[Effect of NaOCl as canal irrigant on microleakage of resin composite restorations]

Statement of problem: Sodium hypochlorite is used as an endodontic irrigant for different purposes. Since it is a strong oxidizing agent it might inhibit the resin polymerization

Purpose: The objective of this in vitro study was to compare the effect of NaOCl on sealing ability of total etch and self etch bonding at different time intervals after root canal therapy

Materials and Methods: The roof of the pulp chambers and roots [1-2 mm below furcation] of eighty human first molar teeth were cut and pulp tissues were completely removed. Teeth were divided in two groups [n=40], based on the type of used adhsive; total etch [Scotchbond Multi-Purpose plus] and self etch [Clearfil SE Bond]. Immediately, chamber pulp of ten teeth of each group were restored with resin composite [control groups]. Thirty teeth in each group were treated with 5% NaOCl for 5 minutes in the chamber pulp and restored with resin composite associated with each bonding agent [Z100, Clearfil Photo Core] in three intervals: immediately, one, and two weeks after irrigation with NaOCl. Fluid filtration method was used for evaluation of microleakage. Data were statistically analyzed using ANOVA and T-test [alpha =.05]

Results: Type of dentin adhesive and different time intervals after NaOCl application and restoration, did not show any significant effect on microleakage value [p>0.05]. The variable of using and not using of NaOCl showed significant difference on microleakage value [p<0.05]. NaOCl treated samples demonstrated significantly higher microleakage

Conclusion: Irrigation with NaOCl during root canal therapy has a negative effect on microleakage of resin composite restorations. Delayed time for restoration did not remove the negative effect of NaOCl

[Effect of based-resin desensitizing agent and self-etching adhesive resin on marginal leakage of class II amalgam restorations]

The purpose of this study was to compare marginal leakage of class II amalgam restorations lined with a resin- based desensitizing agent and a self-etching adhesive system with copal varnish. Fifty six freshly extracted human premolar teeth were divided into four groups. Class II box only cavity preparation was prepared on mesial and distal surfaces of each tooth. While the cavities in two groups were lined with desensitizing agent; Viva Sens [A] and adhesive system; Clear Fil S[3] Bond [B],one group was treated with copal varnish; Copalite [C], and last group was used as control, without any lining [D]. Spherical high copper amalgam [Oralloy] was hand-condensed into each preparation, specimens were thermocycled, stained and sectioned. Microleakage was graded using a stereomicroscope. Microleakage scores were calculated and analyzed. Kruskal-Wallis and Mann-Witheny tests were used for analysis of data [alpha=0.05]. For the leakage values of groups A and B, T-test revealed less microleakage with Viva Sens [P<0.05]. Kruskal-wallis test showed significant difference in four groups [P<0.05]. Clear Fil S[3] Bond showed less microleakage than control group, but leakage in copal varnish and Clear Fil S[3] Bond was similar. Less microleakage was revealed with Viva Sens when compared with the other groups [P<0.05]. Viva Sens reduced microleakage of Class II high copper amalgam restorations significantly more than the Clear Fil S[3] Bond and copal varnish

[Effect of different light curing distances on degree of conversion of multiple coating of two adhesive systems]

Degree of conversion [DC] is one of the most considerable factors in polymerization of composite resin. Cytotoxicity and physico mechanical properties of dentin bonding agents [DBA] are greatly depend on the DC. The aim of this in vitro study was to evaluate the DC of two totals etch dentin adhesives in different layers and different distances of light tip during curing. Two kinds of dentin adhesive systems were selected including optibond solo plus, filled and single bond, unfilled. The dentin adhesives were applied on polyethylene sheets [5x5 cm]. Each group of dentin adhesives was divided into two groups [n=15] based on the number of coating layer [one and four layers]. Each group was divided into three groups based on the distance of light tip during curing. [1, 3 and 6 mm] [n=5]. Each specimen underwent light curing for 20 seconds. The samples were analyzed with FTIR [Fourier Transform Infrared Spectroscopy] for the amount of double bonds [C=C] and [C=O] before and after curing. The DC was calculated and the data were analyzed by three way ANOVA pair wise comparison [alpha=0.05]. Mean amount of DC for optibond solo plus [71.6% +/- 1.4%] was higher than single bond [56% +/- 1.5%]. There was no significant difference in DC using one layer and four layers and also 1 mm and 3 mm distances of light tip and adhesives but 6 mm distant showed a significantly lower mean amount of DC than 1 mm and 3 mm distances. This in vitro study showed that the degree of conversion in dentin adhesives was related to the composition of these materials. Six mm distance of light lip could decrease the DC while 4 layers of DBA were similar to that one of 1 mm

histopathologic study on pulp response to glass ionomer cements in human teeth

Despite the wide range of new dental materials, there is still a need for biomaterials demonstrating high biocompatibility, antimicrobial effects and ideal mechanical properties. The aim of this study was to histologically evaluate the pulpal response to a conventional glass ionomer, a resin modified glass ionomer and a calcium hydroxide in human teeth. Fifty five deep class V cavities were prepared in premolars of 31 patients and were divided into 3 groups based on application of the following liners: resin modified glass ionomer [Vivaglass Liner], conventional glass ionomer [Chembond Superior] and calcium hydroxide [Dycal]. After applying varnish, teeth were filled with amalgam. Each group was further divided into three subgroups according to time intervals of 7, 30 and 60 days. Teeth were then extracted and their crowns were fixed in formalin. Each sample was assessed microscopically for odontoblastic changes, inflammatory cell infiltration, reactionary dentin formation, remaining dentinal thickness and presence of microorganisms. Statistical analysis including Kruskal Wallis and Mann Whitney was carried out for comparison of mean ranks. [P=0.05]. In the Vivaglass Liner group, pulpal response was significantly higher on day 7 as compared to days 30 and 60 [P<0.05]. Reactionary dentin production was significantly lower after 7 days than after 60 days for all materials [P<0.05]. There was no statistically significant difference in pulpal responses among the three groups during the same time intervals [P>0.05]. There was no correlation between pulpal responses with micro-organisms and remaining dentin thickness [P>0.05]. According to the results of this study, light-cured glass ionomer as well as the other tested lining materials were determined to be biologically compatible with vital pulps in deep cavities of sound human teeth

Effect of a 16 percent carbamide peroxide bleaching gel on enamel staining susceptibility

Due to the growing popularity of vital bleaching by Carbamide Peroxide it is imperative to understand the effect of such agents on enamel and dentine. The purpose of this study was to evaluate the effect of a 16% carbamide peroxide bleaching gel; Vivastyle on enamel staining susceptibility.Thirty bovine specimens were selected and randomly divided into two groups of fifteen. The experimental group was subjected to Vivastyle gel and then was immersed in coffee, for half an hour daily for three weeks. The control group was only immersed in coffee. The teeth were evaluated by colorimeter readings to measure L*, a*, b* of each tooth. Total color differences between two colors [DELTAE] were calculated using the following formula: DELTAE= [[DELTAL*] 2 + [DELTAa*] 2+ [DELTAb*] 2]. DELTAE1 represent color difference after bleaching; DELTAE2: bleached and immersed in coffee, and DELTAE3 immersed in coffee. Mean color difference were: 9.478, 13.808, and 7.230 for DELTAE1, DELTAE2, and DELTAE3 respectively. Paired comparison by Duncan test showed that there was a significant difference between DELTAE1 and DELTAE2 [P0.000]. t-test showed that there was no significant difference between DELTAE3 and DELTAE1. [P=0.08], however, DELTAE3 had significant difference with DELTAE2 [P0.000].After vital bleaching, the enamel staining susceptibility is significantly increased

[ comparative study of fracture strength of pulpotomized primary molars after restoration with compomer and composite]

Maintenance of primary teeth has a special importance for development of occlusion and arc stability. Primary teeth which have lost a lot of tooth structure are restored routinely with stainless steel crowns-Bonded restorations reinforce the remnant structure of tooth and increase the fracture strength. The purpose of this study was to determine the fracture strength of pulpotomized primary molars after restoring with Coremax II and Compoglass. In this parallel in vitro interventional study, 60 extracted second primary molars, were selected. After the teeth were mounted in self-curing acrylic resin, the standard pulpotomy was performed. The teeth were divided into 3 groups of 20. Group A was restored with Coremax II, group B with Compoglass and group C [control] with amalgam. All groups were subdivided into 2 subgroups for load cycling Subgroups a[1], b[1] and C[1] were regarded as baseline without load cycling. Subgroups A[2], B[2] and C[2] were loaded for a period of 5 days load cycling. After that, the specimens were placed in Incubator for 24 hours. Finally all groups were fractured in the Instron Machine. compressive test was performed with the round Cross head speed of 5-mm/min. All specimens were examined for type of fracture [adhesive, cohesive] with use of a steriomicroscope [xl6]. Quantitative data analysis was done using ANOVA and Duncan's test with a 95% significance level. Chi-square test was performed for evaluation of kind of fracture. There was an interaction between two factors of time and material [P<0.05]. The time interval had a significant effect on mean fracture strengths of Coremax II and amalgam [P<0.05]. The most fracture strength was observed at base line. Kind of material had a significant effect on fracture strength. At baseline, Compoglass had the least mean fracture strength [97.19 kg] and Coremax II had the greatest one [131.39]. After 5 years there was no significant difference in fracture strength between amalgam and Compoglass, but the fracture strength of Coremax was significantly higher than the others [P<0.05]. There was a correlation between kind of fracture and material. In amalgam, 100% of fracture was of adhesive and in Compoglass, 60% of cohesive type while in Coremax II, 85% of the fracture was of adhesive type. According to this study and because of high fracture strength of teeth restored with Core max II, this material is an acceptable restoration material just for restoration of pulpotomized primary molars

[Microleakage evaluation of four luting cements in full coverage base metal crowns]

It is thought that the most important factor for pulpal stimulation and necrosis is the microleakage of intracoronal and extracoronal restoration. A luting cement with a favorable seal and the least bacterial leakage should be selected. The purpose of this study was to compare the microleakage of four luting cements: Zinc phoshate, zinc polycarboxylate, glass ionomer and panavia F and also three finishing margins: deep chamfer, shoulder, and shoulder bevel, when been applied with porcelain fused to base metal crowns. In this parallel interventional study, 96 intact human premolars were selected and divided into three groups of 32 based on the type of finishing line. Each group was randomly divided into four subgroups of 8, based on the type of luting cement. After cementation, the specimens were thermocycled. Dye penetration was done by 0.5% fushin. The data were statistically analyzed using Kruskal Wallis and Mann-Whitney test [alpha =0.05]. 1. There was a significant difference among cements in respect to mean rank of microleakage [P<0.05] 2. There was a significant difference in mean rank of cements after two by two comparison. [P<0.05] 3. The least microleakage was observed in Panavi F followed by glass ionomer and zinc polycarboxylate. 4. The greatest microleakage was observed in zinc phosphate cement Panavia F as a luting cement could create suitable seal for base metal crown due to its ability in producing the least microleakage and adhesion to dental tissue

Comparison of two methods for eliminating the bleached enamel surface roughness

Vital bleaching technique is an effective method for reducing the teeth discolorations. The results of previous studies have shown that carbamide peroxide causes enamel surface roughness, so the enamel stain susceptibility increases. The purpose of this study was to compare two methods for elimination of the bleached enamel surface roughness. In this Parallel interventional study, 60 sound bovine insicors, [5x5x10mm] were selected. After 14 days of vital bleaching with 20% opalescence gel, the specimens were randomly divided into three groups of 20; i Bond group: the enamel surface was covered by a self etch adhesive [i Bond]; Fluoride group: the enamel surface was polished by a rubber cap and was treated by 2.7% Acidulated phosphate fluoride; Control group: no surface treatment was done. In order to evaluate the lasting of each method, half of the specimens in each group were thermocycled. Data were analyzed using Kruskal-WaIlis and Mann-Whitney tests [alpha=0.05]. The control group revealed a higher degree of roughness than i bond and fluoride groups before thermo cycling [P<0.05]. No significant difference was observed in roughness degree between i Bond and fluoride group before thermocycling [P>0.05].The fluoride group revealed a lower roughness degree than the other groups after thermocycling [P<0.05]. For prevention of enamel stain susceptibility after vital bleaching, polishing with rubber cap and fluoride is an effective method for elimination of the enamel surface roughness

Laboratory evaluation of marginal porcelain extension on microleakage of base metal crowns

The purpose of this study was to evaluate the marginal porcelain extension on microleakage of base metal porcelain crowns when four types of luting cements have been used for cementation. In this invitro experimental study, ninety six base metal-porcelain crowns with three types of finishing margins were made for premolars. Then they were luted with four different luting cements [zinc phosphate, zinc polycarboxylate, glass ionomer and Panavia F]. Next, they were thermocycled [1000 times]. Finally, the microleakage was measured after dye penetration. For data analysis, Non parametric Kruskal-Wallis and Mann-Whithney tests were used [=0.05]. 1. The mean rank of microleakage in buccal margin was more than lingual one [P<0.05]. 2. In all of the finishing margins, zinc phosphate cement showed the highest microleakage in buccal and lingual walls [P<0.05]. 3. In all of the finishing margins, Panavia F showed the least microleakage compared to the other cements in two walls [P<0.05]. For promotion of marginal seal in base metal - porcelain crowns, the use of Panavia F as a luting cement is suggested

Assessment of variation of wedge factor with depth, field size and SSD for Neptun 10PC Linac in Mashhad Imam Reza Hospital

Background: In radiotherapy, wedge filters are used for optimizing the tumor dose distribution in patients. The attenuation in beam intensity due to the presence of wedge filter is compensated by means of a wedge factor measured at the central axis of the beam. The field size, depth and SSD dependence of wedge factor have been assessed for 9MV radiations of Neptun PC linear accelerator

Materials and Methods: Wedge factors [WF] at different SSD, field size [FS] and depth [d] in water were measured for 8 steel wedges with different sizes and angles of 15, 30, 45, and 60 degree. Experimental data were obtained using Neptun 10PC, Linac 9MV X-ray machine, a 3D water phantom, dosimeters and an electrometer. To study the effect of field size on WF, the wedge factor was measured for square field sizes from 5×5 to 20×20 cm, with 1 cm increment intervals for all wedges; and, at the depth of 10 cm, SSD of 100 cm with monitor unit [MU] of 80. Effects of depth on WF were studied by measurement in various depths from 3-19cm for all wedge angles at SSD of 100cm, field size of 10×10cm and 80 MU irradiation. Effects of SSD on WF were investigated by a variation of SSD from 90-110cm with 5cm increment intervals; while the dosimeter was set at depth of 10cm and field size of 10×10cm were irradiated for 80MU

Results: Linear dependence of WF with field size and depth of measurements were confirmed with 95% certainty. Shapiro-Wilk test, showed that the residual data of the regression tests have normal distributions [P>0.05]. There was also found no linear relationship between WF and SSD [P>0.05]

Conclusion: WF has linear dependence with field size and depth of measurements, but the rate of variations are less than 2.2% per 10cm variation in field size and less than 1.3% per 10 cm variation in depth of measurements, therefore, correction of WF for field size and depth of treatments in clinical trials is negligible

[ effect of flowable composite as a liner under amalgam in fracture strength of endodontieally treated posterior teeth]

Introduction: adhesive restorations in endodontieally treated posterior teeth could increase the strength of teeth and decrease the microleakage. The aim of this study was to evaluate the effect of flowable composite as a liner as well as an internal splint. Agent on bond strength of endodontieally treated molars restored with amalgam

Materials and Methods: this study was an interventional study which evaluated the fracture resistance of endodontieally treated molars in two groups based on cavity preparation of class II MOD or MOD in combination with lingual cusp reduction. Each group was divided into four subgroups and restored with 1 and 2] Tetric Flow and amalgam with and without prefabricated post, 3 and 4] Copalite and amalgam with and without prefabricated post. The control group consisted of intact molar teeth. After the restorations were made, the specimens were stored at 37oc with 100% humidity for 24 hours and then submitted to the load cycling [500,000 cycles] simultaneously with thermal cycling [5oc and 55oc]. Analysis of data was done by ANOVA and Duncan test with 95% significance level

Results: two factors [Post and cavity preparation] had a statistical interaction wit11 each other [P<0.05]. This means that without post, amalgam cuspal coverage restorations were able to increase the fracture resistance of teeth significantly but with post, they were not able to do so. Post and Tetric Flow had no effect on fracture resistance individually [P>0.05], and control group showed the most fracture resistance [p<0.05]

Conclusion: in patients with suitable occlusion, lingual cusp reduction and restoration with amalgam without intracanal pin could be an acceptable treatment