The International Journal of Oral & Maxillofacial Implants, 05/2006

Purpose: The capability of micro-computed tomography (µCT) for quantitative analysis of peri-implant bone has not been previously addressed. This study aimed to establish and validate a method to use this technique for 3-dimensional bone-implant integration profiling. Materials and Methods: Unthreaded cylindric implants with a dual acid-etched surface were placed into the right femurs of 7 Sprague-Dawley rats. Two weeks postimplantation, the femurs were harvested and measured with a desktop micro-tomographic scanner with an isotropic resolution of 8 µm. To validate the µCT outcome, ground histologic sections and corresponding CT slices were compared with respect to bone morphometry. Results: Bone-implant integration profiles assessed by µCT revealed that the percentage of cancellous bone gradually increased with proximity to the implant surface, while the percentage of cortical bone was not affected by proximity to the implant. Using the optimized segmentation threshold, the bone configuration in the µCT images corresponded to that observed in the histologic sections. The correlation between µCT and histology was significant for cortical (r = 0.65; P .05) and cancellous bone (r = 0.92; P .05) at distances of 24 to 240 µm from the implant surface, but no significant correlation was found for the area from 0 to 24 µm from the surface. Discussion and Conclusion: The results support the usefulness of µCT assessment as a rapid, nondestructive method for 3-dimensional bone ratio measurements around implants, which may provide new perspectives for osseointegration research. Further study is necessary, however, to address the inherent metallic halation artifact, which potentially confounds peri-implant bone assessment. Keywords: dental implants, histomorphometry, micro-computed tomography, Osseointegration

Purpose: To test (a) whether and when bone augmentation procedures are necessary and (b) which is the most effective augmentation technique for specific clinical indications. Trials were divided into 3 categories: (1) major vertical or horizontal bone augmentation (or both); (2) implants placed in extraction sockets; (3) fenestrated implants. Materials and Methods: An exhaustive search was conducted for all randomized controlled clinical trials (RCTs) comparing different techniques and materials for augmenting bone for implant treatment reporting the outcome of implant therapy at least to abutment connection. No language restriction was applied. The last electronic search was conducted on October 1, 2005. Results: Thirteen RCTs of 30 potentially eligible trials reporting the outcome of 332 patients were suitable for inclusion. Six trials evaluated techniques for vertical and/or horizontal bone augmentation. Four trials evaluated techniques of bone grafting for implants placed in extraction sockets, and 3 trials evaluated techniques to treat fenestrated implants. Conclusions: Major bone grafting procedures of extremely resorbed mandibles may not be justified. Bone substitutes may replace autogenous bone for sinus lift procedures of extremely atrophic sinuses. Both guided bone regeneration procedures and distraction osteogenesis can be used to augment bone vertically, but it is unclear which is the most efficient. It is unclear whether augmentation procedures are needed at immediate single implants placed in fresh extraction sockets; however, sites treated with barrier + Bio-Oss showed a higher position of the gingival margin than sites treated with barriers alone. More bone was regenerated around fenestrated implants with nonresorbable barriers than without barriers; however, it remains unclear whether such bone is of benefit to the patient. Bone morphogenetic proteins may enhance bone formation around implants grafted with Bio-Oss, but there was no reliable evidence supporting the efficacy of other active agents, such as platelet-rich plasma, in conjunction with implant treatment. Keywords: bone augmentation, bone graft, bone substitutes, dental implants, randomized controlled clinical trial

Purpose: Bone formation and the healing of calvarial defects in mice is diminished in chemically induced type 1 diabetes. The present study investigated whether controlled local release of fibroblast growth factor 2 (FGF-2) stimulates bone defect healing in this model of diabetes. Materials and Methods: First, in vitro release kinetics of different doses of recombinant human FGF-2 (rhFGF-2) from polyglycolate:polylactide membranes was determined over a 14-day period by incubating loaded membranes in PBS with constant shaking. The amount of FGF-2 was measured by enzyme-linked immunosorbent assay. Then, the effects of rhFGF-2-loaded and control membranes on calvarial defect healing over a 14-day healing period were determined in diabetic and nondiabetic mice. The degree of healing was determined by histomorphometric analyses of bone area percentage and by area measurements. The significance of the data was determined by statistical analyses, including analysis of variance. Results: Kinetic release data in vitro showed that membranes loaded with 5 µg FGF-2 released measurable levels of growth factor for more than 14 days. Data from the in vivo study supported the previous finding that diabetes inhibits bone formation. Membranes containing rhFGF-2 significantly (P .05) stimulated bone formation in diabetic animals to near normal levels during the healing period. Conclusion: FGF-2-loaded membranes may be useful in further studies aimed at developing therapeutic strategies for correcting deficient bone healing in patients with diabetes. (More than 50 references) Keywords: bone regeneration, controlled release, diabetes, fibroblast growth factors, growth factors

Purpose: Cell proliferation and extracellular matrix formation are primary events in bone formation. At the dental implant-tissue interface, implant surface roughness modulates osteoblast functions. The aim of the present in vitro study was to investigate the effect of varying surface roughness of titanium implant material on cell proliferation and mRNA expression of specific markers of osteoblast phenotype. Materials and Methods: Primary cultures of osteoblasts derived from human mandibular bone were cultured on titanium surfaces. Three titanium surfaces were studied: machined titanium, micro-sandblasted titanium, and macro-sandblasted titanium (average surface roughnesses of 0.5 and 3 µm, respectively). Cell morphology was estimated by scanning electron microscope analysis and cell proliferation by measuring the amount of 3H-thymidine incorporation into DNA. mRNA expression of osteonectin, osteopontin, bone sialoprotein (BSP), and Runx2, which are markers of osteoblastic phenotype, were determined by reverse transcriptase polymerase chain reaction (RT-PCR) analysis. Results: Human osteoblasts cultured on machined titanium spread more and were flatter than cells cultured on rough titanium. All blasted surfaces showed significantly higher DNA synthesis than the machined surfaces. Osteonectin mRNA expression was similar on all surfaces. Other mRNA transcripts were increased in osteoblasts cultured on rough titanium surfaces, particularly the macro-sandblasted surface. Conclusions: An average surface roughness of 3 µm (macro-sandblasted titanium) is more suitable than an average surface roughness of 0.5 µm (micro-sandblasted titanium) in favoring osteoblast differentiation in vitro. Keywords: differentiation, human osteoblasts, proliferation, surface roughness, titanium implants

Purpose: The aim of this study was to compare insertion torque and resonance frequency analysis of different implant systems in an animal model with loaded implants. Materials and Methods: Three types of Brånemark implants (machined MkIII, TiUnite MkIII, and MkIV) and 2 types of Straumann implants (sandblasted, large-grit, acid-etched [SLA] and titanium plasma-sprayed [TPS]) were studied. Thirty-two implants of each type (n = 160) were placed in 16 beagle dogs. Maximum insertion torque values were recorded. After a healing period of 8 weeks, the implants were loaded for 3 months; the animals were then sacrificed. At placement, after healing, and at the end of the loading phase, resonance frequency analysis was performed and implant stability quotients (ISQs) were recorded. Results: Higher insertion torque values were seen for the conical MkIV than for the MkIII. No difference was seen between the Brånemark and Straumann implants on the basis of ISQ value at placement. ISQ and insertion torque values were lower for the cylindric Straumann implants than for the self-tapping implants. For all implant systems a significant decrease in median ISQ was observed, with a median decrease ranging from 3 to 6. ISQ values for self-tapping implants remained stable after loading, whereas the ISQ values for non-self-tapping cylinders decreased. The maximum insertion torque values for failed and successful implants were not significantly different. Significantly higher ISQ values at placement were seen for successful implants (P =.003). Based on this model for ISQ, a threshold of 65.5 was identified, with a sensitivity of 83% and specificity of 61% for prediction of implant loss. ISQ values at the start of loading were not predictive of implant loss in the loading period. Conclusion: Caution should be used when judging implant systems on the basis of resonance frequency analysis and torque measurement. Keywords: animal model, dental implants, insertion torque, primary stability, resonance frequency analysis

Purpose: The aim of this in vitro study was to evaluate the load resistance in a conical implant system by comparing combinations of 2 different abutment head angles and 3 different retaining screw materials. Materials and Methods: The retaining screw materials (titanium alloy, gold alloy, and commercially pure titanium) were tested with abutment-head angles of 20 degrees and 45 degrees. Six groups of 10 specimens each were prepared. An oblique (30-degree) compression test was performed in a Lloyd LRX universal testing machine with the abutment attached to a superstructure with a retaining screw. All specimens were loaded until fracture or permanent deformation occurred. The results were evaluated statistically with Wilcoxon signed rank test for variance distribution (P .05 considered significant). Results: There were statistically significant differences in load resistance between 20-degree and 45-degree abutments. The titanium screws (titanium alloy and commercially pure) in the 45-degree abutment group had almost equal mean values, while the gold alloy had a significantly lower value. In the 20-degree abutment group, significantly higher values were found with commercially pure titanium compared to titanium alloy and gold alloy, but the difference between the values for the gold and titanium alloys was not significant. Discussion: The angulation of the abutment head played the most significant role in determining the amount of load withstood, but the material used for the screw was also relevant. Conclusion: A 45-degree abutment can be combined with a retaining screw of any of these materials to create a functional implant system. The test also substantiated that, irrespective of the retaining-screw material, a 20-degree abutment could resist loading forces of at least 900 N. Keywords: dental implant failures, dental implants, implant abutments, implant loading

Purpose: The aim of the present study was to test the hypothesis that calcium phosphate coating of titanium screw-type implants enhances peri-implant bone formation in the jaw. Materials and Methods: Ten adult female foxhounds received experimental titanium screw-type implants in the mandible 3 months after removal of all premolar teeth. Four types of implants were evaluated in each animal: implants with machined titanium surface (the control group), implants coated with collagen l (the collagen-only group), implants with a composite coating of calcium phosphate and mineralized collagen l (the composite group), and implants with calcium phosphate (hydroxyapatite [HA]) coating (the HA-only group). Peri-implant bone regeneration was assessed histomorphometrically after 1 and 3 months in 5 dogs each by measuring bone-implant contact (BIC) and the volume density of the newly formed peri-implant bone (BVD). Results: After 1 month, BIC was significantly enhanced only in the group of implants with composite coating of calcium phosphate and mineralized collagen (P = .038). Volume density of the newly formed peri-implant bone was significantly higher in all coated implants after 1 month. No significant difference from baseline was found in BIC for the collagen-only and HA-only groups, but BVD was significantly higher in implants with composite coating (P = .041). After 3 months, BIC and BVD were significantly higher in all coated implants than in the controls with machined surfaces. Conclusion: It was concluded that composite coating of dental screw-type implant surfaces using calcium phosphate and collagen can enhance BIC and peri-implant bone formation. Keywords: biomimetic coating, calcium phosphate, collagen, dental implants, Osseointegration

Purpose: Four possible displacements of implant components from a patient model to a definitive cast were assessed to suggest a standard method of comparing the accuracies of implant impression techniques. Materials and Methods: Two techniques for impression making were assessed: a nonsplinted open-tray technique and a light-curing resin splinted open-tray technique. A mandibular model with 5 parallel implants was fabricated. Five definitive casts were fabricated per technique. Using a computerized coordinate measuring machine, 5 part coordinate systems were established, and 7 sets of data were obtained for each sample. From the data, the amount of displacement while connecting components and the linear and angular displacement of components during impression making and cast fabrication were calculated. The Mann-Whitney test was used to determine significant differences between the impression techniques (P .05). Results: The average displacements while connecting impression copings and abutment replicas were 31.3 and 30.4 µm, respectively. Less displacement occurred in the nonsplinted group compared to the splinted group during impression making (P = .001) but greater displacement occurred in that group during definitive cast fabrication (P = .015). Discussion: In contrast to previous studies, the current study excluded displacement resulting from component connection, because displacement from that source has no relation to impression technique and cannot be controlled. Conclusions: Connecting a component produced as great a displacement as that resulting solely from a impression or cast fabrication. The nonsplinted group was more accurate during impression making but less accurate during cast fabrication. Keywords: coordinate measuring machine, displacement, implant, impression

Purpose: It is believed that implant-supported fixed partial dentures (FPDs) should display passive fit. The objective of this in vivo-based finite element analysis (FEA) was to quantify the magnitude of bone loading occurring on account of the fixation of cemented or screw-retained 5-unit superstructures. Materials and Methods: Based on a patient situation with 3 implants, 4 different groups of restorations with 10 samples each were fabricated. Strain gauges on the pontics of the restorations were used for in vivo measurements. Using the values obtained, bone loading in 3-dimensional FE models was simulated as von Mises equivalent stress. Results: The in vivo measured mean strain values ranged from 32 µm/m to 458 µm/m at the different sites. FEA revealed stresses between 5 and 30 MPa in the cortical area, while in trabecular bone values ranging from 2 MPa to 5 MPa were observed. Stress of a similar magnitude was found for axial implant loading with 200 N. Discussion: Assuming that the axial loading of a single implant with 200 N is within the realm of the bone's adaptation ability, it would appear that the amount of stress resulting from the fixation of superstructures alone does not constitute a risk. Conclusions: The level of precision of fit which can be obtained in superstructure fabrication would appear to suffice to produce restorations that do not cause bone damage. Keywords: bone loading, cement fixation, finite element analysis, in vivo strain measurements, passive fit, screw retention

Purpose: The aim of this study was to evaluate the clinical outcome of delayed or immediately loaded implants of 3 different implant macrodesigns. The hypothesis was that no significant differences in implant success would be observed between immediately and delayed loaded implants. Materials and Methods: Between July 2003 and December 2003, 321 patients were consecutively enrolled for this study. Immediate loading was performed in cases where the implant stability quotient (ISQ) values were > 60 (as determined by resonance frequency analysis) and implant insertion torque was > 25 Ncm. In the case of delayed loading, a submerged technique (2-stage) or a single-stage procedure was used. The following variables were statistically analyzed with logistic regression: implant length, implant diameter, implant type, implant site, insertion torque, ISQ, and type of loading (immediate or delayed). Results: Eight hundred two implants were placed. Immediate loading was chosen for 423 implants and delayed loading for 379 implants. All implants were followed up for a minimum of 12 months after prosthetic loading. Only 3 implants were lost, with an overall success rate of 99.6%. No statistically significant differences were found for any variables between the failures in the 2 groups (immediate loading protocol versus delayed loading). Implants with a crestal bone loss greater than 0.2 mm during the first year of observation (69 cases) were evaluated as a group; within this subset, only ISQ value (P .004), implant length (P .002), and implant type (P .049) had a statistically significant effect on crestal bone resorption. Conclusions: Based upon this study of 802 implants, no significant differences in implant success were observed between the 2 groups. (Comparative Cohort Study) Keywords: bone loading, cement fixation, finite element analysis, in vivo strain measurements, passive fit, screw retention

Purpose: The purpose was to evaluate clinical outcome of short (6- and 8-mm) dental implants placed in sites with low bone availability (7 to 11 mm) in a single private practice and to compare their survival with that of longer implants. Materials and Methods: Implants were placed by a single private practitioner in a variety of clinical indications. Exclusion criteria included uncontrolled diabetes mellitus, alcoholism, and systemic immune disorders. Clinical data relating to implant placement and follow-up appointments, including adverse events, were entered into an electronic database. Two-year survival rates were calculated and life table analyses undertaken for implants measuring 6, 8, and 10 to 16 mm. Results: A total of 630 Straumann implants were placed in 264 patients between April 1994 and December 2003. Of these, 35 implants were 6 mm long, 141 were 8 mm long, and 454 were 10 to 16 mm long. Maximum follow-up was 64.6 months, 83.7 months, and 102 months for implants measuring 6 mm, 8 mm, and 10 to 16 mm, respectively. Two-year survival rates were 94.3%, 99.3%, and 97.4% for 6-mm, 8-mm, and 10- to 16-mm implants, respectively. Discussion: The results indicated that the 2-year outcome for 6-mm and 8-mm implants was comparable to that for longer (10- to 16-mm) implants in this patient population. Conclusion: In this study, short (6- or 8-mm) implants were used with good reliability in patients with limited bone availability, without the need for ridge augmentation. Shorter implant length was not associated with reduced survival at 2 years, compared with longer implants. (Case Series) Keywords: life table analysis, private practice setting, short dental implants

Purpose: The purpose of this study was to measure marginal bone loss from the implant-abutment microgap to the bone crest between multiple freestanding implants functionally loaded for up to 7.5 years in the posterior jaws. Materials and Methods: Patients consecutively treated for the replacement of missing posterior teeth were included in the study. Using the implant-abutment interface, which was placed level with the crestal bone as a reference point, standardized follow-up radiographs were obtained to evaluate marginal bone loss. Results were subject to statistical analysis using the Wilcoxon rank sum test and the Wilcoxon signed rank test at the 95% confidence level. Additionally, soft tissue and prosthetic complications were recorded. Results: One hundred seventy-three implants in 54 patients were evaluated. Implants were in function for a mean of 37 months (range, 21 to 91 months). One implant failed, for a survival rate of 99.4%. Overall mean marginal bone loss was 0.65 mm (range, 0.0 to 4.8 mm). For the 80 maxillary and 93 mandibular implants, mean marginal bone loss was 0.56 mm and 0.70 mm, respectively. The frequency of bone loss >= 1.0 mm was 25.0% in the maxilla and 36.0% in the mandible; 23.1% of maxillary implants and 16.7% of mandibular implants demonstrated no bone loss. No significant differences were observed between men and women or between smokers and nonsmokers. The difference between mesial and distal bone levels was statistically significant (P .001), with respective means of 0.53 mm and 0.76 mm. Recorded prosthetic complications included cementation failure (17.7%), porcelain fracture (7.2%), and abutment screw loosening (2.2%). Conclusions: Multiple single-tooth implants placed in the posterior jaws perform extremely well. Furthermore, it is possible to retain bone close to the implant-abutment microgap with certain implant designs. (Case Series) Keywords: bone loading, cement fixation, finite element analysis, in vivo strain measurements, passive fit, screw retention

Purpose: To evaluate long-term follow-up clinical performance of dental implants in use in South Korean populations. Materials and Methods: A retrospective multicenter cohort study design was used to collect long-term follow-up clinical data from dental records of 224 patients treated with 767 2-stage endosseous implants at Ajou University Medical Center and Bundang Jesaeng Hospital in South Korea from June 1996 through December 2003. Exposure variables such as gender, systemic disease, location, implant length, implant diameter, prosthesis type, opposing occlusion type, and date of implant placement were collected. Outcome variables such as date of implant failure were measured. Results: Patient ages ranged from 17 to 71.7 years old (mean age, 45.6 years old). Implants were more frequently placed in men than in women (61% versus 39%, or 471 men versus 296 women). Systemic disease was described by 9% of the patients. All implants had hydroxyapatite-blasted surfaces. Most of the implants were 3.75 mm in diameter. Implant lengths 10 mm, 11.5 mm, 13 mm, and 15 mm were used most often. Differences of implant survival among different implant locations were observed. Implants were used to support fixed partial dentures for the majority of the restorations. The opposing dentition was natural teeth for about 50% of the implants. A survival rate of 97.9% (751 of 767) was observed after 4.5 years (mean, 1.95 ± 1.2 years). Conclusion: Clinical performance of 2-stage dental implants demonstrated a high level of predictability. The results achieved with a South Korean population did not differ from results achieved with diverse ethnic groups. (Cohort Study) Keywords: dental implants, implant survival, implants in Korean populations, implant-supported prostheses

Purpose: To evaluate the influence of macro- and microstructure of the implant surface at the marginal bone level after functional loading. Materials and Methods: Sixty-eight patients were randomly assigned to 1 of 3 groups. The first group received 35 implants with a machined neck (Ankylos); the second group, 34 implants with a rough-surfaced neck (Stage 1); and the third, 38 implants with a rough-surfaced neck with microthreads (Oneplant). Clinical and radiographic examinations were conducted at baseline (implant loading) and 3, 6, and 12 months postloading. Two-way repeated analysis of variance (ANOVA) was used to test the significance of marginal bone change of each tested group at baseline, 3, 6, and 12 month follow-ups and 1-way ANOVA was also used to compare the bone loss of each time interval within the same implant group (P .05). Results: At 12 months, significant differences were noted in the amount of alveolar bone loss recorded for the 3 groups (P .05). The group with the rough-surfaced microthreaded neck had a mean crestal bone loss of 0.18 ± 0.16 mm; the group with the rough-surfaced neck, 0.76 ± 0.21 mm; and the group with the machined neck, 1.32 ± 0.27 mm. In the rough-surfaced group and the rough-surfaced microthreaded group, no statistically significant changes were observed after 3 months, whereas the machined-surface group showed significant bone loss for every interval (P .05). Discussion: To minimize marginal bone loss, in addition to the use of a rough surface at the marginal bone level, a macroscopic modification such as the addition of microthreads could be recommended. A rough surface and microthreads at the implant neck not only reduce crestal bone loss but also help with early biomechanical adaptation against loading in comparison to the machined neck design. Conclusion: A rough surface with microthreads at the implant neck was the most effective design to maintain the marginal bone level against functional loading. (Comparative Cohort) Keywords: machined neck, marginal bone level, microthreads, rough surface

Purpose: In 1998, a modification of the macrostructure of the Frialit-2 implant in the cervical region was introduced to stabilize peri-implant bone. Limited data are available on the clinical effect of this modification. Therefore, the soft-tissue situation, marginal bone loss, and implant failure rate were analyzed after 4 years of clinical experience with the modified Frialit-2 Synchro implant. Materials and Methods: From 1998 to 2001, 190 cervically modified implants were placed and documented prospectively in 58 patients. Of these implants, 147 were placed in original jaw bone, 22 in areas augmented with local osteoplasty, and 21 in iliac crest bone graft. The main indications for implantation were an atrophic edentulous alveolar crest (n = 99) and support for a partial denture (n = 39), followed by restoration of a shortened dental arch (n = 28) and single tooth replacement (n = 24). In a special clinical examination, 39 patients with 134 implants were investigated. Results: The average in situ time of the 134 implants was 23.1 months. Failing osseointegration (n = 10), peri-implantitis (n = 1), and tumor resection (n = 3) in 8 patients resulted in the failure of 14 of 190 implants (7.4%). One patient with 4 implants died (2.1%). Currently, 3 patients with a total of 6 implants have been lost to follow-up (3.1%), and 166 implants remain in situ (87.4% of 190). Discussion: Using different implant success criteria, success rates of 88.8% and 82.8% were calculated. Conclusion: Based on the results, the Frialit-2 Synchro implant appears to be a useful implant system for the indications analyzed. Keywords: machined neck, marginal bone level, microthreads, rough surface

Endoscopic sinus surgery has been performed for various indications in maxillofacial surgical practices. It has been utilized for assessment of antral pathologies, removal of foreign bodies, orthognathic procedures, and treatment of facial fractures. In the cases presented, 3 dental implants which were displaced into maxillary sinuses were removed by endoscopic sinus surgery. Transantral endoscopic surgery is a reliable, minimally invasive method for retrieving displaced objects from the maxillary antrum with minimal complications. Keywords: dental implant, endoscopic surgery, implant displacement, maxillary sinus

The prosthetic rehabilitation of maxillofacial defects is especially challenging when the patient is edentulous. Although dental implants are used to enhance the retention and stability of both facial and maxillary prostheses, combining facial and maxillary prostheses is extremely difficult. This article describes the prosthetic treatment of an edentulous patient with a large maxillary and facial defect. After placing dental implants in the remaining maxilla, a maxillary obturator prosthesis supported by a milled bar attachment was fabricated. The facial prosthesis was retained by a magnetic attachment to the maxillary obturator prosthesis. As the obturator prosthesis was supported securely by this sturdy attachment, the facial prosthesis was stable during mastication and facial movement. The patient reported improvement in prosthesis retention and stability. Both the masticatory and the speech functions of the patient improved. Keywords: dental implants, facial prostheses, magnets, maxillary obturators, milled bar attachments