Faculty Bibliography

Surface topography modifications have become a key strategy for hastening the host-to-implant response to implantable materials. The present study evaluated the effect of three different carefully controlled surface texture patterns achieved through microrobotized blasting (controlled to high, medium and low roughness) relative to a larger scale blasting procedure (control) in early osseointegration in a canine model. Four commercially pure grade 2 titanium alloy implants (one of each surface) were bilaterally placed in the radii of six beagle dogs and allowed end points of 1 and 6 weeks in vivo. Following sacrifice, implants in bone were non-decalcified processed for bone morphologic and histometric (bone-to-implant contact; bone area fraction occupancy) evaluation. Surface topography was characterized by scanning electron microscopy and optical interferometry. Results showed initial osteogenic tissue interaction at one week and new bone in intimate contact with all implant surfaces at 6 weeks. At 1 and 6 weeks in vivo, higher bone-to-implant and bone area fraction occupancy were observed for the high texture pattern microrobotized blasted surface relative to others.

PURPOSE: To compare the removal of torque values of machined implant abutment connections (internal and external) with and without soft tissue entrapment using an in vitro model. MATERIALS AND METHODS: Thirty external- and 30 internal-connection implants were embedded in urethane dimethacrylate. Porcine tissue was prepared and measured to thicknesses of 0.5 and 1.0 mm. Six groups (n = 10) were studied: External- and internal-connection implants with no tissue (control), 0.5, and 1.0 mm of tissue were entrapped at the implant/abutment interface. Abutments were inserted to 20 Ncm for all six groups. Insertion torque values were recorded using a digital torque gauge. All groups were then immersed in 1 M NaOH for 48 hours to dissolve tissue. Subsequent reverse torque measurements were recorded. Mean and standard deviation were determined for each group, and one-way ANOVA and Bonferroni test were used for statistical analysis. RESULTS: All 60 specimens achieved a 20-Ncm insertion torque, despite tissue entrapment. Reverse torque measurements for external connection displayed a statistically significant difference (p < 0.05) between all groups with mean reverse torque values for the control (13.71 +/- 1.4 Ncm), 0.5 mm (7.83 +/- 2.4 Ncm), and 1.0 mm tissue entrapment (2.29 +/- 1.4 Ncm) groups. Some statistically significant differences (p < 0.05) were found between internal-connection groups. In all specimens, tissue did not completely dissolve after 48 hours. CONCLUSIONS: External-connection implants were significantly affected by tissue entrapment; the thicker the tissue, the lower the reverse torque values noted. Internal-connection implants were less affected by tissue entrapment.

PURPOSE: The aim of this study was to evaluate the probability of survival of cemented and screwed three-unit implant-supported fixed dental prostheses (ISFDP) using different implant-abutment horizontal matching configurations (regular vs switching platforms). METHODS: One hundred and sixty-eight implants with internal hexagon connection (4 mm diameter, 10 mm length, Emfils; Colosso Evolution System, Itu, SP, Brazil) were selected for this study according to the horizontal implant-abutment matching configuration (regular or switching) and retention method and divided in four groups (n = 21 per group) as follows: 1) regular platform cemented (IRC); 2) or screw-retained (IRS); 3) switched-platform cemented (ISC); or 4) screw-retained (ISS). Regular and platform-switched abutments (Colosso evolution, 4 mm and 3.3 mm, respectively) were torqued, and 84 three-unit metal bridges were fabricated (first molar pontic). Implants were embedded in polymethyl-methacrylate resin and subjected to step-stress accelerated life testing in water. Weibull distribution was used to determine the probability of survival for a mission of 100,000 cycles at 400 N (90% two-sided confidence intervals). Polarized light and scanning electron microscopes were used for fractographic analysis. RESULTS: The beta values of 0.50, 1.19, 1.25, and 1.95 for groups IRC, IRS, ISC, and ISS respectively, indicated that fatigue accelerated the failure for all groups, except IRC. The cement-retained groups presented significantly higher probability of survival (I

Healing chambers present at the interface between implant and bone have become a target for improving osseointegration. The objective of the present study was to compare osseointegration of several implant healing chamber configurations at early time points and regions of interest within bone using an in vivo animal femur model. Six implants, each with a different healing chamber configuration, were surgically implanted into each femur of six skeletally mature beagle dogs (n = 12 implants per dog, total n = 72). The implants were harvested at 3 and 5 weeks post-implantation, non-decalcified processed to slides, and underwent histomorphometry with measurement of bone-to-implant contact (BIC) and bone area fraction occupied (BAFO) within healing chambers at both cortical and trabecular bone sites. Microscopy demonstrated predominantly woven bone at 3 weeks and initial replacement of woven bone by lamellar bone by 5 weeks. BIC and BAFO were both significantly increased by 5 weeks (p < 0.001), and significantly higher in cortical than trabecular bone (p < 0.001). The trapezoidal healing chamber design demonstrated a higher BIC than other configurations. Overall, a strong temporal and region-specific dependence of implant osseointegration in femurs was noted. Moreover, the findings suggest that a trapezoidal healing chamber configuration may facilitate the best osseointegration. (c) 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2015.

PURPOSE: The purpose of this study was to summarize the recent developments in the field of tissue engineering as they relate to multilayer scaffold designs in musculoskeletal regeneration. METHODS: Clinical and basic research studies that highlight the current knowledge and potential future applications of the multilayer scaffolds in orthopaedic tissue engineering were evaluated and the best evidence collected. Studies were divided into three main categories based on tissue types and interfaces for which multilayer scaffolds were used to regenerate: bone, osteochondral junction and tendon-to-bone interfaces. RESULTS: In vitro and in vivo studies indicate that the use of stratified scaffolds composed of multiple layers with distinct compositions for regeneration of distinct tissue types within the same scaffold and anatomic location is feasible. This emerging tissue engineering approach has potential applications in regeneration of bone defects, osteochondral lesions and tendon-to-bone interfaces with successful basic research findings that encourage clinical applications. CONCLUSIONS: Present data supporting the advantages of the use of multilayer scaffolds as an emerging strategy in musculoskeletal tissue engineering are promising, however, still limited. Positive impacts of the use of next generation scaffolds in orthopaedic tissue engineering can be expected in terms of decreasing the invasiveness of current grafting techniques used for reconstruction of bone and osteochondral defects, and tendon-to-bone interfaces in near future.

Introduction: Cleanliness of the canal space is the ultimate goal of its preparation. Nevertheless, some portion of the canal walls are left un-instrumented during preparation. Therefore, the aim of this ex vivo study was to evaluate the cleanliness of un-instrumented canal walls after root canal preparation for the presence or absence of debris and smear layer. Materials and Methods: A total of 24 single-rooted extracted teeth were prepared with the crown-down technique using Protaper universal rotary file system. Micro-computed tomography (micro-CT) was used to scan the specimens before and after instrumentation. The un-instrumented area was measured and localized. The roots were split longitudinally and then subjected to scanning electron microscopy (SEM). The presence of debris and smear layer in the instrumented and un-instrumented areas of the canal were evaluated by analysing the SEM images with a five-score evaluation system based on the reference photographs. Results: High levels of root canal cleanliness (= score 2) were found for the instrumented areas were detected (P = 0.003). Conclusions: Under the condition of this study, un-instrumented areas of the canal were less clean in comparison to instrumented portion.

PURPOSE: The aim of this prospective controlled study was to evaluate the influence of osteopenia on the levels of osteoclastogenesis-related factors in the peri-implant crevicular fluid (PICF) and on the clinical parameters of immediately loaded implants. MATERIALS AND METHODS: This study included 24 patients who received at least two implants in the mandible, with restorations delivered 48 hours after implant placement. Patients were divided into control (n = 11) and osteopenia (n = 13) groups. Seven days after implant placement (baseline) and 4 months after implant placement, PICF samples were obtained, and clinical parameters (Plaque Index, Gingival Index, bleeding on probing, suppuration, probing depths, clinical attachment levels) were measured. A commercially available enzyme-linked immunosorbent assay was used to analyze PICF samples for levels of soluble receptor activator of nuclear factor of kappaB ligand (sRANKL) and osteoprotegerin (OPG). At the 4-month follow-up visit, the implant-supported restorations were removed and periapical radiographs were acquired to evaluate bone loss around the implants. RESULTS: Eighty-eight immediately loaded implants were included in this study (38 in the control group, 50 in the osteopenia group). The RANKL and OPG levels, the RANKL/OPG ratio, and the clinical parameters were similar between the groups at both time points. However, the levels of these factors in PICF differed significantly between baseline and 4 months after surgery. CONCLUSION: Within the limitations of this short-term study, it can be concluded that osteopenia does not influence the PICF levels of osteoclastogenesis-related factors in immediately loaded implants after 4 months of loading.

PURPOSE: The probability of survival of implant-supported prostheses may be affected by the interplay between different implant diameters supporting screwed or cemented crowns. The purpose of this study was to investigate the effect of implant diameter and prosthesis retention system on the reliability and failure modes of single crowns. MATERIALS AND METHODS: Internal-hexagon implants were divided into six groups (n = 21 each) according to implant diameter (3.3, 4.0, or 5.0 mm) and crown retention system (screwed or cemented). Abutments were torqued to the implants, and crowns were then fixed and subjected to step-stress accelerated life testing in water. Use-level probability Weibull curves and reliability for missions of 50,000 cycles at 100, 150, and 200 N were calculated. Failure analysis was performed. RESULTS: Cemented systems presented higher reliability than screwed ones, except between 3.3-mm-diameter cemented and screwed systems at a load of 100 or 150 N. Failure modes were restricted to the abutment screw and varied with implant diameter only in the cement-retained groups. CONCLUSION: Higher reliability was observed for cement-retained crowns and implants of larger diameter compared to screw-retained and smaller diameter. Failure modes differed between groups.