Citation: Alshehri, H.A.; Altaweel,
S.M.; Alshaibani, R.; Alahmari, E.A.;
Alotaibi, H.N.; Alfouzan, A.F.;
Labban, N. Effect of Different Wax
Pattern Manufacturing Techniques on
the Marginal Fit of Lithium Disilicate
Crowns. Materials 2022, 15, 4774.
https://doi.org/10.3390/ma15144774
Academic Editor: Bruno Chrcanovic
Received: 15 May 2022
Accepted: 5 July 2022
Published: 7 July 2022
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Article
Effect of Different Wax Pattern Manufacturing Techniques on
the Marginal Fit of Lithium Disilicate Crowns
Huda Ahmed Alshehri * , Sara Mohammed Altaweel, Raghdah Alshaibani, Esraa Ahmed Alahmari,
Hanan Nejer Alotaibi, Afnan Fouzan Alfouzan and Nawaf Labban
Department of Restorative Dental Sciences, College of Dentistry, King Saud University,
P.O. Box 60169, Riyadh 11545, Saudi Arabia; staweel-ksu@hotmail.com (S.M.A.); raghdahs@bu.edu (R.A.);
esraa.alahmari@gmail.com (E.A.A.); haalotaibi@ksu.edu.sa (H.N.A.); afnan477@hotmail.com (A.F.A.);
nalabban@ksu.edu.sa (N.L.)
* Correspondence: halshehri@ksu.edu.sa
Abstract:
Purpose: The present study evaluated the marginal gap of lithium disilicate crowns
fabricated through three different wax pattern techniques; Conventional, Milling and 3D-printing.
Materials and Methods: Thirty stone models were replicated from a stainless-steel model representing
a prepared tooth; ten were sent to make conventional wax patterns while the remaining were
sent to a digital dental scanner. The computer aided design was completed and STL (Standard
Tessellation Language) files were sent to either milling or 3D-printing machines. All wax patterns
(n = 30) were pressed, and a stabilizing instrument was used to secure the crowns on the master
model. The marginal gap was measured at 18 points for each crown using a digital microscope (
µ
m)
(n = 540) and compared using One-way ANOVA (p
≤
0.05). Results: There was a significant difference
in the marginal gap value between all three groups (p < 0.01) where the milled group showed the
least mean gap (28.87
±
30.18
µ
m), followed by 3D printed (47.85
±
27.44
µ
m), while the highest
mean marginal gap was found in the conventional group (63.49
±
28.05
µ
m). Conclusion: Milled and
3D-printed wax patterns produced better fitting crowns compared to conventional techniques.
Keywords: marginal fit; wax pattern; Cad/CAM; ceramic crown; 3D-printing; lithium disilicate
1. Introduction
The major determining factors for a successful clinical performance of fixed dental
prosthesis are high marginal accuracy and an adequate internal fit [
1
]. Increased marginal
discrepancies lead to a higher rate of cement dissolving due to its exposure to oral fluids
and chemomechanical dissolution in the oral cavity [
2
]. Consequently, the longevity of
the restored tooth will be compromised by the increased risk of plaque retention, caries
and pulpal pathology [3]. A marginal fit between 25 and 40 µm for cemented restorations
has been suggested as a clinical goal, but these levels are rarely achieved [
1
]. Some studies
indicated that a marginal fit of
≤
120
µ
m is clinically acceptable [
4
], but a more recent study
has concluded that a marginal fit of ≤100 µm is more suitable [5].
Methods used for measuring marginal adaptation include direct inspection by optical
microscopy, view of the cross-section of cemented crowns, and indirect inspection via im-
pression replica technique, scanning electron microscopy and dye penetration methods [
6
].
Direct inspection by optical microscope is ought to be repeatable, less invasive and does
not include intermediate material between crown and its substrate.
The gold standard over the last few decades for posterior teeth rehabilitation was
cast gold restorations, due to its favorable long-term success. Advantages of all-ceramic
crowns over metal ceramic include esthetics, improved functionality and long-term survival
compared to or superior to metal-ceramic crowns [
7
]. Recently, various all-ceramic systems
and manufacturing processes have been introduced to the dental market and have become
popular due to their improved physical properties and the increased demand for esthetic
Materials 2022, 15, 4774. https://doi.org/10.3390/ma15144774 https://www.mdpi.com/journal/materials
