We hypothesized that a supplemental buccal infiltration might increase success compared with a standard IAN block alone. Therefore, we conducted a prospective, randomized, double-blind, crossover study to compare the degree of pulpal anesthesia attained with a mandibular first molar buccal infiltration of 4 percent articaine with 1:100,000 epinephrine versus 2 percent lidocaine with 1:100,000 epinephrine in the mandibular first molar after administration of an IAN block with the use of 4 percent articaine with 1:100,000 epinephrine.

	SUBJECTS, MATERIALS AND METHODS

TOP ABSTRACT SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
Seventy-three men and women participated in this study. The subjects were in good health and were not taking any medications that would alter their perception of pain. Exclusion criteria were as follows: younger than 18 years, older than 60 years (because elderly patients have shorter onset times for infiltration⁷), allergies to local anesthetics or sulfites, pregnancy, history of significant medical conditions, taking any medications that may affect anesthetic assessment, active sites of pathosis in the area of injection or inability to give informed consent. The Ohio State University Human Subjects Review Committee, Columbus, approved both the protocol and informed consent document, and we obtained written informed consent from each subject.

The 73 subjects received a standard IAN block⁸ with the use of 4 percent articaine with 1:100,000 epinephrine (Septocaine, Septodont USA, New Castle, Del.). The subjects then randomly received buccal infiltration injections of a cartridge of 2 percent lidocaine with 1:100,000 epinephrine (Xylocaine, AstraZeneca, Wilmington, Del., now marketed through APP Pharmaceuticals, Schaumburg, Ill.) at one appointment and a cartridge of 4 percent articaine with 1:100,000 epinephrine (Septocaine) at another appointment, with the appointments spaced at least one week apart, in a crossover design. With the crossover design, 146 total infiltrations (73 articaine and 73 lidocaine) were administered, and each subject served as his or her own control. The senior author (A.H.) administered 66 infiltrations on the right side and 80 infiltrations on the left side. The side chosen for the first infiltration was used again for the second infiltration. We chose the first molar as the test tooth for the experiment. We used the contralateral canine as the unanesthetized control to ensure that the pulp tester was operating properly and that the subject was responding appropriately during each experimental portion of the study. Clinical examinations indicated that all teeth were free of caries, large restorations and periodontal disease; in addition, no teeth had histories of trauma or sensitivity.

Before the experiment, we randomly assigned to the two anesthetic solutions six-digit numbers from a random number table. In addition, we randomly assigned each subject to each of the two formulations to determine which anesthetic formulation was to be administered at each appointment. We recorded only the random numbers on the data collection sheets to further blind the experiment.

Under sterile conditions, research personnel masked the lidocaine and articaine cartridges with opaque labels and the cartridge caps and rubber plungers with a black felt-tip marker. The research personnel wrote the corresponding six-digit codes on each cartridge label. Before masking the cartridges, we checked all anesthetic solutions to ensure that they were not past their expiration dates. The senior author (A.H.) administered the infiltration injections using the standard masked cartridges and an aspirating syringe equipped with a 27-gauge 1-inch needle.

Electric pulp tester. At the beginning of each appointment and before any injections were administered, we tested the experimental tooth and control contralateral canine three times with the electric pulp tester (Kerr, Analytic Technology, Redmond, Wash.) to record baseline vitality. We used the contralateral canine as a positive control because it would not be anesthetized by the IAN block and, therefore, would respond to pulp testing. After isolating the tooth to be tested with cotton rolls and drying it with gauze, trained research personnel applied tooth-paste to the probe tip and then placed it midway between the gingival margin and the occlusal edge of the tooth. They set the rate of current at 25 seconds to increase from no output (0) to the maximum output (80). The research personnel recorded the number associated with the initial sensation. Trained research personnel performed all preinjection and postinjection tests.

IAN block. The clinician used a cotton-tipped applicator to place topical anesthetic gel (20 percent benzocaine) passively at the IAN block injection site for 60 seconds. The dentist administered a standard IAN block⁸ with a 27-gauge -inch needle (Monoject, Sherwood Medical, St. Louis) attached to a standard aspirating syringe and used a cartridge of 4 percent articaine with 1:100,000 epinephrine. On the basis of the results of Mikesell and colleagues,² we determined that the use of the 4 percent articaine formulation would not be significantly different—with regard to success, failure or onset of anesthesia—from a 2 percent lidocaine formulation in asymptomatic subjects. After reaching the target area and performing aspiration, the clinician deposited the anesthetic solution over a one-minute period. He did not administer any separate long buccal nerve injection.

Visual analog scale. Before the buccal injection, the research personnel showed each subject a visual analog scale (VAS) and asked him or her to rate the pain for each phase of the injection: needle insertion, needle placement and deposition of solution. We used a Heft-Parker VAS⁹ in this study (Figure 1). During each phase of the injection, the senior author (A.H.) informed the subject when each phase of the injection was complete; immediately after the infiltration, the subject rated the pain for each injection phase on the VAS. The VAS is a 170-millimeter line with various descriptive terms. Subjects placed a mark on the scale at the point that best described their pain level. To interpret the data, we divided the VAS into the following four categories.

View larger version (27K): [in this window] [in a new window]   Figure 1. Heft-Parker visual analog scale (VAS) used for the assessment of pain. The millimeter (mm) demarcations were not shown on the patients’ VAS. Reprinted with permission of the International Association for the Study of Pain from Heft and Parker.9

– No pain corresponded to 0 mm on the scale.

– Mild pain was defined as greater than 0 mm and less than or equal to 54 mm. Mild pain included the descriptors "faint," "weak" and "mild."

– Moderate pain was defined as greater than 54 mm and less than 114 mm.

– Severe pain was defined as equal to or greater than 114 mm. Severe pain included the descriptors "strong," "intense" and "maximum possible."

Infiltration injection. Fifteen minutes after administering the IAN block, the senior author administered the infiltration injection buccal to the mandibular first molar, bisecting the approximate location of the mesial and distal roots. He placed the needle gently into the alveolar mucosa (needle insertion phase) and advanced it until he estimated that it was at or just superior to the apexes of the first molar (needle placement phase). He deposited the anesthetic solution over a one-minute period (solution deposition phase). As noted above, the senior author administered all infiltrations.

Sixteen minutes after completion of the IAN block (corresponding to one minute after the buccal infiltration), the research personnel performed pulp testing on the first molar. At three minutes, they tested the control canine. The cycle of testing was repeated every three minutes for 60 minutes after the injections. At every third cycle, the research personnel tested the control tooth—the contralateral canine—via an inactivated electric pulp tester to test the reliability of the subject. If the subject responded positively to an inactivated pulp tester, then he or she was unreliable and ineligible to participate in the study. We did not exclude any subjects owing to a positive response to the inactivated pulp tester.

In addition, we did not test teeth on the treated side with an inactive pulp tester because it was difficult to isolate other teeth and keep a timeline for the experimental and control teeth. Every minute for 15 minutes, research personnel asked each subject if his or her lip and tongue were numb. If profound lip numbness was not recorded within 15 minutes of the block injection, we considered the block unsuccessful and scheduled the subject for another appointment.

We asked all subjects to complete postinjection surveys after each appointment. Using the VAS as described previously, they rated pain for only the buccal infiltration injection area immediately after the numbness wore off and again each morning on arising for the next three days. Research personnel also instructed patients to describe and record any problems, other than pain, that they experienced.

Our criterion for pulpal anesthesia was no response from the subject at the maximum output (80 reading) of the pulp tester. We considered anesthesia to be successful when we obtained two consecutive 80 readings within 10 minutes after the IAN block and infiltration injections, and the 80 reading was sustained continuously through the 60th minute. With a nondirectional risk of .05 and a power of 80 percent, a sample size of 73 subjects was required to demonstrate a difference in anesthetic success of ± 25 percent.

Using the exact McNemar test, we analyzed differences between the 4 percent articaine and 2 percent lidocaine formulations regarding anesthetic success. We conducted between-group comparisons of needle insertion, needle placement and solution deposition pain and postoperative pain by using analysis of variance with the Tukey-Kramer multiple-comparison test. We considered comparisons to be significant at P < .05.

	RESULTS

TOP ABSTRACT SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
Seventy-three adults (27 women and 46 men) aged 20 to 36 years (mean age, 27 years) participated in this study.

Table 1 presents the subjects’ anesthetic success. The articaine formulation was significantly better than the lidocaine formulation with regard to anesthetic success (P < .01). Figure 2 presents the incidence of pulpal anesthesia (80 readings) across time for the articaine and lidocaine formulations.

View larger version (62K): [in this window] [in a new window]   Figure 2. Incidence of first-molar anesthesia as determined by the lack of response to electrical pulp testing at the maximum setting (percentage of 80/80 readings) at each postinjection time interval for the two anesthetic formulations: 4 percent articaine with 1:100,000 epinephrine and 2 percent lidocaine with 1:100,000 epinephrine.

	DISCUSSION

TOP ABSTRACT SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

Testing the teeth after the IAN block but before the buccal infiltrations would have given us additional information regarding the success of the nerve block alone. Instead, we used lip numbness to confirm a clinically successful nerve block. However, it is important to realize that lip numbness does not always ensure pulpal anesthesia.^1,2,6

Anesthetic success (Table 1) was significantly better with the 4 percent articaine formulation than with the 2 percent lidocaine formulation. This finding confirms the higher success rates observed in previous studies^5,6 of a 4 percent articaine formulation for buccal infiltration of asymptomatic mandibular first molars. The exact mechanism of the increased efficacy of articaine is not known. Borchard and Drouin¹² found that a lower concentration of articaine (a thiophene derivative) was sufficient to block an action potential when compared with other amide anesthetics (benzene derivatives). In a study of rat sensory nerve conduction, Potocnik and colleagues¹³ found that both 2 percent and 4 percent articaine were superior to 2 percent lidocaine in blocking nerve conduction. However, with increased intensity of nerve stimulation, the compound action potential recovered for 2 percent articaine but not for 4 percent articaine.

It may be that factors other than the concentration are responsible for the clinical efficacy of articaine. For instance, the unique chemical structure of articaine (the thiophene ring is not possessed by other local anesthetic agents) may facilitate better diffusion of the anesthetic solution to the teeth. Regardless of the mechanism, 4 percent articaine was superior to 2 percent lidocaine when used for infiltration of the lower posterior teeth. However, Haas and colleagues^3,4 found that 4 percent articaine with epinephrine was similar to 4 percent prilocaine with epinephrine for infiltrations of mandibular canines and second molars. Investigators may want to compare 4 percent articaine formulations with 4 percent prilocaine formulations in infiltrations of the mandibular first molar. Because we studied a young adult population, the results of this study may not apply to children or elderly patients.

In a study of buccal infiltration anesthesia of the first molar, Robertson and colleagues⁶ found that the anesthetic solution appeared to diffuse anteriorly from the first molar site. In other words, they recorded a higher success rate in the premolars and first molar than in the second molar for both articaine and lidocaine formulations. The relatively thick mandibular bone in the second molar region may hinder anesthetic diffusion. Performing a buccal infiltration over the second molar or buccal to the premolars after an IAN block warrants further investigation to determine the success of these injections. In addition, Robertson and colleagues⁶ speculated that the anesthetic solution might have entered the mental foramen, leading to the higher success rates in the premolars and first molar. Although the buccal infiltration of the first molar may have resulted in anesthetic solution’s entering the mental foramen, the superiority of articaine over lidocaine may be related to the higher concentration (4 percent) of articaine, a greater diffusion gradient for articaine or its unique chemical structure.

Anesthetic success. In our study, we defined anesthetic success as attaining two consecutive 80 readings within 10 minutes after the IAN block and the buccal infiltration, and sustaining the 80 reading continuously through the 60th minute. It is important to realize that the initial 10-minute observation period started 16 minutes after the clinician administered the IAN block and buccal infiltrations. Thus, by allowing 15 minutes for the IAN block to take full effect (on the basis of the study results of Vreeland and colleagues¹⁴ and Steinkruger and colleagues¹⁵) and 10 minutes for the infiltration to take full effect (on the basis of the study results of Robertson and colleagues⁶), the effects of each injection were maximized in our definition of success.

As shown in Figure 2, both anesthetic formulations demonstrated a gradual increase in pulpal anesthesia. The gradual increase likely is related to the effect of the infiltrations’ overcoming failure or to slow onset of anesthesia with the IAN block. Therefore, for a maximum effect with the 4 percent articaine formulation, a waiting time is required before achieving onset of pulpal anesthesia.

Although the clinician may not have to wait 15 minutes for the IAN block to take full effect, as we did in this study, it may be prudent to wait for signs of lip numbness before administering the infiltration; without an effective block, buccal infiltration alone has a short duration.⁶ An additional consideration is that buccal infiltration of a full cartridge of anesthetic in the vicinity of the mandibular first molar could produce mental nerve anesthesia in some patients as a result of diffusion of anesthetic anteriorly,⁶ thus precluding the clinician’s ability to assess the IAN block according to the "numb lip" symptom.

For the 4 percent articaine formulation, pulpal anesthesia reached a plateau after the initial gradual increase, and a fairly high percentage of 80 readings was maintained through the 50th minute (Figure 2). Therefore, for dental procedures requiring profound pulpal anesthesia, fairly high success rates will be achieved at least through the 50th minute.

Because we studied only subjects who received IAN blocks with articaine, it would be worthwhile to determine if the higher success rate for articaine versus lidocaine buccal infiltration injections is similar after lidocaine block injections.

Postinjection pain ratings were not statistically different between the 4 percent articaine and 2 percent lidocaine formulations.

For the first molar, the 4 percent articaine formulation demonstrated a decline in the incidence of pulpal anesthesia about 52 minutes after the IAN block (Figure 2). The 2 percent lidocaine formulation demonstrated a decline after about 60 minutes. In the study by Robertson and colleagues⁶ of the first molar, pulpal anesthesia—with only a buccal infiltration of 4 percent articaine or 2 percent lidocaine—peaked at about 10 to 13 minutes and then declined slowly over the next 60 minutes. In our study, it is important to realize that the buccal infiltration injection is reinforcing the initial failure of the IAN block—estimated to occur around 17 to 19 percent of the time for the first molar.^1,2 However, because pulpal anesthesia with the buccal infiltration declines over time, the failure of the IAN block will manifest itself after the infiltration begins to wear off. A possible remedy to shortened anesthesia duration is to administer a second buccal infiltration. Further research is needed to determine the effects of an additional infiltration injection on the duration of pulpal anesthesia.

Pain. Injection pain was not significantly different between the 4 percent articaine and 2 percent lidocaine formulations (Table 2). Kanaa and colleagues⁵ and Robertson and colleagues⁶ found no significant difference in injection discomfort between 4 percent articaine and 2 percent lidocaine formulations for mandibular buccal infiltration of the first molar. Robertson and colleagues’⁶ pain ratings for the three phases of the buccal infiltration for both formulations ranged from 24 to 37 mm on the VAS. In our study, the pain ratings were lower, ranging from 16 to 23 mm.

The contribution of buccal anesthesia from the IAN block typically would not be expected without a separate long buccal injection.¹⁴ However, Vreeland and colleagues¹⁴ showed that buccal soft-tissue anesthesia could be achieved 30 percent of the time with only an IAN block. Perhaps this is why we obtained lower pain ratings compared with those found by Robertson and colleagues.⁶ The pain ratings of the three phases of injection generally were in the faint-to-weak pain area of the VAS (Figure 1 and Table 2). Kanaa and colleagues⁵ and Robertson and colleagues⁶ also found the pain of mandibular infiltration of the first molar to be in the mild range with use of 4 percent articaine or 2 percent lidocaine formulations.

Postinjection pain ratings, at the time at which subjective numbness wore off, were not statistically different between the 4 percent articaine and 2 percent lidocaine formulations (Table 3). The incidence of pain decreased over the following three days. All of the pain ratings were in the faint-to-weak area on the VAS (Figure 1). Robertson and colleagues⁶ found similar ratings for pain after buccal infiltration of 4 percent articaine and 2 percent lidocaine formulations.

Postinjection complications. The only reported postinjection complications were bruising and slight swelling in the area of the injection. In our study, three (4 percent) of 73 subjects reported experiencing swelling and two (3 percent) reported experience bruising with lidocaine. Four (6 percent) of 73 subjects reported experiencing swelling and two (3 percent) reported experiencing bruising with articaine. All complications resolved within three days except for slight swelling and bruising with lidocaine, which was reported by two subjects on day 3, and slight bruising with articaine, which also was reported by two subjects on day 3. Robertson and colleagues⁶ found similar postinjection complications with articaine and lidocaine formulations. Although there have been reports of paresthesia associated with articaine use,^16,17 no subjects in our study reported paresthesias with the IAN blocks or infiltrations. We would not have expected subjects in our study to report paresthesia in light of the finding by Haas and Lennon¹⁶ that paresthesias are relatively rare.

Cartridge labeling. Regarding the labeling of the articaine cartridge as 1.7 milliliters, Robertson and colleagues⁶ measured the amount of anesthetic solution delivered with an aspirating syringe by expressing the contents of 50 articaine cartridges (Septocaine) and 50 lidocaine cartridges (Xylocaine) into a graduated syringe with 0.01-mL increment divisions. They found that even though the articaine cartridge was marked externally as containing 1.7 mL, the anesthetic solution expressed was, on average, 1.76 mL. The lidocaine cartridge was marked as containing 1.8 mL, but the anesthetic solution expressed was, on average, 1.76 mL. In general, Robertson and colleagues⁶ found that a small amount of solution remained in both types of anesthetic cartridges after the clinician delivered the anesthetic solution with an aspirating syringe. On the basis of the findings of Robertson and colleagues,⁶ we conclude that both anesthetic formulations expressed the same amount of anesthetic solution. Therefore, the volume of anesthetic delivered during the buccal infiltration injections in this study was not a contributing factor to the greater success reported with 4 percent articaine compared with 2 percent lidocaine.

	CONCLUSION

TOP ABSTRACT SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
A buccal infiltration of the first molar with a cartridge of 4 percent articaine with 1:100,000 epinephrine resulted in a significantly higher success rate (88 percent) than did a buccal infiltration of a cartridge of 2 percent lidocaine with 1:100,000 epinephrine (71 percent success rate) after an IAN block with the use of 4 percent articaine with 1:100,000 epinephrine.