Outcomes of periradicular surgery in cases with apical pathosis and untreated canals.

OBJECTIVE: Surgical management is intended to eliminate or block infection originating in the root canals. The root end is customarily sealed to prevent pathogenic products remaining in the root canal from reaching the periradicular tissues. The purpose of this study was to evaluate the microbiologic and radiographic outcomes of surgical treatment of periradicular pathosis associated with teeth with necrotic pulps. STUDY DESIGN: One tooth from each of 10 patients was root-end resected and root-end filled without prior root canal treatment. One year postoperatively, the outcomes were assessed radiographically and the root canals were sampled for bacteria. RESULTS: Radiographic examination showed complete or incomplete (scar tissue) healing in 5 teeth and uncertain healing in the other 5 teeth. Bacteriologic samples from the root canals were positive in 9 of the 10 cases. CONCLUSIONS: In teeth with necrotic pulps, treatment of periradicular pathosis by surgery and root-end filling may show radiographic evidence of satisfactory healing 1 year postoperatively. However, viable bacteria may persist in the canals, constituting a potential risk factor for recurrence of periradicular pathosis.

Thermal effects and antibacterial properties of energy levels required to sterilize stained root canals with an Nd:YAG laser.

Thermal effects and antibacterial properties of an Nd:YAG laser were studied to establish clinically safe levels of energy to deliver into the root canal and to determine the energy level needed to sterilize infected root canals. The results indicate that lasing cycles of 3 J-s for 15 s followed by a 15-s recovery interval can be continued for prolonged periods without risk of thermal damage to surrounding tissues. In vitro lasing of root canals inoculated with dark stained bacteria showed that two such lasing cycles sterilized only two out of eight canals, whereas when four cycles were used seven out of eight canals were sterilized. Guidelines for energy levels in endodontic Nd:YAG laser work are discussed, and base data for calculating appropriate energy levels are given.

Clinical management of nonhealing periradicular pathosis. Surgery versus endodontic retreatment.

OBJECTIVES: This prospective randomized study compared the outcome of retreatment and surgical intervention in root canal treated teeth with nonhealing periradicular pathosis. STUDY DESIGN: One such tooth from each of 38 patients was randomly allotted to retreatment or root-end resection and root-end filling. Treatment outcome after 1 year was evaluated and compared clinically and radiographically. RESULTS: The success rate for surgery was higher than for conventional retreatment, but the difference was not statistically significant. CONCLUSIONS: For management of nonhealing periradicular pathosis associated with root canal treated teeth, surgical intervention should be considered as an alternative to retreatment. In cases with a similar prognosis for both modes of treatment, the choice should be governed by consideration of intrinsic and extrinsic factors.

Head segmentation in early cambrian fuxianhuia: implications for arthropod evolution.

The arthropod Fuxianhuia from the Chengjiang fauna displays primitive aspects of cephalic segmentation and trunk limb morphology that indicate a basal position within Euarthropoda. The cephalon consists of an eye-bearing sclerite that articulates with a head shield bearing antennules and subchelate appendages. Eye stalks, antennules, and subchelate appendages are proto-, deuto-, and tritocerebral limbs and organs, respectovely. The anterior position of the eye-bearing sclerite parallels the embryonic origin of arthropod eye lobes. The head of Fuxianhuia includes the acron and one somite and is regarded as a protocephalon. The definitive head of arthropods may have fused separate eye-bearing and appendage-bearing sclerites.

A study in vitro of threaded titanium pins used for retrograde obturation of root canals.

The microleakage of four retrograde filling materials was compared in vitro. Fifty-three single rooted teeth were instrumentated and root filled with resin chloroform and gutta-percha. The gutta-percha cones were left extruding from the access opening. All teeth were apicected and retrograde fillings placed. The materials used were a non gamma 2 amalgam (Amalcap), a glass ionomer cement (ChemFil II), threaded titanium pins cemented with a glass ionomer cement (ChemFil II) and identical titanium pins cemented with a silicone material (Adheseal). After removal of the gutta-percha with tweezers, a radioactive isotope solution was placed in the teeth. Extraradicular samples were taken at 3, 7, 28, 77 and 104 days. All retrograde fillings showed some microleakage. The group with titanium pins cemented with silicone showed the least leakage: significantly less than the teeth with glass ionomer cement (P < 0.01) and with amalgam (P < 0.01). No significant differences were found between other groups.

Evidence for monophyly and arthropod affinity of cambrian giant predators.

The Chinese Early Cambrian Chengjiang fauna includes three different anomalocaridids, a globally spread, extinct marine group including the largest known Cambrian animals. Anomalocaridids were active predators, and their presence implies that a complex ecosystem appeared abruptly in the earliest Phanerozoic. Complete specimens display several sets of characters shared only with some other exclusively Cambrian forms. This evidence indicates that anomalocaridids, Opabinia, and Kerygmachela form a monophyletic clade. Certain features indicate arthropod affinities of the lade, and for this group an unnamed (sub)phylum-level taxon within an arthropod (super)phylum is proposed.