Microstructure of lucite glass-ceramics for dental use

a __

July 1996

__ l!iB

ELSEVIER

Materials Letters 27 (1996) 195-199

Microstructure S. Mud

of lucite glass-ceramics

a**, J. givko-BabiC

for dental use

b, K. Mehuli6 b, M. RistiC a, S. PopoviC “c, K. FuriC a

a Ruder BoSkmiC Institute, P.O. Box 1016. IOOOI Zagreb. Croutia h Faculty of Dentistry, University of Zagreb, 10000 Zagreb, Croatia ’ Department of Physics, Uniursity of Zagreb, P.O. Box 162, 10001 Zagreb, Croatia Received 14 November

1995; accepted

18 November

1995

Abstract Microstructure of lucite glass-ceramics for dental use was investigated using X-ray diffraction, FT-IR spectroscopy and laser Raman spectroscopy. Main features of the IT-IR and laser Raman spectra were similar to those of silicate glasses containing A13+, or other M3+ (M = metal), as network forming ions. Two weak IR bands at 640 and 543 cm-’ were typical of all lucite-type glass-ceramics and these bands disappeared with the conversion of glass-ceramics into the glass state. The laser Raman spectrum of lucite-type glass showed a broad band with center at = 4600 cm- ’ due to fluorescence/luminescence spectral feature with two luminescence sharp peaks at 5037 and 5007 cm- ‘. The results were compared with those obtained for different silicate glasses. Keywords:

Lucite glass-ceramics;

Dental use; IT-IR

spectra; Raman spectra

1. Introduction Glass-ceramics are polycrystalline solids which can be produced by partial crystallization of glass under controlled conditions. These materials found very different applications as engineering materials. Glass-ceramics also became important materials for dental restorations, due to their chemical inertness combined with high mechanical strength and appropriate thermal and physical properties [ 11. The properties of glass-ceramics comprised largely of P-quartz [2], alumina-glass dental composites [3] and DICOR-related glass-ceramics for dental use [4] were investigated. Recently, the dental materials industry paid special attention to lucite-type glass-ceramics

* Corresponding

author.

00167-577X/96/$12.00 Copyright SSDI 0167-577X(95)00280-4

for use in dentistry. Seven dental materials of different manufacturers were tested for their lucite content [5]. Fischer et al. [6] investigated a procedure for increasing the flexural strength of lucite dental material VMK 68. The surface of lucite glass-ceramics (IPS-EmpressR) [7] was in contact with 5% HF for different times. After etching for 120 s most of the surface layer was removed revealing the fine grained etching pattern characteristic for this type of glassceramics. Since the mechanical removal of the surface layer by grinding is not recommended, the above mentioned glass-ceramics should be etched for 120 s or longer to achieve an optimal bond strength to luting composite. Wakasa et al. [8] examined the glass-transition, dehydration, crystallization and melting temperature of several dental porcelains and kaolinite/feldspar mixtures. In the present work, the microstructural properties

0 1996 Elsevier Science B.V. All rights reserved

S. MusiC et crl./Muteriul.~

196

Table I The initial chemical composition of IPS-EmpressR glass-ceramics (wt%,) used in preparation of lucite-type dental glass-ceramics Oxide

Ingot I

Ingot 2

SiO

59.0-63.0 12.5-16.7 I o.o- 14.0 5.8-8.0 0.5-2.0 0.5-2.0 1.o-3.5 0.5-3.0 0.0-0.5

59.0-6 1.O 17.0-2 I .O 10.0-14.0 3.5-6.5 o.o- I .o o.o- I .o 0.5-2.5 o.o- 1.5 0.0-0.5

Al>& K,O Na,O BzO, CeO, cao BaO TiO,

of lucite glass-ceramics for dental use were investigated using X-ray diffraction (XRD) and vibrational spectroscopic techniques (FT-IR and laser Raman). The knowledge of microstructural properties of the glass-ceramics for dental use is particularly important in tailoring the material with better properties for this application.

2. Experimental The original dental ingots (IPS-EmpressR) were obtained by courtesy of Ivoclar-Vivadent, FL-9494 Schaan, Liechtenstein. The manufacturer of these dental materials gave the initial chemical composition of glasses shown in Table 1. The ingots were used for the preparation of the samples by the socalled “Schicht” (layering) or “Mal” (tinting) technique [9,1 O]. The description of the samples investigated in the present work, is given in Table 2. The shaping of lucite glass-ceramics for dental restorations was described in detail elsewhere [9, lo]. The samples were characterized by X-ray diffraction, FTIR spectroscopy and laser Raman spectroscopy.

Lrttrn

27 (19961 195-199

Table 2 The description

of the samples investigated

in the present work

Sample

The history of sample

Ll

Glass-ceramic ingot for “Schicht” technique, as received by Ivoclar-Vivadent Sample L 1 heated at 1300°C in air for 2 h and cooled in furnace to room temperature Glass-ceramic ingot for “Mal” technique, as received by Ivoclar-Vivadent Sample L3 heated at 1300°C in air for 2 h and cooled in furnace to room temperature Class-ceramic crown pressed for “Schicht” technique Glass-ceramic crown pressed for “Ma]” technique

L2 L3 L4 L5 L6

component is much smaller than in Ll. Lucite, cxKAISi,O,, belongs to the feldspathoid group of minerals [ 111. A high temperature polymorph l3KAISi20, (cubic form) is also known. After heating a sample of L 1 to 1300°C in air, the diffraction lines of lucite decrease in intensity (sample L2). However, the diffraction pattern of sample L4, obtained by heating sample L3 to 1300°C shows only a broad amorphous maximum, thus indicating the glass nature of sample L4. The X-ray diffraction patterns of the dental crowns made by the “Schicht” and “Mal”

I

‘I

3. Results and discussion The X-ray diffraction patterns of samples Ll to L4 are shown in Fig. 1. The diffraction pattern of sample Ll contains diffraction lines of lucite and a broad maximum due to an amorphous component. The diffraction pattern of sample L3 also corresponds to lucite, but the fraction of the amorphous

15

10 OI’J

Fig. I. The X-ray diffraction recorded at room temperature.

patterns

of samples

LI

10 L4.

S. Musk! et al./Materials

techniques corresponded to the glass-ceramics of the lucite-type. The FT-IR spectra of the samples are shown in Figs. 2 and 3. The spectrum of sample Ll is characterized by three broad bands at 1170- 1020,769-715 and 454 cm-‘. Two weak bands at 640 and 543 cm-’ are also visible. Heating of sample Ll at 1300°C in air did not cause the changes in the corresponding FlY-IR spectrum (sample L2). However, after heating of sample L3 at 1300°C in air (sample L4), the weak bands at 640 and 543 cm-’ in the FT-IR spectrum were not visible. The weak IR bands at 640 and 543 cm-’ were also observed in the FT-IR spectra of crowns (samples L5 and L6). We have observed that these two IR bands are typical for all lucite glass-ceramics. Handke and Mozgawa [12] suggested that the bands at approximately 630-540 cm-’ could be related with sixmembered ring vibrations which were observed for tridymite and kalsylite. Vibrational spectroscopic results, obtained for silica and silicate glasses, can be used as the reference in the interpretation of the vibrational spectra of lucite glass-ceramics. The precipitated (amorphous)

950

Wave

number

Fig. 2. The Fourier transform infrared L4, recorded at room temperature.

L

I cm-’ spectra of samples

Ll to

197

Letters 27 (1996) 195-199

L6

I

IO

400

950 Wave

number

I cm-’

Fig. 3. The Fourier transform infrared spectra of samples L5 and L6, recorded at room temperature.

silica showed a very strong IR band at 1090 cm-’ with a shoulder at = 1200 cm- ’ , bands at 900 and 800 cm-’ and also a very intense band at 470 cm-’ with a shoulder at = 550-600 cm-’ [13]. In the IR spectrum of pure SiO, glass film three distinct absorption bands were observed [14]. The strongest band at 1060 cm-’ was assigned to the asymmetric vibration of the silicon sublattice against the oxygen sublattice and the shoulder on the high frequency side to the symmetric vibration of the Si-0 sublattices. The weaker bands at 810 and 440 cm-’ were interpreted as bond bending motions of three-atom centers of the kind 0-Si-0 and Si-0-Si in the quasi-lattice. The structural incorporation of metal cations into SiO, glass, which possess network-forming or/and network-modifying properties, influences the corresponding vibrational spectra. Mezbacher and White [15] investigated the structure of alkaline earth aluminosilicate glasses by vibrational spectroscopy. Raman modes at = 1200, 1100, 950, 900 and 850 cm-’ were associated with silicate tetrahedra with 0, 1, 2, 3, and 4 NBOs (NBOS = non-bridging oxygens), respectively, in simple binary silicate glasses.

198

S. Musif rt al. /Muterids

The structural incorporation of tetrahedral aluminium was correlated with a shift of a high frequency envelope to longer wavelengths. The intense Raman band at 525-540 cm- ’ , assigned to Al-O symmetric stretching in CaAI,O,, may contribute to the broad mid-frequency Raman band in Mg-aluminosilicate spectrum. The strong IR band between 700 and 900 cm-‘, characterizing condensed AlO, framework units, could be assigned to the 908 cm ’ TO mode. The 102.5 cm- ’ band is close to the IR mode for pure SiO,. Bands in the mid-frequency region 500600 cm-’ were assigned to bending and rocking motions of the aluminosilicate network, while the low frequency bands (below = 400 cm-’ ) could be related with M-O vibrations (M = alkaline earth cation). Raman spectra of barium gallosilicate glasses (< 40 mol% SiO,) showed that Ga-0-Ga bonding was dominant as monitored by a single major peak at = 530 cm-’ [16]. Konijenendijk and Stevels [17] concluded that A13+ ions in alkali borosilicate glasses were present only in AlO, tetrahedra. The addition of A13+ ions caused a disappearance of the band at 780 cm-’ typical for BO, tetrahedra in six-membered borate rings. Tarte et al. [IS] observed in the IR spectrum of sinhalite, MgAIBO,, a strong band at 700 cm-’ which was assigned to AI-O vibration. Elison and Hess [ 191 investigated the incorporation of R = La, Gd or Yb, in potassium silicate glasses. The increasing RzO, concentration produced partially-polarized Raman bands at 1030, 940 and 860 cm- ’ which were assigned to the symmetric stretching modes of SiO, tetrahedra containing 1, 2 and 4 non-bridging oxygens, respectively, in which the non-bridging oxygens were coordinated primarily with R atoms. The most prominent feature in the mid-frequency region of the IR spectra was the absorption band = 770 cm ’ , presumably the counterpart of the Raman band at 780 cm ’ The relative intensity of the band near 590 cm- ’ increased with R,O, concentration. Music et al. [ 131 observed in the IR spectra of sodium borosilicate glasses doped with iron ions that the shoulder at 800 cm- ’ did not change its intensity and position, while the shoulder at 710 cm-’ appeared as a well resolved peak at the same position, on increasing the iron content. The shoulder at 710 cm-’ was also observed after incorporation of Eu3+

Letters 27 (19Y61 195-199

Fig. 4. Raman spectra of samples L2 and L4, recorded at room temperature. Samples L2 and L4 were crushed to powder before the recording of Raman spectra. ( ’ ) denotes plasma line.

in sodium borosilicate glass [20]. This effect was interpreted as a consequence of the incorporation of Fe3+ or generally M’+ (M = metal) into the borosilicate glass network. In analogy, with these results, it can be suggested that the IR band at 715 cm-’ observed in the present work is due to the incorporation of A13+ ions into the silicate network. Similarly, the IR band at 769 cm- ’ can be attributed to Si-0-Si bending vibrations. The main characteristics of laser Raman spectra

Fig. 5. The Raman spectrum of sample L4, recorded by scattering of laser beam on glass monolith at room tempereture.

S. Mud

et d/Materials

of lucite glass-ceramics for dental use can be compared with those known for aluminosilicate glasses containing M 3t as network forming ions. Fig. 4 shows laser Raman spectra of samples L2 and L4 which were crushed to powder before recording the spectra. The positions of Raman bands in these spectra are almost identical, and only slight differences in relative intensities of the bands are present. The Raman spectrum of sample L4, recorded by scattering of the laser beam on the glass monolith, is shown in Fig. 5. Two well pronounced bands at 52 and 480 cm-’ are observed. Also, the band at 1084 cm-’ with a shoulder at 954 cm-’ and the bands at 772 and 576 cm-’ are visible that are in accordance with the spectra shown in Fig. 4. The Raman spectrum of sample L4 (Fig. 5) also showed a broad band with center at - 4600 cm-’ due to a fluorescence/luminescence spectral feature with two luminescence sharp peaks at 5037 and 5007 cm ’

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[4] J.M. Tzeng, J.G. Duh, K.H. Chung and CC. Chan, J. Mater. Sci. 28 (1993) 6127. 151M. Schmid, J. Fischer, M. Salk and J. Strub, Schweiz. Monatsschr. Zahnheilk. 102 (1992) 1046. [61 J. Fischer, P. Pospiech and W. Gemet, J. Eur. Ceram. Sot. 10 (1992) 221. [71 N. Hofmann, A. Handrejk, B. Haller and B. Klaiber, Schweiz. Monatsschr. Zahnmed. 103 (1993) 1415. Bl K. Wakasa, Y. Yoshida and M. Yamaki, J. Hiroshima Univ. Dent. Sot. 26 (1994) 197. Eine neue Keramik-Technologie, [91 G. Beham, IPS-Empress: Ivoclar-Vivadent Report No. 6, Sept. 1990 (Ivoclar-Vivadent. FL-9494 Schaan, Liechtenstein, 1990) pp.3-15. [lOI Anonymus, Dental-labor 40 (1992) 67. [Ill M. Prim, G. Harlow and J. Peters, Guide to rocks and minerals, The American Museum of Natural History, (Simon and Schuster, Div. of Gulf and Western Corp., New York, 1978). 1121 M. Handke and W. Moagawa, Vib. Spectr. 5 (1993) 75. 1131 S. Music’, K. Furic’, Z. Bajs and V. MohaEek, J. Mater. Sci. 27 (1992) 5269. [141 A.S. Tenney and J. Wong, J. Chem. Phys. 56 (1972) 5516. 1151 C.I. Merzbacher and W.B. White, J. Non-Crystal. Solids 130 (1991) 18. [161CM. Shaw and J.E. Shelby, Phys. Chem. Glasses 32 (1991) 48. 1171 W.L. Konijnendijk and J.M. Stevels, J. Non-Crystal. Solids 20 (1976) 193. [I81 P. Tatte, R. Cahay, A. Rulmont and G. Werding, Spectrochim. Acta 41 A (1985) 1215. iI91 A.J.G. Ellison and P.C. Hess, J. Geophys. Res. 95 (1990) 15717. DOI S. MusiC, Z. Bajs, K. FuriC and V. MohaEek, J. Mater. Sci. Lett. 10 (1991) 889.