Minimally Invasive FullMouth Rehabilitation Adapting Digital Dentistry QUINTESSENCE OF DENTAL TECHNOLOGY 2018

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Editorial

MACHINE LEARNING:

Artificial Intelligence for Diagnosis
and Treatment Planning
One of the most complex tasks of any esthetic oral rehabilitation is the development
of a treatment plan. Assembling all the data gathered from multiple sources—such
as medical and dental history, patient’s chief complaint, radiographs, cone beam computed tomography (CBCT), casts, bite registrations, occlusal analysis, tooth shade
analysis, just to name a few—and then interpreting the data, coming to a conclusion,
and fabricating visually acceptable prototypes (virtual or not) for communication with
the patient and restorative team is not a easy task.
Although it is clear that the advances in digital technology in recent years have
made a highly positive impact, information remains fragmented. The restorative team
still needs to collect different pieces of information using digital and nondigital formats and combine them using different digital platforms or analog methods to prepare an appropriate treatment plan. Not to mention that there are so many variables
involved in an oral rehabilitation that the process of establishing a final treatment
plan itself is very stressful and intricate. Minimal errors in data gathering can lead to
unpredictable outcomes, and the lack of predictability is one of the most challenging
fears in dentistry.
We urgently need digital tools that allow us to record, in an all-in-one single platform, patient data dynamically (lips at rest, teeth display during smile and exaggerated
smile, occlusal excursions and movements), statically (intraoral scan, extraoral scan,
digital dental shade analysis, and CBCT), and historically (medical and dental history). While many systems provide the opportunity to design smiles, plan restorations, determine implant placement, or evaluate underlying structures, most of the
systems available still lack full integration. Furthermore, many digital platforms remain based in traditional dentistry, where
teeth still need to cut in order for the software algorithms to design and propose an acceptable restoration. Ideally we need
fully digital data sequencing, where all digitally recorded data would allow complete analysis and study of occlusion (including vertical dimension of occlusion), dental esthetics, tooth position, enamel and dentin thickness, edentulous space, root
canal therapy, and gingival esthetics to create the ultimate virtual patient.
With the assistance of this technology, the human brain would then design a successful treatment plan with a minimally
invasive approach in mind and monitor its outcome over time in the same digital platform. As the machine stores more

information, better decisions could be drawn. This technology is already available in other fields. In medicine, for instance,
a surge of interest in machine learning has resulted in an array of successful data-driven applications, ranging from medical image processing and diagnosis of specific diseases, to the broader tasks of decision support and outcome prediction.
Through an artificial neural network—which resembles a biologic brain in the sense that it learns by responding to the
environment and stores the acquired knowledge for future decisions—digital technology could help to predict the success
of a given treatment or suggest its limitations. Dentistry could truly benefit from artificial intelligence and artificial neural
networks, or at minimum all-in-one digital platforms offered at a reasonable cost.
Digital workflow is clearly the theme of this year’s Quintessence of Dental Technology, with its collection of essays and
cases demonstrating a combination of human ingenuity, artistry, and technology to promote better and high-quality dentistry. I
welcome you to take the time to explore the possibilities shown in this book, to be curious, and to crave for knowledge with
the excitement of all new possibilities.

Sillas Duarte, Jr, DDS, MS, PhD

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Minimally Invasive Full-Mouth
Rehabilitation Adapting Digital Dentistry

Masayuki Okawa, DDS1
Shigeo Kataoka, CDT2
Takahiro Aoki, CDT2
Koichi Yamamoto, DDS3

Private Practice, Daikanyama Address Dental Clinic,
Tokyo, Japan.
2
Osaka Ceramic Training Center, Osaka, Japan.
3
Private Practice, Yamamoto Dental Clinic, Osaka, Japan.
1

Correspondence to: Dr Masayuki Okawa, Daikanyama
Address Dental Clinic, 17-1-301 Daikanyama-cho,
Shibuya-ku, Tokyo 150-0034, Japan.
Email:

QDT 2018

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7

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OKAWA ET AL

T

he minimally invasive intervention concept has become a standard prosthodontic treatment—a shift
from the old standard concept of “retention and
resistance.” The goal of prosthodontic treatment should be
biomimetics and bioemulation, which lead to the minimally
invasive concept by incorporating the current evolution of
adhesive dentistry with further understanding of the biomechanics of tooth structure.1
Since Magne and Belser introduced various anterior
bonded porcelain restoration cases in 2002,2 many clinicians, including the author, have been publishing welldocumented successful results for anterior teeth.3,4 Magne
et al5,6 and Dietschi and Argente7 later published direct
and indirect adhesive restorative techniques with the minimally invasive concept for posterior teeth. Since then,
Duarte et al,8 Fradeani et al,9 Vailati et al,10 Okawa,11 and
other clinicians have published minimally invasive full-mouth
rehabilitation cases.12 New clinical workflows and materials
for minimally invasive restorations also continue to be introduced. Moreover, the author has presented clinically
successful minimally invasive restorations fabricated using
a microscope to avoid technical errors.13
Since the introduction of digital dentistry—the recent
paradigm shift in dentistry—it is important to understand
its application in the minimally invasive restoration workflow.14 In this article, several important aspects of executing minimally invasive restorations are discussed through
the presentation of full-mouth minimally invasive restorations for a case of severely acid-worn dentition.

CLINICAL GOAL OF INDIRECT
MINIMALLY INVASIVE TREATMENT

As previously noted, the author has been having excellent
case outcomes and prognoses by working under the microscope. In the patient shown in Figs 1 to 6, the fractured
anterior teeth were treated under the microscope with
bonded porcelain restorations. Marginal integrity was stable, with no sign of marginal porcelain chipping or discoloration 9 years posttreatment.
The author did not have much exposure to digital dentistry at the time of treating this patient. However, with
micro dentistry (treatment under the microscope), high accuracy can be obtained and prosthetic errors avoided, with

8 QDT 2018

no compromise on the standard of treatment. For digital
dentistry, this philosophical concept should be the same:
not allowing any compromise on treatment quality. The
treatment approach for maintaining a high-quality outcome
by efficiently combining prosthetic traditional workflow
and digital workflow is presented in this article.

Clinical Questions/Concerns
Regarding Minimally Invasive
Full-Mouth Rehabilitation
1. Recently, cases of minimally invasive or noninvasive fullmouth rehabilitations of severely worn dentition (due to
chemical erosion, occlusal abrasion,15 enamel dysplasia,
etc) have been presented widely. Is tooth reduction
necessary for those cases?16 If necessary, how much
reduction is needed for different types of cases? What
type of finish line is appropriate?
2. Polymer versus all-ceramics: What is required to obtain
accuracy of fit of restorations using a digital workflow?
What kind of material choice is appropriate for milling
the restoration? Should material choice be different depending on the location of the restoration, ie, anterior or
posterior?

3. The provisional stage is extremely important for fullmouth rehabilitation cases in order to evaluate function
and esthetics. Since adhesive restoration preparation
does not require retention and resistance form, how can
we choose the provisional restoration material? How do
we cement the provisional restoration? What kind of
temporary cement can be used?

RESTORATIVE TREATMENT FOR
SEVERELY WORN DENTITION
Severely worn dentition can be caused by acid erosion,
parafunctional habits such as bruxism, malocclusion, or a
combination of these. Severely worn dentition can cause
esthetic, functional, and biologic issues, and this can lead
to complete bite collapse. Restorative treatment is important to prevent further deterioration.17 Adhesive restoration
to preserve the remaining tooth structure should be the
treatment of choice in such cases.18

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1

2

3

Fig 1 Preoperative photograph of patient with four fractured
maxillary anterior teeth.
Fig 2 Teeth preparation.
Fig 3 After completion of restorative treatment under microscope.
Fig 4 Three-year postoperative radiographs. There is no detectable gap between the teeth and restoration margins even
though radiopaque resin cement was used.
4

5a

5b

Figs 5a and 5b Nine-year postoperative photographs. There is
no discoloration on the anterior restoration supragingival
margins.
Fig 6 Magnification of supragingival margin under the microscope. No significant clinical negative changes can be observed
9 years postoperatively.

6

CASE PRESENTATION
Chief Complaints
The patient, a 21-year-old fashion model, was concerned
with the esthetics of her thin and short central incisors.

She also complained of sensitivity in the anterior teeth and
muscle pain caused by her clenching habit. A later interview revealed that she had an eating disorder (bulimia).
The patient wanted treatment to improve the anterior esthetics and posterior occlusion as well as eliminate teeth
sensitivity.

QDT 2018 9

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OKAWA ET AL

7b

7a

Figs 7a to 7c Clinical evaluation of facial esthetics and
face-to-tooth relationships. The incisal edge position of the
maxillary anterior teeth is shorter than the lower lip smile line,
and the mandibular anterior teeth are slightly extruded. Those
are the major esthetic issues.

7c

Initial Clinical Work-up
Analysis of facial features and lip and teeth relationship.

The incisal edge position was concave and did not match
the smile line. The mandibular anterior teeth were slightly
extruded (Figs 7a to 7c).
Intraoral photograph analysis. Figures 8a to 8c show the

anterior teeth in occlusion, anterior rest position, and anterior protrusive movement. There was no significant concern in terms of the maxillary cervical gingival levels, but

the occlusal plane was canted to the right. The midline of
the maxillary central incisors matched the facial midline.
The midline of the mandibular central incisors was shifted
to the right; therefore, the left canine relationship was
Class III. The path of teeth guidance can be analyzed by
examining the anterior teeth working contacts and wear
pattern. This case was diagnosed as pathway to end-toend wear. Spear noted that overjet should be deeper and
overbite shallower for cases such as this, with teeth contacts in functional movement until the end of the mandibular envelope movement.19
The four maxillary incisors appeared very thin (Figs 9a
and 9b). All six maxillary anterior teeth showed incisal chip-

10 QDT 2018

ping and significant wear, so those teeth appeared to be
very short. There was no decay or restorations on these
teeth. The occlusal view (Fig 9b) shows the typical acid
enamel erosion pattern and shiny worn-down occlusal surfaces.17 This wear pattern confirmed that acid erosion
caused the dentin exposure, and the mandibular anterior
labial incline and bruxism caused additional wear of the
maxillary anterior teeth.
Study model analysis. The acid erosion and occlusal wear

of the palatal surfaces of the maxillary anterior teeth could
be seen on the initial study models (Figs 10a to 10d). Hard
tissue defects caused by the acid erosion and occlusal
wear were more prominent on the anterior teeth than the
posterior teeth. The maxillary left first molar seemed to
have been lost much earlier and left unrestored. The second and third molars were tilted mesially and closed the
space of the first molar. The maxillary molars showed significant wear on the functional cusps, and the mandibular
molars showed occlusal concavities, corresponding with

the patient’s complaint of right molar clenching. There also
was pain on palpation of the posterior belly of the digastric
muscle. This implies that the right condyle could locate on
the more posterior position.

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Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

8c

8b

8a

9a

9b

10a

10b

10c

10d

Figs 8a to 8c Initial preoperative photographs.
Figs 9a and 9b Initial preoperative facial and occlusal views of the maxillary anterior teeth.
Figs 10a to 10d Evaluation of initial preoperative study casts. (a) Maxillary anterior teeth, palatal view; (b) maxillary teeth, entire
occlusal view; (c) maxillary right first and second molars, occlusal view; (d) mandibular right first and second molars, occlusal view.

QDT 2018 11

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OKAWA ET AL

11

12

Fig 11 Preoperative full-mouth radiographs.
Fig 12 Anatomy of thick enamel structure of anterior tooth’s lingual and interproximal areas. It is important to preserve those
structures for tooth flexure control.

Radiographic analysis. All teeth were vital (Fig 11). Dental

decay was found on the interproximal surfaces of the mandibular right first and second molars. There were no periodontal concerns. The maxillary left second molar was
mesially tilted.

Restorative Treatment Objectives and
Treatment Planning
An organized and sequenced treatment plan was established along with eliminating the risk factors of the acid

erosion.17 The treatment plan objectives for patients with
acid erosion should be to recover proper anatomical features; reestablish proper occlusion and function; improve
esthetics, such as the smile line; and eliminate teeth sensitivity.11 This particular patient had more significant anterior

12 QDT 2018

teeth wear compared to posterior wear. Since the anterior
teeth were already labially inclined, the ideal treatment
choice preferably included either orthodontic intrusion or
crown lengthening to create space for the future restorations rather than opening the vertical dimension of occlusion (VDO), in order not to create too much postoperative
anterior teeth display. Orthodontic treatment,20 including
uprighting the maxillary left second molar, was discussed
with the patient. However, due to her occupational commitment, she could not undertake the suggested orthodontic
treatment. Therefore, full-mouth rehabilitation with opening of the VDO became the final treatment plan.
A predictable treatment outcome with opening of the
VDO has been shown by Abduo.21 Spear stated that the
ideal VDO21,22 does not exist; VDO can change and adapt
to the patient’s condition, so an appropriate VDO for each
individual patient needs to be determined.20 The restor-

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Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

9 mm

9 mm

9.5 mm

13

14

15

16

10 mm

Fig 13 Two sets of study casts were mounted on the articulator by using the same centric relation registration. One set was for
fabrication of the diagnostic wax-up and the other for fabrication of the provisional restorations and anterior guidance index.
Fig 14 Esthetic evaluation and wax-up of the maxillary central incisors according to the patient’s request. Ideal incisal position was
created by adding wax after evaluating the central incisors and upper lip position during a smile. General length, width, and tooth
proportions were also taken into consideration. Patients with acid erosion tend to get used to the appearance of short teeth and
usually do not request long teeth.23
Fig 15 Establishing the ideal occlusal plane according to proper occlusal plane concepts and esthetic requirements. In this case,
the ideal occlusal plane was created by correcting the mesially tilted maxillary left first molar alignment.
Fig 16 Palatal surfaces of the anterior teeth were recontoured in the wax-up. The maxillary left molars were also waxed and
idealized.

ative treatment should bring back anatomy of the individual tooth by increasing VDO and then restore function and
esthetics by preserving as much of the remaining tooth
structure (Fig 12).

Workflow of Minimally Invasive
Full-Mouth Rehabilitation

The method to determine the ideal VDO for this patient was
to fabricate a diagnostic wax-up on the articulator. The inter-

occlusal record was acquired and mounted on the articulator. Esthetic and functional requirements were evaluated
in this order: maxillary central incisors, lateral incisors and
canines, maxillary premolars and molars, mandibular anterior teeth, mandibular premolars and molars. The diagnostic
wax-up should exhibit the ideal treatment plan goal visually. Meeting the patient’s esthetic demands and the operator’s functional goal should be the most important
determinants of a new VDO. Figures 13 to 21 demonstrate
the mounting of casts on the articulator, the diagnostic
wax-up technique, and determination of the new VDO.

QDT 2018 13

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OKAWA ET AL

17

18

Fig 17 Ideal protrusive movement path provided on the
articulator. With the pathway to end-to-end wear in this
case, overjet should be created deep and overbite
shallow.19
Fig 18 New established VDO appreciated by closing the
articulator.

Fig 19 Mandibular movement paths defined by recontouring the maxillary anterior lingual surface wax.

19

20a

20b

21a

21b

Figs 20a and 20b Ideal maximum intercuspation and nonworking-side molar disclusion were
acquired by changing the mandibular molar shape within the wax-up.
Figs 21a and 21b Mandibular right molars were mainly recontoured in the wax-up according to
the idealized maxillary occlusal plane, thereby establishing the ideal occlusal plane.

14 QDT 2018

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Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry
Figs 22a and 22b Preoperative
study casts and diagnostic
wax-up models were scanned
using a tabletop scanner and the
images then superimposed.

Figs 23a and 23b Superimposed images. There is adequate
space on the buccal, incisal, and
palatal areas of the maxillary
anterior teeth.
Figs 24a and 24b The palatal
veneer restorations for the
maxillary anterior teeth and
occlusal overlay restorations for
the maxillary left molars were
digitally created with the software
after scanning of the preoperative
study casts.

22a

22b

23a

23b

24a

The traditional approach for opening the VDO by using
a familiar articulator to mount the master casts and completing diagnostic wax-up was selected for this treatment.
However, after this step, digital dentistry was implemented.
The microscope was used for restorative steps, such as
teeth preparations, in order to minimize technical errors.
Following are the five main treatment steps for this patient.

Step 1: Full-Mouth Provisional
Restorations (Digital Approach)
As shown in Figs 22 to 36, the full-mouth provisional restorations for this patient were fabricated digitally using the
noninvasive approach, as was the goal.
This case was categorized as Class IV according to the
ACE analysis by Vailati and Belser.18 The author selected

24b

the sandwich veneer technique, with separate buccal and
palatal veneers, for the six maxillary anterior teeth to preserve interproximal sound tooth structure, which has an
important role in controlling the tooth flexure in teeth that
have lost significant hard tissue due to acid erosion and
occlusal wear.
Anterior provisional restorations were cemented with
provisional resin cement (Telio CS Link, Ivoclar Vivadent)
by applying spot acid etch and bond. Posterior overlay
provisional restorations do not have traditional “retention
and resistance” form and yet receive heavy vertical and lateral occlusal loads, so regular provisional resin cement
would not hold those restorations for long. Therefore, the
inner surfaces of the posterior overlay provisional restorations were treated with primer (HC primer, Shofu), and
non–self-adhesive resin cement (HC cement, Shofu) was
used (Figs 32a and 32b).

QDT 2018 15

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OKAWA ET AL
Fig 25a Palatal veneer restorations were milled from the PMMA
disk.
Fig 25b 3D image acquired by
scanning the maxillary cast with
palatal veneer restorations.

25b

25a

Figs 26a and 26b Labial
provisional veneer restorations for
the maxillary anterior teeth were
digitally created.

26b

26a

27a

27b

28a

28b

Fig 27a Maxillary anterior labial veneer provisional restorations milled from PMMA disk.

Fig 27b Maxillary labial and palatal provisional veneer restorations polished and ready for insertion.
Figs 28a and 28b Fabricated sandwich veneer provisional restorations tried on the stone master casts.

16 QDT 2018

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Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry
Figs 29a and 29b Posterior
provisional overlay veneer
restorations (a) designed and (b)
fabricated. The VDO was not
raised much in this case, so the
posterior overlay provisional restorations were thin. These restorations were splinted in order to
avoid stability issues during the
provisional phase.
Figs 30a and 30b Provisional
restorations for the mandibular
molars were fabricated using the
direct bonding technique using a
clear silicone matrix (Reveal,
Bisco) since there was not
enough clearance to fabricate
PMMA provisional restorations
with the noninvasive approach.
Direct bonding was applied on the
mandibular right first and second

molars and first premolar and on
the left first molar and second
premolar.

31a

32a

29a

29b

30a

30b

31c

31b

32b

Figs 31a to 31c After setting preoperative casts with the new VDO on the articulator, an anterior index was fabricated to keep
posterior interocclusal space with the new VDO during fabrication of the provisional restorations. The index is used to transfer the
provisionals from the articulator to the patient’s mouth. It acts as an intraoral vertical stop. After inserting posterior provisional
restorations with the index, the anterior sandwich technique provisional veneer restorations were inserted and anterior stop and
guidance created.
Figs 32a and 32b After the maxillary left molar overlay PMMA provisional restorations were placed using the anterior index, the
direct composite provisional restorations for the mandibular right molars were placed.7 This created a new posterior vertical stop.

QDT 2018 17

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OKAWA ET AL
Figs 33a and 33b Maxillary
sandwich veneer provisional
restoration insertion was performed
under the microscope. It was
difficult to insert these provisional
restorations on the unprepared
labial side because of the convex
surface. Also inserting palatal
provisional restorations at the same
time on the same tooth can be
challenging to perform without error.
33b

33a

Figs 34a and 34b Working under
the microscope is extremely useful
for insertion of palatal provisional
veneer restorations on the
unprepared tooth surface because
it is concave.

34b

34a

Fig 35 Provisional restorations
fabricated for the noninvasive
full-mouth rehabilitation.

35

36a

36b

Figs 36a and 36b Final restoration casts created from the duplicated provisional restoration casts with some minor waxing and
recontouring after the intraoral adjustments. After adjustment of the casts, both arches were scanned for the digital wax-up of the
final restorations.

18 QDT 2018

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Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

38

37

Fig 37 After preparation of the mandibular right first and second molars. A great deal of occlusal wear was noted on the provisional
restorations; interproximal decay was also detected. Therefore, those teeth needed to be prepared for lithium disilicate (IPS e.max
CAD, Ivoclar Vivadent) final restorations.
Fig 38 Measuring the material thickness of the final restoration is an important step. With digital dentistry, this task is performed
easily. After tooth preparation, prepared teeth and the entire arch are scanned by the intraoral scanner (Trios 3, 3Shape) and final
restorations designed by digitally superimposing the scans with the software.

When occlusal rehabilitation treatment for heavy bruxists is carried out with altered VDO, there is a tendency for
muscle activity to become more active 2 to 3 months into
the treatment and for the patient to begin to break down
the provisional restorations.24,25 In this patient, accordingly,
there was chipping and wear of the provisional direct composite restorations on the mandibular right molars. The
right condyle was also deviated forward after opening the
VDO. This gave the assumption that the condyle was deviated posteriorly due to too much compressive stress.
After several anterior and posterior occlusal adjustments,
the patient became accustomed to the altered VDO and
occlusion. The frequency of mandibular right-side provisional restoration repair was reduced and palpation pain in the
posterior belly of the digastric muscle disappeared. Facially, the patient noticed less muscle bulk on the mandibular
angle and she did not clench as much as previously.
After these positive outcomes with the provisional restorations, it was decided to proceed to the final restorations.
But first, impressions of both arches were taken for the
digital wax-up of the final restorations, and the casts were
refined using a curving and waxing technique.

Step 2: Molar Teeth Preparation
(Microscope Technique)
The full-mouth provisional restoration was accomplished
with the completely noninvasive approach. However, be-

cause the direct composite provisional restorations on the
mandibular right first and second molars were constantly
chipping and wearing due to the patient’s strong bruxism,
milled lithium disilicate (IPS e.max, Ivoclar Vivadent) was
selected as the material of choice for the final restorations
given its high strength and capability for etch and bond.
This material will prevent the future loss of VDO and nonideal posterior rotation of the TMJ. The author has been
using lithium disilicate clinically for minimally invasive molar restorations below the manufacturer’s recommended
thickness (thinner than 0.8 mm); however, chipping or
shear fracture has been occurring in patients with heavy
bruxism. The author also believes that the press technique
is an effective fabrication method for those extremely thin
molar occlusal veneer restorations. For this case, preparation of the first and second molars was done to provide 0.8
to 1.00 mm thickness for the ceramic restorations.9 However, the preparation was kept in the enamel since interocclusal space was automatically created by increasing
the VDO. Final preparations of the maxillary left first and
second molars were done by preparing the PMMA provisional restorations under the microscope, and the final
preparations of the mandibular first and second molars
were done by preparing a direct composite resin mock-up
under the microscope.26 The direct composite bonded restorations on the mandibular right and left second premolars and left first molar were in great condition; therefore, it
was decided they would be the final restorations (Figs 37
to 40).

QDT 2018 19

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OKAWA ET AL

39a

39b

40a

40b

Figs 39a and 39b Mandibular right first and second molar PMMA provisional restorations: (a) intraoral view and (b) preinsertion
views of the four PMMA provisional restorations. The mandibular right first and second molar restorations were splinted for retention
and had a holding notch applied on the individual restorations for easy removal. These PMMA restorations had great fit; however,
possible material distortion during milling could occur because the restorations are very thin. Cementation was done with HC cement.
Figs 40a and 40b Digital image of final restoration wax-up cast (provisional restorations modified casts) and digital image of
prepared teeth are double scanned.

Step 3: Fabrication and Insertion of
Posterior Final Restorations (Digital
Approach)
The posterior final restorations were fabricated digitally
using IPS e.max CAD HT A1 block. e.max CAD was chosen
as the restorative material for this case due to its wear re-

20 QDT 2018

sistance and esthetics. e.max CAD ceramic block can be
milled as thin as 0.3 mm with the use of a new milling bur
and setting milling time longer, although there are some
small variations in results. It is rather easy to mill e.max
CAD ceramic block since it is milled in the green stage. If

the margin needs to be as thin as 0.2 to 0.3 mm, it should
be milled thicker and then adjusted on the 3D-printed die
model (Figs 41 to 43).

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Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry
Figs 41a to 41d (a) 3D-printed model is required
for adjustment of occlusion, surface texturing,
staining, margin adjustment, and polishing. IPS e.max
CAD HT A1 block (a, b) before crystallization and (c)
after crystallization. (d) Abutment dies produced by
3D printer and completed ceramic overlay restorations after staining.
Fig 42a Lava Ultimate HT A1 block (3M ESPE),
which is a polymer block, was milled under the same
setting experimentally. It was milled as thin as 0.3 mm
without problem. However, e.max CAD presented
better light transmittance in the same HT A1 block.
Fig 42b Try-in of Lava Ultimate overlay restorations.
The stability and fit of the overlay restorations from
the polymer block was satisfactory.

41a

42a

43a

41d

41c

41b

42b

43b

Figs 43a and 43b IPS e.max CAD ceramic overlay restorations inserted on the mandibular right first and second molars. Rubber
dam should be used for the bonding procedure to control moisture. Highly filled composite resin (ENA HRi, Micerium) was softened
by heat and used as the bonding material due to its high bond strength and hardness. The ceramic overlay restorations on molars
fabricated digitally were as accurate and esthetic as those using the traditional approach.

QDT 2018 21

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OKAWA ET AL

Sandwich approach
ACE Class IV
Facial Ceramic
Palatal Ceramic

44

45a

45b

46

47a

47b

Fig 44 Data from the wax-up model of final restorations, which was refined from the provisional model and the
data before abutment preparation, were superimposed to simulate the final restorations. The sandwich veneer
technique was employed for the maxillary anterior teeth to preserve enamel in the proximal area, which is
important for tooth flexure control.
Figs 45a and 45b Cervical area was prepared 0.2 mm under the microscope.
Fig 46 After completion of abutment preparation.
Figs 47a and 47b Shape of prepared abutments and acquired material space was measured on the software.

22 QDT 2018

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Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry
Figs 48a and 48b Intraoral
scan data from Trios 3 (3Shape).

48a

48b

Step 4: Abutment Preparation of
Anterior Teeth (Under Microscope)
Sandwich veneer restoration was chosen for the maxillary
anterior teeth. Non-preparation provisional restoration was
possible because enough material space was secured at
the time of diagnostic wax-up. When evaluating the provisionals, it was found that the restorations tended to slip
away during the seating procedure due to the labial convex
surface. A 0.2-mm feather-edge chamfer finish line was
placed at the gingival level of the labial cervical area.
Hence, the bonding procedure could be performed with
control and the seating position checked under the microscope. This subtle tooth reduction should not affect the
deflection of the tooth. Preparation of the incisal edge and
lingual aspect involved only rounding the sharp edges.
A microscope is required to perform minimal preparation accurately. And for the intraoral digital scanning, not
limited to subgingival but for the veneer restorations, it is
difficult to scan the tooth surfaces at adjacent contact
points, so stripping reduction of the contact points should
be done within the tolerance to avoid violating tooth flex-

ure. Labial veneers of maxillary anterior teeth can be thin
as long as abutment flexure is minimum and bonding is in
enamel without complications such as chipping or fracture.
Many anterior teeth can be restored without any abutment
preparation. Consideration of strength and direction of
occlusal force and required material space is more critical

in posterior teeth restoration (Figs 44 to 47).

Step 5: Fabrication and Insertion of
Anterior Restorations (Digital and
Traditional Approaches)
Two sets of restorations were fabricated by two dental
technicians using two different fabrication approaches for
study purposes to compare the workflows and the results.
The digitally fabricated restorations were designed using
the digital data obtained by an intraoral scanner. After milling, they were stained and final adjustments were made on
the model generated by the 3D printer (Figs 48 to 58). The
second set of restorations used a combination of traditional and digital approaches. Labial veneers were fabricated

QDT 2018 23

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OKAWA ET AL

49

50

51a

51b

52

53

Fig 49 Palatal veneers were first designed after superimposing the data from the provisional modified cast wax-up for final restorations and the data from intraoral scanning after abutment preparation.
Fig 50 Milled palatal veneer restorations using IPS e.max CAD block according to the design shown in Fig 49.
Figs 51a and 51b Palatal veneer restorations were tried on the 3D-printed model after crystallization and staining. Once fit was
confirmed, scanning with a desktop scanner was carried out with the palatal veneer restorations seated on the 3D-printed model.
Fig 52 Maxillary anterior labial veneers were designed on the superimposed data of the wax-up model of final restorations and
scanned data of the 3D-printed model with palatal veneers seated. Individual dies were fabricated by sectioning the 3D-printed model
and superimposed on the image to reproduce accurate veneer margins of the proximal area.
Fig 53 Milled labial veneers using e.max CAD block from the data of Fig 52.

24 QDT 2018

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Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

54b

54a

55

56a

56b

57

58

Figs 54a and 54b Surface texture was given to the anterior veneers on the 3D-printed model before crystallization. The accuracy of
milling in digital dentistry is sufficient. On the other hand, procedures such as above cannot be achieved digitally. In addition, sprue
removal also makes manual work required.
Fig 55 Completed anterior labial veneer restorations after crystallization and staining.
Figs 56a and 56b Maxillary anterior sandwich veneer restorations completed using the digital approach (technician: Mr Takahiro
Aoki, Osaka Ceramic Training Center).
Fig 57 Try-in of sandwich veneer restorations. Natural shade and esthetics were achieved using the digital approach.
Fig 58 Highly accurate marginal fit was achieved using the digital approach. Gingival margins cannot be distinguished by visually
comparing the veneers before and after try-in.

QDT 2018 25

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OKAWA ET AL
Figs 59a and 59b Lingual
sandwich veneer restorations were
fabricated digitally on the stone
model, and labial veneer restorations were fabricated traditionally.
Silicone rubber impression and the
master stone models are shown.

59b

59a

60b

60a

60c

61

Figs 60a to 60c Palatal veneer restorations were designed after superimposing of the data from the wax-up model for final
restorations and the scan data of the stone master model after abutment preparation. Maxillary anterior palatal veneer restorations
were milled out of IPS e.max CAD, crystallized, and then stained on the stone master model.
Fig 61 Labial veneer restorations were fabricated using the porcelain layering technique on the refractory die (technician: Mr Shigeo
Kataoka, Osaka Ceramic Training Center). Despite the progress in materials for digital fabrication, such as gradation monolithic block
and staining technique, limitations in detailed coloring and light transmittance remain. The shape of mamelons, incisal halos, and
creation of internal structure such as fluorescence still require the creative hand of the master technician, which will not change in the
near future.

on a refractory cast using feldspathic porcelain and finished on the stone master model obtained by silicone impression. The stone master model was scanned and palatal

26 QDT 2018

veneers were designed digitally. They were milled, stained,
and finished on the master model (Figs 59 to 64).

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Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

62

63

64

Fig 62 Completed labial veneer restorations using refractory model technique. Surface texture was finished by
the master ceramist.
Fig 63 Completed sandwich veneer restorations using the traditional and digital approaches.
Fig 64 Fit of labial veneer and palatal veneer restorations is confirmed on the stone model.

QDT 2018 27
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