The International Journal of Oral & Maxillofacial Implants, 01/2012

Purpose: Although several investigations of the fit of computer-aided design/computer-assisted manufactured implant restorations have been reported in the literature, very limited information is available on the accuracy of dental scanners for surface data acquisition. The objective of this research project was to investigate the accuracy and repeatability of a three-dimensional noncontact laser scanning system based on conoscopic holography recording the spatial orientation of an implant in vitro. Materials and Methods: One master cast containing five nonparallel implant replicas with scan abutments (implant position locator [IPL], Nobel Biocare) was repeatedly digitized by two commercially available dental scanners and an industrial highprecision coordinate measuring machine as a reference. Repeated measurements of the center point and vector analysis were applied to determine the accuracy and repeatability of IPL orientation. The Wilcoxon signed rank test modified for equivalence was applied to determine whether the systems were equally accurate based on given threshold limits of 0.010, 0.005, and 0.001 mm. Results: All between-system tests identified significant differences, although most differences were very small in absolute terms. Tests for equivalence based on difference windows were exploratorily significant for 0.010 and 0.005 mm. Conclusion: Conoscopic holography scan technology is a valid option to supplement dental touch-probe scanners for laboratory digitization of implant master casts. Keywords: accuracy testing, computer-aided design/computer-assisted manufacture, implant position, laser scanning, scan abutment

Purpose: This study evaluated the effects of abutment height, airborne-particle abrasion, and type of cement on the tensile resistance to dislodgement of cement-retained implant restorations. Materials and Methods: Three groups of 12 standardized abutments each were prepared with different heights (4 mm, 5 mm, and 6 mm) using a milling machine. Crowns were cast in cobalt-chrome using the lost-wax technique, airborne particle-abraded using 50-µm aluminum oxide, and cleaned with acetone. Restorations were cemented using a noneugenol acrylic urethane cement, a resin-modified glass ionomer, or a zinc oxide-noneugenol cement. A 5-kg load was applied for 10 minutes. Samples were kept at 37°C and 100% humidity overnight. A tensile force was applied to the crown using a testing machine at a crosshead speed of 5 mm/minute until failure occurred. Next, the abutments were airborne particle-abraded with 50-µm aluminum oxide, and the cementation and testing procedures were repeated. The effects of cement, abutment height, and surface treatment were evaluated statistically. Results: There were significant differences among the cements. The resin-modified glass ionomer provided the greatest retention in all the tested conditions, while the zinc oxide-noneugenol cement produced the lowest retention values. Significant differences were also detected between 4-mm and 6-mm abutments, with the 6-mm abutments being more retentive. No differences were found between 4-mm and 5-mm abutments or between 5-mm and 6-mm abutments. The effect of airborne-particle abrasion was also found to be significant. A maximum increase of 90 N in retention force was observed after airborne-particle abrasion for the 5-mm abutments cemented with the acrylic urethane cement. Conclusions: Cement, airborne-particle abrasion, and abutment height can significantly influence retention of implant-supported crowns. Different parameters, including those specific to the patient, should be considered in the selection of a luting agent. Keywords: dental abutments, dental air abrasion, dental cements, dental prosthesis retention, surface properties

Purpose: The purpose of this study was to observe and compare any loosening of screws attaching several interchangeable abutments to internally connected implants after cyclic loading. Materials and Methods: Four different abutment groups mated with Straumann single-stage transmucosal implants (n = 7 each group) were assessed: Straumann solid abutment, Restore COC abutment, Neoplant solid abutment, and AVANA solid abutment. Each implant was fixed rigidly in a special holding jig. Abutments were tightened to 35 Ncm with a torque controller. A cyclic load of 150 N at a 30-degree angle to the long axis was applied to the implants for 1 million cycles. Prior to loading, Periotest values (PTVs) were measured. After cyclic loading, PTVs were measured and removal torque values (RTVs) of abutments were measured with a digital torque gauge. Results: No mechanical failures were noted for the Straumann solid abutment or the Restore COC abutment. Six Neoplant abutment screws fractured (86%), and four implants fractured (57%) in the group restored with AVANA solid abutments. The RTVs of the Straumann solid abutment were significantly higher than those of the other abutments. The final mean PTV of the Straumann solid abutment was significantly lower than the final mean PTVs of the other abutments. The final mean PTV (4.76 ± 5.58) was significantly higher than the initial mean PTV (-4.29 ± 0.47). Conclusions: Although different abutments are interchangeable with each other, they possess different chemical compositions and physical characteristics. The use of an abutment and implant manufactured by the same company is recommended to prevent the loosening of the abutment screw. Keywords: abutment, cyclic loading, implant-abutment interface, internally connected implant, removal torque, screw loosening

Purpose: To analyze the vertical dimension of subsinus alveolar bone that is available for placement of endosseous implants. Materials and Methods: Subsinus alveolar bone height (SBH) was determined via radiographs and categorized into three groups: Group A corresponded to SBH 5 mm; group B SBH of 5 to 9 mm; and group C, SBH > 9 mm. Statistical analysis was carried out using the Wilcoxon paired test with the threshold for statistical significance set at P .05. Results: Five hundred eighty-three panoramic radiographs of edentulous maxillae were analyzed. In 96.9% of radiographs, the anterior border of the maxillary sinus was above the first premolar. Mean SBH values for canine, first premolar, second premolar, first molar, and second molar sites were 11.4 ± 6.2 mm, 10.6 ± 3.8 mm, 5.9 ± 2.5 mm, 3.3 ± 2.2 mm, and 4.5 ± 2.4 mm, respectively. Representations of groups A, B, and C in the canine region were 14.3%, 21.4%, and 64.3%, respectively; in the first premolar region they were 8.3%, 22.3%, and 69.4%, respectively; in the second premolar region, these were 31.6%, 60.9%, and 7.5%, respectively; in first molar region, the values were 73.1%, 25.4%, and 1.5%, respectively; and in the second molar region they were 54.2%, 41.7%, and 4.1%, respectively. Conclusions: The mean SBH is the highest in the area of the anterior border of the sinus; it declines significantly toward the posterior maxilla, reaches its minimum in the area of the first molar, and increases again significantly in the second molar region. From a clinical point of view, the lateral window technique of sinus elevation remains the dominant augmentative procedure in the molar area, whereas in the premolar area, less invasive alternative methods may be more appropriate. Keywords: alveolar bone, bone height, dental implants, sinus elevation, sinus pneumatization

Purpose: Accuracy of panoramic radiographs is essential for distance measurements during implant planning, but it might be compromised by various factors. The aim of the present study was to evaluate the effect of vertical and horizontal head positioning on area-dependent enlargement ratios of digital panoramic radiography. Materials and Methods: The mandible of a dry skull was marked with small steel globes. The skull was moved 1 to 4 degrees in 1-degree increments to the left and right and up and down. A series of 17 panoramic radiographs was obtained with the same digital radiographic device. For the rotated skull, horizontal and vertical distances, indicated by the steel globes, were compared to the distances with the ideal positioning of the skull. The results were analyzed statistically. Results: Head positioning and angulation, anatomical site, and distance orientation influenced horizontal measurements. Enlargement ratios of horizontal distances of the right canine and first molar regions (skull rotation to the right 2 to 4 degrees) were significantly lower than those for the corresponding anatomical sites on the left side. Horizontal distance measurements of the different anatomical sites of the left and the right jaw did not differ significantly from each other when the skull was moved downward. When the skull was rotated upward, no significant differences were obtained for corresponding anatomical sites of the right and left arches. Enlargement ratios of vertical distances of different anatomical sites, as well as within the same anatomical site, were not significantly different from each other for the given skull rotations. Conclusions: Ideal head positioning for digital panoramic radiographs is mandatory to avoid improper enlargement ratios of horizontal distances, which can be important in implant dentistry. Keywords: digital radiography, distances, enlargement ratios, head positioning, panoramic radiography

Purpose: This study sought to determine whether the mechanical properties of titanium dental implants changed after exposure to bacteria. Materials and Methods: Two strains of bacteria (Streptococcus sanguinis and Lactobacillus salivarius) were used in the study. The adhesive properties of the two strains were investigated as follows. Titanium implants were placed in bacteria broth, seeded with the two bacteria strains, and left in the broth for 1 or 3 months. Another group of titanium implants was immersed in artificial saliva at 37°C for 3 months. Ten implants in each group were tested in 37°C artificial saliva to evaluate their mechanical flexural strength and fatigue life. Results: The bacterial cultures grew quickly on titanium surfaces. After 1 month of bacteria culture in vitro, the bacteria had produced corrosion pits on the titanium surfaces. After 3 months of bacterial culture, a 7% decrease in the flexural strength of the implant samples and a decrease of 15% in the number of cycles to failure by fatigue were seen versus implants not exposed to bacteria. Conclusions: These results demonstrate that, in physiologic conditions in vitro, bacteria have the capacity to produce a pitting corrosion phenomenon on exposed titanium surfaces, leading to a significant deterioration in the mechanical properties of the implant. It is therefore logical to conclude that bacteria may produce corrosion that reduces the useful life of dental implants. Keywords: corrosion, dental implants, mechanical properties, titanium

Purpose: The aims of this study were to evaluate the trends in funding, geographic origin, and study types of original articles in the dental implant literature and to investigate the relationships among these factors. Materials and Methods: Articles published in Clinical Oral Implants Research, The International Journal of Oral & Maxillofacial Implants, Clinical Implant Dentistry and Related Research, Implant Dentistry, and Journal of Oral Implantology from 2005 to 2009 were reviewed. Nonoriginal articles were excluded. For each article included, extramural funding source, geographic origin, and study type were recorded. Descriptive and analytic analyses (α = .05), including a logistic regression analysis, and chi-square test were used where appropriate. Results: Of a total of 2,085 articles published, 1,503 met the inclusion criteria. The most common source of funding was from industry (32.4%). The proportion of studies that reported funding increased significantly over time. Europe represented the highest percentage (55.8%) of published articles. Most of the articles reported on clinical studies (49.9%), followed by animal studies (25.9%). Articles from Asia and South America and animal and in vitro studies were significantly more likely to be funded. Conclusion: Almost half of the original dental implant articles were funded. The trend toward internationalization of authorship was evident. A strong association was observed between funding and geographic origin and between funding and study type. Most studies in North America and Europe were clinical studies and supported by industry, whereas a greater proportion of studies in Asia and South America were in vitro or animal studies funded through government resources. Keywords: dental implant, funding, internationalization, study type

Purpose: The present study aimed to evaluate and compare two types of implants: grit-blasted and acidetched implants (SLActive) and nanometer-scale hydroxyapatite-modified implants (NanoTite). Materials and Methods: Twenty-two SLActive and 22 NanoTite implants were inserted into the mandibles of 11 beagle dogs. The animals were divided into three groups according to healing time (group A, 2 weeks; group B, 4 weeks; group C, 8 weeks). Resonance frequency analysis (RFA) was performed immediately after implant placement and after 2, 4, and 8 weeks of healing. Two, 4, and 8 weeks after implantation, the animals were sacrificed and the amount of bone surrounding the implants was assessed using microcomputed tomography. Results: For SLActive and NanoTite implants, the RFA values decreased after 2 weeks and increased after 4 and 8 weeks of healing. After 8 weeks, the mean RFA value for SLActive implants was significantly higher than the mean RFA value for NanoTite implants. For the different healing periods, no significant differences in bone volume were seen for SLActive and NanoTite implants. Conclusions: SLActive and NanoTite implants evoked a similar bone response after implantation for 2, 4, and 8 weeks in a nonsubmerged position in the mandibles of dogs. In addition, the data confirmed that RFA is a reliable and noninvasive method to determine dental implant stability and the bone formation process at the clinical level. Keywords: bone volume, dental implant, dog study, resonance frequency analysis, surface modification, titanium

Purpose: Grafting with bone blocks may be required to restore the alveolar process in extremely atrophic maxillae prior to implant placement to ensure both function and esthetics. The present study was conducted to histologically and histomorphometrically evaluate the application of allograft cancellous bone blocks for the augmentation of the anterior atrophic maxilla. Materials and Methods: Consecutive patients with severe atrophy in the anterior maxilla underwent augmentation with cancellous bone block allografts. Bony deficiencies of at least 3 mm horizontally and up to 3 mm vertically according to computed tomographic para-axial reconstructions served as inclusion criteria. After 6 months, implants were placed and a cylindric sample core from the graft area was collected. All specimens were prepared for histologic and histomorphometric examination. Results: Forty patients were included in the study. Eighty-three implants were placed in bone that was augmented with 60 cancellous freeze-dried bone block allografts. The implant survival rate was 98.8%. Mean follow-up was 48 ± 22 months (range, 14 to 82 months). The mean percentage of newly formed bone was 33% ± 18%, that of the residual cancellous block allograft was 26% ± 17%, and marrow and connective tissue comprised 41% ± 2%. Statistically significant histomorphometric differences regarding newly formed bone and residual cancellous block allograft were found between younger ( 40 years) and older (>= 40 years) patients, respectively. Age did not appear to influence the percentage of marrow and connective tissue. Conclusions: Cancellous bone block allograft is biocompatible and osteoconductive, permitting new bone formation following augmentation of extremely atrophic anterior maxillae in a two-stage implant placement procedure. New bone formation was age-dependent. Keywords: anterior atrophic maxilla, augmentation, block allograft, histomorphometry

Purpose: The purpose of this literature review was to investigate the topography of endosseous blood vessels supplying the anterior mandible to prevent complications both during and after oral surgical procedures. Material and Methods: A comprehensive literature search of MEDLINE-PubMed was performed independently for articles describing the anatomical findings of endosseous blood vessels in the anterior part of the mandible. From about 31 related studies, 14 papers were selected based on specific selection criteria. These studies were related to radiologic findings and cadaver studies. Results: There is significant debate concerning the blood vessels supplying the anterior part of the mandible. Hence, in the literature reviewed, no clear consensus was established. There are no reports of severe endosseous bleeding from the mandible during surgical procedures in the symphysis. Based on computed tomographic images, some papers presented an exact intraosseous path of the canals, as well as frequent blood vessel anastomosis in this region. Dissection studies confirmed the presence of sublingual blood vessels penetrating into the bone. Conclusions: The potential risk of bleeding upon perforation of vessels within the bone needs to be evaluated to avoid such complications. The management of intraoperative surgical problems is of significance. Keywords: anterior mandible, complications, lingual artery

Purpose: The purpose of this study was to evaluate the healing of an injectable mixture of nanoparticles of magnesium-enriched hydroxyapatite (mHA) in peri-implant defects. Materials and Methods: Thirty-two dental implants were placed in 16 tibiae of eight female Large White pigs. In each animal, four implant beds (two sites each tibia) with medial three-wall intrabony defects were prepared. Via random selection, one bone defect in each tibia was filled with injectable mHA putty (n = 16, test group), whereas the other defect was not filled (n = 16, control group). Two animals were sacrificed after 2 weeks, two after 4 weeks, two after 6 weeks, and two after 8 weeks. In all, 32 block section samples were obtained for histologic and histomorphometric analyses. Results: The test group exhibited statistically significantly higher values for bone-to-implant contact (BIC) and lower amounts of connective tissue (CT) over time. The test group showed a remarkable increase in vital bone values between 6 and 8 weeks after implant placement. After 8 weeks, the injectable mHA was almost completely resorbed. Conclusions: Injectable mHA putty could be a useful and suitable bone grafting material in peri-implant defects. Keywords: animal study, bone graft, hydroxyapatite, magnesium-enriched hydroxyapatite, peri-implant defect

Purpose: The purpose of this systematic review was to assess the incidence and types of biologic and technical complications associated with implant-supported fixed complete dental prostheses (IFCDPs) for edentulous patients. Materials and Methods: An electronic MEDLINE/PubMED search was conducted to identify randomized controlled clinical trials and prospective cohort studies with IFCDPs for edentulous patients. Reports with at least 5 years of follow-up after prosthesis insertion were selected. Pooled data were analyzed statistically, and the cumulative complication rates were calculated by meta-analysis and regression. Results: Of a total of 281 one-piece IFCDPs (mean exposure time of 9.5 years) and 653 complication events, the complication rate was estimated at 24.6% per 100 restoration-years. The cumulative rates of "prosthesis free of complications" after 5 and 10 years were 29.3% and 8.6%, respectively. The most common implantrelated biologic complication was peri-implant bone loss (> 2 mm), at rates of 20.1% after 5 years and 40.3% after 10 years. The most frequent implant-related technical complication was screw fracture, yielding a 5-year complication rate of 10.4% and a 10-year rate of 20.8%. The most frequent prosthesis-related biologic complication was hypertrophy or hyperplasia of tissue around the IFCDPs (13.0% and 26.0% after 5 and 10 years, respectively). The most common prosthesis-related technical complication reported with IFCDPs was chipping or fracture of the veneering material (33.3% at 5 years and 66.6% at 10 years). Conclusion: Biologic and technical complications after the placement of IFCDPs occur continuously over time as a result of fatigue and stress. These events may not lead to implant/prosthetic failures, but they are significant in relation to the amount of repair and maintenance needed, time, and cost to both the clinician and patient. Keywords: biologic complications, edentulism, implant-supported full-arch prosthesis, technical complications

Purpose: To compare differences between restoratively projected and surgically acceptable virtual implant positions at sites identified by cylindric radiopaque markers on diagnostic templates for implant-retained mandibular overdentures using cone beam computed tomography (CBCT). Materials and Methods: A retrospective chart audit of a CBCT database identified 77 subjects who had been imaged to assess the residual alveolar ridge in the completely edentulous mandible prior to implant placement for mandibular overdentures. Individuals had been scanned with a diagnostic template using cylindric markers to identify the restoratively derived locations and trajectories for implants. Qualitative and quantitative differences between restoratively projected and surgically acceptable positions on transaxial CBCT images were recorded using implant planning software based on a standard implant. Results: Only 6.4% of restoratively projected positions were within the criteria for surgically acceptable implant placement. However, most implant placement plans (77.9%) could be modified to fulfill surgically acceptable criteria. Of the projected implant positions, 15.7% were deemed inadvisable because of potential anatomical complications. Restoratively projected implant position was more likely to deviate buccally than lingually to the available residual alveolar ridge, as determined by CBCT. The mean angular deviation of the clinical prediction from ideal was 14.0 ± 5.5 degrees, the mean platform translation was 2.1 ± 1.3 mm, and the mean apex translation was 2.3 ± 1.5 mm. The average residual alveolar ridge reduction required in the posterior segment was 3.9 ± 2.5 mm. Conclusion: The restoratively projected trajectory for implant placement determined by visual inspection, diagnostic casts, and panoramic radiography deviated from the surgically acceptable location determined using CBCT data sets. Keywords: cone beam computed tomography, dental implants, dental prosthesis, edentulous jaw

Purpose: This study aimed to microradiographically evaluate the healing of grafted defects using a surgically standardized model that was suitable for comparing the regenerative potential of different grafts. Materials and Methods: Two different biomaterials, bovine porous bone mineral (BPBM) and nanohydroxyapatite (NHA), were used to fill defects produced in the distal epiphyses of 10 adult male rabbits for 2 and 4 months. Three rabbits were left untreated, without defects, as controls. Evaluations were performed on microradiographs of sections of polymethyl methacrylate-embedded rabbit epiphyses. The amounts of graft material and bone were evaluated by splitting the filled hole into three portions. Results: A greater amount of BPBM granules were in contact with bone at both 2 and 4 months versus the NHA (statistically significant difference in the central portion of the defect), and a persistence of the BPBM over time was apparent. The amount of NHA decreased from the inner to the outer portion of the defect, particularly after 4 months. The bone amount increased from the inner to the outer portion, particularly for the NHA graft, which produced an early cortex. The amount of mineralized material reached about 80% in the BPBM and 40% to 60% in the NHA after 4 months. Conclusion: Both the analyzed biomaterials performed adequately for bone regeneration. The two biomaterials are probably suitable for grafting defects related to early cortical formation or spacemaintaining clinical requirements. Keywords: bone regeneration, bovine porous bone mineral, microradiography, nanohydroxyapatite, rabbit femur

Purpose: To evaluate the accuracy of a newly developed open-source system for three-dimensional dental implant planning and fully guided dental implant placement. Materials and Methods: Forty-eight implant positions were planned for eight partially edentulous anatomical patient equivalent models with an opensource implant planning system on the basis of cone beam computed tomography (CBCT) scans. The virtual software planning leads to an output of four different coordinates for each implant position; with these, surgical guides were manufactured using a coordinate-transfer apparatus. During the surgical simulation, drills and implants were fully guided as they were inserted by means of the harmonized components of the vendor's sleeve-in-sleeve system. After follow-up CBCT investigation and reference marker-based software registration, linear horizontal, vertical, and maximal 3D deviations, as well as angular deviations, between the virtual planning data and the surgical results were calculated. Results: The mean three-dimensional deviation values for the final implant positions were 671 µm (95% confidence interval [CI] 452 to 891 µm) at the implant base and 808 µm (95% CI 646 to 971 µm) at the implant tip. Mean vertical deviations were 273 µm (95% CI 200 to 345 µm). Mean angular deviations of 1.9 degrees (95% CI 1.4 to 2.4 degrees) were measured. Conclusions: The open-source implant planning system described in this study demonstrated a level of accuracy that is equal or superior to most descriptions of the literature on computer-aided implant dentistry, allows for predictable implant positioning, and has the potential to reduce postoperative impairment versus conventional implant insertion. Keywords: computer-aided implant placement, computer-aided surgery, cone beam computed tomography, implant dentistry, surgical templates

Purpose: The aim of this study was to systemically review the effect of platform switching on preserving implant marginal bone. Materials and Methods: An electronic search (PubMed and MEDLINE databases) and a hand search of peer-reviewed journals for English-language articles published before June 30th, 2010, were performed. The selected articles included randomized controlled trials (RCTs) and prospective comparative clinical trials with a minimal sample size of 10 subjects and 10 implants followed for at least 1 year after loading. The quality of included RCTs was also assessed. Results: Nine studies met the inclusion criteria; three were prospective comparative studies and six were RCTs. All studies applied either standardized conventional or digital periapical radiographs for the assessment of bone levels. Seven of the nine included articles demonstrated that platform switching was effective in preserving marginal bone around implants. The longest follow-up among these studies was 5 years. Conclusions: Based on the current evidence, the use of abutments with a smaller diameter than their corresponding implant platforms seems to exert beneficial effects on peri-implant marginal bone. Some potential confounding factors, for example, the apicocoronal position of implants in relation to crestal bone, the presence of various implant microtextures, the degree of platform switch, and the reliability of examination methods, should be considered when interpreting the present results. Keywords: crestal bone loss, dental abutments, dental implants, implant design, marginal bone loss, mismatching abutments, platform switch

Purpose: The principle of guided tissue and bone regeneration has long been established for treating bone and periodontal defects. In addition to nonabsorbable barriers, various collagens have become accepted as membrane materials for separating the graft from soft tissue. However, collagen membranes differ significantly in their barrier function and biocompatibility. The objective of this pilot study was to examine, in vitro and in vivo, a novel native collagen membrane extracted from porcine pericardium. Materials and Methods: The morphologic structure of two different native collagen membranes (Remotis, Thommen Medical; Bio-Gide, Geistlich Biomaterials) was examined using a scanning electron microscope. For biocompatibility testing, membranes were incubated with SaOs-2 osteoblastlike cells. After 2 hours, 3 days, and 7 days, proliferation of the cells on the membranes was determined. Evaluation of the biodegradation pattern was performed in a dog model with simultaneous bone augmentation with Bio-Oss (Geistlich Biomaterials) or Cerabone (Botiss Biomaterials) in the lateral anterior maxilla in eight animals with histologic examination after 4, 8, 12, and 24 weeks. Results: An interconnective pore system was identifiable for Remotis, while Bio-Gide displayed a more fibrous structure. In vitro, Remotis showed considerable cell proliferation, which was significantly superior to that observed with Bio-Gide, especially after 7 days (2,910 ± 1,273 and 707 ± 706, respectively). In vivo, both membranes integrated into the surrounding tissue without any inflammatory reaction. Both membranes allowed early vascularization. However, considerable biodegradation was noted within 4 to 8 weeks with Bio-Gide, while Remotis resorbed generally within the first 8 to 12 week. Both membranes supported underlying bone formation. Conclusion: Both examined membranes indicate a high level of biocompatibility. Both are resorbed without inflammation within 8 weeks (Bio-Gide) or 12 weeks (Remotis). The compact interconnective pericardium collagen of Remotis may have stabilized the resorption process. Keywords: biodegradation, collagen membrane, guided bone regeneration, guided tissue regeneration, pericardium

Purpose: The long-term neuromuscular status of edentulous patients with severe mandibular atrophy who wore complete dentures (CDs) or implant-supported overdentures (ISOs) was investigated in the present study. Materials and Methods: Eleven CD patients and 11 patients with ISOs supported by two implants took part in the study. All patients had used their dentures for more than a decade. All patients (average age, 76 years) suffered from severe mandibular atrophy, which was to be quantified using panoramic radiographs and computer software. Kinesiographic parameters such as opening and extension movements as well as opening and closing velocities were recorded by means of a sirognathograph during test food chewing on the left and right sides. Simultaneously, electromyographic recording of masseter and temporalis activities was performed using surface electrodes. Results: The kinesiographic values obtained from ISO patients were higher than those for CD patients: 12.65 mm for vertical opening (CD, 11.79 mm) and 5.66 mm for horizontal extension (CD, 5.11 mm). Opening velocity values were 100.93 mm/s and 91.74 mm/s, respectively. Closing velocity of 78.16 mm/s in ISO patients was significantly different from that measured in CD patients (58.45 mm/s). With regard to electromyographic activities, the increase was significant for the masseter during chewing on the working side (ISO: 189.79 µV, CD: 78.05 µV) and on the nonworking side (ISO: 130.53 µV, CD: 47.25 µV). For the temporalis, values of 194.11 µV and 119.02 µV in the ISO and CD patients, respectively, were observed for working side chewing. Nonworking side values reached 155.48 µV for ISO subjects and 78.35 µV for CD subjects, which was significantly different. The degree of atrophy in both groups did not differ statistically. Conclusions: The use of two interforaminal implants with an overdenture can provide long-term neuromuscular benefits for edentulous patients. Keywords: complete denture, electromyography, implant overdenture, neuromuscular activity, sirognathograph

Purpose: To determine the change in stability of three different implant systems using resonance frequency analysis (RFA) and to correlate RFA measurements with factors related to implant design, length, and diameter, patient gender, and dental arch. Clinical and radiologic evaluations were performed up to 1 year after loading. Materials and Methods: Three different types of implants from three different manufacturers were inserted in the posterior maxilla and mandible. RFA measurements were performed at implant placement and weekly up to 8 weeks postoperatively and were compared with respect to implant type, length, and diameter and dental arch. The implants were loaded after 8 weeks. All implants were examined radiographically at baseline and at 6 and 12 months. Plaque Index, Sulcus Bleeding Index, peri-implant probing depths, and marginal bone loss were recorded. Repeated-measurements analysis of variance, twotailed mixed-model analysis of variance, the Least Significant Differences and Mann-Whitney U tests were used for statistical analyses. Results: All the groups showed high stability values at all time points (above 71). There were statistically significant differences between groups at all time points except 1 and 2 weeks. Mandibular implants showed statistically higher stability values than maxillary implants. Wide implants showed statistically higher stability values than narrow implants. Mean marginal bone loss was 0.22 ± 0.47 mm after 1 year. Conclusions: All three implant systems showed clinically acceptable stability values prior to early loading. The success rates and bone loss were similar to the values reported in the literature. Keywords: early loading, implants, implant stability, resonance frequency analysis

Purpose: This 1-year prospective study evaluated the implant success rate and peri-implant tissue response of narrow (3.0 mm) implants that were immediately provisionalized at maxillary and mandibular incisor sites. Materials and Methods: Immediate provisionalization of single 3.0-mm diameter implants was performed in patients who fulfilled the inclusion/exclusion criteria. Implant success, marginal bone level (MBL), marginal bone level change (MBLC), Periotest value (PTV), modified Plaque Index, modified Bleeding Index, and Papilla Index Score (PIS) were evaluated immediately after implant placement and at 3, 6, and 12 months after surgery. All surgical and prosthetic complications were recorded. The data were analyzed statistically at a significance level of α =.05. Results: Seventeen implants were immediately provisionalized in 13 patients with missing maxillary lateral incisor(s) and/or mandibular incisor(s). The implant success rates at 1 year were 100% (17/17). The mean MBL values at 0, 3, 6, and 12 months were -0.03 ± 0.06 mm, -0.28 ± 0.35 mm, -0.28 ± 0.32 mm, and -0.38 ± 0.36 mm, respectively. The mean MBLC from 0 to 12 months was -0.35 ± 0.35 mm. The mean PTV at 3 months (-2.65) was significantly lower than that at baseline (-1.59). No significant differences in plaque or bleeding indices were observed over time. A slight but significant increase in PIS over time indicated that the implant papillae were stable and well maintained. All complications were prosthetically related (seven fractured provisionals, two debonded provisionals, three loosened provisional abutment screws) and occurred within the first 3 months after surgery. Conclusions: This 1-year prospective study showed a favorable implant success rate and peri-implant tissue response with immediately provisionalized 3.0-mm diameter implants replacing single missing maxillary and mandibular incisors. While prosthetic complications during the provisional phase were common, they were easily resolved without further consequences. Keywords: dental implant, immediate provisionalization, narrow implant, peri-implant tissue response, prospective study

Purpose: A key challenge in implant treatment in the esthetic zone is to provide patients with crowns and peri-implant mucosa that are in harmony with the adjacent teeth to restore both function and esthetics. The aim of the present study was to show the preliminary results of an immediate loading protocol in the maxillary esthetic zone that is designed to preserve the soft tissue. Materials and Methods: Patients were treated with immediately loaded single-tooth implants (Seven, MIS). Implants were inserted in fresh postextraction sites or in single edentulous sites with clinically and radiologically healed bone. After 8 weeks of loading, the provisional crowns and abutments were modified as needed to enhance the esthetics of the gingival margins. Definitive restorations were delivered 4 to 6 months postoperatively. Results: Seventy patients were treated; 25 implants were placed in fresh extraction sites, and the remaining 45 implants were inserted in healed single edentulous sites. All implants were stable, and radiographs showed complete osseointegration after 1 year of functional loading. Conclusions: The present study shows promising results for immediate loading of single implants. All implant sites fulfilled success criteria in terms of function and esthetics, and particularly promising results were seen following additional adjustments of the provisional restorations to preserve interdental papillae. Keywords: dental implants, immediate functional loading, provisional crown, single-tooth restoration

Purpose: The purpose of this pilot study was to apply resonance frequency analysis (RFA) to measure the clinical stability of craniofacial implants and compare the RFA measurements over a 12-month period. Materials and Methods: Patients with auricular or orbital defects were treated with prostheses retained by two or three implants. After healing periods of 3 months for auricular implants and 6 months for orbital implants, prostheses were fabricated. RFA measurements were performed immediately after implant placement, at abutment connection, and at 6 and 12 months. All stability measurements were repeated three times for each implant, and the mean value was used for analyses. For measurements performed after prosthesis delivery, connecting bars and abutments were removed prior to RFA. The stability of both types of implants was compared at different time intervals. Results: Fifty-four implants were placed in 10 patients with auricular defects (26 implants) and 10 patients with orbital defects (28 implants). All auricular implants survived, and four orbital implants in four different patients failed. For auricular implants, statistically significant differences in stability values were noted between implant placement, abutment connection, and 6 months; there was no significant difference between 6 and 12 months. For orbital implants, no significant differences were found between implant placement and abutment connection, a significant increase was observed at 6 months, and no significant difference was seen between 6 and 12 months. No significant differences were found for auricular versus orbital implants between placement and abutment connection, but auricular implants showed significantly higher stability values than orbital implants at 6 and 12 months. Conclusions: The stability of surviving auricular and orbital implants increased with time according to RFA. Prior to failure, the failed implants showed RFA values that were below the mean. Keywords: craniofacial implant, implant stability, resonance frequency analysis

Purpose: While immediate implant placement has demonstrated a high degree of clinical success, questions remain about whether immediate placement of implants into sites demonstrating periapical pathology will result in treatment outcomes equivalent to those attained when implants are placed into sites that do not demonstrate periapical pathology. Materials and Methods: A retrospective study was carried out of patients who presented with periapical pathology and were treated with tooth extraction, defect debridement, and immediate implant placement between 1994 and 2008. All immediately placed implants were followed for a minimum of 24 months after restoration. Implant survival was assessed with the Albrektsson et al criteria and using measurements from the osseous crest to the most coronal extent of the rough surface of the implant on the midbuccal aspect of the implant. A classification system for periapical lesion morphology is also proposed. Results: Four hundred eighteen implants were placed. They were followed for a mean of 67.3 months. Five implants were either lost or demonstrated progressive bone loss beyond acceptable levels, resulting in a cumulative survival rate of 97.8%. Conclusions: Implant placement at the time of extraction of teeth demonstrating periapical pathology will result in implant survival rates comparable to those of implants placed immediately into sites without periapical pathology. Keywords: dental implants, immediate implants, periapical lesions

Purpose: To analyze the risk factors associated with the survival of self-threading implants placed with the ridge expansion technique using self-tapping osteotomes after at least 24 months. Materials and Methods: This retrospective study followed patients for at least 2 years in whom implants had been inserted by means of the ridge expansion technique. The patient was taken as the unit of analysis, and the loss of any implant as a result of mobility at any time during the follow-up period was considered as a failure. A number of patient variables were recorded: sociodemographic (age/sex), anatomical (bone quantity/quality, expansion zone), infection history (prior antibiotic therapy for active infection), prosthodontic (type of provisional prosthesis and type of definitive rehabilitation), and surgical (number of surgical stages, the use of biomaterials or atraumatic maxillary sinus elevation). Risk factors were expressed as values of relative risk (RR) and the odds ratio. Results: Seventy-four patients (157 implants) were followed over a mean period of 38.8 ± 7.7 months. Most patients (91.9%) did not lose any implants, and failures occurred mainly after implant loading (5.4%). Sociodemographic factors (sex and age) were not associated with a significant risk of implant failure. However, the existence of previous local infection (RR = 34.0), the use of an immediate fixed provisional prosthesis (RR = 15.0), and type D3 bone (RR = 5.1) were seen to be the main risk factors involved in this technique for the period assessed. Conclusions: The risk of failure when implants are placed using self-tapping osteotomes was highest in patients who had active local infection; immediate provisionalization and less dense bone were also associated with additional risk of failure. Keywords: alveolar atrophy, dental implants, ridge expansion technique, risk factors

Purpose: There has been considerable controversy about the placement of barrier membranes over osteotomy and graft sites in sinus bone grafts via the lateral window approach. Particularly when the sinus membrane remains intact, clinicians should consider the benefits and costs of a barrier membrane. This article presents clinical and radiologic findings following repositioning of a detached bony window without a barrier membrane in the lateral approach for maxillary sinus bone grafts. Materials and Methods: After a complete 360-degree osteotomy on the lateral maxillary wall, a bony window was outfractured and separated from the sinus membrane by gentle elevation. After the sinus membrane was confirmed to be intact, grafting was carried out and the bony window was repositioned over the graft material without rigid fixation or a barrier membrane. Clinical and radiologic examinations were performed 6 months postoperative. The relationships between the patterns of gap bone healing, number of implants, time of implant placement (simultaneous with grafting or staged), and thickness of the lateral sinus wall were analyzed. The Fisher exact test and Spearman nonparametric correlation coefficient were employed for statistical evaluation. Results: All 23 included patients experienced no complications. Overall external cortical healing and bone regeneration in the gap between the repositioned window and the lateral wall of the sinus were satisfactory. No significant differences in the patterns of gap bone healing were found, with respect to the number of implants placed or time of implant placement. As the lateral sinus wall was thinner, gap bone healing was better. To date, no implants have failed. Conclusion: A detached bony window that is repositioned on graft material might function as a barrier membrane in the lateral approach for maxillary sinus bone grafts. Keywords: bone grafting, dental implants, maxillary sinus, membranes

Purpose: This study aimed to evaluate the effect of the placement of wide-diameter implants on bone stress concentrations and marginal bone loss in the first molar region. Study hypotheses held that increasing implant diameter would decrease peri-implant bone stress levels, but that statistically significant reductions in clinical bone loss would either (1) not be observed for any implant diameter or (2) be observed only for the widest implant diameter. Materials and Methods: Three-dimensional finite element analysis (3D FEA) was used to analyze the relationship between implant diameter and peri-implant bone thickness, cortical bone thickness, occlusal load direction, and percentage of boneto-implant contact on bone stress levels in the first molar region. A retrospective review of patient records was also conducted in three private practices to assess clinical outcomes and bone level changes around one implant design in three diameters (3.7, 4.7, and 6.0 mm) placed in first molar locations. Categorical variable summaries and comparisons of 3D FEA and clinical findings were made using the FREQ procedure, t test procedures (Student t tests, folded F tests, Satterthwaite t tests), and the NONPAR1WAY procedure (Wilcoxon nonparametric test). Results: Cumulative implant success was 98.4% and survival was 98% after a mean of 49.2 months. Although increasing implant diameter always reduced peri-implant stress concentrations in 3D FEA experiments, clinically, only 6.0-mm implants exhibited a statistically significant reduction in bone loss (0 mm) as compared to 3.7-mm and 4.7-mm implants. Conclusion: Only 6.0-mm implants were effective in reducing marginal bone loss in the first molar region. 3D FEA results supported previous clinical findings that maintaining approximately 1.8 mm of buccal plate thickness can help reduce bone stress concentrations and preserve buccal bone height. A history of periodontitis may adversely affect long-term marginal bone stability. Keywords: bone, dental implant, implant diameter, molar, stress