Anti-microbial effect of Piper betle crude extract and essential oil incorporated into short-term soft lining material

Introduction
Using soft lining material to treat denture stomatitis for an extended period of time may result in oral bacterial and fungal accumulations. Several additives, including natural products, have been identified as anti- microbial agents.

Objectives
The aim of the present study was to evaluate the anti-microbial activity of Piper betle crude extract (PBC) and Piper betle essential oil (PBO) incorporated into soft liner with different concentrations against Candida albicans and Streptococcus mutans. Cytotoxicity of various additives applied into soft lining material was also investigated.

Material and methods
Anti-microbial activity of PBC and PBO were assessed using agar disc diffusion method. Agar well diffusion method was also applied to evaluate inhibitory effect of PBC and PBO incorporated into soft lining material. Cell viability of human gingival fibroblast (HGF) cell line after exposing to soft lining materials with PBC was investigated.

Results
With the same minimum inhibitory concentration (MIC) of 2.5% w/w, PBC showed anti-fungal and anti-bacterial activities against C. albicans and S. mutans. However, PBO had a 2.5% v/v MIC against C. albicans, but a 10% v/v MIC against S. mutans. Accordingly, GC soft liner with PBC had MICs of 5% w/w against C. albicans and 10% w/w against S. mutans, whereas GC soft liner with PBO had MICs of 20% v/v and 60% v/v against C. albicans and S. mutans, respectively. Statistical analysis revealed that there was no significant difference in cell viability among GC soft liner, with 5% and 10% w/w PBC and GC soft liner without additive (p > 0.05).

Conclusions
Both PBC and PBO showed anti-bacterial and anti-fungal activity; however, the 10% w/w PBC incorporated into GC soft liner demonstrated the optimal concentration to serve as an anti-microbial agent against both C. albicans and S. mutans, with no toxicity to HGF cells.