Color of Denture Resins

The color of 24 commercially available denture resins was determined visually with Munsell color tabs and by reflection spectrophotometry. Correlation between Munsell and spectrophotometric data was found. The resins characterized for Black patients had a higher degree of specular reflectance and were more opaque than resins for Caucasians.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68003/2/10.1177_00220345770560070901.pd

Dynamic Mechanical Properties of Maxillofacial Materials

Six maxillofacial materials were evaluated by determining their dynamic properties with use of a Goodyear Vibrotester. The dynamic modulus, internal friction, and dynamic resilience were measured for all materials over a temperature range of -15 to 37 C. The dynamic modulus ranged from 11.1 to 124.8 kg/cm2 and the dynamic resilience varied from 1.1 to 63.5%.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67192/2/10.1177_00220345750540062001.pd

Dimensional Stability of Elastomers for Maxillofacial Applications

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68189/2/10.1177_00220345790580091001.pd

Color of Gingival Tissues of Blacks and Whites

Value, chroma, and hue of attached gingiva of blacks and whites were measured clinically with Munsell color tabs. The color of nonmottled gingiva of blacks and whites was similar. The color of gingiva pigmented by melanin in blacks was similar in hue, but lower in value and chroma than nonmottled gingiva.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67985/2/10.1177_00220345770560020301.pd

Late Glacial and Holocene Record of Climatic Change in the Southern Rocky Mountains from Sediments in San Luis Lake, Colorado, USA

Large rapid climate changes occurred over the last glacial cycle in the southwestern United States and elsewhere in many regions of the world. Some of these changes were attributed to alternations between stadial and interstadial conditions in the North Atlantic. But intense debate exists on how climate anomalies in the North Atlantic transmit to the southwest. Here we report a sediment record from San Luis Lake in southern Colorado, through analyses of grain size, magnetic susceptibility, Mg/Ca, total inorganic carbon, δ18O and δ13C, to indicate climatic and environmental changes in the southern Rocky Mountains over the last 16.5 ka. We found that San Luis Lake remained hydrologically closed most of the time but overflowed during the second half of the Mystery Interval (the Big Wet: 15.7–14.9 ka) and the latter part of the mid-Holocene (the Neopluvial: 4–3 ka). Over the course of the last deglaciation, San Luis Lake underwent a series of large millennial-scale hydroclimatic changes such as the Big Dry (16.5–15.7 ka), the Big Wet, the Bølling–Allerød dry (14.9–12.7 ka), and the Younger Dryas wet (12.8–11.6 ka), corresponding to warm/cold phases in the high-latitude Northern Hemisphere. The North American monsoon waxed during the Pre-Boreal interval (11.6–10.5 ka) and waned through the Holocene, in phase with northward and southward displacement of the intertropical convergence zone (ITCZ). The San Luis Lake basin was relatively dry in the early Holocene (10.5–6.7 ka), wet and fluctuating in the mid-Holocene (6.7–2.6 ka), and dry and less variable in the late Holocene (2.6–0 ka). We found evidence that extreme pluvial episodes of the southern Rocky Mountains and elsewhere in the American Southwest were coeval with cold phases of the North Pacific. Our results highlight the role of the North Pacific in modulating atmospheric circulations over the region on millennial timescales

Effect of Processing Temperature on the Properties of a Polyvinyl Chloride Maxillofacial Elastomer

Mechanical properties and color of a plasticized polyvinyl chloride (PVC) maxillofacial elastomer were evaluated at processing temperatures from 140 to 190°C. The properties were dependent on processing temperature. Specimens prepared at 170°C had optimum mechanical properties with minimal discoloration.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66749/2/10.1177_00220345830620102001.pd

Stain Removal from a Silicone Maxillofacial Elastomer

In this study, environmental stains were removed from maxillofacial elastomers by solvent extraction. Silastic 44210, an RTV silicone with proven color and physical property stability, was stained with lipstick, disclosing solution, and methylene blue. These stains were then removed by solvent extraction with each of four chemically dissimilar solvents, namely: toluene, benzene, 1,1,1-trichloroethane, and n-hexane. An additional series of samples was prepared with 11 maxillofacial pigments, not for staining, but for evaluation of pigment stability. Results obtained from spectrophotometric measurements before and after solvent extraction demonstrated the effectiveness of solvent extraction in removing stains, while there was little or no change in the color of the pigments or the base elastomer.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66797/2/10.1177_00220345810600100501.pd

Elastomers for maxillofacial applications

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23271/1/0000208.pd

Physical property comparison of 11 soft denture lining materials as a function of accelerated aging,

Soft denture-lining materials are an important treatment option for patients who have chronic soreness associated with dental prostheses. Three distinctly different types of materials are generally used. These are plasticized polymers or copolymers, silicones, or polyphosphazene fluoroelastomer. The acceptance of these materials by patients and dentists is variable. The objective of this study is to compare the tensile strength, percent elongation, hardness, tear strength, and tear energy of eight plasticized polymers or copolymers, two silicones, and one polyphosphazene fluoroelastomer. Tests were run at 24 hours after specimen preparation and repeated after 900 hours of accelerated aging in a Weather-Ometer device. The data indicated a wide range of physical properties for soft denturelining materials and showed that accelerated aging dramatically affected the physical and mechanical properties of many of the elastomers. No soft denture liner proved to be superior to all others. The data obtained should provide clinicians with useful information for selecting soft denture lining materials for patients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31019/1/0000695.pd

Color Stability of Restorative Resins Under Accelerated Aging

The color stability of seven commercial composite resins, an unfilled resin, and three glazes was studied under conditions of accelerated aging by reflection spectrophotometry and visually with Munsell color tabs. After aging for 900 hours, most of the resins had lower values of luminous reflectance and excitation purity and higher values of dominant wavelength and contrast ratio compared to values at baseline.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66937/2/10.1177_00220345780570111101.pd