Instrumented root canals of extracted human teeth were inoculated with known pulpal bacterial isolates. The inoculated teeth were immersed in the appropriate culture media and incubated at 37 degrees C for varying periods. Streptococci multiplied in the root canals and invaded the radicular dentinal tubules. The extent of bacterial invasion was time-dependent. This experimental model of bacterial invasion was time-dependent. This experimental model may be useful in investigating the effect of intra-canal medicaments on microorganisms lodged in the pulpal dentin wall.

Most oral health surveys in Nigeria have been sporadic and based on convenience samples. Periodontal disease with deep pocketing occurs in Nigerians at an early age, the prevalence being 15‐58% in those aged above 15 years. Caries experience has been reported to vary between very low and low in most studies, but is moderate in some urban communities. Although mean DMFT is below 4 in most communities, the restorative index is extremely low, most carious teeth remaining unrestored. The higher caries prevalence in second than first permanent molars that has been reported is most likely due to a change from traditional to Western‐type diet. Other oral health problems include malocclusion, truamatised teeth, dental fluorosis, and oral tumours. The scanty oral health services available in the country are mainly in urban areas. There is, therefore, a need to develop sustainable strategies for national preventive and therapeutic oral health services in Nigeria.

The prevalence of dental fluorosis is on the increase in different parts of the world, even in areas with fluoride-deficient public water supplies. This may be due to increased use of fluoride in preventive dentistry. In some countries, exposure to apparently low fluoride concentrations in drinking water has resulted in severe dental fluorosis in some children. This underscores the importance of taking into consideration all sources of fluoride intake in a community before prescribing fluoride supplements or recommending appropriate fluoride concentration for the public water supply. Preventive management of dental fluorosis includes de-fluoridation of drinking water in endemic areas, cautious use of fluoride supplements and supervision of the use of fluoride toothpaste by children aged below 5 years. Aesthetically objectionable discolouration of fluorosed teeth may be managed by bleaching, micro-abrasion, veneering or crowning. The choice between these treatments depends on the severity of the fluorosis and this may be satisfactorily determined by the Thylstrup and Fejerskov index.

The caries experience among the primary and intermediate schoolchildren in Riyadh and Qaseem was very high, and that there was no linear correlation between water fluoride level and caries experience in these children.

To investigate the relationship between fluoride levels in well drinking water, severity of dental fluorosis and dental caries in the Hail region of Saudi Arabia, 2355 rural children aged 12-15 years were examined. Over 90% of the children had fluorosed teeth and chi-square tests showed a strong association (P < 0.001) between fluoride level (0.5-2.8 ppm) in well drinking water and severity of dental fluorosis. Although regression analysis showed a statistically significant relationship (P < 0.001) between fluoride concentration and caries experience, the amount of variation explained was very low (R2 = 0.9%). Since fluoride in well water had little influence on caries experience and is causing dental fluorosis, it should be removed by defluoridation or the rural population should be provided with an alternative source of drinking water with lower fluoride concentration.