The International Journal of Oral & Maxillofacial Implants, 02/2012

Purpose: Although the laser has become one of the most commonly used tools for implant dentistry, research is lacking on whether or not the laser causes any changes on the surface of titanium (Ti) implants. The present study analyzed the morphology, composition, crystal structure, and surface roughness changes of machined and anodized Ti surfaces, irradiated with erbium chromium-doped yttrium-scandium-gallium-garnet (Er,Cr:YSGG), erbium-doped yttrium-aluminum-garnet (Er:YAG), and carbon dioxide (CO2) lasers. Materials and Methods: Seventy-two Ti disks were fabricated by machining commercially pure Ti (grade 3); 36 of them were anodized at 300 V. The disks were irradiated with Er,Cr:YSGG, Er:YAG, and CO2 lasers at five different powers (1, 2, 3, 4, and 5 W). The irradiated disks were examined with scanning electron microscopy, electron probe microanalysis, x-ray diffractometry, and optical interferometry. Results: Surface changes were observed on both types of Ti surfaces irradiated with the Er,Cr:YSGG laser when more than 3 W of power were applied. Surface changes were observed on both types of Ti surfaces when irradiated with the Er:YAG laser with more than 2 W of power. No change was observed when the disks were irradiated with the CO2 laser. The proportion of oxide in the machined Ti disk increased after the application of the Er,Cr:YSGG or Er:YAG laser. In the anodized Ti disk, the anatase peak intensity decreased and the rutile peak intensity increased after laser irradiation. The irradiated Ti disks were significantly rougher than the nonirradiated Ti disks. Conclusions: The Er:YAG and Er,Cr:YSGG laser resulted in surface changes on the Ti disks according to the power output. The CO2 laser did not affect the surface of the Ti disks, irrespective of the power output. Keywords: anodic oxidation, crystal structure, laser, roughness, surface composition, titanium disk

Purpose: The purpose of this article was to investigate the distribution of endosseous bony canals in the anterior mandible using cone beam computed tomography (CBCT) technology. Materials and Methods: Two hundred ninety-nine images based on CBCT of the anterior mandible were analyzed for the presence of endosseous canals. The bony canals were observed in relationship to the adjacent anatomical structures, and relationships between their topographic variability and patient age and gender were analyzed. Results: Bony canals were found in the anterior mandible in almost 86% of the examined patients, independent of age and gender. The highest regional frequency was seen in the midline area, followed by the lateral incisor and canine regions. The length of the canals ranged from 5 to 15 mm (mean, 10.55 mm). Multiple (two or three) canals were also observed in approximately 9% of the scans. Varying appearances of these bony canals in the symphysis region were also demonstrated. Conclusions: Endosseous canals in the mandibular symphysis were found using CBCT scans. CBCT seems to be an important diagnostic technique for evaluation of the exact distribution of bony canals in the symphysis region that may help reduce the risk of surgical complications. Keywords: anterior mandible, blood vessels, complications, cone beam computed tomography

Purpose: The appropriate surface composition and topography are crucial for osseointegration of titanium dental implants, and surface properties are known to enhance cell adhesion and promote expression of specific osteoblastic genes. In this study, a translucent titanium coating on glass coverslip (TiGlass) was introduced as a potential tool for direct observation of cell behavior on a titanium surface. Materials and Methods: Scanning electron microscopy, energy-dispersive x-ray analysis, and atomic force microscopy were performed on TiGlass to provide information about its physical properties. Random migration, osteoblastic gene expression, and immunofluorescence cell staining on TiGlass were also examined and analyzed. Results: The translucent titanium surface offered excellent optical characteristics that facilitated transmitted light observations under an optical microscope, transforming the opaque metal into an observable titanium matrix. Random migration analysis of the primary osteoblasts on TiGlass revealed that the titanium coating enhanced the migration speed of the osteoblasts and significantly shortened the time lag for the initial migration behavior. Further study of osteoblastic gene expression on this smooth titanium surface revealed no significant changes. Co-localization of actin filament and vinculin was found on TiGlass under epifluorescent microscopy. Conclusion: The application of a translucent titanium-coated coverslip in vitro altered the migration pattern of osteoblasts. Collectively, the results suggest that titanium promotes initial adhesion and accelerates osteoblast migration. Keywords: dental implants, osteoblast migration, titanium coating, translucent coating

Purpose: The frequency of alveolar ridge resorption and crestal bone loss emphasizes the clinical need for bone graft substitutes to improve local bone quality prior to dental implant placement. Microcomputed tomography has been extensively employed to estimate bone quality more objectively (ie, quantitatively) by relating it to architectural parameters. In the present study, the mechanical properties of open cellular fully interconnected bilayer hydroxyapatite scaffolds, which mimicked the cortical shell/trabecular core architecture of human bone, were investigated for suitability as bone graft substitutes for maxillofacial reconstruction. Materials and Methods: Hydroxyapatite scaffolds with different architectures were fabricated using polymeric template pore sizes of 450 or 340 µm for the inner trabecular cores and 200 or 250 µm for the outer cortical shells in three different core-to-shell volume ratios. The architectural and mechanical properties and fluid permeability of the scaffolds were compared to reported values for maxillofacial bone. Results: Whereas the elastic moduli of the scaffolds were comparable, their compressive strength was observed to be in the lower range of human mandibular trabecular bone. The microcomputed tomography architectural indices for the scaffolds were comparable to those of human trabecular bone at different locations in the human body, including the maxilla and mandible. Scaffold compressive strength, elastic modulus, and fluid conductance were 0.3 to 2.3 MPa, 40.9 to 668.1 MPa, and 8.8 to 49.9 × 10-10 m3s-1Pa-1, respectively. Conclusion: Open-pore bilayer scaffolds can be fabricated to exhibit sufficient mechanical integrity for maxillofacial bone graft applications to match specific bone site architecture while providing sufficient permeability to sustain bone regeneration. Keywords: alveolar resorption, architecture, bone grafts, hydroxyapatite, microcomputed tomography, scaffolds

Purpose: The purpose of the present study was to investigate the stress distribution around the bone-implant interface and the effect of the length of an immediately loaded implant in the anterior maxilla using a finite element model with simulated loading stresses. Materials and Methods: Four-mm-diameter external-hex implants with different lengths (8.5, 10.0, 11.5, 13.0, and 15.0 mm) were used in this study. The anterior maxilla was assumed to be D3 bone quality. All of the material was assumed to be homogenous, isotropic, and linearly elastic. Average bone deformation during implant placement was calculated through the simulation process, and using this, insertion stress was created. The bone-implant interface was constructed using a contact element to simulate a nonosseointegrated condition. Then, 176 N of static force was applied at the middle of the palatoincisal line angle of the abutment at a 120-degree angle to the long axis of the abutment. The von Mises stresses were measured at intervals of 0.25 mm along the bone-implant interface. Results: Prior to loading, the stresses were evenly distributed around the implant and highly concentrated in the cortical area. When the load was applied, von Mises stresses were concentrated in the cortical bone of the implant neck area. More favorable stress distribution was seen with increasing implant length. However, when the implant length reached 15.0 mm, the stresses increased. Conclusions: In the maxilla, when immediate loading is applied after implant placement, 11.5- and 13.0-mm-long single implants showed more favorable stress patterns than the others analyzed. If implants longer than 15.0 mm are used in immediate loading, sufficient bone volume in the recipient site should be considered an important factor. Keywords: anterior maxilla, dental implants, finite element analysis, immediate loading, insertion stress

Changes in an implant assembly after abutment connection might possibly cause deformation in the implant/abutment joint and even in the marginal bone. Purpose: The aim of this study was to evaluate the influence of abutment screw preload through the implant collar on marginal bone stress without external load application. Materials and Methods: Models of three implant parts made of titanium (implant, abutment, and abutment screw) and cortical bone were built and positioned with computer-aided design software. Meshing and generation of boundary conditions, loads, and interactions were performed. Each part was meshed independently. The sole load applied to the model was a torque of 32 Ncm on the abutment screw about its axis of rotation. Results: The implant collar was deformed axially after the screw was tightened (3 µm). This deformation resulted in 60 MPa of stress in the marginal bone. Moreover, pressure on the marginal bone in a radial direction was observed. Conclusions: It can be concluded that, without any external load application, abutment screw preload exerts stresses on the implant collar and the marginal bone. These findings should help guide the development of new implant/abutment joint designs that exert less stress on the marginal bone. Keywords: bone stress, dental implants, finite element analysis, implant/abutment joint, marginal bone, preload

Purpose: The aim of this study was to evaluate the effects of a variety of implant cleaning instruments on different implant surfaces, specifically surface roughness and cleaning efficacy. Materials and Methods: Biofilm layers of Streptococcus mutans were cultivated on titanium disks with four different surface structures (polished, grit-blasted, acid-etched, and acid-etched/grit-blasted). Five disks each were cleaned using nine mechanical implant cleaning instruments or an erbium:yttrium-aluminum-garnet laser. Surface roughness (average, Ra; maximum, Rz) and waviness (Lr) were evaluated by two-dimensional laser profilometry. Surface structure damage and cleaning scores were assessed by scanning electron microscopy. Statistical analyses of the results were performed with one- and two-way analyses of variance and Bonferroni-Dunn multiple-comparison post hoc analysis (α = .05). Results: Ra and Rz values for the acid-etched surfaces and Ra, Rz, and Lr values for the polished and the grit-blasted surfaces showed no significant differences between the different cleaning methods or cleaning instruments compared to the control (not cultured, not cleaned) groups. Significantly lower Ra and Rz values on grit-blasted/acid-etched implant surfaces were found following use of the Sonic-Flex clean with prophylaxis brush and the plastic curette compared to Satelec ProphyMax with Periosoft curette. Ra and Rz values of the different implant structure surfaces before cleaning were significantly different between all implant surfaces except for the polished compared to the acid-etched surfaces. Conclusions: Cleaning effect and alterations of the implant surfaces were strongly dependent on the implant cleaning method used. Keywords: cleaning instruments, implant surfaces, laser profilometry, scanning electron microscopy, surface roughness

Purpose: Current methods for the evaluation of alveolar bone quality and dental implant stability have been shown to provide inconsistent results. The aim of this investigation was to validate a novel diagnostic device (BoneProbe) for the objective classification of alveolar bone during dental implant surgery. Materials and Methods: A metal cylinder (diameter, 3.5 mm) split into six segments was used as a sensor that could be positioned in implant sockets and expanded while the force needed to expand the site was recorded. Simulating all surgical steps, implants were placed into polyurethane foam materials (n = 100 implants) and human cadaver bone (n = 110 implants). Bone quality (cortical bone thickness, trabecular bone density, drilling resistance, implant insertion torque, compressive testing) and primary implant stability (Osstell, Periotest) were evaluated as reference data. Results: In polyurethane foam, significant correlations between all parameters (Pearson correlation coefficients) and a significant influence of the different polyurethane foam materials on all measurement results (multiple analysis of variance with Pillai trace) were found. In general, in human cadaver bone, weaker correlations between the different measurement techniques were seen (Pearson product-moment correlation). With the exception of compressive testing and radiographic assessment of trabecular bone density, all methods were able to differentiate between mandibular and maxillary bone. Conclusions: Based on these in vitro results, it appears that intraoperative testing of alveolar bone allows for a reproducible classification of bone quality. Because the proposed system is independent of any specific implant design, this device could be used for establishing a universally valid bone classification system. Keywords: bone density, bone quality, compressive testing, implant stability

Purpose: The purpose of this study was to investigate the influence of occlusal forces (the contractile forces of the masticatory muscles) during occlusal adjustment on the distribution of forces on combinations of implants and teeth during intercuspal clenching by means of finite element analysis. Materials and Methods: Three-dimensional finite element models of the mandible, one with two implants in the molar region and the other with four implants in the premolar and molar regions, were constructed. Linearly elastic material properties were defined for all elements except the periodontal ligament, which was defined as nonlinearly elastic. The temporomandibular joints and antagonists were simplified and replaced with nonlinear springs. Antagonists were assumed to be a natural tooth or an implant and had two- or three-stage displaceability (ie, very high displaceability under tension and when the displacement was smaller than the clearance assumed to be made by occlusal adjustment, but displaceability of the antagonists themselves when the displacement was greater than the clearance). The clearance by occlusal adjustment was decided beforehand with a trial-and-error method so that the occlusal forces were distributed symmetrically under a prescribed load. Each model was evaluated under loads of 100 N, 200 N, and 800 N for the distribution of occlusal forces on the teeth and implants. Results: In the case of occlusal adjustment under the total occlusal force of 40 N, the stress was concentrated at the most posteriorly located implant in all models under all loading conditions. This concentration was reduced in the case of occlusal adjustment under the total occlusal force of 200 N, except under a load of 800 N. Conclusion: Hard biting appeared to be better for occlusal adjustment to avoid overloading of the most posterior implant. Keywords: displacement, finite element analysis, implant, mandible, nonlinear, occlusal adjustment

Purpose: Algipore is a biologic hydroxyapatite derived from calcifying maritime algae. The present study evaluated this material histologically and histomorphometrically after implantation in rabbit tibia defects for 4 weeks. Materials and Methods: Six New Zealand rabbits were used in this study. In each rabbit tibia, two 7-mm defects were prepared. Control defects were left empty, and test defects were filled with Algipore. Twenty-four specimens (12 test and 12 control) were retrieved and processed for histology. Results: In control sites, newly formed trabecular bone with large marrow spaces was plentiful in the most peripheral areas of the defects but sparse elsewhere. In contrast, in test sites, a large quantity of newly formed bone around the biomaterial particles was detected in the central medullary portion of the defect. In addition, in several areas, the biomaterial particles were bridged by newly formed bone. The percentage of contact between newly formed bone and biomaterial particles was 71.2% ± 9.8%. Inside the central portion of the biomaterial particles, it was possible to see newly formed bone (about 35.3% ± 4.8% in each particle). In test sites, newly formed bone represented 31.1% ± 1.9% of the material, with residual biomaterial particles occupying 33.4% ± 2.8% and marrow spaces another 34.7% ± 4.3%. In the control sites, the values were 30.2% ± 2.2% for newly formed bone and 68.7% ± 4.1% for marrow spaces. A statistically significant difference was found in the percentage of marrow space between the two groups, but no significant difference was observed in the percentage of newly formed bone. Conclusions: The present rabbit study confirmed the high osteoconductivity and resorbability of this biomaterial. Keywords: algae-derived hydroxyapatite, bone regeneration, histology, rabbit defects

Purpose: The aim of this study was to investigate the level of microstrain that is exerted during polymerization of acrylic resins used for splinting during implant impressions. Material and Methods: Two acrylic resins (GC Pattern Resin, Duralay II) and square transfer coping splinting methods were evaluated by means of strain gauge analysis. Two implants were embedded in a polyurethane block, and the abutments were positioned. Sixty specimens were prepared using two square transfer copings that were rigidly connected to each other using the acrylic resins. The specimens were randomly divided into three groups of 20 each for the splinting methods: Method 1 was a one-piece method; in method 2, the splint was separated and reconnected after 17 minutes; and in method 3, the splint was separated and reconnected after 24 hours. In each group, half the specimens were splinted with GC Pattern Resin and the other half were splinted with Duralay II. Three microstrain measurements were performed by four strain gauges placed on the upper surface of the polyurethane blocks at 5 hours after resin polymerization for all groups. The data were analyzed statistically. Results: Both resin type and splinting method significantly affected microstrain. Interaction terms were also significant. Method 1 in combination with Duralay II produced significantly higher microstrain (1,962.1 µε) than the other methods with this material (method 2: 241.1 µε; method 3: 181.5 µε). No significant difference was found between splinting methods in combination with GC Pattern Resin (method 1: 173.8 µε; method 2: 112.6 µε; method 3: 105.4 µε). Conclusions: Because of the high microstrain generated, Duralay II should not be used for one-piece acrylic resin splinting, and separation and reconnection are suggested. For GC Pattern Resin, variations in splinting methods did not significantly affect the microstrain created. Keywords: acrylic resin, microstrain, osseointegrated implants, splinting techniques, strain gauge

Purpose: The aim of the present study was to verify the presence of a microgap between implants and prosthetic abutments on their external surfaces in five different external-hex implant systems and to determine whether bacterial leakage occurs through the implant-abutment (I-A) interface. Materials and Methods: Ten samples of each implant system were used. Eight samples of each implant system were inoculated with 0.3 µL of a suspension of Escherichia coli for bacterial leakage evaluation. Two other samples were used as controls. Sample analysis was accomplished at 24 and 48 hours and on the 5th, 7th, and 14th day after inoculation. After microbiologic analysis, all samples were prepared for I-A interface evaluation by scanning electron microscopy. The mean of the microgap misfit was obtained from six points at ×1,000 and ×3,000 magnifications. Results: The Neodent implant system (0.51 ± 0.39 µm) showed the closest adaptation, followed by Dentoflex (1.44 ± 0.73 µm), Titanium Fix (1.88 ± 1.28 µm), SIN (2.46 ± 3.38 µm), and Conexão (2.68 ± 3.02 µm). Twenty-five percent of the Dentoflex samples showed bacterial leakage through the I-A interface; no other implant system presented bacterial leakage. Conclusion: The width of the microgap at the I-A interface was less than 3 µm in all systems. A direct correlation between bacterial leakage and I-A interface misfit was not observed. Keywords: dental implant, microbial leakage, misfit

Purpose: Zirconia ceramics are a viable alternative to titanium for use as dental implants. However, the smooth surface of zirconia means that longer healing periods are needed to accomplish osseointegration compared to roughened titanium surfaces. Surface modifications can be used to increase the roughness of zirconia. The aim of this study was to assess histologically and compare the degree of early bone apposition around zirconia dental implants with sandblasted, sintered, or laser-modified surfaces to that seen around surface-modified titanium implants. Removal torque was also measured and compared. Materials and Methods: Ninety-six implants-24 each of four types (sintered zirconia, laser-modified zirconia, sandblasted zirconia, and acid-etched titanium)-were placed in 48 New Zealand White female rabbits. One implant was inserted in each distal femur. Half of the specimens were harvested at 6 or 12 weeks and processed for light microscopic analysis; the area of bone-to-implant contact was measured morphometrically. The other half were evaluated for removal torque at 6 and 12 weeks. Results: No statistically significant differences existed in bone apposition between the different surfaces at either time point. Differences in removal torque were significantly different between titanium and sandblasted zirconia and between sintered zirconia and sandblasted zirconia, with the first mentioned demonstrating a higher torque value at 6 weeks. At 12 weeks, the only significant difference in removal torque was between titanium and sandblasted zirconia, with titanium demonstrating the higher value. Conclusion: Comparable rates of bone apposition in the zirconia and titanium implant surfaces at 6 and 12 weeks of healing were observed. Removal torque values were similar for all implants with a roughened surface. Keywords: dental implants, osseointegration, surface modification, zirconia

Purpose: The aim of the present study was to perform a finite element (FE) analysis of a modified sinus elevation procedure involving additional implantation of a cortical bone graft block for stabilization of an implant. A secondary aim was to compare the modified sinus augmentation with the standard technique and to determine whether the FE model to replace a dental implant can be simplified into a cylinder without compromising the accuracy of the outcome. Materials and Methods: Based on computed tomography data, three-dimensional FE models of half of a maxilla were created. A basic model was generated to analyze a conventional sinus elevation procedure and another was created for the modified version, which involved insertion of a cortical bone graft block. Two implant models were used in the premolar region: a typical threaded endosseous dental implant and a simplified 4 × 10-mm cylinder. Occlusal loads were applied in axial, mediotrusive, and laterotrusive directions, and perfect bonding was assumed to be present at all interfaces. Results: The maximum von Mises stresses were significantly lower for the sinus graft models with added cortical bone than for the conventional sinus elevation under all types of loads. No significant difference was observed between the use of threaded implants and the simplified implant cylinders. Conclusion: The addition of a cortical bone graft may be a useful approach to decrease stresses around implants placed into the grafted sinus. Keywords: dental implant loading, finite element analysis, maxillary atrophy, sinus elevation, three-dimensional modeling

Purpose: The purpose of this study was to investigate bone responses to simvastatin-loaded porous implant surfaces in an ovariectomized model. Materials and Methods: Roughened implants were divided into a control group (n = 32), test group 1 (n = 32), and test group 2 (n = 32). Test implants were immersed into 10-7 mol/L (test group 1) or 10-6 mol/L (test group 2) simvastatin solutions for drug adsorption onto implant surfaces. Forty-eight ovariectomized rats randomly received an implant in each tibia. One, 2, 4, and 12 weeks later, the tibiae were retrieved and prepared for histomorphometric evaluation. Bone-to-implant contact and bone area around the implant were determined, and histologic observations were made. Results: New bone formation on test implant surfaces was seen after 1 week, while it was seen on the control implant surface after 2 weeks. There was more bone tissue and bone-to-implant contact along the test implant surfaces than along the control implant surface. The test group 1 and test group 2 implants showed significantly greater bone area and bone-to-implant contact compared to the control implant at all observed time points (P .05). No differences were found between the two types of test group implants after 1, 2, 4, and 12 weeks (P > .05). Conclusion: Simvastatin-loaded porous implant surfaces have the potential to improve implant osseointegration in an ovariectomized rat model. Keywords: bone area, bone-to-implant contact, dental implant, osseointegration, simvastatin

Purpose: This research sought to compare two different systems to monitor sedated patients undergoing implant surgery in the dental office: the bispectral index (BIS) and the Ramsay scale. This information was used to establish an optimal BIS range for surgery in these patients and to calculate differences in drug consumption in both groups. Materials and Methods: Consecutive patients undergoing implant surgery were studied and randomly assigned to two groups. Patients were sedated using intravenous propofol, fentanyl, and midazolam. The sedation level in group A was measured using the Ramsay scale. In group B, the Ramsay scale and the BIS were used together. Heart rate, blood pressure, and peripheral oxygen saturation were monitored in all patients. The levels of anxiety, satisfaction, and drug consumption were compared between groups. Results: Forty-three patients were included; 20 were placed in group A and 23 were included in group B. There were no differences in the hemodynamic and respiratory parameters monitored or in anxiety or satisfaction levels in both groups. In group B patients, the BIS values stabilized around 85; the Ramsay scale stabilized around 3 in both groups and remained at these levels until the end of the procedure. Drug consumption was significantly lower in the BIS group. Conclusion: The optimal BIS value during intravenous sedation in sedated ambulatory patients in dental surgery should be within the 80 to 85 range. BIS monitoring allows for reduced consumption of propofol, fentanyl, and midazolam. Keywords: bispectral index, deep sedation, dental office, oral surgery

Purpose: The design of an implant plays a fundamental role in the osseointegration process, particularly in low-density bone. It has been postulated that design features that maximize the surface area available for contact may improve mechanical anchorage and primary stability in cancellous bone. Two different implant profiles were compared to evaluate the influence of thread pitch on the osseointegration process in bone of low density and limited height. Materials and Methods: "Narrow-pitch" implants (NP) with a 0.5-mm pitch and "wide-pitch" implants (WP) with a 1.7-mm pitch were tested for osseointegration after 0 days and 4 and 8 weeks in a sheep iliac crest model. The two different implants were analyzed with biologic and biomechanical tests. Results: The present findings showed that initial mechanical anchorage and subsequent early endosseous integration in low-density bone could be improved by a reduction of thread pitch. The greater surface area gained by decreasing thread pitch increased bone-implant contact and primary stability from the time of implant placement. This better performance of the NP profile could be appreciated even at an early healing time when the subsequent biologic integration was enhanced not only in terms of a higher quantity of newly deposited bone but also more regular and mature geometric distribution of bone tissue at the interface. Conclusion: These results confirmed that, when primary stability is a concern, as in cancellous bone, increasing the implant surface area by using implants with smaller pitch might be beneficial. Keywords: dental implants, implant design, morphometry, osseointegration, thread pitch, torque tests

Purpose: This cone beam computed tomography study (CBCT) evaluated horizontal and vertical dimensional changes to the facial bone following maxillary anterior single immediate implant placement and provisionalization. Materials and Methods: CBCT scans taken immediately after (T1) and 1 year after surgery (T2) were evaluated. The midsagittal cut of each implant was identified, and measurements were made at predetermined levels. Horizontal facial bone thickness (HFBT) was measured at 0, 1, 2, 4, 6, 9, and 12 mm apical to the implant platform. Vertical facial bone level (VFBL) was the perpendicular distance from the implant platform (0) to the most coronal point of the facial bone. Measurements were recorded and changes between T1 and T2 were calculated. The data were analyzed statistically at a significance level of α = 0.05. Results: CBCT scans of 21 patients were analyzed. At T2, the mean HFBT changes ranged from -1.23 to -0.08 mm at the seven different levels evaluated. The mean VFBL change was -0.82 mm. The HFBT changes at the 1- to 9-mm levels were not significantly different from one another, but they were significantly smaller than the change at the 0-mm level and significantly greater than the change at the 12-mm level. Significant positive correlations were observed only between horizontal and vertical changes and between horizontal change and initial VFBL at the implant platform. While the VFBL of eight implants (38%) was apical to the implant platform at T2, none was noted at T1. Conclusions: Dimensional changes to the peri-implant facial bone following maxillary anterior single immediate implant placement and provisionalization should be expected. The greatest HFBT change was noted at the implant platform level, in part because HFBT change is correlated to the initial VFBL and the change in VFBL at that level. Keywords: cone beam computed tomography, facial bone, immediate implant placement and provisionalization, immediate tooth replacement, maxillary anterior implants, measurement

Purpose: Porous titanium granules (PTG) may have potential as an osteoconductive bone graft substitute to treat peri-implant osseous defects. The aim of this study was to analyze clinical and radiographic outcomes of peri-implant osseous defects after treatment with PTG. Materials and Methods: This prospective, randomized, case-control, clinical 12-month study compared open-flap debridement and surface decontamination with titanium curettes and 24% ethylenediaminetetraacetic acid gel (n = 16) to the same protocol but with the addition of PTG (n = 16). One-, two-, and three-wall infrabony defects were included. Patients were given amoxicillin and metronidazole 3 days before surgery and for 7 days afterwards. Implants were submerged and allowed to heal for 6 months. Probing pocket depths, bleeding on probing, implant stability using resonance frequency analysis, and radiographic evaluation were performed at baseline and at 12 months. The threshold for significance was set at .05. Results: Change in radiographic defect height and percent fill of the peri-implant osseous defect significantly favored patients treated with PTG. Both treatment modalities demonstrated significant improvements in probing pocket depth, but significant differences between groups were not observed. The PTG-treated implants showed an increase in implant stability quotient (ISQ) of 1.6 units, compared with a decrease of 0.7 ISQ for the control group. No adverse effects were associated with PTG treatment. Conclusions: Reconstruction with PTG resulted in significantly better radiographic peri-implant defect fill compared with controls; however, the results do not necessarily imply reosseointegration or osseointegration of PTG particles. Improvements in clinical parameters were seen in both groups, but no differences between groups were demonstrated. Keywords: osseous defects, peri-implantitis, porous titanium granules

Purpose: To evaluate the soft and hard tissue response to orthodontic implant site development (OISD) (ie, forced extraction), to measure the amount of tissue that was regenerated and its relationship to the amount of orthodontic vertical tooth movement, to evaluate the tissue response in teeth with different degrees of periodontal attachment loss, to understand the limits of OISD, and to evaluate the implant survival rate. Materials and Methods: A total of 32 hopeless teeth were treated with OISD, and 27 implants were placed in 13 patients consecutively. The level of periodontal attachment on the teeth to be extracted, amount of augmented alveolar bone, changes in soft tissue volume, and the rate of orthodontic tooth movement were recorded. Results: Mean values after OISD were as follows: orthodontic extrusive movement, 6.2 ± 1.4 mm; bone augmentation, 4 ± 1.4 mm; coronal movement of the gingival margin, 3.9 ± 1.5 mm; coronal movement of the mucogingival junction, 2.1 ± 1.3 mm; keratinized gingival augmentation, 1.8 ± 1.1 mm; gingival thickness (buccolingual dimension) augmentation, 0.7 ± 0.4 mm; recession, 1.8 ± 1.2 mm; bone augmentation/orthodontic movement ratio (efficacy), 68.9% ± 17.3%; gingival augmentation/orthodontic movement ratio (efficacy), 65.2% ± 19.9%; and pocket depth reduction, 1.8 ± 0.9 mm. The implant survival rate was 96.3%. Conclusions: OISD was a viable treatment for these hopeless teeth to regenerate hard and soft tissues. Its efficacy was about 70% for bone regeneration and 60% for gingival augmentation. The residual attachment level on the tooth was not a limitation. OISD might be a valuable treatment option to regenerate tissues for implant site development in patients in need of conventional orthodontic therapy. Keywords: bone augmentation, forced eruption, gingiva augmentation, implant site development, orthodontic forced extrusion, orthodontic implant site development

Purpose: The aim of this study was to compare the survival of implants placed in mature bone with the survival of implants placed in fresh extraction sockets in the same patients. Materials and Methods: A retrospective study of patients treated simultaneously with at least one immediate and one nonimmediate implant was carried out for the period 2005 to 2008. Data were recorded for patient age and sex; implant length, diameter, and position; and, for postextraction implants, distance between the implant and the alveolar bone. Results: One thousand twenty-two implants were placed in 150 patients; 480 were placed immediately and 542 were placed in mature bone. The mean implant survival rate was 93.4%; survival rates were 93.8% for immediate implants and 93.2% for nonimmediate implants. The failure rate in the maxilla was 5.2% and in the mandible it was 2.8%. The failure rate for immediate implants in the posterior maxilla was 8.5%, which was statistically significantly higher than for implants placed elsewhere. Of the failed implants, 72% were early failures. Conclusions: The survival rate of implants placed in fresh extraction sockets was similar to that of implants placed in mature bone. A statistically significantly higher failure rate was seen with immediate implants placed in the posterior maxilla. Keywords: fresh extraction sockets, immediate dental implants, immediate implantation, implant survival rate

Purpose: The aim of this study was to compare definitive acrylic resin prostheses with or without a cast metal framework that were immediately loaded and supported by axial and tilted implants in completely edentulous patients after 3 years of function. Materials and Methods: Patients who were completely or partially edentulous in one or both arches with severe atrophy of the posterior regions were selected for this study. All patients immediately received prosthetic rehabilitations, each supported by four implants (two axial and two tilted). The patients were randomized to receive a definitive prosthesis with a cast metal framework or one made of acrylic resin only. Follow-up visits were performed up to 36 months after implant insertion and included radiographic assessments of bone levels around the implants. Results: Thirty-six patients participated, and 44 complete-arch immediately loaded prostheses (24 maxillary and 20 mandibular ), each supported by four implants (in total 176 implants), were placed. In all, 21 screw-retained full-arch acrylic resin prostheses and 23 cast-metal-framework prostheses were delivered to the patients. The 3-year overall implant survival rate was 100% for axially positioned implants and 96.59% for tilted implants. Implant survival rates were 98.96% in the maxilla and 97.5% in the mandible. None of the 44 fixed prostheses were lost during the observation period, representing a prosthetic survival rate of 100%. No statistically significant differences were seen in crestal bone loss between tilted and axial implants at 12, 24, and 36 months in either arch. Conclusions: The same clinical outcome was seen for patients treated with the so-called All on Four protocol, regardless of whether the acrylic resin restorations were reinforced with metal. Keywords: acrylic resin prostheses, All on Four, metal-reinforced prostheses, tilted implants

Purpose: The objective of this study was to determine whether a synthetic bioresorbable polyethylene glycol (PEG) hydrogel membrane could provide similar clinical and radiographic outcomes as a standard collagen membrane, both in combination with a membrane-supporting material, during follow-up periods of 1 and 3 years. Materials and Methods: This study enrolled patients requiring implant treatment with an expected osseous defect in the posterior maxilla or mandible. Defects around the implants were grafted with deproteinized bovine bone mineral and covered with either a collagen membrane or a PEG hydrogel membrane, which is applied as a liquid and becomes a solid gel in situ. Surgical re-entry was performed after 6 months, and fixed partial dentures were inserted subsequently. Patients were examined clinically and radiographically 1 and 3 years after loading. Results: Thirty-six of the 37 included patients were reexamined in the third year. The implant survival rate at 3 years was 100%. The peri-implant tissues were healthy, with no differences between the two groups. Compared to the time of surgery, the mean changes in the distance between the first bone-to-implant contact to the transition point (ie, rough implant surface to polished neck portion) were 0.43 ± 0.56 mm (PEG) and 0.21 ± 0.36 mm (collagen) at 1 year and 0.61 ± 0.89 mm (PEG) and 0.33 ± 0.64 mm (collagen) at 3 years. The respective differences between groups were 0.13 mm (1 year) and 0.31 mm (3 years), which were not significant at either time point (analysis of covariance). Conclusion: The tested PEG hydrogel was as successful as a standard collagen membrane for the treatment of bony dehiscence defects around dental implants after follow-up periods of 1 and 3 years. Keywords: bone substitute, dental implant, graft material, guided bone regeneration, membranes, randomized controlled trial

Purpose: This study is a retrospective assessment of the long-term efficacy of dental implant therapy in periodontally susceptible patients. Materials and Methods: A private-practice chart review was conducted to identify partially dentate subjects treated with implant-supported restorations that had been monitored annually for at least 9.5 years. Subjects were assigned to either a periodontal group or a control group according to their health histories. Data were entered into spreadsheets on a personal computer and analyzed statistically with dedicated software. Results: Thirty periodontal subjects were treated with 138 implants and 45 prostheses, and 16 control subjects were treated with 35 implants and 21 prostheses. The mean follow-up was 130 months. One implant failed before loading in the periodontal group. Cumulative 10-year survival rates were 99.3% (n = 137/138) for periodontal implants and 100% (n = 35/35) for control implants. Most surviving implants had no bone loss (n = 109/172, 63.4%). Most of the surviving implants with bone loss (n = 63/172, 36.6%) were concentrated in the periodontal cohort (90%, n = 57/63) and among women (60%, n = 15/25) regardless of cohort. Prosthesis failure was 25.2% (n = 16/66), with 12 porcelain fractures, 2 cement failures, and 2 framework fractures. In all cases, failed prostheses were immediately replaced and patients continued to function. Conclusions: Periodontal susceptibility resulted in increased bone loss but did not affect implant survival. The cause of greater bone loss in women could not be determined from the data but may have been related to the postmenopausal status of the subject population (mean age = 54 years). Keywords: bone loss, dental implants, outcome, periodontitis

Purpose: The aims of this clinical study were to evaluate the occurrence of sinus graft infection and the results of a planned surgical and pharmacologic treatment regimen to eliminate infections and preserve the graft. Materials and Methods: Patients were consecutively treated with sinus floor elevations using the lateral window technique. If a clinical diagnosis of sinus graft infection was made for a patient, a postoperative computed tomographic scan was performed to diagnose involvement of the sinus cavity. Results: Of 198 patients treated with 274 sinus grafts, 8 (2.3%) developed a sinus graft infection. These patients were treated with the same surgical and pharmacologic regimen. Symptoms of infection were recognized, the infected graft was removed, and the remaining graft material was cleansed. The remaining defect was not filled with new graft material; instead, it was left to heal for an extended healing period (average of 10.6 months), and residual bone defects were corrected during implant placement. Acute symptoms of infection disappeared within 48 hours of treatment and all patients healed uneventfully thereafter. All 24 implants placed have survived to date (with implant loading times ranging from 1 to 9 years), resulting in a 100% implant survival rate for these sites with postoperative infection. Conclusions: The overall clinical outcome, including patient satisfaction, achievement of optimal graft volume without subsequent sinus elevation, and long-term implant survival, confirmed the success of this treatment protocol. Keywords: postoperative infection, sinus elevation, sinus graft, sinus graft infection, sinusitis

Purpose: The aim of this clinical investigation was to evaluate marginal bone remodeling and soft tissue health surrounding a novel one-piece implant system over a 3-year study period. Materials and Methods: Subjects missing at least one tooth in either arch were consecutively enrolled in this open prospective 3-year investigation. Five clinics were invited to participate. Strict inclusion and exclusion criteria were used. Marginal bone levels were evaluated using radiographs taken at implant insertion, 6 months, and annually thereafter. Plaque and bleeding indices were recorded at 3 and 6 months and 1 and 3 years following implant insertion. The shapes of papillae were evaluated at implant insertion with the provisional restoration in place, at the insertion of the definitive restoration, and at the 3-year follow-up, using Jemt's papilla index. Life tables and the Mann-Whitney U test were used for statistical analyses. Results: Fifty-six patients were restored with a total of 82 one-piece implants; 47 patients attended the 3-year appointment. One implant had to be removed 1 month postinsertion, giving a cumulative survival rate of 98.8% for the 3-year study period. Most bone resorption (mean, 1.19 ± 1.38 mm; n = 61) occurred during the first year of function, while there was minimal change in mean marginal bone levels between 1 and 3 years (-0.07 ± 1.07 mm; n = 58). Normal peri-implant mucosa was registered for more than 81% of the sites, and no visible plaque was registered for more than 54% of the sites. Conclusion: This prospective 3-year multicenter study showed stable marginal bone levels, good soft tissue health, and a high implant survival rate, supporting the hypothesis that the presented one-piece implant system has the capacity to maintain both hard and soft tissues after the first year of initial bone remodeling. Keywords: bone level, immediate function, one-piece dental implants, soft tissue