The Kovacs-customized temporomandibular joint appliance for temporomandibular joint anterior disc displacement: a prospective cohort study of its clinical efficacy and the correlation between pain and functional improvement

The Kovacs-customized temporomandibular joint appliance for temporomandibular joint anterior disc displacement: a prospective cohort study of its clinical efficacy and the correlation between pain and functional improvement | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The Kovacs-customized temporomandibular joint appliance for temporomandibular joint anterior disc displacement: a prospective cohort study of its clinical efficacy and the correlation between pain and functional improvement Jiaxin Jia, Huawei Ming, Xing’an Zhang, Hong Li, Chao Jia, Zilong Liu, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8115203/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Anterior disc displacement of the temporomandibular joint is a common cause of orofacial pain and functional limitation. However, rigorous clinical validation of fully digital, standardized protocols that determine therapeutic jaw position in the management of anterior disc displacement of the temporomandibular joint is lacking. Therefore, the aim of this study was to evaluate the clinical efficacy of the Kovacs-customized temporomandibular joint appliance and explore the correlation between pain reduction and functional improvement in patients with anterior disc displacement of the temporomandibular joint. Methods Forty patients with anterior disc displacement of the temporomandibular joint were prospectively enrolled. All participants received a Kovacs-customized temporomandibular joint appliance fabricated via a standardized digital workflow and were assessed over a 6-month period. Primary outcomes included pain intensity measured using a visual analog scale and maximum mouth opening. The relationship between the changes in these two key outcomes was analyzed using Spearman’s correlation coefficient. Joint sounds and disc positions were recorded on magnetic resonance imaging as exploratory observations. Results Kovacs-customized temporomandibular joint appliance treatment resulted in significant clinical improvement. Mean visual analog scale pain scores decreased from 5.30 ± 2.09 at baseline to 1.66 ± 1.42 at 6 months (t = -11.035, P < 0.001). Concurrently, median maximum mouth opening increased from 36.5 mm (interquartile range: 26.25–39.00) to 39.0 mm (interquartile range: 37.25–40.00) (Z = -4.181, P < 0.001). A statistically significant, moderate negative correlation was identified between reduction in pain intensity and increase in maximum mouth opening (ρ = -0.493, P = 0.001), indicating that greater pain relief was associated with greater functional improvement. Clinical improvement was accompanied by resolution of joint clicking in most patients, whereas exploratory magnetic resonance imaging revealed variable changes in disc position. Conclusions The Kovacs-customized temporomandibular joint appliance is an effective conservative treatment for anterior disc displacement of the temporomandibular joint that significantly alleviates pain and improves mandibular function. The demonstrated correlation between symptomatic and functional recovery provides valuable insights into the therapeutic process and underscores the value of this standardized digital protocol. The Kovacs-customized temporomandibular joint appliance represents a promising option within a patient-centered care framework. temporomandibular joint disorders anterior disc displacement of temporomandibular joint occlusal splint digital dentistry Kovacs-customized temporomandibular joint appliance Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Background Temporomandibular disorders (TMD) are represent a complex set of medical conditions arising from a dynamic interplay of biological, psychological, and social factors, rather than from structural abnormalities alone. Biopsychosocial models of TMD management primarily aim to alleviate pain, restore function, and improve patient quality of life [ 1 ]. TMD is a common condition affecting the oral and maxillofacial systems, and is recognized as the second leading cause of orofacial pain [ 2 ]. Studies suggest that up to 50% of adults in the general population will experience symptoms at some point [ 3 , 4 ]. Common clinical manifestations include joint and muscle pain, joint sounds, and restricted mandibular movements all of which significantly impact daily life [ 5 ]. Although anatomical alterations, such as anterior disc displacement (ADD), are observed in approximately 70% of patients with TMD [ 6 ], disc position alone is a poor predictor of pain and dysfunction. According to current mainstream recommendations and diagnostic criteria, ADD diagnosis is primarily based on clinical findings, with imaging, such as magnetic resonance imaging (MRI), serving as an adjunct for confirmation in complex cases [ 7 – 10 ]. Moreover, current guidelines emphasize that disc position should not be the main focus of treatment, as permanent anatomical “recapture” is typically not feasible histologically and there is a lack of strong evidence to support its value as a primary treatment goal [ 11 , 12 ]. The etiology of anterior disc displacement of the temporomandibular joint (TMJ ADD) is complex and multifactorial, involving an interplay of anatomical, biomechanical, and psychosocial factors, aligning with the biopsychosocial model of TMD [ 13 ]. Potential contributing factors include trauma, joint hypermobility, and masticatory muscle parafunction (e.g., bruxism) [ 14 , 15 ]; however, the role of occlusal factors is considered limited [ 16 ]. Consistent with contemporary standards of care, the management of ADD should follow a conservative-first approach, incorporating patient education, physical therapy, and occlusal appliance therapy to minimally invasive procedures (e.g., arthrocentesis). In select refractory cases, surgical interventions may be required. Within this framework, conservative and reversible therapies remain the cornerstone of TMD management [ 17 ]. Among these, occlusal splints are widely used, and their therapeutic mechanism is primarily attributed to neuromuscular modulation, load reduction, and a potential influence on psychosocial factors, such as stress, that manifest as oral parafunction [ 18 , 19 ]. However, the conventional fabrication of splints is often technique-sensitive and reliant on clinician experience, leading to variable outcomes [ 20 ]. Digital technology offers a means of overcoming these limitations by enhancing precision and reproducibility [ 21 ]. Although digital workflows demonstrate significant potential, a critical gap remains in the rigorous clinical validation of fully digital protocols that integrate a standardized approach to determine therapeutic jaw position. Therefore, the aim of this study was to conduct a prospective proof-of-concept evaluation of the Kovacs-customized temporomandibular joint appliance (KTA). A key feature of this protocol is the incorporation of a standardized muscle deprogramming maneuver to establish a stable, neuromuscularly balanced baseline [ 22 ]. The primary goals were to assess the feasibility of this digital workflow and to evaluate its preliminary efficacy in alleviating pain and improving function in patients with ADD, thereby generating hypotheses for future investigations. We hypothesized that this digitally streamlined protocol offers a more standardized and reproducible conservative treatment option. Methods Study participants Forty patients diagnosed with TMJ-ADD were recruited from the specialized temporomandibular joint (TMJ) clinic of our hospital between October 2022 and October 2023. The cohort included seven males and 33 females, aged from 14 to 56 years (mean ± standard deviation: 24.52 ± 12.00 years). Sixty-seven joints were affected, among which 44 joints were diagnosed with anterior disc displacement with reduction (ADDwR) and 23 joints with anterior disc displacement without reduction (ADDwoR). The inclusion criteria were as follows: (1) diagnosis of ADDwR or ADDwoR based on the Diagnostic Criteria for Temporomandibular Disorders [ 23 ] and confirmed using magnetic resonance imaging (MRI); (2) presence of pain in the TMJ region and/or functional impairment; (3) adequate periodontal and dental support for KTA; and (4) provision of informed consent by patients or their guardians. The exclusion criteria were as follows: (1) presence of any concomitant painful or disabling conditions that could confound the assessment, such as tumors, significant degenerative joint disease, or uncontrolled systemic diseases; (2) diagnosis of significant psychological disorders (e.g., moderate to severe depression or anxiety) that, in the investigator’s opinion, could substantially interfere with pain perception or treatment compliance; (3) history of TMJ fracture or previous TMJ surgery; and (4) having received any invasive TMD treatment (e.g., arthrocentesis, arthroscopy) within the 6 months prior to enrollment. Research methods Intraoral data acquisition Intraoral scans were performed sequentially using an intraoral scanner (TRIOS 3; 3Shape, Copenhagen, Denmark) to capture digital impressions of the mandibular dentition, maxillary dentition, and the patient’s existing occlusal relationship. A facebow was used to transfer the positional data of the maxilla. This process yielded digital models of both dental arches, which were subsequently mounted on a virtual articulator to simulate occlusal relationships (Fig. 1 a-d). Fabrication of the deprogramming device The deprogramming device was designed using Exocad design software (Align Technology, Tempe, AZ, USA). The maxillary component of the device features a flat circular platform, whereas the mandibular component consists of a small cylindrical extension. The device was milled from medical-grade PMMA resin discs using a 5-axis CNC milling machine (Fig. 2 a-c). Determination of therapeutic position A thin uniform layer of dental adhesive was applied to the occlusal surfaces of the deprogramming device and allowed to dry. Subsequently, a silicone registration material was added to the same areas. The device was then carefully positioned lingually on the upper and lower anterior teeth of the patient. After complete polymerization of the silicone material, the device was removed and any excess material was trimmed. The upper and lower components were reinserted into the patient’s mouth to verify stability (Fig. 2 d). The patient was seated upright opposite the operator with back straight, head held erect, and feet flat on the floor. The chair height was adjusted so that the patient’s hips were slightly higher than the knees. The muscle deprogramming maneuvers were performed as follows: (1) Light tapping exercise (Fig. 3 a): The patient was instructed to perform gentle tapping movements starting with the mouth open the breadth of one finger, maintaining a comfortable rhythm (approximately 90 taps/minute). An audible contact between the upper and lower components of the deprogramming device was required for each closure. The exercise lasted for 10 minutes. (2) Medium-tapping exercise (Fig. 3 b): The patient then performed tapping movements starting with mouth open the breadth of two fingers maintaining a rhythm of approximately 60 taps/minute, again ensuring audible contact upon closure. This exercise was continued for 10 minutes. (3) Maximum tapping exercise (Fig. 3 c): The patient was asked to tap with mouth at maximum comfortable opening, sufficient to elicit a stretching sensation in the submental muscles, at a rate of approximately 20 taps/minute. The head remained stationary with movement limited to the mandible. After closure, the mandible was free to naturally advance into contact with the maxilla. Fifty repetitions were performed. (4) Protrusive movement (Fig. 3 d): From a slightly open position, the patient was advised to protrude their mandible forward, hold the position for 2–3 s, and then return to the starting position. This procedure was repeated five times. (5) Lateral excursion movements (Fig. 3 e-f): The patient was instructed to move the mandible to the left and right sides, holding each lateral position for 2–3 s before returning to the starting position. This procedure was repeated five times on each side. (6) Muscle examination and final registration: The masticatory muscles were palpated bilaterally to confirm symmetry and adequate relaxation. The patient was then instructed to gently inhale, perform three small tapping motions, maintain a closed position, and exhale. Silicone occlusal registration material was placed between the posterior teeth. After polymerization, the registration was removed, lightly trimmed, and re-inserted. The patient was asked to perform gentle clenching and relaxation movements with the teeth in contact. Bilateral symmetry and muscle strength were also assessed. Finally, an intraoral scanner was used to capture the post-deprogramming occlusal relationship (Fig. 4 a-b). Fabrication of the temporomandibular joint appliance The appliance was designed using the same design software, and milled from medical-grade PMMA resin discs on a 5-axis CNC milling machine (Fig. 5 a-d). Outcome measures All appliances were delivered and adjusted by a single clinician who received standardized training. Patients were instructed to wear the appliance continuously for six months, except during meals and oral hygiene procedures. Follow-up evaluations were conducted every 4 weeks. The therapeutic outcomes were assessed upon completion of the treatment. Assessment of primary outcomes Pain intensity assessment Pain intensity in the TMJ and surrounding regions was evaluated before and after treatment using a visual analog scale (VAS). A 10-cm horizontal line was presented with endpoints labeled “no pain”(0 cm) and “worst pain imaginable” (10 cm). Patients were asked to mark their current level of orofacial pain on the line, and the corresponding scores were recorded. Maximum mouth opening (MMO) MMO was measured using a stainless-steel ruler. Two measurements were taken for each patient and the average value was recorded for before and after treatment. Exploratory observations Joint sound (clicking) assessment The presence and frequency of joint clicks during opening and closing movements were recorded by a clinician before and after treatment as a descriptive observational measure. A click was defined as a clear, brief, and audible sound during mandibular movement. MRI protocol and exploratory analysis of disc position MRI was performed on all patients at baseline and upon completion of the 6-month treatment period. The imaging protocol adhered to standard clinical procedures for the TMJ. A proton density-weighted imaging sequence in the oblique sagittal plane was obtained for each joint in both closed- and open-mouth positions. As an exploratory analysis to document any structural changes accompanying the clinical outcomes, the disc-condyle relationship was assessed on MRI scans by an experienced oral radiologist who was blinded to the clinical outcomes. This assessment was performed as previously described [ 24 ]. Briefly, the disc condylar angle was measured on the slice displaying the largest condylar surface in the closed-mouth position. An angle exceeding 10° was considered indicative of ADD. The reducibility of displacement was determined by evaluating the disc position on the open-mouth image. The primary focus of this analysis was to observe any positional changes that occurred along with the primary clinical outcomes (pain reduction and improvement in mouth opening). Statistical analysis Statistical analyses were performed using SPSS software (version 31.0; IBM Corp., Armonk, NY, USA). Normality of the data was assessed using the Shapiro–Wilk test. Normally distributed data are presented as mean ± standard deviation (SD), whereas non-normally distributed data are expressed as median and interquartile range (IQR). For the analysis of pain intensity (VAS), the difference between the pre- and post-treatment scores was normally distributed, as confirmed by the Shapiro–Wilk test (P > 0.05). Therefore, a paired-samples t-test was used to evaluate statistical significance. For the MMO analysis, the data violated the assumption of normality (Shapiro–Wilk test, P < 0.05). Consequently, the non-parametric Wilcoxon signed-rank test was used. The relationship between the change in pain intensity and change in MMO was assessed using Spearman’s rank-order correlation coefficient. Statistical significance was set at P < 0.05. Results Primary clinical outcomes Treatment with KTA led to significant clinical improvements. The mean VAS pain score decreased from 5.30 ± 2.09 at baseline to 1.66 ± 1.42 at the 6-month follow-up (t = -11.035, P < 0.001). Concurrently, the median MMO increased from 36.5 mm (IQR: 26.25–39.00) to 39.0 mm (IQR: 37.25–40.00) (Z = -4.181, P < 0.001) (Table 1 ). Table 1 Comparison of VAS scores and MMO (mm) of patients before and after treatment Primary Outcomes Before treatment After treatment t or Z value P value VAS scores 5.30 ± 2.09 1.66 ± 1.42 t = -11.035 P < 0.001 MMO (mm) 36.5 (IQR: 26.25-39.00) 39 (IQR: 37.25-40.00) Z= -4.181, P < 0.001 A clinically significant improvement in MMO (increase of ≥ 5 mm) was observed in 37.5% (15/40) of patients. Subgroup analysis revealed that all 15 responders had a baseline MMO ≤ 35 mm. Within this functionally compromised subgroup (n = 17), the response rate was 88.2% (15/17). Correlation between symptomatic and functional improvement Spearman’s correlation analysis revealed a statistically significant, moderate negative correlation between the reduction in VAS scores and the increase in MMO (ρ = -0.493, P = 0.001) (Fig. 6 ). Exploratory findings Among the 40 joints with initial clicking, the sound resolved completely in 27 (67.5%) joints and was reduced in frequency in another nine (22.5%) joints after treatment. Notably, clicking resolved in three joints that had progressed to irreducible disc displacement (Table 2 ). Table 2 Descriptive summary of joint clicking changes after treatment (n = 40) Change in joint clicking Number of joints Percentage (%) Eliminated 27 67.5 Reduced 9 22.5 Unchanged or increased 4 10.0 Total 40 100.0 Post-treatment MRI, reviewed as an ancillary analysis, showed variable and inconsistent changes in disc position. A sizeable proportion of the ADDwR joints exhibited positional changes, whereas fewer than half of the ADDwoR joints exhibited positional changes (Table 3 ). Crucially, clinical improvements in pain and MMO were observed, irrespective of whether a change in disc position was evident on MRI. Table 3 Changes in the position of the disc-condylar before and after treatment Disc-condylar position relationship n After treatment Recaptured(%) Not recaptured(%) AADwR 44 27(88.6) 6(11.4) AADwoR 23 11(47.9) 12(52.1) Discussion Our findings demonstrate that the KTA, delivered via a standardized digital protocol, is associated with significant improvements in pain and mandibular function in patients with TMJ ADD. Importantly, our findings offer two key advancement: first, the identification of a patient subgroup most likely to achieve functional recovery; and second, novel insights into the coordinated nature of symptomatic and functional improvement. The most clinically significant finding of this study was the identification of a clear predictor of functional response. The capacity for major functional gain (≥ 5 mm increase in MMO) was exclusively confined to patients with baseline MMO ≤ 35 mm, with 88.2% of this subgroup responding. This observation is mechanistically sound because patients with significant restrictions possess a greater latent capacity for recovery once pain and muscle splinting are alleviated. This finding clearly defines the ideal candidate for KTA therapy, shifting the treatment paradigm from generic “improvement” to targeted “functional restoration.” For clinicians, baseline MMO measurements have become a crucial triage tool that enables personalized, function-based treatment planning. Furthermore, we observed a significant correlation between pain reduction and functional gain. The observed moderate negative correlation (ρ = -0.493) suggests these core outcomes are not merely improving in parallel but are intrinsically linked. This aligns with the pathophysiology in which pain leads to protective muscle splinting, directly restricting mandibular function [ 25 ]. This correlation indicates that KTA likely disrupts this self-perpetuating cycle, facilitating comprehensive recovery. While correlation does not prove causation and shared factors such as reduced psychosocial distress or a general placebo effect may contribute [ 26 , 27 ], this coherent pattern underscores a biologically meaningful therapeutic response. Our results support the current biopsychosocial paradigm. Primary clinical improvements occurred independently of consistent MRI disc positional changes (Figs. 7 and 8 ). Symptomatic relief was achieved in patients with disc recapture and those without fundamental anatomical alterations. This underscores that alleviating patient suffering rather than normalizing the anatomy is the primary therapeutic goal [ 1 , 11 , 12 ]. Adherence to this symptom-based approach is crucial to avoid the pitfalls of overtreatment and misdirected therapy, which are significant concerns when disc position is overemphasized, as discussed by Greene et al. [ 28 , 29 ]. The resolution of joint clicking observed in most patients aligns with the common clinical outcome of splint therapy. However, the significance of these findings should be interpreted with caution. The concomitant disappearance of clicking in joints that progressed to ADDwoR demonstrates that the absence of this sign is not a reliable indicator of successful disc recapture or a prerequisite for symptomatic improvement. This observation further reinforces the principle that clinical management should focus on the patient’s primary complaints—pain and functional limitations—rather than the elimination of joint sounds, which may represent an epiphenomenon rather than a core treatment target. The primary limitation of this study was its single-arm, uncontrolled design. Consequently, we cannot definitively rule out the contribution of non-specific effects—such as the placebo effect, the natural history of TMD, or regression to the mean—to the observed clinical improvements. However, the primary objective of this initial investigation was to evaluate the feasibility and preliminary efficacy of the novel digital workflow. The promising outcomes and clear patient stratification identified here provide a robust rationale and essential preliminary data for a future randomized controlled trial that includes sham intervention or standard care, which is necessary to confirm the specific efficacy of the KTA. The efficacy of our digital protocol appears comparable to the positive outcomes achieved by other well-established conservative interventions for TMDs [ 30 , 31 ]. This finding, coupled with the enhanced reproducibility and standardization offered by our digital workflow, suggests that further investigation is warranted as a valuable addition to the armamentarium of reversible, minimally invasive treatments. Conclusions In conclusion, the KTA was associated with improved pain and function in patients with TMJ ADD. Its major contribution lies in enabling a precision medicine approach. By identifying patients most likely to achieve functional recovery, it offers a clear path for personalized care. These findings reinforce the need for subsequent controlled trials to verify their efficacy. Abbreviations TMD, temporomandibular disorder ADD, anterior disc displacement MRI magnetic resonance imaging TMJ ADD anterior disc displacement of the temporomandibular joint KTA, Kovacs-customized temporomandibular joint appliance ADDwR, anterior disc displacement with reduction ADDwoR, anterior disc displacement without reduction VAS, visual analog scale MMO, maximum mouth opening SD, standard deviation IQR, interquartile range Declarations Ethics approval and consent to participate All experimental procedures were approved by the Institutional Ethics Committee of Beijing Anzhen Nanchong Hospital of Capital Medical University & Nanchong Central Hospital. Consent for publication Not applicable. Availability of data and materials The data sets used in this study are available from the corresponding author upon request. Competing interests The authors declare that they have no competing interests, and all authors have confirmed the accuracy of this study. Funding No funding. 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Effects of occlusal splint therapy in addition to physical therapy on pain in patients affected by myogenous temporomandibular disorders: a pilot randomized controlled trial. Cranio. 2025;26:1–18. 10.1080/08869634.2025.2523089 . Pehlivan Tekin G, Yakut Y. Effectiveness of a home exercise program when added to a conventional physiotherapy program in patients with temporomandibular disorders: a comparative study. Cranio. 2025;43:851–62. 10.1080/08869634.2024.2360370 . Additional Declarations No competing interests reported. Supplementary Files SupplementaryData1.xls Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8115203","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":561292960,"identity":"20acc1c0-d38a-467e-9aac-8672984ec4a5","order_by":0,"name":"Jiaxin Jia","email":"","orcid":"","institution":"Beijing Anzhen Nanchong Hospital of Capital Medical University and Nanchong Central Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jiaxin","middleName":"","lastName":"Jia","suffix":""},{"id":561292962,"identity":"b9150c8d-9690-4d38-a9df-ca206b2532fb","order_by":1,"name":"Huawei Ming","email":"","orcid":"","institution":"Beijing 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07:24:29","extension":"html","order_by":29,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":104735,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8115203/v1/81cbec67da8ff8c8141d6dee.html"},{"id":98379116,"identity":"521f6efc-91ed-4b43-9b86-f2450c771977","added_by":"auto","created_at":"2025-12-17 07:24:34","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":885502,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eIntraoral data acquired using an intraoral scanner. \u003c/strong\u003ea: Maxillary dentition; b: Mandibular dentition; c: Pretreatment occlusal relationship; d: Occlusal relationship transferred to a virtual articulator.\u003c/p\u003e","description":"","filename":"figure.1.png","url":"https://assets-eu.researchsquare.com/files/rs-8115203/v1/bdb37f07ab651e833fdb17eb.png"},{"id":98439870,"identity":"1a04a315-fe47-45a3-89d6-5cd87f9c02a5","added_by":"auto","created_at":"2025-12-17 17:03:02","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1998530,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDeprogramming device. \u003c/strong\u003ea, b: Design of the deprogramming device in the software; c: Final fabricated deprogramming device; d: Deprogramming device positioned intraorally.\u003c/p\u003e","description":"","filename":"figure.2.png","url":"https://assets-eu.researchsquare.com/files/rs-8115203/v1/3e6bdc462c4c1d120a3d35fe.png"},{"id":98379064,"identity":"f220118d-378b-40c9-9005-ee915bd3e2df","added_by":"auto","created_at":"2025-12-17 07:24:29","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1314755,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMuscle deprogramming maneuvers.\u003c/strong\u003e a: Light tapping exercise; b: Medium tapping exercise; c: Maximum tapping exercise; d: Protrusive movement; e-f: Lateral excursion movements.\u003c/p\u003e","description":"","filename":"figure.3.png","url":"https://assets-eu.researchsquare.com/files/rs-8115203/v1/1ed3bd01bbd6f75eda8f472c.png"},{"id":98379002,"identity":"45a60700-82ce-4ada-a1cc-f1a5b498bd6a","added_by":"auto","created_at":"2025-12-17 07:24:21","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":862188,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eChanges in mandibular position after deprogramming maneuvers.\u003c/strong\u003ea: Occlusal relationship after deprogramming maneuvers; b: Comparison of occlusal relationships before and after deprogramming.\u003c/p\u003e","description":"","filename":"figure.4.png","url":"https://assets-eu.researchsquare.com/files/rs-8115203/v1/b3d57286412a21f131958cf0.png"},{"id":98379000,"identity":"1b52b600-6c9c-4d67-99fa-58513647642b","added_by":"auto","created_at":"2025-12-17 07:24:21","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1693619,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eKovac customized temporomandibular joint appliance.\u003c/strong\u003ea-b: Design of the Kovac customized temporomandibular joint appliance in the software, ensuring bilateral posterior simultaneous, stable, symmetrical, and force-balanced multipoint contacts; c: Final fabricated Kovac customized temporomandibular joint appliance; d: Intraoral trial placement of the Kovac customized temporomandibular joint appliance.\u003c/p\u003e","description":"","filename":"figure.5.png","url":"https://assets-eu.researchsquare.com/files/rs-8115203/v1/694a85bc8ea067b30ef499f3.png"},{"id":98379120,"identity":"5da6c411-47ab-422a-8f4c-14ad5456730c","added_by":"auto","created_at":"2025-12-17 07:24:35","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":385422,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCorrelation between improvement in pain and mandibular function.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Figure.6.png","url":"https://assets-eu.researchsquare.com/files/rs-8115203/v1/4646dc9151fe2339aca1de3d.png"},{"id":98379084,"identity":"09c34916-7af1-4ea1-b2a8-20bc6618eeca","added_by":"auto","created_at":"2025-12-17 07:24:30","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":812853,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eExploratory MRI findings in a representative patient initially diagnosed with ADDwR.\u003c/strong\u003e a-b: Pretreatment images in the (a) closed-mouth and (b) open-mouth positions demonstrate ADDwR. c-d: Posttreatment images in the (c) closed-mouth and (d) open-mouth positions. It is noteworthy that, in this patient, symptomatic improvement was accompanied by a change in the disc-condyle relationship. These MRI findings are presented as descriptive observations and were not primary outcomes of the study, which focused on clinical symptom resolution.\u003c/p\u003e","description":"","filename":"figure.7.png","url":"https://assets-eu.researchsquare.com/files/rs-8115203/v1/c1a35adaa61f3bf4fb7e216a.png"},{"id":98440703,"identity":"d220c72d-816a-43a2-9799-4765a91603b9","added_by":"auto","created_at":"2025-12-17 17:04:13","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":861832,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eExploratory MRI findings in a representative patient initially diagnosed with ADDwoR.\u003c/strong\u003e a-b: Pretreatment images in both the (a) closed-mouth and (b) open-mouth positions demonstrate persistent anterior disc displacement without reduction. c-d: Posttreatment images in the (c) closed-mouth and (d) open-mouth positions. In this patient, symptomatic improvement occurred without a consistent change in disc position. These MRI findings are presented as descriptive observations and were not primary outcomes of the study, which focused on clinical symptom resolution.\u003c/p\u003e","description":"","filename":"figure.8.png","url":"https://assets-eu.researchsquare.com/files/rs-8115203/v1/05c38a9b19f4c4364ee0de1e.png"},{"id":99310505,"identity":"f8e8a930-eea1-4b02-9200-814d000ac42d","added_by":"auto","created_at":"2025-12-31 16:12:56","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":9428219,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8115203/v1/97971b2e-09bb-4657-a5c4-157b1c5ef98f.pdf"},{"id":98379102,"identity":"74601c5a-9aec-4436-b6b9-8b48cbbfae8c","added_by":"auto","created_at":"2025-12-17 07:24:32","extension":"xls","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":24576,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryData1.xls","url":"https://assets-eu.researchsquare.com/files/rs-8115203/v1/b76557c786483f01f1707e14.xls"}],"financialInterests":"No competing interests reported.","formattedTitle":"The Kovacs-customized temporomandibular joint appliance for temporomandibular joint anterior disc displacement: a prospective cohort study of its clinical efficacy and the correlation between pain and functional improvement","fulltext":[{"header":"Background","content":"\u003cp\u003eTemporomandibular disorders (TMD) are represent a complex set of medical conditions arising from a dynamic interplay of biological, psychological, and social factors, rather than from structural abnormalities alone. Biopsychosocial models of TMD management primarily aim to alleviate pain, restore function, and improve patient quality of life [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTMD is a common condition affecting the oral and maxillofacial systems, and is recognized as the second leading cause of orofacial pain [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Studies suggest that up to 50% of adults in the general population will experience symptoms at some point [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Common clinical manifestations include joint and muscle pain, joint sounds, and restricted mandibular movements all of which significantly impact daily life [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Although anatomical alterations, such as anterior disc displacement (ADD), are observed in approximately 70% of patients with TMD [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], disc position alone is a poor predictor of pain and dysfunction. According to current mainstream recommendations and diagnostic criteria, ADD diagnosis is primarily based on clinical findings, with imaging, such as magnetic resonance imaging (MRI), serving as an adjunct for confirmation in complex cases [\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Moreover, current guidelines emphasize that disc position should not be the main focus of treatment, as permanent anatomical \u0026ldquo;recapture\u0026rdquo; is typically not feasible histologically and there is a lack of strong evidence to support its value as a primary treatment goal [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe etiology of anterior disc displacement of the temporomandibular joint (TMJ ADD) is complex and multifactorial, involving an interplay of anatomical, biomechanical, and psychosocial factors, aligning with the biopsychosocial model of TMD [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Potential contributing factors include trauma, joint hypermobility, and masticatory muscle parafunction (e.g., bruxism) [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]; however, the role of occlusal factors is considered limited [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eConsistent with contemporary standards of care, the management of ADD should follow a conservative-first approach, incorporating patient education, physical therapy, and occlusal appliance therapy to minimally invasive procedures (e.g., arthrocentesis). In select refractory cases, surgical interventions may be required. Within this framework, conservative and reversible therapies remain the cornerstone of TMD management [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Among these, occlusal splints are widely used, and their therapeutic mechanism is primarily attributed to neuromuscular modulation, load reduction, and a potential influence on psychosocial factors, such as stress, that manifest as oral parafunction [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. However, the conventional fabrication of splints is often technique-sensitive and reliant on clinician experience, leading to variable outcomes [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDigital technology offers a means of overcoming these limitations by enhancing precision and reproducibility [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Although digital workflows demonstrate significant potential, a critical gap remains in the rigorous clinical validation of fully digital protocols that integrate a standardized approach to determine therapeutic jaw position.\u003c/p\u003e \u003cp\u003eTherefore, the aim of this study was to conduct a prospective proof-of-concept evaluation of the Kovacs-customized temporomandibular joint appliance (KTA). A key feature of this protocol is the incorporation of a standardized muscle deprogramming maneuver to establish a stable, neuromuscularly balanced baseline [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The primary goals were to assess the feasibility of this digital workflow and to evaluate its preliminary efficacy in alleviating pain and improving function in patients with ADD, thereby generating hypotheses for future investigations. We hypothesized that this digitally streamlined protocol offers a more standardized and reproducible conservative treatment option.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy participants\u003c/h2\u003e \u003cp\u003eForty patients diagnosed with TMJ-ADD were recruited from the specialized temporomandibular joint (TMJ) clinic of our hospital between October 2022 and October 2023. The cohort included seven males and 33 females, aged from 14 to 56 years (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation: 24.52\u0026thinsp;\u0026plusmn;\u0026thinsp;12.00 years). Sixty-seven joints were affected, among which 44 joints were diagnosed with anterior disc displacement with reduction (ADDwR) and 23 joints with anterior disc displacement without reduction (ADDwoR). The inclusion criteria were as follows: (1) diagnosis of ADDwR or ADDwoR based on the Diagnostic Criteria for Temporomandibular Disorders [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] and confirmed using magnetic resonance imaging (MRI); (2) presence of pain in the TMJ region and/or functional impairment; (3) adequate periodontal and dental support for KTA; and (4) provision of informed consent by patients or their guardians. The exclusion criteria were as follows: (1) presence of any concomitant painful or disabling conditions that could confound the assessment, such as tumors, significant degenerative joint disease, or uncontrolled systemic diseases; (2) diagnosis of significant psychological disorders (e.g., moderate to severe depression or anxiety) that, in the investigator\u0026rsquo;s opinion, could substantially interfere with pain perception or treatment compliance; (3) history of TMJ fracture or previous TMJ surgery; and (4) having received any invasive TMD treatment (e.g., arthrocentesis, arthroscopy) within the 6 months prior to enrollment.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eResearch methods\u003c/h3\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eIntraoral data acquisition\u003c/h2\u003e \u003cp\u003eIntraoral scans were performed sequentially using an intraoral scanner (TRIOS 3; 3Shape, Copenhagen, Denmark) to capture digital impressions of the mandibular dentition, maxillary dentition, and the patient\u0026rsquo;s existing occlusal relationship. A facebow was used to transfer the positional data of the maxilla. This process yielded digital models of both dental arches, which were subsequently mounted on a virtual articulator to simulate occlusal relationships (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea-d).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eFabrication of the deprogramming device\u003c/h3\u003e\n\u003cp\u003eThe deprogramming device was designed using Exocad design software (Align Technology, Tempe, AZ, USA). The maxillary component of the device features a flat circular platform, whereas the mandibular component consists of a small cylindrical extension. The device was milled from medical-grade PMMA resin discs using a 5-axis CNC milling machine (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea-c).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eDetermination of therapeutic position\u003c/h3\u003e\n\u003cp\u003eA thin uniform layer of dental adhesive was applied to the occlusal surfaces of the deprogramming device and allowed to dry. Subsequently, a silicone registration material was added to the same areas. The device was then carefully positioned lingually on the upper and lower anterior teeth of the patient. After complete polymerization of the silicone material, the device was removed and any excess material was trimmed. The upper and lower components were reinserted into the patient\u0026rsquo;s mouth to verify stability (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed).\u003c/p\u003e \u003cp\u003eThe patient was seated upright opposite the operator with back straight, head held erect, and feet flat on the floor. The chair height was adjusted so that the patient\u0026rsquo;s hips were slightly higher than the knees. The muscle deprogramming maneuvers were performed as follows:\u003c/p\u003e \u003cp\u003e(1) Light tapping exercise (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea): The patient was instructed to perform gentle tapping movements starting with the mouth open the breadth of one finger, maintaining a comfortable rhythm (approximately 90 taps/minute). An audible contact between the upper and lower components of the deprogramming device was required for each closure. The exercise lasted for 10 minutes.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e(2) Medium-tapping exercise (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb): The patient then performed tapping movements starting with mouth open the breadth of two fingers maintaining a rhythm of approximately 60 taps/minute, again ensuring audible contact upon closure. This exercise was continued for 10 minutes.\u003c/p\u003e \u003cp\u003e(3) Maximum tapping exercise (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec): The patient was asked to tap with mouth at maximum comfortable opening, sufficient to elicit a stretching sensation in the submental muscles, at a rate of approximately 20 taps/minute. The head remained stationary with movement limited to the mandible. After closure, the mandible was free to naturally advance into contact with the maxilla. Fifty repetitions were performed.\u003c/p\u003e \u003cp\u003e(4) Protrusive movement (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed): From a slightly open position, the patient was advised to protrude their mandible forward, hold the position for 2\u0026ndash;3 s, and then return to the starting position. This procedure was repeated five times.\u003c/p\u003e \u003cp\u003e(5) Lateral excursion movements (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee-f): The patient was instructed to move the mandible to the left and right sides, holding each lateral position for 2\u0026ndash;3 s before returning to the starting position. This procedure was repeated five times on each side.\u003c/p\u003e \u003cp\u003e(6) Muscle examination and final registration: The masticatory muscles were palpated bilaterally to confirm symmetry and adequate relaxation. The patient was then instructed to gently inhale, perform three small tapping motions, maintain a closed position, and exhale. Silicone occlusal registration material was placed between the posterior teeth. After polymerization, the registration was removed, lightly trimmed, and re-inserted. The patient was asked to perform gentle clenching and relaxation movements with the teeth in contact. Bilateral symmetry and muscle strength were also assessed. Finally, an intraoral scanner was used to capture the post-deprogramming occlusal relationship (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea-b).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eFabrication of the temporomandibular joint appliance\u003c/h2\u003e \u003cp\u003eThe appliance was designed using the same design software, and milled from medical-grade PMMA resin discs on a 5-axis CNC milling machine (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea-d).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eOutcome measures\u003c/h3\u003e\n\u003cp\u003eAll appliances were delivered and adjusted by a single clinician who received standardized training. Patients were instructed to wear the appliance continuously for six months, except during meals and oral hygiene procedures. Follow-up evaluations were conducted every 4 weeks. The therapeutic outcomes were assessed upon completion of the treatment.\u003c/p\u003e\n\u003ch3\u003eAssessment of primary outcomes\u003c/h3\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003ePain intensity assessment\u003c/h2\u003e \u003cp\u003ePain intensity in the TMJ and surrounding regions was evaluated before and after treatment using a visual analog scale (VAS). A 10-cm horizontal line was presented with endpoints labeled \u0026ldquo;no pain\u0026rdquo;(0 cm) and \u0026ldquo;worst pain imaginable\u0026rdquo; (10 cm). Patients were asked to mark their current level of orofacial pain on the line, and the corresponding scores were recorded.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eMaximum mouth opening (MMO)\u003c/h2\u003e \u003cp\u003eMMO was measured using a stainless-steel ruler. Two measurements were taken for each patient and the average value was recorded for before and after treatment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eExploratory observations\u003c/h2\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003eJoint sound (clicking) assessment\u003c/h2\u003e \u003cp\u003eThe presence and frequency of joint clicks during opening and closing movements were recorded by a clinician before and after treatment as a descriptive observational measure. A click was defined as a clear, brief, and audible sound during mandibular movement.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eMRI protocol and exploratory analysis of disc position\u003c/h2\u003e \u003cp\u003eMRI was performed on all patients at baseline and upon completion of the 6-month treatment period. The imaging protocol adhered to standard clinical procedures for the TMJ. A proton density-weighted imaging sequence in the oblique sagittal plane was obtained for each joint in both closed- and open-mouth positions. As an exploratory analysis to document any structural changes accompanying the clinical outcomes, the disc-condyle relationship was assessed on MRI scans by an experienced oral radiologist who was blinded to the clinical outcomes. This assessment was performed as previously described [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Briefly, the disc condylar angle was measured on the slice displaying the largest condylar surface in the closed-mouth position. An angle exceeding 10\u0026deg; was considered indicative of ADD. The reducibility of displacement was determined by evaluating the disc position on the open-mouth image. The primary focus of this analysis was to observe any positional changes that occurred along with the primary clinical outcomes (pain reduction and improvement in mouth opening).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eStatistical analyses were performed using SPSS software (version 31.0; IBM Corp., Armonk, NY, USA). Normality of the data was assessed using the Shapiro\u0026ndash;Wilk test. Normally distributed data are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD), whereas non-normally distributed data are expressed as median and interquartile range (IQR). For the analysis of pain intensity (VAS), the difference between the pre- and post-treatment scores was normally distributed, as confirmed by the Shapiro\u0026ndash;Wilk test (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Therefore, a paired-samples t-test was used to evaluate statistical significance. For the MMO analysis, the data violated the assumption of normality (Shapiro\u0026ndash;Wilk test, P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Consequently, the non-parametric Wilcoxon signed-rank test was used. The relationship between the change in pain intensity and change in MMO was assessed using Spearman\u0026rsquo;s rank-order correlation coefficient. Statistical significance was set at P\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003ePrimary clinical outcomes\u003c/h2\u003e \u003cp\u003eTreatment with KTA led to significant clinical improvements. The mean VAS pain score decreased from 5.30\u0026thinsp;\u0026plusmn;\u0026thinsp;2.09 at baseline to 1.66\u0026thinsp;\u0026plusmn;\u0026thinsp;1.42 at the 6-month follow-up (t = -11.035, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Concurrently, the median MMO increased from 36.5 mm (IQR: 26.25\u0026ndash;39.00) to 39.0 mm (IQR: 37.25\u0026ndash;40.00) (Z = -4.181, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of VAS scores and MMO (mm) of patients before and after treatment\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePrimary Outcomes\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBefore treatment\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAfter treatment\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003et or Z value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVAS scores\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.30\u0026thinsp;\u0026plusmn;\u0026thinsp;2.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.66\u0026thinsp;\u0026plusmn;\u0026thinsp;1.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et = -11.035\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMMO (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e36.5 (IQR: 26.25-39.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e39 (IQR: 37.25-40.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eZ= -4.181,\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eA clinically significant improvement in MMO (increase of \u0026ge;\u0026thinsp;5 mm) was observed in 37.5% (15/40) of patients. Subgroup analysis revealed that all 15 responders had a baseline MMO\u0026thinsp;\u0026le;\u0026thinsp;35 mm. Within this functionally compromised subgroup (n\u0026thinsp;=\u0026thinsp;17), the response rate was 88.2% (15/17).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003eCorrelation between symptomatic and functional improvement\u003c/h2\u003e \u003cp\u003eSpearman\u0026rsquo;s correlation analysis revealed a statistically significant, moderate negative correlation between the reduction in VAS scores and the increase in MMO (ρ = -0.493, P\u0026thinsp;=\u0026thinsp;0.001) (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003eExploratory findings\u003c/h2\u003e \u003cp\u003eAmong the 40 joints with initial clicking, the sound resolved completely in 27 (67.5%) joints and was reduced in frequency in another nine (22.5%) joints after treatment. Notably, clicking resolved in three joints that had progressed to irreducible disc displacement (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDescriptive summary of joint clicking changes after treatment (n\u0026thinsp;=\u0026thinsp;40)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChange in joint clicking\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNumber of joints\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePercentage (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEliminated\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e67.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eReduced\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnchanged or increased\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e10.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003ePost-treatment MRI, reviewed as an ancillary analysis, showed variable and inconsistent changes in disc position. A sizeable proportion of the ADDwR joints exhibited positional changes, whereas fewer than half of the ADDwoR joints exhibited positional changes (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Crucially, clinical improvements in pain and MMO were observed, irrespective of whether a change in disc position was evident on MRI.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChanges in the position of the disc-condylar before and after treatment\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eDisc-condylar position relationship\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003en\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eAfter treatment\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRecaptured(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNot recaptured(%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAADwR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e27(88.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6(11.4)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAADwoR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11(47.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e12(52.1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eOur findings demonstrate that the KTA, delivered via a standardized digital protocol, is associated with significant improvements in pain and mandibular function in patients with TMJ ADD. Importantly, our findings offer two key advancement: first, the identification of a patient subgroup most likely to achieve functional recovery; and second, novel insights into the coordinated nature of symptomatic and functional improvement.\u003c/p\u003e \u003cp\u003eThe most clinically significant finding of this study was the identification of a clear predictor of functional response. The capacity for major functional gain (\u0026ge;\u0026thinsp;5 mm increase in MMO) was exclusively confined to patients with baseline MMO\u0026thinsp;\u0026le;\u0026thinsp;35 mm, with 88.2% of this subgroup responding. This observation is mechanistically sound because patients with significant restrictions possess a greater latent capacity for recovery once pain and muscle splinting are alleviated. This finding clearly defines the ideal candidate for KTA therapy, shifting the treatment paradigm from generic \u0026ldquo;improvement\u0026rdquo; to targeted \u0026ldquo;functional restoration.\u0026rdquo; For clinicians, baseline MMO measurements have become a crucial triage tool that enables personalized, function-based treatment planning.\u003c/p\u003e \u003cp\u003eFurthermore, we observed a significant correlation between pain reduction and functional gain. The observed moderate negative correlation (ρ = -0.493) suggests these core outcomes are not merely improving in parallel but are intrinsically linked. This aligns with the pathophysiology in which pain leads to protective muscle splinting, directly restricting mandibular function [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. This correlation indicates that KTA likely disrupts this self-perpetuating cycle, facilitating comprehensive recovery. While correlation does not prove causation and shared factors such as reduced psychosocial distress or a general placebo effect may contribute [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], this coherent pattern underscores a biologically meaningful therapeutic response.\u003c/p\u003e \u003cp\u003eOur results support the current biopsychosocial paradigm. Primary clinical improvements occurred independently of consistent MRI disc positional changes (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). Symptomatic relief was achieved in patients with disc recapture and those without fundamental anatomical alterations. This underscores that alleviating patient suffering rather than normalizing the anatomy is the primary therapeutic goal [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Adherence to this symptom-based approach is crucial to avoid the pitfalls of overtreatment and misdirected therapy, which are significant concerns when disc position is overemphasized, as discussed by Greene et al. [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The resolution of joint clicking observed in most patients aligns with the common clinical outcome of splint therapy. However, the significance of these findings should be interpreted with caution. The concomitant disappearance of clicking in joints that progressed to ADDwoR demonstrates that the absence of this sign is not a reliable indicator of successful disc recapture or a prerequisite for symptomatic improvement. This observation further reinforces the principle that clinical management should focus on the patient\u0026rsquo;s primary complaints\u0026mdash;pain and functional limitations\u0026mdash;rather than the elimination of joint sounds, which may represent an epiphenomenon rather than a core treatment target.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe primary limitation of this study was its single-arm, uncontrolled design. Consequently, we cannot definitively rule out the contribution of non-specific effects\u0026mdash;such as the placebo effect, the natural history of TMD, or regression to the mean\u0026mdash;to the observed clinical improvements. However, the primary objective of this initial investigation was to evaluate the feasibility and preliminary efficacy of the novel digital workflow. The promising outcomes and clear patient stratification identified here provide a robust rationale and essential preliminary data for a future randomized controlled trial that includes sham intervention or standard care, which is necessary to confirm the specific efficacy of the KTA.\u003c/p\u003e \u003cp\u003eThe efficacy of our digital protocol appears comparable to the positive outcomes achieved by other well-established conservative interventions for TMDs [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. This finding, coupled with the enhanced reproducibility and standardization offered by our digital workflow, suggests that further investigation is warranted as a valuable addition to the armamentarium of reversible, minimally invasive treatments.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn conclusion, the KTA was associated with improved pain and function in patients with TMJ ADD. Its major contribution lies in enabling a precision medicine approach. By identifying patients most likely to achieve functional recovery, it offers a clear path for personalized care. These findings reinforce the need for subsequent controlled trials to verify their efficacy.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eTMD, temporomandibular disorder\u003c/p\u003e\n\u003cp\u003eADD, anterior disc displacement\u003c/p\u003e\n\u003cp\u003eMRI magnetic resonance imaging\u003c/p\u003e\n\u003cp\u003eTMJ ADD anterior disc displacement of the temporomandibular joint\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eKTA, Kovacs-customized temporomandibular joint appliance\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eADDwR, anterior disc displacement with reduction\u003c/p\u003e\n\u003cp\u003eADDwoR, anterior disc displacement without reduction\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eVAS, visual analog scale\u003c/p\u003e\n\u003cp\u003eMMO, maximum mouth opening\u003c/p\u003e\n\u003cp\u003eSD, standard deviation\u003c/p\u003e\n\u003cp\u003eIQR, interquartile range\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll experimental procedures were approved by the Institutional Ethics Committee of\u0026nbsp;Beijing Anzhen Nanchong Hospital of Capital Medical University \u0026amp; Nanchong Central Hospital.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data\u0026nbsp;sets used in this study are available from the corresponding author upon request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have\u0026nbsp;no\u0026nbsp;competing interests, and all authors have confirmed the accuracy of this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor’s contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTX conceived the experiments; JJ conducted the experiments and\u0026nbsp;drafted the manuscript; XZ, HL, and HM collected the data; CJ and ZL analyzed the data. All the authors have read and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eManfredini D, H\u0026auml;ggman-Henrikson B, Al Jaghsi A, Baad-Hansen L, Beecroft E, Bijelic T, et al. Temporomandibular disorders: INfORM/IADR key points for good clinical practice based on standard of care. Cranio. 2025;43:1\u0026ndash;5. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1080/08869634.2024.2405298\u003c/span\u003e\u003cspan address=\"10.1080/08869634.2024.2405298\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLim PF, Smith S, Bhalang K, Slade GD, Maixner W. Development of temporomandibular disorders is associated with greater bodily pain experience. 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Cranio. 2025;43:851\u0026ndash;62. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1080/08869634.2024.2360370\u003c/span\u003e\u003cspan address=\"10.1080/08869634.2024.2360370\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"temporomandibular joint disorders, anterior disc displacement of temporomandibular joint, occlusal splint, digital dentistry, Kovacs-customized temporomandibular joint appliance","lastPublishedDoi":"10.21203/rs.3.rs-8115203/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8115203/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eAnterior disc displacement of the temporomandibular joint is a common cause of orofacial pain and functional limitation. However, rigorous clinical validation of fully digital, standardized protocols that determine therapeutic jaw position in the management of anterior disc displacement of the temporomandibular joint is lacking. Therefore, the aim of this study was to evaluate the clinical efficacy of the Kovacs-customized temporomandibular joint appliance and explore the correlation between pain reduction and functional improvement in patients with anterior disc displacement of the temporomandibular joint.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eForty patients with anterior disc displacement of the temporomandibular joint were prospectively enrolled. All participants received a Kovacs-customized temporomandibular joint appliance fabricated via a standardized digital workflow and were assessed over a 6-month period. Primary outcomes included pain intensity measured using a visual analog scale and maximum mouth opening. The relationship between the changes in these two key outcomes was analyzed using Spearman\u0026rsquo;s correlation coefficient. Joint sounds and disc positions were recorded on magnetic resonance imaging as exploratory observations.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eKovacs-customized temporomandibular joint appliance treatment resulted in significant clinical improvement. Mean visual analog scale pain scores decreased from 5.30\u0026thinsp;\u0026plusmn;\u0026thinsp;2.09 at baseline to 1.66\u0026thinsp;\u0026plusmn;\u0026thinsp;1.42 at 6 months (t = -11.035, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Concurrently, median maximum mouth opening increased from 36.5 mm (interquartile range: 26.25\u0026ndash;39.00) to 39.0 mm (interquartile range: 37.25\u0026ndash;40.00) (Z = -4.181, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). A statistically significant, moderate negative correlation was identified between reduction in pain intensity and increase in maximum mouth opening (ρ = -0.493, P\u0026thinsp;=\u0026thinsp;0.001), indicating that greater pain relief was associated with greater functional improvement. Clinical improvement was accompanied by resolution of joint clicking in most patients, whereas exploratory magnetic resonance imaging revealed variable changes in disc position.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThe Kovacs-customized temporomandibular joint appliance is an effective conservative treatment for anterior disc displacement of the temporomandibular joint that significantly alleviates pain and improves mandibular function. The demonstrated correlation between symptomatic and functional recovery provides valuable insights into the therapeutic process and underscores the value of this standardized digital protocol. The Kovacs-customized temporomandibular joint appliance represents a promising option within a patient-centered care framework.\u003c/p\u003e","manuscriptTitle":"The Kovacs-customized temporomandibular joint appliance for temporomandibular joint anterior disc displacement: a prospective cohort study of its clinical efficacy and the correlation between pain and functional improvement","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-17 07:23:29","doi":"10.21203/rs.3.rs-8115203/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"531642e2-5f84-45be-8a34-d3abc80b71e9","owner":[],"postedDate":"December 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-12-24T08:40:20+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-17 07:23:29","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8115203","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8115203","identity":"rs-8115203","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}