Nd: YAG laser irradiation in the treatment of live pulp preservation in pediatric cariogenic pulpitis

Abstract

BACKGROUND:

Dental pulpitis significantly impacts oral function and quality of life. Treatments like direct pulp capping aim to preserve pulp vitality.

OBJECTIVE:

This study aims to investigate the application value of Nd:YAG laser irradiation in preserving pulp vitality in children with caries-induced pulpitis.

METHODS:

This study, conducted from June 2019 to June 2023, included 89 children undergoing pulp vitality preservation treatment for caries-induced pulpitis. The children were divided into two groups using sealed envelopes: 44 in the control group received pulp capping treatment, while the study group received Nd:YAG laser-assisted pulp capping treatment. The efficacy, oral indicators, oral function, changes in root apex diameter and root length, changes in gingival crevicular fluid inflammatory factors, and incidence of complications were compared between the two groups before and 3 months after treatment.

RESULTS:

The total effective rates were 97.78% in the study group and 95.45% in the control group, with no significant difference between the groups ( $p>$ 0.05). Before treatment, there were no differences in gingival index, plaque index, and probing bleeding index between the groups ( $p>$ 0.05). After treatment, both groups showed decreased periodontal indexes compared to before treatment, with the study group showing lower values than the control group ( $p<$ 0.05). Chewing and biting function scores were similar between the groups before and after treatment ( $p>$ 0.05), but both groups showed decreased scores after treatment ( $p<$ 0.05). The study group had a higher percentage decrease in root apex diameter and a greater increase in root length compared to the control group ( $p<$ 0.05). During treatment, one case of tooth discoloration occurred in the study group (2.27%), while the control group had two cases of tooth discoloration and one case of secondary caries, resulting in a complication rate of 6.67%. There was no significant difference in the incidence of complications between the groups ( $p>$ 0.05).

CONCLUSION:

Nd:YAG laser irradiation effectively preserves pulp vitality in children with caries-induced pulpitis, improving periodontal health, reducing root apex diameter, and increasing root length with high safety.

Keywords

Nd: YAG laser caries-induced pulpitis children oral function

1. Introduction

Dental pulpitis caused by caries is a common oral disease with a high clinical incidence, which can impair oral function and affect patients’ quality of life [1, 2]. Pulp absorption and loss of periodontal attachment are characteristics of this disease, and direct pulp capping is an important method for its treatment. It involves placing a medicament over the near-exposed pulp to protect the vital pulp [3]. Successful direct pulp capping can preserve pulp vitality and maintain dental function [4]. Dental pulp contains rich nerves, and it has been suggested that direct pulp capping alone may have some limitations and may stimulate periodontal tissues [5]. The Nd (Neodymium-Doped Yttrium Aluminum Garnet) laser operates at a wavelength of 1064 nm, which allows it to penetrate deeply into tissues with minimal absorption by water and hemoglobin. This makes it particularly effective for dental procedures, as it can reach deep into the pulp without causing significant damage to surrounding tissues. Nd:YAG laser has minimal damage to normal dental tissues during caries excavation, making it particularly suitable for treating childhood caries [6]. In recent years, laser therapy has been increasingly used in the treatment of dental caries and pulpitis to alleviate pain and improve clinical outcomes. Studies have shown that the thermal effect of lasers has hemostatic and bactericidal effects and can promote dentinogenesis in oral diseases [7]. Previous research using CO2 laser irradiation in dental cavities has been shown to promote dentin formation, and subsequently Nd:YAG laser, Er:YAG laser, and other lasers have been used clinically [8, 9]. Currently, there is limited research on the treatment effect of Nd:YAG laser irradiation combined with direct pulp capping for dental pulpitis in children with caries. This study aims to investigate the application value of Ndlaser irradiation in preserving pulp vitality in children with caries-induced pulpitis by comparing it to traditional direct pulp capping treatment.

2. Methods

2.1 General information

This study was conducted from June 2019 to June 2023. A total of 89 children with dental pulpitis caused by caries who underwent vital pulp preservation treatment in our hospital were selected. They were divided into two groups using envelope method: 44 children in the control group received direct pulp capping, and 45 children in the study group received Nd:YAG laser combined with direct pulp capping. There were no significant differences in general information between the two groups ( $p>$ 0.05, Table 1). Inclusion criteria: 1. Children aged under 14 years old. 2. Dental pulp exposure caused by caries, with relatively good tooth dentin condition, and clinically diagnosed as caries-induced dental pulpitis. 3. Normal response to electric pulp testing. 4. Children with good compliance who can cooperate to complete various examinations. Exclusion criteria: 1. Children who were lost to follow-up. 2. Children with concomitant other periodontal diseases. 3. Children who received other oral treatments within the 2 weeks before enrollment. 4. Children with abnormal coagulation function.

Table 1
General data

	Control group ( $n=$ 44)	Study group ( $n=$ 45)	$\chi^{2}/t$	$P$
Age (year)	8.12 $\pm$ 3.11	8.03 $\pm$ 3.02	0.139	0.89
Sex			0.27	0.603
Male	26	29
Female	18	16
BMI (kg/m² )	20.65 $\pm$ 1.98	20.23 $\pm$ 2.33	0.915	0.363
Distribution of affected teeth			0.915	0.633
Front teeth	16	13
Premolars	11	15
Molars	17	17

2.2 Treatment methods

For the control group, the following procedure was employed for treatment: 1. Preparation of the Cavity: Carious tissue was removed, and if necessary, local anesthesia was administered. 2. Cavity Sealing: The cavity was rinsed with physiological saline, dried, and isolated. Calcium hydroxide pulp capping agents were applied to cover the exposed pulp, followed by sealing the cavity with zinc oxide eugenol cement. 3. Postoperative Management: If no abnormal symptoms occurred 1–2 weeks postoperatively and pulp vitality tests were normal, most of the temporary filling material was removed, leaving a 1 mm layer of sealing material at the bottom. Zinc phosphate cement was placed as the second layer, followed by permanent composite resin filling. If significant pain occurred after 1–2 weeks postoperatively, further observation was warranted until no symptoms were present before permanent filling. If severe postoperative pain occurred, the filling material was removed for root canal treatment.

For the study group, Nd:YAG laser-assisted pulp capping was performed using the Pulse MasterTM600 Nd:YAG laser machine from the United States. The laser was applied after pulp capping. When pulpal penetration occurred during treatment, immediate isolation was performed. After drying, the pulp chamber was irradiated with pulsed Nd:YAG laser at a distance of 1 mm from the perforation site without the addition of a trigger agent. The pulse frequency was set at 20 Hz, with a pulse laser energy of 40 mJ and an irradiation time of 5 s. After laser irradiation, pulp capping was performed, followed by temporary sealing with zinc oxide eugenol powder.

2.3 Observation indicators

Comparison between the two groups was conducted on efficacy, oral indicators (gingival index, plaque index, bleeding on probing), oral function (chewing function, occlusal function), changes in apical foramen diameter and root length, and recording of complications during treatment.

2.3.1 Efficacy evaluation criteria

(a) Successful: No subjective symptoms, absence of percussion pain, sinus tract closure, complete restoration of chewing function, normal apical rarefaction area, and intact lamina dura. (b) Improved: No subjective symptoms, reduction in the size of the apical rarefaction area compared to before treatment, significant improvement from before treatment. (c) Failure: Subjective symptoms present, percussion pain, unclosed sinus tract, and apical rarefaction area. Total effective rate calculation: Ratio of successful and improved cases to total cases [10].

2.3.2 Oral indicators

(a) Plaque Index: Assessing the extent and distribution of plaque accumulation in the oral cavity, with higher scores indicating more plaque accumulation. (b) Gingival Index: Evaluating the degree of gingival inflammation, with higher scores indicating more severe gingivitis. (c) Bleeding on Probing Index: Scored as follows: 0: no bleeding, 1: bleeding with partial coverage of the gingival sulcus, 2: bleeding with complete coverage of the gingival sulcus. Higher scores indicate more severe bleeding. (d) Root Development: Using X-rays to measure changes in apical foramen diameter and root length before and after treatment.

2.3.3 Oral function

An internally developed assessment scale was used to evaluate the oral function of the children, completed by the children themselves or with the assistance of their parents. It included assessments of chewing function (0–7 points) and occlusal conditions (eating, soft tissue comfort, speech disorders, scored 0–10 points), with higher scores indicating poorer chewing and occlusal function.

2.4 Statistical methods

Data analysis was performed using SPSS 23.0 software. Chi-square tests were used for categorical data, and for normally distributed and homogeneous variance data, $t$ -tests were conducted. Descriptive statistics were used to summarize the data, and inferential statistics were employed to draw conclusions about the differences between groups. The use of SPSS 23.0 software allowed for accurate and efficient handling of the statistical analyses. A significance level of $p<$ 0.05 was considered statistically significant.

3. Results

3.1 Comparison of efficzacy

The total effective rates of treatment for patients in the study group and the control group were 97.78% and 95.45%, respectively. There was no significant difference between the groups ( $p>$ 0.05, Table 2).

Table 2
Comparison of the efficacy

Group	Success	Progress	Fail	Total effective rate
Control group ( $n=$ 44)	36 (81.82)	6 (13.64)	2 (4.55)	42 (95.45)
Study group ( $n=$ 45)	41 (91.11)	3 (6.67)	1 (2.22)	44 (97.78)
$\chi^{2}$				0.369
$p$				0.544

3.2 Comparison of gingival index, plaque index, and bleeding on probing index

Before treatment, there were no significant differences in gingival index, plaque index, and bleeding on probing index between the two groups ( $p>$ 0.05). After treatment, both groups showed a decrease in periodontal indices compared to before treatment, with the study group exhibiting lower values than the control group ( $p<$ 0.05, Table 3).

Table 3
Comparison of gingival index, plaque index and probe bleeding index

Group	Gingival index (points)		Plaque index(points)		The bleeding index was probed (points)
	Pretherapy	Post-treatment	Pretherapy	Post-treatment	Pretherapy	Post-treatment
Control group ( $n=$ 44)	2.02 $\pm$ 0.32	1.22 $\pm$ 0.15^*	2.11 $\pm$ 0.16	1.15 $\pm$ 0.11^*	3.88 $\pm$ 0.65	2.68 $\pm$ 0.31^*
Study group ( $n=$ 45)	2.04 $\pm$ 0.29	0.88 $\pm$ 0.06^*	2.13 $\pm$ 0.15	0.77 $\pm$ 0.09^*	3.86 $\pm$ 0.58	2.22 $\pm$ 0.23^*
$t$	$-$ 0.309	14.097	$-$ 0.609	17.855	0.153	7.962
$p$	0.758	$<$ 0.001	0.544	$<$ 0.001	0.879	$<$ 0.001

Note: ^* is $p<$ 0.05 before treatment with the same group.

3.3 Comparison of masticatory and occlusal function

Before treatment and after treatment, there were no significant differences in masticatory and occlusal function between the two groups ( $p>$ 0.05). However, the masticatory and occlusal function scores of both groups decreased after treatment compared to before treatment ( $p<$ 0.05), as shown in Table 4.

Table 4
Comparison of chewing functions and occlusal functions

Group	Masticatory function (points)		Inclusal function (points)
	Pretherapy	Post-treatment	Pretherapy	Post-treatment
Control group ( $n=$ 44)	4.11 $\pm$ 0.98	1.39 $\pm$ 0.41	5.55 $\pm$ 0.69	2.20 $\pm$ 0.64^*
Study group ( $n=$ 45)	4.13 $\pm$ 0.87	1.33 $\pm$ 0.35^*	5.59 $\pm$ 0.54	2.11 $\pm$ 0.55^*
$t$	$-$ 0.102	0.743	$-$ 0.305	0.712
$p$	0.919	0.459	0.761	0.478

Note: ^* is $p<$ 0.05 before treatment with the same group.

3.4 Comparison of apical foramen diameter and tooth root length

The percentage decrease in apical foramen diameter and the percentage increase in tooth root length were higher in the study group compared to the control group ( $p<$ 0.05, Table 5).

Table 5
Comparison of changes in apical foramen diameter and root length

Group	Percentage of apical hole diameter reduction (%)	Increase in root length (%)
Control group ( $n=$ 44)	11.20 $\pm$ 3.21	11.03 $\pm$ 4.11
Study group ( $n=$ 45)	15.21 $\pm$ 4.26	14.22 $\pm$ 3.68
$t$	$-$ 5.007	$-$ 3.860
$p$	$<$ 0.001	$<$ 0.001

3.5 Incidence of complications

During the treatment period, one case of tooth discoloration occurred in the study group, with an incidence rate of 2.27%. In the control group, there were two cases of tooth discoloration and one case of secondary caries, resulting in a complication incidence rate of 6.67%. There was no significant difference in the incidence of complications between the two groups ( $P>$ 0.05).

4. Discussion

Pulp capping is a method of preserving pulp vitality by covering medication on exposed pulp. In recent years, clinical observations have shown that laser-assisted therapy can further promote pulp tissue healing, reduce infection rates, and play an important role in improving pulp tissue repair and defense capabilities [11]. However, the effectiveness of pulp capping alone needs to be improved in special patients. This study aimed to explore the application value of Nd:YAG laser irradiation in the pulp vitality preservation treatment of children with caries-induced pulpitis.

The results of this study showed that there was no difference in the total effective rate between the two groups ( $p>$ 0.05). After treatment, the periodontal indexes of both groups decreased compared to before treatment, and the study group was lower than the control group ( $p<$ 0.05). This suggests that Nd:YAG laser irradiation has a high application value in the pulp vitality preservation treatment of children with caries-induced pulpitis, significantly improving periodontal health indexes. The pulp capping agents used in pulp capping have good biocompatibility, promoting pulp tissue regeneration. Additionally, their penetrating effect determines their good disinfection and bactericidal effects [12, 13]. Nd:YAG laser irradiation has the effect of promoting tissue proliferation and healing [14]. When using laser beams for periodontal curettage, there is no influence from instrument angles or subjective factors, enabling deep penetration into periodontal depths and concave areas, conducive to removing infected tissues within periodontal pockets, reducing bacterial counts. Furthermore, the laser can also remove endotoxins on the tooth root surface, promoting uniformity for attachment of periodontal fibroblasts, thus providing favorable conditions for improving the periodontal environment [15].

The results showed no significant difference in chewing and biting function scores between the two groups before and after treatment. This suggests that Nd:YAG laser irradiation also has positive significance in improving chewing and biting functions in the pulp vitality preservation treatment of children with caries-induced pulpitis. The use of pulp capping can maintain the integrity of the dental arch to a certain extent, ensuring that the contact relationship between upper and lower teeth is normal, guaranteeing basic adjacency and occlusion [16]. Combined Nd:YAG laser irradiation plays a synergistic role, as Nd:YAG can kill a large number of bacteria in the pulp chamber through thermal effects. After passing through the light, the laser can be absorbed by the pulp, promoting dentin repair and stabilizing tooth function [17]. The combined approach stabilizes the pulp microenvironment and repairs dentin, thus effectively improving patients’ chewing and biting capabilities.

The percentage decrease in root apex diameter and increase in root length in the study group were higher than those in the control group ( $p<$ 0.05). This indicates that Nd:YAG laser irradiation combined with pulp capping can promote continued root development. The remaining dental-origin cells and connective tissue components in the pulp can lead to irregular deposition of dental hard tissues and bone, resulting in root apex closure [18]. If pulp tissue is preserved through treatment, the postoperative morphology and anatomical characteristics of the tooth root tend to be normal, and the root apex may reopen. If there is no residual pulp tissue, root apex closure is irreversible. Preserving intact epithelial sheaths is key to continued root development. Therefore, during treatment, efforts should be made to minimize artificial damage to the epithelial sheath, focusing on maintaining the integrity of pulp tissue at the root apex [19]. In this study, a lower energy Nd:YAG laser was used, and its damage to pulp cells in the irradiated area is reversible, gradually returning to normal after treatment. Activation of pulp cells promotes dentin repair, helping maintain the integrity of the root apex pulp tissue and reducing damage to the epithelial sheath [20]. Nd:YAG laser may promote the quenching of oxygen free radicals in pulp cells, promoting cell proliferation. These advantages effectively promote continued root development. One of the primary limitations of this study is the small sample size, which may affect the generalizability of the results. Additionally, potential biases or confounding factors, such as variations in treatment adherence and differences in individual responses to treatment, could influence the outcomes. Further research with a larger sample size and more rigorous control of variables is recommended to validate these findings and ensure their applicability to a broader population.

The incidence of complications in both groups during treatment showed no difference, demonstrating the safety of using Nd:YAG laser-assisted therapy. Laser can effectively control pulp bleeding, induce dentin formation, and does not increase the incidence of complications, making it worthy of clinical application.

5. Conclusion

In summary, Ndlaser irradiation has a high application value in the pulp vitality preservation treatment of children with caries-induced pulpitis, significantly improving periodontal health indices, promoting the reduction of root apex diameter, and increasing root length with high safety. The study demonstrates that Ndlaser-assisted pulp capping can be an effective and safe alternative to traditional methods. Further studies with larger sample sizes are warranted to confirm these results and explore additional benefits of this treatment modality.

Footnotes

Conflict of interest

The authors declared no conflict of interest.

Ethical approval

This study was approved by the Children’s Hospital affiliated to Capital Institute of Pediatrics’ ethics committee (Approval No. 202203164), and informed consent was obtained from the parents of all children.

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Nd: YAG laser irradiation in the treatment of live pulp preservation in pediatric cariogenic pulpitis

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSION:

Keywords

1. Introduction

2. Methods

2.1 General information

Table 1 General data

2.3 Observation indicators

2.3.1 Efficacy evaluation criteria

2.3.2 Oral indicators

2.3.3 Oral function

2.4 Statistical methods

3. Results

3.1 Comparison of efficzacy

Table 2 Comparison of the efficacy

Table 3 Comparison of gingival index, plaque index and probe bleeding index

Table 4 Comparison of chewing functions and occlusal functions

Table 5 Comparison of changes in apical foramen diameter and root length

4. Discussion

5. Conclusion

Footnotes

Conflict of interest

Ethical approval

References

Table 1
General data

Table 2
Comparison of the efficacy

Table 3
Comparison of gingival index, plaque index and probe bleeding index

Table 4
Comparison of chewing functions and occlusal functions

Table 5
Comparison of changes in apical foramen diameter and root length