Alkaline Tolerance and Biofilm Formation of Root Canal Isolates of Enterococcus faecalis: An In Vitro Study.

INTRODUCTION: The aim of this study was to compare the effects of glucose and glycerol (provided as principal fermentable supplements) on alkaline tolerance and biofilm-forming capabilities of root canal-derived strains of Enterococcus faecalis and those from other environments. METHODS: The planktonic growth kinetics and the biofilm-forming capabilities of E. faecalis isolates (identified by 16S ribosomal DNA sequencing) were compared when supplied with glucose and glycerol at pH levels of 8 and 11 in a microtiter plate. The metabolic activity of the biofilms plate that formed at a neutral pH level (supplied with either glucose or glycerol) was measured after subsequent adjustment to a pH level of 11. RESULTS: Ten isolates (7 from root canals and 3 from other sources) were examined. The lag phase and the doubling time increased under elevated alkalinity irrespective of either the fermentable supplement (glucose or glycerol) or the origin of the isolate. Biofilm formation and metabolic activity varied among strains, but neither was related to the source of isolation. In general, biofilm formation was enhanced when grown in glucose compared with glycerol and at a pH of 8 compared with a pH of 11 (irrespective of the fermentable supplement). The provision of glycerol did not increase either the planktonic growth rate or biofilm development compared with glucose but significantly increased the metabolic activity of biofilms, especially at a pH of 11 compared with a pH of 8. CONCLUSIONS: In the nutrient-deprived environment of a necrotic or root-filled root canal, glycerol may be an alternative energy source that can promote increased metabolic activity of E. faecalis under alkaline treatment conditions.

Traumatic dental injuries among New Zealanders: Findings from a national oral health survey.

BACKGROUND/AIM: Little is known about adult dental trauma experience at the population level. The aim of this study was to estimate the prevalence and associations of dental injuries in New Zealand (NZ) adults. MATERIALS AND METHOD: Information about dental and orofacial trauma in a representative sample of NZ adults (aged 18-94) was collected in a national oral health survey. As well as self-reported information, the maxillary six anterior teeth were examined for signs of dental trauma. Survey weights were used. RESULTS: Of the 40.9% (95% CI: 37.6, 44.2) who reported previous orofacial trauma, 69.1% (95% CI: 64.3, 73.5), or just over one-quarter of the sample, reported that this included a dental injury. More males than females had experienced orofacial trauma (51.3% [95% CI: 45.8, 56.8] and 31.4% [95% CI: 27.9, 35.1], respectively). The most common injury was a "chipped or broken tooth" (66.6%, 95% CI: 60.6, 72.1). Almost three-quarters had sought treatment. Clinical examination revealed an overall trauma prevalence of 23.4% (95% CI: 21.0, 26.0) with more males than females affected. Some 14.9% (95% CI: 12.8, 17.2) had one injured tooth, while 6.5% (95% CI: 5.2, 8.1) had two injured teeth. The maxillary central incisors were the most frequently affected. Most participants with clinical signs of trauma had only one of the six maxillary teeth affected. The most common clinical dental trauma observation was evidence of "treatment" or an "untreated enamel fracture", and these were more common among males and those aged 35-44 years. CONCLUSION: Traumatic dental injuries constitute an important public health issue. More emphasis on preventing them in the NZ adult population is warranted, and public awareness of State-funded cover for dental injuries may need to be bolstered to enable equitable access for injury care. Overall, a greater emphasis on prevention and the importance of initial care for dental injuries could reduce the individual and societal burden.

Qualitative comparison of sonic or laser energisation of 4% sodium hypochlorite on an Enterococcus faecalis biofilm grown in vitro.

The effectiveness of sonic activation, laser activation and syringe irrigation of 4% sodium hypochlorite in removing an Enterococcus faecalis biofilm was compared. Biofilms were grown in extracted human single rooted teeth using a flow cell apparatus. After 4 weeks' growth, teeth were subjected to each treatment using 4% sodium hypochlorite and radicular dentinal surfaces of the root canals were analysed by scanning electron microscopy. Results showed that sonic activation and syringe irrigation with sodium hypochlorite showed reduced numbers of bacterial cells on the radicular dentine but were not effective in eliminating E. faecalis in the dentinal tubules. Laser activation of sodium hypochlorite resulted in clean dentine walls and undetectable levels of bacteria within dentinal tubules. Qualitatively, sonic or laser activation of 4% NaOCl resulted in greater bacterial reduction compared with syringe irrigation, with laser activation producing the greatest overall reduction.