Synthesis and characterization of nisin-incorporated alpha-tricalcium phosphate for pulp capping – An in vitro study

Aim: The present study aimed to synthesize and characterize Nisin incorporated Alpha Tricalcium Phosphate (NTCP) and to evaluate nisin release from NTCP when used as a pulp capping agent. Methods: Alpha TCP(aTCP) powder was synthesized by the wet chemical method. Nisin was incorporated into this prepared aTCP at various ratios and grouped as follows: Group 1 - 1% wt%; Group 2 -2.5wt%; Group 3-5%wt%; Group 4- 7.5%wt%; Group 5 -10%wt% ; Group 6 -Nisin 100 mg; All these samples were characterized using Fourier Transmission Infrared Spectroscopy(FTIR) and Differential Scanning Calorimetry (DSC). For evaluation of nisin release from NTCP using HPLC, around fifteen freshly extracted non-carious human third molars were collected and mounted in gypsum blocks. A standard box-type class-I cavity (4.5x 4.5 mm) was prepared with the pulpal floor ending at deep dentin, The experimental materials were mixed with propylene glycol to prepare it as pulp capping material in paste form. Subsequently pulpal floor of all the cavities were lined with the respective materials. The entire samples were kept to set for 30 minutes in ambient temperature and subsequently immersed in water and stored in an incubator at 37oC. After 14 days of immersion, dentin lying directly below the sample was cut and powdered using mortar and pestle. The powdered dentin was then subjected to HPLC analysis. The peak time of nisin release from experimental groups was recorded. Results: FTIR results revealed Group 5 with highly appreciable corresponding bends of amine N-H, C-H stretching and phosphate peaks at 1100 and 554 close to Control TCP samples. DSC analysis showed that TCP did not change from 30oC to 80oC and sample 1, 2, 3,and 4, did not show any denaturation point. Sample 5 showed denaturation point slightly above the denaturation temperature of nisin. On HPLC analysis, samples 4 and 5 showed higher peaks of nisin release and traces of nisin release from all the groups. Conclusion: Within the limitations of this study, it can be concluded that NTCP can be synthesized successfully without any influence on the properties of each other material. 10% NTCP provides higher release into dentinal tubules when used as a pulp capping agent.