Background and Objectives: All-ceramic prosthesis is widely used in modern dental practice because of its improved physico-mechanical and optical properties. These restorations are exposed to coloring agents from various nutrition and beverages in the oral cavity. Long-term color stability is critical for the success of these restorative materials. The purpose of this in vitro study was to assess the effect of common beverages and mouthwash on the color stability of lithium disilicate (LD), monolithic zirconia (MZ) and bilayer zirconia (BZ) surfaces. Materials and Method: Thirty disc-shaped specimens from each material were fabricated; each group was subdivided (n = 10) according to coffee, green tea and chlorhexidine immersion solutions. The baseline color of ceramic discs was recorded according to the CIE L*a*b* system with a portable spectrophotometer. The second measurement was recorded after 3000 thermocycling and immersion in coloring agents for 7 days. The mean color difference was calculated and data were compared with Kruskal-Wallis and Mann-Whitney post hoc tests (0.05). Results: ΔE values for LD with the immersion of coffee, tea, and Chlorhexidine gluconate (CHG) were 1.78, 2.241 and 1.58, respectively. Corresponding ΔE values for MZ were 5.60, 5.19, and 4.86; marginally higher than the clinically acceptable level of 3.5. Meanwhile, BZ showed better color stability compared to MZ with ΔE values of 4.22, 2.11 and 1.43. Conclusions: Among the ceramics evaluated, LD ceramic was found to be more color stable, while MZ ceramics displayed a higher susceptibility to discoloration. MZ and BZ ceramic colors were significantly altered with coffee immersion, while LD ceramics were more affected by green tea.

Journal of Clinical and Diagnostic Research aims to publish findings of doctors at grass root level and post graduate students, so that all unique medical experiences are recorded in literature.

Haralur SB. J Adv Prosthodont. 2012 Nov;4(4):179-186. http://dx.doi.org/10.4047/jap.2012.4.4.179

The aim was to compare the fracture strength of Molar endocrowns fabricated from different all-ceramic materials and various preparation designs. Ninety extracted human molar teeth were root canal treated and randomly divided into three groups according to the all ceramic materials used for fabrication of the endocrowns (n = 30): (1) Lithium disilicate (IPS e.max Press); (2) Polymer infiltrated ceramic (Vita Enamic); (3) High translucency zirconia (Ceramill Zolid HT). Each group was subdivided into 3 subgroups (n = 10) according to the preparation design as 2 mm occlusal reduction, 4.5 mm occlusal reduction, and 4.5 mm occlusal reduction with 2 mm radicular extension. The endocrowns from each material were fabricated and surface treated according to the manufacturer’s recommendations. After cementation with self-adhesive resin luting cement, the specimens were stored in a humid environment for 72 hours and subsequently subjected to 5000 thermal cycles. After, a compressive, static-axial load was applied using a universal testing machine until failure. Load-to-failure was recorded (N) and the specimens were examined under a stereomicroscope to determine the failure type. The data was statistically analyzed using One-way ANOVA and Tukey HSD tests at p < 0.05. The Lithium Disilicate endocrowns recorded the higher mean fracture strength for 4.5 mm occlusal thickness and 2 mm radicular extension at 3770.28 N and 3877.40 correspondingly. The High translucency zirconia endocrowns at conventional 2 mm thickness showed the highest mean fracture load (3533.34 N). Even though polymer infiltrated ceramic endocrowns displayed comparatively lesser fracture load; they recorded the predominantly favorable fractures. Increased occlusal thickness showed a significant improvement in fracture strength of lithium disilicate and polymer infiltrated ceramic molar endocrowns. Although the 2 mm radicular extension had the substantial enhancement of fracture strength in high translucency zirconia, it resulted in more unfavorable failure types.

Introduction. The endodontically treated teeth (ETT) with thin remaining radicular dentin thickness are predisposed to fracture; hence it requires the diligent selection and the execution of endodontic post treatment. The objective of the study was to evaluate the reinforcing effect of both multiple fiber reinforced composite (FRC) and Ni-Cr cast metal posts at anterior and posterior regions. Material and Methods. Forty recently extracted root canal treated canine and single rooted premolar teeth were used for the study. They were randomly divided into four groups (n=10) as: Group 1, single FRC post; Group 2, multiple FRC posts; Group 3, single Ni-Cr metal post, Group 4, multiple Ni-Cr posts. The posts were cemented with self-adhesive resin cement and subsequently restored with full veneer metal crown. The compressive static load at 130⁰ for canine and 45⁰ for premolar was applied with the cross-head speed of 0.5mm/minute until the fracture. The obtained data was analyzed using the Kruskal–Wallis and Pairwise comparison tests with SPSS. Results. The results indicate that multiple FRC post restored canine had the maximum fracture load (1843.80±7.13 N), followed by cast multiple posts (1648.99±26.84 N), single fiber post (1623±40.31 N), and cast metal single post (1493±27.33 N). A similar trend was observed in premolar with higher max fracture load with multiple FRC posts at 1920.86±20.61 N and multiple cast metal posts at 1735.43±6.05 N. Conclusion. The restoration of ETT with larger canals by multiple FRC and metal posts provides substantially higher fracture resistance in comparison to wider single post.

Background: Remaining dentin wall thickness may influence the fracture resistance of tooth. Aims: To investigate the effect of various coronal dentin wall widths on the fracture strength of root canal treated teeth. Materials and Methods: Fifty recently extracted single canal mandibular premolars were used for the study. Ten unrestored teeth were used as control (Group 1); remaining teeth were root canal treated and divided into four groups (n = 10). The Groups 2a, 2b and 3a, 3b were having 2.5 mm, 1.5 mm remaining dentin with and without post, respectively. The samples fracture resistance was tested under the universal testing machine. The data were analyzed with one-way ANOVA and post-hoc Tukey test for comparative evaluation. Results: The mean fracture strength observed in Group 1 was (29.75 Mpa) followed by Group 2a (28.97 Mpa), Group 2b (27.70 Mpa), Group 3a (23.39 Mpa), and Group 3b (16.38 Mpa). There was no statistically significant difference between control and Groups 2a and 2b with P > 0.05. The post contributed significantly for fracture resistance in Group 3a. Conclusion: The endodontic post is not required in root canal treated teeth >2.5 mm coronal dentin wall width while the post is essential for a tooth with <1.5 mm dentin wall width to improve fracture resistance.