Nathan E Robison1, Daranee Tantbirojn2, Antheunis Versluis3, David R Cagna4. 1. Resident, Advanced Prosthodontics Program, University of Tennessee Health Science Center, Memphis, Tenn. 2. Associate Professor, Department of Restorative Dentistry, University of Tennessee Health Science Center, Memphis, Tenn. 3. Professor and Director of Biomaterials Research, Department of Bioscience Research, University of Tennessee Health Science Center, Memphis, Tenn. Electronic address: antheun@uthsc.edu. 4. Professor and Director of Graduate Prosthodontics, Department of Prosthodontics, University of Tennessee Health Science Center, Memphis, Tenn.
Abstract
STATEMENT OF PROBLEM: Denture tooth fracture or debonding remains a common problem in removable prosthodontics. PURPOSE: The purpose of this in vitro study was to explore factors determining failure strengths for combinations of different denture tooth designs (shape, materials) and injection or compression molded denture base resins. MATERIAL AND METHODS: Three central incisor denture tooth designs were tested: nanohybrid composite (NHC; Ivoclar Phonares II), interpenetrating network (IPN; Dentsply Portrait), and microfiller reinforced polyacrylic (MRP; VITA Physiodens). Denture teeth of each type were processed on an injection molded resin (IvoBase HI; Ivoclar Vivadent AG) or a compression molded resin (Lucitone 199; Dentsply Intl) (n=11 or 12). The denture teeth were loaded at 45 degrees on the incisal edge. The failure load was recorded and analyzed with 2-way ANOVA (α=.05), and the fracture mode was categorized from observed fracture surfaces as cohesive, adhesive, or mixed failure. RESULTS: The following failure loads (mean ±SD) were recorded: NHC/injection molded 280 ±52 N; IPN/injection molded 331 ±41 N; MRP/injection molded 247 ±23 N; NHC/compression molded 204 ±31 N; IPN/compression molded 184 ±17 N; MRP/compression molded 201 ±16 N. Injection molded resin yielded significantly higher failure strength for all denture teeth (P<.001), among which IPN had the highest strength. Failure was predominantly cohesive in the teeth, with the exception of mixed mode for the IPN/compression group. CONCLUSIONS: When good bonding was achieved, the strength of the structure (denture tooth/base resin combination) was determined by the strength of the denture teeth, which may be affected by the processing technique.
STATEMENT OF PROBLEM: Denture tooth fracture or debonding remains a common problem in removable prosthodontics. PURPOSE: The purpose of this in vitro study was to explore factors determining failure strengths for combinations of different denture tooth designs (shape, materials) and injection or compression molded denture base resins. MATERIAL AND METHODS: Three central incisor denture tooth designs were tested: nanohybrid composite (NHC; Ivoclar Phonares II), interpenetrating network (IPN; Dentsply Portrait), and microfiller reinforced polyacrylic (MRP; VITA Physiodens). Denture teeth of each type were processed on an injection molded resin (IvoBase HI; Ivoclar Vivadent AG) or a compression molded resin (Lucitone 199; Dentsply Intl) (n=11 or 12). The denture teeth were loaded at 45 degrees on the incisal edge. The failure load was recorded and analyzed with 2-way ANOVA (α=.05), and the fracture mode was categorized from observed fracture surfaces as cohesive, adhesive, or mixed failure. RESULTS: The following failure loads (mean ±SD) were recorded: NHC/injection molded 280 ±52 N; IPN/injection molded 331 ±41 N; MRP/injection molded 247 ±23 N; NHC/compression molded 204 ±31 N; IPN/compression molded 184 ±17 N; MRP/compression molded 201 ±16 N. Injection molded resin yielded significantly higher failure strength for all denture teeth (P<.001), among which IPN had the highest strength. Failure was predominantly cohesive in the teeth, with the exception of mixed mode for the IPN/compression group. CONCLUSIONS: When good bonding was achieved, the strength of the structure (denture tooth/base resin combination) was determined by the strength of the denture teeth, which may be affected by the processing technique.