Visible Portion of Anterior Teeth at Rest and Analysis of Different Smile Characteristics in the Saudi Population of the Jeddah Region.

This cross-sectional study aimed to determine the degree of visibility of maxillary and mandibular anterior teeth at rest in different age groups and to evaluate the smile line, smile arc, and number of maxillary teeth displayed during smiling among the Saudi population visiting King Abdulaziz University Dental Hospital, Jeddah, Saudi Arabia. A total of 157 participants (77 males and 80 females) were included in this study with an age range of 19 to 69 years. All participants had maxillary and mandibular anterior teeth without restorations. Crown length and visible portions of anterior teeth at rest were measured using a Fowler Electronic Digital Caliper. Three measurements of each variable were recorded by two independent dental interns and calibrating their measurements was performed. Smile line, smile arc, and number of teeth displayed during smiling were examined. The collected data were statistically analyzed using SPSS software. It was found that the average clinical crown lengths in the maxillary lateral incisor, mandibular central incisor, and canine were significantly higher in males than females. At rest position, females displayed more maxillary central and lateral incisors. The displayed length of maxillary teeth at rest is inversely proportional to increasing age; the reverse occurs in mandibular teeth. The common visibility of maxillary teeth during smiling was from the second bicuspid to its counterpart. Average smile line and consonant smile arc were the most common characteristics. It was concluded that both age and gender affect the characteristics of tooth display at rest and in smiling. These effects should be considered during treatment planning and restoration of anterior teeth to obtain a more predictable esthetic outcome.

Effect of Porcelain Shade and Application Time on Shade Reproduction.

PURPOSE: To determine the variability in shade reproduction of metal ceramic restorations fabricated by different laboratory technicians at different fabrication times. MATERIALS AND METHODS: One hundred thirty five metal copings for metal ceramic restorations were fabricated with a standardized method and distributed among three dental laboratory technicians (n = 45). Each technician was requested to match three different shade specifications including 2L1.5, 3M2, 4R2.5 shade tabs of 3D Master shade guide following the manufacturer's instructions. The technicians were instructed to build up each shade 15 times using the same porcelain at three time periods namely first thing in the morning (T1 ), middle of the work day (T2 ), and at the end of the work day (T3 ) (n = 5). Color difference (∆E) was determined with a spectrophotometer. Each restoration was measured and recorded nine times. Data were tabulated and statistically analyzed using a univariate general linear model with Scheffe post hoc test, and one-way ANOVA at 5% level of significance RESULTS: The color difference (∆E) was significantly different among technicians, time of application, and shade matched. Technician 1 demonstrated good color reproduction for all shades in T1 . That was the same as technician 2 for shades 3M2 and 4R2.5, but the lighter shade (2L1.5) was better in T2 and T3 . Technician 3 had better results at T3 . The lowest mean value of ∆E was calculated with technician 3 while the highest mean value was with technician 2. T2 was associated with higher ∆E values in contrast to the other two times for technicians 1 and 2, while T3 was associated with lower ∆E values for technicians 2 and 3. CONCLUSION: Within the limitations of this study, it can be concluded that the shade reproduction is affected by the time of porcelain application. The ability to reproduce the target shade differed among laboratory technicians. No specific time can be considered for all technicians to reproduce the shades with more accuracy.

Color variation between matched and fabricated shades of different ceramics.

PURPOSE: The aim of this study was to evaluate and compare the total color difference (ΔE) between natural teeth and fabricated crowns from three ceramic systems with different thicknesses. MATERIALS AND METHODS: The color of ninety maxillary central incisors was measured from the middle third of the labial surface with a Vita Easyshade spectrophotometer. All-ceramic crown preparations with different thicknesses (0.8, 1.2, 1.5 mm) were done on selected teeth (n = 30). Prepared teeth were randomly divided into three equal groups to fabricate ceramic crowns from three ceramic systems, Duceram LFC (DLFC), In-Ceram SPINELL (ICS), and IPS Empress (IPSE). Colors of cemented crowns were measured and compared with their corresponding measurements before preparations. Data were statistically analyzed using two-way ANOVA at 5% significance level. RESULTS: A significant difference of ΔE was detected between natural teeth and different thicknesses of crowns constructed from the all-ceramic materials investigated. Comparing the three materials at 0.8 mm thickness revealed that the lowest ΔE was recorded for DLFC, which was significantly different from the other ceramic systems while IPSE showed the highest ΔE. At higher thicknesses there was no difference between natural tooth shade and crowns constructed from different ceramic materials. CONCLUSIONS: Reinforcement of ceramics by alumina for In-Ceram and leucite for Empress decreases color production. Level of acceptance between the different ceramic materials and thicknesses varied. DLFC showed the highest color matching at all thicknesses followed by ICS and IPSE in descending order. In general, increasing the thickness of fabricated crowns enhances color match.

Three-dimensional finite element analysis of custom-made ceramic dowel made using CAD/CAM technology.

PURPOSE: This study compares the stress distribution in the structure of a loaded endodontically treated maxillary extracted canine restored with either custom-made zirconia (Cercon) or cast gold dowel and core. MATERIALS AND METHODS: Standard treatments were implemented to prepare the gutta-percha-filled root canal and dowel space. The tooth along with the dowel and core fabricated pattern resin were prepared to receive an all-ceramic (Cercon) crown. An impression was made for the tooth preparation with the zirconia milled dowel and core in place to fabricate the Cercon crown using CAD/CAM. The restored canine was scanned, and from the scan two models were constructed with the surrounding ligament and bone. Three-dimensional finite element elastic analysis was then carried out for the stress distribution within the different regions of the two models due to a concentrated force of 100 N applied at the mid-lingual area. Analyses were made for three load angulations, vertical, buccolingual horizontal, and an in-between oblique force at 45(o) . Each region of the models was assumed isotropic and homogeneous. The two restored canines with zirconia and gold were compared in terms of the resulting maximum tensile, compressive, and Von Mises stresses. RESULTS: Generally, there were no significant differences in the maximum stresses in most regions for both models. Von Mises stresses for zirconia dowel and core was 8.966 MPa and for cast gold dowel and core was 8.752 MPa. The maximum tensile stress for zirconia dowel and core was 9.326 MPa, and for cast gold dowel and core was 8.166 MPa. CONCLUSIONS: The present work validates the use of CAD/CAM zirconia material for ceramic dowel and cores. CLINICAL IMPLICATIONS: CAD/CAM Zirconia can be used for a custom-made dowel and core in an esthetically demanding zone as an esthetic replacement for a metal cast dowel and core when restoring endodontically treated teeth.