Influence of peak oral temperatures on veneer–core interface stress state

Figures & data

Figure 1. Finite elements model (FEM) of a crown composed by layers of quadrilateral elements simulating the core structure (green arrows) and layers of quadrilateral elements simulating the veneer structure (red arrows), green arrows indicate the veneer–core interface.

Table 1. Mechanical and thermal properties of simulated veneer materials.

Model	Veneer material	Cet (µɛ/°C)	E (Gpa)	Pr
1	Lava Ceram	9.8	71	0.32
2	Ceramco Pfz	9.8	69.2	0.19
3	Vita Vm9	9	65	0.21
4	Triceram	8.9	n.r.	0.25
5	Sakura Interaction	9.7	60	0.265
6	Zirox	8	n.r.	0.22
7	Gc Initial	9.4	65.8	0.17
8	Emax	9.5	65	0.24

The first raw indicate the model simulating the corresponding veneer material. In each model, the core material was coupled to the mechanical properties of Yttria-tetragonal-zirconia-polycrystal.

CET, coefficient of thermal expansion; E, Young's modulus; Pr, Poisson's ratio; n.r., not reported from the company.

Figure 2. FE model validation process. Strain gauge and temperature gage measuring systems setup.

Figure 3. Strain–time function. Dotted lines divide the temperature phases applied to the molar crown.

Figure 4. Maximum principal stress values and distribution (a and b) and maximum shear stress values and distribution (b and d) for model 2 Ceramco PFZ (a and c) and model 4 Triceram (b and d) ceramics.

Table 2. Interfacial maximum principal stress (σ-max), ultimate tensile stress of veneer–core interfaces determined by micro-tensile bond strength test (σ-ult), mismatch between core and veneer CETs (Δα) and interfacial maximum shear stress (τ-max).

Model	Veneer material	Δα (µε/°C)	σ-max (MPa)	σ-ult (MPa)	% of σ-max to σ-ult	τ-max (MPa)
1	Lava ceram	0.2	0.94	34.3	2	0.5
2	Ceramco pfz	0.2	0.95	75.7	1	0.5
3	Vita vm9	1	5.4	23.5	22	2.9
4	Triceram	1.1	6	45	13	3.2
5	Sakura interaction	0.3	1.5	23.8	6	0.8
6	Zirox	2	11	56.1	19.6	5.9
7	GC initial	0.6	3.2	27.1	11.8	1.7
8	Emax	0.5	2.6	15.1	17.2	1.4