Donald H. Enlow

GROWTH AND REMODELING OF THE HUMAN MAXILLA.

THE purpose of the present study is to describe and interpret the sequence of remodeling changes which take place during the postnatal growth of the young human maxilla. This report is a sequel to previous studies dealing with principles of bone remodeling and with the postnatal growth of the human mandible.l-” As the growing maxilla increases in size, there is a companion process of remodeling which functions to maintain the constant proportions of the bone’s shape and the relative positions of its component parts. This process of remodeling involves sequential, localized adjustments in bone structure during the constant changes produced by the growth of the entire maxilla. An understanding of these remodeling changes is basic to a meaningful interpretation of the over-all process of growth.

The neurocranial basis for facial form and pattern.

Abstract No Abstract Available. From the Departments of Anatomy, West Virginia University and the University of Michigan.

A morphogenetic analysis of facial growth

Abstract This study is an analysis of facial growth patterns based on known remodeling changes that occur in the various bones and parts of bones in the human face. Serial cephalometric tracings were used to correlate these remodeling changes with successive growth stages. The results of the study provide an account of the actual changes that take place in the facial skeleton during craniofacial growth. The standard system of cephalometric superimposition using fixed reference landmarks provides, in contrast, a picture of apparent growth movements due to the forward thrust (displacement) of the maxilla and mandible away from the cranial base. A more meaningful and complete understanding of over-all facial growth is gained when both systems are used, one supplementing the other. Each component area in the frontal and nasal bones, the maxilla, the zygoma, and the mandible are considered separately. Regional growth movements are described, and relationships are analyzed. A correlation is presented between characteristic age changes that take place in the topographic features of the face and the corresponding remodeling changes that accompany over-all facial growth.

Lamellar Bone is an Incremental Tissue Reconciling Enamel Rhythms, Body Size, and Organismal Life History

Mammalian enamel formation is periodic, including fluctuations attributable to the daily biological clock as well as longer-period oscillations that enigmatically correlate with body mass. Because the scaling of bone mass to body mass is an axiom of vertebrate hard tissue biology, we consider that long-period enamel formation rhythms may reflect corresponding and heretofore unrecognized rhythms in bone growth. The principal aim of this study is to seek a rhythm in bone growth demonstrably related to enamel oscillatory development. Our analytical approach is based in morphology, using a variety of hard tissue microscopy techniques. We first ascertain the relationship among long-period enamel rhythms, the striae of Retzius, and body mass using a large sample of mammalian taxa. In addition, we test whether osteocyte lacuna density (a surrogate for rates of cell proliferation) in bone is correlated with mammalian body mass. Finally, using fluorescently labeled developing bone tissues, we investigate whether the bone lamella, a fundamental microanatomical unit of bone, relates to rhythmic enamel growth increments. Our results confirm a positive correlation between long-period enamel rhythms and body mass and a negative correlation between osteocyte density and body mass. We also confirm that lamellar bone is an incremental tissue, one lamella formed in the species-specific time dependency of striae of Retzius formation. We conclude by contextualizing our morphological research with a current understanding of autonomic regulatory control of the skeleton and body mass, suggesting a central contribution to the coordination of organismal life history and body mass.

A procedure for the analysis of intrinsic facial form and growth An equivalent-balance concept

T his report introduces and describes a method of cephalometric evaluation for in&viduals based on their own particular morphologic and morphogenetic facial patterns. References to statistical population standards are not required. The purpose of the procedure is to analyze the nature of anatomic fit among the different bones of the craniofacial complex of one subject at any age and through time. The method is presented in two parts: (1) a “form analysis” which deals with facial pattern, construction, and dimensions and (2) a “growth analysis” which is concerned with an interpretation of incremental changes. This procedure is based on four basic morphologic concepts which are summarized below. The concept of architectural equivalence. In any functional assemblage of bones, such as the craniofacial complex, certain key dimensions must necessarily correspond between these bones in order to provide proper fit. A prescribed portion of each bone represents a direct architectural (dimensional) counterpart of some segment of another bone (or bones), even though their respective functions and other anatomic relationships are different. These dimensional analogues among bones are termed “equivalents.“3~ * If any two such equivalents match (or nearly match), a dimensional balance is thereby produced and morphologic fit is provided. If a match does not occur, however, corresponding architectural imbalance results and affects not only their own fit but that of other contiguous bones as well. As will be seen, an analysis of the nature of growth increments is a meaningful consideration, since continued growth can (1)

The effects of a 0.12% chlorhexidine gluconate mouthrinse on orthodontic patients aged 11 through 17 with established gingivitis.

The purpose of this study was to assess the effectiveness of a 0.12% chlorhexidine gluconate (CH) mouthrinse, Peridex, on orthodontic patients 11 through 17 years of age with established gingivitis. Thirty-four subjects were divided into two groups (CH and placebo) of 17 subjects each on the basis of gender, and they were evaluated at baseline, at 6 weeks, and at 12 weeks in a double-blinded manner. The gingival index (GI) of Löe and Silness, the plaque index (PI) of Silness and Löe, the Eastman Interproximal Bleeding Index, and the CWRU staining index were recorded for each subject. The subjects in the CH group, as compared with the placebo group, had statistically significant reductions, expressed as percent reductions against baseline, at the conclusion of this 3-month period: PI = 64.9%, GI = 60.0%, and gingival bleeding = 77.2%. Staining was in the moderate range, and it was concentrated on the mandibular lingual surfaces. Peridex, in combination with mechanical plaque removal, proved to be an important therapeutic agent in controlling gingival inflammation, bleeding, and plaque accumulation in orthodontic patients 11 through 17 years of age with established gingivitis.

An Analysis of Black and Caucasian Craniofacial Patterns

Abstract A comparison of basic anatomic relationships among the middle endocranial fossa, the mandibular ramus, the maxillary and mandibular bony arches, and the nasomaxillary complex in the Black and Caucasian craniofacial composites. Major differences were found, especially in those underlying Class III malocclusion.

Facial Variations Related to Headforrn Type

A comparison and evaluation of a range of basic anatomic relationships underlying facial form in Angle Class I and Class II dolichocephalic, brachycephalic, mesocephalic, and dinaric types of headform. Interrelated composites of these structural factors and their contributions to different malocclusion tendencies are described.

Remodeling reversals in anterior parts of the human mandible and maxilla.

Abstract No Abstract Available. From Case Western Reserve University, Cleveland, Ohio and supported in part by USPHS Grant DE05078.

Wolff's law and the factor of architectonic circumstance.

Abstract It is apparent that the gross morphology of a bone is largely adapted to the composite of its functions. Remodeling and relocation are processes that serve to sustain constant morphology during continued growth, thereby providing a basis for continuous, uninterrupted function. The same factors that control growth also apparently regulate the process of relocation, since the process of growth itself simultaneously produces relocation as an integral part of its operation. Stress forces, possible bioelectric factors, differential or selective cell and tissue responses to stimuli, genetic predisposition, tissue and cell induction, and the entire functional matrix (which perhaps includes all of these) should all be regarded, at the present time at least, as potentially contributory to over-all growth control at the local level. Architectonic circumstances, which apparently can draw upon selected combinations of any of these, are structural situations that must necessarily be taken into account in any evaluation of the local control mechanism in bone. The architectonic factor itself deals primarily with the process of relocation, and it requires a specialized mode of growth that is specifically adapted to providing the continuously shifting placement of a bones different parts as the whole bone increases in size. It is suggested that this consideration is fundamental and that it is a factor in determining the essential nature of balance between the different possible sources of control involved in normal morphogenesis. Detailed studies of craniofacial development should now be carried out in the light of Frosts approach to biomechanical analyses. The intermediary role of such factors as the piezo-electric effect appears to be of basic significance, and continued fundamental work in this and other similar directions is needed. Further, a meaningful explanation of the local control mechanism itself is to be sought, since this will provide the only key to resolving the underlying basis for the numerous growth complexities described in preceding pages. An understanding of the actual operation of this critical mechanism is to be regarded as one of the foremost problems relating to bone growth.