An analogy between maxillary anterior teeth dimensions measured using facial proportions and Chu proportion gauge: an in vivo study: An analogy between maxillary anterior teeth dimensions

Background: A fine balancing of geometric concepts and artistic abilities is required while designing smiles. One of the key elements that make up the smile frame is tooth size. The maxillary front teeth are the most noticeable in the smile arch, therefore choosing the right tooth size and positioning it in the maxilla improves both aesthetics and treatment outcomes. Aim: This study aimed to compare the dimensions of maxillary anterior teeth measured with vernier callipers and CHU proportion gauge with facial proportions such as intercanthal distance, interalar width and bizygomatic width. Materials and Methods: On a sample of 100, Facial proportions, mesiodistal width, and height of maxillary anterior teeth were recorded using digital callipers and a Chu proportion gauge. The recorded data were subjected to statistical analysis. Mean comparisons of each width were done using a t-test, ANOVA and Tukey’s Post-hoc test considering a p-value less than 0.05 to be statistically significant. Results: Mean values of the combined width of anteriors calculated using Chu gauge was 45.08, and that calculated using Vernier Callipers was 45.85. Multiplying the factor 1.47 to Inner canthal width and 1.42 to Interalar width results in the combined width of the maxillary anterior teeth. A mean difference of 0.02620 ± 0.91777 and 0.4988 ± 0.91777 exists between Inner canthal and Combined Chu’s width with a 0.04% and 0.34% error in younger and elder age populations, respectively. A mean difference of -11.4775 ± 0.91777 and -11.6039 ± 0.91777 exists between Combined mesiodistal width obtained by using Chu’s width and bizygomatic width with a 0.01% error in younger and elder age populations, respectively. Conclusions: This study reported a negligible 0.7 difference in the means of the combined width of anteriors calculated using Chu gauge and Vernier Callipers. Hence, these two methods can be used as alternatives to calculate the width of anterior teeth

Distinctive analysis of the shear bond strength of Porcelain Fused Metal substructure fabricated by conventional casting, direct metal Laser Sintering and CAD-CAM processing techniques: Shear bond strength of PFM Substructure fabricated by conventional casting, direct metal Laser Sintering and CAD-CAM Techniques

Background: The use of metal-ceramic restorations began in the late 1950’s allowing the development of prosthetic rehabilitation with better cosmetic results replacing previously in-demand precious metals. These restorations are commonly prepared using conventional casting, Direct Metal Laser Sintering and CAD-CAM processing techniques. The present study has been attempted to perform a distinctive analysis of the shear bond strength of porcelain fused metal substructure fabricated by conventional casting, Direct Metal Laser Sintering and CAD-CAM processing techniques.Materials and Methods: The present study follows an in-vitro study design. A total of 45 samples were prepared and divided into 3 groups (n=15 in each group): conventional casting, Direct Metal Laser Sintering and CAD-CAM groups. The shear bond strength of all the specimens was measured using Universal Testing Machine. The specimens were subjected to shear load at the metal-porcelain interface with increasing load and the crosshead speed of 2 mm/sec till the disc debonded completely. The debonded samples were observed under Scanning Electron Microscope to assess the kind of failure.Results: The obtained data of three experimental group samples were analysed using the student’s t-test, One-way ANOVA test and Tukey’s Post-hoc test. Results of t-test showed that, of all the three techniques, Casting technique shows highest mean of force and shear bond strength, and this mean difference was significant. The same results were shown in One way ANOVA test and Tukey’s Post-hoc test.Conclusion: From the observations of the present study, it can be stated that Casting technique showed highest mean of load and shear bond strength followed by the CAD/CAM method and DMLS technique, respectively. The results of this study ranged from 69-87MPa which is within the safety borders. Therefore, it can be concluded that all three methods can be used to fabricate the metal substructure in metal-ceramic restoration.Keywords: CAD-CAM, Casting, Direct Metal Laser Sintering, Shear bond strength

Comparative evaluation of gingival displacement using retraction cord impregnated with Astringedent®, Magic foam and Expasyl: an in vivo study: Gingival displacement using various retraction cords

Background: Gingival retraction helps in achieving good quality impressions. These are needed for a precision fit and long-term success with fixed prosthodontic restorations. Aim: This study aimed to evaluate the clinical efficiency of gingival displacement obtained using Expasyl, Magic foam cord and Medicated retraction cord. Materials and methods: One hundred twenty patients with the requirement of full veneer crowns were selected. They were divided into three groups, forty subjects in each group (twenty subjects by each operator) namely Expasyl, Magic foam cord and Medicated retraction cord. The impressions obtained before and after placing the retraction system were poured with type IV die stone. The casts obtained before and after placing the retraction system were coded in a blind fashion to avoid the influence of the operator. The casts were viewed under tool maker microscope “10X” magnification for the amount of both depth and width of gingival displacement.  Results: Mesial, distal, mid-buccal, mid-lingual were taken as reference points and for Medicated retraction cord, Expasyl and Magic foam cord the mean values are 0.50mm, 0.49mm and 0.29mm respectively in horizontal displacement and 0.56mm, 0.47mm and 0.31mm respectively in vertical displacement. One way ANOVA was used to calculate the p-value and multiple range test by the Tukey-HSD analysis to identify significant groups at 5%   level. The level of significance for all tests was set as p < 0.05. Conclusion: Within the limitations of this study, Magic foam cord showed the ease of placement followed by Expasyl retraction system and Medicated retraction cord. Clinical significance: Gingival retraction helps in achieving good quality impressions. These are needed for a precision fit and long-term success with fixed prosthodontic restorations. Selecting techniques and materials that produce transient retraction and dry field without irreversible damages to the tissues is of utmost importance