Exploring the effects of hypermineralisation in bone tissue by using an extreme biological example

Area of Science:

• Biomaterials Science
• Paleontology
• Biomechanics

Background:

• Bone tissue properties vary significantly with mineral content, influencing its mechanical behavior.
• Understanding extreme bone compositions enhances knowledge of mineral-collagen interactions.
• The rostrum of Mesoplodon densirostris represents the densest bone tissue known.

Purpose of the Study:

• To investigate the composition, static and fatigue strength, hardness, and toughness of Mesoplodon densirostris rostrum bone.
• To compare these properties with less mineralized bone analogues.
• To update established relationships between microhardness, modulus, and mineral fraction using this extreme bone type.

Main Methods:

• Comparative analysis of bone tissue properties.
• Mechanical testing including static and fatigue strength, hardness, and toughness measurements.
• Compositional analysis focusing on mineral and organic matter content.

Main Results:

• Rostrum bone exhibits minimal organic matter and water content.
• Despite high density, its basic mineral stoichiometry is comparable to other bones.
• Updated microhardness vs. modulus and microhardness vs. mineral fraction relationships were established over a wider compositional range.
• The rostrum bone was found to be extremely brittle, with toughness ratios similar to ordinary long bones.

Conclusions:

• The extreme density of Mesoplodon densirostris rostrum bone does not confer unusual toughness.
• Findings contribute to a broader understanding of bone mechanics across diverse mineral compositions.
• The study provides updated quantitative relationships crucial for biomaterial design and bone research.