TITLE: 
Endodontic treatment of chronically infected primary teeth using triple antibiotic paste: An in vivo study



ABSTRACT.AIM:
Maintenance of primary dentition is imperative for the development of arch form, esthetics, function, mastication, and normal eruption of permanent teeth. Premature loss can cause various problems such as ectopic eruption, space loss for the successor permanent teeth, alterations in speech, and impairment of function. Hence, decayed primary teeth should not be extracted and treated whenever possible. Pulpectomy is generally recommended as a treatment of choice in such cases. The purpose of this study was to evaluate the clinical and radiographic success of pulpectomized primary teeth with chronic infection using a mixture of metronidazole, ciprofloxacin, and minocycline (3MIX)-MP as an intracanal medicament before the obturation.

ABSTRACT.METHODOLOGY:
Sixty primary teeth were selected, which were randomly divided into two groups (Group A and Group B) with thirty teeth in each group. In Group A, 3MIX-MP was used as intracanal medicament whereas in Group B, conventional pulpectomy was performed. Resolution of clinical signs and symptoms were evaluated within 2 weeks after the treatment and at recalled 3rd, 6th, and 12th month intervals. The treated teeth were evaluated clinically and radiographically.

ABSTRACT.RESULTS:
High success rate was observed in Group A samples both clinically and radiographically. Although the difference in clinical success was not statistically significant, the difference in radiographic success was statistically significant.

ABSTRACT.CONCLUSION:
All the primary teeth with chronic infection which were treated using 3MIX-MP, followed by the instrumentation and obturation provided excellent clinical and radiographic success when compared to conventional pulpectomy and noninstrumentational lesion sterilization tissue repair therapy.

BODY.INTRODUCTION:
The successful management of chronically infected primary teeth is still a challenge owing to its complex root canal system, difficulty in mechanical debridement, polymicrobial nature of infection, and root resorption.[1] The difficulties of complete root canal disinfection and the liability to reinfection still remain and render the prognosis less favorable in chronically infected teeth. Hence, the importance of chemical means of disinfection has aroused to accomplish complete the sterilization of canal and to improve the treatment prognosis.
The concept of lesion sterilization and tissue repair (LSTR) therapy, which is a noninstrumentation endodontic treatment that employs a mixture of metronidazole, ciprofloxacin, and minocycline (3MIX) has been shown to be very effective in eliminating endodontic pathogens.[2] However, the LSTR therapy was evidenced to be successful but noninstrumentation endodontic treatment using 3MIX cannot substitute the conventional root canal filling, as a long-term therapy in primary teeth. Because performing the treatment of infected root canals with LSTR therapy alone without mechanical debridement and leaving the canal space is not justifiable and the left necrotic pulp that was left might act as nidus for future infection.[3] Hence, complete removal of radicular pulp and additional filling is logical to prevent bacterial proliferation in root canals. The completely filled canals were shown to have long-term success than unfilled or under filled canals.[4]
It was reported that complete sterilization of root canals can be achieved within 2 weeks after the use of triple antibiotic paste,[5] hence, leaving the medicament for longer duration in the canals may not be beneficial. Thus, a protocol of disinfection with antibiotic paste for suggested the period of 2 weeks followed by root canal filling might be useful in the successful management of chronically infected primary teeth.
Thus, a clinical study was carried out with an aim to compare the outcome between conventional pulpectomy technique and root canal disinfection protocol with 3MIX-MP paste before obturation.

BODY.METHODOLOGY:
The study design was approved by Institutional Ethical Committee; the purpose of study was explained to the parents and written informed consent was taken from parents before start of the study. A total of 60 primary teeth (molars and incisors) with chronic infection were included from 55 child patients, aged between 4 and 10 years, who attended the pediatric dentistry department from March 2014 to May 2015.
The primary teeth with chronic infection, gingival swelling or draining sinus, mobility, tenderness to percussion, periradicular radiolucency, and exhibiting not more than two-third of root resorption were included in the study whereas nonrestorable teeth with excessive root resorption of more than 1/2 of the root length, radiolucency involving underlying tooth crypt, medically compromised children, and children with any history of drug allergy were exempted from the study. The selected samples were randomly assigned into two groups, i.e., Group A – experimental group (n = 30) and Group B – control group (n = 30).
Commercially available chemotherapeutic agents such as ciprofloxacin (500 mg) (Ciprobay, Bayer, Germany), metronidazole (400 mg) (Flagyl, Sanofi-Aventis, Thailand), and minocycline (50 mg) (Minocin, Wyeth, China) tablets were procured, and their enteric coating was removed using sterile sharp knife, then these tablets were pulverized into fine powder using sterile porcelain mortar and pestle. These powdered drugs were transferred into three separate sterile glass containers, capped tightly, and stored in the refrigerator until its use. Just before use, each powdered drugs were weighed in the proportion of 1:3:3 (one part of ciprofloxacin, three parts of metronidazole, and three parts of minocycline) using electronic weighing machine and were mixed with propylene glycol and polyethylene glycol to form an ointment. Trairatvorakul and Detsomboonrat, Jaya et al., Cruz et al. also followed the similar protocol of preparation of 3MIX antibiotic paste.[367]
Baseline preoperative clinical and radiographical signs and symptoms were recorded. The teeth were anesthetized using 2% lignocaine with 1:80,000 adrenalin and isolated with rubber dam. Access opening was performed using round bur and both coronal and radicular necrotic pulp was extirpated using barbed broaches. Biomechanical preparation was done using k files from size 10–25. The root canals were chemically cleaned with 1% sodium hypochlorite solution and distilled water and dried with paper points. In Group A, 3MIX-MP paste placed in the pulp chamber and pressed with dampened cotton pellet and temporized with cavit. In Group B, formocresol dampened cotton pellet was placed in pulp chamber followed by closed dressing. The patients were recalled after 2 weeks for evaluation. The teeth which remained asymptomatic were obturated with zinc oxide eugenol cement mixed in the proportions of 1:1.5 (P: L) using lentulo spirals. Then, these teeth were restored with glass ionomer cement and further reinforced by placing stainless steel crowns.
Further, these treated teeth were reevaluated both clinically and radiographically at 3rd, 6th, and 12th month intervals postoperatively. At the time of revisits, the teeth were examined clinically for any signs of failure that includes a report of spontaneous pain, presence of swelling, sinus tract, and mobility and radiographic evaluation was done to check the resolution of radiolucency and signs of resorption. The teeth which were asymptomatic without pain, swelling, sinus tract and mobility were labeled as successful; further, the teeth were labeled as failures which exhibited increase in furcation radiolucency or development of root resorption which is abnormal for the age of the child.

BODY.RESULTS:
The treatment outcome was analyzed based on clinical and radiographic findings; the data were tabulated and subjected to statistical analysis using Fisher's exact test. The results were summarized as follows.
BODY.CLINICAL OBSERVATIONS:
Table 1 depicts the clinical evaluation which was carried out at 3rd, 6th, and 12th month intervals.
Table 1Comparison of treatment outcomes based on clinical findings in both test and control groups at different time intervals
In test group [Table 1], a total number of 30 teeth were subjected to pulpectomy procedure.
At 3rd month recall, 30 teeth were available for evaluation, out of which all the teeth were clinically asymptomatic, which accounted for 100% success.
At 6th month recall, 30 teeth were available for evaluation, out of which, 1 tooth exhibited pain, and it was extracted, thus the remaining 29 clinically asymptomatic teeth were accounted for 97% success.
Moreover, at the 12th month recall, 29 teeth were available for evaluation, out of which all the teeth were clinically asymptomatic; hence, total 29 teeth (97%) were considered successful.
In control group [Table 2], out of 30 teeth, two teeth showed exaggerated clinical signs and symptoms at initial follow-up of 2 weeks and were extracted; thus, a sample of 28 teeth was available for further clinical evaluation.
Table 2Comparison of treatment outcomes based on radiographic findings in both test and control groups at different time intervals
At 3rd month recall, 28 teeth were available for the evaluation out of which, 2 teeth exhibited exaggerated clinical and radiographic signs and symptoms were extracted; thus, the remaining 26 teeth accounted for 87% success.
At 6th month recall, 26 teeth were available for evaluation, out of which, 1 tooth exhibited pain, and it was extracted; thus, the remaining 25 clinically asymptomatic teeth were accounted for 83% success.
Moreover, at the 12th month recall, 25 teeth were available for evaluation; out of which, all the teeth were clinically asymptomatic; hence, a total 25 teeth (83%) were considered successful.

BODY.RADIOGRAPHIC OBSERVATIONS:
Table 2 depicts the radiographic evaluation which was carried out at 3rd, 6th, and 12th months interval.
In the test group [Table 2], all the 30 teeth showed furcation radiolucency at the start of the study. At 3rd month recall, 12 teeth (40%) exhibited bone regeneration, and 18 teeth (60%) showed static bone morphology; hence, it was considered as 100% radiographic success.
At 6th month recall, 14 teeth (47%) exhibited bone regeneration, and 15 teeth (50%) remained static, one tooth exhibited increase in bone loss along with clinical symptoms and was extracted. Thus, the percentage of radiographic success at the end of 6th month was 97%.
At 12th month recall, 16 teeth (53.3%) exhibited bone regeneration and 13 (43.3%) teeth remained static. Thus, the ultimate radiographic success was 97% (29 teeth) at the end of 1 year [Figure 1].
Figure 1Radiographic image of succeeded tooth. (a) Preoperative radiograph. (b) Immediate postoperative radiograph. (c-e) Radiographs at 3rd, 6th, and 12th month recalls
In the control group [Table 2], all the 30 teeth showed furcation radiolucency at the start of the study. Two teeth showed exaggerated clinical signs and symptoms at initial follow-up of 2 weeks and were extracted; thus, a sample of 28 teeth were available for radiographic evaluation.
At 3rd month recall, six teeth (20%) exhibited bone regeneration, and 17 teeth (57%) showed static bone morphology, 5 teeth exhibited increase in bone loss, out of which two teeth exhibited clinical symptoms were extracted, remaining 26 teeth were asymptomatic clinically; hence, they were kept under observation, but the percentage of radiographic success considered was 77% (23 teeth).
At 6th month recall, the available sample was 26, in which seven teeth (23.3%) exhibited bone regeneration and 13 teeth (43.3%) remained static, six tooth exhibited increase in bone loss, out of which one tooth was symptomatic clinically and was extracted and the remaining five teeth which were asymptomatic were kept under observation. Thus the percentage of radiographic success was 67% (20 teeth) at the end of 6th month [Figure 2].
Figure 2Radiographic image of failure tooth. (a) Preoperative radiograph. (b and c) Radiographs at 3rd and 6th month recalls
At 12th month recall, nine teeth (30%) exhibited bone regeneration, and five teeth (17%) remained static, 11 teeth exhibited increase in bone loss which were asymptomatic were kept under observation, Thus, the ultimate radiographic success considered was 47% (14 teeth) at the end of 12th month follow-up.
On comparison of both test and control group, at 3rd and 6th month recall higher number of teeth were radiographically successful and the statistical difference between groups was also significant whereas by the end of 12th month recall, the statistical difference was highly significant.


BODY.DISCUSSION:
The first topical antibiotic introduced to endodontics was Grossman's polyantibiotic paste in 1951 later many topical antibiotics have been introduced with varying combinations, few of those include septomixine forte; PBSC (Combination of Penicillin, Bacitracin, Streptomycin and Caprylate sodium), and clindamycin. However, none of these combinations has proven to be 100% successful in eradicating all the bacterial strains from the root canal system, thus the search for a right combination is still on.[89101112]
The concept of LSTR therapy or NonInstrumentation Endodontic Therapy introduced by Niigata university school of dentistry; Japan has gained reputation as it proved to attain 100% sterility in the root canal system.[2131415] They recommended a technique similar to pulpotomy where debriding only the pulp chamber of chronically infected primary teeth and placing medicament (ciprofloxacin, metronidazole, and minocycline) near the root orifice without preparing the radicular portion. The efficiency of medicament depends on the type of vehicle used. Cruz et al. suggested vehicles such as macrogol and propylene glycol (3MIX–MP) and demonstrated that these vehicles will carry the medicament deep into the dentinal tubules, thus aid in effective eradication of bacteria.[7]
Metronidazole (Nitroimidazole compound) due to its wide spectrum of antibacterial action against anaerobes (Ingham et al. 1975) gained importance as the 1st choice drug for triple antibiotic paste preparation.[1617] Metronidazole binds to the DNA and disrupts its helical structure and thus leads to rapid cell death. However, metronidazole even at higher concentrations could not eradicate all the bacteria thus indicating the necessity of some additional drugs to sterilize these lesions.[15] The two other antibacterial drugs, i.e. ciprofloxacin, and minocycline, in addition to metronidazole (3MIX) were added in an effort to eliminate all bacteria.[35615] The 2nd choice of drug ciprofloxacin is a synthetic fluoroquinolone with rapid bactericidal action. It inhibits the enzyme DNA gyrase of bacteria. It exhibits very potent activity against Gram-negative bacteria but very limited activity against Gram-positive bacteria. Most of the anaerobic bacteria are resistant to ciprofloxacin. Hence, it is often combined with metronidazole in treating mixed infections. The 3rd choice of drug was minocycline. It is a semisynthetic derivative of tetracycline, primarily bacteriostatic, inhibiting protein synthesis by binding to 30S ribosomes in susceptible organisms and exhibits broad spectrum of activity against Gram-positive and Gram-negative microorganisms.[10]
Although the existing literature has demonstrated that the LSTR technique as one of the successful technique for management of chronically infected primary teeth, the controversies aroused about the duration of therapeutic activity of the medicament and leaving the infected material in the radicular region. To address these above-said issues, present study planned where in treated tooth were revisited after 2 weeks for medicament removal and obturation; then, the obtained outcome was analyzed.
In the test group, teeth treated by above-mentioned method yielded 97% clinical success. This confirms the findings of Prabhakar et al.[18] wherein they followed a similar protocol of extirpation of both necrotic coronal as well as all accessible radicular pulp tissue but without subsequent obturation. However, observations of the present study were contradictory to those made by Gould, who reported clinical success of only 82.8% in one appointment pulpotomy like procedure over 16th month follow-up.[19] The high success rate in the present study may be attributed to complete removal of infected tissue, two visit pulpectomy procedure and providing indispensable apical seal by obturating the canals.
In the teeth pulpectomized using formocresol and ZnOE, the obtained clinical success rate was 83%. Although the difference was not statistically significant between the test and control groups, the test group yielded highest success, proving the sanctified properties of 3MIX-MP.
The obtained radiographic success in test group over 12th month follow-up was 97%, similarly Prabhakar et al.[18] also reported 100% radiographic success rate with similar pulpectomy like procedure. Whereas Nakornchai et al.,[2] Duanduan et al.[20] were reported a radiographic success rate in the range of 72%–77% and Trairatvorakul and Detsomboonrat[3] reported only 36.7% radiographic success at 24–27 months follow-up with pulpotomy like procedure of removing only necrotic coronal pulp. This variation in success rate might be attributed to the difference in study design, i.e., (using 3MIX-MP as an intracanal medicament and providing indispensible seal by obturation of the canals).
The obtained radiographic success for control group was 47%. In general, the reported success rate for conventional pulpectomy was 80%–86%.[2122] Where the difference might be attributed to the selection of severely mutilated chronically infected teeth as a sample in the present study.
The achieved success rate stated that chronically infected teeth require therapeutic approach for their management to upturn the success rate, to some extent the technique followed currently delivers.
The study underlines the importance of using stronger antibiotic protocol (3MIX-MP) to get rid of bacteria before obturating the root canal.
BODY.LIMITATIONS:
The limitations of the present study include difficult in carrying out obturation in case of tooth with extensive root resorption, extended duration of procedure and it is a two-appointment procedure.
However, we advocate further clinical studies with long-term follow-up till the period of tooth exfoliation to evaluate the pattern of root resorption and to know the consequences on the developing permanent tooth bud.


BODY.CONCLUSION:
The following conclusions were drawn within the limitations of this study:

Endodontic treatment of infected primary teeth treated with 3MIX-MP followed by instrumentation and obturation provided an excellent success when compared to conventional pulpectomy and noninstrumentational LSTR therapy
As the antibiotic resistance has become an emerging global problem these days, the development of multidrug resistance strains may decrease the success of this treatment modality. Hence, the value of mechanical debridement in ultimate success cannot be ignored.


BODY.FINANCIAL SUPPORT AND SPONSORSHIP:
Nil.

BODY.CONFLICTS OF INTEREST:
There are no conflicts of interest.

Question: Compared to conventional pulpectomy what was the result of mixture of metronidazole, ciprofloxacin, and minocycline (3MIX)-MP on clinical success?
Evidence: Although the difference in clinical success was not statistically significant,
Answer: no significant difference