Level IV Unit A Objectives

Why we do Orthodontics

The modern reasons for doing orthodontics listed in order of importance 01 - Why Do We Do Orthodontics > Goals of Orthodontic Treatment Now:

1. Primarily, to help patients overcome psychosocial handicaps created by discrimination based on facial appearance
2. To improve function of the teeth and jaws
3. occasionally, to improve oral health

Effects of Malocclusion on health, function and psychosocial well-being are reasons for orthodontic treatment

Relationship of malocclusion and oral disease

01 - Why Do We Do Orthodontics

• There is little relationship between malocclusion and hard tissue lesions
• There is only a weak relationship between periodontal disease and malocclusion

Third molars

There are health considerations in the decision to retain or extract third molars.

Third molars can be put into three categories:

1. Those that erupt and become a functional part of the dental arch - Not usually a problem , although may need to be removed if individual has a large mandible and class III tendency or bimaxillary protrusion
2. Those that erupt into the mouth, but are only partially exposed and are not in occlusion - the most probelmatic as much more likely to develop periodontal disease
3. Those that have not entered the oral cavity - Produce health risks related to the bacterial flora around them and development of chronic inflammation

Current Guidelines for third molar extraction

• Removal of exposed 3rd molars decreases the chances of early periodontal disease
• if a partially erupted 3rd molar is retained, monitoring that includes probes for evaluation of the bacterial flora is needed
• An episode of pericoronitis is an indication for extraction
• Recovery after 3rd molar extraction is fater and less problematic in teenagers

Relationship of Malocclusion and Function

There are two aspects to the relationship between dental occlusion and function

1. Masticatory Efficiency
2. TMD/Occlusion

Masticatory Efficiency

• Chewing rarely correlates with occlusion from the dentists point of view as teeth rarely contact during mastication
• While we don’t have a good way to measure increases in masticatory efficiency, we know from patients experiences that orthodontic treatment tends to make it easier to eat foods
  • for example sometimes they avoid eating things if the only way they can eat them is in a social unacceptable way
  • Patients often comment that they can “eat better” after treatment

TM Joint Function and Malocclusion

• In the absence of parafunctional activity, TM pain/Dysfunction related to the occlusion simply does not develop

Some arrangements of the teeth make it easier to hurt yourself by bruxing and grinding than others

Lateral Shift

• The strongest correlation is with crossbite with a lateral shift
• 16% (0.4 correlatoin coefficient) chance that a patient with a crossbite and lateral shift will have symptoms of TMD

TMD and other malocclusions

• 0.3 correlation coefficient for Class III and Class II deep bite ~ 10%
• The severity of Class III malocclusion is inversely related to the prevalence of TMD
  • mild class III’s are more likely to create incisor interferences that can force a shift on closure, more severe class III’s put the incisors beyond occlusal contact

Psychosocial Impact of Malocclusion

• Teeth and Jaw proportions all have an effect on how you are perceived by other people

To Extract or Not to Extract, Part 1 Class I Crowding/Protrusion

For crowding and protrusion of incisors, esthetics and stability determine the decision to expand the dental arches vs reducing tooth mass or number

There are two reasons for extracting teeth in orthodontic treament:

1. Correction of crowding/protrusion
2. Camouflage of jaw discrepancy

As a general rule, extraction for crowding/ protrusion is done for patients with Class I malocclusion and extraction for camouflage is done for patients with Class II or Class III problems

The same extraction space can't be used to correct crowding and again for camouflage

Crowded teeth in a Class II or Class III patient can greatly limit the possibility for camouflage

Extractions for Crowding and Protrusion

Crowding and protrusion are two sides of the same coin , if there isn’t enough room for teeth:

1. Either they remain upright and become crowded and irregular
2. Or they align themselves on the arc of a larger circle and protrude

Evaluating protrusion

• This is best done in oblique and profile views
• Teeth are too protrusive if :
  • The lips are separated at rest and
  • strained and everted on closure

Purpose of extraction in treatment of crowding/protrusion:

• Provide space to align crowded teeth without protruding them
• Provide space to retract protruded teeth to a normal relationship with the lips and jaw
• or perhaps something of both (although note that the same space can’t be used twice to obtain both )

Arch expansion is the best case if teeth are retruded

Stats

• About one-third of crowded patients (Class I) can be treated satisfactorily with or without extraction

**Extraction and Jaw Function **

• no evidence to suggest it effects how you eat
• no evidence to suggest it increases TM dysfunction

Esthetics: Exo vs Expansion

Expansion and extraction affect esthetics by changing the prominence of the teeth.

• Expanding arches: moves incisors facially and makes them more prominent
• Extracting : moves incisors lingually/palatally and makes them less prominent

Controlling the effect

You can control it to some exetent:

• Expansion: control how much you move posterior teeth laterally rather than forward
• Extraction: modulate space closure, i.e. retraction of incisors vs movement of posterior teeth

Does it matter?

• Every patient has an acceptable range of esthetics sometimes extraction and expansion both fit within that range!
  • its only for patients at the boundaries where there would be problems
  • This can be considered a 10-15% rage on eithr side

Extractions and Stability

The behaviour of exos, expansions and stability is very similar to that of esthetics. Although traditionally extraction has had an upper hand:

• some findings that nonextraction cases have the highest irregularity

Recent success of non-extraction and stability

• Non- extraction treatment is more successful than stability due to a variety of reasons:
  • keeping the first permanent molars from shifting forward
    • this allows us to utilize leeway space to relieve crowding
    • this also negates the use of arch expansion, allowing more tooth-tissue stability
  • Heavier use of transverse expansion
    • transverse expansion is more stable than antero-posterior expansion