[The modified lip-tooth-ridge classification: a guide for edentulous maxillary arches]

Abstract

According to the width and height of the maxillary alveolar ridge, the maxillary edentulous jaws can be divided into three categories by using modified lip-tooth-ridge (MLTR) classification. Class Ⅰ is characterized by sufficient bone available for implants in the vertical and horizontal aspects and is suitable for fixed implant-supported prostheses. Class Ⅱ is characterized by sufficient bone amount available for implants in a horizontal aspect but insufficient for lip support and is suitable for a fixed detachable implant-supported prosthesis. Class Ⅲ is characterized by inadequate amount of bone for implants (with vertical or horizontal components) and is suitable for the use of zygomatic implants or traditional complete denture. Patients belonging to Class Ⅰ can be further classified into two sub-categories according to the height of the alveolar ridge. The first subclass is characterized by minimal bone deficiency and is suitable for a conventional implant-supported "crown and bridge" prosthesis. The second subclass is characterized by a larger vertical deficiency than that of the first subclass and is suitable for implant-supported hybrid prosthesis. The MLTR classification system can help the dentist to determine whether the patient is suitable for implanting dentures and whether fixed denture or removable denture is appropriate for the patient, select indications, reduce complications, and achieve long-term results.

Keywords: classification; implant-supported prosthesis; maxillary edentulous.

图 1. 上颌无牙颌MLTR分类，3个主分类及2个亚类的示意图

Fig 1 The MLTR classification of the maxillary edentulous, the sketch maps of the three main categories and two sub-categories A：MLTR-Ⅰ类1亚类；B：MLTR-Ⅰ类2亚类；C：MLTR-Ⅱ类；D：MLTR-Ⅲ类。

图 2. MLTR-Ⅰ类1亚类，冠桥式种植义齿修复

Fig 2 The classification MLTR-Ⅰ, sub-categories 1, and the implant-supported “crown and bridge” prosthesis

图 3. MLTR-Ⅰ类2亚类，复合式种植义齿修复

Fig 3 The classification MLTR-Ⅰ, sub-categories 2, and the implant-supported hybrid prostheses

图 4. MLTR-Ⅱ类可以通过植骨或者降低骨高度转化为MLTR-Ⅰ类

Fig 4 The MLTR-Ⅱ classification could transfer to MLTR-Ⅰ by the alveolar bone augmentation or removal

图 5. 种植固定可摘义齿联合修复，带有4个Locator的覆盖义齿

Fig 5 A fixed detachable implant-supported prosthesis: the overdenture with 4 Locators 上：覆盖义齿戴入前；下：覆盖义齿戴入后。

图 6. 患者治疗前口内观

Fig 6 The patients' intraoral view before treatment 左：上颌；右：下颌。

图 7. 制取印模，确定颌位关系及唇丰满度

Fig 7 Making the impression, determine the relationship of the jaws and the convexity of the lip A：常规制取上下颌全口印模，灌制模型；B：常规制作暂基托蜡堤确定颌位关系，并尽可能降低唇侧基托高度；C：利用标记物标记切缘、龈缘、笑线等位置；D：利用标记物标记拟植入种植体的位置。

图 8. 确定颌位关系时患者正面观（左）和侧面观（右）

Fig 8 Patients' front view (left) and side view (right) when determining the relationship of jaws

图 9. 以CBCT影像12牙位颊舌向横断面为例，可以看到笑线、穿龈位置、牙槽骨宽度和高度等信息

Fig 9 As an example, from the cross section of the cheek and tongue of the 12 teeth in the CBCT image, the smile line, gum position, width and height of alveolar bone could be seen

图 10. 6枚种植体植入上颌完成即刻修复及最终修复

Fig 10 Six implants had been put into the upper jaw and the temporary and final prostheses had been finished A：上颌植入6枚种植体；B：戴入上颌临时修复体；C：戴入正式修复体；D：戴入临时修复体后曲面断层片；E：戴入正式修复体后曲面断层片。

图 11. 戴入正式修复体后正面观（左）及侧面观（右）

Fig 11 The front view (left) and side view (right) with the final prostheses