The International Journal of Oral & Maxillofacial Implants, 01/2010

Purpose: Mandibular flexure may affect stress distribution in implant-supported fixed partial dentures; however, this factor has been overlooked in most finite element analyses of the mandible. The purpose of this study was to investigate the effect of two different superstructures on stress distribution in mandibular bone during mandibular deformation caused by clenching. Materials and Methods: Threedimensional finite element models consisting of the mandibular bone, six implants, and two- or threepiece superstructures were created. Muscle forces with definite direction and magnitude were exerted over areas of attachment to simulate two static bites of incisal and right molar clenching because, during these clenching tasks, a significant amount of mandibular deformation occurs. The stress analysis was performed using von Misses stress values. Results: During right molar clenching, the two-piece superstructure showed increased stress values. During incisal clenching, the three-piece superstructure inhibited mandibular deformation more than the two-piece superstructure. Conclusions: Mandibular deformation was an important factor in the stress distribution of the models, and it should be considered in the design of implant-supported fixed partial dentures in the mandible. Keywords: finite element, implant, mandibular flexure

Purpose: The aim of the present study was to compare the accuracy of casts obtained from nonsplinted and splinted direct impression techniques employing various splinting materials for multiple dental implants. Materials and Methods: A reference model with four Nobel Replace Select implant replicas in the anterior mandible was fabricated with denture base heat-curing acrylic resin. Impressions of the reference model were made using polyether impression material by direct nonsplinted and splinted techniques. Impressions were divided into four groups: group A: nonsplinted technique; group B: acrylic resin-splinted technique; group C: bite registration addition silicone-splinted technique; and group D: bite registration polyether-splinted technique. Four impressions were made for each group and casts were poured in type IV dental stone. Linear differences in interimplant distances in the x-, y-, and z-axes and differences in interimplant angulations in the z-axis were measured on the casts using a coordinate measuring machine. Results: The interimplant distance D1y showed significant variations in all four test groups (P = .043), while D3x values varied significantly between the acrylic resin-splinted and silicone-splinted groups. Casts obtained from the polyether-splinted group were the closest to the reference model in the x- and y-axes. In the z-axis, D2z values varied significantly among the three test groups (P = .009). Casts from the acrylic resin-splinted group were the closest to the reference model in the z-axis. Also, one of the three angles measured (angle 2) showed significant differences within three test groups (P = .009). Casts from the nonsplinted group exhibited the smallest angular differences. Conclusion: Casts obtained from all four impression techniques exhibited differences from the reference model. Casts obtained using the bite registration polyether-splinted technique were the most accurate versus the reference model, followed by those obtained via the acrylic resin-splinted, nonsplinted, and bite registration addition silicone-splinted techniques. Keywords: accuracy, dental implants, impressions, splinting materials

Purpose: Resonance frequency analysis (RFA) is a quantitative method for the measurement of implant stability. Information about the significance of RFA measurements and the relationship between RFA values and implant osseointegration, success, or failure is important from a clinical point of view. In a previous study the authors observed a strong correlation between RFA values and mineralized boneimplant contact percentage in implants retrieved after 6 months. The aim of the present histologic and histomorphometric study was to determine whether the same correlation existed at earlier time points, specifically in implants retrieved after 4 or 8 weeks. Materials and Methods: Sixteen implants, all with a sandblasted and acid-etched surface, were evaluated in the present study. The implants were retrieved for different reasons after 4 or 8 weeks of healing with a 5-mm trephine bur and immersed in 10% buffered formalin to be processed for histology. Results: A statistically insignificant correlation was detected between RFA values and mineralized bone-implant contact percentage (P = .5502) using the Friedman and Spearman tests. Conclusion: RFA should reflect the bone anchorage of the implant; however, the relationship between bone structure and RFA is not fully understood. Keywords: bone-implant contact, histology, histomorphometry, implant stability

Purpose: To examine the bioactivity of differently aged titanium (Ti) disks and to determine whether ultraviolet (UV) light treatment reverses the possible adverse effects of Ti aging. Materials and Methods: Ti disks with three different surface topographies were prepared: machined, acid-etched, and sandblasted. The disks were divided into three groups: disks tested for biologic capacity immediately after processing (fresh surfaces), disks stored under dark ambient conditions for 4 weeks, and disks stored for 4 weeks and treated with UV light. The protein adsorption capacity of Ti was examined using albumin and fibronectin. Cell attraction to Ti was evaluated by examining migration, attachment, and spreading behaviors of human osteoblasts on Ti disks. Osteoblast differentiation was evaluated by examining alkaline phosphatase activity, the expression of bone-related genes, and mineralized nodule area in the culture. Results: Four-week-old Ti disks showed = 50% protein adsorption after 6 hours of incubation compared with fresh disks, regardless of surface topography. Total protein adsorption for 4-week-old surfaces did not reach the level of fresh surfaces, even after 24 hours of incubation. Fifty percent fewer human osteoblasts migrated and attached to 4-week-old surfaces compared with fresh surfaces. Alkaline phosphatase activity, gene expression, and mineralized nodule area were substantially reduced on the 4-week-old surfaces. The reduction of these biologic parameters was associated with the conversion of Ti disks from superhydrophilicity to hydrophobicity during storage for 4 weeks. UV-treated 4-week-old disks showed even higher protein adsorption, osteoblast migration, attachment, differentiation, and mineralization than fresh surfaces, and were associated with regenerated superhydrophilicity. Conclusions: Time-related degradation of Ti bioactivity is substantial and impairs the recruitment and function of human osteoblasts as compared to freshly prepared Ti surfaces, suggesting a "biologic aging"-like change of Ti. UV treatment of aged Ti, however, restores and even enhances bioactivity, exceeding its innate levels. Keywords: aging, dental implants, osseointegration, photocatalysis, superhydrophilicity

The aims of the present review are (1) to identify essential surface parameters; (2) to present an overview of surface characteristics at the micrometer and nanometer levels of resolution relevant for the four most popular oral implant systems; (3) to discuss potential advantages of nanoroughness, hydrophilicity, and biochemical bonding; and (4) to suggest a hypothetical common mechanism behind strong bone responses to novel implant surfaces from different commercial companies. Oral implants from four major companies varied in average surface roughness (Sa) from 0.3 to 1.78 µm and in the developed surface area ratio (Sdr) from 24% to 143%, with the smoothest implants originating from Biomet 3i and the roughest from Institut Straumann. The original Brånemark turned, machined surface had an Sa of 0.9 µm and an Sdr of 34%, making it clearly rougher than the smoothest implants examined. When evaluated for nanometer roughness, there was a substantial variation in Sa in the different implants from the four major companies. Novel implants from Biomet 3i, AstraTech, and Straumann differed from their respective predecessors in microroughness, physicochemical properties, and nano - roughness. When examined with scanning electron microscopy at high magnification, it was noted that these novel implant surfaces all had particular nanoroughness structures that were not present in their respective predecessors; this finding was suggested as a possible common mechanism behind the demonstrated stronger bone responses to these implants compared to adequate controls. Keywords: osseointegration, surface chemistry, surface microroughness, surface nanoroughness, surface physics

Purpose: To obtain more objective presurgical measurements of clinical interest, this study proposes a new method of measuring and classifying bone density. Materials and Methods: The density of bovine bone blocks of different qualities was first measured in Hounsfield units (HU) using computed tomography (CT). Next, bone cylinders corresponding to each examined area were retrieved. Bone quality was then measured by both histomorphometric microCT and by subjective evaluation of bone quality during drilling. Results: A statistically significant correlation was found between CT and microCT measurements. Based on this evidence, a new method of classifying bone density/quality into three classes of clinical interest was developed: hard/dense, normal, and soft (HNS). These statistical data also enabled the creation of a formula to convert ordinary CT values expressed in HU into bone volume percentages (BV%) to objectively measure bone density based on the HNS system. Conclusion: Stable implant placement depends upon measurements of bone quality/density that are site-specific, objective, and quantitative. To meet these standards, this paper reports an innovative method of classifying bone quality/density and then objectively measuring bone density based on this HNS classification system, using a simple, innovative mathematical formula that converts HU values into measurements of bone volume. Keywords: bone classification, bone density, bone morphometry, bone quality, computed tomography, histomorphometry, microcomputed tomography

Purpose: The purpose of this study was to evaluate rotational, vertical, and canting changes in the position of the rotation-safe component in the implant-abutment assemblies of five different implant systems (ITI, Steri-Oss, Camlog, Astra Tech, and Replace Select) after manual removal and reassembly. Materials and Methods: Prefabricated stainless steel models were used for each implant system, into which six implants were fixated with polymethylmethacrylate resin. Rotation-safe abutments (components) were screwed into the implants according to the manufacturers' specifications. Three test persons with varying knowledge of the theory and practice of implant dentistry manually assembled and reassembled the implant-abutment joint using each system-specific screwdriver 20 times each. A coordinate reading machine was used to detect discrepancies in position after each reassembly in relation to a coordinate system. Rotational freedom, changes in vertical height, and deviations in angulation were assessed. Statistical analysis was performed based on the nonparametric analysis of variance of repeated measurements. Results: The tested complexes showed rotational freedom that ranged from 0.92 to 4.92 degrees, with significant differences between the systems. Camlog was significantly different from all other systems tested regarding rotational freedom, whereas Steri-Oss, Astra Tech, and Replace Select showed no significant difference between each other because of their nondiscrepant mean degree of rotational freedom. Vertical alterations in position ranged from 1 to 83 µm. A statistically significant difference was detected between butt-joint and beveled implant-abutment connections, with ITI and Astra Tech showing no significant difference when compared to each other, but displaying a significant difference versus all other systems tested. Canting discrepancies were not significant, with no influence of implant system or test person clearly detectable. Conclusion: Three-dimensional changes in the location of the abutment in relation to the implant result after manual assembly and reassembly of the implant-abutment complex. Keywords: abutment, dental implant, in vitro study, rotational stability

Purpose: The aim of this study was to evaluate the von Mises, compressive, and tensile stresses occurring on three different zirconia dental implants and surrounding bone with three-dimensional finite element analysis. Materials and Methods: Three different zirconia implants (Z-Systems, Ziterion, and White-Sky), 10 mm in length and 4 mm in diameter, and anterior maxillary bone were modeled using three-dimensional finite element analyses. Zirconia implants were placed into the maxillary left central incisor region. Loading was applied in horizontal and oblique axes (at angles of 90 and 30 degrees with respect to the implant long axes). Oblique loading was 178 N and horizontal loading was 25.5 N. Results: Under oblique loading, von Mises stresses for all implants were similar, and under horizontal loading conditions, the highest von Mises stress was found at the buccal and palatal neck region of the Ziterion implant (46.57 MPa). In cortical bone, the highest von Mises stresses were observed at the buccal region of the Z-Systems implant under oblique and horizontal loading conditions (26.65 MPa and 10.74 MPa, respectively). The highest compressive stresses were observed at the implant buccal neck region and cortical bone interface of the Z-Systems implant under oblique and horizontal loading conditions. For both loading conditions, the highest tensile stress values were observed at the implant palatal region and cortical bone interface of the Z-Systems implant. Conclusion: The von Mises, compressive, and tensile stresses that occurred in cortical bone were higher than those observed in trabecular bone. Generally, the stresses in the Z-Systems implant were higher than in the other zirconia implants. The differences between the stress values occurring on the zirconia implants may be related to the different body and thread designs of these implants. Keywords: compressive stress, dental implants, finite element stress analysis, tensile stress, von Mises stress, zirconia

Purpose: Laser treatment has become a popular method for resolving peri-implantitis, but the full range of its effects on implant surfaces is unknown. The purpose of the present investigation was to analyze the influence of different clinically applicable erbium:yttrium-aluminum-garnet (Er:YAG), carbon dioxide (CO2), and diode laser parameters on titanium surfaces that were either polished or sandblasted, large-grit, acid-etched (SLA). Materials and Methods: Six polished and six SLA titanium disks were irradiated at nine different power settings (n = 54 polished, 54 SLA) with Er:YAG, CO2, or diode lasers. The CO2 and diode lasers were used in continuous wave mode, and the Er:YAG laser was used in a pulsed manner. The surface of each disk was analyzed by scanning electron microscopy and confocal white light microscopy. Each disk was irradiated on six circular areas of 5 mm in diameter with the same specific laser setting for 10 seconds. Results: Within the chosen parameters, the CO2 and diode laser did not cause any visible surface alterations on either the polished or SLA disks. In contrast, both polished and SLA disks showed surface alterations when irradiated with the pulsed Er:YAG laser. The SLA surfaces showed alteration after 10 seconds of irradiation with Er:YAG laser at 300 mJ/10 Hz. The surfaces of the polished disks did not show alteration with the Er:YAG laser until they were irradiated at the higher energy of 500 mJ/10 Hz for 10 seconds. The results of confocal white light microscopy were in agreement with scanning electron micrographs. Conclusion: In contrast to continuous-wave diode and CO2 laser irradiation, pulsed Er:YAG laser irradiation caused distinct alterations with power settings beyond 300 mJ/10 Hz on the SLA surface and 500 mJ/10 Hz on the polished surface. Thus, it is only safe to use the Er:YAG laser for implant surface irradiation with settings no higher than 300 or 500 mJ/10 Hz. Keywords: dental implants, peri-implantitis, scanning electron microscopy, titanium disk

Purpose: To evaluate the potential interaction/contribution of inductive and deleterious effects of tobacco compounds on human osteoblastic cells cultured on plasma-sprayed titanium implants exposed to combinations of nicotine, acrolein, and acetaldehyde. Cell response was assessed as proliferation and function. Materials and Methods: Titanium implants, seeded with human bone marrow-derived cells (first subculture), were cultured in osteogenic-inducing conditions for 28 days in the absence (control) and in the presence of tobacco compounds to assess (1) the dose-dependent profile of acrolein (0.01 to 0.12 mmol/L) and acetaldehyde (0.1 to 6 mmol/L) and (2) the effect of the simultaneous exposure to combinations of nicotine, acrolein, and acetaldehyde. In later experiments, seeded implants were exposed to two different concentrations of nicotine (1.2 mmol/L, known to have inductive effects on cell behavior, and 2.4 mmol/L, reported to elicit deleterious effects on cell behavior) with acrolein, acetaldehyde, or both, at a concentration that inhibits 50% (IC50). Results: Acrolein and acetaldehyde caused dose-dependent inhibitory effects at levels similar to and greater than 0.03 and 0.1 mmol/L, respectively; IC50 regarding cell viability/proliferation and alkaline phosphatase was 0.06 mmol/L for acrolein and 0.3 mmol/L for acetaldehyde. Matrix mineralization was prevented at levels higher than 0.03 mmol/L acrolein and 0.1 mmol/L acetaldehyde. Exposure to a combination of nicotine 1.2 mmol/L with acrolein (0.06 mmol/L), acetaldehyde (0.3 mmol/L), or both resulted in a cell behavior intermediate to that observed in nicotine-treated cultures (induced cell response) and aldehyde- treated cultures (deleterious cell response). On the other hand, exposure to nicotine 2.4 mmol/L with acrolein (0.06 mmol/L), acetaldehyde (0.3 mmol/L), or both caused cumulative cytotoxic responses. Conclusion: Results suggest that interactions of tobacco compounds on osteoblasts might contribute to the overall effects of tobacco use on implant osseointegration and long-time survival. Keywords: acetaldehyde, acrolein, human osteoblastic cells, nicotine, plasma-sprayed titanium implants, proliferation and differentiation

Purpose: The purpose of this study was to evaluate the combination of anorganic bovine bone allograft (ABB) with platelet-rich plasma (PRP) when used in vertical bone augmentation. Materials and Methods: Sixteen healthy 6-month-old female New Zealand rabbits were used in this study. Rabbits were randomly divided into two groups of eight animals each. Created calvarial defects were grafted with ABB or PRP in the first group whereas, in the second group, one cylinder was filled with PRP+ABB and the contralateral cylinder was left ungrafted to be filled by autologous blood (control cylinder). Six weeks after intervention, animals were sacrificed and biopsies were taken. Densitometric, histologic, and histomorphometric analyses were performed to evaluate bone mineral density, vertical bone augmentation, and remaining graft volume, respectively. Statistical analyses were performed with the Mann-Whitney test, using a significance level of P .05. Results: Six weeks after rabbit calvariae were augmented, data analysis revealed that the mixture of PRP and ABB produced twice the vertical bone volume of ABB alone (P .0001). Conclusion: Based upon this study of 16 rabbits, it appears that the combination of ABB with PRP resulted in increased vertical bone augmentation when compared with autologous blood in similarly sized created defects. Keywords: anorganic bovine bone, platelet-rich plasma, titanium cylinder, vertical bone regeneration

Purpose: To compare the bone responses to a pure titanium machined implant surface and one that has been modified by laser etching and microarc oxidation. Materials and Methods: Forty-eight threaded implants with a machined surface were manufactured from rods of commercially pure titanium. The control group consisted of 24 implants with a machined surface. The test group consisted of 24 machined-surface implants that were modified by laser etching and treated by microarc oxidation in an electrolyte solution containing Ca2+ and PO4 3- ions. The implants were analyzed by energy-dispersive x-ray and scanning electron microscopy. Next, the two types of implants were inserted in the tibiae of 12 New Zealand White rabbits; one of the two tibiae received two control implants and the opposite side received two test implants. After 2, 4, and 6 weeks, the rabbits were sacrificed. Prior to sacrifice, all rabbits were injected with fluorescent-labeled achromycin and calcein. Samples were cut and ground for histomorphologic observation, and the mineralization appositional rate and the osseointegration index were measured and analyzed. Results: Proportional spacing craters were found with a diameter of 100 µm and a depth of 80 to 100 µm at intervals of 100 µm around the test surface, and a porous titanium dioxide coating on the surface with pores of 1 to 5 µm in diameter was also produced. Carbon, oxygen, calcium, and phosphonium were detected by electronic probe. The ratio of calcium to phosphonium was 1.418, and the crystal structure of x-ray diffractive patterns indicated pure anatase phases. Compared with the control samples, the mineralization ratio and the osseointegration index of the bone around the test implants were higher (P = .00). Conclusions: The porous titanium dioxide coating produced by laser etching and microarc oxidation treatment improved the bone response versus that seen around machined titanium implants and enhanced the bone formation rate. It was concluded that the surface chemistry and topography, either separately or together, play an important role in the bone response to implants. Keywords: implant, laser, microarc oxidation, osseointegration, rabbit, titanium

Purpose: To compare marginal bone loss, soft tissue conditions, and prosthetic outcomes of implants supporting mandibular and maxillary bar-retained overdentures. Materials and Methods: A total of 124 implants (80 in the mandible and 44 in the maxilla) were placed in 35 patients. Bar-retained overdentures were fabricated for each patient. Prosthetic complications were recorded throughout the study. Plaque, peri-implant inflammation, bleeding, and calculus indices were recorded, and standard periapical radiographs were obtained at each implant site for measurement of marginal bone loss. Results: One implant failed in the mandible prior to prosthesis fabrication and one failed in the maxilla 5 years after prosthesis delivery. Both were replaced after 12 weeks of bone healing. The mean marginal bone loss around maxillary implants was greater than that around mandibular implants. Comparative evaluations of subgroups followed for 5 years and >= 5 years showed that soft tissue parameters were similar for maxillary and mandibular implants. One- and 5-year survival probabilities of the mandibular and maxillary overdentures were comparable. Kaplan-Meier and log-rank tests revealed that the probabilities of retightening of retainer and requirements for occlusal adjustments were higher for mandibular overdentures, whereas other maintenance requirements were comparable. The retainers in mandibular overdentures needed retightening more frequently than the retainers in maxillary overdentures. Conclusions: Dental implants supporting mandibular and maxillary bar-retained overdentures have similar peri-implant soft tissue outcomes and overall prosthetic survival probabilities. Keywords: bar retainer, complication, dental implant, overdenture, prosthodontics, soft tissue

Purpose: The purpose of this study was to examine patient responses to load application on natural teeth and implants using a visual analog scale (VAS). Materials and Methods: Ten subjects were selected from the University of Medicine and Dentistry of New Jersey patient pool who had a single implant-supported crown restoration adjacent to a natural tooth. Vibrational loads of 0.2 N, 0.4 N, and 0.6 N were applied to the tooth and implant-supported crown. The VAS was used to measure the magnitude of sensation. Patient responses were recorded in sets of five alternating paired trials and analyzed for differences in the responses to teeth and implant-supported crowns. Results: Patients were able to discriminate between loads to implants and natural teeth 100% of the time (P = .01). The responses to loading of the implant were less strong than those to loading of the natural tooth 100% of the time (P = .01). However, the VAS score ratios between implant and natural tooth consistently increased with an increase in load. Conclusion: Although periodontal ligament receptors are lacking in the periimplant area, patients appear to have some proprioceptive awareness of implant loading. This awareness becomes more similar to that of natural teeth as the vibrational load is increased. Keywords: dental implants, proprioception, sensation, teeth

Purpose: The use of autogenous block bone grafts in bone regeneration procedures for alveolar ridge augmentation can be limited by donor site morbidity and complications. The purpose of the present study was to evaluate the efficacy of allogeneic corticocancellous iliac block grafts used for ridge augmentation prior to implant placement. Materials and Methods: Forty-one patients with severe ridge volume deficiency underwent augmentation using allogeneic corticocancellous iliac block bone grafts. After rigid fixation of the graft, the site was covered with a freeze-dried allogeneic dura mater membrane, and the wound was closed with tension-free suturing. Implants were placed 3 to 4 months after surgery. Three to 6 months after implant placement, panoramic radiographs were taken and implants were uncovered for prosthetic restoration. Results: Of the 57 grafts placed, one showed 2.5 mm of resorption at the superior buccal aspect of the graft. No other clinical problems were observed. The block grafts were clinically well integrated into the recipient sites and the augmented bone remained stable throughout the implant placement procedures. Of the 84 implants placed, only one failed to integrate. Conclusion: These results demonstrate that the use of allogeneic corticocancellous iliac block bone grafts in conjunction with guided bone regeneration principles is a viable alternative to autogenous grafts in selected patients with alveolar ridge deficiencies. Keywords: allograft, alveolar ridge augmentation, block bone grafts, dental implants, guided bone regeneration, membranes

Purpose: To evaluate prosthetic maintenance requirements for implant-retained/supported overdentures via a review of the literature. Materials and Methods: Using the combined search terms "implant and overdenture," "implant-supported overdenture," "implant-retained overdenture," and "implantanchored overdenture," along with specific inclusion and exclusion criteria, eligible articles between 1997 and 2008 (up to April 1) were retrieved from PubMed, EMBASE, OVID, the Cochrane Library databases, and seven journals by hand-searching. The initial search yielded 3,120 titles, and 287 articles were assigned to full-text analysis. Upon classification of the prosthetic complications with regard to the jaws treated and the attachment systems used, within- and between-group comparative frequency analyses were undertaken with the Kruskal-Wallis test or the Mann-Whitney U test at P .05. Results: A total of 49 articles were included. Within- and between-group evaluations with regard to jaw treated as well as the attachment systems used showed that the frequency of complications did not change over time (P > .05). The differences detected were more matrix replacements after 5 years in the maxilla and mandible and more matrix replacements and patrix fractures after the first year in the mandible (P .05). Among the attachment systems, a dislodged, worn, or loose matrix or its respective housing was more common in the ball-attachment group after the first year (P .05). Prosthetic complications for all types of attachments were comparable (P > .05), except for the differences in peri-implant or interabutment mucosal enlargement rates after 1 year. Conclusions: Prosthetic maintenance requirements for overdentures on both jaws seem to be comparable. The impact of attachment system on the prosthetic outcome is negligible. Keywords: dental implants, frequency analysis, implant-supported overdenture, prosthetic complication

Purpose: The purpose of the present study was to evaluate and compare treatment with mandibular overdentures supported by one or two implants placed and loaded immediately. Materials and Methods: Edentulous subjects with maxillary and mandibular complete dentures were recruited to participate in the study. All subjects received new maxillary and mandibular complete dentures, after which they were scheduled for implant surgery. Using a randomized sampling system, one or two implants were placed in the interforaminal area, and separate ball attachments were connected to the implants. The existing mandibular denture was relined, provided with retentive o-rings, and delivered the day of surgery. Subjects were seen for follow-up examinations after 3, 6, and 12 months, during which marginal bone levels and implant stability were measured. Survival rates were calculated and the data were analyzed statistically. Results: Thirty-six subjects (16 men and 20 women with a mean age of 53.2 years [range, 38 to 69 years]) received 55 implants. Seventeen subjects received one implant in the symphyseal area, and the other 19 received two implants in the canine positions. Ten implants in nine subjects failed during the observation period, and three subjects with two implants each withdrew from the study, resulting in a 12-month implant survival rate of 81.8%. Three subjects lost their only implant and one patient lost both implants. The remaining five subjects lost one of their two implants. Six of the failures occurred during the first month after placement. Conclusion: Immediate loading of one or two separate implants by means of ball attachment-supported mandibular overdentures should be performed with caution, as a higher than expected implant failure rate was observed. No statistically significant differences in failure rates between the two groups were observed. Keywords: dental implant, immediate loading, mandibular overdenture, osseointegration

Purpose: The aim of this study was to evaluate the 1-year success rate and marginal bone loss for dental implants placed simultaneously with bone grafts. Materials and Methods: The study sample comprised 37 patients treated with dental implants placed simultaneous with intraoral block bone grafts. The block grafts were harvested from the chin, retromolar area, or maxillary tuberosity. Complications with the bone grafts were categorized as minor or major and, for the graft success rate, the Barone and Covani criteria were used. The definition of implant success was based on the clinical and radiographic criteria of Albrektsson et al. Peri-implant bone loss was measured after 1 year of prosthetic loading. Results: The study involved 39 bone grafts (17 maxillary and 22 mandibular) and 129 implants (73 implants in grafted areas) in 37 patients. No complications were observed at the donor sites. A part of the onlay bone graft was exposed in eight sites; six sites showed spontaneous reepithelialization following chlorhexidine application, but two grafts became infected and had to be removed. Three implants were lost in the grafted areas; the success rate for implants with simultaneous bone grafting was therefore 95.9%. No complications were found at 12 months after prosthesis placement. The mean overall bone loss after 1 year of loading was 0.64 mm. Conclusion: In patients meeting the inclusion criteria, simultaneous placement of bone grafts and implants shortens treatment time without increasing complications or reducing the success rate. Keywords: alveolar ridge augmentation, bone graft, dental implants, intraoral block bone

Autologous bone graft is considered the gold standard for oral and maxillofacial rehabilitation. The purpose of these case reports is to present the palate as a donor site in the oral and maxillofacial region. A surgical technique of palatal bone grafting with computer-aided design is proposed. Computed tomography and three-dimensional study with a software program (Simplant) were used to evaluate bone quality and quantity at the palatal donor site and also provide a preoperative planning tool for placement of implants. This software was also used to determine the amount of bone needed for the implant site. A palatal marginal incision was made and a full-thickness flap was elevated from the central incisor region to the premolar region. A bone trephine was used to harvest corticocancellous palatal blocks. No swelling or hematomas were found at any donor sites. Simplant software can map the bone within a defined palatal area and provide important information about the quality and quantity of bone in the donor area. Keywords: bone graft, computed tomography, computer-aided design, donor site, palatal graft

Implant restoration in the anterior maxilla is a true challenge for clinicians. Facial tissue recession around the implant prosthesis is one of most difficult situations to correct. This report details the treatment of a female patient who presented with a root fracture of the maxillary left central incisor and crossbite of the left canines. The treatment protocol included implant placement and subsequent orthodontic treatment to correct the crossbite, with the implant used as adjunctive anchorage. However, labial tissue recession around the implant restoration occurred following orthodontic therapy. A resubmerged implant technique with connective tissue grafting for implant coverage was employed. The implant was uncovered again 2 months after the resubmergence treatment and the definitive prosthesis was delivered later. The resulting esthetic defect was restored and a 3-year postgrafting follow- up examination revealed that there was no further marginal tissue recession of the implant restoration. A harmonious soft tissue margin was achieved in the anterior esthetic region. Keywords: dental implants, esthetics, orthodontic anchorage, soft tissue recession