Journal of Prosthetic Dentistry

Validation of a shape-optimized 2-unit cantilevered inlay-retained fiber-reinforced resin-bonded dental prosthesis

  • Yung-Chung Chen
    Corresponding author: Dr Yung-Chung Chen, School of Dentistry & Institute of Oral Medicine, College of Medicine, National Cheng Kung University, No.1, University Rd, Tainan City 701, Taiwan, ROC
    Associate Professor, School of Dentistry & Institute of Oral Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan, ROC

    Chief, Division of Prosthodontics, Department of Stomatology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan, ROC
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  • Alex Fok
    Professor and Director, Minnesota Dental Research Center for Biomaterials and Biomechanics, School of Dentistry, University of Minnesota, Minneapolis, Minn
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  • Shao-Chun Wang
    Attending physician, Division of Prosthodontics, Department of Stomatology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan, ROC
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  • Jessica Chia-Yi Wang
    Resident, Division of Orthodontics, Department of Stomatology, National Cheng Kung University Hospital, Tainan, Taiwan, ROC
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Published:December 16, 2022DOI:


      Statement of problem

      Current designs of fiber-reinforced composite (FRC) resin-bonded fixed dental prostheses (RBFDPs) have a limited lifespan, failing mainly through veneer-fiber delamination, debonding, and fracture.


      The purpose of this in vitro study was to validate a new inlay-retained 2-unit cantilevered RBFDP with an optimized cavity and fiber layout proposed in a previous study by using simulated occlusal loading.

      Material and methods

      Two groups of specimens (n=20), 1 with and 1 without glass fibers, were used to test the influence of the cavity design and that of the fiber layout on their load capacity, respectively. The specimens without fibers were directly cut from a resin-ceramic block by using a computer-aided manufacturing system, while those with fibers were manually fabricated with unidirectional glass fibers and composite resin in a silicone mold. The specimens with and without fibers were attached to abutments made of the same resin-ceramic with a cyanoacrylate-based adhesive and a resin-based dental cement, respectively. An increasing compressive load was applied on the mesial fossa of the premolar pontic until failure. Cracking in the specimens during loading was monitored with a 2-channel acoustic emission (AE) system.


      All the specimens without fiber reinforcement debonded from the abutments. Those using the optimized shovel-shaped cavity design had a mean ±standard deviation failure load (50.0 ±17.3 N) that was 193% higher than that of those with the conventional step-box design (17.1 ±6.2 N; P<.001). No significant difference was found between the groups for the mean number of AE events per specimen (step-box: 49 ±34 versus shovel-shaped: 63 ±34; P=.427), the mean amplitude of each event (58.4 ±1.3 dB versus 59.5 ±2.4 dB; P=.299), or the mean time to failure (283.2 ±122.3 seconds versus 297.5 ±66.7 seconds; P=.798). Between the groups of specimens with reinforcing fibers, the mean failure load of the conventional design was approximately half that of the optimized one. Again, no significant difference was found for the mean number of AE events per specimen (conventional: 28 ±18 versus optimized: 52 ±53; P=.248) or the mean amplitude for each AE event (64.9 ±4.2 dB versus 61.7 ±5.2 dB; P=.187). The connectors of 8 fiber-reinforced specimens with the conventional design fractured; the other 2 debonded from the abutments. Half of the shape-optimized fiber-reinforced specimens had fractured abutments, but the cantilevers remained intact, 4 specimens fractured at the connector, and only 1 debonded from its abutment.


      The shape-optimized 2-unit cantilevered FRC RBFDP had a higher load capacity than the conventional design.
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