J Adv Prosthodont.  2017 Apr;9(2):124-129. 10.4047/jap.2017.9.2.124.

Role of span length in the adaptation of implant-supported cobalt chromium frameworks fabricated by three techniques

• Zhou Y
• Li Y
• Ma X
• Huang Y
• Wang J

• KMID: 2376300
• DOI: http://doi.org/10.4047/jap.2017.9.2.124

Abstract

PURPOSE
This study evaluated the effect of span length on the adaptation of implant-supported cobalt chromium frameworks fabricated by three techniques.
MATERIALS AND METHODS
Models with two solid abutment analogs at different inter-abutment distances were digitized using a laboratory scanner. Frameworks of two-, three-, and four-unit fixed prostheses were designed by a computer. Six dots with a diameter of 0.2 mm were preset on the surface of each framework. A total of 54 implant-supported cobalt chromium frameworks were fabricated by milling, selective laser melting (SLM), and cast techniques. The frameworks were scanned and exported as Stereolithography files. Distances between two dots in X, Y, and Z coordinates were measured in both the designed and fabricated frameworks. Marginal gaps between the framework and the abutments were also evaluated by impression replica method.
RESULTS
In terms of distance measurement, significant differences were found between three- and four-unit frameworks, as well as between two- and four-unit frameworks prepared by milling technique (P<.05). Significant differences were also noted between two- and three-unit frameworks, as well as between two- and four-unit frameworks prepared by cast technique (P<.05). The milling technique presented smaller differences than the SLM technique, and the SLM technique showed smaller differences than the cast technique at any unit prostheses (P<.05). Evaluation with the impression replica method indicated significant differences among the span lengths for any fabrication method (P<.05), as well as among the fabrication methods at any unit prostheses (P<.05).
CONCLUSION
The adaptation of implant-supported cobalt chromium frameworks was affected by the span length and fabrication method.

Keyword

Milling; SLM; Cast; Span; Adaptation

MeSH Terms

Chromium*
Cobalt*
Freezing
Methods
Prostheses and Implants
Chromium
Cobalt

Figure

• 

  Fig. 1 Models simulating two implants with two-unit (A), three-unit (B), and four-unit (C) fixed prostheses. The standard distance was defined as the distances between six dots along the X, Y, and Z directions on each designed framework (two-unit), named as X1 (D), X2 (E), Y1 (F), Y2 (G), Z1 (H), and Z2 (I).

• 

  Fig. 2 Schematic diagram of impression replica technique. The framework was filled with a light body silicone (A) and seated on the abutment with pressure for 2 - 3 minutes (B). The framework with light body silicone layer was then removed from the abutment (C) and filled with medium-viscosity silicone (D). After the material was hardened, the silicone was separated and sectioned buccolingually and mesiodistally into four parts (D). The width of the light body silicone layer was measured using a microscope at ×6.6 magnification (E).

• 

  Fig. 3 Differences between standard distances and measured distances, as well as marginal gap widths among milled, SLM, and cast frameworks. (A) Difference of distances; (B) Gap widths. *P < .05.

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