Publications (3)2.78 Total impact
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Article: A comparison of the porcelain fracture resistance of screw-retained and cement-retained implant-supported metal-ceramic crowns.
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ABSTRACT: The presence of a screw opening on the occlusal surface of implant-supported metal-ceramic crowns may decrease the porcelain fracture resistance and shorten the longevity of the crown. The purpose of this study was to compare the porcelain fracture resistance between screw-retained and cement-retained implant-supported metal-ceramic crowns and to assess whether narrowing the occlusal table or offsetting the screw-access opening affects fracture resistance. Forty standardized maxillary premolar metal copings were fabricated with a Pd-Ga alloy (Protocol) on an implant abutment. Copings were divided into 4 groups (n=10): Group 1 (Screw-retained; occlusal surface buccolingual width=5 mm), screw access opening placed in the center of the occlusal surface; Group 2 (Screw-retained; occlusal surface buccolingual width=5 mm), screw access opening positioned 1 mm offset from the center of the occlusal surface toward the buccal cusp; Group 3 (Cement-retained; occlusal surface buccolingual width=5 mm), copings were not altered; and Group 4 (Cement-retained; occlusal surface buccolingual width=4 mm), copings designed to have a reduced occlusal surface width. All castings were finished with aluminum oxide stones and airborne-particle abraded. Two layers of opaque and dentin porcelain were applied, respectively, on all specimens, which were then glazed. The crown specimens were positioned in a custom testing apparatus and vertically loaded on the middle of the occlusal surface with a universal testing machine at a crosshead speed of 0.5 mm/min until fracture. Mean values of load at fracture (Kgf) were calculated in each group and compared with a 1-way analysis of variance and Tukey's Studentized test (alpha=.05). Mean values of loads required to fracture the crowns were as follow: Group 1: 95.01+/-46.6 Kgf; Group 2: 108.61+/-57.9 Kgf; Group 3: 390.94+/-151.3 Kgf; Group 4: 380.04+/-211.8 Kgf. Groups 1 and 2 required a significantly lower force to fracture the crowns compared with Groups 3 and 4 (P=.0001). Comparing Group 1 with 2 (P=.9) and Groups 3 with 4 (P=.6), no significant differences were noted. Screw-retained implant-supported metal-ceramic crowns demonstrated a significantly lower porcelain fracture resistance than cement-retained crowns. Placing the screw access opening 1 mm offset from the center of the occlusal surface did not result in lower fracture resistance. Cement-retained crowns with 4- or 5-mm buccolingual width of the occlusal surface showed similar porcelain fracture resistance.Journal of Prosthetic Dentistry 07/2004; 91(6):532-7. · 1.32 Impact Factor -
Article: Use of imaging guides in preimplant tomography.
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ABSTRACT: The objective of this study was to quantify the variation in use and type of imaging guides used by community-based specialists and general practitioners during dental implant treatment planning phases. The specific aim of this study was to test the hypothesis that specialists are more likely to use some form of cross-sectional imaging in conjunction with imaging guides during the preoperative assessment of dental implant procedures. Records from 630 patients with implants (1640 implants) referred for cross-sectional tomography were reviewed. Imaging guide type and implant sites were noted. The distribution of referring dentists by specialty was as follows: general practitioners (42.2%), periodontists (35.1%), oral and maxillofacial surgeons (13.3%), and prosthodontists (7%). Of patients referred for tomograms, 52% were referred without a surgical guide. Specialists ordered tomograms in conjunction with imaging guides more often than did general practitioners. Prosthodontists and periodontists preferred to use more restrictive guides than did general practitioners or oral and maxillofacial surgeons.Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontics 05/2002; 93(4):483-7. · 1.46 Impact Factor -
Article: A comparison of the porcelain fracture resistance of screw-retained and cement-retained implant-supported metal-ceramic crowns
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ABSTRACT: Statement of problemThe presence of a screw opening on the occlusal surface of implant-supported metal-ceramic crowns may decrease the porcelain fracture resistance and shorten the longevity of the crown.PurposeThe purpose of this study was to compare the porcelain fracture resistance between screw-retained and cement-retained implant-supported metal-ceramic crowns and to assess whether narrowing the occlusal table or offsetting the screw-access opening affects fracture resistance.Material and methodsForty standardized maxillary premolar metal copings were fabricated with a Pd-Ga alloy (Protocol) on an implant abutment. Copings were divided into 4 groups (n=10): Group 1 (Screw-retained; occlusal surface buccolingual width=5 mm), screw access opening placed in the center of the occlusal surface; Group 2 (Screw-retained; occlusal surface buccolingual width = 5 mm), screw access opening positioned 1 mm offset from the center of the occlusal surface toward the buccal cusp; Group 3 (Cement-retained; occlusal surface buccolingual width = 5 mm), copings were not altered; and Group 4 (Cement-retained; occlusal surface buccolingual width = 4 mm), copings designed to have a reduced occlusal surface width. All castings were finished with aluminum oxide stones and airborne-particle abraded. Two layers of opaque and dentin porcelain were applied, respectively, on all specimens, which were then glazed. The crown specimens were positioned in a custom testing apparatus and vertically loaded on the middle of the occlusal surface with a universal testing machine at a crosshead speed of 0.5 mm/min until fracture. Mean values of load at fracture (Kgf) were calculated in each group and compared with a 1-way analysis of variance and Tukey's Studentized test (α=.05).ResultsMean values of loads required to fracture the crowns were as follow: Group 1: 95.01±46.6 Kgf; Group 2: 108.61±57.9 Kgf; Group 3: 390.94±151.3 Kgf; Group 4: 380.04±211.8 Kgf. Groups 1 and 2 required a significantly lower force to fracture the crowns compared with Groups 3 and 4 (P=.0001). Comparing Group 1 with 2 (P=.9) and Groups 3 with 4 (P=.6), no significant differences were noted.ConclusionsScrew-retained implant-supported metal-ceramic crowns demonstrated a significantly lower porcelain fracture resistance than cement-retained crowns. Placing the screw access opening 1 mm offset from the center of the occlusal surface did not result in lower fracture resistance. Cement-retained crowns with 4- or 5-mm buccolingual width of the occlusal surface showed similar porcelain fracture resistance.The Journal of Prosthetic Dentistry.
