Molar Rotation Research Articles

A Modified Transpalatal Arch for Correction of Bucally Placed Maxillary 2nd Molars: Non-Compliant Mechanics

The transpalatal arch (TPA) can be used as an adjunct during orthodontic treatment to help control the movement of the maxillary first molars in three dimensions including molar rotations, uprighting and maintaining transverse dimensions posteriorly. In addition it can also be used to maintain leeway space, as an additional anchorage to achieve active movement of teeth, modified for space maintenance, intrusion, etc. Here modified Transpalatal arch is used with E-chain - a non-compliant mechanics for correction of Maxillary 2 nd

Optimization of unilateral molar rotation correction by a trans-palatal bar: a three-dimensional analysis using the finite element method

The main goal of this study was to optimize unilateral molar rotation correction by modifying a trans-palatal arch (TPA) design using the finite element method. Three-dimensional analysis of different TPA designs was carried out using the finite element method. Department of Orthodontics, Tehran University of Medical Sciences, Iran. For this investigation, 13 three-dimensional finite element models were produced for different TPA designs without pre-activation bends. Each model contained a palatal bar and two tubes. Optimizing unilateral molar rotations was achieved by five separate different paths: incorporating U-loop(s), 'R' loop(s) or helix/helices, a reverse action of the helix/helices and adding a straight wire to the design. The mesial part of the left side tube was displaced 0·1, 0·25, 0·5 and 1 mm, successively towards the midline, simulating palatal bar tab engagement in a mesio-palatal rotated maxillary left molar. The mesio-distal force, moment and energy produced in the normal side (right) molar were recorded for each of the models. Findings showed that in all designs, the associated mesializing force was lower than that seen in the traditional design and the moment showed an increasing pattern when compared with a simple palatal bar. Regarding energy levels, the same increasing pattern was observed in the designs between activations of 0·1 and 1·0 mm. According to our optimized system, the TPA design with the highest energy and moment, but the lowest mesializing force associated with derotating a maxillary molar tooth was a parallel wire II design (i.e. adding a straight wire).

Chiroptical Properties of Carbo[6]Helicene Derivatives Bearing Extended π‐Conjugated Cyano Substituents

New carbo[6]helicene derivatives grafted with π-conjugated cyano-phenyl arms were synthesized in enantiopure forms and their π-conjugation examined by UV-vis spectroscopy. The influence of the π-conjugation on the circular dichroism spectra and molar rotations is discussed based on comparing experimental data with results from quantum-chemical calculations. The results highlight the fact that increasing the spatial extension of the π-system in a helicene molecule is an efficient way of increasing its molar rotation.

Residents' journal review

Residents' journal review

Antifungal Diterpene Alkaloids from the Caribbean Sponge Agelas citrina: Unified Configurational Assignments of Agelasidines and Agelasines

Three new diterpene alkaloids - the hypotaurocyamines, (-)-agelasidines E and F (5-6), and the adeninium salt, agelasine N (9) - were isolated from the Caribbean sponge Agelas citrina along with six known natural products agelasines B-E (7, 10-12), 2-oxo-agelasine B (8), and (-)-agelasidine C (3). The chemical structures of 5, 6 and 9 were elucidated by analysis of NMR spectra and mass spectrometry. This represents the first report of natural products from the sponge A. citrina. Unified assignment of absolute configurations of the new compounds and known compounds were achieved by chemical correlation, quantitative measurements of molar rotations, and comparative analysis by van't Hoff's principle of optical superposition. (-)-Agelasidine C (3) exhibited potent antifungal and modest cytotoxic activity against human chronic lymphocytic leukemia (CLL) cells.

Synthesis of aromatic poly(ether ketone)s bearing optically active macrocycles through Suzuki coupling polymerization

Palladium (Pd)-catalyzed Suzuki coupling polymerization of macrocycle-bearing monomers, obtained through two-step nucleophilic aromatic substitution reactions with three types of diboric acid pinacol esters, produced aromatic poly(ether ketone)s that have optically active macrocycles composed of two 2,2′-dioxy-1,1′-binaphthyl-6,6′-diyl units and two aromatic ether ketone linkers. The macrocycle-bearing aromatic poly(ether ketone)s have excellent thermal and optical properties, that is, high glass-transition temperatures (Tg: 220–257 °C) and large molar rotations ([Φ]D25: +1906–1976 deg). In addition, polyketones have excellent solubility in typical solvents such as CHCl3 and N,N-dimethylformamide (DMF). Pd-catalyzed Suzuki coupling polymerization of macrocycle-containing monomer with diboric acid pinacol esters afforded aromatic poly(ether ketone)s with optically active macrocycles. The resulting aromatic poly(ether ketone)s have high glass transition temperatures (Tg: 220–257°C), large molar rotations ([Φ]D25: +1906–1976 deg) and excellent solubility to typical solvents such as CHCl3 and DMF.

Multifunctional and Reactive Enantiopure Organometallic Helicenes: Tuning Chiroptical Properties by Structural Variations of Mono‐ and Bis(platinahelicene)s

Acetylacetonato-platina[6]- and -platina[7]helicenes have been prepared from 2-pyridyl-substituted benzophenanthrene ligands by following a two-step cycloplatination reaction. The photophysical properties (UV-visible absorption and emission behavior) and chiroptical properties (circular dichroism and molar rotation) of the resolved enantiomers have been measured. These metallahelicenes constitute a novel family of easily accessible helicene derivatives that exhibit large and tuneable chiroptical properties that can be rationalized theoretically and compared to the parent [6]- and [7]carbohelicenes. Furthermore, they are red phosphors at room temperature and their large chiroptical properties can be modulated by oxidation of the metal center to Pt(IV). Hetero- and homochiral diastereomeric bis(metallahelicene)s that possess a rare Pt(III)-Pt(III) scaffold bridged by benzoato ligands have also been prepared. It is shown that the heterochiral (P,M)-bis(Pt(III)-[6]helicene) 9a(1) can isomerize into the homochiral (P,P)- and (M,M)-bis(Pt(III)-[6]helicene) 9a(2). Spectral assignments and an analysis of the optical rotation of these systems were made with the help of time-dependent density functional theory. The calculations highlight the contributions of the metal centers to the chiroptical properties. For 9a(1) and 9a(2), σ-π conjugation between the helicenes and the Pt-Pt moiety may contribute strongly to the optical rotation and electronic circular dichroism.

Synthesis and optical activity of isosorbide chiral derivative containing fluorocarbon group as chiral dopant in liquid crystal materials

Novel isosorbide derivative containing perfluorocarbon group, bi(perfluorooctanesulfonyl)isosorbide ester as chiral dopant in liquid crystal, was synthesized. Chemical structure was characterized by elemental analysis, FT-IR, 1H NMR and 19F NMR. The optical texture of the mixture was observed by polarized optical microscopy (POM). Novel chiral dopant containing perfluorocarbon group had excellent optical activity. Its specific rotation and molar rotation were noticeable higher than those of bi(4-chloromethylbenzenecarbonic)isosorbide ester. The fluorocarbon group improved the molar rotation of chiral compound and did not affect optical rotation direction. The texture of the mixture added isosorbide derivative with fluorocarbon group showed the oily streak texture.

Synthesis and characterization of chiral compounds containing cationic groups as chiral dopants in liquid crystals

Novel chiral molecules containing cationic groups, (N-[4-triethylammoniomethyl]-benzoyl ester)-ethyl lactate chloride and bi-(N-[4-triethylammoniomethyl]-benzoyl ester)-isosorbide chloride, were designed and synthesized. Chemical structures of the molecules were characterized by elemental analysis, FT-IR, and 1H NMR. The photochemical properties of the chiral compounds and their textures in nematic liquid crystals (LCs) were investigated by optical rotation, circular dichroism (CD), and polarizing optical microscopy (POM). The novel chiral molecules exhibited good optical activity. The chiral compound based on a l-ethyl lactate chiral center had a left-handed configuration. The chiral compound based on an isosorbide chiral center had a right-handed configuration. The cationic polar groups did not affect the direction of optical rotation, but could effluence the molar rotation of chiral compounds. The mixtures with dopants showed oily streak textures. Doping of a nematic phase liquid crystal with the chiral molecules converted it to the cholesteric phase.

Mesial rotation of upper first molars in Class II division 1 malocclusion in the mixed dentition: a controlled blind study

Objective To compare the amount of upper molar rotation in subjects with Class II Division 1 malocclusion and subjects with normal occlusion in the intermediate and late mixed dentition phases. Materials and methods Dental cast measurements were performed in a sample of 120 Class II Division 1 subjects (CL2 group, 67 females and 53 males, mean age 9.4 ± 1.1 years), and in a sample of 58 Class I subjects (CL1 group, 34 females and 24 males, mean age 9.7 ± 1.2 years). Independent sample t tests were used for statistical comparisons (P < .05). Results The amount of upper molar rotation was significantly greater in CL2 group when compared with CL1 group as assessed by both the mesial and buccal molar cusp angles. No differences were found with regard to upper or lower arch depths, or upper intercanine width. CL2 group showed a significant deficiency in upper intermolar width along with a significant posterior transverse interarch discrepancy when compared with CL1 group. Conclusions Subjects with Class II malocclusion in the mixed dentition present with mesial upper molar rotation in about 84% of the cases. The correction of molar rotation may provide between 1 and 2 mm of gain in arch perimeter and of improvement in molar relationships per side in 5 out 6 Class II patients.

Discovery of aggregative chirality of surfactants

166 Although both surface activity and optical activity follow from the molecular structure of matter, they reflect different aspects of the structure and need not be related to each other. Surface activity requires the presence of hydrophilic and hydrophobic parts in a molecule. If these parts are particularly pronounced, which is characteristic of colloidal surfactants, then, with increasing concentration, aggregation processes occur in solution, which finally lead to micelle forma� tion (at a temperature above the Kraft point). Optical activity requires the absence of either a center or plane of symmetry. A chiral substance consisting of such molecules rotates the light polarization plane by angle α (optical rotation) according to the Biot law where l is the length of the transmitted sample, с is the concentration (or, for individual substances, density) of the optically active substance, and [α] is a propor� tionality constant (specific rotation)—a tabulated characteristic of optical activity of the substance. The quantity [α] is usually measured, like α, in degrees, which is inconsistent with the dimension of [α]. In this case, it is meant that the length l is measured in milli� meters for solids and in decimeters for solutions (in accordance with the optical cell sizes) and the con� centration is measured in grams per 100 mL (if the number of moles of substance is used instead of grams, then the specific rotation is replaced by molar rota� tion). Most probably, such contrivances were aimed at always dealing with rotation angles within 360°; however, they were in vain because chiral substances with specific rotation 400° and more are already known.

ChemInform Abstract: Synthesis of Dendrimers Containing 2,5-Anhydro-D-mannitol as a Chiral, Tetrafunctional Central Core with C2 Symmetry.

Abstract The synthesis of first through third generation dendrimers containing a chiral, tetrafunctional core and allyl ester termini is described. The molar rotations of the dendrimers were observed to become less negative with increasing generation; however, the rotations of the dendrimers were more negative than the starting central core.

ChemInform Abstract: A Stereoselective Synthesis of 2,6-Dideoxy-6,6,6-trifluoro-arabino-hexoses via an Asymmetric Diels-Alder Strategy.

The enantioselective syntheses of each enantiomer of ethyl 2,6-dideoxy-6,6,6-trifluoro-β-arabino-hexopyranoside (3) and of 2,6-dideoxy-6,6,6-trifluoro-arabino-hexose (4) are described. The key step in the approach is the inverse electron demand Lewis acid catalysed Diels–Alder reaction of the heterodiene (E)-1,1,1-trifluoro-4-[(1R)-1- phenylethoxy]but-3-en-2-one (5) and either ethyl vinyl ether (7a) or benzyl vinyl ether (7b). The titanium(IV) chloride catalysed cycloadditions at low temperature displayed high endo-selectivity and modest diastereofacial selectivity. Hydroboration of the mixture of the cis-cycloadducts (8a) afforded the separable diastereoisomers (9a) and (10a). Hydrogenolysis of (9a) gave ethyl 2,6-dideoxy-6,6,6-trifluoro-β-L-arabino-hexopyranoside (+)-(3), and of (10a) gave the corresponding D-glycoside (−)-(3). Similarly, hydroboration of the cis-cycloadducts (8b) gave the protected benzyl glycosides (9b) and (10b). Hydrogenolysis of each gave 2,6-dideoxy-6,6,6-trifluoro-L-arabino-hexopyranose (−)-(4) and the corresponding D-sugar (+)-(4) respectively. The absolute configurations of fluorinated carbohydrates (+)- and (−)-(3) were determined by comparison of their molar rotations with those of the parent glycosides. These assignments were confirmed by an X-ray crystallographic structure determination of the glycoside (9a).

Implant versus Nance holding arch anchorage during maxillary canine retraction

The aim of the present work is to determine the anchorage potential of titanium microimplant for maxillary canine retraction and to measure the anchorage loss using microscrew implants compared to Nance holding arch as intraoral anchorage during maxillary canine retraction in Angle's class I crowding. Sample of this study consisted of 10 females ranging in age from 18-24 years. 5 received micro-screw implants as a mean of anchorage and the remaining 5 received conventional molar anchorage as Nance holding arch. The molar anchorage loss was determined in both the implant anchored cases and the molar anchored cases by superimposing the lateral cephalometric tracings before and after canine retraction along the palatal plane registered at the anterior nasal spine. The horizontal distances from the pterygoid vertical to the distal surfaces of the first molars were calculated to measure the anchorage loss. In present study all implants remained stable throughout the treatment period and no damage was registered in any implant under the condition of implant loading. Also, no implant deformation was detected in any implant., anchorage loss was detected more significantly (P < .0007) in patients with intraoral anchorage through the Nance holding arch compared to patients with anchorage through orthodontic mini-implants both on the right and left side. In the Nance group the mean anchorage loss was 1.4mm (±0.418) on the right side and 1.42 mm (±0.437) on the left side. On the other hand no molar rotation was detected in the present study either by using the Nance holding arch or the microimplant. So, this study is a further prove of the beneficial use of microimplants as a good anchorage method with profound control of molar rotation.

Assembly of π‐Conjugated Phosphole Azahelicene Derivatives into Chiral Coordination Complexes: An Experimental and Theoretical Study

Aza[n]helicene phosphole derivatives have been prepared from aza[n]helicene diynes by the Fagan-Nugent route. Their photophysical properties (UV/Vis absorption and emission behavior) have been evaluated. Their behavior as P,N chelates towards coordination to Pd(II) and Cu(I) has been investigated: metal-bis(aza[n]helicene phosphole) assemblies are formed by a highly stereoselective coordination process, as demonstrated by X-ray crystallography. An aza[6]helicene phosphole bearing an enantiopure helicene part has been obtained, which allows the preparation of enantiopure Pd(II) and Cu(I) complexes with original topologies and high molar rotation (MR) and circular dichroism (CD). The structure-property relationship established from the experimental data has been studied in detail by theoretical studies (TDDFT calculations of UV/Vis, CD, and MR). Aza[n]helicene phosphole derivatives show pi conjugation extended over the entire molecule, and its influence on the MR of aza[6]helicene phosphole 5 c has been demonstrated. Finally, it has been shown that the nature of the metal (coordination geometry and electronic interaction) can have a great impact on the amplitude of the chiroptical properties in metal-bis(aza[n]helicene phosphole) assemblies.

A randomized clinical trial to compare the Goshgarian and Nance palatal arch

The aim of this trial was to evaluate whether a Nance or Goshgarian palatal arch was most effective for prevention of mesial drift, distal tipping, prevention of mesio-palatal rotation of the upper first permanent molars, and patient comfort and ease of removal. Patients were recruited from a district general hospital and a specialist orthodontic practice and randomly allocated to a Goshgarian (n = 29) or a Nance (n = 28) group. Pre-treatment study models (T1) were taken followed by the placement of the palatal arch, premolar extractions, and upper and lower fixed appliances. The clinical end point was 6 months (T2), at which time, an impression for an upper study model was taken. The amount of upper first permanent molar mesial movement, distal tipping, and mesio-palatal rotation was measured by scanning T1 and T2 study models and then using a software program to calculate molar changes. In addition, the patients recorded their discomfort scores using a seven-point Likert scale at each recall visit. Forty-nine patients (86 per cent) completed the trial. t-tests were used to compare molar movements between the Goshgarian and Nance palatal arch groups. There were no statistically significant differences between the palatal arches in terms of prevention of mesial drift or distal tipping (P > 0.05). There was a statistically significant difference in the amount of molar rotation between the arch types, with both exhibiting some disto-palatal rotation even though they were not activated for this movement. The Goshgarian palatal arch produced marginally more disto-palatal rotation than the Nance arch (P = 0.02), although this may not be considered clinically significant. A Mann-Whitney test revealed that there was also a statistically significant difference in pain scores between the Goshgarian and the Nance arch, with the latter being associated with more discomfort (P = 0.001). This trial did not support any preference in the use of the Goshgarian or Nance palatal arch, unless the slightly reduced patient discomfort with the Goshgarian arch is considered significant.

Maxillary expansion in cleft lip and palate using Quad helix and rapid palatal expansion screw

Background: Management of patients with cleft lip and palate (CLP) includes orthodontic treatment prior to bone grafting. Palatal expansion is done using slow or rapid palatal expansions (RPE). Controversy still exists regarding choice of expansion appliances used. This study was conducted to find out whether the Quad helix appliance represents a reasonable alternative to using conventional rapid maxillary expansion appliance among cleft lip and palate patients. Methods: Twenty cleft lip and palate patients had orthodontic study models taken prior to expansion and at the end of expansion. There pre and post treatment study models were analyzed for changes in intermolar width, molar tipping and molar rotation. Result: The difference in molar tipping, increase in intercanine and molar width between slow palatal expansion (SPE) and rapid palatal expansion (RPE) group was not statistically significant. A difference between the two groups was found in the ability to rotate molars. Conclusion: The clinical findings suggest that maxillary expansion using the Quad helix appliance represents a reasonable alternative to using conventional rapid maxillary expansion appliances among cleft patients.

Modeling of the Chiroptical Response of Chiral Amino Acids in Solution Using Explicit Solvation and Molecular Dynamics.

Molecular dynamics (MD) simulations and TDDFT linear response computations were employed to model the molar rotations of the zwitterionic forms of glycine, alanine, proline, and phenylalanine in aqueous solution. The MD simulations inherently take into account averaging the chiroptical response of different amino acid conformers and also allow the effects from vibrational distortions and explicit solvent perturbations on the optical rotation to be modeled. The results show that the chiroptical response correlates strongly to the conformations of these molecules relative to their carboxylate functional groups. Additionally, the molar rotation of phenylalanine shows a correspondence to the molecule's internal rotation about its phenyl group. These findings may be rationalized with established and revised "sector rules" for optical activity.

Rotational drift of mandibular third molar teeth: a series of four cases

Rotational drift of mandibular third molar teeth is a challenge for clinicians to predict and manage. Evidence on the incidence and degree of rotation is sparse. As the factors influencing rotation are not defined, prediction is impossible. A series of four cases with lower third molar rotation are presented and discussed. Significant rotation can alter the degree of difficulty for an extraction. A lack of well-documented cases has hindered investigation of this phenomenon. Further research is required to identify the aetiology, incidence and increase in risk factors caused by such rotational drift.

Force system generated by an adjustable molar root movement mechanism

Tooth movement simulation is important for planning the optimal force system and appliance design to correct a specific malocclusion. Experimental verification of a 3-dimensional force system is described for a unique molar root movement strategy that can be adapted to many clinical scenarios. The force system was measured for molar root movement springs that had adjustable alpha (anterior) and beta (posterior) moments. A 3-dimensional transducer assessed moments and forces in 3 planes during deactivation and simulated molar rotation. Two experimental situations were compared by using 10 springs in each group: spring reactivation was performed to compensate for changes in the force system caused by molar movement, or there was no reactivation. Without reactivation, the force system becomes unfavorable after approximately 5 degrees of molar movement (rotation). With reactivations, a favorable force system through 20 degrees of molar movement is maintained. Present root-movement appliances require periodic adjustment to achieve optimal tooth movement. Additional studies are needed to design orthodontic appliances for delivering optimal force systems for the entire range of tooth movement.