effect of full crown preparation on normal and inflamed pulp tissue: an animal study

Full crown preparation may have adverse effects on pulp tissue. In this study, the effect of full-crown preparation on intact versus inflamed pulp tissue was studied. Fifteen healthy mature cats were randomly selected for this study. The study was performed on four canine teeth of each cat. Cats were anesthetized and then radiographs were taken from the canine teeth. Class V cavities were prepared in cat canine teeth. Soft decayed dentin was placed on the floor of cavities and sealed. After 1 month, all of the samples prepared for crown fabrication. Before crown preparation, an impression was taken in a custom tray. During crown preparation, the remnants of carious dentin were removed and undercuts were sealed by glass-ionomer. After preparation, self-cured acrylic temporary crowns were fabricated in a direct procedure and cemented permanently by glass-ionomer. One week later, teeth of the opposite jaw were prepared in a similar procedure. After 2 months, vital perfusion performed and the pulp tissue was histologically examined. There was no significant difference between 4 groups, regarding to histologic status of the pulp. In healthy lower jaw, inflammation was the most frequent but in the other groups, necrosis was most frequent. Also, there was no significant difference between the upper jaw and the lower jaw groups regarding to the frequency of necrosis and inflammation. There is no significant difference between intact and inflamed groups regarding the frequency of necrosis and inflammation

Osteoblastic cytokine response to gray and white mineral trioxide aggregate

The materials used for root-end filling and perforation repair are in direct contact with live tissues e.g. bone and connective tissue; their effects however, are uncertain. The aim of this ex vivo study was to evaluate the osteoblastic secretory activity adjacent to gray and white mineral trioxide aggregate [MTA] and Intermediate Restorative Material [IRM]. The studied materials were prepared and placed in 24-wells plate. Human MG-63 osteoblasts were introduced to materials after their initial set. The supernatant fluid was collected after 1, 3, and 7 days and the level of interleukin-1beta was measured by ELISA test. A microscopic exam was also performed to assess proliferation and viability of the cells. Kruskal-Wallis and Tukey tests were used for analysis. There were significant higher levels of interleukin-1beta in the gray and white MTA groups compared to IRM group [P<0.05]. The difference in interleukin-1beta secretion level between two mineral trioxide aggregate groups was not significant [P>0.05]. Morphologic appearance of osteoblasts adjacent to gray and white MTA was similar to normal osteoblasts in all observation periods, however cells adjacent to IRM were round, signifying cytotoxicity of the adjacent material. Human osteoblasts' has a favorable biologic response to white and gray MTA compared to IRM

effect of calcium hydroxide on the sealing properties of MTA apical barrier

The aim of this study was to evaluate the effects of remnant root canal medicament, calcium hydroxide on the short and long term sealing ability of mineral trioxide aggregate [MTA] apical barrier. Fifty single-rooted teeth were prepared and apical resorptions were made using sulfuric acid. The teeth were allocated into two experimental groups and two control groups. In group 1, calcium hydroxide was placed into canals for one week. In group 2, no medication was placed. In both groups, a 4-mm MTA plug was placed in the root canals. The remaining portion of the canal was filled with gutta-percha/sealer. The microleakage was evaluated after 7 days and 3 months using fluid filtration technique. Repeated measurement ANOVA was used for statistical analysis. There was no significant difference in sealing ability between the two groups in either time periods. In both groups, microleakage decreased after three months but this decrease was not statistically significant. Medication with calcium hydroxide had no adverse effect on the short and long-term sealing properties of MTA plug

[ in vitro evaluation of coronal microleakage through four temporary restorations by dye penetration]

Temporary restorations should be able to seal the access cavity and prevent bacterial leakage. The aim of this study was to evaluate the amount of dye penetration through temporary restorations, namely Zonalin, Zamharir, IRM and Coltosol, into the root canal. In this experimental study, 120 sound human premolar teeth were selected. After access cavity preparation, cleaning and shaping were accomplished using step-back technique and obturated by lateral condensation technique using gutta-percha and AH-26 sealer. The teeth were divided into six groups [n=20]. In the first to fourth group, the crown was restored with zonalin, zamharir, IRM and coltozol. Group five and six were considered as positive and negative control. After keeping these teeth in 37[degree sign] C and 100% humidity for 48 hours, samples were immersed in 10% Indian ink for 72 hours. After sectioning the crowns longitudinally the amounts of dye penetration in the two halves of teeth were assessed using stereomicroscope [xlO]. Statistical analyses were performed using ANOVA test. Zonalin had minimum and Coltosol had maximum amount of dye penetration. There were not any significant differences between the Zonalin-Zamharir groups and between the IRM- Coltosol groups [p>0.05]. Regarding different materials with ZOE base used in this study to treat tooth root, zonal in is the best as a temporary restorative material. However more comprehensive studies need to be performed about Zamharir

Post-endodontic pain: factors involved and analgesics

Despite significant advances in dentistry, pain after root canal therapy is still of concern for both patients and dentists. Although the pain does not necessarily indicate endodontic failure, relief of this pain is very important for the patient. In addition, the ability to prevent or control this pain is an important factor for a dentist's professional success. Pain in endodontics is usually due to a periapical inflammatory reaction, which occurs before, during, or following various endodontic procedures. The severity of the inflammatory response is variable, depending on local and systemic factors. The cause of pain and/or swelling in endodontic therapy is not always clear. There are numerous factors accounting for endodontic pain, suggested by researchers. These factors may be classified into three main groups: latrogenic factors, patient factors, and intracanal factors. The most important factor in controlling post-endodontic pain is to have sufficient knowledge about the causes of the problem and to prevent them. The aim of this review article is to discuss factors involved in post-endodontic pain and offer techniques, including the use of analgesics, to prevent or relieve the pain

Microscopic evaluation of cleaning efficiency of three different Nickel-Titanium rotary instruments

This study compared the cleaning efficiency of Mtwo, Race and Medin Nickel-Titanium [NiTi] rotary instruments. Sixty mandibular molar mesial roots were selected with angle curvatures between 25-35 degrees and divided into three groups; each containing 20 teeth. Canals were prepared with the rotary files and irrigated with 2.5% NaOCl solution after each instrument. Total of 5mL of normal saline was used as the final rinse; subsequently the canals were dried with paper points. The amount of debris and smear layer in three parts of the root canal walls was evaluated using SEM and the data were analyzed by using the Kruskal-Wallis test and the Mann-Whitney U test. The results for remnant debris in the coronal part of root canals were similar, whereas in the middle third, Mtwo instruments achieved significantly better results compared to Race and Medin instruments. In the apical third of the root canals more debris was created by Race instruments. Overall, Mtwo instruments had greater success in producing clean canals

In vitro comparison of apical leakage in root canals obturated with 0.04 and 0.02 tapered gutta-percha

Gutta-percha is the most commonly used material for root canal obturation; it has been recently manufactured with different tapers. The aim of this in vitro study was to compare microleakage of canals obturated with standard gutta-percha [0.02 taper] or the new 0.04 taper gutta-percha master cone using the cold lateral condensation technique. Forty-four extracted single rooted teeth were selected. The crowns were removed and all the canals were prepared using RaCe rotary files. The teeth were then divided into experimental [n=2] and control [n=2] groups. In the first study group, the teeth were obturated with 0.02 taper gutta-percha master cone and lateral condensation. In the second study group, the canals were obturated by 0.04 tapered master cones and the same obturation method. The degree of leakage was measured using fluid filtration method. Data were analyzed statistically by student t-test. There was no significant difference between the mean microleakage of two experimental groups [P=0.558]. Lateral condensation technique using 0.04 tapered master cones can provide an effective apical seal similar to 0.02 gutta-percha cones