Neutral zone or conventional mandibular complete dentures: a randomised crossover trial comparing oral health-related quality of life.

There is widespread consensus that the neutral zone (NZ) concept contributes to improved stability for mandibular complete dentures (CDs). However, little is known about its impact on oral health-related quality of life (OHRQoL) of edentulous patients compared to conventionally (CV) manufactured dentures. In this prospective crossover trial, performed at the Oral Health Centre of the University of the Western Cape, CV and NZ mandibular dentures were made for each patient. Scores from the 20-item oral health impact profile (OHIP-20) for both types of dentures were compared with pre-treatment scores using paired t-tests. Treatment effect size (ES) was established. Associations of OHIP-20 scores and several patient variables (age, gender, period of edentulousness, quality of the denture-bearing tissue, denture dimensions, preference) were performed using the generalised linear model. Significance was set at P = 0·05. Records of thirty-five participants were included in the study (mean age of 62·3 years, range 47-85 years). There were highly significant differences between pre-treatment and both post-treatment OHIP-20 scores with t = 6·470 for CV and t = 6·713 for NZ. Treatment ES was large for both types of dentures (>0·8). Difference of ES between NZ and CV dentures was small (ES < 0·2). None of the patient variables showed significant associations with OHIP-20 scores of the two types of dentures, except for preference and NZ OHIP-20 scores. For this group of patients, both treatment methods improved OHRQoL significantly and patient-related factors did not influence impact on OHRQoL differently for both interventions.

Bonding of acrylic denture teeth to resin denture bases.

Anterior teeth debonding from dentures is a common problem. This study tested the bond strength of denture teeth to two types of denture resin, with and without grooving the ridge-lap surface. Bond strength and fracture type of three different groups were compared: 1. Teeth bonded to heat-cured polymethyl methacrylate (PMMA); 2. Teeth bonded to pour-type PMMA; 3. Grooved teeth bonded to pour-type PMMA. Specimens were manufactured following ISO standard 22112. Force values at failure were analysed using one-way analysis of variance, using the mixed procedure with confidence interval of 95%. Types of failure were identified as adhesive, cohesive or combination. In descending order, mean failure forces were 418.55N (Group One), 367.55N (Group Two) and 290.05N (Group Three). There was no significant difference between the means of groups 1 and 2 (p = 0.0627). Group Three differed from both other groups (p < 0.001). Groups One and Two showed predominantly cohesive fractures wthin denture teeth (83% and 72% respectively); group Three showed predominantly cohesive fractures within the denture PMMA (75%). Without ridge-lap modification, the bond strengths of denture teeth to pour-type and heat-cured denture resin were similar. Failures were predominantly of cohesive nature within the teeth themselves. Grooving the ridge-lap reduced fracture resistance and led to breakages predominantly in denture PMMA.

The influence of powder liquid ratio on the flexural strength of fibre reinforced acrylic resin material.

INTRODUCTION: Often the powder liquid (P/L) ratio of polymethyl methacrylate (PMMA) resins is changed to modify the handling properties of the material. While it is known that this may influence the mechanical properties of unreinforced PMMA resin, little is known about its effect on fibre reinforced resin. PURPOSE: The purpose of this study was to determine how different P/L ratios influence the flexural strength (FS) of a glass fibre reinforced autopolymerizing PMMA resin used for fabricating fixed partial dentures. METHODS: Two main groups of PMMA resin, 1 unreinforced and 1 reinforced with glass fibre, had 3 subgroups (n=21) each representing a different P/L ratio. The manufacturer's recommended ratio served as control. The specimens were prepared for a 3-point bending test. Using a universal testing machine, maximum force was recorded and the FS was calculated. Median FS values were compared by means of non-parametric analysis of variance (Kruskal-Wallis). A p-value of less than 0.05 was considered significant. RESULTS: FS values of all reinforced subgroups were significantly higher than the values of the unreinforced subgroups (p<0.05). Among the 3 unreinforced subgroups the difference in FS was insignificant (p>0.05). Within the reinforced group there was a significant difference between the control group, which had a higher median FS value than the two other subgroups (p<0.05). CONCLUSION: When reinforcing PMMA resin with glass fibre, it is important to use the recommended P/L ratio. For unreinforced PMMA resin the P/L ratio can be changed within limits without adverse effects on the FS.

Effect of an antifungal denture liner on the saliva yeast count in patients with denture stomatitis: a pilot study.

Although in vitro studies on the release of antifungal agents from tissue conditioners have been done, no in vivo research on the topic could be found. The purpose of this study was to determine the in vivo effect of an antifungal agent released from a tissue conditioner on the salivary yeast count. Forty edentulous patients with denture stomatitis caused by Candida albicans were divided in two groups. Group 1 (control) was treated with a tissue conditioner only. Group 2 was treated with a tissue conditioner incorporating 500,000 U nystatin. Oral rinses were performed by both groups before treatment and every second day during treatment for a period of 14 days. Total yeast counts of the oral rinses were performed and the averages and standard deviations for both groups calculated and logarithm-transformed data of the counts over time were statistically analysed using the Wilcoxon signed-rank test. The average oral rinse yeast count of the control group decreased up to day 4. Thereafter, the count increased till the end of the test period. At day 14, the oral rinse yeast level was higher than the pre-treatment level. The average yeast count of the test group decreased up to day 7. Thereafter, the count increased but remained significantly lower (P=0.01) than the control group and did not return to its pre-treatment level. A nystatin-containing short-term denture liner significantly decreases the salivary yeast count of patients with denture stomatitis compared with a liner without nystatin.

The use of light-cured acrylic resin for custom trays by undergraduate dental students: a survey.

INTRODUCTION: It is unknown how the use of a light-cured acrylic resin is appreciated over the traditional chemically cured resins for the construction of custom trays in a teaching environment. OBJECTIVE: To evaluate the acceptance of light-cured acrylic resin for custom trays by dental students. METHOD: A questionnaire addressing the use and handling properties of both light-cured (Megatray, Megadent, Germany) and chemically-cured (Excel, Wright Health Group, UK) custom tray materials was distributed amongst undergraduate dental students of the University of the Western Cape. RESULTS: Of a total of 196 dental students, 38 were absent on the day of the survey. Of the 158 questionnaires that were distributed and returned, 18 did not meet the inclusion criteria and 1 person chose not to participate. Of the 139 participating students, 98 were in 4th year, 41 in 5th year. With regards to the light-cured acrylic custom tray material, 77% used it most often, 64% said it saved time and 62 % said that it was easier to handle. Fifty two percent indicated that both types of materials should be taught in undergraduate training, 26% preferred the light-cured acrylic resin custom tray material, 20% suggested that only the light-cured resin be used and no one suggested the chemically-cured resin exclusively. CONCLUSIONS: Most undergraduate students positively accepted the light-cured resin, but training in the use of both materials was recommended.

The impact of new complete dentures on oral health-related quality of life.

OBJECTIVE: To investigate the relationship between complete dentures and oral health-related quality of life (OHRQoL). METHOD: Seventy-six patients were conveniently selected from the waiting list for complete dentures. At the first visit (pre-treatment) the patients were interviewed using the Oral Health Impact Profile for Edentulous Patients (OHIP-EDENT). Sixty-three of these patients were interviewed telephonically 2 to 3 months after receiving their new complete dentures (post-treatment). RESULTS: Mean domain scores were significantly lower post-treatment for psychological discomfort and disability, social disability and handicap. CONCLUSION: This study shows that after the provision of a new set of complete dentures the OHRQoL of patients improved significantly on four of the seven domains for the first 2 to 3 months post-insertion.

Aesthetic clasp design for removable partial dentures: a literature review.

Removable partial dentures (RPD) are an effective and affordable treatment option for partial edentulism. If the main reason for seeking treatment is the need for improved aesthetics, treatment should be geared towards achieving this goal. This article is the result of a literature study on aesthetic clasp design for the conventional RPD. In this context, the position of the clasp on the tooth, clasp types, clasp material and alternative methods of retention are reviewed. Although published in reputable journals, the authors report that many articles published on this subject are of a descriptive nature and lack scientific evidence. Therefore, clinicians are encouraged to be critical in their interpretation of literature and the application of published information in their clinical practices.

A comparison of the accuracy of two methods used by pre-doctoral students to measure vertical dimension.

STATEMENT OF PROBLEM: Measuring vertical dimension is a soft-tissue measurement. Therefore, inaccuracy may occur. PURPOSE: The purpose of this study is to compare the accuracy of the Willis gauge method with the caliper method. MATERIALS AND METHODS: The Willis gauge measures the distance between the septum of the nose and the chin. The caliper method measures the distance between reference points on the tip of the nose and the chin. Twenty predoctoral students applied both methods 10 times in measuring the rest vertical dimension (RVD) and the occlusal vertical dimension (OVD) of a single edentulous patient. The measurements obtained from one experienced clinician were selected as controls for the interocclusal distances (IOD) for the Willis and the caliper methods, respectively. One-sided t tests and a 1-sided nonparametric test were used to determine significant differences between the 2 methods (alpha=.05). RESULTS: The variances in the RVD values for the Willis gauge method were higher than for the caliper method for most students. A Wilcoxon signed rank test showed that the accuracy of the OVD measurements for the caliper method was significantly better than for the Willis gauge method (P=.001). This was not the case for the RVD measurements (P=.073). The average IOD for the Willis method was significantly higher than the control IOD (P=.026). The average IOD for the caliper method was not significantly larger than the control (P=.1303). CONCLUSION: This study showed that the use of the caliper method by predoctoral students was a significantly more reliable method of measuring the OVD for the patient evaluated.

[Lingualized occlusion in the South African context]. / Gelingualiseerde okklusie in die Suid-Afrikaanse konteks.

The search for the ideal artificial tooth arrangement that maximizes denture stability, comfort, aesthetics, and function has occupied the dental literature for many years and still continues to do so. Of the many occlusal schemes that have been presented to the dental profession, that of lingualized occlusion has emerged as one of the more popular. The popularity of lingualized occlusion stems from the simplicity and flexibility of the concept and from its wide application to clinical practice (Parr & Ivanhoe, 1996). The registration of a repeatable correct centric jaw relation is not always possible. We don't know whether the patient will use centric relation during normal function. It is therefore useful to provide the patient with some freedom of movement around centric. lingualized occlusion provides freedom in centric. For many dentists the arrangement of artificial denture teeth into balanced occlusion is difficult and time consuming. As a result this task is most often performed by the dental technician. In the South African countryside dental laboratories are often far away. If dentists perform the arrangement of the denture teeth, time and costs can be saved. The mounting of denture teeth in lingualized occlusion is simple and fast. This will motivate dentists to arrange denture teeth themselves, with obvious benefits for both the patient and the dentist. The School of Oral Health Sciences of the University of Stellenbosch teaches this concept to its undergraduate students in order to improve the prosthetic service to the large edentulous population of South Africa.