Interactions between occlusion and human brain function activities.

There are few review articles in the area of human research that focus on the interactions between occlusion and brain function. This systematic review discusses the effect of occlusion on the health of the entire body with a focus on brain function. Available relevant articles in English from 1999 to 2011 were assessed in an online database and as hard copies in libraries. The selected 19 articles were classified into the following five categories: chewing and tongue movements, clenching and grinding, occlusal splints and occlusal interference, prosthetic rehabilitation, and pain and stimulation. The relationships between the brain activity observed in the motor and sensory cortices and movements of the oral and maxillofacial area, such as those produced by gum chewing, tapping and clenching, were investigated. It was found that the sensorimotor cortex was also affected by the placement of the occlusal interference devices, splints and implant prostheses. Brain activity may change depending on the strength of the movements in the oral and maxillofacial area. Therefore, mastication and other movements stimulate the activity in the cerebral cortex and may be helpful in preventing degradation of a brain function. However, these findings must be verified by evidence gathered from more subjects.

Pressure pain threshold of mucosa after tooth extraction under removable denture bases.

This study explored the pressure pain threshold (PPT) of the mucosa after tooth extraction. The PPTs of the wounded mucosa of eight volunteer subjects were observed at 7, 30, and 90 days after tooth extraction. The PPTs at 30 days and 90 days were approximately two and three times higher respectively, than those at 7 days. As time passed, the values for the PPTs after tooth extraction increased in all regions. At 90 days after tooth extraction, the PPTs are about 97% recovered compared to the PPTs of the contralateral points.

Does the presence of antagonist remaining teeth affect implant overdenture success? A systematic review.

Many patients who need implant overdentures are not completely edentulous; they still have antagonist natural teeth or implant fixed prostheses. In such cases, however, little is known about whether existing natural teeth affect the success of implant overdentures positively or act as a complicating factor. This systematic review attempts to clarify the correlation between existing remaining teeth and the survival/success rate of maxillary and mandibular implant overdentures. An assessment of available relevant articles published in English from 1990 to 2009 was performed using an online database and a manual search in libraries. Although the opposing natural dentition was not sufficiently described in the literature, 10 articles about the mandible and 10 articles about the maxilla were selected. As there was no controlled study on the natural teeth opposing implant overdentures, this review could not reach a clear conclusion. The review did reveal a remarkably high success/survival rate for mandibular implant overdentures; maxillary implant overdentures showed a lower rate. The presence of antagonist teeth hardly seems to be a risk factor for success for mandibular implant overdentures. For maxillary implant overdentures, the existence of antagonist teeth might act negatively for implant survival, but they are certainly not a contraindication. Although a few articles stated this relationship, we could not find an apparent correlation between the remaining antagonist teeth and the success of the implant overdentures. A detailed description of the opposing dentate status and results of randomized controlled clinical trials would be required to characterize this evidence-based implant overdenture treatment.

Investigation of trends and characteristics in patients with obstructive sleep apnea.

BACKGROUND: Oral appliance (OA) therapy for obstructive sleep apnea (OSA) has only been part of Japan's National Health care coverage plan since 2004. Subsequently, not enough time has passed to establish the medical trends and characteristics of OSA patients in Japanese Dental Hospitals. AIM: The aim of this study was to investigate the medical trends and the characteristics in patients with OSA who visited our clinic, and to compare our findings with previous studies. SETTING AND DESIGN: Epidemiological survey (retrospective study). MATERIALS AND METHODS: Two hundred and one patients were recruited at the Internal Medicine Division in the Tsurumi University Dental Hospital from February 2006 to December 2008, consecutively. Patients received a medical interview, and a detailed sleep analysis that included a polysomnography (PSG) to verify the exact nature of their condition. The efficacy of OA was assessed in 49 patients who wore an OA and underwent PSG. RESULTS: Of all subjects, 141 patients visited the Prosthodontic Division to receive OA therapy, 38 patients were treated or received a follow up examination in the Internal Medicine Division. The dropout rate was 10.4% in the all subjects, 17.0% in patients who visited the Prosthodontic Division. The male-to-female ratio was 3.3:1, 3.0:1 in patients who visited the Prosthodontic Division. In addition, females had a lower rate of OAS severity than males. In our patients, the major complication was hypertension and cardiac disease. The success rate of OA was 75.5%. CONCLUSION: This approach allowed us to reveal some of the trends and characteristics in our patients.

Present status of titanium removable dentures--a review of the literature.

Although porcelain and zirconium oxide might be used for fixed partial dental prostheses instead of conventional dental metals in the near future, removable partial denture (RPD) frameworks will probably continue to be cast with biocompatible metals. Commercially pure (CP) titanium has appropriate mechanical properties, it is lightweight (low density) compared with conventional dental alloys, and has outstanding biocompatibility that prevents metal allergic reactions. This literature review describes the laboratory conditions needed for fabricating titanium frameworks and the present status of titanium removable prostheses. The use of titanium for the production of cast RPD frameworks has gradually increased. There are no reports about metallic allergy apparently caused by CP titanium dentures. The laboratory drawbacks still remain, such as the lengthy burn-out, inferior castability and machinability, reaction layer formed on the cast surface, difficulty of polishing, and high initial costs. However, the clinical problems, such as discoloration of the titanium surfaces, unpleasant metal taste, decrease of clasp retention, tendency for plaque to adhere to the surface, detachment of the denture base resin, and severe wear of titanium teeth, have gradually been resolved. Titanium RPD frameworks have never been reported to fail catastrophically. Thus, titanium is recommended as protection against metal allergy, particularly for large-sized prostheses such as RPDs or complete dentures.

Interleukin 2 induced leukocyte adhesion to the normal and tumor microvascular endothelium in vivo and its inhibition by dextran sulfate: implications for vascular leak syndrome.

The maximum dose of interleukin 2 (IL-2) alone or with adoptively transferred lymphocytes is limited by the vascular leak syndrome, resulting from an increase in vascular permeability. Using intravital microscopy to quantify cell interaction in vivo and the Miles assay to assess changes in vascular permeability, we have shown that IL-2 increases both leukocyte-endothelial cell adhesion and vascular permeability in the cutaneous tissue of rabbits. Both of these processes can be reversed to a large extent using dextran sulfate (Mr approximately 500,000; 10 mg/kg body weight), a nonspecific blocker of leukocyte-endothelial adhesion. These results suggest that increased leukocyte (probably lymphocyte) adhesion to the postcapillary microvasculature contributes significantly to the IL-2 induced increase in permeability. Therefore, as more specific inhibitors of leukocyte-endothelial adhesion become available, improved strategies could be developed to control or prevent IL-2 toxicity.

The machinability of cast titanium and Ti-6Al-4V.

This study investigated the machinability (ease of metal removal) of commercially pure (CP) titanium and Ti-6Al-4V alloy. Both CP Ti and Ti-6Al-4V were cast into magnesia molds. Two types of specimens (with alpha-case and without alpha-case) were made for CP Ti and Ti-6Al-4V. Machinability (n = 5) was evaluated as volume loss (mm3) by cutting/grinding the 3.0 mm surface using fissure burs and silicon carbide (SiC) under two machining conditions: (1) two machining forces (100 or 300 gf) at two rotational speeds (15000 or 30000 rpm) for 1 min, and (2) constant machining force of 100 gf and rotational speed of 15000 rpm for 1, 2, 5, 10, and 30 min. As controls, conventionally cast Co-Cr and Type IV gold alloys were evaluated in the same manner as the titanium. When fissure burs were used, there was a significant difference in the machinability between CP titanium with alpha-case and without alpha-case. On the other hand, there was no appreciable difference in the amount of metal removed for each tested metal when using the SiC points.

Wear resistance of experimental Ti-Cu alloys.

After using cast titanium prostheses in clinical dental practice, severe wear of titanium teeth has been observed. This in vitro study evaluated the wear behavior of teeth made with several cast titanium alloys containing copper (CP Ti+3.0 wt% Cu; CP Ti+5.0 wt% Cu; Ti-6Al-4V +1.0 wt% Cu; Ti-6Al-4V+4.0 wt% Cu) and compared the results with those for commercially pure (CP) titanium, Ti-6Al-4V, and gold alloy. Wear testing was performed by repeatedly grinding upper and lower teeth under flowing water in an experimental testing apparatus. Wear resistance was assessed as volume loss (mm(3)) at 5kgf (grinding force) after 50,000 strokes. Greater wear was found for the six types of titanium than for the gold alloy. The wear resistance of the experimental CP Ti+Cu and Ti-6Al-4V+Cu alloys was better than that of CP titanium and Ti-6Al-4V, respectively. Although the gold alloy had the best wear property, the 4% Cu in Ti-6Al-4V alloy exhibited the best results among the titanium metals. Alloying with copper, which introduced the alpha Ti/Ti(2)Cu eutectoid, seemed to improve the wear resistance.

Acute effects of whole-body exposure to static magnetic fields and 50-Hz electromagnetic fields on muscle microcirculation in anesthetized mice.

Acute microhemodynamic effects of static and alternating magnetic fields at a threshold level were investigated on modulating the muscle capillary mirocirculation in pentobarbital-anesthetized mice. The skin in a tibialis anterior was circularly removed with 1.5 mm diameter for intravital-microscopic recording of the capillary blood velocity in the tibialis anterior muscle. Fluorescein isothiocyanate (FITC)-labeled dextran (MW 150 kDa) was used for an in vivo fluorescent plasma marker of the muscle capillaries. Following a bolus injection of FITC-dextran solution into the caudal vein, the peak blood velocity in the muscle capillaries was measured prior to, during, and following exposure to static magnetic fields (SMF) or 50-Hz electromagnetic fields (EMF) using a fluorescence epi-illumination system. The whole body of experimental animals, placed on the observing stage of a fluorescence microscope, was exposed to SMF (0.3, 1 and 10 mT) or 50-Hz EMF (0.3 and 1 mT) for 10 min using a specially devised electromagnet. For sham exposure, the electromagnet was not energized. During exposure and post-exposure to SMF of 10 mT, the peak blood velocity significantly increased as compared to sham exposure. After the withdrawal of SMF and 50-Hz EMF of 1 mT, significant similar effects on the blood velocity were present or enhanced. These findings suggest that field intensity of 1 mT might be considered as a threshold level for enhancing muscle microcirculation under pentobarbital-induced hypnosis.

Acute effects of static magnetic fields on cutaneous microcirculation in rabbits.

The acute microcirculatory effects of locally applied of static magnetic (SMF) to the cutaneous tissue within a rabbit ear chamber (REC) were evaluated during consciousness. Rabbits with REC were subjected to microphotoelectric plethysmography. Power levels of SMF upon the REC were controlled at 1, 5, 10 mT(milli Tesla), respectively. The duration of exposure was 10 minutes. The exposure of SMF induced variation of vasomotion with a latency of about 10 seconds in a non-dose dependent manner. SMF had a biphasic effect upon the microcirculatory system; when the vascular tone was low, the SMF enhanced vasomotion, and when it was high, the SMF suppressed vasomotion. The results suggest that the SMF can modulate vascular tone due to vasomotion which may involve in clinical efficacy for refraining from neck and shoulder stiffness.

Anti-pressor effect of a Chinese-Japanese herbal medicine, saiko-ka-ryukotsu-borei-to on hemodynamics in rabbits.

Saiko-ka-ryukotsu-borei-to (TJ-12) is a traditional Chinese-Japanese medicinal mixture clinically used for the treatment of hypertension and/or atherosclerosis concurrent with neurotic disorders. Study on the effect of TJ-12 on the vasoconstriction of cutaneous arterioles induced by nor-adrenaline (NA) was carried out using a rabbit ear chamber (REC) under conscious conditions. Before and after oral administration of TJ-12 everyday for 2 weeks, the same position of an arteriole within a REC was analyzed using an image shearing monitor every minute up to 15 min after varying doses (0.3, 1.0, 3.0 and 10.0 micrograms/kg i.v.) of NA. The changes of mean arteriolar diameter and vasomotion amplitude, before and after feeding of TJ-12 (1% w/w) supplemented diet were compared in the same position. Consequently, the pretreatment with TJ-12 significantly attenuated the changes of mean diameter of NA-induced vasoconstriction and also shortened its duration. In addition, concurrent with its cutaneous microcirculatory response, the pretreatment with TJ-12 systemically suppressed the increase of blood pressure under NA-induced vasoconstriction. These results suggest that the anti-pressor effect of TJ-12 might be apparently attributable to the inhibition of NA-induced vasoconstriction.

Subchronic effects of static magnetic fields on cutaneous microcirculation in rabbits.

The subchronic effects of locally applied of static magnetic fields (SMF) on the cutaneous microcirculation within the rabbit ear chamber (REC) were evaluated under conscious conditions. The microcirculatory vasomotion within a REC was measured continuously and analyzed multilaterally by microphotoelectric plethysmography and an image shearing monitor. A SMF, a 180 mT (milli Tesla) cylindlical samarium-cobalt permanent magnet was attached on REC for 24 hours to 4 weeks Exposure to SMF for 1-3 weeks significantly induced long-lasting vasodilation with enhanced vasomotion as compared to control group. Thereafter the active vasomotion of SMF group was depressed and/or returned to initial values and there was no difference between SMF and control groups. The results suggest that the subchronic exposure of SMF can bidirectionally modulate microcirculatory vasomotion in cutaneous tissue.

Cutting efficiency of air-turbine burs on cast titanium and dental casting alloys.

OBJECTIVE: The purpose of this study was to investigate the cutting efficiency of air-turbine burs on cast free-machining titanium alloy (DT2F) and to compare the results with those for cast commercially pure (CP) Ti, Ti-6Al-4V alloy, and dental casting alloys. METHODS: The cast metal (DT2F, CP Ti, Ti-6Al-4V, Type IV gold alloy and Co-Cr alloy) specimens were cut with air-turbine burs (carbide burs and diamond points) at air pressures of 138 or 207 kPa and a cutting force of 0.784 N. The cutting efficiency of each bur was evaluated as volume loss calculated from the weight loss cut for 5 s and the density of each metal. The bulk microhardness was measured to correlate the machinability and the hardness of each metal. RESULTS: The amounts of DT2F cut with the carbide burs were significantly (p < 0.05) greater than for the other titanium specimens at either 138 or 207 kPa. The diamond points exhibited similar machining efficiency among all metals except for Type IV gold alloy. The increase in the volume loss of Co-Cr alloy (Vitallium) cut with the diamond points showed a negative value (-29%) with an increase in air pressure from 138 to 207 kPa. There was a negative correlation between the amounts of metal removed (volume loss) and the hardness (r2 = 0.689) when the carbide burs were used. SIGNIFICANCE: The results of this study indicated that a free-machining titanium alloy (DT2F) exhibited better machinability compared to CP Ti and Ti-6Al-4V alloy when using carbide fissure burs. When machining cast CP Ti and its alloys, carbide fissure burs possessed a greater machining efficiency than the diamond points and are recommended for titanium dental prostheses.

Vasodilator effects of cepharanthine, a biscoclaurine alkaloid, on cutaneous microcirculation in the rabbit.

Cutaneous microcirculatory responses to intravenous administration of cepharanthine (CT), a biscoclaurine alkaloid, isolated from Stephania cepharantha, were studied in a transparent round chamber installed in a rabbit ear, under conscious conditions. Vital-microscopic observations were made visually with a microscope-closed TV system and microphotoelectric plethysmography. Following the CT administration in doses of 1.0 and 3.0 mg/kg, an enhancement of rhythmic perfusion of microvascular blood due to vasomotion was developed for a period of 1 h or longer, although no appreciable change was observed following CT administration at 10.0 mg/kg. The microvascular dilator effect of CT appeared to have no direct association with systemic hemodynamics, based on the additional measurements of heart rate, blood pressure, carotid blood flow and auricular arterial blood flow.

Intravital-microscopic observations on the intravascular behavior of blood cell components during dietary-induced hyperlipidemia in the male rabbit.

In normal male rabbits loaded dietary cholesterol, intravital-microscopy revealed a marked acceleration of intravascular adhesiveness of white blood cells and aggregability of red blood cells and a swarming of lipid-laden macrophages in connective tissue space concurrently with a systemic hyperlipidemia and anemia. Possible roles of the microcirculatory changes in the atherogenesis were discussed.

Effects of acupuncture needle application upon cutaneous microcirculation of rabbit ear lobe.

Microcirculatory effects of the application of an acupuncture needle (32-gauge, silver) to the back, corresponding to Geshu (B17) in human beings, were studied in vivo by microscope, using a transparent ear chamber in conscious rabbits. Although no striking findings were obtained during the needle application for a period of 30 minutes, it was clearly observed that the microvascular blood flow increases gradually in parallel with augmenting spontaneous rhythmic fluctuation of the vessel diameter, namely vasomotion, throughout a continuous observation period longer than 2 hours following release from the needle application. Diameters of arterioles and venules at the full-dilating phases of vasomotion reached levels higher than 200% and 250% of the initial values just before application of the needle, respectively. The clinical efficacy of acupuncture was suggested to be explained at least in part by the increased rhythmic microvascular blood flow in parallel with vasomotion, from the physiological point of view based on the previous investigations.

[Structural designs in the removable partial dentures].

Today the removable partial dentures are used as permanent prosthetic devices. Thus, their designs must be considered the prevention of breakage or deformation. A metal plate denture consisting of double structure has been designed with the intention of improved mechanical strength and durability. Principal investigations of this study were to introduce structural design techniques and apply them to denture design, to analyze the double structure using the finite element method, to judge reliability using a statical bending test, to compare the breaking strength of each structure, and to measure movement during function of mandibular extension base removable partial dentures on the simulation model. The summary of results is shown below: 1. Calculated values and experimental values were a fairly good approximation. 2. The reinforcement and Lightweight method of double structure was made evident. 3. Regarding the packing resins, METADENT was slightly superior in mechanical strength to ACRON. 4. Maximum stiffness of the double structure was approximately 7-10 times that of skeleton types, and breaking strength was about 9 times. 5. Tensile strain generated at the double structure was statistical less than for skeleton types. 6. When loads of 10 kg applied, the difference of distal displacement between double structure and skeleton types was between 70-80 microns. 7. The stiffness of the skeleton types decreased remarkably by shortening the denture flanges, but the double structure did not show significant change.

Effect of implant support on distal extension removable partial dentures: in vitro assessment.

The implants in implant-supported removable partial dentures (RPDs) are placed in the edentulous ridge to stabilize the RPD and minimize the resultant rotational movement. This study investigated the effect of implant placement on RPD stability. A model simulating a mandibular bilateral distal extension missing was fabricated using epoxy resin and silicone impression material as thin (1 mm) and thick (2 mm) soft tissues. Five pressure sensors (PS-10K, Kyowa, Tokyo, Japan) were attached near the left and right first molars (#36 and #46), first premolars (#34 and #44) and medio-lingual alveolar crest. Five bilateral distal extension RPDs with Co-Cr frameworks were conventionally fabricated. After the implants were placed at the bilateral second molar areas, healing caps (4.5 mm high) were connected to the denture base with autopolymerized resin to support the RPD. As in a conventional RPD, sealing screws were placed without connecting them. Loads up to 5 kg were applied, and the pressure and displacement of the RPDs (n = 5) were simultaneously measured and analysed using the Wilcoxen test (alpha = 0.05). There was less pressure on both thin and thick soft tissues, the #36, #46 and the medio-lingual alveolar crest from the implant-supported RPD than from the conventional RPD (P < 0.05). There were no significant differences in pressure on #34 and #44 between the two RPDs (P > 0.05). There was significantly less denture displacement of the implant-supported RPD than of the conventional denture (P < 0.05). Implant support helped prevent the displacement of distal extension RPDs and decreased the pressure on soft tissues.