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Molar Regions (molar + regions)
Selected AbstractsClinical evaluation of Procera AllCeram crowns in Japanese patients: results after 5 yearsJOURNAL OF ORAL REHABILITATION, Issue 11 2009Y. KOKUBO Summary, Procera AllCeram crowns were prospectively evaluated clinically in both anterior and posterior regions in Japanese. One-hundred and one crowns were fabricated for 57 patients at the Tsurumi University Dental Hospital from August 2001 to October 2002 and evaluated according to the California Dental Association (CDA) quality evaluation system at baseline and annually at all follow-up examinations for 5 years. The plaque index (PI) and gingival index (GI) were recorded, and chipping and fracture were checked at the same time as well. A total of 75 Procera AllCeram crowns were evaluated, and the cumulative survival rate was 90·2% over the 5-year clinical trial. Six crowns experienced fractures within the veneering porcelain and from aluminium oxide coping, all of which occurred on the premolar and molar regions, and they had to be removed. Small chipping was observed on three crowns. According to the CDA criteria, 98% of Procera AllCeram crowns were rated as satisfactory, and PI and GI were comparable to those of control teeth during the observation period. [source] Quantitative study of bite force during sleep associated bruxismJOURNAL OF ORAL REHABILITATION, Issue 5 2001K. Nishigawa Nocturnal bite force during sleep associated bruxism was measured in 10 subjects. Hard acrylic dental appliances were fabricated for the upper and lower dentitions of each subject. Miniature strain-gauge transducers were mounted to the upper dental appliance at the right and left first molar regions. In addition, thin metal plates that contact the strain-gauge transducers were attached to the lower dental appliance. After a 1-week familiarization with the appliances, nocturnal bite force was measured for three nights at the home of each subject. From the 30 recordings, 499 bruxism events that met the definition criteria were selected. The above described system was also used to measure the maximum voluntary bite forces during the daytime. The mean amplitude of detected bruxism events was 22·5 kgf (s.d. 13·0 kgf) and the mean duration was 7·1 s (s.d. 5·3 s). The highest amplitude of nocturnal bite force in individual subjects was 42·3 kgf (15·6,81·2 kgf). Maximum voluntary bite force during the daytime was 79·0 kgf (51·8,99·7 kgf) and the mean ratio of nocturnal/daytime maximum bite force was 53·1% (17·3,111·6%). These data indicate that nocturnal bite force during bruxism can exceed the amplitude of maximum voluntary bite force during the daytime. [source] Periodontitis-induced lipid peroxidation in rat descending aorta is involved in the initiation of atherosclerosisJOURNAL OF PERIODONTAL RESEARCH, Issue 4 2009D. Ekuni Background and Objective:, Periodontitis is a risk factor for the development of atherosclerosis. Recent studies indicate that oxidative mechanisms, including lipid peroxidation, are involved not only in periodontitis but also in atherosclerosis. Lipid peroxidation may play an important role in the pathogenesis of atherosclerosis, particularly during its earliest stages. The purpose of this study was to investigate the relationship between lipid peroxidation induced by periodontitis and the initiation of atherosclerosis. Material and Methods:, Sixteen rats were randomly divided into two groups of eight rats each. Periodontitis was ligature-induced for 4 wk in the experimental group, whereas the control group was left untreated. After the experimental period, the mandibular first molar regions were resected and then subjected to histological analysis and measurement of hexanoyl-lysine expression as an indicator of lipid peroxidation. Descending aorta was used for measuring the levels of hexanoyl-lysine, reactive oxygen species and lipid deposits, and for real-time polymerase chain reaction microarray analysis. The level of hexanoyl-lysine was also measured in serum. Results:, In the experimental group, the levels of hexanoyl-lysine in periodontal tissue and serum increased. Only aorta samples in the experimental group showed lipid accumulation, with increased expression of hexanoyl-lysine, reactive oxygen species and oxidative stress-related genes (including nitric oxide synthases 2 and 3), whereas the superoxide dismutase 1 gene level was down-regulated. Conclusion:, In a ligature-induced periodontitis rat model, increased lipid peroxidation was found in serum and aorta as well as in periodontal tissue. Atherosclerosis-related gene expression and histological changes were also stimulated. Periodontitis-induced lipid peroxidation in the aorta may be involved in the early stage of atherosclerosis. [source] Location of main occluding areas and masticatory ability in patients with reduced occlusal supportAUSTRALIAN DENTAL JOURNAL, Issue 1 2010Y Nakatsuka Abstract Background:, The purpose of this study was to investigate the differences in location of the main occluding area with reduction of occlusal support and to evaluate the subsequent impairment in masticatory ability. Methods:, One hundred and two patients were recruited according to the Eichner's index, which is based on the number of occlusal support zones. Each subject was instructed to clench a piece of temporary stopping in the particular occluding area that was preferably used during mastication. The main occluding area was judged by locating the tooth on which the temporary stopping rested. Subjective masticatory ability was self-assessed by means of a questionnaire. Results:, Group classification depending upon the location of the main occluding area was significantly associated with the category of the Eichner's index. The level of masticatory ability was significantly associated with the category of the Eichner's index. Moreover, masticatory ability was significantly more impaired in subjects with main occluding areas at the premolar regions compared to those at the molar regions. Conclusions:, The location of the main occluding area may differ under the influence of the remaining natural teeth. The location of the main occluding area and the masticatory ability are likely to be closely related. [source] A Comparative Study of Computed Tomography and Magnetic Resonance Imaging for the Detection of Mandibular Canals and Cross-Sectional Areas in Diagnosis prior to Dental Implant TreatmentCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 2 2004Hideyuki Imamura DDS ABSTRACT Background: Computed tomography (CT) is effective in the diagnosis of dental implants. However, it has the disadvantage of exposing patients to high doses of x-rays, and the mandibular canals cannot be detected by CT in some clinical cases. Purpose: The purpose of this study was to examine the detectability of the anatomic morphology of the molar region in the lower jaw (where implantation is common) by CT and magnetic resonance imaging (MRI), to compare the data, and to determine the usefulness of MRI in diagnosis prior to dental implant treatments. Materials and Methods: Eleven female subjects (average age, 59 years) who had partially edentulous mandibles (total of 19 sites) were included in the study. CT and MRI were performed with the same subjects, and the degrees of identification of the mandibular canal in the first and second molar regions were compared. Dimensional accuracy in the second molar region was also compared. Results: With CT, the canals of the first molar regions were not identified in 11 of 19 sites; however, MRI identified the canals in all 19 sites. Using the kappa index, we found that the inter- and intraobserver identification reliabilities (0.84 and 0.87, respectively) were excellent, especially for MRI. Dimensional positioning of the canal in the second molar region was almost the same with MRI as with CT. Conclusions: MRI is an alternative method in diagnosis prior to dental implant treatment in the mandibular molar region. [source] Effects of splinted prosthesis supported a wide implant or two implants: a three-dimensional finite element analysisCLINICAL ORAL IMPLANTS RESEARCH, Issue 4 2005Heng-Li Huang Abstract Objectives: Three-dimensional finite element (FE) models of splinted prosthetic crowns were studied and stress analyses were evaluated with different types of implant support, including standard, wide or two implant(s) for partial, posterior edentulous restorations. Material and methods: The FE models were constructed based on a cadaver mandible containing the 2nd premolar and the 1st molar. The crowns of these two teeth were modeled as connected and disconnected to mimic the splinted and non-splinted designs, respectively. One standard implant was placed at the premolar region, while three types of implant support, one at a time (the standard implant, wide implant and two implants), were used to support the molar crown. A 100 N oblique load was applied to the buccal cusp on each crown. The FE simulation was validated experimentally via strain gauge measurement. Results: The experimental data were well correlated with the FE predictions (r2=0.97). When compared with the standard implant used in the molar area, the wide implant and two implants reduced the peak stress in crestal bone by 29,37% for both splinted and non-splinted cases. Inserting the standard implant into both the premolar and molar area, the bone stresses were identical for splinted and non-splinted designs. However, splinting the adjacent crowns has shown to decrease the bone stresses at the premolar region by 25%, while the wide implant or two implants were placed at the molar region. Conclusion: The biomechanical advantages of using the wide implant or two implants are almost identical. The benefit of load sharing by the splinted crowns is notable only when the implants on the premolar and molar regions have different supporting ability. Résumé Des modèles d'éléments finis (FE) tridimensionnels de couronnes prothétiques attachés ont étéétudiés et les analyses de stress ont étéévalués avec différents types de support d'implants comprenant le standard, le large ou deux implants pour des restaurations postérieures partielles. Les modèles FE ont été construits sur base de mandibule de cadavre contenant deux prémolaires et une molaire. Les couronnes de ces deux dents ont été modelées comme connectées et non-connectées pour mimer respectivement les modèles avec attache ou sans. Un implant standard a été placé dans la région prémolaire tandis que trois types d'implants supportaient en un temps (l'implant standard, l'implant large et deux implants) ont été utilisés pour porter la couronne molaire. Une charge oblique de 100 N a été appliquée sur la cuspide vestibulaire de chaque couronne. La simulation FE a été validée expérimentalement via une mesure par jauge de force. Les données expérimentales étaient en bonne corrélation avec les prévisions FE (r2=0,97). Comparés à l'implant standard utilisé dans la zone molaire, l'implant large et la combinaison de deux implants réduisait le pic de stress dans l'os crestal de 29 à 37% tant dans les cas attachés que non-attachés. En insérant l'implant standard dans la zone prémolaire et molaire, le stress osseux était identique pour les modèles attachés et non-attachés. Cependant, l'attache reliant les couronnes adjacentes s'accompagnait d'une dimininution des stress osseux dans la région prémolaire de 25%, tandis que l'implant large ou les deux implants étaient placés dans la région molaire. Les avantages biomécaniques de l'utilisation d'un implant large ou de deux implants sont quasi identiques. Le bénéfice d'une charge partagée par les couronnes solidarisées n'est visible que lorsque les implants des régions prémolaires et molaires ont des capacités de support différentes. Zusammenfassung Ziel: Bei der Rekonstruktion von Lücken im hinteren Seitenzahnbereich untersuchte man in einem dreidimensionalen Finiteelement-Modell (FE) zementierte Kronen und wertete in Belastungs-Analysen verschiedene Implantatabstützungen aus, nämlich auf Standardimplantaten, Wide neck-Implantaten oder auf zwei Implantaten. Material und Methoden: Das FE-Modell basierte auf den Werten eines Leichenunterkiefers in der Region des zweiten Prämolaren und ersten Molaren. Die Kronen auf diesen beiden Zähne wurden jeweils zusammenhängend und einzeln modelliert, so dass man die verblockte und unverblockte Situation nachempfinden konnte. In der Prämolarenregion implantierte man ein Standartimplantat. In der Molarenregion wählte man jeweils eine von drei verschiedenen Varianten der Abstützung für die Kronen: ein Standardimplantat, ein Wide neck-Implantat oder zwei Implantate. Auf den buccalen Höcker jeder Krone liess man schräg eine Kraft von 100 N auftreffen. Die FE-Simulation eichte man experimentell mit Hilfe von Dehnmessstreifen. Resultate: Die experimentellen Daten korrelierten sehr gut mit den FE-Voraussagen (r2=0.97). Verglich man die in der Molarenregion verwendeten Standartimplantate mit den Wide neck-Implantaten und zwei Implantaten, so reduzierte sich die Spitzenbelastung im crestalen Knochen um 29,37%, bei den verblockten wie auch bei den unverblockten Versionen. Setzte man sowohl im Prämolaren wie auch im Molarengebiet Standardimplantate, so war die Knochenbelastung für die verblockte wie auch für die unverblockte Version gleich gross. Wenn aber das Wide neck-Implantat oder zwei Implantate in der Molarenregion gesetzt worden waren, so vermochte die Verblockung der Implantat-Kronen die Knochenbelastung in der Prämolarenregion um 25% zu senken. Zusammenfassung: Ob man das Wide neck-Implantat oder zwei Implantate verwendet, die biomechanischen Vorteile sind beinahe identisch. Man erreicht durch das Verblocken von Kronen erst dann einen spürbaren Vorteil bezüglich Lastenverteilung, wenn die Implantate in der Prämolaren- und Molarenregion verschiedene Tragfähigkeiten aufweisen. Resumen Objetivos: Se estudiaron modelos tridimensionales de elementos finitos (FE) de coronas protésicas y se evaluó el análisis de estrés con diferentes tipos de soporte implantario, incluyendo implantes estándar, anchos o dos implantes, para restauraciones parciales en posteriores edéntulos. Material y métodos: Se construyeron dos modelos FE basados en mandíbula de cadáver conteniendo el 2° premolar y el 1er molar. Las coronas de estos dos dientes se modelaron como conectadas y desconectadas para imitar los diseños conectados y desconectados, respectivamente. Se colocó un implante estándar en la región premolar, mientras que para soportar la corona molar se colocaron tres tipos de implantes, uno a la vez, (un implante estándar, un implante ancho y dos implantes). Se aplicó una carga oblicua de 100N en la cúspide bucal de cada corona. La simulación de elementos finitos se validó experimentalmente por medio de medición de tensión. Resultados: Los datos experimentales se correlacionaron bien con las predicciones FE (r2=0.97). Al comparase a los implantes estándar usados en el área molar, el implante ancho y dos implantes redujeron el pico de estrés en el hueso crestal en un 29,37% tanto para los caso ferulizados como para los no ferulizados. Al insertar el implante estándar tanto en la región premolar como en la molar, los estrés óseos fueron idénticos para los diseños ferulizados como para los no ferulizados. De todos modos, la ferulización de las coronas adyacentes mostró un descenso del estrés óseo en un 25%, mientras el implante ancho o los dos implantes se colocaron en la región molar. Conclusión: Las ventajas biomecánicas de usar el implante ancho o dos implantes fueron casi idénticas. El beneficio de compartir la carga al ferulizar las coronas es notable solo cuando los implantes en las regiones premolar y molar tienen diferente capacidad de soporte. [source] Radiologic measurements of the mandible: a comparison between CT-reformatted and conventional tomographic imagesCLINICAL ORAL IMPLANTS RESEARCH, Issue 2 2004Hanazawa Tomomi Abstract: This study was carried out to compare the accuracy of determination of the mandibular contour and the position of the mandibular canal in cadaver mandibles by the multiplanar reconstruction method (MPR-CT), which has recently come to be used widely for preoperative examinations, with those by tomographic techniques and to evaluate the usefulness of MPR-CT. Using three imaging systems, i.e. Quantum CT scanner, Scanora, and OP-100, a total of 6 sites were scanned in the molar regions of 3 cadaver mandibles. The images obtained were measured twice each by 4 radiologists. The anatomic structures measured were the height and thickness of the mandible, distance from the alveolar crest to the mandibular canal, and distance from the buccal cortical bone to the mandibular canal. After scanning, the scanned areas of the mandibles were sliced at a thickness of 2 mm, and soft X-ray images of these slices were obtained. The values of the above 4 anatomic structures obtained by measurements in the soft X-ray radiograms using digital-display calipers were regarded as true values. When compared with the true values, the errors in the distance from the alveolar crest to the mandibular canal were within 1 mm (±1 mm) in 93.7% of the measurements by Direct-CT, 89.6% of the measurements by MPR-CT, 87.5% of the measurements by Scanora, and 47.9% of the measurements by OP-100, and the accuracy of the 4 methods ranked in the order of Direct-CT, MPR-CT, Scanora, and OP-100. A similar tendency was observed in the measurements of other anatomic structures, and statistically significant differences were observed among the methods. Thus, MPR-CT allows more accurate measurements than by the other 2 tomographic techniques,and to be useful as a preoperative examination for implant surgery. Résumé Cette étude a été menée afin de comparer la précision de la détermination du contour de la mandibule et de la position du canal mandibulaire dans des mandiblules de cadavres par la méthode de reconstruction par multi-plans (MPR-CT), qui a récemment été très utilisée pour les examens préopératoires, avec celle des techniques de tomographie et d'évaluer l'utilité de MPR-CT en utilisant trois systèmes d'image; c.-à-d. le scanner CT Quantum, le Scanora et l'OP-100, Six sites ont été balayés dans la région molaire de trois mandibules de cadavres. Les images obtenues ont été mesurées deux fois par quatre radiologues. Les structures anatomiques mesurées étaient la hauteur et l'épaisseur de la mandibule, la distance du rebord alvéolaire jusqu'au canal mandibulaire et la distance de l'os cortical vestibulaire au canal mandibulaire. Après balayage, les zones balayées des mandibules ont été coupées en tranches d'une épaisseur de 2 mm et des images radiographiques de ces tranches ont été obtenues. Les valeurs des quatre structures anatomiques mentionnées précédemment obtenues par les mesures des radiogrammes utilisant les compas digitaux étaient considérées comme valeurs correctes. Lorsqu'elles étaient comparées aux valeurs correctes, les erreurs dans la distance du rebord alvéolaire jusqu'au canal mandibulaire étaient inférieures à 1±1 mm dans 94 % des mesures par CT-Direct, 90% dans les mesures par MPR-CT, 88% des mesures par Scanora et 48% des mesures par OP-100, et la précision des quatre méthodes était dans l'ordre CT-Direct, MPR-CT, Scanora et OP-100. Une tendance semblable a été observée dans les mesures d'autres structures anatomiques et des différences statistiquement significatives ont été observées parmi les méthodes. Le CT-PMR apporte donc plus de mesures précises que les deux autres techniques de tomographie et devrait être utilisé pourl'examen préopératoire lors de la chirurgie implantaire. Zusammenfassung Radiologische Messungen im Unterkiefer: Ein Vergleich zwischen reformatierten CTs und konventionellen tomographischen Bildern Diese Studie wurde durchgeführt, um die Genauigkeit bei der Bestimmung der Kontur des Unterkiefers und bei der Lokalisation des Mandibularkanals in Kadaverunterkiefern durch die multiplanare Rekonstruktionsmethode (MPR-CT) mit konventionellen tomographischen Techniken zu vergleichen. Die MPR-CT wird seit kurzem oft für präoperative Untersuchungen angewendet. Zudem sollte die Anwendbarkeit der MPR-CT untersucht werden. Bei 3 Kadaverunterkiefern wurden je 6 Stellen in der Molarenregion mit 3 verschiedenen Systemen, Quantum CT Scanner, Scanora und OP-100, untersucht. Die erhaltenen Bilder wurden zweimal durch 4 Radiologen ausgewertet. Die folgenden anatomischen Strukturen wurden ausgemessen: Höhe und Dicke des Unterkiefers, Distanz vom Alveolarkamm zum Mandibularkanal und Distanz vom bukkalen kortikalen Knochen zum Mandibularkanal. Nach den Aufnahmen wurden die untersuchten Stellen auf eine Dicke von 2 mm geschnitten und es wurden Röntgenaufnahmen mit weichen Strahlen von den Schnitten angefertigt. Die Werte der obenerwähnten 4 anatomischen Strukturen, welche durch Messungen in den Röntgen mit weicher Strahlung mittels Zirkel mit Digitalanzeige ermittelt worden waren, wurden als wahre Werte angenommen. Im Vergleich zu den wahren Werten lag der Fehler bei der Distanz vom Alveolarkamm zum Mandibularkanal bei 93.7% der Messungen mit direktem CT, bei 89.6% der Messungen mit MPR-CT, bei 87.5% der Messungen mit Scanora und bei 47.9% der Messungen mit dem OP-100 innerhalb von 1mm (±1mm). Die Genauigkeit der 4 Methoden nahm in folgender Reihenfolge ab: direkte CT, MPR-CT, Scanora und OP-100. Eine ähnliche Tendenz konnte bei den Messungen der anderen anatomischen Strukturen beobachtet werden und zwischen den Methoden bestanden statistisch signifikante Unterschiede. Die MPR-CT ergaben genauere Messungen als die zwei anderen tomographischen Techniken. Die Methode ist daher hilfreich bei der präoperativen Untersuchung vor Implantatchirurgie. Resumen Este estudio se llevó a cabo para comparar la exactitud de la determinación del contorno mandibular y la posición del canal mandibular en mandíbulas de cadáver por medio del método de reconstrucción multiplanar (MPR-CT), que recientemente se ha convertido de uso extendido para exámenes preoperatorios, con aquellas técnicas tomográficas y para evaluar la utilidad de MPR-CT. Se escanearon un total de 6 lugares en la región molar de 3 mandíbulas de cadáver usando tres sistemas de imágenes, i.e. escáner Quantum CT, Scanora y OP-100. Las imágenes obtenidas se midieron dos veces cada una por 4 radiólogos. Las estructuras anatómicas medidas fueron altura y grosor de la mandíbula, distancia de la cresta alveolar al canal mandibular, y distancia desde el hueso cortical vestibular al canal mandibular. Tras realizar el escáner, las áreas escaneadas de las mandíbulas se cortaron en lonchas de 2 mm de grosor, y se obtuvieron imágenes radiológicas blandas de estos cortes. Los valores de las ya mencionadas 4 estructuras anatómicas obtenidas por mediciones en los radiogramas radiográficos usando calibres de visualización digital se consideraron como valores reales, los errores en la distancia desde la cresta alveolar al canal mandibular estaban dentro de 1 mm (±1 mm) en 93.7% de las mediciones por CT-directa, 89.6% de las mediciones por MPR_CT, 87.5% de las mediciones por Scanora, y el 47.9% de las mediciones por OP-100, y la exactitud de los 4 métodos se clasificaron en orden de CT-directa, MPR-CT, MPR-CT, Scanora, y OP-100. Se observó una tendencia similar en las mediciones de otras estructuras anatómicas, y se observaron diferencias estadísticamente significativas entre los métodos. De este modo, MPR-CT permite unas mediciones mas exactas que las de las otras 2 técnicas tomográficas, y ser útil como examen preoperatorio para cirugía de implantes. [source] | ||||||||||