Table 2.

Mechanical strengths of the periodontal ligament in various species and of other connective tissues and artificial materials.

Species	Teeth	Age	Mechanical strength (N/mm2)	Mode of testing	Reference
Human	Incisors	20–49 yr	1.5–1.6	extraction of tooth	[5]
	Canines	20–49 yr	1.6–1.7	extraction of tooth	[5]
	Premolars	20–49 yr	1.4	extraction of tooth	[5]
		50 yr	2.6–3.9	tension	[11]
		23–55 yr	2.4–3.0	extrusion	[12]
		78–79 yr	1–3.5	extrusion	[13]
	Molars	20–49 yr	1.2	extraction of tooth	[5]
		13–37 yr	0.3–3.0	tension	[11]
		20–65 yr	1.8–2.7	intrusion	[14]
		20–65 yr	2.1–2.6	extrusion	[14]
Monkey	Maxillary
	Incisor	Young adult	1.2–1.9	extrusion	[15]
Rat	Mandibular
	First molar	5–6 wk	1.3–1.6	extrusion	[16]
		2–24 month	1.4–0.9	extrusion	[17]
	Incisor	5–6 wk	0.7	extrusion	[18]
		6 wk	0.2–1.8	intrusion	[19]
		2–24 month	1–1.6	extrusion	[20]
Mouse	Mandibular
	First molar	4–8 wk	1.9–3	extraction of tooth	Shibata et al. (unpublished)
	Incisor	10 wk	0.5–2	extrusion	[21]
Hamster	Mandibular
	First molar	8 wk	3–7	extrusion	[22]
	Incisor	10 wk	0.4–2.8	extrusion	[21]
Rabbit	Mandibular
	Incisor	17 wk	0.5–1.4	extrusion	[21]
		17 wk	3.2	tension	[23]
Pig	Mandibular
	Molars	adult	3.8	tension	[24]
Bovine	Mandibular
	Molars		1–2.5	tension	[25]
	Third Molar	3–5 yr	3.2–4.3	tension	[26]
	First molar	3–5 yr	6	tension	[27]
Other connective tissues
	Rat skin		6–12	tension	[28]
	Rat tail tendon		10–50	tension	[28]
	Elastin		4–6	tension	[29]
	Bone		150	tension	[29]
	Dentine		40	tension	[29]
	Silk		350	tension	[29]
Artificial materials
	Glass fibre		300–1000	tension	[30]
	Titanium alloys		700–1400	tension	[30]
	Steel		3000	tension	[30]