。
Sometimes underestimating a cavity can put your life at risk.
Literal
Cavity [object-を] disrespect-[if-と] life [target-に] involve case [also-も] exists [explanatory-のです].
A health-warning style sentence. 侮る ('to look down on, underestimate') is a slightly literary verb. The conditional ~と marks the result as automatic — 'if you make light of it, then.' 命に係わる ('to involve one's life' = 'to be life-threatening') is a fixed expression. 場合もある ('there are cases of' = 'sometimes can') hedges the claim. のです adds explanatory weight typical of health/educational writing.