Etiology of Malocclusions Part 2 Flashcards
What can cause a deep bite?
- Skeletal problem (hypodivergent patient)
- Overeruption of anterior
- Undereruption of posterior
What causes a tranverse issue (crossbite)?
- Usually, maxillary transverse deficiency
- Maybe caused by overdeveloped mandible - if there is a low posture of the tongue, there is pressure on molars causing low posterior teeth to be expanded
- Some are also caused by unfavorable dental angulations
What are the different disturbances of dental development?
- Congenitally missing teeth
- Malformed and supernumerary teeth
- Interference with eruption - something on the eruption path of the teeth
- Ectopic eruption - teeth erupting in a different location
- Early loss of primary teeth
What are the types of congenitally missing teeth?
- Anodontia (very rare)
- Oligodontia (6 or more teeth are missing)
What are the explanations for congenitally missing teeth?
- Heredity
- Ectodermal Dysplasia
- Localized inflammations or infections
- Systemic conditions, e.g. Ricketts
- Evolutionary changes in the dentition (specially third molars)
What are the symptoms of ectodermal dysplasia?
- Oligodontia
- Poorly shaped teeth
What are the most frequently missing teeth?
- Upper lateral incisors
- Lower second premolars
- Lower central incisor
What are characteristics of “peg” maxillary lateral incisors?
- Crown can be misshaped
- Root may be shortened
What is the bolton ratio?
Mesio-Distal Size of the Dentition
* Proportionality of tooth sizes within a dentition
In order to develop a proper overbite and overjet, the size of the lower dentition must be ___________ to the size of the upper dentition
proportional
bolton ratio
What is the equation for the bolton ratio?
What will happen to a pts bite with a hypodivergent mandible?
The mandibular plane is very flat so they will have a short face so the anterior bite will be deep
(most of the time hypodivergent pts have a deep bite)
What can an OPEN bite be caused by?
Undereruption of anterior
overeruption of posterior
skeletal component (hypodivergent pts)
also fxnl happens (thumb sucking, tongue thrusting)
Buccal crossbite vs regular crossbite
cross bite - (buccal - when the maxillary palatal cusp of posterior teeth are buccal to the line of occlusion (on posterior lower teeth its the buccal cusp)
buccal crossbite - the palatal cusps are BUCCAL to the buccal cusps of the LOWER posterior teeth (buccal crossbite)
How can early loss of primary teeth cause a disturbance in dental development?
if a deciduous tooth is exfoliated really early, adjacent teeth are going to shift this could create a transverse problem
Ex - a lower 2nd primary molar is an early exfoliation so then the permanent molar is going to shift MESIALLY, the space for the 2nd PM eruption will have less space too
Thus, the 2nd PM will be impacted or ectopic
If ectopic, will erupt lingually or buccally (transverse dental problem)
What is the molar relationship? And what kind of step is it?
Primary dentition -
* Mesial step*
Molar relationship is class II-ish but not full class II and NOT class I so thus its called end-on or end to end class II relationship (when the molar relationship is slightly leaning to one molar relationship than another)
* Class I molar relationship - max MB cusp of 1st molar occludes on the mand buccal groove. This is NOT what is happening. It is mesial to the buccal groove. When its mesial to buccal groove –> class II malocclusion. Since this isnt a FULL class II relationship its called end to end class II
* It becomes a full class II when the MB cusp is in the embrasure space
Is the overal dentition of the lower dentition in the M-D dimension bigger than the M-D of the maxillary dentition?
Mandibular dentition is slightly smaller or thinner than maxillary dentition (bolton ratio)
Is the overal dentition of anterior teeth from canine to canine bigger in the max or mand dentition?
Lower anterior teeth are considerably NARROWER than maxillary dentition (bolton ratio)
What does it mean if the overall ratio is less than 91.3%?
means that the maxilalry dentition is WIDER than mandibular dentition
What is the tx for an overall ratio of less than 91.3%?
You can do IPR on the upper OR leave spaces. If you close spaces you may need to do IPR
What does the 91.3% overall ratio mean?
the M-D width of lower dentition from 1st-1st molar, the ideal should be 91.3% of the M-D width of the maxillary dentition
What does it mean if the anterior ratio is more than 77.2%?
The lower dentition is WIDER
