Ralf J. Radlanski

Stability of the bonded lingual wire retainer-a study of the initial bond strength.

Abstract.Bonded lingual retainers (individually adjusted multistranded wires with one bond site per tooth) are used extensively to maintain the orthodontic treatment result. Failure or loss often leads to a relapse.The bond strength of bonded lingual retainers has not yet been studied in respect of the loads that can be withstood by them through deflection of the interdental archwire region. Furthermore, human anterior teeth have never before been used for a study of this kind.Six different wire/composite combinations were studied (wires: Dentaflex® co-axial 0.018”, Dentaflex® multistranded 0.018”, and Respond® Dead Soft straight, length 0.0175”; composites: Tetric® Flow and Heliosit® Orthodontic) by bonding 1 cm lengths of wire to the lingual surfaces of 360 extracted lower anterior teeth. Using an Instron 6025 universal testing machine, vertical shear bond strength tests at the bond site as well as vertical shear bond strength tests and horizontal tensile strength tests were performed. The failure characteristics after failure at maximum force were evaluated by light microscopy, scanning electron microscopy, and morphometry. Most failures were observed at the enamel/composite interface. The selected wires displayed no significant differences; Tetric® Flow proved to be the most stable resin; and no enamel tear-outs were observed.Zusammenfassung.Geklebte Lingualretainer (individuell angepasste verseilte Drähte mit je einem Klebepunkt pro Zahn) werden für die Rezidivprophylaxe extensiv verwendet. Bruch oder Verlust führt oft zum Rezidiv.Die Haftkraft von Drahtretainern wurde bisher noch nicht dahingehend untersucht, welchen Belastungen sie durch Auslenkung des interdentalen Drahtbereiches standhalten können. Außerdem wurden menschliche Frontzähne für Untersuchungen dieser Art noch nie verwendet.Sechs verschiedene Draht-Komposit-Kombinationen (Drähte: Dentaflex® co-axial 0.018“, Dentaflex® verseilt 0.018“, Respond® Dead Soft straight 0.0175“ und Komposite: Tetric® Flow und Heliosit® Orthodontic) wurden untersucht, wobei an die Lingualflächen von 360 extrahierten Unterkieferfrontzähnen je 1 cm Draht adhäsiv befestigt wurde. In der Universalprüfmaschine Instron 6025 wurden vertikale Abscherversuche an der Klebestelle sowie vertikale Abscher-Zug-Versuche und horizontale Abzugversuche vorgenommen. Die Bruchcharakteristik nach Abriss bei maximaler Kraft wurde lichtmikroskopisch, rasterelektronenmikroskopisch und morphometrisch bestimmt.Die Mehrzahl der Brüche kam an der Schmelz-Komposit-Verbindungsfläche vor. Die Auswahl der Drähte zeigte keine statistisch signifikanten Unterschiede; Tetric® Flow erwies sich als der stabilste Kleber; Schmelzausrisse wurden nicht beobachtet.

Effect of methotrexate upon antigen-induced arthritis of the rabbit temporomandibular joint

BACKGROUND Juvenile idiopathic arthritis (JIA) of the temporomandibular joint (TMJ) can cause severe growth disturbances of the craniomandibular system. Antigen-induced arthritis (AIA) of the rabbit TMJ is simulating the inflammatory process of the TMJ in JIA. The aim of this study was to investigate the effect of a systemic administration of methotrexate (MTX) on AIA in rabbits by means of three different histological staining methods. METHODS After sensitization, a bilateral arthritis of the TMJ was induced by an intra-articular administration of ovalbumin in 12 New Zealand white rabbits aged 10 weeks. From the 13th week of age, six of the 12 rabbits received weekly intramuscular injections of MTX, and the other six animals remained without therapy. Another six animals served as controls, receiving no treatment or intra-articular injections at all. After euthanasia at the age of 22 weeks, all TMJs were retrieved en bloc. Sagittal sections were cut and stained with haematoxylin-eosin (H-E), Safranin-O for the evaluation of the Mankin score and tartrate-resistant acid phosphatase (TRAP). RESULTS In the arthritis group, a chronic inflammation with degeneration of the articular cartilage was visible. In the MTX group, the signs of cartilage degeneration were significantly reduced compared with the arthritis group. In contrast, the joints in the control group were inconspicuous. A correlation between the Mankin score and TRAP-positive cells could be found. CONCLUSIONS Systemic administration of MTX seems to have a positive effect upon the inflammatory process in the rabbit TMJ but fails to eliminate the sign of arthritis completely.

Histomorphometry in antigen-induced arthritis of the rabbit temporomandibular joint

BACKGROUND Juvenile idiopathic arthritis (JIA) of the temporomandibular joint (TMJ) can cause severe growth disturbances of the craniomandibular system. Antigen-induced arthritis (AIA) of the rabbit TMJ is simulating the inflammatory process of the TMJ in JIA. The aim of this study was to investigate the effect of a systemic administration of the tumor necrosis factor-alpha (TNF-α) antagonist etanercept on AIA in rabbits by means of three different histological staining methods. METHODS After sensitization, a bilateral arthritis of the TMJ was induced and maintained by repeated intra-articular administrations of ovalbumin in 12 New Zealand white rabbits aged 10 weeks. From the 13th week of age, 6 of the 12 rabbits received weekly subcutaneous injections of etanercept, and the other 6 animals remained without therapy. Another 6 animals served as controls, receiving no treatment or intra-articular injections at all. After euthanasia at the age of 22 weeks, all TMJs were retrieved en bloc. Sagittal sections were cut and stained with hematoxylin-eosin (H-E), Safranin-O for the evaluation of the Mankin score, and tartrate-resistant acid phosphatase (TRAP). RESULTS In the arthritis group, a chronic inflammation with degeneration of the articular cartilage was visible. In the etanercept group, the signs of cartilage degeneration were significantly reduced but present. In contrast, the joints in the control group were inconspicuous. A strong correlation between the Mankin score and TRAP-positive cells could be found. CONCLUSIONS Antigen-induced arthritis causes severe damage in the TMJ of young rabbits. An improvement seems to be achievable by a systemic administration of etanercept.

Distribution of BMP6 in the alveolar bone during mouse mandibular molar eruption

Abstract Eruption requires synchrony of the tooth with the surrounding tissues, particularly the bone. One important step during eruption is remodelling of the alveolar bone at the base of the tooth and along the roots. Expression of BMP6 was reported to be increased in the basal half of the dental follicle prior to eruption and inhibition of BMP6 affected bone formation at the base of the alveolar crypt. The aim of this study was to further investigate BMP6 protein in relation to tooth eruption and the corresponding bone remodelling using temporospatial correlations of BMP6 localization with morphogenetic events (proliferation, differentiation, apoptosis and bone apposition/resorption), other BMPs (BMP2 and BMP7) and three-dimensional images of tooth–bone development. BMP6 expression pattern was mapped in the mandibular molar teeth and related structures around eruption. Localization of BMP6 dominated in osteoblasts, in regions of bone formation within the alveolar crypt. These findings positively correlated with proliferation at the tooth base region, osteocalcin expression in the osteoblasts/osteocytes and BMP2 and BMP7 presence in the alveolar bone surrounding the tooth. Osteoclast activity and apoptotic elimination in the root region gradually decreased before eruption and totally ceased at eruption stages. Generally, BMP6 positively correlated with BMP2, BMP7 and osteocalcin-positive osteoblasts, and areas of bone remodelling. Moreover, BMP6 was found in the periodontium and cementoblasts. BMP6 expression in the alveolar bone accompanied tooth eruption. Notably, the expression pattern of BMP6 in the bone did not differ around individual molar teeth at the same stage of development. The expression of BMP6 in periodontal ligaments may contribute to interaction between the tooth and bone during the eruption and anchoring process.

Structural, mechanical and chemical evaluation of molar-incisor hypomineralization-affected enamel: A systematic review

OBJECTIVES To systematically assess and contrast reported differences in microstructure, mineral density, mechanical and chemical properties between molar-incisor-hypomineralization-affected (MIH) enamel and unaffected enamel. METHODS Studies on extracted human teeth, clinically diagnosed with MIH, reporting on the microstructure, mechanical properties or the chemical composition and comparing them to unaffected enamel were reviewed. Electronic databases (PubMed, Embase and Google Scholar) were screened; hand searches and cross-referencing were also performed. RESULTS Twenty-two studies were included. Fifteen studies on a total of 201 teeth investigated the structural properties, including ten (141 teeth) on microstructure and seven (60 teeth) on mineral density; six (29 teeth) investigated the mechanical properties and eleven (87 teeth) investigated the chemical properties of MIH-affected enamel and compared them to unaffected enamel. Studies unambiguously found a reduction in mineral quantity and quality (reduced Ca and P content), reduction of hardness and modulus of elasticity (also in the clinically sound-appearing enamel bordering the MIH-lesion), an increase in porosity, carbon/carbonate concentrations and protein content compared to unaffected enamel. FINDINGS were ambiguous with regard to the extent of the lesion through the enamel to the enamel-dentin junction, the Ca/P ratio and the association between clinical appearance and defect severity. CONCLUSIONS There is an understanding of the changes related to MIH-affected enamel. The association of these changes with the clinical appearance and resulting implications for clinical management are unclear. CLINICAL SIGNIFICANCE MIH-affected enamel is greatly different from unaffected enamel. This has implications for management strategies. The possibility of correlating the clinical appearance of MIH-affected enamel with the severity of enamel changes and deducing clinical concepts (risk stratification etc.) is limited.