The aim of this in vitro study was to evaluate the suitability of using chitosan, poly (lactide-co-glycolide) (PLGA), and polymethyl methacrylate (PMMA) to control the release of chlorhexidine digluconate (CHX) from a prototype of controlled release drug device (CRD) for root canal disinfection. Four different prototypes with different formulations were prepared. Group A (n = 12); The device (absorbent paper point) was loaded with CHX as control. Group B (n = 12); same as group A, but the device was coated with chitosan. In Groups C and D, the device was treated in the same way as group A and then coated three times with 5% PMMA (Group C, n = 12), or coated three times with 3% PLGA (Group D, n = 12). The devices were randomly allocated to experimental groups of 12 each.

All CRD prototypes were soaked in 3 mL distilled water. The concentrations of CHX were determined using a UV spectrophotometer. The surface characteristics of each prototype were observed using a scanning electron microscope.

The result showed that release rate of CHX was the greatest in the non-coated group, followed by the chitosan-coated group, the PLGA-coated group, and the PMMA-coated group (P < 0.05). Pores were observed on the surface of the prototypes that were coated with PLGA and PMMA. When the pore size was smaller, the release rate was lower. This data indicate that polymer coating can control the release rate of CHX from the CRD prototypes.

Dental caries is a chronic disease that causes the destruction of tooth structure by the interaction of plaque bacteria, food debris, and saliva.

There has been attempts to induce remineralization by supersaturating the intra-oral environment around the surface enamel, where there is incipient caries.

In this study, supersaturated remineralized solution "R" was applied to specimens with incipient enamel caries, and the quantitative ananlysis of remineralization was evaluated using microradiography. Thirty subjects volunteered to participate in this study. Removable appliances were constructed for the subjects, and the enamel specimen with incipient caries were embedded in the appliances. The subjects wore the intra-oral appliance for 15 days except while eating and sleeping.

The removable appliance were soaked in supersaturated solution "R", saline, or Senstime® to expose the specimen to those solutions three times a day, 5 minutes each time. After 15 days, microradiography was retaken to compare and evaluate remineralization.

The results were as the following:

1. The ratio of remineralized area to demineralized area was significantly higher in the supersaturated solution "R" and Senstime® than in the saline. (p<0.05)

2. Remineralization in the supersaturated buffer solution "R" occurred in the significantly deeper parts of the tooth, compared to the Senstime® group containing high concentration of fluoride.(p<0.05)

As in the above results, the remineralization effect of remineralized buffer solution "R" on incipient enamel caries has been proven. For clinical utilization, further studies on soft tissue reaction and the effect on dentin and cementum are necessary.

In conclusion compared to commercially available fluoride solution, remineralization solution "R" showed better remineralization effect on early enamel caries lesion, so it is considered as effecient solution for clinical application.