Effect of Different Pattern Construction Techniques on the Marginal Adaptation, Internal Fit and Fracture Resistance of Ips-Emax Press Crowns

Abstract

purpose: The purpose of this study was to evaluate the effect of pattern construction technique on the marginal accuracy, internal fitness and fracture resistance of E-max crowns. materials and methods: Thirty caries-free human maxillary first premolars were selected, cleaned by scaling, and stored in 0.9% standardized saline solution at room temperature. Using an industrial lathe machine, the teeth were prepared to receive all ceramic crowns with standardized dimensions of 6 degrees angle of convergence. The preparation had 5mm occluso-cervical height, 6mm cervical diameter and 1 mm deep chamfer finish line. The prepared teeth were divided into three groups (n=10) according to the pattern fabrication techniques used: Group1: Conventional wax patterns. Group2: CAD/CAM wax patterns. Group3: 3D Printing of resin patterns. All patterns were invested to construct E-max crowns. The ceramic crowns were seated on their corresponding prepared teeth and the vertical marginal gap was measured with a binocular microscope (90X). Then internal gap of each ceramic crown was measured using the silicone replica technique. After cementation, each ceramic crown was statically, compressively and axially loaded until fracture at a cross head speed of 1 mm/min using a steel rod placed centrally at the occlusal surface of the crowns to evaluate the fracture resistance of the crowns. results: Group 1 showed the largest marginal gap mean (85.74±2.58μm) followed by group 2; (74.06±3.27µm) and then group3 (69.35± 3.44µm). These differences were statistically significant among the groups. The results of internal gap distances in group 1 (112±7.66µm) followed by group 2 (100±5.76µm) and then group3 (82± 7.2µm), the differences between the groups were statistically significant. The mean fracture resistance values of groups 1, 2 and 3 were 850.67±25.30N, 1080.01±47.06N and 1412.18±28.92N respectively. Post hoc test revealed that the differences between groups 1 and 2 as well as between groups 2 and 3 were statistically insignificant; however, the difference between groups 1 and 3 was statistically significant. Spearman's rank correlation coefficient showed value of-0.781. The negative sign indicates that the fracture resistance of the samples decreased as the internal gaps increased conclusions: The 3D printed pattern resulted in an E-max crown with better marginal adaptation and internal fitness. The fracture resistance of E-max crown was improved as its internal adaptation was enhanced.

Fracture Strength and Marginal Gap of Re-Pressed Ips E.MAX Press Crowns With Different Concentrations

“…Measurements Fig (4) : Comparison between the fracture strength of the tested groups were taken without cementation to omit the relative impact of the cementation process on the marginal fit and to allow determination of the system's precision. (37,40) In the current study, the resultant marginal gap mean values were found to be within the clinically acceptable range, while that of Group V was above this range by 0.9µm. as denoted by Christensen (1966), (41) who considered the clinically acceptable marginal gap range from 34 to 119μm for subgingival and 2 to 51μm for supragingival margins.…”

“…After light polymerization of the new light polymerized modelling resins, high precision and stability are attained. (36)(37)(38) Saleh O et al(2016), (37) reported that the 3D printed patterns offered better marginal fit of IPS e.max Press crowns. They also recorded improved internal adaptation that consequently improved the fracture resistance of the crowns In this study, marginal adaptation was evaluated using a stereomicroscope.…”

Evaluation of Marginal Accuracy & Fracture Resistance of Different CAD/CAM Fabricated Monolithic Vonlays

“…(20,21) The marginal gaps of the uncemented vonlays were evaluated on the prepared tooth for standardization & to exclude the effect of cement. (22,23) Results revealed no statistically significant difference, where CD group showed the best marginal adaptation followed by VE then BC. The recorded marginal gap of all groups lies within the clinically acceptable range, as records were below 120μm.…”

Marginal Integrity of Different CAD/CAM Monolithic Ceramic Crowns with Vertical and Horizontal Finish Line Preparations

“…(26) Crowns were not cemented to the prepared abutment, so that the effect of the cement film thickness was eliminated, as it was proved to increase the marginal gap (22) . Also, CAD/ CAM milling was chosen, to eliminate any human variations during construction, (29,30) as milling is capable of constructing restorations from prefabricated ceramic blocks with high degree of precision & margin adaptation provided by CAD/ CAM software, (26) {CD} crowns being constructed from a fully crystallized ceramic, were only polished without addition of a glaze to avoid subjecting them to additional glazing cycles & subsequently unavoidable marginal variations. Specially that the manufacturers claim that ZLS ceramics attain acceptable margins after restorations milling.…”