The Dahl Concept as a Conservative Approach for Anterior Tooth Wear: A Case Report

Introduction

Tooth wear is a multifactorial, non-carious pathological loss of the dental tissues, classified into attrition (mechanical wear from tooth-to-tooth contact), abrasion (foreign substance-to-tooth contact), and erosion (chemical dissolution by intrinsic or extrinsic acids) [1–3]. These mechanisms frequently coexist, resulting in a combined etiology that may present as localized or generalized wear [1, 2]. To objectively quantify severity, the Basic Erosive Wear Examination (BEWE) is utilized: scores range from 0 (no wear) to 3 (hard tissue loss >50% of the surface area), with a score of 1 denoting initial texture loss and 2 representing a distinct defect affecting <50% of the surface [4]. The prevalence of pathological wear increases with age, rising from 3% at age 20 to 17% by age 70 [5].

In cases with distinct defects of the hard tissues of the anterior teeth, dentine may be exposed, which can increase tooth sensitivity, and negatively affect the person’s appearance and quality of life [6,7]. Furthermore, significant wear increases surface roughness, which facilitates plaque accumulation and further mechanical abrasion [8]. Additionally, the loss of enamel leads to compromised color stability as the more chromatic and porous dentin is exposed [8].

Prosthetic intervention is indicated to arrest further structural loss and restore function and aesthetic [9]. However, localized anterior tooth wear presents a unique clinical challenge due to the phenomenon of dentoalveolar compensation. As tooth structure is lost, the alveolar process undergoes a physiological compensatory mechanism to maintain occlusal contact between the maxillary and mandibular arches [6]. This results in a localized loss of interocclusal restorative space [6].

Traditional prosthetic intervention often necessitates tooth preparation to create the clearance required for restorative materials such as single crowns and fixed dental prostheses. In already shortened clinical crowns, such reduction significantly increases the risk of mechanical pulp exposure, subsequent pulpal necrosis [10–14], and severely compromised resistance and retention forms [13,15].

To avoid pulp injury in worn teeth, obviate the risk of generating minimal resistance and retention forms, and create adequate space for single crowns and fixed dental prostheses materials, the Dahl concept serves as a highly effective clinical strategy [6,16]. The essential mechanism of this technique involves an intentional interocclusal posterior disocclusion, achieved by the placement of interim restorations at an increased occlusal vertical dimension (OVD) [17]. This state is followed by a period of dentoalveolar compensation, characterized by the compensatory eruption of posterior teeth and the relative intrusion of anterior segments, which eventually leads to the re-establishment of posterior occlusal stability [17]. This physiological process allows for creation of the necessary restorative space without the need for extensive tooth reduction [17]. For definitive restorations, monolithic lithium disilicate glass-ceramic (e.max) is an ideal material; it combines superior aesthetic properties with high flexural strength and fracture toughness.

The restorative plan focused on creating interocclusal space through a minimally invasive, reversible biomechanical strategy. This approach obviates the need for extensive tooth reduction or more invasive surgical interventions, such as clinical crown lengthening [18]. While the technique originated with the use of removable anterior bite platforms, it has evolved into a highly predictable restorative modality using fixed interim and definitive materials [16,19].

The long-term predictability of this approach was established by Dahl and Krogstad [20], whose research showed that the increased vertical dimension is maintained for over 5 years. Although minor physiological relapse may occur within the first 6 months after crowns cementation, the vertical dimension does not revert to the original baseline [20].

This case report describes the prosthetic management of moderate localized anterior tooth wear by full-coverage lithium disilicate glass-ceramic single crowns based on the Dahl concept.

Case Report

HISTORY AND CHIEF CONCERN:

This case report presents the minimally invasive rehabilitation of localized anterior wear using the Dahl concept. A 34-year-old woman presented to the dental clinics of the Faculty of Dental Medicine at Umm Al-Qura University, Makkah, Saudi Arabia. Her chief concern was the unaesthetic appearance of her maxillary anterior teeth and gingival asymmetry within the anterior aesthetic zone. She stated that “I feel my anterior teeth have become shorter over time”, and she wished to have more aesthetic and natural-looking smile. The patient reported a history of stress-related parafunction, with a diagnosis of probable sleep bruxism supported by a bed partner’s report of grinding sounds [21]. This diagnosis was further substantiated by clinical symptoms of morning myofascial pain and TMJ discomfort upon awakening. These parafunctional habits appeared to correlate with a history of increased psychosocial stress. She reported her daily diet contains very sour foods and candy. Her medical history was unremarkable for any systemic diseases or regular medication use. She was a non-smoker with no history of alcohol consumption.

CLINICAL FINDINGS:

Intraoral examination showed generalized mild attrition and erosion within the enamel of the maxillary and mandibular anterior and posterior teeth, except for the maxillary central and lateral incisors, which revealed a moderate loss of one-third of the clinical crowns with dentine exposed [1]. Tooth attrition presented with glossy plane surfaces and sharp edges, and erosion appeared clinically as concavities in the smooth surfaces, rounded occlusal cusps, and the presence of cupping and grooves on the cusps and incisal edges [22,23]. The interdental space was limited, particularly on the palatal side of the central and lateral incisors [5]. The patient presented with an Angle’s Class I occlusion bilaterally [24]. Clinical examination revealed significant gingival asymmetry; specifically, the gingival margins of the maxillary right central and lateral incisors (teeth 11 and 12) were positioned more incisally relative to the contralateral zeniths of the maxillary left central and lateral incisors (teeth 21 and 22). Additionally, the mandibular posterior dentition exhibited extensive multi-surface composite restorations, emphasizing the need for a conservative occlusal approach (Figure 1). Extraoral examination revealed that the temporomandibular joints (TMJs) and masticatory muscles (masseter and temporalis) were asymptomatic, with no tenderness upon palpation or joint sounds during mandibular excursions. A comprehensive diagnostic assessment was performed to evaluate the patient’s history of parafunction. In accordance with international diagnostic standards, a diagnosis of “probable” bruxism was established by integrating the patient’s self-report obtained via standardized questionnaires, which included reports of grinding sounds and morning myofascial tension [21]. This was corroborated during the inspection phase of the clinical examination [21], where objective clinical markers, including bilateral masseteric hypertrophy, a distinct linea alba, and tongue crenulations, were identified. Preoperative assessment of the maxillary anterior teeth (13–23) confirmed pulpal vitality via cold thermal testing. This biological baseline was further supported by periapical radiographic evaluation (Figure 2), which demonstrated intact periodontal ligament spaces and the absence of any periapical pathologies.

TREATMENT PLAN AND CLINICAL PROCEDURE:

Following clinical examination and history, the dentist and the patient discussed different treatment alternatives, and the Dahl concept was selected. The patient was counseled on the technique’s advantages and the transient effects of increasing the vertical dimension, such as altered chewing efficiency and discomfort [19].

The clinical length of the anterior teeth was measured using a periodontal probe from the most apical point of the cementoenamel junction (CEJ) of the crown to the most incisal point [25]. Maxillary and mandibular irreversible hydrocolloid alginate impressions and a bite registration using a grey bite registration wax rim were obtained in the maximum intercuspal position (MIP). Diagnostic casts were subsequently mounted in a semi-adjustable articulator [6].

To determine the appropriate increase in the OVD, a comprehensive diagnostic evaluation was performed. An intentional 2- mm increase in the OVD was established to provide sufficient restorative space while minimizing the biological cost of anterior tooth reduction. This 2 mm threshold was selected to accommodate the minimum 1 mm thickness required for the structural integrity of definitive monolithic lithium disilicate crowns [23], while simultaneously restoring the incisal length and anatomical proportions lost to wear, as determined by the diagnostic wax-up and aesthetic facial analysis. Furthermore, phonetic evaluation and clinical monitoring during the simulation phase confirmed that this increase did not interfere with speech, and the patient remained asymptomatic regarding the temporomandibular joint (TMJ) and masticatory musculature. Selecting a 2-mm supra-occlusion is consistent with documented protocols for localized wear; it effectively counteracts the dentoalveolar compensation that occurred during the wear process and facilitates predictable posterior eruption without exceeding the patient’s physiological tolerance.

A diagnostic wax-up was prepared for the maxillary anterior teeth (13–23) in supra-occlusion, establishing even anterior contacts, canine guidance, and anatomically correct contours. To achieve bilateral symmetry, the gingival zeniths of teeth 11 and 12 were recontoured on the diagnostic casts to match the architecture of teeth 21 and 22, thereby guiding the planned gingivectomy (Figure 3).

To address the patient’s chief concern of shortened clinical crowns and gingival asymmetry, a localized gingivectomy was performed. The procedure was specifically targeted to the maxillary right central and lateral incisors (teeth 11 and 12) to harmonize the gingival zeniths with the contralateral teeth (21 and 22) and restore ideal tooth proportions. Prior to surgical intervention, bone sounding was performed to confirm the position of the alveolar crest, ensuring that the supracrestal attached tissues (biologic width) would not be violated. An additive mock-up, fabricated via a putty index from the diagnostic wax-up, served as a biological and aesthetic guide for the tissue resection. Following the gingivectomy, minimal interproximal preparations were performed to facilitate the delivery of fixed interim crowns. These restorations were placed in supra-occlusion, resulting in the planned posterior disocclusion and effectively initiating the Dahl-based vertical dimension increase while protecting the newly established aesthetic harmony (Figure 4).

The patient attended regular follow-up visits to monitor the Dahl effect and ensure adaptation. The initial follow-up visit was conducted 2 weeks after crown provisionalization, with subsequent evaluations performed at monthly intervals. During each follow-up visit, the integrity of the maxillary anterior interim crowns and the stability of the newly established occlusal scheme were meticulously evaluated through intraoral examination, monitoring of masticatory efficiency and phonetics, and verification of gingival health and stability of the established gingival zeniths following the aesthetic gingivectomy. The patient successfully adapted to the increased incisal length and modified anterior guidance within the first week. No complications, such as interim crowns fracture or TMJ tenderness, were recorded during this critical transition period.

The gradual closure of the posterior disocclusion resulting from the compensatory eruption of the posterior segments was tracked using pink modeling wax sheets and photographs. By observing the initial points of incipient contact on the wax, the eruptive movement of the maxillary and mandibular posterior teeth could be accurately monitored month-to-month. Complete intercuspation and stable bilateral posterior contacts were achieved by the fourth month. This re-establishment of the OVD was confirmed using articulating paper strips to verify that the posterior segments had reached full functional contact, providing a stable foundation for the final restorative phase (Figure 5).

Final tooth preparation was carried out based on manufacturer recommendations for full-coverage monolithic lithium disilicate glass-ceramic (e-max) single crowns. A reduction of 1 mm on the axial walls with rounded line angles and a slight chamfer finish line were achieved [26,27]. Finish lines for all single crowns were placed at the equi-gingival level for aesthetic reasons. A conventional final impression for the maxillary arch was made using the one-step technique with heavy- and light-body polyether impression material in a stock tray. The mandibular arch impression was taken with a vinyl polysiloxane impression material. The maxillomandibular relationship was recorded using a grey bite registration wax rim and bite registration material. This ensured the accurate transfer of the relationship between the maxillary and mandibular anterior and posterior teeth to the dental technician (Figure 6). The shade of the final single crowns was selected using a conventional Vita shade guide; the shade of the prepared teeth was also recorded.

Lithium disilicate (e.max) single crowns were fabricated in the dental lab by a dental technician and sent to the clinic. The crowns were tried-in using try-in paste and assessed clinically for marginal fitting, shape, shade, and occlusion. The crowns were shown to the patient before final cementation. After try-in, the fitting (intaglio) surface of single crowns was cleaned with alcohol, 35% phosphoric acid, water, and air spray. The fitting surface was then etched with 5% hydrofluoric acid gel for 20 s, then rinsed with water and air spray, and silanized with Monobond Plus. A rubber dam was applied to control moisture during cementation. Adhesive bonding was applied to the prepared tooth, and Variolink II dual-cure adhesive cement was used for final cementation. Light cure was applied for 2 s, and excess cement on the crown margins was removed with a dental explorer. Final curing was carried out for 40 s per segment, starting at the proximal surface. Excess cement was removed carefully by dental explorer and floss. Mild tooth wear (cupping) in the maxillary was restored with composite (Figure 7).

To ensure the long-term success of the restorations and address the etiology of clinical wear, a comprehensive risk-management protocol was implemented. Given the patient’s history of sleep bruxism and stress-related parafunction, a maxillary full-coverage hard acrylic occlusal splint was fabricated and delivered after cementation. The patient was instructed on the necessity of nightly compliance to protect the monolithic lithium disilicate crowns from excessive parafunctional loading. Additionally, behavioral and dietary counseling was provided to mitigate erosive factors; specifically, she was advised to limit the frequency of acidic food and beverage consumption to reduce the risk of future chemical degradation of the remaining dentition.

Oral hygiene instructions were given to the patient, and regular clinical follow-up recall visits were scheduled 2 weeks after delivery of the final single crowns, with subsequent follow-ups at 1 month, 6 months, and then annually at the Faculty of Dental Medicine, Umm Al-Qura University, Makkah, Saudi Arabia.

The patient regularly attended the follow-up visits, and until 2 years after delivery no complications or failures were observed. At the 2-year follow-up, a comprehensive clinical and radiographic assessment was conducted to evaluate the longevity and stability of the treatment. The definitive lithium disilicate restorations were evaluated; tactile exploration and visual inspection revealed no marginal discrepancies, recurrent caries, or ceramic fractures. Radiographic evaluation confirmed stable alveolar bone levels and the absence of periapical pathology. The 2-mm OVD increase remained stable, and the patient was satisfied regarding aesthetic and masticatory comfort.

Discussion

In this case, the Dahl concept was utilized as the primary clinical strategy to manage localized anterior tooth wear. This approach allowed for the creation of restorative space through physiological compensation rather than aggressive tooth reduction [17,28]. By delivering maxillary anterior interim crowns in a predetermined supraocclusal position, a posterior disocclusion of approximately 2 mm was established [13].

While the literature identifies a combination of anterior intrusion and posterior eruption as the primary mechanisms for re-establishing occlusion, the clinical course of this case was characterized predominantly by posterior eruption [24,29]. Significant anterior intrusion was not observed, which proved to be a favorable outcome for this patient. This lack of intrusion ensured that the gingival zeniths, previously corrected via aesthetic gingivectomy, remained stable at the planned levels without apical migration, preserving the intended smile [13,30].

Upon the successful re-establishment of posterior occlusal contacts, objectively verified at the 4-month mark using articulating paper strips to confirm stable bilateral intercuspation, sufficient restorative space was secured to accommodate the final maxillary anterior crowns without further tooth reduction [29]. While retrospective data suggest an average of 6 months to re-establish posterior occlusion using the Dahl concept, this duration varies significantly among individuals [31]. Furthermore, while some patients may not adapt or fail to establish posterior contact, the inherent reversibility of the Dahl treatment sequence functions as a critical safety mechanism, allowing for clinical intervention without permanent tooth structure loss [32]. The objective achievement of these clinical benchmarks confirms that the 2-mm OVD increase was successfully neutralized through stable dentoalveolar compensation.

The 4-month provisional phase was critical in validating the patient’s biological and functional tolerance of the new occlusal scheme. During this period, she reported a total absence of TMJ discomfort, muscle fatigue, or headaches, confirming that the increase in OVD was well within the patient’s physiologic limits of adaptation [32]. The interim period served as a critical functional trial to evaluate the patient’s phonetics alongside the new restorative contours. The patient demonstrated successful speech adaptation within the first week.

The benefits of using fixed anterior interim crowns are to reduce the risk of patient non-cooperation associated with removable appliances, improve the aesthetic appearance of the anterior teeth during the treatment period, and assess the shape of the final single crowns [32].

Despite the success observed in this case, the Dahl concept is not without limitations, particularly in patients with probable bruxism. The primary risk is the potential for localized mechanical overload during the interim phase, which increases the likelihood of provisional restoration fracture or debonding while the posterior teeth are out of occlusion. In our patient, however, no such complications occurred, and the provisional restorations remained intact throughout the 12-week adaptation period.

Various treatment alternatives can be used to manage localized anterior tooth wear with an inadequate restorative space; one such alternative is preparing the anterior teeth without increasing OVD [29]. Traditional tooth preparation at the existing vertical dimension was contraindicated in this case due to the severe loss of clinical crown height. To achieve adequate resistance and retention forms, over-reduction would have been necessary to accommodate restorative material thickness, creating a high risk of pulp exposure [33]. Such an invasive approach often necessitates elective endodontic therapy and the placement of interradicular posts, which significantly compromise the biomechanical integrity of the tooth and increase the risk of root fracture [13,15,34].

Extending crown margins subgingivally to gain retention was also deemed inappropriate, as it would likely have encroached upon the supracrestal attached tissues (biologic width) [33]. Such an approach jeopardizes long-term periodontal health by complicating plaque control and increasing the risk of chronic gingival inflammation, bleeding, and increased pocket depths, and secondary caries [35–37]. By adopting the Dahl concept, these biological and mechanical complications were avoided, preserving the natural tooth structure for a more conservative and predictable outcome.

Surgical crown lengthening was considered an inappropriate in this case due to the patient’s high smile line. Changing the gingival contour and increasing the clinical crown length via crown lengthening would have resulted in unaesthetic, elongated tooth proportions. Instead, a localized gingivectomy was performed on the maxillary right central and lateral incisors to achieve gingival symmetry with the contralateral side. This procedure was strictly aimed at correcting gingival zenith discrepancies caused by compensatory eruption and uneven wear patterns [38].

Prior to the gingivectomy, a thorough periodontal assessment was conducted, including bone sounding under local anesthesia to map the supracrestal attached tissues (biologic width). This ensured that a minimum of 3 mm existed between the planned restorative margin and the alveolar bone crest. Because the patient’s biological width was sufficient and the desired gingival correction was minimal (approximately 1.5 mm), the procedure was completed without osseous resection, preserving the periodontal supporting structures while achieving the desired aesthetic outcome.

Alternative treatment modalities, including comprehensive orthodontic therapy and a generalized increase in OVD via full-mouth fixed rehabilitation, were also considered [31]. However, these options were deemed less favorable for this specific case due to their higher biological cost and increased clinical complexity [29,31]. Full-mouth reconstruction would have necessitated the invasive preparation of posterior teeth, which contradicted the goal of maximum structural preservation. Similarly, orthodontic intervention would have resulted in a significantly extended treatment duration. In contrast, the Dahl concept offered a minimally invasive, allowing for targeted restoration of the anterior segment while maintaining the integrity of the posterior dentition [29,31].

Minimal invasive, high-strength, full-coverage lithium disilicate (e.max) single crowns were selected as the definitive restorative material to achieve an optimal balance between mechanical durability and superior aesthetic [26,39]. While direct composite resins offer a more conservative approach by preserving circumferential tooth structure, full-coverage crowns were prioritized in this case to provide the geometric resistance and structural rigidity necessary to withstand the heightened occlusal loads of a bruxer patient [40]. Furthermore, the clinical performance of composite resin was anticipated to be limited by its significantly higher wear rate compared to lithium disilicate [9]. In cases involving a 2-mm OVD increase, the use of materials with lower wear resistance poses a risk of gradual vertical collapse and loss of established occlusal contacts. Therefore, the selection of monolithic lithium disilicate was essential to ensure long-term occlusal stability.

Moreover, lithium disilicate mimics the translucency and optical properties of natural enamel more effectively than alternative materials such as composite or monolithic zirconia [39]. Unlike zirconia, lithium disilicate facilitates predictable adhesive bonding to the tooth structure, and this chemical integration was essential in this case to provide secondary retention and marginal sealing for the crowns [39]. By using a monolithic rather than bi-layered crown material, the risk of cohesive porcelain chipping (common mechanical failures in patients with bruxism) was significantly minimized, ensuring greater structural integrity under functional loading [26,39].

The treatment success of the Dahl approach in this patient depended heavily on addressing the multifactorial etiology of her tooth wear, specifically sleep bruxism, an erosive diet, and psychological stress. Dietary counseling was provided to minimize the frequency and duration of acidic/sour intake during the 4-month interim phase. Immediately following the delivery of the definitive crowns, a hard acrylic occlusal splint was provided to safeguard the restorations against catastrophic fracture or debonding resulting from the significant parafunctional loads of sleep bruxism. This appliance served to maintain the newly established vertical dimension and prevent further progression of biological tooth wear [9,27]. Additionally, a referral for stress-management therapy was provided to address the psychological etiology of the patient’s bruxism. Addressing these underlying psychological triggers is essential to reduce the frequency and intensity of bruxism episodes [41].

The complication-free course observed at the 24-month follow-up provides objective clinical evidence for the predictability of the Dahl approach combined with monolithic lithium disilicate single crowns. Specifically, the restorations exhibited no signs of debonding, marginal discoloration, catastrophic fracture, or absence of pathological wear facets on the opposing natural dentition. The absence of ceramic fractures, even in the presence of ‘probable’ sleep bruxism, highlights the superior mechanical performance of monolithic lithium disilicate material. This is consistent with reported survival rates as high as 99.7% over a 6-year period [9,39,40].

Furthermore, while occlusal relapse or instability is frequently cited as a primary concern in Dahl concept applications, the preservation of posterior occlusal contacts and the stability of the 2-mm OVD increase at the 24-month follow-up provide compelling evidence of successful dentoalveolar compensation. This biological process, characterized by a combination of minor anterior intrusion and passive posterior eruption, typically reaches a physiological equilibrium within 6 to 18 months [31,42].

The Dahl concept can be advantageous for patients presenting with moderate to severe localized anterior wear. This approach facilitates the creation of restorative space through physiological compensation, obviating the need for the aesthetic compromise of elongated teeth seen in surgical crown lengthening, as well as the biological risks of elective endodontics and post-and-core foundation.

Conclusions

This case validates the Dahl concept, integrated with monolithic lithium disilicate crowns, as a predictable and minimally invasive strategy for rehabilitating moderate localized anterior wear. The technique’s conservative nature was evidenced by the successful maintenance of pulpal vitality and the preservation of sound tooth structure, effectively bypassing the need for elective endodontic therapy.

Furthermore, the functional efficacy of the approach was confirmed by the rapid re-establishment of posterior occlusal contacts through dentoalveolar compensation within only 4 months. At the 24-month follow-up, the stability of the 2-mm OVD increase and the absence of ceramic fracture even in the presence of sleep bruxism demonstrates the structural resilience of monolithic lithium disilicate when supported by occlusal splint therapy. Ultimately, the integration of gingival contour modification illustrates that aesthetic refinement can be achieved alongside these functional gains, resulting in high patient satisfaction and a balanced restorative outcome.