Effect of industrial scanner and framework

1. Good morning

2. Effect of industrial scanner and
framework material interaction on
the marginal gaps of CAD-CAM
complete arch implant frameworks
Yilmaz et al
2023

3. Introduction

4. • Measuring marginal gaps can be challenging because of the bulk of
the frameworks, which may prevent the marginal gaps being
detected, particularly when they are located subgingivally.
• The triple-scan technique, which is based on optical or tactile
scans, has been used to evaluate the marginal gaps of single- and
multiple-unit restorations.

5. • An industrial CT scanner has been used to scan frameworks and
measure the marginal gap in vitro, with a different working
mechanism compared with structured-light scanners with the triple-
scan technique.
• Industrial CT scanners can capture the interfaces with 1 scan,
without the need to scan and stitch objects together.

6. AIM
To investigate the industrial scanner
(structured-light or CT) and framework material
interaction on the measured marginal gaps of
implant-supported fixed complete arch CAD-
CAM Ti and PMMA frameworks

7. MATERIALS AND METHODS

10. • A screw-retained complete arch acrylic resin prototype with
abutment-level titanium copings fitted on conical multi-unit
abutments was fabricated on a maxillary typodont model.
• 2 straight implants parallel to each other (4.3×13 mm; Nobel Biocare
AG) in the anterior region and 2 implants with a 30-degree distal tilt
in the posterior region.

11. • Straight abutments were attached to the anterior implants and 30-
degree angled abutments to the posterior implants.
• The framework was sectioned and reconnected with the same
acrylic resin to compensate for polymerization shrinkage.

12. • A 3D laboratory scanner was used to digitize the model with titanium
scan bodies.
• The resin prototype was tightened to 15Ncm on each of the 4 screw-
retained abutments to generate an accurately fitting virtual 3D CAD
framework in an STL file.
• A 5-axis milling unit was used to mill 5 frameworks from PMMA and
according to the manufacturer’s instructions.

13. • The frameworks were placed on the typodont model, and the 1-
screw test was performed by tightening the prosthetic screw on the
left molar abutment and right canine using a hand screw driver.
• After further tightening of the prosthetic screw to 15 Ncm at the
terminal location (TL) with a calibrated torque wrench, the screw on
the right canine was unscrewed, and the 3D marginal discrepancy of
frameworks was evaluated by using a CT scanner.

14. • Marginal gaps were measured by using planes created from scan
data of the mating surfaces at the abutment-framework interface of
the left canine (abutment #2), right canine (abutment #3), and right
first molar (abutment #4) locations.
• Marginal discrepancy at the TL (location #1) was ignored because
there was a screw and the STL bridging took place when the gap
was not large enough to distinguish.

15. • The marginal gap was evaluated by using the standard method for
measuring a distance between 2 planes and involved the use of a
reference plane.
• The 3D marginal discrepancy reported was the length of this line.
• The fixture surfaces were considered as the reference plane in this study

16. • Each framework was also scanned by a structured-light scanner.
• Then, the framework was removed from the model, and its occlusal
and gingival surfaces were separately scanned.
• The merged framework scan was imported along with the key scan
into the model scan to bring all scans into a single-coordinate system.

17. • To measure the gaps between the merged frame scan and the
master model scan at the abutment-framework interface, 4 sectional
cuts were made from an occlusal perspective at abutment positions
2, 3, and 4.
• Eight different views were used for gap measurements, and the gaps
were averaged at each abutment site by using a software program

18. The mean 3D marginal gap values for both
PMMA and Ti frameworks from each
industrial-grade scanner (structured-light
versus CT) were calculated for each
location (abutments 2, 3, and 4) and overall.

22. • The structured-light scanner’s precision was higher than that of the
CT scanner when titanium frameworks were scanned.
• The CT scanner’s precision was higher when scanning PMMA
frameworks than when scanning Ti frameworks

23. • No significant effect of scanner, material, or their interaction was
found on the marginal gaps at the canine sites.
• The titanium framework gaps detected by using the computed
tomography scanner were greater than those detected by using the
structured-light scanner at the right molar site and overall.

24. CONCLUSION

25. 1. Measured marginal gaps depended on the material and abutment
location.
2. The overall measured marginal gaps of the titanium framework
varied in the scans from the 2 scanners and also in the scan at the
abutment most distant from the tightened prosthetic screw.
3. The structured-light scanner may be preferred over the CT scanner
for the evaluation of gaps at the interfaces because of the lower
precision observed with the Ti framework scans from the CT scanner.

26. MERITS
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27. DEMERITS
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28. CROSS REFERENCE 1

29. Marginal discrepancy of CAD-CAM
High density polymer frameworks
compared to conventional Titanium
and Zirconia frameworks.
Burak et al
2018

30. AIM
The purpose of this in vitro study was to
evaluate the marginal discrepancy of CAD-CAM
HDP complete-arch implant-supported screw-
retained fixed prosthesis frameworks and
compare them with conventional titanium (Ti)
and zirconia (Zr) frameworks.

31. MATERIALS AND METHODS

32. • A screw-retained complete-arch acrylic resin prototype with multi-
unit abutments was fabricated on a typodont model with 2 straight
implants in the anterior region and 2 implants with a 30-degree
distal tilt in the posterior region.
• A 3D laboratory laser scanner was used to digitize the typodont
model with scan bodies and the resin prototype to generate a
virtual 3D CAD framework.

33. • A CAM milling unit was used to fabricate 5 frameworks from HDP,
Ti, and Zir blocks.
• The 1-screw test was performed by tightening the prosthetic screw
in the maxillary left first molar abutment (terminal location) when
the frameworks were on the typodont model.
• The marginal discrepancy of frameworks was evaluated using an
industrial computed tomographic scanner and a 3D volumetric
software.

34. • The 3D marginal discrepancy at the abutment-framework interface
of the maxillary left canine (L1), right canine (L2), and right first
molar (L3) sites was measured.
• The mean values for 3D marginal discrepancy were calculated for
each location in a group with 95% confidence limits.

36. • The 3D marginal discrepancy measurement was possible only for
L2 and L3 because the L1 values were too small to detect.
• The mean discrepancy values at L2 were 60 μm for HDP, 74 μm for
Ti, and 84 μm for Zir.
• At the L3 location, the mean discrepancy values were 55 μm for
HDP, 102 μm for Ti, and 94 μm for Zir.

37. • There was no statistically significant overall effect for implant
location or an interaction of location and material.
• Statistically significant differences were found overall between HDP
and the other 2 materials.

38. CONCLUSION

39. • When the tested materials were used with the CAD-CAM system,
the 3D marginal discrepancy of CAD-CAM HDP frameworks was
smaller than that of titanium or zirconia frameworks.
• Absolute passive fit was not achieved for the CAD-CAM-fabricated
complete-arch fixed implant-supported frameworks made of HDP
resin, Ti or Zr on 4 implants.
• The marginal discrepancy of the frameworks was not different at
different implant locations (P=.072).

40. CROSS REFERENCE 2

41. Effect of feldspathic porcelain
layering on the marginal fit of
zirconia and titanium complete-arch
fixed implant-supported frameworks
Yilmaz et al
2018

42. AIM
The purpose of this in vitro study was to
evaluate the effect of porcelain layering on the
marginal fit of CAD-CAM–fabricated complete-
arch implant-supported, screw-retained FDPs
with pre-sintered zirconia frameworks
compared with titanium.

43. MATERIALS AND METHODS

44. • An auto-polymerizing acrylic resin fixed CD framework prototype
was fabricated on an edentulous typodont master model (all-on-4
concept)
• There were 2 straight implants in the anterior and 2 distally tilted
internal-hexagon implants in the posterior with multiunit abutments
bilaterally in canine and first molar locations.

45. • A 3D laser scanner was used to digitize the prototype and the
master model by using scan bodies to generate a virtual 3D CAD
framework.
• Five pre-sintered zirconia and 5 titanium frameworks were
fabricated using the CAM milling unit.
• The 1-screw test was applied by fixing the frameworks at the
location of the maxillary left first molar abutment, and an industrial
CT scanner was used to scan the framework-model complex to
evaluate the passive fit of the frameworks on the master model.

46. • The scanned data were transported in STL.
• 3D virtual assessment of the marginal fit was performed at the
abutment-framework interface at the maxillary right canine (gap 3)
and right first molar (gap 4) abutments without prosthetic screws.
• The facial or buccal aspects of the teeth on frameworks were
layered with corresponding porcelain and CT-scanned again using
the same protocol.

47. • Marginal fit measurements were made for 4 groups: titanium (Ti)
(control), porcelain-layered titanium (Ti-P) (control), zirconia (Zir),
and porcelain-layered zirconia (Zir-P).
• 3D discrepancy mean values were computed and calculated, and
the results were analyzed

49. • The 3D fit was measured at gap 3 and gap 4.
• Statistically significant differences in mean 3D discrepancies were
observed between Zir-P (175 μm) and Zir (89 μm) and between Zir-P
and Ti-P (71 μm)

50. CONCLUSION

51. • Porcelain layering had a significant effect on the marginal fit of
CAD-CAM fabricated complete arch implant supported, screw-
retained FDPs with partially sintered zirconia frameworks.
• 3D marginal discrepancy mean values for all groups were within
clinically acceptable limits (<120 μm), except for the layered
zirconia framework.