Papers by Author: Ling Yin

Abstract: An experimental investigation was performed to study the wear of a promising dental ceramic, i.e., machinable lithium disilicate glass ceramic, under lubrication conditions, in particular, to examine effects of the surface finish and applied load on wear. Our previous work has shown that a fine finish in a dry condition did not necessarily translate to the lowest wear volume due to changes in the dominant wear mechanisms. This study tested the ceramic specimens with four average surface roughness values of S_a = 143 nm, 217 nm, 353 nm, and 692 nm on a reciprocating sliding friction rig against alumina balls with two applied forces of 5 N and 25 N in a bath of distilled water. Comparing with the results obtained in the dry conditions, this study shows that surface roughness of approximately 200 nm may be suitable for surface preparation of crowns made from the material in the wet and dry wear conditions in the oral environment.

Abstract: Intraoral adjustment of ceramic prostheses involving cutting process is a central procedure in restorative dentistry because the quality of ceramic prostheses depends on the cutting process. In this paper, an artificial neural network (ANN) model was developed for the first time to forecast the dynamic forces in dental cutting process as functions of clinical operational parameters. The predicted force values were compared with the measured values in in vitro dental cutting of porcelain prostheses obtained using a novel two-degrees-of-freedom computer-assisted testing apparatus with a high-speed dental handpiece and diamond burs. The results indicate that there existed nonlinear relationships between the cutting forces and clinical operational parameters. It is found that the ANN-forecasted forces were in good agreement with the experiment-measured values. This indicates that the established ANN model can provide insights into the force-related process assessment and forecast for clinical dental cutting of ceramic prostheses.

Abstract: This work aimed to establish a suitable procedure for establishing wear particle hardness and to investigate if the hardness of articular cartilage wear particles increases with increasing grades of osteoarthritis. To achieve the goals a selection of fresh sheep knee joints were obtained and consequently worn in a specially designed wear simulator. Wear particles were then removed from the joint using a syringe and prepared for hardness testing. In order to test the hardness of the wear particle samples nanoindentation was used. Once completed statistical analyses and correlation analyses were performed in order to find any relationships present. This was the first time that the hardness of the wear particles was tested and studied. As a result of the tests performed a general relationship between wear particle hardness and osteoarthritis grade was able to be determined. It was also determined that further work needed to be conducted on the experimental procedure to increase the accuracy of the results obtained.

Abstract: Bone biopsy is a common procedure in bone disease diagnoses, therapies and research. In this procedure, bone biopsy needles are inserted into bone tissues. Although needle insertion into bone is often essential for the diagnosis of bone diseases, the hard tissue-needle interactions are not quantitatively understood. In this paper, we describe a quantitative assessment of forces involved in insertion of healthy trabecular bone using clinically applied Jamshidi CrownTM bone biopsy needles of gauge 8 (4-mm diameter). The measured forces were related to the insertion depths up to 25 mm and insertion rates of 1 mm/s to 5 mm/s. At the initial insertion stage, a clear linear force-depth relation was measured. With the increase of the insertion depth, the forces increased nonlinearly. In the final stage of insertion, the forces increased much more quickly at the lower insertion rate than that at the higher insertion rate. The maximum insertion force reached approximately 1000 N when the insertion depth reached 25 mm at the insertion rate of 1 mm/s.

Abstract: 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.

Abstract: Dental ceramics are attractive in restorative dentistry due to their approximations to the appearances and functions of human teeth with which we chew our food. Chewing processes generally occur at cyclic loading range of 70–800 N and up to 1400 cycles per day. Most fatigue studies on dental ceramics were conducted at the loads up to 250 N. These loads are much smaller than the maximum bite forces of 500–700 N and tooth clench or grinding forces of up to 800 N. This paper reports on an investigation of fatigue response of a dental porcelain at the higher end of the load range impacted by a tungsten carbide ball. The responses of surface roughness and contact stress to the applied loads and cyclic numbers were quantitatively studied. The results show that the cyclic numbers had significant influences on both average surface roughness Ra and maximum roughness Rmax (ANOVA, p<0.05). However, the applied loads did not significantly affect Ra and Rmax values (ANOVA, p>0.05). It is also found that the contact stress significantly reduced with the cycles (ANOVA, p<0.05) but did not show a significant change with the applied loads (ANOVA, p>0.05).

Abstract: The application of abrasive technology in dentistry dates from 7000–9000 years. How does this ancient technology affect our modern society where the elderly population needs extensive dental care and ageing well and ageing productively is our first priority Many patients prefer tooth-colored, all ceramics restorations fabricated by dental CAD/CAM systems for reasons of esthetics, biocompatibility and high efficiency. In spite of the advantages of all-ceramic restorations, ceramic prostheses have not always performed as predicted or desired. Catastrophic fracture has been the most frequently reported reason for failure of all-ceramic restorations. This paper gives a brief review on abrasive technology in ceramic restorative dentistry to highlight problems to be solved by our abrasive technology community.