Effect of obturators on facial form following surgery for head and neck cancer and impact on the perception of appearance.

OBJECTIVES: To describe the correlation between changes in the surface area and depth of the face in individuals wearing an obturator compared with it not being in place, and self-reported Quality of Life in relation to appearance. METHODS: Difference images were created from stereophotogrammetry images recorded from research participants with and without their obturators in place. On the difference images of the face, surface areas and mean depths were calculated. Oral health impact profile questionnaires (OHIP-49) were completed. RESULTS: Data from 19 research participants were recorded. The mean size of the outlined area of the face when the obturators were present compared to when they were not was 1411 mm2 (SD ± 848). Similarly the mean depth differences ranged up to 6.14 mm. Although a proportion of the individuals reported effects in relation to their quality of life, there were no statistically significant relations between the surface areas and mean depths with the participants' responses to the quality of life questions. CONCLUSIONS: There are clear changes in facial tissues, both in relation to surface area and depths when obturators are worn compared to when they are not. There is no simple relationship between the extent of facial change with and without an obturator and quality of life around appearance. The determinants of changed quality of life in this group of patients require greater exploration.

A preliminary investigation into the use of denture adhesives combined with dietary advice to improve diets in complete denture wearers.

OBJECTIVES: To investigate how nutritional advice and denture adhesives may be associated with eating healthier foods. METHODS: 35 edentulous subjects (13 males and 22 females, mean age 73.9 years (55-84 years)), wearing complete dentures more than one year old, completed validated questionnaires analysing saturated fat, protein, Vitamin C, the number of servings of fruit/vegetables. In addition subjects completed the NDNS and OHIP Edent questionnaires. At baseline, nutritional information and the use of denture adhesive was provided. Subjects returned after 30 consecutive days and the questionnaires were repeated. A Wilcoxon signed rank test was used to test the effect of the denture adhesive on diet and on quality of life measures. RESULTS: The subjects increased mean intake from 2.2 portions of fruit/vegetables a day to 3.6. Fat and saturated fats were reduced from 23.2g to 11.3g and Vitamin C intake increased by 34.4mg. All were statistically significant (p<0.0001). There was a statistically significant improvement over the 30-day treatment period in subjects' ability as measured by using OHIP Edent scores to bite (p=0.017) and chew a range of foods (p=0.007). CONCLUSION: Within the confines of the study, use of simple dietary advice and denture adhesives improved diet. CLINICAL SIGNIFICANCE: The results of this pilot study suggest that denture fixatives may improve dietary behaviour of complete denture wearers.

The future of teaching of complete denture construction to undergraduates in the UK: is a replacement denture technique the answer?

Due to changes in the amount of curriculum time available for teaching complete denture construction to undergraduate students, course content requires reconsideration and possible modification. The idea that a replica complete denture technique may offer some advantages is explored. A review of the relevant literature fails to support many of the claimed benefits of this technique such as relative ease of adaptation by the elderly to new dentures. This article suggests that the replica denture technique should be considered as no more than an alternative method of making dentures. The relative demerits of the technique are discussed. A modification of the replica block technique to include important aspects of conventional complete denture courses is described. It is suggested that, because less clinical time is required, it may be a suitable way of introducing students to complete denture construction and educating them to a level which would encourage some to take further postgraduate study and would allow all graduates to treat routine cases or diagnose, treatment plan and refer to clinical dental technicians.

Prevalence of temporomandibular dysfunction in a group of scuba divers.

BACKGROUND: Temporomandibular dysfunction (TMD) has been reported to be a common problem in divers, with a prevalence of up to 68%. No evidence for this is available. OBJECTIVE: To investigate the prevalence of TMD in divers. METHOD: Sixty three subjects were asked to retrospectively complete a questionnaire on symptoms of TMD after diving in warm and cold water areas and in daily life. RESULTS: The prevalence of TMD was greater in female divers. The prevalence of TMD while diving was about 26%, comparable to that experienced in daily life. CONCLUSION: Improvements in mouthpiece design and lighter demand valves mean that TMD is now probably exacerbated by diving rather than caused by it.

Personality of dental students in two dental schools in the United Kingdom and in Ireland.

The personality characteristics of students from two dental schools, one in the United Kingdom which admitted students using interviews, and one in Ireland which accepted students solely on examination results, were assessed using the short form of the Eysenck Personality Questionnaire. Results were compared with norms for age and sex. Personality scores of students from the Irish dental school were not significantly different from normal scores. Female and male students from the United Kingdom school scored higher than would be expected on extraversion, and male students from the same school scored lower than would be expected on neuroticism. The differences in personality between the two schools may be explained by the different methods of admission.

Locking acrylic resin dental stent for image-guided surgery.

This article presents a procedure for fabricating a locking acrylic resin dental stent for use in image-guided base-of-skull surgery and neurosurgery. The stent offers advantages over conventional bone screw-anchored systems to surgeons and patients. In view of the increasing use of image guidance in base-of-skull surgery and neurosurgery, prosthodontists will meet a growing demand for this type of device in the future.

An investigation of factors influencing patients' use of new complete dentures using structural equation modelling techniques.

UNLABELLED: A review of the literature demonstrated that research had not identified a set of prognostic indicators for prospective complete denture patients, with different authors publishing contradictory results. OBJECTIVE: To investigate possible relationships between patient and clinical factors and denture wear and use of dentures for eating. METHODS: Patients attending Guy's Dental Hospital, London, for provision of complete dentures were recruited. For each patient relevant history was recorded and an examination of the edentulous mouth and existing dentures, where present, was undertaken at the beginning of treatment. At the first post-insertion appointment the edentulous mouth, previous and new dentures were examined. Three months after the review appointment patients were sent a postal questionnaire to assess patient use of dentures and patient satisfaction. Data were analysed using structural equation modelling techniques. RESULTS: 723 patients were recruited. Significant relationships were found between quality of complete dentures and patients' use of complete dentures and between quality of residual edentulous ridges and patients' use of complete dentures. These results contrast with most previous research into prognostic indicators for success in complete denture treatments. CONCLUSIONS: Quality of residual edentulous ridges and quality of new complete dentures predict patients' use of new complete dentures.

Measurement of misfit at the implant-prosthesis interface: an experimental method using a coordinate measuring machine.

Measurement of misfit at the implant-prosthesis interface is a difficult procedure. One factor common to all methods that attempt to measure 3-dimensional distortion to the micron level is the difficulty in providing verifiably consistent reference points between individual measurement sets. Consequently, the majority of studies use a relative distortion model in which the coordinate reference system is integral to the framework, thus limiting the value of the data gathered. In the method described, the datum plane and the coordinate reference system were set up external to the framework and could be re-established between measurement sets in a verifiable manner.

Design and evaluation of a system for microscope-assisted guided interventions (MAGI).

The problem of providing surgical navigation using image overlays on the operative scene can be split into four main tasks--calibration of the optical system; registration of preoperative images to the patient; system and patient tracking, and display using a suitable visualization scheme. To achieve a convincing result in the magnified microscope view a very high alignment accuracy is required. We have simulated an entire image overlay system to establish the most significant sources of error and improved each of the stages involved. The microscope calibration process has been automated. We have introduced bone-implanted markers for registration and incorporated a locking acrylic dental stent (LADS) for patient tracking. The LADS can also provide a less-invasive registration device with mean target error of 0.7 mm in volunteer experiments. These improvements have significantly increased the alignment accuracy of our overlays. Phantom accuracy is 0.3-0.5 mm and clinical overlay errors were 0.5-1.0 mm on the bone fiducials and 0.5-4 mm on target structures. We have improved the graphical representation of the stereo overlays. The resulting system provides three-dimensional surgical navigation for microscope-assisted guided interventions (MAGI).

Stereo augmented reality in the surgical microscope.

We present an augmented reality system that allows surgeons to view features from preoperative radiological images accurately overlaid in stereo in the optical path of a surgical microscope. The purpose of the system is to show the surgeon structures beneath the viewed surface in the correct 3-D position. The technical challenges are registration, tracking, calibration and visualisation. For patient registration, or alignment to preoperative images, we use bone-implanted markers and a dental splint is used for patient tracking. Both microscope and patient are tracked by an optical localiser. Calibration uses an accurately manufactured object with high contrast circular markers which are identified automatically. All ten camera parameters are modelled as a bivariate polynomial function of zoom and focus. The overall system has a theoretical overlay accuracy of better than 1 mm. Implementations of the system have been tested on seven patients. Recent measurements in the operating room conformed to our accuracy predictions. For visualisation the system has been implemented on a graphics workstation to enable high frame rates with a variety of rendering schemes. Several issues of 3-D depth perception remain unsolved, but early results suggest that perception of structures in the correct 3-D position beneath the viewed surface is possible.

Association between the accuracy of intermaxillary relations and complete denture usage.

STATEMENT OF PROBLEM: Previous studies have investigated possible associations between the accuracy of intermaxillary relations and complete denture usage with variable results. PURPOSE: This study investigated the association between the intermaxillary relations in new complete dentures and the use of these dentures for daily wear and eating. METHODS: A prospective study of patients (n = 523) attending Guy's Dental Hospital for complete dentures was undertaken. Patients were examined at the beginning of treatment and at the first post insertion visit. Rest vertical dimension and vertical dimension of occlusion were measured with a Willis gauge. Quality of registration of centric relation position was assessed and, 3 months later, a postal questionnaire was sent to investigate patients' use of dentures. Data were analyzed with Pearson's chi-squared test with exact nonparametric inference. RESULTS: Adequate interocclusal rest space was associated with daily wear of dentures (chi2 = 7.97, P =. 018). Quality of registration of centric relation was associated with daily wear (chi2 = 32.43, P <.001) and use of dentures for eating (chi2 = 20.23, P =.003). CONCLUSION: Positive associations were found between the accuracy of intermaxillary relations and complete denture usage.

Operator agreement in the use of a descriptive index of edentulous alveolar ridge form.

CAWOOD & HOWELL have proposed a classification of the anatomical form of the residual alveolar processes of edentulous patients. The purpose of this study was to test observer agreement in the clinical assessment of edentulous alveolar ridge form using this classification. This was tested in a pilot study involving 57 edentulous patients, and subsequently in a study of 557 edentulous patients. High levels of observer agreement were found when using this classification for upper and lower edentulous alveolar ridges, suggesting that the classification may be useful as a research tool.

Comparison of patients' appreciation of 500 complete dentures and clinical assessment of quality.

To compare patients' appreciation and clinical assessment of quality of complete dentures 500 patients attending a dental teaching hospital for provision of new complete dentures were recruited. In each case denture quality was assessed by an experienced prosthodontist using a validated classification of aspects of denture quality. Patients graded their appreciation of features of the dentures on a four point scale. Multiple correspondence analysis demonstrated close correspondence between dentist and patient appreciation of dentures when the dentures were rated as poor, but little or no correspondence when dentists or patients rated the dentures highly.

A system for microscope-assisted guided interventions.

We present a system for surgical navigation using stereo overlays in the operating microscope aligned to the operative scene. This augmented reality system provides 3D information about nearby structures and offers a significant advancement over pointer-based guidance, which provides only the location of one point and requires the surgeon to look away from the operative scene. With a previous version of this system, we demonstrated feasibility, but it became clear that to achieve convincing guidance through the magnified microscope view, a very high alignment accuracy was required. We have made progress with several aspects of the system, including automated calibration, error simulation, bone-implanted fiducials and a dental attachment for tracking. We have performed experiments to establish the visual display parameters required to perceive overlaid structures beneath the operative surface. Easy perception of real and virtual structures with the correct transparency has been demonstrated in a laboratory and through the microscope. The result is a system with a predicted accuracy of 0.9 mm and phantom errors of 0.5 mm. In clinical practice errors are 0.5-1.5 mm, rising to 2-4 mm when brain deformation occurs.

Operator agreement in the use of a descriptive index of complete denture quality.

BACKGROUND AND DESIGN: No generally accepted method for classification of clinical quality of complete dentures exists. While various methods have been proposed, little effort has been made to test observer agreement. The purpose of this study was to test observer agreement in the clinical assessment of complete denture quality using a systematic classification. RESULTS: Fifty seven (57) complete denture-wearing patients were examined on two occasions separated by two weeks. Observer agreement was measured using Cohen's? (kappa). High levels of observer agreement were found for upper and lower retention and stability and for quality of retruded jaw relationship. CONCLUSION: High levels of operator agreement were found for a method for classification of clinical quality of complete dentures suggesting that the classification may be useful as a research tool.

Factors associated with the presence of denture related stomatitis in complete denture wearers: a preliminary investigation.

Various factors have been associated with the presence of denture related stomatitis. These include local factors such as continuous denture wear, trauma from dentures and poor denture hygiene Systemic factors, use of various pharmacological agents and smoking have also been implicated. This investigation involved history taking and examination of 250 patients attending Guy's Hospital for the construction of complete dentures. No association was found between systemic factors, use of pharmacological agents or smoking and the presence of denture related stomatitis. Night wear of complete dentures was found to be significantly associated with the prevalence of denture related stomatitis.

A controlled clinical, electromyographic, and kinesiographic assessment of craniomandibular disorders in women.

Clinical, electromyographic, and kinesiographic methods were used to evaluate 35 female patients presenting with craniomandibular disorders. Twenty-six similarly aged, symptom-free women served as controls. Clinical assessments showed that the patients demonstrated a higher prevalence of bruxism than did the controls. Electromyographic results suggested that the rest activity of patients' elevators was significantly greater than that of the controls. Kinesiographic measurements showed that the patient group demonstrated greater vertical and anterior posterior movements from rest to centric occlusion than did the control group, and both the average and maximum opening velocities were smaller in patients than in controls.

Condylar position recorded using leaf gauges and specific closure forces.

Retruded interocclusal records were made for 40 subjects after deprogramming using leaf gauges and controlled incisal forces, which were exerted on a specially constructed occlusal force sensor. These records were used to assess the resulting displacements of the mandibular condyles from their positions in centric occlusion. The leaf gauges were found not to position the condyles inferiorly and posteriorly as has been previously reported.