Introduction

Childhood obesity has emerged as a significant public health concern globally, with its prevalence increasing at an alarming rate. Defined as an excessive accumulation of body fat that adversely affects health, obesity in children is associated with numerous comorbidities, including cardiovascular diseases, diabetes, and orthopedic issues. More recently, its implications for oral health have garnered attention, as evidence suggests a correlation between obesity and alterations in salivary composition, which may impact dental health (1). Saliva, often referred to as the "mirror of the body", plays a critical role in maintaining oral health by facilitating digestion, neutralizing acids, and protecting against microbial colonization. However, metabolic alterations in obesity may disrupt the composition and functionality of saliva, thereby predisposing children to various oral health conditions (2).

Salivary composition is influenced by systemic health, dietary patterns, and metabolic states. Obesity is known to be associated with hyperglycemia, insulin resistance, and low-grade systemic inflammation, all of which can affect the quality and quantity of saliva produced. These changes may manifest as altered salivary flow rates, pH levels, and the concentration of key electrolytes and enzymes. For instance, research has indicated that obese children often exhibit reduced salivary flow and buffering capacity, leading to an increased risk of dental caries and erosion (3). Moreover, elevated levels of pro-inflammatory cytokines, such as interleukin-6 and tumor necrosis factor-alpha, in saliva have been observed in obese individuals, suggesting a systemic link between obesity-induced inflammation and oral health (4).

Dental health in children is a multifaceted concern influenced by dietary habits, oral hygiene practices, and biological factors, including salivary composition. The consumption of a high-calorie, sugar-rich diet, often associated with obesity, not only contributes to weight gain but also fosters the growth of cariogenic bacteria such as Streptococcus mutans. These bacteria thrive in acidic environments, exacerbated by changes in salivary pH and reduced salivary flow in obese children (5). Consequently, a bidirectional relationship between obesity and oral health emerges, where poor dietary choices and metabolic dysfunction mutually reinforce one another. Furthermore, periodontal health, which is critical for maintaining the structural integrity of the oral cavity, may also be compromised in obese children due to the pro-inflammatory state induced by excess adiposity (6). Understanding the impact of obesity on salivary composition and dental health is essential for developing targeted preventive and therapeutic strategies.

Review

The relationship between childhood obesity and oral health is complex, influenced by metabolic, dietary, and inflammatory factors. Obesity-induced changes in salivary composition, such as reduced salivary flow and altered pH, significantly affect oral health by creating an environment conducive to the growth of cariogenic bacteria. High-calorie diets, typically associated with obesity, exacerbate this issue by providing a substrate for bacterial fermentation, leading to increased acid production and subsequent demineralization of dental enamel (7). These dietary habits, coupled with impaired salivary buffering capacity, make obese children more susceptible to dental caries and erosion.

Elevated levels of pro-inflammatory markers, including interleukin-6 and C-reactive protein, have been observed in obese individuals and are thought to influence periodontal health negatively. Chronic inflammation contributes to the progression of periodontal disease by exacerbating tissue destruction and impairing immune responses within the oral cavity (8). This interplay highlights the bidirectional relationship between obesity and oral health, where metabolic and inflammatory factors converge to impact the oral ecosystem. Addressing these issues requires an integrative approach, focusing on weight management, healthy dietary practices, and regular dental care to mitigate the adverse effects of obesity on children’s oral health.

Alterations in Salivary Biochemistry Associated with Childhood Obesity

Childhood obesity is increasingly linked to significant alterations in salivary composition and function, with these biochemical changes reflecting the broader metabolic disturbances caused by excess adiposity. The saliva of obese children frequently exhibits reduced flow rates, potentially due to altered autonomic nervous system function and glandular dysfunction. Studies indicate that this reduction in salivary flow compromises the ability of saliva to maintain an optimal pH and clear carbohydrates effectively, increasing susceptibility to oral health issues such as dental caries and erosion (9). This reduction in functionality underscores the broader impact of metabolic dysregulation on salivary glands. Beyond flow rate, obesity also affects the concentration of key electrolytes and proteins in saliva. Evidence points to elevated levels of salivary calcium, phosphate, and magnesium in obese children, which may initially seem protective due to their role in remineralization. However, these elevated levels often occur alongside increased acidogenic activity, negating their protective effects and promoting mineral loss from the enamel surface (10). This imbalance reflects the dual challenge posed by obesity: systemic metabolic disturbance combined with local environmental changes within the oral cavity.

Protein composition in saliva, particularly enzymes and inflammatory mediators, also undergoes notable shifts in obese individuals. Amylase activity, a critical factor in carbohydrate digestion, tends to increase obesity rates, likely due to heightened demand for glucose metabolism. While this might enhance initial digestion, it creates a nutrient-rich environment for cariogenic bacteria, particularly Streptococcus mutans. At the same time, inflammatory cytokines such as tumor necrosis factor-alpha and interleukin-1beta are found in higher concentrations in the saliva of obese children. These molecules, typically associated with systemic inflammation, further disrupt the oral microbiome, favoring the proliferation of pathogenic species and contributing to periodontal inflammation (11).

Salivary antioxidant capacity is another area of concern, as oxidative stress is a hallmark of obesity. Research reveals that obese children often exhibit diminished levels of key antioxidants in their saliva, such as glutathione and superoxide dismutase. This depletion compromises the ability of saliva to counteract oxidative damage caused by free radicals, exacerbating tissue damage in the oral cavity. Furthermore, lipid peroxidation byproducts, commonly elevated in obesity, may accumulate in saliva and aggravate mucosal irritation and microbial dysbiosis (12). These findings align with broader systemic patterns of oxidative imbalance in obese populations and underscore the interconnectedness of systemic and oral health. Collectively, these biochemical changes in saliva reflect the cascading effects of obesity on oral health. Reduced salivary flow, altered electrolyte balance, increased inflammatory markers, and diminished antioxidant capacity create a multifaceted risk profile for obese children. Addressing these changes requires a comprehensive understanding of the underlying metabolic mechanisms and targeted interventions to restore salivary function and maintain oral health.

Impact of Obesity-Related Changes in Saliva on Dental Caries Risk

The relationship between obesity and dental caries risk in children is strongly mediated by obesity-induced alterations in salivary composition. The metabolic profile associated with obesity disrupts the protective qualities of saliva, enhancing its role as a medium for cariogenic bacterial proliferation. Salivary flow rate, often reduced in obese children, is one of the primary factors influencing caries development. This reduction compromises the mechanical washing effect of saliva, diminishing its ability to clear food debris and bacterial colonies from the oral cavity. As a result, substrates for bacterial fermentation persist for extended periods, facilitating the production of acids that erode dental enamel (13). The reduced flow also limits the delivery of key protective components such as calcium and phosphate, which are critical for remineralization. Beyond flow rate, the buffering capacity of saliva in obese children exhibits significant impairment. This inability to neutralize acids generated by bacterial metabolism creates an oral environment that favors enamel demineralization. Lower salivary pH levels, frequent observation in obese individuals, further exacerbate this condition. This acidic environment not only facilitates the growth of acidogenic species such as Streptococcus mutans and Lactobacillus but also impedes the remineralization process necessary for repairing early enamel lesions (14). The interplay of these factors sets the stage for heightened caries susceptibility in this population.

The composition of salivary proteins in obese children also reveals significant deviations from healthy profiles, with specific changes influencing caries risk. Salivary amylase activity, for example, is often elevated in obese individuals, reflecting increased carbohydrate consumption and metabolic demand. While this enzyme plays a crucial role in the breakdown of dietary starches, its heightened activity produces an abundance of fermentable sugars, creating an ideal substrate for cariogenic bacterial metabolism. Concurrently, the levels of protective proteins such as immunoglobulin A (IgA), which plays a key role in the immune defense of the oral cavity, are often found to be diminished. Reduced IgA levels weaken the immune response against cariogenic microorganisms, allowing bacterial colonies to proliferate unchecked (15). Microbial analysis of the oral cavity in obese children reveals a shift towards a more cariogenic microbiome, influenced directly by the altered salivary environment. The increased availability of fermentable substrates, combined with the reduced antimicrobial activity of saliva, fosters an ecological shift favoring the dominance of acid-producing bacteria. These microbial communities not only accelerate enamel erosion but also contribute to the formation of dental biofilms that are more resistant to mechanical removal. The combination of reduced salivary defense mechanisms and a pathogenic microbiome amplifies the risk of caries development, making obese children a vulnerable population for this oral disease (15, 16).

Interplay Between Obesity, Salivary Composition, and Periodontal Health in Children

The relationship between obesity and periodontal health in children is deeply influenced by the interplay of altered salivary biochemistry and systemic metabolic dysfunction. Obesity is marked by chronic low-grade inflammation, a condition that extends to the oral cavity and disrupts periodontal tissue homeostasis. Pro-inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), commonly elevated in obese individuals, have been detected in salivary secretions. These molecules initiate and amplify inflammatory responses in gingival tissues, contributing to the breakdown of periodontal structures and increasing the risk of gingivitis and periodontitis in children (12, 17, 18). The salivary presence of these cytokines also indicates a systemic connection, linking obesity-induced inflammation with localized oral health challenges.

The microbial profile within the oral cavity further shifts in obese children, influenced by both metabolic changes and alterations in salivary composition. Obesity-related reductions in salivary flow and increases in glucose levels create an environment conducive to the growth of pathogenic periodontal bacteria, including Porphyromonas gingivalis and Tannerella forsythia. These bacteria are known for their role in periodontal destruction, as they stimulate inflammatory pathways and produce proteolytic enzymes that degrade connective tissues and bone. Additionally, the reduced presence of protective salivary peptides, such as defensins and histatins, compromises the oral cavity’s innate defense mechanisms, making periodontal tissues more vulnerable to microbial assault (19). The impact of oxidative stress on periodontal health in obese children cannot be overlooked. Saliva from obese individuals often contains elevated levels of reactive oxygen species and their byproducts, a reflection of systemic oxidative stress commonly associated with excess adiposity. In periodontal tissues, these oxidative molecules exacerbate inflammatory damage by inducing apoptosis in gingival fibroblasts and impairing the repair mechanisms of connective tissues. Salivary antioxidants, such as superoxide dismutase and glutathione, which play a critical role in mitigating oxidative damage, are often diminished in obese children, further compounding the susceptibility of periodontal structures to inflammatory and oxidative harm (20).

Beyond the biochemical and microbial changes, the hormonal imbalances seen in obesity also exert significant influence on periodontal health. Leptin, an adipocyte-derived hormone involved in regulating energy balance, is often elevated in obese individuals and is found in higher concentrations in the saliva of obese children. While leptin is traditionally associated with anti-inflammatory effects, chronic overproduction in obesity may paradoxically enhance inflammatory responses in periodontal tissues. Studies suggest that leptin contributes to the recruitment of immune cells, particularly neutrophils, to gingival tissues, exacerbating inflammation and promoting tissue destruction (21). The interplay of these factors underscores the multifaceted impact of obesity on periodontal health, with salivary alterations acting as both a marker and a mediator of these effects.

Conclusion

Childhood obesity significantly alters salivary composition, impacting dental and periodontal health through reduced salivary flow, disrupted microbial balance, and heightened inflammatory responses. These changes create an environment conducive to caries and periodontal diseases, underscoring the systemic connection between obesity and oral health. Addressing these issues requires integrated approaches targeting metabolic health, dietary habits, and oral hygiene. Understanding these complex interactions is critical for developing effective prevention and management strategies for at-risk pediatric populations.

Disclosure

Conflict of interest

There is no conflict of interest.

Funding

No funding.

Ethical consideration

Non applicable.

Data availability

Data that support the findings of this study are embedded within the manuscript.

Author contribution

All authors contributed to conceptualizing, data drafting, collection and final writing of the manuscript.