Biomedical subjects
P Diedrich
Publications and source records attributed to P Diedrich.
In vitro testing of a measuring system for in vivo recording of orthodontically applied forces and moments in the multiband technique. Part II.
The aim of this study was to measure in vivo the forces and moments acting therapeutically on the individual tooth in connection with the multiband technique. Securing and evaluating the planned in vivo measurements involves analysing the measuring accuracy of the system as a whole by means of corresponding in vitro investigations. Errors in determining the therapeutically effective force system may result from the electrical measurement of the mechanical quantities by the sensor system and from the fixing of the archwire in therapeutic position. The precision of this fixing is influenced by displacements induced by elasticities and mechanical tensions in the measuring system. Calibration test series have shown the sensor system to have a margin of error of less than 2%. The displacements influencing precision fixing of the archwire were determined by means of a laser position measuring system. For a maximum orthodontic force of 1.5 N, they are 0.06 mm in the least favourable case. The resulting measuring accuracy was determined analytically or graphically, depending on the key parameters. Successful in vivo studies of the therapeutically applied force systems are to be expected on the basis of these results.
Wear in the upper and lower incisors in relation to incisal and condylar guidance.
The incisors of 85 patients were examined for tooth wear with the aim to evaluate possible association between the degree of wear and anterior guidance. Apart from clinical functional analysis electronic axiography using the system CADIAX was carried out. Anterior guidance in protrusive movement was marked on individually mounted plaster casts and scanned using a pantograph. The cephalometric analysis program CADIAS was used for the metric determination of the anterior guidance angle to the axis-orbital plane, and in order to relate the anterior guidance to the horizontal condylar inclination. The interincisal angle was included in the evaluation as a further functional angle and according to overjet and overbite there were classified typical incisor relations. Where both anterior guidance and incisor inclination and relation were in the normal range, there was an increase in incisal tooth wear in the group investigated. With reduced functional space, frequently found together with anterior deep bite, incisor wear was less extensive. While the occurrence of parafunction was shown not to be related to anterior guidance and incisor inclination and relation parafunctions were the decisive factor in the occurrence of severe incisor wear. Where anterior guidance and incisor inclination and relation are normal, the area of enamel under load is smaller and the space for bruxism larger. Parafunctional forces thus appear to result in a higher degree of wear than is found with the reduced functional space of a steep incisor position. Anterior guidance could not be evaluated as a parafunctonal inducing factor, but only as determining the wear pattern in the individual.
Radiological assessment of artificial bone defects in the floor of the maxillary sinus.
OBJECTIVE: To compare dental radiographs and axial high resolution (HR) CT scans for the identification of artificial bone defects between the maxillary sinus and the roots of the adjacent teeth and to evaluate the accuracy of HR-CT. METHODS: Artificial bone defects of different dimensions were produced in the antral floor adjacent to 40 roots of 23 premolars and molars in 21 human autopsy specimens of the posterior maxilla. Periapical radiographs were obtained together with 1 mm axial HR-CT scans. The macroscopic and radiological findings of both sets of images were compared. Histological sections were prepared corresponding to the CT scans and the accuracy of the scans evaluated by measurement of five parameters. RESULTS: None of the artificial bone defects could be identified on the dental radiographs. In contrast 62.5% of the antral bone defects could be identified in the axial HR-CT scans. Identification of their margins depended on the location on the tooth root, adjacent bone morphology and visualization of the periodontal ligament space. When the periodontal ligament space was visualised identification of an antral floor between 0.2 and 0.5 mm thick was feasible. CONCLUSION: In certain clinical situations HR-CT is appropriate for identifying antral bone detects between the maxillary sinus and the roots of the adjacent teeth.
Orthodontic retraction into recent and healed extraction sites. A histologic study.
The aim of this experimental study was to assess the advantages of an early or delayed treatment start after tooth extraction on the basis of hard-tissue findings (density, maturity, osteodynamics) and of soft-tissue responses at the extraction site. Following bilateral extraction of the second incisors, reciprocal space closure was initiated in 3 foxhounds (age: 3.5 years): group 1 (6 teeth) 12 weeks after extraction, group 2 (6 teeth) immediately after extraction. After an 8-week bodily tooth movement period and a 2-month retention period, evaluation was undertaken on the basis of clinical/radiologic and histologic criteria (sequential polychromatic bone marking, light microscopy). Histologic analysis yielded the following findings in group 1 (delayed tooth movement): low bone density at the extraction site with more mature lamellar bone, pronounced horizontal atrophy of the alveolar process with periosteal bone apposition in direction of tooth movement, increased tendency towards gingival invagination. The findings in group 2 were characterized by: higher bone density with less maturity (bundle bone) at the extraction site, broader alveolar process, reduced tendency towards gingival invagination. No qualitative difference between the 2 groups was found with respect to root resorption. The histologic findings therefore indicate that orthodontic retraction into extraction sites should be initiated at an early stage.
Primary surgery of skeletal dysgnathias.
Three case studies from the patient population of the University Hospital of Aachen (RWTH) are used to describe indications for primary surgical intervention in skeletal dysgnathia. Such preconditions may apply in the case of mandibulo-alveolar protrusion, anomalies where there is little or no option to fixing orthodontic appliances (enamel hypoplasia or shortened crowns), severe transversal discrepancies and skeletal dysgnathia with pronounced malpositioning in the alveolar process and the teeth. The advantages are improved compliance (through the patient experiencing success at the outset of treatment) and limitation of postoperative orthodontic treatment to occlusive fine adjustments of the occlusion, resulting in an appreciable reduction in both the degree and duration of tooth movement and tissue damage.
Use of diethyl squarate for the coupling of oligosaccharide amines to carrier proteins and characterization of the resulting neoglycoproteins by MALDI-TOF mass spectrometry.
The 8-methoxycarbonyloctyl glycosides of GlcNAc beta, Gal beta 1-4Glc beta, Fuc alpha 1-2Fuc alpha 1-3GalNAc beta and Fuc alpha 1-2Gal beta 1-3[Fuc alpha 1-4]GlcNac beta were converted to primary amines by reaction with neat ethylenediamine and then coupled to bovine serum albumin (BSA) using diethyl squarate as the connector. The average degree of incorporation of the sugar onto the protein, as well as the molecular weight distribution, could be conveniently determined using matrix assisted laser desorption ionization/time of flight (MALDI-TOF) mass spectrometry thus avoiding cumbersome structure-dependent colour-tests or analysis of cleaved ligand. The present coupling method has the advantages of proceeding under very mild conditions, yielding controlled incorporation values and can reliably be used for the coupling of very small amounts (mg) of oligosaccharide.
Integration of three-dimensional cephalometry and 3D-skull models in combined orthodontic/surgical treatment planning.
In 15 adult patients with severe dentomaxillofacial deformities we integrated 3-dimensional cephalometry and 3D-model surgery with individually milled or stereolithographically built skull models in our combined orthodontic/surgical diagnosis and treatment planning. After the generation of contiguous axial CT-scans the CT data sets were transferred to a commonly used computing system (IBM-PC) to reconstruct 3D-images from any point of view. After the definition of measurement points, distances and angles at the skin and bone surface a 3-dimensional cephalometric analysis could be performed directly in the 3D-objects on the monitor. This allows a quantitative assessment of skeletal asymmetries. The transfer of CT data to life-size 3D-skull models and replacement of imprecise dental arches by dental casts different orthodontic and surgical treatment concepts could be evaluated. The 3D-model surgery represents a new quality of treatment prediction in the individual dentomaxillofacial morphology. The orthodontic set-up and 3D-model surgery permit a verification of the feasibility of the most suitable mobilization and placement of bone segments. The clinical treatment sequences indicated that the integration of 3-dimensional cephalometry and 3D-model surgery in patients with severe asymmetric dentomaxillofacial deformities allowed a higher precision of diagnosis and treatment planning.
Preprosthetic orthodontics.
Preprosthetic orthodontic measures are often an integral part of comprehensive oral rehabilitation. The individual aspects of treatment are aimed at optimizing dentofacial esthetics and at improving masticatory function, hygiene potential of prosthetic restorations and abutment quality. The therapeutic systematics of orthodontic/prosthetic cooperation, the limits and problems are outlined and documented with examples of treatment sequences. The conclusion drawn is that preprosthetic orthodontics will continue to gain significance in future esthetic-functionally oriented dentistry and that its integration into multidisciplinary rehabilitation is often indispensable.
The Orthosystem--a new implant system for orthodontic anchorage in the palate.
The present report describes the design and first clinical experiences of a newly developed endosseous orthodontic implant anchor system (Orthosystem, Institut Straumann, Waldenburg, Switzerland) for palatal anchorage. The 1-piece fixture made of titanium consists of a screw-type endosseous implant body (sandblasted, acid-etched, diameter 3.3 mm, lengths: 4 and 6 mm), a cylindrical polished transmucosal neck and an abutment. Clamp-caps provide attachment of square commercially available orthodontic wires (0.032 x 0.032 inch, SS) to the abutment (transpalatal bars). In a pilot study 1 fixture (implant body length: 6 mm) was inserted into the midsagittal anterior palatal region in each of 6 adult patients with Angle class II malocclusion (distocclusion 7 to 8 mm, overjet: approximately 9 mm). The treatment plan included extraction of the first maxillary premolars and retraction of the anterior teeth based on maximum anchorage of the posterior teeth without using compliance-dependent anchorage aids (headgear, class II elastics). Due to the design of the fixture only 1 simple surgical procedure was required for insertion (nonsubmerged method, 1-stage surgery). Accordingly the need for surgical exposure of the abutment for connection and wire insertion was eliminated. Thus, inconvenience to patients was reduced to a minimum. The patients are now at varying active treatment stages. The course of treatment of the most advanced case is described. Evaluation of the clinical and radiological findings after 12 months of treatment (3 months implant healing, 9 months active orthodontic treatment which is equal to the implant loading period) revealed no implant mobility/dislocation, favourable peri-implant soft tissue conditions, no marked mesial movement (approximately 0.5 mm) of the implant/transpalatal bar supported posterior teeth, and 8 mm retraction of the anterior teeth. Retrieval of the fixture and post-operative wound healing were uncomplicated. In the treatment of this case, no compliance-dependent extraoral anchorage was used, and the well aligned mandibular dentition was not bonded provide anchorage support (class II elastics).
Concept and development of a measuring system for in vivo recording of orthodontically applied forces and torques in the multiband technique. Part I.
The cause of tooth movement with a multiband or multibracket appliance is the force system in the bracket, which is generated by an archwire and transmitted by a bracket to the respective tooth. Continuous arch wires are, from the biomechanical point of view, a statically multiply undetermined system. Quantitative determination of the forces and torques acting at the individual teeth, and thus observance of a non-critical level of applied forces, is therefore extremely problematic in practice, the force is applied by the orthodontist more or less "intuitively" on the basis of recommendations evolved in theory and in vitro. The measuring technique presented in this paper is designed to permit these force systems to be recorded in vivo for the first time, allowing account to be taken of the individual situation "tooth-periodontium-bone". Evolvement of an appropriate measuring principle was followed by development of the individual components of the measuring system. The results of the subsequent initial in vitro test series offer the prospect of successful clinical application.
Mandibular incisors, alveolar bone, and symphysis after orthodontic treatment. A retrospective study.
The mandible of a deceased 19-year-old young woman who had been treated with an edgewise appliance was removed during autopsy. The overall tooth movements during the 19 months of treatment were reconstructed (treatment documents) and compared with the macroscopic, radiologic, and micromorphologic findings of the incisor/alveolar bone/symphysis complex of the dry mandible. The initial lateral cephalogram revealed an extremely narrow and high symphysis, with an incisor position straight above the thin bone. During treatment, the incisors had been moved to lingual (lingual root torque) and derotated. Morphologic evaluation of the dry mandible revealed lingual (oral) aspects of the roots reaching some millimeters out of the lingual alveolar bone and largely without cortical plate covering. Lateral dental contact radiographs of any bone/incisor segment showed the sagittal alveolar bone width to be smaller than the labiolingual (orobuccal) diameter of the incisor roots. A comparison of the approximate pretherapeutic alveolar bone height, which was assessed by measuring the distance from the cementoenamel junction to the most coronal margin of any root resorption in scanning electron microscopy, with that of the specimen showed a calculated bone loss on the lingual aspect extending from 2.3 to 6.9 mm. On the labial (buccal) aspect, bone loss was far less pronounced. These results suggest that in the case of a narrow and high symphysis, pronounced sagittal incisor movements and derotation during routine orthodontic treatment with a fixed appliance may be critical and lead to progressive bone loss of lingual and labial cortical plates.
The use of palatal implants for orthodontic anchorage. Design and clinical application of the orthosystem.
This paper presents the Orthosystem (Institute Straumann, Waldenburg/ Switzerland), a new endosseous orthodontic implant anchor system for palatal anchorage. The Orthosystem may replace compliance dependent extraoral anchoring aids for orthodontics and makes a bonding of well aligned mandibular dentition and it's use with class II elastics unnecessary. The fixture is designed for a one-stage application. It consists of an implant of pure titanium with a surface-treated, screw-shaped endosseous part of 3.3 mm diameter and lengths of 4 and 6 mm. Above the polished transmucosal neck follows as abutment where transpalatal arches made of rigid orthodontic wires (0.032 x 0.032 inch) are fixed by means of a clamp-cap. 6 patients with an angle class II malocclusion were implanted with the 6 mm fixture in the proximal midsagittal region of the palate during a pilot study. The treatment goal was extraction of the first maxillary premolars with subsequent retraction of the frontal dentition under maximal anchorage of the lateral teeth. For the implantation a simple surgical procedure of 10 min length was required while no further invasive action are needed until explantation. This way the strain on the patients was reduced to a minimum. They are now at varying stages of active treatment and the most advanced case is demonstrated here. The clinical and radiological findings after 12 months of treatment comprising 3 months of healing revealed no implant mobility or dislocation, favourable periimplant soft tissue conditions, and no marked mesial movement of the implant supported teeth. The frontal dentition was retracted by 8 mm with space closure occurring in a relatively short treatment period.
Biodegradable implants for orthodontic anchorage. A preliminary biomechanical study.
The use of endosseous implants as temporary orthodontic anchoring elements has good results in many clinical applications. The development of a new orthodontic implant anchorage system comprising an implant produced of biodegradable polylactide with a metal superstructure is described. The presented bioresorbable implant anchor for orthodontics system (BIOS) implant is designed to provide orthodontic anchoring functions in adolescents and adult patients, and to then be resorbed without a foreign body reaction or signs of clinical inflammation. Shear strength and maximum vertical strength have been measured in biomechanical in vitro tests. BIOS fixtures can be loaded with horizontal shearing forces of 50 N with a mean deflection of 0.26 +/- 0.13 mm and mean vertical removal forces of 155 +/- 80 N. Clinical studies are currently being undertaken to evaluate clinical practicability and biocompatibility of the BIOS implants.
Human myotatic reflex development of the lower extremities.
Lower extremity (LE) myotatic reflexes were tested by percussion (taps) to the patellar and Achilles tendons. Surface electromyographic recordings were obtained from 5 LE muscles during tendon taps. Results indicated that LE myotatic reflexes underwent considerable change during early human development. The changes were non-linear and highly variable. Reflex irradiation (the presence of reflex responses in muscles other than the one being directly stimulated by a tendon tap) was present in the newborn but to a lesser extent than was in evidence later on during the first year of life. The percentage of time reflex irradiation was detected in heteronymous muscle groups appeared to achieve maximal levels during the first year and then progressively decline. The decline in reflex irradiation was most dramatic between the first and second years of life. Irradiated responses were still recorded from 2 year-old children but with less frequency than in children less than 1 year of age. With the exception of responses in muscles that were direct antagonists to the stimulated muscle, irradiation was not observed in children 3-5 years of age.
Monitoring biosynthetic transformations of N-acetyllactosamine using fluorescently labeled oligosaccharides and capillary electrophoretic separation.
Capillary electrophoresis with laser-induced fluorescence detection was used to monitor biosynthetic transformations of a labeled derivative of N-acetyllac-tosamine (beta Gal (1 --> 4) beta GlcNAc, LacNAc) in crude microsomal extracts. For this purpose, six authentic standards including LacNAc-O-TMR itself (-TMR, a linker arm attached to tetramethylrhodamine), the tri-and tetrasaccharides that would form by either alpha (1 --> 2) or alpha (1 --> 3) fucosylation of LacNAc or both (i.e., H-type 2, LeX and LeY sequences) were chemically synthesized. The potential degradation products produced by galactosidase and hexosaminidase were also prepared. All of the standards were kinetically competent substrates for the enzymes present in HT-29 cells and could be baseline separated in a single run requiring 11 min. The action of competing enzymes acting on the common LacNAc sequence could thus be monitored in a single run with sensitivity routinely as low as a few thousand molecules.