Bramante M A
Graduate School of Orthodontics, Columbia University School of Dentistry, New York, New York.
Dent Clin North Am. 1990 Jan;34(1):91-102.
Three controversial interrelated aspects of orthodontics have been reviewed: retention, the effect of third molars on lower anterior crowding, and extraction and nonextraction orthodontic treatment. Recent studies have shown that unacceptable lower anterior crowding occurs in 90 per cent of well-treated extraction cases. The implication is that nonextraction cases should be 90 per cent or higher. In view of our present general inability to identify the 10 per cent that will remain acceptable, some form of indefinite retention is advised. A literature review of the effect of third molars on lower anterior crowding finds strong opinions on both sides of the issue. Similar studies often show dissimilar conclusions, particularly when observing cases of third molar extraction or agenesis. Certainly the problem is multifactorial; however, the vast bulk of the evidence indicates that the third molars play an insignificant role in lower anterior crowding. Extraction of teeth for orthodontic treatment prior to 1900 was prevalent and indiscriminate. From the turn of the century to the mid-thirties Angle moved the specialty away from extractions to a relatively rigid nonextraction treatment philosophy. Dissatisified with relapsing Class II cases, recurrence and aggravation of crowding, and what he felt were bimaxillary full faces, Tweed and others, circa 1935, redirected the profession back to extractions with a more disciplined approach to treatment by the removal of four first premolars. Fifty years later we have found that extraction treatment and uprighting lower incisors does not prevent long-term postretention crowding and that flattened profiles are not always esthetically desirable. Earlier treatment of maxillomandibular basal discrepancies by old and new treatment philosophies and mechanics have produced more stable nonextraction corrections. Better control of leeway space and a reduction in caries has helped reduce the amount of lower anterior flaring that was seen in the nonextraction cases in the first third of the century. These reasons have moved the specialty of orthodontics to a mixed but more nonextraction-oriented approach to treatment.
保持、第三磨牙对下前牙拥挤的影响以及拔牙和不拔牙正畸治疗。最近的研究表明，在90%治疗良好的拔牙病例中会出现难以接受的下前牙拥挤。这意味着不拔牙病例应占90%或更高。鉴于我们目前普遍无法识别出仍可接受的10%的病例，建议采用某种形式的无限期保持。一项关于第三磨牙对下前牙拥挤影响的文献综述发现，在这个问题上双方都有强烈的观点。类似的研究往往得出不同的结论，尤其是在观察第三磨牙拔除或缺失的病例时。当然，这个问题是多因素的；然而，大量证据表明第三磨牙在下前牙拥挤中起的作用微不足道。1900年以前，正畸治疗拔牙很普遍且随意。从世纪之交到20世纪30年代中期，安格尔将该专业从拔牙转向相对严格的不拔牙治疗理念。大约在1935年，由于对II类病例复发、拥挤的复发和加重以及他所认为的双颌丰满面容不满意，特威德等人将该专业重新转向拔牙，采用更严谨的治疗方法，拔除四颗第一前磨牙。五十年后，我们发现拔牙治疗和直立下切牙并不能防止长期保持后出现拥挤，而且扁平的侧貌并不总是美观的。通过新旧治疗理念和技术对上下颌基骨差异进行早期治疗，已经产生了更稳定的不拔牙矫治效果。对替牙间隙的更好控制和龋齿的减少，有助于减少20世纪前三分之一不拔牙病例中出现的下前牙唇倾程度。这些原因使正畸专业转向了一种混合但更倾向于不拔牙的治疗方法。
