Browsing by Subject "Materials Testing"
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Item Comparison of Frictional Forces Between Three Grades of Low Friction "Colors" TMA(2001) Rosenthall, Mark R.; Oshida, Yoshiki; Baldwin, James; Hohlt, William; Katona, Thomas; Shanks, JamesFrictional forces between archwires and brackets play a significant role in the efficiency of orthodontic tooth movement. The purpose of this investigation were to (1) compare the wet static frictional forces of low friction "Colors" TMA ™ arch wires with arch wires of other materials (stainless steel, NiTi, and uncoated TMA ™) and (2) test the effects of repetitive sliding. Testing was accomplished by using a cantilever testing device, which held the archwire in place between two 303 stainless steel test flats. The test flats were used to simulate an orthodontic bracket. A saliva substitute (Ringer's solution) was used to simulate the oral environment. Six wire types (stainless steel, NiTi, TMA ™, and three types of "Colors" TMA ™ wires [purple, aqua and honeydew]). For each said wire type, 15 archwires were tested. Each archwire type was run five times at three different weights (normal forces) and each wire was subjected to five repetitions. In total, 450 runs were established. The effects of wire type (6 types), normal force (1267g, 2153g, 2533g) and repetition (5 per wire) on wet static frictional were examined using three-way analysis of variance (ANOVA). Pairwise comparisons between treatment combinations were made using Sidak method to control the overall significance level. After wire testing, a sample of untested (0 runs) and tested (1 run, 5 runs) wires were viewed under a light microscope at 160X magnification. The results indicated uncoated TMA ™ wires produced the highest wet static frictional forces. In general, NiTi produced the next highest force levels followed by the three "Colors" TMA ™ wires, and then stainless steel. Repetition was observed to affect only NiTi and uncoated TMA TM wires. NiTi wires showed a decrease in force values between runs 1 and 5 at p < 0.05. Uncoated TMA ™ showed an increase in force values between runs 1 and 2. The cause for these findings could not be validated by light microscope evaluation.Item Effect of Toothbrushing on a Monolithic Dental Zirconia Submitted to an Accelerated Hydrothermal Aging(2022) Almajed, Norah; Sochacki, Sabrina Feitosa; Cook, Norman Blaine; Capin, Oriana ReisItem Evaluation of Second Generation Indirect Composite Resins(2008) Jain, Vishal V.; Platt, Jeffrey A., 1958-; Moore, B. Keith; Xie, Dong; Taskonak, BurakIndirect composites were introduced so that the composites can be cured extraorally to improve the degree of conversion and other material properties. These materials are indicated as long term full coverage dental restorative materials. However the mechanical and physical properties of new Second Generation Indirect Composites for this particular application have not been fully evaluated. The purpose of the study was to compare the appropriateness of the four commercially available laboratory composite resins for application as long term full coverage restorative materials. Water solubility and sorption levels, staining resistance, gloss, surface roughness, wear due to tooth brush abrasion, two-body and three-body wear, fracture toughness and radiopacity of four indirect composite restorative materials; Radica (Dentsply), Sculpture Plus (Pentron), Belleglass-NG (Kerr) and Gradia Indirect (GC America) were determined. The results showed that the four composites differed significantly from each other. Bell eglass-NG and Gradia Indirect showed negative water solubility. All the four groups demonstrated less color stability when exposed to coffee slurry for 3 weeks. Significant decrease in gloss and volume occurred when the omposites were exposed to simulated tooth-brush abrasion. Sculpture Plus v demonstrated lowest abrasion and attrition wear resistance among the four indirect composites. Radica had the highest fracture toughness and radiopacity of all the composites with values close to or less then dentin. In conclusion, different indirect composite systems possessed different mechanical and physical advantages when compared to each other. In general, Belleglass-NG demonstrated superior advantages due to its higher abrasion and attrition wear resistance and stain resistance. This was followed by Radica,Gradia Indirect and Sculpture Plus.Item The Mechanical Properties of Full-Contour Zirconia(2014) Janabi, Anmar Uday; Chu, Tien-Min Gabriel; Matis, Bruce A.; Lund, Melvin R., 1922-; Cochran, Michael A. (Michael Alan), 1944-; Cook, Norman Blaine, 1954-The objectives: 1. To compare the flexural strength, flexural modulus, and fracture toughness of specimens fabricated from recently marketed translucent full-contour zirconia, traditional zirconia, and lithium disilicate glass ceramic. 2. To compare the load-to-failure of crowns fabricated from recently marketed translucent full-contour zirconia, traditional zirconia, and lithium disilicate glass ceramic at their recommended tooth-reduction thickness. Methodology: Four groups of translucent zirconia (BruxZir, KDZ Bruxer, CAP FZ, Suntech zirconia), one group of traditional zirconia (CAP QZ) and IPS e.maxCAD) were tested. Twelve bars of each material were made and tested for flexural strength, and fracture toughness. Fracture patterns were imaged under SEM. Forty-eight crowns (8 from each group) were fabricated with CAD/CAM technique following manufacturers’ recommendations for the amount of tooth reduction. All the crowns were cemented to prepared epoxy resin dies with RelyX Unicem and tested for static load to failure in a universal machine. Result: In bar-shape samples, CAP QZ (traditional zirconia) showed the highest flexural strength (788.12 MPa), fracture toughness (6.85 MPa.m1/2), and fracture resistance (2489.8 N). All translucent zirconia groups show lower mechanical properties than QZ. However, there were no differences between translucent and traditional zirconia in the fracture resistance of the crown-shape samples. There was no significant difference in fracture resistance between IPS e.max crowns at recommended thickness and other zirconia crowns at recommended thickness. Conclusion: With less reduction of tooth structure, a high inherent strength and chip resistance make full-zirconia crowns a good alternative to porcelain-fused-to-metal crowns and all other ceramic crowns.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.