Friday, February 12, 2016

Lower incisor position and profile changes in extraction treatment.  I am often asked about the effect of upper premolar extraction treatment on the facial profile and many believe that this will significantly retract the upper and lower lip positions.  In most orthodontic cases we must treat the occlusion to the labiolingual position of the lower incisors.  This is because the bone surrounding them is thin both on the facial and lingual aspect of their roots.  If the maxillary anterior teeth are more crowded than the lowers and a class II molar relationship is present, there is usually not a significant overjet.  When upper premolars are removed in these cases the maxillary canines are retracted into the missing premolars' positions and the incisors are uncrowded.  The lower incisors are held in their most stable and healthy location while the overbite and overjet is coordinated to them.  Thus, the profile won't change much and proper canine and incisal guidances are obtained.  Next we'll talk about how the anterior-posterior relationship of the maxilla and mandible relate to profile and incisor angulation. 
Facial profile relationship to extraction treatment.  Facial profile and lip fullness go hand in hand with skeletal and dental positions.  When a thin or retracted lip appearance is present we try our best to treat the patient on a non-extraction basis.  Likewise, when there is a very protrusive lip pattern we consider premolar extractions a bit more often.  If severe crowding is present, extractions will not change the lip pattern much because most of the extraction space is utilized to uncrowd the dentition.  This can be both a blessing and a curse.  In thin lip patterns you will not lose lip support by pursuing extraction orthodontic treatment.  Likewise, with very protrusive lips you will not get as much softening as you might desire.  Another item to consider is the nasolabial angle (angle between the bottom of the nose and upper lip.)  An obtuse nasolabial angle (with upturned nose) requires careful consideration before removing premolars for treatment.  Next week we'll consider the relationship of the lower incisor to facial profile changes.
Indicated extractions in treatment of class II and III malocclusions.  Extraction of premolars may be indicated in order to orthodontically correct malocclusions where growth has ceased and the maxilla and mandible are not matching.  In order to mask a prognathic mandible it is sometimes necessary to remove a lower premolar bilaterally in order to incline the lower incisors lingually and distalize the canines. If we are treating a class II malocclusion without significant lower crowding we can extract two upper premolars in order to gain a tight overjet and class I canines.  With these or any extractions it is wise to take the facial profile into account as we treat the malocclusion.

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