Rickets

Rickets is a systemic metabolic bone disease of the growing skeleton caused by defective mineralization of the growth plate and osteoid, resulting from disturbances in calcium, phosphate, or vitamin D homeostasis.[1] The condition affects all skeletal sites, including the jaws and dentition. Impaired apoptosis of hypertrophic chondrocytes in the growth plate produces the characteristic skeletal deformities, while defective mineralization of dentin, cementum, enamel, and alveolar bone generates the oral and maxillofacial manifestations.[2] The two major pathophysiologic categories are calcipenic (hypocalcemic) rickets—most commonly nutritional vitamin D and/or calcium deficiency—and phosphopenic (hypophosphatemic) rickets, of which X-linked hypophosphatemia (XLH) is the most prevalent hereditary form.[3][4] On dental radiographs, the signature pattern includes generalized loss or thinning of the lamina dura, enlarged pulp chambers with prominent pulp horns, thin dentin, and periapical radiolucencies in teeth without caries or trauma.[5][6] Management is directed at the underlying metabolic cause; dental treatment addresses the secondary complications of enamel hypoplasia, caries, and spontaneous endodontic infections.[3][7]

• Rickets is the accepted term for defective mineralization of the growth plate in children; osteomalacia designates the corresponding defect in mature bone osteoid and affects both children and adults.[8][9]
• Calcipenic rickets encompasses nutritional rickets (vitamin D deficiency, dietary calcium deficiency, or both), vitamin D–dependent rickets type I (1α-hydroxylase deficiency), and type II (hereditary vitamin D–resistant rickets).[3][4]
• Phosphopenic rickets includes X-linked hypophosphatemia (XLH, formerly "vitamin D–resistant rickets"), autosomal dominant and recessive hypophosphatemic rickets, and hereditary hypophosphatemic rickets with hypercalciuria.[4][9]
• The older term vitamin D–resistant rickets (VDRR) remains in clinical use for XLH but is imprecise because it conflates several distinct phosphopenic entities.[5][10]
• Hypophosphatasia (HPP) is a separate mineralization disorder caused by deficient tissue-nonspecific alkaline phosphatase (TNSALP) and is not classified under rickets, though dental manifestations overlap.[2][11]

• Age: Rickets is a disease of the growing skeleton; clinical and radiographic features develop during childhood and adolescence while growth plates remain open. Dental manifestations may persist into adulthood.[1][8]
• Nutritional rickets is the most common form worldwide. Incidence varies widely by region: approximately 7.5 per 100,000 children under five in the UK and 2.9 per 100,000 in Canada, with substantially higher prevalence in parts of Africa and Asia.[3]
• At-risk groups for nutritional rickets include exclusively breastfed infants without vitamin D supplementation, dark-skinned children, children in high-latitude regions with limited sun exposure, and infants born to vitamin D–deficient mothers.[3][8]
• XLH is the most common hereditary form, with a prevalence of approximately 4.8 per 100,000. It follows X-linked dominant inheritance; both sexes are affected, though males may be more severely affected skeletally.[9][12][13]
• Dental manifestations—particularly spontaneous periapical abscesses—have been reported in nearly all children with XLH.[6][9]

Systemic Presentation

• Common skeletal features include widened wrists and ankles (metaphyseal swelling), leg bowing (genu varum or valgum), rachitic rosary (costochondral beading), frontal bossing, craniotabes, growth failure, bone pain, and muscle weakness.[1][14]
• Life-threatening complications of calcipenic rickets include hypocalcemic seizures and dilated cardiomyopathy in infancy.[8]
• In XLH, craniosynostosis and Chiari type 1 malformation are recognized craniofacial complications.[9][13]

Oral and Dental Findings

• Enamel hypoplasia is common, particularly when vitamin D deficiency occurs during pregnancy (affecting primary teeth) or early childhood (affecting permanent teeth). Hypoplastic enamel is irreversible and predisposes to accelerated caries.[15]
• Delayed tooth eruption is a recognized feature of both nutritional rickets and XLH.[6][14]
• Spontaneous dental abscesses in clinically intact teeth (without caries or trauma) are the hallmark oral complication of XLH, resulting from defective dentin that permits bacterial ingress to the pulp. These abscesses have been reported in approximately 70% of XLH patients in cross-sectional studies.[6][7][9]
• Taurodontism is observed in a subset of XLH patients.[6][16]
• Gingival and periodontal disease, including periodontitis with alveolar bone loss, is common in XLH.[6]
• In untreated or poorly controlled rickets, poor alveolar bone development may contribute to premature tooth loss.[10]

Location and Distribution

• Radiographic changes in rickets are generalized, affecting both jaws symmetrically. The alveolar bone, lamina dura, and dental hard tissues are involved throughout the dentition.[5][17]
• Findings are present in both primary and permanent dentitions, with severity reflecting the timing and duration of the metabolic disturbance.[2][15]

Alveolar Bone and Lamina Dura

• Loss or thinning of the lamina dura is a characteristic finding, reflecting defective mineralization of the alveolar bone immediately surrounding the teeth. In nutritional rickets with secondary hyperparathyroidism, lamina dura loss may be accompanied by generalized osteopenia of the jaws.[5][10][18]
• Widening of the periodontal ligament space may accompany lamina dura changes.[18]
• Generalized reduction in alveolar bone density (osteopenia) can be appreciated on panoramic and periapical radiographs, with loss of the normal trabecular pattern in severe cases.[17][19]
• In renal-related rickets (renal osteodystrophy), the jaws may show a diffuse ground-glass pattern with cortical thinning.[19]

Internal Architecture of Teeth

• Enlarged pulp chambers with prominent pulp horns are a characteristic radiographic finding, particularly in XLH, where the pulp-to-crown ratio is measurably increased compared to age-matched controls. Pulp horns may extend close to or beyond the dentinoenamel junction.[5][6][16][20][21]
• Thin dentin walls are commonly observed, reflecting hypomineralization and reduced dentin volume.[5][22]
• Thin enamel may be apparent radiographically in severe cases, though enamel hypoplasia is often better appreciated clinically.[5][22]

Effects on Teeth and Adjacent Structures

• Periapical radiolucencies in non-carious, non-traumatized teeth are a hallmark of XLH and occasionally occur in severe nutritional rickets. These represent endodontic infections arising from bacterial penetration through defective dentin rather than from conventional pulpal pathology.[5][7][9][12]
• Short roots have been described, particularly in the primary dentition of XLH patients.[5][16]
• Root resorption of deciduous teeth may be observed.[16]
• Open apices in teeth that would normally have completed root formation have been reported in XLH.[6]
• Delayed eruption of both primary and permanent teeth may be evident radiographically.[6][14]

Periphery and Shape

• Individual teeth may show altered crown morphology with cervical constriction in hypophosphatasia-overlap cases, but in classic rickets the external crown contour is generally preserved; the dominant morphologic change is internal (enlarged pulp, thin dentin).[5][11]

Recognized Variants

• In XLH, the combination of enlarged pulp chambers, prominent pulp horns, thin dentin, periapical radiolucencies in intact teeth, and taurodontism constitutes a recognizable radiographic pattern that may precede systemic diagnosis.[6][7][20]
• In nutritional rickets with secondary hyperparathyroidism, superimposed features of hyperparathyroidism—including generalized loss of lamina dura, widened periodontal ligament spaces, and occasionally focal radiolucent lesions (brown tumors)—may be present.[19][23][24]

CT and MRI of the Craniofacial Skeleton

• In XLH, CT may demonstrate craniosynostosis (premature fusion of cranial sutures) and Chiari type 1 malformation (descent of cerebellar tonsils), both of which can be associated with raised intracranial pressure and require neurosurgical evaluation.[9][13]
• CT of the temporal bones may reveal enthesopathies and hearing impairment-related osseous changes in adult XLH patients.[13]
• In renal osteodystrophy–associated rickets, CT of the jaws may show diffuse expansion with ground-glass density and cortical thinning, aiding differentiation from fibrous dysplasia and other fibro-osseous lesions.[19]

The differential for generalized jaw changes in rickets centers on other metabolic bone diseases that produce loss of lamina dura, altered trabecular pattern, or periapical pathology in non-carious teeth. Clinical history, biochemical profile, and the pattern of dental hard-tissue changes are the primary discriminators.

The highest-risk diagnostic pitfall is misidentifying the spontaneous periapical radiolucencies of XLH as conventional endodontic disease, leading to unnecessary extraction or root canal treatment of vital teeth. When multiple periapical lesions are found in non-carious teeth—especially in a child with short stature or skeletal deformity—serum calcium, phosphate, ALP, PTH, 25-hydroxyvitamin D, and renal function should be obtained before initiating irreversible dental treatment.[5][7][18]

Bone

• Rachitic bone shows accumulation of unmineralized osteoid (increased osteoid volume and thickness) with a mineralization lag on tetracycline-labeled dynamic histomorphometry.[30]
• In calcipenic rickets, secondary hyperparathyroidism produces additional features: increased osteoclastic resorption, peritrabecular marrow fibrosis, and cortical thinning.[30]
• Growth plate histology demonstrates widened, disorganized columns of hypertrophic chondrocytes that fail to undergo normal apoptosis, with deficient provisional calcification of the cartilage matrix.[1][9]

Dentin

• Interglobular dentin—areas of unmineralized dentin matrix between calcospherites—is a hallmark microscopic finding in rachitic teeth, reflecting defective mineralization during dentinogenesis.[2][31]
• In XLH, large tubular clefts or lacunae with prominent pulp horns extend toward or beyond the dentinoenamel junction, creating pathways for bacterial contamination of the pulp.[16][32]
• Dentin is thin and hypomineralized, with reduced mineral content confirmed by backscattered electron imaging.[30][31]

Cementum

• Cementum is commonly deficient or absent in hypophosphatemic rickets, contributing to poor periodontal attachment and susceptibility to tooth loss.[2][9]

Enamel

• Enamel hypoplasia with retention of amelogenins in the maturation zone has been demonstrated in rachitic animal models, indicating impaired enamel maturation.[31]
• Clinically, enamel defects range from pitting to generalized hypoplasia depending on the timing and severity of the metabolic disturbance.[15]

Radiologic-Pathologic Correlation

The enlarged pulp chambers and thin dentin seen radiographically correspond to the histologic findings of interglobular dentin and hypomineralized dentin matrix. Periapical radiolucencies in non-carious teeth correlate with pulpal necrosis secondary to bacterial ingress through defective dentin rather than carious exposure.[5][16][32]

Medical Management

• Nutritional rickets is treated with vitamin D (cholecalciferol or ergocalciferol) combined with adequate calcium intake. The Global Consensus Recommendations endorse combination therapy of vitamin D plus calcium. Treatment duration is typically a minimum of 12 weeks, with biochemical and radiographic monitoring for healing.[3][8][33]
• XLH has historically been managed with oral phosphate supplements and active vitamin D analogs (calcitriol or alfacalcidol). Since 2018, burosumab, a monoclonal antibody targeting FGF23, has been approved for XLH in patients aged 6 months and older. Burosumab improves serum phosphate, heals rickets more reliably than conventional therapy, and reduces the incidence of dental abscesses in both children and adults.[9][13][34][35][36]

Dental Management

• Early and ongoing dental surveillance is essential in all forms of rickets. Preventive strategies include fluoride application, sealants, and meticulous oral hygiene to protect hypoplastic enamel from caries.[7][15]
• Spontaneous periapical infections in XLH require conventional endodontic treatment when pulp necrosis is confirmed; conservative management with monitoring is appropriate for asymptomatic periapical radiolucencies in vital teeth.[5][12]
• Restorative treatment of hypoplastic and carious teeth should be initiated early to prevent pulpal involvement.[7][15]
• Multidisciplinary coordination between the metabolic bone specialist and the dental team is critical, particularly in XLH, where systemic treatment with burosumab or conventional therapy reduces but does not eliminate dental complications.[7][13][21]

Prognosis

• Skeletal deformities from rickets may be partially irreversible despite metabolic correction, though growth and mineralization improve with treatment.[8][37]
• Dental hard-tissue defects (enamel hypoplasia, interglobular dentin) are permanent once formed; however, adequate metabolic control during tooth