The effects of extracting upper second permanent molars on lower second permanent molar position

Area of Science:

• Dentistry
• Orthodontics
• Dental Morphology

Background:

• Controversy exists regarding the effect of upper second permanent molar extraction on unopposed lower second permanent molar eruption.
• Over-eruption of lower molars can lead to occlusal problems and affect orthodontic outcomes.

Purpose of the Study:

• To investigate and quantify the over-eruption of unopposed lower second permanent molars following the extraction of upper second permanent molars during orthodontic treatment.
• To compare the degree of over-eruption in an experimental group with a control group matched for age and sex.

Main Methods:

• A comparative study design was employed, with an experimental group (upper second molar extraction) and a matched control group.
• Objective assessment of vertical tooth positions using study models and a travelling microscope.
• Measurements focused on the distal aspect of the lower second permanent molar relative to controls.

Main Results:

• Statistically significant over-eruption of the lower second permanent molar was observed in the experimental group compared to the control group (P < 0.001 right, P < 0.05 left).
• The mesial aspect of over-eruption was influenced by the upper first permanent molar's position, but the distal aspect was not.
• Upper third molar eruption did not significantly affect lower second molar over-eruption, though they often erupted unfavorably.

Conclusions:

• Extraction of upper second permanent molars in orthodontic treatment is associated with significant over-eruption of the unopposed lower second permanent molars.
• The findings highlight potential complications of this orthodontic extraction pattern that require careful consideration.
• Further research may explore preventative or management strategies for this phenomenon.