COMPARATIVE ANALYSIS OF FRACTURE MODES IN DIRECT COMPOSITE VENEERS PREPARED WITH BEVEL AND INCISAL OVERLAP DESIGNS: AN IN VITRO MICROSCOPIC EVALUATION
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Keywords
direct composite veneer; bevel; incisal overlap; failure mode; adhesive failure; cohesive failure; stereomicroscopy; chi-square
Abstract
Background: Preparation geometry may influence not only how much load a veneer withstands but how it fails information that matters for prognosis and repair.
Objective: To compare failure modes of direct nanohybrid composite veneers
fabricated with bevel versus incisal-overlap preparations.
Materials and Methods: Eighty extracted maxillary central incisors were prepared and restored with a standardized adhesive protocol and nanohybrid composite, then thermocycle (300 cycles, 5–55 °C). Group A received a bevel design; Group B received an incisal-overlap design (n=40 each). Specimens were loaded to failure; fractured teeth and fragments were examined under a stereomicroscope (40×) and categorized as cohesive (in resin), adhesive (tooth–resin interface), or mixed. Failure-mode distributions were compared using chi-square tests (α=0.05).
Results: Failure patterns differed significantly by preparation design (χ²(2) =19.2, p<0.001). Bevel preparations showed more cohesive failures (24/40, 60%) and fewer adhesive (4/40, 10%) and mixed failures (12/40, 30%). Incisal-overlap preparations showed more adhesive (16/40, 40%) and mixed failures (18/40, 45%), with cohesive failures least frequent (6/40, 15%).
Conclusions: Preparation design influences how direct composite veneers fail. Bevel designs are more likely to produce cohesive often more repairable failures, whereas incisal-overlap designs show greater interfacial (adhesive) and mixed failures. These findings support beveling when long-term maintenance and repairability are priorities; validation under cyclic loading and with varied adhesive systems is warranted.
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Dr. Mohammad Anam Uddin
Medical Officer, Department of Conservative Dentistry and Endodontics, Bangladesh Medical University, Dhaka, Bangladesh.
Email: dranam7025@gmail.com ORCID iD: https://orcid.org/0009-0001-8091-8078
Dr. Dilara Jahan
Medical Officer, Department of Paediatric Dentistry, Bangladesh Medical University, Dhaka, Bangladesh.
Email: jahanmitu001@bsmmu.edu.bd ORCID iD: https://orcid.org/0009-0003-9937-9873
Dr. Rabeya Sultana
Consultant, Anam Dental and Endodontics, Kakrail, Dhaka, Bangladesh.
Email: srabeya23@gmail.com ORCID iD: https://orcid.org/0009-0009-2935-0286
Dr. Swapan Kanti Paul
Dental Surgeon, Upazila Health Complex, Bishwambharpur, Sunamganj, Bangladesh.
Email: swapanpaul46@gmail.com ORCID iD: https://orcid.org/0009-0008-5744-5824
Dr. Muhammad Ataullah
Medical Officer, Department of Conservative Dentistry and Endodontics, Bangladesh Medical University, Dhaka, Bangladesh.
Email: dr.ataullah@bsmmu.edu.bd ORCID iD: https://orcid.org/0009-0003-2651-5803
Dr. Md. Asif Mahmud
Dental Surgeon, Shaheed Suhrawardy Medical College Hospital, Dhaka, Bangladesh.
Email: drasifendo@gmail.com Orchid Id-https://orcid.org/0009-0008-3964-4926
Dr. Mohammed Assaduzzaman
Assistant Professor, Department of Conservative Dentistry and Endodontics, Bangladesh Medical University, Bangladesh. Email:m.asad74@gmail.com
Prof. Dr. Md. Mozammal Hossain
Professor, Department of Conservative Dentistry and Endodontics, Bangladesh Medical University, Bangladesh. Email:mozammalresearch@gmail.com