To evaluate the color stability and mechanical properties of two commonly used maxillofacial silicone elastomers after addition of pigments and opacifiers and before and after artificial aging.
This ...study evaluated two maxillofacial silicone elastomers: A-2000 and M511. Two different pigment and opacifier systems (e-Skin and Reality Series) were used with the elastomers. Control groups (no pigment or opacifier) and experimental groups (each with subgroups containing additional pigments and/ or opacifiers) were fabricated for each of the silicone elastomers. A total of 51 specimens were evaluated for color stability, and 100 for mechanical properties. A spectrophotometer was used to assess CIE L*a*b* values before and after aging. CIELAB 50:50% perceptibility threshold (ΔE* = 1.1) and acceptability threshold (ΔE* = 3.0) were used to interpret color changes. A durometer and universal testing machine were used to evaluate the mechanical properties. ANOVA and Fisher least significant difference (LSD) test were performed to determine the statistical significance of the results (P < .05).
Significant differences in color measurements (ΔE*) were found for all silicone groups following artificial aging (P < .05). ΔE* values for the mixed pigment/opacifier subgroups of both elastomers were below the perceptibility threshold. Additionally, after aging, the hardness, tear strength, and tensile strength significantly increased for all silicone groups (P < .05), while percent elongation significantly decreased (P < .05).
Artificial aging affected the color stability and mechanical properties of the pigmented silicone elastomers with added opacifier. Overall, A-2000 with e-Skin group displayed the most color stability, with its mechanical properties being the least affected by artificial aging.
This study aimed to assess the perceived efficacy of aligners (Invisalign; Align Technology, Santa Clara, Calif) at performing extrusive movements of maxillary lateral incisors and to evaluate and ...compare differences in treatment planning protocols and other interventions used when required between orthodontists and general dentists with various degrees of experience.
An original 18-question survey was sent by mail to a randomized and geographically proportionate selection of orthodontic specialists (N = 400) and general dentists (N = 400) listed as providers on the Invisalign Web site. The data were analyzed using analysis of variance and chi-square tests.
One hundred twenty-six providers responded to the survey (15.8% response rate), including 36 general dentists and 90 orthodontists. Overall, the average perceived efficacy was 4.71 out of 10 (95% confidence interval, 4.28-5.14). The threshold for identification of tracking issues was significantly associated with provider type (P = 0.0305). General dentists were significantly more likely to prefer an optimized attachment (P = 0.0001), whereas orthodontists were significantly more likely to prefer a gingivally-beveled horizontal rectangular attachment (P <0.0001). A refinement scan was the most common intervention method, followed by the bootstrap technique.
The average perceived efficacy for extruding maxillary lateral incisors with aligners was 4.71 out of 10. Orthodontists had a lower tolerance than general dentists for tracking issues. A refinement scan was the most common method of intervention. General dentists and orthodontists differed in their treatment planning preferences and timing of intervention.
•Aligners are perceived as only moderately effective at extruding maxillary lateral incisors.•Orthodontists mostly preferred a gingivally-beveled horizontal rectangular attachment.•Orthodontists are more critical of tracking issues than general dentists.•A refinement scan was the most common method of intervention for tracking issues.•Orthodontists wait until the end of the series to take a refinement scan.
Why are some individuals more likely to become owners of small businesses than others? We classify industries using measures of entry barriers and proceed to investigate how determinants of entry ...vary in high- as opposed to low-barrier fields. Claims that neither financial-capital constraints nor the educational backgrounds of aspiring small-business owners predict the likelihood of small-business entry are investigated in this context. These claims of irrelevance, we find, are inconsistent with the facts. The wealth and educational background characteristics potential entrepreneurs possess predispose them to make distinctly different industry choices, both because of the differing rewards available to them and the very different entry barriers they face. The characteristics of potential entrants, in other words, draw them toward some industries and away from others.
► Traits of potential entrepreneurs draw them toward some types of new ventures and away from others. ► High personal wealth sometimes predicts entrepreneurial entry and sometimes it doesn't. ► The college graduate trait negatively predicts entry into many lines of small business.
Multiple studies document both the scarcity of small-business financing in inner-city minority communities and the higher loan application rejection rates among minority business enterprises (MBEs), ...compared with equally creditworthy White-owned firms. When MBEs do receive bank financing, they get smaller loans than Whites. Two aspects of these findings are troublesome. First, urban MBEs are heavily concentrated geographically in minority communities, raising the issue of whether difficulties accessing financing reflect firm location, minority ownership, or both. Second, applicable studies rest on weak theoretical foundations. The authors’ findings suggest that banks engage in discriminatory practices limiting credit availability to MBEs. Controlling for risk factors, however, firm location in a minority or inner-city neighborhood has no apparent impact on loan availability or size. Owner race/ethnicity, in contrast, is important. Subtle processes discourage MBEs from seeking bank loans. Owner race and wealth both powerfully shape loan access: high wealth opens doors, minority ownership closes them.
The consensus view that discriminatory barriers limit the size and scope of America’s minority-business community is factually well-grounded. Rarely examined, however, is the question of why these ...firms are flourishing. The authors examine the scope of this growth and its causes. The process of selectively reducing discriminatory barriers inhibiting minority entrepreneurship’s development began in the 1960s, moved forward in the 1970s, and continues presently. This path-dependent process of lowering barriers has altered the incentive structures, previously making the entrepreneurial choice an unattractive one for most minorities. This, in turn, has drawn into business ownership a younger generation of highly educated and experienced minorities, many of whom have successfully obtained bank loans. Spatially, minority neighborhoods as well have successfully attracted talented, experienced African American and Latino owners and financing for their firms. Those with abundant expertise have driven the substantial gains in numbers of workers employed by minority-owned businesses.
Prior to the 1970s, minority-owned small businesses were small in size and scope, and common in only a few industry niches. Business owners were severely capital-constrained, lacking in higher ...education, and training in skilled occupations. The median owner today, in contrast, is college educated, access to financing has expanded, and opportunities to serve corporate and public-sector clients are commonplace. Nearly 40% of all new firms created nationwide in 2015 were minority owned. Changing attitudes in mainstream society reduced traditional barriers. True equality of opportunity among small minority- and white-owned firms of similar size and scope has nonetheless not been achieved. This issue of Small Business Economics examines lingering barriers impeding the development of a more vibrant minority business community. Focusing on access to financing and government procurement markets, articles in this issue offer explicit analyses of enduring barriers, along with explanations of adoptive strategic firm behavior appropriate for reducing those barriers.
This study of small businesses created between 1989 and 1992, and then closed down between 1993 and 1996, reveals that owners often described their firms as “successful” when the closure decision was ...made. Decisions to discontinue operations of young firms are shaped by intertwined factors including opportunity costs, switching costs, and noneconomic considerations. Empirical investigation is undertaken to explain the seeming paradox of successful small-business closure. Alternative opportunities are identified as a key reason for choosing to discontinue successful firms: If something more attractive comes along, the owner may close down.
We examine causes of black/white gaps in self-employment entry rates in the United States by recognizing that industry context heavily shapes impacts of owner resource endowments on the likelihood of ...successful entry. Barriers to entry, briefly stated, are high in some lines of business and low in others. We therefore proceed by explaining self-employment entry into separate subgroups of high- and low-barrier industries. Higher entry rates typifying whites, relative to African Americans, are traditionally interpreted as reflections of the former group's greater personal wealth and human-capital resources. This consensus view, however, is simplistic: personal wealth holdings have no positive explanatory power for predicting entry into low-barrier lines of business. Our findings demonstrate, furthermore, that high educational attainment is a strong, positive predictor of entry into high-barrier fields, but not into low-barrier industries. Because industry context indeed shapes entry patterns, "one-size-fits-all" econometric models commonly used to predict entry into self-employment fall short.
Limited access to financing restricts the ability of minority business enterprises (MBEs) to achieve viability, to generate new jobs, and, generally, to reach their full potential to contribute to ...the economic development of the communities and regions in which they operate. Although MBEs rely more heavily on financial institutions for loans than all other borrowing sources combined, they experience higher costs than White firms when they borrow, receive smaller loans, and have their loan applications rejected more often. For MBEs in minority neighborhoods, these borrowing problems are compounded. Action is needed. The federal government needs to prosecute financial institutions that discriminate against MBEs on the basis of borrower race. Local governments can assist by weighing bank-lending activity in local minority communities when choosing the local banks with which they do business. Prompt payment of MBE vendor invoices by public-sector clients is needed.
Our study addresses a longstanding question—whether discrimination exists in financial markets. Although empirical evidence demonstrating disparate treatment of minorities is vast, studies have ...inadequately explained why minority customers seeking financing are targeted for discriminatory treatment. We develop a theoretical framework explaining why profitmaximizing capital suppliers may choose to offer minority clients worse terms than those provided to comparable white customers. Our framework stresses search costs and reservation prices. We then test this by comparing the relative profitability of investing private equity in minority- and white-owned small firms, an approach advocated by Gary Becker. Using three empirical tests, we consistently find the financial returns derived from investing in minority firms exceed those of white-firm investments. Conducting Becker's test, in this instance, indicates that disparate treatment of minority clients does not result in loss of profitable investing opportunities for private equity funds but, instead, higher profits.
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