Fine-grit Diamond Bur Research Articles

Influence of surface treatment on the wear of solid zirconia

Objective. Recently there has been talk of the use of full-contour solid zirconia crowns or bridge restorations with no porcelain overlay. This could be a useful solution for patients with bruxism or limited interocclusal space. However, the hardness of zirconia could affect the opposite natural dentition. The aim of this in-vitro study was to investigate the role of surface treatments on the wear of a zirconia material and its antagonist. Materials and methods. Fifty plates (10 × 10 × 1 mm) made of zirconia (LavaMulti™ ZrO2, 3M ESPE), divided into five equal groups, were sandblasted and ground under standardized conditions with a fine-grit diamond bur (Komet Brasseler, Germany) to simulate clinical conditions. Group (a) was only fired, (b) was fired and sandblasted, (c) only ground, (d) was ground and additionally polished (EVE Ceramic Polishing-Set, Pforzheim) and (e) was ground and glazed. Wear behavior was measured with a pin-on-disk apparatus ABREX against 6 mm steatite balls as antagonists (45°, 5 N load, 5000 cycles, water). The amount of wear was determined topographically using a 3-D profilometer (Concept 3D, Mahr, Germany) by measuring the height loss of the antagonist and the depth of wear Pt of the zirconia. Results. In groups (a), (b), (c) and (d) the wear value Pt could not be determined (<1 μm). Wear values of the antagonists (steatite balls) revealed a similar outcome in contact with (b), (c) and (e) in the range of 81–85 μm, whereas (e) was more abrasive but not significantly. A noticeable difference in the wear of the antagonist showed group (d) to have the smallest value. Conclusion. Polished zirconia seems to have the lowest wear on the antagonists, in contrast with the other kinds of surface treatment.

Cracking of Porcelain Surfaces Arising from Abrasive Grinding with a Dental Air Turbine

The purpose of this in vitro study was to evaluate porcelain cracking induced by abrasive grinding with a conventional dental air turbine and abrasive diamond burs. Four commercially available porcelains were examined-Wieland ALLUX, Wieland ZIROX, IPS e.max Ceram, and IPS Empress Esthetic Veneering porcelain. Sixty discs of each porcelain type were fabricated according to manufacturer instructions, followed by an auto-glaze cycle. Abrasive grinding using fine, extra-fine, and ultra-fine diamond burs was carried out, using a conventional dental air turbine. The grinding parameters were standardized with regard to the magnitude of the force applied, rotational speed of the diamond bur, and flow rate of the water coolant. A testing apparatus was used to control the magnitude of force applied during the grinding procedure. The ground surfaces were then examined under scanning electron microscope. Cracking was seen for all porcelain types when ground with the fine bur. Cracking was not seen for specimens ground with the extra-fine or the ultra-fine bur. Wet abrasive grinding with a conventional dental air turbine and fine grit diamond burs has the potential to cause cracking in the four porcelain types tested. Similar abrasive grinding with smaller grit size particles does not cause similar observable cracking.

FEA-Predicted Subsurface Damage in Micro Finishing of a Feldspar Porcelain Using Fine-Grit Dental Burs

Biocompatible ceramic structures are used to replace missing teeth, tooth structure lost to disease or trauma, and un-aesthetic healthy, tooth enamel. Recreating aesthetics and function are the two practical goals of such restorative treatment. However, the failure rate of ceramic prostheses is relatively high due to their inherent brittleness. A primary reason to premature failure of ceramic prostheses is surface and subsurface damage induced in dental intraoral finishing using dental handpieces and abrasive burs. In this paper, finite element analysis (FEA) was applied to predict quantitatively finishing-induced stress fields and subsurface damage depths in dental porcelain surfaces using fine grit diamond burs. The results indicate that while finishing using fine diamond burs diminished subsurface damage, damage depths of smaller than 20 m remained depending on the bur depth of cut and feed rate. In the FEA modeling, the minimum damage was obtained under very fine finishing conditions.

Resin–dentin bond strength as related to different surface preparation methods

To determine the microtensile bond strength and micromorphological structures on bonding of two adhesives (OptiBond FL and Clearfil SE Bond) to dentin surfaces ground with different preparation methods. Extracted human molars were ground flat to expose mid-coronal occlusal dentin surface with one of six preparation methods--P120 grit SiC paper, P400 grit SiC paper, P1200 grit SiC paper, medium grit diamond bur, fine grit diamond bur, and carbide bur. Each of the adhesives was used to bond resin-based composite to the dentin surface. Dumbbell-shaped specimens were fabricated and microtensile bond strengths were determined. The subsequent debond pathway and micromorphological structures of representative dentin surfaces were examined under scanning electron microscopy. ANOVA and survival analyses were performed both assuming independence from and accommodating for within-tooth correlation between specimens. By ignoring the correlations between specimens, statistical analyses revealed no surface preparation effect on microtensile bond strength for each adhesive system. However, effects of surface preparation method on dentin adhesion of both adhesives were detected when accommodating for any within-tooth specimen correlations. Overall, carbide bur group showed the lowest bond strength for both OptiBond FL and Clearfil SE Bond. Dentin surfaces ground with diamond burs tended to present more compact smear layer than those ground with SiC papers and, subsequently, produced an effect on resin-dentin bond strengths. The dentin surface preparation method affects smear layer characteristics and dentin surface topography and, therefore affects resin-dentin bond strength. Smear layer denseness, more so than thickness, may compromise bonding efficacy of adhesives, especially of the self-etch systems.

In vivo evaluation of three cleansing techniques for prepared abutment teeth

Statement of Problem. Residual provisional cement and debris on prepared teeth may have the potential to negatively influence the performance of the definitive luting agent. Purpose. This in vivo study quantified the adherence of provisional cement to abutment teeth prepared with 1 of 2 textures (coarse or fine) and cleaned with 1 of 3 common cleansing techniques. Material and Methods. One hundred ten provisional restorations in 22 patients were luted to maxillary anterior abutment teeth. The teeth were prepared for complete veneer restorations with either a coarse-grit diamond bur or a coarse-grit diamond bur followed by a fine-grit diamond bur. After removal of the restoration, abutment teeth were randomly cleansed with either a No. 23 dental explorer and air-water spray, a prophy cup with fine flour pumice, or a cotton pellet soaked in chlorhexidine gluconate, 0.12%. After the abutments were cleansed, they were evaluated intraorally under a light microscope (magnification, ×64) by 2 blinded examiners. The teeth were given scores based on the number of specks of residual cement found on the surface after the cleansing techniques were performed. Pearson correlation coefficients (α=.96), 3-way analysis of variance, and post hoc Scheffé tests (P<.05) were used to analyze the data. Results. As determined with Pearson correlation coefficient, the interexaminer reliability was α=.96. Three-way analysis of variance revealed significant effects for the cleansing techniques but not for the interaction between cleansing techniques and preparation texture. A post hoc Scheffé test showed that the pumice cleansing technique (1.8 specks/tooth) was significantly better than the explorer or the cotton pellet/chlorhexidine gluconate technique (3.6 and 3.5 specks/tooth, respectively) (P<.05). Conclusion. Within the limitations of this study, abutment teeth cleansed with a prophy cup and flour pumice exhibited the least amount of residual provisional cement. (J Prosthet Dent 2002;88:437-41.)

An in vitro investigation on the loss of root substance in scaling with various instruments

There are differing opinions as to the extent to which root cementum has to be removed during root surface instrumentation over and above that of the debridement of plaque and calculus. Similarly, the amount of tooth material removed by individual instruments is also unclear, but a trend towards less damaging methods of root surface debridement has evolved in recent years. The purpose of this in vitro study was to determine the amounts of root substance removed by 4 different methods of instrumentation, hand curette, ultrasonic scaler, airscaler and fine grit diamond bur. Measurement of tooth substance loss was carried out with a specially constructed measuring device at 360 sites on 90 mandibular incisors following 12 working strokes with a clinically appropriate force of application. Only a thin layer of root substance (11.6 microns) was removed by the ultrasonic scaler, compared to the much greater losses sustained with the airscaler (93.5 microns), the curette (108.9 microns) and the diamond bur (118.7 microns).