Effectiveness and safety of a sonic vibratory endodontic instrument

Abstract An air-driven sonic vibratory handpiece to which specially designed K-type files are attached has been developed. When activated, the root canal instruments will vibrate in a whirling motion, and when moved up and down, will abrade the root canal wall. The sonic system was tested in simulated root canals in plastic blocks and in usage tests in dogs' teeth. Forty-nine roots in 3 dogs were divided into 3 groups. Two of the groups were instrumented with the sonic device under continuous irrigation with 2.5% NaOCl or 15% EDTA. The 3rd group was treated with conventional chemomechanical instrumentation and 2.5% NaOGl. The teeth were then extracted, fixed and split in a longitudinal direction and the root canals examined in the scanning electron microscope. After hand instrumentation and sonic instrumentation using NaOCl for irrigation, the canal wall was covered by a smear layer and dentin chips and occasional tissue remnants were seen. An extraoral fine mist of NaOCl was seen during continuous irrigation with this medicament, causing eye soreness in the operator. Continuous irrigation with EDTA during sonic instrumentation removed the smear layer and gave clean canal walls. The vibratory files appeared safe and size 20 followed curved canals well. The effectiveness of the sonic device was similar to hand instrumentation. It considerably improved the ease and, to some extent, the speed of root canal instrumentation.     

Hypothalamic Na and Ca ions and temperature set-point: New mechanisms of action of a central or peripheral thermal challenge and intrahypothalamic 5-HT, NE, PGE1, and pyrogen

The effects of changes in ambient and central temperature, amines, PGE₁ and pyrogen were investigated with respect to the mechanism of Na⁺−Ca⁺⁺ ratio in the posterior hypothalamus of the unrestrained cat. Guide tubes were implanted bilaterally above the posterior hypothalamic area of 23 cats so as to accommodate push-pull cannulae. After a Na⁺ or Ca⁺⁺ sensitive site was identified by perfusion at 50 μ1/min of an artificial CSF containing 10.4 mM excess Ca⁺⁺ ions or 13.6 mM excess Na⁺ ions, several types of experiments were undertaken with the results summarized as follows: if the cat was exposed to a cold or warm environmental temperature as the posterior hypothalamus was perfused with excess cation, the typical hypothermia was produced by Ca⁺⁺ and hyperthermia by Na⁺ ions. However, if the cat was exposed to peripheral cooling or warming 30 min prior to the perfusion, the fall or rise produced by Ca⁺⁺ or Na⁺ was attenuated or prevented. In other experiments, 1.0 μCi ^{4 5}Ca⁺⁺ was injected in the ion sensitive site in the posterior hypothalamus to label stores of the cation. Raising of ambient temperature caused a retention of ^{4 5}Ca⁺⁺ in this hypothalamic area, whereas a cold environmental temperature enhanced the efflux of ^{4 5}Ca⁺⁺ at the same perfusion site. The magnitude of change in ^{4 5}Ca⁺⁺ efflux depended upon the intensity of the thermal challenge. Similarly, warming of the anterior hypothalamic, preoptic area by means of implanted thermodes caused an immediate diminution in ^{4 5}Ca⁺⁺ efflux in the posterior hypothalamus, whereas cooling of this anterior region augmented the extrusion of ^{4 5}Ca⁺⁺ ions from the posterior area. When substances which produce a temperature change were applied to the same thermosensitive zone, the direction of shift in ^{4 5}Ca⁺⁺ flux in the posterior area corresponded to the signal for heat production or heat loss. That is, the microinjection of 5-HT, PGE₁, or Salmonella typhosa into the anterior hypothalamus enhanced the efflux of ^{4 5}Ca⁺⁺ in the posterior hypothalamus as hyperthermia developed, whereas a similar microinjection of norepinephrine reduced the ^{4 5}Ca⁺⁺ output from the same sites. Finally, locally anesthetizing the cells of the anterior hypothalamus by the nerve blocker, procaine, prevented the cold and heat-induced ^{4 5}Ca⁺⁺ efflux and retention, respectively. These results suggest that if the Na⁴−Ca⁺⁺ ratio in the posterior hypothalamus establishes and maintains the set-point for body temperature of 37°–38°C, the mechanism of lability of Ca⁺⁺ through changes in binding characteristics, transport, or metabolism of the cation serves two purposes: (1) the active defense of the set-point temperature through gradations in ion shifts; and (2) the upward or downward change in set-point value, pathological or normal, triggered by virtue of impulses relayed from the anterior hypothalamus.     

Biomechanical comparison of posterior cruciate ligament reconstruction techniques using cyclic loading tests

Posterior tibial translation (PTT) of the posterior cruciate ligament (PCL) reconstructed-knee under cyclic loading of 1,000 cycles with a 100-N load was compared between four different procedures, including two reconstructions with patellar tendon graft (transtunnel and inlay techniques) and two reconstructions with hamstring tendon graft (Endobutton and EndoPearl techniques) in twelve fresh-frozen human knees. The EndoPearl technique is a direct tendon fixation using biodegradable interference screws and an anchoring device, while the Endobutton technique is an indirect tendon fixation using a titanium button and surgical tape. The change of PTT after cyclic loading in the Endobutton technique was significantly greater than in the other reconstruction technique. No graft rupture at the killer turn or complete pullout from the bone tunnel was found. The advantage of the inlay technique compared to the transtunnel technique with respect to the posterior stability could not be shown in the current study. Posterior laxity of PCL reconstructed-knees with hamstring tendon graft using the Endobutton technique increased more easily than that with patellar tendon graft. For PCL reconstruction using the hamstring tendon graft, anatomical fixation may be preferable to prevent excessive posterior laxity in the early phase of the rehabilitation protocol.     

Delayed intraventricular tension pneumocephalus complicating posterior fossa surgery for cerebellar medulloblastoma

A child is described in whom intraventricular tension pneumocephalus developed 10 days after removal of a cerebellar medulloblastoma and 1 day after suture removal. The tension pneumocephalus was associated with hydrocephalus and CSF leakage from the suture line. The symptoms of the pneumocephalus were rapidly progressing loss of consciousness and hemiplegia which were promptly reversed upon aspiration of the intracranial air. A large amount of intraventricular air present in the immediate postoperative period was, however, clinically silent. The characteristics of this unusual presentation, its relation to asymptomatic pneumocephalus. hydrocephalus and the preventive and therapeutic measures required to deal with such conditions are discussed.     

Histamine-immunoreactive nerve fibers in the rat pineal gland: evidence for a histaminergic central innervation

An immunohistochemical method that utilizes carbodiimide as a fixative and antisera directed against histamine was applied to investigate the location of histamine in the rat pineal complex. Numerous histamine-immunoreactive cell bodies were observed in different subdivisions of the tuberomammillary nucleus of the posterior hypothalamus, and a few cell bodies were present in the posterior and dorsal part of the periventricular hypothalamic nucleus. Histamine-immunoreactive fibers were observed to leave the posterior hypothalamus in various directions of which one dorsally projecting tract was followed in the periventricular area of the caudal diencephalon to the epithalamus. Several histamine-immunoreactive nerve fibers of this tract continued through the posterior commissure directly into the deep pineal gland. A few immunoreactive fibers were also observed in the habenular commissure. In midsagittal sections, histamine-immunoreactive nerve fibers were observed to enter the pineal stalk from the deep pineal gland. Most of histamine-immunoreactive fibers in the stalk continued towards the superficial pineal gland, but their number decreased in more distal locations of the stalk, indicating that some fibers terminate in the stalk as well. A few fibers were found to terminate in the most rostral part of the superficial pineal gland. The immunoreactive nerve fibers in the epithalamus and pineal complex were endowed with prominent varicosities. Taken together, these results indicate that histaminergic nerve fibers, originating from the posterior hypothalamus, project to the pineal complex of the rat. Histamine must therefore be considered a putative neurotransmitter contained in the central innervation of the pineal gland, but its function in pineal physiology has so far not been elucidated.     

Anatomical progression of the Chiari II malformation

To evaluate whether anatomic change of the relationship of the Chiari II malformation and the cranial base was occurring, 22 children with meningomyelocele had serial MRI scans reviewed. A ratio (B/A) was established between the distance from the foramen magnum to the caudalmost portion of herniated cerebellum (B) and the diameter of the foramen magnum (A) and this ratio was compared on serial MRI scans. Eighteen children had an increase in the B/A ratio, two children had a decrease, and two had no change. This indicates that continuous anatomic change of the Chiari II malformation and the skull base is occurring. Clinical deterioration in the older child may be explained by a combination of compressive and traction forces due to this change.     

Full arthroscopic inlay reconstruction of posterior cruciate ligament

We report a full arthroscopic inlay reconstruction technique to avoid the morbidity of traditional open inlay procedure. With the transeptal approach a trough is created arthroscopically at the anatomical tibial insertion of the PCL, which must fit with the patellar bone block of a quadriceps tendon autograft. The bone plug is harvested with two nonabsorbable sutures, each end of which is passed through two holes from the cortical to the cancellous side. The graft is introduced into the knee joint from the posteromedial portal using two traction sutures passed previously through two transtibial tunnels exiting at the middle of the trough. Tibial graft fixation is achieved using the sutures knotted at the anterior aspect of the tibial cortex. Arthroscopic inlay procedure may be a rational surgical alternative because it reduces the crucial steps of an open inlay procedure, such as extensive exposure of the posterior capsule, the need of position change with risk of contamination, longer surgical time, and the risk of bone block fracture if an autograft is harvested. The arthroscopic procedure may also be performed also when hardware presence of previous surgery limits use of the open technique. We initially limited use of this technique to patients: (1) undergoing PCL revision surgery, (2) having hardware from previous tibial surgery, and (3) presenting a PCL lesion following posterior dislocation with previous vascular surgery. The results have been good, and we are now also using this technique for primary PCL reconstruction with favorable results.     

应用几何学计算晶状体后囊撕囊面积的探讨

目的 探讨后囊撕囊面积的理论根据。方法 根据简化眼屈光学原理，应用几何学计算方法进行后囊有效光学区的面积计算。结果 以直径5mm的角膜光学区面积的光线经折射后在后囊上的光斑面积是直径为0．40为mm的范围。结论 结合人工晶状体植入术后有偏心现象认为：后囊撕囊面积直径在1-1．5mm为宜，最大不宜超过2mm，过大的撕囊面积不利于后囊屏障作用的稳定。     

Effectiveness of two different methods for preparing curved root canals

Abstract In this study, the effect of using two different methods for preparing curved root canals of extracted, single-rooted teeth were analyzed with the scanning electron microscope. The instrumentation systems tested were the Canal Master and a standard circumferential filing technique in which conventional K-files were used. Shaping effectiveness was qualitatively evaluated in terms of respect for conservation of the apical constriction and the presence or absence of ledging, specially in the apical third of the root canals. As a result of our observations, it appeared that the Canal Master instrumentation technique provided well-centered and tapered preparations. Conversely, the use of conventional K-files with a standard circumferential filing technique resulted in frequent alterations of the initial pattern of the root canals, showing transportation of the apical foramen and ledge formation.