April 1986 through December 2001 were reviewed. Information on demographics, surgical characteristics, treatment modalities, dentition, implant parameters, prostheses, and hyperbaric oxygen therapy (HBO) was gathered. Kaplan-Meier survival estimates were generated for the 100 implants that satisfied the inclusion criteria. Multivariate Cox proportional hazards regression models accounting for correlated implants within subjects were developed to identify prognostic factors for implant survival. Results: Ninteen implants had been placed in native mandible (3 in irradiated bone) and 81 in fibula bone flap. Six implants failed during the follow-up period (mean 51.7 months). The overall 5- and 10-year CSRs were 97.0% and 79.9%, respectively. In the univariate analysis, variables associated with implant survival were age, gender, chemotherapy, radiation therapy, HBO, irradiated bone, implant diameter, xerostomia, trismus, opposing dentition, and type of prosthesis. At 5 years, the CSR of implants in patients with HBO was 86.7%; HBO was statistically associated with an increased risk for implant failure (P = .005, hazard ratio = 19.79, 95% CI: 2.42 to 161.71). Discussion: The CSR was lower when implants were placed in a previously irradiated mandible. There is still a lack of reliable clinical evidence to support the effectiveness of HBO in these patients. Conclusions: A high survival rate was demonstrated for implants placed in fibula free-flap reconstructed mandibles. The finding that HBO was a risk factor can probably be attributed to the small sample size; further study is needed in this patient population. Keywords: fibula, implant survival, mandibular reconstruction

Purpose: The objective of the present study was to determine standard Implant Stability Quotient (ISQ) values for apparently successfully osseointegrated 1-stage implants in the maxilla. Materials and Methods: To measure implant stability, resonance frequency analysis (RFA) was performed in 35 patients (18 women, 17 men) with a total of 120 maxillary ITI implants. Based on the time interval between implant placement and measurements, the ISQ values of anterior and posterior implants were divided into subgroups: unloaded (n = 41), loaded = 12 months (n = 31), and loaded > 1 year (n = 48). Statistical analysis was performed using a mixed-effects model with the variables lading, implant location, and gender as fixed effects. Results: The mean ISQ of all measured implants was 52.5 ± 7.9 (range 40 to 68). Statistical analysis showed no significant differences in ISQ values between the 3 tested time intervals: unloaded (48.8 ± 3.6), loaded = 12 months (54.1 ± 7.0), and loaded > 1 year (53.1 ± 9.5). Neither for the location in the jaw nor for bone quality (assessed using radiographs) could a significant difference be found. Gender was the only parameter which was found to be significant (P .003); on average, men showed higher implant stability than women (56.3 ± 6.6 versus 48.7 ± 7.4). Discussion: Standard values for osseointegrated maxillary ITI implants exhibited an individual range. Single RFA measurements of an implant do not allow assessment of its current status or prediction of its performance. Repeated measurements over a longer time period would be necessary. Conclusions: No significant differences in ISQ values were found between implants with regard to loading period or location in the jaw. Postmenopausal women exhibited significantly lower ISQ values compared to men of the same age group. Keywords: implant stability, maxilla, resonance frequency analysis

Purpose: The aim of this study was to evaluate interproximal papillae and clinical crown height following the placement of single-tooth implants according to early and delayed protocols. Materials and Methods: Forty-five patients were randomly allocated to either the "early" group or the "delayed" group. They were treated with a single-tooth acid-etched Osseotite implant in the maxillary or mandibular anterior or premolar region an average of 10 days (in the case of early placement) or 3 months (in the case of delayed placement) following tooth extraction. Interproximal papilla dimensions and clinical crown height were evaluated using a score index in 39 patients who attended a follow-up visit 16 to 18 months after prosthesis delivery. The patients were evaluated in photographs taken 1 week after crown placement (baseline) and approximately 1.5 years after crown placement (follow-up). Results: It was demonstrated by logistic regression the risk of presenting no papilla or a negative papilla was 7 times greater at baseline for delayed cases than for early cases (33% versus 8%). However, the soft tissue fill in the proximal spaces improved significantly from baseline to the 1.5-year follow-up in both groups, with no significant difference between the groups found at follow-up. The papilla height almost 2 years after implant placement was inversely correlated with patient age. The clinical crown height was acceptable in significantly more cases in the early group than in the delayed group at follow-up. Half of the crowns in the delayed group exhibited an inappropriate height; of these, almost two thirds were assessed to be too short. Discussion and Conclusion: Early placement of single-tooth implants may be preferable to delayed implant placement technique in terms of early generation of interproximal papillae and the achievement of an appropriate clinical crown height, but no difference in papilla dimensions was seen at 1.5 years after seating of the implant crown. Keywords: delayed implant placement, dental implants, early implant placement, esthetics of dental prostheses, mucosa

Purpose: This study assessed the impact of mandibular ridge height on patients' perceptions of dentures following treatment with a mandibular conventional denture (CD) or an implant-assisted overdenture (IOD). Materials and Methods: Evaluation of patient satisfaction in 63 participants was made with original complete dentures and 6 months after treatment completion with new dentures. Twenty-five patients received a new mandibular CD and 38 received a new mandibular IOD. The subjects were divided into 3 subgroups according to ridge height (low, moderate, or high). Two questionnaires with categorical responses were administered. Questionnaire 1 had 13 questions to determine patients' assessment of their original dentures at entry and of their study dentures at 6 months after treatment completion. Questionnaire 2, which was given at 6 months after treatment completion, had 11 questions assessing the change perceived by patients with new dentures compared to their original dentures. Results: No significant differences between the 2 groups were found for most of the variables in Questionnaire 1 at either time point or in regard to the difference between time points. The retrospective questionnaire 2 showed the IOD group to have significantly better perceptions than the CD group for improvement in chewing comfort, ability to eat hard foods, eating enjoyment, and denture security. The only effect of ridge height was an interaction with denture treatment for eating enjoyment, where mean improvement with the study denture was significantly less for the moderate ridge height group with the CD. Conclusion: The results indicate that patients in all ridge height groups had similar improvement in perceptions of dentures following treatment with either a mandibular CD or IOD and that these perceptions were not dependent on the bone height of the mandibular ridge. Keywords: complete dentures, implant-supported overdentures, mandibular symphysis height, patient satisfaction

Purpose: This study evaluated the survival parameters of single-tooth implants through clinical and radiographic analysis. Materials and Methods: Implants were restored within a 24-hour period with a provisional crown designed to receive an occlusal masticatory load. This approach was compared to implants restored after a healing period (the control group). Forty-six implants were placed in 23 patients who were each treated with 2 Frialit-2 implants placed in sites between the second premolar in the maxilla or mandible. The manufacturer's recommended formal surgical procedure was followed, and primary stability was standardized with a minimum insertion torque of 20 Ncm. The sites were randomly selected, and the clinical and radiographic parameters were standardized with individual templates. Results: Data were collected at 24 h, and at 1, 3, 6, 12, 18, and 24 months. The experimental group included 10 failed implants; 9 of the failed implants had been placed with an insertion torque of 20 Ncm. One implant from the control group failed during the 24-month follow-up period. The survival rate was independent of implant length, site position, and bone quality and quantity. Relative risk for implant failure was associated with insertion torque (relative risk 0.79 [CI: 0.66-0.930]; Cox regression) (P .007), in the experimental group but was not significant for those in the control group (ie, implants placed after a healing period; relative risk 0.78 [CI: 0.34-1.78]; Cox regression) (P .057). To achieve osseointegration, it was found that an insertion torque above 32 Ncm was necessary (x2= 15.68; P .004). Discussion: A careful evaluation is necessary for a better understanding of the survival rates of immediately loaded implants. In this study, insertion torque was associated with the potential for risk, which can be decreased by 20% per 9.8 Ncm added. Conclusion: Given these results, and considering the number of patients treated, immediate provisional crowns should only be proposed with early loading if an appropriate initial insertion torque has been applied. Keywords: immediate provisional crowns, insertion torque, masticatory loading, single-tooth implants

Purpose: A simple technique is described for alveolar reconstruction in cases where resorption has already occurred. The palatal core graft allows immediate regeneration of vertical, horizontal, and combined defects at the alveolus with minimal donor site morbidity and time consumption. Materials and Methods: Seventeen patients (10 female and 7 male) were treated over a 1-year period. Bone core grafts from the palatal vault were harvested with a trephine and used for alveolar reconstruction in the esthetic zone. Patient age and gender, type and location of the defect, size of the graft, simultaneous tooth removal, simultaneous implant placement, need for soft tissue coverage, and postoperative complications were recorded. Results: Mean length of the grafts was 12.5 mm (range 9 to 14 mm). Mean width was 7.3 mm (range 5 to 9 mm). In 11 cases, simultaneous tooth removal was performed and a connective tissue flap with posterior pedicles was used. Patients did not experience discomfort in the donor area. Sixteen cases were successfully restored with single implants and crowns Discussion: Material for osseous reconstruction should ideally be autologous and easy to harvest and provoke minimal morbidity. The palatal core graft compares favorably with previously described techniques and donor sites for alveolar reconstruction. Conclusion: In this preliminary report, experience with a new technique for alveolar reconstruction is presented. The "palatal core graft" for alveolar reconstruction is effective and easy to harvest and has low donor site morbidity, allowing 3-dimensional restoration of alveolar defects. Keywords: alveolar reconstruction, bone grafting, immediate implant placement

Purpose: Knowledge of the blood supply to the sinus is of importance in sinus augmentation, both as it pertains to vascularization of the sinus graft and as its location relates to the position of the required lateral osteotomy. The purpose of this study was to investigate the distribution of the endosseous branches of the maxillary artery in the area of the proposed lateral window. Materials and Methods: Fifty computerized tomographic (CT) scans from 625 available patients undergoing sinus augmentation surgery at the New York University Department of Implant Dentistry were chosen at random for evaluation. In those cases where the maxillary artery could be identified, measurements were taken to determine the distance between the alveolar crest and the lower border of the vessel. Results: The vessel was radiographically identified in 51.4% of right sinuses and 54.3% of left sinuses in the 50 CT scans. The average height of the artery from the alveolar crest was 16 mm (± 3.5 mm). Discussion and Conclusions: Because of its location, the intraosseous artery has the potential to cause bleeding complications in approximately 20% of normally positioned lateral window osteotomies. Although a previous anatomic study on cadavers identified the vessel in 100% of the specimens, it could only be visualized in 53% of the CT scans in the present series. Keywords: maxillary artery, sinus floor augmentation

Purpose: The management of 5 patients with extreme maxillary atrophy and treatment consisting of maxillary fixed prostheses supported by conventional implants and zygomatic fixations positioned according to the sinus slot technique is reported. Materials and Methods: A total of 16 conventional implants were placed, together with 2 pterygoid implants and 10 zygomatic fixations. In 2 cases zygomatic fixation could not be performed on the alveolar ridge, thus requiring palatal displacement. One patient presented nasogenian ecchymosis. The fixed rehabilitations were either screwed or cemented after 5 to 6 months. Results: Follow-up from implantation lasted 12 to 18 months, during which the prostheses and implants remained stable and in function. Discussion: The placement of zygomatic fixations based on the sinus slot technique offers advantages over the conventional technique, though extreme atrophy of the alveolar processes does not allow fixation at the supracrestal level, and complications may develop. Conclusion: While zygomatic fixation is a valid alternative for treating the atrophic jaw, long-term studies are required to confirm its efficacy. Keywords: atrophic maxilla, dental implants, sinus slot technique, zygomatic implants

Purpose: The purpose of this study was the clinical and radiographic comparison of dental implants with surfaces roughened by anodic oxidation (TiUnite), dual acid-etched implants (Osseotite), and machined implants. Materials and Methods: Seventy-four patients (mean age, 52.8 ± 14.2 years; range, 23 to 80 years; 41 men and 33 women) received 198 dental implants-58 TiUnite implants (25 patients), 52 Osseotite implants (27 patients), and 88 machined implants (22 patients). Clinical measurements and radiographs were evaluated at the time of surgery, at the restorative phase, and 2 years postloading. To account for statistical correlation among multiple implants in the same subject, a "per patient" mode of analysis was conducted. A 1-way analysis of variance of bone loss was conducted by type of implant as well by area of the mouth. In addition, differences in mean bone loss were tested for bone density category, gender, and smoking status using Student t tests. Results: Eighteen TiUnite implants (31.0%) were placed in the maxilla and 40 (69.0%) in the mandible. The Osseotite group included 29 maxillary implants (55.8%) and 23 mandibular implants (44.2%). The machined group included 49 maxillary implants (55.7%) and 39 mandibular implants (44.3%). All 198 implants were considered radiographically and clinically successful. No mobility, signs of infection, or inflammation were detected. Discussion: Implant size, location, bone quality, gender, age, and smoking did not influence the comparative clinical outcomes of the 3 groups (P > .05). A trend toward greater coronal bone loss in the TiUnite group was detected. Conclusion: Within the limitations of the present study, TiUnite, Osseotite, and machined dental implants had similar short-term clinical outcomes. No statistically significant differences in bone loss could be detected among implant groups or among the different regions of the oral cavity. The present data underlined the significance of surgical and prosthetic treatment planning. Keywords: anodic oxidation, dental implants, dual acid-etched implants, implant surfaces

Loss of posterior mandibular teeth resulting in insufficient posterior vertical bone height can pose a problem in implant therapy. In the case reported, a modified sandwich osteotomy was used to solve this problem. Keywords: atrophic mandible, sandwich osteotomy