Mechanical and tribological behaviour of three-dimensional printed almond shell particles reinforced polylactic acid bio-composites

Recently, composite filament development for three-dimensional printing has emerged and is used for numerous applications. The present research work develops neat polylactic acid and Almond Shell Particles reinforced polylactic acid bio-composites for three-dimensional printing and investigates the effects of printing orientation, including 0°, 45° and 90° orientation, on the tribological and mechanical behaviours of three-dimensional printed materials. The novel almond shell particles reinforced polylactic acid filaments are extruded by the filament extrusion method with the presence of 10% almond shell particles in the polylactic acid matrix, and the samples are three-dimensional printed by the fused filament fabrication technique. Mechanical characteristics such as tensile, flexural, compressive strength, and shore hardness are evaluated with respect to various three-dimensional printing orientations. The surface quality of the three-dimensional printed polylactic acid composite samples is analysed with respect to length and diameter deviation. Length accuracy of the 90° oriented polylactic acid and almond shell particles reinforced polylactic acid bio-composite samples exploits a better accuracy of 99.12% and 98.81%, respectively. It is shown that adding almond shell particles to the polylactic acid matrix decreases the flexural and tensile strength. Among the printing orientations, 0° flat samples result in the maximum tensile strength of 36 and 28 MPa for the neat polylactic acid and almond shell particles reinforced polylactic acid composites, respectively. The lowest contact angle of 54° is observed on the almond shell particles reinforced polylactic acid bio-composites three-dimensional printed with a 90° orientation. The highest contact angle value of 94° is observed on the neat polylactic acid three-dimensional printed with a 0° printing orientation. A tribological study is carried out under dry conditions on the pin-on-disc tribometer by varying the sliding speed (1, 2, and 3 m/s) and load (10, 20, and 30 N). The result shows that the lowest coefficient of friction of 0.22 is achieved for the almond shell particles reinforced polylactic acid bio-composite samples with a 0° printing orientation under a sliding load of 10 N. These kinds of newly developed compostable materials can be used for developing disposable orthotic foot appliances

Evaluation of the design-driven prediction of removable partial denture retention

Statement of problem: Removable partial dentures (RPDs) are a cost-effective treatment designed to replace missing teeth for partially edentulous patients. However, RPDs often have insufficient retention, which results in treatment failure and patient dissatisfaction. Purpose: The purpose of this clinical study was to investigate the factors related to RPD retention that affect patient satisfaction, to clinically validate a newly published model for predicting RPD retention based on the number and position of missing teeth and clasps, and to identify the predictions of patient satisfaction to improve the guidelines for RPD design. Material and methods: Seventy-five patients treated with 107 RPDs delivered at the McGill University Dental Clinic (Montreal, Canada) and Estaing University Hospital (Clermont-Ferrand, France) participated in this study. Data on the RPD design were collected from the clinical records, and the retention of each RPD was tested with the mathematical model designed for predicting RPD retention. Data on patient satisfaction with their RPDs were collected by using a standardized questionnaire (McGill Denture Satisfaction Instrument). Statistical analysis of factors related to RPD retention and patient satisfaction was performed by using the chi-square test and Mann-Whitney test, while the developed model for predicting RPD retention was evaluated by using sensitivity and specificity analysis. Results: The average satisfaction score for all RPDs was 8.2 �1.7 out of http://dx.doi.org/10. Patients were more satisfied with RPDs in the maxillary arch, tooth-supported, or retained by �3 clasps than with RPDs in the mandibular arch, with distal extension bases, or retained by <3 clasps. The materials used for RPD fabrication (metal-based or acrylic resin-based), the number of missing teeth, and the presence of indirect retention were not associated with patient satisfaction. Participants were significantly more satisfied with RPD designs predicted by the developed mathematical model to have enough retention than with RPD designs predicted to have insufficient retention. The mathematical model for predicting the RPD retention showed a clinical specificity of 83% in predicting patient satisfaction. Conclusions: RPD retention predicted from the number and position of clasps and missing teeth might help to determine patient satisfaction. In addition, patient satisfaction with RPDs was influenced by the arch type, the presence of a distal extension base, and the number of clasps.Scopu

Analytical model of I-bar clasps for removable partial dentures

Objective: Clasps of removable partial dentures (RPDs) often suffer from fatigue stress that leads to plastic deformation, loss of retention, and RPD failure. Recently, computer-based technologies were proposed to optimize clasp geometry design. The objective of this study was to create an analytic model of I-bar clasps for computer-aided design (CAD)-RPD. Methods: The analytical model based on mechanical laws was established to simulate I-bar clasp retention, and optimize its design. The model considered the lengths of the vertical (L1) and horizontal (L2) arms of the I-bar as well as the radius (r) of its half-round cross-section. The analytical model was validated with mechanical experiments evaluating the retention of cobalt?chromium (Co?Cr) clasps in vitro and compared with finite element analysis (FEA). Results: The analytical model was in good agreement with the mechanical experiments and FEA, and showed that I-bar clasp design could provide optimal mechanical performance as long as the length of arms (L1 and L2) do not exceed 6 mm. Clasps with L1 &gt; 8 mm and L2 &gt; 9 mm presented stress values exceeding the fatigue limit of Co?Cr. The proposed solution was to increase the radius of I-bar to conserve the initial mechanical performance of Co?Cr. Significance: Co?Cr I-bar clasps perform best on teeth with reduced mesiodistal dimensions (canine and premolar), and their designs could be optimized to prevent stress from reaching the yield strength and the fatigue failure limit.Scopu