**1. Introduction**

Down through centuries, efforts have been made to use local anesthesia for treatments. In the ancient times, the Assyrians applied pressure over the carotid artery in order to obtain a certain degree of anesthesia, explaining why this artery is called "the artery of sleep" in the Greek literature. In 1532, the Indians of Peru chewed the leaves of coca shrubs to relieve fatigue and hunger and to produce a feeling of exhilaration. A chemical with some anesthetic property was first introduced in the nineteenth century. A German chemist in 1859, however, reported the anesthetic properties of the coca leaf. In 1859, cocaine was first extracted in its pure form by Albert Neimann, a German chemist. In the mid-1860s, Sir Benjamin Ward Richardson introduced the effect of ether spray for skin anesthesia. Around the same time the adverse effects of cocaine on the mood and psyche were demonstrated. As known today, side effects of cocaine include cardiac stimulation, peripheral vasoconstriction, excitation of the central nervous system (CNS) and addiction. In 1943, lidocaine-the first amide local anesthetic was introduced with greater potency, more rapid onset and less allergenicity as compared to the previously introduced esters.

**Pain control in dentistry** presents one of the greatest challenges. Pain leads to increased stress, release of endogenous catecholamines and unexpected cardiovascular responses. Before anesthetization, dentists should evaluate the medical history of each patient and document data on the systemic and psychological status of the patients in order to determine whether the patient is able to tolerate the treatment with no risk from the systemic and psychological points of views. Before the injection of the local anesthetic, the dentist should recognize the potential risks. However, most adverse reactions to local anesthetics are not related to the drug itself, but to the injection of the drug. The injection of the local anesthesia is the most reported cause for fear and discomfort of dental patients. Vasodepressor syncope and hyperventilation

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syndrome are the most common reactions. Others include tonic-clonic spasm, bronchospasm and angina pectoris. Continual research in the field of pain control is still being done in the quest for novel techniques and safer drugs. [1-4].
