The International Journal of Oral & Maxillofacial Implants, 05/2007

Purpose: The purpose of this study was to evaluate the effects of phosphated titanium and enamel matrix derivatives (EMD) on osteoblast function. Materials and Methods: Primary rat osteoblasts were cultured on disks of either phosphated or nonphosphated titanium. In half of the samples 180 µg of EMD was immediately added. The medium was changed every 2 days for 28 days and then analyzed using transforming growth factor-b1 (TGF-b1) and interleukin-1b (IL-1b) enzyme-linked immunosorbent assays (ELISAs). Scanning electron microscopy and light microscopy were used to evaluate nodule formation and mineralization. Results: Microscopic evaluation revealed no differences in osteoblast attachment between the 4 groups. Osteoblast nodule formation was observed in all groups. In the absence of mineralizing media, nodules on the nonphosphated titanium samples showed no evidence of mineralization. All nodules on the phosphated titanium had evidence of mineralization. ELISA revealed no significant differences in IL-1b production between any of the groups. The EMD-treated osteoblasts produced significantly more TGF-b1 than non-EMD-treated cells for up to 8 days, and osteoblasts on phosphated titanium produced significantly more TGF-b1 at 8 days. Discussion and Conclusion: Osteoblast attachment appeared unaffected by surface treatment. EMD initiated early TGF-b1 production, but production decreased to control levels within 10 days. Phosphated titanium increased TGF-b1 production at 8 days and induced nodule mineralization even in the absence of mineralizing medium. Keywords: enamel matrix derivatives, interleukin-1b, osteoblasts, phosphate titanium, transforming growth factor-b1

Purpose: The aim was to assess the influence of connection of the canine teeth to implant-retained long-span fixed dentures on stress in mandibular bone using finite element analysis. Materials and Methods: Each 3-dimensional model included bone, 6 implants, both natural canines, and superstructures. Each model simulated 1 of 4 prosthetic designs: a tooth/implant-retained 1-piece superstructure (One-piece), 3-piece superstructures with an anterior and 2 posterior segments with unconnected teeth (UnConnect), 3-piece superstructures with the teeth connected to the posterior segments (PostConnect), and 3-piece superstructures with the teeth connected to the anterior segment (AntConnect). A nonlinear elastic modulus was applied to the periodontal ligament (PDL). Maximum intercuspal (IP), canine-protected (CP), and group-function (GF) occlusions were simulated. Results: The maximum stresses in the peri-implant regions of the bone were lower for the One-piece than for the other superstructures. In PostConnect and AntConnect, the maximum stress in the PDL was lower than that in UnConnect, but the stress in the peri-implant bone was comparable in those 3 models. The stresses were lower in the GF model than in the CP model. The stress created in the peri-implant bone was insensitive to the modes of the teeth/implant connection in long-span fixed dentures. Conclusion: Within the limitation of the mechanical analysis, it is suggested that the connection of the canine tooth to the implant-retained long-span superstructures is an acceptable option in partially edentulous patients. Keywords: dental implants, finite element analysis, periodontal ligament, tooth-implant support

Purpose: The purpose of this study was to compare the osteoblastic and osteogenic responses to titanium surfaces roughened by 1-step and 2-step acid etching. Materials and Methods: Titanium surfaces created by 1-step (AE1) and 2-step (AE2) acid-etching processes were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), and an optical interferometry (OI). Rat bone marrow-derived osteoblastic cells were cultured on these 2 surfaces. Cell proliferation was evaluated by counting the cells, while gene expression was analyzed using a reverse transcriptase-polymerize chain reaction. The biomechanical establishment of osseointegration was assessed via an in vivo implant push-in test in rat femurs. Additionally, the 2 surfaces were evaluated for their mechanical interlocking capability by a push-out test of titanium rods embedded in a resin block. Results: AFM analysis on a small scale of 5 µm 3 5 µm showed that the 2 surfaces were similar in topography, having comparable micron-level roughness. However, larger scale (1000 µm 3 1000 µm) SEM and OI analyses revealed that the AE1 surface consisted of supramicron convexity structures ranging from 10 µm to 50 µm in size, while the AE2 was relatively flat. No differences were found between the 2 surfaces in regard to the number of the cells proliferated or the expression of the bone-related genes. The biomechanical fixation of implants at week 2 was 22.2 ± 10.94 N and 25.4 ± 4.56 N for AE1 and AE2, respectively, with no significant difference between the 2 groups. The in vitro push-out values were 26.8 ± 7.85 N and 25.4 ± 8.56 N for AE1 and AE2, respectively, with no significant difference between the 2 groups. Conclusion: The different acid-etching procedures of titanium created similar micron-scale roughness profiles but distinct supramicron roughness characteristics. Osteoblastic function and in vivo osseointegration capacity, however, were not affected by this difference between the surfaces. Keywords: bone-titanium integration, dental implants, osteoconduction, push-in test, surface topography

Purpose: Bone collectors are used to harvest bone debris for grafting procedures during implant surgery. The particulate bone debris gathered through filtration has been frequently used in minor regenerative surgical procedures. Nevertheless, the biological potency of such grafts is still unclear. The objective of this study was to systematically review the use of bone collectors in implant dentistry, focusing on the quantity, quality, and bacterial contamination of the bone collected. Materials and Methods: Following the production of a detailed protocol, screening and quality assessment of the literature were conducted in duplicate and independently. The outcome measures that were assessed were: (1) quantity of collected debris, (2) quality of the collected bone debris, and (3) bacterial contamination. Results: There is a limited amount of information on the nature of bone obtained through collectors. Eleven studies satisfied the inclusion criteria. Bone collectors are able to retain a small amount of bone for minor surgical procedures. The presence of vital bone cells has not been demonstrated routinely, while consistent bacterial contamination has been observed. Discussion: Bone collected through bone filters appears to be sufficient for small regenerative procedures. Clinicians should bear in mind that presence of bacterial pathogens is always shown with the use of bone collectors. Presurgical chlorhexidine oral rinsing and a strict aspiration protocol must be used to minimize the bacterial contamination of the debris collected. Conclusions: Although bone collectors are capable of amassing small amounts of bone, the vitality of this bone could not be consistently demonstrated and the collected debris was always contaminated by bacteria. Therefore, the bone debris amassed in bone collectors is not an ideal grafting material and should be utilized with caution. Keywords: bone collectors, bone traps, dental implants, oral surgery, systematic review

Purpose: To evaluate the predictability of Straumann wide-neck dental implants (6.5-mm prosthetic neck with a 4.8-mm endosseous sandblasted, large-grit, acid-etched-surface body) used for molar replacement. Materials and Methods: Four hundred ninety-nine single-tooth implants were restored in molar sites in 410 patients (mean time of loading 23 months; range, 1 to 54 months) by 6 clinicians throughout the United States. Three hundred-fifty nine implants were placed in the mandible and 148 implants in the maxilla. Results: The overall cumulative survival rate was 98.4% for all sites (8 failures). Survival rates of 99.2% for mandibular molars (3 failures) and 96.6% for maxillary molars (5 failures) were achieved. Survival rate of implants placed in conjunction with the bone-added osteotome procedure in the maxillary molars was 89%, with 5 of 45 procedures leading to failure. Discussion: Minimal restorative problems were encountered. No cases of abutment loosening or fractures were observed for cemented restorations on solid abutments. Conclusion: The data suggest that the Straumann solid-screw, wide-neck implants can be a satisfactory choice for molar single-tooth replacement. Keywords: cemented implant crowns, implant survival, prosthetic complications, wide-diameter dental implants

Successful osseointegration is a prerequisite for functional dental implants. Continuous monitoring in an objective and quantitative manner is important to determine the status of implant stability. Historically, the gold standard method used to evaluate degree of osseointegration was microscopic or histologic analysis. However, due to the invasiveness of this method and related ethical issues, various other methods of analysis have been proposed: radiographs, cutting torque resistance, reverse torque, modal analysis, and resonance frequency analysis. This review focuses on the methods currently available for the evaluation of implant stability. (More than 50 references.) Keywords: cutting resistance analysis, implant stability evaluation, radiographic assessment, resonance frequency analysis, reverse torque test

Purpose: Chemical modification to a sandblasted, large-grit, acid-etched (SLA) implant surface has been shown to enhance the rate of osseointegration. The goal of the present study was to examine changes in stability for implants with a chemically modified SLA surface and to compare their outcomes to those of control implants. Materials and Methods: A randomized controlled trial was conducted with 31 patients. Each patient received 2 implants with the same physical properties but with surfaces that were chemically different. The control implants had a standard SLA surface, while the test implants had a chemically modified surface. Resonance frequency analysis was assessed weekly over the first 6 weeks following implant placement. Results: All implants proved clinically successful, allowing for restoration. Most implants were placed in the mandible (50 of 62). A shift in implant stability from decreasing stability to increasing stability (P .001), occurred after 2 weeks for the test implants and after 4 weeks for the control implants. Conclusion: The findings from this pilot study provide clinical support for the potential for chemical modification of the SLA surface to alter biologic events during the osseointegration process and demonstrate levels of short-term clinical success similar to those observed for implants with an SLA surface. Keywords: clinical trial, implant stability, implant surface chemistry, resonance frequency analysis

Purpose: This study evaluated the accuracy of 2 implant-level impression techniques (direct nonsplinted and splinted) for the fabrication of multi-unit internal-connection implant restorations in 2 simulated clinical settings (parallel and divergent) using a laboratory model. Materials and Methods: A dental stone master model was fabricated with 2 pairs of implant replicas. One pair simulated a parallel clinical condition and the other an 8-degree-divergent condition. Ten stone casts were made from vinyl polysiloxane impressions of the master model for each impression technique. Half of the samples were created by a direct nonsplinted technique (square impression copings, custom tray), and the other half were made by a direct splinted technique (square impression copings splinted with autopolymerizing acrylic resin, custom tray). Four strain gauges were fixed on each metal framework to measure the degree of framework deformation for each stone cast in half-Wheatstone-bridge formations. Deformation readings were made twice in 4 directions (anterior, posterior, superior, and inferior). Deformation data were analyzed using repeated-measures analysis of variance at a .05 level of significance. Results: No significant difference in deformation was found between the direct nonsplinted and splinted samples in either simulated clinical condition (P > .05). No significant difference in deformation was found between the techniques regardless of condition (P > .05). Conclusions: Within the limitations of this study, using a 2-implant model, the accuracy of implant-level impressions for internal-connection implant restorations was similar for the direct nonsplinted and splinted techniques in settings with divergence up to 8 degrees. Keywords: implant divergence, implant-level impression, internal connection implant, strain gauge

Purpose: To evaluate the satisfaction of patients with maxillary fixed prostheses supported by conventional and/or zygomatic implants. Materials and Methods: Patients restored with complete maxillary implant-supported fixed prostheses were included in the study. They were divided into 2 groups: those with at least 1 zygomatic implant (the zygomatic group) and those with no zygomatic implants (the nonzygomatic group). Twelve months after prosthesis delivery, subjects indicated their satisfaction with the new prosthesis on a visual analog scale. Prostheses were rated in terms of general satisfaction, comfort and stability, ability to speak, easy of cleaning, esthetics, self-esteem, and functionality. Results: Forty-six patients participated in the study (23 in each group). The mean level of satisfaction was high; the groups differed significantly only in satisfaction with esthetics. Patients in the zygomatic group had a higher average score for esthetics than those in the nonzygomatic group. Those who had previously worn conventional removable prostheses gave a higher score for functionality to the implant-supported fixed prosthesis compared to the removable prosthesis. Conclusion: Patient satisfaction with zygomatic implant-supported fixed prostheses was similar to that for fixed prostheses supported by conventional implants. Keywords: patient satisfaction, zygomatic implants

Purpose: The purpose of this animal study was to confirm that laser Doppler flowmetry (LDF) is a reproducible method for the assessment of maxillary and mandibular alveolar bone vascularity and that there is less vascularity in irradiated mandibular and maxillary bone compared to nonirradiated bone. Materials and Methods: All maxillary and mandibular premolars and molars of 6 Göttingen minipigs were extracted. After a 3-month healing period, 3 minipigs received irradiation at a total dose of 24 Gy. Three months after irradiation, 5 holes were drilled in the residual alveolar ridge of each edentulous site in each minipig. Local microvascular blood flow around all 120 holes was recorded by LDF prior to implant placement. In 1 irradiated and 1 nonirradiated minipig, an additional hole was drilled in a right maxillary site to enable repeated LDF recordings. Results: The alveolar bone appeared less vascularized in irradiated than in nonirradiated minipigs. The effect of radiation appeared more pronounced in the mandible than in the maxilla. LDF was demonstrated to be a reproducible method for assessing alveolar bone vascularity. However, recordings varied by edentulous site as well as by minipig. Conclusion: The authors' hypotheses regarding LDF and vascularity were supported. Further research validating the use of LDF in human beings, especially in those who have undergone radiation therapy for head and neck cancer, is necessary. Keywords: bone, dental implants, irradiation, laser Doppler flowmetry, vascularity

Purpose: To examine the relationship between cortical bone thickness, inter-root distance (horizontal space), distance from alveolar crest to the bottom of maxillary sinus (vertical space) at the prepared site, and implant placement torque and the success rate of mini-implants placed for orthodontic anchorage. Materials and Methods: After computerized tomography examination, mini-implants 1.6 mm wide and 8 mm long were placed in the posterior alveolar bone. The mini-implant was judged a success when orthodontic force could be applied for at least 6 months without pain or clinically detectable mobility. The unpaired t test was performed to examine differences between the success and failure groups. The chi-square analysis or Fisher exact probability test was used to compare the implant success according to placement torque, location, and patient gender. P values less than .05 were considered significant. Results: The subjects included 4 males (11 implants) and 28 females (76 implants) who ranged in age from 14.6 to 42.8 years. The success rate of the 87 implants was 87.4%. Cortical bone thickness was significantly greater in the success group (1.42 ± 0.59 mm vs 0.97 ± 0.31 mm, P = .015). The success rate was significantly higher in the group with an implant placement torque of 8 to 10 Ncm (100%) as compared to implants with higher or lower placement torques. The odds ratio for failure of the mini-implant was 6.93 (P = .047) when the cortical bone thickness was less than 1.0 mm relative to 1.0 mm or more. Conclusion: A relationship between stability after implant placement and the width and height of the peri-implant bone was not demonstrated. The prepared site should have a cortical bone thickness of at least 1.0 mm, and the placement torque should be controlled up to 10 Ncm. Keywords: mini-implants, orthodontic, risk factor, survival, temporary anchorage devices

Purpose: The aim of this prospective randomized study was to compare the clinical accuracy of and surgical time required for mandibular dental implant placement with 2 computer-assisted navigation systems using pre- and postoperative computerized tomographic (CT) data. Materials and Methods: In 16 patients with edentulous mandibles, 4 interforaminal implants per patient were placed with computer-assisted navigation. The implant bed was prepared by transmucosal drilling without mucosal punching. Patients were randomly allocated to either the VISIT navigation system (32 implants; 8 patients) or the Medtronic StealthStation Treon navigation system (32 implants; 8 patients). Pre- and postoperative CT scans were matched using the normalized mutual information 3D registration algorithm to compare preplanned and final implant positions. Operation room time was recorded from start of preoperative preparations to end of surgery. Results: All implants were placed as planned; there were no intra- or postoperative complications. Average implant deviation errors of 0.7 mm and 0.9 mm were recorded for the VISIT and StealthStation Treon navigation systems, respectively. Timing revealed an average operation room time of 81.3 ± 15.8 minutes for the VISIT navigation system and 60 ± 10.4 minutes for the StealthStation Treon navigation system. Conclusions: The accuracy of implant bed preparation and placement was similar in both systems. Both navigation systems are equally precise in a clinical environment. However, total operation room time was 25% shorter with the StealthStation Treon navigation system, probably because of the faster tracking system update rate. (Controlled Clinical Trial) Keywords: accuracy, computer-assisted navigation, dental implants

Purpose: The possibility of expediting dental implant therapy by early or immediate loading protocols requires long-term clinical investigation. The aim of this prospective cohort trial was to determine the 3-year implant success rate and prosthesis complications associated with functional loading 3 weeks after 1-stage placement of Astra Tech single-tooth implants replacing maxillary anterior teeth. A secondary objective was to determine peri-implant tissue responses at these implants. Materials and Methods: The peri-implant bone and mucosal conditions of 43 implants in 39 subjects were radiographically and clinically measured 3 years after implant placement. Results: Of the 48 patients originally treated, 39 patients and 43 implants were examined at the 3-year time point. Three of 54 implants failed within the first year. No additional failures were recorded since the 12-month reporting period. Peri-implant bone levels were stable for the 3-year period following implant placement. The change in marginal bone levels after 3 years was 0.42 ± 0.59 mm. Papilla growth was measured at 1 and 3 years (0.61 ± 0.95 mm and 0.74 ± 0.79 mm, respectively). The buccal peri-implant tissue dimensions at the gingival zenith also increased at 1 and 3 years (0.34 ± 0.94 mm and 0.51 ± 1.42 mm, respectively). No abutment screw loosening or fracture occurred. Discussion and Conclusions: Early loading of endosseous dental implants placed in healed ridges offers select benefits to clinicians and their patients. (Clinical Trial) Keywords: early loading, immediate loading, implant success, peri-implant esthetics, prospective clinical trials, single-tooth implants

Purpose: The aim of this study was to assess whether navigated flapless transmucosal implant bed preparation allows placement of dental implants in edentulous mandibles. Materials and Methods: Each patient was scheduled to receive 4 screw-shaped Ankylos (Dentsply Friadent) implants in the interforaminal region. The VISIT navigation system was used for guided drilling. The mucosa was penetrated without flap elevation. The study protocol did not allow direct visualization of the bone surface during surgery. Data analysis included computed measurements on pre- and postoperative computerized tomographic (CT) images. Results: Twenty patients with fully edentulous mandibles (14 male, 6 female) were included in the study. Computer-based planning for 80 implants was performed intraoperatively. Two implants (2.5%) were not primarily stable because of buccal bone fenestration, which occurred because of uncontrollable shifting of the dental implant drill. These implants were immediately removed. Postoperative CT image evaluation revealed a mean deviation of 0.7 mm in all directions. Conclusions: Navigated flapless transmucosal interforaminal implant placement was found to be a precise, predictable, safe procedure in patients with smooth wide regular mandibular ridges. The technique was less accurate and more complicated in areas where irregular bone existed. (Clinical Trial) Keywords: computer-aided navigation, flapless surgery, transmucosal implant

Purpose: It is believed that maxillary dental implants must be splinted when used to retain removable overdenture prostheses in order to maintain osseointegration. This paper presents clinical cases to demonstrate that contemporary implants can function in an unsplinted manner to retain maxillary removable overdentures with partial palatal coverage. Materials and Methods: Five consecutive patients were treated using a specific surgical and prosthodontic protocol. Twenty-five textured-surface implants were placed to retain overdenture prostheses in five patients, with a minimum of 4 implants per patient. These patients were followed for 12 to 48 months postloading. Results: To date, none of the implants have lost osseointegration, and radiographic marginal bone levels are stable. Patients have been able to maintain soft tissue health around the unsplinted implants. The patients have verbally indicated that they are comfortable and that their maxillary overdentures function well. Conclusion: This preliminary report presents 5 consecutive cases in which unsplinted implants maintained osseointegration when used to retain removable overdenture prostheses with limited palatal coverage. It appears that unsplinted maxillary implants can be used to retain a maxillary overdenture. (Case Series) Keywords: maxilla, partial palatal coverage, unsplinted dental implants

Purpose: To compare the efficacy of immediate nonocclusal loading (test group) versus early loading (control group) in partially edentulous patients. Materials and Methods: Fifty-two patients in 5 Italian private practices were randomized to 1 of the treatments: 25 to the immediately loaded group and 27 to the early loaded group. To be immediately loaded, single implants had to be inserted with a torque of > 30 Ncm, and splinted implants had to be inserted with a torque of > 20 Ncm. Implants in the immediately loaded group were provided with full acrylic resin nonoccluding temporary restorations within 48 hours after placement. After 2 months, full occluding provisional restorations were provided. Implants in the early loading group were not submerged and were loaded after 2 months. At 8 months, provisional restorations were replaced with definitive metal-ceramic prostheses. Outcome measures were prosthesis and implant failures as well as biologic and prosthetic complications recorded by nonblinded assessors. The Fisher exact test was used to compare the proportion of implant failures. Results: Fifty-two implants were placed in the immediately loaded group and 52 in the early loaded group. No dropouts or complications occurred up to 14 months postinsertion. One single implant failed in the immediately loaded group 2 months after placement. There was no statistically difference for the tested outcome measures between the 2 procedures (P > .99). Conclusions: The results of this randomized controlled clinical trial with 25 patients rehabilitated with immediately restored nonocclusally loaded implant-supported prostheses compared to 27 patients restored 2 months following placement suggest that there are no major clinical differences in implant survival between these 2 protocols. No biologic or prosthetic complications occurred. (Clinical Trial) Keywords: dental implants, early loading, immediate loading, partial edentulism

Purpose: The purpose of this retrospective study was to evaluate the effects of implant dimensions, surface treatment, location in the dental arch, numbers of supporting implant abutments, surgical technique, and generally recognized risk factors on the survival of a series of single-stage Straumann dental implants placed into edentulous arches using an immediate loading protocol. Materials and Methods: Each patient received between 4 and 18 implants in one or both dental arches. Periapical radiographs were obtained over a 2- to 10-year follow-up period to evaluate crestal bone loss following insertion of the definitive metal-ceramic fixed prostheses. Univariate tests for failure rates as a function of age (? 59 years versus ? 60 years), gender, smoking, bone grafting, dental arch, surface type, anterior versus posterior, number of implants per arch, and surgical technique were made using Fisher exact tests. The Cochran-Armitage test for trend was used to evaluate the presence of a linear trend in failure rates regarding implant length and implant diameter. Logistic regression modeling was used to determine which, if any, of the aforementioned factors would predict patient and implant failure. A significance criterion of P = .05 was utilized. Results: Data were collected for 344 single-stage implants placed into 56 edentulous arches (39 maxillae and 17 mandibles) of 43 patients and immediately loaded with a 1-piece provisional fixed prosthesis. A total of 16 implants failed to successfully integrate, for a survival rate of 95.3%. Increased rates of failure were associated with reduced implant length, placement in the posterior region of the jaw, increased implant diameter, and surface treatment. Implant length emerged as the sole significant predictor of implant failure. Conclusion: In this retrospective analysis of 56 consecutively treated edentulous arches with multiple single-stage dental implants loaded immediately, reduced implant length was the sole significant predictor of failure. (Case Series) Keywords: dental implants, edentulism, failure risk factors, flapless implant placement, immediately loaded implants, implant-supported dental prostheses, implant surfaces

Purpose: To present a simplified method for assessment of precision of fit between screw-retained frameworks and supporting implants in clinical situations. Materials and Methods: Torque-angle signature analysis is a method for analysis of tension within a joint. The OsseoCare device developed by Nobel Biocare was utilized for the tests. Three titanium frameworks were fabricated on the same master cast according to 3 different methods: (1) 1-piece casting, (2) the CNC (computer numeric controlled) method, and (3) the CTiP (Cresco Ti Precision) method. These frameworks were used to test the device and indirectly the application of the torque-angle signature analysis technology. Results: The frameworks fabricated according to the CNC and CTiP methods demonstrated OsseoCare tracings similar to the reference models of passively fitting joints, while the 1-piece cast framework did not. Conclusion: According to this pilot study, the OsseoCare device and torque-angle signature analysis proved to be feasible for clinical assessment of fit between frameworks and supporting implants. Keywords: assessment of fit, dental implants, titanium frameworks, torque-angle signature analysis