Canine root/cortical bone relation (CRCR) and the orthodontic tooth movement

Area of Science:

• Orthodontics
• Dental Anatomy
• Biophysics

Background:

• Orthodontic canine retraction is a common procedure.
• Understanding root and bone interactions is crucial for predictable tooth movement.
• Labial cortical bone thickness can influence orthodontic outcomes.

Purpose of the Study:

• To three-dimensionally evaluate the relationship between maxillary canine roots and the overlying labial cortical bone during orthodontic retraction.
• To assess the incidence of root contact and fenestration of the cortical bone.
• To investigate the potential impact of this relationship on canine retraction speed.

Main Methods:

• Observational study of 84 maxillary canines in 42 patients undergoing orthodontic retraction.
• Three-dimensional evaluation of canine cusp tip, root apex, and overlying cortical bone using the Classification of Root/Cortical bone relation (CRCR) before and after retraction.
• Use of conventional orthodontic NiTi retraction springs delivering 150gm force.

Main Results:

• Mean distal movement of the canine cusp tip was 3.78 mm; root apex movement was minimal.
• 5.4% of roots remained in medullary bone, 16.1% contacted cortical bone.
• Cortical bone fenestration by canine roots or apices occurred in 78.6% of cases.

Conclusions:

• Maxillary canine roots frequently fenestrate the labial cortical bone during retraction.
• Close proximity and density of the labial cortical bone may decelerate canine retraction.
• The natural bone plate resists displacement, potentially hindering orthodontic biomechanics.