Department of Oral Health Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
Department of Geological Sciences, University of Manitoba, 125 Dysart Road, Winnipeg, MB R3T 2N2, Canada.
Integr Comp Biol. 2020 Sep 1;60(3):581-593. doi: 10.1093/icb/icaa099.
Reptiles with continuous tooth replacement, or polyphyodonty, replace their teeth in predictable, well-timed waves in alternating tooth positions around the mouth. This process is thought to occur irrespective of tooth wear or breakage. In this study, we aimed to determine if damage to teeth and premature tooth extraction affects tooth replacement timing long-term in juvenile green iguanas (Iguana iguana). First, we examined normal tooth development histologically using a BrdU pulse-chase analysis to detect label-retaining cells in replacement teeth and dental tissues. Next, we performed tooth extraction experiments for characterization of dental tissues after functional tooth (FT) extraction, including proliferation and β-Catenin expression, for up to 12 weeks. We then compared these results to a newly analyzed historical dataset of X-rays collected up to 7 months after FT damage and extraction in the green iguana. Results show that proliferation in the dental and successional lamina (SL) does not change after extraction of the FT, and proliferation occurs in the SL only when a tooth differentiates. Damage to an FT crown does not affect the timing of the tooth replacement cycle, however, complete extraction shifts the replacement cycle ahead by 4 weeks by removing the need for resorption of the FT. These results suggest that traumatic FT loss affects the timing of the replacement cycle at that one position, which may have implications for tooth replacement patterning around the entire mouth.
具有连续牙齿替换的爬行动物，即多牙形动物，会在口腔周围的交替牙齿位置上以可预测的、适时的波状方式替换牙齿。人们认为这个过程与牙齿磨损或断裂无关。在这项研究中，我们旨在确定牙齿损伤和过早拔牙是否会长期影响幼年绿鬣蜥（Iguana iguana）的牙齿替换时间。首先，我们通过 BrdU 脉冲追踪分析来检查正常的牙齿发育组织学，以检测替换牙齿和牙齿组织中的标记保留细胞。接下来，我们进行了牙齿拔除实验，以研究功能性牙齿（FT）拔除后的牙齿组织特征，包括增殖和β-Catenin 表达，最长可达 12 周。然后，我们将这些结果与在绿鬣蜥中对 FT 损伤和拔除后长达 7 个月收集的 X 射线的新分析历史数据集进行了比较。结果表明，FT 拔除后，牙和继代层（SL）中的增殖没有变化，只有当牙齿分化时，SL 中才会发生增殖。FT 冠部的损伤不会影响牙齿替换周期的时间，但完全拔除会通过消除对 FT 吸收的需要，将替换周期提前 4 周。这些结果表明，创伤性 FT 丧失会影响该位置的替换周期时间，这可能对整个口腔的牙齿替换模式产生影响。
