AIM: This was to review and assess the studies on aetiology of Molar-Incisor Hypomineralisation (MIH) or, as a proxy, of demarcated opacities in permanent first molars and to consider the potential factors involved with findings obtained in animal experiments. METHODS: A systematic search by Medline® online database was performed. Abstracts behind appropriate titles were studied and finally the full articles were evaluated for their strength of evidence in the aetiology of MIH. RESULTS: From a total of 1,142 articles 28 were identified and selected for review. The selected papers covered medical problems in prenatal, perinatal and postnatal period, medication of the child during the first years of life, and exposure to fluoride or environmental toxicants (dioxins and PCBs) in the early childhood. Based on the assessment of the articles it was still not possible to specifically name those factors causing MIH although correlations between several potential factors and MIH were presented. Among the factors suggested and found to cause enamel defects in animal experiments were: high fever, hypoxia, hypocalcaemia, exposure to antibiotics (amoxicillin, a macrolide), and dioxins. CONCLUSION: Despite increased knowledge on the aetiology of MIH insufficient evidence to verify the causative factors exists. Further studies, especially prospective ones, are needed to improve the level and strength of evidence of the role of the present putative factors and to reveal new factors that may be involved. Any combined effect of several factors should be taken into account. Experimental dose/response studies and research on the molecular mechanisms causing the abnormal function of the ameloblasts are also necessary to deepen our knowledge of MIH.

Aetiology of Molar-Incisor Hypomineralisation: A systematic review.

BACKGROUND: Dental caries is a major public health problem in most industrialised countries, affecting 60% to 90% of school children. Community water fluoridation was initiated in the USA in 1945 and is currently practised in about 25 countries around the world; health authorities consider it to be a key strategy for preventing dental caries. Given the continued interest in this topic from health professionals, policy makers and the public, it is important to update and maintain a systematic review that reflects contemporary evidence. OBJECTIVES: To evaluate the effects of water fluoridation (artificial or natural) on the prevention of dental caries.To evaluate the effects of water fluoridation (artificial or natural) on dental fluorosis. SEARCH METHODS: We searched the following electronic databases: The Cochrane Oral Health Group's Trials Register (to 19 February 2015); The Cochrane Central Register of Controlled Trials (CENTRAL; Issue 1, 2015); MEDLINE via OVID (1946 to 19 February 2015); EMBASE via OVID (1980 to 19 February 2015); Proquest (to 19 February 2015); Web of Science Conference Proceedings (1990 to 19 February 2015); ZETOC Conference Proceedings (1993 to 19 February 2015). We searched the US National Institutes of Health Trials Registry (ClinicalTrials.gov) and the World Health Organization's WHO International Clinical Trials Registry Platform for ongoing trials. There were no restrictions on language of publication or publication status in the searches of the electronic databases. SELECTION CRITERIA: For caries data, we included only prospective studies with a concurrent control that compared at least two populations - one receiving fluoridated water and the other non-fluoridated water - with outcome(s) evaluated at at least two points in time. For the assessment of fluorosis, we included any type of study design, with concurrent control, that compared populations exposed to different water fluoride concentrations. We included populations of all ages that received fluoridated water (naturally or artificially fluoridated) or non-fluoridated water. DATA COLLECTION AND ANALYSIS: We used an adaptation of the Cochrane 'Risk of bias' tool to assess risk of bias in the included studies.We included the following caries indices in the analyses: decayed, missing and filled teeth (dmft (deciduous dentition) and DMFT (permanent dentition)), and proportion caries free in both dentitions. For dmft and DMFT analyses we calculated the difference in mean change scores between the fluoridated and control groups. For the proportion caries free we calculated the difference in the proportion caries free between the fluoridated and control groups.For fluorosis data we calculated the log odds and presented them as probabilities for interpretation. MAIN RESULTS: A total of 155 studies met the inclusion criteria; 107 studies provided sufficient data for quantitative synthesis.The results from the caries severity data indicate that the initiation of water fluoridation results in reductions in dmft of 1.81 (95% CI 1.31 to 2.31; 9 studies at high risk of bias, 44,268 participants) and in DMFT of 1.16 (95% CI 0.72 to 1.61; 10 studies at high risk of bias, 78,764 participants). This translates to a 35% reduction in dmft and a 26% reduction in DMFT compared to the median control group mean values. There were also increases in the percentage of caries free children of 15% (95% CI 11% to 19%; 10 studies, 39,966 participants) in deciduous dentition and 14% (95% CI 5% to 23%; 8 studies, 53,538 participants) in permanent dentition. The majority of studies (71%) were conducted prior to 1975 and the widespread introduction of the use of fluoride toothpaste.There is insufficient information to determine whether initiation of a water fluoridation programme results in a change in disparities in caries across socioeconomic status (SES) levels.There is insufficient information to determine the effect of stopping water fluoridation programmes on caries levels.No studies that aimed to determine the effectiveness of water fluoridation for preventing caries in adults met the review's inclusion criteria.With regard to dental fluorosis, we estimated that for a fluoride level of 0.7 ppm the percentage of participants with fluorosis of aesthetic concern was approximately 12% (95% CI 8% to 17%; 40 studies, 59,630 participants). This increases to 40% (95% CI 35% to 44%) when considering fluorosis of any level (detected under highly controlled, clinical conditions; 90 studies, 180,530 participants). Over 97% of the studies were at high risk of bias and there was substantial between-study variation. AUTHORS' CONCLUSIONS: There is very little contemporary evidence, meeting the review's inclusion criteria, that has evaluated the effectiveness of water fluoridation for the prevention of caries.The available data come predominantly from studies conducted prior to 1975, and indicate that water fluoridation is effective at reducing caries levels in both deciduous and permanent dentition in children. Our confidence in the size of the effect estimates is limited by the observational nature of the study designs, the high risk of bias within the studies and, importantly, the applicability of the evidence to current lifestyles. The decision to implement a water fluoridation programme relies upon an understanding of the population's oral health behaviour (e.g. use of fluoride toothpaste), the availability and uptake of other caries prevention strategies, their diet and consumption of tap water and the movement/migration of the population. There is insufficient evidence to determine whether water fluoridation results in a change in disparities in caries levels across SES. We did not identify any evidence, meeting the review's inclusion criteria, to determine the effectiveness of water fluoridation for preventing caries in adults.There is insufficient information to determine the effect on caries levels of stopping water fluoridation programmes.There is a significant association between dental fluorosis (of aesthetic concern or all levels of dental fluorosis) and fluoride level. The evidence is limited due to high risk of bias within the studies and substantial between-study variation.

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Water fluoridation for the prevention of dental caries

The systematic review was commissioned by the Australian National Health and Medical Research Council (NHMRC) to evaluate the scientific literature relating to the health effects of fluoride and fluoridation. The systematic review's research questions relate to the caries-reducing benefits and associated potential health risks of providing fluoride systemically (via addition to water, milk and salt) and the use of topical fluoride agents, such as toothpaste, gel, varnish and mouthrinse. Although the review summarises the recent evidence, it does not constitute health policy or clinical practice recommendations. A literature search was undertaken using the Medline and Embase databases (via www.embase.com
 ). In addition, the Cochrane Systematic Review and Clinical Trial databases were searched to help identify additional systematic reviews and original studies. Because of the availability of recent systematic reviews, searches were limited to publications from 1996 onwards . The search was conducted in December 2006 and limited to English-language publications. Based on types of intervention (individual or population) and the outcomes assessed (efficacy or safety), the hierarchy of study types considered most relevant for answering each of the clinical questions defined in this review was chosen (Table 1). The levels of evidence used by NHMRC for intervention and aetiological studies are summarised in Table 2.
 Screening of eligible studies was conducted by three reviewers. Data were extracted for all of the included systematic reviews and individual studies using standardised data-extraction forms. This included information about the study design, NHMRC level of evidence, population, intervention, comparator, outcome definitions and results. Information relating to potential biases and study quality were also extracted. Where appropriate, study results were pooled using standard meta-analysis techniques. In total, 5418 nonduplicate citations were identified. After applying the inclusion and exclusion criteria, 408 citations were considered potentially eligible for inclusion in the review. After the review of the full papers of potentially eligible articles, 77 citations were included in the review. The summary of findings was presented in the context of the research questions (Table 3).
 Fluoridation of drinking water remains the most effective and socially equitable means of achieving community-wide exposure to the caries prevention effects of fluoride. It is recommended (see also www.nhmrc.gov.au/news/media/rel07/_files/fluoride_flyer.pdf
 ) that water be fluoridated in the target range of 0.6–1.1 mg/l, depending on the climate, to balance reduction of dental caries and occurrence of dental fluorosis.n particular with reference to care in hospital for those following stroke.

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A systematic review of the efficacy and safety of fluoridation

Objective The objective of this study was to assess the strength of evidence for the aetiology of molar–incisor hypomineralization (MIH), often as approximated by demarcated defects

Method  A systematic search of online medical databases was conducted with assessment of titles, abstracts, and finally full articles for selection purposes The level and quality of evidence were then assessed for each article according to Australian national guidelines

Results  Of 1123 articles identified by the database search, 53 were selected for review These covered a variety of potential aetiological factors, some of which were grouped together for convenience The level of evidence provided by the majority of papers was low and most did not specifically investigate MIH There was moderate evidence that polychlorinated biphenyl/dioxin exposure is involved in the aetiology of MIH; weak evidence for the role of nutrition, birth and neonatal factors, and acute or chronic childhood illness/treatment; and very weak evidence to implicate fluoride or breastfeeding

Conclusion  There is currently insufficient evidence in the literature to establish aetiological factor/s relevant for MIH Improvements in study design, as well as standardization of diagnostic and examination protocols, would improve the level and strength of evidence

Aetiology of molar–incisor hypomineralization: a critical review

Objective The aim of the study is to assess the relationship between caries and dental fluorosis in Ethiopian children living in Rift Valley areas known for endemic fluorosis. Method A total of 306 children (12-15 years old), selected from areas with moderate (0.3-2.2 mg/l), or high (10-14 mg/l) fluoride concentration in the drinking water were interviewed and examined for caries and dental fluorosis. Scorings were recorded according to the DMF system, and the Thylstrup-Fejerskov (TF) Index. Results Prevalence of dental fluorosis (TF-score > or = 1) was 91.8% (moderate area) and 100% (high-fluoride area). The corresponding caries prevalence and mean DMFT in the areas were 45.3% versus 61.6%, and 1.2 versus 1.8, respectively. Age and severity of dental fluorosis were found to be independent predictors for DMFT > or = 1. When compared with 12-year olds with TF-scores 0-4, odds ratios were 3.0 (95% CI 1.6-5.7) and 2.0 (95% CI 1.2-3.2) if TF-scores were > or = 5 and age 13-15 years, respectively. A positive relationship between caries and fluorosis was observed across tooth types in both areas. The percentage of children with DMFT > or = 1 was highest in groups with TF-score > or = 5 in the second molar, followed by the first molar. Conclusion The present findings indicate that the second molar is the tooth most severely affected by dental fluorosis and dental caries. Dental caries increased with increasing severity of dental fluorosis, both in moderate- and high-fluoride areas. Thus, a positive relationship between dental caries and dental fluorosis was observed across various tooth types, in both areas.

The relationship between dental caries and dental fluorosis in areas with moderate- and high-fluoride drinking water in Ethiopia

The study was conducted to assess caries and developmental defects of enamel in relation to fluoride levels in drinking water and the association between caries experience and the severity of diffuse

W. van der Hoek

Papers

Dental Caries and Developmental Defects of Enamel in Relation to Fluoride Levels in Drinking Water in an Arid Area of Sri Lanka

Prevalence and distribution of enamel defects and dental caries in a region with different concentrations of fluoride in drinking water in Sri Lanka.