Strength analysis of Le Fort I osteotomy fixation: titanium versus resorbable plates

PURPOSE

The purpose of this study was to compare the biomechanical characteristics of metallic and polymeric fixation systems using a 3-dimensional skull model to simulate clinical conditions of maxillary advancement and loading.

MATERIAL AND METHODS

Standard titanium, prebent titanium, and resorbable plates and mesh were applied to surgically altered polyurethane skulls. The constructs were loaded using an Instron machine (Instron Inc, Canton, MA) in anterior-posterior (AP) and inferior-superior (IS) directions. The load displacement, load to failure, and deformation magnitudes and modes of failure were recorded. Statistical studies included analysis of variance (ANOVA) at P <.05.

RESULTS

Elastic stiffness was different among groups in the AP direction, but no significant difference was found in the IS direction. The IS loading direction load displacement (stiffness) was significantly greater than that on AP loading. The maximum load for permanent deformation was larger in the AP direction, while the maximum load for breaking was larger in the IS direction.

CONCLUSION

The overall evaluation of the model and test analyses supported the relative value of this in vitro system and study procedure. All systems showed load capacity magnitudes above 285 N (64 lbs) and more elastic resistance in the IS direction. The resorbable systems showed lower elastic stiffness compared with the titanium systems, but they appear to be adequate for fixation and withstanding the forces of mastication.

Knowledge about epilepsy among teachers and epileptic patients

223 epileptics patients and their families and 136 teachers from public and private schools were submitted to similar questionnaires related to inheritance, transmission, cure, complication rates, care during seizures, need for information on the disease, habits, comparison with other diseases and to the educational and social performance of epileptics. Cure and complication rates accounted for the main differences between those populations. Epileptics could recognize a bigger number of complications but still expected to be cured from the disease. The majority of teachers and patients have never been informed about epilepsy and this finding was related to the big number of equivocal answers obtained from them. Put together, the data showed that social and educational performance of epileptic patients could be disturbed by medical and social parameters. Some of them could be improved by an educational program towards these aspects of epilepsy.

Thiamine destruction by sodium bisulfite in infusion solutions

The degree of degradation of thiamine hydrochloride in sodium bisulfite-containing infusion solutions was investigated. Two amino acid and one electrolyte infusion solution containing sodium bisulfite and four infusion solutions (5 and 10% dextrose, Lactated Ringer's, and 0.9% sodium chloride injections) without sodium bisulfite were obtained in 500-ml glass or plastic containers. Three thiamine sources, two commercial multivitamin preparations, and one investigational multivitamin product were added to the infusion solutions. The percentage of added thiamine remaining after storage was determined in four experiments: (1) The investigational product was added to the infusion solutions with bisulfite, and the determinations were made after 24 hours of storage at room temperature (RT) under both light and dark conditions; (2) the two commercial multivitamin preparations were mixed with an amino acid solution containing bisulfite and the determination was made after 24 hours of storage at RT under dark conditions; (3) the investigational product was added to the infusion solutions with bisulfite, and the determinations were made after 2, 4, 6, 8, and 24 hours storage at 7 degrees C and following four hours at RT under dark conditions; and (4) the investigational product was added to the four infusion solutions without bisulfite, and the determinations were made after 24 hours of storage at RT under both light and dark conditions. In the infusion solutions containing bisulfite, the stability of thiamine was inversely related to the pH. In an amino acid solution at a pH of 6.5, only 3-8% of the added thiamine was found after 24 hours storage at RT, and only 37% was found after 24 hours at 7 degrees C. In the electrolyte solution with bisulfite (pH = 5), the percentages of thiamine remaining after 24 hours RT and 7 degrees C storage were 50 and 69%, respectively. Light exposure was not found to affect the stability of thiamine in the solutions containing bisulfite. In the infusion solutions without bisulfite, a minimal loss of thiamine occurred even though the pH range was 4.7-5.6. The degradation effect of light exposure was greater for the solutions stored in plastic than in glass. Infusion solutions containing bisulfite were found to be unsuitable vehicles for the administration of vitamin formulations containing thiamine. If a patient must receive multivitamins in infusion solutions with bisulfite, the solutions should be used immediately after their preparation, and the patient should be monitored for signs of thiamine deficiency.