Peter S. Vig

The validation of the Peer Assessment Rating index for malocclusion severity and treatment difficulty

The Peer Assessment Rating (PAR) index is a British occlusal index that measures the severity of dental malocclusion and has been used in several investigations that have evaluated the effectiveness of orthodontic treatment provision in Europe. As part of its development, the PAR index was validated for malocclusion severity, by using the opinions of a panel of 74 dentists and orthodontists. The present investigation was carried out to validate the PAR index, by using the opinion of an American panel of orthodontists. Eleven orthodontists examined a sample of 200 sets of study casts and rated them for malocclusion severity and perceived treatment difficulty. Multiple regression techniques were used to evaluate the predictive power of the components of malocclusion on the panels scores. Weightings were calculated from the partial regression coefficients and, when these weightings were applied to the PAR index, the association between the panels opinion and the PAR index scores was increased.

The effect of rapid maxillary expansion on nasal airway resistance.

The purpose of this study was to evaluate changes in nasal resistance to airflow in persons undergoing rapid maxillary expansion and to reevaluate the responses at a 1-year follow-up. Nasal resistance measurements, assessed in four modes (natural state, anterior nares dilation with Tygon tubing, following administration of decongestant, and nares dilation with tubing and decongestant), were taken on a group of 38 patients receiving rapid maxillary expansion and compared with a control group not receiving expansion. Thirty-three of the patients were reevaluated 9 to 12 months after expansion was completed. Eighteen subjects in the control group were also reevaluated. Oral/nasal airflow rates (percent nasality) were recorded for the control group and for some of the expansion patients. Results indicated that some subjects receiving rapid maxillary expansion had a significantly higher nasal resistance than the control group. There was a significant median reduction in nasal resistance following rapid maxillary expansion, measured in the natural state only, and this appeared to be stable up to 1 year after maximum expansion was obtained. Rapid maxillary expansion appeared to effect an expansion at the anterior nares, which contributes to nasal resistance reduction. Individual variation in nasal resistance values was considerable and hence the median response for the group was not a reliable estimate of individual response. Due to the high individual response variability, rapid maxillary expansion is not a predictable means of decreasing nasal resistance.

The effectiveness of Class II, Division 1 treatment

The aim of this retrospective study was to evaluate the effectiveness of orthodontic treatment in terms of two outcome variables, namely, the percentage change in a valid and reliable occlusal index, the Peer Assessment Rating (PAR) score, and the duration of treatment. Data were collected from the records of 250 patients with Class II, Division 1 malocclusions who were treated in the Orthodontic Department of the University of Pittsburgh between 1977 and 1989. The relationships between the outcome and the treatment variables were analyzed with multiple regression techniques. Those variables significantly associated with the duration of treatment (p < 0.01) were (1) the pretreatment PAR score, (2) the number of treatment stages, (3) the percentage of appointments attended, (4) the number of appliance repairs, and (5) whether the patient was treated with or without extractions. The only variable that influenced the percentage change in PAR was the pretreatment PAR score (p < 0.01).

Lower anterior face height and lip incompetence do not predict nasal airway obstruction

The controversy regarding nasal obstruction and malocclusion has been largely due to the inability to quantitate nasal airway function and hence objectively determine the mode of breathing. The purpose of this study was to measure the nasal airway resistance of patients before and after rapid maxillary expansion (RME), to compare them to a control group of subjects not receiving RME, and to measure oral/nasal airflow ratios (respiratory mode). An evaluation of the statistical associations between anterior facial height, lip posture, oral/nasal airflow ratios, and nasal resistance was undertaken. The effects of RME on nasal resistance have been reported elsewhere. We found that variation, for resistance values, was very high, and thus the median response for the group was not an adequate estimation of individual response. In this paper we describe associations between lip posture, lower anterior facial height, and nasal resistance. No significant correlations could be established between respiratory and morphologic features. Lower anterior facial height was greater in the lips apart posture group. However, there was no significant correlation between percent nasality and lower anterior facial height. A small negative correlation (r = -0.47) existed between nasal resistance and percent nasality, but this relationship was not linear. Thus, it was not possible to predict percent nasality from nasal resistance data. Furthermore, no correlation was found between the amount of expansion and changes in nasal resistance. This paper was originally submitted June 1986, and revised October 1988.

An improved technique for the simultaneous measurement of nasal and oral respiration

A technique is described to record and measure both the nasal and oral components of respiratory airflow. The method is a modification of a previously reported technique, and represents an improvement in terms of accuracy, speed, convenience, and facility in both the acquisition and analysis of a large set of data per subject. The equipment and associated computer configuration permits a temporal characterization of inspiratory and expiratory parameters of both nasal and oral airflow, nasal airway resistance computation at predetermined flow rates, and the calculation of estimates of the minimum cross-sectional area of the nasal air passage.

Sensitivity and specificity of diagnostic tests for impaired nasal respiration

Diagnostic tests are imperfect and vary in their sensitivity and specificity. The degree of imprecision may be calculated to yield probability estimates of accuracy for both the positive and negative predictions of tests under various conditions. Such information enables clinicians to decide whether to accept or reject test results or the tests themselves. Two pilot studies are reported to establish the diagnostic potential of cephalometric measurements and nasal resistance values for the identification of upper airway impairment. A linear estimate of adenoid size and an area index of adenoid encroachment in the nasopharynx were evaluated as diagnostic tests for increased nasal resistance. The sensitivity of the tests was 31.8% and 18.2%, while specificity was calculated at 83.3% and 66.6%, respectively. In the second study, nasal resistance was evaluated as a test to identify persons whose respiratory mode was equal to or less than 75% nasal airflow. At a NRz value of 5.0 cm H2O per liter per second, the sensitivity of this test was 41.2% and the specificity was 84.0%; with the critical value of NRz at 3.5 H2O per liter per second, the sensitivity was 64.7% and the specificity was reduced to 60.0%. The results suggest that these tests are too imprecise for the reliable identification of either those who might benefit from treatment or those for whom treatment is unlikely to yield benefits.

External nasal morphology and respiratory function.

Clinicians have been known to characterize nasal respiratory function on the basis of subjective appraisal of external facial morphology. Certain nasal morphologic features have been assumed to be associated with impaired nasal function. The purpose of this study was to develop measures of anterior external nasal morphology and to determine whether any of these measures correlate with nasal function. Nasal casts were produced from impressions of 60 postpubertal white subjects from which four measures were made to characterize nasal morphology: (1) nasal base shape, (2) minimum nasal orifice width, (3) nasal orifice shape, and (4) nasal orifice area. Nasal function was evaluated by measuring nasal airway resistance by means of posterior rhinomanometry and by measuring the air respired nasally and orally by means of the simultaneous nasal and oral respirometric technique. No significant correlations were found between external nasal morphology and nasorespiratory function. These findings underscore the necessity of avoiding assumptions about breathing function on the basis of clinical appraisal of external nasal form.

Orthodontics—Guilty until proved innocent: How do we plead? or What kind of orthodontics may we practice?

T he time is past when society accorded doctors unquestioning respect and trust in deference to those whose knowledge, skill, and altruism were beyond question. Despite remarkable advances in biomedical research and technology that today make commonplace what only recently would have been considered miraculous, the concerns of society with the cost of health care overshadow other considerations. There have been drastic and rapid changes in the socioeconomic environment within which we function. The effects are not confined to orthodontics but affect most clinical fields, and are manifested to a greater or lesser extent globally. Perhaps it is attributable to the rapidity of this change, which has occurred within the practicing lifetime of the majority of health professionals, that we appear to be ill prepared to cope with challenges that have no historical precedents in our experience. For most of us, our education and subsequent patterns of practice were shaped by factors other than questions of supply and demand, professional accountability, or considerations of the utility of competing clinical alternatives. Given that societal expectations have changed-for example, where “informed consent” is concerned, we need to rationally evaluate present circumstances and learn as much as we can about our level of performance and the reasons for any discrepancies between our “worth” as perceived by us and by others. Although we may not be accustomed to having our worth questioned and our first reaction may be indignation, it is to be expected that orthodontics, like other health services that deal with treatments of elective and nonfatal conditions, will be subjected to pressure. The