Table 1 Association of D/D+L amino acid ratios with age in tooth dentin, normal cartilage, and paired osteoarthritic articular and meniscal cartilages

Tooth

dentin

Mean D/D+L ratio

0.0599

0.0198

0.0105

0.0077

0.0137

0.0135

r ²

0.961

0.827

0.349

0.018

0.014

0.002

Slope e-10⁵

65.2

30.5

6.9

-3.4

0.5

0.6

P value

<0.0001^a

<0.0001^a

0.0019^a

0.5246

0.5740

0.8497

Normal articular cartilage

Mean D/D+L ratio

0.0463

0.0142

0.0117

0.0125

0.0125

0.0283

r ²

0.778

0.470

0.287

0.060

0.194

0.001

Slope e-10⁵

35.2

18.4

11.6

0.7

2.3

-0.6

P value

<0.0001^a

0.0012^a

0.0181^a

0.3136

0.0590

0.9410

OA

articular cartilage

Mean D/D+L ratio

0.0506

0.0120

0.0105

r ²

0.126

0.173

0.053

Slope e-10⁵

16.0

7.0

6.0

P value

0.081

0.055

0.221

OA

meniscal cartilage

Mean D/D+L ratio

0.0506

0.0127

0.0099

r ²

0.021

0.002

0.0099

Slope e-10⁵

8.0

1.0

-3.0

P value

0.442

0.802

0.595