The evaluation of 3D printed and designed composite based
restorations in patients with dental implants

One of the treatment options to replace a missing tooth, is the insertion of
a dental implant. Dental implants are available in various surface
characteristics, lengths, shapes and design. The ultimate goal of any design of
dental implants is to simulate the function of a dental root. It is of course a
compromise as it will support a superstructure replacing the natural crown.
Dental implants are a predictable long-term method for the replacement of the
roots of teeth. Both soft- and hard-tissue are important factors in
bone-healing and thus in successful long-term integration. In the
osseointegrated period various factors have been described to contribute to
long term success. Superstructures placed in and on these implants could also
contribute to this long term success. Stresses in the prosthesis have been
linked with marginal bone loss and implant failure. The misfit of the
superstructure may also lead to biological complications or mechanical
complications such as screw loosening of the implant abutment, fracture of the
screw, the abutment and/or the implant. The biological complications can cause
an adverse reaction of soft/hard tissue, which can play a role in plaque
accumulation and bacterial overload. The materials used to fabricate crown and
bridgework on dental implants have shown a rapid development during the last 2
decades.. We have gone from cast frameworks with porcelain fused to metal to
milled frameworks from resin structures and ceramics such as zirconia to now 3D
printed structures. Recent development and advancement in digital tools allow
numerous options for restorative dentistry. Digital fabrication technologies
involve CAD/CAM techniques through either subtractive (milling) or additive (3D
printing) manufacturing (AM).
Additive manufacturing has a unique advantage over conventional milling
production methods; it has practically no waste material, no restriction in
geometric shape of the products and tolerance of milled parts is no longer an
issue [1,2]. This allows the AM technologies to be a key component in the mass
production of parts with special geometrical requirements [2]. Relevant to this
is the fabrication of fixed dental crown and bridge restorations with their
unique buccal, lingual, mesial and distal contours as well as the sophisticated
occlusal outlines.
Among the various additive-manufacturing techniques, DLP (direct laser
projection) is gaining increased popularity in the production of dental parts
[3-5]. In a DLP build process a highly complex structure is fabricated on a
layer-by-layer basis directly from 3D data, whereby consecutive liquid
photo-activated monomer layers are exposed to UV light and cured based on the
final shape of the required product. The DLP process involves a digital
micromirror device (DMD) that is used to dynamically define a mask image that
is projected on the resin surface [6-9]. DMDs, consist of hundreds of thousands
of individually moving micromirrors, that control the reflection path of light.
Each pixel of the image corresponds to an individual micromirror, the
orientation of which can be switched between several degrees based on the
geometry of the part to be printed [9,10].
Next Dent (Vertex-Dental) has successfully developed resin/polymer materials
for 3D printing that have been tested on various biocompatibility properties
and have also been clinically tested. They have been registered as a
biocompatible material for crowns and dentures that can be used in the mouth
indefinitely.
In order to evaluate the possible influence of the printing material the
submucosal bmicrobiome of the patients will be evaluated for change before, 6
and 12 months after the prosthetic procedure. This will be carried out by
collecting submucosal plaque samples with the paperpoint technique. The
submucosal microbiome will be sequenced by Illumina
New dental impression technologies have been developed which claim to be more
accurate and ensure a passive fit of crowns on natural teeth and implants.
Apart from the traditional way of impression taking using elastomers, there is
an alternative, namely digital intra-oral scanning. This may be combined with
CAD/CAM to produce crowns and fixed partial dentures. These have been developed
to achieve a higher accuracy than traditional impression methods and to make a
full digital workflow possible. Various methods of CAM of superstructures exit
nowadays. Mostly larger discs of metal or zirconium are designed and milled
down to a fitting proportion. In this way a lot of material gets lost.
Furthermore, due to limitations of the milling machines not every design is
possible.
The new possibilities of 3 dimensional printing could eliminate the loss of
these precious materials.
Objective of the study:
To evaluate the performance of patients with dental implants that have been
restored with CAD CAM 3D printed resin/polymer screw retained crowns on
Straumann dental implants. As no clinical study has been carried out on these
materials up till now we want to evaluate their function in the oral cavity
after a year. The primary outcome of this research is the failure of the
restoration.
As secondary outcome dDiscoloration, mechanical wear, changes in the surface
structure, adhesion of plaque and debris as well as patient-centred
satisfaction with the aesthetic and functional treatment outcome will also be
evaluated.
Study design:
A virtual crown restoration will be designed on the individual implant using
the 3-Shape Dental System TM CAD solution. The crown design will fit the
desired occlusion and articulation requirements of the individual patient as
well as the tie-base that is to be fitted to enable the screw retention on the
dental implant. The crowns will be printed using Rapid Shape D30 DLP printer
(Rapid Shape GmbH, Germany) with each series of 4 crowns being fabricated at
the center of the build platform. The DLP printer involves an LED light source,
DMD device/chip, lens, resin vat, building platform that is moving in Z-axis
.The DMD device is composed of several micromirrors that dynamically reflect
the light either toward the vat (on) or away from it (off) to create light or
dark pixels respectively. The LED light used has a wavelength of 405 nm (narrow
spectrum wavelength of 390-420 nm) and 10,0 W/m2 energy output. The build
platform size is 110*62 mm and the power of resolution was 1080 *1920 pixels.
The pixel size is 0.058 mm and the layer thickness is 30µm. The x-y accuracy of
this DLP system as reported by manufacturer is ±29µm [13]. Fig 1 shows a
schematic drawing of DLP printing technology. All crowns will be printed using
NextDent C&B material (NextDent C&B MHF* Shade: N1 * N1.5 * N2 * N2.5 * N3 * BL
* T1 ) with similar printer settings with similar printer settings. The
material properties as reported by the manufacturer are presented in Table 1.
After printing, all specimens will be cleaned with 96% alcohol for five minutes
and post-cured for 30 minutes using ultraviolet curing unit LC 3DPrint Box
(Next Dent B.V. Netherlands) following the manufacturer*s instructions [14].
All the crowns will be fitted with a Straumann Tie base. The luting agent that
will be used for this is panavia R.
Two crowns will be stored in a lightproof box. One will be tested after a year.
The second will replace the test crown when this is unscrewed and presented for
laboratory analysis. The 3rd crown will be stored under comparable
circumstances as in the mouth in a laboratory environment.

Prior to storage / placement all 3 specimens per patient will be digitally
scanned using a high-resolution optical surface scanner (IScan D104i; Imetric;
Courgenay, Switzerland). Prior to scanning, the scanner will be calibrated
according to the manufacturer*s instructions. The specimens will be examined
for any manufacturing defects and sprayed with a thin layer of anti-reflective
powder (Helling 3D Scan Spray, Helling GmbH, Germany).
The accuracy of the printed crowns will then be evaluated using a digital
subtraction technique. The STL files of the three scanned printed crowns [test
model] and that of the designed crown [reference model] were exported in
Geomagic® studio (3D Systems, Rock Hill, SC, USA; 2014). The exported files
will be aligned to have the same coordinate systems. The alignment will be
further refined using automatic best-fit alignment that is based on the closest
point algorithm (ICP) system. Prior to alignment process, the support structure
will be virtually removed to eliminate any potential error during the
procedure. The accuracy will then then evaluated through root mean square
estimate values (RMSE) and deviation patterns on color maps. All specimens will
be scanned and analyzed by two trained operators.
Intra-observer reliability will be assessed using Interclass correlation
coefficient. To assess the observer bias, measurements will be taken twice by
one observer within a 15 days interval between the two measurements.
Furthermore, possible errors from optical scanning will be excluded by
assessing the repeatability of the measurements six times.
After 12 months the removed crowns will be analysed. Colour stability will be
measured using a spectrophotometer.
The change of the surface will be measured using an electron microscope (SEM).
Mechanical wear will be analysed using a scanning and subtraction technique.

Before, 6, 12 and 24 months after the surgical procedure submucosal fluid and
plaque samples will be collected from the sulci around the implants using the
paper point technique before, 6 and 12 months after the prosthetic procedure .
The submucosal microbiome will be sequenced by Illumina.
Patient centered satisfaction will be assessed by treatment outcome, and
quality of life (VAS, OHIP-49) after 12 months or earlier if the restoration
fails.
To evaluate clinical parameters [pocket probing depth (PPD), bleeding on
probing (BoP) will be recorded.

A nutrition diary will assist in understanding the erosive and discoloration
potential of the patient*s diet. Patients will be asked to fill this out during
month 1 , month 6 and month 12. The researcher responsible for the evaluation
will send the patients the list on line or on paper depending on the patient*s
wishes.


Follow-up per patient: Total treatment time: 1 year
Duration of intervention per patient: 1 year
Study population:
80 Patients treated with Straumann implants
Primary study parameters/outcome of the study:
Failure of the restaurationrestoration
Secundary Secondary study parameters/outcome of the study (if applicable):
discoloration
Plaque retention of the restoration
condition of soft tissue surrounding the restoration
Nature and extent of the burden and risks associated with participation,
benefit and group relatedness (if applicable):
Burden consists of time involved. Procedure is identical to golden standard
so no higher risk involved. No direct benefit for participants.

To evaluate the performance of patients with dental implants that have been
restored with CAD CAM 3D printed resin/polymer screw retained crowns on
Straumann dental implants. As no clinical study has been carried out on these
materials up till now we want to evaluate their function in the oral cavity
after a year. The primary outcome of this research is the failure of the
restoration.
Discoloration, mechanical wear, changes in the surface structure, adhesion of
plaque and debris as well as patient-centred satisfaction with the aesthetic
and functional treatment outcome will also be evaluated.

A virtual crown restoration will be designed on the individual implant using
the 3-Shape Dental System TM CAD solution. The crown design will fit the
desired occlusion and articulation requirements of the individual patient. As
well as the tie-base that is to be fitted to enable the screw retention on the
dental implant. The crowns will be printed using Rapid Shape D30 DLP printer
(Rapid Shape GmbH, Germany) with each series of 4 crowns being fabricated at
the center of the build platform. The DLP printer involves an LED light source,
DMD device/chip, lens, resin vat, building platform that is moving in Z-axis
.The DMD device is composed of several micromirrors that dynamically reflect
the light either toward the vat (on) or away from it (off) to create light or
dark pixels respectively. The LED light used has a wavelength of 405 nm (narrow
spectrum wavelength of 390-420 nm) and 10,0 W/m2 energy output. The build
platform size is 110*62 mm and the power of resolution was 1080 *1920 pixels.
The pixel size is 0.058 mm and the layer thickness is 30µm. The x-y accuracy of
this DLP system as reported by manufacturer is ±29µm [13]. Fig 1 shows a
schematic drawing of DLP printing technology. All crowns will be printed using
NextDent C&B material (NextDent C&B MHF* Shade: N1 * N1.5 * N2 * N2.5 * N3 *
BL * T1 ) with similar printer settings with similar printer settings. The
material properties as reported by the manufacturer are presented in Table 1.
After printing, all specimens were cleaned with 96% alcohol for five minutes
and post-cured for 30 minutes using ultraviolet curing unit LC 3DPrint Box
(Next Dent B.V. Netherlands) following the manufacturer*s instructions [14].
All the crowns will be fitted with a Straumann Tie base. The luting agent that
will be used for this is panavia R.
Two crowns will be stored in a lightproof box. One will be tested after a
year. The second will replace the test crown when this is unscrewed and
presented for laboratory analysis. The 3rd crown will be stored under
comparable circumstances as in the mouth in a laboratory environment.

Prior to storage / placement all 4 specimens per patient will be digitally
scanned using a high-resolution optical surface scanner (IScan D104i; Imetric;
Courgenay, Switzerland). Prior to scanning, the scanner will be calibrated
according to the manufacturer*s instructions. The specimens will be examined
for any manufacturing defects and sprayed with a thin layer of anti-reflective
powder (Helling 3D Scan Spray, Helling GmbH, Germany).
The accuracy of the printed crowns will then be evaluated using a digital
subtraction technique. The STL files of the four scanned printed crowns [test
model] and that of the designed crown [reference model] were exported in
Geomagic® studio (3D Systems, Rock Hill, SC, USA; 2014). The exported files
were aligned to have the same coordinate systems. The alignment was further
refined using automatic best-fit alignment that is based on the closest point
algorithm (ICP) system. Prior to alignment process, the support structure was
virtually removed to eliminate any potential error during the procedure. The
accuracy was then evaluated through root mean square estimate values (RMSE) and
deviation patterns on color maps. All specimens were scanned and analyzed by
two trained operators.
Intra-observer reliability will be assessed using Interclass correlation
coefficient. To assess the observer bias, measurements will be taken twice by
one observer within 15 days interval between the two measurements. Furthermore,
possible errors from optical scanning will be excluded by assessing the
repeatability of the measurements six times.
After 12 months the removed crowns will be analysed. Colour stability will be
measured using a spectrophotometer.
The change of the surface will be measured using an electron microscope (SEM).
Mechanical wear will be analysed using a scanning and subtraction technique.

Before, 6, 12 and 24 months after the surgical procedure submucosal fluid
samples will be collected from the sulci around the implants using the paper
point technique before, 6 and 12 months after the prosthetic procedure . The
submucosal microbiome will be sequenced by Illumina.
Patient centered satisfaction will be assessed by treatment outcome, and
quality of life (VAS, OHIP-49) after 12 months or earlier if the restoration
fails.
To evaluate clinical parameters [pocket probing depth (PPD), bleeding on
probing (BoP) will be recorded.

A nutrition diary will assist in understanding the erosive and discoloration
potential of the patient*s diet. Patients will be asked to fill this out during
month 1 , month 6 and month 12. The researcher responsible for the evaluation
will send the patients the list on line or on paper depending on the patient*s
wishes.


Follow-up per patient: Total treatment time: 1 year
Duration of intervention per patient: 1 year

A 3D printed crown will be placed on a dental implant and stay in the mouth for
one year

Burden consists of time involved. Procedure is identical to golden standard so
no higher risk involved. No direct benefit for participants.