Kritische Anmerkung zum Beitrag von H. Th. Schrems und G. Schrems-Adam: Die terminale Scharnierachsenposition und die instrumentelle Funktionsanalyse in der Kieferorthopädie in Heft 5, Band 45 (1984), 373–381

Ohne Zusammenfassung     

Zur Indikation und Morbidität der Kontinuitätsresektion des Unterkiefers beim Plattenepithelkarzinom der unteren Mundhöhlenetage

Background

Segmental resection of the mandibula in oral cancer surgery leads to both functional and aesthetic problems. The decision to preserve or resect the mandible depends on the vicinity of the lesion to the bone. Consequently, based on the rules of safety margins to all planes that are recommended for soft tissues, each lesion that is closer than 10 mm to the mandible needs resection of the bone.

Patients and methods

To establish data-based treatment modalities, a retrospective study was initiated and the results from all preoperative staging investigations of 152 patients with intraoral squamous cell carcinoma who underwent continuity or marginal resection of the mandible were evaluated. The histological outcome of the resected bone was compared to the staging results. Functional rehabilitation and long-term follow-up including survival rates were evaluated. The study reports on typical complications following segmental resection such as fracture of the reconstruction plate and demonstrates experiences with secondary microsurgical reconstructive surgery.

Results

Mainly in cases of stage T1 and T2 carcinomas which are closer than 10 mm to the bone and clinically do not show any infiltration to the mandible, a marginal resection seems to be adequate. The decision about the extension of mandibular resection can be based on intraoperative cross sectional investigation of the periosteum. The survival rate of patients with intraoral carcinomas close to the mandible who underwent marginal mandibulectomy seems to be the same as in cases of continuity resection. A more conservative management of mandibular resection seems to be adequate and a data-based concept to standardize therapy of mandibular resection is presented.     

Die kondyläre Metastasierung

Background

Metastases in the mandibular condyle are rare. A survey of the literature showed that only 23 of 69 selected cases qualified under the criteria of Meyer and Shklar.

Report of a case

A 48-year-old white male suffering from a previously operated lung carcinoma was referred due to pain and discomfort in the left TMJ. A solitary condylar metastasis of the mandible was revealed. Because of diffuse tumorous infiltration into periarticular tissue, irradiation treatment was performed. During the long-term follow-up growth of additional skeletal metastases occurred.

Discussion

The course of condylar metastases in general is similar to other metastases involving the jaw. Breast cancer as the primary tumor is most frequent, followed by lung cancer. There are no specific clinical or radiological parameters leading to diagnosis. The clinician should take a potential metastasis into account when dealing with TMJ complaints, radiological oddities, and medical history of malignant tumors. For proper treatment planning, diagnosis should be based on histology. Since the diagnosis of metastasis is usually made at an advanced stage of disease, therapy will be mainly intended as palliative.     

The influence of a 0.2% chlorhexidine mouthrinse on plaque regrowth in orthodontic patients

In a prospective plaque regrowth study focusing on oral hygiene during fixed appliance therapy 12 adolescent patients (mean age 14.1 +/- 1.5 years) were evaluated twice over 2-day test periods. In the randomized, double-blind study the influence of a 0.2% chlorhexidine (CHX) mouthrinse (Corsodyl) and a commercially available dentifrice supplementing fluoride (Odol-med-3) were compared intra- and interindividually in a crossover design with regard to plaque and gingivitis. Before starting the first test phase there was a 14-day preliminary phase for upgrading the oral hygiene. Between the 2 test phases was a 5-day "washout". On the last day of the second test phase the patients were asked to fill in a questionnaire concerning their experiences during the study. The 0.2% Corsodyl reduced the plaque index scores significantly (p < 0.001). The gingival index revealed a similar reduction (2nd day of test: p = 0.03). Until the 5th day of washout a clear-cut carryover effect of the chlorhexidine rinse on the gingival index was observed. Both the lower mean values of the 2 clinical parameters at the beginning of the test phases as compared with those at the beginning of the preliminary phase and the evaluation of the questionnaires indicated a possible Hawthorne effect. 0.2% Corsodyl may be employed as an adjunct to other preventive measures such as professional care and patient-oriented instruction on an intermittent basis in order to reduce the plaque-induced iatrogenic side effects and to enhance the efficacy of oral hygiene measures in connection with orthodontic therapy with fixed appliances.     

Torque Deformation Characteristics of Plastic Brackets: A Comparative Study

AIM: The purpose of this study was to compare the torque deformation characteristics of seven commercially available plastic brackets, both amongst each other and with stainless steel brackets. MATERIAL AND METHODS: Ten brackets each of (1) pure polycarbonate, (2) ceramic reinforced polycarbonate, (3) fiberglass reinforced polycarbonate, (4) ceramic reinforced polycarbonate with metal slot, (5) fiberglass reinforced polycarbonate with metal slot, (6) polyurethane, and (7) polyurethane with metal slot were exposed to torsion in a torquemeter, following an aging process according to ISO 10477. Ten stainless steel brackets served as a control group. Torsion was applied continuously using a material testing machine (Zwick Z2.5, Zwick Materialprüfung, Ulm, Germany). RESULTS: The results showed within the group of plastic brackets that metal slot reinforced brackets were subject to the lowest degree of deformation, followed by the brackets made of pure polyurethane, pure polycarbonate and fiberglass reinforced polycarbonate. The ceramic reinforced polycarbonate brackets showed the highest deformation under torque stress. The plastic deformation of the ceramic reinforced, fiberglass reinforced and pure polycarbonate brackets started even in the recommended torque range of 10-20 Nmm. The additional ceramic and fiberglass in the plastic brackets investigated in this study did not improve the torque stability of the polycarbonate brackets. The pure polyurethane brackets showed no significant difference from the pure polycarbonate brackets at the moment of 15 Nmm which is the optimal torque for a maxillary incisor. CONCLUSION: A comparison with the stainless steel brackets illustrated that plastic brackets are suited for clinical application only if they have a metal slot.     

Various Anchorage Approaches in Unilateral Mandibular Molar Distalization Using a Fixed Lingual Arch Appliance

PATIENTS AND METHOD: Mean unilateral mandibular molar distalization of 3.33 +/- 1.28 mm was achieved in 20 patients (average age: 13 years, 1 month) by fitting an asymmetrically activated lingual arch appliance for an average treatment period of 4 months. Three different anchorage techniques were used: Anchorage was provided in seven patients by the lingual arm of the appliance alone, while another seven patients received additional sectional archwires, and another six patients sectional archwires and lip bumpers. RESULTS AND DISCUSSION: Anchorage by means of the lingual arm alone proved to be insufficient to prevent labial tipping of the incisors. The mean protrusion and labial tipping recorded at the lower incisors was 7.67 degrees +/- 1.53 degrees and 2.64 +/- 0.48 mm respectively. The anchorage quality was enhanced and satisfactory stabilization achieved by additionally inserting a sectional archwire. In these cases the mean incisor protrusion and labial tipping was 1.75 degrees +/- 0.96 degree and 0.71 +/- 0.76 mm respectively and thus significantly lower (p < 0.01). The additional fitting of a lip bumper provided no further increase in anchorage quality (incisor protrusion 1.75 degrees +/- 2.87 degrees and 0.67 +/- 1.21 mm respectively). CONCLUSION: Fitting additional anchorage aids appears to have no direct impact on the extent and quality of molar distalization.     

Beanspruchungsuntersuchungen an Rekonstruktionsplatten zur Überbrückung von Kieferwinkeldefekten

Aim

The aim of the present study was to evaluate the mechanical stress in reconstruction plates used for bridging mandibular angle defects and in the screw-plate-bone interface with the finite element method. Additionally, the influence of reconstruction plate geometry, screw configuration, and screw diameter upon the mechanical stress distribution was determined. Suggestions for design improvements of the plate were derived from the results.

Material and methods

Based on the geometrical data of a human mandible, an angle defect bridged by a titanium reconstruction plate was generated and exposed to chewing force. The reconstruction plate was securely fixed by M 2.7 titanium screws. A variation of plate design, screw configuration, and screw diameter was carried out. The mechanical stress was calculated following the von Mises stress hypothesis.

Results

Using the standard plate the mechanical stress in all components exceeded by far the ultimate tensile strength. Possible clinical consequences could be a fatigue fracture of the plate, loosening of the screw, and irreversible damage of the bone leading to infection. Increasing the screw diameter by 50% would lead to a decrease of the mechanical stress by far more than 50%. An increase of the interface area between bone and plate and a triangular screw configuration diminishes the mechanical stress further, which may consequently allow a reduction of plate thickness with better adaptation to the actual jaw geometry.

Conclusion

As a preliminary result the reconstruction plate could be thinned out in areas subject to less mechanical load.     

Kiefergelenkbeschwerden bei juvenilen Patienten mit rheumatischen Erkrankungen

Fragestellung

Ziel der Untersuchung war es, die Häufigkeit von klinischen Kiefergelenkbeschwerden bei Kindern mit rheumatischen Erkrankungen zu erfassen und Zusammenhänge zwischen dem Stadium der rheumatischen Erkrankung und dem klinischen Bild einer Kiefergelenksymptomatik zu evaluieren.

Material und Methodik

Im Rahmen einer prospektiven Untersuchung wurden die Kiefergelenke von 48 Kindern mit einer rheumatischen Erkrankung klinisch untersucht. Folgende Parameter wurden evaluiert: Knacken, Reibegeräusche, Druckdolenzen, Dauer der rheumatischen Erkrankung sowie die Anzahl der betroffenen peripheren Gelenke. Das Stadium der rheumatischen Erkrankung wurde mit Hilfe der Steinbrocker-Klassifikation erfasst.

Ergebnisse

Insgesamt wiesen 26 Patienten (54,17%) eines oder mehrere der o. g. Kiefergelenksymptome auf. Der Chi-Quadrat-Test ergibt keine signifikanten Zusammenhänge zwischen dem Grad der Steinbrocker-Klassifikation und dem Auftreten pathologischer Befunde am Kiefergelenk. Eine erhöhte Anzahl der von der rheumatischen Erkrankung betroffenen Gelenke führt nicht zu einem signifikanten Anstieg von pathologischen Kiefergelenkbefunden. Es zeigt sich jedoch ein signifikanter Zusammenhang zwischen der Erkrankungsdauer und dem Auftreten pathologischer Kiefergelenkerscheinungen. Knack- und Reibegeräusche kommen mit zunehmender Erkrankungsdauer signifikant häufiger vor (p=0,011).

Schlussfolgerung

Kinder mit rheumatischen Erkrankungen neigen häufiger zu Kiefergelenkerkrankungen als Kinder ohne rheumatische Erkrankungen. Mit Fortdauer der rheumatischen Erkrankung steigt die Inzidenz pathologischer Kiefergelenksbefunde.