Introduction
Local anesthesia is a local anesthetic in the area of the nerve endings in the mouth. This results in a local pain elimination and elimination of sensitivity without affecting the patient’s consciousness. After a while, the local anesthetic is broken down by the body and the effect begins to wear off.
In addition to a local anaesthetic, a so-called vasoconstrictor such as adrenaline is often given. Adrenaline constricts the blood vessels so that it takes longer for the local anaesthetic to be transported away with the blood. This prolongs the effect of the local anesthetic.
History of local anesthesia
In 1884, the ophthalmologist Carl Koller accidentally discovered the narcotic effect of cocaine through the use of cocaine, after he discovered that cocaine numbed his tongue. After this discovery, the surgeon William Stewart Halstet used cocaine for the first time in 1885 for local anesthesia in dentistry. This is how surface, conduction and infiltration anesthesia finally developed. In 1905, adrenaline was used for the first time to prolong Heinrich Braun’s anesthesia. In the years that followed, it became increasingly possible to produce local anesthetics artificially, such as the much used lidocaine and procaine.
Indication
The indication depends on the type of procedure on the one hand and on the patient’s wishes on the other. Different forms of anaesthesia are chosen depending on the procedure. For larger operations in the oral cavity, general anesthesia is often necessary. Anaesthesia is also often used because of the patient’s anxiety disorder before dental surgery (dentophobia).
Classification of local anesthesia in dentistry
Surface anaesthesia is used to eliminate pain in the oral mucosa, e.g. as part of pain reduction when the subsequent local anaesthetic is injected or during superficial interventions in the gum area. The sensitive nerve endings are supplied by diffusion and thus anaesthetised. Atricaine, lidocaine and tetracaine are mainly used for surface anaesthesia.
The application takes place as gel, ointment or spray. The anaesthetic is often applied to a cotton swab and placed on the future injection site for about one minute. Similar successes as with surface anaesthesia can be achieved with pressure anaesthesia.
Here, pressure is applied to the future injection site with the finger for about 15 seconds, making the later injection less painful. Infiltration anaesthesia is only used for operations in the upper jaw, as the bone tissue is less dense and therefore less permeable for the anaesthetic. This is in contrast to the lower jaw, where the bone is more pronounced.
Therefore, a conduction anesthesia is usually used here. In infiltration anesthesia, the local anesthetic is injected under the mucous membrane (submucous) and over the periosteum (supraperiosteum), so that it can then spread into the bone via the periosteum. After one to three minutes, the local anesthesia begins to show its first effects, with the maximum effect occurring only after about 20 minutes.
During the time window of the maximum effect, the anesthesia is sufficient to extract a tooth, for example. In conduction anesthesia, the blockage of a nerve tract is used to anesthetize all areas that are supplied by this nerve tract. This form of anaesthesia is mainly used for larger procedures in the lower jaw area.
The bones of the lower jaw are stronger, so that the conduction anesthesia is more effective than the infiltration anesthesia. The anesthetic is injected near the inferior alveolar nerve in the area of the mandibular foramen (point of entry into the jaw). In contrast to the infiltration anesthesia, not only the tooth in question is anesthetized, but also the entire subsequent supply area of the nerve.
This leads to a longer lasting anaesthesia of the lower jaw, the involved mucous membranes and the lower lip. In the course of intraligamenary anesthesia, only the affected tooth is anesthetized. The injection is made into the so-called sulcus gingivae.
The gingival sulcus is a circular depression between the neck of the tooth and the gums. It is suitable for the upper and lower jaw, but with restrictions for the posterior mandible, where the teeth are stronger.This form of anesthesia is called “intraligamentary” because a mini cannula is inserted into the peridontal gap, into the ligaments (lat. “ligamentum”) of the periodontium, and the local anesthetic is injected there.
The anesthetic penetrates the periodontium including the bony structures up to the tip of the tooth root and unfolds its effect within a few seconds. The duration of the effect corresponds to about 20 to 30 minutes. To prolong the effect, anaesthetic can be injected subsequently. Intraligamentous anaesthesia requires only a small amount of anaesthetic per lane, making this form of anaesthesia particularly suitable for patients with cardiovascular problems.
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