Abstract
This paper assesses the impact of preheating of adhesive cement on the fracture resistance of lithium disilicate and zirconia restorations. Methods: A total of 80 human maxillary premolar teeth were assigned into 8 groups (n = 10) according to material type (either lithium disilicate or zirconia) and type of resin cement (either LinkForce or Panavia SA) with preheating temperature at 54 °C or at room temperature (25 °C). Teeth were prepared and restored with either lithium disilicate or zirconia restorations. After cementation, specimens were thermal cycled (10,000 cycles, 5 °C/55 °C), then load cycled for 240,000 cycles (50 N). Each specimen was statically loaded until fracture and the load (N) at fracture was recorded, then the failure mode was detected. Statistical analysis of data was performed (p ≤ 0.05). Results: There was no significant difference (p = 0.978) in fracture mean values between LinkForce and Panavia SA. Statistically significant difference (p = 0.001) was revealed between fracture resistance of lithium disilicate restorations cemented with LinkForce at 25 °C and at 54 °C; however there was no significant difference (p = 0.92) between the fracture resistance of lithium disilicate restorations cemented with Panavia SA used at 25 °C and at 54 °C. Regarding the interaction between ceramic material, cement type, and cement preheating, there was no significant effect (p > 0.05) in fracture resistance. The cement type does not influence the fracture resistance of ceramic restorations. Preheating of resin cement has negatively influenced the fracture resistance of all tested groups, except for lithium disilicate cemented using LinkForce cement.
Highlights
With neglecting the effect of resin cement type and its preheating, zirconia restorations showed statistically (t = 9.58, p = 0.001) higher fracture resistance compared with lithium disilicate restorations
There was statistical significant difference (t = 4.64, p = 0.001) between the fracture resistance values of lithium disilicate restorations cemented with LinkForce cement at 25 ◦ C (613.12 ± 119.65 N) and preheated at 54 ◦ C (1015.39 ± 246.54 N); there was no statistical significant difference (t = 0.10, p = 0.92) between the fracture resistance values of lithium disilicate restorations cemented with Panavia SA cement at 25 ◦ C (722.42 ± 125.52 N) and preheated at 54 ◦ C (714.20 ± 229.01 N) (Table 2)
There was a statistically significant difference (t = 3.37, p = 0.004) between the fracture resistance values of zirconia restorations cemented with LinkForce cement at 25 ◦ C (1572.05 ± 193.08 N) and preheated at 54 ◦ C (1163.67 ± 344.02 N), and there was a statistically significant difference (t = 6.06, p < 0.001) between the fracture resistance values zirconia restorations cemented with Panavia SA cement at 25 ◦ C (1770.92 ± 270.65 N) and preheated at 54 ◦ C (1168.03 ± 160.34 N)
Summary
The main purpose of a luting agent is to fill the space between the prepared tooth and the restoration and to improve the structural durability of the restored tooth [1,2]. The appropriate selection and handling of luting agents is critical for success of indirect restorations [2]. With the capability of strong bond formation between the intaglio surface of the restoration and the prepared tooth structure, can offer benefits of reduced solubility with enhanced esthetics [3,4]. Resin cements could be used in challenging clinical situations of compromised retention or when low-strength ceramic restorations (such as glass-ceramics) are required [4,5]. Resin cements could seal the microcracks at the surface of the restoration and strengthen the restoration during function [6]
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