1. Cov neeg laus uas muaj cov hniav uas ploj lawm los yog puas lawm: Cov hniav hlau zoo dua rau kev kho cov hniav rov qab vim tias lawv cov xim tsis sib xws rau cov hniav thiab cov hlau yog qhov pom tseeb dua. Cov hniav rov qab feem ntau yog siv rau zom, thiab lub siab hardness thiab tuav ntawm cov hniav hlau kom ntseeg tau tias cov hniav rov qab ruaj khov thiab ruaj khov.
2. Cov yas uas xav tau kev tiv thaiv ze: Cov hniav hlau muab kev tiv thaiv ze rau cov yas, thiab tsim nyog rau cov hniav uas raug mob hnyav thiab xav tau kev tiv thaiv ntxiv.