Journal of Pharmacy And Bioallied Sciences

: 2021  |  Volume : 13  |  Issue : 6  |  Page : 1603--1608

Efficacy of glycolic acid on debris and smear removal as a final rinse solution in curved canals: A scanning electron microscope study

Karunakaran Jeyaraman Venkataraman1, Suresh Krishna Boominathan1, Ragavendran Nagappan1, Chris Susan Abraham1, Anbarasi Kaliyaperumal2, Jayaprakash Nachimuthu1, Modachur Muruganathan Premkumar1,  
1 Department of Conservative Dentistry, JKK Nataraja Dental College and Hospital, Komarapalayam, Tamil Nadu, India
2 Department of Oral Medicine and Radiology, Faculty of Dental Sciences, Sri Ramachandra Institute of Higher Education and Research, Chennai, Tamil Nadu, India

Correspondence Address:
Karunakaran Jeyaraman Venkataraman
Department of Conservative Dentistry, JKK Nataraja Dental College and Hospital, Komarapalayam - 638 183, Tamil Nadu


Aim: This study aims to compare intraradicular smear layer removal efficacy of different concentrations of glycolic acid (GA), 17% ethylenediaminetetraacetic acid (EDTA), and 10% citric acid (CA) as final rinses in the canals of curved mesial root of mandibular first molars using the specific irrigant protocols. Materials and Methods: Fifty-eight mandibular first permanent molars with 15°–30° of curvature of the mesial roots were selected, standardized, mesiobuccal canal prepared using the rotary instrumentation. Sodium hypochlorite was used as initial rinse solution (8 ml). The samples were divided into control (n = 5) (I – Normal saline and II – 17% EDTA) and experimental groups (n = 8) (Groups III, IV, V, VI, VII, and VIII) based on the type of final rinse solution (5 ml) used, i.e. 2.5% GA, 5% GA, 10% GA, 17% GA, 37% GA, and 10% CA. Samples were split buccolingually, dehydrated, splutter coated, and examined under a scanning electron microscope. Results: Group IV presented the least amounts of smear among the GA experimental groups at the apical, middle, and coronal one-thirds of the root canal with a mean value of 2.6 ± 1.012, and on comparison with Group II, the results were comparable, and no significant difference found statistically (P > 0.05). Conclusion: The use of GA as final rinse solution for biomechanical preparation during endodontic therapy seems promising. Further evaluation in a clinical setting is recommended.

How to cite this article:
Venkataraman KJ, Boominathan SK, Nagappan R, Abraham CS, Kaliyaperumal A, Nachimuthu J, Premkumar MM. Efficacy of glycolic acid on debris and smear removal as a final rinse solution in curved canals: A scanning electron microscope study.J Pharm Bioall Sci 2021;13:1603-1608

How to cite this URL:
Venkataraman KJ, Boominathan SK, Nagappan R, Abraham CS, Kaliyaperumal A, Nachimuthu J, Premkumar MM. Efficacy of glycolic acid on debris and smear removal as a final rinse solution in curved canals: A scanning electron microscope study. J Pharm Bioall Sci [serial online] 2021 [cited 2022 Oct 2 ];13:1603-1608
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Biomechanical preparation during endodontic therapy prepares, cleanses, and eliminates microorganisms from within the canal system.[1] Smear is formed during the preparation of the canal system and contains both organic and inorganic components. No single irrigant solution effectively removes both.[2] The constituents of smear are propelled into radicular dentin for depths of up to 40 μm during canal preparation.[3],[4],[5] When surface active agents are used to enhance irrigant efficacy, capillary action, and adhesive forces further push smear for depths of up to 110 μm.[6],[7] Cutting debris is forced variable distances into dentinal tubules during smear layer formation. These smear plugs, together with the smear layer decrease permeability, sensitivity, and surface wetness of radicular dentin.[8] The presence of smear acts as a physical barrier, prevents penetration of medicaments into dentinal tubules, and influences adaptation of obturating materials.[9],[10] Different techniques have been suggested for effective smear elimination from canal ramifications.[11],[12],[13]

Different final irrigant solutions such have been tried for effective smear removal. Seventeen percent ethylenediaminetetraacetic acid (EDTA) solution is still the most widely used final irrigant solution in endodontics.[14] Although EDTA is effective at smear removal, it has been found to have undesirable effects such as denaturation of collagen fibrils, erosion when used for longer exposure times, cytotoxicity when extruded beyond the apex, and environmental impact.

The search of a final irrigant that is biocompatible, effective in the removal of smear without causing damage to radicular dentin is needed to ensure successful treatment outcomes. Glycolic acid (GA) is extracted from sugarcane and other sweet vegetables. It is colorless, odorless, and easily dissolves in water. GA is commonly used in dermatology-related applications that range from skin moisturizing to deep chemical peeling. In dentistry, recent studies have shown GA to be less cytotoxic than EDTA and suitable for enamel and dentin etching during restorative procedures.[15],[16] Due to its positive characteristics, GA may be a suitable agent to remove the smear layer from the root canal walls with minimal negative biological side effects.[17] The aim of this study was to determine the efficacy of GA in the removal of debris and smear when used a final rinse solution in curved canals. The null hypothesis was that there is no difference in debris and smear removal between GA, 17% EDTA, and citric acid when used as final rinse solutions in curved canals during endodontic therapy.

 Materials and Methods

Human permanent mandibular first molars were collected, cleaned, teeth devoid of cracks, defects, restorations, and endodontically treated were selected. Fifty-eight teeth were analyzed using radiography. Teeth with intact apices, patent canals, having a mesial root curvature of 20°–35° were selected for the purpose of the study. After access preparation the two roots were separated, distal wall of mesial root restored with composite, dried, and coded. Apical third of the root covered with wax, embedded in transparent plastic cups with soft polyvinyl siloxane material to prevent irrigants from extruding the apex with the aim of simulating in vivo closed apex conditions. The mounted samples were then randomly divided into two control groups (n = 5) and six experimental groups (n = 8) [Table 1] Initial instrumentation done with hand files up to size 20 followed by rotary files from size S1 to F2 (Protaper gold, Dentsply, Maillefer, Ballaigues, Switzerland) as per the manufacturer recommendations. A total of 8 ml of the irrigant was used as initial rinse during biomechanical preparation procedure, and then, a final rinse of 5 ml of irrigant done as per respective group for 3 min. Irrigant was delivered using a 28 G side vent ProRinse needle (Dentsply, Tulsa Dental) at working length. The needle was withdrawn 5 mm, inserted back to working length followed by rotation of needle by 180° three times alternatively during the first minute of irrigant delivery. A F2-size gutta-percha cone (Dentsply Maillefer, Ballaigues, Switzerland) was inserted to working length and withdrawn six times (manual dynamic activation). This customization was done to improve irrigant delivery and replacement at apical third. The irrigant was left alone for the third minute as per the final rinse protocol for the respective groups and a postfinal rinse of 10 mL of distilled water done. The samples were then carefully split longitudinally in a buccolingual plane using a diamond disc dividing them into two halves. The half containing the most visible part of apex of root selected, coded, and stored. The teeth were then placed in 10% neutral-buffered formalin solution at 18°C for 24 h and then postfixed in osmium tetroxide (1% w/v) for 2 h. They were dehydrated in graded solutions of isopropyl alcohol (Nice Chemicals Ltd, India). Separation markings of 5 mm at apical, middle, and coronal thirds were made on split half of the root, samples placed in ultraviolet sterilization chamber and subsequently stored in sterile pouches. The coded samples of each group were mounted on aluminum stubs with carbon tape (NEM TAPE NISSHIN EM.Co., Ltd) with the canal facing upward. Each specimen was coated with a 20–30 nm thin layer of gold in a gold sputter coating machine (QUORUM Q150RS, United Kingdom). The samples were then examined using a scanning electron microscope with a high resolution (ZEISS-SIGMA VP, Munchen, Germany). The photo micrographs were obtained at ×2000 magnification using digital image analysis software, and the most representative micrographs were taken for each millimeter of the specimen and were recorded for apical, middle, and coronal thirds, respectively. The results scored by independent operators, compared, and tabulated for their respective scores of smear, debris, and erosion at apical, middle, and coronal thirds of the canal. Smear, debris, and erosion were evaluated using the criteria developed by Caron et al.,[18] Dadresanfar et al.,[19] and Torabinejad et al.,[20] respectively.{Table 1}


The coronal third presented least amount of debris with a mean value of 2.5 ± 3.40 followed by the middle third with a mean value of 2.6 ± 3.0, and the most amount of debris was seen at the apical third of the canal with a mean value of 2.8 ± 3.10 [Chart 1] and [Figure 1].[INLINE:1]{Figure 1}

Among the experimental groups, Group IV presented the least amount of smear in the coronal, middle, and apical thirds with mean values of 3.06 ± 1.20, 3.40 ± 0.96, and 4.1 ± 0.65 respectively [Chart 2]. In this study, overall, Group VIII presented the least amounts of erosion among experimental groups at all levels [Chart 3].[INLINE:2][INLINE:3]

Group IV is efficient in the removal of smear and debris, and on comparison with Group II, the results were comparable, and no significant difference found statistically (P > 0.05) [Chart 4].[INLINE:4]


GA acid belongs to the group of alpha hydroxyl acids and is a colorless, odorless, and hygroscopic crystalline solid, with good solubility in water.[21] It is used in pharmaceutical industry as an organic component in cosmetic preparations[22] and as poly (lactic-co-GA) (PLGA) in tissue engineering applications. It is readily biodegradable and unlike EDTA, its waste disposal does not cause environmental issues.[23],[24] Studies have demonstrated that GA has the ability to induce proliferation of fiibroblasts and collagen synthesis.[21],[25],[26] It has been suggested for surface etching of enamel and dentin.[16] These properties highlight the potential of GA for the use as rinse solution for the removal of debris and smear layer in endodontic therapy.

GA has been found to have properties and promise for use as a final rinse irrigation solution during endodontic therapy.[27] Surface tension of GA decreased in solutions of higher concentrations. The apatite to collagen ratio was found to reduce with increasing GA concentrations when used on dentin. The flexural strength of dentin was not affected by varying the concentration of GA.[28] In the present study, Group IV presented the least amounts of smear among all the GA groups at the coronal, middle, and apical thirds, respectively. Group II and Group VIII presented with the least smear scores among all groups.

Group IV was effective in the removal of smear and was nearly as efficient when compared to Group II at all thirds of the canal. On statistical comparison and analysis, there was not any significant difference between the Groups II and IV (P > 0.05) [Figure 2]. The present study was done in the curved mesiobuccal canal of the mesial root of the mandibular first permanent molar tooth where curvature and canal preparation was standardised.{Figure 2}

GA has been recently tried in endodontics as a root canal irrigant and for its effect on the properties of dentin. This study has evaluated the role of GA as a final rinse solution in specific irrigation protocols in the curved mesial roots of mandibular first permanent molars. Recent years have witnessed various drug delivery systems among which PLGA has gained enormous attention. As a copolymer of lactic and GA, it has exquisite properties such as biocompatibility, biodegradability, and allowing sustained and controlled release of encapsulated agent. GA has also been successfully used as a nanocarrier molecule.

PLGA, nanoparticles, have been used in the field of endodontics on a trial basis and many areas of application have been identified. The nanoparticles have an advantage due to their size as they can easily traverse the dentinal tubules, isthumi, cul-de-sacs, lateral canal, apical deltas, and other anatomical variations inherent in root canal anatomy where instrumentation is not feasible.[29] The use of PLGA encapsulated moxifloxacin nanoparticles has been shown consistent antibacterial property even in low doses against Enterococcus faecalis. Their ability for a programmed release, effectiveness have made them ideal for use as intracanal medicaments.[30] The role of compatible polymers being used as vehicles for drug delivery vehicles has paved way for newer methods for drug delivery within the root canal system. The advantage of these polymers is that they also biodegradable. The role and use of intracanal medicament during endodontic therapy is vital in eliminating the pathogenic endodontic microflora present within the ramifications of the root canal system without causing resistance. They are routinely used during endodontic therapy.

In an in vitro study of PLGA nanoparticles used in conjunction with the photosensitizer methylene blue and light against E. faecalis found that PLGA nanoparticles in conjunction with photoactive chemicals may be promising for use in intra canal antimicrobial management during endodontic therapy.[31] PLGA when used as a drug delivery agent has a lot advantages such as inertness, biodegradability, and smart release of the drug will take place only with changes with temperature, pH, and fluids which are commonly seen in inflammatory tissue changes. This happens due to the erosive changes of the drug delivery agent releasing the drug due to changes in the environment.

Researchers have also found that GA demonstrated greater capacity to eliminate E. faecalis from within the canal system than did EDTA which is a commonly used final rinse irrigation solution in a concentration of 17%.[6] GA has been tried as scaffolds for releasing antibiotics during regenerative endodontic procedures. It has been hypothesized that the use of this material as a scaffold in conjunction with dental pulp stem cells will restore dentin, innervation, and revascularization of the pulp.[32]

PLGA nanoparticles that contain lovastatin have been tried as a material for direct pulp capping and have been found to form tubular reparative dentin and a complete dentinal bridge.[33] The effects on pulp cells were found to be dose dependent. For clinical application, still an optimal dose regime and concentration have to be established for use in pulp capping procedures. The nanoparticles were found to have good biocompatibility, osteogenic, and odontogenic potential. GA has been evaluated for dental applications as a surface conditioner during restorative procedures and has been found to be effective. In the present study, overall, the Groups IV and VI presented the least amounts of erosion among experimental groups at the apical, middle, and coronal thirds of the root with overall mean values of 0.9 ± 0.4267 [Chart 3]. Among the experimental groups, Group VIII presented with the highest amount of erosion with loss of peritubular and intertubular dentin at all levels. Group II presented with similar levels of erosion as Groups IV and VI.


The use of GA as final rinse solution during biomechanical preparation during endodontic therapy seems promising. Further evaluation in a clinical setting is recommended.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


1Karunakaran JV, Kumar SS, Kumar M, Chandrasekhar S, Namitha D. The effects of various irrigating solutions on intra-radicular dentinal surface: An SEM analysis. J Pharm Bioallied Sci 2012;4:S125-30.
2Diamond A, Carrel R. The smear layer: A review of restorative progress. J Pedodontics 1984;8:219-26.
3Eick JD, Wilko RA, Anderson CH, Sorensen SE. Scanning electron microscop of cut tooth surfaces and identification of debris by use of the electron microprobe. J Dent Res 1970;49:13:59-68.
4El-Backly RM, Massoud AG, El-Badry AM, Sherif RA, Marei MK. Regeneration of dentine/pulp-like tissue using a dental pulp stem cell/poly (lactic-co-glycolic) acid scaffold construct in New Zealand white rabbits. Aust Endod J 2008;34:52-67.
5Galvao De, Souza SM, Silva JL. Demineralization effect of EDTA, EGTA, CDTA and citric acid on root dentin: A comparative study. Brazilian Oral Res 2005:19:188-19.
6Gambin DJ, Leal LO, Farina AP, Souza MA, Cecchin D. Antimicrobial activity of glycolic acid as a final irrigant solution for root canal preparation. Gen Dent 2020;68:41-4.
7Gao X, Miao H, Li L, Zhang S, Zhou D, Lu Y, et al. Efficacy of four different irrigation techniques combined with 60°C 3% sodium hypochlorite and 17% EDTA in smear layer removal. BMC Oral Health. 2014 Sep 8;14:114.
8Pashley DH. Smear layer: Overview of structure and function. Proc Finn Dent Soc 1992;88 Suppl 1:215-24.
9Violich DR, Chandler NP. The smear layer in endodontics – A review. Int Endod J 2010;43:2-15.
10Sen BH, Wesselink PR, Türkün M. The smear layer: A phenomenon in root canal therapy. Int Endod J 1995;28:141-8.
11Haupt F, Meinel M, Gunawardana A, Hülsmann M. Effectiveness of different activated irrigation techniques on debris and smear layer removal from curved root canals: A SEM evaluation. Aust Endod J 2020;46:40-6.
12Gu LS, Kim JR, Ling J, Choi KK, Pashley DH, Tay FR. Review of contemporary irrigant agitation techniques and devices. J Endod 2009;35:791-804.
13Haapasalo M, Shen Y, Qian W, Gao Y. Irrigation in endodontics. Dent Clin North Am 2010;54:291-312.
14Shahravan A, Haghdoost AA, Adl A, Rahimi H, Shadifar F. Effect of smear layer on sealing ability of canal obturation: A systematic review and meta-analysis. J Endod 2007;33:96-105.
15Cecchin D, Bringhenti IL, Bernardi JB, Leal LO, Souza MA, Bedran-Russo AK, Farina AP. Alpha-hydroxy glycolic acid for root dentin etching: Morphological analysis and push out bond strength. Int J Adhes Adhes 2019;90:138-43: ISSN 0143-7496.
16Cecchin D, Farina AP, Vidal CM, Bedran-Russo AK. A novel enamel and dentin etching protocol using α-hydroxy glycolic acid: Surface property, etching pattern, and bond strength stuDies. Oper Dent 2018;43:101-10.
17Barcellos DP, Farina AP, Barcellos R, Souza MA, Borba M, Bedran-Russo AK, et al. Effect of a new irrigant solution containing glycolic acid on smear layer removal and chemical/mechanical properties of dentin. Sci Rep 2020;10:7313.
18Caron G, Nham K, Bronnec F, Machtou P. Effectiveness of different final irrigant activation protocols on smear layer removal in curved canals. J Endod 2010;36:1361-6.
19Dadresanfar B, Khalilak Z, Delvarani A, Mehrvarzfar P, Vatanpour M, Pourassadollah M. Effect of ultrasonication with EDTA or MTAD on smear layer, debris and erosion scores. J Oral Sci 2011;53:31-6.
20Torabinejad M, Cho Y, Khademi AA, Bakland LK, Shabahang S. The effect of various concentrations of sodium hypochlorite on the ability of MTAD to remove the smear layer. J Endod 2003;29:233-9.
21Thibault PK, Wlodarczyk J, Wenck A. A double-blind randomized clinical trial on the effectiveness of a daily glycolic acid 5% formulation in the treatment of photoaging, Dermatologic Surg 1998;24:573-8.
22Kataoka M, Sasaki M, Hidalgo AR, Michiko N, Shimizu S. Glycolic acid production using ethylene glycoloxidizing microorganisms. Biosci Biotechnol Biochem 2001;65:2265-70.
23van der Smissen A, Hoffmeister PG, Friedrich N, Watarai A, Hacker MC, Schulz-Siegmund M, et al. Artificial extracellular matrices support cell growth and matrix synthesis of human dermal fibroblasts in macroporous 3D scaffolds. J Tissue Eng Regen Med 2017;111:390-402.
24Hua X, Cao R, Zhou X, Xu Y. One-step continuous/semi-continuous whole-cell catalysis production of glycolic acid by a combining bioprocess with in-situ cell recycling and electrodialysis. Bioresour Technol 2018;273:515-20.
25Kim S, Won Y. The effect of glycolic acid on cultured human skin fibroblasts: Cell proliferative effect and increased collagen synthesis. J Dermatol 1998;25:85-9.
26Bernstein EF, Lee J, Brown DB, Yu R, Van Scott E. Glycolic acid treatment increases type I collagen mRNA and hyaluronic acid content of human skin. Dermatol Surg 2001;27;429-33.
27Bello YD, Porsch HF, Farina AP, Souza MA, Silva EJ, Bedran-Russo AK, et al. Glycolic acid as the final irrigant in endodontics: Mechanical and cytotoxic effects. Mater Sci Eng C Mater Biol Appl 2019;100:323-9.
28Bello YD, Farina AP, Souza MA, Cecchin D. Glycolic acid: Characterization of a new final irrigant and effects on flexural strength and structural integrity of dentin. Mater Sci Eng C Mater Biol Appl 2020;106:110283.
29Chou LY, Ming K, Chan WC. Strategies for the intracellular delivery of nanoparticles. Chem Soc Rev 2011;40:233-45.
30Makkar H, Patri G. Fabrication and appraisal of poly (Lactic-Co-Glycolic Acid)-Moxifloxacin nanoparticles using Vitamin E-TPGS: A potential intracanal drug delivery agent. J Clin Diagn Res 2017;11:C05-8.
31Pagonis TC, Chen J, Fontana CR, Devalapally H, Ruggiero K, Song X, et al. Nanoparticle-based endodontic antimicrobial photodynamic therapy. J Endod 2010;36:322-8.
32Gangolli RA, Devlin SM, Gerstenhaber JA, Lelkes PI, Yang M. A bilayered poly (lactic-co-glycolic acid) scaffold provides differential cues for the differentiation of dental pulp stem cells. Tissue Eng Part A 2019;25:224-33.
33Lin HP, Tu HP, Hsieh YP, Lee BS. Controlled release of lovastatin from poly (lactic-co-glycolic acid) nanoparticles for direct pulp capping in rat teeth. Int J Nanomedicine 2017;12:5473-85.