Accuracy and efficiency of guided root-end resection using a dynamic navigation system: a human cadaver study.

AIM: To determine and compare the accuracy and efficiency of a dynamic navigation system (DNS) with a freehand (FH) technique when conducting root-end resection in a human cadaver model. METHODOLOGY: Forty roots in cadaver heads were included and divided into two groups: DNS (n = 20) and FH (n = 20). Cone beam computed tomography (CBCT) scans of all teeth were taken. The drilling path and depth were planned virtually to using the X-guide software (X-Nav Technologies, Lansdale, PA, USA). Osteotomy and root-end resection were done under navigation in the DNS group, and freehand under the dental operating microscope in the FH group. Post-operative CBCTs were taken. Linear deviations, angular deflection, time of operation and number of mishaps were compared with determine the accuracy and efficiency. Shapiro-Wilk, one-way ANOVA and Fisher exact tests were used (P < 0.05). RESULTS: Linear deviations, angular deflection and operation time were significantly less in the DNS group (P < 0.05). The number of mishaps was not different between the two groups (P > 0.05). Subgroup analyses revealed that the distance of >5 mm from buccal cortical plate was significantly associated with lower accuracy, increased operation time and greater incidence of mishaps in the FH group (P < 0.05), but not in the DNS group. CONCLUSIONS: The dynamic navigation system was more accurate and more efficient in root-end resection in a cadaver model than the freehand technique. The distance of the roots from the buccal cortical plate had a significant negative impact on the accuracy and efficacy of the root-end resection procedure when using the freehand technique. The dynamic navigation system has the potential to be a safe and reliable technological addition to endodontic microsurgery.

Effect of Residual Bacteria on the Outcome of Pulp Regeneration In Vivo.

It is not known to what extent residual infection may interfere with the success of pulp regeneration procedures. The aim of this study was to determine, radiographically and histologically, the effect of residual bacteria on the outcome of pulp regeneration mediated by a tissue-engineered construct as compared with traditional revascularization. Periapical lesions were induced in 24 canine teeth of 6 ferrets. After disinfection with 1.25% NaOCl and triple antibiotic paste, ferret dental pulp stem cells, encapsulated in a hydrogel scaffold, were injected into half the experimental teeth. The other half were treated with the traditional revascularization protocol with a blood clot scaffold. After 3 mo, block sections of the canine teeth were imaged radiographically and processed for histologic and histobacteriologic analyses. Associations between variables of interest were evaluated through mixed effects regression models. There were no significant differences between the 2 experimental groups in radiographic root development ( P > 0.05). There was a significant association between the presence of persistent periapical radiolucency and root wall thickness ( P = 0.02). There was also no significant difference in histologic findings between the 2 experimental groups ( P > 0.05). The presence of residual bacteria was significantly associated with lack of radiographic growth ( P < 0.001). The amount of dentin-associated mineralized tissue formed in teeth with residual bacteria was significantly less than in teeth with no residual bacteria ( P < 0.001). Residual bacteria have a critical negative effect on the outcome of regenerative endodontic procedures.

Hepatic regeneration in the absence of portal viscera.

In an effort to investigate the influence of portal factors on hepatic regeneration in the rat and to clarify glucagon's apparent regulatory role, a rat preparation was developed which was totally devoid of portal viscera and thus deficient in all possible hepatotrophic substances of portal origin. It was found that, following partial hepatectomy, such an eviscerate rat was able to undergo hepatic deoxyribonucleic acid (DNA) synthesis, but the peak DNA synthetic response was significantly delayed by such portal deprivation. As demonstrated by a group of rats with intact portal viscera, but with a portacaval shunt, reduction of blood supply to the hepatic remnant by diversion of portal flow accounted for only a portion of the delay. The remainder of the delay encountered in the eviscerate group was attributed to the deprivation of specific portal substances. Since glucagon supplementation administered to the deficient eviscerate animal restored peak DNA synthesis to the time of its appropriate shunted control, this hepatotrophic substance is a major portal factor modifying the response to partial hepatectomy. Evidence is cited which suggests that glucagon's influence on DNA synthesis is mediated through the formation of cyclic adenosine monophosphate (AMP) and subsequent histone phosphorylation.

The nonportal origin of the factors initiating hepatic regeneration.

To determine the site of origin of the factors that initiate deoxyribonucleic acid (DNA) synthesis in the liver after partial hepatectomy, normal rats were cross-circulated with totally hepatectomized rats. Half of the hepatectomized rats had also undergone excision of all of the portal organs. After 48 hours of cross-circulation, active DNA synthesis and other evidences of hepatic regeneration were found in normal rats cross-circulated with the hepatectomized portally eviscerated rats. This demonstrates that a blood-borne factor that does not arise from the portal organs is capable of initiating hepatic regeneration. When a normal rat was cross-circulated with a hepatectomized rat with the portal organs still present, hepatic regeneration occurred but was significantly less than when the portal organs had been removed. It is postulated that under these experimental conditions portal factors from the normal rat have a permissive role that allows active regeneration when initiating factors are furnished from the hepatectomized rat. Additional portal organs in the hepatectomized rat decreased DNA synthesis, possibly by alterations of the insulin/glucagon ratio.

Major hepatic resections for neoplasia in children.

In a consecutive series from 1968 to 1978, 11 hepatic resections encompassing at least two hepatic segments were carried out for neoplasia in pediatric patients varying in age from 7 days to 14 years. There were no operative deaths. These resections consisted of four right lobectomies, three extended right lobectomies, one right lobectomy with right nephrectomy and inferior vena caval resection, two left lobectomies, and one left extended lobectomy. Diagnoses were hepatoblastoma in six patients, Wilms' tumor invading the liver in two, hemangioendothelioma in two, and malignant mesenchymoma in one. Selective angiography and technetium Tc 99m sulfur colloid scintigraphy were important preoperative aids. Complications were infrequent and there were no major infections or biliary fistulas. There was one death eight months postoperatively due to recurrent hepatoblastoma. Vigorous hepatic regeneration occurred in all instances. Major hepatic resections are well tolerated in children and allow good subsequent development.

Arterial regenerative activity after prosthetic implantation.

Factors modifying arterial regenerative activity were evaluated by replacing adult rabbit aortas with either absorbable polyglycolic acid (PGA) or nonabsorbable Dacron prostheses, 3.5 mm in internal diameter by 24 mm in length, woven to identical specifications including pore size, wall thickness, and elastic modulus, and were followed up for 12 months. At death, 48 PGA and 20 Dacron specimens were studied grossly and by arteriography, light microscopy, scanning and transmission electron microscopy, and by bursting strength determinations. There were no aortic-related deaths or transaortic hemorrhages. Both materials elicited a surrounding inflammatory reaction containing macrophages which transgressed the interstices of only the PGA prostheses. Between two and four weeks, circumferentially oriented smooth-musclelike myofibroblasts proliferated in the PGA inner capsule yielding a neointima 3.2 times thicker than Dacron's. Early ultrastructurally primitive cells progressively differentiated into these smooth-musclelike myofibroblasts. The few myofibroblasts later appearing with Dacron were radially oriented. After one month proliferation stopped in both groups and neointimal thickness became constant. The luminal surface in the PGA group was endothelial-like but was fibrinous in the Dacron group. All specimens withstood saline infusion at three to five times systolic pressure. These studies demonstrate great arterial regenerative potential and suggest hemodynamic and intercellular mitogens controlling it.

Effects of iron and ascorbic acid on acid phosphatases of the enamel organ of rat molars.

Protein extracts from 6- to 11-day-old rat enamel organs were applied to columns of carboxymethyl-52 cellulose. Protein eluted from the columns was assayed for acid phosphatase activity with substrates para-nitrophenylphosphate (p-NPP), beta-glycerolphosphate (beta-GP), ATP and phosphocasein. A weakly-bound peak of activity (A) emerged first which was insensitive to stimulation by iron and ascorbic acid. This enzyme hydrolysed only the phosphomonoester substrates (p-NPP and beta-GP). A strongly bound peak of activity (B) emerged later and was completely separated from the first activity. It hydrolysed all substrates except beta-GP, and was stimulated at least 10-fold by 0.1 mM ferrous ion (Fe2+) in the presence of a strong reducing agent (1.0 mM ascorbic acid). Both substances were more effective as stimulators when used together than they were when each was used separately. Dependency on these co-factors for the development of full activity increased with purification, especially when phosphocasein was substrate. The results were similar for each age of rat used. These properties of enzyme B are parallel with those of the acid phosphoprotein phosphatases of liver and spleen, and the tartrate-resistant acid phosphatase of rat bone. We conclude that enzyme B requires iron and a reducing agent for full activity and has properties that distinguishes it from the classical acid phosphatases (E.C. 3.1.3.2.).

The in vitro assessment of eye irritancy using isolated eyes.

Rabbit eyes were removed and held in temperature-regulated chambers and irrigated with saline. A dose of 0.1 ml of test irritant was applied to each eye (six eyes per test material) and the induced change in corneal thickness measured over a 5-hour period, using a Zeiss photoslit-lamp microscope. A total of sixty materials were assessed and the results graded and compared with in vivo effects. The results show that this in vitro test can be relied upon to provide a rapid, accurate prediction of the irritancy potential in vivo, with a wide range of chemicals and, as such, offers a reliable alternative to the use of live animals.

Epidermoid cysts of the liver.

To the four recorded cases of epidermoid cysts of the liver are added two cases recently seen in children. One was in a 4-yr-old girl and associated with biliary cirrhosis. The other was in a 5-mo-old boy. The former was treated by roux-en-y cystjejunostomy, the latter by enucleation. The origin of these cysts is unknown. One theory suggests derivation from accessory foregut buds. Because of their malignant potential, treatment should be by excision. Where this is impossible, roux-en-y cystjejunostomy offers satisfactory palliation.

Finding funds under your nose with capital raising techniques.

As competition increases and patient utilization and reimbursement decline, financial managers are faced with exhausted debt capacity and increasing needs for capital. It appears to be an impossible situation. However, techniques that create underlying value can be used to raise needed capital without jeopardizing a hospital's debt capacity and credit rating. These techniques--off-balance sheet financing, sale/leaseback of undervalued assets, sale or lease of existing services, and debt restructuring--create additional sources of capital without threatening future debt capacity.