Browsing by Subject "Shear Strength"
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Item A Comparison of Shear-Peel Bond Forces of Flattened and Unaltered Brackets on Flattened and Curved Enamel Surfaces(2007) Wyatt, Tracy D.; Katona, Thomas R.; Baldwin, James J.; Hohlt, William F.; Moore, B. Keith; Shanks, James C.One aspect of bond strength testing that varies among researchers is the contour of the tooth and bracket bases that are tested. Unaltered teeth with as-manufactured brackets are the most commonly used combination. Flattened teeth with unaltered bracket bases and mechanically flattened teeth and brackets are also used. The intended purpose of this project was to determine the effect of tooth and bracket contour combinations on the shear, tension and torsional bond forces of bonded brackets. The crowns of two-hundred and four bovine incisors were potted in acrylic tubes with their facial surfaces slightly protruding. The facial surfaces of half of them were ground flat on a Wehmer model trimmer (The Wehmer Corporation, Lombard, IL). The remainder were contoured on a Wehmer model trimmer using a jig that rotated the tooth's facial surface on a radius of approximately 3 inches. One-hundred and two maxillary right central incisor brackets (3M Unitek, Monrovia, CA. Victory Series, .022 slot) were flattened, ten at a time with a 2000 N force on a self-leveling plate in the MTS Bionix testing machine (MTS Systems Corporation, Eden Prarie, MN). Another 102 brackets were unaltered. The Day 1 data set samples (shear-peel loading) were etched with 35% phosphoric acid gel and bonded with Transbond XT Light Cured Adhesive Paste (3m Unitek). This provided 17 specimens for each of four groups: curved tooth/curved bracket (C/C), curved tooth/flat bracket (C/F), flat tooth/curved bracket (F/C), and flat tooth/flat bracket (F /F). The samples were de-bonded in the MTS Bionix testing machine with the force applied parallel to the bracket base, (i.e., in shear-peel) and the peak forces were recorded. Due to large variations in the results and low forces compared with previously published studies from this laboratory, the bonding protocol and loading were altered for Day 2 testing. Rather than torsion loading, the shear-peel debond set was repeated. The following changes were made to the bonding protocol. The samples were pumiced following sanding and stored in fresh de-ionized water prior to bonding. The samples were also dried with compressed air following etching and the primer was thinned with compressed air. Following preparation the samples were debonded in the MTS Bionix testing machine and peak forces were recorded. These results were also inexplicably variable and relatively low. Day 3 samples, intended for torsion debonding, were bonded the same as the Day 2 samples except that a 3 7% phosphoric acid liquid (Reliance, Itasca IL) was used to etch the samples and a new bottle and tube of Trans bond XT Light Cured Adhesive Primer and Transbond XT Light Cured Adhesive Paste (3M Unitek) were used. The samples were also debonded in shear-peel in the MTS Bionix testing machine and peak forces were recorded. Despite the outlined efforts, these results were also scattered and relatively lower than obtained previously. An analysis of variance model was used to evaluate the bond forces and showed no statistical difference among the groups except that in the Day 2 data set the C/C group was significantly weaker than the F/F group (p= .0452). In the Day 3 data set the C/C group was also weaker than the F/F group though the results were not significant (p=.0739). There is a trend to suggest that the bracket base and crown curvatures may be important factors in determining shear bond force.Item Effect of halloysite aluminosilicate clay nanotube incorporation into bonding agents on shear bond strength to human dentin(2013) Alkatheeri, Mohammed Saeed; Bottino, Marco C.; Chu, Tien-Min Gabriel; Platt, Jeffrey A., 1958-; Cook, Norman Blaine, 1954-; Cochran, Michael A. (Michael Alan), 1944-In adhesive dentistry, obtaining a good bond is a fundamental goal. It has been suggested that filler addition to the adhesives would increase the bonding strength of the adhesive layer. Halloysite aluminosilicate nanotubes (HNTs) are biocompatible, hydrophilic, durable, and have high mechanical strength. These advantages make them good candidates to be used as reinforcing agents for improving the properties of dental adhesives. The objective of this study was to evaluate the effect of incorporating HNTs into a commercial two-step etch-and-rinse adhesive system or one-step self-etch adhesive system on dentin shear bond strength. HNTs were incorporated into the two commercial adhesive systems in 0 wt%, 5 wt%, 10 wt%, and 20 wt%. The commercial control adhesives and the experimental adhesives were used to bond occlusal dentin of 120 extracted human molar teeth and then tested for shear bond strength by a universal testing machine with a semi-circular edge at a crosshead speed of 1.0 mm/min. Debonded specimens were examined under light microscopy to evaluate the fracture pattern. Resin-dentin interface were evaluated under scanning electron microscopy (SEM) after bonding dentin slabs using commercial control adhesives and experimental adhesive that showed numerically highest shear bond strength from each adhesive system. Two-way ANOVA was used to evaluate the effects of adhesive system and nanofiller content on shear bond strength. Pair-wise comparisons between groups were made using Fisher's (LSD) (p < 0.05). For the self-etch adhesive system, only incorporation of 5 wt% showed a significant increase in shear bond strength to dentin compared with the commercial control group. For the etch-and-rinse adhesive system, there was no significant difference in shear bond strength between HNTs filled adhesives groups and the commercial control group. Resin-dentin interface SEM evaluation showed nanotubes infiltrated into dentinal tubules. In conclusion, incorporating the self-etch adhesive system with 5 wt% HNTs increased the bond strength to dentin. Incorporation of up to 10 wt% filler concentration into both the self-etch and the etch-and-rinse adhesive systems did not adversely affect the bond strength to dentin or the handling properties. HNTs can penetrate along with resin tags into dentinal tubules, which could expand the use of their unique properties.Item Influence of surface treatment on veneering porcelain shear bond strength to zirconia after cyclic loading(2013) Nishigori, Atsushi; Platt, Jeffrey A., 1958-; Brown, David T.; Ando, Masatoshi; Bottino, Marco C.; Levon, John A.Statement of problem: Yttria-partially stabilized tetragonal zirconia polycrystal (Y-TZP) all-ceramic restorations have been reported to suffer from chipping or cracking of the veneering porcelain (VP) as the most common complication. There is little information in the literature regarding the influence of surface treatment on VP shear bond strength to Y-TZP after cyclic loading. Purpose of this study: The goals of this study were (1) to investigate the influence of zirconia surface treatments on veneering porcelain shear bond strength and (2) to investigate the influence of cyclic loading on the shear bond strength between VP and Y-TZP. Materials and Methods: 48 cylinder–shaped specimens (6mm in diameter and 4mm in height) were divided into 4 groups containing 12 specimens each according to the surface treatment. As a control group (C), no further treatment was applied to the specimens after grinding. Group H was heat-treated as a pretreatment according to the manufacturer’s recommendations. Group S was airborne-particle abraded with 50 µm alumina (Al2O3) particles under a pressure of 0.4 MPa for 10 seconds. In the group SH, the heat-treatment was performed after the airborne-particle abrasion. A VP cylinder (2.4 mm in diameter and 2 mm in height) was applied and fired on the prepared Y-TZP specimens. The shear bond strength was tested using a universal testing machine. Six specimens from each group were subjected to fatigue (10,000cycles, 1.5Hz, 10N load) before testing. Results: The 3-way ANOVA showed no statistically significant effect of surface treatment and cyclic loading on shear bond strength. The highest mean shear bond strength was recorded for the air-particle abrasion group without cyclic loading (34.1 + 10 MPa). The lowest mean shear bond strength was the air-particle abrasion group with cyclic loading (10.7 ± 15.4 MPa). Sidak multiple comparisons procedure demonstrated cyclic loading specimens had significantly lower shear bond strength than non-cyclic loading specimens after air-particle abrasion without heat treatment (p=0.0126) Conclusion: Within the limitations of this study, (1) Shear bond strength between Y-TZP and VP is not affected statistically by surface treatment using heat treatment, airborne-particle abrasion, and heat treatment after airborne-particle abrasion. (2) There is significant difference in shear bond strength with air-particle abrasion between with and without cyclic loading groups. This difference suggested that air-particle abrasion should be avoided in clinical situations as a surface treatment without heat treatment.Item Shear Bond Strengths Of A Two-Step Self-Etch Adhesive And A Three-Step Etch-And-Rinse Adhesive In Artificial Dentin Caries Lesions Of Various Depths: An In Vitro Study(2024-07) Buechele, Ryan W.; Cook, Norman B.; Diefenderfer, Kim E.; Capin, Orian R; Sochacki, Sabrina F.; Strother , James M.Background: Minimally invasive caries management philosophy advocates leaving carious dentin as a substrate for adhesive bonding. However, the performance of current resin adhesives in incompletely excavated caries lesions is unknown. Understanding the limitations of bonding to carious dentin is critical for the restoring clinician. Objective: To compare the shear bond strengths of a two-step self-etch adhesive and a three-step etch-and-rinse adhesive to moderate and severe artificial dentin caries. Methods: 96 bovine incisors were prepared and assigned to experimental groups of moderate or severe artificial dentin caries lesions or control groups (sound dentin). Specimens were randomly assigned to a two-step self-etch (Clearfil SE Bond 2) or three-step etch-and-rinse (OptiBond FL) adhesive for bonding to a nanohybrid composite resin. TMR analysis determined lesion depth. Specimens were stored for 30 days in Millipore water (5oC), shear bond strengths were measured, and failure modes observed. Two-way ANOVA with interactions evaluated the effects of adhesive type and demineralization severity on shear bond strength. Failure modes were compared using ordinal logistic regression. A two-sided 5% significance level was used for all tests. Results: Clearfil SE performed significantly better than Optibond FL in both moderate and severe lesions. Both adhesives performed adequately on sound dentin, but poorly in severe lesions. For OptiBond FL, bond strengths were lowest in moderate lesions; failures were predominantly mixed or cohesive within composite resin in both moderate and severe lesions, as well as in sound dentin specimens. For Clearfil SE, bond strengths were lowest in severe lesions; failures were predominantly adhesive in moderate lesions, cohesive within composite resin in severe lesions, and mixed adhesive/cohesive in sound dentin specimens. Discussion: Bonding to demineralized dentin was highly variable for both adhesives. Bonding to sound dentin yielded higher bond strengths. Conclusions: A three-step etch-and-rinse adhesive did not perform better than a two-step self-etch adhesive in this study. A self-etch adhesive may be the better choice when bonding to demineralized dentin. Either adhesive may be acceptable when bonding to sound dentin.