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Clinical Oral Investigations· 2026Q1

Effect of tooth preparation design on fracture load and fracture behavior of deciduous crowns fabricated by subtractive and additive manufacturing

Misaki Hamashima, Kanae Wada, Shinya Oishi, Hidekazu Takahashi et al.

Short summary

Deciduous molar crowns made with knife-edge margins and ESTELITE BLOCK II material had the highest fracture load (n=12/group), but this design also led to non-repairable fractures involving the abutment tooth.

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Key points

  • Crown material and margin design significantly impact fracture load and behavior in deciduous molar crowns (p < 0.05).
  • ESTELITE BLOCK II with knife-edge margins yielded the highest fracture load, but also non-repairable abutment-involving fractures.
  • Deep chamfer margins with Detax material showed high fracture load values.
  • CERASMART PRIME resulted in lower fracture load but predominantly repairable fractures.
  • Fracture behavior in AM materials may be influenced by internal structure and build orientation.

AI-generated from the title and abstract; the full text is not read.

Abstract

Abstract Objectives This study evaluated the effects of crown material and margin design on fracture load and behavior of computer-aided design/computer-aided manufacturing (CAD-CAM) crowns for deciduous molars. Methods Three subtractive-manufacturing (SM) materials and two additive-manufacturing (AM) materials were evaluated. Crowns with knife-edge, chamfer, and deep chamfer margins were fabricated and bonded to standardized deciduous molar abutments ( n = 12/group; total = 180). Fracture load was measured under static loading, and fracture modes were classified by repairability and abutment involvement. Fracture surfaces and crack propagation were examined by scanning electron microscopy. Results Significant effects of material and material–margin interactions were observed ( p < 0.05). ESTELITE BLOCK II exhibited the highest fracture load with knife-edge margins, whereas Detax showed the highest values with deep chamfer margins. However, non-repairable abutment-involving fractures occurred in both materials with knife-edge margins. CERASMART PRIME showed lower fracture load but mainly repairable fractures. SHOFU BLOCK HC and CERASMART PRIME, unified crown–abutment fracture in ESTELITE BLOCK II, interlayer delamination in Detax, and superficial radial cracking in NextDent. Conclusions The effects of margin design on fracture load and fracture behavior were material-dependent. Among subtractive-manufacturing materials, fracture load was generally consistent with reported mechanical properties, whereas fracture behavior in additive-manufacturing materials may have been influenced by internal structure and build orientation. Material selection should consider fracture load, fracture severity, and abutment involvement. Clinical relevance Material and margin selection influence fracture resistance and failure patterns. Fracture severity and abutment involvement should be considered in addition to fracture load.

The authors' abstract, as published at the source. Clinical Oral Investigations, 2026 · DOI ↗

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Field: Orthodontics

OrthodonticsDentistry