Deviations from anthropometric norms related to facial skeletal development are a relatively normal occurrence in the dental management of the vast majority of patients. A consideration for correction is usually warranted only when there is associated morbidity, functional impairment, or psychosocial detriment. The vast majority of jaw and dental abnormalities are developmental and present themselves within a continuum of clinically conspicuous to overtly obvious. This article highlights a variety of developmental abnormalities that present with structural disharmony of the maxillomandibular complex and secondarily associated dental structures.
Key points
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Developmental disturbances in the maxillomandibular skeleton can produce aberrations in facial harmony and subsequent dental maldevelopment.
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Consideration for management relies on the prioritization of dysfunction, morbidity, and subjective psychosocial impact.
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Multidisciplinary care is often involved to correct the skeletal as well as dental aberrations.
Introduction
Observation of deviations from anthropometric norms related to facial skeletal development are a relatively normal occurrence in the dental management of the vast majority of patients. A consideration for correction is usually warranted only when there is associated morbidity, functional impairment, or psychosocial detriment. The vast majority of maxillomandibular and dental abnormalities are developmental and present themselves within a continuum of clinically conspicuous to overtly obvious. The main focus of this article was to highlight a variety of developmental abnormalities that present with structural disharmony of the maxillomandibular complex and secondarily associated dental structures. Case illustrations outline a general review focusing on identification/diagnosis, treatment dilemmas, and potential implication on the dental management of specified patients.
Disturbances affecting teeth development
Cleidocranial Dysplasia
Cleidocranial dysplasia (CCD) is an autosomal dominant genetic disorder with variable expressivity that produces pathognomonic facial and physical features. The locus for CCD has been mapped to the RUNX2 gene located in chromosome 6p21, and any form of chromosomal translocations, deletions, insertions, and nonsense and missense mutations can be present. CCD is characterized by skeletal dysplasia in patent sutures, fontanels, and clavicles and results in wormian bone formation, shortened stature, supernumerary teeth, frontal bossing, and rudimentary or absent clavicles. Other changes of the skull include absent or reduced frontal and paranasal sinuses, small or absent nasal bones, segmental calvarial thickening, underdeveloped maxilla, delayed union of the mandibular symphysis, and a small cranial base with reduced sagittal diameter and a large foramen magnum. These skeletal changes result in characteristic facial and physical features that include a small, flat face with mandibular prognathism, hypertelorism, exorbitism, the ability of the patient to touch his or her shoulders together in the midline, a long neck with narrow, drooping shoulders, and a brachycephalic head with obvious frontal and parietal bossing. A metopic groove may be present in the midline of the forehead, and the scalp may have palpable soft areas due to open sutures.
Oral examination will demonstrate over-retained primary teeth and absent permanent teeth, resulting in a malocclusion. The maxilla will be hypoplastic with a deep, narrow palate and the anteroposterior deficiency of the maxilla will create a pseudoprognathism. Patients in the primary dentition stage will demonstrate normal eruption and formation of all 20 primary teeth on panoramic radiographs, whereas patients in the mixed and permanent dentition stage will demonstrate numerous unerupted and supernumerary teeth. The supernumerary teeth are morphologically similar to premolars even if they form in association with molars. One hypothesis to explain the noneruption of permanent and supernumerary teeth is the lack of cellular cementum in the apical region of the impacted teeth.
The classic triad of hypoplastic/missing clavicles, open fontanelles, and supernumerary teeth are diagnostic for CCD, and diagnosis is made by recognition of the components of this syndrome; however, the clinical presentation is variable. Treatment of CCD is aimed at correcting both the malocclusion and dentofacial deformity and requires a coordinated treatment plan with a restorative dentist, orthodontist, and oral surgeon. Treatment involves removing some, but not necessarily all supernumerary teeth. Supernumerary teeth that are associated with pathology or might interfere with orthodontic treatment are indicated for removal. Orthognathic surgery can be performed to correct the dentofacial deformity followed by orthodontic refinement to fine tune the final occlusion and implant placement to restore to a complete dentition.
The case report shown in Fig. 1 is of a 23-year-old man with a chief complaint of “I have multiple missing teeth and I have difficulty chewing.” The patient had previously been diagnosed with CCD and had multiple unerupted teeth in the maxilla and mandible along with multiple supernumerary teeth. The proposed treatment plan was staged extraction of multiple supernumerary teeth in combination with autologous and allogeneic bone grafting. Because there is no associated metabolic impairment toward bone consolidation, once the bone graft has healed, the respective jaw bone can receive conventional dental implants with routine prosthetic rehabilitation.
Gardner Syndrome
Familial adenomatous polyposis (FAP) is a rare autosomal dominant form of intestinal polyposis and colorectal cancer caused by germ-line mutations in the adenomatous polyposis coli (APC) gene located on chromosome 5. Gardner syndrome is a variant of FAP that is characterized by the triad of colonic polyposis, multiple osteomas, and mesenchymal tumors of the skin and soft tissue that was first described in 1951 by Eldon Gardner who reported the disease in a family from Utah. Other findings in Gardner syndrome include dental abnormalities, such as supernumerary and impacted teeth, gastric and small intestine polyps, and congenital retinal pigmentation. Diagnosis is based on either genetic criteria or gastrointestinal endoscopy, and the presence of 100 or more colorectal adenomas or detection of a deleterious mutation in the APC gene provides a definitive diagnosis of Gardner syndrome.
As dental practitioners it is important to note that the formation of osteomas and other oral signs typically precede the formation of other manifestations of this syndrome, including the formation of intestinal polyposis. Osteomas are the hallmark extracolonic finding of Gardner syndrome, and will often be large, multilobulated masses found at the angle of the mandible and many will be confluent with adjacent osteomas. Radiographically, osteomas appear as round or oval radiopaque masses attached by a broad base.
The presence of odontomas, supernumerary teeth, and impacted teeth occur 17% of the time. Odontomas are benign odontogenic tumors associated with Gardner syndrome and they occur equally in the maxilla and mandible and are typically found in the incisor to premolar area. They are classified into 2 subcategories, complex or compound odontomas. Complex odontomas are unrecognizable as dental tissue, and appear as a mixed radiolucent-radiopaque lesion that cannot be diagnosed by radiographic appearance alone and requires histologic evaluation for definitive diagnosis. Compound odontomas, on the other hand, contain all 3 dental tissues and radiographically appear more organized so that the lesions contain many toothlike structures. These lesions often can be diagnosed from radiographic interpretation alone.
Gardner syndrome that is fully expressed will be easily distinguishable with clinical and radiographic data. Differential diagnosis for other conditions that may produce supernumerary teeth, odontomas, and radiodense masses include cleidocranial dysplasia, florid cemento-osseous dysplasia, and periapical cemento-osseous dysplasia. Turcot syndrome, Cowden syndrome, juvenile polyposis of the colon, and Peutz-Jeghers syndrome are all syndromes associated with intestinal polyposis.
Disturbances affecting jaw and teeth development
Cleft Lip and Palate
Orofacial clefts are a group of developmental structural malformations that result in oral and facial deformities. Cleft lip and cleft palate are the main categories within this group and can occur in isolation, together, or in conjunction with syndromes. The primary palate forms at approximately 6 weeks of embryologic development when the median nasal prominence fuses with the lateral nasal prominences and maxillary prominences. The primary palate forms the base of the nose, nostrils, and upper lip, and when these components fail to fuse, a cleft of the lip and/or maxilla occurs.
At approximately 8 weeks of development, the palatal shelves elevate and fuse with the nasal septum to form the secondary palate. When one palatal shelf fails to fuse with the other components, a unilateral cleft of the secondary palate occurs. When both palatal shelves fail to fuse with each other and the nasal septum, a bilateral cleft of the secondary palate occurs. Clefts can be complete or incomplete depending on the degree of this failure of fusion. The etiology of clefts is thought to be multifactorial with genetics, maternal hypoxia, chemical exposure, teratogenic drugs, radiation, and nutritional deficiencies contributing to their development.
Cleft lip with or without cleft palate is among the most common major congenital craniofacial malformations and occurs in approximately 1 in 700 live births. The highest prevalence occurs in Native American individuals (3.6 per 1000 births) with lower prevalence among Asian (2.1 per 1000 births), White (1 per 1000 births), and African American (0.3 per 1000 births) individuals. Unilateral cleft lips occur more commonly in male than female individuals and unilateral left-sided cleft lips are more common than unilateral right-sided cleft lips. In addition, unilateral cleft lips occur more frequently than bilateral cleft lips, and clefting of both the primary and secondary palates occurs more frequently when bilateral cleft lips are present.
Isolated cleft palate occurs in approximately 1 in 2000 live births with similar predilection across all racial ethnicities. Isolated cleft palate is more commonly seen in female individuals, which is the opposite of cleft lip and palate. Most unilateral cleft lip and palate cases are isolated anomalies that are not associated with any syndromes or other major developmental abnormalities. In contrast, isolated cleft palate is often associated with syndromes such as Stickler, Van der Woude, Treacher Collins, and DiGeorge syndromes. Ocular abnormalities that can lead to severe myopia, glaucoma, and retinal detachment are associated with Stickler syndrome, thus patients with isolated cleft palates should be evaluated within the first year after birth by an experienced pediatric ophthalmologist.
Ultrasound diagnosis of orofacial clefts is not feasible until approximately 15 weeks of gestation because of the position of the head and small size of the face. Once an orofacial cleft has been diagnosed, the family receives a prenatal consultation to an experienced surgeon to explain the diagnosis and different stages of cleft lip and palate reconstruction that may be necessary. This important consultation helps prepare the family for practical considerations of the child, such as feeding, and gives them the opportunity to ask questions, calm fears, and learn about feeding techniques that will be important once the infant is born.
Following birth, the family is referred to a cleft and craniofacial team for a thorough interdisciplinary approach to care. American Cleft Palate-Craniofacial Association–approved teams are required to have a surgeon, orthodontist, speech-language pathologist, and a patient care coordinator. In addition, these teams must have access to an audiologist, geneticist, otolaryngologist, pediatrician, pediatric dentist or dental specialist, psychologist, and social worker. These teams foster a cohesive environment in which families can get the best information available to consider treatment decisions using an interdisciplinary care model that is patient and family oriented.
Cleft lip and nasal repair is the first surgical step in reconstructing a cleft. The goals of initial repair include creation of an intact upper lip with appropriate vertical length and symmetry, repair of the underlying muscular structures producing normal function, and primary treatment of the associated nasal deformity. Cleft palate repair usually occurs between 9 and 18 months of age, and the timing of repair is predicated on growth restriction following early surgery and speech development that requires an intact palate. If the cleft palate is repaired too soon, maxillary hypoplasia can occur later in life. The 2 main goals of cleft palate repair are watertight closure of the oronasal communication involving the hard and soft palates and the anatomic repair of the musculature within the soft palate that is critical for normal creation of speech. Following repair of cleft palate, approximately 20% of patients will develop velopharyngeal insufficiency (VPI), which can produce hyper nasal speech. Diagnosis of VPI occurs between 3 and 5 years of age after a thorough examination by a speech pathologist who is familiar with clefts.
Osseous reconstruction of the maxilla and alveolus can been performed during 3 different stages of development that are based off of the development of the dentition and not necessarily chronologic age. Primary reconstruction refers to osseous reconstruction during the deciduous dentition phase, secondary reconstruction occurs during the mixed dentition phase before eruption of the permanent canines, and tertiary reconstruction occurs during the permanent dentition stage. Timing of osseous reconstruction has been extensively studied in the literature and secondary repair of clefts has significant advantages over primary and tertiary repair and is currently considered the standard of care.
The dental practitioner will most likely be involved in the care of the pediatric patient with cleft lip and palate during the mixed dentition phase (secondary reconstruction) in which these patients are leading up to the surgery that establishes bony continuity of the cleft within the maxillary alveolus. This age is usually between 8 and 11 years old and depends primarily on the prevailing philosophy within the regional craniofacial team. As a dental practitioner, the recognition of the mixed dentition phase, locality, and eruptive progression of the permanent canine and identification of missing permanent teeth would provide helpful guidance to the patient and the parents as they prepare mentally for the “next” surgery ( Fig. 2 ).
In addition, and most importantly, one of the most significant measures toward alveolar grafting surgical success is preemptively addressing obstacles toward clinically acceptable oral hygiene and eliminating parafunctional or digit habits. An interesting nuance is that the cleft site provides an attractive region for tongue habits, and in some children an area for subconscious digit manipulation. In the primary author’s experience, this has been one of the greatest contributors toward postoperative wound dehiscence and partial loss of the bone graft. Whether or not the general practitioner is active within a craniofacial team, paying attention to these details will pay dividends toward the optimization of these patients for treatment success.
Treating these patients is complex by nature and by systematically and methodically staging treatment to coincide with facial growth patterns, visceral function, and psychosocial needs brings clarity to each phase of treatment for both the clinician and family. Future management will likely be influenced by advances in genetic testing and tissue engineering. Meanwhile, continuing to evaluate and treat these patients using logical rationale for the timing, methods, and extent of surgical intervention and then objectively evaluating functional, morphologic (aesthetic), and psychosocial outcomes, the outlook for patients affected by this malformation will continue to improve.
Disturbances Leading to Jaw Asymmetry
The etiology of conditions that manifest as facial asymmetry are generally from 3 broad categories: developmental, neoplastic, or inflammatory. Oftentimes a detailed history of present illness, past medical history, focused head and neck examination, and cursory radiographic imaging will help to refine the list of possibilities to 1 of the 3 broad categories. For the focus of this article, we illustrate 3 developmental causes of facial asymmetry: hemifacial hyperplasia, fibrous dysplasia, and hemimandibular hyperplasia/elongation.
Hemifacial Hyperplasia
Hemifacial hyperplasia (HFH) was initially described by Merckel in 1882 and Wagner in 1839 as a sporadic congenital condition. The classic presentation is a unilateral overgrowth of the orofacial soft tissues, bone, and teeth. The right side of the face is affected more than the left side. HFH is more common in men than in women and in Caucasians compared with other racial groups. Exact etiology of HFH is undetermined, but various theories have been postulated. Most of them fall in the category of developmental and/or metabolic and include endocrine imbalance, neural abnormalities, asymmetrical cell division and division of the twinning process, chromosomal abnormalities, alterations of intrauterine development, and vascular or lymphatic abnormalities.
The following example ( Fig. 3 ) is a 13-year-old patient with an unremarkable medical history and age-appropriate cognitive development. The parents attested to an uncomplicated pregnancy and birth. His primary complaint was with regard to the exaggerated facial asymmetry, malocclusion, and the concomitant psychosocial stigmata that has impacted his peer socialization. The medical-grade computed tomography reconstruction demonstrates a volumetric segmental enlargement of the right maxillary bone, including the zygomatic buttress and the ipsilateral mandibular ramal/body unit. Further analysis of the radiograph demonstrates a contiguous cortical boundary with seemingly normal-appearing marrow content, which is usually altered in the setting of a neoplasm or bone-involving inflammatory process. The overlying skin was normal in thickness with no surface alteration. The ipsilateral ear has excessive conchal bowl cartilage giving it a more procumbent appearance. Intraorally, there was pronounced gingival coverage, which was overlying an exuberant amount of bone development coronal to the cemento-enamel junction of the respective teeth. This was within the confines of an expanded alveolus that was supra-erupted leading to a maxillary cant and concomitant transverse arch discrepancy in relationship to the mandible.
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