The International Journal of Oral & Maxillofacial Implants, 03/2012

Purpose: The aim of this study was to examine the bending moments and fracture patterns of different zirconia abutments with internal implant-abutment connections after static loading and to compare their bending moments to those of internally connected titanium abutments. Materials and Methods: Three types of customized zirconia abutments (Straumann CARES abutments/Straumann BL implants [T1], Astra ZirDesign abutments/Astra Micro Thread OsseoSpeed implants [T2], Zirabut prototype abutments/Straumann SP implants [T3]) and one type of customized titanium abutment (control group, Straumann CARES abutments/Straumann BL implants [C]) were included. All abutments were one-piece abutments with an internal implant-abutment connection and were customized to the same shape but featured different implant-abutment connection designs. For each group, 20 identical copies of a master abutment were fabricated and fixed on their corresponding implants. Half of the abutments in each group were left unrestored, and the other 10 received glass-ceramic crowns. Static loading was applied at a 30-degree angle to the palatal surface until failure, and bending moments were calculated. The type of failure was characterized visually by dismounting the abutments and by examination of cross-sections of the embedded specimens. The results were analyzed statistically. Results: The mean range of bending moments was higher for the unrestored groups (158.2 to 678.2 Ncm) than for the restored groups (117.9 to 419.4 Ncm). The highest mean bending moments were seen in the control group, both restored and unrestored (419.4/678.2 Ncm). Unrestored, T1 and T2 exhibited significantly higher bending moments than T3. This was also observed in the restored groups. Conclusion: Both the abutment material and the implant-abutment connection design affected the bending moments of abutments after static loading. Internally connected zirconia abutments with horizontal mismatch to the implant exhibited significantly higher bending moments compared to those without horizontal mismatch. Schlagwörter: bending moments, horizontal mismatch, implant-abutment connection, implant abutments, titanium abutments, zirconia abutments

Purpose: Piezoelectric surgery is meant to be a gentle method for implant site preparation (ISP). However, the application of load and its influence on heat development over time and effects on soft tissue are unknown. Therefore, this study sought to evaluate heat development in the bone and the duration of the procedure according to load application, as well as preservation of the sinus floor mucosa during piezoelectric ISP. Materials and Methods: One hundred twenty implant sites (6 mm deep × 3 mm wide) were prepared in the calvaria of ex vivo pig heads using piezoelectric surgery. The load applied to the working tip was increased in 100-g intervals up to 1,000 g. The bone temperature was measured, and thermal effects were analyzed histomorphometrically. The duration of each ISP was recorded. Another 12 ISPs were performed at the lateral wall of the maxillary sinus in the vicinity of the sinus floor mucosa, and sites were checked for perforation. Results: Temperature and histologic effects of heat demonstrated a significant positive correlation with the applied load. The duration of ISP was significantly negatively correlated with load application. The maximum temperature generated by piezoelectric surgery was 64.5°C (load of 901 to 1,000 g). At a load of 401 to 500 g, the average temperature was 40.2°C ± 3.3°C, the average thermal damage extended 115.9 ± 16.3 µm beyond the ISP area, and the maximum temperature did not exceed 47°C. The average duration of ISP using this load interval was 45.5 ± 9.4 seconds. Two perforations of the sinus floor mucosa were detected. Conclusions: In the present setting, the applied load during piezoelectric ISP should not exceed 500 g to prevent temperatures above 47°C in the bony implant socket. With a load of 400 to 500 g, ISP took 40 to 50 seconds. Schlagwörter: dental implant, implant site preparation, piezosurgery, sinus floor elevation, thermal tissue alteration, time duration

Purpose: Immediate loading and/or restoration of dental implants requires the assessment of implant stability, which is best performed by resonance frequency analysis (RFA) prior to loading. One-piece dental implants are usually used for immediate loading, but there is currently no available reliable method to assess the primary stability of one-piece dental implants. Therefore, this study sought to validate a novel device designed for RFA measurements of one-piece implants. Material and Methods: Thirty (3.75 × 13 mm) internal-hex implants (Seven, MIS) were divided into two groups; 15 were placed in an acrylic glass block and 15 were placed in fresh porcine jawbone using 30 N/cm2 of insertion torque. Implant stability quotient (ISQ) values were measured using the Osstell Mentor device; then, a new external fixation device was attached to the implant abutment with a 10-mm arm extending from the implant to an internal-hex ring at its proximal end. ISQ values were measured at the implant's internal hex and at the internal hex of the device, and the damping ratio was calculated. The measurements were repeated with 15 (3 × 13 mm) one-piece implants (UNO, MIS) attached to the same device. Results: The damping ratio between the implant and the proximal device was 23.6% ± 4% in acrylic glass (50.1 ± 1.7 ISQ and 38.2 ± 1.8 ISQ, respectively) and 23.1% ± 3% in porcine bone (74.9 ± 2.8 ISQ and 57.5 ± 0.5 ISQ, respectively). ISQ values determined by the device on one-piece and two-piece implants were similar (57.4 ± 0.9 and 57.5 ± 0.5, respectively). Conclusion: With the present validation of this external fixation device for the measurements of implant stability using RFA, it is now possible to measure primary stability of any one-piece implant system, obviating the need for custom-made Osstell adaptors. Schlagwörter: damping ratio, implant stability quotient, one-piece implants, primary stability, resonance frequency analysis

Purpose: To assess the influence of misfit of implant titanium and zirconia frameworks on peri-implant strains. Materials and Methods: Two Brånemark implants were inserted in the areas of the mandibular left second premolar and second molar of an artificial epoxy resin mandible. From this model, five titanium and five zirconia frameworks of similar design were fabricated by means of computer numeric controlled milling. Strain gauges were mounted around each implant to assess strain development as a result of framework fit/misfit. In addition, the vertical gap at the framework-implant interface was measured using an optical microscope when only one screw was tightened (one-screw test) and when both screws were tightened (two-screw test). The vertical fit of the frameworks was altered by introducing one to three nominally 30-µm steel shims on one of the implants. The data were analyzed statistically using one-way analysis of variance and the Mann-Whitney test. Results: For each condition, a measurable amount of strain was recorded. As more vertical misfit was introduced, a linear increase in peri-implant strains was observed. The two framework materials generated similar amounts of strain. A direct relationship was observed between strain and the vertical gap. Conclusions: The magnitude of peri-implant strain is primarily affected by the fit of the framework rather than the material. Titanium and zirconia frameworks showed a similar outcome in relation to fit and strain development. Schlagwörter: computer-aided design/computer-assisted manufacture, computer numeric controlled milling, distortion, framework fit, strain gauge

Purpose: Microgaps at the implant-abutment interface allow for microbial colonization, which can lead to peri-implant tissue inflammation. This study sought to determine the marginal accuracy of three different implant-zirconium oxide (zirconia) abutment configurations and one implant-titanium abutment configuration. Materials and Methods: Three combinations of implants with custom-made zirconia abutments were analyzed (n = 5/group): NobelProcera abutments/titanium inserts on Replace Select Tapered TiUnite implants (Nobel Biocare) (NP); Encode abutments/NanoTite Tapered Certain implants (Biomet 3i) (B3i); Astra Tech Dental Atlantis abutments/Biomet 3i NanoTite Tapered Certain implants (At). Five custom-made Encode titanium abutments/NanoTite Tapered Certain implants (Ti) were used as a control group. All abutments were fabricated with computer-aided design/computer-assisted manufacture. One-hundred twenty vertical gap measurements were made per sample using scanning electron microscopy (15 scans × 4 aspects of each specimen [buccal, mesial, palatal, distal] × 2 measurements). Analysis of variance was used to compare the marginal fit values among the four groups, the specimens within each group, and the four aspects of each specimen. Results: Mean (± standard deviation) gap values were 8.4 ± 5.6 µm (NP), 5.7 ± 1.9 µm (B3i), 11.8 ± 2.6 µm (At), and 1.6 ± 0.5 µm (Ti). A significant difference was found between B3i and At. No difference resulted between NP with the other two groups. Gap values were significantly smaller for Ti relative to all zirconia systems. For each ceramic abutment configuration, the fit was significantly different among the five specimens. For 12 of the 15 ceramic abutment specimens, gap values sorted by aspect were significantly different. Conclusions: The implant-titanium abutment connection showed significantly better fit than all implant-zirconia abutment configurations, which demonstrated mean gaps that were approximately three to seven times larger than those in the titanium abutment system. Schlagwörter: custom abutment, dental implant, marginal accuracy, titanium, zirconium oxide

Purpose: This in vitro study evaluated the dimensional accuracy of two impression techniques (tapered and splinted) with two stock trays (plastic and metal) for implant-supported prostheses. Materials and Methods: A master cast with four parallel abutment analogs and a passive framework were fabricated. Polyvinyl siloxane impression material was used for all impressions with two metal stock trays and two plastic stock trays (closed and open trays). Four groups (tapered plastic, splinted plastic, tapered metal, and splinted metal) and a control group (master cast) were tested (n = 5 for each group). After the framework was seated on each of the casts, one abutment screw was tightened, and the marginal gap between the abutment and framework on the other side was measured with a stereomicroscope. The measurements were analyzed with the Kruskal-Wallis one-way analysis of variance on ranks test followed by the Dunn method. Results: The mean values (± standard deviations) for the abutment/framework interface gaps were: master cast, 32 ± 2 µm; tapered metal, 44 ± 10 µm; splinted metal, 69 ± 28 µm; tapered plastic, 164 ± 58 µm; splinted plastic, 128 ± 47 µm. No significant difference was detected between the master cast, tapered metal, and splinted metal groups or between the tapered and splinted plastic groups. Conclusions: In this study, the rigidity of the metal stock tray ensured better results than the plastic stock tray for implant impressions with a high-viscosity impression material (putty). Statistically similar results were obtained using tapered impression copings and splinted squared impression copings. The tapered impression copings technique and splinted squared impression copings technique with a metal stock tray produced precise casts with no statistically significant difference in interface gaps compared to the master cast. Schlagwörter: closed tray, implant impression accuracy, open tray, splinted squared impression coping, stock tray, tapered impression coping

Purpose: Bacterial leakage along the implant-abutment interface, with consequent species harboring the inner parts of two-part dental implant systems, has been reported in the literature. The aim of this in vitro study was to evaluate bacterial leakage from human saliva to the internal part of the implants along the implant-abutment interface under loaded and unloaded conditions using DNA Checkerboard. Materials and Methods: Sixty dental implants-20 each of external-hexagon, internal-hexagon, and Morse cone-connection designs-and their conical abutments were used in this study. Each group was subdivided into two groups of 10 loaded and 10 unloaded implants. The assemblies were immersed in human saliva and either (1) loaded with 500,000 cycles at 120 N (experimental group) or (2) incubated in static conditions for 7 days at 35°C (unloaded control group). Results: Microorganisms were found in the internal surfaces of all types of connections. The Morse cone connection presented the lowest count of microorganisms in both the unloaded and loaded groups. Loaded implants presented with higher counts of microorganisms than unloaded implants for external- and internal-hex connections. Conclusion: Bacterial species from human saliva may penetrate along the implant-abutment interface under both unloaded and loaded conditions for all connections evaluated. Morse cone-connection implants showed the lowest counts of microorganisms for both conditions. External- and internal-hex implants showed a higher incidence of bacteria and higher bacterial counts after simulated loading. Schlagwörter: bacterial leakage, dental implants, DNA checkerboard, saliva

Purpose: To compare the metabolic activity at the bone-implant interface of implants with machined and rough surfaces using bone scintigraphy during the in vivo process of osseointegration in a rabbit model, as well to establish a correlation between activity index (AI) and the bone-implant contact percentage (%BIC). Materials and Methods: Twenty-four implants were placed (12 with a machined surface and 12 with a rough titanium oxide surface) in 12 New Zealand White rabbits. Preoperatively and during the postoperative period (at 15 days and at monthly intervals), animals underwent bone scintigraphy with technetium 99m-methylene diphosphate (Tc-99m-MDP), and the AI for each implant was calculated by planar and pinhole collimator scintigraphy. A total of 240 AIs were obtained; after animal sacrifice at 105 days postsurgery, the %BIC was measured by scanning electron microscopy in 10 samples of each implant surface type. Results: The activity-time curve showed a similar morphology for both implant types and both scintigraphy techniques. The maximum mean AI appeared after 15 days of implantation and was higher in machined implants. Significant differences were not found in the %BIC according to implant type. A significant correlation between the mean activity registered in the first postoperative scintigraph and the mean %BIC at the end of the study was observed for machined implants only. Conclusions: Tc-99m-MDP is useful for the assessment of osseous metabolic activity associated with different microsurfaces. The association between mean AI and %BIC was only demonstrated for machined implants in the first postoperative scintigraphy image. Schlagwörter: bone scintigraphy, dental implants, implant surface, osseointegration

Purpose: To investigate the physical retention of different cements on one-unit and three-unit implant-supported restorations before and after thermocycling. Materials and Methods: Twenty acrylic resin maxilla models with a single missing tooth and three missing teeth were fabricated and implants were placed. Cast partial denture copings were cemented to Straumann solid abutments with seven different cements. Specimens were placed in a humidifier at 37°C for 24 hours; half of them were then subjected to thermocycling. The tensile force was measured using a universal testing machine with a crosshead speed of 0.5 mm/min. The retention force required to remove the specimens was recorded and the data were submitted to statistical analyses. Results: The retentive strength of the cements was highest for Multilink Implant, followed in descending order by Kavitan Cem, Adhesor Carbofine, Premier Implant, Adhesor, RelyX Temp, and Cavex before and after thermocycling for both one- and three-unit restorations. The bond strength was statistically significantly higher for three-unit than for one-unit restorations before and after thermocycling, and there were statistically significant differences between cements for all groups before and after thermocycling. Both groups showed a statistically significant decrease in bond strength after thermocycling, and the largest differences were seen for Cavex and RelyX Temp for one-unit restorations and Cavex, RelyX Temp, and Kavitan Cem for three-unit restorations. Conclusions: The bond strength value was higher for three-unit than for one-unit restorations, and thermocycling reduced the bond strength of cements, especially Cavex, RelyX Temp, and Kavitan Cem. Schlagwörter: cement retention, dental implants, implant-supported restorations, thermocycling

Purpose: The aim of this study was to examine the wear behavior of conical crowns with electroplated gold copings that are used to connect implants and teeth to a removable denture. Gold alloy and zirconium dioxide ceramic crowns were compared. Materials and Methods: Fifteen crowns each were milled for two groups: gold alloy and zirconium dioxide. Each specimen had a 2-degree taper. The electroplated coping was established by direct electroforming. The retentive forces and the correlating distance during insertion and separation were measured after 10,000 wear cycles were applied. The wear testing was separated into a start phase, an initial wear phase, and the long-term wear period. The retention force value and the force-distance integral of the first 0.3 mm of each cycle were calculated. Results: The changes in retention force and integral did not differ significantly between both groups in the start and the initial wear phase. No differences were seen in force development during the long-term wear period. Only the force-distance integral showed a significant difference: the median values of the gold crowns increased slightly, and they decreased slightly for the zirconia crowns. The median force values never fell below 6 N for gold and 4 N for zirconia. Conclusions: Within the limitations of this study, the tested conical crowns showed clinically acceptable retentive properties. As with other retentive elements for dentures, the specimens tested showed the greatest amount of change in retentive forces during the first 2,000 cycles. The development of retention force in both groups was not significantly different. However, the zirconia specimens showed reduced variability, which is preferable in clinical practice. Schlagwörter: conical crown, electroplated gold, implant attachment, implant-supported denture, wear test, zirconium dioxide

Purpose: The aim of this study was to qualitatively evaluate a poly(lactic acid-co-glycolic acid-co-ε-caprolactone) (PLGC) membrane as a barrier for guided bone regeneration in the canine mandible and to compare it to a nonresorbable polytetrafluoroethylene (PTFE) membrane. Materials and Methods: Two wedge-shaped bone defects were created bilaterally in the mandibles of 12 beagle dogs. The bone defects in the left mandible were divided into three groups and treated as follows: PLGC membrane alone, PLGC membrane plus autogenous cortical bone chips, and titanium-reinforced expanded PTFE (TR-PTFE) membrane. The bone defects in the right mandible of each animal were left without membranes as a control. Computed tomography (CT) was performed at 3 and 6 months postoperative to evaluate bone regeneration. After a healing period of 6 months, the mandibles were removed en bloc for micro-CT and histologic analyses. Results: CT analyses at 3 and 6 months showed that there was significantly more bone augmentation at all experimental sites than at the control sites. The volume of bone at defect sites covered with TR-PTFE was significantly greater than at defect sites covered with PLGC membrane with or without autogenous cortical bone. Micro-CT measurements showed that the volume of new bone formed at sites covered with TR-PTFE was significantly greater than at sites covered with PLGC membrane. However, the density of new bone was significantly higher at sites covered with PLGC membrane, with or without cortical bone, than at sites covered with TR-PTFE. Histologic analysis verified the presence of well-vascularized loose connective tissue in the pores of the PLGC membrane. Conclusions: Compared to TR-PTFE, the macroporous bioresorbable PLGC membrane did not significantly increase the amount of new bone in defect sites, but it facilitated the regeneration of mature bone. Schlagwörter: guided bone regeneration, lateral ridge augmentation, poly(lactic acid-co-glycolic acid-co-ε-caprolactone), titanium-reinforced expanded polytetrafluoroethylene membrane

Purpose: Cone beam computed tomography (CBCT) is a three-dimensional radiographic technique used in planning implant therapy to help clinicians determine the volume and dimension of bone available for implant placement, and CBCT images potentially depict coincident findings. Materials and Methods: Three hundred eighteen patients received CBCT scans prior to receiving implants, which were interpreted by blinded board-certified oral and maxillofacial radiologists. All incidental findings were defined as non-tooth-related pathologies or abnormalities. These findings were categorized and analyzed using descriptive statistics. Results: The patients ranged in age from 16 to 91 years (mean age for men, 64.73 ± 15.05 years; for women, 62.47 ± 15.83 years). Controlling for age, men were 2.13 times more likely to have sinus pathology than women. Patients over age 65 were 5.01 times more likely to demonstrate vascular pathology (eg, carotid artery calcification) than patients ages 41 to 65; the likelihood versus patients ages 16 to 40 was 13.39. Women were 2.63 times more likely to display brain pathology (eg, pineal or pituitary calcifications). Controlling for gender, patients ages 41 to 65 were 3.17 times more likely to exhibit condylar pathology (eg, degenerative changes) than patients ages 16 to 40. Similarly, patients above age 65 were 3.53 times more likely to show condylar pathology than patients ages 16 to 40, and women were 1.61 times more likely to have condylar pathology than men. Versus patients ages 16 to 40, patients ages 41 to 65 were 17.69 times more likely to show signs of vertebral pathology (eg, degenerative disc changes) and patients over age 65 were 28.67 times more likely to display vertebral pathology. Conclusion: CBCT scans frequently reveal non-tooth-related pathologies and/or abnormalities in the head and neck region. Therefore, comprehensive review of the entire CBCT image set is necessary. Schlagwörter: computed tomography, cone beam computed tomography, dental radiology, magnetic resonance imaging, oral and maxillofacial radiology, panoramic radiography

Purpose: The purpose of this study was to compare marginal bone loss and success rates 1 year after implants had been placed in maxillary molar sites, either immediately postextraction or after the extraction sites had healed (delayed). Materials and Methods: A retrospective case study was made of subjects treated with immediate or delayed dental implants in the maxillary molar region between January 2006 and December 2008. A protocol was prepared in which patient age, sex, implant length and diameter, type of prosthesis, buccal plate width, and use of bone grafting were recorded. After 12 months, data relating to the clinical and radiologic conditions of the implants and the success rate according to the criteria of Buser et al were recorded. The variables were analyzed statistically (Student t test, Pearson correlation, Games-Howell test). Results: The study included 123 implants placed in 70 patients; 35 implants were immediate and 88 were delayed. Two immediate and six delayed implants failed, resulting in success rates of 94.3% and 93.2%, respectively. Average marginal bone loss was 0.56 mm for immediate implants and 0.67 mm for delayed implants. Conclusions: The placement of immediate implants in maxillary molar sites achieved similar results to implants placed in healed sites in the same region after 12 months. No statistically significant differences were found between implant survival rates or average marginal bone loss. Schlagwörter: delayed implant placement, dental implants, extraction sockets, immediate dental implants, molar replacement

Purpose: The purpose of this clinical trial was to evaluate the survival rate, bone remodeling, and soft tissue health surrounding variable-thread tapered implants placed in fresh extraction sites and loaded immediately. Materials and Methods: Sixty implants were placed in 55 patients at six centers according to a predetermined protocol. All implants were placed in extraction sockets and were subjected to immediate temporization. Definitive prostheses were placed within the first year. Clinical and radiographic examinations were performed at implant placement and after 3, 6, 12, and 24 months. Assessments of implant stability, Papilla Index, plaque, peri-implant mucosa, and marginal bone levels were performed at the respective visits. Results: Fifty-five patients were treated and were restored with 58 single crowns and 1 two-unit fixed partial prosthesis. The cumulative survival rate was 98.3% after 2 years. One implant failed prior to 3 months. The mean marginal bone remodeling from implant insertion to 1 year was -0.22 ± 1.30 mm (n = 41), followed by an average bone gain of 0.12 ± 0.77 mm (n = 33) between 12 and 24 months. Mean marginal bone remodeling was -0.10 ± 1.38 mm (n = 35) from implant insertion to 2 years. Papilla size increased significantly over the 2-year study period. Patient assessments of function, esthetics, and self-esteem also showed significant improvement. Conclusion: The 24-month results indicate that the variable-thread tapered implant can be used safely and effectively under demanding conditions as an immediate postextraction tooth replacement. Schlagwörter: dental implant, extraction socket, immediate loading, variable threading

Purpose: To monitor the development of stability of immediately loaded implants during early healing. Materials and Methods: A total of 90 interforaminally placed implants with an alkali-treated surface were considered. The stability of each implant was examined at placement and 1, 2, 3, 4, 5, 6, 8, and 10 weeks after the surgery using resonance frequency analysis (RFA) and damping capacity measurement. The development of implant stability, focusing on the decrease in stability (as measured by implant stability quotient [ISQ]) and the interplay of primary (ISQ0) and secondary implant stability, was evaluated. The implants were divided into three groups based on primary stability: group L (ISQ0 68), group M (ISQ0 68 to72), and group H (ISQ0 > 72). Stability curves for each group were created and analyzed statistically. Implant stability measurement results gained with RFA and damping capacity were compared employing the Wilcoxon paired test, correlation coefficients, and regression analysis. The threshold for statistical significance was set at P .05. Results: The most pronounced decrease in ISQ values occurred 1 week after implant placement (mean decrease of 2.2 ISQ). During the 10-week experiment, mean ISQ rose by 5.5 in group L and by 1.3 in group M and dropped by 1.8 in group H (P .001). The coefficient of determination R2 = 0.06 showed a weak dependence of RFA on the damping capacity (P .001). Conclusions: Implants with low primary stability showed a significant increase in stability during healing. In contrast, implants with high primary stability lost some stability over time. Schlagwörter: alkali treatment, damping capacity, dental implants, immediate loading, implant stability, insertion torque, primary stability, resonance frequency analysis

Purpose: The purpose of this study was to evaluate a specific protocol using four implants to support immediately loaded fixed prostheses to restore edentulous and partially edentulous mandibles and report on the outcome after 1 year of function with the definitive prostheses. Materials and Methods: A retrospective study was conducted of all patients who were treated between June 2008 and December 2010 with fixed prostheses that were loaded immediately after placement of implants. The provisional prostheses were later replaced with computer-aided design/computer-assisted manufacture titanium frames supporting acrylic resin and denture teeth in the definitive prosthesis. All patients were followed for a minimum of 12 months and were assessed for implant survival and prosthetic performance, with descriptive statistics utilized to demonstrate results. Results: One hundred eighty-three consecutive patients received immediately loaded axial and tilted implants according to the defined protocol. One implant failed, resulting in a 99.86% implant success rate. There were two catastrophic prosthetic failures (fracture of the titanium framework), for a 98.9% prosthetic success rate. Three patients (1.6%) presented with fracture of a prosthetic mandibular incisor tooth. No prosthetic screw loosening or fractures were seen. Radiographic evaluation revealed no major bone loss around dental implants. Conclusions: Based on this retrospective study, the following conclusions can be drawn: (1) this technique appears to provide a highly predictable implant performance; (2) it is necessary to critically evaluate framework design, especially around the connectors for cantilever extensions around the most distal implants; and (3) minor complications related to acrylic resin tooth fracture may be anticipated during the early phases of prosthetic treatment. Schlagwörter: dental implants, immediate loading, implant-supported fixed prosthesis, tilted implants

Purpose: Two different stereolithographic surgical guide systems, NobelGuide (Nobel Biocare) and SimPlant (Materialise), were compared clinically, and the survival rates of the planned immediately loaded dental implants with prefabricated provisional restorations were evaluated. Materials and Methods: Patients were treated with implants using either the Materialise SimPlant system or the Nobel Biocare system. All implants were planned on cone beam computed tomography (CBCT) or CT-derived images. Mucosa-, bone-, or tooth-supported stereolithographic guides were produced using the two commercial systems. A provisional was placed immediately after implant insertion in all cases. Results: Fourteen patients were enrolled. Seventy-five implants were placed (34 with Materialise, 41 with Nobel Biocare) using stereolithographic surgical guides. All but one implant were loaded immediately with prefabricated provisionals. In all cases, implants were in place for a minimum of 12 months. No complications related to associated anatomy occurred. One implant failed, leading to a combined cumulative survival rate of 98.7%. There were no other intraoperative or postoperative complications. Implants placed by bone-supported guides had increased patient symptoms of postoperative swelling and discomfort. All provisionals were successful. Conclusions: Both types of stereolithographic surgical templates were sufficiently accurate in transferring the planned implant positions to the surgical field, allowing the placement of prefabricated provisionals. These technologies are most beneficial in patients in whom the simultaneous placement of multiple implants in combination with complex restorations is planned. Schlagwörter: guided surgery, stereolithography, surgical template, computed tomography, implant, immediate loading

Purpose: To evaluate the performance of 5-mm-long implants. Materials and Methods: A retrospective cohort study was conducted between January 2008 and December 2009. The sample was composed of patients who had received at least one 5-mm-wide, hydroxyapatite-coated Bicon implant. The outcome variable was implant failure. Descriptive statistics and univariate and multivariate Cox proportional hazards regression models, adjusted for multiple implants in the same patient, were utilized to identify predictors of dental implant failure. Results: Two hundred ninety-one subjects who received 410 locking-taper implants were followed for an average of 20 months. Of these, 211 were ultrashort implants (57 were 5 × 5.0 mm and 154 were 5 × 6.0 mm) and 199 were short implants (5 × 8.0 mm). Three hundred twenty-two implants (93.4%) were restored with single crowns. There was a higher proportion of ultrashort single-tooth implants (94.6%) as compared to short single-tooth implants (92.2%). Nine implants failed, for a cumulative survival rate of 97.5%. Of the failed implants, five were ultrashort (all 5 × 6.0 mm) and four were short. No failures were documented for 5- × 5.0-mm ultrashort implants. There was no statistically significant difference (P = .68) in the Kaplan-Meier survival rates of ultrashort implants (97.6%) and short implants (95.2%). After adjusting for other covariates in a multivariate model, implant length was not associated with implant failure (P = .49). Conclusions: The survival of ultrashort (5- and 6-mm) implants was comparable to that of short (8-mm) implants. Schlagwörter: dental implants, implant length, retrospective cohort study, short implants, single-tooth implants

Purpose: The possible advantages of stereolithographic (SLA) surgical template use have not been adequately demonstrated, and studies of the accuracy of computer-aided implant placement are few. The purpose of this in vivo study was to evaluate the accuracy of a computer-designed (SLA) surgical guide by comparing the three-dimensional positions of planned and placed implants. Materials and Methods: One hundred sixteen implants were inserted in partially and completely edentulous patients using multiple SLA templates. Preoperative and postoperative computed tomographic images were compared. Four deviation parameters-global, angular, depth, and lateral-were defined and calculated between the planned and actual implant positions and analyzed statistically. Results: The mean global deviations between planned and actual implant positions at the coronal and apical ends were 1.47 mm and 1.83 mm, respectively; the mean angular deviation was 5.09 degrees. There were significant linear correlations at the implant level between coronal and angular deviations and between coronal and apical deviations. Conclusions: The study highlighted deviations between the postoperative position and the preoperative plan at the coronal and apical portions of the implant, as well as in the angulation of the implant. Although the reported deviation values were extremely high, they do not appear to have resulted in important clinical complications. This suggests the necessity of always keeping a safety zone of at least 2 mm to avoid critical anatomical structures. Schlagwörter: CAD/CAM surgical guide, computer-aided implantology, dental implants, stereolithography, surgical accuracy, surgical planning, surgical template

Purpose: The aim of this study was to investigate the positions of dental implants at the crestal level and the occlusal level of a fixed dental prosthesis (FDP) in severely and moderately resorbed maxillae. Restorations supported by multiple zygomatic implants were compared with restorations supported by standard implants. Material and Methods: Between 2004 and 2007, measurements were performed on FDPs and working casts. Two groups were investigated: (1) patients with severe atrophy and extensive resorption into basal bone treated with multiple zygomatic implants (Zyg) and (2) patients with moderate atrophy with standard implants only (Stand). The areas bounded by the FDP at the implant level (Aimpl) and at the occlusal level (Aprost) were calculated, and Aprost - Aimpl represented the total horizontal overjet of the FDP. Aprost/Aimpl was established as the degree of overlapping of these two areas. The transverse and sagittal dimensions at the implant level (Timpl and Simpl) and at the occlusal level (Tprost and Sprost) were also measured. Timpl/Simpl and Tprost/Sprost represented the shape of the superstructure at these respective levels. Results: Seven consecutive patients in the Zyg group were matched by age and gender with seven individuals in the Stand group. In the Zyg group, 28 zygomatic and 5 standard implants were placed; in the Stand group, 41 standard implants were placed, of which 3 were lost. All patients received an FDP. Timpl was shorter and Simpl was longer in the Zyg group, yielding a smaller Timpl/Simpl in this group. The Zyg group also displayed less overjet and a smaller Aprost/Aimpl compared to the Stand group. Conclusion: Multiple zygomatic implants emerged through the residual crest with a more even distribution in the sagittal plane compared to standard implants and with a better congruence with the occlusal location of the FDP. Schlagwörter: dental implants, maxilla, zygomatic implants

Purpose: To compare the effect of ceramic and metal implant materials on the expression pattern of inflammatory cytokines in peri-implant soft tissue. Materials and Methods: This split-mouth study included patients who received dental implants. In each patient, four different materials were used for the implant cover screws: the ceramic material titanium niobium oxynitride ([Ti,Nb]ON) with plasma-chemical oxidation treatment, (Ti,Nb)ON, a titanium-tantalum alloy, and tantalum. Biopsy specimens of peri-implant tissue were harvested at reentry, 4 months after the initial surgery. Immunohistochemical staining was performed for tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6). Results: Six patients received a total of 24 dental implants with the four different types of implant cover screws. Quantitative analysis of TNF-α and IL-6 expression showed the lowest expression of IL-6 (1.5; interquartile range, 0 to 8.5) and TNF-α (4.8; interquartile range, 3.5 to 7.5) in tissue adjacent to the (Ti,Nb)ON layer. In comparison to the metal surfaces, the expression of both cytokines was significantly lower (P = .01 and P = .03). Conclusions: The lowest levels of cytokine expression were observed in tissue adjacent to the ceramic (Ti,Nb)ON coating with plasma-chemical oxidation. Based on the results of this study, this ceramic layer shows promise as a biocompatible material, and further study is warranted. Schlagwörter: biocompatibility, cytokine, dental implant, metal-ceramic bonding, peri-implantitis, tantalum, titanium alloy

Purpose: The aim of this study was to assess the clinical status and radiographic and densitometric peri-implant tissue changes as parameters for the success or failure of 40 mandibular implants supporting intracoronal mandibular Kennedy Class I removable partial overdentures in a 2-year prospective study. Materials and Methods: Twenty consecutively treated men who received mandibular implants bilaterally to support an intracoronal Kennedy Class I removable partial overdenture were selected. Plaque and gingival bleeding indices, probing pocket depths, marginal bone loss, and bone mineral density were recorded. Bone loss and density were assessed through intraoral periapical radiographs and dual-energy x-ray absorptiometry, respectively. Data were recorded at the time of overdenture insertion and 6, 12, 18, and 24 months later. Results: Two implants failed, resulting in a success rate of 95% after 24 months. The plaque and gingival bleeding indices changed significantly between the different observational periods. Within the physiologic limit, there were detrimental effects on both marginal bone levels and probing pocket depths. Meanwhile, the bone mineral density around the implants increased significantly in a time-dependent manner. Conclusion: Within the limitations of this study, mandibular implants supporting an intracoronal Kennedy Class I removable partial overdenture can be recommended as a viable treatment modality for rehabilitation of patients with partial bilateral mandibular posterior edentulism. Schlagwörter: bone density, clinical indices, Kennedy Class 1, implant-tooth-supported removable partial overdenture, radiography

Purpose: Patients with skin-penetrating implants sometimes report episodic soft tissue reactions. This pilot clinical trial identified the oral microflora of the peri-implant sulcus of cancer patients with jaw reconstruction and compared sites with and without clinical signs of inflammation. Materials and Methods: Ten patients were selected during routine follow-up of their implant-supported removable prostheses. Eligible patients had at least two intraoral skin-penetrating implants; one showed clinical signs of inflammation with/without symptoms and the other served as a healthy control site. Eight of the 10 patients had undergone osseocutaneous fibula free flap reconstruction and two had received split-thickness skin grafts on the surface of the native mandible. Subjects were assessed on two visits, 30 to 40 days apart. Subgingival microbial samples were obtained and periodontal pocket depths were measured at the test implant abutment. Between visits, patients followed a strict oral hygiene regimen. Radiographic marginal bone loss around implants was measured using cone beam imaging during the second visit. The microflora were identified after isolation and purification of all growing colonies. Results: The number of different microorganisms ranged from 10 to 21 per site. Among all patients, a total of 47 different microorganisms were identified, but none were considered virulent red-complex periodontal pathogens. By the time of the second visit, after adherence to strict mechanical oral hygiene, the average number of microorganisms per site was reduced through elimination of some species. Almost all subjects had identical microbial species in both sites, but the number of visible colonies was lower at the healthy site. Conclusion: Oral peri-implant epidermal proliferation does not appear to be caused by specific microbial pathogens but is likely related to increased microbial load in the implant sulci. Mechanical oral hygiene improves and maintains healthier peri-implant skin tissues. Schlagwörter: dental implants, jaw reconstruction, microvascular flaps, oral cancer, percutaneous implants, peri-implant disease, skin-penetrating implants, subgingival microflora

Purpose: Conventionally, in patients with completely edentulous mandibles, fixed prostheses have been supported by four or more implants. However, an alternative protocol employing three implants and immediate loading has been developed. The objective of the present study was to assess the rehabilitation of edentulous patients treated with a complete fixed mandibular prosthesis with immediate loading and supported by three implants. Materials and Methods: In this observational study, a total of 99 implants placed in 33 patients was evaluated after 18 months in use. Panoramic radiographs were digitized to measure bone loss at the mesial and distal surfaces of each implant. Results: Mean peri-implant bone loss was 0.66 ± 0.51 mm for the left implant, 0.92 ± 0.61 mm for the central implant, and 0.82 ± 0.53 mm for the right implant. The bone loss observed around the distal implants was similar to that seen around the central implant, and there were no statistically significant differences in peri-implant bone loss between the three implant locations. There was no significant correlation between implant length and bone loss. The results were compatible with the peri-implant bone loss that has been described for prostheses of the same type supported by larger numbers of implants. Conclusions: The use of a complete fixed mandibular prosthesis with immediate loading supported by three implants proved to be an adequate option for the rehabilitation of edentulous patients. The protocol allowed simplification of treatment while maintaining similar bone loss to that reported for the same type of treatment supported by a larger number of implants. Schlagwörter: dental implants, edentulism, implant-supported dental prosthesis, mandibular prosthesis

Purpose: When planning implant therapy, knowledge of the bone volume in the implant area is needed to plan and place implants in the most appropriate locations from the prosthetic and surgical perspectives. Commercial software for digital planning of implants in the craniofacial region is not yet available. This article describes a method that enables digital planning of extraoral implants in the mastoid region utilizing commercially available computer-aided design (CAD) software and rapid-prototyping techniques to manufacture a corresponding surgical guide. Materials and Methods: With the aid of CAD software designed for reverse engineering and three-dimensional animation, digital implant planning based on cone beam computed tomography (CBCT) scanning was performed. On the basis of this planning, surgical guides were digitally designed to facilitate the placement of dental implants in the mastoid area. The guides were fabricated using rapid prototyping. The appropriateness of the digitally designed surgical guides for placing extraoral implants was tested on six human cadaver heads with simulated bilateral ear defects. After implant placement, a second CBCT scan was performed to compare preoperative planning with the actual postoperative implant positions. Results: Twenty-four implants were placed. The surgical guide helped the surgeon to place the implants at the preoperatively planned positions. Comparison of the CBCT scans revealed that adequate accuracy of implant placement was achieved, both for deviation of the neck (1.56 ± 0.56 mm) and the tip (1.40 ± 0.53 mm) of the implant, and for deviation of the angulation of the implant (0.97 ± 2.33 deg). Conclusion: The presented method for digitally planning extraoral implants in the mastoid area and designing surgical guides allows for placement of implants in the mastoid area in close proximity to the preoperatively planned implant position. The actual implant positions were satisfactory both surgically and prosthetically. Schlagwörter: auricular prosthesis, computer-aided design, digitally designed surgical guide, extraoral implants, maxillofacial prosthesis, rapid prototyping

Purpose: The aim of this study was to assess the contributions of some prosthetic parameters such as crown-to-implant (C/I) ratio, retention system, restorative material, and occlusal loading on stress concentrations within a single posterior crown supported by a short implant. Materials and Methods: Computer-aided design software was used to create 32 finite element models of an atrophic posterior partially edentulous mandible with a single external-hexagon implant (5 mm wide × 7 mm long) in the first molar region. Finite element analysis software with a convergence analysis of 5% to mesh refinement was used to evaluate the effects of C/I ratio (1:1; 1.5:1; 2:1, or 2.5:1), prosthetic retention system (cemented or screwed), and restorative material (metal-ceramic or all ceramic). The crowns were loaded with simulated normal or traumatic occlusal forces. The maximum principal stress (σmax) for cortical and cancellous bone and von Mises stress (σvM) for the implant and abutment screw were computed and analyzed. The percent contribution of each variable to the stress concentration was calculated from the sum of squares analysis. Results: Traumatic occlusion and a high C/I ratio increased stress concentrations. The C/I ratio was responsible for 11.45% of the total stress in the cortical bone, whereas occlusal loading contributed 70.92% to the total stress in the implant. The retention system contributed 0.91% of the total stress in the cortical bone. The restorative material was responsible for only 0.09% of the total stress in the cancellous bone. Conclusion: Occlusal loading was the most important stress concentration factor in the finite element model of a single posterior crown supported by a short implant.

Purpose: The goal of this study was to compare the stress distribution of tooth-implant-supported prostheses (TISPs) and solely implant-supported prostheses (ISPs) with two different pontic spans (three units versus four units). Materials and Methods: Two-dimensional finite element models were constructed from the radiographs of polyester resin casts to mimic TISPs and ISPs. In all, eight models were analyzed. Occlusal loads of 15 N and 30 N were applied to the premolars and molars, respectively. The lateral and inferior borders of the models were constrained, with all degrees of freedom equal to zero. Eight-node elements with plane strain assumption were used for simulation. Results: The authors found that TISPs with a short span and wider-diameter implants resulted in more homogenous stress distribution and less stress concentration on the implants. The long span yielded higher stress concentrations on the implants and between the pontics. Conclusions: In all models analyzed, stress concentrations were present in the implants.

Purpose: The objective of this study was to investigate the effects of different microthread designs and implant-abutment connection configurations of scalloped implants on stress distribution in bone using three-dimensional finite element analysis. Materials and Methods: Three different designs of scalloped implants (two different microthread designs and one without microthreads) with two different connection systems and two flat-top implants with similar connection systems were compared in a bone model that mimicked the anterior maxilla. Vertical and oblique (30-degree) loading with 100 N of force was applied to eight models. Peak stress levels and the distribution of stress were observed. Results: The stress pattern of scalloped implants was distinctively different from that observed on flat-top implants. Scalloped implants showed peak stresses in the proximal cortical bone as well as in the buccal and palatal cortical bone, whereas flat-top implants showed peak stresses mainly in the buccal and palatal cortical bone and limited stress in the proximal bone. The scalloped implant without microthreads and a conical platform-switched connection demonstrated the lowest peak stress levels. The scalloped implant with a straight platform connection generally showed peak stress that was two to three times higher than that seen in the conical platform-switched model. Conclusions: Peak stress levels in scalloped implants varied with microthread designs, connection configurations, and the direction of loading. The conical platform-switched connection seemed more important for a scalloped implant than the microthread design in reducing loading stresses exerted on the surrounding bone. Scalloped implants without microthread and a with a conical platform-switched connection or closed microthreads and a conical platform-switched connection showed consistently lower buccal bone stress than the flat-top implants in areas where the bone had a sloping and scalloping shape.