UNIVERSIDADE ESTADUAL PAULISTA
“JÚLIO DE MESQUITA FILHO”
Instituto de Ciência e Tecnologia
Campus de São José dos Campos
ORIGINAL ARTICLE DOI: https://doi.org/10.4322/bds.2024.e4154
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Braz Dent Sci 2024 Jan/Mar;27 (1): e4154
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
Marginal gap of zirconia and lithium disilicate frameworks
produced by the CAD-CAM technique through a comparator
microscope – in vitro analysis
Fenda marginal de estruturas de zircônia e dissilicato de lítio produzidas pela técnica CAD-CAM através de um microscópio
comparador – análise in vitro
Ellen Christine Rodrigues de ABREU1 , Vicente Colussi FERREIRA2 , Karina Andrea Novaes OLIVIERI2 ,
William Cunha BRANDT1
1 - Universidade Santo Amaro, Programa de Pós-graduação em Odontologia, Departamento de Implantodontia. São Paulo, SP, Brazil.
2 - Instituto e Centro de Pesquisas São Leopoldo Mandic, Departamento de Implantodontia. Campinas, SP, Brazil.
How to cite: Abreu ECR, Ferreira VC, Olivieri KAN, Brandt WC. Marginal gap of zirconia and lithium disilicate frameworks
produced by the CAD-CAM technique through a comparator microscope – in vitro analysis. Braz Dent Sci. 2024;27(1):e4154.
https://doi.org/10.4322/bds.2024.e4154
ABSTRACT
Objective: The aim of this study was to evaluate the marginal gap of frameworks produced using the CAD-CAM
system, from zirconia and lithium disilicate blocks, adapted to a tooth preparation and a gypsum die. Material and
Methods: For this study, a human rst molar tooth was used as a master model with a full crown preparation. It was
molded 20 times to obtain the gypsum die and randomly divided into 2 groups (n=10) for the fabrication of zirconia
and lithium disilicate frameworks. The frameworks were made using pre-sintered zirconia blocks and lithium disilicate
blocks, both CAD-CAM systems. The marginal gap was measured in µm at four points (buccal, palatal, mesial, and distal)
using a comparator microscope with 30x magnication, with the framework seated on the master model (tooth), and
on the gypsum die. Marginal gap data (µm) were evaluated using two-way analysis of variance and Tukey’s test with
a signicance level of 5%. Results: The results showed that there was no statistically signicant interaction between
the factors studied (p=0.223) or isolated factors (ceramic factor p=0.886 and die factor p=0.786). Conclusion: Both
ceramics produced using the CAD-CAM technique did not exhibit statistical differences in marginal adaptation on the
two types of substrates, both on tooth preparation and on the gypsum die.
KEYWORDS
CAD-CAM; Dental ceramics; Dental prosthesis; Lithium disilicate; Marginal adaptation; Zirconia.
RESUMO
Objetivo: O objetivo deste estudo foi avaliar o espaço marginal de estruturas produzidas usando o sistema CAD-CAM, a
partir de blocos de zircônia e dissilicato de lítio, adaptadas a um preparo sobre dente e a um troquel de gesso. Material e
Métodos: Para este estudo, um dente molar humano foi utilizado como modelo mestre com preparo para coroa total. Este
foi moldado 20 vezes para obter o troquel de gesso e dividido aleatoriamente em 2 grupos (n=10) para a fabricação de
estruturas de zircônia e dissilicato de lítio. As estruturas foram feitas usando blocos de zircônia pré-sinterizados e blocos de
dissilicato de lítio, ambos sistemas para CAD-CAM. O espaço marginal foi medido em µm, em quatro pontos (bucal, palatal,
mesial e distal), utilizando um microscópio comparador com ×30 de ampliação e com a estrutura assentada no modelo mestre
(dente) e no troquel de gesso. Os dados de espaço marginal (µm) foram avaliados usando análise de variância bidirecional
e teste de Tukey com um nível de signicância de 5%. Resultados: Os resultados mostraram que não houve interação
estatisticamente signicativa entre os fatores estudados (p=0,223) ou isoladamente (fator cerâmica p=0,886 e fator troquel
p=0,786). Conclusão: Ambas as cerâmicas produzidas usando a técnica CAD-CAM não apresentaram diferenças estatísticas
em relação à adaptação marginal nos dois tipos de substratos, tanto na preparação dentária quanto no troquel de gesso.
PALAVRAS-CHAVE
CAD-CAM; Cerâmicas odontológicas; Prótese dentária; Dissilicato de lítio; Adaptação marginal; Zircônia.
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Braz Dent Sci 2024 Jan/Mar;27 (1): e4154
Abreu ECR et al.
Marginal gap of zirconia and lithium disilicate frameworks produced by the CAD-CAM technique through a comparator microscope – in vitro analysis
Abreu ECR et al. Marginal gap of zirconia and lithium disilicate frameworks
produced by the CAD-CAM technique through a comparator
microscope – in vitro analysis
INTRODUCTION
The growing demand for aesthetic dental
procedures has driven the use of pure ceramics
as biocompatible and functional alternatives to
conventional restorative materials [1]. In addition
to aesthetics, factors such as mechanical strength,
color stability, and precision in marginal
adaptation are essential for the success of these
restorations [2]. Dental ceramics have a variety
of shades similar to natural teeth, providing high
aesthetics, as well as mechanical strength and
durability [3].
The introduction of digital systems, such as
scanners and milling machines, for the fabrication
of prosthetic restorations from ceramic blocks has
allowed the standardization of the work process
and the use of materials with better performance
and aesthetic quality [4-6]. Tetragonal zirconia
partially stabilized with yttrium oxide (Y-TZP)
has been incorporated into dentistry as a material
for all-ceramic restorations using the CAD-CAM
(Computer-Aided Design/Computer-Aided
Manufacturing) system [7,8]. Zirconia has
made a name for itself as a dental material due
to its biocompatibility, hardness, mechanical
strength, wear resistance, and excellent
chemical and dimensional stability, enabling
the fabrication of xed partial prostheses with
three or more elements, including posterior teeth
and abutments on implants [9-13]. However,
the opacity of this material, due to its high
crystallinity and density, historically required
the use of feldspathic ceramics to achieve the
desired aesthetics [14,15]. Nevertheless, chipping
and debonding of the veneering material were
common failures [13]. Recently, translucent
zirconia has been introduced to the market,
enabling monolithic restorations with superior
strength and aesthetics [16,17].
Lithium disilicate-reinforced ceramics stand
out due to their excellent optical properties. This
vitreous material offers options for both CAD-
CAM systems and pressing techniques. Due to
its favorable translucency and variety of colors,
it is possible to make single-layer (monolithic)
structures, which can subsequently be built up
or simply glazed [18]. Clinical applications of
the lithium disilicate-based system include inlay,
onlay, overlay, laminate veneers, full crowns, and
xed partial prostheses of up to three elements
in the anterior and premolar regions [14,18-20].
The marginal adaptation of ceramic
restorations is one of the crucial factors for
the clinical success and longevity of these
rehabilitations [20,21]. Therefore, maladaptation
that exceeds clinically acceptable limits (up to
120 µm) can result in biofilm accumulation,
predisposing to periodontal disease, recurrent
caries, and pulpal inammation [22]. In addition,
exposure of the luting agent to intraoral uids
can accelerate cement dissolution, leading
to restoration failure [23,24]. Zirconia and
lithium disilicate restorations seem to offer
excellent marginal adaptation with reduced
microgaps, thereby maintaining the health
of periodontal structures and ensuring long-
term clinical success [25-27]. To achieve this,
obtaining the denitive mold, either physically
or digitally, through conventional molding or
digitalization is necessary to provide information
for adequate marginal adaptation [28-33]. While
both materials are classied as dental ceramics,
there are differences between them, such as
resistance, translucency, aesthetics, and hardness.
The latter characteristic poses challenges in
occlusal and proximal adjustments with diamond
burs, potentially causing microcracks after the
crystallization process [34,35].
Although the tips used in milling machines
are specic to each material type, the hardness
of zirconia and the size of the tip can result in
restorations with fewer details when compared
to lithium disilicate restorations [36]. Similarly,
the number of milling machine axes can lead
to marginal gaps with statistically significant
differences [37,38].
Therefore, the objective of this study was
to evaluate the marginal microgap of CAD-
CAM infrastructures made with zirconia and
lithium disilicate blocks when adapted to dental
preparations and gypsum dies. The working
hypothesis is that there are differences in the
marginal microgap between the materials and
their variables.
MATERIAL AND METHODS
This study was submitted to the Research
Ethics Committee of São Leopoldo Mandic
University, (Campinas, SP, Brazil) and registered
under the number 2.270.526.
For this study, an extracted human left lower
rst molar [39] was selected according to the
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Braz Dent Sci 2024 Jan/Mar;27 (1): e4154
Abreu ECR et al.
Marginal gap of zirconia and lithium disilicate frameworks produced by the CAD-CAM technique through a comparator microscope – in vitro analysis
Abreu ECR et al. Marginal gap of zirconia and lithium disilicate frameworks
produced by the CAD-CAM technique through a comparator
microscope – in vitro analysis
following inclusion criteria: absence of enamel
or dentin fracture; dimensions and morphology
of the crown consistent with the size of the
preparation to be performed.
The element was included in a gypsum
base (Durone, Dentsply, Pennsylvania, USA),
leaving 1mm of the cervical area exposed
for crown preparation, denominated master
model (Figure 1). The crown preparation was
performed manually, under visual inspection,
in high rotation under abundant cooling, using
spherical diamond burs #1012 and cylindrical
#3216 (KG Sorensen, São Paulo, SP, BR), with
the following settings: 1.2 mm circumferential
reduction in chamfer, occlusal reduction of
2 mm, and convergence angle of the axial walls
of 6°(degrees).
Twenty impressions of the master model
were made with heavy-body and light-body
polyvinyl siloxane (Futura AD, Nova DFL Produtos
Odontológicos, Taquara, Rio de Janeiro) using
the compression molding method in 1 step to
obtain the gypsum casts, with the aid of an
individual adapted tray. Then the molds was
poured with Type IV gypsum (Durone, Dentsply,
Pensilvânia, EUA) for die casting. The handling
and proportioning of the materials used followed
the guidelines of their respective manufacturers.
As well as the master model, the casts were
included in a gypsum base, leaving the cervical
exposed for better visualization of the end of
the preparation (Figure 2). The 20 gypsum
casts obtained were divided into 2 groups with
10 samples each, according to the infrastructure
ceramic:
Group 1 - zirconia-based frameworks;
Group 2 - lithium disilicate frameworks.
To obtain the frameworks, 10 blocks of
pre-sintered zirconia (ICE Zirkon Transluzent
Plus, Zirkonzahn®, Gais, Itália) and 10 blocks
of lithium disilicate (Rosetta SM, OdontoMega,
Ribeirão Preto, São Paulo, BR) in LT W2 shade
were used and prepared in the CAD-CAM system
from Zirkonzahn®. The master model and the
gypsum dies were scanned (Scanner S600 ARTI,
Zirkonzahn®, Gais, Itália), which features two
high-resolution cameras, allowing a faster and
more accurate scanning. The software used
for digital design (CAD) was Zirkonzahn.Scan
(Zirkonzahn®, Gais, Itália) and the les were
sent to the milling software Zirkonzahn Fräsen
(Zirkonzahn®, Gais, Itália) (Figure 3). The milling
process was performed in the M1 5-Axis milling
machine (Zirkonzahn®, Gais, Itália) and then
Figure 1 - Master model.
Figure 2 – Gypsum die.