Alf Wennberg

Prevalence and distribution of cervical dentine hypersensitivity in a population in Rio de Janeiro, Brazil

The prevalence, distribution and possible causal factors of cervical dentine hypersensitivity were studied in a population from a Marine Dental Clinic in the city of Rio de Janeiro, Brazil. A total of 635 patients were examined for the presence of cervical dentine hypersensitivity by means of a questionnaire and intraoral tests (air and probe stimuli). There were 157 patients (25%) reporting to have hypersensitive teeth, but only 108 patients (17%) were diagnosed as having cervical dentine hypersensitivity. The prevalence of hypersensitivity was higher among females than males, but this difference was not statistically significant. Most females with hypersensitivity were aged 20-49 and most males were aged 40-59. Incisors and premolars had the highest prevalence of dentine hypersensitivity to air and probe stimuli, while molars had the lowest. The presence and history of dentine hypersensitivity were positively correlated with previous exposure to periodontal treatment. Only a few of the patients who claimed to have dentine hypersensitivity had tried treatment with desensitizing toothpastes or sought professional help.

In Vitro Study of Cellular Influence on 45Ca Uptake in Developing Rat Enamel

An in vitro method was used to study the influence of enamel organ cellular activity on the uptake of 45Ca in the developing enamel of rat molars. Heat killing, inhibition with DNP, or stripping of the enamel organ from the tooth had no apparent effect on 45Ca uptake patterns in maturing enamel. However, uptake in newly secreted enamel matrix was increased.

An in vitro method for toxicity evaluation of water-soluble substances

The purpose of the present investigation was to develop a simple method for the evaluation of reversible and irreversible toxic influences in a cell culture system. A cell monolayer established on the bottom of glass scintillation vials was exposed to a toxic substance (phenol). Changes in the DNA synthesis of the cells were utilized as a criterion of toxic influence, and were measured by recording the incorporation of tritium labelled thymidine using a liquid scintillation technique. The exposure of the cells to phenol caused a marked decrease in the rate of DNA synthesis when the phenol concentration was increased from 0.01 to 0.1%. The decrease in the DNA synthesis could be reversed by maintaining the cells in growth medium for 4 hours after the cell-phenol contact. The degree of reversibility was dependent on the cell-phenol contact time, the phenol concentration, and the cell line used. The simple test procedures and the quick and convenient obtainment of results simplify the assay of large test series and make the method particularly useful for screening tests.

Rate of formation of regular and irregular secondary dentin in monkey teeth.

An in vivo hard-tissue labeling technique was used to study the formation of regular and irregular secondary dentin in thirty-one monkey teeth. The formation of regular secondary dentin averaged 0.8 micrometer per day. No difference was found in the rate of formation of regular secondary dentin and irregular secondary dentin associated with attrition. The formation of irregular secondary dentin following restorative procedures averaged 2.9 micrometers per day. During the first 30 postoperative days less irregular secondary dentin was formed subjacent to deep cavities as compared to shallow ones. This could be the result of an initial injury to the odontoblasts caused by the operative and/or restorative procedures.

Cytotoxicity of corroded gallium and dental amalgam alloys: An in vitro study

The cytotoxicity of one gallium and three different dental amalgam alloys was assessed in a cell culture system. Two evaluation methods were used, the filter method and an extraction method. Before being tested, set specimens of the alloys were stored in 0.9% NaCl solution for 1 and 10 weeks, to corrode. The alloys showed various degrees of cytotoxicity, ranging from mild to marked. Differences were found between the two testing methods, but in most cases no major differences in cytotoxicity were found between the Ga alloy and the amalgams. The results encourage further study and development of the Ga alloy, which is mercury-free.

Screening tests for dental materials

Two screening tests for dental materials are described. One test is an in vitro test using cell culture to determine the general cytotoxic effect of a material. Cell-material contact is obtained by means of millipore filters, and changes in enzyme activity of the cells are used as criteria for cell response. The second test is an in vivo test to determine the local initial tissue response to a material. Nonepithelialized tissue was subjected to the influence of materials for 15 minutes. Changes in enzyme activity of the tissue were used as criteria for tissue response.

A method for evaluation of initial tissue response to biomaterials.

In the present paper an implantation technique is described whereby the effect of the surgical operation is eliminated and initial tissue reactions to materials may be studied. A teflon body was implanted intramuscularly in rabbits. After six weeks the overlaying tissue was excised and the implant removed. An intact, nonepithelialized tissue surface was exposed, which due to the shape of the implant showed three indentations. Materials were placed in the indentations for 15 minutes and the tissue reaction was registered by enzyme histochemical methods. Silicate cement, zinc phosphate cement and a 4% phenol solution caused an inhibition in the dehydrogenase enzyme activity in the tissue subjacent to the indentations. The severity of the tissue reaction, indicated by the width of the inhibition zone, varied among the test materials. Silicate cement caused the widest inhibition zone and the phenol solution the narrowest one. These results correlate well with previous tissue compatibility studies and indicate that the method is applicable for in vivo screening of initial tissue response to biomaterials.

In vivo and in vitro study of 59Fe uptake in developing rat molars.

Autoradiographic methods were used to study 59Fe uptake in vivo in mineralizing tissues of young rats. Localization of 59Fe was observed in the ameloblastic layers of molars. In vitro studies were performed which demonstrated that 59Fe uptake in developing rat molar enamel was limited by the metabolic activity of the cells of the enamel organ.

Simplified technique for culturing of cells on microscope slides.

mi 0c-ter glasses that a-e mouniitedI on microscope sldles aftex tic test ps-oce(dtures. The cells mav also le cultured ini plastic (lislies or in flasks. Oni termination of the test, the bottom of the vessel vsitli the attached cell layer is punicied otxt anid miiouniitedl on slidtes. In a techniique developed bv Bergman (A1c6a Pathol Alicrobio/ .Scard 59:.279-291, 1963) , the cells are cultured lirectlx oni microscope slides in glass in-gs fastenedlto tOeC slides wvith molten xaselitse. This methio(d is suxitable foxhistological or cytochemical studies, hut if iadioautographic techniqlues ale attempteed, thie removal of ihe vaselinie from thie slidles to get the photogiaphic emtulsion to stick onito the glass is laboxiots. lI this ankticle, ani applianice that makes it possil)le to attach rings to glass slides wvithotxt a sticks material ssill he (lescribe(l. Silicone rublxer wsas selecte(d as the ring material. It is tiontoXiC (WVIL.ssACK, MEYER, and SMITH, Bionater Sled Devices Artif Organs 1:543-562, 1973) and so flexible that wvith moderate pressure it xvill gixe sufficienit tightening against a glass slide. The diffex-ent parts of the appliance are shown in the illustration. In a Teflon plate 50 x 25 x 10 mm, three holes (diameter, 12 mm) were dtrilled in such a xway that a 2 x 2-mm rim remained at the upper side. The rubber rings (outer diameter, 12 mm; inner diameter, 10 mm; heigiht, 10 mm) xvere inserted into the hioles and because of the rim, they extended 2 mm from the bottom side. The Teflon plate ivas framed with aluminum bars. To avoid cortosioIn as a result of washing and sterilization procecltires, the aluminum was furnished vith an aniodic coatitng. A microscope slide xvas place(d