Faculty Bibliography

Few studies have evaluated the effects of titanium (Ti) surface modifications on polymorphonuclear neutrophils (PMNs). Human PMNs' viability and release of key mediators-such as IL1beta, IL6, TNFalpha, IL12, IL10, IL4, TGFbeta1, IL8, IP-10, and Mig-were evaluated on three different Ti surface treatments: (1) machined Ti; (2) alumina-blasted and acid-etched Ti (AB/AE); and (3) calcium phosphate coating of 300-500 nm by ion beam onto the AB/AE Ti surface (CaP). A polystyrene surface was used as a negative control. The PMNs were purified from whole human blood and cultured for 6 h. Cell viability was determined by flow cytometry, and the supernatant was evaluated to determine the levels of cytokines and chemokines. Results showed that the percentage of viable cells was significantly lower on the CaP surface compared to the control (p < 0.05) relative to the other groups. No differences in the levels of IL8, MIG, and IP10 were detected between groups. Significantly higher levels of IL1beta (p = 0.046) and TNFalpha (p = 0.016) were detected for the CaP surfaces compared to AB/AE surface only. The levels of IL4, IL10, and TGFbeta1 secreted from the PMNs in the CaP group were significantly lower than in the control and machined groups (p < 0.05) that were statistically comparable to AB/AE. Overall, the addition of a thin CaP coating to the AB/AE Ti surface influenced the secretion profile of pro-inflammatory cytokines due to the higher release of pro-inflammatory cytokines (IL1beta and TNFalpha) on these surfaces.

This study aimed to determine the effect of a bioactive ceramic coating on titanium in the nanothickness range on human osteogenic cells, peripheral blood mononuclear cells (PBMC) and on osteogenic cells co-cultured with PBMC without exogenous stimuli. Cell viability, proliferation, adhesion, cytokine release (IL1beta, TGFbeta1, IL10 and IL17) and intracellular stain for osteopontin and alkaline phosphatase were assessed. Morphologic evaluation showed smaller and less spread cell aspects in co-culture relative to osteogenic cell culture. Cell viability, proliferation and adhesion kinetics were differently influenced by surface texture/chemistry in culture versus co-culture. Cytokine release was also influenced by the interaction between mononuclear and osteogenic cells (mediators released by mononuclear cells acted on osteogenic cells and vice versa). In general, 'multi-cell type' interactions played a more remarkable role than the surface roughness or chemistry utilized on the in vitro cellular events related to initial stages of bone formation.

Laminin-1 has been reported as one of the factors responsible for the nucleation of calcium phosphates and, in vitro, has been reported to selectively recruit osteoprogenitors. This article focused on its in vivo effects, and evaluated the effect of laminin-1 local application on osseointegration. Polished cylindrical hydroxyapatite implants were coated with laminin-1 (test) and the bone responses in the rabbit tibiae after 2 and 4 weeks were evaluated and compared to the non-coated implants (control). Before the samples were processed for histological sectioning, they were three-dimensionally analysed with micro computed tomography (muCT). Both evaluation methods were analysed with regards to bone area around the implant and bone to implant contact. From the histologic observation, new bone formation around the laminin-1 coated implant at 2 weeks seemed to have increased the amount of supporting bone around the implant, however, at 4 weeks, the two groups presented no notable differences. The two-dimensional and three-dimensional morphometric evaluation revealed that both histologic and three-dimensional analysis showed some tendency in favour of the test group implants, however there was no statistical significance between the test and control group results.

Step-stress accelerated life testing (SSALT) and fractographic analysis were performed to evaluate the reliability and failure modes of dental implant fabricated by machining (surface treated with alumina blasting/acid etching) or laser sintering for anterior single-unit replacements. Forty-two dental implants (3.75 x 10 mm) were divided in two groups (n = 21 each): laser sintered (LS) and alumina blasting/acid etching (AB/AE). The abutments were screwed to the implants and standardized maxillary central incisor metallic crowns were cemented and subjected to SSALT in water. Use-level probability Weibull curves and reliability for a mission of 50,000 cycles at 200 N were calculated. Polarized light and scanning electron microscopes were used for failure analyses. The Beta (beta) value derived from use-level probability Weibull calculation of 1.48 for group AB/AE indicated that damage accumulation likely was an accelerating factor, whereas the beta of 0.78 for group LS indicated that load alone likely dictated the failure mechanism for this group, and that fatigue damage did not appear to accumulate. The reliability was not significantly different (p > 0.9) between AB/AE (61 %) and LS (62 %). Fracture of the abutment and fixation screw was the chief failure mode. No implant fractures were observed. No differences in reliability and fracture mode were observed between LS and AB/AE implants used for anterior single-unit crowns.

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.

Low temperature degradation of zirconia (3Y-TZP) oral implants and its effect on fatigue reliability is poorly documented. OBJECTIVE: The aim of this investigation was to follow the aging process occurring at the surface of implants exhibiting a porous coating and to assess its influence on their mechanical (fatigue) properties. METHODS: Tetragonal to monoclinic transformation (t-m) was evaluated during accelerated aging tests up to 100h in autoclave (134 degrees C, 2 bars) by X-ray diffraction (XRD) and focused ion beam (FIB). A series of implants were steam-aged for 20h before fatigue testing. Such temperature-time conditions would correspond roughly to 40 years in vivo. The aged specimens and a non-aged control group were step-stress fatigued until failure or survival. RESULTS: The evolution of XRD surface monoclinic content was slow, i.e. 16% and 35% for 20 and 100h respectively. However, FIB revealed a significant transformation, initiated at the interface between the porous layer and the bulk, preferentially growing towards the bulk. FIB is therefore better indicated than XRD to follow aging in such implants. Higher average fatigue strength (aged 1235N versus non-aged 826N) and reliability levels were observed for the 20h aged group. SIGNIFICANCE: After aging for durations compatible with clinical use, 3Y-TZP with porous surface presented higher fatigue performance. This is in contrast to previous studies where loss of strength due to aging was often reported. Generalizations must therefore be avoided when considering aging of zirconia dental products and every new material/process combination should be tested before drawing conclusions.

OBJECTIVES: To evaluate the effect of framework design modification and veneering techniques in fatigue reliability and failure modes of veneered Yttria-Stabilized Tetragonal Zirconia Polycrystals (Y-TZP) crowns. METHODS: A CAD-based mandibular molar crown preparation served as a master die. Y-TZP crown cores (VITA-In-Ceram-YZ, Vita-Zahnfabrik, Bad Sackingen, Germany) in conventional (0.5mm uniform thickness) or anatomically designed fashion (cusp support) were porcelain veneered with either hand-layer (VM9) or pressed (PM9) techniques. Crowns (n=84) were cemented on 30 days aged dentin-like composite dies with resin cement. Crowns were subjected to single load to fracture (n=3 each group) and mouth-motion step-stress fatigue (n=18) by sliding a WC indenter (r=3.18mm) 0.7mm buccally on the inner incline surface of the mesio-lingual cusp. Stress-level curves (use level probability lognormal) and reliability (with 2-sided 90% confidence bounds, CB) for completion of a mission of 50.000 cycles at 200N load were calculated. Fractographic analyses were performed under light-polarized and scanning electron microscopes. RESULTS: Higher reliability for hand-layer veneered conventional core (0.99, CB 0.98-1) was found compared to its counterpart press-veneered (0.50 CB 0.33-65). Framework design modification significantly increased reliability for both veneering techniques (PM9 [0.98 CB 0.87-0.99], VM9 [1.00 CB 0.99-1]) and resulted in reduced veneer porcelain fracture sizes. Main fracture mode observed was veneer porcelain chipping, regardless of framework design and veneering technique. SIGNIFICANCE: Hand-layer porcelain veneered on conventional core designs presented higher reliability than press-veneered with similar core designs. Anatomic core design modification significantly increased the reliability and resulted in reduced chip size of either veneering techniques.

This study evaluated the histometric characteristics of the peri-implant mucosa of human subjects that received textured implant abutments with conventional (implant and abutment with same diameter) or platform-switched (implant diameter wider than that of the abutment) configurations. Wider and longer connective tissue around platform-switched implants was observed compared to that with conventional abutments. Despite the different dimensions between the two abutment types, the abutment-soft tissue interaction was similar for both groups at the histometric level.

OBJECTIVES: This study evaluated the reliability and failure modes of implants with a microthreaded or smooth design at the crestal region, restored with screwed or cemented crowns. The postulated null hypothesis was that the presence of microthreads in the implant cervical region would not result in different reliability and strength to failure than smooth design, regardless of fixation method, when subjected to step-stress accelerated life-testing (SSALT) in water. MATERIALS AND METHODS: Eighty four dental implants (3.3 x 10 mm) were divided into four groups (n = 21) according to implant macrogeometric design at the crestal region and crown fixation method: Microthreads Screwed (MS); Smooth Screwed (SS); Microthreads Cemented (MC), and Smooth Cemented (SC). The abutments were torqued to the implants and standardized maxillary central incisor metallic crowns were cemented (MC, SC) or screwed (MS, SS) and subjected to SSALT in water. The probability of failure versus cycles (90% two-sided confidence intervals) was calculated and plotted using a power law relationship for damage accumulation. Reliability for a mission of 50,000 cycles at 150 N (90% 2-sided confidence intervals) was calculated. Differences between final failure loads during fatigue for each group were assessed by Kruskal-Wallis along with Benferroni's post hoc tests. Polarized-light and scanning electron microscopes were used for failure analyses. RESULTS: The Beta (beta) value (confidence interval range) derived from use level probability Weibull calculation of 1.30 (0.76-2.22), 1.17 (0.70-1.96), 1.12 (0.71-1.76), and 0.52 (0.30-0.89) for groups MC, SC, MS, and SS respectively, indicated that fatigue was an accelerating factor for all groups, except for SS. The calculated reliability was higher for SC (99%) compared to MC (87%). No difference was observed between screwed restorations (