Fracture resistance of human incisors and premolars: morphological and patho-anatomical factors.

305 extracted human front teeth and premolars were investigated for their dynamic resistance to fracture. Morphological factors, such as the anatomical class of tooth and root lengths, and patho-anatomical factors, such as infractions, occlusal and cervical abrasions, composite and amalgam restorations and damage resulting from previous traumatic impacts, were taken into consideration. A comparison of stability after a defined impact stress showed that maxillary canines and premolars had the highest resistance to fracture; this differs significantly from the resistance of maxillary and mandibular incisors. The root length correlates directly with fracture energy and therefore to stability. Composite restorations with an adhesive joint were found to increase the resistance of a tooth to fracture, but amalgam restorations had a weakening effect. Cervical wedge-shaped defects of the tooth cause considerable destabilization, but occlusal abrasion and infractions have only a moderate weakening influence. Previous traumatic stress reduces the resistance to fracture of a tooth by up to 85%. The fracture patterns generated were very similar to clinically observed tooth fractures, indicating the results to be clinically relevant.

Long-term stability of treatment results after upper jaw segmented osteotomy according to Schuchardt for correction of anterior open bite.

Upper jaw osteotomy according to Schuchardt is a relatively rarely performed surgical procedure due to its narrow range of indications. Within the framework of a clinical follow-up examination using this method, we studied the long-term results in 26 patients, employing cephalometric analysis and analyzing the clinical findings. The results of this study show that the outcome of the operative correction of anterior open bite remained largely stable. Although partial relapse occurred in 3 cases (= 11.5%), there was a significant functional and esthetic improvement in comparison with the preoperative initial findings. When indicated, upper jaw osteotomy according to Schuchardt is thus a suitable surgical technique for correction of anterior open bite.

Experimental comparative study of various mouthguards.

The aim of this study was to evaluate the mechanical and physical properties of several standard size commercially available mouthguards. For the purpose of objective testing, a special study model, which the various gum shield devices could be fitted onto, was developed to record tooth deflection caused by impact forces induced by a pendulum ram impact testing machine. The data measured on teeth provided with various gum shield devices were correlated with those of unprotected teeth; this enabled the individual cushioning effects of the respective devices and their specific force conduction to be evaluated. Using mouthguards considerably diminishes the deflection of the teeth subjected to stress in comparison with the row of unprotected teeth. In addition, force is transmitted to the adjacent teeth all the way to the distal regions of the row of teeth. The individual cushioning effects are directly correlated to the thickness of the material; the force distribution is determined by the rigidity of the gum shield device. The devices examined showed considerable differences with regard to force distribution and dimensioning. The study showed that this was due to the thickness of the materials, the manufacturing process and the composition of the materials of the devices examined. In comparison to laboratory-produced devices of similar material thickness, the devices that were designed to be fitted by the user achieved significantly poorer results as regards both cushioning properties and dissipation of exerted forces.

Intraoperative and postoperative kinetics of serum tumor markers in patients with oral carcinoma.

PURPOSE: There are no reliable laboratory procedures to monitor intraoperative tumor antigen dispersal in patients with squamous cell carcinoma of the head and neck. This study evaluated the use of serologic parameters as perioperative indicators of systemic manifestations. PATIENTS AND METHODS: In 28 patients, serial measurements of different tumor markers (squamous cell carcinoma antigen, carcinoembryonic antigen, carbohydrate antigen 19.9, carcinoma antigen 125) were made preoperatively, intraoperatively, and postoperatively at short intervals to determine the influence of tumor ablation on the antigen concentration in the serum. A microparticle enzyme immunoassay was used for the serologic analysis. RESULTS: Squamous cell carcinoma antigen showed elevated serum levels preoperatively, which increased intraoperatively and decreased significantly postoperatively. The serologic examinations in the control group and the other tumor markers showed no correlation with the clinical situation. CONCLUSIONS: The results suggest that the titer of squamous cell carcinoma antigen in serum has a positive correlation with the tumor burden and the operative trauma in the case of surgery. These results support the value of intraoperative and postoperative serum antigen monitoring.

New clinical applications for the Jasper Jumper.

This article describes the use of the Jasper Jumper in the treatment of class III anomalies, both theoretically and with a case report. Contrary to its use in class II anomalies, the Jasper Jumper is fixed to the 6-year-molars in the lower jaw and in the canine area in the upper jaw. This results in a continuously working mechanism--independent of co-operation on the part of the patient.

Impairment of tooth eruption. Pathogenetic aspects.

The genetically determined impairment of tooth eruption in 4 generations is analysed on the basis of an examination of 1 family, and the variability of the characteristic "tooth infraposition" is described. Starting with a 72-year-old female patient with 1 unerupted incisor, infrapositions of primary and permanent teeth in the descendants were diagnosed. We assume hereditary susceptibility resulting from a multifactorial genetic system to be the cause.

Perioperative antibiotic prophylaxis with cefuroxime in oral-maxillofacial surgical procedures.

A study was carried out to investigate the suitability of cefuroxime for perioperative antibiotic prophylaxis in maxillofacial surgical procedures. Serum and tissue samples were taken, to determine the intraoperative cefuroxime concentration, from 40 patients who had been given 1.5 g cefuroxime (Zinacef) i.v. during maxillofacial surgery. The time between i.v. administration and taking the blood and tissue samples varied between 10 and 260 min. The serum tissue kinetics were determined using an HPLC method in the jaw area, particular emphasis being given to the concentrations measured in bone. It was demonstrated that concentrations of cefuroxime were reached which are above the MIC values for many of the pathogens in the maxillofacial area and therefore adequate protection during intraoperative bacterial contamination is guaranteed. Maximum serum levels averaging 80 mg/l were measured within 30 min of administration. An average of 15 mg/l could still be demonstrated after 4 h. The bone samples gave maximum levels of 8-9 mg/kg 90 min after administration. Average levels of 1-3 mg/kg were still measurable after 4 h. It is only possible to describe trends due to the wide variation in the values, particularly of the bone samples. No postoperative wound infection was seen under prophylaxis with cefuroxime. Cefuroxime is suitable for perioperative prophylaxis during maxillofacial surgery procedures because of its favourable kinetics and broad spectrum of action.

[Changing of organ distribution of radioactive yttrium in rats by varying amounts of carrier]. / Anderung der Organverteilung von radioaktivem Yttrium bei Ratten durch unterschiedlich hohe Trägermengen.

There is little change in the organ distribution of yttrium citrate complex after addition of 0.01 mg/kg BW as carrier. Adding increasing amounts of inactive yttrium up to 1 mg/kg BW caused a considerable reduction in bone uptake and an increasing accumulation in the liver and spleen by transformation to colloid. Uptake in the lung indicates formation of macro-particles. The transformation into colloid can be varied by changing the citrate concentration. The 90Y-citrate complex for therapy should be used either without or with very little carrier of inactive yttrium.