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.e4273

Braz Dent Sci 2024 July/Sept;27 (3): e4273

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.

In vitro evaluation of the dimensional accuracy of total single-unit

provisional crowns produced by digital workﬂow

Estudo in vitro avaliativo da acurácia dimensional de coroas totais unitárias provisórias produzidas pelo método digital

André Bueno VIEIRA1 , Diogo Henrique NAKAIE1 , Isabela Inoue KUSSABA1 , Eduardo KURIHARA1 

1 - Universidade Estadual de Maringá. Maringá, PR, Brazil.

How to cite: Vieira AB, Nakaie DH, Kussaba II, Kurihara E. In vitro evaluation of the dimensional accuracy of total single-unit provisional

crowns produced by digital workow. Braz Dent Sci. 2024;27(3):e4273. https://doi.org/10.4322/bds.2024.e4273

ABSTRACT

Objective: This in vitro study aims to digitally analyze and compare the accuracy of single-unit provisional crowns

produced through digital workows, using both subtractive (milling) and additive (3D printing) methods. The

analysis employs image overlay methods and area calculations. Material and Methods: To conduct the research, a

total crown preparation was performed on a dental mannequin for tooth 26, using the silhouette technique. After

scanning the preparation, a provisional single-unit crown was designed using 3D CAD software, resulting in the

production of 30 crowns: 15 milled and 15 printed. All specimens were scanned and analyzed using specialized

3D image software. Measurements were focused on the internal and marginal areas of the crowns, with a total of

30 measurements for the internal area and 120 for the marginal area. The original design, projected in 3D CAD

software, served as the reference. Statistical analysis, including independent samples t-tests, Shapiro-Wilk normality

tests, and descriptive statistics, was applied to all collected data. Results: Regarding the internal area, there was

a statistically signicant difference when comparing groups P (printed) and M (milled). Group P showed higher

discrepancies compared to group M. Conclusion: Milled provisional crowns demonstrated higher accuracy and

delity to the original design projected in 3D software compared to 3D printed crowns in both areas of analysis.

KEYWORDS

Crowns; Digital Technology; Printing Three-dimensional; Workow; Computer-Aided design.

RESUMO

Objetivo: Este estudo in vitro tem como objetivo analisar e comparar digitalmente a precisão das coroas provisórias

unitárias produzidas por meio de uxo de trabalho digital, utilizando métodos tanto subtrativos (fresagem) quanto

aditivos (impressão 3D). A análise emprega métodos de sobreposição de imagens e cálculos de área. Material e

Métodos: Para conduzir a pesquisa, um preparo para coroa total foi realizada em um manequim dentário para o

dente 26, usando a técnica de silhueta. Após a digitalização do preparo, uma coroa provisória unitária foi projetada

usando software CAD 3D, resultando na produção de 30 coroas: 15 fresadas e 15 impressas. Todas as amostras

foram digitalizadas e analisadas usando software especializado em imagens 3D. As medições foram focadas nas

áreas interna e marginal das coroas, com um total de 30 medições para a área interna e 120 para a área marginal.

O design original, projetado no software CAD 3D, serviu como referência. A análise estatística, incluindo testes t

para amostras independentes, testes de normalidade de Shapiro-Wilk e estatísticas descritivas, foi aplicada a todos

os dados coletados. Resultados: em relação à área interna, houve diferença estatisticamente signicante quando

comparados os grupos P (impresso) e M (fresado). O grupo P apresentou maiores discrepâncias em relação ao

grupo M. Conclusão: As coroas provisórias fresadas demonstraram maior precisão e delidade ao design original

projetado no software 3D em comparação com as coroas impressas em ambas as áreas de análise.

PALAVRAS-CHAVE

Coroas dentárias; Tecnologia digital; Impressão tridimensional; Fluxo de trabalho; Desenho assistido por computador.

Braz Dent Sci 2024 July/Sept;27 (3): e4273

Vieira AB et al.

In vitro evaluation of the dimensional accuracy of total single-unit provisional crowns produced by digital workflow

Vieira AB et al. In vitro evaluation of the dimensional accuracy of total single-unit

provisional crowns produced by digital workﬂow

INTRODUCTION

Dental prosthesis is the dental specialty

responsible for the artificial replacement of

one or more dental elements, often including

the total replacement of teeth, in addition to

their associated structures. It is traditionally

divided into two large groups: removable dental

prosthetics and xed dental prosthetics.

In general, xed prosthesis can be dened as

any type of piece that is rmly xed to a natural

tooth, or one or more implants and that cannot

be removed by the patient [1]. The main types

include inlay, onlay, overlay, dental crown, xed

complete denture, and xed partial denture (xed

bridge). Regardless of the type of xed prosthesis

work, a provisional restoration is necessary to aid

in creating the nal prosthesis.

It is through the provisional piece that we

determine important factors for the success of

the rehabilitation treatment, such as occlusion,

periodontal protection, pulp protection, and

aesthetics [2]. In the case of dental crowns,

whether temporary or permanent, a good

marginal and internal adaptation is of great

importance, as failure to seat the piece can result

in low clinical longevity, marginal discoloration,

caries, tooth sensitivity, plaque accumulation,

and dissolution of cement [1].

There are several techniques for producing

provisional using the conventional “analog”

method, namely: alginate matrix, silicone matrix,

stock teeth, pressed and plastic matrix [2]. It is

important to highlight that these procedures

are made up of followed manual steps that may

present failures and depend on the manual skill

of the operator for their success [3].

However, with the advent of digital dentistry

in recent years, the availability of intraoral

scanners has allowed the “virtual reading” of oral

structures and the creation of prostheses through

digital ow, using design software, 3D printers

and /or milling machines. Popularly known by

the acronym CAD\CAM (computer-aided design/

computer-aided machine), the digital method is

capable of consistently producing high-quality

parts using different materials and equipment,

with high patient acceptance [3,4].

Initially, the accuracy of margins in

restorations produced via CAD\CAM faced

significant criticism due to lower fidelity and

lower-than-expected accuracy in the rst systems

available on the market from 1980 onwards,

compared to traditional manufacturing methods.

However, as these technologies have improved

over time, this perception has been reversed.

Currently, it is believed that the marginal

integrity achieved by digital systems can be of

excellent quality [5].

Therefore, the objective of this study is to

digitally compare, through the method of image

overlay and area calculation, the accuracy of

provisional single-unit crowns produced by

digital workflow using both subtractive and

additive methods. At the end of this work, it

is expected to discover which equipment (3D

printer or milling machine) was able to better

reproduce the characteristics determined in the

virtual planning of the provisional crown.

The null hypothesis is that there were no

differences in the crowns produced by the two

production units used compared to the design

projected in the design software.

MATERIAL AND METHODS

Dental preparation and reference crown

fabrication

Initially, a full crown preparation was made

on tooth 26 in a dental mannequin (Pronew, São

Gonçalo, Rio de Janeiro), following the principles

of wear in the silhouette technique. Subsequently,

this preparation was scanned by a benchtop

scanner (Identica Blue, Medit, Seoul, South

Korea), and an STL le of the dental preparation

was obtained.

The preparation le was imported into a

3D CAD dental software (dental CAD Valletta,

Exocad, Darmstadt, Germany), and the design

of a single-unit full crown was performed by a

dental prosthetics technician with over 10 years

of experience (Figures 1 and 2).

Production of crowns using milling machine

and 3D printer

Using the le of the full crown, we began

the fabrication phase of the provisional pieces

using two different production units, a 5-axis

milling machine (Programill dry, Ivoclar, Schaan,

Liechtenstein) and a DLP 3D printer (Photon

mono m5s, Anycubic, Shenzhen, China). Fifteen

milled crowns (Figure 3) and fifteen printed

crowns (Figure 4) were produced. The blocks

Braz Dent Sci 2024 July/Sept;27 (3): e4273

Vieira AB et al.

In vitro evaluation of the dimensional accuracy of total single-unit provisional crowns produced by digital workflow

Vieira AB et al. In vitro evaluation of the dimensional accuracy of total single-unit

provisional crowns produced by digital workﬂow

selected for milling were PMMA (Evoblock

multicolor, Evoden, Pirassununga, São Paulo),

and the resin for printing was provisional type

(Bio prov, Prizma, Birmingham, England).

Scanning of produced crowns

All produced pieces were scanned using

an intraoral scanner (i700 Medit, Seoul, South

Korea), thus generating 30 STL les, which formed

2 groups: group 1 - Milled and group 2 - Printed.

The crowns underwent basic nishing to remove

the supports used in production. The scans were

performed by the same operator scanning each

crown individually. For this step, the pink light

filter was activated on the scanner, and the

operator wore pink gloves. In this way, the pieces

were held in hand, and their external part was

scanned rst, followed by the internal region

Image overlay and analysis method

The aim of the study is to evaluate the internal

and marginal accuracy of these pieces, with the

original design of the provisional crown projected

as a reference. To assess internal accuracy, the

internal area of all produced pieces (Figure 5) and

the internal area of the reference (Figure 6) were

calculated using 3D image analysis software (Medit

Crown Fit., v 1.1.2, Medit Link, Medit, Seoul, South

Korea). Using the same software, marginal accuracy

was also evaluated using the image overlay method.

In this method, each le of the produced crowns

was individually aligned with the design of the

projected crown, and sagittal cuts were made in

the mesio-distal and vestibulo-lingual directions

to measure the value of distortions found in the

cervical region of interest (Figure 7).

Statistical analysis

For all statistical analyses, the Jamovi

software was used, an open-source statistical

Figure 1 - Digital ﬁle of the preparation for total crown.

Figure 2 - Digital ﬁle of the total crown designed in dental modeling

software (Dental CAD Valletta, Exocad, Darmstadt, Germany).

Figure 3 - Milled crowns.

Figure 4 - Printed crowns.

Braz Dent Sci 2024 July/Sept;27 (3): e4273

Vieira AB et al.

In vitro evaluation of the dimensional accuracy of total single-unit provisional crowns produced by digital workflow

Vieira AB et al. In vitro evaluation of the dimensional accuracy of total single-unit

provisional crowns produced by digital workﬂow

platform that offers a wide range of tools for

data analysis (available at www.jamovi.org).

Initially, the data underwent descriptive analysis.

All values obtained from the internal areas were

tabulated, as well as the values of distortions at

the cervical margin of the pieces. The reference

for calculating internal and cervical distortions

was the original design projected in the 3D CAD

dental software (dental CAD Valletta, Exocad,

Darmstadt, Germany). To verify the normality

of the sample data distribution, the Shapiro-

Wilk test was used, with p<0.05 set as the

threshold for signicance. We proceeded with

statistical comparison using Student’s t-test for

independent samples. This test was chosen for

its suitability in analyzing differences within

related groups when the data follows a normal

distribution. We adopted p<0.05 as the criterion

for determining the statistical significance of

these comparisons.

RESULTS

During the process of calculating the

discrepancies found between the manufactured

total provisional single-unit crowns (group M

- milled; group P - printed) compared to the

original reference le designed in the Exocad®

software, we obtained 30 measurements for

internal area analysis and 120 measurements

for marginal analysis of the pieces.

Based on the data obtained through the Medit

crown t® 3D image analysis software, descriptive

statistical analysis was performed for the two

regions of interest (internal area and cervical

area) of the crowns produced.

Based on the data obtained in Table I, it is

observed that for the milled group, the face with

the lowest average discrepancy (0.0353 mm)

compared to the reference le was the Lingual,

while the Vestibular face had the lowest standard

deviation (0.0041), indicating less dispersed

and more uniform measurements. For the

printed crown group, the face with the lowest

average discrepancy (0.143 mm) was the

Mesial, and it also had the lowest dispersion

among the measurements with a standard

deviation of 0.0302. The total average of marginal

discrepancies was 0.04843 millimeters for milled

crowns and 0.2351 millimeters for printed crowns

(p<0.001).

The data presented in Table II are related

to the measurements of the internal areas

of Group M and Group P. Group M (Milled)

showed an average discrepancy of the internal

area of 0.8111 mm2 and a standard deviation

of 0.6429, while group P (Printed) presented

an average discrepancy for the internal area

of 8.580 mm2 and a standard deviation of

Figure 5 - Calculation of the internal area of milled crown 1.

Figure 6 - Calculation of the internal area of the reference crown.

Figure 7 - Mesio-distal and vestibulo-palatal sagittal cuts for

analysis of discrepancy in the cervical region of the fabricated

piece. The red line represents the reference crown and the blue line

the milled crown.

Braz Dent Sci 2024 July/Sept;27 (3): e4273

Vieira AB et al.

In vitro evaluation of the dimensional accuracy of total single-unit provisional crowns produced by digital workflow

Vieira AB et al. In vitro evaluation of the dimensional accuracy of total single-unit

provisional crowns produced by digital workﬂow

0.9306. Thus, regarding the internal area, there

was a statistically signicant difference when

comparing groups P and M. Group P showed

higher discrepancies compared to group M

(p<0.001).

DISCUSSION

The comparative investigation of digitally

manufactured provisional full crowns using

milling machines and 3D printers has been

the subject of extensive study in recent years,

with various analysis methodologies being

employed. Among these, the Silicone Replica

technique stands out, followed by manual sagittal

cuts and microscopic analysis [3]; Silicone

Replica technique followed by microtomographic

analysis [6]; and microtomographic scanning

followed by digital image analysis [1]. A common

point among these methods is the evaluation of

internal and marginal adaptation of the pieces,

through measurements of the internal spaces

formed between the preparation walls and the

interior of the crowns. The systematic review by

Di Fiore et al. [7] describes these methodologies

as also useful for analyzing the internal and

marginal adaptation of partial crowns.

In the present study, an adapted methodology

was implemented for comparing printed and

milled provisional crowns. A double scanning

technique was utilized, where scanning of the

dental preparation and the produced piece

separately allowed alignment of the reference 3D

le with the obtained manufacturers. The results

enabled the assessment of the accuracy of these

crowns in relation to the design projected in

the design software. After statistical analysis

focused on marginal precision, it was observed

that Group M (Milled) exhibited a lower mean

discrepancy (0.04843 mm) compared to Group

P (Printed) (0.2351 mm), along with lower

standard deviation values, indicating greater

delity to the reference le and more uniform

measurements.

These findings corroborate the study by

Wu et al. [6], which found better performance

in the marginal adaptation of milled provisional

crowns compared to printed ones. However, they

diverge from the results of Alharbi et al. [1],

which indicated better marginal adaptation

of printed crowns compared to milled ones.

In Viega’s study [8], which compared the

reproduction trueness and precision of dental

casts made by the conventional, milling, and 3D

printing techniques, it was shown that the milling

technique was found to be signicantly more

accurate than the conventional and 3D printing

techniques, which corroborate our ndings.

Regarding the statistical analysis of the

internal area, it was observed that Group M

exhibited a lower mean discrepancy (0.811mm2)

and standard deviation (0.643) compared to

Table I - Descriptive analysis of the data obtained regarding the marginal discrepancies of the Milled (M) and Printed (P) crowns

Group N Mean Standard

Deviation Standard error p-value

Buccal M 15 0.0516 0.0171 0.00441 *p<0.001

P 15 0.281 0.0424 0.01094

Lingual M 15 0.0353 0.0246 0.00636 *p<0.001

P 15 0.307 0.0657 0.01698

Mesial M 15 0.0710 0.0185 0.00479 *p<0.001

P 15 0.143 0.0302 0.00779

Distal M 15 0.0367 0.0191 0.00493 *p<0.001

P 15 0.208 0.0516 0.01333

*Student t-test with signiﬁcant statistical diﬀerences.

Table II - Descriptive analysis of internal area discrepancies for Group M (Milled) and Group P (Printed)

Group N Mean Standard

Deviation

Standard

error p-value

Diﬀerence in

internal area

M 15 0.8111 0.6429 0.16598 *p<0.001

P 15 8.590 0.9306 0.24027

*Student t-test with signiﬁcant statistical diﬀerences.

Braz Dent Sci 2024 July/Sept;27 (3): e4273

Vieira AB et al.

In vitro evaluation of the dimensional accuracy of total single-unit provisional crowns produced by digital workflow

Vieira AB et al. In vitro evaluation of the dimensional accuracy of total single-unit

provisional crowns produced by digital workﬂow

Group P (8.59 mm2) and (0.931), indicating

higher accuracy. These results contradict the

ndings of Alharbi et al. [1], who demonstrated

better performance in internal adaptation

for printed pieces. These discrepancies may

be attributed to differences in brands and

models of equipment used and in the research

methodologies adopted.

In general, this study has shown that milled

crowns exhibited greater accuracy compared

to the original design projected in the 3D CAD

software (Exocad®) than printed crowns, both

in the internal and marginal areas. One possible

explanation for the lower performance of 3D

printers in this study could be based on the studies

by Della Bona et al. [9], whose systematic review

concluded that the printing angle used can impact

the accuracy of the print, as well as properties such

as strength, morphology, and biocompatibility.

The null hypothesis of this study was

rejected, indicating deviations in both production

methods. However, several studies have already

demonstrated that both 3D printers and milling

machines have the ability to produce restorations

with adaptation within the recommended

parameters [10]. These promising technologies

have contributed to greater predictability and

quality in dental work [11].

The clinical relevance of this study lies in

the analysis methodology employed, which, if

applied in daily clinical practice, allows for the

anticipation of problems and the evaluation of

distortions and mists in the produced prosthesis

before their installation, thus contributing to a

reduction in clinical adjustment time and greater

effectiveness in results.

CONCLUSION

Provisional single-unit total crowns obtained

by milling demonstrated superior accuracy and

precision when compared to their counterparts

produced by 3D printing, both in the internal and

marginal areas. Further studies are recommended,

employing updated methodologies, in the eld

of manufacturing provisional crowns for xed

prostheses using the CAD/CAM system.

Author’s Contributions

ABV: Writing – Review & Editing. DHN:

Conceptualization, Methodology. IIK: Software,

Validation, Writing – Original Draft Preparation.

EK: Visualization, Investigation, Supervision.

Conict of Interest

The authors have no proprietary, nancial,

or other personal interest of any nature or kind

in any product, service, and/or company that is

presented in this article.

Funding

This research did not receive any specic

grant from funding agencies in the public,

commercial, or not-for-prot sectors.

Regulatory Statement

This study was conducted in accordance

with the guidelines and ethical standards of the

Institution. There was no involvement of human

subjects, nor any collection of personal data.

The authors declare that there are no conicts

of interest related to this research.

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provisional crowns produced by digital workﬂow

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Isabela Inoue Kussaba

(Corresponding address)

Universidade Estadual de Maringá, Maringá, PR, Brazil.

Email: isabelaikussaba@gmail.com

Date submitted: 2024 May 15

Accept submission: 2024 Sept 03