The International Journal of Oral & Maxillofacial Implants, 03/2007

Purpose: The aim of this study was to evaluate single-tooth implant-supported restorations placed in conjunction with several methods of maxillary sinus augmentation. Materials and Methods: A retrospective review was conducted of all consecutively treated patients who received single-implant tooth rehabilitation in combination with sinus augmentation. Implant survival rate and peri-implant conditions, such as marginal bone resorption (mm), pocket depth (mm), Plaque and Bleeding Indices, and Periotest values, were compared for the different augmentation procedures. Results: Fifty-one patients were treated with 54 screw-type single implant-supported restorations in the posterior maxilla in combination with isolated sinus floor augmentation. Depending on the residual ridge height and the intended augmentation height, sinus lift elevation was performed either in a 1-stage lateral approach (25 patients, 28 implants), in a 2-stage lateral approach (12 patients, 12 implants), or with the osteotome technique (14 patients, 14 implants). The predominant use of long implants provided for a favorable implant-crown ratio (> 1.0) and produced an overall clinical survival rate of 100% over the observation period (44.5 ± 22.7 months), with no differences between the augmentation procedures and implant types used. The most frequent site for single-tooth replacement in combination with sinus floor augmentation was the first molar region (61%). Implants with wider diameters (94% >= 4.3 mm) were used in this region. The most frequent intraoperative complication was tearing of the sinus membrane (58%) as a result of the restricted access for the lateral 1- or 2-stage approach, and the most frequent prosthetic complication was crown loosening. Conclusion: On the basis of this retrospective review, the following was observed: (1) Successful function and excellent peri-implant parameters may be anticipated for single implant-supported restorations placed in conjunction with sinus elevation procedures. (2) Clinical and radiographic examinations demonstrated similar conditions for single-tooth restorations despite the use of different surgical approaches to sinus augmentation. (More than 50 references.) Keywords: lateral approach, osteotome technique, single implant-supported restorations, sinus augmentation

Purpose: To assess the objective and subjective morbidity of mandibular bone harvesting. Materials and Methods: Forty-five patients who had been subjected to mandibular bone harvesting from the chin region (group 1, n = 15), the retromolar region (group 2, n = 15), or the retromolar region after removal of the third molar (group 3, n = 15) participated in this study. Complications, postoperative morbidity, and patient acceptance of the procedure were evaluated by assessing the medical records and performing standardized routine clinical and radiographic examinations up to 12 months after the augmentation procedure. In addition, the patients were asked to complete a questionnaire on the subjective complaints related to the procedure. Results: Analysis of the questionnaire revealed that there was no significant difference between patients of groups 1 and 2 regarding acceptance of the procedure (scores of 8.6 plusmn 1.1 and 8.5 plusmn 0.9 on a 10-point scale, respectively). Acceptance of the procedure was scored significantly higher by the patients of group 3 (9.3 plusmn 0.7; Student t test, P .05). Six patients of group 1 and 2 patients of groups 2 and 3 reported subjective sensory disturbances related to the donor site. With the exception of 2 patients in group 1, these subjective complaints disappeared within 2 months after surgery. In the 2 patients (group 1) who reported a persistent discrete sensibility disorder in the symphyseal region after 12 months, this disturbance could not be confirmed objectively. Conclusion: Mandibular bone harvesting for reconstructing local alveolar defects is a well-accepted procedure with low objective and subjective morbidity. Amongst the procedures evaluated, harvesting bone from the retromolar region combined with removal of the third molar was best accepted by the patients. Keywords: autologous bone grafts, bone augmentation, endosseous implants, mandible, morbidity

Purpose: The use of osseointegrated implants for maxillofacial prostheses reduces the need for adhesives, provides for a more stable and more esthetic prosthesis with thinner margins, and results in increased patient acceptance and confidence. The purpose of this study was to compare the retention and load transfer characteristics of differently designed implant-retained auricular prostheses. Materials and Methods: A photoelastic model was fabricated of the auricular-temporal region of a human skull. Craniofacial implants 3.75 mm in diameter and 4 mm long were embedded in locations typically selected to retain auricular prostheses. Two retention mechanisms were evaluated on the implants: a Hader bar with 3 clips and the use of 3 Locator attachments. The retentive capacity of the prostheses was determined on an Instron test machine. Initial retention and changes with multiple removals were examined. Dislodgment forces were applied to each retentive device in the field of a circular polariscope. Resulting stresses were monitored and recorded photographically. Results: The highest initial retention demonstrated by the Locator device was 12.4 plusmn 0.9 lb, and the highest retention value for the Hader bar with clips was 7.5 plusmn 1.1 lb. All attachments decreased in retention after multiple removals. The Locator devices produced higher peri-implant stresses compared to the Hader bar-with-clips design. Conclusions: Since higher retention is associated with higher stresses, results of this study suggest that a balance between retention and stress production is necessary in selecting a retention mechanism for the specific requirements of the patient being treated. The Locator attachment was correlated with higher retention values as well as with higher peri-implant stress compared to the Hader bar-and-clip attachment design. Retention decreased and then stabilized after multiple removals. Keywords: auricular prostheses, extraoral implants, photoelastics

Purpose: To compare the efficacy and complications of 2 different techniques for vertical bone augmentation at implant placement: particulated autogenous bone grafts covered either by resorbable collagen barriers supported by osteosynthesis plates (test) or by nonresorbable titanium-reinforced e-polytetrafluoroethylene (e-PTFE) barrier (control). Materials and Methods: Twenty-two partially edentulous patients requiring vertical bone augmentation were randomly allocated to 2 treatment groups of 11 patients each. Early implant failures, the amount of vertically regenerated bone measured intrasurgically, and biologic complications were recorded by an independent assessor blinded to the group allocation. The implant site requiring the most vertical bone regeneration was selected in each patient for the bone gain assessment. Patients were followed from implant insertion with simultaneous augmentation procedure to insertion of the provisional restoration. Paired and independent t tests and Fisher exact tests were conducted to compare means and proportions at the .05 level of significance. Results: No patient dropped out or was excluded. Both procedures obtained significant bone gain and achieved the desired results, 2.2 mm (SD 1.5; P .001) on average for resorbable barriers and 2.5 mm (SD 1.1) for nonresorbable barriers (P .001). There was no statistically significant difference in bone gain between the 2 procedures (P = .58). Complications occurred in 40% of the patients. There was no difference in occurrence of complications between the procedures (P > .99). Three major complications occurred, 2 in the resorbable group and 1 in the nonresorbable group, which determined the complete failure of the augmentation procedure. Conclusions: Both techniques were effective in augmenting bone; however, both were associated with complications. Clinicians and patients must carefully weigh risks and benefits when considering the use of vertical guided bone regeneration. Keywords: bone augmentation, bone grafting, dental implants, guided bone regeneration, vertical augmentation

Purpose: To evaluate the pulp sensitivity and vitality of mandibular incisors and canines before and after bone harvesting in the symphysis. Materials and Methods: In 20 patients requiring bone grafts from the symphysis, pulp sensitivity (carbon dioxide [CO2]) and pulpal blood flow (laser Doppler flowmetry [LDF]) of mandibular incisors and canines were evaluated preoperatively, postoperatively, and 6 months after surgery. Teeth were allocated to 1 of 3 groups according to their initial and final reaction to CO2 (group A = teeth with a positive reaction throughout the study, group B = teeth that exhibited a sensitivity change from positive to negative, and group C = teeth with a negative reaction throughout the study). Results: Preoperative flux measurements (LDF) did not differ between groups A, B, and C. Teeth with sensitivity changes (group B) showed the greatest decrease (a statistically significant decrease) of pulpal blood flow over time, whereas teeth in groups A and C demonstrated an insignificant reduction of flux over time. Discussion and Conclusions: LDF was purely used as an experimental tool in the present study. Pulpal blood flow measurements using LDF demonstrated a decrease of flux over time in anterior mandibular teeth following bone harvesting in the symphysis. A significant change of flux, however, was only observed for teeth that also demonstrated a loss of pulp sensitivity during the same study period. Loss of pulp sensitivity appeared to be correlated to a significant decrease of blood flow assessed by LDF. Keywords: bone harvesting, laser Doppler flowmetry, pulp sensitivity, pulp vitality, symphysis

Introduction: Autologous bone is considered the reference standard for bone-grafting procedures. A barrier membrane covering an autologous bone graft (guided bone regeneration [GBR]) is expected to prevent graft resorption. Good clinical results have been reported for GBR, although potential complications and relatively high costs have been implicated as disadvantages. However, most studies on the subject have been uncontrolled. Purpose: The aim of this systematic review was to evaluate the available evidence that barrier membranes prevent bone resorption in autologous onlay bone grafts. The primary outcome measure was bone resorption. Results: The search yielded 182 articles. Two observers independently appraised 32 relevant studies methodologically, yielding 14 controlled studies. The articles included human and animal experiments with heterogenous objectives and outcome variables. Although most authors concluded that they had found evidence for the protective effect of barrier membrane on bone resorption in bone grafts, this systematic review reveals that the available evidence is too weak to support this. Most included studies were animal experiments; thus, extrapolation to the human situation is difficult. Most studies also had a small number of test sites, and sample size justification was generally not reported. Furthermore, ambiguity and lack of significance were found in many studies, along with additional limitations such as implantation site, nonsuitable designs, and varying outcome measures. Conclusion: Based on a systematic review of the literature, further evidence is needed to determine whether barrier membranes prevent bone resorption in autologous onlay bone grafts. Keywords: artificial membranes, bone grafts, bone

Purpose: The objectives of this study were to (1) evaluate the survival of implants placed in maxillary sinuses augmented with a 70:30 mixture of autogenous bone and anorganic bovine hydroxyapatite (Bio-Oss) at 1 and 5 years, (2) observe the difference in survival rate between 1-stage and 2-stage procedures, and (3) compare the survival rate of rough-surfaced implants with that of machined implants. Materials and Methods: A total of 30 consecutively patients (48 sinuses) with Cawood and Howell Class V and VI atrophy were evaluated. Lateral osteotomy techniques were used in all cases. Implants were placed either simultaneous with grafting (1-stage procedure) or after a delay (2-stage procedure), depending on the amount of residual bone. A 70:30 mixture of autogenous bone and anorganic bovine hydroxyapatite was used as the graft material. All patients were followed up at 1 year after prosthetic loading, while a limited group of these patients was followed up to 5 years. Results: In 8 patients where the residual crestal bone under the sinus floor assessed by computed tomography was at least 4.5 mm (mean, 5.3 mm), the 1-stage procedure was used for 11 sinus elevations and 32 implants. In 22 patients where the residual crestal bone was less than 4.5 mm (mean, 2.5 mm), the 2-stage procedure was used for 37 sinus elevations and 108 implants. For the 140 implants placed, the overall survival rate was 95.7% at the healing abutment surgery, and the cumulative survival rate was 94.9% at 1 and 5 years. The type of surgical technique was significantly associated with implant failure (P .05); implants placed using the 1-stage procedure showed a failure rate of 12.5%, while implants placed with the 2-stage procedure had a failure rate of 2.8%. No significant difference in survival rate was observed with respect to implant surface. Conclusions: A high survival rate was achieved when sinus elevation was performed with a combination of autogenous bone and anorganic bovine hydroxyapatite, even where a minimal amount of residual crestal bone was present. The survival rate was improved when implants were placed after a healing period. Keywords: autogenous bone graft, bovine hydroxyapatite, dental implants, maxillary sinus augmentation

Purpose: The purpose of this retrospective study was to compare a bidirectional distraction system with a unidirectional system with regard to bone height attained and the need for secondary graft procedures. Materials and Methods: Unidirectional and bidirectional distractor devices were used for vertical augmentation of the maxilla and mandible in 2 separate groups of patients (n = 10 and n = 11, respectively). Clinical and radiographic outcome data were collected at postoperative follow-up examinations for up to 2.5 years. The height of the augmented alveolar ridge and the sagittal location of the bone fragment were measured on panoramic radiographs or lateral cephalograms. These data were analyzed with 1-way analysis of variance. Nonparametric data, such as treatment complications, were analyzed with the Fisher exact test. The dental implant survival data were evaluated with a Kaplan-Meier survival analysis. Results: The difference in vertical bone gain observed between unidirectional and bidirectional groups (5.3 plusmn 1.8 mm vs 6.1 plusmn 2.3 mm) was not statistically significant. In the unidirectional group, additional autogenous bone grafting was required in 6 cases, while grafting was required in only 2 cases in the bidirectional group. This difference was due to the more precise control of the distraction process associated with the bidirectional distractor; however, it was not a statistically significant difference. Postaugmentation, 59 implants were placed in the augmented sites. These implants exhibited primary stability and were restored with good functional and esthetic results. Conclusions: The need for additional grafting procedures may be reduced in cases where the distraction vector is optimized, as generally seen with bidirectional distractor use. Keywords: augmentation, bidirectional distraction, complications, dental implants, distraction osteogenesis

Purpose: The aim of this study was to compare the effects of platelet-enriched fibrin glue and platelet-rich plasma (PRP) on the repair of bone defects adjacent to titanium dental implants. Materials and Methods: In 6 mongrel dogs, 3 screw-shaped titanium dental implants per dog were placed into the osteotomy sites in the tibia. Before implantation, a standardized gap (2.0 mm) was created between the implant surface and the surrounding bone walls. Six gaps were left empty (control group), 6 gaps were filled with autogenous particulate bone mixed with PRP (PRP group), and 6 gaps were filled with autogenous particulate bone mixed with platelet-enriched fibrin glue (fibrin glue group). Results: After 6 weeks, the bone-implant contact was 59.7% in the fibrin glue group, 29.2% in the PRP group, and 10.2% in the control defects; this difference was statistically significant (P .05). Discussion and Conclusion: Greater bone-implant contact was achieved with platelet-enriched fibrin glue than with PRP. The results indicate that platelet-enriched fibrin glue can induce a stronger peri-implant bone reaction than PRP in the treatment of bone defects adjacent to titanium dental implants. Keywords: bone grafting, bone regeneration, dental implants, fibrin glue, platelet-rich plasma

Purpose: Immediate restoration of dental implants in patients with a history of periodontal disease was examined. The influence of insertion torque and implant stability quotient (ISQ) on the survival rate was compared in immediately restored, nonrestored, and submerged implants. Materials and Methods: Patients received periodontal treatment after which all in one implant surgery was performed: hopeless teeth were extracted, debridement around remaining adjacent teeth was performed, implants were inserted and, in some cases, a prefabricated screw-retained provisional restoration was immediately delivered. Insertion torque and ISQ were recorded at baseline and 6 and 12 months postsurgery. Results: Nineteen patients were treated, and 74 implants were placed. Twelve implants, 10 of which were maxillary, failed in 4 patients. Survival rates were 100% in partial-arch restorations, 94% in the mandible, and 78% in the maxilla. The survival rate of restored implants was 65% in extraction sites versus 94% in healed, nonextraction sites. Implants exhibited a decrease in ISQ at 6 months followed by an increase at 12 months. There were no statistically significant differences in insertion torque or ISQ between failed and successful implants, restored and nonrestored implants, or extraction-site and nonextraction-site implants. Mandibular implants demonstrated higher insertion torque and higher ISQ at baseline and 6 and 12 months. Conclusions: Within the limits of this study, immediate restoration of dental implants in periodontally susceptible patients had a variable success rate. Several factors were shown to affect these results. (Comparative Cohort) Keywords: dental implants, immediate loading, periodontal disease

Purpose: The aim of this study was to evaluate the success rate of 100 consecutive zirconia dental implants with 2 different rough surfaces after 1 year of follow-up. Materials and Methods: One-piece zirconia dental implants (CeraRoot, Barcelona, Spain) with 1 of 2 different roughened surfaces were designed and manufactured for this study. Five different implant designs were manufactured. Standard or flapless surgical procedures were used for implant placement. Simultaneous bone augmentation or sinus elevation were performed in the cases where bone height or width was insufficient. Implants in the anterior region (canine to canine) were immediately restored with provisional prostheses. Implants placed using less than 35 N torque were splinted with composite resin using an etched and bonded approach to the neighboring teeth or implants to minimize implant mobility and failure. Definitive all-ceramic restorations were placed 4 months after implant placement (8 months for implants where bone augmentation or sinus elevation was performed). Results: The study included 36 patients with a mean age of 50 years. The overall implant success rate after 1 year of follow-up was 98% in both the coated and noncoated groups. Conclusions: From the preliminary results of this investigation, it can be concluded that zirconia dental implants with roughened surfaces might be a viable alternative for tooth replacement. Further follow-up is needed to evaluate the long-term success rates of the implant surfaces studied. (Case Series) Keywords: bioceramic, ceramic, coatings, dental implants, rough surface, rough topography, zirconia, zirconium oxide

Purpose: The aim of this study was to determine a reliable compression testing method for cancellous jawbone specimens and to validate it by high-resolution finite element (FE) modeling based on micro-computerized tomography (CT) images of the specimens. Materials and Methods: Three series of human femoral bone samples were tested to establish a compression protocol for human jawbone cores. A CT scan of each bone sample was obtained. A simple destructive compression test was performed on the first series of 12 femoral bone samples (13 mm height and 6.1 mm diameter). The 5 femoral bone samples of the second series (13 mm height and 6.1 mm diameter) were constrained using end caps and subjected to 10 to 15 conditioning cycles before the destructive test from which the Youngs modulus (Emeas) was determined. The third series of 5 smaller femoral samples (8 mm height and 5.5 mm diameter) and the series of 5 jaw bone samples (8 mm height and 5.7 mm diameter) underwent the same testing protocol. FE models were created based on the CT images, and the simulated E-modulus (Ecalc) was calculated. Results: The intraclass correlation between Emeas and Ecalc corresponded to 0.74 for the first series of femoral bone samples, 0.96 for the second series, and 0.51 for the third series. For the jawbone samples, the intraclass correlation coefficient equaled 0.88. Conclusion: Reliable results for compression testing of cancellous jawbone can be obtained with cylindric specimens with a diameter of 5.7 mm, a length:diameter ratio 1.4, and flat top and bottom surfaces. The recommended compression method is constrained compression with 10 to 15 conditioning cycles, followed by a destructive test. Keywords: cancellous bone, compression, finite element modeling, jaws, micro-computerized tomography

Purpose: For proper preoperative planning of oral implants, the need has increased for tomographic imaging for precise determination of anatomic dimensions. However, concern for radiation exposure, which is substantial with computerized tomography (CT), has also grown. In the present study, the validity of jawbone width assessment and delineation by means of cone-beam CT (CBCT) and spiral tomography on dry mandibles was compared. Secondly, the subjective image quality of CBCT images with those obtained by multi-slice spiral CT (MSCT) of a fixed ex vivo cadaver with its soft tissues was compared. Materials and Methods: The study included 25 dry human mandibles for the dimensional study and 1 formalized maxilla for image quality assessment. Measurements of the mandibles by means of a digital sliding caliper acted as the gold standard. Radiographic examination of the premolar and canine regions was performed with both CBCT and spiral tomography. Observational measurements were carried out by postgraduates in oral imaging. Subjective image quality was assessed on the fixed maxilla, including soft tissues, by comparing CBCT and MSCT. Inter- and intraobserver variability were determined. Results: Direct mandibular measurements were on average 0.23 mm (SD 0.49) and 0.34 mm (SD 0.90) larger than the CBCT and spiral tomography measurements, respectively. Subjective image quality of the CBCT was significantly better than for the MSCT with regard to visualization and delineation of the lamina dura and periodontal ligament space. Subjective image quality of the MSCT was significantly better for the MSCT than the CBCT for the gingiva and cortical bone. Conclusions: These results indicate that on dry mandibles, jawbone width measurements by means of CBCT and spiral tomography are reliable, even if on average they slightly underestimate the bone width. For the subjective image quality, the CBCT offered better visualization of details of the small bony structures. Spiral tomography offered better visualization of the cortical bone and the gingiva. Keywords: computerized tomography, cone-beam computed tomography, dental implants, jawbone, preoperative planning, 3-dimensional imaging

Purpose: The purpose of the study was to develop a finite element model of the human mandible and to compare the functional deformation predicted by the model with that detected clinically. Materials and Methods: Three patterns of mandibular deformation (medial convergence, corporal rotation and dorso-ventral shear) were studied clinically in 12 subjects using custom-fabricated displacement transducers mounted on endosseous implants in the premolar region. The mandibular arches of 12 patients with dental implants were modeled using finite element techniques based on computerized tomographic (CT) scan images of the jaw. Results: The finite element model was found to closely replicate the patterns of observed mandibular deformation. Differences between the predicted and measured deformation values were expressed as a percentage of the measured value and ranged between 0.0% and 22.2%. Medial convergence ranged between 14.4 and 58.4 µm. Dorso-ventral shear and corporal rotation ranged between 0.4 and 2.7 degrees. Conclusions: Using the finite element model described in this study, which represents the living human mandible, and clinical testing, there was close agreement between the predicted and measured deformation values. This study provided a high level of confidence in the finite element model and its ability to provide better insight into understanding the complex phenomena of functional mandibular deformation. (More than 50 references.) Keywords: finite element analysis, jaw deformation, stress

Purpose: The aim of this study was to determine the osseointegration potential of implants with apical primary stability but no resistance to rotation in variable clinical conditions. Materials and Methods: Patient records of treatment performed between October 1993 and May 2004 were reviewed for primary implant stability. Patients who exhibited implants without rotational primary stability (RPS) were reviewed further to determine patient age, gender, implant type, implant surface, loading protocol, and prosthesis type. Results: Forty-four implants without RPS were reported in 12.8% of patients treated during the period reviewed. Statistical significant differences in cumulative survival rate (CSR) were seen with implant location and surface. No significant difference in CSR was observed in relation to loading protocol, despite a higher success rate (17.4% higher) for the immediate loading population. No difference in CSR was observed with respect to gender. Discussion and Conclusion: In the early years of machined implants, there was a higher failure rate of implants without RPS. The results for this implant population show that there are statistically significant differences in survival rate between the maxilla and mandible, and also between titanium oxidesurfaced implants and machined implants. The sample size of this study limited the statistical significance of the difference in CSR observed between loading protocols. Implants without RPS that are not removed at the time of surgery can become osseointegrated with a survival rate of 82%. Survival rates increase when testing sample is limited to titanium oxidesurfaced implants under an immediate loading protocol. Under the appropriate level of risk, implants that have apical primary stability but no resistance to rotation can become osseointegrated when incorporated in a rigid prosthesis under immediate loading circumstances. (Case Series) Keywords: bone-implant interface, dental implants, immediate loading, implant stability

Purpose: The influence of surface modifications on osseointegration in newly formed bone is not well established. The purpose of this study was to compare osseointegration at acid-etched versus turned implants in newly formed and native bone. Methods: Supra-alveolar peri-implant defects were created in 8 hound/Labrador mongrel dogs. Titanium implants 10 mm long (2 turned and 1 dual acid-etched) were placed 5 mm into the surgically reduced alveolar crest, creating 5-mm supra-alveolar peri-implant defects. Recombinant human bone morphogenetic protein-2 (rhBMP-2; 0.4 mg) in a collagen carrier was used to induce new bone formation. A macroporous, expanded polytetrafluoroethylene device was used to delineate new bone formation. The animals were euthanized at 8 weeks for histometric analysis of the experimental sites. Results: There were no significant differences in rhBMP-2induced bone density (mean plusmn SD) at acid-etched versus turned implants (20.6% plusmn 5.3% vs 23.8% plusmn 4.7%; P = .232). However, there was a significant difference in bone-implant contact in favor of the acid-etched implants (12.3% plusmn 6.8% vs 7.9% plusmn 3.1%; P = .05). Native bone density averaged 63.9% plusmn 7.5% and 64.5 plusmn 9.0% for acid-etched and turned implants, respectively (P = .641). Nevertheless, bone-implant contact was significantly enhanced at acid-etched versus turned implants (59.7% plusmn 11.3% vs 40.7% plusmn 21.2%; P = .005). Conclusions: Surface dual acid-etching of titanium implants has a positive effect on osseointegration in newly formed and native bone. Significant differences in bone density do not appear to influence this effect. Keywords: bone, e-PTFE, osseointegration, rhBMP-2, tissue engineering, titanium implants

This article presents the case report of the bilateral 3-dimensional reconstruction of a posterior mandible in a 48-year-old woman. Titanium meshes and Regenaform demineralized freeze-dried bone allograft were used for bone regeneration. After 5 months the titanium mesh was removed, and after another 4 months, 4 Straumann sandblasted, large-grit, acid-etched implants were placed, 2 on each side of the mandible. During implantation a bone specimen was collected and sent for histologic examination. The definitive fixed prosthesis was fabricated after an additional 4 months. The clinical and histologic results are shown. The implants were followed for 18 months after implant loading; no signs of bone loss or infection were observed. Keywords: bone regeneration, demineralized freeze-dried bone allograft, dental implants, titanium mesh