Journal of Indian Society of Pedodontics and Preventive Dentistry
Journal of Indian Society of Pedodontics and Preventive Dentistry
                                                   Official journal of the Indian Society of Pedodontics and Preventive Dentistry                           
Year : 2018  |  Volume : 36  |  Issue : 3  |  Page : 262--267

Comparison of resorption rate of primary teeth treated with alternative lesion sterilization and tissue repair and conventional endodontic treatment: An in vivo randomized clinical trial

Navneet Grewal, Neha Sharma, Sarika Chawla 
 Department of Pedodontics and Preventive Dentistry, Punjab Government Dental College and Hospital, Amritsar, Punjab, India

Correspondence Address:
Dr. Navneet Grewal
Department of Pedodontics and Preventive Dentistry, Punjab Government Dental College and Hospital, SSSS Chowk, Majitha Road, Amritsar - 143 001, Punjab


Background: Complete pulpectomy and elimination of wide range of microorganisms from infected primary root canals is not possible through conventional endodontic procedures. Thus, lesion sterilization and tissue repair (LSTR) therapy employing 3Mix tri-antibiotic paste have been used as an alternative endodontic modality for infected primary teeth. Aim: This study aims to evaluate the root resorption rate of endodontically treated mandibular primary molars with conventional endodontic treatment or LSTR therapy and to compare it with their healthy contralateral teeth. Materials and Methods: Fifty carious first and second primary mandibular molars from 25 healthy children aged 7–10 years were treated with two different endodontic procedures using LSTR Therapy and conventional endodontic treatment. The resorption rate of these teeth with healthy contralateral teeth was compared clinically and radiographically at 3, 6, 12 and 36 months using Chi-square test. Results: At 12 months, clinically, there was no difference in the outcomes of both groups but radiographically, statistically significant difference (P < 0.001) in root resorption between treated teeth and their controls in both the groups was observed. At 36 months, interradicular bone resorption around the crown of succedaneous teeth and their delayed eruption was noted in LSTR group. Conclusions: LSTR therapy could be a viable treatment modality for infected/nonvital primary molars with poor prognosis and intended to be maintained for shorter duration in the oral cavity as natural space maintainers.

How to cite this article:
Grewal N, Sharma N, Chawla S. Comparison of resorption rate of primary teeth treated with alternative lesion sterilization and tissue repair and conventional endodontic treatment: An in vivo randomized clinical trial.J Indian Soc Pedod Prev Dent 2018;36:262-267

How to cite this URL:
Grewal N, Sharma N, Chawla S. Comparison of resorption rate of primary teeth treated with alternative lesion sterilization and tissue repair and conventional endodontic treatment: An in vivo randomized clinical trial. J Indian Soc Pedod Prev Dent [serial online] 2018 [cited 2022 Jan 17 ];36:262-267
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Preservation of the primary tooth is the best method of space maintenance for its successor.[1] However, teeth with infected root canals are a common clinical problem. Microorganisms play an important role in the initiation, progression, and persistence of inflammatory root resorption. Conventional endodontic therapy is aimed at elimination of microorganisms from the infected root canals and prevention of reinfection.

Premixed calcium hydroxide and iodoform paste is a universally accepted obturating material for pulpectomy in primary teeth. However, root resorption of primary molars has been found to be accelerated following pulpectomy with conventional iodoform containing filling materials, leading to their early shedding in comparison with homologous teeth without endodontic treatment.[2]

The Cariology Research Unit of Niigata University School of Dentistry introduced the concept of lesion sterilization and tissue repair (LSTR) therapy, wherein a mixture of antibacterial drugs for disinfection of root canals was used.[3] It has been reported that 1:1:1 mixture of ciprofloxacin, metronidazole, and minocycline can sterilize necrotic pulps and infected root dentin of primary teeth. However, minocycline as well as other tetracycline derivatives may get incorporated into calcifying dentinal tissues and hence stain teeth. Hence, the bacteriocidal efficacy of the mixture of ciprofloxacin and metronidazole along with amoxicillin, cefaclor, cefroxadine, fosfomycin, or rokitamycin have been compared in the past.[4] These new drug combinations were found to be able to sterilize carious lesions and infected necrotic pulps of deciduous teeth. Thus, the present in vivo randomized prospective clinical trial was undertaken to compare the resorption rate of healthy primary mandibular molars with contralateral teeth having undergone LSTR therapy and conventional endodontic treatment in the same oral cavity. The null hypothesis for the present research was that there was no significant difference in the resorption rate of two different endodontic therapies of primary teeth when compared to their contralateral healthy counterparts.

 Materials and Methods

The research protocol and informed consent form were reviewed and approved by the Ethical committee of Baba Farid University of health sciences, Faridkot, Punjab, India, vide letter no. BFUHS/2K13/P-Th/8085 dated August 06, 2013 in accordance with the Declaration of Helsinki. A random screening of 1500 schoolchildren enrolled in different private and government schools in the city of Amritsar, aged 7–10 years was carried out from September 2013 till October 2013. Thirty healthy individuals (17 males and 13 females) showing deep carious lesions in two primary molars indicative of endodontic treatment with healthy contralateral teeth were selected for future investigation to make the final selection. The final sample consisted of 50 carious teeth and contralateral healthy teeth from 25 children (12 males and 13 females) after obtaining informed consent from their parents [Table 1]. Participants were randomly assigned following simple randomization procedures (computer-generated random numbers) to one of the two treatment groups. The sample size was adequate to demonstrate the effect at 90% power and 5% level of significance.{Table 1}

The clinical criteria for case selection in the study was as follows:

Two infected mandibular molars presenting with clinical history and signs/symptoms of pulpal pathology [Table 2], [Figure 1]aAdequate restorable tooth structure for further placement of stainless steel crowns posttreatment.{Figure 1}{Table 2}

Radiographic criteria for inclusion was as follows:

Inflammatory root resorption less than and or not more than apical one-third as assessed from radiographic evaluation with healthy contralateral tooth [Figure 1]b,[Figure 1]c.

Exclusion criteria for teeth were:

Nonrestorable teeth with coronal perforationsPatients undergoing treatment for any medical ailment or disordersPatients with a history of drug allergy to metronidazole, ciprofloxacin, cefaclor or iodoform.

Clinical and radiographic evaluation before inclusion was carried out by two-blinded precalibrated examiners with >15-year clinical experience. The intraexaminer reliability for clinical and radiographic examination was calculated by intraclass correlation coefficient (ICC) and Cronbach's alpha test (1 and 1, respectively). Allocation sequence of participants to each treatment group was made by computer-generated statistical series based on random sampling numbers drawn up for each participant by assistant professor in the department who was not involved in the research. The details of series were unknown to investigator or coordinators and details of allocated group were given on colored cards contained in sequentially numbered, opaque-sealed envelopes to the investigator before beginning the treatment procedure. All treatments were carried out by one operator with clinical experience of pediatric endodontics in more than 50 primary molars.

Preparation of 3Mix

The drugs metronidazole, ciprofloxacin, and cefaclor were pulverized after removing the coating and prepared by a pharmacist. Each drug was weighed on a calibrated microbalance in equal proportion of 3.9 mg and mixed in a 1:1:1 ratio. 9961 mg of excipients (cellulose based) was added to the drug mixture to make a total of 10 g. Propylene glycol and macrogol were added to the mixture to form an ointment. The desired concentration achieved was 0.39 μg/ml taking into consideration the cytotoxicity of the drug mixture above this concentration.[5]

Clinical protocol

Group A – lesion sterilization and tissue repair

After accessing the pulp chamber with a sterile fissure bur in a high-speed handpiece, necrotic pulp was removed using a sterile sharp spoon excavator and irrigated with 2.5% sodium hypochlorite. All the accessible necrotic pulp was removed from the root canal with number 15 K-file without further biomechanical preparation. The pulp chamber was dried using cotton pellet and 3Mix-MP was placed on the orifices of root canals and pulpal floor not entering more than coronal one-third of root portion [Figure 1]e. The tooth was then restored with light-cured glass ionomer cement.[6] After 7–10 days, the tooth was evaluated clinically for any persistent signs/symptoms and restored with stainless steel crown [Figure 1]f.

Group B – conventional endodontic treatment

Access opening was performed and necrotic pulp tissue was removed following the standardized protocol of endodontic procedures for primary teeth. Filing and biomechanical preparation with copious irrigation with 2.5% NaOCl was carried out between the uses of each. The canals were dried with sterile paper points and premixed calcium hydroxide iodoform paste was placed into the root canals using hand lentulo spiral files [Figure 1]d. Radiographic evaluation for voids, under or overfilling of the canals was done. The tooth was restored with light-cured glass ionomer cement followed by stainless steel crown after 7–10 days [Figure 1]f.

Clinical and radiographic evaluation

Clinical and radiographic evaluation was carried out at 3, 6, 12, and 36 months, respectively. Recall evaluation for success of treatment was based on the absence of clinical symptoms of pain or discomfort and signs of gingival inflammation, swelling, or draining sinus assessed by two different calibrated examiners other than the operator. Radiographically, scanned images were evaluated using Autocad software[7] by double-blind examiners and three measurements of the root lengths made alternatively, one by the operator and two by the precalibrated examiners and the mean of three readings was taken as the final value. Manual measurements were made with the help of Fixott–Everett lead grid (1 graduation = 1 mm) by the same examiners. To ensure the standardization of the radiographs, EndoRay II Film Holder (Dentsply) was used while taking radiographs to facilitate the use of paralleling technique and prevent distortion of radiographic images. Radiographic success was measured as a decrease in root length comparable to contralateral healthy tooth at 3, 6, 12, and 36 months. The comparative success rate of both the groups was determined by statistical analysis using Chi-square test with SPSS version 20.00 software (IBM, Armonk, NY, United states of America) at P < 0.005.


Clinical symptoms improved following endodontic treatment in both the groups. Periapical swelling, sinus, and pain disappeared within few days of treatment. Based on clinical findings, no difference was found between the two groups at 12 months and also at 36 months where 15 teeth were available for follow-up.

Radiographically, intergroup comparison of mean decrease in mesial root length and distal root length was measured and compared with the control teeth on contralateral side. Statistically, this difference between the two groups was highly significant from baseline to 6 months, 6 months to 12 months, and baseline to 12 months (P < 0.005) [Table 3] and [Table 4].{Table 3}{Table 4}


The endodontic therapy is based on the premise that, with the removal of the noxious stimuli from the root canal, the normal healing process, already set in motion by chronic inflammation, will be able to complete normal repair of the periodontal tissues. Total removal of the pulp tissue from the root canals of primary teeth is difficult due to multiple tortuous canals, presence of accessory canals, lateral canals. and apical ramifications of pulp.[8] Furthermore, it is difficult to eliminate the wide range of microorganisms, which are often present in infected root canals through instrumentation and irrigation.[9] Thus, in order to increase the chances of success of the endodontic treatment, substances with antimicrobial properties are frequently used as root canal filling materials in deciduous teeth.

Zinc oxide-eugenol cement has long been used as a root canal filling material for deciduous teeth, but its limited antimicrobial action and slower resorption rate led to search for alternative obturating materials for deciduous teeth. Premixed calcium hydroxide and iodoform pastes have better resorbability and disinfectant properties than ZOE. However, at present, there is no high-quality evidence to support the superiority of these materials over ZOE.[10] It has been demonstrated that iodoform-containing obturating materials accelerated root resorption in root canal-treated primary molars compared with homologous teeth without endodontic treatment, thus resulting in their early shedding compared to nontreated counterparts.[2] Concerns about the cytotoxicity of iodoform containing paste on the viability of cultured macrophages and epithelial cells, and on cytokine secretion has questioned their use as root canal obturating materials.[11]

Sato et al.[4] reported the bacteriocidal efficacy of tri-antibiotic mixture (100 μg/ml each) against bacteria isolated from carious dentin and infected pulp tissues of human deciduous teeth. Since then, several authors as Prabhakar et al.[12] reported good clinical and radiographic success with 3Mix antibiotic paste. Comparative evaluation of 3Mix antibiotic paste and Vitapex, as shown by Nakornchai et al.[6] revealed no statistically significant difference in clinical and radiographic success at 12 months. However, there are limited studies on the long-term outcome of this procedure.

Chuensombat et al.[13] in an in vitro study demonstrated that the triple antibiotic mixture was cytotoxic to human pulp and apical papilla at various concentrations of the mixture. However, triple antibiotic mixture in a concentration of 0.39 μg/ml was found to be least cytotoxic and able to reduce the bacteria isolated from necrotic teeth.[5] 3Mix antibiotic mixture used in the present study was prepared under the guidance of a pharmacist to attain the desired concentration of 0.39 μg/ml to ensure least cytotoxicity and was placed only up to coronal-third of the roots without pushing toward the apical area. The present in vivo clinical trial was carried out to reduce the number of confounding factors of age, sex, tooth involved, and immune reaction. Clinical and radiographic assessment was carried out to observe statistically significant changes between the two therapies. Radiographic evaluation was based on amount of root resorption in the treated group and their healthy contralaterals undergoing physiologic resorption as controls. In the present study, rate of root resorption between the two groups, each containing pulpally involved 25 teeth with healthy controls, was statistically significant at P < 0.005. As per evaluation of the recordings, there was an increased root resorption in both Group A and Group B with respect to their controls with physiologic root resorption. However, mean difference in resorption in Group B (conventional endodontic treatment) with respect to control was significantly much greater than Group A (3Mix-MP) and this difference was greater throughout the 12-month period [Figure 1]g,[Figure 1]h,[Figure 1]i,[Figure 1]j and at 36 months. There was no statistically significant difference in clinical outcomes of the two groups at 12 months and at 36 months. However, the teeth in LSTR group followed up till 36 months were overretained compared to conventional endodontic treatment group, and some teeth were associated with interradicular bone loss surrounding the crown of permanent successor [Figure 1]k,[Figure 1]l. In one of the cases, histopathological examination of the soft tissue surrounding the crown of permanent successor after extraction of the overretained tooth, odontogenic keratocyst was diagnosed. Trairatvorakul and Detsomboonrat[13] have also reported low clinical and radiographic success rate (36.7%) at 24–27 months of follow-up in primary molars treated with LSTR.

Comparative evaluation of rate of resorption between Group A and Group B teeth although clearly demonstrated that 3Mix paste had better radiographic and clinical outcome as compared to conventional endodontic treatment using calcium hydroxide/iodoform at 12 months, however, significant pathological changes were observed at 36 months radiographically in LSTR treated teeth. In addition, these teeth were overretained compared to the conventional endodontic treatment with calcium hydroxide/iodoform group. Thus, these results suggest that LSTR cannot be advocated as a long-term alternative to conventional endodontic treatment in primary teeth. Although LSTR procedure had the advantage of shorter chairside procedural time, its long-term follow-up demonstrated radiographic failure and delayed eruption of permanent successors.


The clinical and radiographic outcome of the present study establishes the fact that conventional endodontic therapy still remains the treatment modality of choice for deeply carious molars with predictable long-term outcome. LSTR therapy should be reserved as a short-term therapy for carious primary teeth with poor prognosis such as teeth with root resorption exceeding one-third of root length, presence of internal resorption/furcation radiolucency, and teeth associated with sinus or fistula.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the parent/legal guardian has given their consent for images and other clinical information to be reported in the journal. The parent/guardian understands that names and initials will not be published and due efforts will be made to conceal patient identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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