Experimental findings on customized mandibular implants in Göttingen minipigs - a pilot study.

Reconstructing continuity defects of the mandible is still challenging for surgeons. The currently applied conventional titanium bridging plates have considerable rates of complications. Now, a new technology enables an individual shape-identical creation of a mandibular implant in a form-board design by the method of LaserCUSING using pure titanium. This technology has been successfully performed in previous examinations to individually reconstruct mandibular continuity defects. This pilot study evaluated the surgical procedure in 10 female Göttingen mini pigs. First, a computed tomography scan from a mini pig cranium was performed. A three-dimensional model of the mandible was designed by data conversion. Based on the data, a customized mandibular implant resembling the natural shape was virtually created and manufactured. Then, a continuity defect of the left mandible was created in a standardized way. The implants were inserted into the defect and the wounds were allowed to heal for 21, 35, 56 and 180 days. During the healing period, no signs of inflammation or infection were observed. After the sacrifice of the minipigs the mandibles were resected. Histological microsections using Donath's sawing and grinding technique were manufactured and stained with Masson Goldner trichrome staining. The histomorphological results showed a pronounced ossification at the outer and inner surface of the implants. This animal study describes a promising approach to optimize customized implants for the application in humans.

[Computed tomography evaluation of human mandibles with regard to layer thickness and bone density of the cortical bone]. / Computertomografische Auswertung von humanen Unterkiefern hinsichtlich der Schichtstärke und Knochendichte der Kortikalis.

PURPOSE: Application of function-restoring individual implants for the bridging of defects in mandibles with continuity separation requires a stable fixation with special use of the cortical bone stumps. MATERIALS AND METHODS: Five section planes each of 100 computed tomographies of poly-traumatized patients' jaws were used for measuring the thickness of the cortical layer and the bone density of the mandible. The CT scans of 28 female and 72 male candidates aged between 12 and 86 years with different dentition of the mandible were available. RESULTS: The computed tomographic evaluations of human mandibles regarding the layer thickness of the cortical bone showed that the edge of the mandible in the area of the horizontal branch possesses the biggest layer thickness of the whole of the lower jaws. The highest medians of the cortical bone layer thickness were found in the area of the molars and premolars at the lower edge of the lower jaws in 6-o'clock position, in the area of the molars in the vestibular cranial 10-o'clock position and in the chin region lingual-caudal in the 4-o'clock position. The measurement of the bone density showed the highest values in the 8-o'clock position (vestibular-caudal) in the molar region in both males and females. CONCLUSION: The average values available of the bone density and the layer thickness of the cortical bone in the various regions of the lower jaw, taking into consideration age, gender and dentition, are an important aid in practice for determining a safe fixation point for implants in the area of the surface layer of the mandible by means of screws or similar fixation elements.

An experimental study of the biomechanical stability of ultrasound-activated pinned (SonicWeld Rx+Resorb-X) and screwed fixed (Resorb-X) resorbable materials for osteosynthesis in the treatment of simulated craniosynostosis in sheep.

We compared a conventional resorbable screw osteosynthesis with a resorbable, ultrasound-activated pin osteosynthesis, and studied mechanical load capacity and operative handling. This new form of osteosynthesis aims to reduce operation times, and to avoid torque loads and screw fractures to achieve stability. A sheep craniotomy model simulated an operation for dysmorphia on an infant skull. Two rectangular craniotomies of equal size were created in 13 lamb skulls, and each refixed by different means: the first by mesh and 20 screws, and the second by mesh with 20 pins inserted with ultrasound activation. All osteosynthesis material consisted of resorbable amorphous poly-(d,l)-lactide (PDLLA) (Resorb-X, KLS Martin, Tuttlingen, Germany). The insertion time was recorded. The animals were killed at different times, and areas of the healing skull including the plates and pins or screws were removed and divided into sections, which were then tested. In total 74 pin-fixed and 77 screw-fixed samples were obtained. Bending and tensile tests were used to simulate different forms of loading. The time required for the insertion of pins was significantly shorter than for screws. The mechanical tests showed differences in the stability of the bond between the osteosynthesis plate and bone that depended on the osteosynthesis system and the length of time it was in the animal. The pin osteosynthesis gave a stable mechanical load capacity, which was significantly different from that of screw osteosynthesis. Advantages of ultrasound-assisted, resorbable, pin osteosynthesis, include optimum operative handling, reduced insertion time, avoidance of fractures of the fixation elements and higher three-dimensional load capacity.

In vitro testing of the bond between soft materials used for maxillofacial prostheses and cast titanium.

STATEMENT OF PROBLEM: The choice of soft materials for maxillofacial prostheses is important for covering extraoral defects after tumor surgery or radiation therapy. The use of cast commercially pure titanium as reinforcement seems to be a suitable option. PURPOSE: Making use of the advantages of titanium frameworks for maxillofacial prostheses requires exploring ways of combining it with soft materials. This study investigated such combinations and evaluated discoloration of the soft material to determine whether it was attributable to the titanium reinforcement. MATERIAL AND METHODS: Five soft materials used for maxillofacial prostheses and their bond strengths to cast titanium were tested. Different ways of conditioning the titanium surface and different adhesives were used. Plain mechanical retention was also studied. The Gretag SPM 100 was used to determine the potential effects on coloring after 24 hours of radiation in the Suntest rapid exposure unit. RESULTS: Suitable material combinations for bonding soft materials to titanium were found for all soft materials studied. Bond strength varied depending on the chemical basis of the soft material. Results indicated that maximal bond strengths were obtained by the combinations Supersoft with Super-Bond, Supersoft with subsequent silicoating, and bonding with Dentacolor connector. Few color shifts attributable to the titanium reinforcement were evident in the 2-mm layers of the soft materials applied. CONCLUSION: The results of this study showed that it is possible to combine a titanium framework and soft silicone materials.

Testing of fine motor skills in dental students.

Manual skills form only a part of the capabilities required of future dentists, but they are a very important component, which should be tested. With regard to the dental specialties, the present study tested specialty-independent fine motor skills. No objective, practical solution has been found up to now. 88 dental students and, as a control group, 23 medical students were examined in the longitudinal study. In the course of the analysis, 4 fine motor tests were carried out at the beginning of the 2nd and 6th semesters. The tests comprised the tremometer test, the tremometer test with a mirror, the 2-hand sinusoid test and archery using the Game Gear by SEGA. The test devices facilitate primarily the testing of components of accuracy of movements, indirect working methods, and eye-hand coordination. In the comparison of performances on test day A, the medical students' performance was noticeably better. As testing progressed, results showed stagnation in the performance of the medical students and a significant improvement in the performance of the dental students. That means that the test system can be used for a test over the course of study, but not as an initial test.

Ion beam slope cutting in dentistry: a catalog of applications.

It is very difficult to prepare structures of heterogeneous materials, material interfaces, or sensitive biologic samples. The usual grinding, cutting, or fracturing methods are mostly material destructive because of resulting shear strengths. Ion beam slope cutting allows microcuts to be accurately placed into subsurface areas. The material reduction is based on the principles of ion sputtering, whereby atoms are removed in the area of ion incidence. The speed of removal depends on the sputtered material, amounting to several micrometers per hour. Approximately 40 biologic dental specimens of various origin were examined. Depending on the incidence angle of the ion beam, the typical structures of ion etching can be reduced or intensified. Both variants are used to obtain a precise judgment of morphologic details or an exact topography of failures.

Psychophysiological and epidemiological investigations on the dentist.

This paper selectively shows the results of a psychophysiological study in general dental work. The change in heart rate was a very meaningful indicator. The average stress during dental work can be classified from light to moderately severe. The form of the course of the 0.10 Hz frequency band, diverted from the spectral analysis of heart periods, was successfully used in dental work. The self-assessment scale of Nitsch was used to describe the strain experience. Analysis of the results revealed that dental work involves high psychic stress. Epidemiological values of occupational diseases completed the objective assessment of strain effects and consequences. Representative conclusions include (a) inclusion of dentists in occupational care; (b) ergonomic design of working areas and their use; and (c) coordinated advanced training in the field of dental work design.

[Occupational medical and orthopedic aspects of the dental workplace]. / Arbeitsmedizinische und orthopädische Aspekte der Arbeitshaltung des Zahnarztes.

On the basis of traditionally designed dental workplaces recognized occupational diseases of dentists are presented. Clinical examples indicate the focuses of orthopaedic diseases. By means of improved technical health equipments such working conditions can be designed representing an essential precondition for a load-reduced work. Objectifications of posture parameters are brought in to make optimized use of the equipment and materials base.

[Sediments on the inner surfaces of the tube of spray-mist suction devices]. / Untersuchungen von Ablagerungen an den Schlauchinnenflächen der Spraynebel-Absauggeräte.

Spray mist suction tubes made of polyvinylchloride were examined. Qualitative and quantitative germ determinations of the tube inner surfaces were carried out. To make reproducible examinations a standardized method of germ determination was introduces. Macroscopical model tests, assessments by scanning electron microscopy and chemical analyses dealt with the genesis of the deposits and bacterial coatings in the inner tube. A method has been found which minimizes coating formation by spraying of a contaminating cleaning agent.

[Voice and speech functions from the oral medicine viewpoint]. / Zur Stimm- und Sprachfunktion aus stomatologischer Sicht.

The general performance and correlations of voice and speech are explained. The speech function is characterized in its spheres of activity, its development and acquisition are described.

[The spread of the backspray under different working conditions]. / Untersuchungen zur Ausbreitung des Sprayrückpralls bei unterschiedlichen Arbeitsbedingungen.

The use of high- and highest-speed preparation instruments and the therefore required intensive spray cooling results not only in more efficient working possibilities but also in an increased infection hazard, especially for the dentist and his assistance caused by the spray rebound. Simulated preparations were carried out on different tooth surfaces at different positions of the patient with or without exhaust under clinical conditions to objectify the space spreading of the spray rebound. The arrangement of the equipment has been objectified by photogrammetry so that the measurement data could be clearly classified. The use of the spraying mist exhaust reduces the spray rebound between 50 and 65%.

[The relationships of restorative and prosthetic surgical measures with voice and speech functions]. / Beziehungen restaurativer und chirurgisch-prothetischer Massnahmen im Rahmen der Stimm- und Sprachfunktion.

Prostheses and tooth-related aspects are related to voice and speech function. Phonetic points of view are discussed within prosthetic therapy. It is drawn the attention to possible improvements in the speech sound formation especially in connection with surgical prosthetic cares.

[The potentials for testing voice and speech functions from the oral medicine viewpoint. A review paper]. / Prüfmöglichkeiten der Stimm- und Sprachfunktion aus stomatologischer Sicht. Ubersichtsarbeit.

Selected subjective and objective test methods for the assessment of the voice and speech function are presented. Special attention is drawn to sonography as an important objective method at present. Examples of electroacoustic examination methods complete the test possibilities.

[The long-term effects of noise on dentists]. / Untersuchungen zur Langzeitwirkung von Lärm bei Zahnärzten.

On the basis of analyses of the main noise emitting equipment was carried out an audiometric test of dentists. The high frequencies of various equipment are reflected in a reduced high-frequency hearing. Significant differences became evident with increasing years of service, as well as in comparison to age adequate control groups. The high-frequency audiogram used in addition to the normal threshold audiogram is suitable to prove such occupational changes. The measured hearing loss remained without social importance in all cases.

[Design aspects of selected function areas in outpatient departments of stomatology]. / Gestalterische Aspekte ausgewählter Funktionsbereiche der ambulanten Stomatologie.

From the point of a designer view recommendations to conscious design of the working environment in stomatological care departments were presented.

[Investigations of stomatologic lighting equipment]. / Untersuchungen von stomatologischen Arbeitsfeldleuchten.

12 types of stomatologic lighting equipment were investigated with regard to their specific luminous intensity. The examination of the thermal radiation of the lighting equipment included subjective evaluations. Conclusions were drawn in order to improve the lighting.