الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Dental caries is a major public health problem which commonly affecting children in their early childhood. It has a negative impact on children’s oral as well as general health. Enamel carious lesion are characterized by mineral loss in subsurface body of lesions where the surface remains highly mineralized. White spot lesions are the earliest macroscopic evidence of enamel caries, which appear as opaque white areas with chalky appearance on smooth tooth surfaces, if left untreated it will collapse to non cavitated and finally cavitated lesions. Oral hygiene measures and diet control are used to prevent enamel caries, but they are not sufficient enough to completely prevent tooth decay. In the recent years the treatment has been shifted to noninvasive and minimal invasive preventive technique using fluoride remineralizing agents, non-fluoride based remineralizing agents. Remineralization is defined as the process whereby calcium and phosphate ions are supplied from an external source to the tooth to promote ion deposition into crystal voids in demineralized enamel to produce net mineral gains. Fluoride plays important role in the prevention and control of dental caries by being incorporated into demineralized enamel changing carbonated apatite to a fluoro- apatite like form which is more resistant to acids. The non-fluoride based remineralizing agent were developed and introduced in the market to enhance the remineralizing process to improve the mechanical properties of demineralized enamel. This study was conducted to compare between the effects of noninvasive treatment modalities using fluoride, nano-hydroxyapatite based remineralizing agents versus micro-invasive treatment modality using resin infiltration system (icon) on surface micro-hardness of incipient carious enamel lesions and the stability of these treatment options upon exposure to acidic challenge. A total 80 sound human permanent premolars were used in this study. The specimens were divided into four equal groups 20 teeth for each group. According to treatment modality group A0: resin infiltration material, group A1 nano hydroxyapatite based remineralizing agent, group A2 fluoride varnish and group (A3) artificial saliva as control group. The premolars were decoronated and mounted in self -cured acrylic resin cylindrical molds with buccal surface facing upwards. The buccal surface of each tooth was polished using 400,600,800 and 1200 grit silicon carbide abrasive papers. A standardized window of 5mm * 5mm dimension was created on the buccal enamel surface of each specimen which demarcated by acid resistant nail varnish of different colors. The specimens were immersed in demineralizing solution at pH 4.5 for 72 hours to induce incipient carious enamel lesions, all treatment were applied according to the manufacturer’s instructions. After application of tested materials, all specimens were immersed in artificial saliva for four weeks. The specimens were finally subjected to acidic challenge using the same demineralizing protocol used for inducing caries -like lesions. The surface microhardness (SMH) of each specimen was assessed using Vickers microhardness tester, at baseline of sound untreated enamel (SMH\B), after demineralization (SMH\D), after treatment for four weeks (SMH\T) and finally, after exposure to acidic challenge (SMH\C). Percentage of change in surface microhardness recovery (%SMHR) and percentage of change in surface microhardness (%SMHC) were calculated. Scanning electron microscope were used to assess surface morphological characters of enamel surface at different stage. Color stability of enamel surface at different stage were assessed by spectrophotometer. The results of the current study revealed that both resin infiltration material and nano hydroxyapatite based remineralizing agents showed the highest statistically significant mean surface microhardness values, highest statistically significant mean of color stability also, showed increased of density of enamel crystals and more resistant to acid challenge when compared to fluoride varnish and artificial saliva (control group) Based on the previous results, it was concluded that 1) Micro-invasive treatment modalities (resin infiltration system) and Noninvasive treatment modalities (nano hydroxyapatite based remineralizing agent, fluoride varnish) are both viable options for treatment of sub-surface carious lesions. 2) resin infiltration system and Nano hydroxyapatite based remineralizing agent are the most effective treatment modalities for incipient carious enamel lesions. 3) Resin infiltration system and Nano-hydroxyapatite based remineralizing agent are more color stable and show smooth surface after treatment than other groups. 4) Although some demineralization has occurred with all treatment modalities up on exposure to acidic challenge, they still inhibit further progression of sub-surface carious enamel lesions.