Computerized comparison of histological methods for the evaluation of cranio-facial growth

The significance of a differential distribution of phosphomonoesterases on bone surfaces after prolonged demineralization

An observed differential distribution of alkaline and acid phosphatase on the surfaces of growing bones may serve to describe transformative processes of bone growth. This conclusion has been reached by comparing the distribution of the two enzymes on the surfaces of fibulae from young rats with the patterns of apposition and resorption on the periosteal surfaces of this bone, revealed by in vivo staining with alizarin red S. Presence of reaction to acid phosphatase is, as shown before, an indication of resorptive surfaces, while the presence of reaction to alkaline phosphatase is an indication of depository surfaces.

Characteristics of growing bone surfaces

Both bone-forming and bone-destructing cells may appear in different forms. This conclusion has been drawn as a result of compared observations from histomorphologic, histochemical and vital staining studies. The bone-forming cells may be cuboidal and situated in one or more rows along the bone surfaces, or may be flat. The type of cell reflects the rate of bone formation. The bone-resorbing cells may be big multinucleated cells or small mononucleated cells. The latter cell type is well-known from the literature although not referred to in textbooks of histology. Flat bone-forming cells and small mononucleated bone-resorbing cells resemble each other in the light microscope. Studies of bone growth with the aid of histomorphologic descriptions of cell types have to take this fact into account. Otherwise, erroneous conclusions may easily be drawn.

Palatal growth studied on human autopsy material. A histologic microradiographic study

The postnatal development of the hard palate was studied by conventional histologic and microradiographic means on autopsy material from thirty-three boys and twenty-seven girls aged 0 to 18 years. The findings indicated thet growth in length of the hard palate until the age of 13 to 15 was due to growth in the transverse suture and to apposition on the posterior margin of the palate. After this age the sutural growth was found to cease, whereas the apposition seemed to continue for some years. During the postnatal development the morphology of the transverse suture changed. At birth the suture was broad and slightly sinuous; later it developed into a typical squamous suture, the palatine part covering the maxillary part. During puberty the course of the suture was again slightly sinuous. The importance of this change for the vertical growth of the hard palate was discusses. It was pointed out that the lowering of the anterior part of the palate. The transverse growth of the midpalatal suture continued up to tha age of 16 in girls and 18 in boys. On the basis of morphology, the development of the median suture could be divided into three stages. In the first stage the suture was short, broad, and Y shaped; in the second the course was more sinuous; and in the third interdigitation was so heavy that a separation of the two halves of the maxilla would not be possible without fracturing the interdigitated processes.