Life on earth is regulated by biological rhythms, some of which oscillate with a circadian, monthly or lunar cycle. Recent research suggests that there is a near weekly biorhythm that may exert an influence on human skeletal growth. Evidence for the timing of this biorhythm is retained in tooth enamel as the periodicity of Retzius lines. Studies report that Retzius periodicity (RP) relates to adult human stature and enamel thickness. Adult human stature is sexually dimorphic, and so is enamel thickness of maxillary third molars (M3) but not mandibular M3. Yet, previous studies report sex differences in RP are apparent in some populations but not others, and it is unknown if dimorphism in enamel thickness relates to RP. To further our understanding of this biorhythm we analysed sex-related variation in RP and its relationship with enamel thickness in a sample of M3’s (n=94) from adults in Northern Britain. Results reveal RP was significantly higher in our sample of female molars compared to those of males, which is consistent with the previously reported correlation between the biorhythm and adult stature. The RP of maxillary M3 related to sex differences in enamel thickness, but this relationship was not present in mandibular M3. Our results support previous findings suggesting that this biorhythm is sexually dimorphic and provide the first evidence that RP may be one factor influencing sex differences in enamel thickness. Our study also shows that correlations between RP and enamel thickness appear to be most readily detected for tooth types with sufficiently wide ranges of enamel thickness variation, as is the case for maxillary but not mandibular M3. Achieving a sufficient sample size was critical for detecting a sex difference in periodicity.

地球上的生命受生物节律的调节，其中一些节律随着昼夜节律、每月或月球周期而波动。最近的研究表明，有一种近乎每周的生物节律可能会对人类骨骼的生长产生影响。这种生物节律时间的证据作为 Retzius 线的周期性保留在牙釉质中。研究报告称，Retzius 周期 (RP) 与成人身高和牙釉质厚度有关。成人身高是两性异形的，上颌第三磨牙 (M3) 的牙釉质厚度也是如此，但下颌 M3 没有。然而，先前的研究报告称，RP 的性别差异在某些人群中很明显，而在其他人群中则不然，并且不知道牙釉质厚度的二态性是否与 RP 相关。n=94) 来自英国北部的成年人。结果显示，与男性磨牙相比，我们的女性磨牙样本中的 RP 显着更高，这与之前报道的生物节律和成人身高之间的相关性一致。上颌 M3 的 RP 与牙釉质厚度的性别差异有关，但这种关系在下颌 M3 中不存在。我们的结果支持先前的发现，表明这种生物节律是性别二态的，并提供第一个证据表明 RP 可能是影响牙釉质厚度性别差异的一个因素。我们的研究还表明，对于牙釉质厚度变化范围足够宽的牙齿类型，RP 和牙釉质厚度之间的相关性似乎最容易检测到，上颌骨 M3 的情况也是如此，而下颌骨 M3 则不然。