Prevalence of Taurodontism of Permanent Molars in Dental School of Shahid Beheshti University from 2000 to 2006

Objective: Taurodontism is a dental anomaly characterized by elongation of root body and apical displacement of the pulp chamber floor associated with shortening of roots and their narrowing at  the cementoenamel junction (CEJ). Due to having a dilated apical one-third, these teeth may cause complications during extraction, locating canal orifices and instrumentation. This study aimed to assess the prevalence of taurodontism of permanent molars in a small Iranian population.Methods: This retrospective descriptive study was conducted on 1,100 dental records of patients that were randomly selected among 5,672 records available in the archives of School of Dentistry,  Shahid Beheshti University of Medical Sciences from 2000 to 2010 that met the inclusion and exclusion criteria. Teeth with extensive restorations or carious lesions were excluded. One observer evaluated all the radiographs and the teeth were classified based on the presence or absence of taurodontism. All positive cases were re-evaluated by two examiners and accurate measurements were made using a caliper according to Shifman and Chanannel criteria.Results: A total of 1,184 radiographs were evaluated; of which 447 (47.7%) belonged to males and 737 (62.3%) belonged to females. A total of 5,532 first and second molars of both jaws were evaluated  in  these  radiographs.  There  were  1,310  (23.7%)  maxillary  first  molars,  987 (17.8%)mandibular first molars, 1,731 (31.3%) maxillary second molars and 1,504 (27.7%) mandibular second molars. Overall, 293 teeth had taurodontism; of which, 179 belonged to females and 114 belonged to males.Conclusion: The prevalence of taurodontism in the understudy population was 6.41%.  It appears that taurodontism is not as rare as it is thought to be

Effect of Mixed Foundry Sand and Rice Hull Ash on the Mechanical Properties of Concrete

Waste foundry sand is the by-product of metal casting industry. Rice hull which is often burned after it is removed from rice is also a by-product of the agriculture industry. Disposing of these wastes leads to the environmental pollution. To optimal use of these wastes and avoid the adverse effects of dumping them, regular sand has been partially replaced with the waste foundry sand and rice hull ash pozzolan has been also used as a partial replacement for cement in making concrete. XRF, XRD and SEM experiments, compressive strength, tensile strength (Brazilian), flexural strength, modulus of elasticity and water absorption tests have been conducted. The results showed a slight decrease in compressive strength of samples in which regular sand was replaced with waste foundry sand by 15 percent; however, adding the rice hull ash to this mixture led to make a concrete comparable with control one. Also, using foundry sand in mix designs affects their physical performance. Moreover, the use of waste foundry sand in concrete is both economically and environmentally suitable