Reliability of the Resonance Frequency Analysis Values in New Prototype Transepithelial Abutments: A Prospective Clinical Study.

Resonance frequency analysis (RFA) requires abutment disconnection to monitor implant stability. To overcome this limitation, an experimental transepithelial abutment was designed to allow a SmartPeg to be screwed onto it, in order to determine the prototype abutments repeatability and reproducibility using Osstell ISQ and to assess whether implant length and diameter have an influence on the reliability of these measurements. RFA was conducted with a SmartPeg screwed directly into the implant and onto experimental abutments of different heights of 2, 3.5 and 5 mm. A total of 32 patients (116 implants) were tested. RFA measurements were taken twice for each group from mesial, distal, buccal and palatal/lingual surfaces. Mean values and SD were calculated and Intraclass Correlation Coefficients (ICC) (p < 0.05, IC 95%). The implant stability quotient (ISQ) mean values were 72.581 measured directly to implant and 72.899 (2 mm), 72.391 (3.5 mm) and 71.458 (5 mm) measured from the prototypes. ICC between measurements made directly to implant and through 2-, 3.5- and 5-mm abutments were 0.908, 0.919 and 0.939, respectively. RFA values registered through the experimental transepithelial abutments achieved a high reliability. Neither the implant length nor the diameter had any influence on the measurements' reliability.

Assessment of the Simultaneous Use of Biomaterials in Transalveolar Sinus Floor Elevation: Prospective Randomized Clinical Trial in Humans.

Implants inserted in the posterior maxilla frequently need additional surgery for successful bone augmentation. One of the most common procedures for this is transalveolar sinus floor elevation. There are different protocols for this procedure, and there is controversy over the simultaneous application of grafting material upon elevating. In this prospective randomized clinical study in humans, a total of 49 transalveolar sinus floor elevations were performed in 49 different patients, divided into a control group (without graft, 25 patients) and a test group (with graft, 24 patients). The analyzed variables were obtained through digital orthopantomography on day 0 (day of surgery) and 18 months after surgery. These measurements showed a tendency towards greater vertical bone gain in the test group, but this was not statistically significant. Therefore, considering that sinus elevation and implant placement without the application of grafts is a successful treatment with fewer complications, a critical assessment of the need for these biomaterials is necessary.

Mechanical Characterisation and Biomechanical and Biological Behaviours of Ti-Zr Binary-Alloy Dental Implants.

The objective of the study is to characterise the mechanical properties of Ti-15Zr binary alloy dental implants and to describe their biomechanical behaviour as well as their osseointegration capacity compared with the conventional Ti-6Al-4V (TAV) alloy implants. The mechanical properties of Ti-15Zr binary alloy were characterised using Roxolid© implants (Straumann, Basel, Switzerland) via ultrasound. Their biomechanical behaviour was described via finite element analysis. Their osseointegration capacity was compared via an in vivo study performed on 12 adult rabbits. Young's modulus of the Roxolid© implant was around 103 GPa, and the Poisson coefficient was around 0.33. There were no significant differences in terms of Von Mises stress values at the implant and bone level between both alloys. Regarding deformation, the highest value was observed for Ti-15Zr implant, and the lowest value was observed for the cortical bone surrounding TAV implant, with no deformation differences at the bone level between both alloys. Histological analysis of the implants inserted in rabbits demonstrated higher BIC percentage for Ti-15Zr implants at 3 and 6 weeks. Ti-15Zr alloy showed elastic properties and biomechanical behaviours similar to TAV alloy, although Ti-15Zr implant had a greater BIC percentage after 3 and 6 weeks of osseointegration.

Biomechanical Consequences of the Elastic Properties of Dental Implant Alloys on the Supporting Bone: Finite Element Analysis.

The objective of the present study is to evaluate how the elastic properties of the fabrication material of dental implants influence peri-implant bone load transfer in terms of the magnitude and distribution of stress and deformation. A three-dimensional (3D) finite element analysis was performed; the model used was a section of mandibular bone with a single implant containing a cemented ceramic-metal crown on a titanium abutment. The following three alloys were compared: rigid (Y-TZP), conventional (Ti-6Al-4V), and hyperelastic (Ti-Nb-Zr). A 150-N static load was tested on the central fossa at 6° relative to the axial axis of the implant. The results showed no differences in the distribution of stress and deformation of the bone for any of the three types of alloys studied, mainly being concentrated at the peri-implant cortical layer. However, there were differences found in the magnitude of the stress transferred to the supporting bone, with the most rigid alloy (Y-TZP) transferring the least stress and deformation to cortical bone. We conclude that there is an effect of the fabrication material of dental implants on the magnitude of the stress and deformation transferred to peri-implant bone.

Fracture resistance of three porcelain-layered CAD/CAM zirconia frame designs.

OBJECTIVES: Chipping is the most frequent clinical failure of zirconia crowns. Causes of chipping have not been completely understood and different possible reasons have been considered. The study was aimed at evaluating the fracture resistance of 3 different CAD/CAM zirconia frame designs veneered with porcelain. METHODS: Thirty extracted sound premolars were divided into 3 groups (n=10). Chamfer preparations were performed, impressions were taken. Three zirconia frame designs (Aadva, GC) were realized: reproduction of the abutment contour (flat design, FD); wax-up as for porcelain-fused-to-metal crowns (PFM); anatomically guided, designed to keep constant the thickness of the overlying porcelain veneering (AG). Porcelain veneering was made with pressure layering technique (Initial Zr, GC). Crowns were cemented utilizing a self-adhesive resin cement (G-Cem, GC). After a 24-h water storage at 37°C, using a universal testing machine (1 mm crosshead speed), crowned teeth were loaded in the central fossa in a direction parallel to the longitudinal axis of the tooth. Load at fracture was recorded in Newtons (N). Digital photographs of the specimens were taken in order to assess failure patterns. Between-group differences in fracture strength were statistically analyzed (One-Way Analysis of Variance, Tukey test, p<0.05). RESULT: Load at fractures differed significantly among the groups (p=0.004). AG exhibited significantly higher fracture resistance 1721.6 (488.1) N than PFM 1004.6 (321.3) N and FD 1179.5 (536.2) N, that were comparable. Repairable failures occurred in 80% of AG, 70% of PFM, and 50% of FD specimens. SIGNIFICANCE: Anatomically guided zirconia frames resisted significantly higher loads than flat and PFM-like frame designs.

Microtensile bond strength evaluation of self-adhesive resin cement to zirconia ceramic after different pre-treatments.

PURPOSE: To evaluate the influence of different surface treatments and metal primer application on bond strength of zirconia ceramic to a self-adhesive resin cement. METHODS: 40 cylinder-shaped (Ø 12 x 5.25 mm high) of zirconia ceramic (Aadva Zirconia) were randomly divided into four groups (n= 10), based on the surface treatment to be performed: (1) Sandblasting with 125 microm Al2O3 particles (S) (positive control); (2) Selective infiltration etching (SIE); (3) Experimental heated etching solution applied for 30 minutes (ST); (4) No treatment (C). Half of the zirconia specimens of each group received the application of Metal Primer II. Eight disks for each group were luted using a self-adhesive resin cement (G-Cem Automix) to composite overlays (Paradigm MZ100). After 24-hour storage (37 degrees C, 100% RH) bonded specimens were cut into microtensile sticks and loaded in tension until failure. Data were analyzed with two-way ANOVA and Games-Howell (P < 0.05). Failure mode distribution was recorded and scanning electron microscopy (SEM) was used to examine the fractured microbars. The remaining cylinders of each group (n = 2) were used for SEM surface analysis. RESULTS: Both surface treatments and Metal Primer II application improved bond strength values (P < 0.05). When Metal Primer II was not applied ST treatment achieved highest bond strength values (22.17 +/- 10.37 MPa). Sandblasting in combination with Metal Primer II enhanced bond strength values compared to the other groups (23.46 +/- 11.19 MPa).

Effects of post surface treatments on the bond strength of self-adhesive cements.

PURPOSE: To evaluate whether fiber post surface conditioning techniques would influence the ultimate retentive strength of self-adhesive resin cements into the root canal. METHODS: 50 single-rooted premolars with one root canal were endodontically treated and prepared to receive a fiber post. Five groups were formed (n=10) according to the post surface pre-treatment performed: (1) Silane application (Monobond S) for 60 seconds; (2) 10% hydrogen peroxide application for 20 minutes; (3) Rocatec Pre; (4) Silicate/silane coating (DT Light SL Post); (5) No treatment (DT Light Post). Two self-adhesive resin cements (RelyX Unicem and MaxCem) were used as luting agents. The bonded specimens were stored up to 1 month (37 degrees C and 100% humidity). The force required to dislodge the post (MPa) via an apical-coronal direction was measured with the push-out bond strength test (cross-head speed: 0.5 mm/minute until failure). Failure patterns were evaluated under SEM. Data was statistically analyzed with one-way ANOVA and Tukey tests (P< 0.05). RESULTS: No increase in the push-out bond strength values were observed for RelyX Unicem, independently from the post surface treatment performed. MaxCem attained higher bond strengths when luted to silanated posts.

Resistance to bond degradation between dual-cure resin cements and pre-treated sintered CAD-CAM dental ceramics

Objective: To evaluate the bond stability of resin cements when luted to glass-reinforced alumina and zirconia CAD/CAM dental ceramics. Study design: Eighteen glass-infiltrated alumina and eighteen densely sintered zirconia blocks were randomly conditioned as follows: Group 1: No treatment; Group 2: Sandblasting (125 µm Al2O3-particles); and Group 3: Silica-coating (50 µm silica-modified Al2O3-particles). Composite samples were randomly bonded to the pretreated ceramic surfaces using different resin cements: Subgroup 1: Clearfil Esthetic Cement (CEC); Subgroup 2: RelyX Unicem (RXU); and Subgroup 3: Calibra (CAL). After 24 h, bonded specimens were cut into 1 ± 0.1 mm2 sticks. One-half of the beams were tested for microtensile bond strength (MTBS). The remaining one-half was immersed in 10 % NaOCl aqueous solution (NaOClaq) for 5 h before testing. The fracture pattern and morphology of the debonded surfaces were assessed with a field emission gun scanning electron microscope (FEG-SEM). A multiple ANOVA was conducted to analyze the contributions of ceramic composition, surface treatment, resin cement type, and chemical challenging to MTBS. The Tukey test was run for multiple comparisons (p < 0.05). Results: After 24 h, CEC luted to pre-treated zirconia achieved the highest MTBS. Using RXU, alumina and zirconia registered comparable MTBS. CAL failed prematurely, except when luted to sandblasted zirconia. After NaOClaq storage, CEC significantly lowered MTBS when luted to zirconia or alumina. RXU decreased MTBS only when bonded to silica-coated alumina. CAL recorded 100 % of pre-testing failures. Micromorphological alterations were evident after (..) (AU)

Characterization of micro- and nanophase separation of dentin bonding agents by stereoscopy and atomic force microscopy.

The aim was to study the effect of solvents on the phase separation of four commercial dental adhesives. Four materials were tested: Clearfil™ SE Bond (CSE), Clearfil Protect Bond (CPB), Clearfil S3 Bond (CS3), and One-Up Bond F Plus (OUB). Distilled water or ethanol was used as a solvent (30 vol%) for microphase separation studies, by stereoscopy. For nanophase images, the mixtures were formulated with two different solvent concentrations (2.5 versus 5 vol%) and observed by atomic force microscopy. Images were analyzed by using MacBiophotonics ImageJ to measure the area of bright domains. Macrophase separations, identified as a loss of clarity, were only observed after mixing the adhesives with water. Nanophase separations were detected with all adhesive combinations. The area of bright domains ranged from 132 to 1,145 nm² for CSE, from 15 to 285 nm² for CPB, from 149 to 380 nm² for CS3, and from 26 to 157 nm² for OUB. In water-resins mixtures, CPB was the most homogeneous and OUB showed the most heterogeneous phase formation. In ethanol-resin mixtures, CSE attained the most homogeneous structure and OUB showed the most heterogeneous phase. Addition of 5 vol% ethanol to resins decreased the nanophase separation when compared with the control materials.

Resistance to bond degradation between dual-cure resin cements and pre-treated sintered CAD-CAM dental ceramics.

OBJECTIVE: To evaluate the bond stability of resin cements when luted to glass-reinforced alumina and zirconia CAD/CAM dental ceramics. STUDY DESIGN: Eighteen glass-infiltrated alumina and eighteen densely sintered zirconia blocks were randomly conditioned as follows: Group 1: No treatment; Group 2: Sandblasting (125 µm Al2O3-particles); and Group 3: Silica-coating (50 µm silica-modified Al2O3-particles). Composite samples were randomly bonded to the pretreated ceramic surfaces using different resin cements: Subgroup 1: Clearfil Esthetic Cement (CEC); Subgroup 2: RelyX Unicem (RXU); and Subgroup 3: Calibra (CAL). After 24 h, bonded specimens were cut into 1 ± 0.1 mm² sticks. One-half of the beams were tested for microtensile bond strength (MTBS). The remaining one-half was immersed in 10 % NaOCl aqueous solution (NaOClaq) for 5 h before testing. The fracture pattern and morphology of the debonded surfaces were assessed with a field emission gun scanning electron microscope (FEG-SEM). A multiple ANOVA was conducted to analyze the contributions of ceramic composition, surface treatment, resin cement type, and chemical challenging to MTBS. The Tukey test was run for multiple comparisons (p < 0.05). RESULTS: After 24 h, CEC luted to pre-treated zirconia achieved the highest MTBS. Using RXU, alumina and zirconia registered comparable MTBS. CAL failed prematurely, except when luted to sandblasted zirconia. After NaOClaq storage, CEC significantly lowered MTBS when luted to zirconia or alumina. RXU decreased MTBS only when bonded to silica-coated alumina. CAL recorded 100 % of pre-testing failures. Micromorphological alterations were evident after NaOClaq immersion. CONCLUSIONS: Resin-ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. The MDP-containing and the self-adhesive resin cements were both suitable for luting CAD/CAM ceramics. Despite both cements being prone to degradation, RXU luted to zirconia or untreated or sandblasted alumina showed the most stable interfaces. CAL experimented spontaneous debonding in all tested groups.

Effect of thermal cycling on the bond strength of self-adhesive cements to fiber posts.

The aim of this study was to assess the push-out bond strengths of self-adhesive resin cements to epoxy resin-based fiber posts after challenging by thermocycling. Thirty-six single-rooted premolars were endodontically treated, and the post-spaces were drilled to receive RelyX Fiber posts #1. Three self-adhesive resin cements (RelyX Unicem, G-Cem, and Breeze) were used for luting fiber posts. The bonded specimens were either stored for 1 month in a moist field (37°C) or submitted to thermocycling (5,000 times) prior to push-out test. The maximum force required to dislodge the post via an apical-coronal direction was recorded (megapascal). The data were statistically analyzed with two-way ANOVA and Tukey tests (p < 0.05). The factors "luting cement" and "thermocycling" significantly influenced bond strengths. The initial push-out values of RelyX Unicem and Breeze were higher than those of G-Cem. After thermocycling, the bond strength of G-Cem increased and no differences were found between groups. RelyX Unicem and Breeze bond strengths were not affected by the thermal challenge. Thermal cycling and cement type differently influence the bond strengths of self-adhesive resin cements. Self-adhesive cements can represent an option for luting fiber posts into root canal.

Burnout syndrome among dental students: a short version of the "Burnout Clinical Subtype Questionnaire" adapted for students (BCSQ-12-SS).

BACKGROUND: Burnout has been traditionally defined in relation to the dimensions of "exhaustion", "cynicism", and "inefficiency". More recently, the Burnout Clinical Subtype Questionnaire (BCSQ-12) further established three different subtypes of burnout: the "frenetic" subtype (related to "overload"), the "under-challenged" subtype (related to "lack of development"), and the "worn-out" subtype (related to "neglect"). However, to date, these definitions have not been applied to students. The aims of this research were (1) to adapt a Spanish version of the BCSQ-12 for use with students, (2) to test its factorial validity, internal consistency, convergent and discriminant validity, and (3) to assess potential socio-demographic and occupational risk factors associated with the development of the subtypes. METHOD: We used a cross-sectional design on a sample of dental students (n = 314) from Santiago and Huesca universities (Spain). Participants completed the Burnout Clinical Subtype Questionnaire Student Survey (BCSQ-12-SS), the Maslach Burnout Inventory Student Survey (MBI-SS), and a series of socio-demographic and occupational questions formulated for the specific purpose of this study. Data were subjected to exploratory factor analysis (EFA) using the principal component method with varimax orthogonal rotation. To assess the relations with the criterion, we calculated the Pearson correlation coefficient (r), multiple correlation coefficient (R(y.123)), and the coefficient of determination (R(2)(y.123)). To assess the association between the subtypes and the socio-demographic variables, we examined the adjusted odds ratio (OR) obtained from multivariate logistic regression models. RESULTS: Factorial analyses supported the theoretical proposition of the BCSQ-12-SS, with α-values exceeding 0.80 for all dimensions. The "overload-exhaustion" relation was r = 0.59 (p < 0.001), "lack of development"-"cynicism", r = 0.49 (p < 0.001), "neglect"-"inefficiency", r = 0.47 (p < 0.001). The "overload"-"lack of development" relation was r = 0.21 (p < 0.001), "overload"-"neglect", r = 0.20 (p < 0.001), and "lack of development"-"neglect", r = 0.38 (p < 0.001). The BCSQ-12-SS explained 38.44% of the variability in "exhaustion", (R(y.123) = 0.62), 30.25% in "cynicism" (R(y.123) = 0.55), and 26.01% in "inefficiency" (R(y.123) = 0.51). "Hours spent on studying" was found to be associated with "overload" (p = 0.001), "campus" with "lack of development" (p = 0.013), and ""failed subjects" with "neglect" (p = 0.011). CONCLUSIONS: The results support the definition of burnout as established by the BCSQ-12-SS. As such, the BCSQ-12-SS can be used for the recognition of clinical profiles and for the suggestion of potential intervention strategies specific to the characteristics of each particular case.

Effect of surface pre-treatments on the zirconia ceramic-resin cement microtensile bond strength.

OBJECTIVE: To evaluate the influence of different surface treatments on the microtensile bond strength of resin cement to zirconia ceramic. MATERIALS AND METHODS: Twelve cylinder-shaped (∅ 12×5.25 mm high) blocks of a commercial zirconium-oxide ceramic (Cercon® Zirconia, DENTSPLY) were randomly divided into 4 groups (n=3), based on the surface treatment to be performed: (1) airborne particle abrasion with 125 µm Al2O3 particles (S); (2) selective infiltration etching (SIE); (3) experimental hot etching solution applied for 30 min (ST) and (4) no treatment (C). Paradigm MZ100 blocks (3M ESPE) were cut into twelve cylinders of 4mm in thickness. Composite cylinders were bonded to conditioned ceramics using a resin cement (Calibra®, DENTSPLY), in combination with the proprietary adhesive system. After 24h bonded specimens were cut into microtensile sticks and loaded in tension until failure. Bond strength data were analyzed with Kruskall-Wallis and Dunn's Multiple Range test for multiple comparisons (p < 0.05). Failure mode distribution was recorded and the interfacial morphology of debonded specimens was analyzed using a scanning electron microscope (SEM). RESULTS: Bond strength values achieved after SIE and ST treatment were significantly higher than after S treatment and without any treatment (p < 0.05). Premature failures were mostly recorded in the S group. SIGNIFICANCE: Conditioning the high-strength ceramic surface with SIE and ST treatments yielded higher bond strengths of the resin cement than when zirconia ceramic was treated with airborne particle abrasion or left untreated.

Morphological analysis of three zirconium oxide ceramics: Effect of surface treatments.

OBJECTIVE: To evaluate the effect of different chemo-mechanical surface treatments on the morphology of three recently marketed dental zirconia ceramics. MATERIALS AND METHODS: Ceramic discs (Ø 10 mm x 1 mm height) were obtained from three sintered zirconia ceramics (Lava, Cercon, and Aadva Zr) and treated with: (1) airborne particle abrasion with 125 microm Al(2)O(3) particles (S); (2) selective infiltration etching (SIE); (3) experimental hot etching solution applied for 30 min (ST); (4) no treatment (C). Five discs per group were used for surface roughness analysis using an atomic force microscope (AFM). Data were statistically analyzed by Kruskall-Wallis analysis of variance and Mann-Whitney tests (alpha<0.05). The same discs were evaluated under SEM for surface topography analysis. Three discs per group were cemented to a composite overlay (Paradigm MZ100) with a total-etch resin luting agent (Calibra) and cross-section interfacial analysis was performed under SEM. RESULTS AND SIGNIFICANCE: Airborne particle abrasion improved the average surface roughness of Cercon and Lava (p<0.05) while SIE induced significant changes on Lava and Adava Zr. Statistical differences in surface roughness were recorded after selective infiltration etching when compared to no treated group, independently from the zirconia type. SEM and AFM analyses revealed changes in surface topography for all the tested ceramics and intergrain spaces opening, especially after ST. The effectiveness of the tested chemo-mechanical surface treatments depends on the zirconia type. The hot experimental etching solution increased the surface roughness of all the tested ceramics creating retentive micro-spaces that may potentially improve zirconia/resin cement interfacial strengths.

Sealing properties of one-step root-filling fibre post-obturators vs. two-step delayed fibre post-placement.

OBJECTIVES: The sealing properties of a one-step obturation post-placement technique consisting of Resilon-capped fibre post-obturators were compared with a two-step technique based on initial Resilon root filling following by 24h-delayed fibre post-placement. METHODS: Thirty root segments were shaped to size 40, 0.04 taper and filled with: (1) InnoEndo obturators; (2) Resilon/24h-delayed FibreKor post-cementation. Obturator, root filling and post-cementation procedures were performed using InnoEndo bonding agent/dual-cured root canal sealer. Fluid flow rate through the filled roots was evaluated at 10psi using a computerised fluid filtration model before root resection and after 3 and 9mm apical resections. Fluid flow data were analysed using two-way repeated measures ANOVA and Tukey test to examine the effects of root-filling post-placement techniques and root resection lengths on fluid leakage from the filled canals (alpha=0.05). RESULTS: A significantly greater amount of fluid leakage was observed with the one-step technique when compared with two-step technique. No difference in fluid leakage was observed among intact canals and canals resected at different lengths for both materials. CONCLUSIONS: The seal of root canals achieved with the one-step obturator is less effective than separate Resilon root fillings followed by a 24-h delay prior to the fibre post-placement. Incomplete setting of the sealer and restricted relief of polymerisation shrinkage stresses may be responsible for the inferior seal of the one-step root-filling/post-restoration technique.

Dentin treatment effects on the bonding performance of self-adhesive resin cements.

The effects of dentin surface treatments on the microtensile bond strengths and on the interfacial characteristics of self-adhesive resin cements were investigated. Flat dentin surfaces were obtained from human molars and were treated as follows: (i) no treatment of dentin; (ii) 0.1 M EDTA scrubbed for 60 s; or (iii) 10% polyacrylic acid applied for 30 s. Three self-adhesive cements were used to lute composite overlays on deep-coronal dentin surfaces in the presence of simulated pulpal pressure (15 cm of H(2)O). Bonded specimens were cut into beams 1 mm thick and stressed in tension until failure. Fractured sticks were examined under a scanning electron microscope. Additional specimens were stained with Masson's trichrome and observed under light microscopy for interfacial evaluations. The bond strength to dentin of the hydrophobic and solvent-free cement (RelyX Unicem) was unaffected by the tested dentin treatments. The bond strength of the 2-hydroxyethyl methacrylate (HEMA)-based cement (Bis-Cem) decreased after treatment of dentin with EDTA and/or polyacrylic acid. The hydrophilic and water-containing cement (G-Cem) attained a higher bond strength when luted on polyacrylic acid-conditioned dentin. In conclusion, smear layer removal, opening of dentinal tubules, and the water content of dentin differently influence the bond strengths and the interfacial characteristics of self-adhesive cement-dentin interfaces.

Bond strength of an etch-and-rinse adhesive to KrF excimer laser-treated dentin.

OBJECTIVE: The aim of this work was to evaluate the effect of KrF excimer laser treatment on the bond strength between dentin and an etch-and-rinse adhesive system. MATERIALS AND METHODS: Polished dentin surfaces were subjected to the following treatments: (1) 35% phosphoric acid etching for 15 s; (2) laser surface treatment using KrF excimer laser radiation (1 J/cm(2)); and (3) laser treatment under the same conditions followed by acid etching. After treating the dentin, an etch-and-rinse adhesive (Adper Scotchbond 1 XT, 3M ESPE) was applied and composite (Esthet-X, Dentsply Caulk, Konstanz, Germany) build-ups were incrementally constructed. After 24 h of water storage at 37 degrees C, 1 mm(2) beams were longitudinally cut from the samples. Microtensile sticks were loaded in tension at a crosshead speed of 0.5 mm/min. Bond strength data were analyzed with one-way ANOVA and the Student-Newman-Keuls test (p < 0.05). The dentin surfaces resulting from each surface treatment and the fracture surfaces originated by the bond-strength tests were observed under a scanning electron microscope. RESULTS: Laser-treated surfaces exhibited a cone-shaped topography with a frank occlusion of dentinal tubules, while acid etching produced a smoother surface with open tubules. Application of 35% phosphoric acid on laser-treated dentin surfaces resulted in the partial dissolution of the surface cones. Mean microtensile bond strengths for acid-etched dentin was significantly higher (33.7 +/- 8.7 MPa) than for laser-treated (13.8 +/- 5.1 MPa) and laser-treated and etched surfaces (19.7 +/- 6.9 MPa). A higher percentage of cohesive failures at the base of the cones occurred in the laser-treated group, whereas mixed failures were predominant on acid-etched samples. CONCLUSION: The cone-shaped texture produced by treating dentin with KrF laser radiation does not improve the bond strength of the tested etch-and rinse adhesive system when compared to the traditional acid-etching technique.

Influence of different surface treatments on surface zirconia frameworks.

OBJECTIVES: To evaluate the effect of different chemo-mechanical surface treatments of zirconia ceramic in the attempt to improve its bonding potential. METHODS: Sintered zirconium oxide ceramic discs (Lava Ø10mm x 1mm height) were treated with (n=4): (1) airborne particle abrasion with 125microm Al(2)O(3) particles; (2) 9.5% HF acid etching; (3) selective infiltration etching (SIE); (4) experimental hot etching solution applied for 10, 30 and 60min; (5) no treatment. Ceramic discs surfaces were analyzed by atomic force microscopy (AFM) recording average surface roughness measurements of the substrate. Data were statistically analyzed by Kruskall-Wallis analysis of variance and Mann-Whitney tests (alpha=0.05). The same discs were used for bi-dimensional zirconia ceramic surface characterization with scanning electron microscope (SEM). RESULTS: Ceramic surface treatments significantly influenced surface topography and roughness (p<0.001). Bi-dimensional changes in ceramic surface morphology were assessed on a nanometric scale. The experimental hot etching solution improved surface roughness, independently from the application time. CONCLUSION: Zirconia conditioning with the experimental hot etching solution may enhance ceramic roughness and improve the surface area available for adhesion allowing the formation of micromechanical retention. The influence of this surface treatment with regard to bond strength of zirconia needs to be addressed.

Influence of CAM vs. CAD/CAM scanning methods and finish line of tooth preparation in the vertical misfit of zirconia bridge structures.

PURPOSE: To evaluate the influence of CAD/CAM scanning method (wax-up digitization vs. direct scanning of tooth preparation) and finish line type (chamfer vs. shoulder) on the vertical fit of zirconia frameworks for three-unit posterior-lower bridges. METHODS: 30 sets of two stainless steel master dies were prepared with different marginal designs (chamfer and shoulder) around the contour of each abutment. Over these samples, 30 structures for three-unit posterior-lower bridges were made with Cercon Smart Ceramics CAD/CAM system (Dentsply). An optical laser digitized the wax patterns of 15 bridge structures, and 15 pairs of master dies were directly scanned for designing by computer the remaining half of frames. All zirconia milled structures were luted onto the metallic models with a special clamp made-up to maintain constant seating pressure. Vertical discrepancy around the margins was assessed under scanning electron microscopy (SEM). Misfit data was analyzed using two-way ANOVA and Tukey's test for multiple comparisons at a = 0.05. RESULTS: Vertical discrepancy of the wax-up/digitized bridge structures was significantly higher than that of the computer-designed frameworks (P < 0.0001). No statistically significant differences were found between the chamfer and shoulder vertical misfit values assessed around the metallic models margins (P = 0.55).

Push-out bond strength of fiber posts luted with unfilled resin cement.

PURPOSE: The study evaluates the behavior of different adhesive systems and resin cements in fiber post placement, with the intent to clarify the possible role of unfilled resin as a luting material for fiber posts. MATERIALS AND METHODS: Two luting agents (Dual-Link and Unfilled Resin) for cementing fiber posts into root canals were applied either with All-Bond 2 or One-Step Plus, or without an adhesive system, and challenged with the push-out test. Slices of roots restored with posts were loaded until post segment extrusion in the apical-coronal direction. Failure modes were analyzed under SEM. RESULTS: Push-out strength was significantly influenced by the luting agent (p < 0.05), but not by the bonding strategy (p > 0.05). The best results were obtained in combination with Unfilled Resin with One-Step Plus. Dual-Link groups failed mainly cohesively within the cement, while Unfilled Resin demonstrated more adhesive fracture at the post interface. CONCLUSION: The results of this study support the hypothesis that adhesive unfilled resin application is essential for achieving high bond strength to radicular dentin.