Effect of continuous versus intermittent orthodontic forces on root resorption: A microcomputed tomography study

Area of Science:

• Orthodontics and Dental Research
• Biomaterials Science
• Periodontal Health

Background:

• Orthodontic treatment involves applying forces to move teeth, which can lead to root resorption.
• Continuous force application is common, but its impact on root resorption and tooth movement needs further investigation.
• Intermittent force application presents a potential alternative for managing root resorption during orthodontic therapy.

Purpose of the Study:

• To compare the extent of root resorption and tooth movement between continuous and intermittent orthodontic forces.
• To evaluate the efficacy of intermittent force application in mitigating root resorption during a simulated 4-week orthodontic adjustment period.

Main Methods:

• Twenty-five patients undergoing upper first premolar extraction were included.
• Continuous and intermittent (28 days on, 7 days off) buccally directed forces (150 g) were applied to contralateral premolars for 15 weeks.
• Root resorption was assessed volumetrically, and tooth movement (tipping, rotation) was measured from study models.

Main Results:

• Continuous force resulted in significantly higher root resorption volume compared to intermittent force (P < .05).
• Root resorption was more pronounced on buccal/lingual surfaces and the middle third of the root with continuous force (P < .05 and P < .01, respectively).
• Greater tipping and rotational movement were observed in the continuous force group.

Conclusions:

• Intermittent orthodontic force significantly reduces root resorption compared to continuous force within a 4-week orthodontic adjustment period.
• While intermittent force may result in slightly less tooth movement, it effectively avoids unwanted rotational movement.
• This intermittent regimen is advisable for patients susceptible to orthodontically induced inflammatory root resorption.