[ effect of collagen removal on the microleakage of four single-component adhesive system in class V composite restorations]

The role of collagen fibers in dentin adhesion and hybrid layer has not clearly been established. This study evaluated the effect of collagen removal on the microleakage of four single bottle adhesive systems at resin-dentin interfaces by dye penetration technique. This experimental study was performed on 144 class V cavities prepared in buccal and lingual surfaces of human premolar teeth at the cemento-enamel junction with the cervical margin in dentin or cementum and the occlusal margin in enamel. The cavities were etched with 36% phosphoric acid for 15 seconds, rinsed and divided into 8 groups. In 4 groups the cavities were filled with a composite resin using four different dentin adhesive systems [Single Bond, Excite, One-Step, Prime and Bond NT]. In the other 4 groups the acid etched cavities were treated with a 5.25% NaOC1 solution to remove the collagen and restored using the same adhesive system and composite resin. The specimens were thermocycled and stored in distilled water at 24 °C for three months and were immersed in a 10% solution of methylene blue dye for 72 hours. After rinsing, the restorations were sectioned buccolingually and assessed under an optical stereomicroscope. Microleakage was scored by two independent observers. The data were analyzed by Kruskal Wallis and Dunn multiple comparison tests. Collagen removal resulted in a significant decrease of microleakage for One-Step and an increase or Excite at cervical margin [P<0.001] but did not reduce the microleakage at cervical margins for Prime and bond NT and Single Bond group. Except collagen removal, microleakage of class V composite restoration depends on the type of bonding system which can be related to fillers, functional monomers or solvent of adhesive systems

effect of collagen removal on shear bond strength of four single bottle adhesive systems

Achieving adhesion between restorative materials and dentin as a wet and dynamic surface is an important topic in restorative and especially in conservative dentistry. Adhesion of new dentin bonding systems depends on the formation of hybrid layer and micromechanical retention. Nevertheless, an ideal adhesive system has not yet been introduced .Recent studies reveal an increase in bonding stability when the collagen is removed from demineralized dentin surfaces. This study investigates the effect of collagen removal on the shear bond strength of four single bottle dentin bonding systems regarding their structural differences. This experimental study was performed on 56 intact human premolar teeth. Smooth surfaces of dentin were prepared on buccal and lingual aspects of teeth, providing 112 dentin surfaces. The dentin surfaces were etched with 37% phosphoric acid for 15 seconds and then rinsed. The specimens were divided into 8 groups. Single bottle adhesive systems [Single Bond [3M], One-Step [Bisco], Prime and Bond NT [Dentsply], and Excite [Vivadent]] were then applied on the dentin surfaces of 4 groups using the wet bonding technique. In the other 4 groups, the demineralized dentin surfaces were treated with a 5.25% solution of sodium hypochlorite for one minute in order to remove the surface organic components. The adhesive systems mentioned before were applied to these 4 groups with the same wet bonding technique. A cylinder of Z100 [3M] dental composite with a 3 mm diameter and 2 mm height was placed on the adhesive covered dentin surface of all groups and light-cured [400 mW/cm2 ,40 sec on each side]. The specimens were kept in distilled water at room temperature for one week and then thermocycled for 3000 times [5-55 °c]. Shear bond strength of specimens was measured using an Instron [1495] universal mechanical testing machine with cross-head speed of 0.5 mm/minute and chisel form shearing blade. Data were analyzed by Two Way ANOVA and Tukey HSD tests with p<0.05 as the limit of significance

[ evaluation of distribution of tracheotomy cases according age/sex indications in surgery and complications]

Background: elective tracheotomy is commonly performed in hospitals in association with intensive care units. Otherwise, after failure in attempts for intubation, this surgical procedure is fulfilled when emergency conditions exist. According to the high incidence of this operation and its importance the authors designed study by gathering information about patients including the most common, and postoperative complications, knowledge about these problems, and leads to prevention of complications of intubation and tracheotomy

Methods and Materials: in a retrospective study with randomized sampling files of 249 cases of tracheotomy were studied. 72.65% of cases were male. Ages of patients ranged from 3 months to 85 years. The most common indications for long-term intubation and long airway holding were coma, laryngeal cancer, laryngeal trauma, thyroid cancers, laryngitis and epiglottitis respectively

Results and Conclusion: the time between intubation and tracheotomy was 10 days or less in 20.296, between 11-20 clays in 57.96%, and 21 days or more in 21.6% of cases. The most common complications Post operatively, were ostium infection[8.4%], pneumothorax [1.6%], unilateral atelectasis of lung [1.4%], Hemorrhage of the site of operation [1.2%], Subcutaneous emphysema, [0.8%], tracheomalacia [0.4%], rupture of innominate artery [0.4%], tracheal stricture [0.8%] and at last, large granulation tissue on the anterior wall of trachea [0.4%] respectively, However, 27.48% of cases died because of their basic problem, so evaluation of probable delayed complications was impossible. About 57.15% of cases had no complications