Prevalence of usage of stainless steel crown, strip crown and zirconia in anterior teeth for paediatric dental patients in different age groups

Aesthetic treatment for primary teeth has been considered as the greatest challenge in paediatric dentistry today. While there is a considerable amount of literature available on the subjective influences of aesthetic in adults, little is known about esthetics in children. The knowledge of the children's aesthetic perception is relevant to pediatric dentists because children are conscious of their dental aesthetic appearance and that of the other children. The aim of this study was to assess the prevalence of usage of Stainless steel crowns, strip crowns and zirconia crowns in paediatric dental patients in different age groups. The study was conducted in a university setting. A total of 120 samples were collected and the data was collected from the dental archives software. It was tabulated in an excel sheet and was analysed by SPSS software by IBM. The output was represented in the form of graphs and pie charts. The most common type of crown used for the treatment of anterior teeth was found to be the strip crown (100 %). Based on gender, about 60.3% of males underwent treatment for strip crowns, whereas 39.62% of females underwent treatment for strip crowns. Among the strip crowns, 27.76% of the primary upper maxillary right central incisors, 20.86% primary maxillary right lateral incisors, 29.65% primary maxillary left central incisors, 21.77% primary maxillary left lateral incisors underwent treatment for strip crowns. 28.93% belong to the year of 4 years who underwent treatment for strip crowns. The p-value obtained after running the chi-square analysis for the correlation of the gender of patients treated and the tooth number was statistically insignificant (p = 0.803).

Fracture Strength and Translucency of CAD/CAM Zirconia Crown for Primary Anterior Tooth

The purpose of this study is to evaluate the validity of primary anterior zirconia crown made with Computer Aided Design/Computer Aided Manufacturing (CAD/CAM) technology by analyzing fracture strength and translucency parameter.<br/>Zirconia crown was designed with CAD software, using 3D scanned data of #61 tooth model. Crown fabrication was performed with CAM machine using zirconia block. Zirconia crowns were divided into 3 groups according to thickness(0.3, 0.5, and 0.7 mm), and fracture strength was compared with 1.0 mm thickness of resin strip crown. The compressive force was applied with universal testing machine at 30° along the incisal edge at increments of 1 mm/min. For translucency evaluation, 0.3, 0.5, and 0.7 mm thickness of zirconia specimens were fabricated and translucency was measured with spectrophotometer.<br/>Among zirconia groups, there was a significant increase in fracture strength as thickness increased (<i>p</i> < 0.05). The fracture strength of zirconia crown was significantly higher than resin strip crown in all groups (<i>p</i> < 0.05). Translucency parameter was highest in 0.3 mm group, and significantly decreased as thickness increased to 0.5 and 0.7 mm (<i>p</i> < 0.05).<br/>Thin primary anterior zirconia crown can be designed and fabricated according to individual needs by using CAD/CAM. Restoration with thin crown would reduce the amount of tooth reduction, risk of pulp exposure, and make more esthetic restoration possible.

Application of support vector machine for the prediction of strip crown in hot strip rolling

In order to enhance the prediction accuracy of the strip crown and improve the quality of final product in the hot strip rolling, an optimized model based upon support vector machine (SVM) is proposed firstly. Meanwhile, for purposes of enriching data information and ensuring data quality, the actual data from a hot-rolled plant are collected to establish prediction model, as well as the prediction performance of models was evaluated by using multiple indicators. Besides, the traditional SVM model and the combined prediction models with the particle swarm optimization (PSO) and the cuckoo search (CS) optimization algorithm are also proposed. Furthermore, the prediction performance comparisons of the three different methods are discussed and validated. The results show that the CS-SVM has the highest prediction accuracy compared to the other two methods, and the root mean squared error (RMSE) of the proposed CS-SVM is 2.05µm, and 98.11% of prediction data have an absolute error below 4.5μm. In addition, the results also demonstrated that the CS-SVM not only with faster convergence speed and higher prediction accuracy but can be well applied to the actual hot strip rolling production.

Numerical Simulation of Strip Shape of High-Strength Steel during Hot Rolling Process

High-strength steel is widely applied due to its excellent mechanical properties. However, its high strength in turn brings great difficulties to production and processing such as hot strip rolling owing to the high rolling force, which results in large elastic deformation of roll stack and poses a huge challenge to the control of strip crown and flatness. In this paper, A three-dimensional (3D) elastic-plastic coupled thermo-mechanical finite element (FE) model for hot strip rolling of high-strength steel is developed and then verified experimentally. This model not only calculates the elastic deformation of rolls and plastic deformation of strip simultaneously, but also considers the effect of temperature variation during hot strip rolling. Based on this valid model, the effects of bending force and shifting value of work roll (WR), back-up roll (BR) size, entrance strip crown and rolling force on strip crown have been investigated quantitatively. The results obtained provide valuable guidelines for industrial strip production.