OBJECTIVETo study the post-operative pain-re1ated factors in lower third molar extraction, and to find an effective prevention program.

METHODSThe first phase of the study was a clinical follow-up of 450 cases of lower third molar extraction. Factors associated with post-operative pain were analyzed, and difficulty assessment protocol of the tooth extinction was build. On this hasis, a pain-prevention clinical plan was constitute, and implemented in the second phase of 450 cases (selectively systemic or local medication). Treatment effects were observed.

RESULTSThere were no significant differences between the two phase groups oh the distribution of ages, sex, difficulty of tooth extraction, operation time, and other related factors, means that they were statistically comparable. Tooth extraction difficulty and operation time were most important predictive factors for post-operative pain. Local infective factors (including caries) and women's menstrual cycle also account for late stage pain. Through targeted pre-operative medication or post-operative alveolar socket treatment, pain was significantly reduced or prevented.

CONCLUSIONReasonable peri-operative drug control basing on the difficulty assessment can provide a comprehensive and individualized control of pain after tooth extraction. Also, excessive or inappropriate using of drugs is largely avoided.