Biomedical subjects

R G Ritsco

Publications and source records attributed to R G Ritsco.

6 recordsLinked to original sources

PubMed1998

Marginal adaptation of implant-supported metal-ceramic crowns fabricated with gold cylinders.

PURPOSE: The purpose of this investigation was to determine the mean marginal discrepancy of metal-ceramic crowns fabricated with gold cylinders and cemented on implant abutments. These discrepancies were then compared with those measured previously for implant-supported ceramic crowns. MATERIALS AND METHODS: Fifteen Nobel BioCare CeraOne abutments were connected to implant fixtures embedded in acrylic resin blocks. Marginal discrepancies were determined for gold cylinders, gold cylinders plus ceramic alloy (metal frameworks), completed metal-ceramic crowns, and cemented metal-ceramic crowns using a stereomicroscope equipped with a video camera linked to a computer. A Hotelling's T2 test (p < or = .05) was used to evaluate potential differences in mean marginal discrepancies among groups. RESULTS: The mean marginal discrepancies were: 1) gold cylinders, 7.56 +/- 2.73 microns; 2) metal frameworks, 6.21 +/- 1.34 microns; 3) metal-ceramic crowns, 11.06 +/- 3.21 microns; and 4) zinc-phosphate cemented crowns, 31.47 +/- 6.65 microns. No significant difference between gold cylinders and metal frameworks was found. Mean marginal discrepancies for metal-ceramic crowns were significantly greater than discrepancies for cast gold cylinders. Cemented-crown mean marginal discrepancy was significantly greater than all other means. CONCLUSIONS: Cemented metal-ceramic crowns fabricated using proprietary gold cylinders exhibited well-fitting margins (31.47 microns).

Cementation↗

PubMed1996

A new polymer rigid matrix material.

PRIMM, or polymer rigid inorganic matrix material, is a promising new substance. An original approach to improving resin composites is introduced. Domains of tough, strongly bonded crosslinked ceramic fibers improve physical properties and handling characteristics. PRIMM may be the posterior restoration of the future.

Bicuspid↗

PubMedDate not supplied

The effect of load angulation on fracture resistance of teeth restored with cast post and cores and crowns.

The purpose of this study was to determine if loading post-restored teeth at different angles would affect their fracture resistance. Thirty maxillary central incisors were treated endodontically to within 5.0 mm of the apex. Standardized cast post and cores were fabricated using plastic #4 Parapost patterns. Post and cores were cemented using zinc phosphate cement, followed by crowns of average dimensions. Ten teeth each were loaded at 110, 130, and 150 degrees to the long axis of the tooth. Mean failure loads were: 110 degrees = 372.4 N +/- 140.8 (SD); 130 degrees = 597.6 N +/- 138.5 (SD); 150 degrees = 1274.3 N +/- 429.9 (SD). There were significant differences in fracture resistance between teeth tested at the following angles: 110 degrees versus 150 degrees (P < .0001), and 130 degrees versus 150 degrees (P < .0001), but not for 110 degrees versus 130 degrees (P = .2016). Mean failure loads increased as load angle approached parallelism to the long axis of the teeth. Significant differences in fracture resistance of post-restored teeth can occur as a result of load angle.

Analysis of Variance↗

PubMedDate not supplied

Marginal accuracy of indirect provisional restorations fabricated on poly(vinyl siloxane) models.

Indirect interim restorations have been traditionally fabricated on stone casts. Recently, flexible models fabricated from poly(vinyl siloxane) impression material have been suggested in place of stone casts. This study compared the marginal accuracy of indirect single-unit provisional restorations fabricated on stone casts with units made on poly(vinyl siloxane) impression material models. The mean marginal discrepancy of provisional restorations was compared for restorations fabricated from stone, low-viscosity poly(vinyl siloxane), and medium-viscosity poly(vinyl siloxane). Ten restorations were also fabricated directly on a master metal model (control). The mean marginal discrepancies were: control = 0.161 mm; stone model = 0.180 mm; low-viscosity poly(vinyl siloxane) = 0.245 mm; and medium-viscosity poly(vinyl siloxane) = 0.157 mm. The mean marginal discrepancy for the low-viscosity poly(vinyl siloxane) models was significantly higher than the other three groups. No significant difference was found between the control, stone cast, and medium-viscosity poly(vinyl siloxane) model groups.

Analysis of Variance↗

PubMedDate not supplied

Marginal accuracy of provisional restorations fabricated by different techniques.

Provisional restorations were fabricated on a cast metal model and the resulting marginal discrepancies were measured. In the control group, the restorations were fabricated directly on the die and no coolant was applied. Five other methods of fabricating provisional restorations were evaluated. The mean marginal discrepancies were as follows: Control = 0.228 mm, In Situ (control plus coolant) = 0.196 mm, Removal (removed from die to polymerize) = 0.403 mm, On/Off (repeated removal/replacement) = 0.601 mm, Reline = 0.074 mm, and Indirect = 0.161 mm. The mean marginal discrepancy for the On/Off technique was significantly greater than that for all other techniques. The mean marginal discrepancy with the Removal technique was significantly greater than that with the Control, In Situ, Reline, and Indirect techniques. No significant differences were found between the Control, In Situ, Reline, and Indirect techniques.

Analysis of Variance↗

PubMedDate not supplied

Finishing and polishing of a poly (fluoroalkoxyphosphazene) resilient denture liner.

A raised ridge of Novus resilient denture liner was removed from samples using one of three burs, three stones, or a coarse sandpaper disc. Samples were polished using pumice alone, tin oxide alone, or both agents. A flat, unfinished sample served as a control. Average surface roughness of control samples was 0.96 microns. Average surface roughness measurements for reduced samples ranged from 7.21 microns (sandpaper disc) to 3.34 microns (Prolastic wheel). Without polishing, sandpaper discs and serrated burs produced rougher surfaces than stones or the nonserrated bur. The sandpaper disc reduced the liner the quickest. There were no significant differences between treatments or controls after the use of pumice alone or after the use of a combination of pumice and tin oxide. An acceptable finishing protocol for this poly(fluoroalkoxyphosphazene) resilient liner appears to differ from that previously established for a silicone resilient denture liner.

Analysis of Variance↗