Table 5. Mean dentin thicknesses (mm) of the danger zone (DZ) and safety zone (SZ) at the mesiobuccal canal in maxillary molars are based on gender and age groups. (MB: single canal in the mesiobuccal root, MB1; buccal canal in the mesiobuccal root with two canals, MB2; palatinal canal in the mesiobuccal root with two canals).

				Age groups					Gender
				<18	18-34	35-65	>65		Male	Female
First molar (n=642)	With single canal	MB	DZ	0.88	0.86	0.90	0.96		0.88	0.86
			SZ	1.11	0.92	1.01	1.02		0.96	0.93
	With two canals	MB1	DZ	0.93	0.80	0.83	0.93		0.82	0.81
			SZ	1.15	0.94	1.00	1.04		1.00	0.95
		MB2	DZ	0.86	0.77	0.80	0.91		0.79	0.78
			SZ	0.86	0.90	0.92	0.95		0.95	0.89
Second molar (n=609)	With single canal	MB	DZ	1.32	0.87	0.93	0.89		0.90	0.91
			SZ	1.39	0.95	1.06	1.04		1.01	1.01
	With two canals	MB1	DZ	0.92	0.83	0.73	0.79		0.83	0.78
			SZ	1.05	0.94	0.72	0.84		0.96	0.94
		MB2	DZ	0.85	0.81	0.72	0.85		0.79	0.77
			SZ	0.86	0.87	0.84	0.93		0.83	0.88