Yosuke Kuwahara

New findings in the degenerating tissues of the periodontal ligament during experimental tooth movement

The degenerating tissues found in rat periodontal ligaments during tooth movement were examined morphologically, histochemically, and elementally, with decalcified and unfixed, undecalcified frozen sections. There were two types of degenerating tissues found in the compressed periodontal ligaments: One (type A tissue) was stained differently from collagen and the other (type B tissue) showed the same color as collagen. Type A tissue also showed the deposition of fibrin in Martius scalet blue and Weigert stain. The electron micrograph also showed the deposition of fibrin in type A tissue. No collagen fibers with typical bandings were seen in either tissue. The digestion experiment showed that type A tissue was digested by trypsin but not type B, whereas most of type B tissue was digested by collagenase but not type A. The backscattered electron image by scanning electron microscopy of type A tissue of the unfixed undecalcified frozen sections showed the presence of many small pieces. The elemental analysis of the pieces showed high peaks of phosphorous and calcium. These results indicate that collagen degradation, fibrin deposition, and calcification occurred in the degenerating tissues, especially in type A tissue during the experimental tooth movement.

Preparation of Unfixed and Undecalcified Frozen Sections of Adult Rat Periodontal Ligament During Experimental Tooth Movement

The upper first molars of adult male rats were moved for 7 days and unfixed, undecalcified frozen sections of the molar periodontal ligament were prepared and observed. The upper jaws of the rats were immersed rapidly in liquid nitrogen and sectioned with a cryostat using a super hard knife. Five micrometer serial sections were cut, collected, freeze-dried and observed with both light and scanning electron microscopy. Electron probe microanalysis (EPMA) was also performed on the sections. On the tension side of the periodontal ligament, periodontal fibers were stretched and the osteoblasts were aligned on the osteoid, which showed metamasia with the toluidine blue stain. On the pressure side where the periodontal ligament was extremely compressed, tissue degeneration was caused by tooth movement and the osteoclasts were observed on the bone surface adjacent to the degenerating tissues. Scanning electron microscopy revealed a network arrangement of the collagen fiber bundles on the tension side, but not on the pressure side of the periodontal ligament. The spectrum obtained from EPMA of the osteoid demonstrated X-ray (Ka) peaks of Na, P, S, K and Ca.

Increase in vertical dimension alters mechanical properties and isometric ATPase activity in guinea pig masseter.

To study the changes in mechanical and metabolic properties associated with an increase in the vertical dimension of the face, isometric tension, isometric ATPase activity, unloaded shortening velocity (Vmax), and the tension transients in response to step stretches in length were measured at constant levels of various Ca2+ activations in glycerinated masseter muscles (75 to 150 microns in diameter and about 3 mm long) from normal and bite opened (6 mm increase in the vertical dimension, period of 1 week) guinea pigs. The isometric tension increased sigmoidally with an increase in Ca2+ concentration in both preparations. However, the bite opening shifted the pCa-relative tension relationship in the direction of increasing Ca2+ required for activation, and the pCa at Km (Ca2+ concentration required to develop half maximum tension) was 6.40 +/- 0.08 in control and 6.27 +/- 0.05 in the bite opened preparations. The maximum isometric tension at the saturating Ca2+ concentration was greater in the bite opened preparation. The ATPase activity changed almost in parallel with the tension (i.e., Ca2+ concentration) in both preparations. However, the tension cost (ATPase activity/tension) was significantly (p < 0.05) lower in the bite opened preparation, compared with the control. The Vmax at the saturating Ca2+ concentration was lower in the bite opened preparations. The tension transients in response to step stretch in length were characterized by four distinct phases; the first phase of an immediate tension increase coincident with the stretch, the second phase of a rapid quasi-exponential tension reduction, the third phase of a minute tension increase and the fourth phase of a slow tension reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Histology and tetracycline labeling of a single section of alveolar bone of first molars in the rat

We observed the histology and tetracycline (TC) labeling in a single frontal section of alveolar bone of upper first molars of adolescent rats. A single injection of TC was administered intraperitonealy in adolescent rats. After three weeks, the upper jaws were immersed rapidly in liquid nitrogen and sectioned. Five micrometer unfixed, undecalcified frozen sections were cut and observed by light and fluorescence microscopy. Frontal sections of the upper first molar area revealed that the structural relationships among the roots, the periodontal ligament and the alveolar bone, and also between the cervical enamel and the attachment epithelium were well preserved. The TC labeling lines in the sections were very clear and distinguished new bone from old bone. The brightness of the lines differed among regions. An analysis of the brightness in the same section suggested a difference in the bone forming activity at the time of injection.

Multilingual bracket treatment combined with orthognathic surgery in a skeletal Class III patient with facial asymmetry

A case report is presented on a female adult with a Class III mandibular protrusion. Resolution of her dentoskeletal problem required a combination of comprehensive multibonded orthodontic mechanotherapy and orthognathic surgery. The patient preferred a multilingual bracket appliance because of esthetics. Both surgical and orthodontic treatment were quite successful in the correction of the facial profile and occlusion. Both psychological and esthetic satisfaction were achieved.

Magnetic resonance images and histology of the spheno-occipital synchondrosis in young monkeys (Macaca fuscata)

Magnetic resonance images and the histology of spheno-occipital synchondrosis were examined in young monkeys in order to compare the magnetic resonance images with their histologic observations. In serial magnetics resonance images of posterior cranial base, the spheno-occipital synchondrosis showed a low signal zone with unclear boundaries, running through the posterior cranial base perpendicularly to the clivus. The zone was always interposed between nonsignal zones. These observations were the same as those in young juvenile human beings. The histologic sections also revealed that the low signal zone was really the spheno-occipital synchondrosis, which consisted of hyaline cartilage and that the nonsignal zones were bone tissues. The chondroblasts in the spheno-occipital synchondrosis were arranged bipolarly. Intense alkaline phosphatase activity was located in the areas along the bone. Tetracycline labeling was also noticed in the bone formed in the endochondral ossification. These results suggest that magnetic resonance imaging enables us to observe the spheno-occipital synchondrosis in the posterior cranial base and also to elucidate its influences on the growth of maxilla and mandible in the future.