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Biomedical subjects

R Schwestka

Publications and source records attributed to R Schwestka.

16 recordsLinked to original sources
PubMed1992

Changes in mandibular mobility after different procedures of orthognathic surgery.

A prospective study including 63 adult Class II and Class III patients was carried out in order to examine short- and long-term effects of four different treatment methods on mandibular mobility. The patients were treated either (Group A, control-group) orthodontically alone or (Group B) by a LeFort I-osteotomy, a (Group C) mandibular advancement or (Group D) a two-jaw surgery/mandibular set-back. In the surgery-groups (B, C, and D) maximum opening, protrusion and lateral excursions were measured 2 days pre-operatively (T0), and 3, 8, 14.5, and 25.5 months post-operatively (T1-T4). In the control-group (A) at T0 and T4 was measured, only. Significantly differing effects of the four treatment methods on mandibular mobility were detected. (A) Orthodontic treatment alone, (B) maxillary advancement by LeFort I osteotomy, and (D) two-jaw surgery/mandibular set-back osteotomy did not influence mandibular mobility permanently. Temporary decreases in groups B and D (P less than or equal to 0.05) were observed, however. In contrast, permanent reductions after (C) mandibular advancement took place (P less than or equal to 0.001). Longitudinal survey showed that in all surgery groups recoveries were limited to a short period of 3-14.5 months, depending on the movement. Surprisingly, a closer similarity between the LeFort-I group (B) and the two-jaw surgery group (D), rather than between the sagittal-split groups (C and D), was seen indicating that the problem of reduced mobility after orthognathic surgery can be limited to Class II therapy. It was concluded that in Class III therapy, the application of rigid fixation in combination with a method of maintaining condyle-position, thereby dispensing with maxillomandibular fixation, prevents permanent reductions in mobility and guarantees a rapid recovery to pre-operative mobility levels.

Adolescent↗
PubMed1991

Positioning control of the upper incisors in orthognathic surgery. Pre-operative planning with the Model Positioning Device and intra-operative application of the Sandwich Splint.

In orthognathic surgery a three-dimensional positioning of the maxilla is possible by means of the Le Fort I osteotomy and subsequent maxillary movement. In treatment planning and at the time of surgery it is very important to achieve an exact positioning of the upper incisors in relation to the upper lip and the rest of the skull. The Model Positioning Device described here allows three-dimensional positioning of the upper incisors in one- or two-jaw surgery. The reference plane is the upper surface of the upper part of a semi-individually adjustable articulator. The application of the Sandwich Splint enables the three-dimensional positioning of the maxilla in relation to the rest of the skull. The Sandwich Splint ensures that the vertical position of the mandible in relation to the rest of the skull above the osteotomy plane is exactly reproducible in the pre- and post-operative situation in both model surgery and at time of surgery. To this mandibular position the maxilla is positioned in three dimensions, as preplanned. The vertical dimension, which is identically reproducible before and after surgery is measured with a caliper. After surgery the mandible can be rotated into the planned new intercuspidation.

Calibration↗
PubMed1990

Control of vertical position of the maxilla in orthognathic surgery: clinical application of the sandwich splint.

The Le Fort I osteotomy can be used to change the position of the maxilla in all three dimensions. A presurgically fabricated occlusal splint is used to reproduce the planned sagittal and transverse position of the maxilla. Various methods for determining the proper vertical position have been described. The major difficulty in vertical control when these techniques are used is the sagittal change of the lower reference point as the maxilla is advanced. The relative error in the vertical plane increases with larger sagittal movements. The sandwich splint technique, with two stable intraoral reference points, can be used to ensure proper vertical positioning of the maxilla. This method enables exact measurement of the vertical dimension during cast surgery and in the operating room. Vertical measurements are based on the relationship between the mandible and skull base. This distance remains constant during splint fabrication and when the splint is used at surgery. Postoperatively, the mandible can be rotated into the new centric occlusion.

Dental Occlusion, Centric↗
PubMed1990

Condylar position control during maxillary surgery: the condylar positioning appliance and three-dimensional double splint method.

A new method for positioning the maxilla and condyle after Le Fort I osteotomy maintains the patient's vertical dimension (ie, the relation of the mandible to the skull above the osteotomy plane) in the preoperative and postoperative positions during both cast surgery and actual surgery. During surgery the condylar positioning appliance is fixed to the anterolateral zygoma and the lateral cortex of the mandibular ramus bilaterally to orient the mandible in centric relation. The condylar positioning appliance is used with the three-dimensional double splint method. Two prefabricated splints enable three-dimensional positioning of the maxilla in the fixed mandibular position during surgery. Postoperatively, the mandible can be rotated into the new centric occlusion.

Centric Relation↗
PubMed1990

[Growth of the facial skeleton and biomechanics of the stomatognathic system].

Biomechanical analysis of the stomatognathic system yields that the linkage between posterior and anterior guidance can be modelled by a link quadrangle (throttle crank) with closed linkage. Within this gear system the biochemical ideal position of the couple-line (functional length of the mandible) possesses a special meaning in centric occlusion: Along this line the gear system can be stretched without altering its essential mechanical properties. Interindividual comparison of the arrangement of mandibulary and maxillary structures related to the ideal initial position of the couple-line presents interindividual constants of arrangement and of growth. It is possible to define an individual, non-orthogonal system of coordinates. Its origin represents the individual center of growth. During growth special skeletally defined points run along radius vectors of this center. The rate of growth can depend on the angle between radius vector and couple-line.

Dental Stress Analysis↗
PubMed1990

[Clinical and instrumental examination of tongue motor function].

The examination of tongue motor functions requires a clinical examination of voluntary movements as well an objective evaluation of the intraoral movements during speech, deglutition, mastication and during rest. For a comparison with the simple visual assessment of voluntary movements with the mouth opened, intraoral tongue movements have been studied using various techniques. The use of lateral x-ray palatography and electromagnetic articulography (EMA) for objective intraoral measurement of tongue motor activitiesis described. Case examples are given for simultaneous recording of midsagittal movements of the tongue, the mandible and the velum during swallowing and speaking.

Deglutition↗
PubMed1990

[Intraoral condyle-related positioning of the maxilla in Le Fort 1 osteotomies].

A new technique for positioning control in Le Fort I osteotomies is presented. This intraoral procedure allows three-dimensional positioning of the condyles in the desired centric or therapeutic relation and of the maxilla at the same time. It combines the intraoperative use of the "Condylar Positioning Appliance" with the "3D Doublesplint Method".

Dental Articulators↗
PubMed1989

[The results of scanning electron microscopy research on interdental stripping in vitro].

In an in-vitro study the abrasive qualities of different orthodontic finishing strips were evaluated on the enamel surfaces of human teeth by means of a scanning electron microscope. As a result we can state that even the use of the finest finishing strip cannot eliminate the deep furrows that resulted from prior abrasion with a strip that is more coarse. The remaining furrows caused by the abrasive procedure are so deep and wide, that plaque accumulation may well be expected therein, and thus be predisposing for caries and periodontal pathology.

Dental Enamel↗
PubMed1989

Mobile connection of veneer crowns after orthodontic closure of a wide diastema in the maxillae. A clinical report.

A new, mobile splint for artificial crowns is suggested after orthodontic closure of a wide diastema mediale. A smooth mandibular movement in all excursions in considered essential. This approach sustains a physiologic load on the periodontium and prevents a recurrence of the diastema. The restorations in Fig. 6 have been stable and comfortable for 2 1/2 years with independent mobility of each tooth. Similar splinted prosthodontic devices inserted have also been successful.

Adult↗
PubMed1989

[Arrangement of the stomatognathic coupling system in the cranium].

Interindividually the stomatognathic coupling system is coordinated with the base of the skull with relative consistency. This observation allows the gearing parameters of the posterior guidance to be determined with the aid of conventional axiography. Thus, the curvature of the individual anterior guidance can be assessed for reconstructive purposes and the coordination of the anterior and posterior guidance can be generally estimated by means of functional analysis. Thus, the simple, commonly used diagnostic methods of functional analysis can be applied for the biomechanically harmonic coordination of the anterior and posterior guidances in reconstructive treatment and functional analysis.

Biomechanical Phenomena↗
PubMed1989

[Differences of clinical and axiographic function parameters in patients with skeletal Class II and Class III anomalies].

21 young individuals with skeletal and dental class II-relationships were compared to an analogous group of class III individuals as to their mandibular range of motion. The measurements of clinical movements in pro- and laterotrusion as well as the lengths of axiographic tracings showed a significantly reduced capacity of motion in the class III group. Because all examined individuals exhibited undisturbed TMJ-function or, at most, had mild symptoms (Helkimo-indexes 0 or 1), the reported findings cannot be interpreted as signs of pathology, but seem to demonstrate the broad range of normality.

Humans↗
PubMed1989

[Changes in axiographic patterns in orthodontic treatment. A comparison of findings in upper and lower early displacement pre- and two month post-operation].

It has been shown that electronic axiographic tracings of patients 2.5 months after a surgical advancement of the maxilla by Le-Fort-I osteotomie changed only slightly in comparison to preoperative tracings. The sagital opening path as well as the sagital protrusive path showed alterations in curvature. On the other hand sagital split osteotomie with consecutive advancement of the mandible influenced axiographic patterns profoundly. We found almost regularily shortenings of the tracings and often loss of curvature.

Humans↗
PubMed1988

Plaque accumulations caused by interdental stripping.

Human enamel surfaces were stripped with orthodontic grinding and finishing materials, and evaluated with the scanning electron microscope (SEM). Even under in vitro conditions with the finest finishing strips, it was not possible to produce an enamel surface free of the furrows that result from the initial abrasion caused by the coarse strip. Enamel surfaces stripped gradually from coarse to superfine were left in the mouths of patients for 12 weeks and evaluated with the SEM. The edges of the furrows were found to be smoother but the furrows remained wide and deep enough to facilitate more plaque accumulations than those on untreated surfaces. The use of dental floss did not result in prevention of plaque accumulations along the bottom of the furrows.

Dental Enamel↗