[Patterns of reactive changes in the dentin and protective measures during and after the process of tooth preparation for metal crowns].
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A variety of techniques are currently available to restore dentition in the posterior region, and the selection of the proper modality is dependent upon evaluation and satisfaction of numerous criteria. Direct materials provide limited strength in the posterior segment, and full-coverage indirect techniques (e.g., crown restorations) often require the destruction of sound tooth structure. When proper case selection, preparation design, and clinical protocols are utilized, a laboratory-processed composite resin (belleGlass, Kerr/Sybron, Orange, CA) can provide an optimal means by which to successfully restore posterior dentition without compromising the existing tooth structure.
Bonding of a tooth fragment to the remaining tooth substance can restore crown fracture of an anterior tooth. In this study, sheep central incisors were used. The crowns were fractured transversely and the crown fragment was bonded to the remaining tooth structure. This technique involves acid etching, use of an experimental adhesive (Gluma+) and a BisGMA/TEGDMA resin. The mean fracture strength of the restored teeth was not significantly different from that of intact teeth when tested at a rather low crosshead speed (0.5 mm/min) but different and about 30% lower when tested at a higher crosshead speed (500 mm/min). In studies aiming to test resistance to forces which might cause trauma, it might be appropriate to use a high crosshead speed.
OBJECTIVES: There is currently no standardised technique to measure the amount of coronal dentine remaining in a root-treated tooth after crown preparation. The aim of this study was to develop a method of measuring remaining coronal dentine in root-treated teeth and to propose an index for grading tooth restorability. METHODS: The study recruited 20 patients who had completed molar endodontic treatment at the Eastman Dental Hospital and had been prescribed an amalgam coronal-radicular core with a full coverage cast restoration. Using a series of interlocking special trays and impressions, a method was devised to produce a cast of the amount of remaining dentine coronal to the finish line after crown preparation. This cast was scanned using a laser profilometer and the volume of remaining dentine was calculated. A tooth restorability index (TRI) was developed to assess the strategic value of the remaining dentine. The TRI allowed scores of 0-3 in each sextant with a maximum score of 18 per tooth. RESULTS: Twenty teeth were scored by three examiners and the TRI scores varied from 2 to 13. The volume of coronal dentine varied from 61.73 to 232.22 mm(3). CONCLUSIONS: A tooth restorability index has been devised to assess the strategic value of remaining dentine. A Kappa statistic was calculated to produce values of 0.584, 0.688 and 0.720, giving moderate-good agreement between the examiners.
Patients are increasingly wishing to undergo conventional endodontic treatment rather than to risk the loss of a tooth. Endodontic treatment in teeth that have been previously restored with extensive intracoronal or extracoronal restorations are often difficult to treat. The orientation of the root canals to the crown of the tooth may be lost, and this may often be compounded by the deposition of reparative dentin in the pulp chamber. The operating microscope allows better visualization of the working field, ensuring that the anatomy of the tooth is more readily inspected. This greatly enhances the clinician's ability to locate extra root canals and therefore increase the likelihood of a successful outcome. It should not be forgotten that the operating microscope also has a place in other fields of dentistry, especially restorative dentistry, and is an asset to both the specialist and the generalist.
STATEMENT OF PROBLEM: All-ceramic crowns are being used extensively. Little data are available on their clinical performance. PURPOSE: This study evaluated the clinical performance of In-Ceram (Vita Zahnfabrik) crowns. MATERIAL AND METHODS: Forty-one patients (16 men, 25 women; mean age 47.3 years, range 18 to 77 years) were examined with a total of 80 In-Ceram all-ceramic crowns fabricated at the University of Iowa College of Dentistry from 1994 to 1997. The percentage distribution for crowns included: 67% anterior single crowns, 26% posterior single crowns, 6% anterior implant crowns, and 1% posterior implant crowns. This study documented the integrity of the junction between crown and tooth, color match to adjacent teeth, secondary dental caries, wear of crown and opposing dentition, and visible cracks in the crown. Alpha, Bravo, and Charlie ratings were assigned with a modified USPHS criteria. The patients were also surveyed with respect to oral hygiene and satisfaction of treatment. Estimations of 4-year success rates and corresponding confidence intervals were calculated by fitting a constant hazard function model with the SAS procedure GENMOD. RESULTS: Marginal integrity for 88% of artificial crowns was rated Alpha or Bravo. Shade match for 99% was Bravo or better. Only 1% of the crowns were carious, and 1 crown exhibited occlusal wear. One premolar crown had a small fracture of veneering porcelain. One molar crown was remade after core fracture. All patients (100%) expressed satisfaction with their crowns. The estimated 4-year success rates (Alpha or Bravo), with 95% confidence intervals in parentheses were calculated as: 83.5% (65.7%-94.6%) for marginal integrity, 95.8% (82.9%-99.8%) for shade match, and 95.5% (81.6%-99.7%) for secondary caries, 100% (88%-100%) for wear, and 100% (88%-100%) for cracks.
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