Publication Bias in Five Dental Implant Journals: An Observation from 2005 to 2009

Purpose: This study evaluated possible publication bias and its related factors in implant-related research over time. Materials and Methods: Articles published in Clinical Implant Dentistry and Related Research, Clinical Oral Implants Research, Implant Dentistry, Journal of Oral Implantology, and The International Journal of Oral & Maxillofacial Implants between 2005 and 2009 were reviewed. Nonoriginal articles were excluded. For each article included, study outcome, extramural funding source, type of study, and geographic origin were recorded. Descriptive and analytic statistics (alpha = .05), including the chi-square test and logistic regression analysis, were performed where appropriate. Results: From a total of 2,085 articles, 1,503 met the inclusion criteria. of the articles analyzed, 1,226 (81.6%), 160 (10.6%), and 117 (7.8%) articles reported positive, negative, and neutral outcomes, respectively. In vitro studies, studies from Asia, and funded animal studies were more likely to report positive outcomes compared to others (P = .02, P < .0001, and P = .009, respectively). Industry-funded studies represented the lowest frequency of positive outcomes versus studies funded by other sources. Conclusions: There were a high number of implant-related studies reporting positive outcomes in the five selected journals. Some selected factors were associated with positive outcome bias. In general, funding was not associated with a positive outcome, except for animal studies. Industry-supported research did not show any association with the publication of positive outcomes. INT J ORAL MAXILLOFAC IMPLANTS 2011;26:1024-1032

Platform Switching: Biomechanical Evaluation Using Three-Dimensional Finite Element Analysis

Purpose: The objective of this study was to evaluate, using three-dimensional finite element analysis (3D FEA), the stress distribution in peri-implant bone tissue, implants, and prosthetic components of implant-supported single crowns with the use of the platform-switching concept. Materials and Methods: Three 3D finite element models were created to replicate an external-hexagonal implant system with peri-implant bone tissue in which three different implant-abutment configurations were represented. In the regular platform (RP) group, a regular 4.1-mm-diameter abutment (UCLA) was connected to regular 4.1-mm-diameter implant. The platform-switching (PS) group was simulated by the connection of a wide implant (5.0 mm diameter) to a regular 4.1-mm-diameter UCLA abutment. In the wide-platform (WP) group, a 5.0-mm-diameter UCLA abutment was connected to a 5.0-mm-diameter implant. An occlusal load of 100 N was applied either axially or obliquely on the models using ANSYS software. Results: Both the increase in implant diameter and the use of platform switching played roles in stress reduction. The PS group presented lower stress values than the RP and WP groups for bone and implant. In the peri-implant area, cortical bone exhibited a higher stress concentration than the trabecular bone in all models and both loading situations. Under oblique loading, higher intensity and greater distribution of stress were observed than under axial loading. Platform switching reduced von Mises (17.5% and 9.3% for axial and oblique loads, respectively), minimum (compressive) (19.4% for axial load and 21.9% for oblique load), and maximum (tensile) principal stress values (46.6% for axial load and 26.7% for oblique load) in the peri-implant bone tissue. Conclusion: Platform switching led to improved biomechanical stress distribution in peri-implant bone tissue. Oblique loads resulted in higher stress concentrations than axial loads for all models. Wide-diameter implants had a large influence in reducing stress values in the implant system. INT J ORAL MAXILLOFAC IMPLANTS 2011;26:482-491

A comparison of profilometer and AutoCAD software techniques in evaluation of implant angulation in vitro

Purpose: The aim of this study was to compare 2 different methods of assessment of implants at different inclinations (90 degrees and 65 degrees)-with a profilometer and AutoCAD software. Materials and Methods: Impressions (n = 5) of a metal matrix containing 2 implants, 1 at 90 degrees to the surface and 1 at 65 degrees to the surface, were obtained with square impression copings joined together with dental floss splinting covered with autopolymerizing acrylic resin, an open custom tray, and vinyl polysiloxane impression material. Measurement of the angles (in degrees) of the implant analogs were assessed by the same blinded operator with a profilometer and through analysis of digitized images by AutoCAD software. For each implant analog, 3 readings were performed with each method. The results were subjected to a nonparametric Kruskal-Wallis test, with P <= .05 considered significant. Results: For implants perpendicular to the horizontal surface of the specimen (90 degrees), there were no significant differences between the mean measurements obtained with the profilometer (90.04 degrees) and AutoCAD (89.95 degrees; P=.9142). In the analyses of the angled implants at 65 degrees in relation to the horizontal surface of the specimen, significant differences were observed (P=.0472) between the mean readings with the profilometer (65.73 degrees) and AutoCAD (66.25 degrees). Conclusions: The degrees of accuracy of implant angulation recording vary among the techniques available and may vary depending on the angle of the implant. Further investigation is needed to determine the best test conditions and the best measuring technique for determination of the angle of the implant in vitro.

Effect of Metal-Ceramic or All-Ceramic Superstructure Materials on Stress Distribution in a Single Implant-Supported Prosthesis: Three-Dimensional Finite Element Analysis

Purpose: This three-dimensional finite element analysis study evaluated the effect of different material combinations on stress distribution within metal-ceramic and all-ceramic single implant-supported prostheses. Materials and Methods: Three-dimensional finite element models reproducing a segment of the maxilla with a missing left first premolar were created. Five groups were established to represent different superstructure materials: GP, porcelain fused to gold alloy; GR, modified composite resin fused to gold alloy; TP, porcelain fused to titanium; TR, modified composite resin fused to titanium; and ZP, porcelain fused to zirconia. A 100-N vertical force was applied to the contact points of the crowns. All models were fixed in the superior region of bone tissue and in the mesial and distal faces of the maxilla section. Stress maps were generated by processing with finite element software. Results: Stress distribution and stress values of supporting bone were similar for the GP, GR, TP, and ZP models (1,574.3 MPa, 1,574.3 MPa, 1,574.3 MPa, and 1,574.2 MPa, respectively) and different for the TR model (1,838.3 MPa). The ZP model transferred less stress to the retention screw (785 MPa) than the other groups (939 MPa for GP, 961 MPa for GR, 1,010 MPa for TP, and 1,037 MPa for TR). Conclusion: The use of different materials to fabricate a superstructure for a single implant-supported prosthesis did not affect the stress distribution in the supporting bone. The retention screw received less stress when a combination of porcelain and zirconia was used. Int J Oral Maxillofac Implants 2011;26:1202-1209

Three-Dimensional Finite Element Analysis of Vertical and Angular Misfit in Implant-Supported Fixed Prostheses

Purpose: Three-dimensional finite element analysis was used to evaluate the effect of vertical and angular misfit in three-piece implant-supported screw-retained fixed prostheses on the biomechanical response in the peri-implant bone, implants, and prosthetic components. Materials and Methods: Four three-dimensional models were fabricated to represent a right posterior mandibular section with one implant in the region of the second premolar (2PM) and another in the region of the second molar (2M). The implants were splinted by a three-piece implant-supported metal-ceramic prosthesis and differed according to the type of misfit, as represented by four different models: Control = prosthesis with complete fit to the implants; UAM (unilateral angular misfit) = prosthesis presenting unilateral angular misfit of 100 pm in the mesial region of the 2M; UVM (unilateral vertical misfit) = prosthesis presenting unilateral vertical misfit of 100 pm in the mesial region of the 2M; and TVM (total vertical misfit) = prosthesis presenting total vertical misfit of 100 pm in the platform of the framework in the 2M. A vertical load of 400 N was distributed and applied on 12 centric points by the software Ansys, ie, a vertical load of 150 N was applied to each molar in the prosthesis and a vertical load of 100 N was applied at the 2PM. Results: The stress values and distribution in peri-implant bone tissue were similar for all groups. The models with misfit exhibited different distribution patterns and increased stress magnitude in comparison to the control. The highest stress values in group UAM were observed in the implant body and retention screw. The groups UVM and TVM exhibited high stress values in the platform of the framework and the implant hexagon, respectively. Conclusions: The three types of misfit influenced the magnitude and distribution of stresses. The influence of misfit on peri-implant bone tissue was modest. Each type of misfit increased the stress values in different regions of the system. INT J ORAL MAXILLOFAC IMPLANTS 2011;26:788-796

Evaluation of the Effect of Retightening and Mechanical Cycling on Preload Maintenance of Retention Screws

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Finite Element Stress Analysis of Edentulous Mandibles with Different Bone Types Supporting Multiple-Implant Superstructures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Trends in Funding, Internationalization, and Types of Study for Original Articles Published in Five Implant-Related Journals Between 2005 and 2009

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 (alpha = .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. INT J ORAL MAXILLOFAC IMPLANTS 2012;27:69-76

Utilization of autogenous bone, bioactive glasses, and calcium phosphate cement in surgical mandibular bone defects in Cebus apella monkeys

Purpose: the purpose of the present study was to evaluate the histologic results of bone cavities that were surgically created in the mandibles of Cebus apella monkeys and filled with autogenous bone, PerioGlas, FillerBone, or Bone Source. Materials and Methods: Surgical cavities 5 mm in diameter were prepared through both mandibular cortices in the mandibular angle region. The cavities were randomly filled, and the animals were divided into groups according to the material employed: Group 1 cavities were filled with autogenous corticocancellous bone; group 2 cavities were filled with calcium phosphate cement (BoneSource); and group 3 and group 4 cavities were filled with bioactive glass (FillerBone and PerioGlas, respectively). After 180 days the animals were sacrificed, and specimens were prepared following routine laboratory procedures for hematoxylin/eosin staining and histologic evaluation. Results: the histologic analysis showed that autogenous bone allowed total repair of the bone defects; bioactive glasses (FillerBone and PerioGlas) allowed total repair of the defects with intimate contact of the remaining granules and newly formed bone; and the cavities filled with calcium phosphate cement (BoneSource) were generally filled by connective fibrous tissue, and the material was almost totally resorbed. Discussion: the autogenous bone, FillerBone, and PerioGlas provided results similar to those in the current literature, showing that autogenous bone is the best Choice for filling critical-size defects. Synthetic implanted materials demonstrated biocompatibility, but the bioglasses demonstrated osteoconductive activity that did not occur with calcium phosphate (BoneSource). Conclusion: According to the methodology used in this study, it can be concluded that the utilization of autogenous bone and bioactive glasses permitted the repair of surgically created critical-size defects by newly formed bone; the synthetic implanted materials demonstrated biocompatibility, and the bioactive glasses demonstrated osteoconductive activity. The PerioGlas was mostly resorbed and replaced by bone and the remaining granules were in close contact with bone; the FillerBone showed many granules in contact with the newly formed bone; BoneSource did not permit repair of the critical-size defects, and the defects were generally filled by connective fibrous tissue.

Use of BioGran and Calcitite in bone defects: Histologic study in monkeys (Cebus apella)

The present study compares the biologic behavior of BioGran and Calcitite as fillers for surgical cavities in the mandibles of 4 adult monkeys (Cebus apella). The surgical cavities were prepared through both mandibular cortices, with a diameter of 5 mm, in the angle region. Two cavities were prepared on the right side and 1 on the left and divided into 3 groups: R-1 sites were filled with bioglass (BioGran), R, sites were not filled, and L sites were filled with hydroxyapatite (Calcitite). After 180 days the animals were sacrificed and the specimens were removed for histologic processing. Results showed no bone formation in group R, (empty cavities). BioGran-treated sites showed bone formation and total repair of the bone defect, and the bioglass particles were almost totally resorbed and substituted by bone. The few remaining crystals were in intimate contact with newly formed bone. Calcitite did not allow bone formation, and granules inside the cavities were involved by connective tissue. Based upon those results, the authors concluded that bioglass resulted in total obliteration of the surgical cavity with bone and hydroxyapatite was present in a large amount and involved by connective tissue, without bone formation.

Influence of Implant Design on the Biomechanical Environment of Immediately Placed Implants: Computed Tomography-Based Nonlinear Three-Dimensional Finite Element Analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biomechanical Evaluation of Platform Switching in Different Implant Protocols: Computed Tomography-Based Three-Dimensional Finite Element Analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Early Bone Healing and Biomechanical Fixation of Dual Acid-Etched and As-Machined Implants with Healing Chambers: An Experimental Study in Dogs

Purpose: To evaluate the biomechanical fixation, bone-to-implant contact (BIC), and bone morphology of screw-type root-form implants with healing chambers with as-machined or dual acid-etched (DAE) surfaces in a canine model. Materials and Methods: The animal model included the placement of machined (n = 24) and DAE (n = 24) implants along the proximal tibiae of six mongrel dogs, which remained in place for 2 or 4 weeks. Following euthanasia, half of the specimens were subjected to biomechanical testing (torque to interface failure) and the other half were processed for histomorphologic and histomorphometric (%BIC) assessments. Statistical analyses were performed by one-way analysis of variance at the 95% confidence level and the Tukey post hoc test for multiple comparisons. Results: At 4 weeks, the DAE surface presented significantly higher mean values for torque to interface failure overall. A significant increase in %BIC values occurred for both groups over time. For both groups, bone formation through the classic appositional healing pathway was observed in regions where intimate contact between the implant and the osteotomy walls occurred immediately after implantation. Where contact-free spaces existed after implantation (healing chambers), an intramembranous-like healing mode with newly formed woven bone prevailed. Conclusions: In the present short-term evaluation, no differences were observed in BIC between groups; however, an increase in biomechanical fixation was seen from 2 to 4 weeks with the DAE surface. INT J ORAL MAXILLOFAC IMPLANTS 2011;26:75-82

Effect of Severe Dietary Magnesium Deficiency on Systemic Bone Density and Removal Torque of Osseointegrated Implants

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effectiveness of Screw Surface Coating on the Stability of Zirconia Abutments After Cyclic Loading

Purpose: Different surface treatments have been developed in attempts to prevent the loosening of abutment screws. The aim of the current study was to compare the effectiveness of titanium alloy screws with tungsten-doped diamond-like carbon (W-DLC) coating and uncoated screws in providing stability to zirconia (ZrO2) ceramic abutments after cyclic loading. Materials and Methods: Twenty prefabricated ZrO2 ceramic abutments on their respective external-hex implants were divided into two groups of equal size according to the type of screw used: uncoated titanium alloy screw (Ti) or titanium alloy screw with W-DLC coating (W-DLC/Ti). The removal torque value (preload) of the abutment screw was measured before and after loading. Cyclic loading between 11 and 211 N was applied at an angle of 30 degrees to the long axis of the implants at a frequency of 15 Hz. A target of 0.5 x 10(6) cycles was defined. Group means were calculated and compared using analysis of variance and the F test (alpha=.05). Results: Before cyclic loading, the preload for Ti screws was significantly higher than that for W-DLC/Ti screws (P=.021). After cyclic loading, there was no significant difference between them (P=.499). Conclusions: Under the studied conditions, it can be concluded that, after cyclic loading, both abutment screws presented a significant reduction in the mean retained preload and similar effectiveness in maintaining preload. INT J ORAL MAXILLOFAC IMPLANTS 2012;27:1061-1067