Porzier J, Benner-Jordan L, Bourdeau B, Losfeld R
Faculté de Chirurgie Dentaire de Paris VII.
Cah Prothese. 1991 Mar(73):6-20.
Although we know that the most favourable situation for preparations margins is above gingiva, it has been proven that in numerous clinical cases, this situation is modified in an apical direction and becomes subgingival. This location of the margins then becomes unfavourable from a periodontal point of view as well as in the control of adaptation. However, the major problem arises when the impression is taken. In fact, the marginal gingiva constitutes an obstacle to the access of the impression material to these margins. Nevertheless, numerous techniques allow the free marginal gingiva to be retracted under such conditions that the principal aim can be reached without injuring the conjunctive epithelio-connection. The procedures used to retract the gingiva are either mechanical, chemico-mechanical or surgical. The mechanical techniques may use copper bands and ring collars, the latter being the procedure of choice when indicated. Another technique uses retraction cords, providing a gingival sulcus enlargement without using impregnated cords with haemostatic or astringent solutions. This last technique, nonetheless, must be avoided if there is a risk that might lead to bleeding when the cord is removed. The second retraction technique uses these same cords impregnated with haemostatic or astringent solutions. It seems that 15.5% ferric sulfate impregnated braided cords represent the procedure of choice, allowing both the retraction of the sulcus and the total absence of bleeding, since haemostasis is ensured definitively via the situ application of the pure product. The final technique is the gingival surgery. It may use Ingraham's diamonds that simultaneously finish the subgingival preparation margins and make a superficial epithelium curettage. Following this surgical retraction, haemostasis is ensured, but the rotative instrument used provides, at once, the best profile of the internal wall of the free marginal gingiva for the impression. The second procedure is electro-surgery which provides constant results when use, thereof, is well indicated. Finally, the CO2 laser can also provide another possibility for surgical retraction. Nonetheless, it seems that the CO2 laser is not the best procedure, given the difficulties in directing it. Depending on the case, all these techniques allow the expected results to be obtained, but, unfortunately, their innocuity is not absolute. In fact, it is proven that following any type of gingival retraction, a lesion is caused both by the practitioner and the equipment used, which thus, leads to a loss of about 1/10th millimeter in the height of the free marginal gingiva.
虽然我们知道对于预备边缘而言，最有利的情况是位于龈上，但已证实，在众多临床病例中，这种情况会向根尖方向改变并变为龈下。从牙周角度以及在边缘适应性控制方面来看，边缘的这种位置随后就变得不利了。然而，在取印模时会出现主要问题。实际上，边缘龈会阻碍印模材料进入这些边缘。尽管如此，有许多技术可使游离边缘龈在能达到主要目的且不损伤结合上皮连接的条件下退缩。用于使龈退缩的方法有机械法、化学 - 机械法或手术法。机械技术可使用铜带和环形圈，后者在有指征时是首选方法。另一种技术使用退缩线，能在不使用浸有止血或收敛溶液的线的情况下扩大龈沟。然而，如果存在去除线时可能导致出血的风险，就必须避免使用这最后一种技术。第二种退缩技术使用浸有止血或收敛溶液的同样的线。似乎浸有15.5%硫酸铁的编织线是首选方法，它既能使龈沟退缩又能完全不出血，因为通过现场应用纯产品能确保确切止血。最后一种技术是牙龈手术。它可使用英格拉姆钻针，能同时完成龈下预备边缘并进行浅表层上皮刮治。在这种手术退缩后能确保止血，而且所使用的旋转器械能同时为印模提供游离边缘龈内壁的最佳形态。第二种方法是电外科手术，当使用指征明确时能提供稳定的效果。最后，二氧化碳激光也可为手术退缩提供另一种可能性。然而，鉴于其操作难度，二氧化碳激光似乎并非最佳方法。根据具体情况，所有这些技术都能获得预期效果，但不幸的是，它们的安全性并非绝对。实际上，已证实，在进行任何类型的牙龈退缩后，术者和所使用的设备都会造成损害，从而导致游离边缘龈高度损失约十分之一毫米。
