Comparative Efficacy of Digital 3D‐Printed and Conventional Stable Occlusal Splints in the Treatment of Temporomandibular Disorders

ABSTRACT

Background

Temporomandibular disorders (TMD) are a group of diseases that affect the temporomandibular joint (TMJ), masticatory muscles and associated structures.

Objective

This present study aims to explore the clinical comparative efficacy of digital 3D‐printed and conventional handmade stable occlusal splints in the treatment of TMD and provide evidence for clinical promotion.

Methods

A total of 130 patients diagnosed with TMD using the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) were recruited and randomly assigned to two groups. One group received conventional handmade occlusal splints, while the other group received digital 3D‐printed splints. The treatment efficacy, craniomandibular index scores and splint fabrication time were compared between the two groups at follow‐up.

Results

The findings indicated that digital 3D‐printed stable occlusal splints offered comparable efficacy and satisfaction levels to traditional stabilisation splints while significantly cutting down on production time and enhancing overall efficiency. This study demonstrated that the use of fully digital technology, including digital intraoral scanning, virtual adjustments, computer‐aided design and 3D printing, in fabricating occlusal splints for TMD patients not only maintained therapeutic effectiveness but also streamlined the production process.

Conclusions

Digital 3D‐printed stable occlusal splints can not only alleviate TMD symptoms as effectively and satisfactorily as the conventional handmade stable splint, but also reduce production time and improve accuracy and efficiency, promising good clinical application prospects.

1. Introduction

Temporomandibular disorder (TMD) is one group of diseases that affect the temporomandibular joint (TMJ), masticatory muscles and associated structures. Patients with TMD most frequently present with pain, limited or asymmetric mandibular motion and TMJ sounds [1]. TMD predominantly affects the young aged 20–40 years, with a higher incidence among females than males. It is a significant public health issue affecting approximately 5%–12% of the people [2]. Nowadays, treatments of TMD include health education/self‐management, physical therapy, medication, manual repositioning, acupuncture, occlusal splints, arthrocentesis, intra‐articular injection of medication and surgery. Conventionally, TMD is considered self‐limited, and conservative treatment is prioritised.

Stable occlusal splints are the first line of treatment and the most commonly used in clinical practice because they are a reversible, noninvasive and conservative treatment. TMD‐related symptoms and signs may be relieved by increasing the occlusal height to eliminate occlusal interference, reduce muscle tension and alleviate intra‐articular pressure [3]. The conventional fabrication process of handmade stable occlusal splints involves denture impression, making and trimming plaster mould, making splint framework and trimming, clinical fitting, self‐curing based resin mixing and shaping and complicated clinical occlusal adjustments. This fabrication process is laborious, time‐consuming and highly experience‐dependent.

With the development and prevalence of digital technology in dentistry, various oral treatment devices based on computer numerical control (CNC) machining and 3D printing technology have been applied to dental clinical practice, significantly improving the quality and efficiency of treatments [4]. However, there are few reports on the application of digital technology in the field of TMD treatment. The present study aims to explore the clinical comparative efficacy of digital 3D‐printed and conventional handmade stable occlusal splints in the treatment of TMD and provide evidence for clinical promotion.

2. Materials and Methods

2.1. Source of Data

Data were collected from 130 patients admitted to the TMD Clinic in the School of Stomatology, the Fourth Medical University, from March 2023 to July 2023 who participated in this study. The inclusion criteria were as follows: (1) aged between 18 and 65 years; (2) diagnosed with TMD according to DC/TMD; (3) Dentition with sufficient teeth for splint retention; (4) never received TMD‐related treatment. The exclusion criteria were as follows: (1) unable to obtain a denture impression because of limited mouth opening distance; (2) obvious periodontal disease; (3) accepting orthodontic treatment; (4) patients with removable dentures or improper dental restorations; (5) maxillofacial trauma or TMJ surgery history; (6) pregnant or lactating females; (7) severe mental diseases; (8) significant systemic diseases.

2.2. Ethical Clearance

The present study was a single centre, parallel randomised trial. A total of 130 patients with TMD were included in the present study. Informed consent to participate was obtained from all the participants. This study was approved by the Medical Ethics Committee of the School of Stomatology, the Fourth Military Medical University (Approval No.: IRB‐REV‐2021088) and conformed to the Declaration of Helsinki. The study was registered with the ChiCTR (Chinese Clinical Trial Registry) under no. ChiCTR2100048985.

3. Methods

3.1. Sample Size Determination

In order to determine an appropriate sample size for the present study, a pilot study was conducted on a small group of 10 patients to obtain preliminary data which were used to estimate the sample size needed for the main study. The sample size was estimated utilising G power 3.1.9.2(German). With an effect size (d) set at 0.5, an alpha level (α) of 0.05 and a desired power (1‐β) of 0.85, the initial calculation indicated a required sample size of 59 participants for each group. To account for a potential dropout rate of 10%, the expected sample size was adjusted to 65 participants per group. All the enrolled patients were randomly (lottery method) divided into the digital group and the conventional group.

3.2. Digitalized Design and 3D‐Printing for the Digital Group

3.2.1. Digital Model Acquisition

A TRIOS oral scanner (3Shape, Denmark) was used to record the dentition. The occlusal‐raised device was used to make a silicone rubber occlusal record at an occlusal‐raised position, and the intraoral scanner was used to capture the maxillary and mandibular occlusion relationship after occlusal‐raised, which was exported in STL format.

3.2.2. CAD Design

Using the mandibular dentition as the working model, a digital splint was designed in computer‐aided design software Exocad DentalCAD 3.1 (Exocad GmbH, AmannGirrbach, Germany). The occlusal surface of the splint was dynamically adjusted for centric, lateral and protrusive movements using a virtual articulator by the software itself with mean parameters.

3.2.3. 3D Printing Fabrication

The designed digital splint data in the CAD software were imported into an SLA 3D printer Form 2 (Formlabs, USA). Then the 3D‐printed stable occlusal splint was printed using a medical‐grade transparent resin bite splint material (Dental LT Clear V2 Resin Formlabs, USA), followed by cleaning, light curing and support structure removal to complete the fabrication of the digital occlusal splint. The workflow is shown in Figure 1.

FIGURE 1.

The workflow of Design and fabrication method for the digital stable splint. (a) Digital model acquisition; (b and c) CAD design; (d–f) 3D printing fabrication; (g) Clinical fitting.

3.2.4. Design and Made for the Conventional Group

A silicone rubber two‐step impression technique was used to take the denture impression and cast a plaster mould. As shown in Figure 2, a transparent resin bite splint shell was fabricated using a vacuum forming machine Erkoform‐3d motion (Erkodent, Germany) over the mandibular working mould. One mandibular resin shell was made according to the shape of the orthodontic retainer. Then, the resin shell was fitted in the mouth of the patient. Subsequently, dental self‐curing base resin (Artificial Teeth Resin, Xinshiji, Shanghai, China) was placed on the occlusal surface of the posterior teeth region of the resin shell. After the resin shell was put into the mouth, the patient was asked to bite comfortably and slightly in one position near the maximum intercuspal position (MIP) to ensure proper occlusion. After the proper biting, the resin shell with the dental self‐curing base resin was taken out of the mouth and put into warm water to let the self‐curing base resin cure naturally and combine tightly with the resin shell together.

FIGURE 2.

The workflow of Design and fabrication method for the conventional stable splint. (a) Mandibular denture impression; (b) Pouring plaster and trimming; (c) Framework fabrication; (d) Clinic fitting; (e) Self‐curing based resin shaping; (f) Adjustments.

3.2.5. Clinical Occlusal Adjustment for Two Groups

After the fabrication of occlusal splints in both groups, the dentist checked the fit, retention and stability of the occlusal splints intraorally. Occlusal point adjustments were made to the splints based on the patient's maxillary teeth and occlusion marked by articulating paper. After occlusal adjustment, the bite splints were polished to a high degree of smoothness. Patients were instructed to accept splints treatment all day (except chewing time) and return for follow‐up adjustments at the 2nd, 4th and 12th weeks of treatment. They were advised to return for treatment if they experienced any discomfort during the treatment.

3.3. Clinical Evaluation

3.3.1. Working Time

The splint fabrication time and clinical occlusal adjustment time were both recorded for the two types of splints.

3.3.2. Patients' Subjective Evaluation

A questionnaire was administered to patients via phone 3 days after occlusal splint treatment. The questionnaire included four subjective indicators related to the performance of the occlusal splints, including retention, stability, comfort and aesthetics. These were individually rated on a scale of excellent, good and poor, with the former two considered satisfactory. If at least one of the four items observed was poor, the subject was classified as unsatisfactory.

3.3.3. Treatment Efficacy

The treatment efficacy of the two types of splints for TMD was evaluated at the 4th week and 12th week.

3.3.4. Craniomandibular Index (CMI)

Clinical examinations related to the TMJ were performed on the patients according to methods described in previous literature [5], including mandibular movement, joint sounds, joint palpation and muscle palpation. The dysfunction index (DI) and palpation index (PI) were calculated, and the average of DI and PI was taken as the craniomandibular index (CMI).

3.3.5. Pain VAS

The visual analogue scale (VAS) ranging from 0 to 10 for pain was used to assess the level of pain. Patients marked their pain level on a 10 cm horizontal line, where 0 indicated no pain and 10 represented unbearable pain. For the further analysis, the percentage of △pain VAS was calculated as follows: (pretreatment baseline − [posttreatment range at 4/12‐weeks follow‐up] / pretreatment baseline) × 100%.

3.3.6. Maximum Mouth Opening (MMO)

The maximal vertical distance between the upper and lower central incisors, measured at the midline of the dental arch, when a patient opens their mouth as wide as possible. For the further analysis of each patient, the percentage of △MMO was calculated as follows: ([posttreatment range at 4/12‐weeks follow‐up − pretreatment baseline] / pretreatment baseline) × 100%.

3.4. Statistical Analysis

Statistical analysis was performed using SPSS 26.0 (IBM). The Shapiro–Wilk test was used to assess the normality of the data. Data following a normal distribution were expressed as mean ± standard deviation (x̄ ± s) and analysed using an independent samples t‐test. Categorical data were expressed as percentages and analysed using the χ² test. Ordinal data were analysed using the Mann–Whitney U test. p < 0.05 was considered statistically significant.

4. Results

Finally, 126 patients (4 dropouts) were selected and randomly divided into two groups using a random number, with 63 patients in each group. The digital group comprised of 11 males and 52 females, aged 27.97 ± 1.22 years. The conventional group comprised of 13 males and 50 females, aged 27.57 ± 10.42 years.

4.1. Working Time

The splint fabrication time of the digital occlusal splint was 133.65 ± 50.03 min, which was significantly shorter than that of the conventional handmade occlusal splint (234.02 ± 89.38 min, p < 0.001). The clinical occlusal adjustment time of the digital group was 12.80 ± 4.60 min, which was also significantly shorter than that of the conventional group (26.09 ± 7.85 min, p < 0.001).

4.2. Subjective Feeling of Patients

The subjective evaluation of patients after 3 days of the occlusal splint treatment is shown in Table 1. In the digital group, 59 of 63 patients were satisfied, with a satisfaction rate of 93.65%. In the conventional group, 57 of 63 patients were satisfied, with a satisfaction rate of 90.48%. There was no statistically significant difference in satisfaction between the two groups (χ2 = 0.510, p = 0.744).

TABLE 1.

Comparison of patients' subjective feeling between the two groups (n, %).

Group	Retention			Stability			Comfort			Aesthetics			Satisfaction rate
	Excellent	Good	Poor	Excellent	Good	Poor	Excellent	Good	Poor	Excellent	Good	Poor
Digital group	54	8	1	58	5	0	63	0	0	26	34	3	59 (93.65)
Conventional group	55	8	0	58	4	1	57	3	3	30	31	2	57 (90.48)
χ2													0.510
p													0.744

4.3. Treatment Efficacy

4.3.1. CMI, Pain VAS

As shown in Table 2, compared with pretreatment, both the digital group and the conventional group showed significant reductions in the CMI at the 4th week and 12th week of treatment, indicating good clinical efficacy (p < 0.001). There was no statistically significant difference in the CMI between the digital group and the conventional group at pretreatment (p > 0.05). However, the CMI in the digital group was significantly lower than that in the conventional group at both the 4th week and 12th week of treatment (p < 0.05). As shown in Table 3, compared with pretreatment, the pain VAS exhibited a significant reduction in both the digital group and the conventional group at the 4th week and 12th week of treatment (p < 0.05). There was no statistically significant difference in △pain VAS% between the digital group and the conventional group at both the 4th week and 12th week (p > 0.05).

TABLE 2.

Comparison of CMI between the two groups.

Group	CMI
	Pretreatment	4th week	12th week
Digital group	0.0982 ± 0.0435	0.0518 ± 0.0557 a , b	0.0381 ± 0.0468 a , b
Conventional group	0.1052 ± 0.0744	0.0667 ± 0.1001 a	0.0438 ± 0.0491 a

^a Significant difference compared with pretreatment (p < 0.05).

^b Significant difference compared with the conventional group (p < 0.05).

TABLE 3.

Comparison of pain VAS and △pain VAS% between the two groups.

	Digital group	Conventional group	t	p
Pretreatment	4.22 ± 2.22	2.37 ± 1.21	−5.836	0.001
4th week	2.89 ± 2.32 a	1.86 ± 1.20 a	−3.132	0.002
12th week	2.13 ± 2.63 a	1.37 ± 1.58 a	−2.266	0.025
(Pretreatment‐4th week)/Pretreatment	25.19 ± 57.91	17.46 ± 27.18	−0.959	0.339
(Pretreatment‐12th week)/Pretreatment	42.92 ± 48.95	35.45 ± 51.11	−0.838	0.403

^a Significant difference compared with pretreatment (p < 0.05).

4.3.2. Maximum Mouth Opening

As shown in Table 4, there was no statistically significant difference in △MMO% between the two groups at both the 4th week and 12th week (p > 0.05), which indicates the similar efficacy of the two stable occlusal splints about improving maximum mouth opening.

TABLE 4.

Comparison of △maximum mouth opening (MMO)% between the two groups.

	Digital group	Conventional group	t	p
4th week‐Pretreatment	2.15 ± 7.03	2.23 ± 6.09	−0.067	0.946
12th week‐Pretreatment	2.85 ± 6.80	4.97 ± 13.37	−1.118	0.267

5. Discussions

Temporomandibular disorders (TMDs) affect the temporomandibular joint (TMJ), masticatory muscles, and/or related structures and are generally and conventionally treated with stable occlusal splints in clinical practice [6]. This study utilised fully digital technology (including digital intraoral scanning, virtual adjustments, computer‐aided design and 3D printing) to fabricate digital stable occlusal splints for TMD patients. The results showed that digital 3D‐printed stable occlusal splints were as effective and satisfactory as conventional stable occlusal splints but significantly reduced production time, improving efficiency. To the best of our knowledge, the present study was the first comparative study to investigate the efficacy of digital 3D‐printed stable occlusal splints.

With the increasing precision of digital technology, its extensive clinical applicability has been realised. In addition, compared with traditional manual procedures, it is easy to store and highly reproducible. Impression‐taking is a critical step in the splint fabrication process. Early digital optical impression technology had lower accuracy for full‐arch scans. However, new intraoral scanners now offer comparable accuracy to traditional impressions [7, 8, 9, 10]. Patients prefer digital workflows over traditional alginate impressions because the small scanning wands used in intraoral scanning increase comfort [11] and eliminate taste stimuli and reduce risks associated with traditional methods [12, 13, 14, 15].

Computer‐aided design significantly reduces clinical time. First, conventional stabilisation splints are a common clinical device for treating TMD, but their traditional fabrication process is labour‐intensive and time‐consuming. Instead, digital impressions bypass the need for impression disinfection, packaging and physical transport to the laboratory, saving extra time [16, 17]. Patzelt et al. compared the working time of full‐arch conventional and digital optical impressions in a study and found that digital impressions took less time (digital: 17–20 min, conventional: 21–30 min) [18]. Wang et al. found that compared with conventional occlusal splints, the digitally manufactured splints exhibit significantly improved wearing comfort and time efficiency [19] for the treatment of bruxism. Second, clinicians can precisely outline the splint's borders and simulate visualised mandibular movements for virtual adjustments, reducing the need for clinical bedside modifications. Thirdly, the digital denture and splint‐designed data allow for the reproducibility of splints, thereby reducing the number of patient visits and the production cycle of occlusal splints, making replacement easier. For instance, if the original occlusal splint is lost or damaged, the stored digital data can be used to create a new one, thereby avoiding the visits for repeating the complicated fabrication process [20].

3D printing (additive manufacturing) is worthy of clinical promotion and application from the perspective of feasibility and cost‐saving. A recent study found that the cytotoxicity of resins used for 3D printing, thermoforming and heat‐curing occlusal splints was almost identical, indicating similar biocompatibility to conventional splint materials [21]. In addition to 3D printing (additive manufacturing), digital splint fabrication methods also include milling (subtractive manufacturing) [20, 22, 23]. Compared with milled splints, 3D‐printed splints have comparable or slightly lower production accuracy, but are also clinically acceptable [24, 25]. The efficacy of splints appears unrelated to the manufacturing process, with both additive and subtractive methods being equally successful in treating TMD [26, 27]. However, due to the subtractive manufacturing of the milling process, material waste is inevitable, resulting in approximately 70% of nonrecyclable material waste [19]. In clinical practice, typically only two splints can be produced from a single material disc through milling, which incurs additional costs.

Digital splint effectively treats TMD by increasing joint space, restoring tissue coordination, reducing pain and improving mandibular function, all while maintaining patient safety [28, 29]. The analysis suggests that the clinical effect of digital occlusal splint therapy lies in posterior–upper joint space increases by moving the mandibular condyle forward, effectively restoring tissue coordination and relieving pain factor levels. Additionally, by altering the relationship between the maxilla and mandible with the splint, the pressure on the soft tissues of the posterior mandibular joint is reduced, thereby improving mandibular function for TMD patients. During the observation of this study, no adverse events occurred in either group of TMD patients, indicating the good safety of the digital splint and its worthiness of clinical promotion and application.

The underlying mechanisms contributing to the efficacy of 3D‐printed splints likely stem from the precision of digital workflows, material properties and biomechanical optimisation inherent to the technology. First, the digital design process allows for precise customisation of the splint's occlusal surface. Traditional splints relying on manual adjustments may introduce unintended occlusal interferences due to human error, whereas digital splints minimise such discrepancies through algorithmic precision. Second, 3D‐printed resins exhibit uniform material density and structural integrity; the layer‐by‐layer additive manufacturing process also enables intricate geometries that conform precisely to patient‐specific dental anatomy, improving retention and stability without compromising comfort. Thirdly, the digital workflow facilitates biomechanical optimisation. Furthermore, the ability to store and reproduce splints from digital files ensures treatment consistency, particularly for patients requiring splint replacements or adjustments over time. Finally, the reduced clinical adjustment time observed in the digital group may indirectly reduce patient discomfort and muscle fatigue.

The present study has several limitations. First, the study's data reliance on a single centre may lead to regional biases, impacting the generalizability of the findings. Second, the main limitation of digital 3D‐printed stable occlusal splints lies in the high cost of digital hardware and software. However, as digital technology becomes more widespread in dental clinics, the digital equipment and workflow for splint fabrication are likely to become more available and cheaper.

6. Conclusions

Digital 3D‐printed stable occlusal splints can not only alleviate TMD symptoms as effectively and satisfactorily as the conventional handmade stable splint but also reduce production time and improve accuracy and efficiency, promising good clinical application prospects.

Author Contributions

S.Y., S.G., H.Q., Y.L. and H.M. designed the main study, analysed the data and edited the manuscript. T.W., X.C., L.L., M.Z. and H.Z. contributed to the data acquisition, collection and assembly. S.Y., H.Q. and J.Z. wrote the manuscript. All authors were involved in revising the manuscript and approved the final submitted version of the manuscript. All authors have read and approved this version of the article, and due care has been taken to ensure the integrity of the work. No part of this paper has been published or is under consideration for publication elsewhere.

Conflicts of Interest

The authors declare no conflicts of interest.

Peer Review

The peer review history for this article is available at https://www.webofscience.com/api/gateway/wos/peer‐review/10.1111/joor.14032.

Data Availability Statement

Data available on request from the authors.