Craniofacial & Developmental Abnormalities
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DIASTEMA
A diastema is a space between any two teeth, but usually refers to a midline diastema (space between maxillary central incisors). 98% of 6 year olds and around 50% of 11 years olds have a midline diastema. They tend to close when canines erupt if the space is 2mm or less. The larger the diastema, the less likely it will close spontaneously.
A diastema could also be due to:
- tooth size discrepancy.
- mesiodens (supernumerary between centrals).
- abnormal frenum attachment/anatomy. If a diastema is caused by an abnormal frenum, orthodontic treatment is completed first, followed by a frenectomy after the permanent canines erupt.
Common methods of closing a diastema:
- Lingual arch, finger springs
- Hawley appliance, finger springs.
Full fixed appliance with inter tooth traction.
ECTOPIC ERUPTION
A tooth may not erupt into its correct position, called ectopic eruption. Ectopic teeth are common in the maxilla and are linked to Class II growth patterns, seen in about 2-6% of people. Most (~60%) spontaneously correct. The most likely teeth to be involved are the maxillary first molars and mandibular incisors.
Molars have the tendency to want to drift mesially. If the maxillary first molar erupts mesially it can become “trapped” under the distal curvature of the deciduous second molar. This can cause damage to the baby tooth, and if left untreated will cause crowding in the arch. If the neighboring baby tooth is damaged, the best course of treatment is to remove this deciduous tooth, followed by the placement of a space maintainer. If the deciduous tooth is intact, a brass wire ligature or orthodontic spacer can be placed to try and distalize the molar to set it free.
IMPACTED TEETH
These teeth get stuck on their way out. The most likely tooth to become impacted is the maxillary canine, often a high priority impaction. Impaction can cause:
- orthodontic problems.
- prosthodontic/aesthetic problems for patients.
- damage to adjacent teeth.
Impacted teeth may be an incidental finding on a radiograph or seen because of change in position of an erupted tooth, or the retention of a deciduous tooth. Approximately one-third of impacted maxillary canines are located labially and two-thirds are located palatally. If the upper adult canines cannot be palpated in the labial sulcus of a 10-12 year old patient, it may be prudent to take a radiograph to rule out impaction. The distal part of the root of the lateral incisor is used by the erupting canine for guidance. If there is any change (like a diminutive lateral/peg lateral/missing lateral) this can lead to impaction. Teeth can become ankylosed with age.
If an impacted canine is diagnosed early, the removal of the deciduous canine could be indicated. The removal of the deciduous canine before the age of 11 will normalize the position of the ectopically erupting permanent canines in 91% of the cases if the canine crown is distal to the midline of the lateral incisor. The expected success rate is only 64% if the canine crown is mesial to the midline of the lateral incisor. Other treatment options include:
- Nothing, aesthetic treatment to “replace missing tooth” (crown, veneer, bridge etc).
- Removal of the adult tooth, space closure.
- Removal of the adult tooth, open space, replace tooth (implant etc).
- Surgical exposure, traction, orthodontic treatment.
During surgical exposure, the flap should position so that the tooth is pulled through keratinized soft tissue, not mucosa.
FACIAL CLEFTS
Cleft lip (CL) and Cleft Palate (CP) are the most common craniofacial defects (1/700 births) resulting from a failure in fusion of the frontonasal (medial nasal) process and maxillary process in the first trimester around 5-8 weeks in utero (CL 5-6 weeks, CP 6-8 weeks). Recall the first branchial arch (mandibular arch) gives rise to the maxilla, mandible, Meckel’s cartilage, incus, malleus, muscles of mastication and the anterior belly of the digastric muscle.
CL and CP accounts for half of all facial cleft defects, CL is more common in males and more often seen unilaterally on the left side. CP is more common in females. The fusion of the lip, alveolar ridge, and palate can be involved, affecting speech, swallowing and aesthetics. CL & CP can occur unilaterally, often linked with a birth defect that is not associated with a syndrome, or bilaterally, possibly linked to Stickler’s, Vander Woude’s, and DiGeorge syndrome. There are four classes of CL:
- Class I: Unilateral notching of vermillion not extending to lip.
- Class II: Class I but involving the lip, not to the floor of the nose.
- Class III: Class II but extending into the floor of the nose.
- Class IV: Any bilateral cleft of the lip.
There are four classes of CP:
- Class I: only the soft palate is involved.
- Class II: the soft palate and hard palate are involved, but not the alveolar processes.
- Class III: the soft palate, hard palate and alveolar process on one side of the premaxilla.
- Class IV: the soft palate, hard palate and alveolar process on both sides of the premaxilla.
CL is repaired 10 weeks after birth, CP 9-18 months after birth. CL is reviewed around age 5. Then another pharyngeal flap surgery or pharyngoplasty 3-5 years later, alveolar reconstruction at 6-9 years (based on dental development), and orthognathic surgery at 14-18 years (14-16 for girls, 16-18 for boys).
SUPERNUMERARY TEETH
An extra tooth anywhere in the mouth is called a supernumerary tooth. They are usually diminutive (smaller), may be peg shaped, and are twice as common in male patients. The most common supernumerary tooth is between upper central incisors, called a mesiodens. They may cause unwanted space (diastema) or interfere with normal eruption patterns. The most common treatment is removal, and may require surgical removal if unerupted/impacted. The following conditions are associated with presence of supernumerary teeth:
- Gardener’s syndrome
- Cleidocranial dysplasia
- Sturge–Weber syndrome
- Down’s syndrome
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MISSING TEETH
The most commonly missing teeth are the third molars, lower second premolars, lateral incisors, and upper second premolars in that order. In the case of missing premolars, you could consider keeping the deciduous molar for as long as possible, or orthodontic closure of the space. With a missing lateral incisor, you could shift the canine into its spot and adjust the canine to improve aesthetics, or open the space back up for a replacement of the tooth.
- Oligodontia – A term for the absence of one or more teeth (not including third molars).
- Hypodontia – A term for the absence of 6 or more teeth. Usually part of syndrome.
- Anodontia – All teeth are missing. This is very rare.
MISCONCEPTIONS
Large adenoids lead to mouth breathing, but cannot be held as the cause of malocclusion because studies show that the majority of the people with a long face have no nasal obstruction. Tongue thrust swallowing is where the tongue pushes forward as the patient swallows. It seems to stem from the need to establish an oral seal, especially in anterior open bite cases. The tongue thrust swallow is likely not the cause of the malocclusion, but the result of one.
