A clinical evaluation of midface advancement using intraoral distractors in management of bone stock deficiencies.

BACKGROUND: Cleft lip and palate patients present large osseous defects of the alveolus and midface hypoplasia. Traditional orthognathic surgery has limitations of relapse and limited age group. Distraction osteogenesis (DO) as a modality for midface advancement is relatively new. Modular internal distractor (MID) offers the advantage of patient compliance and minimal discomfort. The purpose of this study was to evaluate the versatility of intraoral distractors in midface advancement. METHOD: Nineteen patients with midface bone stock deficiency were selected for maxillary advancement. At the first surgery under general anaesthesia, after the osteotomy (Le Fort I/II), MID system was used. After distraction, evaluation was done for ease of the procedure, stability, and complications. Lateral cephalograms were evaluated at three stages: T1, pre-distraction; T2, post-distraction; and T3, one year post-distraction. RESULTS: Significant changes showed 13.3 mm mean midface advancement bone formation at the pterygomaxillary region. The results were stable even at one year follow-up. CONCLUSION: Maxillary position improved in relation to the cranial base. This study showed that the MID was versatile in midface advancement in stability and patient compliance with minimal complications.

Fractures in the Maxillofacial Region: A Four Year Retrospective Study.

INTRODUCTION: The incidence of maxillofacial injuries is on the rise due to motor vehicle accidents and increased incidence of violence in recent times. The aim of this retrospective study was to determine the incidence, aetiology, the pattern of fractures, their management with open reduction and internal fixation (ORIF) and complications, if any. METHODS: A retrospective analysis of 621 fractures in 361 patients managed by ORIF over a four year period was carried out. RESULT: The average age of patients was 24.3 years with a male to female ratio of 21.2:1. Panfacial fractures comprised 4.7%, frontal bone fractures 8.9%, orbital fractures 0.7%, naso-orbito-ethmoid complex (NOE) fractures 0.7%, zygomatic complex fractures 23.5%, fracture maxilla 11.5% and mandibular fractures 52.2% of all facial fractures. All the cases were successfully managed by ORIF under general anaesthesia (GA). Complications were noticed in 6.8% of cases in the form of reactive implants in 3.6%, deranged occlusion in 1% and infection at operated site in 1% cases which were managed satisfactorily. CONCLUSION: The findings of this study reveal sharp annual increase in the number of cases of maxillofacial trauma. Road traffic accidents (RTA) were the commonest cause and the age group most affected was between 20-25 years. ORIF of these fractures was chosen for its obvious advantages of direct anatomical reduction, early return to function and minimal complications.

Staggered molecular packing in crystals of a collagen-like peptide with a single charged pair.

The crystal structure of the triple-helical peptide, (Pro-Hyp-Gly)(4)-Glu-Lys-Gly-(Pro-Hyp-Gly)(5) has been determined to 1.75 A resolution. This peptide was designed to examine the effect of a pair of adjacent, oppositely charged residues on collagen triple-helical conformation and intermolecular interactions. The molecular conformation (a 7(5) triple helix) and hydrogen bonding schemes are similar to those previously reported for collagen triple helices and provides a second instance of water mediated N--H . . . O==C interchain hydrogen bonds for the amide group of the residue following Gly. Although stereochemically capable of forming intramolecular or intermolecular ion pairs, the lysine and glutamic acid side-chains instead display direct interactions with carbonyl groups and hydroxyproline hydroxyl groups or interactions mediated by water molecules. Solution studies on the EKG peptide indicate stabilization at neutral pH values, where both Glu and Lys are ionized, but suggest that this occurs because of the effects of ionization on the individual residues, rather than ion pair formation. The EKG structure suggests a molecular mechanism for such stabilization through indirect hydrogen bonding. The molecular packing in the crystal includes an axial stagger between molecules, reminiscent of that observed in D-periodic collagen fibrils. The presence of a Glu-Lys-Gly triplet in the middle of the sequence appears to mediate this staggered molecular packing through its indirect water-mediated interactions with backbone C==O groups and side chains.

Electrostatic interactions in collagen-like triple-helical peptides.

Collagen-like peptides with potential for ion pair formation were studied to investigate the role of electrostatic interactions in the triple-helix conformation. Three peptides--(POG)10, the EK-containing peptide (POG)4EKG(POG)5, and T3-487, a peptide with 18 residues of type III collagen and a C-terminal (GPO)4 tail--all form stable triple helices in aqueous solution, with melting temperatures of 58, 46, and 26 degrees C, respectively, at neutral pH. The thermal stabilities of these peptides correlate with their imino acid content, which is 66%, 60%, and 41%, respectively. Variation of pH over the range of 1-13 led to 8-9 degrees C changes in the Tm of the EK-containing peptide and peptide T3-487, with the greatest stability seen at pH values where both acidic and basic residues are ionized. Equilibrium ultracentrifugation shows these peptides are largely trimeric at low temperature, with no hexamers or larger aggregates, indicating that the pH-dependent stability arises from intramolecular interaction. Computer modeling indicates both intrachain ion pairs and interchain ion pairs can form and stabilize the triple helix. Studies of the pH dependence of the thermal stability of (POG)10 and the N-terminal acetylated form of T3-487 indicate that repulsion of the three charged N-terminal or C-terminal ends has a destabilizing effect. Taking into account these end effects, the energy contribution of two oppositely charged residues in a triple helix which are sterically capable of participating in ion pairs and backbone hydrogen bonding is 0.5-1 kcal/mol ion pair. It is possible that the stabilizing influence of ion pairs arises indirectly, through elimination of like charge repulsion, formation of ion pairs in the single chain form, or solvent effects.

Effects of pH on conformational properties related to the toxicity of Bacillus thuringiensis delta-endotoxin.

The delta-endotoxin of Bacillus thuringiensis subspecies kurstaki is an intracellular crystalline proteinaceous inclusion which, upon ingestion, is toxic to lepidopteran insects. Upon dissolution at pH > 9 it yields a protein subunit called protoxin. Under appropriate conditions, protoxin is hydrolyzed to a toxin molecule, which is responsible for killing the insect. It is known that this toxic activity decreases considerably above pH 10. In this study, circular dichroism spectroscopy has been used to examine the secondary structures of the protoxin and toxin molecules at different pH values to determine if there are detectable conformational changes associated with their pH-dependent functional properties. At pH 10, where toxic activity is approximately maximal, both the protoxin and toxin molecules were found to assume a conformation that is on an average approx. 26% alpha-helix and approx. 45% beta-structure. As the pH was increased above 10, where the insecticidal activity decreases, the magnitude of the CD spectrum at 222 nm decreased for protoxin and the calculated alpha-helix contents of both protoxin and toxin molecules decreased. The net secondary structure did not change significantly at pH values below 10. Significant conformational differences are observed between the secondary structure of the protoxin and toxin molecules at different pH values. The pH-dependent changes in secondary structure of the protoxin and toxin can be correlated with the effects of pH on the insecticidal activity of these proteins.