Browsing by Author "Carlson, Timothy J."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Clinical Evaluation of a Universal Adhesive in Non-Carious Cervical Lesions
    (2016) Rouse, Matthew A.; Platt, Jeffrey A.; Jackson, Richard D.; Carlson, Timothy J.; Matis, Bruce A.; Cook, Norman Blaine
    The “total-etch” or “etch-and-rinse” systems have been the gold standard of dental bonding for decades. However, these systems are very technique-sensitive and time-consuming compared to newer “self-etch” or “self-adhesive” systems and have been implicated in cases of postoperative sensitivity. The purpose of this study was to compare the effects of two surface treatment protocols (self-etch vs. selective-etch) on the clinical performance of a universal adhesive and resin composite in Class V non-carious cervical lesions (NCCLs). Thirty-three volunteer subjects (17 male; 16 female; age range = 20 to 75 years) having at least two NCCLs were selected from patients of record at Indiana University School of Dentistry. Each subject received one resin composite restoration (Tetric EvoCeram, Ivoclar Vivadent) utilizing a self-etch (SfE) universal adhesive (Adhese Universal, Ivoclar Vivadent) with no separate enamel etching and another restoration utilizing adhesive and selective enamel etching (SelE) with 37% phosphoric acid (H3PO4). Both the adhesive and composite were placed following the manufacturer’s instructions. The two techniques were compared for differences in sensitivity, retention, marginal discoloration, marginal adaptation, and clinical acceptability at baseline and 6 months using the Cochran-Mantel-Haenszel tests for stratified, ordered categorical outcomes. Seventy-four restorations (37 SfE, 37 SelE) in 30 volunteers were evaluated at 12 months. No significant differences were found between the SfE and SelE groups for any variable at the 12-month recall (p>0.21). Retention was 100% at 12 months for both groups. Marginal adaptation was significantly worse at 12 months than at baseline for SelE (p=0.0163), but there was no difference for SfE (p=0.08). Sensitivity improved significantly from baseline to 12 months for both SelE (p=0.0113) and SfE (p=0.0128). The results obtained from this study are comparable to results observed in similar studies. Like similar studies involving self-etch adhesives in non-carious cervical lesions, our study showed no restorations lost to caries and excellent retention. The deterioration of selective-etch dentin margins was a result that differed from similar studies. A likely explanation for this finding would be the difficulty of controlling precise placement of phosphoric acid gel, causing undesired etching of dentin; this could result in suboptimal bonding to dentin. This report on 12-month data for a two-year study indicates significantly reduced sensitivity for both the SelE and SfE groups, and deterioration of SelE marginal adaptation. No decreases in retention, marginal discoloration, or clinical acceptability were observed in either group.
  • Thumbnail Image
    Item
    Generation of Transient Deformations and Strains by Light Polymerization
    (2002) Hamula, David W.; Katona, Thomas R.; Carlson, Timothy J.; Chen, Jie; Hohlt, William F.; Shanks, James C.
    A significant factor in the long term viability of resin composite dental restorations is minimizing the stress development along the wall of the cavity as the material shrinks during polymerization. The stress of polymerization shrinkage can lead to gap formation between the restoration and the walls of the cavity (microleakage). Clinical manifestations associated with material shrinkage include tooth sensitivity, discoloration, loss of restoration, secondary decay and tooth fracture. Recent research in resin composite polymerization has incorporated Finite Element (FE) stress analysis. An FE model predicted initial extrusion of the resin composite surface during light curing in a bulk-filled Class V restoration. The purpose of this project was to measure transient events during the polymerization of a light-cured resin composite. The hypothesis tested was that during light-activated polymerization of a Class V type restoration, the resin composite surface initially extrudes and measurable stresses occur along the cavity walls. In Experiment 1, initial surface movements were measured. A specifically configured test apparatus enabled surface resin movements to be recorded by a profilometer. Eight identical Class V preparations were drilled into a black acrylic block. The preparations were filled with Herculite and cured. For each of the eight trials, the profilometer recorded an initial extrusion of the resin composite surface. This experiment proved that during light activate polymerization of the resin composite, the FEM predicted counterintuitive initial surface extrusion does take place. In Experiment 2, initial strains were measured. For this pilot study a thin walled black acrylic tube was used as the Class V type restoration. Miniature strain gauge strips were placed along the wall of the cavity at right angles to measure circumferential and longitudinal strains along the cavity surface as the polymerization front advances. The preliminary data suggests the largest circumferential and longitudinal strains initially recorded were closest to the resin surface. The results of these experiments demonstrated initial resin composite surface extrusion and measurable strains along the cavity wall. This experimental data served as a partial validation of the FEM approach.