Stability of a locking plate and self-drilling screws as orthodontic skeletal anchorage in the maxilla: a retrospective study.
OBJECTIVE
The aim of this retrospective study was to determine the success rate of an orthodontic skeletal anchorage system consisting of a locking plate and 2 self-drilling screws to intrude the upper molars and detect factors that contribute to its stability.


METHODS
The subjects were 32 orthodontic and generally healthy patients who had skeletal anchorage plates placed supraperiosteally and unilaterally or bilaterally. The anchorage plate was considered successful if the plate remained stable throughout the period of intrusion of the upper molar without any movement, persistent pain, or infection and was then retrieved without difficulty. The success rates of the anchorage plate were statistically analyzed on the basis of clinically categorized variables.


RESULTS
The 32 patients comprised 6 male and 26 female individuals with ages ranging from 11.4 to 35.1 years. The overall success rate of the total 61 plates was 93.4%. No significant differences were observed among the respective success rates analyzed in accordance with gender, age, side of placement, and length of the screws. The thickness of the bony walls that supported the screws was significantly greater in the success group (mean 1.6 +/- SD, 0.2 vs 1.0 +/- 0.1 mm, P < .001).


CONCLUSIONS
Bone thickness is a critical factor in supporting the self-drilling screws and locking plate. Skeletal anchorage combining the plate and 2 screws promises a higher success rate with a thicker bone than with the threshold value of thickness that exists within the 1.1 to 1.4 mm range in the maxillary walls.
Hibi
Hideharu
H
Department of Oral and Maxillofacial Surgery, Nagoya University, Graduate School of Medicine, Showa-ku, Nagoya, Japan. hibihi@med.nagoya-u.ac.jp
Sakai
Kiyoshi
K
Oda
Tomoo
T
Hattori
Hisashi
H
Ueda
Minoru
M
Sakai
Masaru
M
D000293:Adolescent; D000328:Adult; D015519:Bone Density; D001860:Bone Plates; D001863:Bone Screws; D002648:Child; D003799:Dental Stress Analysis; D005260:Female; D006801:Humans; D008297:Male; D008437:Maxilla; D008963:Molar; D024343:Open Bite / Q000628:therapy; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D012189:Retrospective Studies; D014087:Tooth Movement Techniques / Q000295:instrumentation*; D016896:Treatment Outcome; D055815:Young Adult