Faculty Bibliography

OBJECTIVES: The objective of this histologic study was to determine the effect of three drilling protocols (oversized, intermediate, and undersized) on biologic responses to a single implant type at early healing periods (2 weeks in vivo) in a beagle dog model. MATERIALS AND METHODS: Ten beagle dogs were acquired and subjected to surgeries in the tibia 2 weeks before euthanasia. During surgery, each dog received three Unitite implants, 4 mm in diameter by 10 mm in length, in bone sites drilled to 3.5, 3.75, and 4.0 mm in final diameter. The insertion torque was recorded during surgery, and bone-to-implant contact (BIC), and bone area fraction occupied (BAFO) measured from the histology. Each outcome measure was compared between treatment conditions with the Wilcoxon signed-rank test. Bonferroni-corrected statistical significance was set to 95%. RESULTS: Insertion torque increased as an inverse function of drilling diameter, as indicated by significant differences in torque levels between each pair of conditions (P = 0.005). BIC and BAFO levels were highest and statistically similar in the recommended and undersized conditions and significantly reduced in the oversized condition (P < 0.01). CONCLUSIONS: Reduced drilling dimensions resulted in increased insertion torque (primary stability). While BIC and BAFO were maximized when drilling the recommended diameter hole, only the oversized hole resulted in evidence of statistically reduced integration.

Composite resins have been routinely used for posterior cavities due to a phasedown on amalgam as a restorative option. However, clinical problems related to polymerization shrinkage demands careful and specific techniques for placement of the composite layers. New low shrinkage composites are now marketed for bulk filling of cavities without the need of a traditional layering. With this new concept, the restoration can be built in one or two layers, depending on the classification of the bulk fill material. This article discusses and presents two alternative techniques using the low shrinkage composites, suggesting a called "amalgam-like sculpting technique," one using a flowable bulk fill and other a regular bulk fill material. Clinical cases illustrate these two alternatives compared with the layered technique. CLINICAL SIGNIFICANCE: New techniques using low shrinkage composites for bulk filling can provide a simpler technical approach for the clinician in sculpting and generating highly esthetic posterior composites.

The aim of this study was to compare the influence of graft material (non-ceramic hydroxyapatite versus autologous bone) on bone behaviour and perform a resonance frequency analysis of implants placed in augmented sites to evaluate stability. For this study, 11 patients with bilateral edentulous areas in the mandibular posterior region were selected. Alveolar augmentation osteotomies were bilaterally (split mouth design) performed. In one hemiarch, the space generated by the osteotomy was grafted with an interpositional intra-oral autologous bone graft (control group). In the other hemiarch, the space generated by the osteotomy was grafted with an interpositional non-ceramic hydroxyapatite (ncHA) (test group). The groups were randomized. After 6 months of healing, a bone sample was retrieved from each side for histological evaluation using a trephine drill that was 2-mm in internal diameter. The implant stability quotient (ISQ) was measured by the resonance frequency immediately following implant placement at baseline and after 6 months of follow-up. Good incorporation of the graft was observed in both groups; however, in the test group, a residual-grafted material was observed. Bone density and marrow spaces were similar between groups. Correlations between the ISQ values and the histometric variables were not observed (p>0.05). The results of this trial suggest that both intra-oral autologous bone and ncHA may be elected as interpositional grafting materials to vertically augment posterior atrophic mandibles.

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.

Abstract The aim of this study was to evaluate the physico-chemical properties and the in vivo host response of a surface sandblasted with particles of titanium oxide (TiO2) followed by acid etching as an alternative to aluminium oxide. Thirty titanium disks manufactured in the same conditions as the implants and 24 conventional cylindrical implants were used., Half of the implants had a machined surface (Gcon) while in the other half the surface was treated by with particles of TiO2 followed by acid etching (Gexp). Surface characterization was assessed by Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectrometry (EDS), profilometry, and wettability. For the in vivo test, 12 implants of each group were implanted in the tibia of 6 rabbits, and were reverse torque tested after periods of 30 or 60 days after implantation. Following torque, SEM was utilized to assess residual bone-implant contact. The surface characterization by SEM showed a very homogeneous surface with uniform irregularities for Gexp and a small amount of residues of the blasting procedure, while Gcon presented a surface with minimal irregularities from the machining tools. Wettability test showed decreased contact angle for the Gcon relative to the Gexp. The Gexp removal torque at 30 and 60 days was 28.7%, and 33.2% higher relative to the Gcon, respectively. Blasting the surface with particles of TiO2 represents an adequate option for the surface treatment of dental implants, with minimal risk of contamination by the residual debris from the blasting procedure.

Although preclinical and sparse human histology retrieval studies have shown that the interface between implant and bone is constantly remodeling, no human retrieval database has been developed to determine the effect of functional loading time and other clinical/implant design variables on osseointegration. The present study tested the hypothesis that bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) increase over functional loading time around dental implants. Due to prosthetic retreatment reasons, 93 human implant retrievals from the same manufacturer (Bicon LLC, Boston, MA, USA) were obtained over a period of approximately 15 years. The retrieved implants were under functional loading from 120 days to approximately 18 years and were histomorphologic/metrically evaluated. BIC/BAFO were assessed as a function of multiple independent variables: implant surface type, diameter, length, jaw (maxilla/mandible), region (anterior/posterior), and time of functional loading. The results showed that both BIC and BAFO increased over time independently of implant design/clinical variables, supporting the postulated hypothesis. (c) 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2014.

OBJECTIVES: To evaluate the influence of implant-abutment interface (IAI) placement depth on bone remodeling around implants with two different types of tapered internal IAI: screwed-in (SI) and tapped-in (TI) connections in dogs. MATERIALS AND METHODS: Eight weeks post mandibular tooth extraction in six beagle dogs, two SI implants (OsseoSpeed , Astra Tech, DENTSPLY) and two TI implants (Integra-CP , Bicon LLC) were placed in one side of the mandible. The four experimental groups were as follows: (i) SI-placed equicrestally (SIC); (ii) TI-placed equicrestally (TIC); (iii) SI-placed 1.5 mm subcrestally (SIS); and (iv) TI-placed 1.5 mm subcrestally (TIS). Healing abutments were connected 12 weeks after implant placement. Sixteen weeks later, the dogs were sacrificed and histomorphometric analysis was performed. Histometrical outcomes were evaluated using a nonparametric Brunner-Langer model. RESULTS: Mean distance from the IAI to first bone-implant contact (IAI-fBIC) was 0.88 mm (median: 0.77; SD: 0.54) for SIC group, 1.23 mm (median: 1.22; SD: 0.66) for TIC group, 0.41 mm (median: 0.31; SD: 0.36) for SIS group, and 0.41 mm (median: 0.26; SD: 0.45) for TIS group. Subcrestal groups showed lower IAI-fBIC compared with equicrestal groups (P < 0.001). Connective tissue presented similar measurements regardless of the IAI placement depth and IAI type (P > 0.05), but the epithelium length and peri-implant soft tissue length in subcrestal groups were significant larger than that in the equicrestal groups (P < 0.001 and P = 0.004, respectively). CONCLUSION: Subcrestal implant placement with tapered internal IAI is beneficial for bone contact with the implant neck, and concurrently, it may not increase the soft tissue inflammation around IAI.

OBJECTIVES: To evaluate the probability of survival and failure modes of implant-supported resin nanoceramic relative to metal-ceramic crowns. METHODS: Resin nanoceramic molar crowns (LU) (Lava Ultimate, 3M ESPE, USA) were milled and metal-ceramic (MC) (Co-Cr alloy, Wirobond C+, Bego, USA) with identical anatomy were fabricated (n=21). The metal coping and a burnout-resin veneer were created by CAD/CAM, using an abutment (Stealth-abutment, Bicon LLC, USA) and a milled crown from the LU group as models for porcelain hot-pressing (GC-Initial IQ-Press, GC, USA). Crowns were cemented, the implants (n=42, Bicon) embedded in acrylic-resin for mechanical testing, and subjected to single-load to fracture (SLF, n=3 each) for determination of step-stress profiles for accelerated-life testing in water (n=18 each). Weibull curves (50,000 cycles at 200N, 90% CI) were plotted. Weibull modulus (m) and characteristic strength (eta) were calculated and a contour plot used (m versus eta) for determining differences between groups. Fractography was performed in SEM and polarized-light microscopy. RESULTS: SLF mean values were 1871N (+/-54.03) for MC and 1748N (+/-50.71) for LU. Beta values were 0.11 for MC and 0.49 for LU. Weibull modulus was 9.56 and eta=1038.8N for LU, and m=4.57 and eta=945.42N for MC (p>0.10). Probability of survival (50,000 and 100,000 cycles at 200 and 300N) was 100% for LU and 99% for MC. Failures were cohesive within LU. In MC crowns, porcelain veneer fractures frequently extended to the supporting metal coping. CONCLUSION: Probability of survival was not different between crown materials, but failure modes differed. SIGNIFICANCE: In load bearing regions, similar reliability should be expected for metal ceramics, known as the gold standard, and resin nanoceramic crowns over implants. Failure modes involving porcelain veneer fracture and delamination in MC crowns are less likely to be successfully repaired compared to cohesive failures in resin nanoceramic material.

PURPOSE: Implant design and the implant-abutment interface have been regarded as key influences on crestal bone maintenance over time. The aim of the present study was to determine crestal bone changes around implants placed at different depths in a dog model. MATERIALS AND METHODS: Thirty-six two-piece dental implants with a medialized implant-abutment interface and Morse taper connection (Ankylos, Dentsply) were placed in edentulous areas bilaterally in six mongrel dogs. On each side of the mandible, three implants were placed randomly at the bone crest, 1.5 mm subcrestally, or 3.0 mm subcrestally. After 3 months, the final abutments were torqued into place. At 6 months, the animals were sacrificed and samples taken for microcomputed tomographic (micro-CT) and histologic evaluations. RESULTS: Micro-CT analysis revealed similar crestal or marginal bone loss among groups. Both subcrestal implant groups lost significantly less crestal and marginal bone than the equicrestal implants. Bone loss was greatest on the buccal of the implants, regardless of implant placement depth. Histologically, implants placed subcrestally were found to have bone in contact with the final abutment and on the implant platform. CONCLUSION: Implants with a centralized implant-abutment interface and Morse taper connection can be placed subcrestally without significant loss of crestal or marginal bone. Subcrestal placement of this implant system appears to be advantageous in maintaining bone height coronal to the implant platform.