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$Assessment of flexural strength and fracture of ... - Dental Press$

original articleAnalysis of forces developed during root canal fillingby different operatorsMaria Rosa Felix de Sousa G. GUIMARÃES, DDS, MSc 1Henner Alberto GOMIDE, DDS, MSc, PhD 2Maria Antonieta Veloso C. de OLIVEIRA, DDS, MSc 3João Carlos Gabrielli BIFFI, DDS, MSc, PhD 4AbstractObjectives: Endodontic procedures might contribute tothe development of vertical root fracture as well as otherlocalized defects such as craze lines or incomplete cracksin root dentine. The objective of this study was to evaluatethe maximum fracture resistance and the force producedby five different operators in lateral and verticalcondensation during root canal filling. Methods: 74 humanteeth, superior canines (SC) and inferior premolars(IPM) were selected. In order to determine the maximumfracture resistance during condensation, 24 teeth weresubmitted until failure to an axial compression load in auniversal testing machine. Fifty teeth were used in orderto measure the axial condensation force by means of adevice developed to simulate clinical working conditions.Results: Fracture resistance mean values in kg were: SC= 14.96±2.65 and IPM = 7.56±1.05. Mean values of forceapplied by each of the five operator in Kg were, respectively:2.49; 3.75; 2.24; 2.08 and 1.18. None of the operatorsachieved teeth’s maximum fracture resistance duringprocedures. Conclusions: Different behaviors amongfive professionals monitored were observed for the sametechnique of root canal filling. The increase in strengthduring condensation had no radiographic improvement ofroot canal filling. During the root canal filling, lateral andespecially vertical condensation, must be performed withreduced apical strength and pressure, avoiding excessiveand unnecessary stress to root dentin.Keywords: Lateral condensation technique. Root canalfilling. Condensation force.Guimarães MRFSG, Gomide HA, Oliveira MAVC, Biffi JCG. Analysis of forces developed during root canal filling by different operators. Dental Press Endod. 2011 apr-june;1(1):52-7.1Professor, Department of Endodontics, São Lucas Dental School, Porto Velho, RO, Brazil.2Retired Professor, Faculty of Mechanical Engineering, Federal University of Uberlândia,Uberlândia, MG, Brazil.3Department of Endodontics, Faculty of Dentistry, Federal University of Uberlândia, Uberlândia,MG, Brazil.4Professor, Department of Endodontics, Faculty of Dentistry, Federal University of Uberlândia,Uberlândia, MG, Brazil.Received: January 2011 / Accepted: February 2011Correspondence address: Maria Rosa Felix de Sousa Gomide GuimarãesAv. Pará, 1720, bloco 2B s/25, bairro UmuaramaZip code: 38.403-036 - Uberlândia/MG, BrazilE-mail: antocassia@hotmail.com© 2011 Dental Press Endodontics 52 Dental Press Endod. 2011 apr-june;1(1):52-7
Guimarães MRFSG, Gomide HA, Oliveira MAVC, Biffi JCGIntroductionEndodontic procedures may contribute to the developmentof the vertical root fracture as well as otherdefects such as fissures and incomplete cracks on rootdentin. 1 These located defects may have the potential todevelop fractures 2 and should, therefore, be prevented.Vertical root fracture is a clinical implication that maybe associated with endodontic treatment 3 and, being alongitudinal fracture, it extends throughout the entirethickness of dentine from the root canal to the periodontium.4 The prognosis is very unfavorable, resultingin tooth extraction or resection of the affected root. 3,4Several factors may be responsible for increasing theroot fracture risk; some may not be controlled by thedentist such as tooth structure’s reduced physical propertiescaused by physiological and pathological processes.5 But there are many other factors that may becontrolled during and after the endodontic treatment.Amongst others, we can list: access cavity and root canalpreparation, irrigation, obturation, post space preparation1,5 and coronal restoration. 5In vitro studies examined the effect of various obturationtechniques on endodontically treated teeth’sfracture resistance. 1,2,6-11 Greater forces occur when lateralcondensation obturation warm vertical compactionor thermomechanical compaction techniques areused, in comparison with the thermoplasticized condensationtechnique. 6,7 During lateral condensation,the use larger than # 25 spreaders caused a significantreduction on roots fracture resistance. 11 This is due tothe fact that the insertion of the spreader during obturationcan generate stresses within the root canal. 12However, even when thin spreaders are used duringlateral condensation, root surface craze lines occur. 2The pressure applied during lateral condensation isno sufficient to cause vertical root fracture, 10 but it canproduce a greater number of root dentin defects 12 thannoncompaction canal filling was used. 1This way, the present study evaluated the fractureresistance and the force produced by five different operatorsin lateral and vertical condensation during rootcanal filling.Material and MethodsSeventy-four freshly extracted single canals humanteeth (superior canines and inferior premolars) werestored in 10% aqueous formol solution. Teeth werehorizontally sectioned by means of a diamond disc(KG Sorensen, Barueri, SP, Brazil) under water cooling,near their cement-enamel junction. Then, the measuredroots were stored individually and their moisturewas maintained using a piece of gauze soaked inphysiological solution.Roots were embedded into Adesivo B Flexible EpoxiResin (Polipox, Interlagos, São Paulo, Brazil), parallel tothe walls of 25 mm- height PVC cylinders with an externaldiameter of 25 mm and an internal diameter of 21mm. Silicone was used to facilitate the positioning andfixation of the roots inside the cylinder.Passed 48 hours from the teeth´s inclusion, whichcorresponded to the period of resin’s final polymerization,the samples were randomly divided. Fifty sampleswere used to measure the axial force applied during lateraland vertical condensation. Five endodontists participatedin this study. The professionals were namedas A, B, C, D and E. Each professional received 10samples, being the 2 first used to calibrate the equipmentduring the monitoring of the lateral and verticalcondensation procedures according to each professional.The remaining 8 samples were obturated by thelateral and vertical condensation obturation. Aiming toreproduce dentists working conditions in their offices, adevice was specially developed for this study: a 60 cmmetallic stem was adapted to the universal testing machine(EMIC DL-2000, São José dos Pinhais, PR, Brazil)with a 20 kg load-cell in a way that the samples’ positionwas similar to that in the oral cavity (Fig 1A). Besidesthat, over this bar, a metallic support was used so thatthe professionals could rest their hands on it during theclinical procedures (Fig 1B). During the procedures, thegenerated forces were recorded by the testing machineM Test software and turned into graphs in order to analyzethe applied forces in Kg afterwards.Root canal instrumentation was carried out with theconcern of standardizing its dilatation, following the techniquedescribed by Goerig, Michelich and Schultz. 13 Aftercanals drying, the main gutta-percha cone was selected,in way that it presented a locking 1 mm short the radicularapex, matching the work length. A sealer based on zincoxide and eugenol (Endofill, Dentsply, Petrópolis, Brazil)was inserted into the canal using the main cone and itwas applied to the whole canal wall. After the positioningof the main cone, spaces were generated by meansof a finger spreader (Maillefer, Ballaigues, Switzerland)© 2011 Dental Press Endodontics 53 Dental Press Endod. 2011 apr-june;1(1):52-7
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