The use of three sets of universal primers allowed the identification of 38 novel bacterial phylotypes. There were marked differences in the composition of the libraries generated by the different primer sets. A combination of molecular and cultural techniques is recommended to maximise the coverage of detection of bacterial taxa in oral samples.

The gingival health of 201 schoolchildren aged 11-14 years was assessed at 6 sites on all the incisor and first molar teeth by recording separately the presence or absence of redness and bleeding on probing. Crowding of the incisor teeth was recorded as labio-lingual displacement and mesio-distal overlap. A 2nd examiner recorded the presence or absence of plaque at these sites and assessed mouthbreathing, lipseal and upper lip coverage of the maxillary incisors. Mouthbreathing, increased lip separation and decreased upper lip coverage at rest were all associated with higher levels of plaque and gingival inflammation. Multivariate analysis indicated that this association was statistically significant for mouthbreathing and lip coverage but increased lip separation was not independently related to plaque and gingivitis. The relationship of mouthbreathing and decreased upper lip coverage with gingivitis was most evident in the upper anterior segment and was still evident after covariate analysis to take account of variations due to gender, overcrowding and amount of plaque. However, allowance for these factors also suggested that the influence of mouthbreathing was restricted to palatal sites, whereas lip coverage influenced gingival inflammation at both palatal and labial sites.

Few studies have investigated directly the possible role of dietary sugar in the etiology of periodontal disease, although an association between the amount of plaque formed and the frequency of sugar intake has been demonstrated. The purpose of this study was to examine the influence of frequent sugar intakes on experimental gingivitis in young adults. Twenty male dental students took part in a single blind crossover study which involved two 3-week experimental periods with random allocation to high or low sugar diets. The experimental site was the lower anterior area. The labial aspects of the lower anterior teeth were examined at baseline and Weeks 1, 2 and 3. Inflammation was assessed by recording bleeding on probing at 12 sites at 2 levels of severity--"pin prick" and "excess." In addition gingival crevicular fluid flow was recorded and plaque amount was assessed. At 3 weeks significantly higher bleeding scores at the two designated levels were found with the high sugar diet but no significant differences were observed with crevicular fluid flow and plaque amount. It was concluded that frequent sugar intakes result in increased gingival inflammation in experimental gingivitis, as measured by gingival bleeding on probing.

The reproducibility of subjects in clinical trials of dentine hypersensitivity may therefore contribute to difficulties in establishing treatment efficacy of agents in clinical trials.