Page 22 - GP Fall 2020

a high-speed handpiece and a diamond bur to the study groups, which could have mini- Dr. Roya Zandparsa is
in a manner similar to what most clinicians mized the biological variation. a Clinical Professor, Post-
experience when delivering a restoration. graduate Prosthodontics and
This adjustment, along with the consequent Physiologic occlusal biting forces were not Advanced Education in
low-speed polishing, have resulted in the re- simulated in this study. However, sliding is Esthetic Dentistry, Prostho-
moval of the superficial glazing layer from an essential component of a wear testing dontic Division, Tufts Uni-
the top of all of the ceramic disks, which method, as a material is stressed in terms of versity School of Dental
may play a role in decreasing the wear of micro-fatigue only. This configuration has Medicine, Boston, MA.
their opposing cusps. 32,33 Few studies have been shown to build up more homogenous
also shown that a rough external surface is forces, and avoid the uncontrolled force im- Dr. Rabie El huni is an
Assistant Lecturer and
needed to allow for perfect glazing. When pulses seen in configurations that involve Clinical Supervisor
43
the antagonist cusp has worn the glazed top lifting of the stylus. in the Department of
layer, the cusp hits the rough surface of the Prosthodontics, Faculty of
ceramic layer, which results in increased For higher accuracy, both volumetric (3D) Dentistry at the University
enamel wear. 32,34,45,54 A meta-analysis of in and liner (2D) measurements were per- of Benghazi in Benghazi,
vitro and clinical research indicated the formed in this study (Figures 3, 4). The dif- Libya.
increase potential of certain materials for ferences in 2D and 3D rankings of studied
enamel wear of antagonist teeth and others materials could be due to the fact that 2D Dr. Hiroshi Hirayama is
highlight the between-material variations. comparisons measure only the height loss at a Professor at the Boston
53
Monolithic zirconia as well as convention- selectable points on the longitudinal cross University School of
Dental Medicine in Boston,
al porcelain restorations showed evidence section of the cusps, putting the approach MA.
of increased wear potential on the enamel. under question.
On the contrary, surface treatment, such as Laboratory studies on the contact relation-
polishing of zirconia materials, was found ship between restorative materials and the
to bear a less pronounced effect. It has opposing enamel may be helpful for pre- Mr. Mark Johnson is
53
been documented that wear increases with dicting the clinical performance accurately. the president of Texture
the increasing number of cycles. However, They may also assist researchers for stan- Technology Corporation.
24
in vitro wear test methods demonstrated an dardizing the wear test parameters so that a
even linear pattern with a steep increase in better correlation with clinical circumstanc-
wear at the initial phase and a flattening of es can be achieved. However, to date, not
the curve after. 39
many in vitro or in vivo studies are avail- References
In the present study, the force exerted by able on the comparison of opposing enamel 1. Geurtsen W, Schoeler J. A 4-year retrospective
clinical study of class I and II composite fillings. J
the cyclic loading device was not controlled wear among the currently used advanced Dent 1997;25:229-32.
during all movements of the natural enam- ceramic restorations. 2. Bergman MA. The clinical performance of ce-
el cusps. The force applied by each enamel Conclusions ramic inlays: A review. Aust Dent J 1999;44:157-88.
3. Fischer H, Marx R. Fracture toughness of dental
cusp on its opposing disk was only mea- Within the limitations of this in vitro study, ceramics: comparison of bending and indentation
sured once before the test was run, which it can be concluded that there were no stati- method. Dent Mater 2002;18:12-9.
could be considered as one of the limiting cally significant differences in liner and vol- 4. Schmalz G. The biocompatibility of non-amal-
gam dental filling materials. Eur J Oral Sci
factors. 1998;106:696-706.
umetric reduction of natural enamel cusps 5. Sobrinho LC, Cattell MJ, Glover RH, Knowles
In this study, specimens were not exposed abraded against natural enamel surfaces JC. Investigation of the dry and wet fatigue proper-
ties of three all-ceramic crown systems. Int J Prost-
to thermocycling or application of constant and those abraded against evaluated ce- hodont 1998;11:255-62.
temperature. Heat application has been ramic materials by using a newly designed 6. Kelly JR, Nishimura I, Campbell SD. Ceramics
proven to be effective in some studies, and wear-stimulating testing devices and an in dentistry: historical roots and current perspec-
tives. J Prosthet Dent 1996;75:18-32.
somewhat insignificant in others. 46-48 How- electro-mechanical cyclic loading machine 7. Dong JK, Luthy H, Wohlwend A, Schärer P.
ever, these studies tested the effect of tem- in a chamber filled with artificial saliva. All Heat-pressed ceramics: technology and strength.
perature changes on different composite ceramic systems exhibited high durability, Int J Prosthodont 1992;5:9-16.
8. McNeill C. Science and Practice of Occlusion.
materials. Further studies are required to and they were wear-friendly to opposing Carol Stream, Illinois: Quintessence Publishing Co,
assess this factor on advanced ceramic sys- natural dentition. Inc; 1997. p. 421.
tems. 9. Stober T, Dreyhaupt J, Lehnung U, Rammelsberg
Clinical Significance P. Occlusal Wear of Metal-Free Ceramic-Filled
In terms of biological spread, unfortunately The findings of the current study point to ad- Polymer Crowns after 2 Years in Service. Int J
Prosthodont 2008;21:161-5.
this study did not divide the extracted hu- vanced ceramic systems may be appropriate 10. Elmaria A, Goldstein G, Vijayaraghavan T, Le-
man teeth based on the patient’s age and choices for the fabrication of full-contour geros RZ, Hittelman EL. An evaluation of wear
when enamel is opposed by various ceramic materi-
sex. Such factors have been proven to be restorations in the oral cavity, since they are als and gold. J Prosthet Dent 2006;96:345-53.
influencing variables on the process of wear esthetically appealing, and produce oppos- 11. Krämer N, Kunzelmann KH, Taschner M, Mehl
of human tooth structure. However, cusps ing enamel wear similar to that caused by A, Garcia-Godoy F, Frankenberger R. Antagonist
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enamel wears more than ceramic inlays. J Dent Res
of extracted teeth were randomly assigned natural tooth surfaces. 2006;85:1097-100.
12. Kelly JR. Dental ceramics: Current thinking
and trends. Dent Clin North Am 2004; 48:513-30.
13. Lee A, Swain M, He L, Lyons K. Wear be-
www.nysagd.org l Fall 2020 l GP 22 havior of human enamel against lithium disilicate
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