CHAPTER 11 Correction of Malocclusion
Orthodontics (from the Greek ortho = straight; and odons = tooth) is the specialist branch of dentistry that aims to produce: (i) ideal tooth positioning in relation to the lips, teeth and jaws within the face and (ii) improved occlusion. All these ultimately aim to achieve improved facial aesthetics (appearance) and function.
Most orthodontic patients are children or teenagers, but adults are increasingly seeking orthodontic treatment and even older individuals may seek it. Teenagers and adults are also often more interested in cosmetic alternatives such as lingual orthodontics or aesthetic brackets, to traditional orthodontic appliances.
The IOTN is a tool used by the clinician to help decide which patients really need orthodontic treatment, that is whether there will be a benefit to dental health by having treatment. The index is designed so that a malocclusion may be quickly assessed clinically or from dental models (see Figure 9.2). Because treatment needs to be justified on either dental health or aesthetic needs, there are two components to the IOTN:
The DHC has five categories ranging from 1 (no treatment need) to 5 (great need). Examples of patients in grade 1 are those with minor tooth displacements. In contrast grade 5 patients are, for example, those with cleft lip and palate or multiple missing teeth.
The aesthetic component of the IOTN consists of a 10-point scale. The 10 points are represented by photographs of teeth in worsening alignment from 1 to 10. The patient’s teeth are compared with the photographs to see which one they match with to get a score. (The photographs were rated for attractiveness by a panel of lay people during the development of the index. The degree of worsening of the attractiveness is the same between each set of photographs, that is, between 1 and 2 and 2 and 3, and so on.)
Malocclusion is the term used for the misalignment of teeth and/or incorrect relationship between the maxillary and mandibular teeth. The most common malocclusions requiring orthodontic treatment are:
Malocclusion can be accompanied by disharmony between the jaw bones themselves, that is, where the relationship between the upper and lower jaw is not appropriate. In these patients, the dental problem of malocclusion is usually due to the skeletal disharmony.
The Angle classification is the most common classification of malocclusion. It is based on the relative position of the maxillary first molar to the mandibular first molar as measured from front to back (the sagittal plane).
Apart from a full clinical assessment as usual, the following are taken:
The British Orthodontic Society (BOS) has issued guidelines on the legal background of orthodontics, applications of different radiological techniques and selection criteria for the techniques. These are described in Chapter 14. Here we limit the discussion to radiographs specifically taken for orthodontic purposes.
Cephalometrics is the study of lateral skull radiographs taken under standardised conditions. The patient is placed carefully in a machine called a cephalostat, which positions the head in a standardised, reproducible manner. The film is placed 381 mm (15 inches) from the head, a standard distance for all cephalometric radiographs taken worldwide. Features seen on the X-ray film are then traced, and various standard landmarks, lines an/>