Survival analyses of surgical miniscrews as orthodontic anchorage.
BACKGROUND
The objectives of this study were to determine the survival rate of titanium surgical miniscrews and the clinical parameters that posed the highest risks for failure.


METHODS
Ninety-seven titanium surgical miniscrews (diameter, 1.2 mm; length, 8-12 mm) were placed in the maxilla of 49 patients, at either a high level (nonkeratinized area) or a medium level (mucogingival junction), with the 1-stage or the 2-stage surgical technique. Survival time, event of each screw (survival or failure), and 7 clinical parameters were gathered for survival analysis. Age and latency factors were analyzed with t tests.


RESULTS
The cumulative survival rates were 85% at 6 months and 57% at 1 year. The Kaplan-Meier log rank test indicated significant differences in 3 explanatory variables: surgical stage, level of placement, and tissue response. Cox proportional hazards regression indicated that the 2-stage surgical procedure had a higher risk than the 1 stage. Placement at the high level had a greater risk than placement at the medium level. Inflammatory hypertrophy tissue reaction showed a higher risk than normal or mild inflammation. The t test showed that age and latency period were not significant.


CONCLUSIONS
Titanium surgical miniscrews can be satisfactorily used as orthodontic anchorage. Controlling some aspects of the surgical protocol could reduce the failure rate.
Viwattanatipa
Nita
N
Department of Orthodontics, Faculty of Dentistry, Mahidol University, Bangkok, Thailand. Nitaviw@hotmail.com
Thanakitcharu
Sukalya
S
Uttraravichien
Akasith
A
Pitiphat
Waranuch
W
D000293:Adolescent; D000328:Adult; D001641:Bicuspid; D001672:Biocompatible Materials; D001863:Bone Screws; D003764:Dental Materials; D004868:Equipment Failure; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008311:Malocclusion, Angle Class I / Q000628:therapy; D008312:Malocclusion, Angle Class II / Q000628:therapy; D008422:Materials Testing; D008437:Maxilla / Q000601:surgery; D008875:Middle Aged; D008963:Molar; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation* / Q000379:methods; D009969:Orthodontic Wires; D012307:Risk Factors; D013524:Surgical Flaps; D016019:Survival Analysis; D014025:Titanium; D014087:Tooth Movement Techniques / Q000295:instrumentation / Q000379:methods; D055815:Young Adult
D001672:Biocompatible Materials; D003764:Dental Materials; D014025:Titanium