Both chemotherapy and radiation therapy can cause multiple cosmetic and functional abnormalities of dentition, most predominantly in children treated before age 5 years who have not yet developed deciduous dentition.[1,2,3,4,5,6,7,8,9] However, even older prepubertal children are at risk. Developing teeth are irradiated in the course of treating head and neck sarcomas, Hodgkin lymphoma, neuroblastoma, central nervous system leukemia, nasopharyngeal cancer, and as a component of total-body irradiation (TBI). Doses of 20 Gy to 40 Gy can cause root shortening or abnormal curvature, dwarfism, and hypocalcification. More than 85% of survivors of head and neck rhabdomyosarcoma who receive radiation doses greater than 40 Gy may have significant dental abnormalities, including mandibular or maxillary hypoplasia, increased caries, hypodontia, microdontia, root stunting, and xerostomia.[6,7]
Chemotherapy for the treatment of leukemia can cause shortening and thinning of the premolar roots and enamel abnormalities.[1,11,12] Childhood Cancer Survivor Study investigators identified age younger than 5 years and increased exposure to cyclophosphamide as significant risk factors for developmental dental abnormalities in long-term survivors of childhood cancer. TBI has been linked to the development of short, V-shaped roots, microdontia, enamel hypoplasia, and premature apical closure.[2,3,13] The younger a patient is when treated with hematopoietic stem cell transplantation (HSCT), the more severely disturbed dental development will be and the more deficient vertical growth of the lower face will be. In children who have undergone HSCT, busulfan has been as deleterious to dental development and craniofacial growth as single-dose TBI. Children who undergo bone marrow transplantation with TBI for neuroblastoma are at substantial risk for a spectrum of abnormalities and require close surveillance and appropriate interventions.
Salivary gland irradiation incidental to treatment of head and neck malignancies or Hodgkin lymphoma causes a qualitative and quantitative change in salivary flow, which can be reversible after doses of less than 40 Gy but may be irreversible after higher doses, depending on whether sensitizing chemotherapy is also administered. Dental caries are the most problematic consequence. The use of topical fluoride can dramatically reduce the frequency of caries, and saliva substitutes and sialagogues can ameliorate sequelae such as xerostomia.
It has been reported that the incidence of dental visits for childhood cancer survivors falls below the American Dental Association's recommendation that all adults visit the dentist annually. These findings give health care providers further impetus to encourage routine dental and dental hygiene evaluations for survivors of childhood treatment. (Refer to the PDQ summary on Oral Complications of Chemotherapy and Head/Neck Radiation for more information about oral complications and cancer patients.)