BACKGROUND

Provisional restorative materials require good mechanical properties, such as sufficient flexural strength, to remain functional within the oral cavity. Developments in provisional materials have resulted in the production of bis-acryl resins with varying curing methods. However, their performance in a moist environment remains uncertain.

OBJECTIVE

This in-vitro study aimed to assess the effect of aging by storage on the flexural strength of self-cured and dual-cured bis-acryl resin materials.

METHODS

Self-cured (Protemp 4) and dual-cured (Care C&B) bis-acryl resins were used in this study. A total of 40 bar-shaped specimens were fabricated and stored in distilled water at 37 ± 1°C. The control group was stored for 1 day (24 hours) while the treatment group was stored for 7 days prior to testing. Flexural strength was determined through a Three-Point Bending Test using a universal testing machine. Paired t-test was used to compare the mean flexural strengths of the bis-acryl resins after 1 day and after 7 days of storage. Independent T-test was used to compare the mean flexural strengths of the self-cured and the dual-cured bis-acryl resin materials within the same storage period.

RESULTS

The results showed that after 7 days of aging by storage in distilled water at 37 ± 1°C, both self-cured and dual-cured bis-acryl resin materials exhibited a statistically significant decline in mean flexural strength (p < 0.05). Within the same storage period, the difference in mean flexural strengths of the two materials was not statistically significant (p > 0.05).

CONCLUSION

Within the limitations of the study, it was found that aging by storage significantly decreased the mean flexural strength of the self-cured (Protemp 4) and dual-cured (Care C&B) bis-acryl resin materials. Future studies simulating actual intraoral conditions are recommended.

Flexural Strength

BACKGROUND AND OBJECTIVE

Orthodontic brackets predispose dental biofilm accumulation causing caries and gingivitis. Chlorhexidine is an adjunct to mechanical plaque removal, but has side-effects (tooth staining, bacterial resistance) due to long term use. This study tested the efficacy of Photodynamic Therapy, which produces reactive oxygen species, to reduce Streptococcus mutans in dental biofilm on orthodontic brackets.

METHODS

A 5-day S. mutans biofilm was grown on forty enamel-bracket specimens. Thirty-nine specimens were randomized to three treatment groups: A. Distilled Water; B. 0.12% Chlorhexidine (CHX); C. Photodynamic Therapy (PDT) using Toluidine Blue O (TBO) as a photosensitizer, activated by red LED (630nm). After treatment, one random specimen from each group was viewed under Environmental Scanning Electron Microscopy (ESEM); the other 12 specimens, biofilms were collected, weighed, and cultured onto BHI agar plates to determine the number of CFU/mg. For baseline evaluation, one clean and one untreated specimens were preserved for ESEM.

RESULTS

Based on Tukey HSD test, group A had the most S. mutans (37.0573 CFU/mg) and was significantly different (pCONCLUSION

Both Photodynamic Therapy and 0.12% Chlorhexidine showed a significant reduction of S. mutans in dental biofilm on orthodontic brackets. However, there is no significant difference between them in reducing S. mutans CFU/mg. Photodynamic therapy could be an alternative adjunctive tool to mechanical removal of plaque adhered to orthodontic brackets.

Bacteria ; Photochemotherapy ; Photodynamic Therapy ; Microscopy, Electron, Scanning ; Biofilms ; Orthodontic Brackets ; Chlorhexidine

BACKGROUND AND OBJECTIVE

Orthodontic brackets predispose dental biofilm accumulation causing caries and gingivitis. Chlorhexidine is an adjunct to mechanical plaque removal, but has side-effects (tooth staining, bacterial resistance) due to long term use. This study tested the efficacy of Photodynamic Therapy, which produces reactive oxygen species, to reduce Streptococcus mutans in dental biofilm on orthodontic brackets.

METHODS

A 5-day S. mutans biofilm was grown on forty enamel-bracket specimens. Thirty-nine specimens were randomized to three treatment groups: A. Distilled Water; B. 0.12% Chlorhexidine (CHX); C. Photodynamic Therapy (PDT) using Toluidine Blue O (TBO) as a photosensitizer, activated by red LED (630nm). After treatment, one random specimen from each group was viewed under Environmental Scanning Electron Microscopy (ESEM); the other 12 specimens, biofilms were collected, weighed, and cultured onto BHI agar plates to determine the number of CFU/mg. For baseline evaluation, one clean and one untreated specimens were preserved for ESEM.

RESULTS

Based on Tukey HSD test, group A had the most S. mutans (37.0573 CFU/mg) and was significantly different (p < 0.05) from groups B (0.1712 CFU/mg) and C (1.1193 CFU/mg), where both showed less bacteria than group A. The statistical difference between groups B and C was insignificant. ESEM images showed specimen A covered with more abundant and denser S. mutans biofilm than specimens B and C, with almost similar morphology showing sparse, less dense, and disintegrated biofilm with unclear cellular walls and presence of amorphous masses.

CONCLUSION

Both Photodynamic Therapy and 0.12% Chlorhexidine showed a significant reduction of S. mutans in dental biofilm on orthodontic brackets. However, there is no significant difference between them in reducing S. mutans CFU/mg. Photodynamic therapy could be an alternative adjunctive tool to mechanical removal of plaque adhered to orthodontic brackets.

Bacteria ; Photochemotherapy ; Photodynamic Therapy ; Microscopy, Electron, Scanning ; Biofilms ; Orthodontic Brackets ; Chlorhexidine