MOLARS
臼齿
The molars are the largest teeth in the mouth and are also very strong — there are four at the top and four at the bottom.
臼齿是口腔内较大的牙齿，同样十分坚韧，分布于左右颊部后端，上下各四颗。
PROBLEMS: These are the most likely to need fillings because they are harder to reach when brushing; it’s a -problem for upper molars because salivary ducts in the cheek next to them produce saliva and this causes plaque to harden.
问题：位置靠内而难以清洁，所以臼齿是最需“补牙”的牙齿。而上臼齿十分接近脸颊两侧的唾液腺，因为十分容易导致牙菌斑的产生。