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Biomedical subjects

H Wehrbein

Publications and source records attributed to H Wehrbein.

49 records · Page 3Linked to original sources
PubMed1991

[Clinically relevant biomechanics. 2. Mechanics of non-symmetric front teeth-intrusion].

Front teeth can be intruded by the segmented arches described by Burstone. The article analyses the vertical forces under the influence of symmetric intrusion arches and examines the static situation caused by non-symmetric activation of symmetric intrusion mechanics. It shows that in some cases even extrusive forces can occur in the anterior segment, whereas intrusive forces are intended to be applied.

Dental Stress Analysis↗
PubMed1991

[Clinically relevant biomechanics. 3. Critical reflections about the Burstone intrusion mechanics].

A segmented arch for intrusion of front teeth, as described by Burstone, is compared to a coil-and-stylus-model. The mechanics of constructive modifications are analyzed and their consequences for the movements of front teeth are discussed. It is shown, that in some cases extrusive forces occur, while intrusive forces are applied. In these cases it is necessary to reduce intrusive forces below 0.20 Newton per side. In order to avoid extrusive forces, it is recommended to apply intruding forces between the centers of resistance of the central and lateral incisors.

Dental Stress Analysis↗
PubMed1991

[Problems in orthodontic space closure after loss of first permanent molars].

Space closure after loss of first permanent molars represents a difficult treatment task. To arrive at a reasonable treatment result a great variety of factors has to be evaluated in each individual case. These are among others: patient's age, topography of toothless alveolar bone, specific periodontal conditions and general orthodontic problems. In case of several unfavourable prognosticated factors alternative treatment methods should be taken into consideration.

Adolescent↗
PubMed1991

[The principles of two-teeth-mechanics in straight-wire-technique].

Application of straight-wire-technique leads to expression of complicated biomechanical systems. If these--according to Burstone--are subdivided into simple couples of teeth, it is possible to determine the moments and forces acting on one side of a tooth. However the significant factor for clinical tooth movement are the resulting forces and moments. These can be computed by adding the vectors of the forces and moments acting on both sides of a tooth. Consequently the movement of a single tooth results from the geometry of three teeth. This can be simulated by the superimposition of two systems of two teeth.

Dental Stress Analysis↗
PubMed1991

[Limitations of intrusion of periodontally involved maxillary buccal teeth for furcation treatment].

In a study on three dogs 12 two-rooted premolars with reduced periodontia were intruded to reestablish marginal attachment. In eight roots intrusion into the basal cortical bone of the nasal sinus was found. The histological findings showed that in these cases a possible gain of new attachment in the interradicular space may be impaired by a loss of bone support in those sites where the root intruded into the sinus. The greater the extent of intrusion into the sinus the higher the expected loss of periodontal attachment.

Alveolar Bone Loss↗
PubMed1990

[The effect of the maxillary sinus floor on orthodontic tooth movement].

By superimposing 40 pre- und post-therapeutic orthopantomograms the degree of tipping and kind of movement of 87 teeth could be described quantitatively, dependent on configuration and extension of the basal maxillary sinus. It has been shown that, with a more vertical extension (VL = 1) in front of the tooth to be moved one can expect an obviously higher degree of tipping (about 10 degrees) as compared to teeth moved through a more horizontal maxillary sinus base (VL = 2). In the group of teeth VL = 1 a correlation between the depth of the maxillary sinus recessus and the degree of tipping could be found (p less than or equal to 0.05); i.e. the deeper the maxillary sinus recessus, the higher the degree of tipping. For VL = 2 this correlation is statistically not significant. In the group VL = 1 rather a tipping movement, in VL = 2 a translatory movement can be expected.

Adult↗
PubMed1990

[Experimental bodily tooth movement through the bony floor of the nose--a pilot study].

Our experiment on animals was carried out in order to show to which degree the dog's bony nasal floor--taken as an equivalent of the recessus of the human maxillary sinus--is an obstacle to bodily tooth movement. The metric analysis showed that the movement of the upper teeth in comparison with the teeth of the lower jaw was markedly impaired by the basal cortical bone of the cavum nasi. Extended resorption of the basal bone of the nose was found histologically. The pressure side of the root surface too showed resorption lacunae which reached into the dentine deeply and were bordered by some osteoclasts.

Animals↗
PubMed1990

[Bodily movement of teeth in atrophic jaw segments].

This experimental animal study was conducted to evaluate the extent of bone restructuring after bodily movement of teeth into an area of atrophied alveolar bone. The measured values as well as the radiographic and histologic data indicate that partial or total bone restructuring occurs depending on the rate of tooth movement. In our experiment we observed marked bone formation at an average tooth movement rate of 15 microns/day, whereas no noteworthy bone formation occurred at higher rates of tooth movement (26-40 microns/day). Basically, an improvement in attachment is possible with bodily movement in atrophic alveolar bone. However, it is important to remember the delayed periosteal reaction when planning the mechanics to be applied.

Alveolar Bone Loss↗
PubMed1990

[Intrusion of periodontally affected teeth using a polyglactin-910-membrane (Vicryl)].

The present study was to determine, if the use of a Vicryl membrane following a full flap procedure and combined with subsequent orthodontic intrusion renders the formation of new attachment more predictable. In an animal experiment eight premolars with reduced periodontia were intruded. The findings were analyzed histologically, histometrically and radiologically. The results provided the basis for a new general classification of the formation of new cementum and bone substance. This classification may serve as a reference system for future studies. The combined orthodontic/periodontologic approach resulted in complete repair and functional restructuring of the destructed interradicular bone and may be a promising alternative in the treatment of furcation invasion. The proximal root surfaces showed less increase in attachment or even further bone loss. Histometric comparison revealed no significant differences between interradicular and proximal root surfaces.

Alveolar Bone Loss↗
PubMed1990

[Rates of root resorption in orthodontically moved, periodontally affected and healthy teeth].

The aim of this SEM-study was to obtain a quantitative analysis for comparing the extent of root resorption in orthodontically treated teeth, in teeth with reduced periodontium and in healthy teeth. By using a statistically valid method the highest amount of root resorption was established in orthodontically moved teeth. The teeth with loss of attachment showed a significantly higher amount of root resorption than healthy teeth. This finding complicates orthodontic treatment in teeth with reduced periodontal attachment.

Adolescent↗