Changing the Risk Paradigms Can be Good for Our Health: J-Shaped, Linear and Threshold Dose-Response Models.

Both the linear (at low doses)-no-threshold (LNT) and the threshold models (S-shapes) dose-response lead to no benefit from low exposure. We propose three new models that allow and include, but do not require - unlike LNT and S-shaped models - this strong assumption. We also provide the means to calculate benefits associated with bi-phasic biological behaviors, when they occur and propose:THREE HORMETIC (PHASIC) MODELS: the J-shaped, inverse J-shaped, the min-max, andMethod for calculating the direct benefits associated with the J and inverse J-shaped models.The J-shaped and min-max models for mutagens and carcinogenic agents include an experimentally justified repair stage for toxic and carcinogenic damage. We link these to stochastic transition models for cancer and show how abrupt transitions in cancer hazard rates, as functions of exposure concentrations and durations, can emerge naturally in large cell populations even when the rates of cell-level events increase smoothly (e.g., proportionally) with concentration. In this very general family of models, J-shaped dose-response curves emerge. These results are universal, i.e., independent of specific biological details represented by the stochastic transition networks. Thus, using them suggests a more complete and realistic way to assess risks at low doses or dose-rates.

Perceived long-term prognosis of teeth with orthodontically resorbed roots.

OBJECTIVES: To investigate the perceived significance of root resorption in the dental community. STUDY DESIGN AND SAMPLE: Mail out survey questionnaire accompanied by morphed images of 10-50% root resorption. General practitioners, periodontists, prosthodontists and orthodontists were the participants. OUTCOME MEASURES: Correlations between 'significant' and 'detrimental to the longevity of the tooth'. These assessments were conducted within specialty groups and among. Also measured was the source of knowledge upon which practitioner assessments were based. RESULTS AND CONCLUSIONS: General practitioners were the most concerned about root resorption. Although most practitioners feel 50% root resorption is significant and detrimental to the longevity of the tooth, extraction followed by prosthetic replacement was not an option. No agreement among practitioners when orthodontic treatment should be terminated; the general practitioners were conservative suggesting termination after 35% root loss. History of trauma, genetic disposition and root morphology are the most cited predisposing factors. Lengthy treatment time concerns general practitioners more than the orthodontists. With the exception of orthodontists, dentists believe excessive force is detrimental to the root, but no one is able to define what excessive force is. Overall, dental school curricula overstate the causes of root resorption. Generally, dental professionals seem to base their opinions on myths and are largely inconsistent in their assessments.

A stochastic evaluation of the decision to specialize in orthodontics.

OBJECTIVE: The objective of this paper is to identify under different scenarios, and from a financial point of view, the conditions required to successfully switch from the general dentistry practice to orthodontics. STUDY DESIGN: A mail survey was used to collect the data from the practicing orthodontists. They estimated the income, at certain points, in the working life of an orthodontist. The general practitioner data were taken from the American Dental Association figures. Subsequently, a stochastic model was constructed. RESULTS AND CONCLUSION: Those who decide to buy an existing practice expect higher profits in the near future, and therefore the required minimum number of remaining years of practice is lower than for those deciding to start a new practice. For both scenarios, the 3-year residency will delay the profits compared with a 2-year residency. Thus, an increased number of remaining years of practice is required. There must be more than 10 working years left in the practitioner's life to make the switch profitable.

Treatment time, outcome, and patient satisfaction comparisons of Damon and conventional brackets.

Efficiency of treatment mechanics has been a major focus throughout the history of orthodontics. Self-ligating brackets were developed on the premise that elimination of ligature ties creates a friction-free environment and allows for better sliding mechanics. It is expected that the self-ligating bracket will reduce the treatment time. This study was designed to compare the effectiveness and efficiency of Damon self-ligating (SL) brackets to those brackets ligated with either steel ligatures or elastomeric 'O' rings. Not only treatment time and the number of appointments needed were addressed, but the quality of the treatment outcome was also assessed. American Board of Orthodontics (ABO) grading criteria for models and panoramic radiographs were employed. Additionally, a nine-question survey was sent to the 215-patients in this study (108 Damon, 107 conventionally-ligated) to elicit their perceptions of how their orthodontic treatment progressed and finished. The results showed that patients treated with Damon SL brackets had significantly lower treatment times, required significantly fewer appointments, and had significantly higher ABO scores than those treated with conventionally-ligated edgewise brackets. There were no significant differences in Damon or non-Damon ABO scores with respect to gender. Damon patients over the age of 21 had significantly higher ABO scores. Conversely, the non-Damon patients under the age of 21 had significantly higher ABO scores. For pre-treatment Angle classification, no significant differences were noted. Patient responses showed that Damon patients perceived their treatment time as being shorter than expected. It appears that faster orthodontic treatment can be better as measured by the ABO criteria.

Defining characteristics of financially successful orthodontists.

Financially successful personality profiles in most of the business world have been reported to be the choleric (powerful) and the melancholy (perfect) types. In 1996, Hughes proposed that the same relationship possibly exists in the profession of orthodontics. The purpose of this study was to explore whether a dominant personality profile exists for the most financially successful orthodontists. A questionnaire was used to gather information regarding the financial sophistication and the dominant personality profile of each participating orthodontist. One hundred twenty-six of the 300 surveys distributed to orthodontists were returned for a response rate of 42%. For every question, the null hypothesis of independence was tested with the chi-square test. The null hypothesis of independence was rejected for a P value of less than.05. The results revealed that no correlation exists between the financial sophistication of orthodontists and their personality profiles. However, over two thirds of the orthodontists had the choleric (powerful) and the melancholy (perfect) as dominant personality types. Interestingly, the questionnaire shed much light on factors that do contribute to financial success in orthodontics. Although statistical differences are lacking in these data, certain traits about successful practitioners could be identified. These orthodontists (1) allow their practices to grow if it will increase the net income, (2) view control of overhead as a key principle, (3) emphasize the competence of staff in determining the success of practice, and (4) believe in marketing. Implementation of these simple and common sense principles in some orthodontic practices might affect the business significantly.