Efficacy of Differents Anaesthetics in Mandibular Third Molar Germectomy

The surgical extraction of a tooth that exhibits at least a third of its root in formation, with a periodontal ligament discernible on panoramic x-ray, is defined as germectomy. Early germectomy is a usefull intervention to avoid problems caused by lower third molar retention and impaction, and it is often required before or after orthodontic treatment. This surgical technique would also allow to avoid complications, such as inferior alveolar and lingual nerve damage.

The control of the patient's pain and anxiety by using local anaesthesia is essential in oral surgery: these aspects become more important in adolescents, above all in the case of third molar germectomy. Local anaesthetic (LA) injection is often the only painfull part of the dental procedure, and the fear associated with this technique is the main reason that leads patients to avoid dental treatment.

During the execution of dental surgical procedures, anaesthesia of the structures innervated by the mandibular nerve is necessary, and many local anaesthetic techniques are described in the literature. Generally, infiltration plexus technique is usually performed for maxillary procedures while IANB is used for molar mandibular sites with 2% local anaesthetics. Failure rates for IANB are high, sometimes reaching 80% for the lower incisors with this technique, and numerous approaches for the implementation of a new technique of IANB have been described. Among them, the articaine 4% already has been successfully used to achieve local anesthesia and facial infiltration anaesthetic technique in the mandible showed efficacy with encouraging result that can be overlapped to the IANB technique. Articaine (4-methyl-3-[2-(propylamino)-propionamido]-2-thiophene-carboxylic acid, methyl ester hydrochloride) contains a thiophene ring instead of benzene and an ester group. The thiophene ring allows for higher lipid solubility so a greater portion of an administered dose can enter in neurons. Gazal found that a combination of nerve block anaesthesia, buccal infiltration and intra-ligamentary injection resulted in more profound anaesthesia (P =0.003) and higher success rates compared to IANB alone in mandibular first molar pulp anaesthesia. Other studies reported the use of articaine in implantology interventions in which it was used with subperiosteal technique on the buccal and vestibular sides.

Thus, the literature showed several conflicting results on the mandibular facial plexus infiltration technique used with different anesthetics.

Recent studies of this anaesthetic technique found that 1.8 cc of 4% articaine facial infiltration in the mandible can be effective when the thickness of mandibular facial cortex is < 2.0-3.0 mm, with 5-10 minutes needed for the adequate anaesthesia.

It was reported that many dental procedures on deciduous molars could be accomplished with infiltration of articaine alone in the pediatric population.

As above mentioned, the difficulty in achieving reliable anaesthesia in the third mandibular molars in adults with facial infiltration of local anaesthetic is related to the thickness of the cortical bone and inability to achieve consistently inferior alveolar nerve.

An ideal local anaesthetic should have the following characteristics:

1. short latency time;
2. strength of the intense effect;
3. duration of prolonged action;
4. lack of harmful local and systemic effects. Currently, mepivacaine is among the most used and studied anaesthetics in dentistry; however, articaine is nowadays increasingly used for its manageability, lack of side effects and high anaesthetic potency. Mepivacaine is an amide-type anaesthetic with fast action from the beginning and 30-120 minutes duration. Its maximum allowed dose is 300 mg with epinephrine or 500 mg alone. The dose for children is 4-6 mg/kg/dose (maximum: 270 mg) without epinephrine.

Articaine, due to its chemical characteristics, is quickly soluble and rapidly released from adipose/lipid tissue. The ester side chain of articaine is hydrolyzed by plasmaesterases rendering the molecule inactive. Evidence suggests that it is the local anaesthetic that best spreads within soft and hard tissues. Then, it has a non-conducive effect on extended operations having a shorter half-life of 25 minutes compared to approximately 90 minutes of other amides (115 minutes for mepivacaine) that require hepatic clearance. Accordingly, it was suggested that articaine does not own any relevant side effects or systemic toxicities.

For this reason, articaine has been used at higher concentrations (4%), associated with epinephrine, compared to other local dental anesthetics. This higher concentration ensures an excellent spread both in hard and soft tissues, also promoted by a pKa very similar to the physiological pH of tissues. Its great liposolubility allows a rapid diffusion in adipose tissue (spread coefficient = 17,0) and involves a lower adherence to the nerve membranes and, above all, lower toxicity for the tissues. Moreover, articaine has a high protein-based bond (94%) which allows a better affinity for the protein-based membrane receptors, and it is a direct sign of its increased anaesthetic potency.

Dental local anaesthetics are often combined with vasoconstrictors, such as epinephrine, to increase the depth and duration of analgesia. Clinical experiments, in which articaine without vasoconstrictor was used, did not show any satisfying results, whereas the use of articaine combined with low concentrations of vasoconstrictors produced better anaesthetic effects than other common local anaesthetics such as bupivacaine and mepivacaine. It is well documented that vasoconstrictors have a safety range if used at low doses, and not directly injected in the blood vessels, even in particular care patients.

The present study aimed to compare the clinical efficacy of articaine 4% (epinephrine 1:100.000) versus mepivacaine 2% (epinephrine 1:100.000) for the surgical germectomy of mandibular third molars with two different conventional anaesthetic techniques in young patients whom jawbone is not completely mineralized yet and more penetrable by the articaine molecule.