FIGURE 6 Full-scale simulation with modified hydrodynamic conditions at 20°C Green lines represent model simulation results obtained by assuming d = 0.01 for all chambers; red lines by assuming d = 10,000 for continuous-flow stirred tank reactor for contacting chamber and d = 0.01 for reactive chambers; and blue lines by using d = 0.01 for all chambers and reduced ozone input (to achieve the same target inactivation as shown in Figure 5).

Increasing amount of construction waste and, concrete remnants, in particular pose a serious problem. Concrete waste exist in large amounts, do not decay and need long time for disintegration. Therefore, in this work old demolished concrete is crashed and recycled to produce recycled concrete aggregate which can be reused in new concrete production. The effect of using recycled aggregate on concrete compressive strength has been experimentally investigated; silica fume admixture also is used to improve recycled concrete aggregate compressive strength. The main parameters in this study are recycled aggregate and silica fume admixture. The percent of recycled aggregate ranged from (0-100) %. While the silica fume ranged from (0-10) %. The experimental results show that the average concrete compressive strength decreases from 30.85 MPa to 17.58 MPa when the recycled aggregate percentage increased from 0% to 100%. While, when silica fume is used the concrete compressive strength increase again to 29.2 MPa for samples with 100% of recycled aggregate.

Introduction: With the availability of diff erent post systems and various studies on the strength of teeth restored with posts, the controversy as to which post systems provide better stress distribution of post and longevity of tooth has not been resolved. The purpose of this study was to compare the stress distribution of three diff erent post materials using fi nite element analysis.Materials and nethod: Three dimensional fi nite element models of central incisor, three posts with crown were constructed on computer with software. Posts of three diff erent materials (Ni-Cr post, Glass fi ber post, and Zirconia post)with zirconia crown were virtually generated and a force of 100 N was applied at an angle of 450 on the palatal surface of the crown. Von Mises stresses were evaluated on the cervical, middle and apical third of the root. Results:The maximum stresses were seen on the cervical one-third in each post material indicating that this region is more prone to fracture in tooth restored with posts. Among the three materials tested, Ni-Cr post showed maximum stress generation followed by Zirconia post and glass fi ber post. The maximum stresses generated by the posts were 11.4 MPa, 10.58 MPa and 4.11 MPa respectively. Conclusion:The less rigid post material like glass fi ber post can be used in an endodontically treated anterior teeth.

A bstract Introduction An accurate impression is one of the prime factors for success of any restoration, more so in field of fixed prosthodontics. The critical aspect is to reproduce fine surface details along with ease of use. Knowledge of impression materials and the techniques to which each is best suited is essential in achieving consistent results. Objective of the study The purpose of this study is to evaluate the accuracy of various putty-wash techniques in a laboratory model that simulated the clinical practice. Materials and methods A metal master model, containing three full crowns fixed partial denture (FPD) abutment preparations, was fabricated. A perforated custom tray was fabricated that can be placed in the same position on the master model for each impression. For each technique, 10 impressions of the master model were made and poured using a die stone. The measurements were made of the models using a measuroscope and the accuracy of the impressions was recorded. Results The statistical comparison between groups I, II, III, and IV casts measurements by using the Mann–Whitney test showed highly significant statistical difference between the various groups from each other ( p < 0.001) Conclusion The accuracy of the working casts obtained from group III impression (two-step using 1 mm coping) was the best, whereas it was least with group II impression (two-step using polyethylene spacer). How to cite this article Gautam N, Ahmed R, Sharma S, et al. A Comparative Study to Evaluate the Accuracy of Various Spacer Thickness for Polyvinyl Siloxane Putty-wash Impression Techniques: An In Vitro Study. Int J Clin Pediatr Dent 2020;13(5):536–542.

White spot lesions are an early stage of tooth decay formation. White spot lesions are commonly associated with the fixed orthodontic treatment and it poses a significant problem in the clinical setup. These lesions are caused by tooth demineralization which results in visible enamel changes. Accumulation of plaque around the brackets and its improper removal is the main etiological factor behind the incidence of white spot lesions. The purpose of this study is to review the literature on the prevalence of white spot lesions and methods with which it can be prevented.