Clinical influencing factors of vital pulp therapy on pulpitis permanent teeth with 2 calcium silicate-based materials: A randomized clinical trial

Abstract

Background:

Compared with traditional root canal therapy (RCT), vital pulp therapy (VPT) is a personalized and minimally invasive method for the treatment of pulpitis caused by dental caries. However, there are still no clear guidelines for VPT because high-quality randomized clinical trials are scarce. This prospective cohort study evaluated the clinical efficacy of VPT with the light-curable calcium silicate-based material TheraCal LC (TH) and bioceramic material iRoot BP Plus (BP) in reversible and irreversible pulpitis permanent teeth with carious exposures.

Methods:

115 teeth with reversible or irreversible pulpitis caused by deep care were randomly divided into 2 groups. TheraCal LC and iRoot BP Plus were used for the pulp capping. Direct pulp capping (DPC), partial pulpotomy (PP) and full pulpotomy (FP) were performed based on observation of the exposed pulp. Postoperative discomforts were enquired and recorded via follow-up phone calls. Clinical and radiographic evaluations were performed 3, 6, and 12 months postoperatively.

Results:

The overall clinical success rate in the first year was 90.4% (47/52) in both groups. The TH group required less operating time, showed lower levels of pain, and had shorter pain duration post-operative (P < .001). According to the binary logistic regression model, preoperative pain duration was significantly correlated with the prognosis of VPT (P = .011).

Conclusion:

VPT with TheraCal LC and iRoot BP Plus in pulpitis permanent carious teeth both achieved good clinical outcomes, and TheraCal LC can be easily operated for clinical use. Preoperative pain duration of the affected tooth might have a significant correlation with the prognosis of VPT.

1. Introduction

Vital pulp therapy (VPT), which includes indirect pulp capping (IPC), direct pulp capping (DPC), partial pulpotomy (PP) and full pulpotomy (FP), is a treatment procedure based on the capping of asymptomatic vital pulp tissue with biocompatible materials to maintain the vitality of all or part of the dental pulp.^[1] For a long time, VPT has been recommended only in teeth with open apices in young patients or pulp exposure produced mechanically or traumatically, because the outcome of VPT performed on cariously exposed pulps of mature teeth was unpredictable.^[2] But with the development of pulp capping materials, aseptic technology and microscopic magnification technology, more recent studies have reported successful outcomes when VPT was performed in curiously exposed pulps of vital teeth that presented with signs and symptoms of irreversible pulpitis and even apical periodontitis.^[3,4] Compared to root canal therapy (RCT), VPT is a minimally invasive method for the treatment of pulpitis. However, there are still no clear guidelines regarding VPT, because high-quality randomized clinical trials with large sample sizes and long follow-up periods are scarce.^[5]

Among these factors, pulp capping materials play an important role in the success of VPT. The materials to be applied should have the ability to form reparative dentin, impermeability, biocompatibility, and antibacterial effects.^[6] iRoot BP Plus (BP) is a bioceramic material based on calcium silicate, which has shown similar results to Mineral Trioxide Aggregate (MTA) in in vivo experiments.^[7] iRoot BP Plus has been proven to possess good biocompatibility, the ability to induce mineralization and odontoblast differentiation, and is widely used for pulp-capping, permanent root canal repair, apical microsurgery, and retrograde filling in clinical practice.^[7,8] Nevertheless, poor adhesion to the tooth structure, difficulty in handling, and high costs have been reported as major drawbacks.^[8]

VPT has not been widely adopted in clinical practice, and the uncertain prognosis and relatively strict operating requirements might be possible reasons. Therefore, it is necessary to identify more convenient and easily operated materials for clinical use. TheraCal LC (TH) is a calcium silicate-filled light-cured resin-modified material with high calcium-releasing ability and low solubility.^[9] As a result of the addition of resin monomers that are hardened with a light source, the hardening properties are strengthened, and problems related to the composite resin binding to the underlying system can be prevented.^[9] Despite its high physical properties, low resolution, and ease of use, whether it would cause cytotoxic effects because of the resin monomer content is a new concern.^[10]

Based on the above background, the purpose of our study was to evaluate the clinical success rate and factors influencing VPT in permanent teeth with reversible or irreversible pulpitis caused by caries. In addition, the other important objective of this study was to observe the clinical application results of resin content (TheraCal LC) and bioactive (iRoot BP Plus) calcium silicate pulp capping materials. These results will facilitate a deeper understanding of VPT and calcium silicate-based materials for clinical applications.

2. Materials and methods

2.1. Study design

This study was a single-blind, non-inferiority, randomized, controlled trial comparing the clinical results of 3 VPT techniques (DPC, PP, and FP) using 2 calcium silicate-based materials (BP and TH). IPC was not included in this study because the pulp was not exposed to IPC, and pulp status could not be assessed by direct inspection with a microscope. Patients who had symptomatic deep carious teeth (including both mature and immature permanent teeth) and visited the Department of Stomatology, Shenzhen Longgang Otolaryngology Hospital, from July 2020 to July 2021 were recruited for the study. The study protocol was approved by the Institutional Ethics Committee (Ethics Committee of ZSSOM 2020-0512) and was registered in the Chinese Trials Registry (No. ChiCTR2300073708). Informed consent was obtained from all the patients prior to treatment. The inclusion and exclusion criteria were as follows:

2.2. Inclusion criteria

1. Permanent teeth with deep caries and possible pulp exposure, including mature and immature teeth.

2. The tooth should be vital via an electric pulp test.

3. The teeth can be completely restored.

4. The probing pocket depth and mobility of the tooth were within normal limits.

5. No signs of pulpal necrosis including sinus tract or swelling.

6. The patient had a noncontributory medical history.

2.3. Exclusion criteria

1. No pulp exposure after caries excavation.

2. Bleeding could not be controlled after full pulpotomy within 5 minutes.

3. Insufficient bleeding after pulp exposure and the pulp is judged necrotic or partially necrotic.

Since there is no previous study on iRoot BP Plus and TheraCal LC for VPT of pulpitis permanent teeth, there is a lack of reference for sample size calculation. Referring to previous literature on the use of MTA and CH for pulpotomy,^[11] considering the difficulty of case collection and follow-up, at least 50 affected teeth were included in each group.

A history of the chief complaint (including intensity and duration of pain) and a clinical examination including visual inspection of the caries status, percussion, and responses to cold and heat stimuli were recorded, and periapical radiographs were taken. Pain indicative of reversible pulpitis was defined as provoked short-duration pain that lasted for a few seconds and disappeared after stimulus removal. Pain suggestive of irreversible pulpitis was defined as spontaneous pain or pain exacerbated by cold stimuli lasting from a few seconds to several hours (interpreted as lingering pain), which could be reproduced using cold testing.^[12]

2.4. Interventions

After clinical and radiographic examination, the tooth was anesthetized using articaine 4% with epinephrine 1/1000,000 (Septodont, Allington, UK), and was isolated using a dental dam. The tooth surface was disinfected with 3% sodium hypochlorite (NaOCl). The cavity was prepared using a sterile high-speed bur with a water coolant. Following thorough caries excavation, the exposed pulp was carefully observed under an operating microscope (OMS2380, Zumax, Suzhou, China or Leica M300, Leica Microsystems, Wetzlar, Germany) to analyze the status of the involved tissues and guide the subsequent procedure. Direct pulp capping was applied to teeth with reversible pulpitis when red, homogeneous, and blood-filled tissue was observed on the surface of the pulp wound, and hemostasis was achieved within 5 minutes after flushing with 3% NaOCl and gently pressing with a cotton pellet soaked with 3% NaOCl on the surgical wound. However, if the subjacent pulp was unhealthy with yellowish liquefied areas or dark non-bleeding zones or it was difficult to achieve homeostasis, PP was performed using a round high-speed diamond bur under ambient water spray to amputate a depth of 2 to 3 mm pulpal tissue, until the above-mentioned healthy pulp tissue was observed. A full pulpotomy was performed when the entire coronal pulp tissue was removed. The detailed pulp status, hemostasis time, and total operative time were recorded. If these optimal conditions were not encountered, RCT was initiated and the teeth were excluded.

Once hemostasis was confirmed, each tooth was semi-randomly allocated to the experimental or control group according to the end number of the patients’ clinic ID. Singular numbers were assigned to the control group and even numbers were assigned to the experimental group. Eventually, 58 teeth received TheraCal LC (Bisco Inc., Schamburg, IL) and the other 57 received iRoot BP Plus (Innovative Bioceramix, Vancouver, BC, Canada). In the control group, iRoot BP Plus was placed over the exposed pulp and surrounding dentin to a thickness of 2 to 3 mm. In the experimental group, TheraCal LC was light-cured layer-by-layer over the exposed pulp to the same thickness. Subsequently, the pulp-capping agent was covered by a layer of light-cured glass ionomer (Ionosit; DMG, Hamburg, Germany), and the remaining cavity was restored with a resin-bonded composite (Filtek Z350, 3M ESPE, St.Paul). Postoperative periapical radiographs were obtained.

2.5. Clinical grading standard and evaluation

The patients underwent clinical and radiographic evaluations at 3 months, 6 months and 1 year postoperatively. Demographic data, including age, sex, tooth position and classification of decay, were registered at the first visit. Postoperative pain intensity and duration were recorded through follow-up phone calls 3, 7, and 14 days after surgery. Pre- and postoperative data, including responses to cold and heat stimuli and electric pulp tests (EPT; <5, 5–10 or > 10 compared with control teeth) were also recorded. Pain intensity was measured using a pain numeric rating scale between 0 and 9 pre- and postoperative. Radiographs were evaluated by 2 experienced endodontists on 2 separate occasions. Intraobserver reliability was calculated using Cohen kappa coefficient of agreement index.

The success criteria were as follows: no history of spontaneous pain or discomfort except during the first few days after treatment; no tenderness to palpation or percussion, and the tooth was functional; soft tissues around the tooth were normal with no swelling or sinus tract; and no pathosis evident on radiography such as periapical lesion, root resorption, internal resorption or furcal lesion. Persistent severe spontaneous pain, tenderness to percussion, development of a sinus tract, and swelling were considered clinical failures; periapical lesions on the recall radiograph were considered radiographic failures, and root canal treatment was initiated in such cases.

2.6. Statistical analysis

All statistical analyses were performed using IBM SPSS Statistics, version 22 (IBM, Armonk, NY). Differences between the experimental and control groups were compared using the T test or χ² test. Data differences between the DPC, PP, and FP groups were compared using a One-Way ANOVA. A binary logistic regression model was used to explore the relationship between VPT prognosis and its influencing factors. The significance level was set at P < .05.

3. Results

3.1. Demographic and clinical data

The patients’ flow chart is shown in Figure 1. The overall recall rate was 90.4% (of 104/115). A total of 104 teeth (52 TH and 52 BP) qualified for analysis. Demographic and clinical data of the participants are summarized in Table 1. Analysis of baseline data showed no statistical difference between the 2 groups in terms of age, sex, tooth position, or classification of caries (P > .05). Preoperative pain intensity and duration were similar between the 2 groups (P > .05). The clinical diagnosis of pulp status, in terms of reversible or irreversible pulpitis, was not statistically different between the 2 groups (P > .05). There was also no statistical difference in percussion test results (P > .05). Hemostasis time was similar between the 2 groups (P > .05). However, the treatment duration (in minutes) was significantly different (P < .001). The VPT procedure with TheraCal LC could take less time than iRoot BP Plus. Postoperative pain analysis also showed a significant difference between the 2 groups (P < .001). The TH group showed lower levels of pain and a shorter duration of pain. Detailed information on the treatment length, postoperative pain intensity, and pain duration between the different groups is compared in Figure 2. Means, standard deviation and P values are shown in Supplemental Content Tables 1, http://links.lww.com/MD/M322, 2, http://links.lww.com/MD/M323, and 3, http://links.lww.com/MD/M324 respectively.

Figure 1.

Patients’ flow diagram.

Table 1.

Demographic and clinical data of the study participants.

	BP (n = 52)	TH (n = 52)	T/χ2	P value
Demographics
Age (yr ± SD)	23.8 ± 16.9	26.5 ± 13.5	−0.898	.372
Sex, n (%)			0.699	.403
Male	19 (36.5)	15 (28.8)
Female	33 (63.5)	37 (71.2)
Pre-operative factors
Preoperative pain intensity, 0–9 scale (mean ± SD)	2.5 ± 1.2	2.2 ± 0.9	1.470	.145
Preoperative pain duration, days (mean ± SD)	15.4 ± 11.8	19.1 ± 13.6	−1.476	.143
Pulp status/clinical, n (%)			0.971	.325
Reversible pulpitis	21 (40.4)	26 (50.0)
Irreversible pulpitis	31 (59.6)	26 (50.0)
Percussion test, n (%)			0.965	.326
Negative response	22 (42.3)	27 (51.9)
Positive response	30 (57.7)	25 (48.1)
Tooth position, n (%)			0.956	.620
Anterior	3 (5.8)	5 (9.6)
Premolar	7 (13.5)	9 (17.3)
Molar	42 (80.8)	38 (73.1)
Classification of cavities, n (%)			5.204	.074
I	24 (46.2)	13 (25.0)
II	25 (48.1)	34 (65.4)
III/IV	3 (5.8)	5 (9.6)
Apexogenesis, n (%)			1.529	.216
Closed apical	31 (59.6)	37 (71.2)
Unclosed apical	21 (40.4)	15 (28.8)
Intra-operative factors
Type of VPT, n (%)			3.192	.203
Direct pulp capping	16 (30.8)	21 (40.4)
Partial pulpotomy	18 (34.6)	21 (40.4)
Full pulpotomy	18 (34.6)	10 (19.2)
Haemostasis time, min (mean ± SD)	2.4 ± 1.6	2.0 ± 1.4	1.160	.249
Treatment length, min (mean ± SD)	38.1 ± 10.0	28.2 ± 8.0	5.562	.000*
Post-operative factors
Postoperative pain intensity, 0–9 scale (mean ± SD)	1.5 ± 1.2	0.4 ± 0.7	5.561	.000*
Duration of pain postoperative, min (mean ± SD	2.0 ± 2.2	0.4 ± 1.1	4.638	.000*
1-yr postoperative
EPT result compared with control tooth, n (%) (n = 47)			0.921	.631
<5	19 (40.4)	22 (46.8)
5–10	14 (29.8)	15 (31.9)
>10	14 (29.8)	10 (21.3)
Formation of calcified barrier, n (%) (n = 47)			4.917	.086
Complete/obvious	25 (53.2)	16 (34.0)
Incomplete/vague	15 (31.9)	16 (34.0)
no	7 (14.9)	15 (31.9)

BP = iRoot BP Plus, TH = TheraCal LC.

^*Correlation is significant at 0.01 level (2-tailed).

Figure 2.

Comparison of treatment length, postoperative pain intensity and pain duration between different groups. Note: Means, standard deviation and P values are shown in Supplemental Content Tables 1, 2, and 3 respectively.

At the 1-year recall session, the EPT test results were not significantly different between the 2 groups (P > .05). The formation of dentinal bridges adjacent to the exposed pulp at the 1-year recall also showed no significant difference between the 2 groups (P > .05). However, more teeth had complete dentinal bridges in the BP group (25/47, 53.2%) than in the TH group (16/47, 34.0%). Pulp canal calcification and narrowing can be observed to various degrees in both groups.

Immediate failure occurred in 2 teeth (one in the TH group and 1 in the BP group), in which severe spontaneous pain occurred 2 days after the procedure. Two patients came to us for help with symptoms of acute periapical inflammation; one was in the TH group at 3-month, and the other was in the BP group at 12-month. All other failure cases were detected at their regular visit for periapical lesions on the radiograph without subjective symptoms. All failed cases underwent root canal treatment. Radiographs and microscope photographs of typical cases with TheraCal LC and iRoot BP Plus are shown in Figure 3.

Figure 3.

Partial and full pulpotomy with iRoot BP Plus and TheraCal LC. (A). The preoperative periapical radiograph of the upper right second molar in a 16-yr-old female patient with symptoms of irreversible pulpitis; (B). Microscope photographs after partial pulpotomy; (C). The exposed pulp was covered with iRoot BP Plus; (D). Radiograph of 1-yr, complete dentinal bridge can be observed where the arrow points. (E). The preoperative periapical radiograph of the lower right first molar in a 17-yr-old female patient with symptoms of irreversible pulpitis; (F). Microscope photographs after partial pulpotomy; (G). The exposed pulp was covered with TheraCal LC; (H). Radiograph of 1-yr, complete dentinal bridge can be observed where the arrow points. (I). The preoperative periapical radiograph of the upper left second premolar in an 11-yr-old female patient with symptoms of irreversible pulpitis; (J). Microscope photographs after full pulpotomy; (K). The exposed pulp was covered with iRoot BP Plus; (L). Radiograph of 1-yr, thick dentinal bridge can be observed and the root development continued. (M). The preoperative periapical radiograph of the lower right second premolar in a 29-yr-old female patient with symptoms of irreversible pulpitis; (N). Microscope photographs after full pulpotomy; (O). The exposed pulp was covered with TheraCal LC; (P). Radiograph of 1-yr, thin layer of calcification barrier can be observed where the arrow points.

3.2. Binary logistic regression of influencing factors

The overall clinical success rate in the first year was 90.4% (47/52) in the TH and BP groups. The relationship of 1-year success rate with other clinical factors such as type of pulpitis, type of VPT, and whether apical closure was performed or not are shown in Table 2, but no statistical difference was found.

Table 2.

The relationship of 1-yr success rate with different factors.

	Success, n(%)	Failure, n(%)	χ 2	P value
Pulp capping agent			0.000	1.000
BP	47 (90.4)	5 (9.6)
TH	47 (90.4)	5 (9.6)
Apexogenesis			0.106	.744
Closed apex	61 (89.7)	7 (10.3)
Unclosed apex	33 (91.7)	3 (8.3)
Pulp status/clinical			1.066	.302
Reversible pulpitis	44 (93.6)	3 (6.4)
Irreversible pulpitis	50 (87.7)	7 (12.3)
Type of VPT			0.157	.924
Direct pulp capping	34 (91.9)	3 (8.1)
Partial pulpotomy	35 (89.7)	4 (10.3)
Full pulpotomy	25 (89.3)	3 (10.7)
Integrated analysis			2.965	.397
Irreversible/closed apex	24 (82.8)	5 (17.2)
Irreversible/open apex	26 (92.9)	2 (7.1)
Reversible/closed apex	37 (94.9)	2 (5.1)
Reversible/open apex	7 (90.4)	1 (12.5)

BP = iRoot BP Plus, TH = TheraCal LC.

SPSS software (version 22.0) was used to construct a binary logistic regression model, and a logistic regression analysis was performed on the prognosis of VPT and its influencing factors. According to the model structure, taking prognosis as the dependent variable, the independent variables were sorted and summarized in Table 3, and the values were assigned according to the law.

Table 3.

Variable assignment of binary logistic regression model in VPT.

Variable name	Variable description	Assignment
Sex	Male	1
	Female	2
Root maturation	Open	1
	Closed	2
Cave shape	Occlusal surface only	1
	Proximal surface involved	2
Percussion sensitivity	(−)	0
	(+)	1
Pulpitis type	Reversible pulpitis	1
	Irreversible pulpitis	2
Preoperative pain intensity	Pain numeric rating scale	0–5
Preoperative pain duration	≤7 d	1
	>7 d, ≤14 d	2
	>14 d, ≤30 d	3
	>30 d	4
Haemostasis time	Minutes	1–5
VPT type	Direct pulp capping	1
	Partial pulpotomy	2
	Full pulpotomy	3
Pulp capping material	BP	1
	TH	2

BP = iRoot BP Plus, TH = TheraCal LC.

The fitting results of the binary logistic regression model showed that among the 10 variables, only one, preoperative pain duration, had a significant correlation with prognosis (P = .011). A long preoperative pain duration may be associated with a poor prognosis. The detailed results of the regression model fitting and P-values are shown in Table 4.

Table 4.

Results of regression model fitting.

	B	S.E.	Wald	Sig.	Exp(B)
Pulp capping material	−0.548	0.892	0.378	0.539	0.578
Cave shape	−0.160	1.165	0.019	0.891	0.852
Percussion sensitivity	−0.967	0.901	1.153	0.283	0.380
VPT type	−0.714	0.973	0.539	0.463	0.490
Pulpitis type	−0.393	2.005	0.038	0.845	0.675
Sex	−0.130	0.826	0.025	0.875	0.878
Preoperative pain intensity	0.524	0.531	0.972	0.324	1.688
Preoperative pain duration	1.363	0.536	6.465	0.011*	3.907
Haemostasis time	−0.037	0.315	0.014	0.905	0.963
Root maturation	0.632	1.120	0.318	0.573	1.881
Constant	−3.819	4.320	0.781	0.377	0.022

^*Correlation is significant at 0.05 level.

4. Discussion

Pulpitis caused by deep dental caries is one of the most common problems encountered in dental clinics. Compared with traditional RCT, VPT can significantly reduce the operating time and treatment costs and improve the long-term retention rate of affected teeth.^[13] With the development of pulp capping materials, aseptic technology, and microscopic magnification technology, many recent studies have reported successful outcomes when VPT was performed in cariously exposed pulps of vital teeth that presented with the signs and symptoms of irreversible pulpitis and apical periodontitis.^[1,2] VPT may provide a more personalized and conservative treatment option for pulpitis. There are 4 types of VPT: IPC, DPC, PP, and FP. IPC was not included in this study because the pulp is not exposed to IPC and pulp status cannot be assessed by direct inspection with a microscope.

Precise determination of the pulp condition plays an important role in the success of VPT. Ricucci et al found that 16% of teeth with a clinical diagnosis of irreversible pulpitis showed a histological diagnosis of reversible pulpitis. Even in the cases with matching clinical and histologic diagnoses, it was possible to observe non-inflamed coronal pulp tissue with normal architecture in areas contralateral to the exposure site.^[14] Because histologic evaluation of pulp tissue is not possible in clinical situations, the appearance of pulp tissue and the time used to control bleeding have been used as indicators of pulp status in most studies.^[3,6,15] In our study, different VPT procedures were adopted according to the amount of pulp tissue that needed to be amputated to achieve hemostasis. If the subjacent pulp was unhealthy with yellowish liquefied areas or dark non-bleeding zones, or it was difficult to achieve homeostasis even when the whole coronal pulp tissue was removed, RCT was initiated, and the teeth were excluded. Profuse pulpal bleeding, which is difficult to arrest, is indicative of advanced pulpal inflammation.^[16] According to a recent systematic review, published studies presented variable time to achieve hemostasis, ranging from 2 to 25 minutes, without impact on the outcome.^[5] As a compromise, we used effective hemostasis within 5 minutes as one of the inclusion criteria, considering that a long hemostatic time might affect the sterility effect of the pulp. If bleeding could not be stopped within 5 minutes, the treatment procedure was modified.

Pulp-capping materials are another extremely important factor in the success of VPT. The materials to be applied should have the ability to form reparative dentin, impermeability, biocompatibility, and antibacterial effects.^[6] iRoot BP Plus (BP) is a bioceramic material based on calcium silicate, which has shown similar results to Mineral Trioxide Aggregate (MTA) in in vivo experiments.^[7] Lei Yue et al performed a full pulpotomy with iRoot BP Plus on 40 deciduous molars, and the 1-year follow-up success rate was as high as 95%.^[17] In a study by Wang Shuang et al, 28 pairs of deciduous molars were paired with iRoot BP Plus and MTA for pulpotomy, and the success rates at 1-year follow-up were 87% and 96%, respectively.^[18] Liu, S.Y et al used iRoot BP Plus for direct pulp capping on 50 mature permanent teeth with pulp exposure caused by caries and found that the success rates at 1, 2, and ≥ 3 years were 98%, 89%, and 81%, respectively.^[19] TheraCal LC (TH) is a calcium silicate-filled light-cured resin-modified material with a high calcium-releasing ability and low solubility. Although TheraCal LC was reported to show inferior histological results compared to ProRoot MTA and Biodentine,^[10,20] it is still a promising material when considering the need to shorten the clinical operation time in dental practice. And its improved dual-cured version, TheraCal PT was reported to be comparable to ProRoot MTA in terms of biocompatibility.^[20] Alqahtani et al performed direct or IPC with the calcium silicate material TheraCal LC in 79 patients and reported a 3-month clinical success rate of 85.5% in a retrospective study.^[21] Peskersoy et al conducted a randomized controlled clinical study of direct pulp capping with TheraCal LC on 105 teeth, and the clinical and imaging success rates for 3 years were 72.1% and 73.6%, respectively.^[22] In a previous study reported by our team,^[23] the 18-month success rates of TheraCal LC and iRoot BP Plus for full pulpotomy of primary teeth were 85.7% and 86.7%, respectively. In this study, the overall clinical success rate in the first year was both 90.4% (47/52) in the TH and BP groups, which was superior to the outcomes of previous studies. This may have been because the observation time was not sufficiently long. Several studies on direct pulp capping have reported a time-dependent decline in success rate.^[24,25]

In our study, all operators performed treatment under the same strict protocol, thus increasing the validity of the treatment. The operator could not be blinded because of the distinct differences between the appearance and clinical use of the 2 materials. However, the clinical criteria were explicit and depended entirely on the patients’ reports of their symptoms, thus reducing the effect of bias on the clinical examiners. VPT with TheraCal LC and iRoot BP Plus in caries-exposed permanent teeth achieved good clinical outcomes in this study. TheraCal LC is more comfortable and can be easily operated for clinical use. The treatment length (min) was significantly different between the 2 groups (P < .001). The VPT procedure with TheraCal LC could take less time than iRoot BP Plus. Postoperative pain analysis also showed a significant difference between the 2 groups (P < .001). The TH group showed lower levels of pain and a shorter duration of pain. We inferred that this was because iRoot BP Plus had a longer setting time and the pulp was irritated with moderate inflammation until it was completely set,^[26] whereas TheraCal LC was cured immediately with a light source and the stimulation of pulp during curing was reduced.^[27] But it is also noteworthy that almost 36.5% (19/52) of patients in the TH group had transient sensitivity to heat and cold at the 3-month visit and gradually relieved in subsequent observation, while in the BP group, the sensitivity was only found in the first 1 or 2 weeks. As for the formation of dentinal bridges adjacent to the exposed pulp, more teeth were observed with complete dentinal bridges in the BP group (25/47, 53.2%) than in the TH group (16/47, 34.0%) at the 1-year follow-up. This result is consistent with the findings of animal research that light-curable calcium silicate-based materials may cause slight cytotoxic effects because of the resin monomer content, and TheraCal LC was reported to reduce the viability of osteoblasts in comparison to iRoot BP Plus.^[9,28] The limitation of this study was that evaluating dentin bridge formation and pulp canal obliteration from overlapping 2-dimensional radiographs was difficult. Only about one-third of the patients agreed to undergo the CBCT examination at the 1-year visit, while the others required 2-dimensional radiography with a smaller radiation dose. De Rossi et al reported that radiographs were unable to detect thin dentin bridges (<0.5 mm),^[29] and we found that CBCT is a more accurate method for evaluating pulp canal obliteration and dentin bridge formation and may need to be supplemented in later experiments.

It is generally believed that the pulp tissue of young permanent teeth with open apices has stronger regeneration ability than that of mature permanent teeth. However, in this study, the maximum age of the included patients was 65 years, which did not affect their treatment effect. The 1-year success rate showed no statistical difference, regardless of whether the apex was closed. The relationship of 1-year success with other factors, such as pulpitis type and VPT procedure type, also showed no statistical difference. A previous study using a dog model indicated that the presence of short-term preoperative inflammation did not jeopardize the outcome of full pulpotomy.^[30] But their pulpal inflammation model induced by dentin exposure was relatively slight and short-term, with no signs of microabscesses or infection, which was different from the clinical pulpitis. In our study, after constructing a binary logistic regression model, the preoperative pain duration was found to be significantly correlated with prognosis (P = .011). This means that a long preoperative pain duration may be associated with poor prognosis. We inferred that this was because with prolonged inflammation, the tissue infiltrated by bacteria and their toxins may spread from the bottom of the decay to the entire coronal pulp, even to the root pulp. The success rate of VPT might decrease in patients with stimulation pain or spontaneous pain lingering for more than a month. However, the significance of this model Hosmo test was 0.018, which means that it might not be a very good fit. This is probably because the sample size was not large enough, and so many independent variables were involved. This paper is just a preliminary clinical exploration, which showed good application prospects of resin-modified calcium silicate-based materials. Clinical trials with larger sample sizes and longer follow-up periods will be carried out in our future research.

5. Conclusions

VPT with TheraCal LC and iRoot BP Plus in pulpitis permanent carious teeth both achieved good clinical outcomes, and TheraCal LC can be easily operated for clinical use. Preoperative pain duration of the affected tooth might have a significant correlation with the prognosis of VPT.

Author contributions

Conceptualization: Linlin Zhang, Li Yin.

Data curation: Linlin Zhang.

Formal analysis: Linlin Zhang.

Funding acquisition: Linlin Zhang.

Investigation: Jianbo Wu, Jiahui Huang.

Supervision: Quanli Li.

Validation: Li Yin, Jianbo Wu, Xiaoyan Wang.

Visualization: Linlin Zhang, Li Yin, Jiahui Huang.

Writing – original draft: Linlin Zhang.

Writing – review & editing: Li Yin, Quanli Li.