Pain is an unpleasant sensory and emotional experience, and can be thought of as one of the oldest of all dental problems. In fact, the control of pain during routine dental procedures is an important part of dental care delivery. Pain relievers routinely are referred to as analgesics. Specifically, the use of topical and local anesthetics provided by the dental hygienist is necessary for many dental hygiene appointments. Local anesthesia creates a numbing feeling which eliminates the feeling of sensation in a specific area, without loss of consciousness. Although pain is seemingly associated with dental care, dental providers have the ability to control and alleviate pain during and after procedures. This chapter details the history of pain control and anesthetics in general, introduces the concept of anesthesia in dental hygiene practice, and discusses pain control in practice.
Pain control is the mechanism that alleviates pain. Although some methods of pain control have probably always existed, historical evidence suggests that modern anesthetics can be traced to medieval times.1 Early methods of pain reduction included religious techniques of scaring off demons and praying for the touch of God to stop the suffering.2 Plants and herbs, including roots, berries, and seeds, became the prominent method for treating pain.2
The use of narcotics to reduce pain was a universally accepted practice and involved the use of cannabis, opium, and alcohol3 (Box 1-1). However, these drugs used were not completely effective at altering pain, caused side effects, and were addictive. Opium was most useful for pain control. In fact, opium proved even more effective when converted into a more potent form, morphine, and injected into the bloodstream.4
Interestingly, chemists had also prepared acetylated salicylic acid, a plant compound used in headache powder, which often left the patient with severe gastric distress. A new compound, introduced as aspirin in 1899, was highly effective as an analgesic and antipyretic, and proved to be remarkably safe and well tolerated by patients.2 However, for severe pain, more pain reducers and controllers were still in need.
The chemical to finally prove to be an effective surgical anesthetic was ether.3 Several individuals were involved in the development of the concept of gas inhalation for anesthesia. In 1842, it was reported that William Clarke administered ether via a towel to a woman as one of her teeth was extracted by a dentist.4 Horace Wells, a dentist, first tried nitrous oxide for dental pain control after attending several “laughing gas” parties. He practiced on himself by using nitrous oxide, which he considered safer than ether, and having a fellow dentist extract his tooth. He felt nothing during the extraction and discovered nitrous oxide to be an effective anesthetic. Halothane, a safe, stable chemical for inhalation anesthesia, was introduced in 1956. Short-acting anesthetics have also been introduced and are generally administered intravenously.5
In both Europe and the United States during the 1800’s, there was an extended debate over the ethics of operating on an unconscious patient and whether the relief from pain might actually retard the health process. Furthermore, some found religious offense in the new practice. Evidently, some physicians felt that it violated God’s law, whom they believe inflicted pain to strengthen faith.2 Physicians used a calculus (measurement benchmark) to determine which patients were of the correct sensibility (exhibiting overall health) and need to benefit from the use of anesthesia.2,6–7
During World War II, Dr. Henry Beecher observed that seriously wounded soldiers reported much lower levels of pain than had his civilian patients. Based on his inference that clinical pain was a compound of the physical sensation and a cognitive and emotional reaction component he challenged laboratory studies in healthy volunteers and argued that pain could only be legitimately studied in the clinical situation. These observations formed the basis for real clinical research trials on pain control.2,8–11 Eventually, in 1956, the gate control theory was published. The classic articles proposed a spinal cord mechanism that related the transmission of pain sensations between the periphery nervous system and the brain.12
The first local anesthetic, cocaine, was isolated from coca leaves by Albert Niemann and Francesco Di Stefano in Germany in the 1860s.13 Cocaine was first used as a local anesthetic in 1884 by Karl Koller, who demonstrated the use during painless ophthalmological surgery.14,15 Although effective as an anesthetic, it was addictive, and many of those pioneer researchers who first studied cocaine’s effects on themselves became addicted.3
In 1905, the ester procaine (Novacaine) was created in Germany and, when mixed with a proportion of epinephrine, was found to be effective and safe1 (Box 1-2). Procaine took a long time to produce the desired anesthetic result, wore off quickly, and was not as potent as cocaine. Additionally, many patients were allergic to procaine because procaine is an ester and esters have a high potential for allergic reactions.
In the 1940s a new group of local anesthetic compounds, the amides, were introduced. The initial amide local anesthetic, lidocaine, was synthesized by Swedish chemist Nils Lofgren in 1943. Lidocaine revolutionized pain control in dentistry worldwide, because it was both more potent and less allergenic than procaine. In the succeeding years, other amide local anesthetics (prilocaine in 1959, bupivacaine and mepivacaine in 1957) were introduced. These new amide local anesthetics provided the dental practitioner with an array of local anesthetics ranging in pulpal anesthesia for periods lasting from 20 minutes (mepivacaine) to 3 hours (bupivacaine with epinephrine). In 1969, Rusching and colleagues prepared a new drug, carticaine, which differed from the previous amide local anesthetics. Renamed articaine in 1984, the drug was derived from thiophene and thus contained a thiophene ring in its molecule instead of the usual benzene ring. Articaine became available in 2000 for marketing in the United States in a 4% 1 : 100,000 epinephrine formulation. Today, lidocaine remains the most popular anesthetic used in dentistry in the United States, but many patients do not understand the distinction between the agents and still ask for Novocain which is no longer available in dentistry.
Dental hygienists often treat patients with painful gingival and/or periodontal infections, which is why it is paramount for dental hygienists to be able to reduce and control pain while treating patients. Local anesthetics work by blocking the travel of the pain signal to the brain.16 In addition to pain control, local anesthetics can provide vasoconstriction if vasoconstricting drugs such as epinephrine or levonordefrin is added to the anesthetic. During the course of treatment, patients may have gingival inflammation and bleeding. Hemostasis is achieved via the vasoconstrictor in the anesthetic. By controlling the bleeding, proper visualization of the tissues and the working end of the instrument can be achieved.17
Many dental practices will hire a dental hygienist with certification in local anesthesia to provide local anesthesia for all dental and dental hygiene patients in the practice. Much like a nurse anesthetist or anesthesiologist focuses his or her nursing or medical specialization in the provision of anesthetics, so do many dental hygienists exclusively provide local anesthesia without providing any traditional dental hygiene services.
The delivery of local anesthetic has been added to the scope of dental hygiene practice over the past 40 years (Table 1-1 and Figure 1-1). Washington State added the provision of local anesthesia to state law in 1971, followed by New Mexico in 1972 and Missouri in 1973. Currently, 44 states allow dental hygienists to deliver local anesthetics. Maryland, New York, and South Carolina are states where dental hygienists may provide local infiltration but not block anesthesia.18