Comparison of Different Cervical Finish Lines of All-Ceramic Crowns on Primary Molars in Finite Element Analysis

Abstract

This study aimed to conduct a stress analysis of four types of cervical finish lines in posterior all-ceramic crowns on the primary roots of molar teeth. Four different types of finish lines (shoulder 0.5 mm, feather-edged, chamfer 0.6 mm, and mini chamfer 0.4 mm) and two all-ceramic crown materials (zirconia and lithium disilicate) were used to construct eight finite element primary tooth models with full-coverage crowns. A load of 200 N was applied at two different loading angles (0 • and 15 • ) so as to mimic children's masticatory force and occlusal tendency. The maximum stress distribution from the three-dimensional finite element models was determined, and the main effect of each factor (loading type, material, and finish line types) was evaluated in terms of the stress values for all of the models. The results indicated that the loading type (90.25%) was the main factor influencing the maximum stress value of the primary root, and that the feather-edged margin showed the highest stress value (p = 0.002). In conclusion, shoulder and chamfer types of finish lines with a 0.4-0.6 mm thickness are recommended for deciduous tooth preparation, according to the biomechanical analysis.2 of 11 to both parents and children (because of their metallic appearance), time-consuming, and unprofitable. Resin-faced SSCs have emerged as a better alternative to metal SSCs, as they are more esthetic [10,11]. However, they are more prone to fracturing, debonding, and wearing of the buccal surface [12,13]. Pediatric all-ceramic crowns were introduced in 2010, and have gained popularity because of their improved esthetics and durability [12,[14][15][16]. These zirconia crowns are prefabricated [15] using computer-aided design/computer-aided manufacturing (CAD/CAM) systems [17]. Zirconia (ZrO 2 ), also known as ceramic steel, has favorable esthetics for primary teeth and has excellent mechanical properties, which include a high elastic modulus (215 Gigapascal (GPa)) and high flexure strength (1000 Megapascal (MPa)). Aiem et al. [18] found that zirconia crowns exhibited better gingival health and fewer crown fractures than the other ceramic crowns. Lithium disilicate (Li 2 Si 2 O 5 ) [19], a popular glass-ceramic material, was first used in 1998 and is named the Ivoclar Porcelain System (IPS) Empress 2 (Ivoclar Vivadent, Schaan, and Liechtenstein). IPS Empress 2 is a second-generation, heat-pressed lithium disilicate crystal embedded in a glassy matrix. Later, IPS e.max (Ivoclar Vivadent, Schaan, and Liechtenstein) entered the market using the heat-pressed CAD/CAM fabrication method, with a flexural strength (biaxial) reaching 400 ± 40 MPa [20] and a Young's modulus of 95 ± 5 GPa [20]. Glass-ceramic is more transparent than zirconia and is easier to surface-etch for resin cement bonding. However, all-ceramic crowns cannot be manipulated with crimping or contouring, and may require a passive fit and extensive tooth reduction.Prefabricated primary zirconia crowns are thicker than SSCs, with occlusal thicknesses varying from 1 to 2 mm ...

Influence of the Operator`s Experience, Working Time, and Working Position on the Quality of the Margin Width: In Vitro Study

“…Rammersberg et al showed that a minimally invasive 0.5 mm width of the chamfer would result in good stability for posterior metal-free Artglass crowns cemented by adhesive technique [ 34 ]. According to Pan et al, for deciduous tooth preparation, a 0.4–0.6 mm shoulder and chamfer finish lines are recommended to ensure material strength and preserve the restoration’s marginal integrity [ 35 ]. Our results show wide variations regarding the obtained width of the heavy chamfer ( Table 1 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 ).…”

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