Robert Andreas W. Fuhrmann

Human histologic tissue response after long-term orthodontic tooth movement

UNLABELLED The maxilla of a deceased 19-year-old young woman who had been treated with an edgewise appliance was removed during autopsy. The specimen was prepared histologically in the horizontal plane. The type of tooth movement was reconstructed by comparing the treatment documents at outset (photograph of dental cast, radiograph) with the photograph and radiographs of the specimen. This permitted the histological findings to be correlated to the type of tooth movement. RESULTS the localization and extent of tissue changes at the roots depend on the type of tooth movement and the structure of the bone. In case of an atrophied alveolar bone in front of the tooth movement direction, a partial increase of osseous tissue may be induced by bone apposition in the subperiosteal layer. After tooth movement in the maxillary sinus region, however, bone resorption was found in the subperiosteal layer in front of the roots. The histologic findings are more pronounced than the radiographs would suggest. Histologically verified bony dehiscences or fenestrations in the facial or oral cortical plate could not be diagnosed by macroscopic inspection of the specimen.

Periodontal conditions after facial root tipping and palatal root torque of incisors

UNLABELLED The maxilla of a deceased 19-year-old young woman who had been treated with a fixed appliance was removed during autopsy. The sagittal movements of the incisors could be reconstructed by using the treatment records, which were also at our disposal. The anterior segment of the specimen was prepared histologically in the sagittal plane and stained with toluidine blue. RESULTS The tooth movements were executed in two phases: an uncontrolled tipping (root movement to vestibular) was followed by palatinal root torque. The histologic changes, induced by the palatinal root torque were (1) root resorption with apical slope from facioapical to orocoronal, and (2) pronounced subperiosteal bone apposition (palatinal) with partial protrusion of the cortical plate thinning toward coronal. No osseous perforations occurred. The extent and the localization of root resorptions were not verified in the orthoradial x-ray film of the specimen.

Treatment prediction with three-dimensional computer tomographic skull models

Orthodontic and surgical treatment planning in the conventional articulator is compared with three-dimensional computer tomographic (3D-CT) model surgery in an individually milled skull model. After computer tomography has been completed of the patients skull that has a bimaxillary asymmetric disharmony, the data set is transferred to generate individually milled polyurethane foam models. The imprecisely delineated dental arches of the skull model are replaced by dental casts that allow the simulation of various orthodontic and surgical treatment procedures. Expected segment displacement, the best osteotomy lines, and the resulting skeletal and dental symmetry in relation to the orthodontic set up can be evaluated. Although the technique is both time-consuming and expensive compared with the traditional treatment planning through the articulator, we have included 3D-CT model surgery in our presurgical work-up of patients with severe dentofacial disharmonies. Especially in asymmetric cases, the individually milled skulls allow a higher precision of orthodontic and surgical treatment planning.

Dreidimensionale computertomographische Darstellung des bezahnten Alveolarkamms

ZusammenfassungEin Ober- und Unterkieferhumanpräparat mit jeweils zehn Zähnen wurde mittels der hochauflösenden Computertomographie (CT) in aufeinanderfolgenden parallelen Schnitten axial und koronar mit 1 mm und 2 mm Schichtdicke und Tischvorschub dargestellt (Somatom plus, Siemens). Die Kiefersegmente wurden analog in 1-mm-Abständen planparallel aufgeschnitten. Von den korrespondierenden anatomischen Präparaten wurden Kontaktfilme belichtet und danach histologische Dünnschliffe angefertigt. Der Vergleich zwischen den CT-Bildern, den Kontaktfilmen und den histologischen Schnitten ergab bei den axialen CT-Bildern eine durchschnittliche absolute Abweichung von 0,3 bis 0,5 mm, bei den koronaren CT-Schnitten von 0,3 bis 1,6 mm. Eine quantitative Detailinterpretation zwischen Zähnen und Knochenkompakta war bis zu einer minimalen Knochenauflagerung von 0,5 mm möglich. Rechnergestützte Sekundärrekonstruktionen erlaubten eine zusätzliche qualitative Beurteilung der Knochenoberfläche und frei definierter Schnittebenen. Dicht aufeinanderfolgende axiale CT-Schichten ermöglichen eine überlagerungsfreie, maßstabgetreue Darstellung des bezahnten Alveolarkamms, des parodontalen Knochenniveaus und der radikulären Wurzeltopographie.SummaryHuman bone segments of the toothed jaw with ten upper and ten lower teeth were scanned by high resolution computer tomography in continuous parallel axial and coronal slices (Somaton plus, Siemens). In both directions scanning was performed to 1 mm and 2 mm thicknesses and at 1 mm and 2 mm intervals. The jaw segments were dissected analogously in 1 mm thick slices. Contact films of the corresponding bone segments were exposed and then histological thin sections prepared. The statistical comparison between the CT exposures, the contact films, and the histological sections revealed an average absolute deviation of 0.3 to 0.5 mm with the axial CT exposures and a deviation of 0.3 to 1.6 mm with the coronal sections. It was possible to interpret in a quantitatively detailed manner the teeth and surrounding bone compacta up to a 0.5 mm minimum bone thickness. Computer enhanced secondary reconstructions made possible an additional qualitative interpretation of the bone upper surface and the freely definable planes. Continuous parallel axial CT clices enable an interference-free, proportionally accurate representation of the apical base, the periodontal bone structure, and the radice-root topography.Human bone segments of the toothed jaw with ten upper and ten lower teeth were scanned by high resolution computer tomography in continuous parallel axial and coronal slices (Somaton plus, Siemens). In both directions scanning was performed to 1 mm and 2 mm thicknesses and at 1 mm and 2 mm intervals. The jaw segments were dissected analogously in 1 mm thick slices. Contact films of the corresponding bone segments were exposed and then histological thin sections prepared. The statistical comparison between the CT exposures, the contact films, and the histological sections revealed an average absolute deviation of 0.3 to 0.5 mm with the axial CT exposures and a deviation of 0.3 to 1.6 mm with the coronal sections. It was possible to interpret in a quantitatively detailed manner the teeth and surrounding bone compacta up to a 0.5 mm minimum bone thickness. Computer-enhanced secondary reconstructions made possible an additional qualitative interpretation of the bone upper surface and the freely definable planes. Continuous parallel axial CT slices enable an interference-free, proportionally accurate representation of the apical base, the periodontal bone structure, and the radice-root topography.

Distal movement of premolars to provide posterior abutments for missing molars

In 24 patients with missing molar teeth in the upper and/or in the lower jaw, 32 premolars were distalized. The mean orthodontic distalizing distance was 9.4 mm (SD 2.6). After distalization all these teeth served as posterior abutments for fixed restorations. The investigation period ranged between 2.5 to 14.1 years, average 9.6 years (SD 3.2). The clinical examination criteria were sensitivity, mobility, probing depth, sulcus bleeding index; the radiologic criteria were root resorption (lateral and apical) marginal bone level and axial position. None of the 32 premolar abutments were lost during investigation period. All the teeth maintained their vitality. The measured probing depths and sulcus bleeding indices were low. Of the teeth tested 40.6% revealed localized lateral root resorption on the pressure side; the average postorthodontic depth of root resorption was 0.7 mm (SD 0.3), and the length 2.3 mm (SD 0.6). The follow-up examination revealed a partial repair of the lateral root lesions. The extent of apical root resorption amounted to 0.9 mm (SD 1.1). The marginal bone level showed a bone loss of 0.5 mm mesially and 0.2 mm distally. The findings confirm that the distalized premolar functioning as a posterior bridge abutment represents a prognostically favorable alternative to an implant.

In vitro evaluation of a measurement method to analyze the interdental, mesially directed force

In order to evaluate interdental forces as a benchmark for mesial drift, a measurement technique was tested and evaluated on a human specimen. The measurement technique is based on the principle that a mesially directed horizontal force (FH) within a complete dental arch has an effect on interdental friction at the points of contact. The dynamic force (Fz), needed to pull out a defined metal strip from the interdental space is equal to the interdental frictional force (FR). Assuming unmodified approximal surfaces and unchanged tooth mobility in a complete dental arch, relative modifications of the interdental frictional force level provide a way of measuring horizontal force fluctuations. The validity of this measurement technique was measured by applying mesially directed forces of 1 to 5 N to the distal surface of the 2nd molar in a human specimen. The frictional forces measured increased in proportion to the distally applied force. The mesially directed force on the 2nd molar was transmitted in the dental arch anteriorly up to the incisor region and resulted in an increase of frictional forces. The reproducibility of this measurement technique was tested by quantitative analysis of potential measurement errors in the human specimen. The effect on interdental force measurement of the speed at which the metal strip is pulled was evaluated in a range of 50 to 500 mm/min. At the maximum pulling speed of 500 mm/min, a maximum scatter of 8% was recorded. Dependency of the dynamic force on direction of pull was measurable only when the metal strip was angled at more than 15o. Experimental tests on the human specimen confirmed that the measurement technique presented here is sufficiently valid and reproducible for clinical long-term studies of interdental forces.ZusammenfassungZur Verlaufskontrolle der interdentalen Kräfte als Maßstab für die Mesialdrift wurde zunächst eine Meßmethodik an einem Humanpräparat erprobt und überprüft. Die Meßmethodik basiert auf dem Prinzip, daß sich eine mesial gerichtete horizontale Kraft (FH) innerhalb einer geschlossenen Zahnreihe auf die interdentale Reibung an den Kontaktpunkten auswirkt. Die Zugkraft (FZ), um einen definierten Metallstreifen aus dem Interdentalraum herauszuziehen, entspricht dabei der interdentalen Reibungskraft (FR). Unter der Voraussetzung von unveränderten Approximalflächen und gleichbleibender Zahn-beweglichkeit in einer geschlossenen Zahnreihe sind relative Änderungen der interdentalen Reibung ein Maß für horizontale Kraftschwankungen. Zur Überprüfung der Validität dieser Meßmethodik wurden in einem Humanpräparat auf die Distalfläche des zweiten Molaren mesial gerichtete Kräfte von 1 bis 5 N appliziert. Die gemessenen Reibungskräfte stiegen proportional zu der distal applizierten Kraft an. Die mesial gerichtete Kraft auf den zweiten Molaren pflanzte sich in der geschlossenen Zahnreihe bis in die Eckzahnregion fort und führte zu einer Erhöhung der Reibungskräfte. Zur Überprüfung der Reproduzierbarkeit dieser Meßmethodik wurden potentielle Meßfehler im Humanpräparat quantitativ analysiert. Der Einfluß der Zuggeschwindigkeit des Metallstreifens auf die interdentale Kraftmessung wurden in einem Untersuchungsbereich von 50 bis 500 mm/min ließ sich eine Streuung von maximal 8% nachweisen. Eine Abhängigkeit der Zugkraft von der Zugrichtung ließ sich erst ab einer Angulation des Metallstreifens von mehr als 15o messen. Die experimentellen Überprüfungen am Humanpräparat bestätigten der vorgestellten Meßmethodik eine ausreichende Validität und Reproduzierbarkeit zur Bestimmung interdentaler Kräfte in einer klinischen Longitudinalstudie.

Digitale Nachbearbeitung von unter- und überbelichteten Röntgenfilmen mit einem Personal Computer

ZusammenfassungEin IBM-kompatibler Personal Computer wurde modular zu einem elektronischen Bildverarbeitungsplatz für die Digitalisierung und interaktive Nachbearbeitung von unter- und überbelichteten Röntgenbildern aufgebaut. Überbelichtete Röntgenbilder ließen sich durch die kontrollierte Veränderung des Kontrastes, der Helligkeit und die interaktive Anwendung verschiedener digitaler Filtertechniken qualitativ verbessern. Bei unterbelichteten Röntgenfilmen konnte ohne die Anwendung digitaler Filtertechniken ein ausgeglichener Grauwertverlauf durch Kontrast- und Helligkeitsregelung interaktiv eingestellt werden. Zur Gewährleistung der anatomischen Feinzeichnung im digitalen Bild wurde eine maximale Bildpunktgröße von 0,1 mm als Qualitätsnorm definiert. Da jeder Digitalisierprozeß mit einem Verlust an Ausflösung einhergeht, hat es sich bewährt, nur den interessierenden Bildausschnitt auszuwählen und interaktiv zu bearbeiten.SummaryAn image processing work station for digitalizing and interactively manipulating under- and overexposed X-rays was set up by adding modules to an IBM compatible personal computer. Overexposed X-rays can be qualitatively enhanced by means of controlled manipulation of contrast and brightness and by means of the use of various digital filtering techniques. With underexposed X-rays an equalized grey scale can be achieved by means of regulating contrast and brightness. Digital filtering is not required. To assure a high degree of anatomical detail (periodontal ligament) in the digitalized image and maximum pixel of 0.1 mm was defined as a qualitative norm. Since in every digitalization process resolution is diminished, it proved best to select for interactive manipulation out of the total image only the section of interest.An image processing work station for digitalizing and interactively manipulating under- and overexposed X-rays was set up by adding modules to an IBM compatible personal computer. Overexposed X-rays can be qualitatively enhanced by means of controlled manipulation of contrast and brightness and by means of the use of various digital filtering techniques. With underexposed X-rays an equalized grey scale can be achieved by means of regulating contrast and brightness. Digital filtering is not required. To assure a high degree of anatomical detail (periodontal ligament) in the digitalized image a maximum pixel of 0.1 mm was defined as a qualitative norm. Since in every digitalization process resolution is diminished, it proved best to select for interactive manipulation out of the total image only the section of interest.

Dreidimensionale Bilddiagnostik mit einem Personalcomputer

During orthodontic and surgical treatment planning of severe dentofacial deformities, 3D-reconstruction imaging from axial CT-scans could previously only be handled by high-capacity computers in radiological centers. The improved performance of personal computers enables CT-scan data be transferred to a standardized MS-DOS computer. The presented software displays a 3D-reconstruction and secondary reformed vertical slices within seconds on the monitor. The symmetry of the 3D-objects can be evaluated with a freely definable grid. The distance between two different landmarks in the 3D-image can also be measured. Various tools for data manipulation permit surgical treatment simulation. The advantage of 3D-imaging with a personal computer is the user-specified orientation of the software. The off-line computing system permits a high degree of flexibility independent of any computing center.ZusammenfassungIm Rahmen der interdisziplinären Behandlungsplanung schwerwiegender Dysgnathien war bisher die 3D-Bilddiagnostik aus planaren computertomographischen Schnittbildern wenigen radiologischen Zentren mit aufwendigen Rechenanlagen vorbehalten. Die Leistungssteigerung der Personalcomputer eröffnet die Möglichkeit, CT-Schnittbilddaten auf einem handelsüblichen Rechner des MS-DOS-Industriestandards weiterzuverarbeiten. Die vorgestellte Software erlaubt, 3D-Oberflächenrekonstruktionen und sekundär berechnete vertikale Schnittebenen in wenigen Sekunden auf dem Monitor darzustellen. Die Symmetrie der 3D-Objekte kann mit einem beliebig positionierbaren Meßgitter quantitativ beurteilt werden. Ebenso läßt sich der Abstand zwischen zwei beliebigen Punkten im Raum vermessen. Unterschiedliche Werkzeuge zur Bilddatenmanipulation erlauben eine chirurgische Therapiesimulation. Hauptvorteil der dreidimensionalen Bilddiagnostik im Offline-Betrieb auf einem Personalcomputer sind der anwenderorientierte Einsatzbereich und der hohe Grad an Flexibilität unabhängig von Rechenzentren.SummaryDuring orthodontic and surgical treatment planning of severe dentofacial deformities, 3D-reconstruction imaging from axial CT-scans could previously only be handled by high-capacity computers in radiological centers. The improved performance of personal computers enables CT-scan data be transferred to a standardized MS-DOS computer. The presented software displays a 3D-reconstruction and secondary reformed vertical slices within seconds on the monitor. The symmetry of the 3D-objects can be evaluated with a freely definable grid. The distance between two different landmarks in the 3D-image can also be measured. Various tools for data manipulation permit surgical treatment simulation. The advantage of 3D-imaging with a personal computer is the user-specified orientation of the software. The off-line computing system permits a high degree of flexibility independent of any computing center.

Perioperative Progress Check of Interdental Forces Following Extraction of the Third Molars A Prospective Long-Term Study

Abstract: With the aim of checking the progress of mesially directed forces in a complete dental arch, we measured the interdental frictional forces in a population of 44 patients with erupting maxillary and mandibular third molars. The measurements were taken preoperatively and postoperatively 1, 2, 3, 7, and 12 weeks and also 1 year after extraction of surgical removal of the third molars in all 4 quadrants. In addition, the interdental frictional forces of a total of 40 test persons in 3 control groups were similarly measured in a state of inertia, after a period of 1 hour spent in supine position, and after a 5-minute period of chewing activity.Over the first 4 to 12 weeks the interdental forces showed a significant postoperative average decrease of 16.1% in the maxilla and 18.0% in the mandible. After 1 year the average reduction in the level of interdental forces in the patient population was 10.3% in the maxilla and 10.9% in the mandible. A significant postoperative reduction in force of 40.7% was registered for third molars with a mesial angle of 66° to 90° to the tooth axis of the second molar in the mandible. Following a 1-year control period, the level of interdental force in the patient population was found to be on the average 27.4% below the preoperative baseline value.In control group I, the margin of fluctuation of interdental forces in a state of inertia was ± 3.5% over a 3-month period. In control group II, a significant average decrease in interdental forces was measured in the maxilla (15.1%) and mandible (13.2%) following a 1-hour period in supine position. In control group III a non-significant average reduction in interdental forces was established in the maxilla (7.8%) and mandible (8.6%) following a 5-minute period of chewing activity.Zusammenfassung: Zur perioperativen Verlaufskontrolle mesial gerichteter Kräfte in einer geschlossenen Zahnreihe wurden die interdentalen Reibungskräfte von 44 Patienten mit durchbrechenden dritten Molaren im Ober- und Unterkiefer zunächst päoperativ und anschließend postoperativ ein, zwei, drei, sieben, zwölf Wochen und ein Jahr nach der Extraktion bzw. der operativen Entfernung der dritten Molaren in allen vier Quadranten bestimmt. Zusätzlich wurden bei drei Kontrollgruppen mit insgesamt 40 Probanden die interdentalen Reibungskräfte in Ruhe, nach einstündiger Rückenlagerung und nach fünfminütiger Kautätigkeit analog bewertet.Die interdentalen Kräfte verringerten sich in den ersten vier bis zwölf Wochen postoperativ signifikant um durchschnittlich 16,1% im Ober- und um 18,0% im Unterkiefer. Nach einem Jahr verblieb eine Reduktion des interdentalen Kräfteniveaus von 10,3% im Ober- und 10,9% im Unterkiefer.Für diejenigen dritten Molaren mit einem mesialen Angulationsgrad von 66° bis 90° zur Zahnachse des zweiten Molaren im Unterkiefer konnte zwölf Wochen postoperativ eine signifikante Kraftreduktion von 40,7% nachgewiesen werden. In dieser Patientengruppe lag nach einer Kontrollzeit von einem Jahr das durchschnittliche interdentale Kraftniveau 27,4% unter dem präoperativen Ausgangsniveau.In der Kontrollgruppe I ließ sich eine Schwankungsbreite der interdentalen Kräfte in Ruhe von ± 3,5% über drei Monate nachweisen. Für die Kontrollgruppe II ergab sich nach einstündiger Rückenlage eine signifikante durchschnittliche Verringerung der interdentalen Kräfte von 15,1% im Oberkiefer und von 13,2% im Unterkiefer. In der Kontrollgruppe III war nach fünfminütiger Kautätigkeit eine nicht signifikante durchschnittliche Reduktion der interdentalen Kräfte von 7,8% im Oberkiefer und 8,6% im Unterkiefer nachzuweisen.

Radiologisch-histologische Interpretation artifizieller Knochendefekte der basalen Kieferhöhlenkortikalis

Twenty-one lateral maxilla specimens were taken from human autopsy specimens and after removing soft tissue 40 differing tooth roots of 23 molars and premolars were ground to create large artificial bone defects in the supporting cortical bone of the basal maxillary sinus. Conventional dental radiographs and axial CT scans were then compared with the macroscopic findings in relation to the identification of the artificial bone defects. Next the jaw segments were dissected analogous to the axial CT scan and corresponding histological microsections were prepared for a radiological-histological comparison. None of the artificial bone defects were identifiable on the dental radiographs. In comparison to this, however, cortical bone defects were identifiable on 25 tooth roots (62.5%) on the CT scans. The lateral demarcation of the antral defects on the CT scans depends on the setting of the tooth root, on the adjacent bone morphology, and on the visualization of the periodontal ligament space. If the periodontal space shows up on the CT images, it becomes possible to demarcate of a thin, 0.2 to 0.5 mm, cortical bone layer of the basal maxillary sinus.ZusammenfassungAn 21 post mortem entnommenen Humanpräparaten der lateralen Maxilla wurden nach der Entfernung der Weichgewebe an 40 verschiedenen Zahnwurzeln von 23 Molaren und Prämolaren unterschiedlich große artifizielle Knochendefekte in die auflagernde Kieferhöhlenkortikalis gefräst. Konventionelle Zahnfilme und axiale CT-Schnitte wurden hinsichtlich der Identifikation der Kortikalisdefekte mit den makroskopischen Kieferbefunden verglichen. Anschließend wurden die Kiefersegmente analog der axialen CT-Schichtung aufgetrennt und korrespondierende histologische Dünnschliffe für einen radiologisch-histologischen Vergleich hergestellt. In den Zahnfilmen war kein artifizieller Knochendefekt sicher zu erkennen. Dagegen ließen sich in den CT-Schnitten an 25 Zahnwurzeln (62,5%) Kortikalisdefekte identifizieren. Die laterale Abgrenzung der Defekte in den CT-Schnitten war von der Lage des antralen Kortikalisdefekts auf der Zahnwurzel, dem marginalen Übergangsbereich und der Erkennbarkeit des Parodontalspalts abhängig. Bei identifizierbarem Parodontalspalt ist die Abgrenzung einer antralen Kortikalisauflagerung von 0,2 bis 0,5 mm Dicke möglich.SummaryTwenty-one lateral maxilla specimens were taken from human autopsy specimens and after removing soft tissue 40 differing tooth roots of 23 molars and premolars were ground to create large artificial bone defects in the supporting cortical bone of the basal maxillary sinus. Conventional dental radiographs and axial CT scans were then compared with the macroscopic findings in relation to the identification of the artificial bone defects. Next the jaw segments were dissected analogous to the axial CT scan and corresponding histological microsections were prepared for a radiological-histological comparison. None of the artificial bone defects were identifiable on the dental radiographs. In comparison to this, however, cortical bone defects were identifiable on 25 tooth roots (62.5%) on the CT scans. The lateral demarcation of the antral defects on the CT scans depends on the setting of the tooth root, on the adjacent bone morphology, and on the visualization of the periodontal ligament space. If the periodontal space shows up on the CT images, it becomes possible to demarcate of a thin, 0.2 to 0.5 mm, cortical bone layer of the basal maxillary sinus.