Maxillary premolars have variable root canal morphology, most commonly they are bi- rooted and two canalled teeth but there is a small incidence of being three roots system. In case of three root canals this third canal can be missed easily. In these cases true knowledge of tooth morphology, properly evaluate diagnostic x-rays and access cavity preparation could help successful root canal treatment. This article reports retreatment of three root canalled maxillary first premolar and treatment principles.

 

Objectives: The aim of the current study was to measure and evaluate the surface hardness of tooth substrates (enamel and dentin) and different tooth colored restorative materials (resin composites, GIC and their drivatives) after immersion for certain time in different acidic food and drinks.
 

Methods: Different acidic food and drinks used in this study include: Cola soft drink, yogurt, orange juice, sports drink, and some sore food like Tom-yum soup. Immersion of specimens in previously mentioned acidic food\drinks were for 15 seconds then immersed in artificial saliva for 10 cycles to simulate what happened in oral cavity. These procedures repeated daily for 14 days. Surface hardness for specimens

were measured by Vickers hardness device before and after immersion. Data were collected, tabulated and analyzed using one-way ANOVA followed by a least significant different test.

Results: In comparison between tooth substrates (enamel & dentin), the surface hardness values of enamel were decreased than of dentin after immersion in cola soft drinks. Same results were observed after immersion in orange juice and sports drink but with less effect than cola soft drinks. Significant decrease in surface hardness values were detected for micro-filled composite and resin modified glass ionomer cement after immersion in cola soft drinks (p>0.05). On the other hand, there were no statistical significant effect on surface hardness values of all specimens after immersion in yogurt and Tom-yum soup.
 

Conclusion: Some public acidic food and drinks have an erosive harmful effect on surface hardness of tooth substrate (enamel and dentin) in addition to their bad effect on mechanical properties of some tooth colored restorative materials.