In vitro comparison of the antimicrobial effect of calcium hydroxide mixed with different vehicles on infected root canals

The main purpose of root canal treatment is to eliminate microorganisms and their by-products. The use of antimicrobial agents besides mechanical preparation ins necessary to achieve this goal. On the other hand, calcium hydroxide is ineffective in Killing some resistant microorganisms. The aim of this in vitro study was to compare the effectiveness of calcium hydroxide mixed with different vehicles [Distilled water, Sodium hypochlorite or Chlorhexidine] in disinfecting the root canal and dentin of the infected teeth. After root canal preparation of 130 single rooted teeth, they were sterilized and randomly divided into three experimental [n=40 in each grou] and two control groups. Then, the specimens were experimentally infected with E. faecalis and C. albicans during a period of 21 days. The infected specimens were exposed to the pastes of calcium hydroxide mixed with distilled water solution, CHX or NaOCl. Antimicrobial assessment was performed at 24h, 48h, 1 week and 2 week [n=10 in each time interval]. Microbial samples were obtained from the root canals before and after the experiment. Also, the dentin samples were obtained for evaluating dentin disinfection. The data were analyzed, using Two-way ANOVA test. This study showed that there was no significant difference between the three intracanal medicaments and also between the four periods of time [p>0.05]. However, the mixture of calcium hydroxide/distilled water did not completely eradicate E. faecalis from dentinal tubules at any period of time. According to the results of this study, calcium hydroxide mixed with CHX or NaOCl is better than calcium hydroxide mixed with distilled water for dentin disinfection in cases of persistent intracanal infection

[Evaluation of the relation between bond strength of ah26 and dorifill to dentin and gutta percha and their apical microleakages]

The sealing ability of different endodontic sealers has been evaluated using micro-leakage tests and/or measuring their bond strength [adhesion] to dentin and gutta percha. However, the micro-leakage studies do not determine the location of the micro-leakage. Therefore, to determine whether the micro-leakage occurs in the dentin-sealer or the gutta percha- sealer interfaces, the bond strength studies are required. The purpose of the present study was to measure the bond strength of AH26 and Dorifill to dentin and gutta percha and to compare their relationship with their apical microleakage values using electrochemical test. In this laboratory study, to evaluate the tensile strength of AH26 and Dorfill, the dentinal coronal surface of the twenty four extracted maxillary and mandibular first and second molars were used. Twenty four disk shape specimens of the gutta-percha were prepared. Two groups of sealers [AH26, Dorifill] were placed within the aluminum customized cylinders [n=48] and stabilized on the dentin and gutta-percha. The tensile strength of each sealer with dentin; and gutta- percha were measured separately by a universal testing machine [zwick] in four groups [12 samples in each groups]. The data were analyzed using independent samples t-test. To evaluate the sealers' apical leakages using electrochemical method, 36 maxillary and mandibular canines were used. The selected teeth randomly divided into 2 groups [16 sample in each group] and 4 teeth as control. After canal preparation, each group was filled with one of the sealers and guttapercha using lateral condensation method. Measurment of current flow through the test system were recorded as a voltage drop across the 100-ohm resistance by a digital multimiter every 72 hour. The data were analyzed using Mann- Whitney test. The bond strength of AH26 to both dentin and gutta-percha was significantly stronger than Dorifill. AH26 had a significantly lower magnitude of apical microleakage than Dorifill. The results of this study showed a direct relation between sealers' bond strength to dentin and gutta-percha with their resistance to apical micro-leakages

Effect of Profile and Race rotary systems on original canal anatomy in simulated severely curved canals

Recent advances in technology have permitted manufacturers to produce endodontic files from NiTi alloy and rotary systems. According to manufacturers, these files maintain original canal shape better than hand files and reduce treatment time. The aim of this study was to compare a new rotary system [Race] with an older one [Profile] in maintaining the original shape of curved canal and the working length as well as the procedural accidents rate. In this experimental study, 40 polyester blocks with curved canals [45], were fabricated and divided into 2 groups. After primary working length determination and staining with methylene blue, photographs were taken. Canal preparation was done with Profile and Race rotary systems according to manufacturers and working length was measured again. Canal staining by eosin was performed and photographs were taken for the second time. The two images were superimposed and changes in canals anatomy in 5 sections were recorded. Data were analyzed by t test with p<0.05 as the limit of significance. There was no significant difference in inner and outer canal walls transportation between 2 groups [P> 0.05]. Changes in working lengths and procedural accidents were similar in the studied groups [P> 0.05]. Based on the results of this study, changes in canal anatomy and working length of simulated severely curved canals as well as procedural accidents rate are similar in two rotary systems and both are suitable for canal preparation. The mean and standard deviation of shear bond strengths [in Mpa unit] of all groups were as follows: One-Step - 19.60 +/- 1.83 One-step +H = 19.72 +/- 2.01 Single Bond-21.44 +/- 3.94 Single Bond +H =18.26 +/- 2.85 Prime and Bond NT-26.51 +/- 5.02 Prime and Bond NT+H -26.98 +/- 5.70 Excite -29.78 +/- 3.85 Excite +H -19.07 +/- 9.94 Analysis of the results revealed that the use of 5.25% sodium hypochlorite for one minute on the surface of demineralized dentin significantly decreased the shear bond strength of Excite and Single Bond [P<0.05]. For Prime and Bond NT and One-Step, shear bond strength increased with this treatment but was not statistically significant [P>0.05]. Based on the results of this study, collagen removal from demineralized dentin surface caused a significant decrease in shear bond strength of alcohol and water/alcohol based bonding systems, while the bonding strength of the acetone based systems was not affected. Therefore, the effect of collagen removal on shear bond strength depends on the bonding system applied and its solvent type

Comparison of the maintenance of root canal anatomy in severely curved resin blocks using RaCe and Flexmaster rotary systems

Various rotary systems are available on the market, therefore selection of a proper instrument for root canal therapy is difficult. The aim of this study was to compare the maintenance of working length and original shape of curved canals and the incidence of procedural errors, using the newly introduced Race and the older Flexmaster rotary systems. In this experimental study, 40 resin blocks with a 45°Curvature were randomly divided into two groups. After determination of the working length and staining with methylen blue, photographs were obtained. All root canals were prepared using Flexmaster and Race rotary systems according to the manufacturers' instructions. The working lengths were determined once more and the prepared canals were stained with Eosin and photographs were taken. Pre- and post-preparation images were superimposed and changes in the canal walls were evaluated. Data were analyzed using Mann-Whitnney and student t-tests. The mean canal transportation [determined from the inner and outer width measurements] was higher for Race as compared to Flexmaster. The mean loss of working length in the Race [0/54mm] and Flexmaster groups [0/59 mm] was similar. The incidence of zips and elbows was%20 and%35 in the Race and Flexmaster groups, respectively. Based on the results of this study, Race instruments produce more changes in the anatomy of severely curved simulated root canals, as compared to Flexmaster instruments

investigation on the adhesion of two endodontic sealers [AH 26, Dorifill] to dentin

Tensile bond strength of endodontic sealers to dentin is an indicative of sealer's adhesion to dentin. Due to the fact that Gutta-percha is not bonded to dentin walls, the adhesion of a root canal sealer to dentin is an important issue in endodontics. The goal of this study was to compare the tensile bond strength of two sealers, AH[26] and Dorifill, with dentin. In this experimental study, 30 extracted human first and second molars, with no occlusal carries, were stored in 0.9% Nacl. The enamel was removed 1mm below the central occlusal groove. The roots were cut at 2mm below the CEJ. Wire hooks, made of orthodontic wire [0.5mm], were fixed to dentin surfaces and sealers. Aluminum cylinders were used to place sealer on the dentin surface and stabalized with two drops of wax. Two groups of sealers [AH26, Dorifill] were placed within the cylinders [n=15]. The lower end of the wire hook was lowered into the soft unset sealer. After 24 hours, wax drops were removed and each specimen was tested by zwick tester at the speed of 2mm/min. Data were subjected to Independent samples t-test. The mean tensile bond strength values were 1.855 +/- 0.383 Mpa for AH[26] and 0.135 +/- 0.04 Mpa for Dorifill attributing higher tensile bond strength to AH[26] than Dorifill. Applying AH[26] in root canal therapy would be more successful than dorifill

Influences of posterior teeth's pain intensity and duration on the incidence and characteristics of orofacial pain

Referred pain from toothache may obscure accurate identification of the offending tooth. For example, in the presence of pulpal pathology, patients may complain not only of pain in the offending tooth, but they also report widely pain in other orofacial structure. This study examined the influence of posterior toothache intensity, quality and duration on the incidence and characteristics of referred orofacial pain. In this cross sectional study, 462 subjects with posterior toothache were recruited randomly from patients referred to the faculty of dentistry. After clinical and radiographic examination, the patients were asked to complete a questionnaire consisting of a numerical rating scale for pain intensity and chose verbal descriptors from McGill questionnaire to describe the quality of their pain. Data were analyzed using chi-square test, Fisher exact and Mann-Whitney test. There was significant differences in intensity quality and duration of toothache and orofacial referred pain [P<0.05]. These results indicate that there is a positive correlation between referral pain and intensity, quality and duration of toothache