Search

Purpose: The introduction of computer-aided design/computer-aided manufacturing (CAD/CAM) technology to the field of removable prosthodontics has recently made it possible to fabricate complete dentures using prepolymerized polymethyl methacrylate (PMMA) blocks that are claimed to have better mechanical properties. However, little was published concerning the clinical deformation of CAD/CAM PMMA. The purpose of this study was thus to compare the clinical deformation of CAD/CAM processed PMMA and conventionally processed heat-cured PMMA implant retained mandibular overdenture bases.Materials and Methods: Thoroughly selected ten completely edentulous patients have received two dental implants in the lower canine region. Two duplicate mandibular overdentures were constructed using CAD/CAM milled PMMA and conventionally constructed heat-cured PMMA. Self cure acrylic resin was used to pick up the attachments to the fitting surface of the mandibular overdenture base. Six linear strain gauges were attached to the lingual side of the polished surface of both overdenture bases to measure strains induced during maximal clenching and gum chewing.Results: Higher strain values were recorded with the conventionally constructed heat-cured PMMA overdentures compared to CAD/CAM constructed PMMA overdentures. The recorded strains were mainly compressive at the midline while the strains at implant sites were tensile. Higher strains were recorded during clenching compared to gum chewing in both assessed overdentures. Conclusion: CAD/CAM constructed PMMA implant-retained mandibular overdenture exhibits less denture deformation during function compared to conventionally constructed heat-cured PMMA overdenture.

Introduction: Computer-aided technology is an innovative method for fabrication of removable prosthodontics. Thus, more prospective clinical trials are necessary to validate this technology. Purpose: The purpose of this study was to evaluate the impact of computer-aided design and computer-aided manufacturing (CAD-CAM) milling technique of prepolymerized Poly Ether Ether Ketone (PEEK) and Poly methyl methacrylate (PMMA) implant assisted overdentures on the chewing efficiency and bite force compared to the conventionally fabricated heat cured acrylic resin overdentures. Materials and Methods: Ten completely edentulous patients with persistent complaint of poor retention and stability of their mandibular complete dentures were selected. Each participant received four dental implants in the anterior mandible. Three identical overdentures were constructed for each patient. According to the processing technique and denture base material, the processed overdentures were classified into three groups. Group I: comprised CAD/CAM milled PEEK overdentures. Group II: comprised CAD/CAM milled PMMA overdentures. Group III: comprised conventional heat cured acrylic resin overdentures. Chewing efficiency of all overdenture groups in terms of measuring the unmixed chewing gum fraction was assessed using two-colour mixing ability test. Biting force was also assessed by a bite force transducer. All assessments were carried out three months after overdenture insertion of each type .Results: Chewing efficiency and biting force increased significantly with the CAD-CAM milled PEEK and CAD-CAM milled PMMA overdentures compared to the conventionally processed heat cured overdentures. However, no statistically significant difference was detected in the chewing efficiency and biting force when PEEK and PMMA overdentures were used. Conclusions: The CAD-CAM fabricated overdentures provided increased chewing efficiency and better biting force compared to conventionally processed heat cured overdentures.

Background: The overall success of denture base resins depends on both mechanical behaviour and biocompatibility, especially in the rehabilitation of diabetic patients. The growth and nourishment of microorganisms is enhanced in diabetes mellitus specially in presence of dentures resulting in denture stomatitis. This study was prompted to assess the microbiological growth and the development of salivary immunoglobulin A (s-IgA) in relation to newly introduced denture base materials used in the rehabilitation of diabetic patients.Materials and Methods: Forty eight completely edentulous patients were selected and divided into two groups: group (A), which included controlled diabetic patients and group (B) included non-diabetic patients. Each group was further divided into four sub groups according to the denture base material. Sub group I, patients were received thermoplastic VertexTM ThermoSens denture bases; sub group II, patients were received heat cure acrylic resin dentures reinforced with nano zirconia oxide particles (nano-ZrO2); sub group III, patients were received conventional heat cure acrylic resin dentures; where sub group VI, patients were received conventional heat cure acrylic resin dentures relined with self-cure acrylic resin. For each participant, non-stimulated saliva samples were collected before denture insertion, and one, two and three months after wearing dentures. Samples were inoculated and incubated both aerobically and anaerobically on selective media for Streptococcus mutans, Lactobacilli and Candida. Then, isolated microorganisms were identified, the characteristic colony forming units per millilitre (CFUs/ml), were calculated and the salivary immunoglobulin A level was measured by Enzyme-linked immunosorbent assay (ELISA).Results: The results revealed increase in the CFU values of Candida, Streptococcus mutans, Lactobacilli and the level of salivary immunoglobulin A in all the assessed patients following denture insertion. However, significant lower values were evident in patients rehabilitated with ThermoSens and nano-ZrO2 reinforced bases compared to heat cure acrylic and self-cure relined bases. Significant increase in CFU values and level of s-IgA were found in diabetic compared to non-diabetic patients after insertion of all denture bases. Conclusion: ThermoSens and nano-ZrO2 reinforced denture bases showed less microbial growth and salivary immunoglobulin A level compared to heat cure and self-cure relined bases in both controlled diabetic and non-diabetic patients, hence, more biocompatible. Keywords: Thermoplastic polyamide, Vertex ThermoSens, Reinforced acrylic, Zirconia oxide nanoparticles, Diabetes mellitus, Candida, Oral bacteria, Salivary Immunoglobulin A.

Aim of the study: Denture adhesives have long been recognized by denture wearers as a valuable assistant to denture retention and stability especially for patients reporting dissatisfaction with conventional dentures as diabetic patients. There is no available guide to select the proper adhesive form with least effect on oral mucosa. This clinical study assessed the impact of different complete denture adhesive forms on oral epithelial cells’ DNA in elderly patient with controlled diabetes.Materials and Methods: Fifteen completely edentulous controlled diabetic patients were selected and complete dentures were constructed. After two weeks of complete denture insertion, patients were prescribed with denture adhesives for another two weeks. According to the used adhesive form, patients were divided into three equal groups; group (I) used denture adhesive paste, group (II) used denture adhesive powder, where group (III) used denture adhesive cushion. The maxillary alveolar mucosae of all patients were swabbed to collect epithelial cells before denture insertion, two weeks after wearing the denture and two weeks after adhesive application. DNA analysis was carried out for the swabbed epithelial cells. The percentage of Genomic Template Stability (GTS %) was assessed and compared for all patients at various time intervals. Results: Genomic Template Stability decreased significantly in all patients two weeks after denture insertion while, significant increase in GTS% was observed two weeks after denture adhesives application. Cushion adhesive showed a significant increase in GTS% compared to paste and powder adhesives. Conclusion: Genomic Template Stability of controlled diabetic denture wearers improved when paste, powder or cushion adhesives were used. Cushion adhesive had a better effect on GTS% compared to paste or powder adhesives.

Purpose : Prosthodontic complications related to implant assisted maxillary overdentures are reported more often. This in vitro study examined the influence of implant number and palatal coverage on retention, cyclic fatigue and denture base deformation of maxillary overdentures supported by five versus seven unsplinted mini implants.Materials and methods: An edentulous model of maxillary arch with mini diameter implant dummies was fabricated. The implants were inserted into the anterior, premolar, and molar areas. Maxillary experimental dentures with complete and partial palatal coverage were fabricated. Cyclic dislodging forces were applied to assess cyclic fatigue and the resulting change in denture retention. Strain gauges were used to assess the deformation induced into the dentures when cyclic fatigue test was carried out on overdentures assisted by seven implants and five implants after excluding the posterior implants. Results: Cyclic fatigue and denture base deformation induced in overdentures with partial palatal coverage assisted by five mini implants were significantly higher than overdentures with complete palatal coverage whether assisted by seven or five implants (P < .05). Overdentures with partial palatal coverage assisted by seven mini implants exhibited non-significant changes in retention, cyclic fatigue and base deformation when compared to overdentures with complete palatal coverage assisted by five mini implants.Conclusion: Maxillary five mini implant assisted overdentures with partial palatal coverage revealed much higher cyclic fatigue and induced denture base deformation than overdentures with complete palatal coverage regardless of the mini implant number. With respect to retention, fatigue failure and denture deformation, maxillary seven mini implant assisted overdentures with partial palatal coverage exhibited no significant difference comparable to five mini implant assisted maxillary overdenture with complete palatal coverage.

Purpose: This study was conducted to determine the effect of various impression techniques on the displacement of flabby tissues overlying the edentulous maxillary ridge. In this study Ten completely edentulous maxillary arches patients with anterior flabby ridges participated in this study. For each patient five secondary impressions were recorded and divided into five groups according to impression technique used. Group I: comprised impressions following the mucocompressive technique. While, in Groups II, III, IV and V had used different mucostatic impression techniques. Soft tissue displacements in X, Y, Z axes and total 3-D in relation to a fixed reference point were recorded for each impression using modified Measurescope. The data were collected and statistically analyzed. The results obtained showed that there were significant differences in soft tissue displacement of all tested groups in both three coordinates (X, Y and Z) and total 3-D. Also; the results showed significant difference in soft tissue displacement of tissues recorded by the four mucostatic impression technique groups compared to mucocompressive impression technique. A significant difference was found between one step mucostatic impression technique group, and two step mucostatic impression techniques. Conclusions: Based on the results of this study, soft tissue displacement of maxillary flabby ridge during impression procedure occurred along X, Y and Z directions for all tested impression techniques. The mucostatic impression techniques generated less soft tissue displacement than the mucocompressive technique. Two-step mucostatic impression techniques produced less soft tissue displacement compared to the one step mucostatic impression technique.

A total number of 50 rectangular specimens, made of hybrid visible light cured composite were used in the present study. The specimens were divided into 5 groups (10 specimens each). Each group was treated with one of the post-cure heat-treatment methods. It was found that, the specimens exposed to the normal post-cure heat-treatment method demonstrated the minimum dimensional change values (0.62%, 0.166%, 1.4% and 2.23%) for length, width, and volume respectively. On the other hand, the specimens exposed to the (delay-heat) water ageing method displayed the maximum values (2.9%, 0.56%, 9.2%, and 9.98%) for the length, width, height, and volume respectively.