Chapters 6–11 outline some of the treatment objectives and principles of various malocclusions and skeletal discrepancies. Cases are presented throughout the chapters to help oral health therapists and dental hygienists to gain a better understanding of some of the possible treatments carried out by orthodontists. The mechanics and details of treatment modalities are not discussed in depth, as these are beyond the scope of this textbook.

The objective of treating class I malocclusion is correction of the dental discrepancies, as patients typically present with a favourable soft tissue environment and harmonious skeletal structures, with an exception for bimaxillary cases. Some of the dental concerns seen in class I malocclusion are discussed in this chapter, although these are not confined to class I and are common in other malocclusions. Examples of these dental concerns include spacing, crowding, ectopic teeth, impacted teeth, cross bites and open bites.

Spacing and Crowding

The decision on how to close excessive spaces or relief crowding depends on some of the following factors:

• the skeletal profile of the patient
• the type of malocclusion
• the degree of crowding
• the inclination of the teeth
• the space available
• the space needed for correction of the malocclusion.

Spacing

Spacing can occur because of congenitally missing teeth, premature tooth loss, microdontia, fraenal attachment to the incisive papilla or supernumeraries. The cause of spacing must be eliminated if possible; for example, frenectomy is indicated if a median diastema is due to a large labial fraenum. Typically, a periapical radiograph is also necessary in cases with a median diastema to check for presence of supernumeraries.

Primary Dentition

Excessive spaces in the primary dentition are monitored and active treatment is not indicated.

Mixed Dentition

Spacing can be monitored in mild cases, depending on the age of the patient, aetiology and degree of spacing. Mild divergence and increased spacing between the upper incisors between the ages of 7 and 12 years can be considered normal (the ‘ugly duckling’ stage) and is corrected upon eruption of the upper canines.

During the mixed dentition stage, the premature loss of posterior teeth (particularly the primary second molars) can be an issue, as there is a risk of a mesial drift of the permanent first molars. In these cases, a space maintainer is necessary to preserve the space for the eruption of the permanent successors. Examples of space maintainers include the Nance holding appliance (Figure 6.1A) and the lower lingual holding arch (Figure 6.1B) and the transpalatal arch (Figure 6.1C). This also aims at preventing a midline shift in early loss of deciduous canines.

Permanent Dentition

Excessive spaces can be treated with a series of clear aligners if there is a favourable soft‐tissue environment in the absence of severe skeletal discrepancies. Space closure is also easily achieved with fixed appliances. If the space is due to tooth loss, an option would be creating sufficient space with fixed appliances for an implant or bridge, depending on the periodontal health status. A combination of orthodontic and restorative treatment provides optimum results in cases of microdontia and peg laterals (Figures 6.2 and 6.3).

Crowding

A size discrepancy between the dental arches and teeth leads to crowding. The space needed for the correction of crowding can be achieved in several ways, such as arch expander appliances or extraction for large spaces and active open‐coil spring for gaining minor spaces.

Primary Dentition

Crowding at this early stage is due to a lack of primate spaces (see Chapter 3) and is an indication that crowding will occur in the permanent dentition. Regular check‐ups are therefore critical and the eruption of the permanent teeth must be monitored closely.

Mixed Dentition

In mild to moderate crowding resulting in ectopic eruption or impaction of permanent teeth, phase I treatment aids in creating space in several ways. In mild cases, the incisors are grouped by partial fixed‐appliance therapy (known as 2 × 4; see Chapter 3). Once sufficient space is created, a fixed lingual retainer is placed on the palatal of the incisors to prevent relapse after the fixed appliances are removed. The eruption of the permanent dentition is monitored and space maintainers are bonded to preserve the space. The aim of this early intervention is to prevent severe crowding in the permanent dentition, to prevent ectopic eruptions and to eliminate the need for extraction of permanent teeth for gaining space once growth is ceased.

Before the growth spurt occurs, an expander plate, such as a the rapid maxillary expander, or a slow maxillary expander (quad helix) is used to create spaces in narrow arches. This type of treatment can be used in combination with partial braces to align the erupted teeth once sufficient space has been gained with the use of an expander.

Permanent Dentition

Mild to moderate crowding in the absence of skeletal discrepancies can be treated with a series of aligners. A tipping movement of only one or two teeth can be achieved with the use of a removable appliance. High patient compliance is necessary for optimum results with removable appliances.

Beyond the growth spurt and in cases of severe crowding, extractions are indicated. The decision for extraction is always made by an orthodontist. In adults, the need for space maintainers is highly dependent on the degree of anchorage needed. Extractions are therefore always carefully planned with sufficient anchorage in adults.

Case Study

An example of treating crowding using fixed appliance therapy is seen in the case presented in Figures 6.4 and 6.5. The patient presented with:

• brachyfacial
• convex profile
• facial symmetry
• competent lips
• an anterior traumatic deep bite
• overretained upper right deciduous canine.

Further findings of significance indicated that the roots of the upper incisor teeth appear long and slender and there appeared to be some root curvature in the apical thirds of the central incisors. The treatment objectives of the patient and the specialist were to:

• improve the facial profile
• improve the soft‐tissue lip pattern
• improve the skeletal base relationship
• correct overjet and overbite
• develop the upper arch form
• relieve crowding
• align and level the dental arches
• coordinate the dental arch forms
• align and coordinate the centre lines
• establish a class I molar relationship
• establish a class I canine relationship
• reduce or eliminate any temporomandibular joint pain and/or discomfort
• reduce or eliminate any psychosocial issues re: teeth and smile
• allow normal eruption of permanent teeth
• reduce the need for (or severity of) phase II orthodontic treatment
• produce stable treatment results.