Lec5_Etiology Flashcards
If we don’t know the cause of a malocclusion, & if that causal factor is still exerting influence on the malocclusion, it may be difficult to p______ the outcome of treatment, to a______ the desired outcome, & to r_____ the outcome achieved.
Predict
Achieve
Retain
If we don’t know the cause of a malocclusion, & if that causal factor is still exerting influence on the malocclusion, it may be difficult to predict the outcome of treatment, to achieve the desired outcome, & to retain the outcome achieved.
How often will we know the cause of an individual malocclusion? How does that affect management?
About 5% of patients have specific, known cause, 60% have a complex and poorly understood cause)
- -> address the causal factor
- ->manage the effect.
- ->delay treatment until after the causal agent is no longer active.
- Communicate
- Leave good options open, monitor, reassess when needed
- Do no harm
What are the 2 major categories of causal agents? How are they correlated with the 2 major categories of malocclusions (dental & skeletal)?
Genetics and environment
Looking at the patient’s face can give us some indication of etiologic factors (if skeletal- etiology is more likely to be genetic).
Heritability of skeletal characteristics = high.
Heritability of dental characteristics = low.
Thumbsucking: what malocclusion does it cause, how do we manage it?
Openbite! Flared and spaced max incisors, lingually inclined lower incisors, narrow upper arch. Also, the posterior teeth have excessive eruption.
Note: Not an etiologic factor- don’t treat it as one. –> Avoid ineffective treatments
- If: Permanent teeth are beginning to erupt;
- If: Habit continues at 6 hrs or more per day.
- Develop internal motivation 1st (so they want to stop- peer pressure, talk with DDS), then help once they want help.
Fix:
• Address the cause = internal motivation! Help when they want it.
Tongue posture: what malocclusion does it cause, how do we manage it?
Tongue posture can cause a malocclusion- either openbite or generalized spacing.
Hard to manage:
– Tongue reduction surgery (low predictable benefit, high cost);
– Tongue crib or arch expansion for openbite (may be problematic for long-term stability- may need long-term and significant retainer wear);
– Space closure for spacing (if change position of teeth buccal- lingually, stability may be problematic- lots of retainer wear).
– No treatment or limited objectives (get the teeth straight, leave the openbite or some spaces)- may be good options.
Condylar fracture: what malocclusion does it cause, how do we manage it?
Can cause asymmetric molar occlusion.
-A fractured condyle in a growing child can cause asymmetric mandibular growth if scarring in area restricts growth movements (can’t pull mandible forward). Still can have 75% normal growth.
– If growth is asymmetric- assess restriction of condylar translation. If translation is possible - modify growth. If no translation- consider surgery to remove restriction, then modify growth. Be sure to use early mobilization of the joint.
-Earlier age breaks = better outcomes.
Surgery is very risky: causes more scar tissue and scar tissue is the enemy!
Early loss of primary teeth: what malocclusion does it cause, how do we manage it?
If a primary molar or canine is lost early:
- Maintain space if minimal drift has occurred
- Block the teeth from drifting
- Regain space and reposition teeth if needed
- If drift has occurred- move the teeth back and hold them.
Malocclusion is due to:
Forces from the active contraction of transseptal fibers in the gingiva, + pressures from the lips and cheeks
Can cause crowding when the permanent teeth come in. Can also cause asymmetry if lost on one side only.
Mouth breathing: what malocclusion does it cause, how do we manage it?
Can create a patient with openbite and long lower face.
Lips are flaccid, openbite with increased overjet and narrowing of the maxilla. Molars may supererupt because they are open more often than usually.
- Recognize and communicate uncertainty re etiology (and predictability of result, stability);
- Avoid surgery for nasal airway obstruction as part of orthodontic therapy (likely ineffective, potentially costly/risky)
- Note if they do have surgery for snoring or sleep apnea, may have the beneficial side effect of fixing the open bite issues.
Skeletal abnormality, class II and openbite: what malocclusion does it cause, how do we manage it?
– How do we manage?
• Decrease uncertainty when possible (interview re habits, family similarities, tongue posture, mouth breathing, history of change in malocclusion)
• Manage uncertainty
• Address most likely cause or effect
What are the options for managing an anterior openbite?
**Need to know the cause of the malocclusion!
- Let the anterior teeth erupt (let nature run its course, remove thumb, use braces)
- Intrude the posterior teeth (surgery or growth modification, use mini-implants to move teeth)
Does tongue thrust during swallowing cause malocclusion?
No. Swallowing does not come even close to taking up 6 hours/day. This actually might be the RESULT of an openbite.
This is NOT an etiologic factor.
What are possible etiologic factors if malocclusion is due to skeletal anomalies?
- Genetics
- Mouth breathing
- Fetal molding, birth injuries
- Muscle dysfunction (muscle weakness syndromes)
What are possible etiologic factors if malocclusion is due to dental anomalies?
- Shift of teeth
- Ex: Early loss of primary second molar(s)
Skeletal Class II walks in - how do you manage this case?
- Interview and exam
- Manage the uncertainties:
- communicate! might need to camouflage by just moving teeth, may need surgery. Do no harm and avoid irreversible errors. - Address the likely etiology. Probably genetics - use growth modification and then wait until done growing for further action.
Openbite walks in - what might be the etiologic factors?
How do you manage?
-Genetics -Digit habit -Tongue posture -Mouth breathing -Muscle weakness -Idiopathic condylar resorption
Exam, manage uncertainty, figure out most likely cause.
