László Seres

Donor site angiography before mandibular reconstruction with fibula free flap

The use of fibular free flaps has become established as a reliable and popular method for reconstruction of segmental mandibular defects. The role of routine preoperative angiography remains controversial. Sixty four digital subtraction angiograms were studied in a series of 39 consecutive patients clinically judged to be satisfactory candidates for fibula free transfer. Angiographic findings revealed vascular anomalies in 10 extremities (15.6%). Regarding the high potential for significant donor site morbidity authors consider vascular imaging essential part of preoperative evaluation.

Closure of severe skeletal anterior open bite with zygomatic anchorage.

An open bite is commonly one of the main symptoms of an overall dentofacial deformity. Most anterior open-bite cases are characterized by excessive vertical development of the posterior maxilla. Intrusion of the overerupted molar teeth by traditional orthodontic methods is hardly possible; there is therefore no real alternative to a combined orthodontic and surgical approach. Skeletal anchorage has recently been proposed for the orthodontic movement of teeth. Titanium miniplates implanted in the zygomatic buttress area can serve as the absolute anchorage for maxillary molar intrusion. The aim of this study was to evaluate the use of skeletal anchorage for the closing of open-bite malocclusions. Seven patients with severe anterior open bites were selected, in all of whom the deformity was due to overeruption of the maxillary molars. Titanium miniplates were inserted bilaterally in the zygomatic buttress region and fixed with miniscrews. Elastic bands or coil springs were used to reduce excessive maxillary molar heights. In all cases, the anterior open bite improved significantly. The mean duration of active treatment was 6 months. No significant side effects were observed. Our results show that skeletal anterior open bites due to posterior maxillary dentoalveolar hyperplasia can be closed with intrusion of the upper molar teeth. This method is a safe, quick, and less expensive alternative to orthognathic surgery.

Correlation of retention indices with van der Waals' volumes and surface areas: Alkanes and azo compounds

SummaryVan der Waals’ volumes (VW) and surface areas (SW) of alkanes, (E)-azoalkanes and structurally similar alkenes (R1-X=X-R2, X=N, CH) were calculated by a semiempirical quantum-chemical method (AM1). The calculated data are in reasonable agreement with the experimental values of Bondi and good correlations were found between the calculated data and Kovats’ retention indices (IR). While theVWs of alkanes with the same carbon number are very close to one another, theSWs follow the scatter of theIR values for branched alkanes. The difference in theIR of (E)-azo compounds and the structurally similar alkenes can be explained by the difference inVWs.

Color Doppler ultrasound for monitoring free flaps in the head and neck region.

The use of microvascular free flaps has become established as a very reliable reconstructive technique following tumor surgery or trauma in the head and neck region. Occasionally, flap compromise may occur which will require immediate re-exploration. Early diagnosis of vascular insufficiency is essential. Clinical signs are not always reliable. Numerous systems have been described for monitoring the viability of microsurgical free flaps. The authors consider that color Doppler ultrasound is one of the most useful diagnostic tools. Three cases are reviewed in which this technique aided the decision whether re-exploration was necessary.

Correction of a severe facial asymmetry with computerized planning and with the use of a rapid prototyped surgical template: a case report/technique article.

Management of significant facial asymmetry presents a challenge due to the geometric complexity of the bony and other facial structures. Manual model surgery is an essential part of treatment planning but it can be complicated, time-consuming and may contain potential errors. Computer-aided surgery has revolutionized the correction of maxillofacial deformities. The aim of this study was to report a case of facial asymmetry when computerised simulation surgery was performed instead of manual model surgery and a virtually planned wafer splint was fabricated. A 26-year-old male was presented with a severe right-sided hemimandibular elongation. Following presurgical orthodontics high-resolution computer tomography scan was performed. The stack images were reformatted into a three-dimensional structure. Virtual Le Fort-I osteotomy was performed and the symmetry of the maxilla was corrected with the help of a three-dimensional planning software. A virtual intermediate surgical wafer was designed and produced with three-dimensional rapid prototyping technology. The mandible was rotated into the correct position following virtual bilateral sagittal split osteotomy to visualize the movements of the osteotomised mandibular segments. The two-jaw procedure was performed according to the virtual plan. The facial symmetry was improved significantly and stable occlusion was achieved. This complex case shows the advantages of computer-aided surgical planning and three-dimensional rapid prototyping for the correction of facial asymmetries.

Combination and disproportionation reactions of the CH3CH -. N -. NC2H5 radical

The radical CH3CH [graphic omitted] N [graphic omitted] NC2H5(1) was produced in the di-tert-butyl peroxide-initiated and thermal decompositions of azoethane. Self-combination of 1 takes place almost exclusively at the carbon radical centre (1C). The disproportionation: combination ratio Δ(Ċ2H5, 1N)≈ 0.38 (Δ=kd/kc) and the rate constant ratio kb(ĊH3, 1N)/kc(ĊH3, 1C)= 0.15 ± 0.03. The cross-combination ratio ϕ(ĊH3, 1C)= 1.38 ± 0.11, which is lower than the cross-reaction ratio ϕ*(ĊH3, 1)≈ 2.5.

Thermal reaction of azoisopropane in the presence of (E)-CH3CH = CHCH3: Reactions of the radical 2-Ċ3H7

The azoisopropane-initiated thermal reaction of (E)-CH3CHCHCH3 has been studied in the temperature range 489.5–542.0 K.For the reactions (CH3)2CHNNCH(CH3)2→ 2 2-Ċ3H7+ N2(1), 2-Ċ3H7+(E)-CH3CHCHCH3→ C3H8+(E)-Ċ4H7(4), →(CH3)2CHCH(CH3)ĊH(CH3)(5), 2 2-Ċ3H7→(CH3)2 CHCH(CH3)2(2) the following Arrhenius parameters were determined: log(k1/s– 1)=(16.42 ± 0.30)–(201.9 ± 3.0) kJ mol– 1/θ, log[(k4/k1/22)/dm3/2 mol– 1/2 s– 1/2]=(3.64 ± 0.40)–(46.9 ± 2.1) kJ mol– 1/θ, log[(k5/k1/22)/dm3/2 mol– 1/2 s– 1/2](2.53 ± 0.60)–(39.5 ± 2.4) kJ mol–1/θ where θ=RT In 10.For the cross-combination ratios of the radicals 2-Ċ3H7 and (Z)-Ċ4H7, ϕ[2-Ċ3H7, (Z)-Ċ4H7]t= 2.12 ± 0.10 was obtained, where the subscript t refers to the terminal combination.Formation of certain characteristic products was observed in various addition/isomerization/dissociation processes. 2-Ċ3H7 addition to (E)-CH3CHCHCH3 is suggested as the rate-determining step, followed by 1, 4- and 1,5-H-atom shifts.

Reaction of methyl radicals with azoethane

The methyl radical was generated by the thermal decomposition of di-tert-butyl peroxide in the temperature range 397–444 K. The relative Arrhenius parameters of the H-abstraction and addition reactions ˙CH3+ C2H5NNC2H5→ CH4+ CH3CHNNC2H5(6), ˙CH3+ C2H5NNC2H5→ C2H5NN(CH3)C2H5(7), log[(k6/k1/25)/dm3/2 mol–1/2 s–1/2]=(3.1 ± 0.3)–(30.7 ± 2.6) kJ mol–1/θ, log[(k7/k1/25)/dm3/2 mol–1/2 s–1/2]=(4.0 ± 0.5)–(40.5 ± 5.1) kJ mol–1/θ where θ=RT ln 10 and k5 is the rate constant of the reaction 2 ˙CH3→ C2H6(5) were determined from the rate of accumulation of products in the early stages of the reaction.

Radical-initiated tautomerization of azoethane to acetaldehyde-ethylhydrazone; Reactivity of the CH3CHNNC2H5 radical

Abstract The N radical centre of the stabilized CH 3 CHNNC 2 H 5 radical is capable of H-abstraction from azoethane and radicals at 397–445 K. The tautomerization of azoethane to its hydrazone isomers was observed in both homogeneous and heterogeneous processes.

Determination of the Arrhenius parameters of the decomposition of azoisopropane: investigation of possible systematic errors via computer simulation

Abstract The different methods for the determination of Arrhenius parameters of the initiation step of azoisopropane (AIP) thermal decomposition in the presence of isobutene were investigated via computer simulation. The systematic errors in the methods were estimated.