Effect of Repair Gap Width on the Strength of Denture Repair: An In Vitro Comparative Study

Abstract

Purpose To evaluate the effect of repair gap width on the flexural strength and impact strength of a repaired acrylic denture with and without thermal cycling. Materials and Methods A total of 240 heat‐polymerized acrylic resin specimens were fabricated in dimensions of 65 × 10 × 2.5 ± 0.2 mm and 55 × 10 × 10 ± 0.2 mm for flexural strength and impact strength testing, respectively. All specimens were sectioned into halves then divided into 6 groups according to repair gap width (n = 10). The repair gap of the control group was 2.5 mm at the base, while the repair gaps of the test groups were prepared as 2.0, 1.5, 1.0, 0.5, and 0 mm at the base. All specimens were prepared with a 45° bevel joint. Each specimen was placed into the mold that retained the original length of the specimen and modified only the repair gap, which was packed with repair resin. After polymerization, specimens were finished and polished, and half of the specimens were thermal cycled for 5000 cycles. Three‐point bending test and Charpy impact test were used to determine the flexural strength and impact strength, respectively. ANOVA and Tukey's HSD test were used for statistical analysis, where α was set at 0.05. Results Decreasing repair gap significantly increased the flexural strength in comparison to control group (p < 0.05); 0.5‐mm repair gap showed the highest flexural strength values. Changing the repair gap significantly increased the impact strength of groups 2.0‐ and 1.5‐mm (p < 0.05). Thermal cycling significantly decreased the flexural strength of all tested groups as well as impact strength for groups with wide repair gaps (2.5‐, 2.0‐, and 1.5‐mm) (p < 0.05), while other tested groups had nonsignificant effect on impact strength (p > 0.05). Conclusion Decreasing repair gap increased the flexural and impact strengths of repaired acrylic resin. A repair gap of 0‐, 0.5‐, or 1.0‐mm with beveled repair surface is recommended to improve repair strength and overcome the drawbacks of increased amounts of autopolymerized repair resin.

Comparative Effect of Glass Fiber and Nano‐Filler Addition on Denture Repair Strength

“…In contrast, the presence of nanofillers on the surface of repaired area may contribute to the improvement in surface properties and provide biological benefits . Further investigations of the addition of nano‐ZrO 2 in concentrations more than 0.75% and nano‐SiO 2 in concentrations less than 0.25%, or combining two or more fillers with repair gap modifications may show promising results. In this study, it was noticed that there was a good matching of repair resin with denture base resin for all tested groups except a minor and negligible whitish discoloration observed with high concentration of zirconia, this observation did not exhibit any aesthetic problem.…”

Effect of SiO2 Nanoparticles Addition on the Flexural Strength of Repaired Acrylic Denture Base

“…3,16,21 A metal mold with internal dimensions of 65 × 10 × 2.5 mm was used for repair procedure standardization. To repair the sectioned specimens, repair surfaces were treated with monomer for 120 seconds 22 and then each pair of a specimen was assembled in the mold insuring a repair gap of 2.5 mm at the intaglio side. Prepared repair resin with the different nano-SiO 2 concentrations was mixed independently according to manufacturer instructions and packed into the repair gap.…”

“…The nature of failure was examined by bare eye and SEM as described by Gad et al 22 and Qaw et al 23 The morphology of the fractured surfaces of specimens was further examined using SEM (FEI; INSPECT S50, Czech Republic), where various magnifications were used to classify the nature of failure. Compact and smooth surface represents brittle fracture, while rough and jagged appearance represents ductile fracture mode.…”

Polymethylmethacrylate Incorporating Nanodiamonds for Denture Repair: In Vitro Study on the Mechanical Properties

“…Recording of the maximum load at fracture was performed, and the flexural strength (FS) and elastic modulus were calculated as described in previous studies. 5,21 Charpy's impact testing machine (Digital Charpy Izod impact tester, XJU 5.5, Jinan Hensgrand Instrument Co., Ltd., Jinan, China) was used to measure the impact strength. After horizontal placement of the specimen on a metal jig with 40 mm distance between two supports, a pendulum with 0.5 J weight was fallen at the back side of the specimens (opposite to the notch).…”