Inferior alveolar nerve block agents

Achieving good local anaesthesia is a key element in modern dental practice. Studies have suggested that failure rates if inferior alveolar nerve (IAN) block range between 17-58%. Administration of 3% mepivacaine plain followed by 2% lidocaine with 1:100,000 epinephrine for IAN blocks is advocated by some clinicians as theoretically mepivacaine may decrease the pain of injection, provide quicker onset an increase anaesthetic success and possible potentiate the effect of the lidocaine.

The aim of this study was to compare the degree of pulpal anesthesia obtained with a combination of 3% mepivacaine/2% lidocaine (1:100,000 epinephrine) versus a combination of 2% lidocaine (1:100,000 epinephrine)/2% lidocaine (1:100,000 epinephrine) in IAN blocks.

Methods

100 asymptomatic adult patients (aged 18-65) were randomly given a combination of a 1-cartridge volume of 3% mepivacaine plus a 1-cartridge volume of 2% lidocaine with 1:100,000 epinephrine and a combination of a 1-cartridge volume of 2% lidocaine with 1:100,000 epinephrine plus a 1-cartridge volume of 2% lidocaine with 1:100,000 epinephrine for the IAN block at 2 separate appointments.

At the beginning of each appointment and before any injections were given, the experimental teeth and control contralateral canine were tested 3 times with the electric pulp tester to record baseline vitality. Pain was rated by the patient using the Heft-Parker visual analog scale (VAS). Patients rated pain for needle insertion, needle placement, and solution deposition. The molars, premolars, and incisors were tested with an electric pulp tester in 4-minute cycles for 60 minutes. Anesthetic success was defined as the subject achieving 2 consecutive 80 readings within 15 minutes after completion of the IAN blocks and sustaining the 80 reading for 60 minutes.

Results

100 patients (50 men; 50 women) participated
There were no significant differences between the mepivacaine/lidocaine and lidocaine/lidocaine combinations for any of the teeth tested (P > .05).
Anesthetic success rates for each tooth type are shown below

Tooth	Number	Percentage anaesthetic success
Tooth	Number	Mepivacaine/lidocaine	Lidocaine/lidocaine
Second molar	99	51%	57%
Frist molar	100	44%	40%
Second premolar	93	45%	41%
First premolar	97	53%	50%
Lateral incisor	100	30%	27%
Central incisor	100	10%	10%

The mean onset times for the mepivacaine/lidocaine combination ranged from 6.9 to 16.2 minutes, and mean onset times ranged from 6.0 to 12.2 minutes for the lidocaine/lidocaine combination

Conclusions

The authors concluded

The combination of 3% mepivacaine plus 2% lidocaine with 1:100,000 epinephrine was equivalent to the combination of 2 cartridges of 2% lidocaine with 1:100,000 epinephrine in terms of injection pain, onset time, and pulpal anesthetic success for the IAN block.

Commentary

The trails involved 100 patients and used a cross-over design so 200 combination sets of IAN blocks were given. The clinical and trial methodology is also very clearly described and there is a good discussion of the findings.