Faculty Bibliography

Despite the increasing utilization of all-ceramic crown systems, their mechanical performance relative to that of metal ceramic restorations (MCR) has yet to be determined. This investigation tested the hypothesis that MCR present higher reliability over two Y-TZP all-ceramic crown systems under mouth-motion fatigue conditions. A CAD-based tooth preparation with the average dimensions of a mandibular first molar was used as a master die to fabricate all restorations. One 0.5-mm Pd-Ag and two Y-TZP system cores were veneered with 1.5 mm porcelain. Crowns were cemented onto aged (60 days in water) composite (Z100, 3M/ESPE) reproductions of the die. Mouth-motion fatigue was performed, and use level probability Weibull curves were determined. Failure modes of all systems included chipping or fracture of the porcelain veneer initiating at the indentation site. Fatigue was an acceleration factor for all-ceramic systems, but not for the MCR system. The latter presented significantly higher reliability under mouth-motion cyclic mechanical testing

Few areas of translational medicine carry as much excitement and hope as stem cell therapies. Because of recent advances in material science and stem cell and developmental biology that help to target molecules and pathways to restore the body's regenerative capacity, the "engineering" of missing tissue is quickly becoming a reality. Classically, tissue engineering has been thought to require external regenerative resources including a scaffold, cells, and growth factors. The allure of providing an exact replica of a missing bone that incorporates to become indistinguishable from self, has the capacity to heal and grow, is resistant to infection, and has minimal morbidity is a "holy grail" to all surgeons who work with bone. This article attempts to shed light on the use of stem cells for craniofacial reconstruction, including important principles learned from other scientific disciplines, relevant animal models for tissue engineering, early clinical reports from our experience and that of others, and future directions.

BACKGROUND: The aim of this study was to calculate and analyze the cost of treatment for stage IV pressure ulcers. METHODS: A retrospective chart analysis of patients with stage IV pressure ulcers was conducted. Hospital records and treatment outcomes of these patients were followed up for a maximum of 29 months and analyzed. Costs directly related to the treatment of pressure ulcers and their associated complications were calculated. RESULTS: Nineteen patients with stage IV pressure ulcers (11 hospital-acquired and 8 community-acquired) were identified and their charts were reviewed. The average hospital treatment cost associated with stage IV pressure ulcers and related complications was $129,248 for hospital-acquired ulcers during 1 admission, and $124,327 for community-acquired ulcers over an average of 4 admissions. CONCLUSIONS: The costs incurred from stage IV pressure ulcers are much greater than previously estimated. Halting the progression of early stage pressure ulcers has the potential to eradicate enormous pain and suffering, save thousands of lives, and reduce health care expenditures by millions of dollars

BACKGROUND:: Pediatric temporomandibular joint (TMJ) dysfunction, resulting from either soft tissue or skeletal disorders, may be congenital or acquired. Congenital TMJ disorders are uncommon. Here we review our experience with pediatric TMJ disorders and propose a new classification system. METHOD:: Clinical records, cephalograms, computed tomography, magnetic resonance images, and pathologic specimens of all pediatric patients (< 18 years) with trismus or restricted mandibular excursion from 1976-2008 were reviewed. Cases were stratified according to soft tissue or skeletal pathology; skeletal abnormalities were further characterized as intra- or extra-capsular. RESULTS:: 38 patients, ranging in age from 1 day to 18 years of age at diagnosis, were identified with TMJ disorders. Ten cases (26.3%) were due to soft tissue pathology. The remaining 28 cases (73.7%) were due to skeletal pathology, consisting of 14 congenital and 14 acquired cases (50% each). Acquired skeletal deformities included 12 (85.7%) intracapsular ankyloses and 2 (16.7%) extracapsular ankylosis (extra-articular bone blocks). Congenital skeletal deformities accounted for 5 (35.7%) intracapsular ankyloses and 9 (64.3%) extracapsular ankyloses. CONCLUSION:: On initial survey, the data are consistent with published reports that attribute TMJ dysfunction to acquired pathology (i.e., trauma and infection). However, we observed a significantly higher percentage (50%) of congenital TMJ skeletal disorders than previously reported. Most congenital cases involved extracapsular pathology (i.e., coronoid hypertrophy); only a minority of cases had glenocondylar fibro-osseous fusion (i.e., intracapsular ankyloses). Since the diagnosis and classification of TMJ disorders determines treatment options, we provide a new classification that characterizes the extent of capsular involvement

The present study focused on determining the effect of high strain rate loading on the deformation and fracture characteristics of syntactic foams and relating them with the initial foam microstructure. The high strain rate testing was carried out using a split-Hopkinson pressure bar system and the damage evaluation was carried out using microCT-scan and scanning electron microscope. The strength was found to be 50-150% higher at high strain rates when compared to quasi-static values for various grades of syntactic foams. Damage evaluation revealed crushing of particles in the surface layer, shear cracking, and propagation of longitudinal cracks as the main fracture modes at different strain rates and material compositions. Wall thickness and volume fraction of hollow particles used in syntactic foams played an important role in determining the failure mechanism. At low strain rates shear cracking of specimens was prominent, whereas at high strain rates longitudinal cracks were the main failure mode. Understanding the strain rate dependence of failure mechanisms is important for aerospace applications of these lightweight composites. (C) 2010 Elsevier B.V. All rights reserved.

Cocktail stick (CS) ingestion injury has rarely been reported in the literature. It is a serious clinical problem with considerable morbidity and mortality, largely due to the fact that the event is unnoticed by the patient. We report a case of CS ingestion that went unrecognised by the patient and caused a perforation in the mid-small bowel. We discuss how injuries from such events can become a diagnostic challenge. The history should be re-evaluated in any undiagnosed abdominal pain which has an unclear aetiology and negative radiology.

OBJECTIVES: To compare the reliability of the disto-facial (DF) and mesio-lingual (ML) cusps of an anatomically correct zirconia (Y-TZP) crown system. The research hypotheses tested were: (1) fatigue reliability and failure mode are similar for the ML and DF cusps; (2) failure mode of one cusp does not affect the failure of the other. METHODS: The average dimensions of a mandibular first molar crown were imported into CAD software; a tooth preparation was modelled by 1.5 mm marginal high reduction of proximal walls and occlusal surface by 2.0 mm. The CAD-based tooth preparation was milled and used as a die to fabricate crowns (n=14) with porcelain veneer on a 0.5 mm Y-TZP core. Crowns were cemented on composite reproductions of the tooth preparation. The crowns were step-stress mouth motion fatigued with sliding (0.7 mm) a tungsten-carbide indenter of 6.25 mm diameter down on the inclines of either the DF or ML cusps. Use level probability Weibull curve with use stress of 200 N and the reliability for completion of a mission of 50,000 cycles at 200 N load were calculated. RESULTS: Reliability for a 200 N at 50,000 cycles mission was not different between tested cusps. SEM imaging showed large cohesive failures within the veneer for the ML and smaller for the DF. Fractures originated from the contact area regardless of the cusp loaded. CONCLUSION: No significant difference on fatigue reliability was observed between the DF compared to the ML cusp. Fracture of one cusp did not affect the other