Comparative adaptation accuracy of acrylic denture bases evaluated by two different methods.
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This study examined the adaptation accuracy of acrylic denture base processed using fluid-resin (PERform), injection-moldings (SR-Ivocap, Success, Mak Press), and two compression-molding techniques. The adaptation accuracy was measured primarily by the posterior border gaps at the mid-palatal area using a microscope and subsequently by weighing of the weight of the impression material between the denture base and master cast using hand-mixed and automixed silicone. The correlation between the data measured using these two test methods was examined. The PERform and Mak Press produced significantly smaller maximum palatal gap dimensions than the other groups (p<0.05). Mak Press also showed a significantly smaller weight of automixed silicone material than the other groups (p<0.05), while SR-Ivocap and Success showed similar adaptation accuracy to the compression-molding denture. The correlationship between the magnitude of the posterior border gap and the weight of the silicone impression materials was affected by either the material or mixing variables. (+info)
Color differences between artificial and natural teeth in removable partial denture wearers.
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The purpose of this study was to investigate differences between natural tooth color and that selected for artificial teeth in partial dentures at our department with a view to establishing criteria for obtaining greater harmonization between colors. The participants in this study comprised partial denture wearers visiting the Department of Prosthodontics, Tokyo Dental College Chiba Hospital, in whom both artificial teeth and natural teeth were present in the maxillary anterior tooth area. Natural tooth color was measured according to VITA classical shade guide number using a dental color measurement apparatus. Artificial tooth color in partial dentures produced at our department was investigated by referring to medical records. Color of 28 participants' natural teeth and 345 participants' artificial teeth was investigated. Differences in color distribution between the natural and artificial tooth were analyzed using the Fisher exact test. The most frequent color of natural tooth was C-type, accounting for 39%, followed by D- at 32%, A-at 22% and B-type at 7%. In terms of artificial tooth color, A-type was the most common (97%). The color distribution of natural teeth differed significantly from that of artificial teeth in partial dentures. These results suggest that artificial tooth color did not harmonize with the color of the natural teeth in partial denture wearers. (+info)
Stress distribution in retentive arms of combination clasps used on premolars.
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INTRODUCTION: Stresses resulting from cast clasp arms during insertion and the removal of removable partial dentures are the main causes of deformations or fractures. Therefore, achieving clasp designs producing less stress is very important. OBJECTIVE: Retentive clasp arms used for premolars were investigated through the reverse engineering approach. The aim was to determine stress distribution in oval and half-oval clasps cross-sections in order to analyse biomechanical behavior. MATERIAL AND METHODS: Purposely designed experimental three-dimensional (3D) models of the clasp arms were constructed on the buccal surface of an upper first premolar, to be used for structural simulations. 3D teeth models obtained after laser scanning were used as a support for retentive clasp arms modeling. Parameters of the clasp arms like length, thickness and cross-section were considered for the simulation of stainless steel wires. A concentrated load of 5 N was applied at the inner tip of the clasp arm. RESULTS: A precise model of the coronal buccal surface of an upper first premolar was generated. This model was a useful tool in designing stainless steel clasp arms of different thickness and cross-section. In all cases, high stress values were located on the inner surface of the clasp arm, in the part located above the height of the contour. A similar bending stiffness was observed between the half-round cross-section design with a diameter of 1 mm and the round cross-section design with a diameter between 0.6 and 0.7 mm. CONCLUSIONS: This in vitro study demonstrated that the reverse engineering approach and structural analyses provide a powerful tool for designing clasps and visualizing fracture risk areas and for choosing the adequate cross-section for each case. Within the limitations of this study, it was suggested that, on premolars, the biomechanical performance of half-round cross-sections for the retentive arms may be higher than round sections of clasp arms showing similar mechanical stiffness. (+info)
Implant overdentures: dental students' performance in fabrication, denture quality, and patient satisfaction.
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The purpose of this study was to evaluate dental students' performance when fabricating a mandibular two-implant overdenture (OD) as compared to conventional dentures (CD) and to determine if these prostheses were successful. Twenty students and twenty patients were divided into two groups: complete denture group (CDG) and maxillary denture and two-implant OD group (ODG). Students' progress was evaluated at each appointment as they were given a clinical assessment score (CAS), which varied from 1 (unacceptable, needs to repeat procedure) to 4 (acceptable, no errors). The success of the prosthesis was evaluated by the patients using a visual analog scale (VAS) and an expert (a prosthodontist) using a denture quality assessment (DQA) form. Performance for both groups was not statistically different across all eight appointments (CDG 3.16 versus ODG 3.25; p=0.46). Patients with ODs reported greater stability with their dentures (p=0.048) and greater ability to chew than patients with CDs (p=0.03). There were no differences between the groups in terms of expert appraisal (ODG 71.1 versus CDG 67.5; p=0.59). The performance of dental students when fabricating a two-implant OD is thus not different from that of a CD. Students can successfully fabricate a two-implant OD as perceived by both patients and prosthodontists. (+info)
Evaluating tooth color matching ability of dental students.
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Visual shade matching has remained a skill acquired through clinical experience. The purpose of this study was to evaluate the shade matching ability of dental students as they progress through their education. Sixty-five students, representing four levels of experience by year enrolled in dental school, participated in this study. Students were given a preclinical shade tab matching task. They were also asked to choose the best shade match for a natural tooth in each of three patients. The natural tooth shade matching task was designed to have simple, moderate, and complex cases to match. The frequency of correct answers was compared across samples across the four levels of fundamental tab match ability and clinical experience. On average, 51 percent of the students were able to match the correct shade tab in the matching task in a bench setting. For the natural tooth color matching task, 49.2 percent of the students selected the clinically acceptable color matched shade tabs (DeltaE*+info)
Viability of using enamel and dentin from bovine origin as a substitute for human counterparts in an intraoral erosion model.
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