Separated root tip formation associated with a fractured tubercle of dens evaginatus: A case report

BACKGROUND Several previous studies have reported an unusual root formation in which a fractured apical fragment of an immature root continued to develop independent of the main root after trauma to an immature tooth.To date,there have been only rare reports of the continuing apical formation of the fractured root associated with dens evaginatus(DE).This paper presents a case of a separated root tip formation associated with a fractured tubercle of DE.CASE SUMMARY An 11-year-old boy was referred for gingival sinus on the buccal side of the right mandibular second premolar(tooth#45).Clinically,tooth#45 was free of caries,but there was a sign of a fractured tubercle of DE on the occlusal surface.Radiography showed that the root canal of tooth#45 was widely radiolucent.A separated root apex was found apically under the main root and was nearly completely formed with an apical orifice at the apical tip.Tooth#45 was diagnosed as tubular fracture of DE with chronic apical periodontitis.A revascularization technique was recommended to treat the tooth.At 3-mo and 1-yr follow-up,the patient remained asymptomatic.Periapical radiography revealed that the separated root tip distally drifted with closure of the apex.However,the root length and thickness of the main root did not increased.CONCLUSION Clinicians should be aware that even if tubercle of DE is fractured in an immature tooth,the root tip may be separated from the main root and completely formed.

Non-adiabatic flow characteristics of micro impeller

Non-adiabatic working condition is one of the major causes of performance deterioration in micro gas turbine engines.Complex micro scale geometry,low Reynolds number operating condition and high surface to volume ratio all lead to severe heat transfer.This paper first established a simple heat transfer model to determine appropriate non-adiabatic boundary condition for computational fluid dynamics(CFD)simulations.Isothermal wall temperature is identified as a heat transfer boundary based on model analysis in combination with material selection for pre-design of the engine and verified by the experiment carried out on directed structure applied in the model.A series of numerical simulations with adiabatic and non-adiabatic boundary conditions is then carried out to study the flow characteristics of high speed,low Reynolds number micro impeller.The physical nature for significant performance degradation related to flow behavior changes due to heat transfer effect is revealed by detailed analysis of typical flow features extracted from the comparative investigation.The result established the basis for heat transfer modeling of micro impeller purposing implications for design modification in order to attain high efficiency and better performance.