Differences between buccal and lingual bone quality and quantity of peri-implant regions.

The objective of the current study was to examine whether peri-implant bone tissue properties are different between the buccal and lingual regions treated by growth factors. Four dental implant groups were used: titanium (Ti) implants, alumina-blasted zirconia implants (ATZ-N), alumina-blasted zirconia implants with demineralized bone matrix (DBM) (ATZ-D), and alumina-blasted zirconia implants with rhBMP-2 (ATZ-B). These implants were placed in mandibles of six male dogs. Nanoindentation elastic modulus (E) and plastic hardness (H) were measured for the buccal and lingual bone tissues adjacent and away from the implants at 3 and 6 weeks post-implantation. A total of 2281 indentations were conducted for 48 placed implants. The peri-implant buccal region had less bone quantity resulting from lower height and narrower width of bone tissue than the lingual region. Buccal bone tissues had significant greater mean values of E and H than lingual bone tissues at each distance and healing period (p<0.007). Nearly all implant treatment groups displayed lower mean values of the E at the lingual bone tissues than at the buccal bone tissues (p<0.046) although the difference was not significant for the Ti implant group (p=0.758). The DBM and rhBMP-2 treatments stimulated more peri-implant bone remodeling at the lingual region, producing more immature new bone tissues with lower E than at the buccal region. This finding suggests that the growth factor treatments to the zirconia implant system may help balance the quantity and quality differences between the peri-implant bone tissues.

An initial study of diffusion bonds between superplastic Ti-6Al-4V for implant dentistry applications.

STATEMENT OF PROBLEM: Production of precisely fitting fixed partial denture implant superstructures with titanium alloys is limited by casting techniques that introduce distortion. After alignment of the framework with existing implants, the remaining misfit may generate stresses that cause screw loosening and adversely affect the implant/bone interface. PURPOSE: The purpose of this study was to prepare diffusion-bonded joints between superplastic (SP) Ti-6Al-4V plates and indenters (representing analogs to implant-supported fixed frameworks and abutments) and determine if this process has potential for producing strong, dimensionally precise prostheses. MATERIAL AND METHODS: Seven sets of trial indenter and plate specimens with dimensions of 6.4 mm x 6.4 mm x 5 cm and 8.5 mm x 1.5 cm, respectively, were prepared. Several indenter designs were used (35- or 45-degree half-angle, presence or absence of a notch, and SP versus no SP condition for Ti-6Al-4V); all plates were prepared from SP Ti-6Al-4V. For the results-guided experimental design, there was 1 trial indenter/plate combination for each design/processing condition. Diffusion bonding was performed at 10(-6) Torr, while the temperature was increased 10 degrees C/min to 900 degrees or 920 degrees C. Following 10 minutes of equilibration, the indenter was pressed 2.5 mm into the plate at 0.13 mm/min. Joint strength was evaluated in tension, and the ductile or brittle character of fracture surfaces was assessed by the presence or absence of a dimpled rupture surface from secondary electron SEM observations. Fractured specimens were cross-sectioned and examined with an optical microscope to evaluate overall joint integrity and quality, and used for Vickers hardness measurements to gain insight into the variation in mechanical properties of the indenter and plate with distance from the joint. One-way ANOVA (alpha=.05) was used to compare hardness at the joint for the trial specimen with highest joint strength with hardness values for adjacent regions at 125-mum intervals in the indenter and plate. The Ryan-Einot-Gabriel-Welsch (REGW) multiple range test was used to identify any specific location having significantly (alpha=.05) different hardness. Backscattered electron SEM observations were also performed on the cross-sectioned specimens to investigate whether a layer of alpha-stabilized titanium, which would decrease joint strength, was present. Fits of Ti-6Al-4V implant analogs prepared by this diffusion-bonding process were assessed qualitatively from visual observation. RESULTS: The maximum joint strength of 820 MPa was achieved for a diffusion bonding temperature of 900 degrees C for an SP Ti-6Al-4V indenter with a 35-degree half-angle and no notch. This joint strength is nearly 90% of the maximum tensile strength of the parent Ti-6Al-4V, which can range from approximately 930 to 1015 MPa. The hardness at the joint was significantly higher (P<.05) than the hardness of the indenter and plate at 125-mum distances from the joint. The mean hardness of the indenter at 125 mum from the joint was significantly greater (P<.05) than the mean hardness of the plate at a distance of 500 mum from the joint. All other mean hardness values at the different measurement distances from the joint were not significantly different. Ductile fracture occurred for all superplastic processing conditions, and no alpha-titanium layer was present. Minimal asperities were observed with the optical microscope, and fits of implant prosthesis analogs were considered acceptable. CONCLUSIONS: A 900 degrees C processing condition for diffusion-bonding an SP Ti-6Al-4V indenter with a 35-degree half-angle and no notch to a Ti-6Al-4V SP plate yielded a joint with nearly the same strength as the parent alloy. Use of this processing temperature with a 0.13 mm/min rate of pressing the indenter into the plate yielded minimal distortions for implant prosthesis analogs when observed visually.

Enhanced functions of osteoblasts on nanometer diameter carbon fibers.

The present in vitro study investigated select functions (specifically, proliferation, synthesis of intracellular proteins, alkaline phosphatase activity, and deposition of calcium-containing mineral) of osteoblasts (the bone-forming cells) cultured on carbon fibers with nanometer dimensions. Carbon fiber compacts were synthesized to possess either nanophase (i.e., dimensions 100 nm or less) or conventional (i.e., dimensions larger than 100 nm) fiber diameters. Osteoblast proliferation increased with decreasing carbon fiber diameters after 3 and 7 days of culture. Moreover, compared to larger-diameter carbon fibers, osteoblasts synthesized more alkaline phosphatase and deposited more extracellular calcium on nanometer-diameter carbon fibers after 7, 14, and 21 days of culture. The results of the present study provided the first evidence of enhanced long-term (in the order of days to weeks) functions of osteoblasts cultured on nanometer-diameter carbon fibers; in this manner, carbon nanofibers clearly represent a unique and promising class of orthopedic/dental implant formulations with improved osseointegrative properties.