Fracture of porcelain-veneered gold-alloy and zirconia molar crowns using a modified test set-up

Figures & data

Figure 1. Illustration of the cutting template used to ensure a uniform 1 mm thickness of veneering material.

Figure 2. Application of the load aligned with the core-veneer interface, tangentially to the highest point of curvature between the buccal and the occlusal cusps. The dotted line shows three different crack pathways in the interface region; cohesive in the unsupported porcelain, cohesive in the core material or adhesive in the interface.

Table 1. Load at fracture.

Material	Crown nr	Load (N)
Y-TZP	1*	1599
	2	1243
	3	1479
	4	1862
	5**	1720
	6	1636
	7	1449
	8	1391
	9	1293
	10	1628
	11	1306
	12	1456
Mean load at fracture (N)		1505
Standard deviation		188
MC	14	2103
	15	2239
	16	2172
	17	2266
	18	2342
	19	2052
	20	1887
	21	2241
	22	2048
	23	2329
	24	1956
	25	2231
Mean load at fracture (N)		2155
Standard deviation		146

*Fracture trough both cusps.

**Complete fracture.

Figure 3. (A) Fracture surface of MC crown (nr 14) at 30 × magnification (light microscopy); (B) Fracture surface of MC crown (nr 14) at 44 × magnification (SEM).

Figure 4. Surface mapping of MC crown (nr 14).

Figure 5. (A) Fracture surface of Y-TZP crown (nr 9) at 30 × magnification (light microscopy); (B) Fracture surface of Y-TZP crown (nr 9) at 45 × magnification (SEM).

Figure 6. Surface mapping of Y-TZP crown (nr 9).