Anesthetic efficacy in vital asymptomatic teeth using different local anesthetics: a systematic review with network meta-analysis
Article information
Abstract
Objectives
This study aimed to evaluate the efficacy of various local anesthesia (LA) in vital asymptomatic teeth.
Materials and Methods
Randomized controlled trials comparing pulpal anesthesia of various LA on vital asymptomatic teeth were included in this review. Searches were conducted in the Cochrane CENTRAL, MEDLINE (via PubMed), EMBASE, ClinicalTrials.gov, Google Scholar and 3 field-specific journals from inception to May 3, 2019. Study selection, data extraction, and risk of bias assessment using Cochrane Risk of Bias Tool were done by 2 independent reviewers in duplicate. Network meta-analysis (NMA) was performed within the frequentist setting using STATA 15.0. The LA was ranked, and the surface under the cumulative ranking (SUCRA) line was plotted. The confidence of the NMA estimates was assessed using the CINeMA web application.
Results
The literature search yielded 1,678 potentially eligible reports, but only 42 were included in this review. For maxillary buccal infiltration, articaine 4% with epinephrine 1:100,000 was more efficacious than lidocaine 2% with epinephrine 1:100,000 (odds ratio, 2.11; 95% confidence interval, 1.14–3.89). For mandibular buccal infiltration, articaine 4% with epinephrine 1:100,000 was more efficacious than various lidocaine solutions. The SUCRA ranking was highest for articaine 4% with epinephrine when used as maxillary and mandibular buccal infiltrations, and lidocaine 2% with epinephrine 1:80,000 when used as inferior alveolar nerve block. Inconsistency and imprecision were detected in some of the NMA estimates.
Conclusions
Articaine 4% with epinephrine is superior when maxillary or mandibular infiltration is required in vital asymptomatic teeth.
INTRODUCTION
Local anesthesia (LA) is indispensable for pain control in dentistry. It is defined as the loss of sensation in a confined area of the body caused by the inhibition of excitatory process in nerve endings or inhibition of the conduction process in peripheral nerves without inducing a loss of consciousness [1]. In scientific publications, clinical researchers often categorize anesthetic efficacy in dentistry as either soft-tissue anesthesia or pulpal anesthesia [23]. While the former is essential for procedures such as wound management and biopsy, the latter is essential for most restorative work and is harder to achieve clinically.
The different solutions of LA offer a dentist several choices as appropriate for the patient for any given dental procedure. It is unclear which LA is the most efficacious in eliciting pulpal anesthesia because previous reviews synthesized the evidence using pairwise meta-analysis, comparing 2 interventions at a time [45]. The contemporary approach of network meta-analysis (NMA) offers a unique advantage over pairwise meta-analysis as it allows multiple treatments to be compared concurrently, thereby synthesizing a more comprehensive body of evidence [6]. Furthermore, evidence for treatment differences can be strengthened and extended by combining indirect and direct evidence [7]. Recently, NMA was used to identify efficacious strategies to anesthetize mandibular molars with irreversible pulpitis. Lidocaine 2% with epinephrine 1:100,000 delivered using intraosseous injection, or articaine 4% with 1:100,000 epinephrine delivered using intraosseous injection or buccal and lingual infiltrations were recommended [8].
For decades, randomized controlled trials (RCTs) have been carried out in the vital asymptomatic teeth of healthy adults to compare the anesthetic efficacy of various LA. Such an experimental model has eligibility criteria that facilitate the recruitment of research participants and are more controlled than studies that tested LA in symptomatic patients. Although the findings may not be applicable to symptomatic patients, they are still invaluable to inform clinicians on the pharmacological characteristics of a particular LA when restoring vital asymptomatic teeth. There is a limit, however, on the number of LA that could be tested in each trial. The plethora of LA types, volumes, concentrations, and combinations with vasoconstrictors poses a challenge in synthesizing the evidence. In this instance, NMA could further elucidate on the matter by pooling information from various trials.
The experimental model in vital asymptomatic teeth allows variations, such as split-mouth design and cross-over designs, to be implemented efficiently. This renders it difficult, however, to synthesize the evidence using NMA because the independence assumption does not hold. Correlation between data can be adjusted by the standard approach, the reducing weight approach, and the adjusting variance approach [9].
Thus, this review aimed to evaluate the anesthetic efficacy of various LA in achieving pulpal anesthesia for vital asymptomatic teeth when administered through maxillary/mandibular buccal infiltrations or inferior alveolar nerve block (IANB). The review was intended to answer the following research question: In vital asymptomatic teeth, what is the most efficacious LA to achieve pulpal anesthesia?
MATERIALS AND METHODS
Scope of the review
The systematic review was reported according to the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) for Network Meta-Analyses (Supplementary Table 1) [10]. The PICOS framework was used to define the scope of the review.
Types of participants
Trials in healthy participants older than 16 years old were included. Trials involving medically compromised patients were excluded. The diagnostic terminology approved by the American Association of Endodontists and the American Board of Endodontics was used to guide the selection of the trials. We considered teeth to be vital and asymptomatic if the teeth tested in the studies had normal pulp (the pulp was free of symptom, and the tooth was responsive to pulp testing) and normal apical tissue (the tooth was not sensitive to percussion or palpation; intact lamina dura and uniform periodontal space were observed radiographically) [11]. Trials in which participants were taking medications that could alter pain sensation were excluded.
Types of interventions and comparisons
The teeth tested needed to be randomly allocated to receive an injection with one type of LA solution, with or without vasoconstrictor. The techniques of injection considered in this review include maxillary buccal infiltration, mandibular buccal infiltration, and the conventional IANB. In this review, an LA volume of 1.5 mL to 2.2 mL was defined as one cartridge and an LA volume of 3.0 mL to 4.4 mL was defined as 2 cartridges. Trials using LA volume less than 1.5 mL or more than 4.4 mL for each administration were excluded. Trials designed to test a combination of different LA solutions in a single administration, different routes of administration, supplemental injection, or computer-controlled LA delivery were excluded. Studies comparing various additives of LA, such as buffering and carbonating agents, opioids, steroids and other drugs were excluded.
Types of outcomes
The primary outcome of interest was pulpal anesthetic success, defined as the proportion of participants who did not respond to electric pulp testing (EPT) in the maximum setting. Studies not reporting the primary outcome were excluded.
Types of studies
Only RCTs comparing the administration of various solutions and volumes of LA were included. The design of the trials could be parallel-group design, crossover design, or split-mouth design. Observational studies, cluster-RCTs, and quasi-RCTs were excluded.
Study identification and search method
The National Library of Medicine Medical Subject Heading (MeSH) terms were identified and used to search for appropriate trials in the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (via PubMed), and EMBASE databases from the inception of the databases to May 3, 2019. Language restriction was not applied. The detailed search strategies for each database are listed in Supplementary Table 2. Electronic searching of web archives for the Journal of Endodontics, International Endodontic Journal, and Anesthesia Progress was also performed. Subsequently, we manually scanned the reference lists of articles that met the inclusion criteria and published reviews on the topic. Additional searches were also conducted on ClinicalTrials.gov and Google Scholar (in English) to ensure the identification of all trials.
Selection of studies and data extraction
Title and abstract screening, appraisal of the full-text articles, trial selection, and data extraction were carried out in duplicate by 2 independent investigators (A.L. and D.A.). At the end of each stage, the 2 investigators met to discuss. Any discrepancies were resolved by consensus between the investigators. Review Manager (RevMan 5, Cochrane Collaboration) was used to record details, such as characteristics of the trial participants, the tooth type, sample size, the type and volume of LA used, the definition of anesthetic success, the success rate, and the incidence of paresthesia. In trials with multiple arms or repeated measures, only data from the testing relevant to the research question were extracted.
Assessment of risk of bias
Two investigators (A.L. and D.A.) assessed the risk of bias for individual studies using the Cochrane Risk of Bias Tool, independently and in duplicate. Disagreements were resolved through discussion to achieve consensus. The methodological quality of the included articles was assessed to identify selection, performance, detection, attrition, and reporting biases [12].
Statistical analysis
Statistical analysis was performed using STATA version 15.0 (StataCorp LP, College Station, TX, USA). Trials with split-mouth or cross-over design were identified, and the adjusting variance approach was implemented to adjust for the dependency of observations within the same patient [9]. Network graphs were plotted for maxillary buccal infiltration, mandibular buccal infiltration, and IANB.
Using the network command in STATA, NMA was implemented with the random-effects model to synthesize both direct and indirect evidence from the included trials and derive the relevant estimates as odds ratios (ORs) with associated 95% confidence intervals (CIs). The design-by-treatment interaction model was fitted to check for overall consistency [1314]. Loop inconsistency was assessed using the methods described by Lu and Ades [15]. Inconsistency between the direct and indirect evidence was evaluated using the side-splitting model [16].
The surface under the cumulative ranking (SUCRA) line was estimated to determine the ranking of the LA relative to one another. The higher the SUCRA value (reported in percentage), the greater the probability that the LA was of higher rank [17]. Funnel plots and Egger’s test were used to assess small-study bias and publication bias.
Quality of evidence
Within-study bias, reporting bias, indirectness, imprecision, heterogeneity, and incoherence of the NMA estimates were evaluated using the CINeMA web application (University of Bern, Bern, Switzerland) [18]. Indirectness was manually rated down when carious teeth were tested. Based on the CINeMA output and guidelines [18], the investigators discussed and achieved consensus on the overall confidence—i.e., very low, low, moderate, or high. The overall confidence was downgraded according to the magnitude of the investigators’ concerns.
RESULTS
The literature search yielded 1,678 potentially eligible reports, but only 42 were considered appropriate for this review (Figure 1). The reasons for exclusion for 51 full-text articles are listed in Table S3. The number of included trials and participants were as follows: i) maxillary buccal infiltration: 19 trials, 793 participants [19202122232425262728293031323334353637], ii) mandibular buccal infiltration: 10 trials, 465 participants [25263839404142434445], and iii) IANB: 16 trials, 477 participants [35464748495051525354555657585960].
The characteristics of the included studies are summarized in Table 1. Of the 42 articles selected, 2 [2930] had an identical control arm; hence, these were analyzed as a single trial with 3 arms. Of a total of 41 trials, 2 had a parallel-group design [2949], another 4 had a split-mouth design [25263548], and the remaining 35 had a crossover design [1920212223242728313233343637383940414243444546475051525354555657585960]. The LA was tested with various tooth types, mostly in young adults. All the selected studies involved vital asymptomatic adult permanent teeth with established baseline responsiveness to electrical stimuli, but additional criteria (e.g., free of caries, without large restorations, no periodontal diseases, no history of trauma, and no sensitivity) often apply. Similarly, all the included studies assessed the primary outcome using EPT, but some studies were more specific in their timeframe for measuring the primary outcome.
Of the 41 included trials, 18 had a low risk of bias, 17 had a moderate risk of bias, and 6 had a high risk of bias (Supplementary Figures 1 and 2). The forest plots indicated that most direct pairwise comparisons were informed by a single study (Supplementary Figure 3). When multiple studies were available for direct comparison, heterogeneity between studies was low (p > 0.05).
Based on the injection techniques, 3 network plots are presented (Figure 2). Each node represents a type of LA, with the size of the nodes indicating the number of patients assigned to this type of LA. Comparisons between LA are linked by a straight line. The thickness of the line represents the number of trials for each pair being compared. All interventions in the network for mandibular buccal infiltration could be included in the NMA. The network plot for maxillary buccal infiltration and IANB were partly disconnected, however, forming separate clusters. The minor cluster for maxillary buccal infiltration consists of prilocaine 3% plain and prilocaine 3% with felypressin, while the minor cluster for IANB consists of ropivacaine 0.2%, ropivacaine 0.5%, and ropivacaine 0.75%. Hence, these separate clusters were excluded from the NMA. In all 3 networks, lidocaine 2% with 1:100,000 epinephrine was the most universal LA compared.
Wide CIs were noted in most of the cells in the league table (Table 2). For maxillary buccal infiltration using a single cartridge, articaine 4% with epinephrine 1:100,000 had higher odds of anesthetic success than lidocaine 2% with epinephrine 1:100,000 (OR, 2.11; 95% CI, 1.14–3.89). Long-acting LA, such as ropivacaine 0.5% plain, ropivacaine 0.5% with epinephrine 1:200,000, and bupivacaine 0.5% with epinephrine 1:200,000, were less efficacious than short- to medium-acting LA with a vasoconstrictor. Articaine 4% plain, mepivacaine 0.75% plain, and mepivacaine 1% plain, had lower odds of success than all other LA. For mandibular buccal infiltration, 2 cartridges of articaine 4% with epinephrine 1:100,000 were more efficacious than a single cartridge of various solutions. A single cartridge of articaine 4% with epinephrine 1:100,000 was more efficacious than the lidocaine or prilocaine solutions.
For IANB, articaine 4% plain was less efficacious than articaine 4% with epinephrine 1:200,000 (OR, 0.31; 95% CI, 0.15–0.65) and articaine 4% with epinephrine 1:100,000 (OR, 0.35; 95% CI, 0.17–0.74). Prilocaine 3% with felypressin was less efficacious than lidocaine 2% with epinephrine 1:80,000 (OR, 0.12; 95% CI, 0.02–0.69). Similarly, mepivacaine 3% plain recorded lower odds of anesthetic success than did lidocaine 2% with epinephrine 1:80,000 (OR, 0.29; 95% CI, 0.09–0.90).
In general, articaine with epinephrine dominated the ranking chart of LA when used as maxillary and mandibular buccal infiltration (Table 3). For IANB, lidocaine 2% with epinephrine 1:80,000 was ranked best when 2 cartridges were used and second best when one cartridge was used. In maxillary buccal infiltration, the ranking of 2 cartridges of lidocaine 2% with epinephrine 1:100,000 was lower than a single cartridge of the same LA (Table 3), but the OR for this pair included the null value (Table 2). In mandibular buccal infiltration, 2 cartridges of articaine 4% with epinephrine 1:100,000 ranked higher than a single cartridge of the same LA (OR, 2.31; 95% CI, 1.34–3.97). For IANB, the ranking of 2 cartridges of lidocaine 2% with epinephrine 1;80,000 was higher than the single cartridge, but the reverse pattern was observed for lidocaine 2% with epinephrine 1:100,000 and 1:50,000. Nonetheless, all 3 pairs of comparisons have ORs that include the null value.
For maxillary and mandibular buccal infiltrations, no gross inconsistency was detected when tested using the design-by-treatment interaction model, loop inconsistency model, or side-splitting model (p > 0.05). For IANB, statistical significance was not detected in the design-by-treatment interaction model or loop inconsistency model (p > 0.05). In the side-splitting model, inconsistency was detected between the direct and indirect evidence comparing single cartridges of lidocaine 2% with epinephrine 1:100,000 and prilocaine 4% with epinephrine 1:200,000 (p = 0.049). In addition, inconsistency was detected between the direct and indirect evidence comparing single cartridges of lidocaine 2% with epinephrine 1:100,000 and mepivacaine 2% with levonordefrin 1:20,000 (p = 0.049).
Publication bias and small-study effects were unlikely, as observed using funnel plots (Supplementary Figure 4) and Egger's graphs (Supplementary Figure 5). Statistical significance was not evident in Egger's tests for maxillary buccal infiltration, mandibular buccal infiltration, or IANB (p > 0.05). The estimates were derived from studies of variable risk of bias (Supplementary Figure 6). The quality concerns were mostly for imprecision (Supplementary Table 4).
DISCUSSION
Articaine 4% with epinephrine achieved greater pulpal anesthesia in vital asymptomatic teeth when delivered as maxillary or mandibular infiltration. Articaine is more lipid-soluble and has a fast onset [61]. When used in maxillary infiltration, the odds of achieving pulpal anesthesia were higher for articaine 4% with 1:100,000 epinephrine than with lidocaine 2% with 1:100,000 epinephrine. This concurs with earlier pairwise meta-analysis in teeth with irreversible pulpitis [62]. A statistically significant difference, however, was not apparent when these were compared with various solutions of lidocaine when used in IANB. The present findings also supported a common claim that articaine 4% with epinephrine 1:100,000 was more efficacious than other agents in mandibular infiltration. Further studies are needed, however, to evaluate whether mandibular infiltration using articaine 4% with epinephrine 1:100,000 can replace conventional IANB.
For IANB, lidocaine 2% with epinephrine 1:80,000 was ranked best when 2 cartridges were used and second when one cartridge was used. Most of the comparisons to lidocaine 2% with epinephrine 1:80,000, however, have CIs that include the null value. When only one cartridge of lidocaine was used, the efficacy of the LA did not differ statistically with different concentrations of epinephrine. In addition, a mixed pattern was shown for the SUCRA ranking, favoring different concentrations of epinephrine in different situations. Theoretically, epinephrine contributes to the vasoconstriction effect, thereby retaining the LA in the localized region and slowing down the metabolism of the LA [61]. This may lengthen the duration of action. However, a dose-response relationship in anesthetic success is unlikely [47].
Recent NMA has suggested that mepivacaine is better than lidocaine in eliciting pulpal anesthesia when delivered as IANB to teeth with irreversible pulpitis [863]. We could not conclude whether this is also true in vital asymptomatic teeth because the interventions in the present NMA are categorized by the type of anesthetic as well as its concentration of vasoconstrictor. The division into finer categories reduces the sample size in each group and therefore leads to imprecision. Nevertheless, finer categorization allows for comparisons of different formulations: e.g., mepivacaine 2% with epinephrine ranked lower than lidocaine 2% with epinephrine 1:80,000 but higher than lidocaine 2% with epinephrine 1:100,000 and 1:50,000. Prilocaine and mepivacaine are agents with milder vasodilatory effects. Hence, several formulations without vasoconstrictor were available commercially. Nevertheless, the anesthetic success for these agents was generally poorer than the same agents with a vasoconstrictor.
Ropivacaine is a newer long-acting LA and is unavailable in dental cartridges [30]. Despite this, it is included in this NMA because NMA plays a crucial role in providing comparative evidence for new drugs before approval [64]. Ropivacaine was found to be less efficacious than most commercially available dental anesthetics.
Conflicting findings were found for the effect of doubling the volume of several LA. In irreversible pulpitis, increasing the volume of LA to more than one cartridge does not improve the success of IANB [8]. The additional volume may appear beneficial when profound anesthesia after the second injection is observed. This is, however, most likely due to the longer onset time of the first injection [65].
In short, articaine remains a good choice for buccal infiltrations. Lidocaine 2% with epinephrine 1:80,000 ranked best for IANB, but wide CIs including null values were observed for most comparisons involving lidocaine 2% with epinephrine 1:80,000. The findings for IANB should be interpreted with caution, as inconsistency was detected in the side-splitting model. The main concern about using articaine is paresthesia [66].
Several limitations were noted in this review. While all of the studies included defined pulpal anesthesia as having no response upon maximal electrical stimulus, some authors further defined the onset and duration of no response. Ideally, a standardized measure should be used. The studies at the Ohio State University used the most comprehensive and consistent definition. For maxillary infiltration, anesthetic success was defined as the percentage of patients who showed no response to an EPT (2 consecutive 80 readings) within 10 minutes of the initial injection [22242733]. Anesthetic success for IANB was defined as the percentage of patients who showed no response to an EPT (2 consecutive 80 readings) within 15 minutes of injection and continuously sustained the 80 reading for 60 minutes [5051525359]. In addition, criteria for slow onset and non-continuous pulpal anesthesia were listed in several studies [3447515860]. Therefore, outcome measurement using the binary variable of success and failure is an oversimplification of the actual pharmacodynamics. Ultimately, the choice of LA is also dependent on the type of procedure being carried out, the length of time required for anesthesia, and the pharmacodynamics of each medication [67].
Confounding factors, such as route of administration, were noted before the commencement of the review. Hence, categorization based on the route of administration was planned. This reduces the heterogeneity among studies but results in a smaller number of studies in each category, yielding reduced statistical power for hypothesis testing and a larger variance of estimation. Further, some comparisons were informed only by the direct evidence of a single trial. Similarly, caution is warranted in the interpretation of the funnel plot and Egger’s regression because there were only a few studies in each network.
In addition, the type of tooth tested varied among studies. This is a major concern for IANB, as explained in the central core theory. The fasciculi supplying molars are located at the periphery of the nerve and are exposed to a higher concentration of LA, while the fasciculi supplying the anterior teeth are located in the core of the nerve and are exposed to a lower anesthetic concentration [1].
Our assessment indicated that the quality of evidence was negatively affected by inconsistency and imprecision. The implications for future research are twofold. First, it suggests the need for additional large RCTs. Second, it emphasizes the importance of scientific rigor and standardized outcome measurements. To that end, we support using the standardized protocol developed by the Ohio State University and trial registration for RCTs testing LA in the future.
CONCLUSIONS
Articaine 4% with epinephrine is superior when maxillary or mandibular infiltration is required in vital asymptomatic teeth. Generally, LA without a vasoconstrictor has a lower success rate in achieving pulpal anesthesia. Doubling the volume of LA may not always be beneficial.
Notes
Funding: This study was supported by a grant from New South Bound Policy Academic Field Alliance Project, Ministry of Education, Taiwan (Grant No. 107K311).
Conflict of Interest: No potential conflict of interest relevant to this article was reported.
Author Contributions:
Conceptualization: Liew AKC, Abdullah D, Tu YK.
Data curation: Liew AKC, Yeh YC, Abdullah D.
Formal analysis: Liew AKC, Yeh YC.
Funding acquisition: Yeh YC, Tu YK.
Investigation: Liew AKC, Yeh YC, Abdullah D.
Methodology: Liew AKC, Yeh YC, Tu YK.
Project administration: Yeh YC, Tu YK.
Resources: Abdullah D, Yeh YC, Tu YK.
Software: Yeh YC, Tu YK.
Supervision: Tu YK.
Validation: Yeh YC, Tu YK.
Visualization: Liew AKC, Yeh YC.
Writing - original draft: Liew AKC, Yeh YC.
Writing - review & editing: Liew AKC, Abdullah D, Tu YK.