If dental office does not file insurance for service done and the patient pays the deductible..can the dental office charge the patient for the balance never charged to the insurance company?

Yes ... the patient, in all cases, is wholly responsible for assuring proper and timely payment of insurance claims. Chances are, the dental office submitted the claim within the time limits and the claim was returned for whatever reason, so the dental office then sends you a statement for the entire bill due instead. You might check with your dental insurance company to make certain everything is okay with your particular coverage plan.