Effect of finish line design and metal alloy on the marginal and internal gaps of selective laser melting printed copings

Adel Al Maaz; Geoffrey A Thompson; Carl Drago; Hongseok An; David Berzins

doi:10.1016/j.prosdent.2019.02.009

Effect of finish line design and metal alloy on the marginal and internal gaps of selective laser melting printed copings

J Prosthet Dent. 2019 Aug;122(2):143-151. doi: 10.1016/j.prosdent.2019.02.009. Epub 2019 Apr 1.

Authors

Adel Al Maaz¹, Geoffrey A Thompson², Carl Drago³, Hongseok An⁴, David Berzins⁵

Affiliations

¹ Resident, Graduate Prosthodontics, Marquette University School of Dentistry, Milwaukee, Wis.
² Associate Professor and Director, Graduate Prosthodontics, Marquette University School of Dentistry, Milwaukee, Wis. Electronic address: geoffrey.thompson@marquette.edu.
³ Assistant Professor, Graduate Prosthodontics, Marquette University School of Dentistry, Milwaukee, Wis.
⁴ Assistant Professor, Department of General Dental Sciences, Marquette University School of Dentistry, Milwaukee, Wis.
⁵ Professor and Director, Graduate Dental Biomaterials, Department of General Dental Sciences, Marquette University School of Dentistry, Milwaukee, Wis.

PMID: 30948295
DOI: 10.1016/j.prosdent.2019.02.009

Abstract

Statement of problem: Selective laser melting (SLM) technology has been introduced for printing metal dental restorations from Co-Cr base alloys or Au-Pt high noble alloys. However, information regarding the fit of restorations fabricated by using this technique is limited.

Purpose: The purpose of this in vitro study was to determine the effect of 3 different finish line designs on the marginal and internal gaps of metal copings made from a base (Co-Cr), high noble (Au-Pd-Ag), and noble alloy (Co-Pd) by using the SLM technology.

Material and methods: Three Ivorine right maxillary central incisors were prepared with a chamfer, deep chamfer, or shoulder finish line. The preparations were scanned by using a TRIOS scanner, and a total of 90 dies were printed using DPR 10 Resin (30×3 finish line designs). Ten SLM copings were fabricated for each margin design and metal alloy combination for a total of 90 copings (10×3 finish line designs×3 alloys). Copings were cemented onto dies using an autopolymerizing composite-resin luting material. All coping-die assemblies were sectioned buccolingually by using a low-speed diamond saw, and images were obtained by using an inverted bright field metallurgical microscope at ×100 magnification. Marginal and internal gaps were measured at 5 locations: buccal margin, midfacial, incisal, midlingual, and lingual margin. After gap measurements, representative specimens were embedded in autopolymerizing resin and prepared for metallographic examination. A 2-way multivariate analysis of variance (MANOVA) was conducted to determine the overall significance, followed by ANOVA for each dependent variable (α=.05).

Results: The results indicated that alloy type and finish line had a significant influence on marginal gap of copings (P<.001). Relative to the internal gap, alloy type had a significant effect (P<.001), but the type of finish line had no statistically significant influence (P=.337). No statistically significant interactions occurred. Base alloys were printed with almost no observable porosity, whereas noble and high noble alloys exhibited hot tears and porosity.

Conclusions: Thefinish line type did not influence the internal gap between copings and dies, whereas the alloy type influenced the marginal gap between copings and dies. SLM-fabricated Co-Cr copings on teeth prepared with a deep chamfer finish line demonstrated the lowest marginal gap.

MeSH terms

Adaptation, Psychological
Crowns*
Dental Marginal Adaptation*
Dental Prosthesis Design
Printing, Three-Dimensional