LEENA BALICAT, RDH, BSDH, MS, is a clinical assistant professor in the Division of Comprehensive Health Oral Health at the University of North Carolina, Chapel Hill, Adams School of Dentistry. She can be reached at [email protected]. AMBER W. HUNT, BSDH, MS, RDH, is a clinical assistant professor at the Gene W. Hirschfeld School of Dental Hygiene at Old Dominion University (ODU) in Norfolk, Virginia, where she serves as junior clinic coordinator and director of the Bachelor of Science of Dental Hygiene Post-Licensure Online Program. She teaches dental hygiene theory didactic courses and clinical courses. Additionally, Hunt is a member of Dimensions of Dental Hygiene’s Peer Review Panel. BRENDA BRADSHAW, BSDH, MS, RDH, is an assistant professor in the Gene W. Hirschfeld School of Dental Hygiene at ODU. Her research interests include disaster preparedness and response as they relate to the dental hygiene profession with special focus on disaster victim identification through forensic odontology. The authors have no commercial conflicts of interest to disclose. dimensionsofdentalhygiene.com January/February 2024 • Dimensions OF DENTAL HYGIENE 29 The anomaly in the clavicle allows for exaggerated shoulder movement.2 In some cases, repeated infection of the respiratory tract and ear may be present.3 The nasal bones may be missing or hypoplastic, dense alveolar crestal bone can be present in the mandible, maxillary sinuses can be either unusually small or missing, and the zygomatic arch may be narrow or uneven.2 The clinical appearance of CCD varies widely even among people who are genetically related. Distinct radiographic features of CCD include diminished or missing clavicles in the thoracic area and hindered ossification of skull and pelvic bones. The clavicles are typically hypoplastic or broken, either unilaterally or bilaterally. In 10% of cases, the clavicles are completely absent.2,5 The presence of Wormian bones (extra bones within the sutures of the skull) may also occur due to abnormal ossification. Brachycephaly, bell-shaped thorax, and pelvic anomalies (such as hypoplastic iliac wings and wide symphysis pubis) can also be found radiographically.6 Radiographic evaluation of the patient is important in confirm- ing the diagnosis, which can be made as early as the prenatal period via ultrasound.3,5 Pathophysiology This genetic disorder was mapped to chromosome 6p21 by Mundlos et al7 in 1995. The gene responsible for this disorder, core-binding factor alpha 1 (CBFA1), now known as runt-related transcription factor 2 (RUNX2), was identified in 1997 by Mundlos et al.8 Since then, more than 100 mutations of RUNX2 have been identified and 55 of those are associ- ated with CCD.9–11 The RUNX2 gene specializes in osteoblastic differentiation (formation and accumulation of bone), chondrocyte (cells responsible for cartilage formation) matura- tion, and bone formation.12,13 Mutations in the RUNX2 gene are responsible for two-thirds of CCD cases.9,14 In one-third of CCD cases, the mutated gene is not found, and the cause is unknown.2,9,15,16 Maxillofacial Considerations Common dental anomalies of CCD include multiple supernumerary teeth, a small maxilla with a normal sized mandible that gives an appearance of prognathism, abnormal perma- nent teeth morphology (especially involving the roots), midface retrusion, and delayed erup- tion of permanent teeth, usually leading to prolonged retention of primary teeth.5,17,18 If left untreated, these dental anomalies can lead to crowding, malocclusion, and anterior open bite.3 In a study of patients with CCD, 93.5% displayed dental anomalies, making this a pri- mary feature of the disorder.19 Additionally, abnormal crown development with hypoplastic enamel and dentigerous cysts/taurodontia have been documented in research.4 Studies show that supernumerary teeth appear in 39% to 100% of patients with CCD.4,6,20,21 Several theories have been suggested to explain the causes of supernumerary teeth such as genetic atavism (reappearance of a trait that has been lost during evolution), separation of a tooth germ, dental lamina hyperactivity, and incomplete or delayed resorp- tion of dental lamina.22 Excess teeth may be normal or developmentally abnormal and located in the front, behind, or within rows of teeth. They may also be arranged as a dou- ble row of teeth or located sporadically throughout the jaw. Several studies have reported the occurence of retained primary teeth and impacted primary teeth in most patients with CCD.3–6,20 Various factors contribute to these phe- nomena, including the presence of supernumerary teeth, deformed roots of permanent teeth with a lack of cellular cementum, and abnormal resorption of primary teeth and alveolar bone.23 Several studies have found class III malocclusion present in patients with CCD, as well as open bites, crossbites, crowding, and high-arched palate.3,15,21,24,25 Malocclusion in SECTION 2
