Dental caries in South Pacific populations: a review.

Dental caries (tooth decay) was uncommon in Pacific Island communities before European trading and migration expanded into the Region. The etiology of this oral microbial disease is a consequence of changed diets, food preparation and lifestyle. In particular, the easy availability of a high level of frequent dietary supplementation with refined sucrose (sugar) and carbohydrates is the key factor in the etiology of tooth decay. While tooth decay initially developed as a health problem in the more accessible Pacific islands over a century ago, it has spread increasingly as trading, travel and cash economies have developed to include even the more geographically remote communities. In this review selected epidemiological data are presented to show the magnitude, variation and secular changes in the prevalence of tooth decay in different communities. Tooth decay in conjunction with the historically endemic adult gum diseases poses a major public health problem in terms of pain, premature loss of teeth and the need for oral rehabilitation. Implementation and monitoring of caries control programs is a priority need in most communities. It is impractical to consider a return to indigenous diets and lifestyles as a strategy for caries prevention. Instead promotion of proven modern community preventive programmes, notably appropriate use of fluorides, 'fissure sealants' together with control of excessive consumption of diets rich in refined sugar is required if a significant increase in the levels of tooth decay is to be avoided.

Periodontal health in South Pacific populations: a review.

Periodontal (or gum) disease is historically endemic in all indigenous communities in the South Pacific Region. While the disease becomes evident in mature adults the pathology becomes overt by adolescence or earlier. The initial gum inflammation progresses increasingly with age and may lead to pathological destruction of the tooth supporting tissues, tooth loosening and potential tooth loss. For most adults the disease presents as an adult-onset generalized chronic marginal-gingivitis-periodontitis-calculus complex. Microbiological components of dental plaque on tooth surfaces and dental calculus initiate the pathology. While the general clinical features are similar between adults and between communities, epidemiological studies have identified variations in disease progression. Also severity of the disease may be influenced by systemic health factors such as diabetes, known to be common in the Region. A common outcome, loss of teeth, usually becomes evident from the fourth decade onwards. Once established the plaque- gingivitis- calculus- periodontitis complex becomes increasingly difficult to reverse. Early adoption and maintenance of routine oral care actions through family, social, community and educational actions will improve long-term oral health, tooth loss, potentially adverse systemic health and in general better lifestyles.

Calcium phosphate deposition in human dental plaque microcosm biofilms induced by a ureolytic pH-rise procedure.

The objectives were to develop and characterize a procedure based on a ureolytic pH rise to deposit calcium phosphate into microcosm dental plaque biofilms and to test the importance of the plaque pH range. Plaque biofilms were cultured in a multiplaque culture system ('artificial mouth') with a continuous supply of a simulated oral fluid (basal medium mucin; BMM) with 146 mmol/l (5% w/v) sucrose periodically applied over 6 min every 8h. After initial plaque growth, the biofilms were periodically exposed for up to 16 days to 6-min applications of calcium phosphate monofluorophosphate urea (CPMU) solution containing 20 mmol/l CaCl(2), 12 mmol/l NaH(2)PO(4), 5 mmol/l monofluorophosphate and 500 mmol/l urea (pH 5.0). Three application regimes were examined, one included a sucrose-induced acidic pH fluctuation. Plaque hydrolysis of the urea in CPMU caused the pH to rise to between 8.2 and 8.8, depositing fluoridated and carbonated calcium phosphates, and possibly some calcium carbonate, into the plaque. Calcium, phosphate and fluoride deposition was rapid for about 4 days and then slowed. After 10 days' treatment under standard conditions (BMM containing 1 mmol/l urea and 1 mmol/l arginine), plaque calcium and phosphate concentrations had increased up to 50-fold and 10-fold to approximately 2-4 and 1-2 mmol/g plaque protein, respectively. The calcium, phosphate and fluoride content increased steadily. Calcium phosphate deposition was proportional to the plaque resting pH, increasing over four-fold when the BMM urea concentration was increased from 0 to 20 mmol/l, which raised the resting pH from 6.4 to 7.2 and yielded a mean plaque calcium concentration of 14.3 mmol/g protein, one subsample reaching 20.8 mmol/g protein. Supplementation of BMM with 20% human serum inhibited deposition. These results support the hypothesis that an alkaline pH in plaque is critical in promoting plaque mineralization and that mineral deposition is modulated by serum. These factors are likely to be important in regulating calculus formation.

Changed oral conditions, between 1963 and 1999, in the population of the Tokelau atolls of the South Pacific.

In 1999, an oral health survey was included in an assessment of the community oral health programme of the Tokelau Islands population. This provided a comparison with a similar survey in 1963. In a convenience sample of 386 children and adults, approximately 30 percent of the total population, the deciduous (number of df teeth) and permanent (number of DMF teeth) tooth scores across all age groupings were higher in 1999 compared with 1963. For 15- to 19-year-olds, the mean DMF scores were 8 and 1; and for 35- to 44-year-olds, the scores were 18 and 4 in 1999 and 1963 respectively. The prominent feature of the DMF scores for those over age 25 years was the numbers of missing (M) teeth. The mean number of M teeth at 20-24 years was 5 and 0, and at 35-44 years, 13 and 2 respectively in 1999 and 1963. Periodontal disease was endemic in adults in both surveys. A serious decline in oral health has occurred over the past 35 years.

Human supragingival in vivo calculus formation in relation to saturation of saliva with respect to calcium phosphates.

The aim was to establish if there is a correlation between the rate of formation of supragingival calculus and the degree of supersaturation of saliva with respect to apatite, brushite and other calcium phosphates. The rate of calculus formation was estimated by measuring the calculus formed on lingual surfaces of the lower incisors in 15 individuals during 30 days. Submandibular saliva stimulated with citric acid and resting whole saliva, alter pH determination and ultrafiltration to remove protein was analysed for calcium, phosphate, sodium, potassium and carbonate. The degree of saturation with respect to calcium phosphates was calculated using a computer program. The rate of calculus formation among the 15 participants ranged widely, from a score of 0.5 to a high of 15. A close correlation (r = 0.91) between salivary pH and degree of supersaturation was found A weak correlation between calcium and calculus formation was also found. But neither for unstimulated nor stimulated saliva was a significant relation between supersaturation with respect to any of the calcium phosphates and the rate of calculus formation observed. Therefore, taking into consideration the background of the wide range of rates of calculus formation and of degrees of supersaturation, it was concluded that relation between them is unlikely, and the use of degree of saturation as a diagnostic tool seems unreliable.

[An experimental study on effects of arsenic on dental fluorosis in rats].

In order to study the effects of arsenic on fluorosis and interaction between arsenic and fluoride, nuclear proton microprobe technique and quantitative histological method were used to observe the distribution of arsenic and fluoride in teeth and their effects in rats fed with water containing arsenic (30 mg/L) and fluoride (100 mg/L). Results revealed (1) fluoride could cause dental fluorosis in rats, similar to that seen in human beings, and characteristics of fluorosis was evaluated by a grading system; (2) no detectable amount of arsenic was deposited in dentine, and no damage to teeth could be seen; (3) no obviously combined effects of arsenic and fluoride on dental tissues were seen, and the toxic effect of fluoride was not influenced by arsenic; and (4) a synergistically inhibitory effect of both arsenic and fluoride on body weight was found.

Fluoride uptake into the developing enamel and dentine of sheep incisors following daily ingestion of fluoridated milk or water.

Incomplete availability of fluoride from fluoride compounds when added to milk is claimed to reduce the effectiveness of fluoridated milk in caries prevention in humans. This study attempts to add to the understanding of the systemic bioavailability of fluoride ingested with milk compared with water, by measuring its uptake into developing incisors of sheep. Twenty-five sheep, aged approximately 10 months, were randomised into five groups and farmed under identical conditions. They were dosed orally each day for 22 weeks with fluoride as sodium fluoride in water or bovine milk. The doses of fluoride were 0.5 or 0.2 mg/kg body weight in milk or water; a control group received no additional fluoride. Tooth length was labelled at the start of dosing with intramuscular injection of tetracycline. After sacrificing, incisors were removed, sectioned, and analysed for fluoride and calcium by proton microprobe scans from the enamel surface to the pulp. Concentrations of ionised fluoride in the milk samples were 30 percent and 20 percent respectively for added fluoride at concentrations of 300 and 750 micrograms/ml. The mean fluoride concentrations in surface enamel, deep enamel, and dentine were dependent on the daily fluoride dose and independent of the carrier (milk or water). The teeth of sheep receiving the higher fluoride dose (0.5 mg/kg body weight) had significantly higher fluoride than those receiving the lower fluoride dose (0.2 mg/kg body weight), which were significantly higher than in the teeth of the control sheep. It was concluded that the bioavailability of fluoride from sodium fluoride mixed with milk or water was similar following metabolism, despite 20-30 percent and 100 percent ionisation in milk and water respectively.

Immunolocalization of basic fibroblast growth factor (bFGF) in human periodontal ligament (PDL) tissue.

The distribution of basic fibroblast growth factor (bFGF) in periodontal ligament (PDL) tissue was investigated in samples which were obtained from freshly extracted human teeth. The PDL tissue was collected by scraping, and bFGF was identified and localized by immunohistochemistry. Fibroblasts, endothelial cells, some fibrocytes and extracellular matrix (ECM) stained positively for bFGF. It was observed that cells from healthy PDL stained more intensely than those from PDL of teeth associated with chronic periodontitis; histological cell counts revealed that the numbers of fibroblasts was greater (p < or = 0.0005) in healthy PDL than in diseased PDL tissue. The results of this study show that bFGF is produced primarily by PDL fibroblasts and endothelial cells in the PDL and that bFGF levels may be decreased in tissue associated with chronic periodontal lesions.

Inhibition by ethanol of the growth of biofilm and dispersed microcosm dental plaques.

Inhibition of microcosm plaque biofilm growth by periodic application of ethanol was compared with the minimum inhibitory concentration (MIC) and bactericidal effects of ethanol on liquid cultures of dispersed plaque bacteria. Microcosm plaques were cultured from saliva in a multiplaque 'artificial mouth' and their growth in wet weight measured daily. Nutrient conditions included: a continuous supply of a medium containing 0.25 percent mucin, and 8-hourly 5 percent (w/v) sucrose (1.5 ml over 6 min). Plaque biofilm growth was strongly inhibited by exposure to 40 percent (v/v) ethanol applied in volumes of 3.75 ml over 15 min, six times daily. Application of 1.5 ml over 6 min inhibited much less or not at all. Ethanol concentrations lower than 40 percent caused less inhibition, with 10 percent having almost no effect. The pH response to sucrose was unchanged by prior application of 40 percent ethanol for 30 min. Some evidence was obtained for either bacterial adaptation to ethanol or selection of ethanol-resistant bacteria. The MIC and bactericidal effects of ethanol were assessed by growth of dispersed plaque in liquid culture; the bactericidal effect was measured as the induced delay in growth. The aerobic and anaerobic MIC of ethanol for growth was 10 percent and 8 percent; 50 percent inhibition of growth rate occurred at 3.7 percent and 2.8 percent. Ethanol (40 percent) was bactericidal within 1-2 min, but 10 percent had almost no effect. It was concluded that, despite the well-known high ethanol sensitivity of dispersed plaque bacteria, prolonged application of ethanol concentrations in the order of 40 percent are necessary to inhibit growth of plaque biofilms.

Fluoride content of the enamel and dentine of human premolars prior to and following the introduction of fluoridation in New Zealand.

The fluoride content of the enamel and dentine of premolars was used as a determinant of the availability of ingested fluoride in New Zealand prior to and following the introduction of water fluoridation 40 years ago. Premolar teeth, which developed during the periods (PRE and POST respectively) under study, were selected from teeth extracted from 12 to 14-year-old children resident in different geographic areas in the country. The fluoride content, determined by multiple proton microprobe analyses, of surface enamel, deep enamel, and dentine, were for PRE teeth 440, 65 and 115, respectively. For POST teeth the mean values were significantly (p<0.001) higher, by 69, 29 and 102% respectively. The relevance of the change in fluoride content was assessed by comparison with published reports on the fluoride content of teeth developed in communities exposed to low (<0.5 ppm), optimal (1-2 ppm) and high (>3 ppm) naturally occurring fluoride levels in drinking water. The PRE teeth had a fluoride content associated with a low fluoride exposure and POST teeth with optimal fluoride exposure during tooth development. It was concluded that fluoride availability in New Zealand teeth had increased over the past 30 years but this increase is compatible with exposure of the community to optimal rather than excessive levels of ingested fluoride.

Patterns and rates of growth of microcosm dental plaque biofilms.

Rates of growth in wet weight and changes in them over time were established for microcosm dental plaques cultured from the mixed salivary bacteria in an artificial mouth. Standardized conditions included a continuous supply of medium containing 0.25% mucin and 1.5 ml of 5% w/v sucrose in 6 min every 8 h. Plaques were weighed daily. Plaque wet weight and total protein were highly correlated. Plaque doubling times were 3-7 h over day 1 and 9-21 h over day 2, which is similar to in vivo plaques. Subsequently, growth curves were either linear or between a linear and exponential increase. Evidence was obtained for plaque blooms. Methyl paraben (0.2%) applied for 15 min (3.75 ml) 6 times daily inhibited growth but only for 3 days, after which the rate was similar to control plaques, indicating that selection for resistance had occurred. It was concluded that the regulation of plaque growth rates is complex and does not conform to simple growth pattern models. Detailed studies of plaque growth and the effects of antiplaque agents can be carried out using this experimental system.

Proton microprobe assessment of the distribution of fluoride in the enamel and dentine of developing central incisors of sheep and changes induced by daily fluoride supplements.

Ten sheep were given 0.5 mg fluoride (F) and 10 sheep 0.2 mg F/kg body wt orally for periods of 1-6 months while 8 sheep received no additional F. One incisor from each sheep was sectioned longitudinally in the midline and, using the proton microprobe, multiple scans for calcium and F were made across the enamel and dentine. F was determined by proton-induced gamma-ray emission and calcium by X-ray emission. Tooth length and hence the stage of ameloblast activity for each of the 28 teeth at the start of the experiment was determined using a tetracycline marker. In addition, the stage of enamel development of the eight control teeth (no dietary F) at the time of their extraction was assessed from their macroscopic appearance. Continuous changes in F levels occurred in both enamel and dentine throughout tooth development and also in the mature enamel and associated dentine after ameloblast regression. All scans for all stages of tooth development and all F treatments showed a high F concentration at the enamel surface. Early in the secretory phase, a wide-based F peak occupied the entire width of the enamel with a similar F peak in the dentine. In the control teeth, no consistent increase in F concentration occurred at the enamel surface during later development. When F supplements were started early in the maturation phase an increase in F concentration only at the enamel surface was recorded. When F supplements were also given during the secretory phase, higher F concentrations were recorded not only at the enamel surface but also for the inner enamel and dentine plateau. These findings, based on a small number of sheep, indicate that further research is needed to clarify the method and control of F uptake and to determine the changes in these processes during the different stages of tooth development.

Effects of fluoride-supplemented sucrose on experimental dental caries and dental plaque pH.

Sucrose, 5% and 10% (w/v), supplemented with between 0 and 5 ppm fluoride (F), was tested for its influence in vitro on plaque-induced experimental in vitro enamel caries and plaque pH. Plaque growth on bovine enamel was initiated from saliva inocula and sustained in a multiple plaque growth system for up to 31 days by means of a basal medium with periodic applications of sucrose or sucrose supplemented with F. Change in enamel mineralization was assessed, before and after plaque growth, by microhardness testing and microradiography; pH was monitored with microelectrodes. It was found that enamel demineralization was inversely related to the F concentration in the range 2 to 5 ppm, for both 5% and 10% sucrose. Plaque pH responses were unaffected by the F supplements.

Stoichiometry of fluoride release from fluorhydroxyapatite during acid dissolution.

Release of F from fluorhydroxyapatite (FHAp) during acid dissolution was studied to validate the use of this mineral as a plaque reservoir of F. FHAp minerals having a wide range of F concentrations were synthesised by aqueous precipitation, and samples repeatedly exposed to 50 mM lactic acid solution, pH 4.5, or similar lactic/acetic/formic acid mixtures, until dissolution was complete. While the Ca/P ratio in solution remained relatively constant and close to the ratio in the solid, the solution F/Ca ratio invariably changed during dissolution. During initial stages the F/Ca solution ratio was lower than in the solid but rose to reach a plateau higher than in the solid as dissolution progressed, an effect that was more pronounced with low-F FHAp. With these minerals the plateau F/Ca level never reached 0.2, suggesting that a F-enriched FHAp rather than pure fluorapatite precipitates during dissolution. It is concluded that a high-F FHAp mineral would best serve as an apatitic plaque reservoir of F.

Studies on the influence of fluoride on the equilibrating calcium phosphate phase at a high enamel/acid ratio.

Data obtained in a previous study suggested that brushite is the solubility-determining phase when enamel is first exposed to acid solution in a series of repeated equilibrations. Fluoride in solution might be expected to inhibit brushite formation, and experimental studies at low solid/solution ratio support this. We have now re-examined the effect at a very high ratio, in an attempt to mimic what happens in an enamel caries lesion. Powdered enamel was repeatedly exposed to HCl solution, 10-70 mmol/l, containing 2 ppm F, for 24 h, initially in a ratio of 1 g/3 ml. Ion activities were determined after 20 min and 24 h and potential plot diagrams constructed. In early repetitions the -log (Ca2+) (OH-)2 vs. -log (H+)3(PO4(3-)) points tended to follow the brushite line, rather than the hydroxyapatite (HAp) line which one would expect if enamel behaved as pure HAp. Solution F was below measurable limits after 20 min and F then had little influence on the brushite equilibrating phase. In later (> 13) repetitions, points fell closer to the HAp line, with or without F added to the acid solution. However, added F, which was not then completely removed from solution, caused the slope of the regression line through the points to approach the Ca/P ratio of HAp, and therefore may have had a small effect in reducing the brushite phase. It is concluded that high solid/solution ratio, a previously neglected factor in enamel dissolution studies, has a profound effect in increasing the manifestation of a brushite surface phase and reducing the inhibitory effect of F on this phase.