The extent of root resorption and tooth movement following the application of ascending and descending magnetic forces: a prospective split mouth, microcomputed-tomography study.
OBJECTIVE
Various factors have been examined in the literature in an attempt to reduce the incidence and severity of root resorption. The purpose of the present investigation is to test the null hypothesis that there is no difference in relation to force level using gradually increasing (ascending) and decreasing (descending) orthodontic force generated by magnets on the severity of Orthodontically Induced Inflammatory Iatrogenic Root Resorption (OIIRR) and amount of tooth movement.


METHODS
Twenty maxillary first premolars from 10 patients were subjected to ascending (25-225 g, magnets in attraction) and descending (225 to 25 g, magnets in repulsion) buccal forces using a split mouth design over an 8-week period. Polyvinyl siloxane impressions were taken at week 0, 4, and 8 to record the tooth movement. After 8 weeks, the teeth were extracted, scanned, with micro-CT in 16.9 µm resolution, and the root resorption craters were localized circumferentially and quantified at each level of the root.


RESULTS
The total volume of OIIRR with ascending force was 1.20 mm3, and with descending force was 1.25 mm3, and there was no statistically significant difference between them. OIIRR on the palatal surface (0.012 mm3) was significantly less than on the buccal surface (0.057 mm3) and than on the mesial surface (0.035 mm3). There is no statistically significant difference in the degree of OIIRR between different level of the root (cervical, middle, and apical) at different surfaces. Moreover, the amount of tooth movement, at 0-, 4-, and 8-week interval, secondary to an ascending and descending force application was not statistically significant.


CONCLUSIONS
There is no short-term (8 weeks) statistically significant difference between orthodontic ascending and descending forces, from 25 to 225 g and from 225 to 25 g, respectively, in term of severity and location of OIIRR as well as the amount of tooth movement. The buccal surface of the root showed highest degree of OIIRR compared to other root's surfaces.
Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Australia.
Tiffany Teen Yu
TTY
Huang
Department of Orthodontics, Faculty of Dentistry, Ondokuz Mayis University, Samsun, Turkey.
Selma
S
Elekdag-Turk
Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Australia.
Oyku
O
Dalci
Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Australia.|Department of Orthodontics, John Radcliffe Hospitals, Oxford University Hospitals, Oxford, UK.|Department of Orthodontics, Eastman Dental Institute, London, UK.
Mohammed
M
Almuzian
Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Australia.|Department of Orthodontics, Faculty of Dentistry, Karadeniz Technical University, Trabzon, Turkey.
Ersan Ilsay
EI
Karadeniz
Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Australia.
Carmen
C
Gonzales
Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Australia.|Department of Statistics, Macquarie University, Sydney, Australia.
Peter
P
Petocz
Department of Orthodontics, Faculty of Dentistry, Ondokuz Mayis University, Samsun, Turkey.
Tamer
T
Turk
Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Australia.
M Ali
MA
Darendeliler
D000293:Adolescent; D001641:Bicuspid / Q000000981:diagnostic imaging / Q000503:physiopathology; D005260:Female; D006801:Humans; D055909:Magnetic Field Therapy / Q000009:adverse effects* / Q000379:methods; D008297:Male; D011446:Prospective Studies; D012391:Root Resorption / Q000000981:diagnostic imaging / Q000209:etiology*; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000009:adverse effects* / Q000379:methods; D014092:Tooth Root / Q000000981:diagnostic imaging; D055114:X-Ray Microtomography / Q000379:methods