Anesthesia in Dentistry

By Vishaal on Tuesday, December 4, 2007 with 0 comments

Painful feelings that are associated with most of dental surgeries can be dealt with relatively well by an anesthesia. Anesthetics are chemicals of various structure and properties that interrupt reversibly the conductance of sensory neural fibrils. According to chemical composition, these chemicals can be divided into:

  1. procaine - related anesthetics: Procain, Tetracain

  2. lidocaine - related anesthetics: Lidocain, Neolidocaton, Mesocain D, Ultracain D-S, Supracain.

An irreplaceable part of anesthetics are vasoconstrictive substances. These substances slow down the absorption of an anesthetic into the blood circulation thus reducing its toxicity, prolonging its effect, simplifying the overview of an operation field and reducing the duration of a surgery itself. Vasoconstrictive substances in use are synthetically made, although most of them are made by an organism under physiological conditions. They include adrenaline (epinephrine) - a hormone secreted by the adrenal medulla, noradrenaline (norepinephrine) that is secreted both by the adrenal medulla and the postganglional fibers of the sympathetic nerves, vasopressin, a hormone of the neurohypophysis (the drugs POR 8, Octapressin).

The local anesthetics can be applied by various ways:

  1. Surface anesthesia (mucous, contact). Anesthetics are applied to the dried oral mucosa in a form of sprays, solutions, creams or gels. By this way, a short-term anesthesia is achieved which is used for particular indications, such as for desensitization of injection anesthesia, removal of tartar, incision of submucosal abscesses, at children and sensitive patients.

  2. Terminal, infiltration anesthesia. Disposable syringes and needles are used for this kind of anesthesia. Subcutaneous anesthesia is used in cases of outer incisions or extirpations of small tumors; submucous anesthesia is used at the oral cavity for teeth extractions, for vital extirpations of the pulp, for grinding of vital teeth in order to fit it under prosthetic dentures etc. The effect of an anesthetic is based on a sufficient penetration of a solution through the periosteum and the compact bone to sensitive nerves of the upper and lower jaws. Intraosseal anesthesia (intra-spongious) may be applied at young individuals; an anesthetic is applied into the spongy part of the interdental septum.

  3. Regional anesthesia. An anesthetic is applied by instillation to bone canals and apertures through which the sensitive nerve fibers enter the upper or lower jaws. At the upper jaw, this kind of anesthesia is used on tuber maxillae, foramen infraorbitale, foramen incisivum, and foramen palatinum majus. At clinical praxis it is sufficient to employ the infiltration anesthesia by depositing an anesthetic at the level of the root apexes. Regional anesthesia is more often used at the lower jaw, where a thick cortical part at the molars area prevents diffusion of a solution to sensitive nerves. Anesthesia should be applied at foramen mandibulae and foramen mentale.

  4. Trunk anesthesia. An anesthetic is applied directly to exits of the trigeminus branches from the ganglion semilunare. Upon instillation at the foramen rotundum area, anesthesia is achieved for the second branch innervation area, after application at foramen ovale, anesthesia is achieved for the third branch area. The trunk anesthesia is rarely used in common praxis. It is devoted to neurosurgeries in cases of the trigeminus neuralgias.

Complications that may occur during anesthesia may be either local or general.

Local complications.

  1. breaking an injection needle at a patient’s sudden move

  2. misplacement of an injection solution

  3. introduction of infection deeply into a tissue, or infecting a hematoma resulting from a break in a blood vessel

  4. damage of the periosteum or neural branch followed by pain, after a deep puncture

  5. ischemic necrosis of a tissue after application of a large amount of an anesthetic and a vasoconstrictive substance

  6. muscle contraction after anesthesia at foramen mandibulae. It may be caused by a muscle injury, hematoma infection or toxic effects of the anesthetic.

General complications.

  1. Toxic reaction in case of exceeding a maximum dose of an anesthetic. It can occur by a cumulative effect of two different anesthetics - absolute overdosing - or by an accidental intravasation - relative overdosing.

  2. Allergic reaction is quite frequent after application of procaine-like anesthetics. Allergic reactions include hives with exanthema, angio-neurotic edema, oral mucosa erythema etc. The most serious condition is the anaphylactic shock with a sharp onset of the heart and respiratory insufficiency (accelerated, later weakening breathing, heart arrhythmia or even heart arrest). Therapy of general reactions to anesthetics should be carried out according to general rules of reanimation, which every physician should be familiar with. Relatively frequent reaction, which sometimes occurs even before an anesthetic is applied, is fainting (peripheral collapse). It results from a sudden failure of blood circulation into the brain, caused by a decrease of the peripheral resistance of blood vessels due to vasodilatation. Numerous other factors play a role here, such as mental stress, fear from a treatment, hypotonicity and hypoglycemia caused by hunger, lack of sleep or fatigue. A patient turns pale, gets nausea and loses his/her consciousness temporarily. These states can usually be managed without a medication. A doctor should keep talking to a patient and try to calm him/her down. A deep leaning over, with head close to the knees sometimes works well, due to pressing of the splanchnic area together with a low position of the head which increases blood circulation of the brain tissues. In all cases, a patient’s clothing should be released and fresh air should be supplied. A patient may as well be laid at the dentist’s chair, with his/her legs raised.

General anesthesia is indicated for large surgeries at the oro-facial area that are performed in the form of the inpatient care. A short-term intravenous general anesthesia is used in the ambulatory praxis (Sombrevin) for non-cooperating patients (children, neurotic patients, mentally affected individuals). It requires a patient’s general preoperative examination, ensuring his/her escorting and a home care at the day of a surgery.

Analgesia deadens sensing of painful stimuli while maintaining a patient’s full consciousness. Various forms, such as pharmacological, hypnotic or reflexive (acupuncture or transcutaneous electroneurostimulation - TENS) are used.

Category: Oral Medicine Notes



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