Developing a schedule of normative denture treatment need.

OBJECTIVES: The aim of the study is to assess the reliability and validity of a schedule to determine the normative denture treatment needs of older people. DESIGN: The design used assessed inter-examiner reliability (criterion validity), test-retest reliability, and content and face validity of the schedule. SETTING: The inter-examiner reliability study took place in a Department of Prosthetic Dentistry, the remainder of the work took place in a community setting. RESULTS: The results showed that the schedule in terms of an index performed well with reasonable inter-examiner and test-retest reliability. Difficulties however were encountered with regard to subjective judgements about denture quality and design; consequently, there was modest inter-examiner agreement for stability, retention, and occlusal balance. CONCLUSIONS: The findings from this preliminary work suggest that the schedule may be useful in the assessment of normative denture treatment need in a community setting. Nevertheless more work will be required to obtain further information on the validity of this new assessment measure.

Assessing expressed need and satisfaction in complete denture wearers.

OBJECTIVES: The need to assess both lay and professional views of oral health is believed to be at the centre of success when providing dental health care for older patients. Self-perceived physical (oral) health and perceptions of psychosocial functioning must be included if expressed need is to be assessed. The aim of this work was to construct an expressed need schedule and to assess the ability of this assessment to predict older community-based patients' satisfaction with complete dentures. DESIGN: Survey of 260 people aged 65 years and over. SETTING: Community setting. MAIN OUTCOME MEASURES: The participants were interviewed using a 55 item modified version of the Oral Health Impact Profile (OHIP) to assess their psychological, social and perceptions of their oral health. All participants were subjected to an oral examination. RESULTS: The results showed that complete denture wearers compared had greater experience of difficulties associated with oral health and psychological functioning. Factor analysis allowed the identification of three dimensions associated with psychological, social and self-perceived physical (oral) health. When these factors were regressed with normative denture treatment need against satisfaction with complete dentures, satisfaction was characterised by high self-perceived physical (oral) health, low social health problems and no identifiable normative need. CONCLUSION: This work supports the inclusion of self-perceived physical (oral) health and psychosocial health (expressed need) questions in a schedule when predicting satisfaction with complete dentures.

Photoelastic stress analysis in perforated (Rochette) resin bonded bridge design.

Rochette described the perforated cast metal bonded design for splinting periodontally compromised teeth. The design was later used for replacing missing teeth. The main causes of failure of the perforated (Rochette) type design were attributed to inappropriate case selection and erosion of the composite from perforations. The aim of this study was to analyse the effect of stress magnitude and direction on failure of perforated resin bonded bridges (RBBs). The objective was to compare stress magnitudes in this design with those reported on the non-perforated RBBs. Photoelastic modelling materials were selected to represent the relative stiffnesses of a posterior mandibular and an anterior maxillary perforated (Rochette) type design. The sizes of the models were scaled to x 2.5 in order to enhance visual analysis of the stress patterns. Stress magnitudes were quantified from isochromatic fringes and stress directions were evaluated from stress trajectories. These revealed a high-stress concentration around the perforations, particularly for those at the proximo-lingual/palatal (connector) areas. This experimental study revealed that the main reason for failure of Rochette designs is deformation at the perforations.

An investigation of the variables which may affect the bond between plastic teeth and denture base resin.

OBJECTIVES: The failure of the bond between acrylic resin denture base material and resin teeth remains a significant problem. This study evaluated the tensile bond strength of specimens produced by commonly employed tooth preparation and processing methods as used in dental laboratories. METHODS: Twenty-two experimental groups, each consisting of 36 specimens, were investigated by subjecting the tooth-resin bond to tensile loading. The groups were allocated to one of five experimental sets to investigate: (a) effect of resin dough time, (b) effect of tooth surface condition, (c) effect of processing variables, (d) effect of monomer cementing, and (e) effect of acrylic resin cement. The results were analysed statistically using a one factor ANOVA and a Student t test. RESULTS: A significantly stronger bond was obtained when the resin was packed late in the dough stage, and a superior bond, in all cases, when high-impact resin was used. Tooth surface modification by grinding or grooving made no significant difference when compared with unmodified surfaces. Wax-contaminated surfaces produced highly significant weaker bonds. Time of introduction and duration of water-bath processing had no significant effect on bond strength. Monomer cementing of the tooth surface, especially with high-impact monomer. significantly improved the bond strength. The application of resin cements was found to produce the most significant increase in denture tooth bond strength. CONCLUSIONS: The important steps in obtaining a consistently high value denture tooth bond are thorough dewaxing of the tooth surface followed by the application of a suitable resin cement.

Photoelastic stress analysis in a pier retainer of an anterior resin-bonded fixed partial denture.

STATEMENT OF PROBLEM: A clinical situation may arise with 2 edentulous spaces and a single intact pier tooth. A dentist may restore these edentulous spaces with a long span resin-bonded fixed partial denture using the pier and the 2 terminal abutments for bonding. PURPOSE: This study analyzed the stresses induced in a pier retainer of an anterior resin-bonded fixed partial denture and determined the effect on a pier abutment. MATERIAL AND METHODS: Photoelastic materials were selected to represent the relative stiffness of 3- and 5-unit resin-bonded fixed partial dentures. The models were scaled to x2.5 to enhance visual analysis of the stress pattern. RESULTS: Isochromatic fringes indicated a stress magnitude at the proximolingual areas of the pontic in the 3-unit resin-bonded fixed partial denture. In the 5-unit resin-bonded prosthesis, the stress pattern appeared to involve the entire surface of the pier retainer. CONCLUSION: The use of pier abutments should be avoided and it is more favorable to use 3-unit resin-bonded fixed partial dentures.

A survey of the pre-bonding preparation of denture teeth and the efficiency of dewaxing methods.

OBJECTIVES: Denture tooth debonding remains a significant problem, with the surface condition of the tooth playing a pivotal role. The purpose of this investigation was to determine the methods used in tooth preparation. The efficiency of wax removal from teeth using a range of water temperatures was also investigated. METHODS: (a) A postal survey on the methods of denture tooth preparation, prior to denture processing, was conducted amongst dental instructors in prosthodontic departments of dental schools in Great Britain and Ireland. (b) Tooth surfaces contaminated with fluorescence wax were subjected to agitation in water at a range of temperatures and the surfaces examined under ultraviolet radiation. RESULTS: (a) The majority of operators did not use a solvent for the removal of the wax film from the teeth. Modification of the tooth ridge lap surface was carried out by 52% of the respondents on initial processing but increased to 85% when rebonding teeth. (b) Dewaxing denture teeth at a range of water temperatures showed wax retention on the tooth surfaces up to 90 degrees C. Rough surfaces retained more wax than smooth surfaces. Wax eliminator was shown to be necessary for complete wax removal. CONCLUSIONS: No standard technique exists amongst dental instructors for the preparation of denture teeth prior to acrylic resin polymerization. The use of a wax solvent is to be recommended.

Temperature changes in bovine mandibular bone during implant site preparation: an assessment using infra-red thermography.

OBJECTIVES: Changes in bone temperature during the sequence of drilling for implant site preparation using the Branemark technique were monitored using infra-red thermography. METHODS: Bovine mandibles were used to provide cortical bone of a similar quality to human mandibular bone. To ensure the consistency in the drilling procedure, one operator used a conventional dental handpiece with a motor provided by Nobelpharma. The manufacturer's specifications were followed during the implant site preparation, except that no irrigation was employed since infra-red radiation does not transmit through water. Thermal images were recorded using the Thermovision 900 system. A sequence of images was recorded during implant site preparation. Three drills were examined in terms of temperature changes during drilling over the entire area involved. The three drills used were a round bur, which determines the site of the fixture, a spiral drill (2 mm twist drill) which establishes the direction of the implant and finally a pilot drill (3 mm) which progressively increases the diameter of the site. RESULTS: Average values (n = 10 drill sequences) for maximum recorded temperature (Max T degrees C), change in temperature (delta T degrees C) from baseline and the area of involvement (mm2) for each drill in the 10 drill sequences were as follows: round, spiral (2 mm) and pilot (3 mm) drills gave maximum temperatures of 82.7 degrees C, 130.1 degrees C and 126.3 degrees C, respectively. The changes in temperature, delta T degrees C, were 45.7 degrees C, 79.0 degrees C and 78.9 degrees C for the round, 2 mm twist and 3 mm pilot drill, respectively. The average areas recorded for the round, spiral and pilot drills were 49 mm2, 140.1 mm2 and 273.0 mm2, respectively. CONCLUSIONS: It is concluded that the methodology employed accurately recorded temperature changes at and around the dental implant site, and provided preliminary baseline data against which the cooling efficacy of different irrigant systems may be compared.

A new technique for determining the denture tooth bond.

Defective bonds between resin teeth and denture base material remain a continuing source of failure. Findings from the limited number of studies on this topic are diminished by the numerous experimental approaches adopted. National and international standard specifications also adopt different methods of specimen preparation and physical straining. A critical appraisal of the various standards is carried out and a new procedure for determining the denture tooth to acrylic resin bond is described. A study using this technique found that physical modification and alginate contamination of the tooth had no significant effect on the bond strength. Ineffectual wax elimination was the main cause of failure.

The clinical success and periodontal evaluation of patients rehabilitated with light-cured obturators.

The clinical performance of a visible light-cured (VLC) resin for obturators was evaluated in 10 patients. All patients had undergone ablative surgery of the maxilla, previously worn conventional heat-cured hollow bulb acrylic obturators and were currently rehabilitated with VLC obturators. The obturators were assessed on their performance for each of the following: weight, retention, speech, eating and comfort. An evaluation of the periodontal status of those who retained teeth in the maxilla was also performed. It is concluded that patients found VLC obturators to have a more acceptable clinical performance than conventional acrylic obturators due primarily to a reduction in appliance weight.

Photoelastic stress analysis in resin bonded bridge design.

The aim of this investigation was to determine the stress magnitudes and directions in resin bonded bridges. 3D models (2.5 x life size) were prepared from photoelastic materials that represented the ratio of the elastic moduli of enamel and metal. The models were loaded during a stress freezing cycle and sectioned to view in a transmission polariscope. The fringes observed, indicated that the stress magnitudes concentrated at the proximo-lingual line angles to the pontic. The stress trajectories were plotted to show the pattern of stress direction. The stress factors which may contribute to debonding of these designs were analysed. It is suggested that the use of vertical grooves at the proximolingual line angles to the edentulous area in the preparation should reduce the stresses and hence improve the long term prognosis.

Bond strength variation of synthetic resin teeth in dentures.

The bond strength of denture teeth to acrylic resin denture bases was determined by producing tensile test specimens from standardised and anonymously presented partial dentures. Ten dentures were produced by randomly selected commercial dental laboratories and five were produced in a university dental laboratory. The tooth debonding forces exhibited a wide range of variation both within and between dentures. The university-produced dentures showed, on average, a slightly improved tooth bond strength. This study highlights the need for further investigation of this problem and for the development of a standardised technique to provide satisfactory denture tooth bonding.

Playing the blues: an unusual prosthetic problem.

This is a case report of a prosthodontic problem associated with harmonica playing, which has been solved by a previously undocumented treatment.

Sorption determination of hollow VLC resin obturators.

Visible light cured (VLC) resin can be used to produce hollow dental obturators but the quantity of water absorbed by this material, in comparison to heat cured acrylic, as reported in previous studies, may make the appliance unhygienic. A model was designed to compare sorption and permeability. It was found that the VLC resin had a lower sorption value than heat cured acrylic, making it a more suitable material for producing hollow obturators.

Light-cured hollow obturators.

Obturators used in the rehabilitation of large defects of the upper jaw should be easily made to produce a comfortable and stable prosthesis. This goal has been difficult to achieve by using traditional materials and techniques. This article describes a technique to overcome these problems by using a visible light-cured resin. Results indicate that resultant obturators are easily and quickly constructed, and provide a light, comfortable, and well-tolerated prosthesis.

Post-surgical prosthodontics: clinical notes.

This paper discusses some of the problems and techniques that are involved in the prosthetic management of patients who are to undergo surgery to the upper and lower jaws. It stresses the importance of a close relationship between the surgeon and the prosthodontist so that the necessary treatment plan may be prescribed pre-operatively rather than post-operatively. The dental management where maxillary surgery is anticipated is discussed under the following headings: Pre-operative assessment; Pre-operative treatment; The operation; Post-operative care; The intermediate obturator; The definitive obturator. Where surgery is anticipated in the lower jaw the problems are related to whether the patient has lost all the mandibular bone on one side or only the alveolar section and whether they are able to retain any of the lower teeth to stabilize the appliance. However, even when edentulous, these patients are now able to control their lower appliance much better since the advanced plastic and maxillo-facial surgical techniques produce a good denture-bearing area and less mandibular deviation.

An injection impression technique for palatal defects.

A master cast suitable for fabricating a retentive flexible base using any of the materials and techniques previously mentioned is provided. The flexible extension fits snugly into the defect laterally and extends above the remnants of the soft palate posteriorly and into the nasal floor anteriorly on either side of the remnants of the nasal septum (Fig. 9). The use of a thin flexible extension such as Molloplast will provide a good chemical bond to the acrylic resin of the denture base, allows for easy cleaning, and will maintain flexibility for several years. Prostheses constructed with this technique are retained well. The technique described will provide increased mechanical retention of prostheses for defects of the palate by engaging undercuts around the borders of the defect with a flexible material. The impression is made by injecting an elastic impression material with a syringe through a hole prepared in the palate of the impression tray. This technique may not always be required, but is recommended where a retention problem is anticipated and there is difficulty in obtaining a satisfactory flow of the impression material to the appropriate undercut. A correct impression can be secured the first time, overcoming further discomfort and inconvenience to the patient.