Olivera María I, Bozzini Clarisa, Meta Isaac F, Bozzini Carlos E, Alippi Rosa M
Department of Physiology, Faculty of Odontology, University of Buenos Aires, Argentina.
Growth Dev Aging. 2003 Fall;67(2):85-93.
The present study provides baseline data for a number of mandibular growth dimensions, specially on bone mass and bone strength, that were collected between the 21st and the 180th days of postnatal life, which are intended as a reference for researchers designing experimental studies, specially on mandibular catch-up growth, and as an aid for clinicians who must evaluate results from published animal studies for validity and potential extrapolation to the human clinical situation. Fifty weanling female Wistar (Hsd:Wi) rats were fed ad libitum a diet previously shown to allow normal, undeformed mandibular growth. Five of them were randomly selected at different times between 21 and 180 d of life. Mandibular growth was estimated directly on the right hemimandible by taking measurements between anatomical points; mandibular bone mass (calcium mass) was estimated from the mg of calcium, determined by atomic absorption spectrophotometry, present in the ashes of the left hemimandible; and mechanical properties of the right hemimandible were determined using three-point bending mechanical test. Dimensions, bone calcium mass and bone strength of the female rat mandible increased linearly from day 21 to approximately day 90. Bone growth, as expected, was more than twice when assessed from bone weight than when derived from mandibular area, length or height when the parameters were expressed as the relative increase from the mean infant condition. The growth rate of the posterior part of the mandible (behind the third molar) was almost five times greater than that of the anterior part. The rates of growth of the studied parameters showed a marked decline after day 90. ANOVA indicated that no statistical differences were found between day 90 and day 120 values. It could be concluded that the female rat mandible attains its adult size, peak bone calcium mass and bone structural mechanical properties at some point between 90 and 120 d of postnatal life. Because of the extremely high positive correlation between mandibular bone calcium mass and both mandibular area and mandibular weight, it was possible to calculate the mandibular peak bone mass from the relations 7.69 mgCa/cm2 and 0.19 mgCa/mg bone.
本研究提供了一些下颌生长维度的基线数据，特别是关于出生后第21天至第180天期间收集的骨量和骨强度的数据，这些数据旨在为设计实验研究（特别是下颌追赶生长研究）的研究人员提供参考，并帮助临床医生评估已发表动物研究结果的有效性以及将其外推至人类临床情况的可能性。五十只断乳雌性Wistar（Hsd:Wi）大鼠自由采食一种先前已证明能使下颌正常、无畸形生长的饲料。在出生后21至180天的不同时间随机选取五只大鼠。通过测量解剖点之间的距离直接估计右侧半下颌骨的生长；通过原子吸收分光光度法测定左侧半下颌骨灰中钙的毫克数来估计下颌骨量（钙量）；使用三点弯曲力学试验测定右侧半下颌骨的力学性能。雌性大鼠下颌骨的尺寸、骨钙量和骨强度从第21天到大约第90天呈线性增加。正如预期的那样，当以骨重量评估时，骨生长比以下颌面积、长度或高度评估时多两倍以上，此时参数表示为相对于平均婴儿状态的相对增加。下颌骨后部（第三磨牙后方）的生长速率几乎是前部的五倍。研究参数的生长速率在第90天后显著下降。方差分析表明，第90天和第120天的值之间未发现统计学差异。可以得出结论，雌性大鼠下颌骨在出生后90至120天之间的某个时间达到其成年大小、峰值骨钙量和骨结构力学性能。由于下颌骨钙量与下颌面积和下颌重量之间存在极高的正相关关系，因此可以根据7.69 mgCa/cm2和0.19 mgCa/mg骨的关系计算下颌骨峰值骨量。
