Local anaesthetics


2 per cent articaine. Therefore, it might be advisable to limit the use of 4 per cent articaine to infiltrations and avoid for nerve blocksı7


.


Articaine has also been shown to be superior for infiltrations in the mandible and does not cause neural toxicity unless injected near the mental nerveı8


. Paraesthesia has been associated with the


use of local anaesthetics, especially when administered using the inferior alveolar nerve block techniqueı9


. Observational


research performed in Denmark reported a 20-fold greater risk of nerve injury when articaine was used compared with other local anaesthetics and administered via the IANB techniqueı7


. Given that


articaine is less neurotoxic than other anaesthetics, the findings of this research were unexpected20


. It is important to


consider that the aetiology of paraesthesia may be the result of a needle injury to the lingual and inferior alveolar nerve. Factors including intra-neural haematoma, extra- neural haematoma, oedema and chemical neurotoxicity of articaine may also play a role2ı


.


Dentists must also consider the ‘Weber effect’22. This occurs when a new product is


launched onto the market and is scrutinised more closely. Immediately after 4 per cent articaine containing ı:ı00,000 adrenaline was introduced, there was a significantly increased incidence of paraesthesia. But, two years later, a reduction was recorded despite an increased number of cartridges being sold2ı


. The literature reports that the lingual


nerve is more frequently damaged than the inferior-alveolar nerve. Approximately 70 per cent of permanent nerve damage is sustained by the lingual nerve, whereas a 30 per cent occurrence was recorded affecting the inferior alveolar nerve23


.


Current data indicates that 85-94 per cent of non-surgical paraesthesia caused by local anaesthetics recovers within two months. After a two month period, two thirds of those patients whose paraesthesia has not resolved will never completely recover23


. Articaine is also used in areas of medicine


such as plastic and reconstructive surgery, ophthalmology and orthopedic surgery. It is interesting that there are no reports of paraesthesia from articaine following its use in medicine. Is it possible that articaine only affects nerves supplying the oral cavity and specifically the lingual nerve? It is thought that paraesthesia affects the lingual nerve twice as much as the inferior alveolar nerve due to the fascicular pattern of the injection site. Also when a patient opens their mouth for treatment the lingual nerve is stretched and more anteriorly


Fig 1


N C4 H9


Lignocaine C2 H5


C2 H5 Prilocaine


C3 H7 H


C3 H7 Mepivacaine N CH3 Bupivacaine CH3 CH3 OCHN CH3 CH3 N H2 COCHN


CH CH3 3


CH3 N H2COCHN CH3 CH3


thiophene ring ester link


benzene ring


Adapted from the Handbook of local anesthesia2


Chemical structure of local anaesthetics


placed, this decreases it’s level of flexibility which is needed to deflect the needle. During administration the barbed needle can damage the inferior alveolar or lingual nerve during withdrawal24


. Interestingly, in 2006 when Hillerup


raised concerns that articaine was responsible for neurosensory disturbances, it was found that 80 per cent of all these reports came from Denmark. It is worth noting that, at the time, the Danish population was approximately 5.6 million compared with 50ı million in the wider EU community. This research lead to the Pharmacovigilance Working Party of the European Union conducting an investigation involving 57 countries and over ı00 million patients treated with articaine. The conclusion was emphatic, stating that all local anaesthetics may cause nerve injury. They estimated that the incidence of sensory impairment following administration of articaine was


CH3 OCHN


Articane H


N CH3 HCOCHN CH3 S COO CH3


one in every 4.6 million treated patients. Therefore, no medical evidence existed to prohibit the use of articaine and the safety profile of the drug remained unchanged. It is worth considering that, before articaine was introduced to the USA the incidence of permanent nerve damage from inferior alveolar nerve blocks was ı:26,762. In 2007, Pogrel also concluded that nerve blocks can cause permanent damage regardless of which anaesthetic agent is used. Both articaine and lignospan have been associated with this phenomenon in proportion to their use.


NEGATIVE SIDE-EFFECTS Articaine can result in restlessness, anxiety, light-headedness, convulsions, dizziness, tremors, drowsiness and depressionı3


.


Ocular complications have been reported due to interference with sensory and motor pathways25


. Other adverse effects


include headaches, facial oedema and gingivitisı3


administration of articaine have also been cited in the literature26


. Skin rashes with itching after . Skin necrosis


on the chin has also been reported after administration of 4 per cent articaine using the IANB technique27.. With regards to the cardiovascular


system, 4 per cent articaine can decrease cardiac conduction and excitability. Complications such as reduced myocardial contractility, peripheral vasodilation, ventricular arrhythmia, cardiac arrest and, rarely, death have been reported in the literature28


. It is important to


exercise caution in patients with severe hepatic impairment. However, the rapid breakdown of articaine into inactive metabolites results in low systemic toxicity29


.


CONCLUSIONS ON ARTICAINE Since ı973, there have been more than 200 papers published on articaine. Virtually all of these studies have concluded that articaine is as effective and safe as other comparable local anaesthetic agents such as lignospan, mepivacine or prilocaine. It was shown that articaine is the least likely anaesthetic to induce an overdose caused by administration of too many cartridges. No significant difference in pain relief has been observed between adrenaline containing formulations of 4 per cent articaine and 2 per cent lignospan. The time of onset and duration of anaesthesia for 4 per cent articaine is comparable to other commercially available local anaesthetics. Furthermore, the majority of studies have indicated that the incidence of complications including paraesthesia


Continued » Ireland’s Dental magazine 25


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