Robert Woodwards

Catecholamine sensitivity in the rat femoral artery after microvascular anastomosis.

Tissue can demonstrate vasospastic instability after microvascular anastomosis. This study investigates the in vitro effect of increasing concentrations of phenylephrine on the rat femoral artery after microvascular anastomosis. Bilateral groin flaps based on the inferior epigastric artery were raised on 55 Wistar male rats. On the test side, a microvascular anastomosis was performed, but not on the control side. On days 2–12 postoperatively, the rats were sacrificed and the femoral arteries harvested and suspended in increasing concentrations of phenylephrine. The vascular tone on the test and control sides were recorded and compared. Increased sensitivity was found on the test side as compared with the control side (P = 0.000). This supersensitivity to phenylephrine was blocked by the addition of phentolamine and it is believed to be the result of sympathetic denervation, which occurs when the sympathetic fibers are cut during the harvesting of the flap. The resulting vascular instability is believed to contribute to flap failure.

Diamond films grown on cemented WC–Co dental burs using an improved CVD method

Abstract A modified hot-filament chemical vapour deposition system was used to deposit adherent diamond films onto cutting edges of cemented tungsten carbide (WC–Co) dental burs. Generally, the as-grown films were found to be polycrystalline and displayed good coverage. Micro-Raman spectroscopy was used to characterise the stress distribution at three positions: (i) bur tip, (ii) middle of the bur and (iii) end of bur. The stress at the back, in the middle and at the tip of the bur was calculated to be −1.7, −2.3 and −3.4 GPa in compression, respectively. It was noted that the filament temperature, as measured by the two colour optical pyrometer, varied along the coils of the filament. The coiled filament was at higher temperatures around the central region as compared to the filament edges. The temperature of the cutting edges was higher at the tip of the bur compared to the middle and back of the bur. The cutting teeth were closer to the filament and therefore expected to be at a slightly higher temperature. Consequently, a thicker coating was deposited on the edges of the cutting teeth as compared to the flat bur base material.

Fragile histidine triad expression in oral squamous cell carcinoma and precursor lesions

Pupose: Fragile histidine triad (FHIT) expression in precursor oral lesions (POL) and oral squamous cell carcinomas (OSCC) was studied with regard to (a) the frequency of loss of FHIT expression, (b) whether loss of FHIT expression correlates with degree of dysplasia in POLs, (c) whether FHIT loss predicts high-risk POLs that are more likely to transform, and (d) whether FHIT loss in OSCCs correlates with survival. Experimental Design: Ninety-four POLs and 86 OSCCs were immunostained for FHIT. Survival analysis was done for cases with validated clinical outcomes. Results: By optimizing the immunostaining protocol, we found that FHIT is expressed in a distinctive strong nuclear and weak cytoplasmic pattern in oral tissues. Loss of FHIT expression was found in 42 of 94 (45%) POLs and in 66 of 86 (77%) OSCCs. We observed a statistically significant positive correlation between frequency of FHIT loss and increasing grade of dysplasia (χ2 = 13.8; degrees of freedom = 4; P = 0.008). Loss of FHIT expression in POLs that progressed to malignancy was more frequent than in those that did not [17 of 25 (68%) versus 12 of 29 (41.4%), respectively]. This difference was statistically significant (χ2 = 3.8; degrees of freedom = 1; P = 0.046). In OSCCs, loss of FHIT staining indicated a worse prognosis (survival rate, 36.2%) than when positive FHIT staining was observed (survival rate, 50%), but the difference was not statistically significant (P = 0.546, Kaplan-Meier, log-rank). Conclusions: FHIT seems to localize to both nuclear and cytoplasmic domains. FHIT inactivation occurs early in oral carcinogenesis and may be useful molecular marker for progressive dysplastic oral lesions.

Mandibular central mucoepidermoid carcinoma with distant metastasis.

Mucoepidermoid carcinoma is the most common malignant salivary gland tumour. Central mucoepidermoid carcinomas (CMC) are an exceedingly rare subgroup, representing 2-4% of all cases. The authors report on a case of CMC in a patient who presented with trigeminal neuropathy, trismus and distant metastasis. The possible pathogenesis of CMC and criteria for diagnosis are discussed.

Novel diamond-coated tools for dental drilling applications

The application of diamond coatings on cemented tungsten carbide (WC-Co) tools has been the subject of much attention in recent years in order to improve cutting performance and tool life in orthodontic applications. WC-Co tools containing 6% Co metal and 94% WC substrate with an average grain size of 1 – 3 μm were used in this study. In order to improve the adhesion between diamond and WC substrates it is necessary to etch cobalt from the surface and prepare it for subsequent diamond growth. Alternatively, a titanium nitride (TiN) interlayer can be used prior to diamond deposition. Hot filament chemical vapour deposition (HFCVD) with a modified vertical filament arrangement has been employed for the deposition of diamond films to TiN and etched WC substrates. Diamond film quality and purity has been characterized using scanning electron microscopy (SEM) and micro Raman spectroscopy. The performances of diamond-coated WC-Co tools, uncoated WC-Co tools, and diamond embedded (sintered) tools have been compared by drilling a series of holes into various materials such as human tooth, borosilicate glass, and acrylic tooth materials. Flank wear has been used to assess the wear rates of the tools when machining biomedical materials such as those described above. It is shown that using an interlayer such as TiN prior to diamond deposition provides the best surface preparation for producing dental tools.

Wear of Dental Cutting Tools Coated With Nanocrystalline Diamond Coatings

Dental cutting tools have traditionally been made using resin-bonded diamonds that have a tendency to breakdown during drilling operations with the consequent loss of diamonds and resin binder into the patient’s mouth. Recent developments in chemical vapor deposition have made it possible to create binderless diamond cutting tools that are useful for machining and drilling enamel, dentine, amalgam, and cast alloys used for crowns and bridges. The paper compares newly developed tools with conventional tools that are used for orthodontic and maxillofacial operations. The reduction in wear using coated diamond tools is significant.Copyright