Biomedical subjects

T Gedrange

Publications and source records attributed to T Gedrange.

32 records · Page 2Linked to original sources

PubMed2005

An evaluation of resonance frequency analysis for the determination of the primary stability of orthodontic palatal implants. A study in human cadavers.

BACKGROUND: The primary stability of short orthodontic implants is important for anchorage. METHODS: For this study 14 cadaveric human heads were used. The stability of orthodontic implants (Straumann) with lengths of 4 and 6 mm and different localization (palatal suture or paramedially) were evaluated. The implants with length of 6 mm were only placed in the suture and primary stability was non-invasively determined with the resonance frequency (Osstell). The invasive method for the analysis of the morphometric parameters of the implant/bone contact was carried out by means of histological and radiological examinations. RESULTS: The 6 mm implants have significant better primary stability in the palatal suture as 4 mm implants paramedially (P<0.05). No differences were found between 6 and 4 mm implants in the palatal suture and between 4 mm implants in palatal suture to paramedially. The histological and radiological results demonstrate the ability to measure the implant stability by investigation of the bone offer and density around the implant. Bone structure, especially the pore size in the trabecular bone and the precision of placement may influence the stability. CONCLUSION: This study shows that the short implant gives sufficient bone fixation, independently of placement. The quality of implantation and bone structure are more important than the length of the orthodontic implant.

Bone Density↗

PubMed2005

X-ray microanalysis of elements in the masticatory muscle after paresis of the right masseter.

Muscle activity and function appear to be related to ionic concentrations in the muscle. We investigated whether muscle paresis induced by injection of Botulinum toxin A (Botox) in 16-week-old pigs over a 56-day period is associated with ionic changes in the affected muscles. Tissue samples were taken from the masseter, temporalis, medial pterygoid, and geniohyoid muscles by a standardized method and used for energy-dispersive x-ray microanalysis in an environmental scanning electron microscope. The largest increase in Na(+) was measured in the right and left sides of the masseter muscle in treated animals. Additionally, a significant elevation of Na(+) was measured in the anterior part of the temporalis muscle and in the pterygoid muscle (P < 0.05). In temporalis and pterygoid muscles, an increase in sulfur in both sides of treated pigs' heads was observed. Botox((R)) has an indirect impact on ion concentrations, resulting in changes in muscle functional capacity and adaptive compensation of paretic muscle function by other muscles.

Animals↗

PubMed2003

Three-dimensional analysis of endosseous palatal implants and bones after vertical, horizontal, and diagonal force application.

The effects of bite and orthodontic forces exerted on endosseous palatal implants are not completely understood. This applies especially to the biomechanical properties inherent in the different implant geometries and resulting bone remodelling reactions on the one hand, and to the influence on the direction and magnitude of the applied forces on the other. The results of this study should help in the selection of implants for clinical use. Three types of endosseous implants (all 9 mm in length and 3.3 mm in diameter, made of titanium) were used for this investigation. Type 1 was a simple, cylinder-shaped implant; type 2 a cylinder-shaped implant with a superperiosteal step; and type 3 a cylinder-shaped implant, subperiosteally threaded, with a superperiosteal step. The load on the implant was investigated under three conditions of bite and orthodontic forces from 0.01 to 100 N (vertically, horizontally, and diagonally). The study results were calculated by means of a finite element (FE) method. Vertical loading caused bone deformation of more than 600 microeps at the simple implant. The largest deformations at this load were found in the trabecular bone with all three implant geometries. However, trabecular bone deformation was reduced by a superperiosteal step. Horizontal loading of the implants shifted the deformation from the trabecular to the cortical bone. Furthermore, a large deformation was measured at the transition from cortical to trabecular bone. The smallest deformations (less than 300 microeps) were found for implants with a superperiosteal step and diagonal loading (type 2). The use of threads provided no improvement in loading capacity. All implant types investigated showed good biomechanical properties. However, endosseous implants with a superperiosteal step had the best biomechanical properties under low loads. Thus, the trend should be to optimize the design of implants by producing small implants with additional anchorage on the bone surface.

Biomechanical Phenomena↗

PubMed2003

Regional alterations in fiber type distribution, capillary density, and blood flow after lower jaw sagittal advancement in pig masticatory muscles.

Muscular remodeling is known to be a prerequisite for permanent correction of mandibular-maxillary malocclusion. The objective of this study was to clarify if an increase in type I fiber number is accompanied by an increased capillary density and improved muscular blood flow. Juvenile pigs received build-ups on the molars, which induced a protrusion of 7.6 + 1.5 mm. After 4 weeks of treatment, chronic lower jaw protrusion induced a marked muscle blood flow increase in the anterior and medial regions of the superficial part of the masseter and in the medial pterygoid muscle (P < 0.05). Furthermore, an increase in capillary density and in the amount of type I fibers was found in all regions of masticatory muscles with an increased muscle blood flow (P < 0.05). Finally, the capillary-to-fiber ratio increased (P < 0.05). Muscle blood flow and capillary density showed a strong linear correlation (r = 0.89, P < 0.01). These changes suggest a complex muscle adaptation for long-term, fatigue-resistant activity during the early corrective period of mandibular-maxillary malocclusion treatment.

Animals↗

PubMed2003

[Simulation of bone strain by orthodontic implants using the finite element method].

Load direction of applied forces, implant geometry and other biomechanical parameters lead to varying reactions in the surrounding bone structure. Three types of endosseous implant measuring 9 mm in length and 3.3 mm in diameter with and without superperiosteal step, and a threaded surface were investigated with the aid of a finite element method using the COSMOS/M 2.5 program. The load on the implant was investigated under vertical, horizontal, and diagonal forces of between 0.01 N and 100 N. Vertical loading of simple implants caused bone deformation of more than 600 mu eps. The application of the superperiosteal step clearly reduced the deformation. The largest deformations under vertical loading were observed in the trabecular bone with all 3 implant geometries. On horizontal loading the deformation shifted from the trabecular to the cortical bone and was particularly marked at the transition between the two. The smallest deformations, less than 300 mu eps, were measured at implants with a superperiosteal step under diagonal loading. The thread did not improve loading capacity. Implants with a superperiosteal step are recommended since they contribute to more rapid healing and strengthening of the bone.

Bone and Bones↗

PubMed2002

Influence of the sagittal advancement of mandibulae on myofibrillar ATPase activity and myosin heavy chain content in the masticatory muscles of pigs.

Endurance muscle stress leads to polymorphic expression of myosin heavy chains (MyHC). Histochemical and electrophoretic analyses were performed on different masticatory muscles (masseter, temporal, geniohyoid and medial pterygoid) of 10 weeks old pigs after 28 days of chronic sagittal advancement of the mandibulae. The differentiation between fiber types was investigated histochemically with the myofibrillar ATPase (mATPase) method and by immunohistochemistry. Expression of different MyHC isoforms was also assessed by means of immunoblotting with monoclonal antibodies. The results of both methods were compared. Chronic sagittal advancement of the mandibulae led to an increase in the cross-sectional area of type I fibers and type I MyHC in the anterior part of the masseter, the distal part of the temporal and the medial pterygoid muscle. In the present study, clear differentiation between type I and type II muscle fibers in all histological analyses was possible. However, mATPase classification of subtypes of type II fibers may lead to misinterpretations. Additionally, a direct correlation between the type I MyHC concentration and the type I fibers was seen in enzyme histochemical and immunohistochemical staining. The defined cross section of fibers is important for the histological investigation in small muscles. The immunoblot method seems to be more sensitive and less subjective for measurement of muscle changes. It can be concluded that the immunoblot method used for measuring the MyHC content is a valid alternative for fiber typing in small muscles as it is less time-consuming and more sensitive than qualitative histochemistry.

Adenosine Triphosphatases↗

PubMed2001

Differential expression of myosin heavy-chain mRNA in muscles of mastication during functional advancement of the mandible in pigs.

Surgical and orthodontic treatment of retrognathia aims to improve orofacial function by adaptation and training of muscle capacity, which is connected with a change in muscle fibre-type proportions. The aim here was to analyse the proportion of myosin-heavy chain (MyHC) gene expression in type I (slow twitch/ST) and type IIb (fast twitch/FT) fibres during sagittal advancement of the mandible by reverse transcriptase-polymerase chain reaction (RT-PCR). The experiments were carried out on 10-week-old pigs (six test animals, six controls) over a 28-day period. Six pigs were fitted with acrylic bite blocks for sagittal advancement of the mandible. Tissue was taken from seven different regions of the masseter, temporal, medial pterygoid, and geniohyoid muscles. The 84 samples were used for histological fibre differentiation with ATPase staining and for isolation of total RNA. To measure the two MyHC isoforms, RT-PCR (in a single tube reaction with MyHC I, MyHC IIb, and GAPDH primers) was used. A significant increase was registered in the percentage of ST fibres and in mRNA from MyHC I in the anterior region of the masseter and in the posterior region of the temporal muscle of the treated animals. The proportion of ST fibres to FT fibres was increased by up to 12% after functional advancement of the mandible. The histological findings corresponded with the data for fibre mRNA generated by RT-PCR.

Acrylic Resins↗

PubMed2001

Sensitivity of titanium brackets to the corrosive influence of fluoride-containing toothpaste and tea.

Titanium brackets are used in orthodontic patients with an allergy to nickel and other specific substances. In recent studies, the corrosive properties of fluoride-containing toothpastes with different pH values were investigated. The present in vivo study tested how the surfaces of titanium brackets react to the corrosive influence of acidic fluoride-containing toothpaste during orthodontic treatment. Molar bands were placed on 18 orthodontic patients. In these same patients, titanium brackets were bonded on the left quadrants and stainless steel brackets on the right quadrants of the upper and lower arches. Fifteen patients used Gel Kam containing soluble tin fluoride (pH 3.2), whereas 3 used fluoride-free toothpaste. The brackets were removed for evaluation by light microscopy and scanning microscopy 5.5 to 7.0 months and 7.5 to 17 months after bonding. The quality and quantity of elements present were measured by scanning microscopy. Macroscopic evaluation showed the matte gray color of titanium brackets dominating over the silver gleam of the steel brackets. The plaque accumulation on titanium brackets is high because of the very rough surface. Pitting and crevices were observed in only 3 of the 165 brackets tested. The present in vivo investigation confirms the results of in vitro studies, but the changes are so minor that titanium brackets can safely be used for up to 18 months. Wing surfaces should be improved by modifying the manufacturing process.

Adult↗

PubMed2001

Oxidative state and histological changes in muscles of mastication after conditioning training.

Stress due to endurance training of striated muscles leads to adaptive changes in the distribution of muscle fiber types (i.e. ratio of type I and type II fibers). Moreover, severe training leads to tissue hypoxia and oxidative stress in muscles. In the current study, we examined the relationship between histological changes and oxidative state in muscles of mastication during the acute adaptation phase to a sustained muscle load. Six domestic pigs received build-ups on the molar teeth in order to induce a sustained load of the muscles of mastication for a duration of four weeks. Afterwards the masseter (M1, M2, M3), medial pterygoid (PM), temporal (TP1, TP2), and geniohyoid muscles (GH) were removed and the fiber type distribution was determined by enzyme histochemistry. Additionally, the tissue content of glutathione and lipid peroxidation (LPO) products were measured. The above treatment led to muscle fiber transformation of type II into type I (M1, M2, TP2, PM) and a decrease of the GSH content (M1, M2 and TP2). The changes in the GSH/GSSG ratio were in accordance with the changes in proportions of muscle fiber types, with the lowest GSH/GSSG ratios in the most stressed muscles of the treated animals. No significant changes in LPO products were found. The decrease of the GSH/GSSG ratio in the most stressed muscles indicates an increased intracellular oxidative stress, which may be caused by tissue hypoxia during the chronic phase of muscle adaptation.

Adaptation, Physiological↗

PubMed2001

Effects of 28-day mechanical and chewing stress on content of bound and diffusible ions in muscles of mastication.

Type I and type II muscle fibres have different ion concentrations. Muscles adapt to chronic stress by changing of fibre types and remodelling of the myosin heavy chains in the muscle fibres. The present investigation on ionic change during muscular contraction was carried out on 10-week-old pigs (6 treated animals, 6 controls) over a 28-day period. Six pigs received acrylic build-ups to induce mechanical advancement of the lower jaw and chronic chewing stress. Muscle tissue was taken from the masseter (M1, M2, M3), temporal (TP1, TP2), medial pterygoid (PM) and geniohyoid (GH) muscles by a standardized method. Eighty-four muscle samples were used for histological fibre differentiation with mATPase. Energy-dispersive X-ray microanalysis of muscles was carried out in an environmental scanning electron microscope. Endurance stress in the stressed muscles was seen as an increase of type I fibres (P < 0.001). This histological change and ionic alterations were measured in the anterior region of the masseter (M1 and M2) and in the posterior region of the temporal muscle (TP2). Smaller changes were found in the medial pterygoid muscle. We measured in this muscles increases in potassium, sulphur, chloride (P < 0.05) and even larger increases in phosphate (up to 1.5 mmol/g to 2.3 mmol/g, P < 0.001) and sodium (3-fold, P < 0.001). The results reveal the effects of chronic stress on muscle fibres and ion concentration in the muscle. Chronic stress resulted in an increase of type I fibres and increased ion concentration in the same muscle region. These are considered to be indicators of more efficient contraction. The changes in ion concentration are an important factor in muscle contraction.

Animals↗

PubMed2001

Hard palate deformation in an animal model following quasi-static loading to stimulate that of orthodontic anchorage implants.

The aim of the present investigation was to identify adequate implant treatment for young patients. In an animal model palate deformation was investigated by acute quasi-static loading. Three series of tests (with newborn, young and adult pigs) were performed, each with two groups (one or two-point stress) and 5-7 animals per group. Discs with a diameter of 3 and 5 mm were placed in group 1 in the suture area, and in group 2 at both the right and left sides of the suture. Deformation was analysed by a computerized three-dimensional (3D) photo-imaging evaluation system. In young animals the one-point load at a significantly lower force level led to fractures in comparison with the two-point load (P < 0.001). Similar results were measured by an increase in the size of one disc from 3 to 5 mm (P < 0.001). In contrast, adult pigs showed stable results with both methods. In general, a larger disc diameter led to less instability. The one-point load seems to be suitable for adult animals, whereas a two-point load might be favourable during ossification. The advantage of the two-point load is the generation of a higher stress and therefore improved control of dental fixation. However, further tests are necessary to investigate the long-term effects.

Age Factors↗

PubMed1998

Influence of hypoxia and hypoxia/hypercapnia upon brain and blood peroxidative and glutathione status in normal weight and growth-restricted newborn piglets.

Glutathione (reduced (GSH) and oxidized (GSSG)), lipid peroxidation products (TBAR) and in vitro production of reactive oxygen species (ROS, by means of stimulated lipid peroxidation, H2O2 formation and amplified chemiluminescence (CL) in 9000 xg brain supernatants) were studied in the cerebellum (C) and temporoparietal area (TP) of the brain of normal weight (NW) and spontaneously intra-uterine growth-restricted newborn piglets (IUGR) after 1 hour hypoxia (fractional inspired oxygen concentration (FiO2) 8%), and in combination with 10% CO2, followed by 3 hours recovery (FiO2 30%). The strong GSH depletion accompanied by an increased concentration of GSSG and TBAR, more distinct in IUGR, is the most important result in the brain after hypoxia and reoxygenation. Hypercapnia-related acidosis seems to protect the brain of IUGR from hypoxia/reoxygenation induced injury by reducing GSH depletion as well as GSSG and TBAR increases. But stimulated lipid peroxidation and H2O2 formation in 9000 xg supernatants of C and TP were found to be higher in acidosis and hypercapnia. Decreased or unchanged amplified CL, demonstrating lower in vitro production of ROS, cannot explain the GSH depletion after hypoxia and reoxygenation. The scarce changes in erythrocyte GSH and GSSG as well as plasma TBAR concentrations did not reflect the findings in the brain. Nevertheless, the changes in the brain support the hypothesis that oxidative stress plays a role in neuronal damage after hypoxic stress, but the brain of IUGR did not reveal a special response to moderate hypoxia.

Acid-Base Equilibrium↗

PubMed1998

Influence of hypoxia and hyperthermia upon peroxidative and glutathione status in growth-restricted newborn piglets.

Normal weight (NW) and spontaneously intra-uterine growth-restricted newborn piglets (IUGR) were submitted to 1 hour hypoxia and hyperthermia followed by 3 hours reoxygenation. Glutathione (GSH, GSSG), lipid peroxidation products (TBAR) and cytochrome P450 dependent production of reactive oxygen species were studied by determination of H2O2 production and amplified chemiluminescence (CL) in brain and peripheral organs of NW and IUGR. A severe decrease of GSH was accompanied by enhanced H2O2 formation and lipid peroxidation in the brain of both NW and IUGR after hypoxia/hyperthermia and reoxygenation. In the other organs studied, only muscles showed enhanced lucigenine amplified CL and TBAR production. Nearly the same results in NW and IUGR reveal no higher risk of IUGR.

Animals↗

PubMed1995

Brain peroxidative and glutathione status after moderate hypoxia in normal weight and intra-uterine growth-restricted newborn piglets.

In order to investigate the pathogenetic factors causing the relatively frequent occurrence of brain injury in intrauterine growth-restricted newborns, lipid peroxidation products (TBAR), glutathione (GSH, GSSG) and in vitro production of reactive oxygen species (chemiluminescence, stimulated lipid peroxidation, H2O2 formation) were studied in the brain of normal weight (NW) and intra-uterine growth-restricted newborn piglets (IUGR) after 1 hour of hypoxia (FiO2 11%) and 90 min reoxygenation. Cardiocirculatory parameters and catecholamine release into the blood were also measured. In the cerebellum, higher GSH content, but also higher in vitro production of lucigenin amplified chemiluminescence were found in comparison to other brain regions, independent of growth restriction and hypoxia. Moderate hypoxia without acidosis and hypercapnia resulted in GSH depletion especially in the brain of IUGR, but no changes in GSSG concentrations were measured. Though TBAR decreased after hypoxia/reoxygenation, in some brain areas of IUGR higher TBAR values were found in comparison to NW. H2O2 formation, stimulated lipid peroxidation and lucigenin and luminol amplified chemiluminescence in the 9000 x/g supernatant of brain tissue did not reveal special response of IUGR to hypoxia/reoxygenation. Hypoxia-induced circulatory centralisation due to increased release of catecholamines into the plasma prevented oxygen deficiency also in the brain of IUGR. The role of brain monoamine metabolism in the production of reactive oxygen species, followed by greater GSH depletion and higher in vivo formation of lipid peroxides in IUGR is discussed.

Animals↗