Caries assessment by clinical examination with or without radiographs of young Chinese adults.

OBJECTIVE: To compare caries status assessment of posterior teeth of young Chinese adults by using clinical examination alone and with the supplemental use of bitewing radiographs. METHODS: Two calibrated dentists examined the posterior teeth of 200 Chinese university students (aged 18-24 years) using dental mirrors and probes under optimal lighting. Caries was diagnosed by visual detection of carious cavities. Duplicate examinations were performed to monitor intra- and inter-examiner variations. Bitewing radiographs were taken and examined by an independent dentist. Caries was recorded when a lesion extended into dentine. RESULTS: Among the 3,162 posterior teeth examined, 113 were detected with caries. More than one third (35.4%) of the caries found in the posterior teeth was not detected from reading the radiographs but was detected by clinical examination. About half (51.4%) of the caries was found on the bitewing radiographs only, leaving 13.2% being detected by using either method. With the supplement of bitewing radiographs, there was a 105% increase in the number of carious lesions detected. This leads to a correction factor of 1.13 for adjustment of the mean DMFT score obtained from conducting clinical examinations alone. CONCLUSION: Due to the significant number of clinically undetected carious cavities in these young Chinese adults who live in a community with water fluoridation, it may be advisable to use a correction factor to adjust the caries experience obtained from epidemiological surveys when bitewing radiographs are not available.

Regulation of neurosecretory habituation by cAMP. Role of adaptation of cAMP signals.

The role of adaptation in receptors was studied with regard to the processing of neural information by cAMP in PC12 cells. Both secretin and adenosine A2 receptors elevated cAMP levels. During prolonged stimulation, secretin receptors demonstrated adaptation of cAMP levels, while adenosine A2 receptors did not. Incubation of cells with secretin increased the norepinephrine secretion resulting from stimulation by acetylcholine, but not from high potassium depolarization. The difference in the adaptation of cAMP by secretin and adenosine A2 receptors was responsible for the changes observed in norepinephrine secretion. This difference in secretory responses was caused by protein-kinase-C activation, which occurred during acetylcholine stimulation but not during depolarization by high potassium. Secretin receptors also demonstrated a reduced ability to elevate cAMP levels during repetitive stimulation, even for stimulation times where no adaptation of cAMP signals was observed, suggesting that secretin receptors possess the ability to habituate in addition to undergoing adaptation. These results are discussed with regard to the modulatory roles cAMP may play in neurosecretory habituation.