Editorial Type:
Article Category: Research Article
 | 
Online Publication Date: 15 Mar 2024

Accuracy of Selective Laser Melted Bar Retaining Mandibular Implant-Assisted Overdenture: An In Vitro Comparison of Different Impression Materials and Techniques

BDS, MSc, PhD,
BDS, MSc, and
BDS, MSc, PhD, Dr Med Dent
Page Range: 590 – 598
DOI: 10.1563/aaid-joi-D-23-00068
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This study aimed to assess the accuracy of the marginal fit of 2 implant-supported overdenture bars fabricated with selective laser melting technology, using polyvinyl siloxane and vinyl siloxane ether impression materials and different impression techniques. Two implants with multi-unit abutments were inserted in a 3D-printed mandibular model and used as a reference model, then duplicated into a stone cast to fabricate custom trays for obtaining impressions with polyvinyl siloxane and vinyl siloxane ether impression materials, using both open and closed-tray techniques. This resulted in a total of 4 groups, each with 8 specimens. The impressions were poured and scanned, and 32 cobalt-chromium bars were fabricated using selective laser melting technology. Each bar was screwed onto one abutment of the reference model, and a standardized digital periapical radiograph of the opposite unscrewed side was taken; this process was repeated to the other abutment. The vertical misfit was measured at 3 predetermined positions on the unscrewed side, and 6 values per bar were recorded. The mean gap distance was measured, and the data were subjected to statistical analysis; the present study found that the open-tray technique with vinyl polyether siloxane impression material may offer improved accuracy for obtaining impressions for 2 implant-supported bars. The open-tray technique groups also showed better marginal fit than the closed-tray groups. However, further clinical research is required to confirm these findings.

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<sc>igure 1.</sc>
F igure 1.

(a) Reference model with screwed scan bodies. (b) Digital model.


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F igure 2.

Reference custom tray with 3 acrylic pillars as reference positioning points.


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F igure 3.

The special tray was drilled and fitted with pick-up impression copings.


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F igure 4.

(a) Stone cast with screwed scan bodies. (b) Digital cast. (c) Virtual bar design.


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F igure 5.

(a) Measurement scale settings: black line (a) implant length = 10 mm, red line (b) implant width at the crest = 4 mm, yellow line (c) abutment length = 1.5 mm. (b) Points of measurement (mesial, distal, and middle).


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F igure 6.

Gap distance = yellow lines (1, 2, and 3) representing the distance from implant crest to base of the bar – green line (4) representing abutment length.


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F igure 7.

Comparison of mean gap distance between VSXE closed-tray, PVS closed-tray, PVS open-tray, and VSXE open-tray.


Contributor Notes

Corresponding author, e-mail: Emad.agamy@mu.edu.eg; Emad.agamy@deltauniv.ed.eg
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