Evaiuation of Cracks Propagation in Retroflllings with Cinalloy Amalgam

One of the major goals of preradicular surgery is to create a good apical seal. This can be done by sectioning approximately one third of the apex, preparation of a class I cavity, and filling with a biocompatible material. The purpose of this in vitro study was to compare crack propagation in retro filling with two commercially available amalgams. Thirty-four extracted single rooted teeth were divided into two groups. After instrumentation and filling with Gutta percha by lateral condensation method, three millimeter of apex was resected and retro preparations were done by a low speed hand piece and '/> round bur. Then cavities were filled with cinalloy and luxalloy amalgam in-group "one" and "two" respectively. The surface of resected root ends was examined in two stages, after doing retro preparation and retro filling and the presence of any cracks or structural changes was inspected by stereomicroscope 50x. Regard to number and type of cracks, the result of this study showed that there was no significant difference between cinalloy or luxalloy retro fillings. By considering the conditions of this study, cinalloy amalgam can be used as a retro filling material

Comparing and studying crack formation during apical cavity preparation using ultrasonic instruments

One of the major goals of periradicular surgery is to create a good apical sea! at the apex. This"nis done by sectioning of 2 to 3mm from the apex, preparation of a class I cavity and filling with a"nbiocompatible material."nThe purpose of this in vitro study was to determine whether ultrasonic units used for root end"npreparations could change the surface & structure of resected root ends, as competed to common"nmethods of retropreparation. Eighty-five extracted single rooted teeth were divided into five similar"ngroups. Then instrumented and filled with lateral condensation method. Then three millimeter of apex"nwas resected, retropreparaiions in two groups were done with low speed handpiece and round V) ^ur"nand cavities in two other groups prepared with the highest power of dentspiay ultrasonic unit with TFI-"n10 tip and in one other group prepared with the highest power of neo sonic ultrasonic unit with diamond"ncoated CT-1 retro tip."nFollowing root resection and retropreparation the surface of resected root ends were examined for the"npresence of any cracks or structural changes on the surface of resected root ends with stereo microscope"n50x."nThe results of this study showed thai high power settings of ultrasonic units can increase the potential of"ncrack formation on resected root surfaces. In conclusion it is better to use low power setting of ultrasonic"nfor retropreparation

Shear bond strength; Blood contamination; Prompt L-Pop, Composite resin; Compomer

Statement of Problem: Root canal cleaning and elimination of the source of infection are the most important basis and the main requirements for successful root treatment since the main cause of failure in root treatment is the permeation of bacteria or their products into the periapical tissues. Nowadays, the newly designed and prcsented instruments for canal instrumentation can improve root treatment. Purpose: The aim of this study was to compare the decrease in the number of intracanal Enterococcus-faecalis (Ef) among three mechanical instrumentation methods: manual (K-type) and rotary (Race, Profile). Materials and Methods: In this experimental study, 30 single rooted teeth were selected. Three cases were considered as negative and three cases as posetive controls and 24 remainder cases were divided into three experimental groups. All root canals were inoculated by Ef and samples were taken from all canals to prepare microbial cultures. The three instrumentation procedures were: - Crown- down technique with K-type manual system file - Crown- down technique with Profile rotary system - Crown- down technique wiht Race rotary system After instrumentation, microbial cultures were taken from root canals and the reduction rate of bacteria were evaluated and compared using one way ANOVA test with P<0.05 as the limit of significance. Results: There was no significant difference among the three instrumentation procedures regarding bacterial elimination. Conclusion: According to the finding of this study, K-type manual file, Profile and Race rotary systems, all can be used in canal instrumentaion. However, since manual files are more accessible and require less equipment compared with rotary systems, and since the ability of all of these methods is identical regarding bacterial elimination, manual files can be used in straight canal instead of rotary systems

In vitro evaluation of mutagenicity and cytotoxicity of four root canal sealers

Background and Aim: Root filling materials are usually in close contact with living tissues. So their biological properties like mutagenicity and cytotoxicity are important. These properties help us determine the potential damage to periapical tissues, or potential DNA mutations, and malignant transformation of the cells. The aim of this study was to evaluate the mutagenicity and cytotoxicity of four root canal sealers: AH Plus (Dentsply, DeTrey), Ketac-Endo Aplicap (3M ESPE), Sankin Apatite III (Sankin K.K), and Tubli-Seal EWT (Kerr).Materials and Methods: In this experimental in vitro study fresh and set specimens from AH Plus, Ketac-Endo Aplicap, Sankin Apatite III, and Tubli-Seal EWT were immersed in culture medium for 1, 2 and 7 days. Cytotoxicity was assessed using tetrazolium bromide reduction assay (MTT) after 1, 2 and 7 days exposure of diluted extracts to L929 cells. Extracts of sealers in phosphate buffer saline (PBS) were used to examine the mutagenic effects by sos-umu test according to standard procedures. Data were analyzed using one way ANOVA, Kruskall Wallis, Mann Whitney and Post hoc tests with P<0.05 as the level of significance. Results: Extracts of all freshly mixed sealers were cytotoxic. Ketac-Endo Aplicap and Sankin Apatite III showed the lowest toxicity respectively and Tubli-Seal EWT the highest. In contrast to other sealers, the cytotoxicity of Tubli-Seal showed no decrease with time. -galactosidase did not increase significantly thus none of the sealers showed mutagenic effects.Conclusion: Based on the results of this study, Tubli-Seal EWT showed the highest cytotoxicity with time. Other sealers showed decreasing cytotoxicity with time. No mutagenicity effects was observed in none of  tested materials

A Statistical Approach To The Configuration Interaction Problem

A new statistical approach to the configuration interaction problem is proposed. It will potentially reduce the size of CI vectors significantly and thus alleviate one of the main hindrances to doing very large CI calculations. This method will also provide us with statistical confidence limits on lower and upper bounds. These confidence bounds are qualitative different from mathematically more rigorous lower bounds discussed elsewhere. The approach is discussed and possible algorithms presented. © 1991

A Histologic Evaluation on Tissue Reaction to Three Implanted Materials (MTA, Root MTA and Portland Cement Type I) in the Mandible of Cats

Statement of Problem: Nowadays Mineral Trioxide aggregate (MTA) is widely used for root end fillings, pulp capping, perforation repair and other endodontic treatments.Investigations have shown similar physical and chemical properties for Portland cement and Root MTA with those described for MTA.Purpose: The aim of this in vitro study was to evaluate the tissue reaction to implanted MTA, Portland cement and Root MTA in the mandible of cats.Materials and Methods: Under asepsis condition and general anesthesia, a mucoperiosteal flap, following the application of local anesthesia, was elevated to expose mandibular symphysis. Two small holes in both sides of mandible were drilled. MTA, Portland cement and Root MTA were mixed according to the manufacturers, recommendation and placed in bony cavities. In positive control group, the test material was Zinc oxide powder plus tricresoformalin. In negative control group, the bony cavities were left untreated. After 3,6 and 12 weeks, the animals were sacrificed and the mandibular sections were prepared for histologic examination under light microscope. The presence and thickness of inflammation, presence of fibrosis capsule, the severity of fibrosis and bone formation were investigated. The data were submitted to Exact Fisher test, chi square test and Kruskal-Wallis test for statistical analysis.Results: No statistically significant differences were found in the degree of inflammation,presence of fibrotic capsule, severity of fibrosis and inflammation thickness between Root MTA, Portland cement and MTA (P>0.05). There was no statistical difference in boneformation between MTA and Portland cement (P>0.05). However, bone formation was not found in any of the Root MTA specimens and the observed tissue was exclusively of fibrosis type.Conclusion: The physical and histological results observed with MTA are similar to those of Root MTA and Portland cement. Additionally, all of these three materials are biocompatible. However, in order to replace Root MTA and Portland cement type I as less expensive and suitable substitutes for MTA, more longer- term studies with larger number of samples are suggested