18090
At the submicroscopic [ < 1 mu m ] level of collagen fibrils , suppression of bone turnover allows continued addition of non - enzymatic cross links that can reduce collagen ' s plasticity and this in turn contributes to reduced bone toughness .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None