Effect of preparation design on fracture strength of compromised molars restored with lithium disilicate inlay and overlay restorations: An in vitro and in silico study

Jelte W Hofsteenge; Marco Aurelio Carvalho; Pauline M Borghans; Marco S Cune; Mutlu Özcan; Pascal Magne; Marco M M Gresnigt

doi:10.1016/j.jmbbm.2023.106096

Effect of preparation design on fracture strength of compromised molars restored with lithium disilicate inlay and overlay restorations: An in vitro and in silico study

J Mech Behav Biomed Mater. 2023 Oct:146:106096. doi: 10.1016/j.jmbbm.2023.106096. Epub 2023 Aug 28.

Authors

Jelte W Hofsteenge¹, Marco Aurelio Carvalho², Pauline M Borghans³, Marco S Cune⁴, Mutlu Özcan⁵, Pascal Magne⁶, Marco M M Gresnigt⁷

Affiliations

¹ University of Groningen, University Medical Center Groningen, Center for Dentistry and Oral Hygiene, Department of Restorative Dentistry, Groningen, the Netherlands. Electronic address: j.w.hofsteenge@umcg.nl.
² Dental School, Evangelical University of Goias, Anapolis, Brazil.
³ University of Groningen, University Medical Center Groningen, Center for Dentistry and Oral Hygiene, Department of Restorative Dentistry, Groningen, the Netherlands.
⁴ University of Groningen, University Medical Center Groningen, Center for Dentistry and Oral Hygiene, Department of Restorative Dentistry, Groningen, the Netherlands; St. Antonius Hospital Nieuwegein, Department of Oral-Maxillofacial Surgery, Prosthodontics and Special Dental Care, Nieuwegein, the Netherlands.
⁵ University of Groningen, University Medical Center Groningen, Center for Dentistry and Oral Hygiene, Department of Restorative Dentistry, Groningen, the Netherlands; University of Zurich, Center of Dental Medicine, Division of Dental Biomaterials, Clinic for Reconstructive Dentistry, Zurich, Switzerland.
⁶ Center for Education and Research in Biomimetic Restorative Dentistry (CER BRD), Beverly Hills, CA, USA.
⁷ University of Groningen, University Medical Center Groningen, Center for Dentistry and Oral Hygiene, Department of Restorative Dentistry, Groningen, the Netherlands; Martini Hospital, Department of Special Dental Care, Groningen, the Netherlands.

PMID: 37659167
DOI: 10.1016/j.jmbbm.2023.106096

Abstract

Purpose: The objective of this study was to determine the influence of different preparation designs on the fracture strength, failure type, repairability, formation of polymerization-induced cracks, and tooth deformation of structurally compromised molars restored with lithium disilicate inlays and overlays in combination with Immediate Dentin Sealing (IDS).

Material and methods: Human molars (N = 64) were randomly assigned to four different preparation designs: Undermined Inlay (UI), Extended Inlay (EI), Restricted Overlay (RO), and Extended Overlay (EO). The teeth were restored using lithium disilicate partial restorations and subjected to thermomechanical fatigue in a chewing simulator (1,2 × 10 (Mondelli et al., 2007) cycles on 50 N, 8000x 5-55 °C), followed by load to failure testing. In silico finite element analysis was conducted to assess tooth deformation. Polymerization-induced cracks were evaluated using optical microscopy and transillumination. Fracture strengths were statistically analyzed using a Kruskal-Wallis test, while the failure mode, repairability, and polymerization cracks were analyzed using Fisher exact test.

Results: The propagation of polymerization-induced cracks did not significantly differ among preparation designs. All specimens withstood chewing simulator fatigue, with no visible cracks in teeth or restorations. Fracture strength was significantly influenced by preparation design, with restricted overlay (RO) showing higher fracture strength compared to extended inlay (EI) (p = .042). Tooth deformation and fracture resistance correlated between in vitro and in silico analyses). UI exhibited a statistically less destructive failure pattern than EO (p < .01) and RO (p = .036). No statistically significant influence of the preparation design on repairability was observed. Groups with higher repairability rates experienced increased tooth deformation, leading to less catastrophic failures.

Conclusions: The preparation design affected the fracture strength of compromised molars restored with lithium disilicate inlays and overlays, with significantly lower fracture strength for an extended inlay. The failure pattern of lithium disilicate overlays is significantly more destructive than that of undermined and extended inlays. The finite element analysis showed more tooth deformation in the inlay restorations, with lower forces in the roots, leading to less destructive fractures. Since cusp coverage restorations fracture in a more destructive manner, this study suggests the undermined inlay preparation design as a viable option for restoring weakened cusps.

Keywords: Adhesion; Adhesive dentistry; Ceramic; Cusp coverage; Dental materials; FEA; Failure mode; Fatigue; Fracture strength; Inlay; Lithium disilicate; Overlay.

MeSH terms

Dental Porcelain
Fatigue
Flexural Strength*
Fractures, Bone*
Humans
Molar

Substances

lithia disilicate
Dental Porcelain