Condyle-fossa modifications and muscle interactions during Herbst treatment, part 1. New technological methods

Changes in the condyle, the glenoid fossa, and the muscles of mastication were investigated in subjects undergoing continuous orthopedic advancement of the mandible with a Herbst-block appliance. The total sample consisted of 56 subjects and included 15 nonhuman primates (in the middle mixed, early permanent, and permanent dentitions), 17 human Herbst patients in the early permanent dentition, and 24 human controls from the Burlington Growth Center. The 8 nonhuman primates in the middle mixed dentition were the focus of this study. Mandibular advancement was obtained progressively in 5 animals by adding stops to the telescopic arms of fixed functional Herbst appliances with occlusal coverage; activations of 5.0 mm, 7.0 mm, and 8.0 mm were achieved. Two primates served as controls, and the third was a sham control. Two experimental animals and the 2 controls also wore surgically implanted electromyographic electrodes in the superior and inferior heads of the lateral pterygoid muscles and in the superficial masseter and anterior digastric muscles. Changes in condylar growth direction and amount were assessed with the Björk method from measurements made on serial cephalometric tracings superimposed on metallic implants. Undecalcified sections, treated with intravenous tetracycline vital staining, were viewed with fluorescence microscopy to examine histologic changes in the condyle and the glenoid fossa. New bone formation in the fossa associated with continuous mandibular protrusion was quantified by using computerized histomorphometric analysis of decalcified histological sections and polarized light. The unique combination of permanently implanted electromyographic electrodes, tetracycline vital staining, and histomorphometry represents a significant technological advancement in methods and materials. Together, they demonstrated different muscle-bone interaction results for functional appliances than those reported in previous studies. In Part 1 of this study, we describe and discuss the techniques used in this research and give a brief overview of the findings; in Part 2 (to be published next month), we offer a more in-depth discussion of the results and the implications of our findings

Condyle-fossa modifications and muscle interactions during Herbst treatment, Part 2. Results and conclusions

Herbst appliances were activated progressively in growing nonhuman primates, and the results were compared with primate and human controls. The methods and materials of this research are explained in Part 1 of this study. The results are discussed here in Part 2. All experimental subjects developed large super Class I malocclusions, the result of many factors including posterior movement of the maxilla and the maxillary teeth, an increased horizontal component of condylar growth, and anterior displacement of the mandible and the mandibular teeth. The growth modification measured in the glenoid fossa was in an inferior and anterior direction. Restriction of the downward and backward growth of the fossa observed in the control subjects might additionally contribute to the overall super Class I malocclusion. Clinically, these combined effects could be significant at the fossa. The restriction of local temporal bone (fossa) growth cannot be observed clinically; thus, these results might also clarify some Class II correction effects that cannot be explained with functional appliances. Differences in the area and maximum thickness of new bone formation in the glenoid fossa and in condylar growth were statistically significant. The bony changes in the condyle and the glenoid fossa were correlated with decreased postural electromyographic activity during the experimental period. Results from permanently implanted electromyographic sensors demonstrated that lateral pterygoid muscle hyperactivity was not associated with condyle-glenoid fossa growth modification with functional appliances, and that other factors, such as reciprocal stretch forces and subsequent transduction along the fibrocartilage between the displaced condyle and fossa, might play a more significant role in new bone formation. These results support the growth relativity concept

Visualizing⋅matching⋅generalizing: Case identification hypotheses and case-level data analysis

The traditional and still dominant logic among nearly all empirical positivist researchers in schools of management is to write symmetric (two-directional) variable hypotheses (SVH) even though the same researchers formulate their behavioral theories at the case (typology) identification level. The behavioral theory of the firm, theories of buyer behavior, and Miles and Snow's typology of organization's strategy configurations (e.g., "prospectors, analyzers, and defenders") are iconic examples of formulating theory at the case identification level. When testing such theories, most researchers automatically, unconsciously, switch from building theory of beliefs, attitudes, and behavior at the case identification level to empirically testing of two-directional relationships and additive net-effect influences of variables. Formulating theory focusing on creating case identification hypotheses (CIH) to describe, explain, and predict behavior and then empirically testing at SVH is a mismatch and results in shallow data analysis and frequently inaccurate contributions to theory. This paper describes the mismatch and resulting unattractive outcomes as well as the pervasive practice of examining only fit validity in empirical studies using symmetric tests. The paper reviews studies in the literature showing how matching both case-based theory and empirical positivist research of CIH is possible and produces findings that advance useful theory and critical thinking by executives and researchers