The application of the neutral zone technique in complete dentures with a lingualized occlusion in edentulous patients : a comparative analysis

Abstract

Purpose and Aim of the study: Wearing complete dentures reduces the masticatory efficiency of patients. This reduction is directly related to the lack of stability and retention of the prosthesis caused by the progressive resorption of the residual alveolar bone causing a shift in the position of the ridge on which the prosthesis rests on. This occurrence is typically exhibited in patients who have been edentulous for many years. To aid this issue, a specialized technique may be used to construct the mandibular denture which aims to improve and restore to a certain degree the masticatory function. This technique is called the neutral zone technique. Accompanying this method of construction, lingualized occlusion is used for the setting-up of the posterior teeth, theoretically suggesting improved results pertaining to comfort in patients with significant ridge resorption. Therefore, the aim of this study was to check if there is a significant difference in patient’s quality of life, denture satisfaction and masticatory efficiency between dentures constructed using the neutral zone technique and the conventionally constructed dentures. Materials and methods: In this cross over study, edentulous patients, the majority wearing complete denture prostheses, were recruited. They were each given a set of lingualized occlusion complete dentures, and an additional mandibular denture fabricated using either the neutral zone technique or conventional denture setup. The patients were asked to wear one mandibular denture with the maxillary denture for two weeks, followed by another two weeks of wearing the other mandibular denture with the same maxillary denture. For the subsequent two months, the patients were allowed to use whichever lower denture they wanted. They were then asked to identify their lower denture of choice. At the first appointment (baseline), those patients having previous dentures were given the questionnaires (OHIP-14 and DSQ) to answer. The questionnaires were given to all the patients again two weeks after each insertion appointment, and at the two months post-insertion appointment. The patients were observed for a minimum of two months. Results: A total of 26 patients (mean age: 72.3 - 8.5 years; 50% men, and 50% women; n= 13 per group) were analyzed. Between group comparisons were conducted using the Mann-Whitney U test for independent variables, and the Wilcoxon Signed Rank test for dependent variables. Friedman’s test was used to compare mean ranks within groups across time. A significant difference was noted in satisfaction with quality of life in all patients between two months and six months post-insertion (p=0.046, Wilcoxon Signed Rank Test). There was a significant difference in quality of life within the group of patients who chose the conventional denture (p=0.029, Friedman’s Test). Significant differences were registered for denture satisfaction between the groups between baseline and the scheduled time points (p<0.05, Wilcoxon Signed Rank Test). Significant differences were also found for the total satisfaction (p=0.030, Mann-Whitney U test), maxillary satisfaction (p=0.043, Mann-Whitney U test), and functional satisfaction (p=0.050, Mann-Whitney U test) between the type of lower denture groups once they chose their preferred lower denture. Finally, there was a significant difference in maxillary (p=0.029, Friedman’s Test) and functional (p=0.035, Friedman’s Test) denture satisfaction within the group of patients who chose the neutral zone technique denture. Conclusion: Within limits of the study, it can be suggested that patients did not perceive any difference between dentures constructed using the conventional method and the neutral zone technique.