what is overbite
amount of overlap of the lower incisors by the central incisors
- vertical dimension= overlapping of max incisors over mand incisors
- deep bite when you have exaggerated overbite
How are overbites measured
in percentages: normal is 20% (+- 5%)
- the amount is not directly related to severity of malocclusion
what are etiological factors of overbite
- over eruption of upper incisors
- over eruption of lower incisors
- under eruption of lower posterior teeth
- genetic development (CL II Div 2- when they have deep bite and max incisors are tipped back)
What dimensions do we grow in
transverse, vertical and sagital
what is a class II deep bite
- over eruption of max incisors
- over eruption of mand incisors
- look at occlusal plane of posterior teeth to anterior teeth
- if both max and mand incisors are on different plane- theres a problem in both arches
Management of overbite
- intrusion arch: corrects the two-step occlusal plane by intruding the max incisors
- leveling the curve of spee: intruding anteriors and extruding posteriors
ways to avoid relapse of overbite
hawley retainer: removable appliance that continues to open bite
- the incisors touch an acrylic plate and posterior teeth will not be in occlusion
- wearing this helps cause supra eruption of posteriors which will open the bite more
Ways to correct an overbite caused by mandibular incisor intrusion
- posterior blocks
- intrusion of lower incisors with light wire and constant force
- upper incisors are left at the same level
treatment options for overbite caused by extrusion of posterior segments and maxillary incisors intrusion
- bite plate at night
- lower intrusion arch
- also need to correct class 2 skeletal relationship
Therapeutics
- cervical pull HG (head gear) to correct class II molar relation, extrude molars
- intrusion arch for maxillary incisors, lower molar eruption with a bite plate (allows for over-eruption of molars)
what is an open bite
maxillary incisors do not overlap mand incisors
causes of an open bite
genetic origin
functional origin- like tongue thrust
parafunctional habit- like thumb sucking
combination of those
what are the multifactorial etiology of an open bite
skeletal (genetic)- maxillary vertical excess instead of horizontal= causes mand/condyle to rotate down and back
tongue thrust- 2 types (active and passive, passive is WORSE)
finger habit- thumb sucking causes proclination of max incisors and mand incisors, narrow palate and post crossbite
sleep apnea
neuromuscular
open bites
- present in many malocclusions
- etiology ill defined
- no prospective studies
- relapse rate is significant and higher than non open bite malocclusions
are all anterior open bites the same
no, some are caused by growth, some are by habits like pacifier
Facial Characteristics of an open bite
facial type: variable but usually dolychocephalic
lip support: altered
lip seal: deficient- cannot close lips together
upper incisor showing at rest: variable but usually increased
smile line: altered
facial proportions: variable- usually long lower 1/3
what is a dentoalveolar reponse causing an open bite
- displacement of maxillary incisors in the vertical and A-P plane
- intrusion and proclination of mand incisors
- over eruption of max and/or mand molars
occlusal plane analysis
- assess the position of posterior and anterior teeth in relation to the functional occlusal plane
- hard to determine as the anterior teeth are often times displaced in the vertical plane
differential diagnosis for an open bite
anterior tongue thrust
thumb sucking habits
genetics (look at fam history)
sleep apnea
combination of any
what are parafunctional habits
- thumb sucking habit: constricted maxilla, deep palatal vault
- anterior tongue posture: does not have tendency for cross bute and high palatal vault
- dentoalveolar deformation and lack of tooth eruption
How to manage a thumb sucking patient
- fixed appliance
- tongue crib: puts the tongue behind bars
- psychologic support
- myofunctional therapy
once you remove the etiology, the open bite will usually correct itself
Anterior open bites that are neuromuscular origin
- anterior tongue posture
- max incisors pushed labially
- mand incisors under erupted
- good posterior occlusion
- good facial balance
What does the ismar modified appliance do
keeps the tongue away to fix the open bite
What is one of the most difficult malocclusions to correct?
class III open bite
