Indiana University-Purdue University Indianapolis (IUPUI) / The objective of this study was to evaluate the in vivo performance of the hydroxyapatite (HA) coating and hydrofluoric acid (HF) etching zirconia (ZrO) implants and to compare the result with titanium (Ti) implants treated in a similar manner. A total of four different implant types were tested in this study. Threaded zirconia implants with HA coating (Test 1) and zirconia implants with HF-treated surfaces (Test 2) were used to compare to the same size of titanium implants treated in identical fashion (control 1 and control 2). All implants measured about 3.5 mm at the thread diameter and 7.0 mm in total length. Each rabbit received two zirconia and two titanium implants treated in the same manner (either HA-coated or HF-etched). The samples were implanted into the rabbit tibias and retrieved at 6 weeks. Upon retrieval, 24 specimens (6 samples for each group) were fixed and dehydrated. The samples were then embedded undecalcified in PMMA for histomorphometry to quantify the bone-to-implant contact (BIC). Another 24 samples were kept in 0.9% saline and were evaluated using removal torque (RT) analysis to assess the strength of the implant-to-bone interface. The histomorphometric examination demonstrated direct bone-to-implant contact for all four groups. HA particle separation from the implants surface was seen in a majority of the HA-coated samples. No signs of inflammation or foreign body reaction were found during examination. Due to the HA particle smear contamination in the ZrO-HA group, no data was collected in this group. The mean BIC at the first three threads of the Ti-HA, Ti-HF and ZrO-HF were 57.78±18.22%, 46.41±14.55% and 47.41±14.05%, respectively. No statistically significant difference was found pair-wise among these three groups. When comparing the BIC data with the machined-surface implants, a statistically significant difference was found between the Ti-HA versus Ti implant group and the Ti-HF versus Ti implant group. The mean bone area (BA) at the first three threads for Ti-HA, Ti-HF and ZrO-HF showed statistically significant difference (p<0.05) between the ZrO-HF and Ti-HA groups, favoring the ZrO-HF group. The value of the peak removal force could only be collected from the Ti-HA group during the removal torque test. The mean RT value for the Ti-HA group was 24.39±2.58 Ncm. When comparing the RT result with our pilot study using machined-surface implants, the Ti-HA group showed statistically significant (p<0.05) higher values than the machined-surface Ti implants. The result of this study proves the in vivo biocompatibility of all four implant types tested. In the three measurable implant groups, the histomorphologic analysis showed comparable osseointegration properties in this animal model.

Indiana University-Purdue University Indianapolis (IUPUI) / THE EFFECT OF FULL-CONTOUR Y-TZP CERAMIC SURFACE ROUGHNESS ON THE WEAR OF BOVINE ENAMEL AND SYNTHETIC HYDROXYAPATITE: AN IN-VITRO STUDY by Alaa Hussein Aref Sabrah Indiana University School of Dentistry Indianapolis, Indiana Full-contour yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) restorations have been advocated recently in clinical situations where occlusal/palatal space is limited, or to withstand parafunctional activities. The objectives of this in-vitro study were to investigate the effects of different polishing techniques on the surface roughness of Y-TZP (Ardent Dental, Inc.) and to investigate the effects of different polishing techniques on the wear behavior of synthetic hydroxyapatite (HA) and bovine enamel. An in-vitro study was conducted by fabrication of 48 Y-TZP sliders (diameter = 2 mm × 1.5 mm in height) using CAD/CAM technique; then the samples were embedded in acrylic resin using brass holders. Samples were then randomly allocated into four groups according to the finishing/polishing procedure: G1-as-machined (n = 8), G2- glazed (n = 16), G3-diamond bur-finishing (Brasseler, USA) (n = 8) and G4- G3+OptraFine polishing kit (Ivoclar-Vivadent) (n = 16). Thirty-two sintered HA disks (diameter = 11 mm × 2.9 mm in height) and 16 bovine enamel samples with a minimum surface area of 64 mm2 were mounted in brass holders. Baseline surface roughness (Ra and Rq, in μm) were recorded using a non-contact profilometer (Proscan 2000) for all the samples. A two-body pin-on-disk wear test was performed for 25,000 cycles at 1.2 Hz in which the four zirconia groups were tested against HA, and only G2-glazed and G4- G3+OptraFine polishing kit (Ivoclar-Vivadent) were tested against bovine enamel. Vertical substance loss (μm) and volume loss (mm3) of HA were measured (Proscan). Zirconia height loss was measured using a digital micrometer. One-way ANOVA was used for statistical analysis. The results indicated that surface roughness measurements showed significant differences among the surface treatments with G1 (Ra = 0.84, Rq = 1.13 μm) and G3 (Ra = 0.89, Rq = 1.2 μm) being the roughest, and G2 (Ra = 0.42, Rq = 0.63 μm) the smoothest. The glazed group showed the highest vertical loss (35.39 μm) suggesting wear of the glaze layer, while the polished group showed the least vertical loss (6.61 μm). HA antagonist volume loss and vertical height loss for groups (G1, G2 and G3) were similar, while polished group (1.3 mm3, 14.7 μm) showed significant lower (p = 0.0001) values. Antagonist height loss and antagonist volume loss were significantly higher for bovine antagonist than for HA antagonist (197.6 μm/116.2 μm, and 28.5 mm3/17.7 mm3 for bovine against glazed/polished zirconia sliders, respectively) (p < 0.0001). From the results it can be concluded that glazed zirconia provided an initially smooth surface, but a significant increased antagonist wear compared with the polished surface was seen. Bovine enamel showed higher wear compared with HA, which suggested that more studies should be performed to validate the use of bovine enamel as a substitute for human enamel in wear studies.