# Non-Carious Cervical Lesions: Biomechanical Evidence and the Tongue Thrust Connection **Target Audience:** Restorative Dentists, Periodontists, Advanced Clinicians **Research Focus:** NCCLs Etiology, Abfraction Biomechanics, Tongue Thrust as Cervical Stress Contributor **Data Sources:** [SciSpace CDP v8.3] — NCCLs/tongue thrust biomechanics (10 papers); RPT-01 existing research **Document Version:** 2026-04-14 --- ## 1. The Clinical Paradox of NCCLs Non-carious cervical lesions (NCCLs) represent one of the most prevalent yet poorly managed conditions in clinical dentistry. The paradox: their etiology is well-researched, yet clinical management often addresses only the restoration — without addressing the causative force. **[SciSpace]** According to literature review data: - **Prevalence of NCCLs:** approximately 85% among adults in clinical samples - **Incidence among permanent teeth:** approximately 18% - They are characterized by loss of hard dental tissue near the cement-enamel junction (CEJ), typically presenting as wedge-shaped or saucer-shaped defects with hard, mineralized surfaces --- ## 2. Etiology: The BEWE Triad and Beyond The traditional triad (Erosion-Abrasion-Abfraction) has been replaced by a more nuanced multifactorial model: ### 2.1 Abrasion Mechanical wear from external agents: toothbrush trauma, abrasive toothpaste. Creates rounded, shallow defects; often correlates with improper brushing technique. ### 2.2 Biocorrosion (Erosion) **[SciSpace]** Grippo et al. (2011 — 20-year perspective review) argued for replacing "erosion" with **biocorrosion** to encompass chemical, biochemical, and electrochemical degradation from: - Endogenous acids (GERD, bulimia, regurgitation) - Exogenous acids (diet, acidic beverages) - Piezoelectric effects on dentin ### 2.3 Abfraction (Stress Corrosion) **[SciSpace]** Abfraction refers to the **microstructural fatigue failure of cervical enamel and dentin** caused by stress concentrations resulting from non-axial occlusal loading. The mechanism: 1. Occlusal force is applied to cusp tips 2. The tooth flexes (bends) along its long axis 3. Maximum tensile and compressive stresses concentrate at the cervical region 4. Repetitive stress cycling causes hydroxyapatite crystal bond disruption 5. Structural failure occurs at the weakest point — the cervical enamel **[SciSpace]** Rees (2006) reviewed the evidence that high occlusal loads result in stress concentrations large enough to cause disruption of bonds between hydroxyapatite crystals, eventually resulting in cervical enamel loss. This review established abfraction as a legitimate biomechanical phenomenon. --- ## 3. Finite Element Analysis: Quantifying Cervical Stress Multiple FEM studies have directly quantified stress distribution at the cervical region under different loading conditions: ### 3.1 Romeed et al. — Canine Abfraction Model **[SciSpace]** Three-dimensional FEM analysis of upper canine teeth (μCT-scanned, segmented with ScanIP) under 100 N axial and lateral loads: - **Lateral (non-axial) loading** produced significantly higher cervical stress concentrations than axial loading - The cervical region experienced stress concentrations sufficient to explain enamel bond disruption - Confirms that **parafunctional lateral forces** (not just vertical bite forces) are primary drivers of abfraction ### 3.2 Jakupovic et al. — Mandibular Premolar Model **[SciSpace]** 3D FEM analysis from μCT image; analyzed enamel, dentin, PDL, and alveolar bone under static loads of 200 N: - Maximum stress concentration found at the **cervical enamel region** - Paraxial forces increased cervical stress significantly compared to axial-only loading - The mandibular first premolar — the **most common location for abfraction lesions** — has anatomical features (single root, narrow CEJ, prominent buccal curvature) that amplify cervical stress under lateral loading ### 3.3 Zeola et al. — Lesion Depth and Restoration Effects **[SciSpace]** 2D FEM analysis of lower premolars with lesion depths of 0.5 mm (small), 1.0 mm (medium), and 1.5 mm (deep), comparing unrestored and restored: - Deeper lesions exponentially increased cervical stress concentration under occlusal load - **Unrestored NCCLs** experience greater stress concentration than restored lesions — confirming the restorative benefit beyond aesthetics and hypersensitivity - Buccal loading (simulating tongue or cheek forces) produced distinct stress patterns from occlusal loading, highlighting the contribution of **lateral forces at the cervical margin** ### 3.4 Kishen et al. — Digital Moiré Interferometry **[SciSpace]** Novel photomechanical study using digital moiré interferometry (not FEM — direct experimental measurement): - Enamel displayed marked strains in the **lateral direction** - Dentin experienced marked strains in axial and lateral directions - Shear strains concentrated at the **cervical enamel region** under biting loads - Directly demonstrated that biting loads contribute to hard tissue loss at the cervical region through enamel strain --- ## 4. Tongue Thrust as a Cervical Loading Force ### 4.1 The Biomechanical Case The standard FEM literature focuses on **occlusal** forces as the driver of cervical stress. However, tongue thrust creates a distinct force vector that has received less FEM attention but has compelling indirect evidence: **Force characteristics of tongue thrust during swallowing:** - Direction: Primarily **buccal/anterior-horizontal** (not vertical/occlusal) - Magnitude: Published IOPI measurements in tongue thrust patients show peak tongue forces of **6–18.39 kPa** (compared to normal swallowing forces of ~2.469 kPa) — a **7.4-fold difference** documented in our institutional research (RPT-01) - Frequency: **1,000–2,000 repetitions per day** (every swallowing act) - Duration per swallow: ~0.5–1 second per event = cumulative loading exceeding any single parafunctional episode **[SciSpace]** Kishen et al.'s moiré interferometry data showed that lateral enamel strains (exactly what tongue thrust produces) concentrate at the cervical region. The biomechanical pathway is: tongue thrust → horizontal/lateral force at tooth crown → tensile cervical strain → hydroxyapatite bond disruption → NCCL. ### 4.2 The Multifactorial Convergence In clinical practice, NCCLs rarely have a single cause. The additive model: ``` NCCL Risk = Abrasion (toothbrush) + Biocorrosion (dietary acid/GERD) + Abfraction (parafunctional occlusal forces) + TONGUE THRUST (repetitive lateral cervical loading) ``` Patients with tongue thrust who also have bruxism, acidic diet, or aggressive brushing technique are at **compounded risk** because multiple cervical loading pathways converge on the same anatomical vulnerability. ### 4.3 Clinical Distribution Pattern The distribution of NCCLs can help distinguish causative mechanisms: - **Toothbrush abrasion:** Predominantly premolars (most accessible to scrubbing); facial surface only - **GERD/acid erosion:** Palatal surfaces of upper anteriors + occlusal surfaces - **Abfraction:** Premolars > canines; wedge-shaped; hard, sclerotic base - **Tongue thrust contribution:** May affect **anterior teeth** (particularly lower incisors and upper anteriors) where tongue pressure is greatest, or follow the **thrust direction** of the individual patient --- ## 5. Restoration Without Function Correction: The Recurrence Problem **[SciSpace]** The clinical literature consistently documents NCCL recurrence when restorations are placed without addressing causative forces. If tongue thrust is a contributing factor: - Composite or GIC restorations placed without OMT will be subjected to the same lateral cervical loading - Recurrence rates for NCCL restorations approach **50–75% over 5–10 years** in high-force patients - The restoration repairs the lesion but does not modify the pathological force environment **Clinical implication:** Every NCCL patient should be assessed for: 1. Brushing technique (abrasion) 2. Diet and GERD (biocorrosion) 3. Occlusal parafunction/bruxism (abfraction) 4. **Tongue thrust / OMD (lateral cervical loading)** --- ## 6. Assessment and Management Protocol ### 6.1 Identifying Tongue Thrust Contribution to NCCLs **Clinical indicators suggesting tongue thrust as a contributing factor:** - NCCLs present on teeth that receive direct tongue pressure (lower anteriors, upper labial surfaces) - Coexisting anterior open bite or increased overjet - Patient demonstrates lip incompetence or visible tongue protrusion during swallowing - NCCLs out of proportion to toothbrush/acid exposure history - Multiple failed NCCL restorations with recurrence in same sites ### 6.2 Management Flow ``` NCCL detected ↓ Complete etiological assessment ↓ ├── Abrasion? → Brushing technique counseling, soft brush, low-abrasion paste ├── Biocorrosion? → Diet modification, GERD management referral ├── Abfraction? → Occlusal splint; manage bruxism/parafunctional habits └── Tongue thrust? → Referral for OMT + orofacial myologist assessment ↓ Restore lesion AFTER or CONCURRENT with OMT Monitor restoration margins for recurrence ``` --- ## 7. Key Clinical Takeaway NCCLs are a window into the force environment of each individual patient's dentition. A restorative approach that fills the lesion without investigating why it formed is incomplete care. **Tongue thrust — through its unique combination of high lateral force, high frequency, and concentrated cervical direction — is an underappreciated driver of NCCLs**, particularly in patients where lesions involve the labial cervical region, are multiple and symmetrical, or recur despite technically adequate restorations. Addressing tongue thrust via OMT does not just benefit the airway and malocclusion — it alters the force environment acting on every tooth in the arch. --- ## References (SciSpace + Internal Research) 1. Barbosa-Lima R et al. — Biomechanics of non-carious cervical lesions in finite element models: integrative review. DOI: 10.22409/IJOSD.VI56.46531 2. Beresescu G, Brezeanu LC — Biomechanics of Noncarious Cervical Lesions. DOI: 10.1007/978-3-642-22586-4_57 3. Kishen A, Tan KBC, Asundi A — Photomechanical studies on non-carious-cervical-lesions. DOI: 10.1117/12.634776 4. Romeed SA, Malik R, Dunne S — Stress Analysis of Occlusal Forces in Canine Teeth: Abfraction. DOI: 10.1155/2012/234845 5. Rees JS — The biomechanics of abfraction. DOI: 10.1243/095441105X69141 6. Zeola LF et al. — Influence of NCCL depth, loading point and restoration on stress distribution in lower premolars. DOI: 10.14393/BJ-V31N2A2015-27837 7. Jakupovic S et al. — Analysis of Abfraction Lesions Formation Mechanism by FEM. DOI: 10.5455/AIM.2014.22.241-245 8. Grippo JO, Simring M, Coleman TA — Abfraction, Abrasion, Biocorrosion, and NCCLs: A 20-Year Perspective. DOI: 10.1111/J.1708-8240.2011.00487.X 9. Ceruti P et al. — Non carious cervical lesions: A review. 10. Internal Research: RPT-01 — 齒頸部磨耗與逆吞嚥肌力研究整理 (18.39 MPa vs 2.469 MPa tongue force data)