[6]. The observations for calcium were also witnessed in dentate vs. edentate geriatric populations in other countries [7, 8]. These results were generally explained by a decreased consumption of hard to chew foods, such as meat or vegetables.
In contrast to the aforementioned Niigata study, inadequate calcium intake was associated with increased tooth loss in a cross-sectional, observational study in “healthy young women” in Argentina [9]. These findings mirrored those from a longitudinal study on a larger Danish population (Danish Monitoring Trends and Determinants in Cardiovascular Disease [MONICA] study; 30- to 60-year-old men and women) [10]. This study also demonstrated that in particular the increased intake of calcium from dairy products is associated with a reduced risk of tooth loss [11]. Furthermore, a longitudinal study on female registered nurses in the US showed that those who lost teeth during a 2-year follow-up had smaller increases in potassium intake compared to women who did not lose any teeth [12].
An obvious remaining question, however, is if these relationships are truly causative or more or less incidental. As the macroelements are not consumed in the absence of other nutrients (e.g., dairy products also contain other minerals and a range of proteins and carbohydrates) and are present in a wide range of foods at varying concentrations, more well-controlled, prospective studies would be required to draw firm(er) conclusions. One such study, conducted on a geriatric US population (n = 145), investigated the effects of calcium (and vitamin D) supplementation on tooth loss as a secondary outcome [13]. Participants who supplemented their diet with 500 mg of calcium (as calcium citrate malate) and 700 IU of vitamin D per day for 3 years exhibited a 60% lower risk of tooth loss compared to those who took placebos. During a 2-year follow-up, a similar reduction in tooth loss was observed in those who had an overall calcium intake of at least 1,000 mg compared to those who took less.
Dental Caries and Erosive Tooth Wear
The mineral phase in the teeth can be described as a calcium-deficient, non-stoichiometric hydroxyapatite, with calcium and phosphate being the main components. Both of these macroelements obviously play a role in the teeth’s de- and remineralization. However, many ions, including sodium, potassium and chloride, can substitute for calcium and phosphate in the crystal lattice [14] of the various mineral phases present in the teeth [15], thereby potentially affecting tooth de- and remineralization and/or the interaction of the teeth with anti-caries/erosion prevention agents, such as fluoride.
Table salt (sodium chloride) is being used as a vehicle to deliver cariostatic amounts of fluoride as a public health measure in some countries [16]. Concerns that chloride impacts the interaction of fluoride with enamel, assuming the effect of fluoridated salt is primarily topical, were alleviated in vitro [17, 18]. Somewhat related are mechanistic observations that caries lesion formation is potentiated at increasing ionic strengths (i.e., increasing concentrations of “inert” potassium chloride in the dissolution medium), which were partially explained by reduced diffusive coupling [19]. However, to what extent these findings relate to the importance of ionic strength in cariogenic biofilms, in which subtle fluctuations in ionic strength have been shown [20], remains to be determined. Likewise, there is currently no evidence on whether a diet rich in electrolytes has an impact on the ionic strength in dental biofilms.
The consumption of milk and milk products, the 2 main sources of dietary calcium and phosphate intake, which will be discussed in more detail separately (see Chapter 8), has been linked to a reduction in caries prevalence in a variety of studies, including the aforementioned Niigata study [21]. The consumption of milk and/or yogurt has also been linked to a reduced prevalence of erosive tooth wear [22]. Milk components, such as casein phosphopeptide amorphous calcium phosphate, have also been shown to prevent caries in vivo and in situ when incorporated into chewing gums [23] and to enhance the ability of milk to remineralize early enamel caries lesions in situ [24]. Likewise, the addition of casein phosphopeptide amorphous calcium phosphate to erosive soft drinks was shown to negate their detrimental impact on enamel in vitro [25].
In terms of general calcium intake, the aforementioned Argentinian study [9] provided some evidence for an association between low calcium intake and a high caries prevalence. A study on a geriatric population in the US [26], however, pointed to the opposite; that is, a positive association between calcium intake and the number of coronal caries lesions was observed. The authors argued that this association was likely due to a recent dietary change (e.g., consumption of cookies with milk). Contrasting findings in the same study were that adequate calcium and phosphorus intakes were positively associated with the number of teeth and number of functioning teeth.
Calcium supplementation of foods (e.g., orange juice, cereals, non-dairy milk) has become increasingly popular and offers an alternative source of calcium intake to those who cannot tolerate milk and milk products [27] and/or to individuals who suffer from celiac disease who often have inadequate calcium intake [28]. The effects on raising intra-oral calcium concentrations have not been studied yet but are likely to be more pronounced from these foods than from supplements, which in most cases are in tablet form with little to no contact with the oral cavity when administered (with the exception of calcium-containing gummy candies). In this context, the importance of biofilm-contained calcium, which in turn determines the concentration of retained fluoride, must be noted [29]. Several studies [e.g., 30, 31] have shown that it is possible to enhance intra-oral fluoride retention through prior application of ionic calcium (as lactate) in a rinse format. Somewhat similar effects can be expected if a fluoride application immediately follows the consumption of calcium-fortified foods (e.g., orange juice with calcium at breakfast followed by tooth brushing with fluoride toothpaste). However, calcium bioavailability and concentration, but not total dose, are lower in the case of orange juice with calcium versus a 150 mM calcium lactate rinse [30] (350 mg Ca in an 8 oz serving correspond to 36 mM Ca vs. 150 mM in a 20 mL rinse corresponding to 120 mg Ca).
Perhaps a more important aspect of calcium supplementation is that related to pregnancy, as decreased salivary calcium and phosphate concentrations have been reported during late pregnancy [32],
