82 TMJ 2010, Vol. 60, No. 1
Time domain oCT in galvano-CeramiC fixed
parTial prosTheses invesTigaTions
Cezar Clonda1, Cosmin Sinescu1, Meda Negrutiu1, Mihai Rominu1,
Adrian Bradu2, George Dobre2, Adrian Gh. Podoleanu2
Introducere. Procedurile tehnologice de realizare a protezelor partiale fixe galvano-ceramice pot duce la incluziuni aerice, în straturile ceramice la
adâncimi diferite. Aceste defecte de material ar putea iniţia fracturi parţiale sau totale în părţile estetice al protezelor dentare cu detaşare acestora
de pe infrastructură. Scopul acestui studiu a fost de a folosi o metoda non-invaziva pentru a analiza protezele parţiale fixe galvano-ceramice.
Material şi metodă. 23 de proteze parţiale galvano-ceramice fixe au fost folosite pentru acest studiu. 250 de slice-uri la un interval de 20 de microni
fiecare au fost create pentru fiecare investigaţie. Sistemul de tomografie optică coerentă (OCT)utilizat în acest studiu a utilizat o lungime de undă
de1300mm. Rezultate. Ca urmare a acestui studiu, diferite defecte de material încastrate în masa ceramică cu precădere în zona cervicală a protezelor
parţiale fixe au fost identificate. Pentru fiecare defect s-au generat reconstrucţii tridimesionale. Concluzii. În concluzie, OCT este o tehnică non-invazivă
care permite detectarea imperfecţiunilor structurale în protezele fixe parțiale galvano-ceramice.
Cuvinte cheie: ceramică, tomografie optică coerentă, defecte de material, linii de fractură.
Introduction. The technologic procedures to realise galavano-ceramic fixed partial dentures can lead to aeric inclusions, at various depths in the
ceramic layers. These material defects could initiate partial or total fractures in the esthetic parts of the dentures with the detachment of these from
the infrastructure. The aim of this study was to use a non-invasive method in order to analize galvano-ceramic fixed partial dentures. Method and the
material. Twenty-three units galvano-ceramic fixed dentures have been used for this study (fig.1, 2). 250 slices at an interval of 20 microns each have
been created for each investigation. The OCT system employed in this investigation was the one using the 1300 mm wavelength. Results. As a result of
OCT investigation of the galvano-ceramic fixed partial prosthesis, various material imperfections of the ceramic mass, situated at the cervical areea, with
different volumes and forms, have been identified. 3D reconstructions were developed from bidimensional image slices. Conclusions. In conclusion,
the optical coherent tomography is a non-invasive technique that permits the detection of structural imperfections in the galvano-ceramic fixed partial
Key words: ceramic, optical coherence tomography, material defects, fracture lines.
Received for publication: Oct. 02, 2009. Revised: Nov. 22, 2009.
1Department of Dental Materials, Faculty of Dental Medicine, Victor
Babeş University of Medicine and Pharmacy of Timişoara, Romania
2University of Kent, Canterbury, UK
Dr. Cezar Clonda
Romania, Timisoara, Str. Cozia nr. 26
Surface transformations can be performed on
metals in order to combine their load-bearing properties
to the inertness and wear resistance of ceramics. In
the fixed partial prosthodontics, metals are useful
for their high fatigue strength and ductility, but they
are more sensitive to superficial corrosion and wear
than ceramics. Coating a ceramic on a metallic surface
will improve the qualities of the metallic component.
The adhesion strength and thus, the lifetime of the
Cezar Clonda et al 83
ceramic layers depend on the binding forces and on
between metal and ceramic.1 Galvano-ceramic fixed
partial prostheses have been promoted as alternatives
to conventional metal-ceramic restorations. However,
little is known about the relationship between tooth
preparation design and marginal adaptation for this
type of crown. The marginal adaptation of galvano-
ceramic crowns is affected by finish line design and
sequentially diminished by porcelain firing procedures.2
The technologic procedures to obtain galavano-
ceramic fixed partial dentures can lead to aeric
inclusions in the ceramic layers at various depths.3,4
These material defects could initiate partial or total
fractures in the esthetic layers with the detachment of
these from the infrastructure.5,6
The ceramist needs a maximum thickness of
porcelain to “move light” and create the illusion of
natural teeth.7 Galvanoceramic restorations may be
used as an alternative to all ceramic restorations or
ceramic restorations with cast metal substructures.
Electroforming technology is used with remarkable
accuracy to create a thin, yellow-gold substructure
of uniform thickness. The galvanic process involves
the electrolytic deposition of gold ions on a specially
prepared die. Advantages of this method include a
thin, warm substrate for improved esthetics, marginal
integrity of 15 to 20 μm, and a simplified, economical
procedure for fabricating substructures. This article
describes both clinical and laboratory steps for creating
The marginal designs of the preparations had much
less influence on the marginal fit of high precious alloy
castings than expected. There is considerable reason to
assume that technical but clinical parameters influence
the quality of fixed prosthodontics much more than has
been believed in the past.8 In this study, ninety volunteer
patients’ teeth which were intended for extraction due
to medical reasons were prepared prior to extraction.
Three different types of finishing line chamfer, 135°
shoulder and 90° shoulder were employed. Two each
c-silicone and pvs impressions were taken of each
tooth using either a two-stage or a one-stage putty-wash
technique. After preparation and impression taking
the teeth were extracted. Gypsum casts were poured
from the impressions and high precious alloy castings
fabricated on the dies and marginal discrepancies were
determined on the extracted teeth. The median value
of marginal discrepancies was lower than 150 μm for
all groups. The difference between the three different
preparation types was significant (H-test, p
84 TMJ 2010, Vol. 60, No. 1
obtained using the SX and SY mirror to fl y the beam
in raster fashion over the sample, while maintaining
the depth constant.14 A computer driven translation
stage (TS) is used to construct B-scan images after
stopping the frame scanner15 and moving TS along the
optical axis of the reference beam (fi g. 3).
Figure 1. Technological aspects from the galvanoforming of the fi xed
Figure 2. Ceramic layers fi red on the galvanoformed infrastructure.
Figure 3. Anatomy of an en-face OCT at 1300 nm SLD=superluminescent
diode, SX, SY: galvo-scanners; L1, L2, L3, L4: lenses: MO, MO1-3:
microscope objectives; PD1, 2: pin photo detectors; PM: polarization
controller; DA: differential amplifi er; M: fl at mirrors, TS1,2: computer
controlled translation stages; DC1.2: directional couplers.
As a result of OCT investigation of the galvano-
ceramic fi xed partial prosthesis, various material
imperfections of the ceramic mass, situated at the
cervical area, with different volumes and forms, have
been identifi ed (fi g. 4, 5). 3D reconstructions were
developed from bidimensional image slices (fi g. 6).
The defects were identifi ed in twelve bridges (60 %),
eight exhibiting defects in one unit (4 premolar, 4
molar) and four displaying defects in both premolar
and molar units.
Figure 4. 2D image of a defect investigated with Time Domain OCT (a)
combined with confocal microscopy (b).
Fracture lines at different depths in the ceramic
layers were also depicted. These fractures connect
some of the material defects. The detection of ceramic
material defects in the cervical region of galvano-
ceramic fi xed partial prostheses by optical coherence
tomography, prior to their insertion in the oral cavity,
allows their repair and thus the avoidance of short and
long term failures.
In conclusion, the optical coherent tomography is
a non-invasive technique that permits the detection of
structural imperfections in the galvano-ceramic fi xed
Cezar Clonda et al 85
Figure 5. 3D reconstruction of the defects inside the ceramic layers from
a three unit bridge.
Figure 6. 3D reconstruction of one defect inside the ceramic layer.
1. Rieu J. Ceramic formation on metallic surfaces (ceramization) for
medical applications. Clin Mat 1993;12(4):227-35.
2. Shiratsuchi H, Komine F, Kakehashi Y, et al. Infl uence of fi nish
line design on marginal adaptation of electroformed metal-ceramic
crowns. J Prost Dent 2006;95(3):237-42.
3. Sinescu C, Negrutiu ML, Marsavina L, et al. Effect of masticatory
load on crack defl ection/penetration investigated with en-face optical
coherence tomography in ceramic fi xed partial dentures. Proceed
4. Negrutiu ML, Sinescu C, Hughes M, et al.. Optical coherence
tomography and confocal microscopy investigations of dental
prostheses. Proceed SPIE 2008;7139:71390N.
5. Sinescu C, Negrutiu M, Hughes M, et al. An optical coherence
tomography investigation of materials defects in ceramic fi xed partial