Faculty Bibliography

OBJECTIVE: Biological and mechanical implant-abutment connection complications and failures are still present in clinical practice, frequently compromising oral function. The purpose of this study was to evaluate the reliability and failure modes of anterior single-unit restorations in internal conical interface (ICI) implants using step-stress accelerated life testing (SSALT). MATERIALS AND METHODS: Forty-two ICI implants were distributed in two groups (n = 21 each): group AT-OsseoSpeed() TX (Astra Tech, Waltham, MA, USA); group SV-Duocon System Line, Morse Taper (Signo Vinces Ltda., Campo Largo, PR, Brazil). The corresponding abutments were screwed to the implants and standardized maxillary central incisor metal 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. Differences between groups were assessed by Kruskal-Wallis along with Bonferroni's post-hoc tests. Polarized-light and scanning electron microscopes were used for failure analyses. RESULTS: The Beta (beta) value derived from use level probability Weibull calculation was 1.62 (1.01-2.58) for group AT and 2.56 (1.76-3.74) for group SV, indicating that fatigue was an accelerating factor for failure of both groups. The reliability for group AT was 0.95 and for group SV was 0.88. Kruskal-Wallis along with Bonferroni's post-hoc tests showed no significant difference between the groups tested (P > 0.27). In all specimens of both groups, the chief failure mode was abutment fracture at the conical joint region and screw fracture at neck's region. CONCLUSIONS: Reliability was not different between investigated ICI connections supporting maxillary incisor crowns. Failure modes were similar.

OBJECTIVES: This study evaluated the effect of implant surface blasting variables, such as blasting media size, velocity, and surface coverage and their two- and three-way interaction in surface roughness parameters. MATERIAL AND METHODS: Machined, grade IV titanium-alloy implants (n = 180) had their surfaces treated by a combination of 36 different blasting protocols according to the following variables: aluminum oxide blasting media particle size (50, 100, and 150 mum); velocity (75, 100, 125, and 150 m/s), and surface coverage (5, 15, 25 g/in.(2) ) (n = 5 per blasting protocol). A single 0.46 inch nozzle of the blaster was pointed at the threaded area and spaced 0.050 inches away. Surface topography (n = 5 measurements per implant) was assessed by scanning electron microscopy. Roughness parameters Sa, Sq, Sdr, and Sds were evaluated by optical interferometry. A GLM statistical model evaluated the effects of blasting variables on the surface parameters, and their two- and three-way interaction (P < 0.05). Statistical inferences for Sa and Sq were performed after a log(10) transformation to correct for data skewness. RESULTS: Prior to the log(10) transformation, Sa and Sq values for all processing groups ranged from ~0.5 to ~2.6 mum and from ~0.75 to 4 mum, respectively. Statistical inferences showed that Sa, Sq, and Sdr values were significantly dependent on blasting media, velocity, and surface coverage (all P < 0.001). Media x velocity, media x coverage, and media x velocity x coverage also significantly affected Sa, Sq, and Sdr values (P < 0.002). The highest levels were obtained with 100 mum blasting media, coverage for 5 g/in.(2) , and velocity of 100 m/s. No significant differences were observed for Sds (P > 0.15). CONCLUSIONS: The blasting variables produced different surface topography features and knowledge of their interaction could be used to tailor a desired implant surface configuration.

Objectives: This preliminary investigation aimed to evaluate the potential of contaminated implants to reosseointegrate into pristine sites and, in addition, to assess the potential of osseointegration of new implants in peri-implantitis sockets in a canine model. Methods: All mandibular premolars were bilaterally extracted from two mongrel dogs. Following 12 weeks of healing, two dental implants were inserted on each hemiarch. Forty-five days following implant placement, a silk ligature secured with cyanoacrylate was placed around the implants' cervical region in order to induce peri-implantitis. After another 45 days from ligature placement, the implants were mechanically removed using counter rotation with a ratchet and were reimplanted without any decontamination (neither rinsing nor chemical or mechanical cleaning) in adjacent pristine zones. In sites where implants were removed, new, wider-diameter implants were placed in the infected sockets. Forty-five days following reimplantation surgery, the dogs were sacrificed; nondecalcified specimens were processed and toluidine blue stained for morphologic and morphometric (bone-to-implant contact [BIC]) assessment under an optical microscope. Results: In dog 1 all the implants (both in the pristine and in the infected sites) survived and osseointegrated while in dog 2, six out of eight implants failed to osseointegrate and exfoliated. Overall, the mean BIC of all implants was 51.08% (SD 20.54). The mean BIC for the infected implants placed into pristine sites was 51.48% +/- 26.29% (SD) and the mean BIC for the new implants in peri-implantitis socket was 50.58% +/- 14.27% (SD). Conclusions: Within the limitations of this preliminary investigation, especially the small number of animals, osseointegration seems to be achievable both in infected sites and around contaminated implant surfaces.

PURPOSE: The present study evaluated the effect of different drilling dimensions (undersized, regular, and oversized) in the insertion and removal torques of dental implants in a beagle dog model. METHODS: Six beagle dogs were acquired and subjected to bilateral surgeries in the radii 1 and 3 weeks before euthanasia. During surgery, 3 implants, 4 mm in diameter by 10 mm in length, were placed in bone sites drilled to 3.2 mm, 3.5 mm, and 3.8 mm in final diameter. The insertion and removal torque was recorded for all samples. Statistical analysis was performed by paired t tests for repeated measures and by t tests assuming unequal variances (all at the 95% level of significance). RESULTS: Overall, the insertion torque and removal torque levels obtained were inversely proportional to the drilling dimension, with a significant difference detected between the 3.2 mm and 3.5 mm relative to the 3.8 mm groups (P < 0.03). Although insertion torque-removal torque paired observations was statistically maintained for the 3.5 mm and 3.8 mm groups, a significant decrease in removal torque values relative to insertion torque levels was observed for the 3.2 mm group. A different pattern of healing and interfacial remodeling was observed for the different groups. CONCLUSIONS: Different drilling dimensions resulted in variations in insertion torque values (primary stability) and stability maintenance over the first weeks of bone healing.

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.

OBJECTIVES: (1) To chemically characterise Y-TZP surface via X-ray photoelectron spectroscopy (XPS) and evaluate the surface energy levels (SE) after non-thermal plasma (NTP). (2) To test the microtensile bond strength (MTBS) of Y-TZP bonded to cured composite disks, after a combination of different surface conditioning methods. METHODS: Twenty-four Y-TZP discs (13.5mmx4mm) were obtained from the manufacturer and composite resin (Z-100) discs with similar dimensions were prepared. All discs were polished to 600 grit and divided into 8 groups (n=3 disks each), four control (non-NTP treated) and four experimental (NTP treated for 10s) groups. All groups received one of the four following treatments prior to cementation with RelyxUnicem cement: sand-blasting (SB), a Clearfil ceramic primer (MDP), sand-blasting+MDP (SBMDP), or baseline (B), no treatment. SE readings and surface roughness parameters were statistically analysed (ANOVA, Tukey's, p<0.05). Mixed model and paired samples t-tests were used to compare groups on MTBS. RESULTS: XPS showed increase in O and decrease in C elements after NTP. The polar component increased for BP (42.20mN/m) and SBP (43.77mN/m). MTBS values for groups BP (21.3MPa), SBP (31MPa), MDPP (30.1MPa) and SBMDPP (32.3MPa) were significantly higher in specimens treated with NTP than their untreated counterparts B (9.1MPa), SB (14.4MPa), MDP (17.8MPa) and SBMDP (24.1MPa). CONCLUSIONS: (1) Increase of O and decrease of C led to higher surface energy levels dictated by the polar component after NTP; (2) NTP application increased MTBS values of Y-TZP surfaces.

PURPOSE: Modifications in implant surface topography and chemistry may alter the early bone response at different levels. This study characterized four implant surfaces and evaluated the biomechanical fixation and histologic response at early implantation times in a canine radius model. MATERIALS AND METHODS: External-hexagon Branemark-type implants were used with four experimental surfaces: microblasted (MI), acid-etched and microblasted (AAM), anodized (A), and discrete crystalline deposition (DCD). Surface topography was assessed by scanning electron microscopy, interferometry, and x-ray photoelectron spectroscopy. The implants were placed in the central region of the radii of eight beagle dogs and remained in vivo for 10 or 30 days. The implants were torqued to interface failure, and a general linear statistical model with torque as the dependent variable and implant surface and time in vivo as independent variables was used. RESULTS: All surfaces presented were textured, and different surface chemistries were observed. No significant differences between implant surfaces were observed for torque at 10 days. However, at 30 days, the AAM surface presented significantly higher torque values compared to the DCD and A surfaces. Significantly higher torque values were observed at 30 days compared to 10 days (P < .001). CONCLUSIONS: Significantly different biomechanical fixation dependent on surface preparation was observed after 30 days, and all surfaces were biocompatible and osteoconductive.

PURPOSE: This study evaluated the reliability and failure modes of anterior implants with internal-hexagon (IH), external-hexagon (EH), or Morse taper (MT) implant-abutment interface designs. The postulated hypothesis was that the different implant-abutment connections would result in different reliability and failure modes when subjected to step-stress accelerated life testing (SSALT) in water. MATERIALS AND METHODS: Sixty-three dental implants (4 x 10 mm) were divided into three groups (n = 21 each) according to connection type: EH, IH, or MT. Commercially pure titanium abutments were screwed to the implants, and standardized maxillary central incisor metallic crowns were cemented and subjected to SSALT in water. The probability of failure versus number of cycles (95% 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% two-sided confidence intervals) was calculated. Polarized-light and scanning electron microscopes were used for failure analyses. RESULTS: The beta values (confidence intervals) derived from use-level probability Weibull calculation were 3.34 (2.22 to 5.00), 1.72 (1.14 to 2.58), and 1.05 (0.60 to 1.83) for groups EH, IH, and MT, respectively, indicating that fatigue was an accelerating factor for all groups. Reliability was significantly different between groups: 99% for MT, 96% for IH, and 31% for EH. Failure modes differed; EH presented abutment screw fracture, IH showed abutment screw and implant fractures, and MT displayed abutment and abutment screw bending or fracture. CONCLUSIONS: The postulated hypothesis that different implant-abutment connections to support anterior single-unit replacements would result in different reliability and failure modes when subjected to SSALT was accepted.

Although the use of zirconia abutments for implant-supported restorations has gained momentum with the increasing demand for esthetics, little informed design rationale has been developed to characterize their fatigue behavior under different clinical scenarios. However, to prevent the zirconia from fracturing, the use of a titanium connection in bi-component aesthetic abutments has been suggested. OBJECTIVE: Mechanical testing of customized thin-walled titanium-zirconia abutments at the connection with the implant was performed in order to characterize the fatigue behavior and the failure modes for straight and angled abutments. MATERIAL AND METHODS: Twenty custom-made bi-component abutments were tested according to ISO 14801:2007 either at a straight or a 25 degrees angle inclination (n=10 each group). Fatigue was conducted at 15 Hz for 5 million cycles in dry conditions at 20 degrees C+/-5 degrees C. Mean values and standard deviations were calculated for each group. All comparisons were performed by t-tests assuming unequal variances. The level of statistical significance was set at p