Effectiveness of 20% Benzocaine as a Topical Anesthetic for Intraoral Injections: DISCUSSION

In: Anesthesia

1 Nov 2009


The effectiveness of topical anesthesia to reduce needle insertion pain has been met with mixed results. In our study, topical anesthetic effectiveness was found to be related to the location of the injection. For the inferior alveolar nerve block injection (Figure), no significant difference was found between the no pain/pain ratings when topical anesthetic was used. Our results and those of Nakanishi et al and Meechan et al agree on the lack of effectiveness of 20% benzocaine in reducing pain during needle insertion in the pterygomandibular raphe area when using a 27-gauge needle for an inferior alveolar nerve block. Similarly, topical anesthetic did not significantly reduce the pain of needle insertion over the maxillary first molars (Figure).

The greatest effect of the topical anesthetic in our study was found in the maxillary anterior region over the maxillary lateral incisors (Figure). Here subjects re-Table 2. Logistic Regression Analysis for Topical Anesthetic Use ported significantly more “no pain” ratings (37%) with the use of 20% benzocaine (adjusted odds ratio; 2.35 times more likely) as compared with those not receiving the topical anesthetic (28% no pain). Thus the use of 20% benzocaine in this area may be beneficial in reducing the pain of needle insertion over the maxillary lateral incisors (P = .0041). However, some patients (18% of maxillary lateral incisor injections) still reported moderate-to-severe pain on needle insertion when topical anesthetic was used.
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Our overall results agree with a number of investigators who also found that topical anesthetics are more effective in certain locations or for specific injections (ie, the maxillary mucobuccal fold infiltrations) than in other regions/injections (inferior alveolar nerve blocks).

A variety of factors have been reported to influence the effectiveness of topical anesthetics. The duration of application is one such factor. Increasing the duration of exposure to the topical anesthetic has been related to increased effectiveness. In our study, a 1-minute application was utilized. Hutchins et al also reported success in the maxillary mucobuccal fold with a 1-minute application of 20% benzocaine. Vongsavan and Vongsavan reported success with a 2-minute application of 20% benzocaine. Rosivack et al utilized a 3-minute application of 20% benzocaine in the maxillary buccal sulcus with success. Gill and Orr reported on the failure of 3 topical anesthetics (including 22% benzocaine) when applied for only 30 seconds. Meechan et al reported that a 2-minute application of 20% benzocaine was unsuccessful in reducing pain of an inferior alveolar nerve block, whereas Nakanishi et al. reported that a 4-minute application was also unsuccessful. It appears from our results and those of others that 20% benzocaine requires at least a 1-minute application to be effective in the maxilla, but that increased duration of application may still not be effective with an inferior alveolar nerve block. Viagra Soft Tabs

The type of topical anesthetic utilized is another major factor. Research has been conducted on a number of different topical anesthetics including benzocaine, lidocaine (5%, 10%, 20%, and 60% concentrations), and EMLA (5% eutectic mixture of lidocaine and prilocaine). Results with these and other forms of topical anesthetics have been varied. In general, benzocaine has been found to be effective at a 20% concentration when applied for at least 1 minute, but ineffective with 30-second and 20-minute applications. Lidocaine has been reported to be effective at concentrations of 5%, 10% and 20% (via patch), and 60% when applied for 2-20 minutes. Ineffectiveness of 5% lidocaine has been reported for 30-second applications and a 2.5-minute application via a patch. EMLA was found to be successful after 2 and 5 minute applications.

The placebo effect of topical anesthetics has also been investigated. Kincheloe et al reported that patients expecting pain fulfilled their expectations and experienced more pain even when a topical anesthetic was applied and the patient informed of how well it worked. Martin et al reported that patients receiving a topical anesthetic (20% benzocaine) anticipated less pain and therefore experienced less anxiety prior to receiving an injection. However, they reported that the use of a topical anesthetic did not reduce the reported pain experience. Differences in the manner a provider delivers an injection is another consideration related to pain of needle insertion. Initial analysis of our results showed that there was a significant difference in needle insertion pain ratings between operators (P < .0001). However, statistically, we were able to control for operator differences through logistic regression analysis. Levine and De Simone reported that the sex of the experimenter has a differential effect on the degree of pain reported by male and female subjects. This may have played a factor in this study, as well as the differences in skills between operators and differences in group populations between the studies. You can afford your pills. buy female viagra online

Other factors that could contribute to reported pain include the age and sex of the patient. Research has shown that female patients will tolerate pain less than men and that older individuals will report less pain than younger individuals when receiving a dental injection. In our study, we compiled data from 25 studies. Unfortunately, these studies recorded the total number of men/women and overall ages in each study, but not for individual topical versus no topical groups, thus making it impossible to include these factors in our regression models. The studies we sampled utilized a young adult population; therefore, the results of this study may not apply to children or the elderly. The results we compiled present indications of the effectiveness of 20% benzocaine on reducing, but not eliminating, the pain of needle insertion in the maxillary anterior region.

In conclusion, the use of topical anesthetic significantly (P = .0041) increased the odds of patients experiencing no needle insertion pain during maxillary anterior infiltrations. There was no significant effect (P > .05) for the maxillary posterior infiltration or the inferior alveolar nerve block. Although some studies have demonstrated the effectiveness of topical anesthetic, others have reported no significant pain reduction with the use of topical anesthetic. Martin et al found that if the patients thought they were receiving topical, whether they did or not, they anticipated less pain. Therefore, the most important aspect of using topical anesthetic may not be its clinical effectiveness, but rather the psychological effect on the patient who feels the practitioner is doing everything possible to prevent pain. generic singulair

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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.