Clinical threshold for carious tissue removal.

There would appear to be little logic in the current practice of caries removal. Biologically, it would appear to be potentially damaging even to attempt to remove all infected dentin in a symptomless, vital tooth. It is neither possible nor necessary to achieve this. The evidence would seem to show that, provided a restoration is placed that seals the cavity, infected dentin may be left. It does not prejudice pulpal health, and the caries lesion does not progress.

Effect of biofilm growth on expression of surface proteins of Actinomyces naeslundii genospecies 2.

The predominant surface proteins of biofilm and planktonic Actinomyces naeslundii, a primary colonizer of the tooth surface, were examined. Seventy-nine proteins (the products of 52 genes) were identified in biofilm cells, and 30 of these, including adhesins, chaperones, and stress-response proteins, were significantly up-regulated relative to planktonic cells.

The treatment of deep dentine caries lesions.

UNLABELLED: This paper discusses the excavation of deep caries lesions, focusing on indirect pulp-capping and the stepwise excavation approach. The concept of a modified and less invasive stepwise excavation is presented, based on considerations of caries pathology. The aim of the first excavation is primarily to make a change within the cariogenic environment, and not to remove carious dentine close to the pulp because this risks an iatrogenic pulp exposure. Microbiological and clinical studies have shown that the number of bacteria decrease during stepwise excavation procedures, and that lesions clinically arrest. The active, soft-yellowish, demineralized dentine turns into a darker, harder and drier demineralized dentine, resembling a slowly progressing lesion, where the carious dentine is easier to remove at the final visit. The final excavation has two aims: (i) to verify that arrestation has taken place, ie a clinical control of the tooth reactions and (ii) to remove the slowly progressing but still slightly infected discoloured demineralized dentine, before carrying out the permanent and final restoration. CLINICAL RELEVANCE: Knowledge of guidelines for treatment of deep dentine caries may reduce the risk of pulpal exposure.

Effect of the environment on genotypic diversity of Actinomyces naeslundii and Streptococcus oralis in the oral biofilm.

The genotypic diversity of Actinomyces naeslundii genospecies 2 (424 isolates) and Streptococcus oralis (446 isolates) strains isolated from two sound approximal sites in all subjects who were either caries active (seven subjects) or caries free (seven subjects) was investigated by using the repetitive extragenic palindromic PCR. The plaque from the caries-active subjects harbored significantly greater proportions of mutans streptococci and lactobacilli and a smaller proportion of A. naeslundii organisms than the plaque sampled from the caries-free subjects. These data confirmed that the sites of the two groups of subjects were subjected to different environmental stresses, probably determined by the prevailing or fluctuating acidic pH values. We tested the hypothesis that the microfloras of the sites subjected to greater stresses (the plaque samples from the caries-active subjects) would exhibit reduced genotypic diversity since the sites would be less favorable. We found that the diversity of A. naeslundii strains did not change (chi2 = 0.68; P = 0.41) although the proportional representation of A. naeslundii was significantly reduced (P < 0.05). Conversely, the diversity of the S. oralis strains increased (chi2 = 11.71; P = 0.0006) and the proportional representation of S. oralis did not change. We propose that under these environmental conditions the diversity and number of niches within the oral biofilm that could be exploited by S. oralis increased, resulting in the increased genotypic diversity of this species. Apparently, A. naeslundii was not able to exploit the new niches since the prevailing conditions within the niches may have been deleterious and not supportive of its proliferation. These results suggest that environmental stress may modify a biofilm such that the diversity of the niches is increased and that these niches may be successfully exploited by some, but not necessarily all, members of the microbial community.

In vitro validation of carious dentin removed using different excavation criteria.

PURPOSE: To compare directly the extent of cavity preparation instigated by either clinical hardness or a caries detector dye. Caries removal was histologically validated against the autofluorescence of carious dentin within the same samples. METHODS: 50 human molars were sectioned longitudinally through occlusal lesions, color photomicrographs obtained and the pre-excavation autofluorescent signatures captured using a confocal laser scanning microscope (488 nm excitation, > 515 nm emission). The hydrated lesions were excavated using sterile hand instruments until the dentin cavity surface was hard to a dental probe. Color photomicrographs were obtained and then caries detector dye was then placed in the cavities and excavation continued until no pink stain was visible. Final color photomicrographs were obtained. RESULTS: Digital image superimpositions indicated that the extent of cavities prepared using the clinical hardness criterion correlated closely to the corresponding autofluorescent signal outlines of the original lesions. Caries detector dye-assisted excavation resulted in over-prepared cavities by as much as 58.2% relative to the validating autofluorescence outline. In conclusion, the use of caries dyes can lead to clinically significant over-preparation of cavities when compared to those prepared using clinical hardness.

The effect of medicated chewing gums on oral health in frail older people: a 1-year clinical trial.

OBJECTIVES: To determine the effects of a medicated chewing gum on the oral health of frail older people. DESIGN: A controlled, double-blind trial using three groups based on random allocation of residential homes. SETTING: Sixteen residential homes in West Hertfordshire, England. PARTICIPANTS: One hundred eleven dentate subjects aged 60 and older who completed the 12-month study. INTERVENTION: Subjects were assigned to a chlorhexidine acetate/xylitol gum (ACHX) group, a xylitol gum (X) group, or a no-gum (N) group. Subjects in the gum groups chewed two pellets for 15 minutes twice daily for 12 months. MEASUREMENTS: Primary outcome measures were salivary flow rate, denture debris score, prevalence of angular cheilitis, and denture stomatitis; secondary outcome measures were salivary levels of caries-associated microorganisms. A single examiner, who was blinded to group allocation, made all measurements at baseline before gum usage and at subsequent examinations after 3, 6, 9, and 12 months. Separate analyses were performed for subjects with dentures. RESULTS: Subjects in the three groups were similar in most of their baseline characteristics. The stimulated whole saliva flow rate +/- standard deviation increased significantly for the ACHX (1.4 +/- 0.7 mL/min) and X (1.6 +/- 0.9 mL/min) groups (P <.01) over baseline (ACHX = 0.9 +/- 0.6 mL/min, X = 0.8 +/- 0.6 mL/min) and N group levels (0.6 +/- 0.9 mL/min). The levels of mutans streptococci, lactobacilli, and yeasts significantly increased (P <.05) in the X and N groups. Denture debris status was significantly lower in the ACHX and X groups than at baseline or in the N group (P <.01). The reductions of 91% and 75% in denture stomatitis and angular cheilitis prevalence, respectively, that occurred in the ACHX group were significantly greater (P <.01) than the reductions in the X group (denture stomatitis 62%, angular cheilitis 43%). Prevalence of denture stomatitis and angular cheilitis were not significantly changed in the N group. CONCLUSION: The use of a medicated chewing gum significantly improved oral health in older occupants of residential homes. Chewing gums should be considered as a potential adjunct to other oral hygiene procedures in older subjects.