Faculty Bibliography

PURPOSE: The objective of this study was to evaluate the influence of 4 different amoxicillin administration protocols on osseointegration of dental implants. MATERIALS AND METHODS: Thirty-five Wistar rats received an implant in the right tibia and were divided into 5 groups (n = 7): the control group (G1), a group that received a single dose of amoxicillin suspension (40 mg/kg) hour before surgery (G2), a group that received amoxicillin suspension 1 hour before surgery and a 10-mg/kg dose every 12 hours for 3 days (G3), a group that received amoxicillin suspension 1 hour before surgery and a 10-mg/kg dose every 12 hours for 5 days (G4), and a group that received amoxicillin suspension 1 hour before surgery and a 10-mg/kg dose every 12 hours for 7 days (G5). The animals were sacrificed by anesthesia overdose 28 days after implant placement. The samples were retrieved for bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) analyses. RESULTS: BIC analysis indicated 3 different statistical groups: G1 plus G2, G3, and G4 plus G5. There was no statistical difference between G1 and G2 or between G4 and G5. G3 presented lower values, with statistical difference for G1 plus G2 and G4 plus G5. Also, a statistical difference was found between G1 plus G2 and G4 plus G5. For BAFO evaluation, no statistical difference was found for the experimental groups. CONCLUSION: The results of this study suggest that prolonged use of amoxicillin might have a negative effect on bone formation around implants.

Particulate bone augmentation is an established clinical alternative to regenerate bone. However, in regions of poor bone quality or previously infected sites, the clinical outcomes are more inconsistent. For that purpose, peptides have been added to particulate materials in an attempt to render them with antibacterial properties or to improve their osseoconductivity. For instance, competence-stimulating peptide (CSP) has been studied to decrease the division rate of Streptococcus mutans. Also, the addition of a specific short amino acid sequence peptide derived from type I collagen (P-15) to the bone substitutes has been introduced in an attempt to increase its osseoconductivity. The present study hypothesized that xenogeneic graft materials with and without CSP would present improved host-to-biomaterial response when used in combination with P-15. Particulate graft materials with and without P-15, OsteoGraf with CSP and OsteoGraf, were implanted in an 8-mm rabbit calvarial defect for 4 weeks, and thereafter, histological and histomorphometrical evaluation was performed. The results showed that both OsteoGraf and CSP groups with the addition of P-15 induced bone growth towards the center of the defect. Furthermore, the addition of CSP to Osteograf showed a tendency to increase its osteoconductivity when combined with P-15. The results of the current study suggested that P-15 had some impact on osteogenesis; however, the effect differed between different bone substitute materials. Further investigation is necessary to clarify its effectiveness when used in combination with bone substitutes.

The objective of this study was to characterize the chemical and physical properties of bioactive ceramics prepared from an aqueous paste containing hydroxyapatite (HA) and beta tri-calcium phosphate (beta-TCP). Prior to formulating the paste, HA and beta-TCP were calcined at 800 degrees C and 975 degrees C (11 h), milled, and blended into 15%/85% HA/beta-TCP volume-mixed paste. Fabricated cylindrical rods were subsequently sintered to 900 degrees C, 1100 degrees C or 1250 degrees C. The sintered specimens were characterized by helium pycnometry, X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), and inductively coupled plasma (ICP) spectroscopy for evaluation of porosity, crystalline phase, functional-groups, and Ca:P ratio, respectively. Mechanical properties were assessed via 3-point bending and diametral compression. Qualitative microstructural evaluation using scanning electron microscopy (SEM) showed larger pores and a broader pore size distribution (PSD) for materials sintered at 900 degrees C and 1100 degrees C,whereas the 1250 degrees C samples showed more uniform PSD. Porosity quantification showed significantly higher porosity for materials sintered to 900 degrees C and 1250 degrees C (p < 0.05). XRD indicated substantial deviations from the 15%/85% HA/beta-TCP formulation following sintering where lower amounts of HA were observed when sintering temperature was increased. Mechanical testing demonstrated significant differences between calcination temperatures and different sintering regimes (p < 0.05). Variation in chemical composition and mechanical properties of bioactive ceramics were direct consequences of calcination and sintering.

PURPOSE: This evaluation aimed to (1) validate micro-computed tomography (microCT) findings using scanning electron microscopy (SEM) imaging, and (2) quantify the volume of voids and the bonded surface area resulting from fiber-reinforced composite (FRC) dowel cementation technique using microCT scanning technology/3D reconstructing software. MATERIALS AND METHODS: A fiberglass dowel was cemented in a condemned maxillary lateral incisor prior to its extraction. A microCT scan was performed of the extracted tooth creating a large volume of data in DICOM format. This set of images was imported to image-processing software to inspect the internal architecture of structures. RESULTS: The outer surface and the spatial relationship of dentin, FRC dowel, cement layer, and voids were reconstructed. Three-dimensional spatial architecture of structures and volumetric analysis revealed that 9.89% of the resin cement was composed of voids and that the bonded area between root dentin and cement was 60.63% larger than that between cement and FRC dowel. CONCLUSIONS: SEM imaging demonstrated the presence of voids similarly observed using microCT technology (aim 1). MicroCT technology was able to nondestructively measure the volume of voids within the cement layer and the bonded surface area at the root/cement/FRC interfaces (aim 2). CLINICAL SIGNIFICANCE: The interfaces at the root dentin/cement/dowel represent a timely and relevant topic where several efforts have been conducted in the past few years to understand their inherent features. MicroCT technology combined with 3D reconstruction allows for not only inspecting the internal arrangement rendered by fiberglass adhesively bonded to root dentin, but also estimating the volume of voids and contacted bond area between the dentin and cement layer.

PURPOSE: To demonstrate the degree of stability decrease and subsequent increase of dental implants at early implantation times in a beagle model. MATERIALS AND METHODS: The mandibular premolars and first molars of eight beagle dogs were extracted and the ridges allowed to heal for 8 weeks. Thirty-two (n = 16 each group) implants were placed bilaterally, and remained in vivo for 1 and 3 weeks. The implants with comparable dimensions were divided as follows: group 1, Straumann Bone Level with SLActive surface; group 2, Nobel Speedy Replace RP with TiUnite surface. During insertion and following sacrifice, the implants were torqued to determine insertion and interface failure values. Histologic sections were prepared for microscopy. Statistical analysis was performed using Kruskal-Wallis and multiple paired and non-paired t tests considering unequal variances at a 95% level of significance. RESULTS: High insertion torque values were observed along with a significant decrease at 1 week in vivo (P = .003). At 3 weeks, the biomechanical fixation levels increased and were comparable to the insertion torque value. Histology showed that interfacial bone remodeling and initial woven bone formation was observed around both implant groups at 1 and 3 weeks. CONCLUSIONS: As time elapsed early after implantation, the biomechanical stability of dental implants initially decreased and subsequently increased.

PURPOSE: The present study was conducted to determine whether biomechanical and histologic parameters would differ between implant surfaces blasted with bioactive ceramic resorbable media (biologic blasting) and blasted with alumina and acid-etched. MATERIALS AND METHODS: Fourteen beagle dogs were used. Eight animals received two implants of each surface per limb, and each limb provided samples that remained in vivo for 3 and 6 weeks. The other six animals received two implants of each surface in one limb, which remained in vivo for 1 week. After euthanization, half of the implants were subjected to torque-to-interface fracture; the other half of the implants were processed for nondecalcified histology to calculate bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). Statistical analysis was performed with the Kruskal-Wallis test (95% level of significance). RESULTS: While no significant differences were observed for BIC and BAFO between surfaces at all three times in vivo and for torque levels at 1 and 3 weeks, a significantly higher torque was observed for the biologic blasting group after 6 weeks in vivo. Bone morphology was similar between groups at all times. CONCLUSION: A significant increase in early biomechanical fixation was observed for implants with the biologic blasting surface. However, no significant differences were observed for BIC and BAFO at any observation point.

This study investigated the effect of an Argon-based nonthermal plasma (NTP) surface treatment-operated chairside at atmospheric pressure conditions applied immediately prior to dental implant placement in a canine model. Surfaces investigated comprised: Calcium-Phosphate (CaP) and CaP + NTP (CaP-Plasma). Surface energy was characterized by the Owens-Wendt-Rabel-Kaelble method and chemistry by X-ray photoelectron spectroscopy (XPS). Six adult beagles dogs received 2 plateau-root form implants (n = 1 each surface) in each radii, providing implants that remained 1 and 3 weeks in vivo. Histometric parameters assessed were bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). Statistical analysis was performed by Kruskall-Wallis (95% level of significance) and Dunn's post-hoc test. The XPS analysis showed peaks of Ca, C, O, and P for the CaP and CaP-Plasma surfaces. Both surfaces presented carbon primarily as hydrocarbon (CC, CH) with lower levels of oxidized carbon forms. The CaP surface presented atomic percent values of 38, 42, 11, and 7 for C, O, Ca, and P, respectively, and the CaP-Plasma presented increases in O, Ca, and P atomic percent levels at 53, 12, and 13, respectively, in addition to a decrease in C content at 18 atomic percent. At 1 week no difference was found in histometric parameters between groups. At 3 weeks significantly higher BIC and BAFO were observed for CaP-Plasma treated surfaces. Surface elemental chemistry was modified by the Ar-based NTP. Ar-based NTP improved bone formation around plateau-root form implants at 3 weeks compared with CaP treatment alone. (c) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A:98-103, 2013.

Lateral or vertical bone augmentation has always been a challenge, since the site is exposed to constant pressure from the soft tissue, and blood supply only exists from the donor site. Although, for such clinical cases, onlay grafting with autogenous bone is commonly selected, the invasiveness of the secondary surgical site and the relatively fast resorption rate have been reported as a drawback, which motivated the investigation of alternative approaches. This study evaluated the bone-forming capability of a novel nanoHA alloplast infused with collagen graft material made from biodegradable polylactic acid/polyglycolic acid versus a control graft material with the same synthesized alloplast without the nanoHA component and collagen infiltration. The status of newly formed bone and the resorption of the graft material were evaluated at 6 weeks in vivo histologically and three dimensionally by means of 3D microcomputed tomography. The histologic observation showed that newly formed bone ingrowth and internal resorption of the block were observed for the experimental blocks, whereas for the control blocks less bone ingrowth occurred along with lower resorption rate of the block material. The three-dimensional observation indicated that the experimental block maintained the external geometry, but at the same time successfully altered the graft material into bone. It is suggested that the combination of numerous factors contributed to the bone ingrowth and the novel development could be an alternative bone grafting choice.

Purpose: To investigate the reliability of titanium abutments veneered with indirect composites for implant-supported crowns and the possibility to trace back the fracture origin by qualitative fractographic analysis. Materials and Methods: Large base (LB) (6.4-mm diameter base, with a 4-mm high cone in the center for composite retention), small base (SB-4) (5.2-mm base, 4-mm high cone), and small base with cone shortened to 2 mm (SB-2) Ti abutments were used. Each abutment received incremental layers of indirect resin composite until completing the anatomy of a maxillary molar crown. Step-stress accelerated-life fatigue testing (n = 18 each) was performed in water. Weibull curves with use stress of 200 N for 50,000 and 100,000 cycles were calculated. Probability Weibull plots examined the differences between groups. Specimens were inspected in light-polarized and scanning electron microscopes for fractographic analysis. Results: Use level probability Weibull plots showed Beta values of 0.27 for LB, 0.32 for SB-4, and 0.26 for SB-2, indicating that failures were not influenced by fatigue and damage accumulation. The data replotted as Weibull distribution showed no significant difference in the characteristic strengths between LB (794 N) and SB-4 abutments (836 N), which were both significantly higher than SB-2 (601 N). Failure mode was cohesive within the composite for all groups. Fractographic markings showed that failures initiated at the indentation area and propagated toward the margins of cohesively failed composite. Conclusions: Reliability was not influenced by abutment design. Qualitative fractographic analysis of the failed indirect composite was feasible.

This study evaluated the early biomechanical fixation and bone-to-implant contact (BIC) of an alumina-blasted/acid-etched (AB/AE) compared with an experimental resorbable blasting media (RBM) surface in a canine model. Higher texturization was observed for the RBM than for the AB/AE surface, and the presence of calcium and phosphorus was only observed for the RBM surface. Time in vivo and implant surface did not influence torque. For both surfaces, BIC significantly increased from 2 to 4 weeks.