Complete dentures revisited.

UNLABELLED: The aim of the article is to assist practitioners in the diagnosis and management of complete denture problems by addressing the problems from a theoretical viewpoint and in a clinically diagnostic way. CLINICAL RELEVANCE: To assist practitioners and undergraduates to understand the clinical basis of complete denture prosthodontics.

A contemporary update on 'soft' linings.

UNLABELLED: This article presents a contemporary overview of soft or compliant denture lining materials. It does not focus on denture bases, which are intrinsically flexible, and suggests some clinical options which readers might wish to consider. CLINICAL RELEVANCE: The aim of this article is to update clinicians on the types of compliant linings currently available and to advise on how some might be used.

An update on the replica denture technique.

UNLABELLED: This paper reviews the principles of the replica denture technique, including some of the techniques previously described. The failing of any previous technique to cater for specific support problems is brought to light and the remainder of the article is devoted to describing how the replica denture technique may be modified to treat patients more appropriately and, hopefully, result in better treatment outcomes. CLINICAL RELEVANCE: This article offers general dental practitioners a practical guide on how to adapt a useful denture replication technique to suit patients with denture-support problems.

Contemporary techniques for denture fabrication.

This article reviews the fabrication of complete dentures and presents findings of recent technological studies that have relevance to current complete denture practice. In addition, summaries of two recent randomized controlled studies demonstrate the need for more deliberate prescription of impression materials.

Colonization and deterioration of soft denture lining materials in vivo.

Colonization of denture lining materials by microorganisms including Candida albicans can result in deterioration of the material, as observed by a previous in vitro study by the authors. The current in vivo study monitored the microbial colonisation and penetration of five types of denture liners and their topography over six months. There was no significant difference in the microbial colonisation on the denture liners and no penetration observed, indicating a slower rate of deterioration of materials in vivo. However the surface roughness of all materials increased during use, which might alter susceptibility to subsequent microbial colonisation.

The shortened dental arch--an assessment of patients' dental health state utility values.

OBJECTIVES: The aim of this study was to determine how patients value the potential outcomes from different treatments for the shortened dental arch (SDA). METHODS: 110 partially dentate patients were interviewed and presented with illustrative models as well as a description of the process and likely outcome of six possible treatments for the shortened dental arch. The patients were asked to indicate on a standardised visual analogue scale how they would value the health of their mouth if they had received each of the treatments described. RESULTS: With a utility value of 0.0 representing the worst possible health state for a mouth and 1.0 representing the best, the mean utility value for 'no treatment' for a SDA was 0.28 (sd=0.29). For a cobalt-chromium based removable partial denture, an acrylic-resin based removable partial denture, implant treatment, a resin-bonded cantilevered bridge and a conventional cantilevered fixed bridge the utility values were 0.42 (sd=0.3), 0.49 (sd=0.31), 0.53 (sd=0.35), 0.63 (sd=0.26) and 0.64 (sd=0.28) respectively. CONCLUSIONS: The treatment outcome from a cantilevered bridge attracted the highest mean utility value. Participants did not value implant treatment as highly as fixed bridgework, but they did rate the utility of implants more highly than the utility value of removable dentures. However, the patients placed a very low value on the outcome from 'no' treatment. Thus, the appropriateness of the shortened dental arch as an oral health goal can be questioned.

Does the nature of the definitive impression material influence the outcome of (mandibular) complete dentures?

The effects of impression materials on the outcome of complete dentures are poorly understood. This double-blind cross-over randomized controlled trial investigated eleven adult edentulous patients. Each received a maxillary denture and three mandibular dentures (which differed only in the three materials used to record the definitive impressions). The three mandibular dentures were given in a random order. Patients' opinions of each denture were recorded using a Linear Analogue Scale. There was a statistically-significant difference between the outcome of the dentures constructed when zinc-oxide eugenol was used, this material being least favoured (p < 0.001). It would therefore appear that care should be exercised when selecting impression materials when constructing mandibular complete dentures.

A clinical investigation of the morphological changes in the posterior mandible when implant-retained overdentures are used.

OBJECTIVES: The widespread use and broad acceptance of osseointegrated dental implants as a means of retaining and supporting mandibular overdentures provide potentially stable three-dimensional reference structures, which have been used to examine the morphological changes of the surface contours of the mandibular ridges distal to implants. Unlike traditional methods that tended to measure changes in ridge morphology and quantity radiographically, this prospective study investigated the changes in the sagittal surface contours of the posterior residual ridges over a 1-year period by an alternative, non-radiographic method using serial casts of residual ridges of a group of patients. MATERIAL AND METHODS: The residual ridges of the serial casts produced were examined using a profiling apparatus and computer software programs that allowed the orientation, digitised recording and measurement of the sagittal surface contours of the posterior residual ridges of mandibular casts in terms of area (cm(2)). RESULTS: Statistical analysis revealed that the detected reductive changes in the surface contour of the posterior residual ridges following the wearing of an implant-retained mandibular overdenture over a 1-year period were highly significant (P<0.001). CONCLUSION: It is concluded that the methodology presented in this study can be used reliably as an alternative to radiographical examination for detecting changes that occur in the distal residual alveolar ridges of the implant containing edentulous mandible when implant-retained overdentures are used. Thus, the method presented may be used to contribute to a reduced exposure to ionising radiation for patients wearing implant-retained overdentures.

Microbiological hazard analysis in dental technology laboratories.

Dental technicians are trained in a range of skills involved in the fabrication of prostheses used in the mouth and facial region. Items entering the dental laboratory are essentially inert materials which have been in contact with the patient's mouth, saliva, and possibly blood. Appliances leaving the laboratory are then returned to the clinician to be tried/inserted in the patient's mouth. Relatively little attention has been paid to infection control policy within dental laboratories, perhaps due to perceived and/or actual remoteness from patients, lack of appropriate training, and lack of relevant research. More controlled studies are desirable, in order to identify any potentially hazardous procedures, and to make an assessment of risk for these procedures.

Systematic review of the evidence supporting intra-oral maxillofacial prosthodontic care.

The literature on maxillofacial prosthodontics may be considered to be dominated by articles describing case reports or case series. Prospective, well-controlled clinical trials are scarce owing to the inherent difficulty of performing such trials in patients suffering from oral cancer. The aim of this study was to perform a systematic review of the literature relating to intra-oral maxillofacial prosthodontics based on the principles of evidence-based dentistry. A detailed report of the findings is presented and critically assessed and a discussion of the outcome in respect to the various confounding factors is carried out. Finally, suggestions for future research in the field of maxillofacial prosthodontics are made.

Mathematical analysis of tooth and restoration contour using image analysis.

OBJECTIVES: The aim of this study was to develop a methodology for comparison of the contour of artificial crowns in the mid bucco-lingual plane with their equivalent natural teeth on the opposing side of the same arch (antimeres) using a novel application of image analysis software. The objective was to determine whether artificial crowns were overcontoured. METHODS: Specimens consisted of thin sections of silicone putty impressions of the buccal and lingual surfaces of 55 full crown restorations and their natural antimeric teeth. A thin slice of the putty was obtained in the mid-tooth bucco-lingual plane and a digital image was captured and this was analysed to produce a data set (x, y) representing the curvature of the tooth surface. Further analysis was performed in order to describe the profile in optimum mathematical terms. RESULTS: The curves were best represented by three equations: y = a + bx(0.5), ln(y) = a + bx2, and y2 = a + bx. In all equations parameter (b), which expresses the contour curvature, was used as a deciding factor in comparing the degree of contour of the crown restorations with their natural antimeres. Most artificial crowns were found to be either similarly or undercontoured when compared with their natural antimeres. When overcontouring was present in the artificial crowns this tended to occur on the lingual aspects of anterior and posterior crowns. SIGNIFICANCE: Simplifying tooth contour into a mathematical model can be useful in determining whether restorations are overcontoured. Clinically, particular attention should be directed towards the lingual aspects of restorations which were more likely to be overcontoured.

Prosthetic dentistry and the unilateral cleft lip and palate patient. The last 30 years. A review of the prosthodontic literature in respect of treatment options.

All cleft lip and palate patients are unique and present with their own diagnostic and prosthodontic problems. Many patients have benefited, recently, from alveolar bone grafting and orthodontic realignment and require little or no prosthodontic treatment. Some treatment, however, has been planned with a prosthesis as the final restoration, as a sizeable number of such patients have not undergone the alveolar graft procedure, (or this has been unsuccessful), or they were deemed to be unsuitable because of the extent of their defect. The patients who have not received grafting and orthodontic realignment are therefore the patients who present the greatest prosthodontic challenge. This paper presents an overview of the work that has been carried out over the last thirty years in relation to the prosthodontic rehabilitation of the cleft lip and palate patient. It is clear that multidisciplinary treatment planning by surgeons, orthodontists and restorative dentists is required for the long-term benefit of this small but challenging group of patients.

Colonization and penetration of denture soft lining materials by Candida albicans.

OBJECTIVES: Colonization of denture soft lining materials by Candida albicans can result in clinical problems, and deterioration of the material. This study aimed to monitor this interaction by comparing the short-term adhesion of C. albicans to six denture lining materials and to monitor any longer term penetration of material by the yeast. METHODS: Denture lining materials (Molloplast B, Flexor, Permaflex, Luci-soft, Eversoft and Ufi Gel hard C) were processed against glass slides or dental stone. Adhesion of yeast to surfaces was monitored after one hour incubation (37 degrees C) of standardized (2.8 x 10(6) cfu/ml) washed cell suspension with test materials. Attached cells stained with acridine orange were counted microscopically. Penetration of yeast into materials bonded onto acrylic after six weeks incubation (culture medium was replaced weekly) was observed through sections stained using acridine orange. Hyphal and yeast penetration was estimated (qualitatively and quantitatively, respectively) for three levels of the liner (subsurface, central section and adjacent to lining-acrylic junction). RESULTS: None of the materials produced a zone of inhibition when compared with the nystatin control. There was no significant difference (p>0.5) in cell numbers on any of the smooth surfaces. Significantly, (p<0.001) higher numbers of cells were observed on roughened surfaces. Both hyphal and yeast forms were observed when penetration was monitored. Penetration was greatest into Ufi Gel hard C (no hyphae observed), but not at the acrylic-liner junction and least into Eversoft. SIGNIFICANCE: Different denture lining materials exhibit different properties in terms of susceptibility to yeast penetration, although the initial attachment is comparable. Smoother surfaces retain fewer cells. The selection of appropriate materials for a given function, and their fabrication may affect performance.

Prevention of bone loss for edentulous patients.

This paper examines the consequences of being edentulous particularly on the intra-oral hard tissues. Short, medium and long-term studies of the overall post-extraction changes are reviewed and the bone loss that might be anticipated quantified. Following on from this, means by which bone loss may be prevented are reviewed. The bone-preserving potential of conventional and implant-retained overdentures is presented, advantages and potential problem areas highlighted.

A clinical overview of removable prostheses: 5. Diagnosis and treatment of RPD problems.

This, the fifth and final article in the series, addresses the diagnoses and treatment of problems which may arise following provision of removable partial dentures (RPDs). These include difficulties seating the denture, pain and discomfort, looseness and functional problems.

A clinical overview of removable prostheses: 4. Technological considerations when designing removable partial dentures.

This fourth article in a series concerning the prescription of removable partial dentures is a précis of the technical aspects of RPD construction, commencing with the definitive or 'working' impressions, although all impressions ought to be considered as 'working' impressions.

A clinical overview of removable prostheses: 2. Impression making for partial dentures.

This, the second article in a series on the prescription of removable partial dentures, will deal with the issue of primary impression and primary casts for partial dentures. The principles of definitive impressions and master cast planning will be described.

Factors that affect the adhesion of two irreversible hydrocolloid materials to two custom tray materials.

STATEMENT OF PROBLEM: Little evidence is available on the length of time that adhesive should be allowed to dry before irreversible hydrocolloid impression making. PURPOSE: This study investigated the effect of adhesive drying times on the bond strengths of 2 irreversible hydrocolloid impression materials to 2 "custom" tray materials. MATERIAL AND METHODS: A total of 1,632 specimens were tested: 816 in tensile tests and 816 in tests of the shear bond strength (megapascals) of 2 irreversible hydrocolloid impression materials to an autopolymerizing and a visible light-polymerizing acrylic resin tray material. In the first part of the investigation, a single coat of adhesive was applied to specimen plates that simulated the custom impression tray surface; in the second part, a second coat of adhesive was applied after the irreversible hydrocolloid was removed, and the effect of this second coating on bond strength was examined. In both parts, the adhesive was allowed to dry for a range of times (0 to 8 minutes at 30-second intervals, for a total of 17 time periods) before the addition of the impression material. The specimen plates were placed in a humidor and separated in a universal testing machine operated at a crosshead speed of 100 mm/min with 0- to 5-kN load cell. Data from each of the 1,632 specimens were collected and evaluated with analysis of variance, regression analysis, and t tests (P<.05). RESULTS: Significant differences in mean bond strengths were found between specimens with a 4-minute adhesive drying time (0.179 MPa tensile, 0.068 MPa shear) and specimens with a 0-minute drying time (0.065 MPa tensile, 0.015 MPa shear). Any period over 4 minutes produced no significant difference. The mean bond strengths of the single-coated specimens were 0.179 MPa (tensile) and 0.076 MPa (shear). These values were significantly greater than those for specimens with a second adhesive layer (0.136 MPa tensile, 0.035 MPa shear) over all time periods. Mean tensile bond strengths (0.158 MPa) were consistently higher than shear bond strengths (0.056 MPa) for all combinations of tray material, adhesive application, and time. CONCLUSION: Within the limitations of this study, the results suggest that adhesive applied to the autopolymerized and light-polymerized custom tray materials tested should be allowed to dry for at least 4 minutes before irreversible hydrocolloid is applied. Better results were obtained when the adhesive layer from a failed irreversible hydrocolloid impression was removed and replaced rather than overlaid with an additional adhesive coating.

A clinical overview of removable prostheses: introduction.

This series of articles has been written with the intention of simplifying the processes involved in the prescription of removable partial dentures. The scene is set in this introduction, and the first article addresses basic clinical and patient-related factors involved in decision-making before commencing active prosthodontic treatment. The second paper will outline a variety of impression techniques for primary and definitive impressions, while the third discusses designing principles. The fourth article is a brief overview of some technological aspects of removable partial denture-making and the fifth attempts to provide a useful guide showing how to diagnose and manage common clinical problems associated with removable partial dentures.