I recently purchased an indoor infrared sauna that pulls 18.3 amps I read that the max capacity for 14 gauge wiring is 17 amp on a 110 volt service Can I safely use a 20 AMP breaker with 14 gauge wiring for an appliance pulling 18.3 amps?
No. No no no no no.
The sole purpose of the breaker is to protect the wiring from overheating. It's not just there to be a buzzkill. If you use a breaker that is too high for the wire you will lose that protection and there is a very real possibility of overheating and starting a fire.
An 18.3 amp device needs to be on a 20 amp circuit, meaning the receptacle, wiring, and breaker all need to be rated for 20 amps. (That would mean 12 gauge wire or bigger.) By the way, is your sauna really 120V? I thought most of them were 240V, which of course is a whole new thing.
The NEC provides the ampacities per wire size and type. A 14 can supply up to 15A, although it depends on the length of the wire and usage.
You should typically size your breakers to 125% of the load if it's going to be constant. In this case you'd want at least a 25A breaker and then appropriately sized wires and connections.