The oral health burden of rural paediatric populations exposed to differing concentrations of naturally occurring fluoride in Vanuatu

The Melanesian island nation of Vanuatu sits on the Pacific Ring of Fire and hosts six active volcanoes, including Ambrym volcano, which is a globally significant point source of volcanic emissions. These emissions contaminate multiple rural island environments with fluoride, including community drinking-waters at variable levels. Fluoride is described as the most potent agent influencing mineralization processes on developing and erupted tooth enamel, with drinking- water concentrations up to 1.0 mg/L of fluoride known to prevent and control dental caries. However, while some fluoride exposure is considered beneficial to oral health, consistent exposure at elevated levels is detrimental, causing irreversible dental fluorosis.

In this project, the association between volcanogenic fluoride from Ambrym volcano and the oral health burden of 1026 rural children was investigated, in three study areas along a gradient of assumed exposure to Ambrym’s volcanic plume with a further area investigated which had no exposure to volcanic emissions. Dental caries rates and levels of dental fluorosis are described for these children for both the permanent and primary dentitions. Timings of the emergence and sequencing of permanent teeth for these Melanesian children are detailed for the first time. Children also reported their toothbrushing habits and levels of oral pain, detailing these in questionnaires offered in their native language of Bislama, to help inform future public health initiatives. Finally, this project also investigated whether there are other important natural sources of fluoride to community drinking-waters. It measures and maps, for the first time, highly variable fluoride concentrations in diverse community drinking-water sources on Vanuatu’s volcanically active Tanna Island.

Fluoride concentrations in drinking waters ranged from less than 0.05 mg/L on remote Aneityum Island in the south of the archipelago to 4.6 mg/L in groundwaters, on the western coast of Tanna Island. Permanent tooth emergence was up to 1.2 years earlier for ni-Vanuatu children than for their Pacific peers. The mean age for first mandibular permanent molars emergence was 4.9 years of age for girls and 5.3 years of age for boys. The lowest prevalence of dental caries for both permanent and primary dentitions was associated with fluoride concentrations in community drinking-waters averaging 0.59 mg/L. No teeth presented as restored or extracted in either dentition, revealing unmet need. Self-reported oral pain prevalence was high: 21% across the whole cohort, and 43% for children of Aneityum. Although children in this cohort had access to health professionals, oral health services and equipment were not available at any location.

This work highlights the need for substantial investment in health facilities to address the oral health needs of children living in Vanuatu. Prevention strategies such as molar fissure protection should target children as early as four years of age to assist with tooth preservation for the permanent dentition. Where fluoride is only present at very low concentrations (<0.05 mg/L F) in community drinking-waters, use of fluoride toothpastes might be encouraged alongside community toothbrushing programmes. It is likely that that the drinking-water standard of 1.5 mg/L F is too high for Vanuatu with dental fluorosis seen at lower levels. Where fluoride in community drinking-waters is above the World Health Organization recommendation for tropical climates (0.8 mg/L F), alternative water supplies are urgently recommended for children during the development of their permanent dentition to prevent dental fluorosis.