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Wear behaviour of monolithic zirconia crowns – clinical results
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d e n t a l m a t e r i a l s 3 0 S ( 2 0 1 4 ) e1–e180
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Orthodontic loading influence on root resorption susceptibility: Finite element analysis
Wear behaviour of monolithic zirconia crowns – clinical results
Roscoe 1,∗ ,
M.G. J.B.C. P.M. Cattaneo 2
Meira 1 ,
M.
Dalstra 2 ,
1
University of Sao Paulo, Biomaterials and Oral Biology Department, Sao Paulo, Brazil 2 Aarhus University, Department of Orthodontics, Aarhus, Denmark Purpose: (1) To compare the strains and the stresses values within the periodontal ligament (PDL) following the application of three types of loading regimes: pure intrusion (PI), buccal tipping (BT), and intrusion combined with buccal tipping (IT). (2) To verify the correlation between these results and the available clinical findings regarding root resorption (RR) occurrence. Methods and materials: A tridimensional finite element (FE) model was constructed with axisymmetric geometry to simulate the tooth root. The model includes root, cementum, PDL, cortical and trabecular bone. All materials were considered linear elastic, except the PDL that was modeled as a nonlinear hypo-elastic material. Based on the literature that evaluates the influence of force magnitude on the RR occurrence, the loading magnitude was defined: PI simulated by applying 25-g or 225-g of axial loading; BT by applying the same force magnitudes 90◦ to the long axis; IT combining PI and BT. The displacement of the root within the PDL was calculated as percentage of the original thickness of the PDL to verify the amount of PDL deformation. Strains and stresses at the nodes at the PDL–cementum interface at cervical, middle and apical thirds were also assessed. Results: For the PI movement, the root displaced vertically within the PDL uniformly (9% of the PDL total thickness for 25-g and 36% for 225-g). For the PI and BT, the maximum root displacement occurred at the cervical buccal third (8% and 13% for 25-g, and 33% and 57% for 225-g; respectively). Higher forces generated higher values of strains and stresses within the PDL. For the PI movement, the apical and middle thirds showed higher values of strains than the cervical third. For the BT, the apical and cervical thirds showed higher values of strains than the middle third. For the IT, the cervical and middle thirds at the buccal side showed the highest values of strain. The maximum stresses were seen at the cervical third for the PI, and at the cervical and buccal lingual sides for the BT and IT (tensile sides). Conclusion: As expected, higher orthodontic forces generated higher values of strains and stresses within the PDL. From clinical findings, it is possible to verify that the RR occurred mostly in areas under compression. Therefore, our results support that RR might be related with changes of the blood supply associated with the constriction of the PDL at the compression sides. Keywords: Finite element analysis; Periodontal ligament; Root resorption http://dx.doi.org/10.1016/j.dental.2014.08.203
T. Stober 1,∗ , J.L. Bermejo 2 , S. Rues 1 , P. Rammelsberg 1 , M. Schmitter 1 1
Department of Prosthodontics, University Hospital Heidelberg, Germany 2 Institute of Medical Biometry and Informatics, University Hospital Heidelberg, Germany Purpose: To quantify enamel wear caused by antagonistic monolithic zirconia crowns, and to quantify the wear of the zirconia crowns by opposing natural dentition. Methods and materials: Monolithic zirconia crowns were placed in 20 patients requiring full molar crowns. For evaluation of wear, vinyl polysiloxane impressions and gypsum casts were made after crown cementation and at 12-months follow-up. Mean and maximum wear of the occlusal contact areas of the crowns, of their natural antagonists, and of two contralateral natural antagonists were measured by 3D laserscanning methods. Wear differences were investigated by use of two-sided paired Student t-tests and by linear regression analysis. Results: After 12 month mean vertical loss (maximum vertical loss in parentheses) of enamel caused by antagonistic monolithic zirconia crowns was 41 (143) m, whereas for the contralateral natural antagonists 14 (68) m and 13 (60) was found. The zirconia crowns showed occlusal wear of only 12 (52) m. Both mean and maximum enamel wear were significantly different between the antagonists of the zirconia crowns and the contralateral control teeth. Activity of the masseter muscle at night (bruxism) measured by use of a disposable electromyographic device were identified as confounders which significantly affected wear. Conclusion: Under clinical conditions monolithic zirconia crowns caused greater wear of opposed enamel than natural antagonistic teeth. The amount of enamel wear after 12 months was comparable with, or even lower than, that caused by other ceramic materials in previous studies. Therefore, clinical use of monolithic zirconia crowns seems justifiable. Keywords: Wear; Zirconia crowns; Zirconium oxide http://dx.doi.org/10.1016/j.dental.2014.08.204 204 12-Months clinical evaluation of composite restorations in smoking patients L.D. Carvalho ∗ , G.C. Lopes, R.G. Machado
Department of Operative Dentistry, Federal University of Santa Catarina, Florianópolis, Brazil Purpose: To evaluate the clinical performance of composite restorations in non-carious cervical lesions performed in smokers and non-smoking patients with different adhesive strategies. Methods and materials: Among the 152 selected lesions, four experimental groups were formed according with the
d e n t a l m a t e r i a l s 3 0 S ( 2 0 1 4 ) e1–e180
202
203
Orthodontic loading influence on root resorption susceptibility: Finite element analysis
Wear behaviour of monolithic zirconia crowns – clinical results
Roscoe 1,∗ ,
M.G. J.B.C. P.M. Cattaneo 2
Meira 1 ,
M.
Dalstra 2 ,
1
University of Sao Paulo, Biomaterials and Oral Biology Department, Sao Paulo, Brazil 2 Aarhus University, Department of Orthodontics, Aarhus, Denmark Purpose: (1) To compare the strains and the stresses values within the periodontal ligament (PDL) following the application of three types of loading regimes: pure intrusion (PI), buccal tipping (BT), and intrusion combined with buccal tipping (IT). (2) To verify the correlation between these results and the available clinical findings regarding root resorption (RR) occurrence. Methods and materials: A tridimensional finite element (FE) model was constructed with axisymmetric geometry to simulate the tooth root. The model includes root, cementum, PDL, cortical and trabecular bone. All materials were considered linear elastic, except the PDL that was modeled as a nonlinear hypo-elastic material. Based on the literature that evaluates the influence of force magnitude on the RR occurrence, the loading magnitude was defined: PI simulated by applying 25-g or 225-g of axial loading; BT by applying the same force magnitudes 90◦ to the long axis; IT combining PI and BT. The displacement of the root within the PDL was calculated as percentage of the original thickness of the PDL to verify the amount of PDL deformation. Strains and stresses at the nodes at the PDL–cementum interface at cervical, middle and apical thirds were also assessed. Results: For the PI movement, the root displaced vertically within the PDL uniformly (9% of the PDL total thickness for 25-g and 36% for 225-g). For the PI and BT, the maximum root displacement occurred at the cervical buccal third (8% and 13% for 25-g, and 33% and 57% for 225-g; respectively). Higher forces generated higher values of strains and stresses within the PDL. For the PI movement, the apical and middle thirds showed higher values of strains than the cervical third. For the BT, the apical and cervical thirds showed higher values of strains than the middle third. For the IT, the cervical and middle thirds at the buccal side showed the highest values of strain. The maximum stresses were seen at the cervical third for the PI, and at the cervical and buccal lingual sides for the BT and IT (tensile sides). Conclusion: As expected, higher orthodontic forces generated higher values of strains and stresses within the PDL. From clinical findings, it is possible to verify that the RR occurred mostly in areas under compression. Therefore, our results support that RR might be related with changes of the blood supply associated with the constriction of the PDL at the compression sides. Keywords: Finite element analysis; Periodontal ligament; Root resorption http://dx.doi.org/10.1016/j.dental.2014.08.203
T. Stober 1,∗ , J.L. Bermejo 2 , S. Rues 1 , P. Rammelsberg 1 , M. Schmitter 1 1
Department of Prosthodontics, University Hospital Heidelberg, Germany 2 Institute of Medical Biometry and Informatics, University Hospital Heidelberg, Germany Purpose: To quantify enamel wear caused by antagonistic monolithic zirconia crowns, and to quantify the wear of the zirconia crowns by opposing natural dentition. Methods and materials: Monolithic zirconia crowns were placed in 20 patients requiring full molar crowns. For evaluation of wear, vinyl polysiloxane impressions and gypsum casts were made after crown cementation and at 12-months follow-up. Mean and maximum wear of the occlusal contact areas of the crowns, of their natural antagonists, and of two contralateral natural antagonists were measured by 3D laserscanning methods. Wear differences were investigated by use of two-sided paired Student t-tests and by linear regression analysis. Results: After 12 month mean vertical loss (maximum vertical loss in parentheses) of enamel caused by antagonistic monolithic zirconia crowns was 41 (143) m, whereas for the contralateral natural antagonists 14 (68) m and 13 (60) was found. The zirconia crowns showed occlusal wear of only 12 (52) m. Both mean and maximum enamel wear were significantly different between the antagonists of the zirconia crowns and the contralateral control teeth. Activity of the masseter muscle at night (bruxism) measured by use of a disposable electromyographic device were identified as confounders which significantly affected wear. Conclusion: Under clinical conditions monolithic zirconia crowns caused greater wear of opposed enamel than natural antagonistic teeth. The amount of enamel wear after 12 months was comparable with, or even lower than, that caused by other ceramic materials in previous studies. Therefore, clinical use of monolithic zirconia crowns seems justifiable. Keywords: Wear; Zirconia crowns; Zirconium oxide http://dx.doi.org/10.1016/j.dental.2014.08.204 204 12-Months clinical evaluation of composite restorations in smoking patients L.D. Carvalho ∗ , G.C. Lopes, R.G. Machado
Department of Operative Dentistry, Federal University of Santa Catarina, Florianópolis, Brazil Purpose: To evaluate the clinical performance of composite restorations in non-carious cervical lesions performed in smokers and non-smoking patients with different adhesive strategies. Methods and materials: Among the 152 selected lesions, four experimental groups were formed according with the