Effect of Lithium Disilicate Ceramic Microstructure and Intracoronal Depth on the Circumferential Marginal Fit of Maxillary Premolar Endocrowns

Endocrown; lithium disilicate; marginal adaptation; microstructure; premolar; preparation depth; CAD/CAM.

Salma Issa Duhaim
Department of Dentistry, Al-Mansour
University College, Baghdad, Iraq
Department of Dental Science, Pusat Kanser
Tun Abdullah Ahmad Badawi, Universiti Sains
Malaysia, 13200 Kepala Batas, Pulau Pinang,
Malaysia

Husniyati Roslan
Department of Dental Science, Pusat Kanser
Tun Abdullah Ahmad Badawi, Universiti Sains
Malaysia, 13200 Kepala Batas, Pulau Pinang,
Malaysia
Biomaterials Group, Pusat Kanser Tun
Abdullah Ahmad Badawi, Universiti Sains
Malaysia, 13200 Kepala Batas, Pulau Pinang,
Malaysia

Rana Mowafaq Khdeir3
College of Dentistry, Ashur University,
Baghdad, Iraq

Received: 15-07-2026
Revised:25-07-2026
Accepted: 12-08-2026

European Journal of Prosthodontics and Restorative Dentistry (2026) 34,7(s) 721–731

Effect of Lithium Disilicate Ceramic Microstructure and Intracoronal Depth on the Circumferential Marginal Fit Maxillary
Premolar Endocrowns

Objectives: To evaluate whether lithium disilicate ceramic microstructure and intracoronal preparation depth influence the circumferential marginal fit of maxillary premolar endocrowns. Methods: Twenty-eight extracted human maxillary first premolars were randomly allocated to four groups (n = 7): IPS e.max CAD or Amber Mill at 2-mm or 4-mm intracoronal depths. After standardised endodontic treatment, digital fabrication, adhesive cementation and thermocycling, marginal gaps were measured at 12 circumferential sites. Crystalline phase abundance and crystal morphology were assessed by X-ray diffraction and scanning electron microscopy, respectively. One-way and two-way analyses of variance with Tukey post hoc testing were applied (p < 0.05). Results: Material and depth significantly affected marginal gap (p = 0.004 and p < 0.001, respectively), with no interaction (p = 0.906). Amber Mill at 4 mm produced the lowest mean gap (52.8 ± 5.7 µm), whereas IPS e.max CAD at 2 mm produced the highest mean gap (74.6 ± 7.9 µm). Amber Mill showed a denser distribution of shorter crystals and fewer marginal machining defects. All group means were below 120 µm. Conclusions: Restorative material and intracoronal depth independently influenced the marginal behaviour. Amber Mill showed an overall lower marginal gap and fewer edge defects, while the 4-mm preparation improved overall seating without altering the bulk phase abundance or crystal morphology. Clinical Relevance: Both ceramics achieved mean marginal gaps below 120 µm under the tested conditions. Material-specific machinability and preparation geometry may improve marginal quality, but preservation of sound dentine and long-term clinical validation remain essential.

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