Faculty Bibliography

OBJECTIVES: Bone formation and maintenance around implants placed immediately after tooth extraction may be affected by implant surface treatment and compromise long-term esthetic results. This study morphometrically evaluated buccal bone loss and bone-to-implant contact (BIC) of four implant systems placed immediately after tooth extraction in a dog model. MATERIAL AND METHODS: The premolars of eight beagle dogs were bilaterally extracted with a full-thickness flap, and root-form dental implants were placed on the root extraction socket. Implants (n = 16 each) with different surface treatments were placed from sites 1 to 4 and alternated between animals to allow evaluation of the same number of implants at sites and evaluation time points. Implant surface treatments were as follows: anodized, discrete crystalline deposition, SLActive, and microblasted. The left and right side provided implants that stayed for 2 and 4 weeks, respectively. Submerged healing was allowed and bone-to-implant contact (BIC) and buccal bone loss were morphometrically measured. Linear mixed models (P < 0.05) were used to assess differences between groups, across time, and their interaction. RESULTS: Buccal bone loss was observed to approximately double between 2 and 4 weeks (P = 0.01). BIC also increased between 2 and 4 weeks, by 20-25% (P = 0.01). These changes were statistically similar for each surface. CONCLUSION: When placed immediately after tooth extraction, the evaluated histomorphometric parameters vary only with time.

PURPOSE:: Commercial implants differ at macro-, micro-, and nanolevels, which makes it difficult to distinguish their effect on osseointegration. The aim of this study was to evaluate the early integration of 5 commercially available implants (Astra OsseoSpeed, Straumann SLA, Intra-Lock Blossom Ossean, Nobel Active, and OsseoFix) by histomorphometry and nanoindentation. MATERIALS AND METHODS:: Implants were installed in the tibiae of 18 beagle dogs. Samples were retrieved at 1, 3, and 6 weeks (n = 6 for each time point) and were histologically and nanomechanically evaluated. RESULTS:: The results presented that both time (P < 0.01) and implant system and time interaction (P < 0.02) significantly affected the bone-to-implant contact (BIC). At 1 week, the different groups presented statistically different outcomes. No significant changes in BIC were noted thereafter. There were no significant differences in rank elastic modulus (E) or in rank hardness (H) for time (E: P > 0.80; H: P > 0.75) or implant system (E: P > 0.90; H: P > 0.85). CONCLUSIONS:: The effect of different implant designs on osseointegration was evident especially at early stages of bone healing.

Background: To date, very few experimental studies have addressed the effect of bone drilling technique and sequence on dental implant osseointegration. In this study, we hypothesized that there would be no differences in osseointegration when reducing the number of drills for osteotomy compared to the conventional drilling protocols. Methods: Seventy-two implants (diameter 3.75 mm and diameter 4.2 mm, n=36 for each diameter) were bilaterally placed in the tibia of 18 beagles for 1, 3, and 5 weeks. Half of the implants of each diameter were placed using a simplified drilling procedure (pilot and final drill) and the other half were placed using a conventional drilling procedure (all drills in sequence). The retrieved samples were subjected to histologic/histomorphometric evaluation. Results: Histology showed that new bone formed around the implant and inflammation or bone resorption was not evident for both groups. Histomorphometrically, the simplified group presented significantly higher bone-to-implant contact and bone area fraction occupancy as compared to the conventional group after 1 week, however, no differences were detected at 3 and 5 weeks. Conclusion: It can be suggested that bone responses to the implant with the simplified protocol is comparable to the conventional protocol.

OBJECTIVE: This study evaluated the effect of drilling speed on early bone healing in dog tibiae. STUDY DESIGN: Thirty-six implants (4.0-mm diameter x 10-mm length) were placed in the proximal tibiae of 6 beagles with drilling speeds of 100, 500, and 1000 rpm, and insertion torque was recorded. Bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) were evaluated. RESULTS: Significant increase from 1 to 3 weeks was observed for all groups for BIC, whereas no significant differences between 1 and 3 weeks were detected for the 100- and 500-rpm groups for BAFO (P > .34 and P > .46, respectively). A significant difference from 1 to 3 weeks was observed for the 1000-rpm group (P < .03). The 100- and 500-rpm groups presented significantly higher BAFO than the 1000-rpm group at 1 week (P = .002). CONCLUSIONS: Drilling speed is one of the decisive factors for early osseointegration, and overall, drilling at 1000 rpm seemed to yield the strongest biologic responses.

Although histology has proven to be a reliable method to evaluate the ossoeintegration of a dental implant, it is costly, time consuming, destructive, and limited to one or few sections. Microcomputed tomography (microCT) is fast and delivers three-dimensional information, but this technique has not been widely used and validated for histomorphometric parameters yet. This study compared microCT and histomorphometry by means of evaluating their accuracy in determining the bone response to two different implant materials. In total, 32 titanium (Ti) and 16 hydroxyapatite (HA) implants were installed in 16 lop-eared rabbits. After 2 and 4 weeks, the animals were scarified, and the samples retrieved. After embedding, the samples were scanned with microCT and analyzed three-dimensionally for bone area (BA) and bone-implant contact (BIC). Thereafter, all samples were sectioned and stained for histomorphometry. For the Ti implants, the mean BIC was 25.25 and 28.86% after 2 and 4 weeks, respectively, when measured by histomorphometry, while it was 24.11 and 24.53% when measured with microCT. BA was 35.4 and 31.97% after 2 and 4 weeks for histomorphometry and 29.06 and 27.65% for microCT. For the HA implants, the mean BIC was 28.49 and 42.51% after 2 and 4 weeks, respectively, when measured by histomorphometry, while it was 33.74 and 42.19% when measured with microCT. BA was 30.59 and 47.17% after 2 and 4 weeks for histomorphometry and 37.16 and 44.95% for microCT. Direct comparison showed that only the 2 weeks BA for the titanium implants was significantly different between microCT and histology (p = 0.008). Although the technique has its limitations, microCT corresponded well with histomorphometry and should be considered as a tool to evaluate bone structure around implants. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2013.

OBJECTIVES:: To investigate the effect of implant-abutment connection types on reliability and failure modes of anterior single-unit crowns. METHODS:: Fifty-four implants were divided in 3 groups (n = 18 each): external hexagon (EH), internal hexagon (IH), and Morse taper (MT) connection. Abutments were screwed to the implants, and maxillary central incisor metal crowns were cemented and subjected to step-stress accelerated life testing. RESULTS:: The beta values derived from use-level probability Weibull calculations for groups IH (2.52), EH (1.67), and MT (0.88) indicated that fatigue influenced the failure only of IH and EH groups. The reliability for a mission of 100,000 cycles at 175 N was 0.99 (0.98-1.00), 0.84 (0.62-0.94) and 0.97 (0.87-0.99) for the EH, IH, and MT, respectively. The characteristic strength was not significantly different between EH (290 N) and IH (251 N) but significantly higher for MT (357 N). For IH and EH groups, failure involved screw fracture, and the MT implants primary failure mode was abutment fracture. CONCLUSIONS:: Reliability was higher for the EH and MT relative to IH groups, whereas the characteristic strength was significantly higher for implants with MT connection.

Bioglasses are considered osteoconductive and osteoproductive biomaterials and some types also exhibit angiogenic, bacteriostatic and anti-inflammatory properties. Despite these facts, bioglasses have only a few commercial applications, mainly because they do not exhibit as good mechanical properties as titanium. This study evaluated the biological performance of titanium implants coated with a highly bioactive glass. The experimental study was performed in vivo and in vitro. The in vitro study was conducted by evaluating the adhesion and cell viability on titanium disks treated with highly bioactive glass. For the in vivo study, implants were installed in the mandibles of dogs Beagles. A group of implants presented a surface with double acid-etched and the other group had a surface with double acid-etched + highly bioactive glass. The results confirmed that coating pattern tested in this study is non cytotoxic and does not adversely affect the new bone formation on the implant interface, showing performance comparable to that of physically modified surface with double acid-etched. The results of this research do not demonstrated a significant increase in bone formation after the incorporation of bioactive glass on titanium surfaces, but indicates the possibility of modifying titanium surfaces in a predicable and promisingway

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 &lt; 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 &lt; 0.05). Variation in chemical composition and mechanical properties of bioactive ceramics were direct consequences of calcination and sintering.

PURPOSE:: Slow-resorbing deproteinized bovine bone grafts have presented high success rates when used for sinus augmentation. However, histologic evaluation shows that this material is eventually excreted as a result of a foreign body reaction. The purpose of this study was to compare and to evaluate the performance of a recently introduced particulate porous graft material, consisting of pure titanium granule (PTG) to the deproteinized bovine bone grafts, when used as a sinus augmentation material. MATERIALS AND METHODS:: To understand the histological aspects of PTG, deproteinized bovine particulates (Bio-Oss) and PTG were placed contralaterally as sinus grafting materials in 2 patients. After 9 months, biopsies were performed for histologic and 3-dimensional analysis. RESULTS:: Both materials were in contact with newly formed bone. The Bio-Oss showed signs of foreign body reaction. In contrast, bone filled the space between the single PTG particulates, and no foreign body reaction was observed. CONCLUSIONS:: From a bone formation perspective, PTG grafts were comparable with the commonly used Bio-Oss grafts and may be regarded as a possible alternative for permanent grafting in sinus augmentation.

This study evaluated 3 implant surfaces in a dog model: (1) resorbable-blasting media + acid-etched (RBMa), alumina-blasting + acid-etching (AB/AE), and AB/AE + RBMa (hybrid). All of the surfaces were minimally rough, and Ca and P were present for the RBMa and hybrid surfaces. Following 2 weeks in vivo, no significant differences were observed for torque, bone-to-implant contact, and bone-area fraction occupied measurements. Newly formed woven bone was observed in proximity with all surfaces.