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At least 1,153 records · Page 64Linked to original sources
PubMed2000

Dimensional accuracy of castings produced with ringless and metal ring investment systems.

STATEMENT OF PROBLEM: The ringless casting procedure is in use in clinical dentistry, although there is no adequate scientific data to support its use. PURPOSE: This study compared the vertical margin accuracy of lost wax castings produced with the conventional casting technique using a metal ring and a technique that uses a ringless system. MATERIAL AND METHODS: From copings fabricated on a metal die, 30 castings were produced from a high palladium alloy for metal ceramic restorations (Argedent). Ten castings were cast with Bellavest T (Bego) phosphate-bonded investment with the ringless technique, 10 were cast with the same investment with a metal ring, and the final 10 were cast using Hi-temp (Whip Mix) phosphate-bonded investment with a metal ring. The internal surface of the castings were not modified before seating with finger pressure. For vertical margin discrepancy measurements, an optical microscope at a magnification of 100x was used. Data were analyzed with 1-way multivariate ANOVA (repeated measures) and the Student-Newman-Keuls test. RESULTS: When following the manufacturers' recommendations, the castings of the ringless technique provided less vertical margin discrepancy (mean value 181 +/- 71 microm) than the castings produced with the conventional metal ring technique (290 +/- 87 microm and 291 +/- 88 microm). The difference was significant (P <. 001). CONCLUSION: The ringless technique may produce accurate castings for use in fixed prosthodontics, therefore further investigation is needed to develop a protocol for its use.

Analysis of Variance↗
PubMed2000

Prefabricated acrylic resin bars for splinting implant transfer copings.

Splinting of implant transfer copings with acrylic resin during impression procedures is performed to accurately transfer the spatial relationships of implants to the master cast. However, distortion may occur during the splinting procedure because of resin polymerization shrinkage. This article describes a simple technique for minimizing this effect by fabrication of resin bars.

Acrylic Resins↗
PubMed2002

Clinical evaluation of all-ceramic crowns.

STATEMENT OF PROBLEM: There are few in vivo studies on the clinical performance of all-ceramic crowns. PURPOSE: The aim of this study was to evaluate the clinical performance of IPS Empress crowns. MATERIAL AND METHODS: Thirty-seven all-ceramic IPS Empress crowns were placed in 20 patients. Twenty crowns were luted with Variolink II low-viscosity resin cement in combination with Syntac Classic dentin adhesive; the remaining 17 were luted with Variolink II in combination with Syntac Single Component. All procedural steps were performed by the same prosthodontist. Using the California Dental Association's (CDA) quality evaluation system, 2 calibrated evaluators examined the crowns for margin integrity, anatomic form, surface, and color for a period of 12 to 41 months, with a mean of 24.56 months after insertion. Kaplan-Meier statistical analysis was used to calculate the survival rate of the crowns. Values obtained for plaque and gingival conditions were compared to control teeth with use of the Wilcoxon signed ranks test (P<.05). RESULTS: Based on the CDA criteria, 94.6% of the crowns were rated satisfactory. Fracture was registered in only 1 crown. One endodontically treated tooth failed due to the dislodgement of the prefabricated dowel. No significant difference was observed in the gingival health status of crowns that had margins placed above or at the level of the gingival margin. However, in crowns that had subgingival margin finish lines, the percentage of bleeding on probing was significantly higher than that of the contralateral control teeth. CONCLUSION: In this in vivo study, IPS Empress crowns luted with both dentin bonding agents functioned satisfactorily with a relatively low fracture rate over a mean evaluation period of 24.56 months.

Adult↗
PubMed2002

Compositional stability and marginal accuracy of complete cast crowns made with as-received and recast type III gold alloy.

STATEMENT OF PROBLEM: The effect of combining new and recast metal on the compositional stability of the alloy used and accuracy of the final restoration is not known. PURPOSE: This study characterized the elemental compositional stability of as-received and recast type III gold alloy. The effect of combining these alloys on the marginal accuracy of complete cast crowns also was evaluated. MATERIAL AND METHODS: Sixty standardized type III gold alloy complete crowns were made on epoxy resin dies duplicated from a metal master die with conventional laboratory techniques. Three casting protocols (n = 20 each) were established in relation to the proportion of as-received and recast gold alloys: Group A (100% as-received metal), Group B (50% wt new metal, 50% wt once recast metal), and Group C (100% once recast metal). An elemental analysis was performed at 3 sites along the cast crown (cervical, middle, and occlusal) with x-ray energy-dispersive spectroscopy. Marginal accuracy was measured with a microscope before and after cementation. Results were subjected to 1-way analysis of variance followed by the Ryan-Einot-Gabriel-Welsch multiple-range test at a 1% level of significance. RESULTS: Elemental composition was significantly different among the casting groups (P<.001). The mean weight percentage values were 72.4% to 75.7% Au, 4.5% to 7.0% Pd, 10.7% to 11.1% Ag, 7.8% to 8.4% Cu, and 1.0% to 1.4% Zn. Statistically but not clinically significant differences also were found for marginal accuracy. The marginal discrepancy was less than 25 microm for all casting conditions, with the lowest value recorded for Group A (7 microm), the highest for Group C (12 microm), and an intermediate value for Group B (9 microm) specimens. CONCLUSION: Recasting type III gold alloys may adversely affect the marginal accuracy of complete cast crowns. In this study, however, such effects were not clinically significant.

Analysis of Variance↗
PubMed2002

Prosthetic complications in an implant-retained mandibular overdenture population: initial analysis of a prospective study.

STATEMENT OF PROBLEM: The clinical success of implant-retained, tissue-supported mandibular overdenture prostheses has been documented. However, few studies have evaluated the return visits and associated cost required to maintain these prostheses. PURPOSE: The purpose of this investigation was to evaluate the amount of maintenance required to provide acceptable and satisfactory implant-retained mandibular overdentures in a prospective clinical trial. MATERIAL AND METHODS: Fifty-eight patients received new maxillary and mandibular complete dentures followed by placement of microthreaded/TiOBlast implants in the mandibular left and right canine regions. At 3 months, ball abutments were placed, and the mandibular prostheses were relined to receive Dalla Bona-type ball housings (baseline). Prostheses were prospectively evaluated, and adjustments were made at 3-, 6-, 12-, 24-, and 36-month recall visits and at nonscheduled visits for 9 types of prosthetic complications. RESULTS: Of 58 patients, 6 required no adjustments. The remaining 52 patients made 327 return visits (including 194 nonscheduled visits) for prosthesis and/or abutment adjustments. One hundred and fifteen practitioner hours were required to provide prosthetic solutions to patient concerns at the return visits. The total estimated cost for all professional and laboratory services was $12,624.00 ($218.00 per patient). CONCLUSION: Although mandibular implant-supported overdentures with Dalla Bona-type ball attachments are an acceptable treatment option for edentulous patients, routine maintenance is required to ensure successful long-term outcomes.

Adult↗
PubMed2002

Effect of posterior crown margin placement on gingival health.

STATEMENT OF PROBLEM: The clinical impact of posterior crown margin placement on gingival health has not been thoroughly quantified. PURPOSE: This study evaluated the effect of posterior crown margin placement with multivariate analysis. MATERIAL AND METHODS: Ten general dentists reviewed 240 patients with 480 metal-ceramic crowns in a prospective clinical trial. The alloy was randomly selected from 2 high gold, 1 low gold, and 1 palladium alloy. Variables were the alloy used, oral hygiene index score before treatment, location of crown margins at baseline, and plaque index and sulcus bleeding index scores recorded for restored and control teeth after 1 year. The effect of crown margin placement on sulcular bleeding and plaque accumulation was analyzed with regression models (P<.05). RESULTS: The probability of plaque at 1 year increased with increasing oral hygiene index score before treatment. The lingual surfaces demonstrated the highest probability of plaque. The risk of bleeding at intrasulcular posterior crown margins was approximately twice that at supragingival margins. Poor oral hygiene before treatment and plaque also were associated with sulcular bleeding. Facial sites exhibited a lower probability of sulcular bleeding than lingual surfaces. Type of alloy did not influence sulcular bleeding. CONCLUSION: In this study, placement of crown margins was one of several parameters that affected gingival health.

Adult↗
PubMed2002

Retrofitting crowns to an existing removable partial denture clasp: a simple technique.

The fabrication of a new crown to replace an existing abutment tooth for a removable partial denture is one of the most labor-intensive chairside and laboratory procedures. The process can become more complicated when the patient requests a tooth-colored esthetic restoration. Numerous techniques are described in the literature, some for all-metallic restorations and others for metal-ceramic restorations. This article describes a simplified technique that makes use of a polymer ceramic material.

Crowns↗
PubMed2002

Treating the modern complete denture patient: a review of the literature.

This article reviews the physical and mental compromises of today's patients, techniques, materials, occlusion, impressions, and soft liners and makes recommendations as to managing these compromises when fabricating complete dentures. References used were primarily from the "classical literature," and an effort was made to ascertain whether these treatment recommendations are appropriate for today's more difficult patients. An effort was made to incorporate recent recommendations where appropriate.

Attitude to Health↗
PubMed2003

An implant-retained auricular impression technique to minimize soft tissue distortion.

Achieving adaptation of an auricular prosthesis begins with an accurate impression. It is important to consider how the selection of the impression materials will affect the final outcome of the prosthesis. A procedure is presented to minimize the distortion of the soft tissues caused by the impression materials and procedure. The procedure consists of splinting the implant impression copings, then recording the soft tissue in silicone impression material, followed by the application of acrylic tray resin to provide rigidity.

Acrylic Resins↗
PubMedDate not supplied

Computed tomography evaluation of shoulder prosthesis retroversion.

Computed tomography (CT) allows calculation of anatomic and prosthetic humeral head retroversion. The purpose of this study was to demonstrate how the retroversion angle measured by CT scan varied with changes in arm position in the CT scan reference system. A trigonometric analysis shows that the measured retroversion angle decreases when the arm is in extension and increases when it is in flexion, compared with the true retroversion angle determined perioperatively. For the same degree of flexion, or extension, the error of measurement is greater when the initial true retroversion is low. A shoulder prosthesis with 20 degrees of true head retroversion was radiologically scanned with different degrees of flexion, extension, and abduction. The results validate the theoretical analysis. Trigonometric formulas are proposed to correct the retroversion angle measured by CT scan.

Biomechanical Phenomena↗
PubMed2001

Eccentric stent graft compression: an indicator of insecure proximal fixation of aortic stent graft.

PURPOSE: The purpose of this study was to determine whether radiographically demonstrated proximal stent graft contour can be used as a marker for security of proximal neck fixation after endovascular aneurysm repair. METHODS: Stent graft structure was examined in 100 consecutive patients with abdominal aortic aneurysms who were treated with the stent graft. Stent graft integrity, stent contour, angulation, compression, and position were assessed by use of plain abdominal radiography, and the results were correlated with contrast computed tomography (CT) scanning, clinical findings, and outcomes. Repeated imaging was carried out during follow-up of 3 to 38 (mean, 12) months. RESULTS: Stent graft repair was successful in all 100 patients. No stent fractures were identified. Concentric compression of the proximal portion of the stent graft was visible in 69% of patients and reflected deliberate oversizing of the stent graft at the time of implantation. In 5% of patients, a short eccentric compression deformity of the proximal stent was observed. This finding was associated with an increased risk of stent graft migration (P <.01) and with an increased risk for development of a late proximal (type I) endoleak (P <.01). Compared with CT scanning, abdominal radiography was less useful for assessment of short distances of migration (sensitivity 67%; specificity 79%). However, they provided better definition of the stent graft in relation to bony landmarks and better visualization of aortic calcification than CT with three-dimensional reconstruction. CONCLUSION: Plain abdominal radiographs are important in the postoperative evaluation of patients with aortic stent grafts. They allow for more precise evaluation of the structural elements of the stent graft than CT scanning and may disclose inadequate proximal fixation by demonstration of an eccentric compression deformity. They are less useful for assessment of migration.

Aortic Aneurysm, Abdominal↗
PubMed2002

An in situ adjustable endovascular graft for the treatment of abdominal aortic aneurysms.

Twenty-nine patients underwent placement of the Teramed Ariba Endovascular Graft System (Maple Grove, Minn) as part of a European Feasibility study (14 patients) and a US phase I trial (15 patients). Salient features of this modular endograft system include a crimped seamless polyester bifurcation graft supplied in three diameters and three iliac limb lengths, three types of nitinol stents including a suprarenal stent with aortic barbs, a flexible delivery system capable of controlled incremental sheath retraction, a flexible tapered lead balloon, and a telescoping technique for adjusting the length of graft coverage during surgery over a range of 3 cm. Twenty-eight of the 29 patients met the primary objective of this evaluation, which was to confirm the safety of the system, defined as the absence of major device-related adverse events and type I, III, or IV endoleaks within 1 month of implantation. Three major adverse events occurred within 1 month of discharge: renal failure, which was related to deployment of the device close to the renal arteries; pulmonary edema, which was related to the procedure but not the device; and peripheral ischemia, which was related to the patient's pre-existing condition. Seven patients had type II endoleaks noted by means of computed tomography scanning at 1 month; the endoleaks were identified by means of angiography and classified at the time of surgery. There were no deaths, aneurysm ruptures, stent-graft migrations, stent fractures, graft ruptures, graft thromboses, or surgical conversions at 1 month. This early clinical experience indicates that the Ariba Bifurcated Endovascular System can be safely implanted.

Aged↗