Orthodontics for Internship program

Classification Of Malocclusion

WHO SHOULD BE TREATED?

• In order to assess the need for orthodontic treatment, various indices have been developed.The one used most commonly in the United Kingdom is the Index of Orthodontic Treatment Need(IOTN). This index attempts to rank malocclusion, in order, from worst to best. It comprises two parts, an aesthetic component and a dental health component .

WHO SHOULD BE TREATED?

• The dental health component consists of a series of occlusal traitsthat could affect the long-term dental health ofthe teeth. Various features are graded from 1–5(least severe — worst). The worst feature of the presenting malocclusion is matched to the list and given the appropriate score.

• The aesthetic component consists of a series of ten photographs ranging from most to least attractive. The idea is to match the patient’s malocclusion as closely as possible with one of the photographs

Patient assessment and

examination I • EXTRA-ORAL EXAMINATION

It is helpful to follow the examination sequence outlined: • Skeletal pattern • Soft tissues • Temporomandibular joint examination

Patient assessment and examination II

• INTRA-ORAL EXAMINATION: • There are various systems available to assess this

aspect in the following sequence

• Dental health • Lower arch • Upper arch • Teeth in occlusion • Radiographs

Treatment planning

• TREATMENT AIMS: Some of the problems that may need to be addressed during treatment are: • Improve dental health • Relieve crowding • Correct the buccal occlusion • Reduce the overbite • Reduce the overjet • Align the teeth

Relieve crowding

• The decision to extract teeth needs to be

carefully considered and depends on the degree of crowding, the difficulty of the case and the degree of overbite correction.

Correct the buccal occlusion • The key to upper arch alignment is to get the

canines into a Class I relationship.

• In order to get the canines Class I there are, in general two choices for the molar relationship at the end of treatment; either Class I or a full unit Class II.

Overbite and overjet reduction

• The overbite should always be reduced before overjet reduction is attempted. A deep overbite will physically prevent the overjet from being reduced because of contact between the upper and lower incisors.

Retention

• Retainers are designed to reduce the risk of relapse post treatment by allowing remodelling and consolidation of the alveolar bone around the teeth and reorganization and maturation of the periodontal fibers.

• There are many different types of retainers but they are generally removable or fixed. There are no hard and fast rules regarding the length of time retention should continue.

Cephalometric Analysis

• Standardised technique to ensure reproducibility and minimise magnification.

• X-ray source at a fixed distance to the midsagittal plane (about 152.5cm) and to the film .

Uses of lateral cephalometric analysis

• To aid diagnosis by allowing dental and skeletal characteristics of a malocclusion to be assessed

• To check treatment progress during fixed or functional treatments and to monitor the position of unerupted teeth.

• To assess treatment and growth changes

Class I malocclusion Crowding

• Mild crowding is best accepted • Moderate crowding usually

requires first premolar extractions.

• Severe crowding is often managed expediently by the removal of most displaced teeth or by the extraction of more than one tooth per quadrant. Anchorage planning is critical .

• Late lower labial segment crowding is common in mild to late teens.

Class I malocclusion Spacing

• Spaced dentition is generally rare in Caucasians. It results from a disproportion in the size of the teeth relative to the arch size, or from the absence of teeth. When spacing is mild, acceptance is usually best, or consider composite additions or porcelain veneers to increase the mesiodistal width of the l abial segment teeth. If spacing is more marked, orthodontic treatment to localise spacing at specific sites may be necessary prior to fitting a prosthesis or to implant placement.

Class II division 1

• Growth modification. This is only possible just before and during the pubertal growth spurt using a functional appliance, headgear, or

Both. • Orthodontic camouflage. This

usually involves the extraction of 4[4 and fixed appliances to bodily

retract upper incisors to achieve class II molar occlusion.

• Orthognathic surgery. This is indicated where there is a marked Class II skeletal pattern with considerably reduced or increased facial proportions and/or a gummy smile in an adult.

Class II Division 2

Class III malocclusion

• Consider the degree of anteroposterior and vertical skeletal discrepancy, the potential direction and extent of future facial growth, incisor inclinations, the amount of overbite, the ability to achieve edgeto- edge incisor relationship, and the degree of upper and lower arch crowding. The prognosis is usually more favourable where the skeletal pattern i s mildly Class III with average to low FMPA, deep overbite, upper arch crowding, proclined lower incisors, and the ability to achieve an edge-to-edge incisor relationship

exists.

Crossbite

• Buccolingual molar relationship of upper and lower teeth.Anterior or posterior (unilateral or bilateral)with or without mandibular displacement.

• Buccal crossbite. Lower teeth occlude buccal to corresponding upper teeth

• Lingual crossbite (scissors bite). Lower teeth occlude lingual to palatal cusps of upper teeth.

Anterior crossbite

• If one or two incisors are in crossbite, mandibular displacement usually exists. Correct early in mixed dentition if adequate overbite is likely

Posterior Crossbite

Scissors Bite

Anterior Openbite

IMPACTED CANINES

• A canine that is prevented from erupting into a normal position, either by bone, tooth or fibrous tissue, can be described as impacted.

• Correction of canine position Favourable indications for correction of impacted canines.

• The treatment of buccally or palatally impacted canines involves exposure and then a form of traction to pull the tooth into the correct position in the arch.

• Other options include: Accept and observe

Extract the impacted canine Transplantation

Removable Appliances Indications

Removable Appliances

1. Springs 2. Bows 3. Screws

•Retention component

1. Adams clasp. 2. Southend clasp. 3. Long labial bow. 0.7 mm

wire (0.8 mm if it includes reverse loops).

• Baseplate:This is usually made of cold-cured acrylic but may be heat-cured. It connects the other components; guards palatal springs; aids anchorage by contact with the palate and with teeth intended not to move; and transfers active component forces to the anchorage. It may also be active.: 1. Flat anterior bite plane. 2. Posterior bite platform.

Removable Functional Appliances

Fixed Appliances

• An appliance fixed to teeth by attachments through which force application is by archwires or auxiliaries.

• Indications for fixed appliances: 1.Bodily movement, particularly of incisors to correct mild to moderate skeletal discrepancies; 2. Overbite reduction by incisor intrusion; 3. correction of rotations extensive lower arch treatment; 4. alignment of grossly misplaced teeth, particularly those

requiring extrusion; 5. closure of spaces; 6. multiple tooth movements required in either one or both

arches.

Components Of Fixed Appliances

Anchorage Control

Extraoral Anchorage &Distilization

A Reverse pull Headgear to treat Class III malocclusion

Risks of Orthodontic treatment INTRA-ORAL RISKS:

Enamel demineralisation/caries Root resorption

Periodontal tissues

Trauma

Orthodontic Tooth Movement

Properties of wires

Properties of wires

•Consider wire as a beam

–temporarily deform -elasticity

–resistance to indentation -hardness

–point at which wire -proportional limit permanently deforms

–amount of deflection prior to permanent -range deformation

– force required to bend wire -stiffness

Properties of wires

Properties of wires

• strength of materials the capacity of materials to withstand stress (the internal force exerted by one part of an elastic body upon an adjoining part) and strain (the deformation or change in dimension occasioned by stress). Hooke's law states that, within the elastic limit, strain is proportional to stress.