Cleidocranial dysplasia (CCD), also known as cleidocranial dysostosis or Marie-Sainton syndrome, is a disorder that affects most prominently those bones derived from endochondral and intramembranous ossification and it's characterized by defective development of the cranial bones and by the complete or partial absence of the clavicles. Diagnosis is based on clinical and radiographic findings, that include imaging of the cranium, thorax, pelvis and hands. Frequently these patients presents a delayed ossification of the skull fontanels and a premature closing of the coronal suture that leads to a frontal, parietal and occipital bossing of the skull; a short stature, occasionally accompanied by a spinal scoliosis; a wide and flat nasal bridge due to hypertelorism; different anomalies of pubis and hipbone, with flat feet and knock knees; a brachycephaly with an high arched palate and sometimes cleft palate; a prolonged retention of deciduous teeth and several impacted permanent successors and supernumerary elements, sometimes accompanied by follicular cysts and eruptive pseudocysts [
1,
2]. This pathology is transmitted as an autosomal dominant trait or it's caused by a spontaneous genetic mutation and is present at a frequency of one in one million individuals. To date, RUNX2(CBFA1) is the only gene known to be associated with CCD; although not all cases clinically diagnosed have mutations in RUNX2, there is little additional evidence for locus heterogeneity. Mutations in RUNX2 have a high penetrance and extreme variability. CCD affects all ethnic groups [
3,
4].
Children with CCD should be monitored for orthopedic complications, dental abnormalities, upper airway obstruction, sinus and ear infections, hearing loss, and osteoporosis.
Intelligence is normal in individuals with classic CCD
The most important dental problem associated with this syndrome is the malocclusion and the crowding of the dental arches caused by the retention of multiple deciduous teeth and the presence of several supernumerary. These supernumerary, associated with a diminished alveolar bone resorption, also lead to the impaction or the ectopic location of the permanent teeth [
6,
7].
The previous approach to the dental problems of these patients consisted in no treatment or in the extraction of the impacted or malformed teeth and their prosthetic replacement [
8,
9], with a consequent important bone loss.
In the last years a more conservative approach has been developed, combining orthodontics and maxillofacial surgery. Orthodontic treatment consist in the extraction of the supernumerary teeth and the deciduous with delayed exfoliation, followed by the surgical exposure of impacted permanent teeth and their orthodontic guided eruption. Extractions are not accomplished in one time: there must be a staged approach in order to maintain the vertical occlusal dimension while the different groups of unerupted teeth are exposed and pulled in their ideal position.
If there isn't any, or just a mild, skeletal discrepancy between maxilla, mandible and cranium, the treatment is finished with the alignment of all permanent teeth, obtaining a correct occlusion and an agreeable smile aesthetics ([
10].
In presence of an important skeletal discrepancy, most commonly a mandibular prognathism, that preclude the possibility to achieve an acceptable orthodontic camouflage, it's necessary to wait until the completion of skeletal growth and then restoring a correct bone position through orthognatic surgery, followed by the orthodontic finishing [
11‐
14].
Traditional dental radiographs are very useful tools for the diagnosis of CCD, permitting to observe two features of the classical triad considered pathognomonic for diagnosis of this syndrome: multiple supernumerary teeth and open suture and fontanels of the skull (the third sign is the partial or complete absence of the clavicles). They also show other features helping in the diagnostic process like the presence of impacted teeth, the underdevelopment of maxillary sinuses and the parallelism of mandibular ramus, with an upward and posteriorly pointing coronoid process [
15].
Unfortunately, especially when there are a lot of supernumerary teeth, traditional dental radiographs are not enough rich in details to allow correct planning the orthodontic treatment of patients in late mixed dentition.
In these cases it's appropriate to use a multi-slice computed tomography (MSCT) scanner with an accurate tridimensional information regarding the anatomy of every single tooth, the spatial relation between adjacent teeth and face to the surrounding anatomical structures.
These data are of crucial importance in order to perform the best orthodontic treatment for different reasons: they permit to surely identify the supernumeraries teeth, often with some hidden malformations like dilacerations or dental invagination; they give the exact position of the impacted teeth in relation to the roots of the adjacent erupted teeth, preventing damage of these roots during the forced orthodontic eruption of the impacted teeth; and they also define the position of every tooth inside the alveolar bone and near some important vascular vessels and nerve fibers, avoiding unexpected complications during the extraction or the surgical exposition of impacted teeth, like bone fracture, local hemorrhage or denervation.
Unfortunately a conventional MSCT exam expose the patient to an high dose of x-ray, thereby limiting the application of this techniques only to the most complex cases.
Recently a relatively new technique, the CBCT, reducing the dose of radiation adsorbed by the patient, had been improved by different manufacturer, obtaining good quality images. The principal difference between MSCT and CBCT is that conventional CT uses a fan of x-rays and a narrow detector, so multiple slices are stacked to obtain a complete image, whereas CBCT use a cone of x-rays and a two-dimensional square detector allowing a single rotation of the radiation source to capture an entire region of interest: hereby the total radiation is less important than with conventional CT [
16].