Learning outcomes: questions and answers Flashcards
Describe ideal occlusion in terms of the relationship of the teeth to the line of occlusion:
The maxillary teeth should follow the line of occlusion in the maxillary fossae. the line of occlusion of the mandibular teeth should follow the buccal cusps and ridge.
Teeth outside the line of occlusion are said to either have buccoversion (buccal leaning), linguoversion (lingual leaning), or torsiversion (twisting away from the line of occlusion)
There is often some deviation from the line of occlusion and this exists on a spectrum and so judgement can be subjective as to what is good and what is bad.
Discuss the advantages of the Angle system for classification.
Angle’s system simplifies everything by only really looking at the A-P dimensions and taking out the complexities associated with soft tissue proportions and protrusion.
Describe the functional, health and psychosocial reasons for orthodontic treatment, and place them in perspective in terms of their relative importance.
Psychosocial reasons include looking good being inherently useful for having a good position in work. It is much less likely for people who don’t have good occlusion to climb to the higher ranks at workplaces due to bias in selection at workplaces.
Having malocclusion can cause insecurity in people especially when they are minor cases of malocclusion due to not being sure of how they appear and this can lead to some anxiety in social settings.
Malocclusion can affect function in severe cases leading to pain and difficulty eating.
Malocclusion has been theorized to lead to more difficulties with dental hygiene due to creating hard to reach places for toothbrushes and other cleaning equipment and so treatment can be an adjunct to disease control.
Describe realistic goals for orthodontic treatment, and indicate the way they have changed as modern dentistry developed.
The 2 paradigms used for looking at treatment goals in orthodontics are:
Angle’s paradigm that looked at occlusion on the basis of all the hard tissues present. Primary goal was ideal dental occlusion. Secondary goal was to treat jaw relationships.
Soft tissue paradigm looked at occlusion on the basis of all soft tissue proportions and adaptation. Primary goal was to achieve these ideal proportions. Secondary goal was to achieve functional occlusion.
Angle’s classification believes that ideal skeletal/dental relationships produce ideal soft tissue and so should be the target of treatment. Soft tissue paradigm looks at soft tissues that are ideal and then looks for the ideal skeletal/dental proportions to create that ideal soft tissue proportion.
Discuss how need for orthodontic treatment compares with demand in the US at present and
how demand is likely to change in the near future.
65% of people in the population of the US have malocclusion. Dentists that were asked believe that 55% of them need treatment whereas patients felt like only 35% need treatment.
Discuss how need for orthodontic treatment compares with demand in the US at present and
how demand is likely to change in the near future.
65% of people in the population of the US have malocclusion. Dentists that were asked believe that 55% of them need treatment whereas patients felt like only 35% need treatment this number becomes 50% if it were for free.
Lay people can understand the need for it and can discriminate what bad teeth look like from what good teeth look like. However, their value for the different treatment needs differ from dentists’ value.
5 - 40% of people get orthodontic treatment. Adult demands for orthodontic treatment are increasing. reasons for this include job advancement (need to “trade up”)
Describe known causes of malocclusion in terms of major categories, and put
the known causes in perspective relative to the total number of patients with
malocclusion
Only 5% of cases of malocclusion are known they can be due to:
Hereditary factors appear to be the least common causes. 3 theories exist for this and they include:
- Outbreeding (different races coming together with different sizes causing malocclusion),
- Evolution is proposed due to the shrinkage of the size of the jaw in modern times there is more crowding that takes place (alignment of teeth was excellent until ~100k years ago)
- Familial characteristics (Skeletal characteristics are inherited more than dental characteristics. Eg familial mandibular prognathism)
Developmental abnormalities such as:
Foetal alcohol syndrome
Craniofacial microsomia
Pierre sequence
Trauma:
- Scarring of the labial and buccal mucosa can push the teeth back when tissue is lost the opposite occurs.
- Direct damage to a tooth may
Disturbance with normal function
Indicate the two types of malocclusion most likely to be due to inherited jaw
proportions, and describe the evidence to support your categorization.
Mandibular prognathism. The ADAMTSL1 gene
Indicate the mechanism by which trauma to the mandible can affect its future
growth.
A fracture to the condyle can lead to damage to adjacent soft tissue structures causing fibrosis. The functional matrix theory indicates that this will lead to growth disturbances in the region. The fracture itself can cause ankylosis in some cases if gliding along the joint doesn’t happen as often. The lateral pterygoid displaces the mandible to the opposite direction.
Identify the magnitude of force needed to cause movement of a tooth, and
relate this to the observed threshold for tooth movement.
3 grams of force are required for longer than 4 hours.
Forces can be applied by opposing soft tissue and this can lead to a resting pressure to form. Resting pressure is the equilibrium pressure at rest.
Identify the duration of force needed to cause movement of a tooth, and relate
this to the impact of habits like thumb sucking on the dentition.
Intermittent light force affects eruption and movement of teeth. If the force is applied:
10% of the time there is little or no effect
25% of the time there is an intermediate effect and this is variable.
50% of the time there is a similar to continuous force
Describe the possible role of nasal obstruction in the etiology of malocclusion,
and indicate the probable mechanism by which it would have an effect
Nasal obstruction affects occlusion by creating an upward posture in order to open up the airway for breathing. The mandible also protrudes forward and downward to allow breathing to take place more easily.
This leads to changes in resting pressures and thus teeth move to reach equilibrium again.
2 studies show this:
Linder-aronson experiments
VIG experiments
Describe the possible role of nasal obstruction in the etiology of malocclusion,
and indicate the probable mechanism by which it would have an effect
Nasal obstruction affects occlusion by creating an upward posture in order to open up the airway for breathing. The mandible also protrudes forward and downward to allow breathing to take place more easily.
This leads to changes in resting pressures and thus teeth move to reach equilibrium again. The consequence is often increase in face height.
2 studies show this:
Linder-aronson experiments
VIG experiments
