Читать книгу The Impact of Nutrition and Diet on Oral Health - Группа авторов - Страница 29

The role of macroelements in the following topics relating to oral health will be discussed in more detail: tooth loss, dental caries and erosive tooth wear, periodontal disease, and saliva.

Tooth Loss

Tooth loss can occur due to a variety of reasons and is not necessarily related to periodontal disease or dental caries. Therefore, care must be taken when interpreting data, especially from cross-sectional but also from longitudinal studies, and in particular those that did not investigate the aetiology of tooth loss.

Table 1. Macroelements in the diet and their physiological importance [73–79]

A longitudinal study conducted on individuals born in 1927 and, at the beginning of the study in 1998, residing in Niigata (Japan) provided valuable insight into the “relationship between general health status, including nutrient intake and anthropometry, and dental diseases” [4]. The impact of the overall diet on the number of teeth was studied in a small subset of participants for which a positive association between the intake of sodium, potassium and phosphorus, but not calcium, on the number of teeth was demonstrated. However, only sodium intake was of significance when comparing between those with 20+ versus <20 teeth [4]. Furthermore, the study participants provided evidence for the fact that nutrient intake also depends on oral health status. Those with a compromised dentition or an ill-fitting denture had less intake of potassium and calcium, but not sodium [5]. Over a period of 5 years, a greater decline in intake of sodium, potassium and calcium was shown in participants with an impaired dentition compared to those with an uncompromised dentition [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], thereby leading to increased caries risk [33]. A recent review by the Cochrane Group considered the current evidence for calcium supplementation in preventing hypertensive disorders and related problems, including caries [34]. However, only one caries-related study could be retrieved which, nonetheless, demonstrated a caries reduction in the 12-year-old offspring of those mothers receiving calcium supplements during pregnancy [35]. A somewhat related study was able to demonstrate that a high intake of cheese during pregnancy, but not milk, was able to reduce caries risk during childhood [36].

Calcium supplementation of erosive foods and in particular acidic beverages has attracted attention over the last decades. Here, calcium addition increases the degree of saturation of the solution (beverage) with respect to tooth minerals, thereby lessening the erosive potential of the contained acids. A range of commercial and experimental products have been found to reduce erosion otherwise caused by the same beverage without calcium supplementation, although sometimes at the expense of organoleptic properties. Likewise, linear chain polyphosphates, added to some beverages as a preservative (and dog food for the control of tartar [37]), have also been investigated for their ability to reduce erosion (for review of research thus far on these topics, see [38]). Lastly, the consumption of beverages containing phosphoric acid has been linked with increased risk of osteoporosis in some populations [39], although this was postulated to be due to replacement of milk with such beverages [40]. Nonetheless, there appears to be no conclusive evidence thus far as to the role of excess dietary phosphorus and bone health [41].

A considerable body of evidence, derived from animal studies, exists on the role of phosphate supplemented diets in caries prevention [42]. A subsequent multi-year study in 2,262 children in Sweden [43], with dicalcium phosphate being added to flour used for baked goods and to table sugar, was able to demonstrate that a calcium and phosphate supplemented diet can reduce the incidence of caries. However, the dicalcium phosphate used was contaminated in that it contained fluoride during the first year of the study, and caries was determined on only 4 proximal surfaces. Subsequent studies in the US (1,672 and 969 children, respectively; same dicalcium phosphate administration), however, failed to demonstrate anti-caries benefits of added calcium and phosphate [44, 45].

An animal caries study to determine the effect of phosphate structure to reduce caries incidence compared sodium ortho-, pyro-, tripoly-, trimeta-, and hexametaphosphate when present in the diet [46]. Sodium trimetaphosphate (TMP), a compound with a ring structure, was found to be most efficient, followed by hexametaphosphate (chain structure). TMP was later unsuccessfully evaluated as an anti-caries agent when formulated in a fluoride toothpaste [47]; however, TMP is still being researched to this day [48]. Sodium hexameta-, pyro-, and tripolyphosphate are nowadays used primarily for the purpose of tartar prevention and chemical stain removal in oral care products [1], although recent research on nano-sized sodium hexametaphosphate has shown promise for its ability to enhance caries lesion remineralization [49].

Sodium phytate, the sodium salt of the hexaphosphate ester of inositol and present in unrefined sugars and whole grains, legumes, nuts and seeds, has been shown to retard demineralization in vitro [50] and in animal caries studies [51]. However, a later study was unable to replicate earlier findings [52]. It has also been postulated that the effect of phytate (and presumably other compounds naturally present in foods) is restricted to its isolated application in the absence of the food matrix [53]. Similar to phytate, calcium glycerophosphate has attracted attention in the past, although less as a dietary constituent than it being formulated into oral care products alongside fluoride (for review, see [54]). Nonetheless, the present animal caries data on calcium glycerophosphate, when administered as part of the diet, is encouraging [e.g., 55]. In the context of animal caries studies, it must be noted that the salivary phosphate content in rats is approximately one tenth that in humans [56], which suggests that the anti-caries effects of dietary phosphate is likely to be more pronounced in rats than in humans. This explains earlier mentioned discrepancies for anti-caries effects of calcium phosphate enriched diets in animals versus humans.

More recently, phosphoryl oligosaccharides of calcium (POs-Ca) have been evaluated for their anti-caries and erosion prevention properties when added to foods. Three studies on chewing gums fortified with POs-Ca were able to demonstrate enhanced enamel caries lesion remineralization in vivo [57] and in situ [58, 59]. Similar erosion prevention effects were observed when POs-Ca were added to an apple juice drink [60].

Periodontal Disease

The role of macroelements in periodontal disease has not been the primary concern of studies relating to this disease, although a recent, comprehensive review summarized the current evidence for a range of elements [61], including those of interest here.

Some anecdotal evidence exists correlating urinary potassium excretion (linked to potassium food intake) inversely to the severity of periodontitis [62], although other studies were not able to demonstrate an association [63, 64].

The evidence for calcium intake, however, is stronger, and in particular to alveolar bone health. A total of 12 studies in humans and 5 in animals have been discussed [68], with the National Health and Nutrition Examination Survey (11,787 participants) [65] and Danish Health Examination Survey (3,287 participants) studies [66] being perhaps the most relevant, despite their cross-sectional nature. Both studies provided evidence for an inverse relationship between calcium intake and the severity of periodontitis. Further evidence was also provided by the earlier mentioned Niigata [67] and MONICA [10] studies. Some indirect evidence on the value of calcium (and vitamin D) supplements in preventing periodontal disease (bone loss from the hip and tooth loss were determined) was provided in an aforementioned study [13]. A trend for better periodontal health in participants taking calcium and vitamin D supplements was observed in a small cross-sectional study (51 participants) [68, 69]. However, further studies are necessary as there is insufficient evidence to recommend an appropriate dose of calcium and vitamin D.

Similar to potassium, the evidence for phosphorus is equivocal as 2 studies reported no evidence, whereas one did [61]. It could be argued that because of phosphate’s importance in calcium metabolism, phosphorus deserves more attention.

Saliva

It would perhaps be logical to assume that an increase in, for example, calcium intake would result in an increase in salivary calcium via systemic means, thereby reducing risk to caries, erosive tooth wear, and potentially also periodontal disease. However, this does not appear to be the case as salivary calcium (approximately 24 mg calcium is secreted via saliva daily [70]) is directly related to the tightly controlled plasma calcium concentration with excess calcium being excreted via the kidneys rather than in saliva [71] – intake of a single dose of calcium (1,215 mg) had no effect on salivary and plasma calcium concentrations [72]. Therefore, saliva does not appear to be contributing to calcium (and phosphate) homeostasis. Furthermore, it must be noted that our understanding of the intra-oral pharmacokinetics of the macroelements, when administered topically, is still rather poor.