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Year : 2022  |  Volume : 25  |  Issue : 5  |  Page : 463-480
Antibacterial efficacy of antibiotic pastes versus calcium hydroxide intracanal dressing: A systematic review and meta-analysis of ex vivo studies

1 Iranian Center for Endodontic Research, Research Institute of Dental Sciences, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran
2 Department of Endodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran
3 Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran
4 Department of Advanced Oral Sciences and Therapeutics, School of Dentistry, University of Maryland, Baltimore, Maryland, USA

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Date of Submission02-Apr-2022
Date of Decision15-May-2022
Date of Acceptance20-May-2022
Date of Web Publication05-Jul-2022


Background: Conflicting findings on the potency of antibiotic pastes versus calcium hydroxide (CH) have been evident in the literature.
Aims: To compare the antibacterial efficacy of single antibiotic paste (SAP), double antibiotic paste (DAP), triple antibiotic paste (TAP), and modified TAP (mTAP) with CH on bacterial biofilms.
Methods: PubMed, Scopus, and Embase were comprehensively searched until August 23, 2021. The study protocol was registered in the PROSPERO. Ex vivo studies performed on Enterococcus faecalis or polymicrobial biofilms incubated on human/bovine dentin were selected. The quality of the studies was assessed using a customized quality assessment tool. Standardized mean difference (SMD) with a 95% confidence interval (CI) was calculated for the meta-analysis. Meta-regression models were used to identify the sources of heterogeneity and to compare the efficacy of pastes.
Results: The qualitative and quantitative synthesis included 40 and 23 papers, respectively, out of 1421 search results. TAP (SMD = −3.82; CI, −5.44 to −2.21; P < 0.001) and SAPs (SMD = −2.38; CI, −2.81 to − 1.94; P < 0.001) had significantly higher antibacterial efficacy compared to the CH on E. faecalis biofilm. However, no significant difference was found between the efficacy of DAP (SMD = −2.74; CI, −5.56–0.07; P = 0.06) or mTAP (SMD = −0.28; CI, −0.82–0.26; P = 0.31) and CH. Meta-regression model on E. faecalis showed that SAPs have similar efficacy compared to TAP and significantly better efficacy than DAP. On dual-species (SMD = 0.15; CI, −1.00–1.29; P = 0.80) or multi-species (SMD = 0.23; CI, −0.08–0.55; P = 0.15) biofilms, DAP and CH had similar efficacy.
Conclusions: Ex vivo evidence showed that antibiotic pastes were either superior or equal to CH. The studied SAPs had considerably higher or similar antibacterial effectiveness compared to DAP, CH, and TAP. Hence, combined antibiotic therapy was not necessarily required for root canal disinfection ex vivo.

Keywords: Antibiotic paste; bacterial biofilm; calcium hydroxide; intracanal medicament

How to cite this article:
Vatankhah M, Khosravi K, Zargar N, Shirvani A, Nekoofar MH, Dianat O. Antibacterial efficacy of antibiotic pastes versus calcium hydroxide intracanal dressing: A systematic review and meta-analysis of ex vivo studies. J Conserv Dent 2022;25:463-80

How to cite this URL:
Vatankhah M, Khosravi K, Zargar N, Shirvani A, Nekoofar MH, Dianat O. Antibacterial efficacy of antibiotic pastes versus calcium hydroxide intracanal dressing: A systematic review and meta-analysis of ex vivo studies. J Conserv Dent [serial online] 2022 [cited 2023 Oct 2];25:463-80. Available from:

   Introduction Top

Endodontic treatments must strive to eliminate as many bacteria as possible from the root canal system.[1] Chemomechanical preparation plays an essential role in removing bacteria, necrotic tissues, and infected dentin for this aim. Different instrumentation systems leave an unpredictable range of 2.6%–80% of the root canal walls untouched.[2],[3] Hence, instrumentation, irrigation, and obturation cannot predictably render canals bacteria-free,[4] and residual bacteria may reside in unaffected areas.[5],[6] Most of these species may not survive after the treatment or may persist in low virulence and numbers, insufficient to sustain the periapical inflammation.[7] The microbial etiology of these persistent lesions was reported to comprise different community profiles[8] or single robust species such as Enterococcus faecalis.[9]

E. faecalis is commonly identified in persistent endodontic infections.[10],[11] The presence of E. faecalis in secondary infections is of particular relevance since it is seldom discovered in infected but untreated root canals.[12] There are several unique characteristics for E. faecalis, such as inherent antimicrobial resistance[10],[13] and ability to withstand extreme environmental conditions.[14] It could sustain viability for 12 months and might serve as a long-term nidus for future infection.[15]

Intracanal medicament (ICM) aids further bacterial elimination after chemomechanical preparation in multivisit endodontic treatments of necrotic teeth.[16] Calcium hydroxide (CH) is the most commonly used ICM in the literature.[1] However, both in vitro and in vivo studies have shown that CH has limited antibacterial efficacy.[17],[18],[19] For instance, CH favors the population of E. faecalis in multi-species biofilms, as E. faecalis survives the high pH of CH.[20],[21]

Antibiotic therapy in various formulations is vastly used in medical-related professions to prevent and treat bacterial infections. Given the insufficient spectrum of action of available commercial antibiotic pastes, various antibiotic formulations were developed.[22] It is critical to sterilize the root canal and radicular area during endodontic regenerative procedures since tissue repair and healing are best achieved in a relatively aseptic environment.[23],[24] However, the need for a potent antibacterial agent does not solely limit to regenerative procedures.[24] Antibiotic pastes could be used in the treatment of large/persistent periapical lesions[25],[26] before/parallel with surgical interventions.[27] A systematic review of 16 articles concluded that even when CH cannot reduce symptoms and heal the periapical lesions, TAP could be effective.[28]

Although numerous studies have compared the antibacterial efficacy of antibiotic pastes with CH, the results are inconsistent.[29],[30],[31],[32] Furthermore, clinical evidence on this issue is limited. The present systematic review and meta-analysis aimed to compare the antibacterial efficacy of single antibiotic paste (SAP), double antibiotic paste (DAP), triple antibiotic paste (TAP), and modified TAP (mTAP) with CH as an ICM on bacterial biofilms from the available ex vivo studies.

   Materials and Methods Top

Protocol and registration

The protocol of this systematic review was registered in the PROSPERO database (registration number: CRD42021184650), and its report adhered to the preferred reporting items for systematic review and meta-analysis statement.[33]

Formulating the review question

The review question was developed using the PICOS framework: In human/bovine extracted permanent teeth or dentin samples infected with bacterial biofilm (Population), does antibiotic paste (Intervention) provide higher antibacterial efficacy (Outcome) compared to CH (Comparison) in ex vivo settings (Study type)?

Eligibility criteria

Ex vivo studies with the following criteria were included: (1) performed on human/bovine extracted permanent teeth or dentin slabs, (2) in press and published papers with full-text available, (3) comprising at least two experimental groups of CH and an antibiotic paste, (4) performed on E. faecalis mono-species or polymicrobial (i.e., composed of more than one species) biofilms.

In vivo studies, animal studies, review articles, expert opinions, cross-sectional studies, clinical trials, case reports, and case series were excluded. Furthermore, studies with the following criteria were excluded: (1) assessing the residual antimicrobial efficacy of the medicaments, (2) conducted on immature/deciduous teeth, (3) performed on endotoxins, fungal species, and mono-species bacteria other than E. faecalis, and (4) using substrates other than sound dentin.

Search strategy

A combination of medical search heading, Emtree, and free text terms was piloted during the preliminary electronic searches. The search strings were formulated using Boolean operators “OR” and “AND” in three databases: MEDLINE, Scopus, and Embase. No language or date restrictions were applied. The search was last updated on August 23, 2021. The references of the included studies were manually searched for eligible articles. [Supplementary Table 1] presents the search queries.

Study selection

Search results were exported to EndNote x9 software (Clarivate, Philadelphia, PA, United States), and the duplicates were automatically removed. Two authors (K.K., M.V.) independently screened titles and abstracts of the identified publications according to the inclusion/exclusion criteria. Potentially appropriate studies were further assessed for eligibility by full-text screening. Disagreements were negotiated with a third author (N.Z.) and resolved.

Data extraction

The same authors (K.K., M.V.) performed the data extraction from the full-text papers covering: (1) general information: first author, year, and country; (2) methodology: bacterial strain, incubation period, type of the teeth, sample dimensions, total sample size, medicament ingredients, concentration, and retention period, outcome measuring technique, depth of dentin, and sampling technique/instrument [Supplementary Table 2]; (3) results of culture plate counts, biofilm structural alterations visualized by scanning electron microscopy, colony-forming unit (CFU) counts, viable/dead bacterial cells discovered by confocal laser scanning microscopy, optical density (OD) values, and DNA amounts detected by quantitative polymerase chain reaction.

A third author (O.D.) verified the data sheets and discussed any disagreement between the two authors during the data extraction to achieve consensus. An e-mail was sent to the corresponding author if the desired data were not appropriately mentioned in a manuscript during the data extraction, risk of bias assessment, and meta-analysis. In response, a total of 11 authors supplied the requested information.[30],[32],[34],[35],[36],[37],[38],[39],[40],[41],[42]

Risk of bias assessment

A specified bias assessment table was provided inspired by the modified Cochrane risk of bias tool[43] and the tool for before–after studies.[44] The table consisted of 11 items particularly selected for this review to critically assess the studies' methodology.

Two reviewers (K.K., M.V.) independently rated low risk for items that were done and reported accurately, high risk for domains that were not performed/imprecisely reported, not applicable, and not mentioned (NM). In case of disagreement, a third author (N.Z.) was consulted for deliberation. The same authors independently assessed the overall risk of bias. Cohen's Kappa was used to measure the agreement between the two authors using SPSS 25 (IBM corp. Released 2017. IBM Statistics for Windows, Ver. 25.0. Armonk, NY, USA).

Data synthesis and statistical analysis

Standardized mean difference (SMD) with 95% confidence intervals (CIs) was calculated to compare the continuous data on the number of CFUs, percentage of live/dead bacteria, and OD values between the antibiotic and CH groups. Due to the small sample sizes in the studies, the SMDs were computed using Hedges' g statistic. Mean values were calculated from the median in some studies, based on the method proposed by Wan et al.[45] The summary estimates were computed using a random-effects model. Statistical heterogeneity in the pooled results was calculated via Chi-square and I2 statistics, with a P = 0.05 significance threshold.

If heterogeneity significantly influenced the summary estimate, random-effects multivariable meta-regression analysis was applied to explore potential sources.[46] When no statistical heterogeneity was observed in the pooled estimate, no further analysis was performed. The first meta-regression model included the variables that were most likely to have an effect on the pooled meta-analytic outcomes: ICM concentration, retention time, and dentin depth. Moreover, the second model compared the efficacy of different antibiotic pastes, while variables of the first model were adjusted. Galbraith plot was employed to display the potential outliers visually. Sensitivity analysis was performed by excluding the outlier study.

Each type of analysis was conducted individually for mono-, dual-, and multi-species biofilm groups, with a restricted maximum likelihood method, using STATA 16 (StataCorp. 2019, College Station, TX, USA).

   Results Top

Literature search and study selection

[Figure 1] displays the flow diagram of the studies. The search resulted in 1417 studies from different databases. Four more articles were added by manual searching. After duplicate removal, 959 records were identified, 46 of which were subjected to full-text screening. Forty and twenty-three studies were included in the qualitative and quantitative synthesis, respectively. Reasons of the exclusion for each synthesis are presented in [Table 1].
Figure 1: Flow diagram of the identified studies based on The Preferred Reporting Items for Systematic Reviews and Meta-Analyses

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Table 1: Reasons for and the number of excluded studies in each synthesis

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Characteristics of the included studies

[Table 2] represents a synopsis of included studies. Thirty-five studies (87.5%) were merely conducted on mature/immature E. faecalis, 2 (5%) on dual-species mature, and 3 (7.5%) on multi-species mature/immature biofilms. TAP and DAP were the most frequently used antibiotics in 23 (57.5%) and 13 (32.5%) studies, respectively. Out of 40 studies, 3 (7.5%) used spectrophotometry/colorimetry to assess optical density values, 8 (20%) implemented the CLSM approach to quantify the percentage of live/dead bacterial cells, 21 (52.5%) performed culture methods to calculate CFUs, and 8 (20%) used a combination of ≥2 different methods.
Table 2: Characteristics of the included studies

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Risk of bias assessment

Totally, 20 studies (50%) were considered as low overall risk, 6 (15%) were deemed as moderate overall risk, and 14 (35%) were rated as high overall risk of bias. The appraisal of the risk of bias for each study is presented in [Table 3]. Two authors agreed on 88.86% of the items (391/440) with a Cohen's Kappa of 0.82. They were in agreement in 87.5% of the overall scores, yielding a Cohen's Kappa of 0.75.
Table 3: Risk of bias appraisal of the included studies

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Meta-analysis and meta-regression on Enterococcus faecalis biofilm

Triple antibiotic paste versus calcium hydroxide

In 31 incorporated comparisons from 13 studies, TAP had significantly higher antibacterial efficacy compared to the CH [[Figure 2]a, SMD = −3.82; 95% CI, −5.44 to −2.21; P < 0.001]. The effect sizes, however, were statistically heterogeneous (I2 = 98.27%, P < 0.001). One study was excluded from the meta-regression model as an outlier.[30] This model, which is presented in [Table 4], showed that concentration (P = 0.136), retention time (P = 0.150), and depth of dentin (P = 0.642) were not significant predictors for the antibacterial efficacy of TAP.
Figure 2: (a) Forest plot comparing the efficacy of TAP and CH on E. faecalis biofilm (negative interval favors antibiotic). (b) Forest plot comparing the efficacy of DAP and CH on E. faecalis biofilm. (c) Forest plot comparing the efficacy of mTAP and CH on E. faecalis biofilm. (d) Forest plot comparing the efficacy of SAPs and CH on E. faecalis biofilm (negative interval favors antibiotic).

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Table 4: Meta-regression model comparing the efficacy of antibiotic pastes with calcium hydroxide

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Double antibiotic paste versus calcium hydroxide

There was no statistically significant difference between the DAP and CH in 17 integrated comparisons from 7 studies [[Figure 2]b, SMD = −2.74; 95% CI, −5.56–0.07; P = 0.06]. However, the pooled data analysis was significantly influenced by heterogeneity (I2 = 98.90%, P < 0.001). The same study was excluded from the meta-regression model.[30] Moreover, another study was dropped[74] so that the model could precisely determine the influence of the variables. The model revealed a strong association between the concentration (P = 0.021) and the higher antibacterial efficacy of DAP. In contrast, retention time (P = 0.167) and dentin depth (P = 0.702) were not significant predictors of efficacy [Table 4].

Modified triple antibiotic paste versus calcium hydroxide

No significant difference between mTAP (metronidazole, ciprofloxacin, and clindamycin) and CH was seen in three integrated comparisons from two studies [[Figure 2]c, SMD = −0.28; 95% CI, −0.82–0.26; P = 0.31] with no statistical heterogeneity (I2 = 0.00%, P = 0.48).

Single antibiotic pastes versus calcium hydroxide

In 26 incorporated comparisons from 5 studies, SAPs (including ciprofloxacin, clindamycin, doxycycline, oxytetracycline, erythromycin, metronidazole, and co-amoxiclav) were considerably more effective than CH [[Figure 2]d, SMD = −2.38; 95% CI, −2.81 to −1.94; P < 0.001] with substantial heterogeneity among effect sizes (I2 = 81.16%, P < 0.001). One study[40] was dropped due to the collinearity, and the rest of the comparisons fit the meta-regression model [Table 4]. Higher concentration (P = 0.036) or retention time (P = 0.021) of SAPs was strongly associated with higher antibacterial efficacy. However, the antibacterial efficacy of SAPs was significantly reduced in deeper dentin (P = 0.002).

Antibiotic comparison

Multiple meta-regression analyses comparing antibiotic pastes with adjusted variables are presented in [Table 5]. All investigated SAPs showed better efficacy compared to DAP (P < 0.05). Nonetheless, when compared to mTAP, only clindamycin (P = 0.034), erythromycin (P = 0.021), and metronidazole (P = 0.021) had significantly higher efficacy. Compared to oxytetracycline (as the weakest SAP), metronidazole, erythromycin, and ciprofloxacin were all substantially superior (P < 0.05); however, clindamycin, doxycycline, and co-amoxiclav were not (P > 0.05). Moreover, the differences between SAPs and TAP were not statistically significant (P > 0.05). TAP had significantly higher efficacy than DAP (P = 0.034). Nevertheless, there was no significant difference between TAP or DAP compared to mTAP (P > 0.05).
Table 5: Meta-regression analysis comparing the efficacy of antibiotic pastes used on Enterococcus faecalis biofilm with adjusted covariates (concentration, retention time, depth)

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Meta-analysis and meta-regression on dual-species biofilm

No statistically significant difference in antibacterial efficacy was seen between the DAP and CH in 5 integrated comparisons from 2 studies [[Figure 3]a, SMD = 0.15; 95% CI, −1.00–1.29; P = 0.80]. Effect sizes were considerably heterogeneous (I2 = 81.58%, P < 0.001). The meta-regression model indicated that both higher concentration (P = 0.035) and retention time (P < 0.001) could contribute to increased antibacterial efficacy of DAP. However, in deeper dentin, DAP offered a significantly lower antibacterial efficacy (P = 0.005).
Figure 3: (a) Forest plot comparing the efficacy of DAP and CH on dual-species biofilm (negative interval favors antibiotic). (b) Forest plot comparing the efficacy of DAP and CH on multi-species biofilm

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Meta-analysis on multi-species biofilm

In 10 incorporated comparisons from 2 studies, the difference between the CH and DAP was not statistically significant [[Figure 3]b, SMD = 0.23; 95% CI, −0.08–0.55; P = 0.15], with negligible statistical heterogeneity among the data (I2 = 12.67%, P = 0.27).

Sensitivity analysis

The Galbraith plots associated with the studies on E. faecalis biofilm are depicted in [Figure 4]a, [Figure 4]b, [Figure 4]c. Despite the abundance of outliers, only one study[30] was excluded, and the rest were not removed due to their symmetrical distribution around the regression line. The results of the sensitivity analysis are shown in [Figure 4]d and [Figure 4]e. No significant change in the pooled estimate findings or the degree of heterogeneity was detected, confirming the pooled results' robustness.
Figure 4:. (a) Galbraith plot comparing antibacterial efficacy of SAP and CH on E. faecalis biofilm. (b) Galbraith plot comparing antibacterial efficacy of DAP and CH on E. faecalis biofilm. (c) Galbraith plot comparing antibacterial efficacy of TAP and CH on E. faecalis biofilm. (d) Sensitivity analysis by excluding the outlier from the comparison of DAP and CH. (e) Sensitivity analysis by excluding the outlier from the comparison of TAP and CH

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   Discussion Top

The present systematic review compared the antibacterial efficacy of various antibiotic pastes versus CH on different bacterial strains incubated on human/bovine dentin structure from available ex vivo studies. As an overview of the results, TAP and SAPs were significantly superior to CH on E. faecalis biofilm, while mTAP and CH displayed similar efficacy. No statistical difference was noticed between DAP and CH in terms of antibacterial potency on mono-, dual-, and multi-species biofilms.

Study findings

On Enterococcus faecalis biofilm

The superiority of TAP compared to CH was in agreement with the results of a recently published systematic review,[81] including both clinical and in vitro studies.[82] The antibacterial efficacy of CH directly lies within the diffusion of alkaline hydroxyl ions.[83] After a week of CH introduction inside the canal, pH reaches its maximum values[84],[85] and then begins to drop. As the pH falls, the residual bacteria may regrow in the canals treated with CH, while the samples treated with antibiotics may not get affected. However, there was no superiority for DAP/mTAP compared to CH in our review. This unusual phenomenon warrants more investigation as TAP and SAPs were more effective against E. faecalis than CH.

Our findings revealed that SAPs were more potent antibacterial agents than CH. One of the included studies employed antibiotics with a minimum inhibitory concentration.[76] Another included study assessed the antibacterial efficacy after only 5 and 10 min of ICM retention.[36] Surprisingly, in both studies, antibiotic groups were significantly more effective than CH. This may indicate a turning point for future research to examine the efficacy of different SAPs, with lower concentrations and reduced retention times.

The comparison of antibiotic pastes with adjusted covariates revealed that each kind of SAPs could reduce E. faecalis as effectively as TAP while showing significantly better efficacy than DAP. Combination antibiotic therapy has been used to improve treatment efficacy, broaden the antibiotic range of activity, slow the evolution of drug resistance, and minimize toxicity by lowering the dosage of each active component.[86] However, synergistic effects will not always occur as antibiotics may exhibit inhibitory interactions. The combination of bacteriostatic and bactericidal agents is less effective than the bactericidal agent alone.[87] TAP is a mixture of two bactericides and a bacteriostatic antibiotic. Hence, the probable interactions between minocycline and the bactericidal agents may be responsible for such results obtained comparing the efficacy of SAPs and TAP. Altogether, the underlying philosophy behind most antibiotic interactions is yet to be understood.[88]

Furthermore, the polymicrobial nature of the persistent endodontic infection, with the most predominant species being E. faecalis and Porphyromonas gingivalis, is different from that of primary infection.[89] Different SAPs, such as metronidazole, could have notable antibacterial efficacy against these species; obligate and facultative anaerobic bacteria.[72] Furthermore, metronidazole is suggested for topical use since it is unlikely to develop resistance.[90] Based on our findings, using combination antibiotic therapy may not be necessary as SAPs could effectively reduce E. faecalis colonies.

The ability of an ICM to disperse into the root canal system appears to be critical for its successful antibiofilm efficacy.[83] Based on the findings by Abbott et al.,[91] the diffusion of a drug across dentinal tubules is directly related to its concentration, retention time, and the area of the inner canal exposed to the agent.

On polymicrobial biofilms

Of the two studies conducted on dual-species biofilms, one was performed on the E. faecalis and Prevotella intermedia,[74] while the other one was on E. faecalis and Streptococcus gordonii[38] combined biofilms. These species were chosen for their capacity to coexist in a biofilm. However, the difference in the bacterial combination could presumably account for part of the heterogeneity of the pooled results. On the other hand, the two studies on the multi-species biofilms were performed on isolated bacteria from mature/immature teeth with necrotic pulps, which were believed to have a similar bacterial population according to a clinical study.[92] Moreover, these two studies had more methodological characteristics in common (DAP as antibiotic, 7-day retention time, evaluating CFU/mL at the dentin surface), which resulted in low heterogeneity of the pooled results.

Hypothetically, the overall better efficacy of antibiotics compared to CH on E. faecalis biofilm might be related to the functioning proton pumps of the bacteria. These pumps maintain cell survival by acidifying the cytoplasm.[20] However, this function might be hindered in polymicrobial biofilms to some extent. Therefore, CH could appear with equal efficacy as antibiotics in such biofilms. Clinical studies have proved this claim by showing equal efficacy of TAP or moxifloxacin compared to CH.[93],[94] However, DAP was the only antibiotic investigated on polymicrobial biofilms in this review. Hence, based on the difference between the mono- and polymicrobial biofilms, studying different antibiotic pastes on polymicrobial biofilms is recommended.

In our review, the outcomes of meta-analyses were mostly influenced by substantial heterogeneity. The high degree of statistical heterogeneity was probably explained by focusing on the intrinsic methodological aspects of the studies. The potential confounding factors included bacterial strain, incubation period, type of the teeth, sample dimensions, sample size, cementum removal, ICM vehicle, biofilm development confirmation, sampling technique, and outcome measure technique.

Methodological appraisal of studies

E. faecalis has been reported to be the most prevalent species isolated from root-filled teeth with apical periodontitis.[95] This bacterium, however, is no longer in the spotlight as the only cause of persistent infections,[96] as it is not identified in 100% of the secondary infection cases.[97] E. faecalis is simply cultured in the laboratory with little sensitivity to different conditions. Hence, the regular selection of E. faecalis by different studies could be explained.[96] Polymicrobial biofilms are also favored for ex vivo biofilm investigations, as they more precisely mimic clinical infection. Therefore, this paper systematically reviewed the effect of ICMs on the polymicrobial biofilms as well as the mono-species of E. faecalis.

Since single-rooted human and bovine teeth are alike in terms of dentin structure,[98] both were included in this review. Moreover, mature biofilms behave differently than single bacterial strains since they are composed of a complex microbial community.[99] As a result, studies with immature biofilms were excluded from the final meta-analysis in this review.

Antibiotics' retention time in root canals is vital to eradicate as many bacteria as possible. According to the quantitative results of the included studies, the antibacterial efficacy of SAP and DAP increased with time after application. However, when applied for more than 48 h, antibiotic pastes could induce cytotoxicity and genotoxicity on human stem cells.[100] This issue raises an essential question: Could we benefit from antibiotic pastes in shorter application times? Addressing this question, we included all reported retention times in the meta-analysis to analyze its influence.

Similar to most ex vivo systematic reviews, this study used a modified tool for quality assessment.[101] Based on the published evidence, randomization and operator blinding are not regularly performed/reported in ex vivo settings.[102] Likewise, no study reported the operator blinding in the present review, and very few reported the randomization procedure or sample size calculation rationale. As performing these steps increases the generalizability of evidence, authors are strongly recommended to use/mention them in their studies.

Four processes should be considered while simulating clinical infection within the dentinal tubules ex vivo. First, the smear layer should be removed. This layer seals the tubules' entrance; hence, leaving it intact may decrease the penetration of bacteria[103] and the diffusion of ICMs through the tubules.[104] Second, experiments should be conducted on mature bacterial biofilms, defined as ≥3-week-old incubated biofilm wherein bacteria develop more resistance to the disinfectants.[105],[106] All included studies in the meta-analysis followed these two criteria. Third, the cementum layer should be eliminated. Its removal permits easier infiltration of bacteria into the dentinal tubules, resulting in noticeable infection.[107] Fourth, biofilm formation after the incubation period should be verified since ex vivo biofilm development depends on various laboratory steps.[96] Cementum removal was NM by most studies, while biofilm development confirmation was rather well performed by the majority of the studies included in the meta-analysis.

Recommendations for the future research

  1. Ex vivo studies are encouraged to test ICMs on polymicrobial infections. The most acceptable source of such biofilm would be an obturated root canal with a persistent lesion
  2. Clinical studies, especially randomized clinical trials, are recommended for testing antibiotic pastes on endodontic outcomes
  3. Ex vivo studies are suggested to examine new ICMs with minimum concentration and retention time parameters chosen reasonably.

Strengths and limitations

To date, no systematic review has been conducted to compare the antibacterial efficacy of the two commonly-used ICMs via meta-analytic pooling of data. Concerning the limited number of clinical evidence, the abundance of existing ex vivo studies, and the lack of consensus toward selecting the proper ICM, only ex vivo articles were included.

As strength, a meta-regression analysis was conducted to ascertain the sources of heterogeneity. Moreover, sensitivity analysis indicated the stability of the results.

In addition, data on ICM efficacy against polymicrobial biofilms were obtained and pooled; however, the number of studies on this subject was restricted. Therefore, it is not proper to draw generalized conclusions about polymicrobial biofilms.

Although it has been demonstrated that greater concentrations of CH have enhanced bactericidal activity,[108] it was not possible to calculate/convert the concentrations in all studies. Therefore, as an important limitation, dosage differences for CH were neglected in the meta-analysis.

   Conclusions Top

Within the constraints of this review, antibiotic pastes were either superior or comparable to CH in terms of overall effectiveness. SAPs, while having the same potency as TAP, exerted significantly better antibacterial efficacy compared to DAP or CH against E. faecalis biofilm. Considering the overall superiority of SAPs to other medicaments, a combination of antibiotics (as in DAP, mTAP, or TAP) seems not to be a necessity for root canal disinfection.


This study was financially supported by the Iranian Center for Endodontic Research, Research Institute of Dental Sciences, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran. The authors would like to thank Dr. Venkateshbabu Nagendrababu for providing technical assistance to this study.

Financial support and sponsorship

This study was financially supported by the Iranian Center for Endodontic Research, Research Institute of Dental Sciences, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

Conflicts of interest

There are no conflicts of interest.

   References Top

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Correspondence Address:
Dr. Omid Dianat
Division of Endodontics, Department of Advanced Oral Sciences and Therapeutics, School of Dentistry, University of Maryland, Baltimore, 650 West Baltimore Street, 4th Floor, Baltimore, MD 21201
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcd.jcd_183_22

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