In an attempt to increase the effectiveness of lidocaine delivered through inferior alveolar nerve block, several experiments combining lidocaine with other substances have been conducted. Yet these studies have conflicting results. Nevertheless, the decision on using a particular lidocaine combination should lie on the validity and reliability of the experiments that support the use of such preparation because the effectiveness of anesthesia is very critical in delivering quality dental care.
The study conducted by Kanaa et al. (2009) employed a randomized controlled double-blind cross-over research design to test the hypothesis that supplementary articaine infiltration is more effective than lidocaine inferior alveolar nerve block alone. The subjects were selected from a group of volunteers aged 18 years and above “with a vital mandibular ﬁrst molar, ﬁrst or second premolar and lateral incisor” (Kanaa et al., 2009) on either side and who were able to complete the trial experiment. Those who were pregnant and unhealthy such as those with the allergy to amide local and those with bleeding and neurological disorders were excluded in the study. This resulted to a sample size consisting of 36 participants which is big enough considering that an earlier published and reviewed study indicated that this sample size had 90% power to detect a difference with a 21% success rate given a 5% signiﬁcance level and a 0.5 correlation between responses from the same participant (as cited in Kanaa et al., 2009). However, the subjects were predominantly from the university and some are even dental students which do not necessarily reflect the actual population. This can also result in biases since the subjects have knowledge of the procedure is done; thus, their expectations may influence the result of the study.