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ageing. Clinically, with a decreasing pulp size, particularly with a collagenous plug formation, root
canal treatment in older adults may be considered more challenging than in a younger patient.
It comes as no surprise that increasing age is associated with loss of attachment in the periodontal tissue. Several hypotheses exist to explain the loss of attachment(10). The cumulative hypothesis relates to the long- term exposure and cumulative effects of chronic periodontitis. Another
hypothesis is age- related susceptibility– which relates to the dysregulation of the immune system.
A newer hypothesis relates to cellular senescence(11). This theory relates to the irreversible arrest
of the proliferative capabilities of cells. Senescent cells are able to upregulate genes that block the
p16 and p21 cell cycle and the development of senescence- associated secretory phenotype(12).
8.4 Cellular, Molecular andPhysiological Mechanisms ofAge- related
Changes inOral Mucosal Tissues andSalivary Glands
The oral mucosa in older adults and younger persons often presents similarly. Over time, the appearance of the oral mucosa may be modified by trauma, mucosal disease, systemic disease and salivary
gland hypofunction. With increasing age, atrophy of the oral mucosa, reduction of elasticity and
thinning of squamous epithelium may be seen(9). Thinning of the oral mucosa contributes to alteration of the mucosa immunity, where there is an increased susceptibility to infection and trauma(13).
From a cellular perspective, ageing of the mucosa is characterised predominantly by changes to
the oral epithelium. Features include less prominent rete ridge, decreased mean thickness,
decreased cell density, reduction of mitotic activity and decreased tissue regeneration and healing(14). A study reporting on cellular morphometric features reports that epithelial cells change
shape and become larger with age when measured by cellular perimeter and area(14). Regarding
shape, epithelial cells become flatter with age, and this may be due to the level of maturation of
cells. These changes may account for the histopathological appearance of increased number of
cells in the granular and keratin layers with a reduction of cells in the prickle cell layer.
In older adults, the incidence of oral mucosal conditions increases. A study from Thailand noted
an incidence of 83.6% of oral mucosal conditions for those over 60 years of age. Varices, fissured
tongue and traumatic ulcer were the most prevalent mucosal conditions. The study also reported
an increased prevalence of pathosis in denture wears (62.7%) compared with non- denture wearers
(28.5)(15). Furthermore, the incidence of oral cancer increases with age and is often associated
with cellular dysregulation.
Ageing induces structural, functional and metabolic changes in the salivary glands. Histological
studies have demonstrated a significant decline in the volume of acini by up to 30%. The decline in
acinar volume is considered progressive as age increases(16). Salivary gland function can be impaired
through parenchyma structures of salivary gland. Where there is a loss of functional parenchyma, it
can be compensated by the ‘reserve’ functional capacity of the salivary glands, particularly when
there is no further stress placed on the system(17). On the other hand, the percentage of adipose
tissue, fibrotic tissue and ductal irregularity increases with age(18). The functional changes to saliva
composition and salivary flow rate are discussed in Section8.6. Metabolic changes in salivary glands
are influenced by several factors including genomics, proteomic, transcriptomic and environmental
changes(19). The field of salivary gland metabolic changes has focused on disease biomarkers. For
example, in Sjogren’s syndrome, choline, taurine, alanine and glycine concentrations have been
reported to be significantly higher in primary Sjogren’s syndrome(20). The field of metabolomic
analysis is considered a novel approach, and there is emerging evidence that salivary metabolites
may lead to the early diagnosis of diseases, such as oral cancer or periodontal disease(21).
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8.5 Microbiological Changes ofthe Ageing Oral Mucosa
During the course of life, the oral microbiome is constantly changing. From infancy, the structure
of the oral microbiome is simple and becomes more complex throughout life(22). In later years of
life, increased levels of Candida, Lactobacilli and Staphylococci are present in saliva and the oral
cavity(13). Their presence is often associated with medications, use of oral appliances or dentures,
salivary gland hypofunction and deteriorating general health. These changes may predispose older
adults or elderly to opportunistic infections.
Age- related factors can influence resident oral microbiome. Over time, there is a shift in the oral
microbiome, even without disease. Several physiological changes occur including a reduction in
salivary gland secretion. In addition, changes in hormones, medications, dentures, diet and
reduced oral hygiene practices may also contribute to older adults having a different oral microbiome to younger individuals(23).
Different anatomical sites are prone to exhibit a diverse range of bacteria. These anatomical sites
include the dorsal surface of the tongue, mucosa and hard palate. In older adults, Streptococcus,
Veillonella and Fusobacteria may be reported at these sites(23).
In ageing, there are alterations in mucosal immunity and deterioration of general health. This
predisposes the oral mucosa to opportunistic infections. Opportunistic infections may take place
due to a lower threshold to infection of previously established microorganisms or superinfections.
There is a decreased clearance of oral microbiome in ageing due to reduced saliva production and
alterations in the composition of saliva. Older adults have a propensity to harbour superinfecting
microorganisms including enteric rods and pseudomonas(13).
8.6 Age- related Changes ofInnate Antimicrobial Factors
atOral Mucosa
The innate antimicrobial defence of the oral mucosa is typically influenced by pH, nutrient availability, antimicrobial peptides, lysozymes and other proteins in saliva(24). The innate immune
system improves physical and chemical barriers through the synthesis of antimicrobial factors. As
a first line of defence, it can protect against Gram- positive and Gram- negative bacteria, viruses,
parasites and fungi.
Saliva, containing several antibacterial properties, may alter the formation of biofilm. The pH of
saliva in health is 7(25), and pH alterations will allow for different bacteria to grow. Periodontal
disease will alter the pH of saliva. Lactoferrin is able to bind iron, reducing the amount available
for the microorganisms(26). Salivary lysozymes are membrane- bound organelles and are able to
kill Gram- positive bacteria through hydrolysing linkages in the peptidoglycan wall. Salivary thiocyanate and lactoperoxidase also augment its antibacterial action. Furthermore, the flow of saliva
is useful because it mechanically flushes away bacteria before it forms a biofilm.
Salivary changes as a result of ageing may, in turn, affect innate immunity. With age, secretion and properties of saliva change. Both stimulated and unstimulated salivary flow rates
decline in older adults, particularly from the submandibular and sublingual salivary glands(27).
Salivary composition, including organic and inorganic components, also alters significantly in
older adults. There is generally an increase in inorganic components, particularly potassium,
chloride and phosphate ions. With an increase of ionic concentration(28), a reduction of salivary volume is expected. Regarding organic components in older adults, some proteins increase
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and others decrease. In unstimulated saliva, lysosome, amylase and IgA increase while MUC1,
MUC2, lactoferrin, transferrin, oxidised glutathione and peroxidase activity decrease(28). A
study has also reported reduced MUC1 and MUC2in xerostomia patients, and hence MUC1
and MUC2 can be involved in the subjective perception of dry mouth(17). Salivary proteins,
particularly mucins, lactoferrin and peroxidase, are imperative for the innate antimicrobial
defence system.
8.7 Cellular, Molecular andPhysiological Changes inthe Craniofacial
Muscles During Ageing
Ageing is often characterised by a reduction in muscle mass and strength (29). Sarcopenia is
defined as the gradual loss of muscle mass, strength and function(30). Total muscle mass decreases
with advancing age. Over time, there is a reduction in muscle fibres as opposed to fibre size.
Sarcopenia is associated with an increased risk of falls and mortality(31). Vitamin D levels are
imperative for both bone and muscle function(32). Vitamin D has a critical role in maintaining
calcium and phosphate homeostasis in bone health. Low levels of vitamin D are associated with
atrophy of muscles and fibres and hence muscle weakness. The vitamin D receptor is also expressed
in skeletal muscle and contributes to muscle contractions. In older adults, lower vitamin D status
is associated with poor physical performance(32).
Specifically in the craniofacial region, there is a decline in muscle mass and compactness with
age. In older adults, electrophysiological studies have reported a loss of motor units leading to a
reduction in muscular activity and masticatory forces(33). Regarding masticatory function, lower
muscle activity will lead to an increased chewing duration. Furthermore, computed tomography
(CT) studies have also reported a continual decline in mass and density of pterygoid and masseter
muscles after 20 years of age(34). The reduction of bite strength in older adults through combined
loss of muscle and density is estimated to be over 60%(35).
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8.8 Cellular, Molecular andPhysiological Changes inthe Craniofacial
Bones During Ageing
Bone is considered a dynamic tissue, and it undergoes different phases throughout life. In children
and adolescents, the modelling phase is prevalent where there is greater formation of bone compared with resorption. In mature adults, the balance is generally at equilibrium, and in older
adults, bone resorption is dominant(36). In older adults, levels of cyclo- oxygenase 2 (COX- 2)
enzyme decline significantly. COX- 2 plays a role in bone repair. Although multifactorial, the levels
of COX- 2may contribute to delayed bone healing with age. Facial bones are analogous to tectonic
plates, with even slow changes leading to significant facial shape changes(37). Throughout life,
craniofacial bones continue to change at varying rates, depending on the anatomical site. For
instance, in a craniometric analysis of 160 skulls in regard to ageing, there was a marked reduction
in facial height, particularly the maxilla and mandible. On the other hand, there was a modest
increase in facial width and depth, as well as a coarsening of bony prominences(38).
The maxilla undergoes significant resorption with age. Retrusion of the maxilla increases, which
leads to an increased prominence of the nasolabial fold(39). The maxillary angle also decreases in
older adults, which may be associated with a reduction of vertical facial height. Loss of dentition
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104
will also cause bone loss around the alveolar process and the lower portion of the maxilla.
Reduction of alveolar height represents the most predominant change of the mandible with
age(37). Resorption of alveolar bone and increased labiomental fold can lead to the appearance of
a ‘witch’s chin’. Overall, bone loss is more extensive and rapid in the mandible than in the maxilla.
The association between ageing and progressive bone reduction with ensuing osteoporosis is wellknown(40). Osteoporosis results in alterations of jaw bone structure. The links between osteoporosis and periodontitis are greatly debated and remain inconclusive (36). Both processes are
multifactorial and may progress with advanced age, smoking, family history and oestrogen
deficiency.
8.9 The Crosslink Between Ageing andSystemic Diseases
andConditions inOral Mucosal Tissues
Numerous systemic diseases can manifest as mucosal changes(41). Pathology which can
affect the mucosa includes white blood cell lineage disorders, red blood cell lineage disorders,
bleeding disorders, pancytopenia, oral mucosal complications secondary to haematologic
cancer treatment, liver disease, kidney disease, connective tissue disease, endocrine disease,
pulmonary disease, immunological disease, nutritional deficiencies, dermatologic disease,
vascular disease, gastrointestinal disease and oral neoplasms. Many systemic conditions tend
to occur with age, and as individuals age, it is common to present with several conditions
simultaneously.
8.10 The Impact ofAgeing onOral Health
Oral health is considered imperative to general health. In the global health agenda, oral health
is often overlooked and rarely prioritised by policymakers(42). Most oral diseases are preventable, and particularly in the elderly population, neglect of oral health is often seen. The highest
incidence of dental caries is in those aged over 70 years. In addition to caries, periodontal disease, edentulousness and oral cancer also significantly increase with age. According to the 2019
Global Burden of Disease study, severe periodontitis, untreated caries and edentulousness
accounted for 23.1million disability- adjusted life- years(43). The largest risk factors of oral
disease for the elderly include tobacco, alcohol and low socioeconomic status (42). Smoking
and chewing tobacco- related products are considered risk factors for oral cancer, periodontal
disease and premature tooth loss. The overall risk of developing oral cancer is approximately 3
times for smokers. Those who smoke more than 40cigarettes a day have a 5.6 times increased
risk(44). Alcohol and tobacco together have synergistically increased the risk of oral cancer.
Socioeconomic status is also considered a major determinant of global oral health. As socioeconomic status decreases, the prevalence of oral diseases increases, particularly caries, periodontal disease and oral cancer(42). This is predominantly due to decreased access to oral health
care services and the ability to afford such services. In addition, those residing in urban areas
are more likely to receive oral health care for similar conditions compared with those in rural
areas(45). Furthermore, several systemic conditions contribute to oral health in ageing. Decline
in oral health is particularly noticeable in aged care facilities. This can be due to salivary gland
hypofunction associated with polypharmacy, fewer remaining functional teeth, and declining
physical and cognitive ability limiting oral hygiene practices(9). The elderly may exhibit an
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References
increase in dental plaque adhering to the teeth or dental prosthesis(46). This often leads to
common dental conditions including caries and periodontal disease(47). There is also evidence
to support an association between cardiovascular disease and oral health (48), as well as a
bidirectional relationship between type 2 diabetes and periodontitis(49). In order to improve
the quality of life in the ageing population, the need to focus on oral health should be greatly
emphasised.
8.11 Conclusion andSummary
The ageing process and its impact on the oral cavity parallel the changes occurring in the body as
individuals enter their seventh decade and beyond. Although the precise criteria for healthy oral
ageing are still being refined, there are general guidelines to consider. These include maintaining
a dentition without active caries, having no more than four missing teeth and achieving a functional occlusion. It is crucial to emphasise the correlation between overall health and oral health
and recognise the significant role that good oral health plays in the process of ageing effectively.
Oral health care professionals should assess an older adult’s oral health concerning disease presence and function.
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9
Endocrine andMetabolic Dysfunction andOro- Facial Diseases
Prazwala Chirravur1 and Pradeep Chirravur
1
Department of Oral and Maxillofacial Diagnostics, UConn Health, Connecticut, USA
2
Department of Anesthesiology, Apollo Hospitals, Chennai, India
2
9.1 Introduction
Endocrine organs are an interconnected systemic network that controls varied biological cascades
of events. This assemblage of structures releases hormones directly into the bloodstream to maintain homeostasis. The system is meticulously regulated by the nervous system by biofeedback
mechanism to maintain fundamental functions such as metabolism, growth, reproduction,
immune regulation and preserving intellectual and emotional quotient(1, 2). Dysfunction of the
endocrine system negatively impacts an individual’s quality of life and welfare.
9.2 An Overview ofthe Endocrine System
The components constituting the endocrine complex are the hypothalamus, pituitary, major endocrine organs and their hormones.
The hypothalamus lies beneath the thalamus and above the pituitary at the base of the brain. Its
association with the neuro- endocrine system is one of the significant elements for preserving
internal stabilisation and essential determinants of organic rhythm. The hypothalamus secretes
releasing and inhibiting factors influencing major endocrine organs and their hormones(3).
9.3 Pituitary Functions inHealth
The pituitary is a pea- sized master endocrine organ embodied in Sella turcica, encompassed within
the mid- brain. Pituitary hormones are complex chemical messengers that regulate other major
endocrine glands. The hypothalamus directs stimulatory and inhibiting hormones to the anterior
and posterior pituitary to release specific hormones to reach the target organs(4). Hormones are a
group of protein biomolecules secreted by the endocrine glands to reach specialised organs. They
Pathological Basis of Oral and Maxillofacial Diseases, First Edition. Edited by S. R. Prabhu, Syed Ali Khurram,
Omar Kujan and Merva Soluk Tekkesin.
© 2025 John Wiley & Sons Ltd. Published 2025 by John Wiley & Sons Ltd.
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bind to the surface receptor for subsequent signalling and normal functioning(5). The anterior
pituitary synthesises growth hormone, adrenocorticotropic hormone (ACTH), thyroid stimulating
hormone (TSH), prolactin and gonadotropins. The posterior pituitary typically secretes antidiuretic hormones and oxytocin. These hormones regulate stress management, metabolism, glucose
and calcium balance, water- electrolyte equilibrium, conception and development(6, 7).
9.4 Pituitary Dysfunction andIts Oro- facial Manifestations
Disruption in pituitary hormone and other primary endocrine hormone secretion results in
homeostasis dysregulation and systemic manifestations. However, orofacial, head and neck
manifestations are observed and more pronounced in pituitary, thyroid, parathyroid and adrenal
dysfunction.
9.4.1 Hypopituitarism
Primary or secondary causes can influence decreased secretion of pituitary hormones/
hypopituitarism. Primary outcomes originate from malignancy, auto- immune, infection,
medication- induced and genetic susceptibility. On the other hand, secondary hypopituitarism is
caused by impediments at the hypothalamus, resulting in not enough pituitary hormones (8).
Hypopituitarism in children is called pituitary dwarfism. This is more prevalent in boys and diagnosed in 1.8– 2.9 children per 100,000(9). This condition not only presents as short stature but is
also associated with comorbidities such as cardiovascular disorders and musculoskeletal growth
deficiency, which has a negative impact on well- being. Growth hormone deficiency in adults is less
intense, with mild to no undesirable outcomes. Radioimmunoassay may demonstrate decreased
levels of pituitary hormone. Hormone replacement is the favoured treatment for managing pituitary dwarfism(10). Craniofacial features of hypopituitarism are listed in Table9.1.
109
9.4.2 Hyperpituitarism
Hyperpituitarism, or abnormally increased production of the pituitary hormone, specifically
growth hormone, is primarily caused by pituitary tumours such as adenomas. Secondary causes
include discrepancy at the hypothalamus, McCune Albright syndrome, and multiple endocrine
neoplasia, specifically type- 1(11). Gigantism, or excessive growth hormone in children, occurs
before the fusion of long bone epiphysis. In contrast, acromegaly is adult hyperpituitarism,
which occurs after the fusion of epiphysis leading to long extremities. Only 100 cases of gigantism havebeen reported so far, and the prevalence of acromegaly has been reported as 78 cases
per million(12, 13). Gigantism manifests as symmetric body growth, whereas disproportionate
craniofacial structures and limbs characterise acromegaly. Diagnostic images reveal enlarged
Sella turcica secondary to pituitary adenoma. Management comprises surgical removal of
adenoma as a solitary treatment option or with radiation therapy, growth hormone receptor
antagonists and somatostatin agonists(14). Craniofacial features of hyperpituitarism are listed
in Table9.1.
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Table9.1 Craniofacial manifestations ofhypo andhyperpituitarism.
Hypopituitarism Hypopituitarism Hyperpituitarism Hyperpituitarism
Children
Pituitary dwarfism
Small face Expressionless face Frontal bossing Increased facial height
Normal- sized teeth but
malocclusion
Early exfoliation of deciduous
teeth, defect/delay in
permanent dentition, impacted
or agenesis of third molars
Micrognathia Mandibular
Amelogenesis imperfecta Macroglossia
Adults Children/Adolescents
Gigantism
Non- specific oral
manifestations
Hypercementosis Thick lips and facial skin
Interdental spacing Interdental spacing and
prognathism
Adults
Acromegaly
open bite
Class III with mandibular
prognathism
Hypertrophy of
oropharyngeal tissues
9.5 Thyroid Functions inHealth
Embryonically, the thyroid gland arises from the base of the tongue and terminates in the anterior
aspect of the neck. It comprises two lobes and a central connecting isthmus(15). The intramural
architecture of the thyroid produces thyroglobulin from the follicular component and calcitonin
from the parafollicular, respectively (16). Thyroglobulin acts as a substrate to secrete principal
hormones triiodothyronine (T3) and tetraiodothyronine (T4) for basic metabolism, growth, development, maturation and function of varied organ systems. Calcitonin further interacts with
parathyroid, calcium and vitamin D to preserve skeletal remodelling(17).
The hypothalamus- pituitary thyroid axis (HPTA) has an interplay between the systems and
their hormones T3 and T4, influenced by stimulatory and inhibitory effects. These outcomes
are affected by dysregulated T3 and T4 secretion or secondary acceleration or decline. Typically,
thyrotropin- releasing hormone (TRH) is released from the hypothalamus in response to a
metabolic necessity; TRH directs the pituitary to secrete TSH, which further influences the
production of T3 and T4. Conversion of T4 to T3, regression in hormone level and their direct
influence on the pituitary depend on the negative feedback mechanism similar to other
endocrine system components(17).
9.6 Thyroid Dysfunction andIts Oro- facial Manifestations
9.6.1 Hypothyroidism
Inadequate production of thyroid hormones causes hypothyroidism due to primary or secondary
origin. Primary due to thyroid hormone deficiency and secondary from suppression of the pituitary or hypothalamus, neoplasia, surgery, irradiation, autoimmune and iodine deficiency with an
ensuing decrease in TSH(18).
t.me/Dr_Mouayyad_AlbtousH
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