Fracture resistance of zirconia‐based all‐ceramic crowns after bur adjustment
Abstract Intra‐oral grinding is often required to optimize occlusion of all‐ceramic restorations. The effect of burs of different grit size on the fracture resistance of veneered zirconia crowns was investigated in this study. Forty‐eight standardized zirconia copings were produced. The ceramic vene...
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| Hauptverfasser: | , , , , |
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| Dokumenttyp: | Article (Journal) |
| Sprache: | Englisch |
| Veröffentlicht: |
09 June 2017
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| In: |
European journal of oral sciences
Year: 2017, Jahrgang: 125, Heft: 4, Pages: 310-313 |
| ISSN: | 1600-0722 |
| DOI: | 10.1111/eos.12353 |
| Online-Zugang: | Verlag, Volltext: https://doi.org/10.1111/eos.12353
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| Verfasserangaben: | Rues S, Schwindling FS, Meyer A, Rammelsberg P, Schmitter M. |
| Zusammenfassung: | Abstract Intra‐oral grinding is often required to optimize occlusion of all‐ceramic restorations. The effect of burs of different grit size on the fracture resistance of veneered zirconia crowns was investigated in this study. Forty‐eight standardized zirconia copings were produced. The ceramic veneer was designed with a positive ellipsoidal defect on the palatal aspect of the crowns. To simulate adjustment of dental restorations by burs, this palatal defect was removed by use of three different diamond‐coated burs with grit sizes 46, 107, or 151 μm (fine, medium, or coarse, respectively). Each different grit size of bur was used to grind 16 crowns. All crowns were then polished and surface roughness was measured. Half of the specimens underwent thermomechanical aging (10,000 thermocycles between 6.5°C and 60°C) and 1.2 million cycles of chewing simulation (F = 108 N). A linear regression model was computed to test the effect of aging and grinding grit size at a level of significance of α = 0.05. Fracture loads increased with decreasing grit size. Grit size and aging had a significant effect on the fracture resistance of the crowns. Use of fine and coarse burs for intra‐oral adjustments resulted in different fracture resistance of veneered zirconia crowns. Coarse burs should be avoided in the final stage of grinding before polishing. Bruxism may be involved in the aetiology of myofascial neck pain. The objective of this study was to test the hypothesis that anterior and posterior neck muscles co-contract during jaw clenching. Ten test subjects developed different feedback-controlled submaximum bite forces in a variety of bite-force directions by means of bite-force transducers. The electromyographic activity of the sternocleidomastoid and supra/infrahyoidal muscles, and of the semispinalis capitis, semispinalis cervicis, and multifidi muscles was recorded by use of surface electrodes and intramuscular wire electrodes, respectively. For normalization of electromyography data, maximum voluntary contraction tasks of the neck muscles were conducted in eight different loading directions. The results confirmed co-contraction of the neck muscles in the range of 2-14% of the maximum voluntary contraction at a bite force ranging from 50 to 300 N. Significant activity differences were observed as a result of the different force levels and force directions exerted by the jaw muscles. Long-lasting tonic activation of specific neck muscles triggered by the jaw-clenching tasks was also detected. These findings support the assumption of a relationship between jaw clenching and the activity of the neck muscles investigated. The low level of co-contraction activity, however, requires further study to elucidate possible pathophysiological interactions at the level of single motor units. |
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| Beschreibung: | Gesehen am 09.05.2018 |
| Beschreibung: | Online Resource |
| ISSN: | 1600-0722 |
| DOI: | 10.1111/eos.12353 |