- Email: [email protected]
Initial implant position and crestal bone remodeling
designed with a smaller occlusal surface width. After finishing and abrasion, the castings received 2 layers of opaque and dentin porcelain, then were glazed. The crowns were next placed in a testing apparatus and loaded vertically in the middle of the occlusal surface. Measurements of the mean value of load at fracture were obtained and compared between the groups. Results.—Group 1 specimens had a mean load at failure of 95.01 Kgf, group 2 had 108.61 Kgf, group 3 had 390.94 Kgf, and group 5 had 380.04 Kgf. The force required to fracture the crowns was significantly less for group 1 and 2 crowns than for group 3 and 4 crowns. Groups 1 and 2 did not differ significantly from each other in the outcomes, nor did groups 3 and 4. Discussion.—Crowns retained with screws fractured when exposed to a significantly lower level of force than crowns retained with cement. The porcelain fracture resistance was essentially the same whether the occlusal table was 4 or 5 mm wide in the groups with cement-retained
crowns. Where the screw access holes were located did not influence the porcelain fracture resistance value.
Clinical Significance.—Because fracture of porcelain veneering may limit the life span of a restoration, this study examined cement and screw retention as well as the effect of offsetting the screw hole and reducing the buccolingual width of the occlusal table. Cemented fared better than screw-retained and no difference was noted for the other 2 variables.
Torrado E, Ercoli C, al Mardini M, et al: A comparison of the porcelain fracture resistance of screw-retained and cement-retained implantsupported metal-ceramic crowns. J Prosthet Dent 91:532-537, 2004 Reprints available from C Ercoli, Div of Prosthodontics, Univ of Rochester Eastman Dental Ctr, 625 Elmwood Ave, Rochester, NY 14620; fax: (585) 244-8772; e-mail: [email protected]
Initial implant position and crestal bone remodeling Background.—An important aspect to be considered in implant success is the determination of crestal bone levels around the implant. Whether a microgap (implant-abutment interface) is present or absent and where it is located with respect to the alveolar crest significantly influence the amount of peri-implant bone loss in dogs. When a 1-piece, nonsubmerged implant system with a rough-smooth border is placed at the crest, the biologic width dimension resembles that of natural teeth, with a more stable coronal gingival margin than is found with a 2-piece system wherein the microgap is at the crest. Significant apical displacement of the crestal bone occurred when the 2-piece system was used and the microgap was at or below the alveolar crest. In addition, this latter configuration produced a long junctional epithelial attachment and a more apical gingival margin location. Increased biologic width dimension was produced with
44 Dental Abstracts
minimal changes in gingival margin by placing the roughsmooth border of the 1-piece implants 1.0 mm below the alveolar crest. The radiographic bone level changes that occurred in the first 5 years after implant placement were tracked for 1-piece implants whose shoulder was placed at various locations relative to the original bone crest. Bone remodeling was quantified to assess crestal bone levels and determine the magnitude and stability of alterations. Methods.—Maxillary implants were placed in 27 patients and mandibular implants in 15. The nonsubmerged surgical technique was used in all cases, with the roughsmooth border location varying with respect to the alveolar crest. On the day of placement, after 6 months, and annually for 5 years, clinical examinations were done and radiographs were taken. Digitized radiographs were used
smooth border relative to the alveolar crest. Implants whose rough-smooth border was below the crest averaged more remodeling after 6 months than implants in which the rough-smooth border was at or near the crest. The average remodeling was 1.72 mm for the former and 0.68 for the latter.
Fig 4.—Schematic of bone remodeling from baseline to 6 months for A, maxillary and B, mandibular implants. For both A and B at baseline and 6 months, the number on the left indicates the linear dimension in millimeters from the beveled shoulder of the implant to the rough-smooth border.The number on the right indicates the linear dimension in millimeters from the beveled shoulder of the implant to the alveolar crest. (Courtesy of Hartman GA, Cochran DL: Initial implant position determines the magnitude of crestal bone remodeling. J Periodontol 75:572-577, 2004.)
to measure linearly from the implant shoulder to the first bone-to-implant contact at each of these evaluations. Results.—At the 6-month evaluation, compared with baseline values, the amount of bone remodeling was 1.10 mm, which was significant. None of the remaining time points showed any significant change. The amount of bone remodeling was related to the location of the rough-
Discussion.—The degree of remodeling depended on the implant’s apico-coronal position. Thus, a specific dimension was found between the microgap location and the first bone-to-implant contact point. The remodeling in all cases occurred within the first 6 months, reached a similar level, and did not change over the ensuing months, up to 5 years after implant placement. The specific biologic width achieved for implants was similar to that for natural teeth. Implants in the anterior maxilla had the rough-smooth border located 1.3 mm (average) below the alveolar crest and reached an average of 3.2 mm from the implant shoulder to the first bone-to-implant contact. Implants in the mandible were located more supracrestally than the maxillary implants and averaged 0.68 mm of remodeling after 6 months, yielding a 3.4-mm distance from the implant shoulder to the crest. Regardless of their placement relative to the alveolar crest, both mandibular and maxillary implants remodeled to achieve about 3.3 mm (Fig 4). As this relationship becomes better understood, the esthetic predictability of a restoration will be improved, with more accurate and precise implant positioning possible during placement surgery.
Clinical Significance.—Predictable gingival height and papillary contour are essential for esthetic results. In this study with 1piece implants, a specific biologic width, as found in natural teeth, was shown to be established within 6 months and remained fairly stable.
Hartman GA, Cochran DL: Initial implant position determines the magnitude of crestal bone remodeling. J Periodontol 75:572-577, 2004 Reprints available from D Cochran, UTHSCSA, Dept of Periodontics, 7703 Floyd Curl Dr, San Antonio, TX 78284; e-mail: cochran @uthscsa.edu
Volume 50 • Issue 1 • 2005 45
crowns. Where the screw access holes were located did not influence the porcelain fracture resistance value.
Clinical Significance.—Because fracture of porcelain veneering may limit the life span of a restoration, this study examined cement and screw retention as well as the effect of offsetting the screw hole and reducing the buccolingual width of the occlusal table. Cemented fared better than screw-retained and no difference was noted for the other 2 variables.
Torrado E, Ercoli C, al Mardini M, et al: A comparison of the porcelain fracture resistance of screw-retained and cement-retained implantsupported metal-ceramic crowns. J Prosthet Dent 91:532-537, 2004 Reprints available from C Ercoli, Div of Prosthodontics, Univ of Rochester Eastman Dental Ctr, 625 Elmwood Ave, Rochester, NY 14620; fax: (585) 244-8772; e-mail: [email protected]
Initial implant position and crestal bone remodeling Background.—An important aspect to be considered in implant success is the determination of crestal bone levels around the implant. Whether a microgap (implant-abutment interface) is present or absent and where it is located with respect to the alveolar crest significantly influence the amount of peri-implant bone loss in dogs. When a 1-piece, nonsubmerged implant system with a rough-smooth border is placed at the crest, the biologic width dimension resembles that of natural teeth, with a more stable coronal gingival margin than is found with a 2-piece system wherein the microgap is at the crest. Significant apical displacement of the crestal bone occurred when the 2-piece system was used and the microgap was at or below the alveolar crest. In addition, this latter configuration produced a long junctional epithelial attachment and a more apical gingival margin location. Increased biologic width dimension was produced with
44 Dental Abstracts
minimal changes in gingival margin by placing the roughsmooth border of the 1-piece implants 1.0 mm below the alveolar crest. The radiographic bone level changes that occurred in the first 5 years after implant placement were tracked for 1-piece implants whose shoulder was placed at various locations relative to the original bone crest. Bone remodeling was quantified to assess crestal bone levels and determine the magnitude and stability of alterations. Methods.—Maxillary implants were placed in 27 patients and mandibular implants in 15. The nonsubmerged surgical technique was used in all cases, with the roughsmooth border location varying with respect to the alveolar crest. On the day of placement, after 6 months, and annually for 5 years, clinical examinations were done and radiographs were taken. Digitized radiographs were used
smooth border relative to the alveolar crest. Implants whose rough-smooth border was below the crest averaged more remodeling after 6 months than implants in which the rough-smooth border was at or near the crest. The average remodeling was 1.72 mm for the former and 0.68 for the latter.
Fig 4.—Schematic of bone remodeling from baseline to 6 months for A, maxillary and B, mandibular implants. For both A and B at baseline and 6 months, the number on the left indicates the linear dimension in millimeters from the beveled shoulder of the implant to the rough-smooth border.The number on the right indicates the linear dimension in millimeters from the beveled shoulder of the implant to the alveolar crest. (Courtesy of Hartman GA, Cochran DL: Initial implant position determines the magnitude of crestal bone remodeling. J Periodontol 75:572-577, 2004.)
to measure linearly from the implant shoulder to the first bone-to-implant contact at each of these evaluations. Results.—At the 6-month evaluation, compared with baseline values, the amount of bone remodeling was 1.10 mm, which was significant. None of the remaining time points showed any significant change. The amount of bone remodeling was related to the location of the rough-
Discussion.—The degree of remodeling depended on the implant’s apico-coronal position. Thus, a specific dimension was found between the microgap location and the first bone-to-implant contact point. The remodeling in all cases occurred within the first 6 months, reached a similar level, and did not change over the ensuing months, up to 5 years after implant placement. The specific biologic width achieved for implants was similar to that for natural teeth. Implants in the anterior maxilla had the rough-smooth border located 1.3 mm (average) below the alveolar crest and reached an average of 3.2 mm from the implant shoulder to the first bone-to-implant contact. Implants in the mandible were located more supracrestally than the maxillary implants and averaged 0.68 mm of remodeling after 6 months, yielding a 3.4-mm distance from the implant shoulder to the crest. Regardless of their placement relative to the alveolar crest, both mandibular and maxillary implants remodeled to achieve about 3.3 mm (Fig 4). As this relationship becomes better understood, the esthetic predictability of a restoration will be improved, with more accurate and precise implant positioning possible during placement surgery.
Clinical Significance.—Predictable gingival height and papillary contour are essential for esthetic results. In this study with 1piece implants, a specific biologic width, as found in natural teeth, was shown to be established within 6 months and remained fairly stable.
Hartman GA, Cochran DL: Initial implant position determines the magnitude of crestal bone remodeling. J Periodontol 75:572-577, 2004 Reprints available from D Cochran, UTHSCSA, Dept of Periodontics, 7703 Floyd Curl Dr, San Antonio, TX 78284; e-mail: cochran @uthscsa.edu
Volume 50 • Issue 1 • 2005 45