Orthodontics seeks to achieve esthetic and functional improvement via mechanical therapy that moves teeth into a more ideal position. Determining the ideal dental position for each patient depends on several factors, such as the facial profile, facial balance, and aesthetic concerns.
In addition to facial problems, orthodontics looks to improve the relationship between the maxillary and mandibular teeth when they come together and function. The biological and functional coordination of how teeth come together is termed occlusion. Over the years, a consensus has been reached on what features are regarded as an ideal or normal occlusion.
However, it is not common to find individuals who exhibit the qualities of an ideal occlusion without receiving orthodontic treatment. Morphological differences in tooth shape and size and sagittal positions of the maxilla and mandible create a plethora of occlusions that an individual can display. Only 8% of cases of malocclusion have a known cause. The remaining 92% have unknown etiology but likely result from environmental and genetic factors.
Classification of Malocclusion
Acknowledged as the "father of modern orthodontics," Dr. Edward Hartley Angle established three classes of malocclusion according to the position of the mesiobuccal cusp of the upper first molar concerning the buccal groove of the lower first molar.
Angle class I molar classification (also known as neutroclusion) is determined by the mesiobuccal cusp of the maxillary first molar occluding with the buccal groove of the mandibular first molar. A class II molar classification (mesoclusion) is determined by the mesiobuccal cusp of the maxillary first molar, occluding mesial to the buccal groove of the mandibular first molar. Lastly, a class III molar classification is determined by the mesiobuccal cusp of the maxillary first molar occluding distal to the buccal groove of the mandibular first molar (distoclusion).
Class I malocclusion is further categorized into three types by Dewey. In Dewey type 1, the incisors are crowded, the canines are positioned labially, or both. In Dewey type 2, the maxillary incisors protrude. In type 3, the anterior teeth occlude edge to edge, or there is a crossbite or both. The Anderson classification further categorizes class I malocclusion into types 4 and 5. In type 4, there is a posterior crossbite, which could be unilateral or bilateral. Type 5 occlusion is a class I molar relationship with mesioversion of the permanent first molar due to the extraction of a second deciduous molar or premolar.
Around 32% of individuals with malocclusion have a class II. A class II molar relationship is when the mandible is positioned retrognathic to the maxilla. Class II interarch relationship is categorized into two divisions. A Class II division 1 is when the maxillary incisors are protruded with an excessive overjet and deep overbite. The maxillary arch is often v-shaped and narrow in the canine region and broad between molar regions. Patients with a class II molar relationship division 1 have a shorter upper lip and often fail to close their anterior lip.
A class II division 2 is when the maxillary central incisors are palatally inclined and may be overlapped by the maxillary lateral incisors. A deep overbite and a broad maxillary arch define a class II division 2. There is a normal upper lip seal and a deep mental groove. Unlike division 1, division 2 has a normal-sized mandible.
A Class III molar relationship occurs when the mandible is positioned anterior to the maxilla. Mandibular teeth protrude over the maxillary teeth. Class III malocclusion is distinguished by the alignment of teeth into three types. In class 3 type 1, the arch is abnormally shaped. In class 3 type 2, the mandibular teeth are tilted lingually. In class 3 type 3, the maxillary teeth are tilted lingually.
Ackerman and Profitt's classification system for malocclusion is used to classify and describe different types of misalignment of the teeth and jaws. It is based on Angle classification.
In Ackerman and Profitt's classification system, malocclusion is divided into classes I, II, III, IV, V, and VI. These categories are based on the relationship between the maxillary and mandibular teeth and the jaw position.
Class I: The maxillary teeth are slightly forward of the mandibular teeth, and the jaw is aligned properly.
Class II: The maxillary teeth are significantly forward of the mandibular teeth, and the jaw is underdeveloped.
Class III: The mandibular teeth are significantly forward of the maxillary teeth, and the jaw is overdeveloped.
Class IV: The maxillary teeth are significantly behind the mandibular teeth.
Class V: The maxillary teeth are significantly forward of the mandibular teeth, and the jaw is overdeveloped.
Class VI: The mandibular teeth are significantly behind the maxillary teeth.
Several skeletal causes of malocclusion may require surgery. These include jaw discrepancies, facial asymmetry, cleft lip and palate, and craniofacial abnormalities. Additionally, although much less common, injury to the face or jaw can cause malocclusion. It is important to note that surgical treatment of malocclusion is typically only recommended in severe cases, and other treatment options, such as braces, may be tried first. A thorough evaluation by an orthodontist or oral and maxillofacial surgeon is needed to determine the most appropriate treatment approach.
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