Meaning: This sentence explains that consuming excessive amounts of sugar can lead to tooth decay.
Choice of Words: "Excess" means more than what is necessary or normal. "Sugar" is a sweet substance found in many foods. "Causes" is the present tense of the verb "cause", which means to make something happen. "Tooth decay" is a condition in which the teeth are damaged by bacteria that feed on sugar and produce acids that dissolve the teeth.