Faculty Bibliography

The critical length of 30 mm beyond which nerve regeneration was not possible limited up to now the use of tubulization. In this pilot study, a novel animal model is introduced using tubulization techniques for long-nerve defects (40 mm) in brachial plexus surgery. Twelve Sprague-Dawley rats were divided into 3 groups. A poly-DL-lactide-epsilon-caprolactone tube (group 1), a collagen tube (group 2), and a nerve graft (group 3) were, respectively, used to bridge a 40-mm gap between the right C7 root and the left musculocutaneous nerve. Animals were euthanized on day 30. Evaluation consisted of behavioral assessment, needle electromyography studies, biceps muscle weight measurements, qualitative, and quantitative morphometry. Only group 3 demonstrated axon regeneration and reinnervation potentials. There was statistical significant difference for biceps weight left/right ratio (P = 0.010) but not for behavioral results (P = 0.10) between group 3 and groups 1 and 2. This study introduced a novel rat model for the studying of nerve regeneration along long-nerve gaps (4 cm). Although using an autologous nerve graft regeneration achieved, the use of synthetic conduits failed to show regeneration. This may be attributed to gap length; duration of follow-up; and to no administration of a neurotrophic factor

BACKGROUND: Half of the patients with head and neck squamous cell carcinoma (HNSCC) can be expected to fail therapy, indicating that more aggressive treatment is warranted for this group. We have developed a novel risk model that can become a basis for developing new treatment paradigms. Here we report on the performance of our model in a new multicenter cohort. DESIGN: Eligible patients from 3 institutions (Montefiore Medical Center, University of Manitoba, and New York University Medical Center) were identified and pathology slides from their resection specimens were reviewed by Margaret Brandwein-Gensler; risk category was assigned as previously published. Kaplan-Meier analysis was performed for disease progression and survival. Cox proportional hazards regression was performed, adjusted for potential confounders. A teaching module was also developed; attending pathologists were asked to score coded slides after a lecture and multiheaded microscope teaching session. Agreement was assessed by calculating Cohen unweighted kappa coefficients. RESULT: The validation cohort consisted of 305 patients, from the above institutions, with 311 primary HNSCC of the oral cavity, oropharynx, and larynx. The median follow-up period for all patients was 27 months. Risk category predicts time to disease progression (P=0.0005), locoregional recurrence (P=0.013), and overall survival (P=0.0000) by Kaplan-Meier analysis. High-risk status is significantly associated with decreased time to disease progression, adjusted for clinical confounders (P=0.015, hazard ratio 2.32, 95% confidence interval 1.18-4.58) compared with collapsed intermediate and low-risk groups. We also demonstrate substantial interrater agreement (kappa=0.64), and very good rater agreement when compared with the standard (kappa=0.87). CONCLUSIONS: We demonstrate significant predictive performance of the risk model in a new cohort of patients with primary HNSCC, adjusted for confounders. Our training experience also supports the feasibility of adapting the risk model in clinical practice

The purpose of this study in rats was to identify whether a minimal dose of FK506 could enhance nerve regeneration along a 4-cm cross-chest saphenous nerve graft. Our center established a cross-chest nerve regeneration model previously using the contralateral C7 root transfer to the musculocutaneous nerve. Using this model, 10 adult male Sprague-Dawley rats were divided into two groups: group 1 (N = 5) consisted of animals that did not receive any further treatment, and group 2 (N = 5) consisted of animals that received a daily subcutaneous dose of 0.7 mg/kg FK506 for a period of 4 weeks. Evaluation methods of the study groups consisted of behavioral assessment, needle electromyography studies, and qualitative and quantitative morphometry. In the FK506 group, the middle of the graft and the musculocutaneous nerve contained larger axons and thicker myelin, bicep muscle weight recovered to an average of 68% of the normal (right) side, and overall behavioral results were better (P = 0.03175) than for untreated controls. Although the FK506 group achieved higher average myelinated fiber counts in all histologic sections, higher amplitude, and shorter latency results, there was no statistically significant difference between the two groups. Contralateral C7 transfer in the rat brachial plexus is a good experimental model to assess nerve regeneration and test treatments designed to enhance recovery in lesions with long nerve gaps (40 mm). FK506-treated animals demonstrated more advanced axonal regeneration, myelinated fiber maturation, and bicep muscle reinnervation. These results suggest a potential clinical use of low-dose FK506 in patients with severe nerve injuries

This study evaluated the stress levels at the core layer and the veneer layer of zirconia crowns (comprising an alternative core design vs. a standard core design) under mechanical/thermal simulation, and subjected simulated models to laboratory mouth-motion fatigue. The dimensions of a mandibular first molar were imported into computer-aided design (CAD) software and a tooth preparation was modeled. A crown was designed using the space between the original tooth and the prepared tooth. The alternative core presented an additional lingual shoulder that lowered the veneer bulk of the cusps. Finite element analyses evaluated the residual maximum principal stresses fields at the core and veneer of both designs under loading and when cooled from 900 degrees C to 25 degrees C. Crowns were fabricated and mouth-motion fatigued, generating master Weibull curves and reliability data. Thermal modeling showed low residual stress fields throughout the bulk of the cusps for both groups. Mechanical simulation depicted a shift in stress levels to the core of the alternative design compared with the standard design. Significantly higher reliability was found for the alternative core. Regardless of the alternative configuration, thermal and mechanical computer simulations showed stress in the alternative core design comparable and higher to that of the standard configuration, respectively. Such a mechanical scenario probably led to the higher reliability of the alternative design under fatigue

OBJECT: The 2 aims of this study were as follows: 1) to establish outcome measures of nerve regeneration in an axolotl model of peripheral nerve injury; and 2) to define the timing and completeness of reinnervation in the axolotl following different types of sciatic nerve injury. METHODS: The sciatic nerves in 36 axolotls were exposed bilaterally in 3 groups containing 12 animals each: Group 1, left side sham, right side crush; Group 2, left side sham, right side nerve resected and proximal stump buried; and Group 3 left side cut and sutured, right side cut and sutured with tibial and peroneal divisions reversed. Outcome measures included the following: 1) an axolotl sciatic functional index (ASFI) derived from video swim analysis; 2) motor latencies; and 3) MR imaging evaluation of nerve and muscle edema. RESULTS: For crush injuries, the ASFI returned to baseline by 2 weeks, as did MR imaging parameters and motor latencies. For buried nerves, the ASFI returned to 20% below baseline by 8 weeks, with motor evoked potentials present. On MR imaging, nerve edema peaked at 3 days postintervention and gradually normalized over 12 weeks, whereas muscle denervation was present until a gradual decrease was seen between 4 and 12 weeks. For cut nerves, the ASFI returned to 20% below baseline by Week 4, where it plateaued. Motor evoked potentials were observed at 2-4 weeks, but with an increased latency until Week 6, and MR imaging analysis revealed muscle denervation for 4 weeks. CONCLUSIONS: Multiple outcome measures in which an axolotl model of peripheral nerve injury is used have been established. Based on historical controls, recovery after nerve injury appears to occur earlier and is more complete than in rodents. Further investigation using this model as a successful 'blueprint' for nerve regeneration in humans is warranted

Since the founding of the osseointegration concept, the characteristics of the interface between bone and implant, and possible ways to improve it, have been of particular interest in dental and orthopaedic implant research. Making use of standardized tools of analysis and terminology, we present here a standardized characterization code for osseointegrated implant surfaces. This code describes the chemical composition of the surface, that is, the core material, such as titanium, and its chemical or biochemical modification through impregnation or coating. This code also defines the physical surface features, at the micro- and nanoscale, such as microroughness, microporosity, nanoroughness, nanotubes, nanoparticles, nanopatterning and fractal architecture. This standardized classification system will allow to clarify unambiguously the identity of any given osseointegrated surface and help to identify the biological outcomes of each surface characteristic.