Isumi Toda

A torque removal study on the primary stability of orthodontic titanium screw mini-implants in the cortical bone of dog femurs.

The aim of this study was to biomechanically evaluate the primary stability of pure titanium orthodontic mini-implants, inserted into pre-drilled cavities of differing diameters. Mini-implants (1.2 mm diameter) were placed into 1.0 mm and 1.2 mm diameter cavities prepared in the mid-region of the bilateral hind leg femurs of anesthetized beagles. Removal torque strengths were measured immediately, 1, 3, 6, 9 and 12 weeks post-insertion of the implant. For mini-implants placed into 1-mm cavities, removal torque values decrease over the first 6 weeks (p<0.01), after which values remained static. Average values obtained immediately, 1, 3 and 6 weeks post-insertion were 10.98, 8.83, 7.20 and 5.12 Ncm, respectively . Immediately post-insertion, removal torque values of mini-implants placed in a 1.2-mm cavity, were 11-fold lower than those placed in 1.0-mm cavities, which then demonstrated a significant increase in strength from 3 weeks (1.35 Ncm) to 6 weeks (5.17 Ncm) post-insertion (p<0.01). Measurements 6, 9 and 12 weeks post-insertion were similar to those in the 1.0-mm cavity. Initial stability of titanium mini-implants is considered necessary for immediate and early use in orthodontics, and an implant without this initial stability should be replaced or isolated until it develops the appropriate stability supported by osseointegration.

In vivo bioactivity of porous polyetheretherketone with a foamed surface

The in vivo bioactivity of porous polyetheretherketone (PEEK) with a foamed surface was evaluated using rabbit femoral bone. Cylindrical porous PEEK scaffolds, with pore diameter of 550 μm and porosity of 70%, were first prepared and immersed in 98% sulfuric acid, and then washed and immersed in 3 M potassium carbonate solution used as a foaming reagent. Numerous open pores of various sizes, as well as new functional groups, were visualized on the treated PEEK surface by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Micro computed tomography (micro-CT) showed that the volumetric density of treated PEEK was higher than that of bare PEEK at 8 weeks after surgery (p<0.05). Additionally, von Kossa staining indicated ingrowth of mature new bone tissue at 4 weeks relative to the bare PEEK group. Our data indicate that surface-treated PEEK exhibited improved bioactivity in vivo.

Morphological Study of the Articular Disc and Capillary of the Retrodiscal Tissue in a Type 2 Spontaneous Diabetes Mellitus Rat Model.

The objective of this study was to evaluate morphological changes at the articular disc of the temporomandibular joint and capillary of the retrodiscal tissue in a rat model for type 2 spontaneous diabetes mellitus (DM) (i.e., Goto-Kakizaki [GK] rats) compared to normal Wistar rats. A total of 20 experimental rats were used in this study; the rats were categorized into the normal (n = 10 male 8-week-old Wistar rats) and DM (n = 10 male 8-week-old GK rats) groups. Hematoxylin-eosin stained specimens were obtained from 5 rats from each group. Image analyses of the hematoxylin-eosin stained specimens were conducted using light micrographs, which allowed comparisons of the thickness of the anterior, central, and posterior parts of the articular disc. Afterwards, the microvascular corrosion cast specimens were obtained from 5 rats from each group. The diameter of the capillary of the retrodiscal tissue was determined by analyzing scanning electron micrographs of the microvascular corrosion cast specimens. Students t-test was used to test for statistical significant differences between the 2 groups. Differences were considered significant when p < 0.01. We found that the thickness of the anterior, central, and posterior parts of the articular disc, and the diameter of the capillary of the retrodiscal tissue was significantly lower in the DM vs. normal group. Therefore, we consider that DM-associated the hyperglycemia causes atrophy of the articular disc and microangiopathy of the capillary of the retrodiscal tissue in GK rats.

Gas gangrene in the deep spaces of the head and neck visualized on computed tomography images

Cellulitis accompanied by gas gangrene is a rapidly-spreading and potentially fatal infection. Here, we present a case of gas gangrene in the deep spaces of the head and neck in an elderly woman, diagnosed by computed tomography (CT). An 86-year-old woman with Alzheimer’s disease, hypertension, hyperlipidemia, and osteoporosis was referred to our institute by her local dentist. The patient exhibited trismus caused by severe swelling in the left submandibular area. CT images of the head and neck area showed swelling of the cervical tissue with air in the parapharyngeal and masticator spaces. She was treated with antibiotics, followed by drainage. Although the therapy was continued, the patient died from a cardiac complication on hospital day 42. Our case highlights the usefulness of CT for diagnosing gas gangrene in the deep spaces of the head and neck in a woman with Alzheimer’s disease.

Scanning Electron Microscopic Study on Microvasculature Surrounding Titanium Implants.

Recently, more concern has been directed to pen-abutment tissues as they relate to the marginal design of the superstructure, hygiene management, and sequelae of peri-implantitis. Especially, since penabutment tissues lack periodontium, whether or not they play a role as a biological defense mechanism against various external stimuli has been in question. In this study, the microvasculature around implant was investigated.Titanium screw-type implants were used in this study. Three adult Japanese monkeys were used. At weeks 2, 4, and 8 after the abutment connection, the animals were sacrificed, and microvascular casts were prepared for examination by scanning electron microscopy.At week 8, as was observed at weeks 2 and 4, the capillary network surrounding the abutment had developed a running horizontal structure and was well defined. At the superior margin of the alveolar bone, the pen-abutment capillary network was anastomosed to the periosteum capillary network. Extension of the pen-abutment capillary network into the alveolar bone surface corresponding to the fixture flange was not observed.If peri-implantitis exacerbates, or lasts long, due to poor microvascularization lacking periodontal ligament in this region, it is easy for external stimuli to cause damage the alveolar bone. Hygiene control around the implant is more important than around natural teeth.