Rose E C, Hagenmüller M, Jonas I E, Rahn B A
Department of Orthodontics, School of Dental Medicine, University of Freiburg i. Br., Germany.
Eur J Orthod. 2005 Apr;27(2):190-5. doi: 10.1093/ejo/cjh091.
Bone changes its structural and physical properties during maturation. In order to validate ultrasound measurements with regard to their usefulness in assessing cortical bone maturation, speed of sound (SOS) data were compared with mechanical properties (elastic modulus, bending strength, and cortical surface hardness), density and water content. Thirty pig mandibles were selected from three different age groups. Rectangular specimens of the buccal cortical bone of the body of the mandible were prepared. SOS was measured with pulsed ultrasound at a frequency of 2 MHz in all three dimensions, bone mineral density (BMD) by quantitative computed tomography, breaking strength and apparent elastic modulus in a three-point bending test to failure, water content using the lyophilization technique, and micro-indentation hardness using a modified Vickers' technique. While SOS in all three directions, BMD, surface hardness, and bending strength increased significantly (P < 0.001), bone tissue water content decreased significantly (P < 0.001) with age. Changes in the elastic modulus were not significant. Changes in SOS in the antero-posterior and apico-occlusal directions can be partly explained by BMD. In a bucco-lingual direction the increase is inadequately explained by the physical parameters investigated, and has possibly to be attributed to structural differences. Maturation of the mandible implies changes in its architectural organization, in material composition, and in the mechanical properties of cortical bone. In vitro SOS measurements reflect different structural and physical properties that are all age dependent. It thus seems feasible that age-related changes in bone maturation could be monitored by SOS measurements.
骨骼在成熟过程中会改变其结构和物理特性。为了验证超声测量在评估皮质骨成熟度方面的有效性，将声速（SOS）数据与力学性能（弹性模量、抗弯强度和皮质表面硬度）、密度和含水量进行了比较。从三个不同年龄组中选取了30个猪下颌骨。制备了下颌骨体颊侧皮质骨的矩形标本。在三个维度上用2MHz的脉冲超声测量SOS，通过定量计算机断层扫描测量骨矿物质密度（BMD），在三点弯曲试验至破坏时测量断裂强度和表观弹性模量，采用冻干技术测量含水量，采用改良维氏技术测量微压痕硬度。随着年龄的增长，三个方向的SOS、BMD、表面硬度和抗弯强度均显著增加（P < 0.001），而骨组织含水量显著降低（P < 0.001）。弹性模量的变化不显著。前后方向和根尖-咬合方向的SOS变化部分可由BMD解释。在颊舌方向上，所研究的物理参数无法充分解释其增加情况，可能归因于结构差异。下颌骨的成熟意味着其结构组织、材料组成和皮质骨力学性能的变化。体外SOS测量反映了所有与年龄相关的不同结构和物理特性。因此，通过SOS测量来监测与年龄相关的骨成熟变化似乎是可行的。
