Search

The purpose of this in vitro study was to compare the precision of fit of substructures milled from semi-sintered zirconia blocks fabricated with two different computer-assisted design (CAD)/computer-assisted manufacturing (CAM) systems. Three-unit posterior fixed dental prostheses (FDP) were fabricated for standardized dies (n = 10) with the Lava CAD/CAM system (Lava) and the Procera-bridge-zirconia CAD/CAM system (Procera). After cementation to the dies, the FDP were embedded and sectioned. Four cross-sections were made of each abutment tooth, and marginal and internal fit were evaluated under an optical microscope. A one-way analysis of variance was used to compare data (alpha = 0.05). Mean gap dimensions at the marginal opening for Lava and Procera were 15 (+/-7) microm and 9 (+/-5) microm, respectively. Mean marginal openings (P = 0.012) and internal adaptation at two out of three measurement locations were significantly different. Within the limitations of this study, the results suggest that the accuracy of both investigated systems is satisfactory for clinical use.

Objectives: To evaluate microleakage and marginal gaps in full cast crown restorations bonded with six different types of cementing agents., Methods: Sixty non-carious human premolars and molars were prepared in a standardized manner for full cast crown restorations. The mesial and distal margins were located in dentin, while the vestibular and palatal/lingual margins were located in enamel. Crowns were made from a high-gold alloy using a standardized technique. The specimens were randomized to six groups of cementing agents: one zinc-phosphate cement (Harvard cement), one conventional glass-ionomer cement (Fuji I), one resin-modified glass-ionomer cement (Fuji Plus), two standard resin cements (RelyX ARC, Panavia F), and one self-adhesive universal resin cement (RelyX Unicem). After 4 weeks of storage in distilled water at 37 degrees C, the specimens were subjected to 5000 thermocycles ranging from 5 to 55 degrees C. Then, they were placed in a silver nitrate solution, embedded in resin blocks, and vertically cut in buccolingual and mesiodistal direction. Subsequently, the objects were evaluated for microleakage and marginal gap using a high-resolution digital microscope camera., Results: A number of inter-group differences were statistically significant. RelyX Unicem showed the smallest degree of microleakage both in enamel and in dentin. Panavia F und RelyX Unicem were associated with significantly larger marginal gaps than all other cementing agents. No association was observed between microleakage and marginal gap other than a weak direct correlation when using Harvard cement on enamel., Significance: The cementing agents investigated revealed different sealing abilities. These differences were not associated with specific types of materials.

The amount of tooth structure removed for various innovative and conventional preparation designs for fixed prosthodontics was quantified. Four Typodont resin teeth representing maxillary and mandibular premolars and molars were prepared in various abutment designs: adhesive, box (A2); adhesive, wing and groove (A3); mesioocclusal or distoocclusal inlay; mesio-occlusodistal inlay (13); mesio-occlusodistal onlay; partial crown; half crown (only molars); complete crown, 0.8-mm circumferential tapered chamfer (F1); complete crown, 1.0-mm circumferential rounded shoulder; and complete crown, 1.4-mm axial reduction facial shoulder, 0.7-mm lingual chamfer (F3). After tooth preparation (10 per group), the root was separated from the anatomic crown at the cementoenamel junction. Removal of tooth structure was measured by gravimetric analysis in a high-precision balance. Preparations A3 and F3 were assigned as abutments for metal-supported restorations, whereas all other preparations were used for all-ceramic restorations. When the mean structure removal of all teeth tested was compared, the adhesive and inlay abutments were the least invasive preparation designs, ranging from approximately 5.5% (A2) to 27.2% (13) tooth structure removal. Complete crowns required the most invasive preparations, ranging from 67.5% (F1) to 75.6% (F3) tooth structure removal. The tooth structure removal required for F3 retainers was almost 14 times greater than for an A2 preparation. Tooth structure removal was also influenced by the morphology of the tooth. The first comprehensive tooth preparation design classification system was introduced. The measurement system used in this study provides an accurate method of quantifying tooth structure removal for fixed prosthodontic preparations. The innovative preparation designs studied conserved significant amounts of tooth structure, yielding a better prognosis for the restored tooth.

Purpose: The aim of the study was to compare results after 1 and 3 years when single crowns supported by CerAdapt (test) ceramic abutments or CeraOne (control) titanium abutments were loaded., Materials and Methods: The material was divided into two groups: in group A, 69 (34 test, 35 control) abutments/crowns from all involved clinics were followed for 1 year; and in group B, 20 (10 test, 10 control) abutments/crowns from one of the clinics were followed for 3 years., Results: No implant failed, giving a cumulative success rate of 100% for the implants. Two CerAdapt abutments in group A fractured, giving a cumulative success rate of 93% for the CerAdapt and 100% for the CeraOne abutments after 1 year. No abutment failed in group B, giving a cumulative success rate of 100% both for the CerAdapt and the CeraOne abutments between 1 and 3 years. The CerAdapt fractures might have been due to the fact that the abutments were impaired through too-extensive preparation and/or had been exposed to a too-high bending moment. Almost no marginal bone loss was recorded, indicating a stable bone situation both at CerAdapt and CeraOne abutments on single-tooth implants. Healthy conditions, with a relatively stable level of the periimplant mucosa in relation to the abutment/crown, were recorded for soft tissues both at CerAdapt and CeraOne abutments. Both clinicians and patients rated the esthetic result as excellent for practically all cases., Conclusion: The results demonstrate the esthetic possibilities and the safety of single-tooth replacement when accepted treatment concepts are followed and documented components are used. The tested abutments worked well, although the fractured CerAdapt abutments indicate that ceramic abutments are more sensitive to handling procedures than the titanium abutments.

The IPS Empress system is a highly esthetic hot pressed glass ceramic material for fabrication of single crowns. Adhesive cementation of the system not only contributes to the esthetics but is necessary for increased strength of the crown. The purpose of this prospective clinical trials was to evaluate the longevity of 75 adhesively cemented Empress full crowns. An additional aim was to assess the adhesive cementation methodology and potential side effects. At the three-year point, one molar crown fractured for a 1.3 percent failure rate. The resin cementation technique that was employed exhibited a low incidence of microleakage with few clinical side effects. There was a 5.6 percent incidence of post-cementation sensitivity, with all symptoms subsiding by eight weeks. None of the crowns in the study required endodontic therapy.

Although porcelain-fused-to-metal (PFM) restorations are the most widely used full-coverage crown restoration systems, their inherent properties make the achievement of natural aesthetic restorations an elusive task. In contrast, the all-ceramic system (IPS Empress, Ivoclar North America, Amherst, NY) offers excellent translucency and vitality, without the opacity associated with PFM restorations. Its vitality is further enhanced by an adhesive resin cementation method that conducts the color of the underlying tooth structure. This article reports the status of a 5-year investigation, initiated in 1992, of the clinical performance of the IPS Empress all-ceramic system and the resin cementation system used with it.

Although porcelain-fused-to-metal (PFM) restorations are the most widely used full-coverage crown restoration systems, their inherent properties make the achievement of natural aesthetic restorations an elusive task. In contrast, the all-ceramic system (IPS Empress, Ivoclar North America, Amherst, NY) offers excellent translucency and vitality, without the opacity associated with PFM restorations. Its vitality is further enhanced by an adhesive resin cementation method that conducts the color of the underlying tooth structure. This article reports the status of a 5-year investigation, initiated in 1992, of the clinical performance of the IPS Empress all-ceramic system and the resin cementation system used with it.

The swaged metal matrix provides a method for rapidly making a metal substructure for ceramic crowns. This study determined the vertical and horizontal marginal fidelity of swaged metal substrate crowns made with four methods. No significant difference in vertical or horizontal marginal fidelity was found for metal margin crowns formed with either a plastic spacer or a paint-on die spacer. The vertical marginal fidelity was significantly better in crowns made with a metal margin (37 microns) than in crowns made with a porcelain facial margin (62 microns), and the latter were significantly better than crowns made with a 360-degrees porcelain margin (86 microns). Crowns made with all four methods were overcontoured by 46 to 82 microns. The 360-degrees porcelain margin was technically more difficult and time-consuming to make.

This study measured the in vitro microleakage of conventional and new FPD luting agents. Standardized preparations were made on 42 freshly extracted premolars. Facial and lingual chamfer margins were placed in enamel, mesial and distal in dentin and cementum, and castings were made in Rexillium III alloy and were then cemented with a standardized technique. Six groups of seven samples were tested, (1) polycarboxylate, (2) zinc phosphate, (3) glass ionomer, (4) Den-Mat Thin Film cement, (5) Panavia Ex, and (6) Den-Mat Thin Film cement with Tenure. The ranking of groups for stain ingress was from the greatest (1) to the least (6). A one-way analysis of variance and Tukey-Student range analysis revealed significantly similar groups, p less than 0.05:(1,2,3,4) (5,6).

This study was conducted to determine the effectiveness of a silicone disclosing medium, G-C Fit-Checker, as an aid in the improvement of marginal integrity. Standardized preparations were made on 42 freshly extracted premolars. Base metal alloy castings were finished externally and initially adjusted internally. The castings were placed on their respective teeth and the marginal opening was determined. They were then adjusted twice using the silicone material and remeasured. The preadjustment mean marginal opening was 92 microns and the postadjustment measurement 55 microns, yielding a mean reduction of 37 microns (SEM 3 microns) or 39%.

This study obtained anamnestic data from a questionnaire given at the conclusion of a 7-week chlorhexidine gingival enhancement study regarding patients' oral hygiene practices, perception of change in gingival health, and side effects. In the patient population using the 7-week chlorhexidine treatment regimen, most patients noticed an improvement in gingival health, were willing to continue usage after the study, and would recommend the rinse to others. Of the patients who reported side effects, taste alteration was more objectionable than staining. The patients' observed gingival health benefits were more important than the patients' perception of the side effects such as staining and taste alteration.

This study assessed the changes of the subgingival/marginal microflora during fixed prosthodontic procedures and evaluated the effect of adjunctive rinsing with 0.12% chlorhexidine on the subgingival/marginal microflora during fixed prosthodontic treatment. Thirty patients scheduled for fixed prosthodontics were randomly assigned to either rinsing with 15 ml of tap water b.i.d. (control) or rinsing with 15 ml of 0.12% chlorhexidine gluconate b.i.d. (experimental). Subgingival and marginal plaque was analyzed at baseline, before crown preparation (2 weeks), before crown cementation (5 weeks), and 2 weeks after cementation (7 weeks). The fixed prosthodontic procedures alone altered the subgingival and marginal microbiota toward a more health-associated flora. Adjunctive rinsing twice daily with 0.12% chlorhexidine had a significantly greater effect in reducing putative periodontal pathogens compared with the control regimen. This medication was a useful adjunct to regular oral hygiene during fixed prosthodontic procedures by permitting the establishment and maintenance of a microflora compatible with periodontal health.

Previous research on crown margin fidelity is reviewed and methods of measurement are compared and scrutinized. A standardized method for the determination of crown margin fidelity is introduced. A biologically oriented rationale is presented for analysis of the measurement parameters. This system places a strong emphasis on measuring factors that impact upon accumulation of plaque and the microbiologic environment around crowns, ultimately affecting gingival health. Crown samples were cemented on master dies and were embedded for sectioning buccolingually and mesiodistally. Photographs of margins with plastic overlays indicating emergence profiles were used to determine vertical and horizontal marginal discrepancies. Three observers measured seven crown systems for the vertical and horizontal marginal discrepancies of each crown system. The interobserver variance was 10 microns for the horizontal and 9 microns for the vertical marginal discrepancy.

Heat treatment during the burnout procedure may cause corrosion of the stainless steel post. This study was undertaken to determine whether alteration of the corrosion resistance of stainless steel posts occurs as a result of various simulated burnout procedures. Stainless steel posts were divided into five groups of five posts: group 1, control; 2, gypsum-bonded investment, bench cooled; 3, gypsum-bonded investment, quenched; 4, phosphate-bonded investment, bench cooled; and 5, phosphate-bonded investment, quenched. The posts were placed in individual containers of Ringer's solution and observed at 30, 180, and 600 days. Scanning electron microscopy, energy dispersive x-ray spectroscopy, optical emission spectroscopy, and optical microscopy were used to evaluate the posts qualitatively and quantitatively. Investment and heat treatment altered the metallic structure of stainless steel posts. Prefabricated posts submitted to simulated burnout procedures had a noticeable reduction in corrosion resistance. Direct casting to stainless steel posts is contraindicated.

When a method of intracoronal reinforcement is selected, many factors must be weighed. The hazards include (1) the induced stresses and the risk of fracture during placement of the dowel, (2) the probability of root perforation during post space preparation, (3) the wedging action of tapered dowels, and (4) the incidence of fracture with self-threading pins in devitalized teeth. The amount of tooth structure that remains after endodontic therapy and post space preparation is paramount. Endodontic and restorative treatment must be aimed at preserving tooth structure to provide strength and resistance to fracture of the pulpless tooth. To fabricate a large-diameter dowel with a strength that greatly exceeds that of the endodontically treated root decreases the prognosis for clinical success.

The sequence of the initiation, formation, development, and maturation of dental plaque was reviewed. The gingival response to plaque formation was identified to control plaque growth for prolonged gingival health. A strong implication has been established between rough, overcontoured metal ceramic restorations and periodontal disease. Unsightly soft tissue around crowns result from increased plaque accumulation. In comparing esthetic crowns, three critical variables are considered. The factors that mediate plaque accumulation and influence gingival health at the tissue-restoration interface are (1) surface roughness, (2) marginal fit, and (3) contour. Minimizing plaque accumulation is crucial for gingival health.

The inherent problems in present shade matching procedures and communication between dentist and ceramist have been discussed. These five areas of weakness include the observer, variable viewing conditions, commercially available shade guides, inadequate technology, and poor communication. A systematic procedure that breaks down shade selection to the elements of opaque, body, and incisal porcelain shades was presented. This method simplifies and adds clarity in the registration of shades, improving the communication chain between dentist and ceramist. The system is suggested as a means to overcome many of the inherent problems in shade selection and communication. This approach enhances the dentist-ceramist team's ability to esthetically match metal-ceramic restorations to the natural dentition. Future parts of this series will present procedures for improved communication and a system for porcelain application.