1 (P)- etiology of malocclusion- genetic basis

What may lead to an uncoordinated inheritance of teeth and jaws?

Inheriting dissimilar genetic material, race, ethnicity, regional intermixture

What 3 factors are genetically influenced and have an effect on each other and the overall dentition?

Muscles inserted in bone- alters it function and shape

Teeth in bone- normal or malocclusion

Muscles influence bone growth- condition it’s position

What 2 considerations maximise the chance of successful Ortho treatment?

Identify cause of problem before treating

Identify factors that will influence the treatment outcome

What can a pedigree be used to help understand and what is it especially useful in?

Approx likelihood sibling may develop same trait

Monogenic traits-

class 3 malocclusion

hypodontia

primary failure of eruption

developmental dysplasias- (dentinogenesis/amelogenesis imperfecta)

What 5 malocclusions have a strong genetic influence?

Mandibular prognathism/class 3 skeletal

Size and shape- BL MD dimensions

Number of teeth

Chronology

Root formation

What parts of the dentition have a low genetic association?

Tooth position and dental relationship-

Width and arch length

Overbite

Overjet

Molar relationship

What is mandibular prognathism also known as and how does it present?

Habsburg jaw due to inbreeding

Upper lip thicker

prominent nose

Everted lower eyelids

Maxilla hypoplasia

What is mandibular prognathism caused by?

Deficiency of maxillary growth, excessive mandibular growth- or combo

What is dental agenesia (most frequent dental anomaly), its link to genetics, correlation with other teeth and presentation?

One or more teeth fail to erupt/develop

High heritability

Rarely caused by mutation

Other teeth have smaller md dimension

Peg shaped or lateral conical- can skip generations

What is the difference between anodontia, oligodontia, hypodontia?

Total vs multiple vs some teeth absence

In which teeth is a congenital absence more likely?

Permanent dentition

Maxillary lateral incisors

Usually if temp teeth absent- permanent teeth won’t form

Associated with ectodermic dysplasia

Which teeth are frequently supernumerary teeth?

Mesiodens- between max ci- concern if blocks eruption of permanent incisors

Lateral incisors, 2pm, 4m

If impacted- risk of cyst formation

What can supernumerary teeth cause and how can we treat it?

Adjacent teeth won’t erupt or delayed

Deflect erupting teeth into abnormal locations

Crowding

Extract early

How do peg-shaped lateral incisors vs macrodontic teeth affect occlusion, and what are their treatment options?

Both alterations of Bolton index

Open space and reconstruct with filling, crown or veneer

Interproximal reduction

Need to achieve desirable intercuspation and class 1 canine

How does an impacted canine present?

Palatine 85%, 15% Buccal

With other anomalies-

peg shaped or lateral incisor agenesia

Hypodontia

Diastema

Retarded development

How can you diagnose and treat an impacted canine?

Diagnose with axial tomography, Ortho, x ray

Early treatment to prevent lateral incisor root resorption

What are local factors that contribute to malocclusion?

Tooth size arch length discrepancy

Ectopic euption

Premature loss of temp teeth

Absence of permanent teeth

What causes are the consequences of a large tooth-size arch-length?

Dietary change, racial mix

Crowding- specially in last teeth to erupt

Protrusion- leads to lip hypotonicity- low muscle tone of lips

Which teeth suffer from ectopic eruption?

Lower incisors

1st permanent upper molar

Canine

How do lower incisors suffer in ectopic eruption and how do you treat it?

Changes normal tooth eruption pathway

Improve the positions and extract temp tooth

How does the ectopic eruption of the upper first molars effect the tooth size arch length?

When erupting mesially, reabsorbs 2nd temp molars prematurely

Negative discrepancy

If root resorption limited to 1-1.5mm- no treatment

Treat if blocks for over 6 months or root resorption continues

Why do canines tend to erupt ectopically and how to treat it?

Last teeth to erupt- may lack space so erupt buccally and high in arch

Create space, analyse discrepancy, extract premolars

What may happen if there’s a premature loss of temp teeth and how do you treat it?

Adjacent teeth drift so less space for permanent teeth to erupt

Treat by space maintainers or regain lost space with appliances

What does treatment of absent permanent teeth depend on?

Facial profile

Incisor profile

Space available or lack of

Usually 2pm

or upper lateral incisor- often replaced spontaneously by permanent canines

If 2nd permanent premolar missing…

If acceptable occlusion- maintain 2nd temp molar and reduce MD width

But extract if convex profile or protrusive incisors- will allow upper 1st molar to erupt mesially and occupy the space

What are the effects in breath, pressure and the tongue in mouth breathers?

Air enters nasally

Creates negative pressure between tongue and palate

Tongue rests against palate- is positive stimulus for maxillary development

What are 4 causes mouth breathing?

Chronic allergic

Deviated nasal septum

Abnormal development of nasal cavities

Enlarged adenoid tonsils

What are the facial features of a mouth breather?

Long narrow face and nose

Short upper lip

Expressionless

How does mouth breathing affect dentition?(5)

Protrusion of maxillary incisors

Decreased transversal development

Posterior crossbite

Anterior openbite

Chronic marginal gingivits

How to treat mouth breathing?

Remove etiological causes

Ortho treatment- expand maxilla, align and level teeth

Promote nasal breathing

What is tongue thrusting and what malocclusions does it form in the maxilla vs mandible?

Forward movement of tongue tip between teeth to meet the lower lip during deglutition

Class 2 div 1

Maxillary constriction

General spacing between teeth

Anterior open bite

Vs Retroinclination of incisors

How to treat tongue thrusting?

Speech therapy to train correct swallowing and posture of tongue

Appliance therapy- lingual interposition grid

What are 5 features of finger sucking?

Maxillary protrusion

Mandibular retrusion

Increased overjet

Tongue placed inferiorly leading to posterior crossbite due to maxillary arch contraction

Anterior open bite

How do you treat thumb sucking?

Bitter taste on thumb

Ace bandage approach

Insert palatal crib

What are the features and treatment of lip sucking?

Protrusion of upper anteriors and retrusion of lower anteriors

Lip trap

Muscular imbalance

Lower incisor collapse with lingual crowding

Mentolabial sulcus become accentuated

Treat- Lip bumper