Objective: The study was to investigate the flexural strength of poly methyl methacrylate (PMMA) denture base specimens when they were repaired using various methods at different periods of water immersion.
Methods: Ninety-six rectangular specimens measuring 64 x 10 x 2.5 mm were fabricated from heat-polymerized PMMA. After one month water immersion at 37C°, the specimens were randomly divided into 4 groups. Control group was left intact without repair (C) Other specimens were cut into 2 halves and repaired with an auto-polymerized resin. One group was prepared with conventional repair method (R). Two of the repair groups had in addition a cavity (21.5 X 3.5 X 2 mm) prepared at the joint ends to provide space for reinforcement material; one group was repaired with E-glass fiber embedded within the cavity (R+Ca+G) while the other group was repaired without fiber reinforcement (R+Ca). A three-point flexural bending test was carried out to evaluate the flexural strength of all groups after one day, one week and one month water immersion. Data were analyzed using two- way ANOVA and Dunnett T3 (p=0.05).
Results: Flexural strength values (mean±S.D. in MPa). The same superscripts indicate no significant difference (p>0.05)
|
| One Day | One Week | One Month
|
| C | 81.7±2.2 a | 79.7±1.5ab | 73.4±4.b |
| R+Ca+G | 61.9±1.9c | 61.9± 2.1c | 62.2±3.9c |
| R+Ca | 50.3±6.2d | 54.3±4.4cd | 52.9±7.8cd |
| R | 54.9±4.cd | 54.6±5.cd | 33.6±5.5e |
ANOVA showed significant difference for the repair methods, immersion period and their interactions (p<0.05). After 1 month water immersion, C and R groups showed significant decrease in the flexural strength (p<0.05) but no significant difference were observed in R+Ca and R+Ca+G groups.
Conclusion: The study showed that glass fiber reinforced the repair strength. The effect of cavity preparation in the repair joints was to decrease the deterioration effect of water on the flexural strength.