Fluoride Treatment Prior to Orthodontic Bracket Placement.  If you are providing a prophylaxis immediately prior to placement of orthodontic brackets, we suggest not utilizing fluoride at that appointment.  It can weaken the bond strength of the composite leading to brackets dislodging easier.  We always supply the patient with their first bottle of acidulated fluoride rinse at their bonding and ask them to use it nightly throughout treatment.

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.

How anterior overbite relates to extraction needs.  The amount of anterior overbite or openbite a patient has plays an important role in uncrowding of the dentition.  When we see a slightly open or shallow overbite malocclusion that displays crowding a red flag can go up.  Uncrowding of the teeth tends to lean the incisors somewhat labially and this will lead to more opening of the anterior overbite.  Even if the vertical elastics are used to deepen the bite, open bite tendencies may return after removal of the braces.  On the other hand, spaced dentitions will tend to deepen during orthodontics and space closure.  An easy way to visualize this is to think of a draw bridge and what happens as the two halves are leaned upward or brought back toward the water. 

More about expansion versus extraction treatment.  I prefer to treat cases in a non-extraction manner whenever possible.  If the patient does not display posterior crossbites we must be careful to not overly expand the maxillary arch into buccal crossbite.  If the lower arch needs, and will withstand, some expansion I will expand the upper arch slower in hope that the occlusion with "drag" the lower posterior teeth along.  Severe mandibular crowding may necessitate premolar extraction treatment so that we do not flare the lower incisors labially and out of the alveolar bone.  This can lead to future boney and gingival dehiscence and periodontal problems.  Over the next few Weekly Tips we will discuss how lip appearance, class II and class III occlusion, overbite and upper/lower tooth size discrepancies affect extraction decisions. 

Expansion versus extraction treatment decisions.  I probably get the most questions regarding the decision to expand the arches versus extract permanent teeth.  I'll limit the discussion here to children and adolescents.  Anatomical development finds the mandibular midline suture closed before one year of age while the maxillary midline suture can widened into the teens in many cases.  For this reason significant upper expansion is much more obtainable than the same procedure in the lower arch.  Thus, extraction decisions in many cases are made after carefully reviewing the amount of space needed in the mandibular dentition.  We have to look not only at the amount of crowding present but also the degree of overbite correction, class II or III correction and tooth uprighting necessary.  More on how I make these decisions next week.