Faculty Bibliography

OBJECTIVES: The aim of the study was to analyze the effects of ovariectomy on periodontal tissues following immediate tooth replantation by histomorphometric, immunohistochemistry, and muCT analysis. MATERIALS AND METHODS: Eighty wistar rats (Rattus norvegicus albinos) with normal estrous cycles were randomly divided into two groups: ovariectomized (OVX) and Sham. Two months after surgery, the rats' upper right incisor was extracted followed by immediate reimplantation. The animals were sacrificed after 28, 45, and 60days healing time. Histomorphometric and immunohistochemical analysis were performed by evaluation of PCNA and TRAP straining. RESULTS: The periodontal ligament was reinserted into the bone and cementum in the both groups. The immunohistochemical analysis revealed PCNA positive cells on the periodontal ligament in both groups at 28 days. Root resorption was noted at 45days with immunoreactive cells for TRAP present in bone and tooth surface however no statistical differences between the groups were noticed. Histomorphometric analysis showed significant difference between groups in the periodontal ligament and root resorption parameters for the sub-items: intensity of chronic inflammatory infiltrate at 60days (p<0.01), the organization of the periodontal ligament at 28days (p<0.05), depth of root resorption at 45days (p<0.05) and at 60days (p<0.001). The muCT analysis showed multiple areas of bone resorption in association with OVX at 28 and 60days with no significant differences between times in vivo. CONCLUSION: The ovariectomy did not have significant influence in periodontal tissue parameters following tooth reimplantation.

One-stage implants were placed in the mandibles of eight beagle dogs with laser-etched (LL) and machined abutments. After 4 weeks, half of the LL abutments were disconnected and reconnected after 10 minutes of saline storage, and the other half were replaced with a new LL abutment (impression simulation) with or without sulcus de-epithelialization. After abutment change, systems remained in vivo for 3 weeks. Results showed that LL abutments can be reconnected and that sulcus scoring prior to LL placement of one-stage implants receiving machined abutments may be beneficial.

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.

BACKGROUND: This study aimed to compare the histomorphometric and histological bone response to laser-sintered implants followed by resorbable-blasting media (RBM) process relative to standard machined/RBM surface treated implants. MATERIAL AND METHODS: Six male sheep (n=6) received 2 Ti-6Al-4V implants (1 per surface) in each side of the mandible for 6 weeks in vivo. The histomorphometric parameters bone-implant contact (BIC) and bone area fraction occupancy (BAFO) were evaluated. RESULTS: Optical interferometry revealed higher Sa and Sq values for the laser-sintered/RBM surface in relation to standard/RBM implants. No significant differences in BIC were observed between the two groups (p>0.2), but significantly higher BAFO was observed for standard/RBM implants (p<0.01). CONCLUSIONS: The present study demonstrated that both surfaces were biocompatible and osseoconductive, and the combination of laser sintering and RBM has no advantage over the standard machined implants with subsequent RBM.

This study evaluated the effect of microrobotized blasting of titanium endosteal implants relative to their manually blasted counterparts. Two different implant systems were utilized presenting two different implant surfaces. Control surfaces (Manual) were fabricated by manually grit blasting the implant surfaces while experimental surfaces (Microblasted) were fabricated through a microrobotized system that provided a one pass grit blasting routine. Both surfaces were created with the same ~50microm average particle size alumina powder at ~310KPa. Surfaces were then etched with 37% HCl for 20min, washed, and packaged through standard industry procedures. The surfaces were characterized through scanning electron microscopy (SEM) and optical interferometry, and were then placed in a beagle dog radius model remaining in vivo for 3 and 6 weeks. The implant removal torque was recorded and statistical analysis evaluated implant system and surface type torque levels as a function of time in vivo. Histologic sections were qualitatively evaluated for tissue response. Electron microscopy depicted textured surfaces for both manual and microblasted surfaces. Optical interferometry showed significantly higher Sa, Sq, values for the microblasted surface and no significant difference for Sds and Sdr values between surfaces. In vivo results depicted that statistically significant gains in biomechanical fixation were obtained for both implant systems tested at 6 weeks in vivo, while only one system presented significant biomechanical gain at 3 weeks. Histologic sections showed qualitative higher amounts of new bone forming around microblasted implants relative to the manually blasted group. Microrobotized blasting resulted in higher biomechanical fixation of endosteal dental implants and should be considered as an alternative for impant surface manufacturing.

The degree of interplay among variables in dental implant treatment presents a challenge to randomized clinical trials attempting to answer questions in a timely, unbiased, and economically feasible fashion. Further adding complexity to the different scenarios is the varied implant designs and related bone response, area of implantation, implant bulk material, restoration, abutments and related screws, fixation mode (screwed, fixed, or a combination), and horizontal implant-abutment matching geometry. This article critically appraises the most common mechanical testing methods used to characterize the implant-prostheses complex. It attempts to provide insight into the process of construction of an informed database of clinically relevant questions regarding preclinical evaluation of implant biomechanics and failure mechanisms. The use of single load to failure, fatigue life, fatigue limit, and step-stress accelerated life testing is discussed with emphasis on their deliverables, weaknesses, and strengths. Fractographic analysis and challenges in the correlation between laboratory- and in-service-produced failures of dental ceramics, resin composites, and titanium are introduced. In addition, examples are presented of mechanical characterization studies used in our laboratory to assess some implant-supported rehabilitation variables.

The objective of this split-mouth clinical study was to compare a combination of in-office and at-home dental bleaching with at-home bleaching alone. Two applications of in-office bleaching were performed, with one appointment per week, using 38% hydrogen peroxide. At-home bleaching was performed with or without in-office bleaching using 10% carbamide peroxide in a custom-made tray every night for 2 weeks. The factor studied was the bleaching technique on two levels: Technique 1 (in-office bleaching combined with home bleaching) and Technique 2 (home bleaching only). The response variables were color change, dental sensitivity, morphology, and surface roughness. The maxillary right and left hemiarches of the participants were submitted to in-office placebo treatment and in-office bleaching, respectively (Phase 1), and at-home bleaching (Phase 2) treatment was performed on both hemiarches, characterizing a split-mouth design. Enamel surface changes and roughness were analyzed with scanning electron microscopy and optical interferometry using epoxy replicas. No statistically significant differences were observed between the bleaching techniques for either the visual or the digital analyses. There was a significant difference in dental sensitivity when both dental bleaching techniques were used, with in-office bleaching producing the highest levels of dental sensitivity after the baseline. Microscopic analysis of the morphology and roughness of the enamel surface showed no significant changes between the bleaching techniques. The two techniques produced similar results in color change, and the combination technique produced the highest levels of sensitivity. Neither technique promoted changes in morphology or surface roughness of enamel.

PURPOSE: To investigate the probability of survival of different implant-abutment connection designs in narrow versus standard-diameter implants supporting anterior crowns. MATERIALS AND METHODS: A total of 108 implants of either 3.5-mm or 4.0-mm diameter (narrow and standard, respectively) (10 mm in length, Implacil de Bortoli) were divided into six groups (n = 18 each) as follows: external hexagon 3.5 mm or 4.0 mm (EH3.5 or EH4.0), internal hexagon 3.5 mm or 4.0 mm (IH3.5 or IH4.0), and Morse taper 3.5 mm or 4.0 mm (MT3.5 or MT4.0). The corresponding abutments were screwed to the implants, and standardized maxillary central incisor metal crowns were cemented and subjected to step-stress accelerated life testing in water. Use-level probability Weibull curves and reliability for a mission of 50,000 and 100,000 cycles at 100 N and 150 N (90% 2-sided confidence intervals [CI]) were calculated. Polarized-light and scanning electron microscopes were used to assess the failure modes. RESULTS: The calculated reliability with 90% CI for a mission of 50,000 cycles at 100 N and 150 N showed that cumulative damage from the respective loads would lead to ~93% and ~18% implant-supported restoration survival in group EH3.5, ~99% and ~1% in group IH3.5, ~97% and ~89% in the MT3.5, ~100% and ~99% in the group EH4.0, ~100% and ~100% in group IH4.0, and ~99% and ~99% in group MT4.0. For the 100,000-cycle mission, the probability of survival estimated at 100 N and 150 N was, respectively: 0% for EH3.5 and IH3.5 at both load levels, ~96% and ~87% for the MT3.5, 100% and ~99% for EH4.0, 100% and ~99% for IH4.0, and 98% and ~92% for the MT4.0. CONCLUSION: A significant decrease in the probability of survival as a function of elapsed fatigue cycles and load increase was observed for narrow implants only with EH and IH implant-abutment connections, but not on Morse taper.

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.