Lesion Sterilization and Tissue Repair in Nonvital Primary Teeth: An In vivo Study.

AIM AND
OBJECTIVE: The aim of this study is to evaluate the clinical and radiographic success of endodontic treatment of nonvital primary teeth using lesion sterilization and tissue repair (LSTR) therapy.
MATERIALS AND METHODS: A sample size of 40 primary molars from 34 children of 3-10 years of age were selected for the study. Nonvital primary molars were treated using LSTR technique with a combination of antibacterial drugs comprising ciprofloxacin, metronidazole, and doxycycline with propylene glycol as vehicle. The procedure was completed in a single appointment. Only analgesics were prescribed postoperatively. Postoperative evaluation was done after 1, 3, 6, and 12 months.
RESULTS: Clinical signs and symptoms got resolved in the 1st-month follow-up itself and continued in the subsequent visits. Radiographic evaluation showed a gradual improvement in success rates through the 12-month follow-up period.
CONCLUSION: LSTR technique can be considered as an alternative treatment option for nonvital primary teeth avoiding a course of systemic antibiotics to the children. Doxycycline can be used in the drug combination instead of minocycline which also gives higher clinical and radiographic success. Copyright:

Introduction

The ultimate goal of pediatric dentistry is to ensure that the best of oral health care is made available to all children and people with special health-care needs. The prevalence of dental caries remains high in spite of increased awareness and modern modes of caries prevention. Endodontic treatment of primary teeth with necrotic pulps is routinely done in dental practices. This often presents a challenging task to the clinician, due to the typical primary tooth morphology (tortuous root canals, presence of multiple accessory canals, ramifications, and ample medullary bone spaces that favor dissemination of infection).[123] In addition to that, obtaining a hermetic seal is difficult due to the lack of apical closure following physiologic root resorption owing to the proximity of the developing permanent tooth germ to the roots of the primary teeth. A further challenge presented to the dentist in rendering effective endodontic treatment is the behavior management of uncooperative children.[4]

Numerous measures have been described to reduce the number of microorganisms using instrumentation techniques, irrigation regimens, and intracanal medicaments. The complexity of root canals, however, precludes complete elimination of bacteria from the root canal system by instrumentation alone.[5] Hence, local application of antibacterial drugs represents one of the methods of eradicating bacteria in the root canal treatment. Due to the complexity of root canal infections, it is unlikely that any single antibiotic could result in effective and predictable disinfection of all canals. More likely, a combination would be needed to address the diverse flora encountered. A combination of antibiotics would also decrease the likelihood of the development of resistant bacterial strains.[6] Hoshino et al. in their in vitro studies stated that a combination of ciprofloxacin, metronidazole, and minocycline was able to disinfect infected root dentine. Sato et al. found that this combination was sufficient to disinfect infected root dentine in situ.[7]

In 1990, the Cariology Research Unit of Niigata University School of Dentistry has developed the concept of lesion sterilization and tissue repair (LSTR) therapy that employed a mixture of antibacterial drugs for disinfection of oral infections, including dentinal, pulpal, and periapical lesions. Repair of damaged tissues can be expected if lesions are disinfected. Based on this concept, Takushige et al. in 2004 conducted a study on endodontic treatment of primary teeth using 3Mix-MP containing metronidazole, ciprofloxacin, and minocycline with macrogol (M) as the ointment base and propylene glycol (P) as the carrier.[8] Following this study, newer combinations of drugs are being tried nowadays to improve the efficacy of this procedure.[910]

Hence, the aim of this study was to assess the efficacy of triple antibiotic paste containing ciprofloxacin, metronidazole, and doxycycline with propylene glycol as obturating material in pulpectomy procedure of nonvital primary teeth.

Materials and Methods

The children aged 3–10 years of both the sexes visiting the Outpatient Clinic of the Department of Paedodontics and Preventive Dentistry, Sree Balaji Dental College and Hospital, Pallikaranai, were considered eligible for the study. Personal details such as name, age, sex, address, contact number, a complete medical history, and drug history were recorded in a pro forma by the chief examiner (A). With the data obtained, five children with known systemic illness or under antibiotic coverage for the past 2 weeks were excluded from the study. A thorough clinical examination was performed and preoperative radiographs were taken using standard X-ray holders and the findings were recorded in the pro forma. A total of 52 teeth which fulfilled the inclusion criteria [Table 1] were selected for the study. Ethical committee clearance was obtained from the Institutional Ethical Committee and the trail has been registered in Clinical Trials Registry – India [Registration number-CTRI/2016/07/007120]. Parents of these selected children were informed/explained about the study and written informed consent was obtained from the parents before the study.

Table 1

Inclusion criteria

Criteria	Criteria Description
Clinical criteria	Pain on mastication
	Intraoral abscess or fistula
	Mobility other than physiological mobility
	Restorable
Radiographic criteria	Root length >50%
	Furcation involvement not extending to the developing tooth germ

Preparation of antibacterial mix

Commercially available chemotherapeutic agents such as ciprofloxacin, metronidazole, and doxycycline were used in this study. After removal of enteric coating, the drugs were pulverized, kept separately in tightly capped dark glass containers to prevent exposure to moisture and light. These powdered drugs were taken in the ratio of 1:1:1 (one part of ciprofloxacin, metronidazole, and doxycycline) mixed with propylene glycol to form an ointment just before use.

Clinical procedure

Clinical procedure was done by the chief examiner (A). After obtaining adequate anesthesia using 2% lignocaine hydrochloride with adrenaline 1:80,000, isolation of the selected tooth was achieved using a rubber dam. Previous restoration if present was removed. Access opening was done and coronal pulp if present was removed using a spoon excavator. Canals were located and the patency of the canals was checked with size 10 K-file. Canals were cleaned up to size 20 H-file. Canals were irrigated using normal saline. To visualize the orifices clearly, the pulp chamber was dried using cotton pellets. Canals were dried using size 15 paper points. Freshly prepared Trimix antibiotic paste was placed on the pulpal floor to form a thin layer. IRM was then placed to seal the cavity and stainless steel crown was placed as final restoration [Figure 1]. Treatment procedure was completed in one visit. Postoperatively, only analgesics were prescribed.

Figure 1

Schematic representation of tooth being treated with lesion sterilization and tissue repair therapy: (1) IRM cement, (2) 3Mix Paste, (3) stainless steel crown

Postoperative clinical follow-up was done after 1 month to evaluate for the presence or absence of pain, abscess, and mobility and recorded in the pro forma. The same clinical criteria were evaluated and IOPA radiographs were taken at 3, 6, and 12 months and recorded in the pro forma by examiner A. Postoperative radiographic evaluation was done by two examiners, examiner B and examiner C and recorded in the pro forma. 40 teeth from 34 children who turned up for the complete follow-up schedule were considered as samples for the study. Clinical and radiographic evaluation criteria were given in Table 2.

Table 2

Evaluation criteria

Criteria	Criteria Description
Clinical evaluation	Presence or absence of
	Pain
	Abscess
	Mobility
Radiographic evaluation	The amount of furcation radiolucency in comparison to preoperative radiograph
	Regeneration - decrease in radiolucency
	Static - remains the same
	Increase - increase in radiolucency

Results

The results given by the examiners A, B, and C were tabulated and subjected to statistical analysis using SPSS software and Chi-square test was used to compare different groups. The interexaminer reliability value was calculated using Kappa statistics for examiners B and C. It showed a strong agreement between the examiners. P ≤ 0.05 was considered for statistical significance.

Preoperatively, all the 40 teeth had pain on mastication. Follow-up after 1 month showed the complete absence of pain in all the 40 teeth which continued in the 3, 6, and 12 months reviews. The result was statistically significant with P = 0.000 [Table 3].

Table 3

Results - clinical evaluation

Clinical evaluation	Pain		Abscess		Mobility
	Present	Absent	Present	Absent	Present	Absent
Preoperative	40	0	40	0	40	0
1 month	0	40	0	40	0	40
3 months	0	40	0	40	0	40
6 months	0	40	0	40	0	40
12 months	0	40	0	40	0	40
χ2	200.00
P	0.000*
Success (%)	100

*Statistically significant

Preoperatively, abscess was present in relation to all the 40 teeth. After 1 month, there was no abscess present in all the 40 teeth. Follow-up after 3, 6, and 12 months also showed complete resolution of abscess which was statistically significant with the P = 0.000 [Table 3].

Preoperatively, all the 40 teeth were mobile. In all the 40 teeth, mobility was not present in the 1st-month follow-up itself. Follow-up after 3, 6, and 12 months also showed complete absence of mobility with a significant P value of 0.000 [Table 3].

In comparison with the preoperative radiograph after 3 months by two examiners, a mean of 56.3% of the samples showed decrease in radiolucency, 33.7% of the samples observed to be static, and 10% of the samples showed an increase in radiolucency. After 6 months, 77.5% of the samples showed decrease in radiolucency, 13.75% of the samples were considered to be static, and 8.75% of the samples showed an increase in radiolucency. After 12 months, 80% of the samples showed decrease in radiolucency, 12.5% of the samples showed a static condition, and 7.5% of the samples showed an increase in radiolucency [Table 4].

Table 4

Results - radiographic evaluation

Radiographic evaluation	Mean
	3 months	6 months	12 months
Regeneration (%)	56.30	77.50	80.00
Static (%)	33.70	13.75	12.50
Increase in radiolucency (%)	10.00	8.75	7.50

Discussion

The success of pediatric endodontics depends on the mechanical debridement and subsequent filling which is greatly influenced by the presence of multiple tortuous and accessory canals.[11] Conventional pulpectomy procedure removes the microbes present in the superficial layer of infected root canal walls leaving some residual microbes in deeper layers of dentin which may leak out into the periapical region.[12] Hence, sterilization of the root canals and periradicular region should be achieved to ensure a successful outcome which results in good healing of periapical diseases.[13] LSTR technique can help us to overcome all the above-said problems with a combination of antibiotics and a vehicle, propylene glycol. Commonly used combination of drugs in LSTR therapy includes ciprofloxacin, metronidazole, and minocycline with propylene glycol and macrogol as vehicles. Newer combinations of drugs are being tried nowadays to improve the efficacy of LSTR therapy. In our study, we used a different combination of drugs replacing minocycline with doxycycline as it is easily available, economical and is also having the same spectrum of activity as that of minocycline.

Regarding methodology, Prabhakar et al. compared LSTR technique with and without instrumentation and showed a 100% and 83.3% clinical and radiographic success in teeth with instrumentation and 93.3% and 36.7% clinical and radiographic success in teeth without instrumentation.[14] Hence, we removed the accessible pulp tissue from the root canals in our study. Originally, the ratio of each drug suggested by Hoshino was 1:3:3 and later the ratio of 1:1:1 was considered adequate by the same author which was followed by Siriruk Nakornchai in his study on LSTR therapy.[15] Thus, the ratio of each drug used in our study was 1:1:1. Routinely, a medication cavity would be prepared at the root canal orifices in LSTR technique for the placement of Trimix paste. In our study, the medication cavity was not prepared as in a comparison study by Siriruk Nakornchai who showed a good success rate.[15] Postoperatively, only analgesics were prescribed and no systemic antibiotics were given thus avoiding a course of systemic antibiotics to children.

We could see a 100% clinical success throughout the postoperative follow-up period of our study [Figure 2] which was similar to the success rate given by Prabhakar et al.[14] Gould JM suggested that the more the infected tissue removed, the greater are the ultimate chances of the success.[16] Thus, the higher success rate in our study could be attributed to the removal of necrotic radicular pulp by instrumentation and irrigation.

Figure 2

Clinical evaluation: (a) Preoperative clinical picture (b) postoperative clinical picture (12 months)

Postoperative radiographic evaluation was done by examiners B and C. The evaluation was based on the amount of furcation radiolucency seen in postoperative radiographs in comparison with the preoperative radiograph which was categorized as decrease in radiolucency (regeneration of bone) [Figure 3a] or static condition (no change) [Figure 3b] or increase in radiolucency (increased bone loss) [Figure 3c]. The mean value of teeth with regenerative changes increased, static condition decreased, and increase in radiolucency decreased in 3, 6, and 12 months follow-up. This shows a gradual increase in radiographic success rate of our study. These values are comparable with the results given by Prabhakar et al. who showed an increase in regeneration from 80% to 83.3%, static condition decreased from 20% to 16.7%, and no sample seen with increase in radiolucency in 6 and 12 months follow-up.[14] In our study, increase in radiolucency was seen in three samples (7.5%). This can be attributed to the fact that radiolucent areas were often seen in samples with erupting succedaneous teeth and there might be a superimposition of the follicle of the erupting tooth and furcation radiolucency. Reduction of root length was also seen with those three teeth, but clinically, they were asymptomatic.

Figure 3

Radiographic evaluation: (A) Preoperative radiograph (B) postoperative radiograph (12 months) (a) Regeneration. (b) Static. (c) Increase in radiolucency

Sterilization of infected root canals and regeneration seen in the furcation region can be explained by the removal of infected pulp tissue from the root canals and properties of each drug in the antibacterial combination. Irrespective of using doxycycline in the drug combination, we could get good clinical and radiographic success rates comparable to studies using the regular combination of drugs and studies using different combinations of drugs. Thus, doxycycline can be effectively used in the drug combination of LSTR therapy.

No allergic reactions have been reported with the placement of these drugs as intracanal medicament as for as our study is concerned. More studies with long-term follow-up periods are required to confirm the results of this study. Hence, within the limitations of our study, LSTR technique can be considered as an alternative treatment option for nonvital primary molar teeth avoiding a course of systemic antibiotics to the children and doxycycline can be used in the drug combination instead of minocycline which also gives higher clinical and radiographic success.

Conclusion

Based on the results of this present study, we conclude that the success rate for clinical evaluation criteria such as pain, abscess, and mobility is 100% in 1, 3, 6 and 12 month follow-ups and on radiographic evaluation, 80% of the samples showed decrease in radiolucency, 12.5% of the samples showed a static condition, and 7.5% of the samples showed an increase in radiolucency after 12 months. Therefore, LSTR technique can be considered as an alternative treatment option for nonvital primary molar teeth avoiding a course of systemic antibiotics to the children. We also add that doxycycline can be used in the drug combination instead of minocycline which also gives higher clinical and radiographic success.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.