Comparison of Fracture Resistance of Endodontically Treated Teeth Restored with Different Aesthetic Post and Core Systems Under All Ceramic Restoration Luted with Two Types of Cements

Context: Fracture of endodontically treated teeth is a grave sequela that a clinician should seriously ponder. Suitable selection of restorative materials is a requisite for long?term clinical success. Aims: To compare the fracture resistance of endodontically treated teeth restored with three different posts luted using two different cements under all ceramic crowns. Settings and Design: This in vitro study was conducted in the Department of Prosthodontics, Government Dental College, Kottayam, Kerala, India. Methods and Material: Thirty endodontically treated single?rooted mandibular premolars in which post spaces were prepared and divided into three different groups. Group 1 (n = 10): zirconia post group. Group 2 (n = 10): quartz fibre post group. Group 3 (n = 10): glass fibre post group. Each group is sub?divided into two based on the luting system: resin?modified glass ionomer cement (RMGIC) or dual?cure resin cement (DCRC). The fracture resistance testing was performed in a universal testing machine with a crosshead speed of 0.5 mm/min. Statistical Analysis Used: The mean fracture resistance were analysed using independent sample Student t?test and one?way ANOVA. Results: Within the zirconia post group, the mean fracture resistance was higher in DCRC sub?group compared to the RMGIC sub?group and the difference was statistically significant (p = 0.017). The difference in fracture resistance between three different post systems was not found to be statistically significant with respect to both the luting systems. Conclusions: It was observed that when zirconia post is used, the mean fracture resistance was higher in dual?cure resin group compared to the resin?modified GIC group.

Microleakage of endodontically treated teeth restored with three different esthetic post and cores / 대한치과보철학회지

STATEMENT OF PROBLEM: At present, as the esthetic demands are on the increase, there are many ongoing studies for tooth-colored post and cores. Most of them are about fiber post and prefabricated zirconia post, but few about one-piece milled zirconia post and core using CAD/CAM (computer-aided design / computer-aided manufacturing) technique. PURPOSE: The objective of this study was to compare microleakage of endodontically treated teeth restored with three different tooth-colored post and cores. MATERIAL AND METHODS: Extracted 27 human maxillary incisors were cut at the cementoenamel junction, and the teeth were endodontically treated. Teeth were divided into 3 groups (n = 9); restored with fiber post and resin core, prefabricated zirconia post and heat - pressed ceramic core, and CAD/CAM milled zirconia post and core. After the preparation of post space, each post was cemented with dual-polymerized resin cement (Variolink II). Teeth were thermocycled for 1000 cycles between 5 - 55 degrees C and dyed in 2 percent methylene blue at 37 degrees C for 24 hours. Teeth were sectioned (bucco - lingual), kept the record of microleakage and then image-analyzed using a microscope and computer program. The data were analyzed by one-way ANOVA and Scheffe's multiple range test (alpha= 0.05). RESULTS: All groups showed microleakage and there were no significant differences among the groups (P > .05). Prefabricated zirconia post and heat-pressed ceramic core showed more leakage in dye penetration at the post - tooth margin, but there was little microleakage at the end of the post. Fiber post and resin core group and CAD/CAM milled zirconia post and core group indicated similar microleakage score in each stage. CONCLUSION: Prefabricated zirconia post and heat-pressed ceramic core group demonstrated better resistance to leakage, and fiber post and resin core group and CAD/CAM milled zirconia post and core group showed the similar patterns. The ANOVA test didn't indicate significant differences in microleakage among test groups. (P > .05)

Finite element analysis of the influence of esthetic posts on incisors / 대한치과보철학회지

STATEMENT OF PROBLEM: Most posts are metallic, but in response to the need for a post that possesses optical properties compatible with an all-ceramic crown, an esthetic post has been developed. Although there have been many studies about the esthetic post materials, 3-dimensional finite element studies about the stress distribution of them are in rare. PURPOSE: The purpose of this study is to investigate comparatively the distribution of stresses of the restored, endodontically treated maxillary incisors with the esthetic post materials and the displacement on the cement layer on simulated occlusal loading by using a 3-dimensional finite element analysis model. MATERIAL AND METHOD: Four 3-dimensional finite element models were constructed in a view of a maxillary central incisor, a post, a core, and the supporting tissues to investigate the stresses in various esthetic posts and cores and the displacement on the cement layer (Model 1; Cast gold post and core, Model 2; Glass fiber post with composite core, Model 3; Zirconia post with composite core, Model 4; Zirconia post with ceramic core). Force of 300N was applied to the incisal edge and the cingulum (centric stop point) with the angle of 135-degree to the long axis of the tooth. RESULTS: 1. The stresses and displacement on the incisal edge were higher than on the cingulum. 2. The stresses in dentin were the highest in Model 2 (Glass fiber post with composite core), and the second was Model 3, the third Model 1, and the lowest Model 4. 3. The stresses in post and core were the highest in Model 4 (Zirconia post with ceramic core), and the second was Model 1, the third Model 3, and the lowest Model 2. 4. The displacement on the cement layer was the highest in Model 2 (Glass fiber post with composite core), and the second was Model 3, the third Model 1, and the lowest Model 4. CONCLUSION: When a functional maximum bite force was applied, the distribution of stresses of the esthetic post and core materials and the displacement on the cement layer were a little different. It seems that restoring extensively damaged incisors with esthetic post and core materials would be decided according to the remaining tooth structure.

Evaluation of the fracture resistance of all-ceramic zirconia posts by 3 different methods / 대한치과보철학회지

STATEMENT OF THE PROBLEM: All-ceramic post-and-core restorations offer a number of advantages compared with systems that use metal build-ups. In certain clinical cases, however, fractures at the joint between the post and core build-up have been reported. PURPOSE: The objective, therefore, is to improve the joint between the post and the core build-up. MATERIAL AND METHODS: Three different methods were used to prepare all-ceramic post-andcore restorations; pressing IPS Empress core build-ups to CosmoPost zirconia posts, cementing IPS Empress core build-ups to CosmoPost zirconia posts and Celay-milling of zirconia blanks. A series of ten restorations was prepared for each of the three methods. The post-and-core complexes were tested to failure with the load applied perpendicular to the post axis. The load and deflection at fracture were recorded. RESULTS: The highest breaking load and highest deflection were recorded for the cementing technique with values of 25.3 N and 394 micrometer, respectively. The corresponding values for the pressed core build-ups and the milled zirconia core build-ups were 22 N and 301 micrometer, and 13 N and 160 micrometer, respectively. All the differences are statistically significant (p=0.05). Regarding the load-dependence of the deflection, the cemented core build-ups again demonstrated the highest value with 15.5 micrometer/N. The difference in the values of 13.6 micrometer/N and 13 micrometer/N recorded for the pressed-on and milled core build-ups, respectively, were statistically insignificant. CONCLUSION: In regard to the high fracture resistance of zirconia post, adhesive cementing the core build-up to the post offers a viable alternative to the conventional pressing technique. The elastic bond between the rigid high-strength zirconia post and the core build-up presents an additional advantage.