Shigaku = Odontology; journal of Nihon Dental College最新文献

Dose dependent effects of EDTPO on morphology and mineralization of hard tissues as well as calcium (Ca), inorganic phosphorus (IP) and alkaline phosphatase (ALP) levels in serum were examined in growing rats. Five groups of male S.D. rats weighing 110-120g were received s.c. injections of 0 (control), 1, 2, 4, and 8mg P/kg body wt. of EDTPO once daily (at noon) for 10 days respectively. Tetracycline (Tc.) were i.p. injected three times, one day before drug treatment (1st), 5th (2nd) and 10th (3rd) day of experimental period. All rats were received i.p. injection of 185kBq (5 microCi) of 45Ca six hours after the 10th injection of EDTPO. On the next day, blood samples were taken from the carotid artery. Then the animals were killed and both tibias, submandibular teeth and right femur were removed. Serum Ca, IP and ALP were determined by spectrophotometry. Wet, dry and ash bone weight were measured and bone calcium was determined by atomic absorption method. 45Ca activity was counted by the liquid scintillation counter. Serum Ca levels revealed decreasing tendency at the dose of 1mg P/kg and 2mg P/kg of EDTPO but increasing tendency at 4mg P/kg and significant increase at the dose of 8mg P/kg. Specific activity of 45Ca in serum increased slightly at 2mg P/kg, but at the dose of 8mg P/kg increased five times compared to that of control. Decrease of IP and increase of ALP level were observed only at the dose level of 8mg P/kg. Wet, dry, and ash weight, and Ca content of femur and 45Ca activity were decreased dose-dependently. In histological examination, changes of tibia and teeth were observed at the dose of 2mg P/kg and following dose increase these changes were more significantly. Ultraviolet line of Tc. appeared three in proximal metaphysis of tibia and dentin at the dose of 1mg P/kg and 2mg P/kg, but at the dose of 4mg P/kg and 8mg P/kg 2nd and 3rd line could not be detected. These result indicated that the effects of EDTPO on serum ingredients, long bone and teeth are initiated at the dose of 2mg P/kg, appeared at the dose of 4mg P/kg significantly, and at the dose of 8 mg P/kg severely. In addition, increase of the ratio of 45Ca specific activity between serum and bone observed at the dose of 4mg P/kg and 8mg P/kg suggested that these effects of EDTPO would be due to inhibitory action on mineralization.

The term "esthetics" has recently been also used in the dental field, and a field called esthetic dentistry is increasingly being noted. The number of not only adult but also pediatric patients who visit for treatment aiming at esthetic recovery is being increased. Inpedodontics, composite resin of the coronal color is generally used in the restoration of deciduous incisors. However, the method using metal crowns for the deciduous teeth is used for the deciduous molars at present. We applied a composite resin jacket crown to the deciduous molar in a way similar to that of esthetic crown restoration for the anterior teeth. The surgical procedure before crown preparation varied slightly according to the presence or absence of pulpal treatment of vital teeth and with non-vital teeth, but the application was performed as follows: 1) Desensitization of pulp, pulpal treatment and core construction. 2) Preparation of crown. 3) Selection, trial set and occlusal equilibration of a metal crown for the deciduous tooth. 4) Precision impression with a silicone impression material. 5) Removal of the metal crown for the deciduous tooth from the impression material. 6) Making of an under-cut to the abutment tooth on the buccal lingual side. 7) Filling of the impression with chemical polymerization resin. 8) Application of pressure in the oral cavity. 9) Adjustment of edge and crown forms. Thus, the preparation method for the composite resin jacket crown was relatively simple. Since this surgery, the patient has been followed up for 1 year and 6 months, and no specifically troublesome points have been observed clinically. The patient and her parents are satisfied with the results.(ABSTRACT TRUNCATED AT 250 WORDS)

For clinical application of ceramics such as porcelains that are frequently used as crown restoration materials, it is important to quantitatively evaluate and determine brittleness. This quality is expressed as a fracture toughness value, KIC, but no distinct method for its determination has yet been established. In order to standardize conditions for the determination of KIC by the indentation method, effects of indentation load and loading time on KIC of calcium phosphate crystalline ceramics (CP) were studied at various Vickers indentation loads and various loading times in CP plate-like segments. Furthermore, plate-like segments of each of CP, apatite (AP), mica-beta-spodumene (MIS) and mica (MIC) groups were subjected to experiment at various indentation loads at a fixed loading time to study the effects of indentation load on KIC in four kinds of Castable Ceramics. The results are summarized as follows: 1) The Vickers hardness degree of CP was decreased with an increase in indentation load and loading time, reaching the maximum value (499Hv) at 1kgf of indentation load and 5s of loading time. 2) The value of half of the crack length of CP was increased with an increase in indentation load and loading time, reaching a maximum (530 microns) at 20kgf of indentation load and 30s of loading time. 3) KIC of CP reached the maximum value (2.78MNm-3/2) at 5kgf of indentation load and 5s of loading time, and the minimum (1.52MNm-3/2) at 20kgf of indentation load and 30s of loading time. 4) Optimal experimental conditions for KIC of CP determined by indentation method were 5kgf or 10kgf of indentation load and 15s of loading time. 5) KIC values (MNm-3/2) determined at 5kgf of indentation load and 15s of loading time for CP, AP, MIS and MI were 2.27, 0.95, 1.82 and 1.81, respectively. 6) The course of cracks due to indentation force showed a linear pattern of intra-granular fracture. 7) The cracks were revealed to show median cracks by fractography.

Material resistance to brittle fracture was quantitatively evaluated in the commercial porcelains, CERA 8 (CE 8), VITA DUR (VITD), VITA VMK 68 (VIT), CERAMCO II (CE II), UNIBOND (UNB), NORITAKE SUPER PORCELAIN AAA (AAA), PENCRAFT (FEN), COSMOTECH (COM) and OPTEC HSP OPT) from values of fracture toughness (KIC) obtained in the crack on a mode I, determined upon insertion of Vickers indenter. The results are summarized as follows: 1) Mean maximum and minimum values of Vickers hardness degree of 9 kinds of commercial porcelains at 5kgf of load for 15s were 1348 (SD 98.1) for OPT abd 666 (SD 74.6) for CE 8, respectively. 2) The value of half of the diagonal of indentation (a) ranged from 42 (SD 1.5) to 58 (SD 3.3) microns, and that of half of the crack length (c) ranged from 101 (SD 4.0) to 175 (SD 17.2) microns. 3) The ratio of (c) to (a) (c/a ratio) was within the range of 2.3 to 3.3, and median cracks were present. 4) KIC in the commercial porcelains determined by the indentation method was within the range of 2.04 to 4.69MNm-3/2, showing a maximum for OPT and minimum for VITD. 5) KIC of OPT was significantly greater than that of any other material. 6) The porcelains were divided by fractography of the direction of crack course into 2 groups: a group of intra-granular fracture showing linear cracks (AAA, COM and OPT) and a group of Inter-granular fracture showing a range of non-linear cracks (CE 8, VITD, VIT, CE II, UNB ND PEN).

This experimental study was performed to obtain fundamental data for the development of highly reinforced calcium phosphate crystalline ceramics (CPCC) by evaluation of fracture toughness by adding a single metal oxide such as B2O3, Na2O, Li2O, SiO2, MgO and Al2O3, which are thought to solidify and reinforce ceramics. In experiment I, values of fracture toughness for CPCC to which each oxide was added were determined by indentation method, and in experiment II dynamic test method by repeated loading was studied. The results are summarized as follows: 1) One half (a) of the diagonal of indentation was increased with an increase in indentation load, and the test fragment of CPCC with 4.7 mol% Na2O added at 10kgf of indentation load showed the maximum diagonal of indentation (145 microns), while the test fragment of CPCC containing 3.0mol% Al2O3 showed the minimum value (29 microns) at 1kgf. 2) One half (c) of the crack length was increased with an increase in indentation load, and the test fragment of CPCC containing 4.7mol% Li2O showed the maximum crack length (411 microns) at 10kgf, while the test fragment of CPCC with 4.7mol% B2O3 showed the minimum value (55 microns) at 1kgf. 3) The maximum value (2.98MNm-3/2) of fracture toughness (KIC) was observed in CPCC containing 4.7mol% B2O3 at 10kgf, while the minimum (1.02MNm-3/2) was observed in CPCC with 4.7mol% Li2O added, at 5kgf. 4) (a) was increased with an increase in the number of repetitions of loading, showing the maximum value (111 microns) for a test fragment at 10kgf with 100 repetitions and the minimum (31 microns) for a test fragment at 1kgf with just 1 repetition. 5) (c) was increased with an increase in the number of repetitions of loading, showing the maximum value (337 microns) for a test fragment at 10kgf with 100 repetitions and the minimum (64 microns) for a test fragment at 1kgf with 1 repetition. 6) KIC reached a maximum value (2.35MNm-3/2) at 5kgf and 1 of the repetition, and a minimum (1.54MNm-3/2) at 3kgf and 10 repetitions of loading.

We experienced general anesthesia of two patients with cerebral palsy presupposed to have difficulties in tracheal intubation by reason of scoliosis. Case 1 is a 26-year-old woman. Chest X-ray photography and respiratory sounds in both pulmonary areas indicated neither airway stricture nor respiratory distress, but severe scoliosis presupposed difficult tracheal intubation. However, under the impression of possible intubation obtained by preoperative laryngoscopy, orotracheal intubation was tried with rapid induction. Epiglottis deviation to the left noted upon developing larynx made the glottis direct invisible, but some compression of cricoid from outside barely succeeded in intubation. The fixation of the endotracheal tube found much difficulties in its proper positioning so as to make stethoscopy uniform in both pulmonary areas, but trial rotations of the tube both in various directions and at various depths barely managed to find a position of uniform stethoscopy in both pulmonary areas, in which position the tube was fixed as proper positioning. Anesthesia was performed by nitrous oxide.oxygen.halothane; peroperative hemodynamics remained stable and arterial blood gas analysis presented no problems. Case II is a 16-year-old man. Resting respiration presented stridor and chest X-ray photography indicated scoliosis and laryngeal stricture. Patient's lack in the degree of cooperation made laryngoscopy impossible. Thus, in view of a high possibility of difficult tracheal intubation, orotracheal intubation was tried under the control of spontaneous respiration. While the intubation was being carried out by means of a stylet without developing larynx, severe bronchostriction was palpable at the point when the tube barely passed through the glottis, making the intubation impossible. However, the tube barely managed to be inserted while rotating with the stylet being extracted. Anesthesia was carried out by nitrous oxide.oxygen.halothane; peroperative hemodynamics underwent no remarkable change and arterial blood gas analysis presented no problems.

The purpose of this study was to evaluate the relationship of the functional lip posture to the anterior teeth and gingiva and at the same time establish an objective esthetic standard in the clinic. The functional lip posture referred here were the smiling lip line and the maximum opening lip line. From an esthetic and clinical point of view, the functional lip posture was described, classified and scored using the relationship of the border of the upper and lower lip to the labial surface of the anterior teeth and gingiva. A device for taking standardized oral photographs with a high degree of reproducibility was used. Tjan, et.al. studied the esthetic factors in a smile. Using their classification the result of this study were as follows: high smile, 32%; average smile, 42%; and low smile, 26%. The difference in the amount of maxillary and mandibular gingival exposure were also determined in this study. The measurement of the maxillary area was used in classifying the smile since the mandibular area showed interproximal gingiva only. In analyzing the maximum opening lip line, it was not possible to apply Tjan's classification since it referred only to the smile line. A scoring system (smile score) was devised, instead, to evaluate the functional lip posture. By this scoring system, the smiling lip line was classified using the maxillary teeth and gingiva only. The classification were as follows: high smile, score was over 4; average smile, from 3-4; and low smile, under 3. Note that the maxilla was used as reference in analyzing the smiling lip line and the mandible for the maximum opening lip line.

With the purpose of studying the influence of enamel acid etching technique, and the effectiveness of a strengthening of tooth enamel by silicahydro gel method, the following groups were compared, analyzed and observed by the measurements of diffracted X-ray from thin layer specimens and by microarea X-ray diffraction from an X-ray crystallographic point of view. Group I: non-treated tooth enamel Group II: acid-etched tooth enamel Group III: tooth enamel by application of silicahydro gel method after being acid etched. The results obtained were as follows: 1. Qualitative analyses by the measurements of diffracted X-ray from thin layer specimens 1) Ca5(PO4)3F, Ca5F (PO4)3 and Ca3(PO4)2.xH2O were detected in every group, and Ca3(PO4)2.xH2O demonstrated a high reliable value in group III. 2) In comparison with groups I and II, group III clearly revealed a peak shift toward high angle side, however, a halo peak was not recognized in every group. 3) As a result of evaluating crystallinity, crystallinity became favorable in order of group II, group I and group III. 4) A-axis lattice constant shortened in order of group II greater than group I greater than group III, and c-axis lattice constant shortened in order of group II greater than group I = group III. 2. Qualitative analyses by microarea X-ray diffraction 1) Solid solution of Ca5(PO4)3F and Ca5(PO4)3(OH) proved to exist in every group and in each microarea. 2) A halo peak appeared in group II and showed the trend of disappearance in group III, however, no peak shift was observed in all groups. From the foregoing results, the loss of the utmost enamel surface layer exhibiting high crystallinity and the lowering of crystallinity by acid etching technique were revealed from an X-ray crystallographic point of view and furthermore if silicahydro gel method was applied, it was suggested that enamel would be restored or that crystallinity would be enhanced.