In: Anesthesia24 Nov 2009
A number of methods may be used to reduce the discomfort of local anesthetic injections. These might include the application of topical anesthetics before needle penetration and a slow rate of injection. However, there is little evidence in the literature that the various methods proposed are reliable. Even the use of topical anesthetics before injection is not found to be universally effective.
In addition to attention to technique, recommendations concerning the temperature and pH of the solution have been proposed as being important in relation to injection discomfort. There is evidence in the medical literature that these factors influence injection pain. However, there is little indication that they affect discomfort during intraoral anesthesia. A number of workers have shown that the temperature of the anesthetic does not affect intraoral injection pain as long as the solution is at or above room temperature. Similarly, although it has been suggested that using solutions with a pH closer to physiological should decrease injection discomfort, there is little evidence in the dental literature that this occurs during intraoral anesthesia. Oi-karinen et al noted that in volunteers, the injection into the maxillary buccal sulcus of 3% mepivacaine solutions of different pHs produced different levels of pain; the solution with the lower pH produced more discomfort. On the other hand, Primosch and Robinson reported the results of a volunteer investigation that showed no difference in injection discomfort during maxillary buccal infiltrations and palatal injections in the permanent canine region with buffered lidocaine solutions.
It is apparent to those who administer dental local anesthetics that injection discomfort varies in different areas of the mouth. The sites used in this investigation were chosen because it was believed that they would produce different levels of injection discomfort. The buccal sulcus in the premolar area is usually considered a relatively comfortable region for local anesthetic administration. In this investigation, 50% of the volunteers did not achieve an injection discomfort score that merited inclusion in the study, rating the injection pain as mild. The palatal region, however, is considered more uncomfortable. In the present study, only 7 of the 24 subjects considered palatal injection pain to be mild for both solutions.
The present study was designed to determine the influence of the choice of different commercially availablelocal anesthetic solutions on injection discomfort at 2 sites in the mouth. All other parameters were standardized. The results of this investigation show that different anesthetic solutions can affect discomfort for some injections in those patients who report more than mild pain. Buccal infiltration pain was less when plain lido-caine was used. The plain solution had a pH closer to physiological than the epinephrine-containing anesthetic. These findings are in agreement with those of Oi-karinen et al. The differences in pain scores between solutions may be attributed to their different pHs, although the design of this study was such that it could not rule out other effects that epinephrine might produce. However, Oikarinen et al noted that the addition of epinephrine to mepivacaine solutions did not significantly affect injection pain. Similarly, McKay et al noted that the addition of epinephrine to lidocaine without alteration of the pH did not increase discomfort during subcutaneous injections, whereas buffering of lidocaine solutions did reduce perceived pain. The present results differ from those of Primosch and Robinson. This may be because of the different sites of injection. In the present study and in the study reported by Oikarinen et al, buccal infiltrations were given in the maxillary premolar region, whereas in the Primosch and Robinson investigation, injections were given in the maxillary canine region. Submucosal tissues are looser in the more posterior region, which may account for the difference. In addition, the rate of injection in this study was the same as that used by Oikarinen et al, whereas the rate by Primosch and Robinson was not as slow. Another difference between the present study and the study reported by Primosch and Robinson was that in the latter study the perceived pain scores of their 10 volunteers during buccal infiltration were low (the mean pain being less than that considered moderate in intensity). In the present study, only individuals who recorded pain that was classified as moderate were included in the trial because the sensitivity of visual analogue scales depends on the production of moderate pain.
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In agreement with the findings reported by Primosch and Robinson, this study found no significant difference between solutions for palatal injections. This difference between buccal and palatal injections may be attributed to the factors that produce injection discomfort at different sites. During palatal anesthesia, the pain may be mainly a result of pressure because of the relatively noncompliant nature of this tissue. In the buccal sulcus, the loose nature of the submucosal tissues may cause solution-dependent factors such as the pH to have a greater influence on perceived discomfort. The results of this study add support to this belief.
Although the results of this investigation suggest one benefit for the use of plain lidocaine solutions, this local anesthetic is not recommended for definitive anesthesia of the teeth. A number of studies have shown that epinephrine-containing local anesthetics provide longer-lasting and more profound pulpal anesthesia compared with plain solutions when injected by various methods intraorally. Therefore, lidocaine with epinephrine is preferred as the definitive anesthetic. Plain solution may produce satisfactory soft tissue anesthesia, but the duration may be shorter than that obtained with vasoconstrictor-containing solutions.
Although the results of this study demonstrate a reduction in perceived discomfort when a plain lidocaine solution is used, it is important to point out that this finding relates to those individuals who find buccal infiltration anesthesia moderately painful. It is also important to point out that injection pain was not completely eliminated when the plain solution was used.
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Consideration of the data presented in the Figure and Tables 1 and 2 might be used to confirm the clinical impression mentioned earlier that palatal injections appear to be more uncomfortable than buccal infiltrations. However, such a conclusion cannot be drawn using the present results because the palatal injections were always given after the buccal administrations. Thus, an order effect cannot be excluded. Indeed, an order effect is apparent in relation to the palatal injections. The fact that palatal injection pain was dependent on the order of injection confirms results of other investigations of intraoral injection discomfort. For example, Martin et al found that patients who received bilateral buccal injections in the maxillary premolar region reported the second injection to be significantly more uncomfortable than the first administration. This suggests that the best chance of obtaining comfortable anesthetic delivery is at the first injection. Thus, choosing an area where such a possibility exists as the first site of injection is to be encouraged. If further administrations can be delivered into areas where the initial anesthetic has spread, the overall pain experience for the patient might be reduced.
Blog invites submissions of review articles, reports on clinical techniques, case reports, conference summaries, and articles of opinion pertinent to the control of pain and anxiety in dentistry.