ABSTRACT
The aim of this study was to assess the effect of closed fitting mouth guard with fluoridegel (1.1% NaF gel) or fluoride toothpaste (0.11% NaF) on surface hardness of enamel aftersoaking in chlorinated water at pH 3.4 for 2 hours. Fifty two human premolars extracted fororthodontic reasons were divided into 5 groups (13 specimens in each group): enamel slabswithout mouth guard (control group; C), enamel slabs with mouth guard only (experimentalgroup 1; E1), enamel slabs with mouth guard and fluoride gel (experimental group 2; E2),enamel slabs with mouth guard and fluoride toothpaste (experimental group 3; E3) andenamel slabs with mouth guard and Vaseline (experimental group 4; E4). Before and aftersoaking in chlorinated water, ten specimens of each group were measured for enamelmicrohardness and 3 specimens of each group were prepared to examine the enamelappearance using scanning electron microscope (SEM). The results showed that enamelmicrohardness decreased in all specimens significantly (p \< .05) except E2. Group C had thehighest means of difference Vickers microhardness number (VHN) before and after soaking inchlorinated water. (147.75ฑ11.25) E1, E4, E3 and E2 had lower means of difference in VHN.The lowest one was E2 (10.36ฑ6.74). There were significant differences between groups(p \< .05) except between E3 and E4. After soaking in Chlorinated water, SEM revealedhoneycomb-liked etched patterns on enamel surface only in group C. This study indicated thatenamel which exposed to strong acidic water had decreased surface hardness and hadchanges in enamel surface significantly. Using mouth guard either with or without other agentscould maintain enamel surface hardness and enamel appearance better than not using mouthguard. Using mouth guard with fluoride gel provides the most effective result.Key words: dental erosion; enamel microhardness; erosion; fluoride gel; mouth guard