Faculty Bibliography

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

Optimized experimental conditions for extracting accurate information at subpixel length scales from analyzer-based X-ray imaging were obtained and applied to investigate bone regeneration by means of synthetic beta-TCP grafting materials in a rat calvaria model. The results showed a 30% growth in the particulate size due to bone ongrowth/ingrowth within the critical size defect over a 1-month healing period.

BACKGROUND: Novel implant surface treatments with a nanothickness bioactive ceramic deposition onto rough surfaces have been recently introduced. This study aims to evaluate histologically and histomorphometrically (bone-to-implant contact [BIC] and bone area fraction occupancy [BAFO]) the early bone response to plasma-sprayed calcium-phosphate (PSCaP)-coated versus a 300- to 500-nm thickness bioactive ceramic nano-coated plateau root form implants in a rabbit femur model. METHODS: A total of 48 plateau root form implants were bilaterally placed in the distal aspect of the femur of 12 white New Zealand rabbits, remaining for 20, 30, and 60 days in vivo (n = 4 animals per time in vivo, n = 2 implants per surface per animal). After sacrifice, the implants in bone were non-decalcified processed to slides of approximately 30 mum thickness, and were morphologically and morphometrically (BIC and BAFO) evaluated. RESULTS: Higher degrees of bone structural organization were temporally observed for the PSCaP surface compared to the nano surface over time. BIC and BAFO was significantly higher (P <0.05) for PSCaP at all implantation times evaluated. CONCLUSIONS: Within the limits of this study it is possible to state that bioactive ceramic coatings of both thicknesses were biocompatible and osteoconductive. However, the early bone response was favored by the presence of the thicker PSCaP coating.

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

Rodent pain models play an important role in understanding the mechanisms of nociception and have accelerated the search for new treatment approaches for pain. Creating an objective metric for orofacial nociception in these models presents significant technical obstacles. No animal assay accurately measures pain-induced orofacial dysfunction that is directly comparable to human orofacial dysfunction. We developed and validated a high throughput, objective, operant, nociceptive animal assay, and an instrument to perform the assay termed the dolognawmeter, for evaluation of conditions known to elicit orofacial pain in humans. Using the device our assay quantifies gnawing function in the mouse. We quantified a behavioral index of nociception and demonstrated blockade of nociception in three models of orofacial pain: (1) TMJ inflammation, (2) masticatory myositis, and (3) head and neck cancer. This assay will be useful in the study of nociceptive mediators involved in the development and progression of orofacial pain conditions and it will also provide a unique tool for development and assessment of new therapeutic approaches

Since 1976, experimental and clinical studies have suggested the superiority of vascularized nerve grafts. In this study, a 27-year experience of the senior author is presented regarding vascularized nerve grafts and fascia for complex upper extremity nerve reconstruction. The factors influencing outcomes as well as a comparison with conventional nerve grafts is presented. Since 1981, 21 vascularized nerve grafts, other than vascularized ulnar nerve, were used for reconstruction of nerve injuries in the upper extremity. Indications were prolonged denervation time, failure of the previously used conventional nerve grafts, and excessive scar in the recipient site. Injury was in the hand/wrist area (n = 5), in the forearm (n = 4), in the elbow (n = 2), in the arm (n = 4), or in the plexus (n = 6). Vascularized sural (n = 9), saphenous (n = 8), superficial radial (n = 3), and peroneal (superficial and deep) nerves were used. The mean follow-up was 31.4 months. Vascularized nerve grafts for upper extremity injuries provided good to excellent sensory return in severely scarred upper extremities in patients in whom conventional nerve grafts had failed. They have also provided relief of causalgia after painful neuroma resection and motor function recovery in selective cases even for above the elbow injuries. Small diameter vascularized nerve grafts should be considered for bridging long nerve gaps in regions of excessive scar or for reconstructions where conventional nerve grafts have failed

OBJECTIVES/HYPOTHESIS: AlloDerm (LifeCell Corp., Branchburg, NJ) is commonly employed for reconstruction of ablative soft tissue and mucosal defects following surgical resections. Although devoid of growth factors, AlloDerm may serve as an adhesive matrix for binding of growth factors, increasing local angiogenesis, and wound healing. We hypothesized that AlloDerm would enhance angiogenesis and might be altered with autologous blood products to enhance initiation of the angiogenic response. METHODS: We used a human placental vein in a fibrin-thrombin clot-based angiogenesis model. Four groups, human placental vein (HPVM), HPVM with AlloDerm, HPVM with AlloDerm plus platelet-poor plasma, and HPVM with AlloDerm plus platelet-rich plasma were evaluated. Endothelial cell growth was evaluated visually (40x). Hematoxylin and eosin staining and immunofluorescent staining for growth within the AlloDerm matrix were also performed. To assess human umbilical vein endothelial cell (HUVEC) sites of attachment to AlloDerm, we incubated HUVEC cells with AlloDerm for a period of 2 weeks and evaluated attachment with anti-factor VIII immunofluorescence. RESULTS: Angiogenic initiation decreased in the combined placental vein with AlloDerm group (P < .0001 at day 7, 14, 21). Additionally, initiation in the AlloDerm plus platelet-poor plasma group was significantly better than the AlloDerm alone group when placentas 2 and 3 were compared (P < .0001). On hematoxylin and eosin staining and immunofluorescent factor VIII staining, no endothelial growth into the AlloDerm was noted in the samples analyzed. CONCLUSIONS: AlloDerm may be enriched with platelet-poor plasma to stimulate greater initiation and wound healing; however, AlloDerm inhibits angiogenic initiation in this model.

The viability of fat grafts harvested with an established technique after cryopreservation remains unknown. This study was conducted in vitro to evaluate the viability of autologous fat grafts harvested with the Coleman technique and subsequently preserved with our preferred cryopreservation method. Eight adult females were enrolled in this study. In each patient, 10 mL of fat grafts were harvested with the Coleman technique by a single surgeon from the lower abdomen. In group 1, 5 mL of fresh fat grafts were mixed with cryoprotective agents and underwent cryopreservation with controlled slow cooling and fast rewarming. In group 2, 5 mL of fresh fat grafts without cryopreservation from the same patient served as a control. The fat graft samples from both groups were evaluated with trypan blue vital staining, glycerol-3-phophatase dehydrogenase assay, and routine histology. Viable adipocyte counts were found similar in both group 1 and group 2 (3.46 +/- 0.91 vs. 4.12 +/- 1.11 x 10/mL, P = 0.22). However, glycerol-3-phophatase dehydrogenase activity was significantly lower in group 1 compared with group 2 (0.47 +/- 0.09 vs. 0.66 +/- 0.09 u/mL, P < 0.001). Histologically, the normal structure of fragmented fatty tissues was found primarily in both groups. Our results indicate that autologous fat grafts harvested with the Coleman technique and preserved with our preferred cryopreservation method have a normal histology with near the same number of viable adipocytes as compared with the fresh fat grafts. However, those cryopreserved fat grafts appear to have a less optimal level of adipocyte specific enzyme activity compared with the fresh ones and thus may not survive well after they are transplanted without being optimized

Large temple and suprabrow lesions can pose a reconstructive challenge. When the lesion extends anterior to the hairline, esthetically acceptable local flaps may be difficult to design. We describe a modified scalp flap (ie, part Converse scalping flap and part scalp rotation flap) that can be tailored to reconstruct a variety of difficult temple and suprabrow lesions while simultaneously maintaining eyebrow position.The modified scalp flap is raised in a subgaleal plane until approximately 2.5 cm above the brow. At this level, dissection proceeds in the subcutaneous plane to protect the frontal branch of the facial nerve and to keep the flap thin. (The key to the modified scalp flap is the dissection plane change that protects the frontal branch of the facial nerve.) The extent of posterior subgaleal dissection is dictated by the amount of anterior rotation necessary. A temporal dog-ear is removed subfollicularly to permit modified flap rotation and preserve the superficial temporal artery.The modified scalp flap has been used to reconstruct temple and suprabrow lesions in 10 patients ranging in age from 4 months to 22 years. There were no complications. Four typical cases are presented.Temple and suprabrow lesions can be excised and successfully reconstructed in one stage using a modified scalp flap that is extended from the hair-bearing scalp onto the glabrous skin of the forehead. This novel modified scalp flap prevents eyebrow/hairline distortion and avoids facial nerve injury