Comparative invitro evaluation of microleakage of adhesive resin core buildup with amalgam

Amalgam and adhesive resin core with cemented dowels are commonly used to restore endodontically treated teeth. These restorations have widely been studied for their mechanical properties; however, less is known about their sealing ability. In this study, we compared the microleakage of adhesive resin core buildup [Core Max II] of amalgam and adhesive in enamel margins and compared it with amalgam. In this interventional experimental parallel group study, 30 intact human premolars were randomly selected. Class V cavities were prepared on the buccal surface of each tooth with occlusal margin in enamel and gingival margin in cementum. Then, the teeth were divided into two groups with 15 teeth. Next, one group was filled with amalgam and another group with Core Max II according to manufacturer's instructions. After thermocycling and dye penetration, the teeth were sectioned and microleakage was assessed. Data were analyzed by T-student and paired t tests through SPSS VII with 95% confidence interval. 1. The mean microleakage of occlusal margins [enamel] of adhesive resin core, Core Max II [30.84 +/- 5.01] was significantly greater than amalgam Oralloy [13.07 +/- 3.5] [P=0.001]. 2, The mean microleakage of cervical margins [cementum] of Core Max II [39.81 +/- 4.92] was not significantly different from amalgam [34.56 +/- 2.03]. However, the mean for Core Max II was greater than amalgam [P=0.337]. 3. The mean microleakage of cervical margins of amalgam [34.56 +/- 2.03] was significantly greater than occlusal margins [13.07 +/- 3.50, P=0.001]. 4. Mean microleakage of cervical margins [cementum] of adhesive resin core, Core Max II [39.81 +/- 4.92] was not significantly different from occlusal margins [enamel, [30.8 +/- 5.01, P=0.197]]. Amalgam restorations especially at enamel have less microleakage than adhesive resin cores [Core Max II] and the mean microleakage of enamel margins is less than cementum margins

[Laboratory evaluation of targis color stability in comparison with porcelain and composite by colorimeter]

Color stability is crucial for the success of any restorative material. Despite composites, color stability of ceromers has not been studied widely. The purpose of this study was evaluation of color stability of one type of ceromers and comparing it with porcelain and composite. In this invitro experimental study, one type of ceromers [targis], a light cured direct composite [tetric ceram] and a porcelain [vita] were chosen. The samples were evaluated in CIELAB color order system by a colorimeter in 3 stages: before UV exposure, after 100 hours UV exposure and after 200 hours UV exposures. l*, a* and b* peculiarities and their changes in examination steps were calculated. The results were analyzed by ANOVA and LSD statistical tests. The results revealed the porcelain and targis had the highest and lowest color stability after 100 [P=0.05] and 200 [P=0.014] hours periods, respectively. In comparison among the different colors of ceromers, C3 and D3 had the highest and the lowest color stability respectively [P= 0.001 in 100 and P= 0.008 in 200 hours]. In all of studing groups, the final color change were clinically acceptable. All of the groups revealed acceptable color stability and among them porcelain had the best characteristics

[Evaluation of the fracture strength of the post - crowned teeth with and without ferrule]

Various factors affect the distribution of stress and fracture resistance of restored teeth by post and core. One of the major causes is the remaining body of the teeth, [ferrule] which was embraced by crown. The purpose of this study was to asses the effect of developing the ferrule via a crown lengthening procedure, on the fracture strength of endodontically treated teeth. 24 recently extracted second premolar of mandible were selected in this descriptive study and their crowns were cut so far that no more than 15 mm of the root remained. Then they were divided randomly into two groups of 12 and their canals were undergone rootcanal therapy. In the first group, a post-core and full metal crowns were made without ferrule, while in the second group with changing in the optimum ratio of the crown/root height, 2mm ferrule was designed and then the cast post- core and full-metal crowns were made. Finally, in both groups, a compressive load with 1 mm per minute speed and an angle to 150 on the long axis of the tooth was applied. The force was exerted in mesial marginal ridge, in 7 teeth and on the buccal cusp edge in the other 5 teeth to induce fracture. Statistical analysis of the data was performed with student t-test, chi-square and two-way ANOVA analyses 1. There was a significant difference between the mean of fracture load in the ferrule and non-ferrule groups [P<0.001]. 2. No significant difference in the mean fracture load was observed when the load was applied in the buccal-cusp edge instead of mesial marginal ridge. By adding a 2 mm cervical ferrule on top of the finishing line of mandibular premolars restored by cast post-core and crown, we can increase the fracture resistance of these teeth

[Comparative study of crown retention on composite core by glassionomer luting cement, adhesive resin and zinc phosphate after thermocycling]

One of the important points in dentistry is retentive strength of crown on teeth or bridge on abutments. One the effective factors in retention is cement type and its relation to core buildup materials. One of the core buildup materials which has a wide usage in Iran, is the commercial Core Max II composite. The aim of this study is to compare the retention of cemented crowns by zinc phosphate, glassionomer and resin cements of panavia F on Core Max II dies. In this research silver cast alloy crowns were made on 90 similar dies of core max II, these dies were divided to 3 groups of 30: In each group the crowns were cemented on Core Max II dies with one of three cements. Then the crowns were pulled tensively in Instron machine, and the results were analyzed with SPSS V.11.5 software. In this study the analytic tests of ANOVA and Tuky test were used [alpha= 0.05]. According to quantitative analysis between 3 cements glassionomer, zinc phosphate and panavia F had significant difference [P=0.001]. The evaluation of mode of failure revealed that the most common failure pattern in panavia F was cohesive in core [80%], which reveals more retention between core, panavia [as cement] and crown, however in glassionomer this was [26/7%], and there was no cohesive failure in zinc phosphate. Considering retentive characteristics when the Core Max II composite cores are made the best cements are panavia F and glassionomer respectively

[ in vitro study on the effect of the temperature of cylinders and liner on the dimensions of casting posts in base metals]

Casting posts are recommended for endodontically treated teeth, specially in cases with extensive damaged crowns. Because the length and diameter of the post are effective in generating stress on the roots, and can be influenced according to the casting conditions, the purpose of this research was to study the effect of using liners and the temperature of burn out on the dimensions of the casting posts in base metals. In this experimental study, 80 acrylic posts with the length of 12.095 mm and the diameter of 2.096mm were made. On top of each post a reference point was contrived and the posts were grouped into 4 groups of 20. In the first group, humidified liner and casting temperature of 900 degree C were used, the second group were without liner and the temperature was 900 degree C, the third group were with humidified liner and temperature of 600 degree C and the fourth group were without liner and were casted in 600 degree C temperature. The lengths of the posts were measured from top to the bottom in the center [diameter in the upper most part in the reference point] with a metallurgy microscope and the results were statistically compared using student-t, Mann-Whitney and Kruskal-wallis tests. Mean and standard deviation of the acrylic post lengths were obtained. The difference [0.127mm] was significant [P<0.001]. Also, mean and standard deviation of the diameter of the acrylic posts [2.87mm +/- 0.118] was significantly less than that of metal post [2.97mm +/- 0.166], [P<0.001]. Differences in length was significant among studied groups so that in the group with 600 degree C temperature and without liner, the least measures occurred compared to the other groups [P=0.001]. Difference in the diameter of the acrylic and metal posts in the four groups showed that the use of 600 degree C temperature without humidified liner produced the least differences compared with the other groups [P=0.001]. It can be concluded that the best condition for investing and casting the casting posts is 600 degree C temperature without using the liner

[ effect of finishing line form on the microleakage of cement in implant supported fixed prosthesis with cups to marginal ridge occlusion]

Resistance to sliding and tipping of a restoration must be considered at the time of treatment planning. Some factors have influence in resistance such as type of occlusion, size of occlusal table in comparison with cervix, and place and amount of occlusal forces. When the occlusal table of a restoration is wide and the cervical part is narrow, it is very probable that the line of action of an applied force on marginal ridges passes outside the margins of the restoration and produce destructive torque and causes dislodgment of the restoration. Leverage is probably the predominant factor in the dislodgment of cemented superstructure of implant supported prosthesis, that results in disruption of the cement film. The purpose of this study was to evaluate the effect of finishing line form on cement microleakage in implant supported prosthesis following occlusal forces in cusp to marginal ridge occlusion. In this experimental study, 90 metal models were made similar to implant abutment with three types of finishing lines [Shoulder, Sloping shoulder, and Knife edge]. Ninety crowns were made from base metal alloy with the occlusal table similar to mandibular first molar and cemented on the models. All specimens were subjected to 1000 thermocycles between 5[0c], and 55[0c], with a dwell time of 15 seconds. Each group was divided into 2 subgroups. The subgroups were subjected to 50000 masticatory cycles [equal to 3 months of mastication] with 60 and 100 N occlusal forces on the marginal ridge. All samples were then immersed in 5% basic foshin solution for 24 hours and mounted in polyester to be sectioned vertically. Microleakage was measured under a microscope with magnification of 40 times. The results were analyzed using One-Way and Two-Way ANOVA and t-test. There was no difference in microleakage rate between 3 forms of finishing lines. The interaction between finishing lines and occlusal force of 60 N showed significant difference [P= 0.0182<0.05]. The results of this study showed that the least microleakage was observed in shoulder finishing line

[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

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

[Comparison of three different methods for setting the artificial teeth of complete dentures]

Introduction: the occlusion of complete denture has been a subject of argument from the first attempts for treatment of edentulous patients. This study was performed to determine the subjective success of three different methods for setting the artificial teeth of complete dentures

Materials and Methods: 10 patients with normal residual alveolar ridge and jaw relationship were selected. Three complete dentures were made for each patient, the first one with normal occlusion, the second one with monoplane and the last one with lingualized occlusion. At first dentures were delivered randomly to the patients to be used for one month. The patients filled out a questionnaire 24hrs, 72hrs, 15days and one month after delivery. After one month, the second denture and then the third one were delivered to them randomly. After three months of using dentures, the patients filled out a comparative questionnaire

Results: the results showed that lingualized occlusion apparently has important advantages and deserves further evaluation and research

Conclusion: in contrast with the current concept indicating that normal occlusion is the best occlusion, this study showed that the lingualized occlusion was the best for complete denture

[Comparison of the effect of different locations of occlusal contact on the porcelain fracture in base metal-ceramic crown]

Introduction: the base metal ceramic restorations are one of the most popular restorations in the world. No research has been done about the porcelain metal junction on the occlusal surface yet. The main purpose of this study was to find the best location for porcelain metal junction with regard to occlusal contact in base metal- ceramic crown

Materials and Methods: 75 Porcelain Fused to Metal [P.F.M] crowns were made for metal dies. C were cemented on the respective die with zinc phosphate cement and were divided into three groups of 25 samples. Occlusal contact in each group was as follows: First group [A]: On the porcelain metal junction. Second group [B]: 2mm away from the porcelain metal junction on the Data were analyzed with one way ANOVA and Duncan tests

Results: 1] The average force was different in each of the 3 groups significantly. 2] Group B had the lowest amount of force [290kgF] and group C had the greatest amount [7 13kgF]. 3] Group A developed a force between Band C [529kgF]

Conclusions: 1- The best location for occlusal contact in the porcelain metal junction restorations is on the metal. 2- When the occlusal contact is on the porcelain metal junction, It needs more force for porcelain fracture than when it is on the porcelain

[ effect of metal ring and liner on dimensional precision of base-metal casting]

Introduction: several procedures have been suggested for compensating the solidification shrinkage of the casting through investment expansion, among which using the metal ring or liner inside the ring may be mentioned. The purpose of this study was to evaluate the effect of metal ring and liner on the marginal integrity of base metal crown

Materials and Methods: 30 metal dies were made and divided into 3 groups of 10 .Metal copings were waxed up for all dies and invested using 3 methods. Group 1: with metal ring and liner; Group 2: with metal ring and without liner; Group 3: without metal ring and liner. Castings were cemented on their dies. Horizontal and vertical marginal discrepancy was measured microscopically. The results were analyzed using ANOVA test

Result: group1 [using metal ring and liner] showed the least horizontal and vertical marginal discrepancy [p=0.001] and group 3 showed the highest discrepancy

Conclusion: considering the results, it is suggested that a metal ring and liner should be used for casting base metal restorations

[ 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

[Invitro evaluation of intracanal microleakage of two core buildup materials after thermocycling]

Introduction: amalgam and adhesive resin cores with prefabricated dowels are commonly used to restore endodontieally treated teeth. These restorations have been widely studied for their mechanical properties; however, less is known about their sealing ability. The purpose of this study was to compare the intracanal microleakage of amalgam and adhesive resin cores [Coremax]

Materials and Methods: in this interventional study, 30 intact human single root premolars were randomly divided into two groups each with fifteen teeth. Class V cavities with the dimension of 4mmx5mm were prepared on the buccal surface of each tooth with gingival margin in cementum and the cavity to be passed through the canal orifice. Then one group was filled with amalgam [oralloy] and another group with Coremax II according to manufacturer's. After thermocycling and dye penetration, the teeth were sectioned and microleakage was assessed under a stereomicroscope SPSS software [version II] was used for data analysis [student t-test]

Results: the mean microleakage of intracanal dye penetration of Coremax II was not significantly different from amalgam although it was greater for Coremax II compared to amalgam. [P-value= 0.720]

Conclusion: amalgam cores have less microleakage than adhesive resin cores but there was no significant difference between them