Do Tooth Loss and Dentures Cause Body Image Disturbance?

PURPOSE

To investigate the psychologic morbidities associated with tooth loss despite treatment with technically successful dentures.

MATERIALS AND METHODS

This cross-sectional questionnaire-based study compared the psychologic disturbance and functional difficulties in two groups: individuals with tooth loss who wore optimal-quality removable dentures (test group), and individuals with tooth loss who did not wear dentures (control group). The questionnaire used was developed and validated previously. The short-form revised Eysenck personality questionnaire was also used to assess the relationship with personality traits. A total of 138 participants were recruited (denture group = 70; control group = 68).

RESULTS

There was a significant difference in body image dissatisfaction between the groups (χ² = 7.72, P value = .005). The denture group had 5.75-times higher probability than the control group of suffering from body image disturbance. Older patients were predicted to have 75% less probability of body image disturbance (OR = 0.25), and men were predicted to have up to 70% less disturbance (OR = 0.3). As for psychologic morbidities, participants in both groups presented with somatic symptoms related to depression or anxiety, which were nearly double that expected in the general population (15.7% and 7.8%, respectively). Furthermore, participants who complained about body image impairment were more likely to have higher scores on the neuroticism scale (OR = 3.64).

CONCLUSION

Tooth loss and dentures could be associated with body image dissatisfaction and psychologic morbidity. Planning for patient-centered care is paramount prior to extracting any teeth and providing replacement options.

Dentists' perspectives on denture provision after radiotherapy for head and neck cancer: an exploratory study using the theoretical domains framework

Introduction Patients are often keen to replace their missing teeth after radiotherapy for head and neck cancer (HNC), yet such replacement does not always take place.Aims This study aimed to investigate the influences on dentists' provision of dentures for patients treated with radiotherapy for HNC, including whether risk of osteoradionecrosis (ORN) is a factor influencing intention to provide dentures.Methods An online cross-sectional survey including a case scenario, self-reported behaviour and measures of factors (selected using the theoretical domains framework) that may affect dentists' decisions was completed by general dental practitioners (n = 150) and HNC multidisciplinary team dentists (n = 25) in England.Results Dentists' reluctance to provide dentures for HNC patients post-radiotherapy was often due to concerns about dry mouth and radiation caries rather than risk of ORN. Knowledge of guidelines and beliefs about consequences were independently associated with dentists' intention to replace missing teeth with dentures.Conclusion The likelihood of replacing missing teeth with dentures increased with awareness of clinical guidance on the use of dentures in HNC and that denture provision would have positive consequences that outweigh the costs.

Use of dentures, receipt of information, quality of life, and oral function following radiotherapy for head and neck cancer

BACKGROUND

Teeth with a poor prognosis are often extracted prior to radiotherapy for head and neck cancer (HNC) in order to help prevent the need for dental treatment after radiotherapy that might in turn lead to the development of osteoradionecrosis. However, the details and impact of replacing missing teeth after radiotherapy for HNC have received little attention, especially from the patients' perspective.

AIMS

This study aimed to assess the use, satisfaction, and impact of denture use following radiotherapy for HNC. The study also sought to determine patients' satisfaction with information about replacing their missing teeth postradiotherapy. Finally, this study also aimed to assess interest in replacing missing teeth for those who had not done so.

METHODS

A structured, validated, and reliable questionnaire was sent to HNC patients who had received radiotherapy and had missing teeth at the time of discharge. In addition to demographic details and self-reported oral hygiene, the questionnaire included questions on use of (or interest in) dentures, satisfaction with dentures, satisfaction with information about replacing missing teeth, QoL as measured by two questions from the short version of WHOQoL-BREF, and oral functioning as measured by BCSQ-H&N. Demographic details and clinical details were extracted from the hospital records.

RESULTS

N = 80 (24%) returned a completed questionnaire. Participants had an average of 12 missing teeth (SD = 8.05). Most (n = 60, 75%) had not replaced their missing teeth. Of these, 35 (58%) were very or extremely interested in doing so. For HNC survivors who wore dentures, there was variable satisfaction and a number of side-effects of wearing dentures. Satisfaction with information about replacing missing teeth was low. There was no statistical difference in QoL or oral functioning between participants who wore dentures and participants who did not wear dentures. However, those with dentures reported fewer problems with carrying out daily routines as measured by the oral functioning tool.

CONCLUSIONS

QoL and oral functioning were similar regardless of denture use, highlighting reduced oral function in both those with and without dentures. In those who had not replaced their missing teeth, there was substantial interest in doing so and thus may be an unmet need. The dental team could offer HNC survivors more support after radiotherapy and following denture provision to improve information about denture use and increase satisfaction with dentures.

Denture use and dental risk factors associated developing osteoradionecrosis after head and neck radiotherapy: A retrospective analysis of hospital records

OBJECTIVES

This study aimed to assess the association between denture use and occurrence of osteoradionecrosis (ORN) following radiotherapy for head and neck cancer (HNC).

MATERIALS AND METHODS

Medical records of 439 HNC patients treated with radiotherapy at Guy's & St Thomas' NHS Foundation Trust (London, UK) (2014-2019) who had missing teeth at the time of discharge were reviewed. Descriptive statistics were used to summarise the participant characteristics and outcome measures. Logistic regression analysis was used to identify factors associated with occurrence of ORN.

RESULTS

Patients had an average of 14 missing teeth and 39 % wore dentures. Twenty-two (5 %) developed ORN. Out of 22 who developed ORN, 11 (50 %) wore dentures. Of these, 5 patients developed ORN in areas contacted by dentures. Denture use was not significantly associated with the occurrence of ORN (OR = 1.94; 95%CI = 0.79-4.81; p-value = 0.150). Longer duration of radiotherapy (OR =1.03; 95%CI = 1.00-1.06; p-value= 0.048) and more missing teeth in the lower anterior area (OR = 1.11; 95%CI = 1.01-1.22; p-value = 0.024) were significantly associated with the development of ORN.

CONCLUSIONS

Within the limitations of this single-centre study in which few patients developed ORN, denture use may not be a risk factor for ORN following radiotherapy for HNC. This is likely to be the case if dentures are well-fitting and not causing sores or irritation.

CLINICAL SIGNIFICANCE

Replacement of the missing teeth with dentures in HNC patients post-radiotherapy may be a suitable choice for many HNC survivors. However, a powered study in a large cohort that includes clinical evaluation of dentures and the quality of fit alongside denture wearing experience would be useful to further assess the impact of denture use on the development of ORN.

Assessment of Psychological Disturbance in Patients with Tooth Loss: A Systematic Review of Assessment Tools

PURPOSE

To systematically review the available evidence on screening tools to detect the psychological disturbance in patients with tooth loss and technically successful removable dentures (partial and complete).

MATERIALS AND METHODS

The study protocol was registered with the National Institute of Health Research Database (I.D. CRD42017082125). The PICOS tool (patients, intervention, control, outcomes measure, and study design) was used to formulate an effective search strategy. Participants were adults (≥ 18), who were edentulous or had significant tooth loss (< 9 remaining teeth). The intervention included undergoing replacement with technically successful dentures (partial or complete). A control group of adults were either edentulous or had significant tooth loss and without dentures. Outcomes included assessing psychological disturbance due to treatment with dentures or due to no treatment using a validated tool. A structured search strategy was used to complete a standard systematic search of the electronic database without any date limit and/or language restriction. Only quantitative studies using a validated measuring tool to screen for psychological distress in adults with significant tooth loss were included. Two authors independently assessed the risk of bias in the included studies. Data homogeneity was assessed in regards to the screening tools to measure psychological disturbance following the management of tooth loss with dentures. The significant level was set at 0.05, using IBM SPSS Statistics 24.0 (SPSS Inc., New York, NY). The psychometric properties and the validation processes of the screening tools were assessed.

RESULTS

From the original 3510 studies identified, only eight studies were found to meet the inclusion criteria. All eight studies used the same questionnaire to screen for the emotional distress of tooth loss. In addition, one study also used the Patient Health Questionnaire-9 (PHQ-9) to screen for the association of depression with tooth loss. Six studies suggested that a significant number of patients have difficulties in accepting tooth loss, were less confident, and had emotional distress related to tooth loss. However, two studies reported no significant link. All studies found a marked impact on functional activities and social interaction. However, four studies had a potentially biased selection process, and the questionnaire used was assessed to be at high-risk of measurement bias, as the development and validation process was not clear. There was also a lack of well-defined control groups in all studies.

CONCLUSION

Tooth loss could cause psychological disturbance in some patients. To date, there is a lack of available tools that are suitable to screen and measure psychological disturbance in patients with tooth loss. Additional research is required to develop tools to identify and measure such impact and to recommend suitable interventions when needed.

The Effect of Radiotherapy for Treatment of Head and Neck Cancer on Oral Flora and Saliva

PURPOSE

Radiotherapy causes xerostomia in patients treated for head and neck cancer. This study investigated changes in quality and quantity of saliva after radiotherapy and possible associations between these changes and alterations in oral flora.

MATERIALS AND METHODS

The study was a prospective cohort study of patients receiving radiotherapy for head and neck cancer. Suitable patients were recruited before treatment commenced, and informed consent was obtained. Patients were examined, and provided unstimulated and stimulated saliva samples. Quantity of saliva, buffering capacity and pH were measured. Oral flora was cultured from the saliva samples. Oral clearance of glucose and of lactose was measured. These interventions were repeated at intervals after radiotherapy had been completed.

RESULTS

Eighteen patients were recruited. Stimulated and unstimulated saliva flow rates, glucose clearance, salivary pH and buffering capacity were significantly reduced after radiotherapy. Candida albicans counts were significantly increased. These increases were significantly correlated with reductions in stimulated and unstimulated salivary flow rates. Counts of lactobacilli, Streptococcus mutans and Bifidobacteriaceae increased, but not statistically significantly.

CONCLUSIONS

Therapeutic radiotherapy significantly reduced the quality and quantity of saliva in head and neck cancer patients. These reductions were associated with increased C. albicans counts.

An investigation into the prevalence of combination syndrome

OBJECTIVES

To investigate the prevalence of Combination Syndrome, and to investigate if provision of a mandibular removable partial denture has any influence on the prevalence of Combination Syndrome.

METHOD

Patients attending Kings College London Dental Institute, Guys Hospital who wore maxillary conventional complete dentures opposing mandibular anterior teeth only, with or without mandibular partial dentures were examined by one examiner. Oral health, residual alveolar ridge and denture quality were assessed. Features putatively associated with Combination Syndrome were recorded. Patient ratings of dentures were recorded.

RESULTS

99 patients were recruited who were wearing maxillary removable complete dentures opposing only mandibular anterior teeth. Of these, 64 patients wore mandibular removable partial dentures and 35 patients did not. Only 8 patients displayed two features of Combination Syndrome and 38 patients displayed one feature of Combination Syndrome, excessive resorption of the anterior maxillary sextant. These findings are not compatible with previous research which suggested that the five features of Combination Syndrome were prevalent in patients wearing maxillary complete dentures opposing mandibular anterior teeth.

CONCLUSIONS

Evidence supporting the existence of Combination Syndrome was not discovered in this research. Prevalence of Combination Syndrome appeared to be low or non-existent. Patient treatment modalities and teaching in relation to Combination Syndrome may need to be modified.

Two-piece obturator using "lock-and-key" mechanism

This paper describes a method used for the fabrication of a two-piece denture obturator for a patient who had surgical removal of the premaxilla due to squamous cell carcinoma. The patient had been wearing a two-piece obturator but encountered difficulty in inserting the prosthesis. In this case report, a lock-and-key mechanism was used to easily assemble the two-piece prosthesis intraorally. A keyhole was designed on the obturator to act as the lock while the denture was used as the key that fitted into the keyhole. This mechanism facilitated insertion and provided retention for the prosthesis. Heat-cured resilient acrylic material (Molloplast B®), which was used to fabricate the obturator, was a nonirritant, nontoxic, tissue-compatible material. It also did not contain plasticizers, therefore eliminating the problems associated with leaching out of plasticizers. The use of this flexible and resilient material allowed the obturator to engage in the undercuts without causing trauma and irritation to the soft tissues in the region of the defect. To conclude, the "lock-and-key" mechanism used in the fabrication of the two-piece denture obturator provided the patient with a lightweight, comfortable, and user-friendly form of prostheses.

Maxillary Midline diastema closure after replacement of primary teeth with implant prosthesis

This case shows an excellent esthetic treatment outcome using implant-retained crowns replacing maxillary laterals and canines in hypodontia patient with unusual incidence of spontaneous diastema closure after the placement of implants. To our knowledge, this is the first case report showing maxillary midline diastema closure after implant placement.

The role of the general dental practitioner in managing the oral care of head and neck oncology patients

The general dental practitioner (GDP) plays a critical role in managing head and neck cancer patients. The first and most important role is to offer preventive services, particularly to smokers and to patients who drink alcohol to excess. It is of critical importance that every patient has a systematic examination of oral soft tissues when seen by a GDP. All patients with suspicious lesions should be referred for urgent attention to a specialist centre. Once oral cancer has been diagnosed, GDPs may be presented with patients requiring urgent dentistry, including extractions before commencement of treatment, requiring palliation of symptoms during treatment, or requiring general dentistry after treatment. Radiotherapy provides increased survival but has serious adverse consequences, which may be lifelong, including dry mouth, radiation caries, limitation of mouth opening and high risk of osteonecrosis after extractions. Extraction of teeth in irradiated bone should be referred to specialist centres. Improving survival rates and an ageing population mean that GDPs will see many more survivors of head and neck cancer in the future, with an increased burden of dental care in the longer-term and an increased need for monitoring and secondary prevention.

CLINICAL RELEVANCE

The management of patients with head and neck cancer is complex and involves a multi-disciplinary team, both in the primary treatment but also in the long-term care. This paper reviews the consequences of treatment for head and neck cancer and gives practical advice for GDPs and their team in the long-term care of these patients.

Submillimetric target-registration error using a novel, non-invasive fiducial system for image-guided otologic surgery

OBJECTIVE

Otologic surgery is undertaken to treat ailments of the ear, including persistent infections, hearing loss, vertigo, and cancer. Typically performed on otherwise-healthy patients in outpatient facilities, the application of image-guided surgery (IGS) has been limited because accurate (<1 mm), non-invasive fiducial systems for otologic surgery have not been available. We now present such a fiducial system.

METHODS

A dental bite-block was fitted with a custom-designed rigid frame with 7 fiducial markers surrounding each external ear. The bones containing the ear (i.e., the temporal bones) of 3 cadaveric skulls were removed and replaced with discs containing 13 surgical targets arranged in a cross-hair pattern about the centroid of each ear. The surgical targets (26/skull) and fiducial markers (14/skull) were identified both within CT scans using a published algorithm and in physical space using an infrared optical tracking system. Fiducial registration error (FRE), fiducial localization error (FLE), and target registration error (TRE) were calculated.

RESULTS

For all trials, root mean square FRE = 0.66, FLE = 0.72, and TRE = 0.77 mm. The mean TRE for n = 234 independent targets was 0.73 with a standard deviation of 0.25 mm.

CONCLUSIONS

Using a novel, non-invasive fiducial system (the EarMark), submillimetric accuracy was repeatably achieved. This system will facilitate image-guided otologic surgery.

Factors affecting survival and usefulness of implants placed in vascularized free composite grafts used in post-head and neck cancer reconstruction

BACKGROUND

Bone-containing vascularized grafts have been used successfully to reconstruct post-cancer surgical defects. Dental implants can be placed in these bone-containing grafts to allow implant-supported prosthodontic reconstruction of these patients.

PURPOSE

The aim of this study was to evaluate the survival of dental implants used in the rehabilitation of subjects treated with bone-containing vascularized grafts to compare usability of implants placed at the time of reconstruction and after healing.

MATERIALS AND METHODS

A cross-sectional study was undertaken to examine survival rates of implants placed in vascularized bone-containing grafts either immediately at the time of surgical reconstruction or after 3 months healing. Other factors such as graft type, whether radiation therapy was given, and implant type were recorded.

RESULTS

A total of 41 patients had 145 implants placed in 47 vascularized bone-containing flaps. Increased failure rate of implants was seen in immediately placed implants. There was also a significant increase in the number of osseointegrated implants that were prosthodontically unusable or sub-optimally placed in the immediate placement group. Radiation therapy was associated with a significant increase in failure rate. Modern implant surfaces appeared to perform better than machined/turned surfaces. Graft donor site did not influence implant survival.

CONCLUSION

This study demonstrated the difficulties encountered with immediate placement of dental implants at the time of post-cancer reconstructive surgery.

An audit of letters of referral to a prosthodontic department in a dental teaching hospital

The purpose of this study was to investigate the quality and number of letters of referral for new patients received in the Prosthodontics Department of a Dental Teaching Hospital. Letters received during the month of May 2006 were included. Each letter of referral was tested against five criteria which might be expected in an appropriate letter of referral. These were information on the following: relevant dental history, relevant medical history, teeth present, diagnosis, and treatment plan. The results showed that only 8% of letters met all five criteria and 11% met none of them. Letters requesting better information were sent to referring practitioner as a result of this audit. However a re-audit in May 2007 showed that 9% of letters met all five criteria and 15% met none of them. A need has been identifiedfor better referral letters and ways of achieving this were discussed.

Validation of PET imaging by alignment to histology slices

The aim of this project is to verify the accuracy of positron emission tomography (PET) in identifying the tumour boundary and eventually to enable PET-guided resection with removal of significantly smaller margins. We present a novel use of an image-guided surgery system to enable alignment of preoperative PET images to postoperative histology. The oral cancer patients must have a high resolution CT scan as well as undergoing PET imaging. Registration of these images to the patient during surgery is achieved using a device that attaches to the patient's upper or lower teeth. During the procedure markers are placed around the lesion within tissue that is to be resected. These are marked along with any convenient anatomical landmarks using the image guidance system, providing the location of the points in the preoperative images. After the sample has been resected, slices through at least 3 of these points are made and photographed. Registration should be possible using these landmarks, but the accuracy of alignment is much improved by marking the bone surface in the histology image and registering to preoperative CT.

In vitro assessment of image-guided otologic surgery: submillimeter accuracy within the region of the temporal bone

OBJECTIVES

Application of image-guided surgery to otology has been limited by the need for submillimeter accuracy via a fiducial system that is easily usable (noninvasive and nonobstructive).

METHODS

A dental bite-block was fitted with a rigid frame with 7 fiducial markers surrounding each external ear. The temporal bones of 3 cadaveric skulls were removed and replaced with surgical targets arranged in a bull's-eye pattern about the centroid of each temporal bone. The surgical targets were identified both within CT scans and in physical space using an infrared optical tracking system. The difference between positions in CT space versus physical space was calculated as target registration error.

RESULTS

A total of 234 independent target registration errors were calculated. Mean +/- standard deviation = 0.73 mm +/- 0.25 mm.

CONCLUSIONS

These findings show that image-guided otologic surgery with submillimeter accuracy is achievable with a minimally invasive fiducial frame. Significance In vivo validation of the system is ongoing. With such validation, this system may facilitate clinically applicable image-guided otologic surgery.

EBM RATING

A.

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.

A preliminary study to investigate the potential of plasma screen technology in small group teaching for dental undergraduates

AIM

This preliminary study was devised to ascertain whether students considered that they had an adequate view of demonstrated procedures, while observing these directly at the workbench, or indirectly on a remote plasma screen. In addition, this study sought to identify whether the students observing remotely believed that they had been disadvantaged by the inability to question the demonstrator during the demonstration.

METHODS

Seventeen students divided into two groups observed a live demonstration of a laboratory technical procedure either at the workbench, or remotely at a plasma screen with the aid of video cameras. They subsequently observed a second demonstration with the roles reversed. Questionnaires were used to obtain the students' views of their ability to see and interact with the demonstrator.

RESULTS

The responses of the students observing the demonstration at the plasma screen indicated that (they felt that) they were able to see the demonstration more clearly than those observing at the workbench. Those observing at the plasma screen first, in particular indicated this. The majority of students acknowledged their inability to ask questions while observing at the plasma screen. There was overwhelming support for the idea that the plasma screen should be used to complement the demonstration at the workbench.

CONCLUSION

Plasma screen technology has considerable potential as a teaching tool for small groups of students, where it can afford significantly superior views of practical procedures. The students considered that the plasma screen would be best employed to provide close-up views to supplement a live demonstration. When used remotely, the apparatus may be used more satisfactorily if videoconferencing technology is also employed to facilitate interaction with the demonstrator.

A prospective study of single stage surgery for implant supported overdentures

OBJECTIVES

To investigate the clinical and psychological outcomes with ball attachment supported mandibular overdentures on Branemark implants placed in a single stage surgical approach. MATERIAL AND METHODS Sixteen edentulous patients aged 32-74, with atrophic (flat) mandibular residual alveolar ridges, and a history of having difficulty coping with technically adequate mandibular dentures made within the last 2 years were recruited. Mark II Branemark implants were placed using a single stage surgical technique with healing abutments placed at time of surgery. Mandibular complete dentures were modified by relieving the areas over the abutments and a resilient liner was placed. After a period of 3 months, healing abutments were replaced with ball abutments and new complete dentures were made and the patients followed for a period of 2 years. Patients completed the General Health Questionnaire (GHQ) and answered further questions relating to the functional and psychological impact of complete denture wearing before treatment and 3 months after the dentures were provided. Patients additionally completed the GHQ 2 years after overdenture insertion.

RESULTS

Six patients suffered from loss of one of their two implants in the first 2 years after placement. Three of the implants had failed to osseointegrate, which was detected at initial loading 3 months after placement. General Health Questionnaire scores were statistically significantly reduced after treatment and the improvement was maintained over 2 years. Responses to the functional and psychological questions were similarly improved.

CONCLUSION

Single stage surgery led to a higher rate of implant failure than expected. Patients showed significant psychological health benefits from the treatment provided.

Agreement between clinical measures of quality and patients' rating of fit of existing and new complete dentures

OBJECTIVES

To assess agreement between patients' appreciation of fit and clinical assessment of quality of existing and new complete dentures.

MATERIALS AND METHODS

In each case existing complete dentures at the initial visit and new complete dentures at the first post insertion visit were assessed by a prosthodontist using a validated method for assessing denture quality. Patients rated fit of existing and new complete dentures on four-point scales. Weighted Cohen's kappa and multiple correspondence analyses were the statistical methods employed in this study.

RESULTS

459 patients completed the study. A statistically "fair" level of agreement was found between clinical and patient assessment of dentures. There was close correspondence between dentist and patient appreciation when the existing dentures were rated as poor and when the new dentures were rated highly.

DISCUSSION

A worthwhile level of agreement between patients' appreciation of fit of complete dentures and the clinical assessment of quality of existing and new complete dentures was found. Marked differences in the nature of agreement for patients' and clinicians' rating of new and existing dentures were demonstrated. These results emphasize the importance of denture quality in achieving patient approval.

CONCLUSION

Agreement and correspondence between patient and clinician appreciation of existing and new complete dentures were determined.

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.

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.

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).

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

Accuracy of fit of cobalt-chromium removable partial denture frameworks on master casts

Fifty-six cobalt-chromium removable partial denture frameworks made to the same design were found to fit their master casts poorly. Spaces were significantly greater between palatal aspects of abutment teeth and palatal reciprocal arms, and between buccal aspects of occlusal rests and rest seats. Excessive contraction towards the centre of the palate was found. Expansion of the refractory investment may not have compensated adequately for solidification and cooling contraction of the cobalt-chromium alloy. Although dimensional changes in investment and casting are by volume, no evidence of anisotropic expansion of castings in a vertical direction was found.

Validity of a patient self-completed health questionnaire in a primary care dental practice

1500 patient medical histories derived from self-completed health questionnaires alone and from a combination of questionnaire, structured interview by a dentist, and selective reference to family doctors were compared. In 4.25% of cases, the questionnaire medical history was significantly deficient. Such questionnaires yield an inadequate medical history when used on their own.

Medical screening of 1500 patients in a dental surgery: a prospective study

Communication between medical and dental practitioners about patients they have in common enhances total patient care, but such communication rarely occurs. This may be due to lack of appreciation by doctors of the medical risks to certain patients undergoing dental treatment. To ascertain a relevant medical history, prospective medical screening was performed on 1500 new patients attending a general dental practice using a standard health questionnaire followed by an interview between the patient and dentist. There were 382 (25.5%) patients with a current or past medical history of relevance to dentistry, 90 (6.0%) were taking medication of potential importance and 105 (7.0%) considered they had an intolerance to certain drugs. The screening provided a patient data base for medical and medico-legal purposes. A total of 376 (25.1%) questionnaires were filled out incorrectly and 63 of these (16.8%) had major misinformation about medical history. A small but important group deliberately misled the dentist either from fear of refusal of treatment or embarrassment about their medical history. Therefore interviews are an essential adjunct to written health questionnaires in eliciting accurate information. Formal screening of new patients is essential in general dental practice. Furthermore, general medical practitioners need to become aware of the common risks to patients undergoing dentistry. Better formal and informal communication between general medical and dental practitioners is recommended for the benefit of their mutual patients.