Antagonist enamel wears more than ceramic inlays.

J Dent Res. 2006 Dec;85(12):1097-100

Authors: Krämer N, Kunzelmann KH, Taschner M, Mehl A, Garcia-Godoy F, Frankenberger R

Wear phenomena of ceramic inlays are not fully understood. The aim of the present study was to evaluate ceramic wear, antagonist enamel wear, and luting cement wear over 8 years. The two-fold null hypothesis was that there would be (1) no difference in wear behavior between ceramic and enamel, and (2) no influence of filler content of luting composites on composite wear. From 96 restorations, 36 Class II inlays from 16 participants were selected. For inlays with opposing enamel cusps (n=17), replicas of inlays and enamel were scanned with a 3-D laser scanner. Luting gaps of inlays (n=36) were analyzed with a profilometer, including 3-D data analysis. Ceramic and enamel wear increased between 4 and 8 years, with significantly higher values for enamel after 6 years (p<0.05). Luting gap wear increased continuously up to 8 years (p<0.05), with no influence of luting composites (p>0.05) and location of teeth (p>0.05).

PMID: 17122161 [PubMed - indexed for MEDLINE]

Apparent interfacial fracture toughness of resin/ceramic systems.

J Dent Res. 2006 Nov;85(11):1037-41

Authors: Della Bona A, Anusavice KJ, Mecholsky JJ

We suggest that the apparent interfacial fracture toughness (K(A)) may be estimated by fracture mechanics and fractography. This study tested the hypothesis that the K(A) of the adhesion zone of resin/ceramic systems is affected by the ceramic microstructure. Lithia disilicate-based (Empress2-E2) and leucite-based (Empress-E1) ceramics were surface-treated with hydrofluoric acid (HF) and/or silane (S), followed by an adhesive resin. Microtensile test specimens (n = 30; area of 1 +/- 0.01 mm(2)) were indented (9.8 N) at the interface and loaded to failure in tension. We used tensile strength (sigma) and the critical crack size (c) to calculate K(A) (K(A) = Ysigmac(1/2)) (Y = 1.65). ANOVA and Weibull analyses were used for statistical analyses. Mean K(A) (MPa.m(1/2)) values were: (E1HF) 0.26 +/- 0.06; (E1S) 0.23 +/- 0.06; (E1HFS) 0.30 +/- 0.06; (E2HF) 0.31 +/- 0.06; (E2S) 0.13 +/- 0.05; and (E2HFS) 0.41 +/- 0.07. All fractures originated from indentation sites. Estimation of interfacial toughness was feasible by fracture mechanics and fractography. The K(A) for the systems tested was affected by the ceramic microstructure and surface treatment.

PMID: 17062746 [PubMed - indexed for MEDLINE]

Influence of temporary cement remnant and surface cleaning method on bond strength to dentin of a composite luting system.

J Oral Sci. 2005 Mar;47(1):9-13

Authors: Kanakuri K, Kawamoto Y, Matsumura H

The aim of the current study was to evaluate the influence of polycarboxylate temporary cement remaining on the dentin surface on the bond strength of a composite luting system. An acrylic resin plate was luted to bovine dentin with a polycarboxylate temporary cement (HY-Bond Temporary Cement Hard, HYB). The temporary cement was not used for the control groups. After removing the temporary cement with an excavator, dentin specimens were divided into five groups; 1) no subsequent treatment, 2) cleaning with a rotational brush (RTB), 3) cleaning with a rotational brush and non-fluoridated flour of pumice, 4) sweeping with an air scaler, and 5) treated with a sonic toothbrush. A silane-treated ceramic disk (IPS Empress) was bonded to each dentin specimen with a composite luting system (Panavia F). Shear testing results showed that the RTB groups exhibited the highest bond strength regardless of the use of temporary cement (P < 0.05). The use of a rotational brush with water coolant is recommended to achieve ideal bond strength between the Panavia F luting system and dentin to which HYB temporary cement was primarily applied.

PMID: 15881223 [PubMed - indexed for MEDLINE]

[The study of clinical effects of IPS Empress 2 all-ceramic bridges]

Shanghai Kou Qiang Yi Xue. 2002 Dec;11(4):376-7

Authors: Huang JS, Song GB, Zhu XB, Huang Y

PMID: 14983387 [PubMed]

Effect of surface roughness on flexural strength of veneer ceramics.

J Dent Res. 2003 Dec;82(12):972-5

Authors: Fischer H, Sch&#xE4;fer M, Marx R

The strength of ceramic restorations depends on the occlusal surface roughness of the veneering porcelain, which is influenced by the final preparation. The hypothesis of the study was that roughnesses below a critical microscopic defect size--based only on fracture mechanics considerations--also affect flexural strength. The bending failure stress was evaluated on standard specimens of 4 veneer ceramics with 4 different surfaces of defined roughnesses, respectively. A linear correlation was found between roughness and failure stress. A "roughness-free" failure stress value was predicted for each tested material. This theoretical value can represent the "true" strength of the respective ceramic material. We conclude from our results that the final preparation of a ceramic restoration is critical to the strength of the material, and that ceramic veneering materials can be compared more objectively with respect to their strength by means of roughness-free strength values.

PMID: 14630897 [PubMed - indexed for MEDLINE]

Lifetime prediction of all-ceramic bridges by computational methods.

J Dent Res. 2003 Mar;82(3):238-42

Authors: Fischer H, Weber M, Marx R

There has been limited use of ceramic materials for all-ceramic posterior bridges. Major reasons are the low strength, the strength scatter, and the time-dependent strength decrease of ceramics due to slow crack growth. The objective of this study was to predict the long-term failure probability and loading capability of all-ceramic bridges (Empress 1, Empress 2, In-Ceram Alumina, and ZrO(2)) by computational techniques. The lifetimes of different bridge model designs were predicted by means of the NASA post-processor CARES. Bridges made of zirconia showed a very high mechanical long-term reliability. Empress I and InCeram Alumina seem to be insufficient as posterior bridge materials based on this prediction. The lifetime of the all-ceramic bridges can be significantly increased by improving the design in the connector area. We conclude that computational techniques can help to judge a ceramic material and a specific ceramic bridge design with respect to mechanical reliability before clinical use.

PMID: 12598556 [PubMed - indexed for MEDLINE]

R-curve behavior of dental ceramic materials.

J Dent Res. 2002 Aug;81(8):547-51

Authors: Fischer H, Rentzsch W, Marx R

Some technical ceramics exhibit the R-curve effect, i.e., an increasing fracture resistance with crack extension which is a desirable material property because more energy is necessary to propagate a microscopic crack. The objective of this study was to prove whether dental ceramic materials exhibit R-curve behavior. Nine dental ceramics were examined by the indentation-strength method. It was found that all of the tested ceramic materials exhibit a rising R-curve with crack extension. The R-curve behavior was more pronounced for the high-strength materials In-Ceram Alumina, monolithic alumina, and especially Empress 2. We conclude from our results that the mechanical behavior of a dental ceramic material can be judged more comprehensively, if the R-curve of the respective material is known.

PMID: 12147745 [PubMed - indexed for MEDLINE]

Improvement of strength parameters of a leucite-reinforced glass ceramic by dual-ion exchange.

J Dent Res. 2001 Jan;80(1):336-9

Authors: Fischer H, Marx R

An innovative dual ion-exchange process can improve the limited strength and the scatter-in-strength of technical glasses. The objective of this study was to prove whether such a two-stage ion-exchange process can also improve the limited strength and the problematic scatter-in-strength of dental ceramic materials. The first exchange was done in KNO3 on a leucite-reinforced glass-ceramic material, the second exchange in 70 mol% KNO3, 30 mol% Na NO3 at different treatment times and temperatures. The dual-exchange process approximately doubled the Weibull strength. Moreover, the Weibull modulus showed a four-fold increase, i.e., the coefficients of variation were reduced from 18.3 to 4.7%. We conclude that the dual-exchange process may help significantly to increase the clinical reliability of glass-ceramic dental restorations, because the strength and the scatter-in-strength will be substantially improved by this treatment.

PMID: 11269725 [PubMed - indexed for MEDLINE]