Therapeutic mouthwash (MW) is an adjunctive tool along with a regular oral hygiene routine of daily tooth brushing and daily flossing. Previous systematic reviews have demonstrated that it is effective against dental biofilm and gingival inflammation, for prevention of dental caries, and for managing one's bad breath condition according to the active ingredients. MWs prevent the microorganisms from bacterial adhesion that corresponds to the initial step in biofilm formation. This review summarized the current state of evidence such as anti-biofilm, anti-gingivitis and cariostatic properties of MWs by evaluating systematic reviews from the past six years. The anti-biofilm property has been proven to be effective, with strong evidence of three main clinical efficacies. The most commonly studied active agent was chlorhexidine gluconate (CHX), followed by essential oil (EO) and cetylpyridinium chloride. All the systematic reviews are in complete agreement that CHX and EO provide statistically significant improvements in terms of plaque and gingival indices. These effects have held up over the years as the number of studies has increased. While the use of fluoride MW is proven to be effective in improving the oral health of both children and adults, the quality of evidence is still regarded as low.

Root canal treatment is performed to treat apical periodontitis, and various procedures and techniques are currently used. Although animal models have been used in the developmental research of root canal treatment, little of this research has used small animals such as rats, because of their small size. In this study, root canal treatment was performed on the rat mandibular first molar, which had four root canals, using a microscope, and the therapeutic effect was evaluated bacteriologically, radiologically and histopathologically. By performing root canal treatment, the level of bacteria in the mesial root of the treated teeth was reduced by 75% compared with the control. Additionally, the volume of the periapical lesions of the treated teeth as measured by micro-computed tomography decreased significantly 2 weeks after the root canal treatment when compared with the control. Histological evidence of healing was observed in the treatment group 8 weeks after root canal treatment. These results suggest that a root canal treatment model using rats can be used in developmental research for novel methods of root canal treatment.

Chlorhexidine gluconate (CHG) has been proven to be effective in preventing and controlling biofilm formation. At the same time, an increase in calculus formation is known as one of considerable side effects. The purpose of this study was to investigate whether mineral deposition preceding a calculus formation would occur at an early stage after the use of CHG using an in vitro saliva-related biofilm model. Biofilms were developed on the MBEC™ device in brain heart infusion (BHI) broth containing 0.5% sucrose at 37 °C for 3 days under anaerobic conditions. Biofilms were periodically exposed to 1 min applications of 0.12% CHG every 12 h and incubated for up to 2 days in BHI containing a calcifying solution. Calcium and phosphate in the biofilm were measured using atomic absorption spectrophotometry and a phosphate assay kit, respectively. Morphological structure was observed using a scanning electron microscope (SEM), and chemical composition was analyzed with an electron probe microanalyzer (EPMA). The concentrations of Ca and Pi following a single exposure to CHG increased significantly compared with the control. Repeatedly exposing biofilms to CHG dose-dependently increased Ca deposition, and the amount of Ca was five times as much as that of the control. Pi levels in CHG-treated biofilms were significantly higher than those from the control group (p < 0.05); however, the influence of the number of exposures was limited. Analyses using an SEM and EPMA showed many clusters containing calcium and phosphate complexes in CHG-treated biofilms. Upon composition analysis of the clusters, calcium was detected at a greater concentration than phosphate. Findings suggested that CHG may promote mineral uptake into the biofilm soon after its use. It is necessary to disrupt the biofilm prior to the start of a CHG mouthwash in order to reduce the side effects associated with this procedure. The management of patients is also important.

Antimicrobial mouthwash improves supragingival biofilm control when used in conjunction with mechanical removal as part of an oral hygiene routine. Mouthwash is intended to suppress bacterial adhesion during biofilm formation processes and is not aimed at mature biofilms. The most common evidence-based effects of mouthwash on the subgingival biofilm include the inhibition of biofilm accumulation and its anti-gingivitis property, followed by its cariostatic activities. There has been no significant change in the strength of the evidence over the last decade. A strategy for biofilm control that relies on the elimination of bacteria may cause a variety of side effects. The exposure of mature oral biofilms to mouthwash is associated with several possible adverse reactions, such as the emergence of resistant strains, the effects of the residual structure, enhanced pathogenicity following retarded penetration, and ecological changes to the microbiota. These concerns require further elucidation. This review aims to reconfirm the intended effects of mouthwash on oral biofilm control by summarizing systematic reviews from the last decade and to discuss the limitations of mouthwash and potential adverse reactions to its use. In the future, the strategy for oral biofilm control may shift to reducing the biofilm by detaching it or modulating its quality, rather than eliminating it, to preserve the benefits of the normal resident oral microflora.