Adding vaso constrictors to the local anaesthetics used in dentistry has meant an important advance due to the advantage it offers. Many discussions have arisen among medical science professionals as to its possible contra indications. The authors reported on the result of 158 cases of teeth extractions in which simultaneous registers revealed different variants produced in the cardio vascular system. The conclusion they came to is that the local anaesthetics with levo arterenol used in odontology in usual doses is not of risk even in patients who suffer from cardio vascular affections.