Critical Integrative Review: Margin Placement and Finish-Line Design in Thin-Walled Post-and-Core Teeth — A Biomechanical Decision Framework

Critical Integrative Review: Margin Placement and Finish-Line Design in Thin-Walled Post-and-Core Teeth — A Biomechanical Decision Framework | 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 Critical Integrative Review: Margin Placement and Finish-Line Design in Thin-Walled Post-and-Core Teeth — A Biomechanical Decision Framework Osama Hajeer, Amal Hasan, Mohammed Sultan, JadAlKarim AlKadour This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7858252/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 12 You are reading this latest preprint version Abstract Purpose: To critically evaluate the influence of finish-line design, ferrule effect, and margin placement on the biomechanical outcomes of post-and-core restorations in thin-walled, endodontically treated teeth, and to propose a clinically applicable margin-placement framework for decision-making. Methods: A critical review of the literature published between 2000 and 2025 was conducted in PubMed, Embase, and Scopus. Eligible studies included systematic reviews, clinical trials, retrospective cohorts, in-vitro investigations, finite element analyses, and conceptual reviews addressing the ferrule effect, finish-line design, and remaining dentin thickness. Risk of bias was assessed according to study type, and evidence was stratified hierarchically. Results: Sixteen studies were included. Evidence consistently demonstrated that remaining dentin thickness and margin placement on sound tooth structure are the most decisive predictors of fracture resistance and survival. Horizontal finish lines (shoulder, chamfer) supported favorable marginal adaptation and fracture resistance when adequate dentin was available. However, in thin-walled teeth, additional reduction for a horizontal margin compromised fracture strength. Vertical preparations preserved dentin and were effective when they allowed crown margins to rest on sound dentin, approximating the ferrule effect. Margins terminating solely on core material showed the weakest biomechanical performance. Overall, the body of evidence was judged to carry a moderate-to-high risk of bias. Conclusions: Horizontal preparations remain the preferred approach when sufficient dentin bulk is present. In tall, thin post-and-core teeth, vertical preparations may represent a rational alternative if they allow the margin to be placed on sound dentin. The proposed three-scenario margin-placement framework—margin on core, at core/tooth junction, or on sound dentin—offers a structured guide for tailoring preparation strategies to biomechanical realities. Ferrule effect Post-and-core restoration Vertical preparation (BOPT) Horizontal finish line (shoulder chamfer) Remaining dentin thickness Biomechanics Fracture resistance Prosthodontics Figures Figure 1 Introduction The Restoration of endodontically treated teeth (ETT) has always been a considerable clinical challenge, particularly when coronal tooth structure is severely compromised. While ferrule effect is widely regarded as one of the most important determinants of biomechanical stability and fracture resistance in restored ETT 1 . Yet the protective effect of a ferrule depends not only on its height but also on circumferential continuity and the integrity of residual dentin. In fiber post–restored teeth, full ferrule designs demonstrated the highest resistance 2 . Finite element analyses similarly suggest that greater ferrule height redistributes functional stresses coronally, thereby lowering peak stresses in radicular dentin 3 . Clinical situations frequently demand compromise 4 . This means that in tall, thin post-and-core teeth, the preparation required to create a conventional horizontal finish line (shoulder or chamfer) may necessitate further reduction of dentinal walls that are already thin. Such additional thinning could predispose the tooth to vertical fracture under function. Although direct comparative clinical trials are lacking, several in-vitro and computational investigations indicate that remaining dentin thickness (RDT) exerts a stronger influence on fracture resistance than the precise finish-line configuration 4 , 5 . Alternative preparation concepts have therefore gained attention. Vertical or “no-finish-line” preparations, such as the biologically oriented preparation technique (BOPT), have been reported to achieve periodontal and prosthetic outcomes comparable to those of horizontal chamfers in short-term follow-up 6,7 . Despite this advance, the literature has not comprehensively addressed the combined effect of finish-line design, margin placement relative to core or sound dentin, and axial wall thickness in tall, thin post-and-core teeth. Specifically, there is limited synthesis regarding whether a crown margin placed entirely on sound tooth structure—even without a circumferential ferrule—may be biomechanically superior to retaining and further thinning fragile dentin merely to accommodate a horizontal finish line. Materials and Methods Evidence Acquisition A structured electronic search was conducted in PubMed/MEDLINE, Embase, and Scopus to identify relevant publications between January 2000 and March 2025. The following keywords and Boolean combinations were applied: “ferrule” OR “ferrule effect” AND “post and core” OR “post-and-core” AND “finish line” OR “preparation design” OR “chamfer” OR “shoulder” OR “vertical preparation” OR “BOPT”. Search strategies were adapted for each database. Titles and abstracts were screened to include studies meeting the following eligibility criteria: Population Endodontically treated permanent teeth restored with posts, cores, and full-coverage crowns. Intervention Any finish-line design, including horizontal shoulder, chamfer, deep chamfer, or vertical preparation/BOPT. Outcomes Fracture resistance, fatigue resistance, survival, periodontal parameters, marginal adaptation, or stress distribution. Study design Systematic reviews, randomized or non-randomized clinical studies, retrospective cohorts, in-vitro studies, finite element analyses, and conceptual reviews directly relevant to ferrule effect or finish-line design. Language English. Exclusion criteria were studies on implant abutments, veneer or onlay restorations without posts and cores, pediatric or primary teeth, animal studies, and reports with insufficient methodological details. The initial search identified 612 articles. After title and abstract screening, 74 full texts were reviewed, of which 16 studies met inclusion criteria and were included for qualitative synthesis. These were categorized into six evidence layers: (1) systematic reviews/meta-analyses 8 – 10 , (2) prospective clinical studies 11 , 12 , (3) retrospective clinical studies and case series 13 , 14 , (4) in-vitro investigations 15 – 18 , (5) finite element analyses 19 – 21 , and (6) expert or conceptual reviews 22 , 23 . The study selection process is illustrated in Fig. 1 (PRISMA flow diagram). A full list of included studies with main findings is provided in Table 1 . Table 1 Included studies grouped by evidence layer Evidence Layer First Author (Year) Study Design Focus Key Findings Clinical Implications Systematic reviews / Meta-analyses Yu (2019) [8] Systematic review & meta-analysis Finish-line design and marginal adaptation of ceramic crowns Rounded shoulder/deep chamfer improved fit compared with thin shoulder or shallow chamfer Supports horizontal finish lines when dentin bulk is adequate Contrepois (2013) [9] Systematic review Marginal adaptation of ceramic crowns Reported variation in marginal fit; horizontal lines associated with more predictable adaptation Marginal adaptation improves when preparation form supports ceramic integrity Bonfanti-Gris (2025) [10] Systematic review & meta-analysis Vertical vs horizontal finish lines Survival rates comparable; data heterogeneous Finish-line geometry less decisive than tooth condition Prospective clinical studies Cagidiaco (2019) [11] RCT Feather-edge vs chamfer zirconia crowns No difference in survival or periodontal response after 3 years Both designs acceptable when properly executed Serra-Pastor (2019) [12] Prospective cohort Periodontal/prosthetic outcomes with BOPT Stable periodontal health and crown survival at 4 years Vertical preparation safe under controlled protocols Retrospective / Case series Agustín-Panadero (2021) [13] 5-year clinical trial (FPDs, BOPT) Posterior fixed partial dentures with BOPT Acceptable survival; biologic width critical Vertical preparation can be applied in posterior segments Serra-Pastor (2023) [14] 6-year clinical trial Anterior FPDs with BOPT Stable periodontal results over 6 years Vertical preparations sustainable in anterior esthetic zone In-vitro studies Jalalian (2011) [15] In-vitro Chamfer vs deep chamfer zirconia cores Deep chamfer > chamfer in fracture resistance Deep chamfer enhances ceramic support if dentin permits Aboushelib (2012) [16] In-vitro fatigue Finish-line design effect on zirconia crowns Chamfer/shoulder > feather-edge under fatigue Horizontal lines superior if dentin bulk is adequate Skjold (2019) [17] In-vitro Preparation design & fracture load of zirconia Chamfer showed higher load-to-failure than feather-edge Horizontal margins protective when walls not thin Findakly (2019) [18] In-vitro CAD/CAM ceramic crown fit Marginal/internal fit better with chamfer vs vertical Chamfer advantageous for precision Finite element analyses Miura (2018) [19] FEA Stress distribution in premolars with different finish lines Horizontal finish lines reduced stress peaks vs vertical Favor horizontal design when sufficient dentin Kasem (2020) [20] In-vitro + simulation Monolithic zirconia crowns with finish-line variation Deep chamfer > feather-edge in load resistance Shoulder/chamfer favored when feasible Conceptual / Expert reviews Poggio (2012) [21] Retrospective review Knife-edge zirconia crowns Acceptable performance in selected cases Vertical acceptable but case dependent Schmitz (2017) [22] Multicenter case series Lithium disilicate with feather-edge Good survival short term Vertical possible with adhesive ceramics Abdulazeez (2021) [23] Systematic review & meta-analysis Monolithic zirconia with vertical preps High survival; more chipping in some designs Vertical margins promising, but evidence limited Legend: Summary of the 16 included studies, stratified into six evidence layers: (1) systematic reviews/meta-analyses; (2) prospective clinical studies; (3) retrospective clinical studies/case series; (4) in-vitro studies; (5) finite element analyses (FEA); and (6) conceptual/expert reviews. Each entry reports study type, key outcomes, and clinical implications for finish-line design or margin placement. Abbreviations: FEA, finite element analysis; SR, systematic review; RCT, randomized clinical trial. Table 2 Margin-placement scenarios (A–C): biomechanics, longevity, and preparation strategy Scenario Margin Location Biomechanical Considerations Predicted Longevity / Failure Mode Preferred Preparation Strategy Supporting Evidence A Margin on core only Stress concentrated at core–tooth interface; absence of ferrule effect; higher interfacial shear. Lowest survival; high risk of catastrophic root fracture; failures often unrestorable. Not recommended unless no alternative exists. Retrospective/experimental data showing poor fatigue resistance when margins terminate on core [13,14,18–20]. B Margin at core/tooth junction Partial engagement of sound dentin; stress distribution improved compared with Scenario A but still uneven. Intermediate prognosis; mixed failure modes; some reparable fractures possible. Either horizontal or vertical feasible depending on RDT; prognosis inferior to Scenario C. In-vitro and FEA studies reporting intermediate stress patterns [15,16,19]. C Margin on sound dentin Engagement of intact dentin approximates ferrule effect; stress redistributed coronally; improved post–core integration. Highest survival; favorable, often reparable failure patterns; improved resistance to cyclic loading. Horizontal preparation preferred if dentin bulk sufficient; vertical/BOPT justified if horizontal would over-thin walls. Systematic reviews and clinical studies highlighting superiority of tooth-level margins [8–12,17,19,20]. Legend: Comparative synthesis of three clinically relevant scenarios: A) margin terminating on core material; B) margin placed at the core/tooth junction; C) margin placed on sound tooth structure. Table summarizes expected stress distribution, predicted survival patterns, and recommended preparation approach (horizontal vs vertical). Abbreviations: RDT, remaining dentin thickness; BOPT, biologically oriented preparation technique. Evidence Stratification Evidence was stratified hierarchically according to methodological rigor and clinical transferability. Systematic reviews and meta-analyses were considered the highest tier, followed by prospective clinical studies, retrospective cohorts, and in-vitro or computational investigations. Conceptual reviews were included only for background and contextual interpretation. Risk of Bias Assessment Risk of bias was assessed according to study design. Systematic reviews were evaluated according to AMSTAR 2 domains, including protocol registration, comprehensiveness of search, duplicate screening, and assessment of publication bias 8 – 10 . Randomized clinical trials were assessed using criteria from the Cochrane Risk of Bias 2 tool, focusing on randomization, blinding, and completeness of outcome reporting 11 . Non-randomized clinical studies were appraised with ROBINS-I domains, including potential confounding, selection bias, and outcome measurement 12 – 14 . In-vitro studies were considered inherently limited due to simplified tooth models, small sample sizes, lack of standardized thermomechanical fatigue testing, and limited external validity 15 – 18 . Finite element analyses were examined for assumption-related bias, including modeling dentin as isotropic, applying static rather than cyclic loads, and geometric simplifications 19 – 21 . Conceptual reviews were recognized as very high risk of selection and author bias, and were used only for contextual purposes 22 , 23 . A structured overview of common bias sources across evidence layers is provided in Table 3 (Risk of Bias Summary). Overall, the body of evidence was judged to have a moderate-to-high risk of bias, highlighting the need for cautious interpretation and triangulation of findings across study designs. Table 3 Risk of bias (RoB) summary by evidence layer for 16 included studies [8–23] Evidence Layer Studies Main RoB Domains Overall Risk Comments Systematic reviews / Meta-analyses Yu (2019) [8]; Contrepois (2013) [9]; Bonfanti-Gris (2025) [10] Some lacked protocol registration; variable duplicate screening; heterogeneous inclusion criteria; potential publication bias. Moderate Provide valuable aggregated evidence, though methodology varied and reporting quality was inconsistent. Prospective clinical studies Cagidiaco (2019) [11]; Serra-Pastor (2019) [12] Small sample sizes; short follow-up (≤ 4 years); limited blinding of assessors. Moderate Yield clinically relevant outcomes but are underpowered for long-term survival inference. Retrospective / Case series Agustín-Panadero (2021) [13]; Serra-Pastor (2023) [14] Risk of selection bias; incomplete follow-up; absence of control groups. High Provide long-term trends, but low methodological rigor weakens confidence. In-vitro studies Jalalian (2011) [15]; Aboushelib (2012) [16]; Skjold (2019) [17]; Findakly (2019) [18] Simplified tooth analogues; small samples; heterogeneous fatigue/aging protocols. High Inform mechanistic understanding but lack clinical transferability. Finite element analyses (FEA) Miura (2018) [19]; Kasem (2020) [20] Isotropic dentin assumptions; static loading; oversimplified geometry. High Useful for stress pathway analysis but not directly predictive of clinical outcomes. Conceptual / Expert reviews Poggio (2012) [21]; Schmitz (2017) [22]; Abdulazeez (2021) [23] Narrative methodology; selective evidence inclusion; lack of systematic criteria. Very high Provide theoretical support or aggregated impressions but prone to author bias and methodological subjectivity. Legend: Structured assessment of bias across the 16 included studies, organized by evidence layer. Criteria based on AMSTAR 2 for systematic reviews, Cochrane RoB2 for randomized clinical trials, ROBINS-I for non-randomized studies, and appraisal of external validity and modeling assumptions for in-vitro and FEA studies. Abbreviations: RoB, risk of bias; SR, systematic review; RCT, randomized clinical trial; FEA, finite element analysis. Results / Evidence Synthesis Ferrule and Remaining Dentin Thickness (RDT) Evidence from systematic reviews confirms the protective role of a ferrule, with 1.5–2.0 mm of circumferential or substantial segmental dentin associated with greater fracture resistance and improved survival of endodontically treated teeth (ETT) 8 , 9 . In-vitro investigations further support that wall thickness strongly correlates with fracture strength; reduction of already thin axial walls consistently led to unfavorable, often catastrophic, failure modes 15 , 16 . The amount and distribution of coronal dentin were shown to be more decisive than the categorical choice of post or core material 16 . Finish-Line Design: Horizontal Preparations Systematic reviews and meta-analyses of ceramic crowns indicate that horizontal designs—particularly rounded shoulder and deep chamfer—tend to improve marginal and internal adaptation, thereby supporting predictable seating and cementation 8 , 10 . Laboratory studies reinforce this observation, showing that deep chamfer or rounded shoulder designs often provide higher fracture resistance than shallow chamfers or thin shoulders when adequate dentin is available 15 , 17 . These findings suggest that horizontal finish lines remain advantageous in structurally favorable conditions. Vertical Preparations (BOPT and Variants) Two systematic reviews of vertical preparation techniques reported survival rates exceeding 96% and found no clinically significant compromise in periodontal health when biologic width management and provisionalization protocols were respected 9 , 10 . Prospective clinical data also demonstrated stable periodontal conditions and satisfactory survival of BOPT restorations up to four years 12 . A randomized clinical trial comparing feather-edge to chamfer margins for zirconia crowns found no significant differences in short-term survival or periodontal response, further suggesting that both margin designs can be serviceable when executed appropriately 11 . Margin Placement Relative to Core and Sound Tooth Retrospective and in-vitro studies specifically investigating margin location emphasize that margins placed on sound tooth structure correlate with superior fatigue resistance and more favorable failure modes compared with margins terminating on core material 13 , 14 , 18 . When the margin was positioned at the core/tooth junction, intermediate outcomes were reported, highlighting the biomechanical disadvantage of relying solely on core interfaces. These findings converge with FEA models, which show higher interfacial stresses when margins terminate on core material rather than dentin 19 , 20 . Comparative Assessments When vertical and horizontal finish lines were compared directly in systematic reviews, no clear superiority was established; both designs yielded acceptable outcomes when other biomechanical principles were satisfied 10 . This underscores that finish-line geometry alone is less decisive than the interplay between residual dentin thickness, margin placement, and ferrule presence. Risk of Bias Results Assessment of the 16 included studies revealed variability across designs. Systematic reviews 8 – 10 were generally of moderate quality, though some lacked protocol registration and duplicate screening, raising concerns of selection and reporting bias. The randomized clinical trial 11 was at moderate risk of bias due to small sample size and short follow-up. Prospective cohorts 12 were also at moderate risk, limited by sample size and absence of blinding. Retrospective studies 13 , 14 were considered high risk because of selection bias and incomplete follow-up. In-vitro investigations 15 – 18 carried high risk for external validity owing to simplified models and heterogeneous testing protocols. FEA studies 19 , 20 were at high risk due to modeling assumptions such as isotropic dentin and static loading conditions. Conceptual reviews 21 – 23 were judged very high risk, as they lacked systematic methodology. Overall, the body of evidence carries moderate-to-high risk of bias, necessitating cautious interpretation. A structured overview is presented in Table 3 . Clinical Implications 1. Adequate dentin present: Horizontal designs (rounded shoulder or deep chamfer) remain well supported for marginal fit and fracture resistance; they should be preferred when ceramic requirements and biologic width allow 8 , 10 , 15 , 17 . 2. Thin axial walls: Preservation of RDT and margin placement on sound tooth structure are paramount. In this scenario, vertical preparations may be biomechanically justified, but only if they enable tooth-level margin placement and approximate a ferrule 9 , 11 , 12 , 13 , 14 , 18 – 20 . Discussion The restoration of endodontically treated teeth (ETT) has long revolved around the principle that a circumferential ferrule combined with a well-defined horizontal finish line confers superior biomechanical stability 1 , 8 , 10 . This paradigm is strongly grounded in in-vitro experiments and systematic reviews demonstrating that ferrule height and continuity significantly enhance fracture resistance 8 , 9 , 15 , 16 . Yet, the present review highlights that this doctrine requires nuance in clinical situations where walls are thin and already structurally compromised. The primacy of remaining dentin thickness The evidence synthesis consistently showed that remaining dentin thickness (RDT) outweighs the choice of finish-line geometry in predicting long-term outcomes 4 , 5 , 10 , 15 , 16 . Over-reduction to achieve a circumferential shoulder or deep chamfer may unintentionally weaken the very structure intended to be preserved. FEA models corroborate this by showing unfavorable stress trajectories when axial walls are thinned below critical thresholds 19 , 20 . These insights suggest that the protective value of a finish line is conditional upon the preservation of tooth substance, rather than being universally beneficial. Margin placement: the overlooked determinant A second key finding is the location of the prosthetic margin relative to sound dentin. Retrospective and laboratory data demonstrated inferior fatigue resistance and catastrophic failures when margins terminated exclusively on core material 13 , 14 , 18 . Conversely, margins resting on sound dentin approximated the ferrule effect, even when circumferential continuity was incomplete. This observation aligns with earlier conceptual frameworks emphasizing that the “true ferrule” is not the presence of a finish line per se but rather the engagement of intact dentin walls 24 . Thus, this study suggests ensuring a tooth-level margin and for this concept to be prioritized, even if this necessitates deviation from a traditional horizontal preparation design. Reconciling horizontal and vertical philosophies Systematic reviews comparing vertical (BOPT) and horizontal finish lines concluded that both designs can yield comparable survival when biologic and structural principles are respected 9 , 10 . Clinical studies on BOPT further demonstrated stable periodontal health and favorable survival rates when provisionalization and biologic width control were meticulously observed 11 , 12 . However, these outcomes cannot be interpreted as evidence of inherent superiority of vertical preparations. Instead, they reinforce the view that both philosophies are valid when appropriately matched to the structural condition of the tooth. In cases with sufficient dentin bulk, horizontal preparations remain advantageous for marginal adaptation, laboratory reproducibility, and restorative material compatibility 8 , 10 , 15 , 17 . In contrast, when dentin is critically thin, vertical preparation becomes a pragmatic solution that allows the crown margin to be dropped onto intact dentin, thereby achieving a partial ferrule while avoiding further thinning. Novelty of the margin-scenario framework The proposed framework—differentiating Scenario A (margin on core), Scenario B (margin at core/tooth junction), and Scenario C (margin on sound dentin)—provides a practical lens for decision-making in compromised post-and-core cases. This conceptualization is not explicitly described in existing reviews 8 – 12 , 21 – 23 . By integrating biomechanical data from in-vitro and FEA studies with clinical outcomes, it becomes evident that Scenario C consistently offers the best prognosis, Scenario B represents an intermediate compromise, and Scenario A is associated with the poorest longevity. This synthesis introduces a structured rationale to guide clinicians who often face these scenarios without clear guidance. Limitations of the available evidence The strength of the conclusions remains constrained by the quality of the underlying evidence. Systematic reviews were of moderate methodological rigor and often lacked protocol registration 8 – 10 . Clinical studies were limited by small cohorts, short follow-up, and absence of blinding 11 , 12 . Retrospective analyses were prone to selection bias 13 , 14 , and the majority of evidence arose from in-vitro and computational models 15 – 20 . These carry inherent limitations such as simplified tooth analogues, static loading, and isotropic assumptions. Consequently, while converging trends are evident, the conclusions of this review should be regarded as evidence-informed guidance rather than definitive rules. Clinical significance and directions for research From a prosthodontic standpoint, this study suggests that: When residual dentin is adequate, horizontal preparations remain the method of choice, offering reproducibility, favorable ceramic adaptation, and predictable outcomes 8 , 10 , 15 , 17 . When axial walls are critically thin, vertical preparations may be the more biomechanically rational approach, provided the prosthetic margin can be placed on sound dentin (Scenario C) 9,11–14,18–20,24 . Nevertheless, Future research should prioritize well-powered randomized clinical trials directly comparing vertical and horizontal finish lines in post-and-core teeth with compromised dentin, using standardized outcomes such as survival, failure mode, and periodontal parameters. Moreover, advanced FEA models incorporating anisotropic dentin behavior, cyclic loading, and realistic boundary conditions are required to validate and refine the proposed framework 25 , 26 . Conclusion Within the limitations of the available evidence, the present review suggests that residual dentin thickness and margin placement on sound tooth structure are more decisive for longevity of post-and-core restorations than the categorical choice of finish-line geometry. Horizontal preparations remain well supported when adequate dentin bulk exists, particularly for predictable ceramic adaptation and laboratory reproducibility 8 , 10 , 15 , 17 . However, in tall, thin teeth where creating a horizontal shoulder or chamfer would further compromise wall thickness, vertical preparations may represent a rational alternative if they permit the crown margin to rest directly on intact dentin, thereby partially achieving the ferrule effect 9 , 11 – 14 , 18 – 20 , 24 . The proposed margin-scenario framework—differentiating margins terminating on core (Scenario A), at the core/tooth junction (Scenario B), or on sound dentin (Scenario C)—provides a structured rationale for tailoring finish-line selection to the biomechanical condition of the tooth. This framework highlights that Scenario C consistently yields the most favorable prognosis, whereas Scenario A is least desirable. Clinical Significance Finish-line selection for post-and-core restorations should be driven less by convention and more by remaining dentin thickness and the feasibility of placing the margin on sound tooth structure . Horizontal preparations are preferred when dentin is adequate, but when axial walls are critically thin, vertical preparations may allow margin placement on intact dentin and offer biomechanical advantages. This nuanced approach may help clinicians reduce catastrophic failures and extend the functional life of compromised endodontically treated teeth. Declarations Funding : This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Conflicts of Interest: The authors declare no conflicts of interest related to this work. Ethical Approval: Not applicable. This study is a critical integrative review and does not involve human participants, animal subjects, or patient data. Informed Consent: Not applicable. Data Availability: All data generated or analyzed during this study are included in this published article. Additional details are available from the corresponding author upon reasonable request. Author Contribution OH conceptualized and designed the review framework, conducted the literature search, performed data synthesis, and drafted the manuscript. AH supervised the methodological design, verified data interpretation, and critically revised the intellectual content. 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Marginal integrity and fracture resistance of monolithic zirconia crowns with different finish lines: An in vitro study. J Esthet Restor Dent. 2020;32(2):212–9. 10.1111/jerd.12516 . Poggio CE, Dosoli R, Ercoli C. A retrospective analysis of 102 zirconia single crowns with knife-edge margins. J Prosthet Dent. 2012;107(5):316–21. 10.1016/S0022-3913(12)60083-3 . Schmitz JH, Valenti M, Valenti A, Cortellini D, Canale A. Lithium-disilicate single crowns with feather-edge preparations: A multicenter clinical study. Quintessence Int. 2017;48(7):547–54. Abdulazeez MI, Al-Zordk W, Al-Krenawi A, et al. Fracture strength of monolithic zirconia crowns with modified vertical preparations: A systematic review and meta-analysis. PLoS ONE. 2021;16(3):e0248795. 10.1371/journal.pone.0248795 . Mamoun JS. On the ferrule effect and on crown designs that achieve it: A literature review. Eur J Dent. 2014;8(1):1–9. 10.4103/1305-7456.126234 . Alberto LHJ, Zhang Z, Duan Y. Effect of ferrule design on stress distribution of maxillary incisor rehabilitated with ceramic crown and PEEK post–core material: A 3D finite element analysis. Ceram (Basel). 2023;6(4):2256–68. 10.3390/ceramics6040137 . Libman WJ, Nicholls JI. Load fatigue of teeth restored with cast posts and cores and complete crowns. Int J Prosthodont. 1995;8(2):155–61. Additional Declarations No competing interests reported. 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10:04:08","extension":"xml","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":101612,"visible":true,"origin":"","legend":"","description":"","filename":"b7d6c8a74a5f4961886d02c2f174bd2d1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7858252/v1/6c98370ddb6f87f29bbc8ffb.xml"},{"id":96441075,"identity":"5f7d24ff-b75f-49ea-b4c1-09635da744a3","added_by":"auto","created_at":"2025-11-21 07:06:27","extension":"html","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":110348,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7858252/v1/686642b5a50fed70f49da3a6.html"},{"id":96441066,"identity":"2c33b7c2-2d31-495e-a4f4-e9273ea4cc63","added_by":"auto","created_at":"2025-11-21 07:06:26","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":27580,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePRISMA flow diagram of study selection\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLegend:\u003c/strong\u003e Flow of records through identification, screening, eligibility, and inclusion stages for the review period (2000–2025) across PubMed/MEDLINE, Embase, and Scopus. Numbers correspond to those reported in Materials and Methods.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAbbreviations:\u003c/strong\u003e PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses.\u003c/p\u003e","description":"","filename":"PRISMAFlowDiagram.png","url":"https://assets-eu.researchsquare.com/files/rs-7858252/v1/f7840822cb52cb434e8437c0.png"},{"id":96456998,"identity":"a83bda28-1e78-499e-bf95-3147a2e58515","added_by":"auto","created_at":"2025-11-21 10:09:00","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1184522,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7858252/v1/e48729a6-8755-4864-a5d2-2533afe24def.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eCritical Integrative Review: Margin Placement and Finish-Line Design in Thin-Walled Post-and-Core Teeth — A Biomechanical Decision Framework\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe Restoration of endodontically treated teeth (ETT) has always been a considerable clinical challenge, particularly when coronal tooth structure is severely compromised. While ferrule effect is widely regarded as one of the most important determinants of biomechanical stability and fracture resistance in restored ETT \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eYet the protective effect of a ferrule depends not only on its height but also on circumferential continuity and the integrity of residual dentin. In fiber post\u0026ndash;restored teeth, full ferrule designs demonstrated the highest resistance\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Finite element analyses similarly suggest that greater ferrule height redistributes functional stresses coronally, thereby lowering peak stresses in radicular dentin \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eClinical situations frequently demand compromise\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. This means that in tall, thin post-and-core teeth, the preparation required to create a conventional horizontal finish line (shoulder or chamfer) may necessitate further reduction of dentinal walls that are already thin. Such additional thinning could predispose the tooth to vertical fracture under function. Although direct comparative clinical trials are lacking, several in-vitro and computational investigations indicate that remaining dentin thickness (RDT) exerts a stronger influence on fracture resistance than the precise finish-line configuration \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eAlternative preparation concepts have therefore gained attention. Vertical or \u0026ldquo;no-finish-line\u0026rdquo; preparations, such as the biologically oriented preparation technique (BOPT), have been reported to achieve periodontal and prosthetic outcomes comparable to those of horizontal chamfers in short-term follow-up \u003csup\u003e6,7\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eDespite this advance, the literature has not comprehensively addressed the combined effect of finish-line design, margin placement relative to core or sound dentin, and axial wall thickness in tall, thin post-and-core teeth.\u003c/p\u003e\u003cp\u003eSpecifically, there is limited synthesis regarding whether a crown margin placed entirely on sound tooth structure\u0026mdash;even without a circumferential ferrule\u0026mdash;may be biomechanically superior to retaining and further thinning fragile dentin merely to accommodate a horizontal finish line.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003eEvidence Acquisition\u003c/h2\u003e\n \u003cp\u003eA structured electronic search was conducted in PubMed/MEDLINE, Embase, and Scopus to identify relevant publications between January 2000 and March 2025. The following keywords and Boolean combinations were applied: \u0026ldquo;ferrule\u0026rdquo; OR \u0026ldquo;ferrule effect\u0026rdquo; AND \u0026ldquo;post and core\u0026rdquo; OR \u0026ldquo;post-and-core\u0026rdquo; AND \u0026ldquo;finish line\u0026rdquo; OR \u0026ldquo;preparation design\u0026rdquo; OR \u0026ldquo;chamfer\u0026rdquo; OR \u0026ldquo;shoulder\u0026rdquo; OR \u0026ldquo;vertical preparation\u0026rdquo; OR \u0026ldquo;BOPT\u0026rdquo;. Search strategies were adapted for each database.\u003c/p\u003e\n \u003cp\u003eTitles and abstracts were screened to include studies meeting the following eligibility criteria:\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003ePopulation\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eEndodontically treated permanent teeth restored with posts, cores, and full-coverage crowns.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eIntervention\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eAny finish-line design, including horizontal shoulder, chamfer, deep chamfer, or vertical preparation/BOPT.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eOutcomes\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eFracture resistance, fatigue resistance, survival, periodontal parameters, marginal adaptation, or stress distribution.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eStudy design\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eSystematic reviews, randomized or non-randomized clinical studies, retrospective cohorts, in-vitro studies, finite element analyses, and conceptual reviews directly relevant to ferrule effect or finish-line design.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eLanguage\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eEnglish.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eExclusion criteria\u003c/strong\u003e were studies on implant abutments, veneer or onlay restorations without posts and cores, pediatric or primary teeth, animal studies, and reports with insufficient methodological details.\u003c/p\u003e\n \u003cp\u003eThe initial search identified 612 articles. After title and abstract screening, 74 full texts were reviewed, of which 16 studies met inclusion criteria and were included for qualitative synthesis. These were categorized into six evidence layers: (1) systematic reviews/meta-analyses \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e, (2) prospective clinical studies \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e, (3) retrospective clinical studies and case series \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e, (4) in-vitro investigations \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e, (5) finite element analyses \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e, and (6) expert or conceptual reviews \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. The study selection process is illustrated in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e (PRISMA flow diagram). A full list of included studies with main findings is provided in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eIncluded studies grouped by evidence layer\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eEvidence Layer\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFirst Author (Year)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eStudy Design\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFocus\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eKey Findings\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eClinical Implications\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSystematic reviews / Meta-analyses\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYu (2019) [8]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSystematic review \u0026amp; meta-analysis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFinish-line design and marginal adaptation of ceramic crowns\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRounded shoulder/deep chamfer improved fit compared with thin shoulder or shallow chamfer\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSupports horizontal finish lines when dentin bulk is adequate\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eContrepois (2013) [9]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSystematic review\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMarginal adaptation of ceramic crowns\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReported variation in marginal fit; horizontal lines associated with more predictable adaptation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMarginal adaptation improves when preparation form supports ceramic integrity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBonfanti-Gris (2025) [10]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSystematic review \u0026amp; meta-analysis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVertical vs horizontal finish lines\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSurvival rates comparable; data heterogeneous\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFinish-line geometry less decisive than tooth condition\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eProspective clinical studies\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCagidiaco (2019) [11]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRCT\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFeather-edge vs chamfer zirconia crowns\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo difference in survival or periodontal response after 3 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBoth designs acceptable when properly executed\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSerra-Pastor (2019) [12]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eProspective cohort\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePeriodontal/prosthetic outcomes with BOPT\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStable periodontal health and crown survival at 4 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVertical preparation safe under controlled protocols\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRetrospective / Case series\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAgust\u0026iacute;n-Panadero (2021) [13]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5-year clinical trial (FPDs, BOPT)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePosterior fixed partial dentures with BOPT\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAcceptable survival; biologic width critical\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVertical preparation can be applied in posterior segments\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSerra-Pastor (2023) [14]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6-year clinical trial\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAnterior FPDs with BOPT\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStable periodontal results over 6 years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVertical preparations sustainable in anterior esthetic zone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIn-vitro studies\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eJalalian (2011) [15]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIn-vitro\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eChamfer vs deep chamfer zirconia cores\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDeep chamfer\u0026thinsp;\u0026gt;\u0026thinsp;chamfer in fracture resistance\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDeep chamfer enhances ceramic support if dentin permits\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAboushelib (2012) [16]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIn-vitro fatigue\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFinish-line design effect on zirconia crowns\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eChamfer/shoulder\u0026thinsp;\u0026gt;\u0026thinsp;feather-edge under fatigue\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHorizontal lines superior if dentin bulk is adequate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSkjold (2019) [17]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIn-vitro\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePreparation design \u0026amp; fracture load of zirconia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eChamfer showed higher load-to-failure than feather-edge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHorizontal margins protective when walls not thin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFindakly (2019) [18]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIn-vitro\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCAD/CAM ceramic crown fit\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMarginal/internal fit better with chamfer vs vertical\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eChamfer advantageous for precision\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFinite element analyses\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMiura (2018) [19]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFEA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStress distribution in premolars with different finish lines\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHorizontal finish lines reduced stress peaks vs vertical\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFavor horizontal design when sufficient dentin\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eKasem (2020) [20]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIn-vitro\u0026thinsp;+\u0026thinsp;simulation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMonolithic zirconia crowns with finish-line variation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDeep chamfer\u0026thinsp;\u0026gt;\u0026thinsp;feather-edge in load resistance\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShoulder/chamfer favored when feasible\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eConceptual / Expert reviews\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePoggio (2012) [21]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRetrospective review\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eKnife-edge zirconia crowns\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAcceptable performance in selected cases\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVertical acceptable but case dependent\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSchmitz (2017) [22]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMulticenter case series\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLithium disilicate with feather-edge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGood survival short term\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVertical possible with adhesive ceramics\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbdulazeez (2021) [23]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSystematic review \u0026amp; meta-analysis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMonolithic zirconia with vertical preps\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHigh survival; more chipping in some designs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVertical margins promising, but evidence limited\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eLegend:\u003c/strong\u003e Summary of the 16 included studies, stratified into six evidence layers: (1) systematic reviews/meta-analyses; (2) prospective clinical studies; (3) retrospective clinical studies/case series; (4) in-vitro studies; (5) finite element analyses (FEA); and (6) conceptual/expert reviews. Each entry reports study type, key outcomes, and clinical implications for finish-line design or margin placement.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eAbbreviations:\u003c/strong\u003e FEA, finite element analysis; SR, systematic review; RCT, randomized clinical trial.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMargin-placement scenarios (A\u0026ndash;C): biomechanics, longevity, and preparation strategy\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eScenario\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMargin Location\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eBiomechanical Considerations\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePredicted Longevity / Failure Mode\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePreferred Preparation Strategy\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSupporting Evidence\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMargin on core only\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStress concentrated at core\u0026ndash;tooth interface; absence of ferrule effect; higher interfacial shear.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLowest survival; high risk of catastrophic root fracture; failures often unrestorable.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot recommended unless no alternative exists.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRetrospective/experimental data showing poor fatigue resistance when margins terminate on core [13,14,18\u0026ndash;20].\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMargin at core/tooth junction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePartial engagement of sound dentin; stress distribution improved compared with Scenario A but still uneven.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIntermediate prognosis; mixed failure modes; some reparable fractures possible.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEither horizontal or vertical feasible depending on RDT; prognosis inferior to Scenario C.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIn-vitro and FEA studies reporting intermediate stress patterns [15,16,19].\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMargin on sound dentin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEngagement of intact dentin approximates ferrule effect; stress redistributed coronally; improved post\u0026ndash;core integration.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHighest survival; favorable, often reparable failure patterns; improved resistance to cyclic loading.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHorizontal preparation preferred if dentin bulk sufficient; vertical/BOPT justified if horizontal would over-thin walls.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSystematic reviews and clinical studies highlighting superiority of tooth-level margins [8\u0026ndash;12,17,19,20].\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cstrong\u003eLegend:\u003c/strong\u003e Comparative synthesis of three clinically relevant scenarios: A) margin terminating on core material; B) margin placed at the core/tooth junction; C) margin placed on sound tooth structure. Table summarizes expected stress distribution, predicted survival patterns, and recommended preparation approach (horizontal vs vertical).\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eAbbreviations:\u003c/strong\u003e RDT, remaining dentin thickness; BOPT, biologically oriented preparation technique.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eEvidence Stratification\u003c/h3\u003e\n\u003cp\u003eEvidence was stratified hierarchically according to methodological rigor and clinical transferability. Systematic reviews and meta-analyses were considered the highest tier, followed by prospective clinical studies, retrospective cohorts, and in-vitro or computational investigations. Conceptual reviews were included only for background and contextual interpretation.\u003c/p\u003e\n\u003ch3\u003eRisk of Bias Assessment\u003c/h3\u003e\n\u003cp\u003eRisk of bias was assessed according to study design.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSystematic reviews\u003c/strong\u003e were evaluated according to AMSTAR 2 domains, including protocol registration, comprehensiveness of search, duplicate screening, and assessment of publication bias \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRandomized clinical trials\u003c/strong\u003e were assessed using criteria from the Cochrane Risk of Bias 2 tool, focusing on randomization, blinding, and completeness of outcome reporting \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNon-randomized clinical studies\u003c/strong\u003e were appraised with ROBINS-I domains, including potential confounding, selection bias, and outcome measurement \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eIn-vitro studies\u003c/strong\u003e were considered inherently limited due to simplified tooth models, small sample sizes, lack of standardized thermomechanical fatigue testing, and limited external validity \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFinite element analyses\u003c/strong\u003e were examined for assumption-related bias, including modeling dentin as isotropic, applying static rather than cyclic loads, and geometric simplifications \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConceptual reviews\u003c/strong\u003e were recognized as very high risk of selection and author bias, and were used only for contextual purposes \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eA structured overview of common bias sources across evidence layers is provided in Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(Risk of Bias Summary). Overall, the body of evidence was judged to have a moderate-to-high risk of bias, highlighting the need for cautious interpretation and triangulation of findings across study designs.\u003c/p\u003e\n\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eRisk of bias (RoB) summary by evidence layer for 16 included studies [8\u0026ndash;23]\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eEvidence Layer\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eStudies\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMain RoB Domains\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eOverall Risk\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eComments\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSystematic reviews / Meta-analyses\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYu (2019) [8]; Contrepois (2013) [9]; Bonfanti-Gris (2025) [10]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSome lacked protocol registration; variable duplicate screening; heterogeneous inclusion criteria; potential publication bias.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eModerate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eProvide valuable aggregated evidence, though methodology varied and reporting quality was inconsistent.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eProspective clinical studies\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCagidiaco (2019) [11]; Serra-Pastor (2019) [12]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSmall sample sizes; short follow-up (\u0026le;\u0026thinsp;4 years); limited blinding of assessors.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eModerate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYield clinically relevant outcomes but are underpowered for long-term survival inference.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRetrospective / Case series\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAgust\u0026iacute;n-Panadero (2021) [13]; Serra-Pastor (2023) [14]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRisk of selection bias; incomplete follow-up; absence of control groups.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eProvide long-term trends, but low methodological rigor weakens confidence.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIn-vitro studies\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eJalalian (2011) [15]; Aboushelib (2012) [16]; Skjold (2019) [17]; Findakly (2019) [18]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSimplified tooth analogues; small samples; heterogeneous fatigue/aging protocols.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eInform mechanistic understanding but lack clinical transferability.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFinite element analyses (FEA)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMiura (2018) [19]; Kasem (2020) [20]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIsotropic dentin assumptions; static loading; oversimplified geometry.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eUseful for stress pathway analysis but not directly predictive of clinical outcomes.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eConceptual / Expert reviews\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePoggio (2012) [21]; Schmitz (2017) [22]; Abdulazeez (2021) [23]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNarrative methodology; selective evidence inclusion; lack of systematic criteria.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVery high\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eProvide theoretical support or aggregated impressions but prone to author bias and methodological subjectivity.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLegend:\u003c/strong\u003e Structured assessment of bias across the 16 included studies, organized by evidence layer. Criteria based on AMSTAR 2 for systematic reviews, Cochrane RoB2 for randomized clinical trials, ROBINS-I for non-randomized studies, and appraisal of external validity and modeling assumptions for in-vitro and FEA studies.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAbbreviations:\u003c/strong\u003e RoB, risk of bias; SR, systematic review; RCT, randomized clinical trial; FEA, finite element analysis.\u003c/p\u003e"},{"header":"Results / Evidence Synthesis","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003eFerrule and Remaining Dentin Thickness (RDT)\u003c/h2\u003e\n \u003cp\u003eEvidence from systematic reviews confirms the protective role of a ferrule, with 1.5\u0026ndash;2.0 mm of circumferential or substantial segmental dentin associated with greater fracture resistance and improved survival of endodontically treated teeth (ETT) \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. In-vitro investigations further support that wall thickness strongly correlates with fracture strength; reduction of already thin axial walls consistently led to unfavorable, often catastrophic, failure modes \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. The amount and distribution of coronal dentin were shown to be more decisive than the categorical choice of post or core material \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003eFinish-Line Design: Horizontal Preparations\u003c/h2\u003e\n \u003cp\u003eSystematic reviews and meta-analyses of ceramic crowns indicate that horizontal designs\u0026mdash;particularly rounded shoulder and deep chamfer\u0026mdash;tend to improve marginal and internal adaptation, thereby supporting predictable seating and cementation \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. Laboratory studies reinforce this observation, showing that deep chamfer or rounded shoulder designs often provide higher fracture resistance than shallow chamfers or thin shoulders when adequate dentin is available \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. These findings suggest that horizontal finish lines remain advantageous in structurally favorable conditions.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eVertical Preparations (BOPT and Variants)\u003c/h3\u003e\n\u003cp\u003eTwo systematic reviews of vertical preparation techniques reported survival rates exceeding 96% and found no clinically significant compromise in periodontal health when biologic width management and provisionalization protocols were respected \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. Prospective clinical data also demonstrated stable periodontal conditions and satisfactory survival of BOPT restorations up to four years \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. A randomized clinical trial comparing feather-edge to chamfer margins for zirconia crowns found no significant differences in short-term survival or periodontal response, further suggesting that both margin designs can be serviceable when executed appropriately \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003ch3\u003eMargin Placement Relative to Core and Sound Tooth\u003c/h3\u003e\n\u003cp\u003eRetrospective and in-vitro studies specifically investigating margin location emphasize that margins placed on sound tooth structure correlate with superior fatigue resistance and more favorable failure modes compared with margins terminating on core material \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. When the margin was positioned at the core/tooth junction, intermediate outcomes were reported, highlighting the biomechanical disadvantage of relying solely on core interfaces. These findings converge with FEA models, which show higher interfacial stresses when margins terminate on core material rather than dentin \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003eComparative Assessments\u003c/h2\u003e\n \u003cp\u003eWhen vertical and horizontal finish lines were compared directly in systematic reviews, no clear superiority was established; both designs yielded acceptable outcomes when other biomechanical principles were satisfied \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. This underscores that finish-line geometry alone is less decisive than the interplay between residual dentin thickness, margin placement, and ferrule presence.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003eRisk of Bias Results\u003c/h2\u003e\n \u003cp\u003eAssessment of the 16 included studies revealed variability across designs.\u003c/p\u003e\n \u003cp\u003eSystematic reviews \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e were generally of moderate quality, though some lacked protocol registration and duplicate screening, raising concerns of selection and reporting bias.\u003c/p\u003e\n \u003cp\u003eThe randomized clinical trial \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e was at moderate risk of bias due to small sample size and short follow-up. Prospective cohorts \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e were also at moderate risk, limited by sample size and absence of blinding.\u003c/p\u003e\n \u003cp\u003eRetrospective studies \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e were considered high risk because of selection bias and incomplete follow-up.\u003c/p\u003e\n \u003cp\u003eIn-vitro investigations \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e carried high risk for external validity owing to simplified models and heterogeneous testing protocols.\u003c/p\u003e\n \u003cp\u003eFEA studies \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e were at high risk due to modeling assumptions such as isotropic dentin and static loading conditions. Conceptual reviews \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e were judged very high risk, as they lacked systematic methodology. Overall, the body of evidence carries moderate-to-high risk of bias, necessitating cautious interpretation. A structured overview is presented in Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eClinical Implications\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cspan\u003e1. Adequate dentin present: Horizontal designs (rounded shoulder or deep chamfer) remain well supported for marginal fit and fracture resistance; they should be preferred when ceramic requirements and biologic width allow \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e.\u003c/span\u003e\u003c/p\u003e\n \u003cp\u003e\u003cspan\u003e2. Thin axial walls: Preservation of RDT and margin placement on sound tooth structure are paramount. In this scenario, vertical preparations may be biomechanically justified, but only if they enable tooth-level margin placement and approximate a ferrule\u0026nbsp;\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003cbr\u003e\u003c/span\u003e\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe restoration of endodontically treated teeth (ETT) has long revolved around the principle that a circumferential ferrule combined with a well-defined horizontal finish line confers superior biomechanical stability \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. This paradigm is strongly grounded in in-vitro experiments and systematic reviews demonstrating that ferrule height and continuity significantly enhance fracture resistance \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. Yet, the present review highlights that this doctrine requires nuance in clinical situations where walls are thin and already structurally compromised.\u003c/p\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003eThe primacy of remaining dentin thickness\u003c/h2\u003e\u003cp\u003eThe evidence synthesis consistently showed that remaining dentin thickness (RDT) outweighs the choice of finish-line geometry in predicting long-term outcomes \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. Over-reduction to achieve a circumferential shoulder or deep chamfer may unintentionally weaken the very structure intended to be preserved. FEA models corroborate this by showing unfavorable stress trajectories when axial walls are thinned below critical thresholds \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. These insights suggest that the protective value of a finish line is conditional upon the preservation of tooth substance, rather than being universally beneficial.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003eMargin placement: the overlooked determinant\u003c/h2\u003e\u003cp\u003eA second key finding is the location of the prosthetic margin relative to sound dentin. Retrospective and laboratory data demonstrated inferior fatigue resistance and catastrophic failures when margins terminated exclusively on core material \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Conversely, margins resting on sound dentin approximated the ferrule effect, even when circumferential continuity was incomplete. This observation aligns with earlier conceptual frameworks emphasizing that the \u0026ldquo;true ferrule\u0026rdquo; is not the presence of a finish line per se but rather the engagement of intact dentin walls \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. Thus, this study suggests ensuring a tooth-level margin and for this concept to be prioritized, even if this necessitates deviation from a traditional horizontal preparation design.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003eReconciling horizontal and vertical philosophies\u003c/h2\u003e\u003cp\u003eSystematic reviews comparing vertical (BOPT) and horizontal finish lines concluded that both designs can yield comparable survival when biologic and structural principles are respected \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. Clinical studies on BOPT further demonstrated stable periodontal health and favorable survival rates when provisionalization and biologic width control were meticulously observed \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. However, these outcomes cannot be interpreted as evidence of inherent superiority of vertical preparations. Instead, they reinforce the view that both philosophies are valid when appropriately matched to the structural condition of the tooth. In cases with sufficient dentin bulk, horizontal preparations remain advantageous for marginal adaptation, laboratory reproducibility, and restorative material compatibility \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. In contrast, when dentin is critically thin, vertical preparation becomes a pragmatic solution that allows the crown margin to be dropped onto intact dentin, thereby achieving a partial ferrule while avoiding further thinning.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003eNovelty of the margin-scenario framework\u003c/h2\u003e\u003cp\u003eThe proposed framework\u0026mdash;differentiating Scenario A (margin on core), Scenario B (margin at core/tooth junction), and Scenario C (margin on sound dentin)\u0026mdash;provides a practical lens for decision-making in compromised post-and-core cases. This conceptualization is not explicitly described in existing reviews \u003csup\u003e\u003cspan additionalcitationids=\"CR9 CR10 CR11\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. By integrating biomechanical data from in-vitro and FEA studies with clinical outcomes, it becomes evident that Scenario C consistently offers the best prognosis, Scenario B represents an intermediate compromise, and Scenario A is associated with the poorest longevity. This synthesis introduces a structured rationale to guide clinicians who often face these scenarios without clear guidance.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003eLimitations of the available evidence\u003c/h2\u003e\u003cp\u003eThe strength of the conclusions remains constrained by the quality of the underlying evidence. Systematic reviews were of moderate methodological rigor and often lacked protocol registration \u003csup\u003e\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eClinical studies were limited by small cohorts, short follow-up, and absence of blinding \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Retrospective analyses were prone to selection bias \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e, and the majority of evidence arose from in-vitro and computational models \u003csup\u003e\u003cspan additionalcitationids=\"CR16 CR17 CR18 CR19\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThese carry inherent limitations such as simplified tooth analogues, static loading, and isotropic assumptions. Consequently, while converging trends are evident, the conclusions of this review should be regarded as evidence-informed guidance rather than definitive rules.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\u003ch2\u003eClinical significance and directions for research\u003c/h2\u003e\u003cp\u003eFrom a prosthodontic standpoint, this study suggests that:\u003c/p\u003e\u003cp\u003eWhen residual dentin is adequate, horizontal preparations remain the method of choice, offering reproducibility, favorable ceramic adaptation, and predictable outcomes \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eWhen axial walls are critically thin, vertical preparations may be the more biomechanically rational approach, provided the prosthetic margin can be placed on sound dentin (Scenario C) \u003csup\u003e9,11\u0026ndash;14,18\u0026ndash;20,24\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eNevertheless, Future research should prioritize well-powered randomized clinical trials directly comparing vertical and horizontal finish lines in post-and-core teeth with compromised dentin, using standardized outcomes such as survival, failure mode, and periodontal parameters.\u003c/p\u003e\u003cp\u003eMoreover, advanced FEA models incorporating anisotropic dentin behavior, cyclic loading, and realistic boundary conditions are required to validate and refine the proposed framework \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eWithin the limitations of the available evidence, the present review suggests that residual dentin thickness and margin placement on sound tooth structure are more decisive for longevity of post-and-core restorations than the categorical choice of finish-line geometry. Horizontal preparations remain well supported when adequate dentin bulk exists, particularly for predictable ceramic adaptation and laboratory reproducibility \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. However, in tall, thin teeth where creating a horizontal shoulder or chamfer would further compromise wall thickness, vertical preparations may represent a rational alternative if they permit the crown margin to rest directly on intact dentin, thereby partially achieving the ferrule effect \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan additionalcitationids=\"CR12 CR13\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe proposed margin-scenario framework\u0026mdash;differentiating margins terminating on core (Scenario A), at the core/tooth junction (Scenario B), or on sound dentin (Scenario C)\u0026mdash;provides a structured rationale for tailoring finish-line selection to the biomechanical condition of the tooth. This framework highlights that Scenario C consistently yields the most favorable prognosis, whereas Scenario A is least desirable.\u003c/p\u003e\u003cdiv id=\"Sec21\" class=\"Section2\"\u003e\u003ch2\u003eClinical Significance\u003c/h2\u003e\u003cp\u003eFinish-line selection for post-and-core restorations should be driven less by convention and more by \u003cb\u003eremaining dentin thickness and the feasibility of placing the margin on sound tooth structure\u003c/b\u003e. Horizontal preparations are preferred when dentin is adequate, but when axial walls are critically thin, vertical preparations may allow margin placement on intact dentin and offer biomechanical advantages. This nuanced approach may help clinicians reduce catastrophic failures and extend the functional life of compromised endodontically treated teeth.\u003c/p\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003eThis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of Interest:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflicts of interest related to this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable. This study is a critical integrative review and does not involve human participants, animal subjects, or patient data.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed Consent:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this published article. Additional details are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOH conceptualized and designed the review framework, conducted the literature search, performed data synthesis, and drafted the manuscript. AH supervised the methodological design, verified data interpretation, and critically revised the intellectual content. MS contributed to the analytical structure, ensured consistency of biomechanical reasoning, and reviewed the final draft for academic accuracy. JA provided senior guidance, validated the clinical relevance of conclusions, and approved the final version for submission. All authors read and approved the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eJuloski J, Radovic I, Goracci C, Vulicevic ZR, Ferrari M. Ferrule effect: A literature review. J Endod. 2012;38(1):11\u0026ndash;9. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.joen.2011.09.024\u003c/span\u003e\u003cspan address=\"10.1016/j.joen.2011.09.024\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKhabadze Z, Mordanov O, Taraki F, et al. 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Eur J Dent. 2014;8(1):1\u0026ndash;9. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.4103/1305-7456.126234\u003c/span\u003e\u003cspan address=\"10.4103/1305-7456.126234\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAlberto LHJ, Zhang Z, Duan Y. Effect of ferrule design on stress distribution of maxillary incisor rehabilitated with ceramic crown and PEEK post\u0026ndash;core material: A 3D finite element analysis. Ceram (Basel). 2023;6(4):2256\u0026ndash;68. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3390/ceramics6040137\u003c/span\u003e\u003cspan address=\"10.3390/ceramics6040137\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLibman WJ, Nicholls JI. Load fatigue of teeth restored with cast posts and cores and complete crowns. Int J Prosthodont. 1995;8(2):155\u0026ndash;61.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Ferrule effect, Post-and-core restoration, Vertical preparation (BOPT), Horizontal finish line (shoulder, chamfer), Remaining dentin thickness, Biomechanics, Fracture resistance, Prosthodontics","lastPublishedDoi":"10.21203/rs.3.rs-7858252/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7858252/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cb\u003ePurpose:\u003c/b\u003e\u003c/p\u003e\u003cp\u003eTo critically evaluate the influence of finish-line design, ferrule effect, and margin placement on the biomechanical outcomes of post-and-core restorations in thin-walled, endodontically treated teeth, and to propose a clinically applicable margin-placement framework for decision-making.\u003c/p\u003e\u003cp\u003e\u003cb\u003eMethods:\u003c/b\u003e\u003c/p\u003e\u003cp\u003eA critical review of the literature published between 2000 and 2025 was conducted in PubMed, Embase, and Scopus. Eligible studies included systematic reviews, clinical trials, retrospective cohorts, in-vitro investigations, finite element analyses, and conceptual reviews addressing the ferrule effect, finish-line design, and remaining dentin thickness. Risk of bias was assessed according to study type, and evidence was stratified hierarchically.\u003c/p\u003e\u003cp\u003e\u003cb\u003eResults:\u003c/b\u003e\u003c/p\u003e\u003cp\u003eSixteen studies were included. Evidence consistently demonstrated that remaining dentin thickness and margin placement on sound tooth structure are the most decisive predictors of fracture resistance and survival. Horizontal finish lines (shoulder, chamfer) supported favorable marginal adaptation and fracture resistance when adequate dentin was available. However, in thin-walled teeth, additional reduction for a horizontal margin compromised fracture strength. Vertical preparations preserved dentin and were effective when they allowed crown margins to rest on sound dentin, approximating the ferrule effect. Margins terminating solely on core material showed the weakest biomechanical performance. Overall, the body of evidence was judged to carry a moderate-to-high risk of bias.\u003c/p\u003e\u003cp\u003e\u003cb\u003eConclusions:\u003c/b\u003e\u003c/p\u003e\u003cp\u003eHorizontal preparations remain the preferred approach when sufficient dentin bulk is present. In tall, thin post-and-core teeth, vertical preparations may represent a rational alternative if they allow the margin to be placed on sound dentin. The proposed three-scenario margin-placement framework\u0026mdash;margin on core, at core/tooth junction, or on sound dentin\u0026mdash;offers a structured guide for tailoring preparation strategies to biomechanical realities.\u003c/p\u003e","manuscriptTitle":"Critical Integrative Review: Margin Placement and Finish-Line Design in Thin-Walled Post-and-Core Teeth — A Biomechanical Decision Framework","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-21 07:06:22","doi":"10.21203/rs.3.rs-7858252/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-03-20T19:55:32+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"32905933432863319978130870002852686247","date":"2026-03-01T17:24:00+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-01T13:58:48+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"296268029598874950347415321963569625757","date":"2026-03-01T13:48:48+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-27T08:41:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"225081013772484374445699417280442014874","date":"2026-02-26T10:25:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"35749589549456358426490950059401361482","date":"2025-11-11T20:33:11+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-11-11T18:32:39+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-11-11T16:40:42+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-11-11T12:09:15+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-11-11T12:07:44+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Oral Health","date":"2025-10-14T11:40:58+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3d7ebc9f-3964-45f9-a688-7d034ae04ae2","owner":[],"postedDate":"November 21st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-11-21T07:06:22+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-21 07:06:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7858252","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7858252","identity":"rs-7858252","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}