Hard Denture Base Research Articles

Rehabilitation of Combined Hard and Soft Palate Defects with a Soft Relining Prosthesis: A Clinical Report.

It remains a significant challenge in prosthetic rehabilitation for combined hard and soft palate defects on account of two primary reasons. At first, conventional impressions can hardly get an accurate analogue and usually bring about a terrible experience for the patients. Secondly, conventional hard denture base resins used in obturator prostheses exhibit limitations in marginal sealing, undercut retention, and elastic buffering when in contact with the soft palate. This article presents a case where combined hard and soft palate defects were successfully and rapidly reconstructed by using digital intraoral impression technology and denture soft reline material.

BASIC PROBLEMS WITH THE USE OF RESILIENT DENTURE LINING MATERIALS: LITERATURE REVIEW

Complicated cases in the treatment of totally edentulous patients, as well as in the fabrication of obturators and epitheses, require the use of resilient lining materials (RLMs). These materials have several disadvantages, which is why many dental practitioners do not recommend them. The tendency to breaking the bond between the hard acrylic resin and the resilient liner is a fact with unpleasant consequences, mainly found with the use of cold-curing silicone-based resilient liners. Methods to improve the bond between the hard denture base and the RLM have been the subject of numerous publications. The efforts of the authors are focused in two directions: mechanical or chemical treatment of the denture base or a combination of both. Other commonly discussed problems with the use of RLMs are the difficult and even impossible repair and the retention of oral fluids, fungi and other microorganisms due to the porosity of RLMs. Despite the wide variety of tools offered by different manufacturers, the issue of optimal and high-quality mechanical treatment of the polymerized resilient material has not yet been fully resolved.

Comparison of adhesiveness of chewing gum to hard and soft denture base materials

PurposeThe purpose of this study was to compare the adhesiveness of chewing gum to hard and soft denture base materials to investigate food retention associated with the basal surface of the denture. MethodsTest specimens were fabricated using acrylic resin[Re], cobalt-chromium alloy[Co], zirconia[Zr], silicone soft relining material[SS], and acrylic soft relining material[AS]. Samples were set on a top-and-bottom pair lifting platform equipped with a digital force gauge. The experimenter chewed 3.0 g of chewing gum for 5 min. After surface saliva was wiped off, the chewing gum was placed on the lower test fragment and compressed until the distance between the upper and lower test fragments decreased to 1 mm. The upper test fragment was pulled at a crosshead speed of 100 mm/min. Adhesiveness was measured under dry conditions, and under wet conditions with inter-positioned artificial saliva. ResultsUnder dry conditions, the adhesive strength was 17.04 ± 1.99 N for Re, 12.88 ± 2.20 N for Co, 3.80 ± 1.03 N for Zr, 5.76 ± 1.41 N for SS, and 12.54 ± 2.44 N for AS. Under wet conditions, the adhesive strength was 5.26 ± 1.64 N for Re, 0.96 ± 0.21 N for Co, 3.32 ± 0.40 N for Zr, 5.20 ± 1.35 N for SS, and 6.78 ± 1.97 N for AS. ConclusionsAmong the hard denture base materials, zirconia recorded low adhesiveness and Re recorded high adhesiveness under both wet and dry conditions. The adhesiveness of Co was low under wet conditions but high under dry conditions. Among the soft denture base materials, SS under dry conditions recorded lower adhesiveness than that of AS. The adhesiveness of SS was low under both wet and dry conditions.

Clinical evaluation of chewing efficiency for flexible removable partial dentures in bilateral free-end saddle cases

Statement of problem: Increasing flexibility of removable partial denture increase the patient comfort and esthetics at the cost of bite force and chewing efficiency. Purpose: To compare and study the variation of chewing efficiency in different types of thermoplastic denture base materials used for restoring Kennedy class I removable partial dentures. Materials and Methods: Eight patients were included in the study. Four types (groups) of removable partial dentures will be made for every patient in the test group: thermoplastic Nylon RPD, thermoplastic Acetal RPD, thermoplastic PMMA RPD and thermoplastic PMMA with hard PMMA combination. Nylon and Acetal dentures were made using thermo-injectable technique. F. PMMA and H. & F. PMMA dentures were made using compression moulding technique. Chewing efficiency was measured after 1 week, 3 months and 6 months follow-up period for the two types. Chewing efficiency was evaluated by colored chewing gum and computerized color analysis. The test data were collected and analyzed. Results: H. & F. PMMA and F. PMMA had higher chewing efficiency than Nylon and Acetal 1 week after insertion for all chewing cycles. Only 10 chewing cycles affected by increasing the follow up period and denture adaptation for all types. Conclusion: Combination of flexible denture base materials with hard denture base material is recommended to enhance chewing efficiency.

A Novel Approach to Treat Traumatized Alveolar Ridges: Two Case Reports.

Functional forces are transmitted to the basal seat mucosa through a hard denture base during mastication. Such hard base dentures are not comfortably tolerated in patients with fragile oral mucosa and will cause sore spots, masticatory pain, and further resorption of alveolar bone. Soft liners materials can be advocated successfully to manage such clinical situations. The soft liner material absorbs masticatory forces by means of the cushioning effect and distributes occlusal forces uniformly to prevent trauma to compromised residual ridges.

Fabrication and relining of dentures with permanent silicone soft liner: A novel way to increase retention in grossly resorbed ridge and minimize trauma of knife edge and severe undercuts ridges

The aim of this study is to suggest a technique to improve the retention of the prosthesis in grossly resorbed ridge and minimize the trauma of thin, atrophic knife edge ridge with severe undercuts. Significant numbers of patients seek treatment for edentulism throughout the world. In the current scenario, implant retained/supported prostheses have been considered a standard of care for rehabilitation of completely edentulous patients, but still this treatment modality is out of reach of many patients due to economic factor. In such patients, conventional removable complete dentures are considered for functional rehabilitation. However, in some of the patients with grossly resorbed ridges and knife edge ridges or ridges with severe undercuts, these prostheses have compromised retention and also continuously causes trauma to knife edge ridges and mucosa covering the undercuts during insertion and removal of the prosthesis thereby reducing the compliance of the patient. By incorporating, a layer of resilient permanent silicone soft liner on the tissue surface of a new or old denture is a novel way to reduce the trauma of thin and severe undercut ridges and also improve the retention of the prosthesis. This study described the successful functional rehabilitation of three completely edentulous patients with grossly resorbed, thin knife edge, and severe undercut mandibular ridges with permanent silicone soft liner. Permanent silicone soft liner act as a shock absorber, helps in equal dissipation of occlusal stresses, maintains an intimate contact with the underlying tissues and compressed during function thereby increasing retention and minimizing trauma by preventing a direct contact of hard denture base with compromised tissues.

Patient's Satisfaction and Durability of Vertex Line Maxillary or Mandibular Complete Dentures

The aims of this study were to evaluate the effect of lining maxillary or mandibular complete denture with different length of flange periphery with or without heat cured denture base material on the Patient's Satisfaction and Durability of VertexP®P Line materials. Materials and Methods: Twenty patients (11 Females, and 9 Males), age range 45-73 years with sever resorption completely edentulous arch (8 Patients) or arches (12 Patients) attend prosthodontic department clinic, College of Dentistry University of Mosul with complain of uncomfortable, soreness with previous prosthesis. All the participants were with history of extraction (8±2) years ago. Sixty four complete maxillary and mandibular dentures were constructed, (32) complete denture was done in conventional method and the other half maxillary and mandibular dentures were lined with VertexP®P (Heat cured liner), 2±0.5mm. of flange periphery without hard denture base material, and the other with 4±0.5mm. Each patient answers the Arabic version of (PDSQ) before and after insertion of the prosthesis and after 6months, and 12 months with follow up to 24months. Statistical analysis was done by using Mann-Whitney Test. Results: the results showed that a significant difference between gender, and significant differences between maxillary and mandibular denture for comfort. Durability factor showed significant differences with low percentage of patient comfort after 12 months (p≤0.05). Percentage of cracks in hard denture base flange materials was higher in mandibular denture with 4mm. vertex lined materials. Conclusions: Complete denture lined with VertexP®P heat cured material was more comfortable than conventional denture; Durability of this material was not more than 12 months. Vertex flange periphery should not more than 2±0.5mm

Effect of chemical disinfection on the surface roughness of hard denture base materials: a systematic literature review.

To assess the effect of chemical disinfection procedures on the surface roughness of hard denture base materials. A systematic literature review was conducted using five electronic databases (Medline, Cochrane Library, OpenGrey, Lilac, and Google Scholar) along with hand searching of the bibliographies of all located articles. The review yielded 193 articles. This number was reduced to 25 by using defined inclusion and exclusion criteria. Only one in vivo study was included; all others were in vitro evaluations. For every disinfecting agent, studies were found that reported surface alteration after chemical disinfection. The current literature suggests that changes in roughness might be more often associated with sodium perborate (three out of three studies with positive correlation) and less often with chlorhexidine digluconate and glutaraldehyde (two out of seven and one out of four studies with positive correlation, respectively). Because only single studies were found for glycine-type amphoteric surfactant solution, enzyme solution, ethanol, berberine hydrochloride, chlorine, reactive oxygen species, peracetic acid, cetylpyridinium chloride, and citric acid, no conclusions can be drawn about these disinfectants. Physical surface alteration is only one aspect when deciding on the use of chemical disinfection procedures. More research is needed to clarify whether these procedures can be recommended to patients.

Influence of thickness increase of intraoral autopolymerizing hard denture base liners on the temperature rise during the polymerization process

Increasing the thickness of intraoral autopolymerizing hard denture base liners may result in a temperature rise and a burning sensation for patients. The purpose of the study was to determine whether increasing the thickness of hard autopolymerizing reline resin increases the temperature of the basal seat area of a denture during the polymerization process. Four polyethyl methacrylate and 1 polymethyl methacrylate autopolymerizing reline resin products of 3 different thicknesses were tested. A cobalt-chromium edentulous maxillary cast was used to obtain 150 stone casts, 50 for each thickness of 1, 2, and 3 mm (n=10). Polystyrene record bases were filled with the autopolymerizing reline resin mixture and placed on the cobalt-chromium cast, which was mounted on a reline index, to serve as denture substitutes. Two thermal probes were used to monitor the temperature rise, which was recorded at 30-second intervals until no further increase was noted. Collected data were subjected to a 2-way ANOVA and the Tukey honestly significant difference test (α=.05). The mean temperature increase for the chairside denture reline procedure ranged from 39.45°C for the 1-mm thickness to 46.10°C for the 3-mm thickness. The 2-way ANOVA found significant differences (P<.001) among the different reline resin materials and thicknesses tested. All materials produced an exothermic chemical reaction. An increase in thickness was always accompanied by an increased temperature. The Tukey honestly significant difference test found that the highest temperature increase for all 3 thicknesses occurred in the polymethyl methacrylate resin. The polymethyl methacrylate autopolymerizing hard denture base liner produced a significantly higher (P<.001) exothermic reaction than the other materials included in this study. One of the polyethyl methacrylate resins presented a higher exothermic reaction than the polymethyl methacrylate product at a 3-mm thickness, but the difference was not statistically significant. The polymethyl methacrylate resin presented the highest mean time to reach the maximum temperature for all 3 thicknesses.

Biofilm formation of Candida albicans on the surface of a soft denture‐lining material

Soft denture lining-materials are more susceptible to microbial adhesion than hard denture base acrylic resin. Poor oral hygiene and Candida albicans infection are common among elderly denture wearers as these patients usually have difficulty in keeping them clean. To evaluate the influence of the oral hygiene methods on the formation of a biofilm over a soft denture-lining material. Twenty volunteers were randomly separated into two groups: G1 and G2. Ten volunteers performed daily hygiene of the prostheses with a soft toothbrush and toothpaste. The G2 performed a treatment identical to G1 but also immersed the prostheses in sodium hypochlorite 0.5% for 20 min, once a week. Quantification of the mean score values of biofilm formation at different times were statistically analysed using analysis of variance and Tukey's test (alpha = 0.05). G1 (0.65 +/- 0.52) showed the lowest mean score values of biofilm formation. There was statistical difference between G1 and G2. The highest mean score values were found at 6 weeks (1.3 +/- 1.08) and were statistically different from other times. The oral hygiene methods had a significant effect in the formation of the biofilm over a soft denture-lining material.

Bond strength and rupture properties of some soft denture liners.

The bond strength and rupture properties of three soft acrylic liners (Coe-Soft, Coe Super-Soft and Vertex Soft) and two silicone liners (Molloplast-B and Flexibase) were tested immediately after processing and following immersion in water at 37 degrees C for 7 and 90 days. The bond test gave variable results, as some materials partly peeled and then stretched until rupture occurred. After saturation the acrylic liners exhibited an increase in tear resistance, whilst silicone materials deteriorated, in the case of Flexibase to approximately 25% of its original value. Vertex Soft was the exception, as tear resistance decreased as water sorption increased. Scanning electron microscopy revealed indefinite demarcation between soft acrylic resins and hard denture base, which was not altered after saturation in water. On the other hand, the interface between denture base and silicone liners was clearly visible before and after saturation. The results indicated that denture soft liners had variable water sorption values depending on their basic structure, and some properties changed after immersion in water, a finding that is of relevance to prosthodontic practice.

The Use of a Soft Denture-Base Material in the Management of the Post-Radiation Denture Problem

One of the problems in treating malignant tumors about the oral cavity has been that of maintaining adequate dentition or a substitute following high doses of radiation to that area. With therapeutic doses of radiation to the salivary glands there is an induced dryness of the mouth, which is associated with or precipitates caries of any teeth remaining in the oral cavity (1). Because of this and the difficulty of removing teeth after radiation, it has been a policy in our institution to remove the teeth before radiation therapy to the oral cavity. Occasionally, following treatment we have seen sores develop when the denture has been improperly fitted or fitted too soon after completion of therapy. In these situations and in other denture-sore problems related to diabetes and other diseases, it has been observed that by introducing a soft denture liner between the methyl methacrylate dental base and the epithelium covering the alveolar ridges, the sore could be treated (2, 3). Since this observation, we have instituted a program of using the soft denture base prophylactically in the post-treatment reconstruction of the dentures. Figure 1 shows a cross section of the denture base in relation to the mucosa and bone. The mandible has the shape shown with slight flanges or ridges laterally. It is logical to see why the introduction of additional cushioning material between the hard denture base and the patient's alveolar ridge prevents trauma to the epithelium covering the ridge and effectively distributes the pressure of mastication evenly over the irradiated epithelium. In designing the soft liner it is important to make sure that it adequately covers the denture base at both the apex and the base. Soft denture liners have been tried in the past (4), but a material of permanent resiliency has not been available until recently. This material is durable, nontoxic, is dimensionally stable, odorless, tasteless, and easy to work and to mold by technics not uncommon to the dental office and laboratory. It has excellent bonding characteristics to the methyl methacrylate denture base (5). Technic (6, 7) During the fabrication of the denture it is necessary to press the acrylic denture-base material, then in a doughy state, into a two-part combination metal and dental stone flask. One half of the flask contains the denture teeth and the other half an exact stone model representation of the tissue of either the maxilla or mandible against which the denture will be seated. It is over this model that a wax layer or spacer is formed which is designed as a prototype of the eventual soft denture liner. As the acrylic dough material is pressed into the mold cavity it not only fills the cavity, but takes the contour of the wax layer covering the model of the oral denture-bearing areas.