60 - Temporal Assessment of Remineralizing Demineralized Enamel Using Micro-Computed Tomography

Abstract

Remineralizing enamel is an important approach of treating early carious lesion without surgical intervention allowing for preservation of tooth structure. This study objective is longitudinal assessment of enamel microstructure using non-destructive micro-CT to monitor the remineralization process undergoing fluctuating changes in pH after treatment with different remineralization agents. Twelve human extracted premolars were collected. Calculus and soft tissue were removed from the root, kept in distilled water, and stored at 4 C. The teeth were screened using Swept Source OCT (SANTEC IVS-2000) to identify a 3 ×3 mm2 caries-free region of interest on the crown for artificial caries induction. The whole crown, except for the identified sound area, was coated with two layers of acid-resistant nail varnish. Then samples were mounted using acrylic resin and customized mounts to standardize successive scans with micro-Ct. Each mounted sample was incubated in 20 ml of buffered lactic acid (2.2 mM CaCl 2 , 2.2 mM K 2 HPO 4 , 0.1 M Lactic acid adjusted pH to 4.5) for 72 hours in 37 C to induce caries-like lesions of approximately 100 micron in depth. After 72 hours, the samples were rinsed with deionized water and stored in distilled water to be scanned. The samples were grouped into four groups (n=3) that consist of three intervention groups and one negative control group. The 3 intervention groups consist of two fluoride varnish and one polypeptide-based remineralization agents. Each sample received the remineralizing treatment after the lesion formation according to manufacturers instructions. After that all samples were subjected to pH cycling for 2 weeks in 37 C incubation on a shaker table. Ph cycling solutions were refreshed at the end of every cycle following [ten Cate and Duijsters, 1982] protocol which is: 1-three hours in demineralization solution,2-rinse for 30 s with distilled water and 3- 21 hours in artificial saliva.Micro-Ct scans were carried out after 6 and 12 pH cycles. Lesion depth, ld and Delta Z, ΔZ were calculated The mean lesion depth developed in the different groups showed no noticeable difference after 6 ph. cycles while after 12 ph. cycles lesion depth were decreased in the different groups with more observable decrease in the experimental fluoride group. Both self-assembly peptide agent and experimental fluoride showed no further increase in the lesion depth after the acidic challenge at the end of the ph. cycles. Remineralized enamel with different remineralizing agents reacts differently under the same fluctuating ph. conditions at different time intervals.