Bioceramic putty versus calcium hydroxide for direct pulp capping in immature permanent molars: a 12-month randomized controlled trial

INTRODUCTION

Diagnosis and treatment of immature permanent molars, especially carious and post-traumatic ones, are challenging in clinical practice. Without treatment, pulpitis and necrosis can lead to apical periodontitis, hindering root development and decreasing the likelihood of teeth remaining in the oral cavity. Preserving pulp vitality to ensure normal root growth is the primary objective [1]. In order to ensure normal root development, vital pulp therapy was focused on immature teeth without evidence of irreversible pulpitis. However, with the passing time, the idea of vital pulp therapy was extended to include immature permanent molars with irreversible pulpitis [2]. Adults and children respond to dental pulp differently. When compared with mature teeth, the pulp of immature teeth exhibits a higher success rate for vital pulp treatment, because of the pulp’s innate defenses and variable vascularity, which strengthen the pulp’s resistance to bacterial invasion in long-term [3].
Permanent first molars (PFMs) are the most essential teeth in the dental arch, which typically erupt around the ages of 6 and 7 years. However, at this age, there is an increased risk for PFM’s dental caries. A number of reasons for dental caries in these teeth include high-carb diet, inadequate oral hygiene, and parental ignorance about PFM eruption timing [4]. Moreover, dental decay is more common in children aged between 6 and 18 years, as it was reported to affect 60-90% of school-age children [5].
Therefore, different pulp capping techniques, such as indirect and direct pulp capping, are necessary due to pinpoint, accidental, and carious pulp exposure. These procedures aim to maintain not just the tooth’s pulp vitality, but also its functions against different injuries, such as carious or traumatic [6].
Direct pulp capping (DPC) might be the best procedure when pinpoint (1 mm or less) pulp exposure occurs. It has several advantages, including preserving pulp’s vita­lity to avoid complicated procedures in an immature permanent molar with a large open apex, reducing the cost of treatment, allowing odontoblasts to form dentin bridge, permitting continuous root formation, and maintaining pulp function [7]. Its success does not only depend on the usage of a bio-active capping material, but also on some variables, including patient’s age, pulp assessment, root development, exposure site and size, bleeding management, and type of filling [8]. Therefore, the materials used for pulp capping have been undergoing continuous development and investigation. Over the years, with differing degrees of efficacy, many chemical and biological components were employed as well as various materials were utilized as DPC, such as calcium hydroxide (CH), propolis, stem cells, new endodontic cement, endogen, and mineral trioxide aggregate (MTA) [9].
Previously, CH has been considered the ideal ma­terial for DPC in young permanent teeth, revered as the gold standard [10] due to a number of advantages, including its high pH and good antibacterial activity [11]. For a considerable amount of time, CH has been shown to be reasonably priced, safe, and successful in dental pulp treatment, e.g., pulpotomy, and its efficacy in the­rapeutic treatment has been confirmed [12]. However, there are a number of evident drawbacks associated with calcium hydroxide, such as development of capillary flaws within the dentin bridge, high oral fluid dissolution, and low mechanical resistance [13]. Taking the above into consideration, with the use of bio-active cement, the prognosis for pulp capping has significantly improved. Even though MTA and Biodentine demonstrated an excellent rate of success, errors in the ratio of powder to liquid can negatively impact their qualities, causing challenges in handling [6].
Therefore, one of DPC materials recommended as both efficient and effective is bioceramic (BC). BC materials were introduced into dentistry, because they are chemically stable, bio-compatible, and inorganic, demonstrating osteogenic and odontogenic properties. Also, they possess high mechanical and biological characteristics [14].
Furthermore, BCs have several advantages, including homogeneity in consistency, avoiding material wasting, they are easily condensable, can be delivered to inaccessible areas, do not cross-contaminate, and are hydrophilic in nature, which makes them less technique sensitive, and moisture and blood contamination resistant [15].

OBJECTIVES

This randomized controlled trial aimed to compare the effectiveness of BC putty and CH as DPC agents in immature PFMs with carious pinpoint pulp exposure occurring in the occlusal cavity. This comparison was based on clinical and radiographic assessments over a 12-month follow-up period.

MATERIAL AND METHODS

Study setting and population

The current study was performed among 36 children, who were chosen from outpatient clinic of the Department of Pedodontics and Oral Health, Al-Azhar University’s Faculty of Dental Medicine (Cairo-Boys).

Ethical consideration and consent form

Before starting of this trial, the study protocol was approved by the Ethics Committee, Faculty of Dental Medicine (Cairo-Boys), Al-Azhar University, Egypt, with code number of 991/82. Informed consent forms were signed by parents or guardians, and a comprehensive information document in plain, simple language (Arabic) was delivered beforehand.

Inclusion criteria

Clinically, cooperative children, with good oral hygiene, aged between 6-9 years, who had vital immature PFMs with occlusal caries, were enrolled in the present trial. After removal of caries, only teeth showing carious pinpoint exposure (1 mm or less) and occurring in the occlusal cavity were selected.
Radiographically, included teeth were assessed for caries extension to be more than half of the thickness of the dentin, but not rendering the tooth as non-restorable. Additionally, no signs of internal or exterior root resorption, intact the lamina dura, and the furcation or periapical region devoid of radiolucency.

Exclusion criteria

PFMs with a large pulp exposure (more than 1 mm), which after carious tissue removal showed any clinical signs or symptoms of non-vital pulp were excluded. Also, patients with bad oral hygiene, systemic diseases, such as uncontrolled diabetes, immunosuppressive medication, or blood disorders as well as patients receiving chemotherapy or radiotherapy were excluded.

Patient enrollment

In line with the methodology depicted by Elhag et al. [9], who compared the success rate of DPC using CH and acemannan, 36 patients were enrolled and divided into two groups. Initially, 50 patients presenting with deep caries affecting their immature PFMs were examined clinically and radiographically, out of whom, 14 did not meet inclusion criteria. Finally, 36 patients with a carious pinpoint (1 mm or less) pulp exposure in an occlusal cavity, which occurred during treatment, were enrolled in the study.

Blinding and assessors criteria

Here, double-blinding was employed, so neither the patient nor assessors knew the material administered. Four dentists were qualified and trained as assessors before the study in order to precisely select carious lesions suitable for inclusion, which could be monitored by the principal investigator. The assessors were not involved in restoration procedures.

Randomization process

Depending on the capping material used, patients were randomly assigned at a 1 : 1 allocation ratio within both groups (n = 18). In group 1 (control), patients were treated with DPC using CH material, while in group 2, patients were treated with DPC using BC material.

Sequence generation

Computer sequence creation (www.random.org) was applied to generate a sequence for patient numbers from 1 to 36. Sample size was specified, a two-column format was instructed, and the sequence generator symbol was chosen from the main page. After that, the outcome was duplicated for groups 1 and 2 using participants’ numbers assigned at random (18 numbers per group).

Allocation concealment

Prior to applying the appropriate substance, the guardian of every patient selected a closed white packet containing the sequence generation number. To ensure allocation concealment, paper charts within the unopened white envelopes were folded multiple times in order not to reveal their contents.

Treatment procedure

After obtaining participants’ medical history and clini­cal investigation, a pre-operative preapical X-ray was done according to ADA guidelines [16]. First molars were treated under local anesthesia using 2% mepivacaine with epinephrine 1 : 100,000 (mepivacaine, Alexandria Co. For Phar­maceuticals, Alexandria, Egypt), and nerve block or infiltration techniques. Application of rubber dam isolation to the nominated tooth (Ivory system) was performed. Following that, all carious dentin tissues were removed according to the American Association of Endodontists (AAE) guidelines [2]. When there was a carious pinpoint exposure (1 mm or less) on the occlusal cavity, the exposure sites were rinsed with sterile saline to remove debris. A cotton pellet wetted with 2.5% sodium hypochlorite (Hyposol; Prevest DenPro Limited, Jammu, India) was applied for 1 to 2 minutes to stop pulp’s bleeding and clean the exposed area. Next, 2 ml of saline was used to remove any remaining sodium hypochlorite. The tooth was dried with a cotton pellet, and either capping paste BC (Well-Root PT, Vericom, Korea) or chemical cure CH (Dycal^®, Dentsply, USA) were applied for the selected group. A resin-modified glass ionomer liner (Vitrebond, 3M/ ESPE) was placed over the pulp capping paste as a temporary restoration. After 1 week, a layer of temporary restoration was replaced by composite filling.

Clinical and radiographic examinations

At 3-month, 6-month, and one year post-treatment follow-up visits, assessments were conducted by the assessors, who were not involved in restoration procedures, nor knew the materials utilized. A periapical radiograph was taken at each follow-up visit (3, 6, and 12 months) to evaluate the continuous root development, root resorption, and signs of peri-radicular bone destruction. Clinical examinations were performed at every follow-up time point to evaluate the post-operative pain, sensitivity, vitality, and tenderness (Figures 1A-C and 2A-C).

Criteria for successful treatment

Intra-oral examination: Treatment was deemed successful if patient did not experience pain (neither with percussion nor spontaneous). Moreover, vitality testing was positive throughout the entire period of follow-up (one year) [1].
Radiographic examination: Radiographically successful treatment was considered when root formation and maturation were observed, with no evidence of internal or external root resorption or periodontal widening of ligament [1].

Statistical analysis

Statistical analysis was carried out using SPSS Statistics version 21.0. Normality of distribution was examin­ed with Kolmogorov-Smirnov test, while Student’s t-test was utilized to compare patients’ ages. Efficacy of both materials was investigated using Cochran’s Q test at different follow-up time points. Fisher’s exact test was employed to compare the expected and observed proportions of success/failure rates amongst both tested groups. A significance threshold was established with p < 0.05.

RESULTS

Demographic data

There were 18 participants in each group. The mean age for both the groups was similar, with the mean age of 8.0 ± 0.8 years in the BC group, and the mean age of 8.1 ± 0.7 years in the CH group (p = 0.825). In terms of gender distribution, there were 9 females (50.0%) in the BC group and 10 females (55.6%) in the CH group (Table 1).

Success rates of the two groups at different time intervals

The success rate in the BC group remained consistently high (94.4%), with 17 patients classified as successful at each follow-up visit. Moreover, the BC group consistently had only 1 unsuccessful patient at each time point. In contrast, the success rate in the CH group declined from 88.9% (16 patients) at 3 months to 83.3% (15 patients) at 6 months, and further to 77.8% (14 patients) at 12 months post-treatment. The number of unsuccessful cases in the CH group increased from 2 at 3 months to 3 at 6 months, and 4 at 12 months. Overall, there were non-significant variations in the success rates amongst the BC and CH groups at any of the assessed time intervals (p = 1.000 at 3 months, p = 0.60 at 6 months, and p = 0.34 at 12 months) (Table 2 and Figure 3).

Effect of time on success rates of both groups

The success rates for the BC group remained consistently high (94.4%), with 17 patients classified as successful, and only 1 unsuccessful patient at each follow-up visit. However, there was a non-significant (p = 0.23) decrease in the success rate of CH group over time, with a higher number of failures observed at 12 months compared with 3 and 6 months post-treatment (Table 3 and Figure 4).

DISCUSSION

Maintaining pulp vitality is important for teeth to survive over an extended time. The presence of deep caries and its subsequent therapy can damage the vitality of the tooth’s pulp [17]. Therefore, direct and indirect pulp capping are suggested as treatment strategies to preserve the vitality of the pulp [18]. A more conservative therapy approach called, DPC, is based on the idea that a substance with biological activity applied directly to the pulp exposure can identify the pulpal reaction, and lead to the formation of reparative dentin to maintain pulp vitality [19]. Moreover, DPC involves prompt sealing of the pulpal wound using a regenerative material in order to treat a critical pulp that was mechanically or bacteriologically exposed [20]. In order to effectively seal the pulp exposure and stop bacterial leakage, the best regenerative material should stimulate the synthesis of reparative dentin. If successful, this process may eliminate the requirement for more involved, expensive, and invasive root canal therapy [21].
In this study, DPC procedure was used for the preservation of pulp vitality in PFMs of children aged 6-9 years, due to a higher risk of becoming carious, as it could be mistakenly identified as a deciduous molar (because it is the first permanent molar to erupt in the mixed dentition stage) as well as due to its importance in the dental arch, as it is considered the key to occlusion [4].
For a long period of time, CH has been considered the most common material for pulp preservation procedures, including pulpotomy, DPC, and indirect pulp capping [22]. According to previous reports, CH is bio-compatible enough to maintain pulp tissues’ vitality without impairing their functions, and to encourage the development of hard tissues. Despite limited quali­ties, this material has been the gold standard for pulp capping for over forty years, showing reasonable clini­cal outcomes [6]. Therefore, in the present trial, CH was chosen as the material used in the control group. However, compared with conventional calcium hydro­xide, BC putty produced superior outcomes in pulp capping, although receiving less interest [14]. Recently, BC showed to be a great choice material for DPC due to its inorganic, osteogenic, and odontogenic characteristics as well as chemical stability and bio-compatibility. BC putty has excellent biological and mechanical properties [23]. Additionally, it induces the creation of a whole reparative dentin bridge with odontoblast-like cells, demonstrating its capacity to promote dentin regeneration and tissue healing [14].
Furthermore, teeth with carious pinpoint exposure in the occlusal cavity rather than the proximal one, were selected as they are more permeable, difficult to isolate from debris, and more difficult to fully excavate caries, to apply capping material, and seal the cavity. For these reasons, occlusal exposure was related to higher survival success than proximal site exposure [24]. Additionally, the adoption of a good sealing occlusal filling that might avoid micro-leakage, accurate diagnosis, and whole removal of soft dentin, could play a role in the favorable clinical and radiographic results of the present study [25].
Here, a 2.5% sodium hypochlorite was used, as it has several advantages, such as antimicrobial properties, ability to clean contaminated dentin debris around the exposure area, and capacity to prevent the development of a fibrin clot [26].
A major contributing factor to pulp capping failure is the existence of bacteria and the sealing ability of temporary restoration against bacterial invasion [10]. Therefore, resin-modified glass ionomer restoration as a temporary restoration was applied after capping agent placement for 1 week, as it has some benefits, such as adherence to the tooth structure, offering excellent marginal seal, depriving the bacteria from the oral cavity, fluoride release, bio-compatibility, and simple handling of light-induced polymerization [27].
The aim of the current randomized clinical controlled trial was to evaluate CH’s and BC’s clinical and radiographic responses to DPC of immature PFMs over the course of a one-year follow-up. The outcomes showed a higher success rate of the BC group (94.4%), while that of the CH group (77.8%) revealed no significant diffe­rences between both the groups. This difference could be attributed to the ability of BC material to encourage the production of mineralized tissue, and to sustain vitality of the pulp compared with CH [14].
Another explanation for this difference may be the tunnel flaws in the CH-stimulated reparative bridges, but their dissolution is difficult [28]. On the other hand, because BC stimulates the growth of human dental pulp cells and encourages the development of hard tissue at the pulp exposure locations, it was discovered to have strong sealing capability along with favorable biological qualities. BC may be more suitable for DPC therapy due to these qualities [29]. Such outcomes are in line with Rao et al. [12], who indicated that CH has higher failure rates than BC, when utilized as DPC materials.
Regarding BC, the released CH by-product is comparatively stable and encourages dentin bridging; it may be able to repair the damaged pulpal tissue in contrast to pure CH that degrades over time. Compared with that caused by CH, inflammation triggered by these compounds is transient, milder, and less widespread [7]. A previous investigation found that all teeth treated with BC underwent the development of reparative dentin bridges over six weeks, and the majority of these bridges were free of tunnel deficiencies [30].
As for CH, it keeps the pulp alive, permits the production of reparative dentin, protects the pulp from damaging stimuli, and contains antibacterial proper­ties [31]. CH’s alkaline pH and bio-compatible character, in particular, indicate re-mineralization at the pulp-dentine interface. Due to inflammatory reaction against the irritating character of CH, hard tissue deve­lopment occurs, which is why CH acts as a pulp capping material [32].
The success rates described in the present study are in line with those from a study by Çalışkan et al. [33], who found that the success rate after DPC using CH was 77.6%. However, it was not similar to that described by Kundzina et al. [34], where the pulp success rate was 52% after DPC using CH. The lower success rate in that trial can be attributed to the longer period of follow-up (36 months).
Furthermore, it was found that pulp cell growth was stimulated by BC. This might be because BC is a putty that is ready for utilization, and does not need to be mixed; its main ingredients are calcium silicates, calcium phosphate, zirconium oxide, and tantalum oxide. Additionally, BC contains fine hydrophilic calcium silicate [35]. Calcium silicates react with H2O to create calcium silicate hydrogel and calcium hydroxide, when the material comes into touch with naturally occurring wetness in the dentinal tubules. CH then combines with calcium phosphate to generate hydroxyapatite and H2O. H2O is intended to initiate the next chemical cycle [36].
A research by Liu et al. [37] assessed the impact of BC as a DPC agent. The authors found BC to be highly compatible with pulp tissues and stimulating the growth of dental pulp cells to develop reparative dentin bridges.
In order to better understand the formation of dentin bridge, future studies with bigger sample size, follow-up time of more than one year, and histological investigations, are recommended.

CONCLUSIONS

Within the limitations of this study, we can conclude that BC putty and CH are similarly effective for DPC of permanent teeth with pinpoint pulp exposure in the occlusal cavity.

Disclosures

1. Institutional review board statement: This study was approved by the Ethics Committee, Faculty of Dental Medicine (Cairo-Boys), Al-Azhar University, Egypt (approval number: 991/82).
2. Assistance with the article: None.
3. Financial support and sponsorship: None.
4. Conflicts of interest: The authors declare no potential conflicts of interest concerning the research, authorship, and/or publication of this article.

References