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Emergence angle and profile at implant-supported crowns with and without cantilever extension: A digital study in
1Shanghai Perio-Implant Innovation Center, Institute of Integrated Oral, Craniofacial and Sensory Research, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; College of Stomatology, Shanghai Jiao Tong University, National Center of Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai, China.
Objectives:
To compare the emergence angle between cantilever and non-cantilever digital designs for implant-supported crowns at molar sites, offering digital analysis insights for evaluating restoration strategy selection.
Methods:
One hundred patients missing the first molar underwent intraoral scanning and CBCT imaging. Data were imported into digital platforms for prosthetic-driven planning and virtual design of implants, abutments and crowns. Two designs (cantilever and non-cantilever) were created for each patient. Emergence angles were measured using both 2D and 3D software. Simple and multiple linear regression models were employed to analyze associations between emergence angles and clinically relevant parameters (crown height and edentulous space).
Results:
The mesio-distal width of first molar edentulous spaces averaged 10.5 ± 0.8 mm (range: 9.0-12.5 mm). For cantilever restorations, 2D angles measured 23.0 ± 4.5° (mesial) and 22.4 ± 4.6° (distal). Non-cantilever restorations exhibited greater angles, with 2D measurements of 29.1 ± 5.6° (mesial) and 30.4 ± 6.3° (distal) (p < 0.001). When categorizing edentulous spaces into three ranges (9.0-9.9 mm, 10.0-10.9 mm, and 11.0-12.5 mm), mesio-distal emergence angles exceeding 30° occurred in 1.6 %, 2.3 %, and 10.0 % of cantilever designs respectively, compared to 25.8 %, 54.6 %, and 58.0 % in non-cantilever designs (p < 0.001). Cantilever designs consistently produced smaller emergence angles across all edentulous space dimensions.
Conclusions:
Cantilever implant restorations demonstrated smaller emergence angles than non-cantilever designs, suggesting potential advantages for peri‑implant health maintenance. These findings provide geometric evidence that may support cantilever designs for first molar replacements when anatomically feasible, though long-term clinical validation remains needed.
Clinical Significance:
The proposed digital emergence angle analysis represents a useful diagnostic method to optimize prosthetic design in use of implant-supported crowns with cantilever extension.
