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Biomedical subjects

U Teuscher

Publications and source records attributed to U Teuscher.

17 recordsLinked to original sources
PubMed1998

Changes in peri-implant tissues subjected to orthodontic forces and ligature breakdown in monkeys.

The aims of this investigation were to histologically evaluate in monkeys the effect of a repetitive mechanical trauma alone on the peri-implant tissues, and the effect of a repetitive mechanical trauma in combination with ligature-induced peri-implantitis on the peri-implant tissues. The study used 5 male cynomolgus monkeys. Prior to the start of the study, all premolars and the first and second molars in the mandible were extracted. After a healing period of 12 weeks, following tooth extraction, split/full thickness flaps were elevated on both sides of the mandible in order to expose the bony ridge. Four implants, of 3.75 mm in diameter and 7 mm in length, were then inserted on each side and the flaps were readapted and sutured in place. Following a healing period of 16 weeks, the second stage procedure was performed, impressions were taken, and custom-made crowns using a non-precious metal alloy were fabricated and inserted on all implants 4 weeks after abutment connection. At the same time peri-implantitis was induced on one side of the mandible by placing plaque-retentive ligatures around the implants. On the other side, an oral hygiene program consisting of thrice weekly brushing with a toothbrush and flour of pumice mixed with 2% chlorhexidine was initiated. Four months later, a repetitive mechanical trauma was initiated on implants 1 and 2 on both sides in the mandible. Consequently, a split mouth design was obtained: 1) test 1=ligature-induced peri-implantitis alone (LPNO); 2) test 2=ligature-induced peri-implantitits with a repetitive mechanical trauma (LPMT); 3) test 3=healthy peri-implant tissues with a repetitive mechanical trauma (MT); and 4) control (NO)=healthy peri-implant tissues with no repetitive mechanical trauma. Following 16 weeks of repetitive mechanical trauma the animals were sacrificed. Histologic observations and computed-assisted histometric and histomorphometric analyses were performed to determine the amount of peri-implant bone loss and the percentage of direct mineralized bone-to-implant contact around each endosseous oral implant. Histologically, all implants yielded osseointegration at the light microscopic level. There was a significant difference regarding the mean direct mineralized bone-to-implant contact length as a fraction of the total implant length between the healthy (i.e., MT and NO) and diseased sites (i.e., LPNO and LPMT) (P < 0.05). When comparing the percent of direct mineralized bone-to-implant contact for the 2 best threads of each implant and group, no significant difference (P=0.675) could be detected. Under the conditions of this study, the repetitive mechanical trauma showed no histologic effect on the peri-implant bone loss neither in healthy nor in diseased implant sites. The effects of excessive loading on osseointegration are presently not clearly understood. The key problem seems to be the determination when loading on implants exceeds the physiological range of bone adaptation which may then cause implant failure. Further research to elucidate this problem is essential.

Adaptation, Physiological↗
PubMed1989

Facial growth after treatment of unilateral temporomandibular joint ankylosis in childhood without growth centre transplantation. A serial cephalomorphometric study.

Our aim was to study the influence of early surgical treatment of temporomandibular joint ankylosis on further facial growth and development. At the Department of Maxillo-Facial Surgery, Zurich, 11 children with a unilateral TMJ-ankylosis met the criteria of a maximal preoperative interincisal mouth opening of 15 mm, of a minimal long-term postoperative interincisal mouth opening of 30 mm, and of excellent documentation. 30 anatomical landmarks were defined on the copies of the follow-up cephalograms using the structure-superimposition technique. The points were perforated and digitized. Analysis and graphic-plotting were followed by computer. The hypothesis that mandibular growth continues once the ankylosis was successfully treated (without transplantation of a growth centre) and mandibular function definitely restored, was confirmed. The treatment does normalize the growth rate, but it seems that abnormal growth patterns cannot be influenced by it. As a consequence, the surgical release of the ankylosis should be performed as early as possible.

Adolescent↗
PubMed1986

An appraisal of growth and reaction to extraoral anchorage. Simulation of orthodontic-orthopedic results.

The purpose of this article was to simulate graphically the probable orthodontic-orthopedic results of different types of extraoral traction applied to the upper dentition. Forces and movements are vectors; apart from individual variation in the amount of reaction to forces, the reactive movement vector at any given site of an influenced hard-tissue unit depends mainly on the position of its center of resistance relative to the force vector and on the amount and time of force application. In growing patients the resulting movement can then be appraised by the addition of reactive movement and average growth-movement vectors. Standardized assumptions have been made to simulate and compare qualitatively the significance and implications of five different types of commonly used extraoral traction on the upper dentition. Biomechanical parameters (such as the system factor describing the reciprocal relation between the lever arm of a force and the corresponding distance between the centers of resistance and rotation) have been arbitrarily assessed. Where cervical gear on the upper dentition is used, the resulting simulations suggest that raising the outer arms of the face-bow means less posterior effect on the upper dentition, less vertical molar control, and an increased tendency to open the bite. Where high-pull traction is applied, graphic simulations using a constant angulation, but different position of the force vector, indicate that moving the force line from a backward to a more forward position would mean a change from posterior to anterior rotation, from pronounced to no vertical molar control, from excessive incisor elongation to complete vertical incisor control, and from considerable distal effects to nearly none on the upper dentition.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar Process↗
PubMed1984

Relationship between peritubular membrane potential and net fluid reabsorption in the distal renal tubule of Amphiuma.

Amphiuma kidneys were isolated and perfused with modified Ringer solution and peritubular and transepithelial membrane potentials (p.d.s) in distal tubules measured with micro-electrodes during rapid changes of luminal electrolyte concentrations. Peritubular membrane potential and net fluid reabsorption (split-oil-droplet method) were also measured with and without application of various drugs known to alter transport. Raising the luminal sodium concentration from 10 to 100 mM reversibly increased the peritubular p.d. The magnitude of the peritubular p.d. was a saturable function of luminal sodium concentration. In the presence of chloride in the lumen the peritubular hyperpolarization following increased luminal sodium could be inhibited by luminal amiloride (10(-4)M). Sodium-induced hyperpolarization of the peritubular p.d. could be completely inhibited by 10(-5)M-ouabain. Adding amiloride (10(-4)M) to the luminal fluid rapidly and reversibly depolarized the peritubular p.d. and inhibited fluid reabsorption. Addition of amphotericin B (20 micrograms/ml) to the luminal perfusion solution had no effect on peritubular p.d. at 100 mM-luminal NaCl but at 10 mM-NaCl, peritubular p.d. hyperpolarized. Fluid reabsorption was stimulated (with 100 mM-NaCl in the lumen). Addition of amphotericin when the tubule was perfused on both sides with solutions containing a constant potassium concentration of 78 mM and a variable sodium concentration ranging from 7.8 to 34.5 mM revealed strong dependence of the peritubular hyperpolarization on the sodium concentration. Luminal furosemide (10(-4)M) and chlorothiazide (10(-4)M) and peritubular ethacrynic acid (10(-4)M) all reduced fluid reabsorption but hyperpolarized the peritubular p.d. The data suggest the presence of an electrogenic sodium transport process in the peritubular membrane that directly contributes to the generation of the peritubular potential. In addition, chloride transport has an important role in determining this potential.

Absorption↗
PubMed1983

Edgewise therapy with cervical and intermaxillary traction--influence on the position of the bony chin.

Comparison of treatment and control samples was intended to reveal those factors which, during Class II correction using Tweed Edgewise technique in conjunction with intermaxillary traction and low cervical traction to upper molars, may lead to undesirable posterior rotation of the mandible. Both samples exhibited similar condyle growth rates. Increased variability of the parameters tested was found within the treatment group. No significant difference was found in the vertical movement of the upper molars, while anterior movement of the upper molars was significantly inhibited in the treatment sample. The treatment sample displayed increased vertical and decreased anterior movement of pogonion, accompanied by posterior rotation of the mandible. Close and similar correlations were found in both samples between the anterior movements of the upper molars and pogonion, between the angles of upper molar and pogonion displacement in relation to Frankfort Horizontal, and between both of the upper molar parameters and changes of mandibular rotation. In the treated sample it was inhibition of anterior movement of the upper first molars, not enhancement of vertical movement that appeared to cause posteroinferior rotation of the mandible and displacement of pogonion through a geometric interdependence. The direction of upper molar movement and condyle growth rate both exert important influences on changes in position of the growing mandible and thus on the nature of profile changes in Class II correction.

Adolescent↗
PubMed1982

Stability of Le Fort I osteotomy in class III cases with retropositioned maxillae.

Of 65 adult class III patients with retropositioned maxillae subjected to Le Fort I Osteotomy, 16 were selected at random for a clinical and cephalometric examination of postoperative stability. Lateral head plates prior to treatment, 6 weeks post-treatment and 1 year post-treatment were compared. In 9 out of the 16 cases 5 year post-treatment head plates were available. Statistical evaluation of the longitudinal differences revealed the repositioned maxilla to remain stable. The upper lip, however, lost 44% of its postoperative advanced position within the 1st year subsequent to the operation. In the period between 1 year and 5 years postoperatively no further cephalometric changes of any significance were recorded.

Adult↗
PubMed1978

A growth-related concept for skeletal class II treatment.

The use of a combined activator--high-pull headgear appliance for treatment of Class II, Division 1 malocclusion is presented as a preliminary report. The activator itself is equipped with a palatal bar, lower lip pads, and torque-control auxiliaries for the upper incisors. The face-bow is mounted directly on the activator, and the extraoral force vector is equivalent to that of an anterior high-pull vector. During bite registration the veritcal displacement of the mandible is restricted to a minimum, and the anterior displacement should not exceed 6 mm. On the basis of current knowledge of the growth of the bony facial structures, treatment objectives and a specific approach for skeletal Class II correction are defined. Following these objectives, the therapy aims at correcting the malocclusion without diverting the anterior landmarks of the bony face from their specific lines of growth. This is brought about by the corresponding mechanics of the activator-headgear combination. The corrective effect of this appliance may be assumed to be the result of several different factors. The maxillary dentition is restrained in a posterior cranial direction, and an inhibitory effect on the maxilla counter to its line of development is attained. The mandibular dentition is influenced in an anterior downward direction by means of the bite registration, and the occlusion is unlocked during treatment. Any transfer of distally directed headgear forces from the maxilla to the mandible is prevented. Temporary stimulation of condylar growth, possibly combined with temporary posterior deflection of condylar growth, may also be induced. In this way it is possible to take maximum advantage of condylar growth in the sagittal dimension. Thus, not only is the malocclusion corrected but, at the same time, decisive profile improvement is achieved by anterior development of the mandible. From the experience gained so far with a Class II, Division 1 sample undergoing treatment with the activator-headgear combination, it would appear that skeletal control of the direction of facial growth during treatment is possible. A quantitative report on this group of approximately forty patients, some of whom are still receiving treatment, is in preparation.

Activator Appliances↗
PubMed1977

[Therapeutic methods in class III cases].

Mandibular overjet is caused by one or a series of genetic and environmental factors. Control of mandibular growth seems to be questionable, multilocal compensation within certain limits, therefore, remains an instrument of attacking the problem in cases which can be treated by orthodontic means. The totality of the different compensating procedures, referring to the various functional, skeletal and dentoalveolar aspects can lead to considerable corrective effects.

Child↗