11: Correction of Malocclusion: Orthodontics

CHAPTER 11 Correction of Malocclusion

Orthodontics

Chapter points

• This chapter covers the requirements of the NEBDN syllabus Section 11: Orthodontic procedures. For the examination, you need to gain knowledge of removable, fixed and functional orthodontic appliances.
• In addition this chapter briefly covers orthognathic surgery and cleft lip and palate. This is because patients may have had or heard about or require treatment in these areas. Therefore you need to be aware about them.

Introduction

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.

Term to Learn

Occlusion: this is the dental term for ‘bite’, that is, the way the upper and lower teeth bite together on closing the mouth.

Reasons for Doing Orthodontic Treatment

Orthodontic treatment is carried out largely for aesthetic reasons, and it can have significant psychological benefits. It is also required for:

• Reduction of the risk of traumatic injuries to prominent incisors (by reducing their prominence)
• Alignment of teeth
• Correction of crossbites
• Correction of deep traumatic overbites
• Correction of anterior openbite or Class III incisor relationship (see below) to improve incising function
• To enhance the results of restorative treatment by ensuring that the teeth are positioned correctly before they undergo restorative treatment (multidisciplinary care).

Terms to Learn

Crossbite: the condition in which teeth bite the wrong way round, for example the upper incisors behind the lower incisors when the person bites.

Overbite: the amount of overlap of the lower anterior teeth by the upper anterior teeth when a person bites. It is normally 1–2 mm.

Overjet: the amount the upper teeth project beyond the lower.

Openbite: the condition in which there is no overlap or even a space between some of the upper and lower teeth when the person bites.

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.

There is often a conflict between the real need for, and a person’s wish to have, orthodontic treatment. To put things in perspective the Index of Orthodontic Treatment Need (IOTN) was developed.

Index of orthodontic treatment need

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:

• Dental Health Component (DHC)
• Aesthetic Component (AC).

The DHC

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.

To measure the DHC of a patient, the clinician uses a simple ruler and notes the single worst feature of the malocclusion. The features are looked for in the following order:

1. Missing teeth
2. Overjet
3 Crossbites
4. Displacement of contact points
5. Overbite
The acronym MOCDO can be used to remember the hierarchical scale.

The AC

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.)

Term to Learn

Lay people: those who are not trained in the condition that is being looked at.

Find Out More

Look at a hard copy of the Aesthetic Component of the IOTN kept in your workplace.

Malocclusions

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:

• Anteroposterior discrepancies – these are deviations between the maxillary and mandibular teeth in the front to back direction. For example, the maxillary teeth can be too far forward relative to the mandibular teeth (‘increased overjet’). Depending on the severity of the problem, this can be treated using: removable functional appliances, headgear, fixed appliances or orthognathic surgery to reposition the jaw bones (in the most severe cases). All these terms are explained later in the chapter.
• Crowding – this usually occurs due to insufficient room in the jaw for the normal complement of adult teeth. A few teeth (usually premolars) may need to be extracted to make room for the remaining teeth.
• Asymmetry – this is when the centre lines of the upper and lower anterior (front) teeth do not match.
• Deep bite – this is when the maxillary teeth cover the mandibular teeth too much when the patient bites on their posterior (back) teeth.
• Reverse bite – this is when the maxillary incisor teeth bite (occlude) inside the mandibular incisor teeth.
• Anterior openbite – this is when there is a gap between the anterior upper and lower teeth when the patient bites on their posterior teeth.
• Impacted teeth – this is when teeth fail to erupt due to a mechanical obstruction or simply a failure in the mechanism that is responsible for tooth eruption. An example of obstruction is that the root of another tooth may be too close and the impacted tooth may get stuck against it.

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.

Identify and Learn

Take a set of adult upper and lower models and identify the anterior buccal cusp of the first permanent molar and anterior buccal groove of the lower first permanent molar.

Classification of Malocclusion

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).

There are three categories in this classification. The Class II malocclusion has two subdivisions.

Angle Class I Molar Relationship

This is the ‘ideal relationship’ in which the anterior buccal cusp of the upper first permanent molar should occlude with the anterior buccal groove of the lower first permanent molar.

Angle Class II Division 1 Molar Relationship

• The anterior buccal cusp of the upper first permanent molar occludes anterior to the buccal groove of the lower first permanent molar.
• The lower incisor edges lie posterior to the cingulum of the upper incisors, but the upper incisors are normally inclined or they are proclined.
• There is an increased overjet.
• The overbite is also frequently increased.

Angle Class II Division 2 Molar Relationship

• The molar relationship is the same as in Class II division 1.
• The lower incisor edges lie posterior to the cingulum of the upper incisors.
• The upper central incisors are retroclined but the upper lateral incisors may be proclined.
• The lower anterior teeth are frequently retroclined.
• There is an increased overbite. In severe cases the lower incisors may occlude with and damage the palatal mucosa (traumatic overbite).

Angle Class III Molar Relationship

• The anterior buccal cusp of the upper first permanent molar occludes posterior to the buccal groove of the lower first permanent molar.
• The lower incisor edges lie anterior to the cingulum of the upper incisors.
• Frequently there is a ‘reversed overjet’. This means the lower anterior teeth lie in front of the upper anterior teeth.
• The upper incisors are often crowded and usually proclined.
• The lower incisors are retroclined.

Terms to Learn

Cingulum: the bulging out portion of the lingual/palatal surfaces of the crown of anterior teeth, closest to the root.

Proclined/retroclined: protruding excessively/excessive lingual or palatal tilting.

Orthodontic assessment

Key Point

When referring to the Angle classification, the class is always given in Roman numbers. The subdivisions of Class II are always written as Arabic numbers.

Apart from a full clinical assessment as usual, the following are taken:

• Photographs
• Impressions for study models
• Radiographs.

Study models (also called casts) of the upper and lower teeth are used to analyse the tooth and jaw relationships in detail. Thus they must be of good (diagnostic) quality. For this reason:

• The liquid plaster of Paris is carefully poured into the impression (mould) so that no large voids or bubbles are present.
• The models are adequately trimmed (without extra bits of plaster jutting out from the sides). A way to check this is that when the models are put together and placed on their heels, the upper and lower teeth should remain in touch at the maximum possible points (in the mouth this is called centric occlusion).
• They are labelled and kept in protective model boxes to ensure they do not break.
• The models and boxes are labelled with the patient’s name and model box number and stored in a safe place.

Study models are part of the patient record and thus must be kept until:

• The patient’s 25th birthday
• If the patient was 17 or over at conclusion of treatment, until their 26th birthday
• Until eight years after the patient’s death if sooner.

Radiology

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/>

Related posts:

  1. 16: Dental Emergencies
  2. 12: Dental Drugs, Materials, Instruments and Equipment
  3. 2: Medical Emergencies and First Aid in the Dental Surgery
  4. 5: Oral Disease
  5. 10: Surgical Procedures
  6. 17: Human Diseases and Health Promotion

Stay updated, free dental videos. Join our Telegram channel
Tags:
Jan 8, 2015 | Posted by in Dental Nursing and Assisting | Comments Off on 11: Correction of Malocclusion: Orthodontics

VIDEdental - Online dental courses
Get VIDEdental app for watching clinical videos