Missing a molar. Is an implant a good idea?

I am missing my lower left second molar (#18 for you dentists). My dentist tells me the upper one will eventually fall out if I don't get an implant. Will that really happen and will it be a problem or is he trying to make some money? Will I have any other problems like bite issues too?
Answer:
MALLORY,BECAUSE MOLARS ARE IMPORTANT,LOL, IF YOU LIKE CHEWING FOOD, THEY SHOULD BE REPLACED. IF IT'S POSSIBLE TO DO A CROWN ON #19 WITH A DISTAL EXTENSION THAT WOULD PROVIDE SOMETHING TO OPPOSE #15, THEN THIS IS AN OPTION. AN IMPLANT IS ANOTHER MORE EXPENSIVE ALTERNATIVE.
FYI IT TAKES YEARS FOR AN OPPOSING TOOTH TO CAUSE PROBLEMS.

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Moloars arent that important i dont think.if you can keep biting nearer to the front of your teeth ittll be fine.but if you do use your molars for biting an implant will hgurt and cost $ but itll be worth it.I wouldnt suffer so id pay if i really needed it.

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I don't know if it would fall out but a fixed bridge should be ok since you're only missing one tooth in a row.

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my dentist told me that the tooth opposite to the space will start growing longer.not fall out. When you close your jaw each tooth has an opposing tooth that puts pressure on it and it will not grow beyond that.With the space there, it will start growing.
The other thing is that the rest of the teeth next to the space might shift--since they do not have to be quite so %26quot;squished%26quot; together--
He did not say anything about my tooth falling out.

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