Possible role of tensile stress in the etiology of cervical erosive lesions of teeth

A tensile stress hypothesis for the etiology of idiopathic cervical erosions of human teeth is presented. It is proposed that when occlusion is not ideal, lateral forces cause the teeth to bend. The tensile stresses created during bending disrupt the chemical bonds of the crystalline structures of enamel and dentin. Small molecules may enter between the crystals and prevent the reestablishment of the chemical bonds. As a result, the disrupted tooth structure is more susceptible to loss through dissolution and abrasion and results in the development of the typically wedge-shaped lesions. Patients with lesions typical of hundreds examined by the authors were presented to illustrate the concept. The possible consequences of the proposed hypothesis were discussed. The hypothetical conclusions made in this article will be tested by experimentation.

Surgical judgment in the management of abdominal stab wounds. Utilizing clinical criteria from a 10-year experience

A 10-year retrospective study of patients with stab wounds to the abdomen managed under a protocol of selective management has been performed. Patients were assessed on the basis of clinical presentation and physical examination, with minimal diagnostic studies. Peritoneal lavage was not utilized in the evaluation of the patients. Two hundred and nineteen such patients were identified. One hundred and eleven of these patients were treated nonoperatively. Ninety patients were treated by immediate laparotomy. Eighteen patients, initially observed, underwent delayed laparotomy. One patient, not explored despite clear-cut indications for laparotomy, died of sepsis, emphasizing the need for strict adherence to the stated protocol. The negative or unnecessary laparotomy rate was 7.8%. The false-negative examination rate was 5.5%. Overall mortality rate was 2.3%. The accuracy of careful clinical evaluation and observation is comparable to, or better than, any other method currently available to identify intra-abdominal injuries in patients with abdominal stab wounds. The study suggests that selective management of stab wounds of the abdomen may be safely practiced in a smaller community hospital.

Hepatitis B antigen in infants born to mothers with chronic hepatitis B antigenemia in Taiwan

Hepatitis B antigen (HB Ag) was detected by complement fixation (CF) in serum samples of 7.5% of 1,106 pregnant Chinese women tested in Taipei, Taiwan. HG Ag persisted in all but one of 42 women followed for 1 to 18 months (average, nine months) after delivery, and 27 of the 43 infants (63%) born to those women became antigen-positive. Persistance of the antigen was more common than transient or intermittent antigenemia. Twelve had antigenemia when first tested, while 15 later developed antigenemia, usually during the first six months of life. Only one infant developed antibody to HG Ag (anti-HB Ag), and this occurred after transient antigenemia. The HB Ag was found in two of 32 (6%) fathers, and in 18 of 27 (67%) older siblings. The antigen was more common among siblings of antigen-positive than among those of antigen-negative infants. These findings demonstrate that in Taiwan, infants born to mothers who are asymptomatic carriers of HB Ag commonly become infected by heaptitis B (HB) virus. Exposure of infants near the time of birth may be important maintaining the high, chronic HB Ag carrier rate in Taiwan.

Particle deposition in systems of repeatedly bifurcating tubes

Deposition of half-micron particles from steady inspiratory flows was measured in the daughter branches of the second bifurcations in a symmetric airway model consisting of two successive generations of bifurcation. Two different configurations were studied: (1) both bifurcations in the same plane and (2) the second bifurcation normal to the plane of the first. The results indicate that the deposition in the daughter branches in configuration (2) is relatively uniform, while that in configuration (1) has a distinct second deposition hot spot, in addition to the one at the carinal ridge. The deposition velocities in the branch which has secondary flows in the opposite sense to those in its parent branch are about 50% lower than those in other types of branches. The deposition patterns are consistent with the observed flow profiles in these tubes.

Vertical transmission of hepatitis B antigen in Taiwan

To determine the frequency of vertical transmission of hepatitis B antigen (HB5 Ag) from asymptomatic carrier mothers in Taiwan to their offspring, HB5 Ag was sought by radioimmunoassay and complement fixation. Of 158 babies born to carrier mothers, antigenemia developed in 63; 51 of these antigenemic babies had become antigen positive within the six months of life. Three inter-related factors were found to increase the risk that antigenemia would develop in the infant: a high maternal complement-fixation titer for HB5 Ag: presence of HB5 Ag in the baby's umbilical-cord blood: and antigenemia in siblings. In contrast to previous studies, these findings indicate that vertical transmission from carrier mothers frequently occurs, at least in Taiwan, and may partially explain Taiwan's high prevalence of HB5 Ag.