Assessment of the middle mesial canals of mandibular first molars using cone-beam computed tomography: an in vivo study

OBJECTIVE

For a successful root canal therapy, it is necessary to locate all the canals debride and seal them with an inert filling material. The clinician must be aware of the internal morphology and variations in a permanent tooth. Mandibular first molars are widely studied to identify variations in the anatomy of the pulp space. In this study, the primary objective was to measure the distance between the mesiobuccal (MB) and mesiolingual (ML) canals in patients with and without a middle mesial canal (MMC) using cone-beam computed tomography (CBCT). The secondary objectives were to assess the tapering degree of the mesial root and to measure the dentinal thickness in relation to the danger-zone area in patients with and without an MMC.

MATERIALS AND METHODS

A total of 200 CBCT scans were evaluated for the presence of an MMC. Two observers performed the observations, and the results obtained were subject to statistical analyses.

RESULTS

The results revealed the prevalence of MMC was 5%. The average distance between the MB and ML canals was higher when there was an MMC [M(SD) = 3.61 (0.6) vs. 2.69 (0.66)]. However, there were no differences between the groups in the distance to the danger-zone area and the tapering degree of the mesial root. On CBCT images, the MMC was clearly visible 3 mm apical to the level of the cementoenamel junction; beyond 3 mm, the MMC could not be traced.

CONCLUSIONS

Based upon the results of this study, the average distance between the MB and ML canals was higher when there was an MMC. A lesser degree of taper would be preferred to prepare the MMC than to prepare the other canals. It is recommended that careful examination of the canal 3 mm apical to the cementoenamel junction should be carried out when attempting to detect an MMC.

Pulmonary vasodilator effects of norepinephrine during the development of chronic pulmonary hypertension in neonatal lambs

BACKGROUND

This experimental study was performed to determine the effects of norepinephrine on: (i) the pulmonary vascular tone during the development of pulmonary hypertension (PH) in the fetus and (ii) the circulatory adaptation at birth after chronic intrauterine PH.

METHODS

Chronically instrumented fetal lambs were randomized into two groups: (i) a group with PH obtained by antenatal partial ligation of the ductus arteriosus (DA) (n=9) and (ii) a control group without DA ligation (n=6). Pulmonary vascular responses to norepinephrine (1.5 microg min(-1)) were measured in utero 7 days after surgery. At day 8 post-surgery, after delivery, animals were ventilated for 3 h with oxygen 100%. The group with PH was randomly assigned to receive norepinephrine or saline.

RESULTS

Mean pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR) were higher in the PH group (P<0.01). Norepinephrine-induced decrease in PVR was more pronounced in the PH group than in the control group (63 vs 35%, respectively; P<0.01). In the PH group, the decrease in PVR during mechanical ventilation was greater in the animals receiving norepinephrine than in the animal receiving saline (from 1.05 (0.12) to 0.1 (0.02) vs from 1.04 (0.1) to 0.2 (0.04) mm Hg ml(-1) min(-1), respectively; P<0.01). After 3 h of ventilation, mean PVR in the PH lambs treated by norepinephrine was similar to those measured in the control lambs. Aortic pressure was higher in the group treated with norepinephrine.

CONCLUSION

The data suggest that norepinephrine may improve post-natal pulmonary adaptation in the newborn with persistent PH both by increasing systemic vascular pressure and by increasing pulmonary blood flow.

[Gluten enteropathy in children from south-eastern France (author's transl)]

Between 1969 and 1979, 123 cases of gluten-induced enteropathy were diagnosed in south-eastern France. The overall incidence of the disease was estimated at approximately one for 4 600 births. The mean age of the patients was 3.2 years. At the time of diagnosis, 71 children (57,7%) were less than 2 years old, and 52 children (42,3%) were above that age. There was a strong predominance of girls (60%) and North-Africans (48%). Children younger than 2 years presented with the usual malabsorption syndrome, whereas growth retardation, often isolated, was the main feature in older children. The relative increase observed since 1976 in the number of patients of the latter group despite a lower incidence of the disease was probably due to the withdrawal of infants' foods containing gluten. In 58 children followed up dietetic measures resulted in rapid clinical improvement, but healing of the mucosal lesions was much slower (19 months on average). In 28 patients who could be followed for longer periods, reintroducing gluten into the diet regularly led to histological relapse. These patients, however, had been selected for particular reasons. The true incidence of transient intolerance to gliadin is difficult to determine, since most subjects in perfect health refuse control biopsies.