Methods of local anesthesia
The indication for local anesthesia is any procedure in the maxillofacial region (involving soft tissues, jaws, or teeth) that is accompanied by pain.
There are two main groups of methods:
- Injection methods: infiltration and conduction anesthesia.
- Non-injection methods: provide only surface anesthesia. These include:
- Chemical (topical) method: application of medications to the mucosal surface.
- Physical method: exposure to low temperatures (freezing), laser, or electromagnetic waves.
- Physicochemical method: administration of an anesthetic via electrophoresis.
Depending on the chosen method, the mechanism of action consists either in desensitizing peripheral receptors (in infiltration, topical anesthesia, and cooling) or in blocking the nerve trunk and its branches (in conduction anesthesia).
Pharmacological toolkit: premedication
To relieve psychoemotional stress, fear, and anxiety before the procedure, pharmacological preparation is used. In some cases, inhalation of small doses of dinitrogen monoxide (nitrous oxide) is used.
Tranquilizers (benzodiazepines):
- Diazepam: dose 10–20 mg. Depresses the limbic system and reticular formation. Exhibits anticonvulsant and mild hypotensive effects, and potentiates analgesics.
- Phenazepam: dose 0.03 mg/kg. Has a stronger anxiolytic and antidepressant effect.
- Midazolam: short-acting drug. Administered slowly (1 mg over 30 s), with onset of action in 2 minutes. Causes transient amnesia. Contraindicated in myasthenia gravis.
Analgesics:
- Fortral (pentazocine): synthetic drug that does not depress respiration. Administered orally (50–75 mg) or intravenously (30–60 mg).
- Tramadol: potent, low-toxicity analgesic. Effect lasts 3–5 hours. Contraindicated in pregnant women, nursing mothers, and children under 14 years of age.
- Butorphanol: superior to promedol (trimeperidine), does not cause gastrointestinal spasms. Administered intramuscularly (4 mg) or intravenously (2 mg). Contraindicated in hypertension and coronary artery disease.
- Piritramide (Dipidolor): acts 1.5–2 times faster and stronger than morphine, does not cause addiction.
- Nalbuphine: semi-synthetic drug, may cause drowsiness. Analgesic dose is 0.15 mg/kg.
Emergency care: Cardiopulmonary resuscitation
If cardiac arrest and respiratory arrest occur during the appointment, clinical death ensues. Its signs include loss of consciousness, absence of pulse in major arteries, absence of breathing, and dilated pupils unresponsive to light.
The first three stages of CPR, mandatory for a dentist:
- Airway clearance: the patient is placed on a hard surface, the head is tilted back, the lower jaw is pushed forward, and the oral cavity is cleared of mucus, blood, or foreign bodies.
- Artificial pulmonary ventilation (APV): performed using mouth-to-mouth, mouth-to-nose, or mechanical ventilation devices (RPA-1). Frequency is at least 12 breaths per minute. During inflation, the chest should rise.
- Closed chest massage: the doctor places their hands on the lower third of the sternum. Energetic compressions should displace the sternum 3–5 cm toward the spine. Frequency is at least 60 compressions per minute.
Coordination of actions:
- If there is one rescuer: 2 breaths per 15 compressions.
- If there are two rescuers: 1 breath per 5 compressions.
- Chest compressions are always combined with artificial ventilation, but compressions must strictly not be performed at the moment of air inflation.
Drug therapy and defibrillation in CPR
Medications are administered strictly against the background of chest massage and artificial ventilation (intravenously, intra-arterially, or intracardiacally):
- Epinephrine (Adrenaline): 0.5–1 ml fractionally every 5 min. Enhances myocardial tone and facilitates defibrillation.
- Sodium bicarbonate 4.2%: 1–2 ml/kg to improve therapy efficacy.
- Calcium chloride 10%: 5–10 ml to improve contractility.
- Atropine 0.1%: 1 ml to reduce vagal tone.
Defibrillation: Start with a voltage of 3.5 kV, and if ineffective, increase to 6 kV. One electrode is placed under the right scapula, the second over the apex of the heart (using damp pads moistened with isotonic solution). If a series of shocks fails, procainamide and sodium bicarbonate are administered, after which attempts are repeated.
Briefly: answers to topical questions
What types of syringes are used for local anesthesia in dentistry?
Disposable plastic and reusable metal syringes are used for local anesthesia in dentistry.
- Disposable plastic syringes consist of a graduated barrel and plunger, requiring preliminary drawing of the anesthetic solution.
- Dental cartridge syringes are reusable metal syringes designed for use with pre-filled anesthetic cartridges. Depending on the method of cartridge fixation, they are classified into:
- Spring-loaded syringes (with a ring and return spring mechanism on the plunger rod).
- Bayonet syringes (cylindrical in shape with a side-loading clamp lever).
- Breech-loading syringes (with a hinge mechanism for hard-to-reach areas).
- Syringes for intraligamentary anesthesia (pistol-type with a powerful lever mechanism).
What elements does a local anesthetic cartridge (carpule) consist of?
A local anesthetic cartridge (carpule) is a hermetically sealed structure ensuring sterility, long-term storage, and precise injection dosing.
- Barrel (cylinder) — glass or plastic; initial volume 2 ml, actual filling 1.7–1.8 ml.
- Silicone plunger — located at one end of the cylinder.
- Rubber stopper with a metal cap — located at the other end of the cylinder.
What standards for thickness (gauge) of dental needles exist?
The thickness of dental needles is measured by two standards: in international units (G), defining the internal lumen, and in millimeters (mm), defining the outer diameter.
| Lumen size (G) | Outer diameter (mm) |
|---|---|
| 20G | 0,9 |
| 21G | 0,8 |
| 22G | 0,7 |
| 23G | 0,6 |
| 25G | 0,5 |
| 27G | 0,4 |
| 30G | 0,3 |
What instruments are used for intraligamentary anesthesia?
Instruments used for intraligamentary anesthesia allow the delivery of anesthetic directly into the periodontal ligament under pressure.
- Injectors: specialized syringes with a reducer that create strong, controlled pressure and regulate the volume of anesthetic; standard Record-type syringes; special syringes with an angled attachment or rotating head to achieve the correct angle relative to the tooth axis; specialized pistol-type syringes with a powerful lever mechanism.
- Needles: standard domestic thin needles with a diameter of 0.4 mm; ultra-short needles with a length of 8 or 12 mm and an outer diameter of 0.3 mm; short needles with a length of 10 or 12 mm and a diameter of 0.3 mm; less commonly, 12 mm needles with an inner diameter of 0.03 mm.
For the correct compression-to-ventilation ratio during CPR: "One rescuer — two breaths to fifteen compressions; two rescuers — one breath to five compressions."
Class and exam questions
What restrictions apply to the administration of Midazolam in an outpatient clinic?
The total dose must not exceed 5 mg. The patient may only be discharged home with an escort no earlier than 3 hours later, and driving is prohibited on that day.
When should resuscitation efforts be discontinued?
If cardiac activity does not resume 10–15 minutes after the initiation of effective chest compressions and artificial ventilation, and the pupils remain dilated and unresponsive to light, it indicates irreversible brain death.
What else to study on this topic
- Specifics of conduction anesthesia in the maxilla and mandible
- Mechanism of action and pharmacokinetics of local anesthetics
- Specific applications of RPA-1 and RDA-1 devices for artificial ventilation
- Indications and contraindications for the use of nitrous oxide
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