Effect of metal primer and thermocycling on shear bonding strength between the orthodontic bracket and gold alloy / 대한치과교정학회지

OBJECTIVE: The aim of this study was to evaluate the effect of metal primers and thermocycling on shear bond strength between the orthodontic bracket and gold alloy. METHODS: For this study, 80 specimens made of dental gold alloy were divided into 8 groups based on the combination of metal primers (none, Alloy primer, Metaltite, V-primer) and thermocycling (with and without thermocycling). Shear bond strength testing was performed with a universal testing machine. Bond failure sites were classified by a modified ARI (Adhesive Remnant Index) score. RESULTS: All metal primer treated groups showed a significantly higher shear bond strength than the only sandblasting treated group without thermocycling (p0.05). Bond failure sites of the metal primer treated group without thermocycling occurred at gold alloy/adhesive interface, whereas there were no differences on bonding failure sites in the groups with thermocycling. CONCLUSIONS: These findings suggest that using metal primer on gold alloy enhances the initial bracket bond strength. But, this effect was not shown with thermocycling.

Reactions with 6-substituted-2-thiouracil-5-carbonitrites, synthesis of tetrazolo [1,5-c] and ditetrazolo [1,5 -a: 1,5-c] pyrimidines

Heating a ternary mixture of 6-furyl or 6-thienyl-4- oxo- 1, 2, 3, 4 - tetrahydro-2- thioxopyrimidine-5-carbonitrile [I a, b], chloroacetic acid and a suitable aromatic or heterocyclic aldehyde, led to the formation of 2- arylmethylene-2, 3- dihydro-3, 5 - dioxo-7- substituted- 5H- thiazolo [3, 2 - a] pyrimidine-6-carbonitriles [II a- i]. Alkylation of Ia, gave the s-alkyl derivatives IVa, b. Compounds IV and the thienyl analogue V reacted with benzylamine to give the 2- benzylamino derivatives. Heating IVa and V with phosphorus oxychloride gave the corresponding 4- chloropyrimidine derivatives [VIIa, b]. The 4- phenylthio-, 4-phenylhydrazino-, 4-benzylamino and 4- anilino-2- ethylthio-6- thienylpyrimidine-5- carbonitriles [VIIIa- d] were prepared from VIIb. Whereas compound VIIa gave, on heating with hydrazine hydrate, the 4-hydrazino-2-ethylthio and the 2, 4-dihydrazino derivatives IXa and X, respectively, compound VIIb gave only the 4-hydrazine derivative IXb. The latter compound reacted with nitrous acid to give 5-ethylthio-7-thienyltetrazolo [1, 5-c] pyrimidine-8-carbonitril XI. Diazotization of X led to the formation of 5-furyl ditetrazolo [1, 5-a, 1, 5-c] pyrimidine-6-carbonitrile [XII]