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Abstract

Removable complete dentures have recently entered the digital area, through various workflows constantly evolving with the maturity of digital technologies. Indeed, practitioners and laboratories are particularly challenged with the integration of digital tools and techniques in the daily treatment of complete edentulism. The aim of this narrative review was to summarise the current knowledge about digital removable complete dentures, to enable practitioners and laboratories to decide either to move to a fully digital workflow or to integrate some of these new tools into their current practice. The first part of this article reviews different techniques for recording edentulous ridges and the maxillo-mandibular relationship. Then, the second part describes the digital steps involved in designing prostheses, while the last part describes the materials and manufacturing technologies. As a conclusion, digital technologies provide several options for the treatment of edentulous patients, but there is a need for remaining vigilant on the quality of the delivered prostheses and treatment.
French Journal of Dental Medicine | November 2020 | 1
Wulfman et al.:Digital removable complete dentures: a narrative review
INTRODUCTION
e removable complete denture (RCD) is the most com-
mon rehabilitation of edentulous patients worldwide.1-4 Proto-
cols for the fabrication of RCDs following the traditional
workow consist of registering the geometry of supporting tis-
sues and peripheral musculature (through one or two impres-
sions), recording the maxillo-mandibular relationship,
designing the denture (with tooth arrangement), try-in, fabri-
cation and insertion. is prosthetic chain is a succession of
clinical and laboratory steps involving multiple operators, and
consequently, prone to errors.5-7
e development of computer-aided design (CAD) and
computer-aided manufacturing (CAM) technologies is pro-
foundly changing complete denture treatment. Edentulous
ridges and maxillo-mandibular relationships can nowadays be
recorded with intra-oral scanners (IOS), RCDs can be digitally
designed through multiple commercially available soware, and
traditional asks can be replaced by milling and printing ma-
chines.8-17 More importantly, these technologies can guarantee
for the rst time a reproducible manufacturing quality. How-
ever, the diversity of tools and protocols complicates their inte-
gration into daily practice, especially since they have not all
reached the same level of maturity. Nevertheless, the digital
transformation is gradually revolutionising complete dentures.18
e objective of this narrative review was to summarise the
current knowledge about digital RCDs through a presentation
of currently available devices and technologies to produce re-
movable dentures and implant-supported dentures for edentu-
lous patients.
Digital removable complete dentures: a narrative review
Abstract:
Removable complete dentures have recently entered the digital area, through various workflows constantly evolving
with the maturity of digital technologies. Indeed, practitioners and laboratories are particularly challenged with the
integration of digital tools and techniques in the daily treatment of complete edentulism. The aim of this narrative
review was to summarise the current knowledge about digital removable complete dentures, to enable practitioners
and laboratories to decide either to move to a fully digital workflow or to integrate some of these new tools into
their current practice. The first part of this article reviews different techniques for recording edentulous ridges and
the maxillo-mandibular relationship. Then, the second part describes the digital steps involved in designing pros-
theses, while the last part describes the materials and manufacturing technologies. As a conclusion, digital tech-
nologies provide several options for the treatment of edentulous patients, but there is a need for remaining vigilant
on the quality of the delivered prostheses and treatment.
Key words: CAD/CAM, additive manufacturing, milling complete dentures, intraoral scanner, digital denture,
digital impression, 3D printing, digital workflow
Manuscript submitted: 10 June 2020. Manuscript accepted: 9 September 2020.
Doi: https://doi.org/10.36161/FJDM.0005
Corresponding author: Dr. Maxime Ducret, Prosthodontics, Université de Lyon, Faculty of Dentistry, France.
Email: ducret.maxime@gmail.com
Claudine Wulfman,1,2 Guillaume Bonnet,3,4 Delphine Carayon,5,6,7 Cindy Batisse,3,4 Michel Fages,5,6,8
Virard François,9,10 Marwan Daas,1,11 Christophe Rignon-Bret,1,12 Adrien Naveau,13,14 Catherine Millet9,10 and
Maxime Ducret9,10
1. Université de Paris, UR 4462, F-92049, Montrouge, Sorbonne Université Paris Nord, F-93000, Bobigny, France
2. Département d’Odontologie, AP-HP, Hôpital Henri Mondor, F-94010 Créteil, France
3. Université Clermont Auvergne, CROC EA4847, Faculté d’Odontologie, Clermont-Ferrand, France.
4. CHU Clermont-Ferrand, Service d’Odontologie, Clermont-Ferrand, France.
5. Faculté d’Odontologie, Université de Montpellier, Montpellier, France.
6. CHU de Montpellier, Service d’Odontologie, Montpellier, France.
7. Laboratoire AMIS, UMR 5288 CNRS, Université Toulouse III-Paul Sabatier, Toulouse, France.
8. Laboratoire Bioingénierie et Nanosciences, EA4203, Université de Montpellier, Montpellier, France.
9. Faculté d’Odontologie, Université Claude Bernard Lyon 1, Lyon, France.
10. PAM d’Odontologie, Hospices Civils de Lyon, Lyon, France.
11. Département d’Odontologie, AP-HP, Hôpital Louis Mourier, F-92700 Colombes, France
12. Département d’Odontologie, AP-HP, Hôpital Charles Foix, F-94200 Ivry sur Seine, France
13. Unité de parodontologie et prothèse dentaire, Hôpital Saint André, CHU de Bordeaux, Bordeaux, France
14. Département de prothèses, UFR des sciences Odontologiques, Université de Bordeaux, Bordeaux, France.
Digital impression for RCD
A digital scanner is a non-contact measuring device that
records and reconstructs three-dimensional (3D) surfaces or
volumes.16,19 It consists of an optical acquisition system in as-
sociation with a 3D reconstruction soware (Figure 1). IOS are
mobile and record directly in the mouth, while extra-oral scan-
ners (EOS) are used to digitise impressions/models in labora-
tories. Facial scanners can be used for recording aesthetic lines
or extra-oral defects in maxillofacial prosthetics.
Digital scanning of edentulous ridges
Scanning of edentulous arches presents three recording chal-
lenges: the lack of anatomical landmarks, the functional
borders,20 and the posterior palatal seal. Intraoral scans allow
preliminary non-compressive digital scanning of the ridges.8-12
However, it is necessary to follow specic scanning protocols
to record areas without anatomical landmarks such as the
palate or edentulous ridges.20-23 Placement of composite mark-
ers or use of a dermal marker on the mucosa facilitates the im-
pression.21,24,25 A custom impression tray can then be fabricated
from this preliminary impression to make a conventional nal
impression. e accuracy of digital scanning is similar to that of
conventional materials in the maxilla, with 0.70 ±0.18 mm for
IOS, 0.75 ±0.17 mm for polyvinylsiloxane and 0.75 ±0.19 mm
for eugenol zinc oxide-modied polyvinylsiloxane.26 However,
these results remain to be conrmed for the mandible as well.
Borders stretching is the most dicult area to record with dig-
ital scanning.21,25 Jung et al. proposed to match conventionally
registered functional borders with the original digital
scanning.27 Other authors proposed mobilising so tissues with
a nger or a mirror to record their position.22,24,25 Concerning
the posterior palatal seal, the anterior and posterior vibrating
line on the so palate could be delineated by using an indelible
pencil or small spots of light-polymerised gingival barrier ma-
terial before scanning.21 e accuracy of digital scanners is sen-
sitive to other factors such as learning curve, brightness during
scanning, presence of saliva or scanning strategy.28-33 Each IOS
requires specic settings and training.
Digital impression of implants
Scan bodies used in digital scanning for implant-supported
prosthetic rehabilitation are landmarks on edentulous ridges.
However, the similarities between the landmarks create a risk
of confusion for the reconstruction algorithm when individu-
alising each implant.34,35 Two technologies were proposed for
digital scanning of implants: confocal microscopy (IOS) and
stereo photogrammetry.36 Both systems were documented in
short-term clinical studies and the conclusions were similar:
satisfactory survival rate aer 1 to 2 years and clinical and ra-
diological passivity of the prosthetic frameworks.37-39
Several in vitro studies measured the accuracy of digital
scanning for distance and angulation, and recent IOS oered
superior or equal results when compared to conventional im-
pressions.40-47 However, caution is needed when interpreting
these measurements because deviations measured in vivo could
be doubled compared to in vitro measurements.48
Wulfman et al.:Digital removable complete dentures: a narrative review
French Journal of Dental Medicine | November 2020 | 2
Figure 1: Strategies to obtain digital scans of edentulous patients, using an
intraoral scanner (A), or by digitisation of the prothesis (B) or the cast (C)
A
B
C
e accuracy of digital scanning is improved when the inter-
implant distance is short,49 the scan bodies are high and simple
in design, the operator is experienced50 and complies to the
manufacturer’s recommended scanning strategy.37,45,50,51 How-
ever, implant angulation, depth, and type of connection do not
inuence the accuracy.45,52,53 Similarly, implant transfers splint-
ing does not increase accuracy.49,54 Finally, a digital scan is twice
as fast as a conventional impression, with the possibility of par-
tial retake.39 ese recommendations were validated for digital
scanning of 4 to 6 implants in both the maxilla and the
mandible. On the other hand, the optical impression is not yet
validated for overdentures on two implants.55
Extraoral scanners
Many laboratories already use EOS in their daily practice to
scan impressions and models. Regardless of the measurement
acquisition technology (laser, structured light or contact), a
soware program generates a 3D reconstruction of the object
and an STL le that can be used in most CAD soware pro-
grams. Although the performance of IOS and EOS are close,56
EOS is generally considered more accurate than IOS because
of the conditions controlled during acquisition (temperature,
light and humidity).19,57,58 Optical scanners are faster than con-
tact scanners due to the controlled conditions, but they could
be aected by the optical properties of the scanned object.
Facial scanners
e digitalisation of the face was proposed by some authors
to improve denture design and facilitate communication.26,59,60
e facial 3D le could, in theory, be matched with the edentu-
lous ridge le, but this combination has not been described yet.
Maxillomandibular
relationship record
None of the currently available workows is entirely digital
for recording the maxillo-mandibular relationship; all ap-
proaches rely on conventional or 3D-printed baseplates sup-
porting wax occlusion rims.61-65 In the Ivoclar-Vivadent®
workow, the maxillo-mandibular relationship is recorded in
two steps. First, the practitioner records the preliminary im-
pressions conventionally and a preliminary jaw relation with a
specic device. Aer connection, the whole set is then scanned
in the laboratory with an EOS,13 and positioned on a virtual ar-
ticulator (Figure 2). e occlusion rims are then digitally de-
signed in a position close to the clinical situation, facilitating
the nal recording.
For the realisation of occlusion rims, the CAD soware is
able to detect the anatomical landmarks on the ridges to visu-
alise the situation of the future prosthetic teeth (centre of the
incisal papilla, maxillary tuberosity, labial frenulum, retro-
molar trigone). e occlusal rims may be designed for a max-
illo-mandibular co-adaptation procedure or to receive devices
such as central bearing tracing.13,14,22 In this case, the height of
the occlusal rim will be underestimated to facilitate device
French Journal of Dental Medicine | November 2020 | 3
Wulfman et al.:Digital removable complete dentures: a narrative review
Figure 2: Maxillomandibular relationship record. Digital transfer of the
preliminary jaw relation (A) and design of the occlusion rims (B)
A
B
Figure 3: Computer assisted design of complete denture. The software offers an automatic proposition of maxillar and mandibular tooth alignment (A),
that could be modified following anatomic landmarks (B). The digital set-up could also be matched with a picture of the patient to improve
communication and esthetic outcomes (C).
ABC
placement and registration. Other authors prefer silicone bite
registration and a secondary scan in the laboratory (EOS) or
directly with an IOS.17,24,26,65
Computer-assisted
design of complete denture
Numerous soware programs were developed specically
for RCD: 3Shape Dental System®, Ceramic D-Flow®, Exocad®,
Lucy®, Dental Wings®, 3Shape Digital Denture®, Modier®.
ese digital tools are increasingly used in dental laboratories
independently from the dentist’s clinical workows, as they
save time, increase accuracy and reproducibility of RCD.65,66
CAD of complete denture:
prosthetic bases and teeth
e soware includes teeth libraries of dierent brands and
shapes, yet it is also possible to personalise the shape of teeth
according to the needs of the set-up (morphological tooth
adaptation).
e occlusal plane and the insertion axis of the denture are
dened according to anatomical landmarks (Figure 3). e so-
ware then automatically proposes a bilaterally balanced set-up,
which signicantly saves time when compared to conventional
techniques.67 e operator can then customise the set-up by
modifying the position of one or more teeth, or even remove
them. e virtual articulator allows static and dynamic occlusal
analysis. Finally, the volumes, the dimensions of the papilla and
the canine eminences, the marginal curve, and the nish can
be adjusted. e les are then prepared for the production of
the denture and/or templates for try-in and functional valida-
tion of the set-up.67 ese templates can serve as transitional
dentures in the treatment of patients with temporomandibular
disorders or can be used as radiological and/or surgical tem-
plates for a subsequent implantation project.67
CAD of the single-arch RCD
In these rehabilitations, occlusal balance is essential. Several
soware programs oer an ideal teeth assembly and indicate
the corrections to be made in the antagonist arch. is allows
the operator to easily switch from the ideal set up to a set up
without modifying the antagonist arch. As with the anterior
teeth, the size and shape of the teeth can be customized to fa-
cilitate occlusal balance.
CAD of immediate RCD
With new tools such as digital extraction, the practitioner
also handles the transition to complete edentulism.68-70 e
working model is prepared by superimposing the model with
the patient’s CBCT for post-extraction crest modelling.60 A du-
plicate of the future immediate RCD can also serve as a surgical
guide. e patient’s face can be integrated into the model using
photographs or facial scans to optimise the determination of
the interincisor point.
It is also possible to superimpose the patients RCD and their
residual teeth during the design. e objective is to position
the interincisal point according to its optimal situation and to
facilitate the choice of tooth shape and size (Figure 4).
Design of implant-supported framework
e use of CAD/CAM processes for the fabrication of im-
plant infrastructures has been used for decades. New materials,
not available for traditional casting techniques, have appeared
with increased biocompatible and aesthetic properties.71 In-
Wulfman et al.:Digital removable complete dentures: a narrative review
French Journal of Dental Medicine | November 2020 | 4
Figure 4: Illustration of the virtual protocol of immediate denture design, before (A) and after digital extraction and ridge modelling (B)
AB
Figure 5: Computer assisted manufacturing of complete denture, using a
milling machine
deed, zirconia is easily machined into pre-sintered blocks and
the design soware eectively compensates for sintering
shrinkage.72 However, the mechanical properties of the metal
are superior when the framework is milled from industrial
blocks with fewer micro-defects, porosities and impurities.73
Deformations and stresses stored in the material disappear as
there is no longer any need of the cooling phase.72 e tting
accuracy is less than 150 μm, which guarantees the passivity of
the implant framework.74 In addition, these techniques are less
operator-dependent, more reproducible, and at a lower cost
than the casting of precious alloy frameworks.72 It should be
noted that these CAD/CAM frameworks do not tolerate braz-
ing and cannot be modied.
Computer-assisted
manufacturing (CAM)
New manufacturing processes have also inuenced the ma-
terials used in the manufacture of RCDs. e main and univer-
sally used component is polymethyl methacrylate (PMMA). Its
exothermic polymerisation causes material shrinkage. In the
conventional process, strict control of temperature, pressure and
polymerisation time improve the material homogeneity and in-
tegrity of the denture surface, and also reduce the shrinkage and
porosities. However, these traditional protocols were operator
dependent. Fabrication of RCDs, whether by milling or 3D
printing, reduces these sources of error (Figure 5).
Computer-assisted milling
of complete denture
Milling from polymerised resin discs is the most developed
CAM process. e inversion of the shaping and polymerisation
steps removed shrinkage diculty and shied the quality con-
trol of the polymerisation process to the manufacturer. e
main clinical consequence is the excellent t of the denture on
the supporting tissues, with increased comfort and better re-
tention.15,75-77 It also became possible to optimise the composi-
tion of the materials in order to improve their mechanical
properties (exural strength, fracture resistance, hardness) and
biocompatibility.78-80 However, the properties of resin materials
commercially available vary considerably and do not currently
represent a uniform class of materials.76,79,81
Although milling processes are currently the most widely
used, they nevertheless have economic and environmental
costs, since a large part of the disc is not used.
Computer-assisted printing
of complete denture
Additive processes thus seem very promising.82 3D printing
consists of shaping the dental prosthesis by successive addition
of material.16 Stereolithography (SLA) or digital light processing
(DLP) achieve satisfying precision with resin layers from 20 to
150 μm thick, which are compatible for the manufacture of the
base and/or the teeth.83 Several commercial systems, such as
Dentca CAD-CAM (DENTCA Inc) or Pala (Kulzer) digital
denture, already propose medical devices and clinical proto-
cols.84-85 It is also possible to print dentures directly with CE
marked Class IIa resins (Next-Dent B.V. and Envisiontec Inc).
First, the base is printed with compartments to glue the printed
dental arch or commercially available teeth.84-85 Repositioning
of the teeth is then facilitated by a printed transfer key.26 3D
printing must still be used with caution when making a nal
RCD, due to the lack of clinical evidence regarding mechanical
properties, wear resistance, ageing and biocompatibility.86 In-
deed, it appears that the accuracy of the printed RCD is lower
than that of milling, but remains clinically acceptable, satises
patients, requires less equipment and less sophisticated ma-
chinery than milling.86-87 Finally, milling or 3D printing gives
monochrome shades to the bases and prosthetic teeth, which
may require the laboratory team to stain with dierent shades
of pink composite (Figure 6).
French Journal of Dental Medicine | November 2020 | 5
Wulfman et al.:Digital removable complete dentures: a narrative review
Figure 6: Examples of denture characterisation using pink composite
Wulfman et al.:Digital removable complete dentures: a narrative review
French Journal of Dental Medicine | November 2020 | 6
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... The digital method was associated with reduced fabrication time and higher technique accuracy [40,41,54]. However, Schwindling and Stober [55] and Wulfman et al. [56] dissented from this characterization and reported a longer working time using the digital procedure. CAD/CAM technology simplifies the laboratory effort, allowing the dental technician to conveniently construct precise and well-organized prostheses [11,57]. ...
... Computer-engineered complete dentures (CECDs) are superior to the rapidly prototyped conventional dentures in terms of the trueness of the intaglio surfaces [37,56,61]. Bacali et al. stated that it was possible to achieve improved speed, precision, data reproducibility, comfort, chewing efficiency, and reduced costs due to the standardization of the treatment steps in CECDs [62]. ...
... Alhallak and Nankali stated that the biocompatibility of CECDs still requires better follow-up and documentation [63]. Data storage allows for a quick replacement of dentures when they are missing or damaged [43,44,56]. Additionally, the time needed for the manufacturing and processing of CECDs was only two visits, resulting in one less hour of chair time for the dentist and five hours less time for the dental laboratory. ...
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CAD/CAM technology is gaining popularity and replacing archaic conventional procedures for fabricating dentures. CAD/CAM supports using a digital workflow reduce the number of visits, chair time, and laboratory time, making it attractive to patients. This study aimed to provide a comparative review of complete dentures manufactured using CAD/CAM and conventional methods. The PubMed/Medline, Science Direct, Cochrane, and Google Scholar databases were searched for studies published in English within the last 11 years (from 2011 to 2021). The keywords used were "computer-engineered complete dentures", "CAD/CAM complete dentures", "computer-aided engineering complete dentures", and "digital complete dentures". The search yielded 102 articles. Eighteen relevant articles were included in this review. Overall, computer-engineered complete dentures have several advantages over conventional dentures. Patients reported greater satisfaction with computer-engineered complete dentures (CECDs) due to better fit, reduced chair time, shorter appointments, and fewer post-insertion visits. CAD/CAM allows for precision and reproducibility with fewer procedures compared to conventional dentures. Polymethyl methacrylate is used as the denture base material for conventional dentures. For CECDs, the resin can be modified and cross-linked to improve its mechanical properties. The advantages of CECDs include a reduced number of appointments, saving chairside time, a digital workflow allowing easy reproducibility and greater patient satisfaction with a better fit.
... Historically, 3D files are considered as relatively inaccessible educational tools, mainly because they required 3D designers and significant technological and human resources. However, in the medical field, imaging devices are already well developed, such as in dentistry for many clinical applications [1,2]. These devices could also open up many applications through the use of digitized 3D files [3][4][5][6][7]. ...
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Three-dimensional files featuring patients’ geometry can be obtained through common tools in dental practice, such as an intraoral scanner (IOS) or Cone Beam Computed Tomography (CBCT). The use of 3D files in medical education is promoted, but only few methodologies were reported due to the lack of ease to use and accessible protocols for educators. The aim of this work was to present innovative and accessible methodologies to create 3D files in dental education. The first step requires the definition of the educational outcomes and the situations of interest. The second step relies on the use of IOS and CBCT to digitize the content. The last “post-treatment” steps involve free software for analysis of quality, re-meshing and simplifying the file in accordance with the desired educational activity. Several examples of educational activities using 3D files are illustrated in dental education and discussed. Three-dimensional files open up many accessible applications for a dental educator, but further investigations are required to develop collaborative tools and prevent educational inequalities between establishments.
... Historically, 3D files are considered as relatively inaccessible educational tools, mainly because they required 3D designers and significant technological and human resources. However, in the medical field, imaging devices are already well developed, such as in dentistry for many clinical applications [1,2]. These devices could also open up many applications through the use of digitized 3D files [3][4][5][6][7]. ...
Article
Full-text available
Three-dimensional files featuring patients' geometry can be obtained through common tools in dental practice, such as an intraoral scanner (IOS) or Cone Beam Computed Tomography (CBCT). The use of 3D files in medical education is promoted, but only few methodologies were reported due to the lack of ease to use and accessible protocols for educators. The aim of this work was to present innovative and accessible methodologies to create 3D files in dental education. The first step requires the definition of the educational outcomes and the situations of interest. The second step relies on the use of IOS and CBCT to digitize the content. The last "post-treatment" steps involve free software for analysis of quality, re-meshing and simplifying the file in accordance with the desired educational activity. Several examples of educational activities using 3D files are illustrated in dental education and discussed. Three-dimensional files open up many accessible applications for a dental educator, but further investigations are required to develop collaborative tools and prevent educational inequalities between establishments.
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Full-text available
Aim: This study aims to evaluate the accuracy of scanned images of 4 clinically used intraoral scanners (CS3600, i500, Trios3, Omnicam) when scanning the surface of full arch models with various kinds of orthodontic brackets in the presence of artificial saliva. Materials and Methods. Four study models were prepared; bonded with ceramic, metal, and resin brackets, respectively, and without brackets. Reference images were taken by scanning the models with an industrial scanner. Study models were then applied with an artificial saliva and scanned 10 times, respectively, with the above 4 intraoral scanners. All images were converted to STL file format and analyzed with 3D analysis software. By superimposing with the reference images, mean maximum discrepancy values and mean discrepancy values were collected and compared. For statistical analysis, two-way ANOVA was used. Results: Omnicam (1.247 ± 0.255) showed higher mean maximum discrepancy values. CS3600 (0.758 ± 0.170), Trios3 (0.854 ± 0.166), and i500 (0.975 ± 0.172) performed relatively favourably. Resin (1.119 ± 0.255) and metal (1.086 ± 0.132) brackets showed higher mean maximum discrepancy values. Nonbracket (0.776 ± 0.250) and ceramic bracket (0.853 ± 0.269) models generally showed lower mean maximum discrepancy values in studied scanners. In mean discrepancy values, the difference between scanners was not statistically significant whereas among brackets, resin bracketed models (0.093 ± 0.142) showed the highest value. Conclusion: Intraoral scanners and brackets had significant influences on the scanned images with application of artificial saliva on the study models. It may be expected to have similar outcomes in an intraoral environment. Some data showed the discrepancy values up to about 1.5 mm that would require more caution in using intraoral scanners for production of detailed appliances and records.
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Background: The purpose of this study was to investigate the trueness of intraoral scanning of residual ridge in edentulous regions during in vitro evaluation of inter-operator validity. Methods: Both edentulous maxillary and partially edentulous mandibular models were selected as a simulation model. As reference data, scanning of two models was performed using a dental laboratory scanner (D900, 3Shape A/S). Five dentists used an intraoral scanner (TRIOS 2, 3Shape A/S) five times to capture intraoral scanner data, and the "zig-zag" scanning technique was used. They did not have experience with using intraoral scanners in clinical treatment. The intraoral scanner data was overlapped with the reference data (Dental System, 3Shape A/S). Regarding differences that occurred between the reference and intraoral scanner data, the vertical maximum distance of the difference and the integral value obtained by integrating the total distance were analyzed. Results: In terms of the maximum distances of the difference on the maxillary model, the means of five operators were as follows: premolar region, 0.30 mm; molar region, 0.18 mm; and midline region, 0.18 mm. The integral values were as follows: premolar region, 4.17 mm2; molar region, 6.82 mm2; and midline region, 4.70 mm2. Significant inter-operator differences were observed with regard to the integral values of the distance in the premolar and midline regions and with regard to the maximum distance in the premolar region, respectively. The maximum distances of the difference in the free end saddles on mandibular model were as follows: right side, 0.05 mm; and left side, 0.08 mm. The areas were as follows: right side, 0.78 mm2; and left side, 1.60 mm2. No significant inter-operator differences were observed in either region. Conclusions: The present study demonstrated satisfactory trueness of intraoral scanning of the residual ridge in edentulous regions during in vitro evaluation of inter-operator validity.
Article
Purpose: This study aimed to determine the most reliable scanning strategy and scanner type, using a new protocol for assessing the accuracy (trueness and precision) of intraoral scan data. Materials and methods: Five different maxillary and mandibular typodont pairs (n = 10) and 2 intraoral scanners were used for the study. A reference scan for each arch was obtained with an industrial scanner. Scanning strategies were classified into 2 continuous methods-continuous scan in horizontal direction (CH group) and continuous scan with vertical rotation in anterior region (CV group)-and 1 segmental method (S group). In the CH group, the scanner head was maintained mostly in a horizontal position. In the CV group, the scanners were rotated 180° around the anterior tooth region to allow smooth scanning through the area. The intraoral scan data were individually superimposed over their corresponding reference scan data. Raw data of the distances between paired surface points were extracted from the superimposed pairs of datasets, with (original distance values) or without consideration (absolute distance values) of the value signs. Trueness values were calculated using absolute distance values, while precision values were obtained from original distance values. Data were analyzed with a 2-way repeated-measures analysis of variance using α = 0.05 as the level of significance. Results: The CV group produced significantly inferior outcomes compared to the CH and S groups in terms of trueness (p < 0.001, F = 24.67), whereas no significant differences were observed among the 3 scanning strategies with respect to precision (p = 0.451, F = 0.83). Scanner type did not produce significant differences in terms of either trueness (p = 0.058, F = 4.72) or precision (p = 0.742, F = 0.12). Conclusions: The segmental approach for scanning the region of interest first and continuous scanning with the scanner head held mostly in a horizontal position are both acceptable as full-arch scanning strategies. However, vertical rotation of intraoral scanners should be minimized. This article is protected by copyright. All rights reserved.
Article
Statement of problem: Digital scans should be able to accurately reproduce the different complex geometries of the patient's mouth. Mesh quality of the digitized mouth is an important factor that influences the capabilities of the geometry reproduction of an intraoral scanner (IOS). However, the mesh quality capabilities of IOSs and the relationship with different ambient light scanning conditions are unclear. Purpose: The purpose of this in vitro study was to measure the impact of various light conditions on the mesh quality of different IOSs. Material and methods: Three IOSs were evaluated-iTero Element, CEREC Omnicam, and TRIOS 3-with 4 lighting conditions-chair light, 10 000 lux; room light, 1003 lux; natural light, 500 lux; and no light, 0 lux. Ten digital scans per group were made of a mandibular typodont. The mesh quality of digital scans was analyzed by using the iso2mesh MATLAB package. Two-way ANOVA and Kruskal-Wallis 1-way ANOVA statistical tests were used to analyze the data (á=.05). Results: Significant differences in mesh quality values were found among the different IOSs under the same lighting conditions and among the different lighting conditions using the same IOS. TRIOS 3 showed the highest consistency and mesh quality mean values across all scanning lighting conditions tested. CEREC Omnicam had the lowest mean mesh quality values across all scanning lighting conditions. iTero Element displayed some consistency in the mesh quality values depending on the scanning lighting conditions: chair light and room light conditions presented good consistency in mesh quality, indicating better mesh quality, and natural light and no light conditions displayed differing consistency in mesh quality values. Nevertheless, no light condition led to the minimal mean mesh quality across all IOS groups. Conclusions: Differences in the mesh quality between different IOSs should be expected. The photographic scanning techniques evaluated presented higher mesh quality mean values than the video-based scanning technology tested. Moreover, changes in lighting condition significantly affect mesh quality. TRIOS 3 showed the highest consistency in terms of the mean mesh quality, indicating better photographic system in comparison with iTero Element.
Article
Statement of problem. Digital scans have increasingly become an alternative to conventional impressions. Although previous studies have analyzed the accuracy of the available intraoral scanners (IOSs), the effect of the light scanning conditions on the accuracy of those IOS systems remains unclear. Purpose. The purpose of this in vitro study was to measure the impact of lighting conditions on the accuracy (trueness and precision) of different IOSs. Material and methods. A typodont was digitized by using an extraoral scanner (L2i; Imetric) to obtain a reference standard tessellation language (STL) file. Three IOSs were evaluateddiTero Element, CEREC Omnicam, and TRIOS 3dwith 4 lighting conditionsdchair light 10 000 lux, room light 1003 lux, natural light 500 lux, and no light 0 lux. Ten digital scans per group were recorded. The STL file was used as a reference to measure the discrepancy between the digitized typodont and digital scans by using the MeshLab software. The Kruskal-Wallis, 1-way ANOVA, and pairwise comparison were used to analyze the data. Results. Significant differences for trueness and precision mean values were observed across different IOSs tested with the same lighting conditions and across different lighting conditions for a given IOS. In all groups, precision mean values were higher than their trueness values, indicating low relative precision. Conclusions. Ambient lighting conditions influenced the accuracy (trueness and precision) of the IOSs tested. The recommended lighting conditions depend on the IOS selected. For iTero Element, chair and room light conditions resulted in better accuracy mean values. For CEREC Omnicam, zero light resulted in better accuracy, and for TRIOS 3, room light resulted in better accuracy.
Article
Statement of problem: Simplified edentulous jaw impression techniques have gained popularity, while their validity has not yet been evaluated. Purpose: The purpose of this clinical study was to compare the trueness of maxillary edentulous jaw impressions made with irreversible hydrocolloid (ALG), polyvinyl siloxane (PVS), PVS modified with zinc oxide eugenol (ZOE) (PVSM), and an intraoral scanner (TRI) with a conventionally border-molded ZOE impression (control). Material and methods: Twelve edentulous maxillary impressions were made with the impression techniques. The analog impressions were scanned using a laboratory scanner, imported into 3-dimensional comparison software, and superimposed against the corresponding control. Trueness was evaluated by calculating the effective deviation known as root mean square (RMS) for the entire surface (ES) and for specific regions of interest such as peripheral border, inner seal, midpalatal suture, ridge, and posterior palatal seal. The secondary outcomes for this study were the patients' perception of the impression techniques. Statistical analyses with the Wilcoxon tests were carried out (α=.05). Results: For ES, significant differences were found when comparing ALG (1.21 ±0.35 mm) with PVS (0.75 ±0.17 mm; P=.008), PVSM (0.75 ±0.19 mm; P=.012), and TRI (0.70 ±0.18 mm; P=.006) but not among the other groups. Significant differences were found for peripheral border when comparing ALG (2.03 ±0.55 mm) with PVS (1.12 ±0.32 mm; P=.006), PVSM (1.05 ±0.29 mm; P=.003), and TRI (1.38 ±0.25 mm; P=.008), as well as TRI and PVSM (P=.028). Significant differences were also found for inner seal when comparing ALG (0.74 ±0.36 mm) with PVSM (0.52 ±0.13 mm; P=.041), as well as TRI (0.8 ±0.25 mm) versus PVS (0.56 ±0.14 mm; P=.005) and PVSM (P=.005). The difference at the ridge was significant when comparing PVS (0.18 ±0.07 mm) with PVSM (0.28 ±0.19 mm; P=.015) but not among the other groups. A significant difference was also found for posterior palatal seal when comparing PVS (0.55 ±0.41 mm) with PVSM (0.60 ±0.43 mm; P=.034). Patient perceptions showed significantly better satisfaction scores for ALG (1.83 ±2.03) and PVS (3.17 ±2.40) than for TRI (4.08 ±2.71), PVSM (4.58 ±2.35), and ZOE (6.83 ±1.75). Conclusions: Edentulous impressions made with PVS, PVSM, and TRI had similar deviations and may yield clinically acceptable results. Irreversible hydrocolloids are contraindicated for definitive impression making in completely edentulous jaws.
Article
Statement of problem: Studies evaluating the dimensional stability of denture bases fabricated by the double processing method are lacking. Purpose: The purpose of this in vitro study was to evaluate the dimensional stability of denture bases fabricated by 3 different techniques: compression molding, injection molding, and computer-aided design and computer-aided manufacturing (CAD-CAM) subtraction milling. Material and methods: Forty-five mandibular denture bases were fabricated from a master cast by a standardized process. A double processing protocol was used with 3 methods: compression molding (PRESS), injection molding (INJECT), or CAD-CAM (CAD). The bases were compared with the titanium master cast after the first processing. By a digital subtraction process, the dimensional stability of the bases was measured at 22 different locations on the intaglio surface. Denture teeth were then positioned according to a standardized protocol, and the denture was processed a second time and finished. The dimensional discrepancy was reassessed after the second processing and compared with the titanium master cast. Results: In all groups, most of the dimensional changes occurred during the first processing (P<.05), with no statistically significant deformation occurring during the second processing (P>.05). The CAD group presented significantly smaller dimensional changes than PRESS (P<.05) and INJECT (P<.05) groups. No significant difference was found in the dimensional stability in the PRESS and INJECT groups (P>.05). Conclusions: Denture bases fabricated by a CAD-CAM methodology exhibit fewer dimensional changes than either compression or injection molding. Distortion occurred during the fabrication of the denture base, and a second processing did not significantly affect the dimensional stability of the denture base.
Article
Statement of problem: Scanning of completely edentulous arches remains a challenge because of the large surface to scan and the lack of anatomic indexes. Whether the presence of impression transfer copings with digital scanning provides enough markers for acceptable precision and clinical use has not been determined. Purpose: The purpose of this systematic review was to assess the accuracy of digital scanning for complete-arch implant-supported restorations. Material and methods: A systematic review of peer-reviewed literature was conducted to analyze articles published between 2008 and 2019. Among the 208 retrieved articles, 20 were selected for review. Results: Five articles reported the use of digital scanning in clinical situations and satisfying short-term results. Fifteen in vitro studies were also included for complementary information, including measurement accuracy. Most of the intraoral scanners used in vitro provided acceptable accuracy below a threshold of 150 μm. When directly compared, the digital technique was at least equivalent to conventional impression techniques. Conclusions: In vitro, intraoral scanners have shown acceptable accuracy. The main parameters identified for their influence on precision were interimplant distance, body scan design, scanning pattern, and operator experience. Clinical evidence is limited by the lack of a definitive method of assessing the fit of the framework.
Article
For the retention and stability of removable complete dentures, the denture base should be fabricated with appropriate borders and polished surfaces. A technique for transferring the contour of a functional impression for digitally fabricated removable complete dentures is described.
Article
Objective: Summarizing the new state of the art of digital dentistry, opens exploration of the type and extent of innovations and technological advances that have impacted - and improved - dentistry. The objective is to describe advances and innovations, the breadth of their impact, disruptions and advantages they produce, and opportunities created for material scientists. Methods: On-line data bases, web searches, and discussions with industry experts, clinicians, and dental researchers informed the content. Emphasis for inclusion was on most recent publications along with innovations presented at trade shows, in press releases, and discovered through discussions leading to web searches for new products. Results: Digital dentistry has caused disruption on many fronts, bringing new techniques, systems, and interactions that have improved dentistry. Innovation has spurred opportunities for material scientists' future research. Significance: With disruptions intrinsic in digital dentistry's new state of the art, patient experience has improved. More restoration options are available delivering longer lifetimes, and better esthetics. Fresh approaches are bringing greater efficiency and accuracy, capitalizing on the interest, capabilities, and skills of those involved. New ways for effective and efficient inter-professional and clinician-patient interactions have evolved. Data can be more efficiently mined for forensic and epidemiological uses. Students have fresh ways of learning. New, often unexpected, partnerships have formed bringing further disruption - and novel advantages. Yes, digital dentistry has been disruptive, but the abundance of positive outcomes argues strongly that it has not been destructive.