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PubMed1999

Dental materials: 1997 literature review.

This review of the published literature on dental materials for the year 1997 has been compiled by the Dental Materials Panel of UK. It continues a series of annual reviews started in 1973. Emphasis has been placed upon publications, which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, dentine bonding, dental amalgam, endodontic materials, casting alloys, ceramometallic restorations and resin-bonded bridges, ceramics, denture base resins and soft lining materials, impression materials, dental implant materials, orthodontic materials, biomechanics and image processing, resin composites, and casting investment materials and waxes). Three hundred and thirty three articles have been reviewed.

Dental Materials↗
PubMed2000

Customized abutments to shape and transfer peri-implant soft-tissue contours.

With the functional successes of implant therapy being realized, the emphasis is shifting to the creation of tooth-like esthetics with implant therapy. Dental implants are placed after careful planning and site preparation, which may include bone and soft tissue grafting. The final soft tissue appearance is enhanced through the early use of provisional restorations. A combination technique is described to fabricate provisional healing abutments for cement-on prostheses and to transfer the individualized peri-implant soft-tissue contours to the dental laboratory. This technique will allow the practitioner to deliver highly customized implant care with familiar techniques and readily available materials.

Dental Abutments↗
PubMed2001

Comparative in vitro evaluation of two provisional restorative materials.

STATEMENT OF PROBLEM: Provisional crowns traditionally have been associated with problems such as poor occlusion, contour, fit, and finish. Fabrication procedures should be uncomplicated and predictable within a realistic time frame. PURPOSE: The purpose of this study was to compare the quality of provisional restorations fabricated by dental students from 2 different materials (bis-acryl composite resin and PMMA) and identify the advantages and disadvantages associated with each material. MATERIAL AND METHODS: This study evaluated the occlusion, contour, marginal adaptation, and finish of 222 provisional crowns fabricated by 2 groups (A and B) of dental students. One bis-acryl composite resin material (Integrity) and 2 PMMA resins (C&B Resin and Snap) were evaluated. RESULTS: For group A, Integrity was statistically superior (P<.05) to C&B Resin in all 4 categories for anterior provisional crowns. For posterior provisional crowns, Integrity proved superior in the categories of contour and marginal adaptation, but no significant differences were established for occlusion and finish. For group B, Integrity was statistically superior to Snap in the categories of occlusion, contour, and marginal adaptation, whereas there was no statistical difference in finish. When all 4 categories were analyzed, Integrity was found to be statistically superior. CONCLUSION: Bis-acryl composite resin (Integrity) was significantly superior to PMMA (C&B Resin and Snap) as a provisional restorative material.

Composite Resins↗
PubMed2006

Dimensional accuracy of a new polyether impression material.

OBJECTIVES: The purpose of this study was to evaluate the dimensional accuracy of stone dies produced from standardized impressions with 1 new and 1 conventional polyether impression material and a polyvinyl siloxane reference material. METHODS AND MATERIALS: Impressions with the polyether materials P2 and Impregum and with the polyvinyl siloxane Flexitime were produced at 23 degrees C or 37 degrees C from a truncated steel cone in cylindrical steel trays giving 4-mm impression layer thickness at the prominence line. Stone dies were poured after 1 or 24 hours of storage at ambient atmosphere. Additional impressions were stored at different relative humidity levels (0%, 33%, 50%, 75%, or 100%) for 24 hours prior to die pouring. The accuracy of the stone dies was determined as axial discrepancy between a steel ring, which fit perfectly on the steel die and the occlusal die surface. The base-diameter deviation (deltad) was calculated. RESULTS: After 1 hour, a similar increase in deltad was noticed for impression materials when dies were poured at impression temperature. Impressions made at 37 degrees C exhibited significantly higher deltad than at 23 degrees C. Light-bodied P2 showed the highest deltad increase when dies were poured after 24 hours. Flexitime showed moderate deltad differences at the 2 pouring times. The deltad of dies made from polyether materials decreased significantly with increasing humidity, whereas polyvinyl siloxane was not adversely affected. CONCLUSION: The dimensional accuracy of P2 is comparable to that of the conventional polyether impression material after short-term storage. Polyethers may absorb water, significantly compromising die accuracy upon storage at high humidity.

Absorption↗
PubMed1998

A cadaveric study of maxillary sinus size as an aid in bone grafting of the maxillary sinus floor.

PURPOSE: This study measured maxillary sinus volume as an aid in determining graft bone volume before grafting of the maxillary sinus floor. MATERIALS AND METHODS: Maxillary sinus size was measured in 32 cadavers (59 sinuses) using casts of the maxillary sinus made using dental impression material. RESULTS: Anteroposterior length, height, width, and volume of the maxillary sinus (mean+/-SD) were 30.1+/-5.65 mm, 34.6+/-7.71 mm, 25.4+/-5.71 mm, and 11.3+/-4.60 cm3, respectively. When the sinus-lift procedure was simulated, inferior sinus volumes (mean +/- SD) were 3.51+/-1.23 cm3 for a 15-mm lift and 5.66+/-1.71 cm3 for a 20-mm lift. CONCLUSIONS: In bone grafting of the maxillary sinus floor, taking into consideration individual differences in maxillary sinus volume and resorption of the grafted bone, 4.74 cm3 or more of the graft is required for a 15-mm lift, and 7.37 cm3 or more is required for a 20-mm lift.

Aged↗
PubMed1990

Prevention of acquired immunodeficiency syndrome and hepatitis B. Part IV: The effect of impression material on glutaraldehyde solution.

Immersion of dental impressions in 2% glutaraldehyde has been shown to be an effective disinfection procedure for viral contamination. This study compared the effect of immersing impression materials on the concentrations of glutaraldehyde. Contamination with saliva slightly affected the concentration of glutaraldehyde. Irreversible hydrocolloid impression material markedly decreased the concentration of glutaraldehyde, whereas the immersion of silicone rubber impression material only slightly affected the concentration of glutaraldehyde. Attention should be paid to the concentration of glutaraldehyde solution when irreversible hydrocolloid impression material is immersed in the disinfectant.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Tensile strength of elastomeric impression materials, adhesive and cohesive bonding.

Numerous factors are known to effect the accuracy of elastomeric impression materials. Factors often overlooked are the quality of the bond between low-viscosity and high-viscosity elastomers and the presumed cohesive bond between materials during an impression reline procedure. This study examined the bond strength of condensation polymerization polysiloxanes, addition polymerization polysiloxanes, polyethers, and a light-cured polyether urethane dimethacrylate. Of the tested materials, light-cured polyether urethane dimethacrylate exhibited the greatest bond strength. The reline technique, light-body cured to previously cured heavy-body putty, yielded results similar to the simultaneous-cure technique. In terms of bond strength there is no advantage of one technique over the other. The corrective reline technique yielded acceptable results in bond strength. In general, the tested materials exhibited greater tensile strength than bond strength.

Dental Bonding↗
PubMed1991

Determination of polymerization shrinkage kinetics in visible-light-cured materials: methods development.

An instrument for the reproducible measurement of polymerization shrinkage kinetics is described, constructed around a disc-shaped specimen sandwiched between two glass plates. Test specimens of light-sensitive dental restorative materials were irradiated through the lower, rigid plate. The upper, non-rigid plate was readily deflected by an increase of the adhesive stress from the polymerizing and shrinking sample. Deflection was measured by an LVDT transducer and computer-recorded. Dimensional changes were confined to the specimen disc-thickness dimension, such that the fractional linear shrinkage approximated the volumetric shrinkage. Shrinkage data are reported for representative materials: unfilled and resin composites, base-lining materials, and an impression material. Equilibrium shrinkage magnitudes ranged from 0.65%, for the impression material, to 7.9% for the unfilled resin. The kinetic behavior was approximately characterized by an overall time constant, ranging from 12.5 to 280 s, associated with an exponential growth curve, although the initial shrinkage was near-linear in time, for many materials, due to non-steady-state concentrations of polymer free-radicals. The test-specimen geometry facilitates rapid and essentially uniform cure and hence the determination of minimum possible time-constants at each ambient temperature and incident light-intensity. Study of hybrid glass-ionomer materials, without spurious dehydration effects, was also achieved.

Acrylic Resins↗