Korean J Orthod.  2018 Sep;48(5):339-345. 10.4041/kjod.2018.48.5.339.

Effects of continuous force application for extrusive tipping movement on periapical root resorption in the rat mandibular first molar

Affiliations
  • 1Department of Orthodontic Science, Division of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan. y.matsumoto.orts@tmd.ac.jp
  • 2Private Practice, Bangkok, Thailand.

Abstract


OBJECTIVE
The purpose of this study was to clarify the effects of continuous force application for extrusive tipping movement and occlusal interference on periapical root resorption in the rat mandibular first molar.
METHODS
We constructed an appliance comprising a titanium screw implant with a cobalt-chromium post as the anchorage unit and a nickel-titanium closed coil spring (50 cN) as the active unit. Force was applied on the mandibular left first molar of rats for 8 (n = 10) and 15 days (n = 10; experimental groups), with the tooth in occlusion. Five rats were included as a non-treated control group to examine the body effect of the appliance. Active root resorption lacunae, identified using tartrate-resistant acid phosphatase, were evaluated in terms of the length, depth, and area.
RESULTS
The rat mandibular first molars were mesially tipped and extruded in the occlusal direction. This mesio-occlusal tipping movement and occlusion resulted in the formation of a compression zone and active root resorption lacunae in the distoapical third of the distal roots. However, there was no significant difference in the amount of root resorption between the two experimental groups. The control group did not exhibit any active root resorption lacunae.
CONCLUSIONS
Periapical root resorption was induced by continuous extrusive tipping force and occlusal interference in rat mandibular molars. These data suggest that we orthodontists had better take care not to induce occlusal interference during our orthodontic treatment.

Keyword

Apical root resorption; Tooth movement; Mechanical stimuli; Rat mandibular molar

MeSH Terms

Acid Phosphatase
Animals
Molar*
Orthodontists
Rats*
Root Resorption*
Titanium
Tooth
Tooth Movement
Acid Phosphatase
Titanium
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