Latency of the jaw-opening reflex in the premature, preweaning and adolescent pig (hanford strain miniature pig, Sus scrofa)

The jaw-opening (digastric) reflex was elicited by electrical stimulation of oral mucosa in miniature pigs (Sus scrofa) varying in age from 5 days premature to 101 days post-term. The latency of reflex electromyographic activity varied between 12–14 ms in the most immature animals and 9–11 ms in the oldest animals. The very long-latency digastric responses found in the immature young of nesting mammals were not seen in the relatively precocious young of this species.     

Surgical treatment of severe dysthyroid ophthalmopathy — long-term results

Conservative therapy in cases of severe dysthyroid ophthalmopathy (DO) has not given satisfactory results. Since 1986, 51 patients (99 orbits) with marked DO have been treated by surgical decompression of the orbits.The procedure begins within the upper eyelid. The excision of the excessive skin and subcutaneous tissue is performed and eyelid fat is removed. In order to obtain the correction of the upper eyelid retraction, the levator aponeurosis is divided by 2–3 transverse incisions in its central part and Muller's muscle is sectioned at the level of its tarsal insertion. Through an incision in the lower eyelid, the posterior part of the orbital floor, the lateral orbit wall, as well as the periorbital and intraorbital fat are removed. Through an incision made over the medial margin of the orbit, the ethmoidal part of the medial orbital wall and the retrobulbar fat are removed. The periorbital periosteum should be incised at several sites.After operation all patients showed a significant reduction of exophthalmos (5–11 mm, 7.16 mm on average), significant reduction of intraocular pressure, marked improvement in ocular muscle function, as well as considerable reduction or disappearance of subjective symptoms. There was an improvement in vision in 68% patients who had impaired vision before the operation. There were no cases of subsequent impairment of vision or ocular motility. Mild relapse was recorded in three cases only and only one patient required unilateral reoperation. Strabismus surgery had to be performed in five patients due to unsatisfactory correction of double vision.It can be concluded that this method of orbital decompression gives very good functional and aesthetical long-term results.     

Wear of dental restorative and prosthetic materials in vitro

The aim of this study was to evaluate the wear of some modern materials for fixed crown and bridge restorations and fillings in vitro. Eighteen commercial materials (8 composites, 4 alloys, 4 fa?ade materials, and 2 denture-base resins) were tested. Enamel was used as the control. Test specimens were abraded on abrasion discs under water or in artificial saliva. There was a great variation in the wear rates of the tested materials. The greatest wear was shown by resins used for base material and the smallest by gold and Cr-Co alloys and porcelain. Most of the composites had a wear rate near that of enamel. The wear for amalgam was slightly greater than for most of the composites. When one is using several different materials for reconstructing occlusion, differences in wear resistance should be taken into account.     

Incorporation of magnesium into rat dental enamel and its influence on crystallization

The incorporation of magnesium into the enamel of immature rats was studied by chemical analysis and X-ray diffraction. Magnesium solutions were injected subcutaneously and later intra-orally into growing rats. Increased magnesium was detected in the enamel at the late developmental stage, and a delay in enamel mineralization resulted from increased magnesium uptake. Incisal enamel from the Mg-injected rats had significant line-broadening on X-ray diffraction, characteristic of poorly crystallized enamel.     

Clinical effects of electromagnetic stimulation as an adjunct to periodontal therapy

The clinical effects of electromagnetic stimulation (EMS) on periodontal soft tissues and alveolar bone level were studied among 23 patients. The sides of the arch to receive EMS were randomly selected and exposed for a period of eight weeks following periodontal surgery. The contralateral control sides received surgery only. The electromagnetic signal was a multiple pulse signal with 21 asymmetrical quasirectangular pulses per burst and a burst frequency of 16.9 Hz. The peak magnetic field strength reached 0.46 Gauss. Changes from baseline in clinical attachment level, probing depth, and radiographic alveolar bone level were assessed at six, 12, and 18 months postsurgically. A greater gain of clinical attachment level following EMS was observed only for pockets with initial depth of 1 to 3 mm. There were no consistent differences between test (EMS) and control sides in the change of clinical attachment level or probing depth for pockets deeper than 4 mm. Radiographically, the test sides demonstrated statistically significant gain of alveolar bone level compared with the control sides at six months following surgery. Hereafter, the rates of change were similar in the stimulated and unstimulated sides, and the total gain of alveolar bone level remained greater in the test side throughout the observation period. Within the limitations of this study, it was concluded that electromagnetic stimulation does not promote gains in clinical attachment or alveolar bone level to the extent that it can be recommended as an adjunct to conventional periodontal therapy.     

Radiobiologic risk estimation from dental radiology. Part I. Absorbed doses to critical organs

The aim of the present study was to generate one consistent set of data for evaluating and comparing radiobiologic risks from different dental radiographic techniques. To accomplish this goal, absorbed doses were measured in fourteen anatomic sites from (1) five different panoramic machines with the use of rare-earth screens, (2) a twenty-film complete-mouth survey with E-speed film, long round cone, (3) a twenty-film complete-mouth survey with E-speed film, long rectangular cone, (4) a four-film interproximal survey with E-speed film, long round cone, and (5) a four-film interproximal survey with E-speed film, long rectangular cone. The dose to the thyroid gland, the active bone marrow, the brain, and the salivary glands was evaluated by means of exposure of a tissue-equivalent phantom, fitted with lithium fluoride thermoluminescent dosimeters (TLDs) at the relevant locations.     

An evaluation of a glass ionomer luting agent: pulpal histological response

Pulpal histological response after crown cementation with a glass ionomer luting agent was evaluated and compared with the response to a polycarboxylate cement or a varnish plus zinc phosphate cement. Pulpal histological response was evaluated on teeth that had full crowns cemented with the test luting agents 3, 10, and 56 days after cementation. No statistically significant differences were found in pulpal histological response between the materials tested during all periods. These findings suggest that factors other than pulpal inflammation are contributing to the reported hypersensitivity after cementation associated with glass ionomer luting agents.     

In vivo effects of a SnF2 gel on acid-softened enamel

The purpose of this investigation was to study the intra-oral rehardening of acid-softened enamel and fluoride uptake from SnF2 gel. Bovine enamel slabs were softened with 0.1 mol/L lactate buffer at pH 4.0 for 14 hrs and then mounted in a mandibular removable Hawley appliance. Control slabs were worn for 96 hrs by seven adult males whose teeth were brushed daily with a fluoride-free dentifrice. Test slabs were exposed once/day to 0.4% SnF2 gel. The gel was swabbed onto the slabs for one minute before being replaced in the mouth unrinsed. The natural dentition was brushed 4 X /day with a fluoride-free dentifrice. Microhardness testing was performed after intra-oral exposure (IOE) and after acid-resistance-testing (ART) following immersion in 0.01 mol/L lactate buffer for 24 hrs at pH of 4.0. Fluoride uptake was measured on separate controls, test slabs, and test slabs after ART, with 0.5 mol/L HClO4 etches of from 15 to 60 sec. The F content was measured with a F-ion-specific electrode and the phosphate content by spectrophotometry. Following IOE, microhardness recovery was 35.6% for control and 37.9% for test slabs, and control slabs retained 1.4% resistance to acid, as compared with 18.6% for the test slabs. The F content of control slabs was significantly less than that of SnF2-treated slabs from 5 to 60 micron in depth, and the F content of SnF2-treated slabs after ART was significantly less at depths of from 5 to 35 micron than that of SnF2-treated slabs not exposed to ART. Both control and SnF2 enamel slabs demonstrated rehardening after IOE, but only SnF2-treated enamel retained a significant fraction of that rehardening after ART.     

The use of panoramic radiography in the evaluation of asymptomatic adult dental patients

This article examines the efficacy of panoramic radiography alone and in combination with intraoral films as part of the "full-mouth" radiographic evaluation of asymptomatic dental patients in the diagnosis of dental caries and periodontal disease. Three full-mouth radiographic surveys--the panoramic alone, the panoramic plus posterior bitewing, and the periapical plus posterior bitewing--are compared. Two forms of measurement--comparative and incremental--were used to identify the radiographic survey with the highest single diagnostic yield when measured against the consensus standard. The findings show that the panoramic radiograph alone exhibits very low sensitivities to dental caries, ranging from 0.6% on anterior teeth to 25.6% on premolars. Even when posterior bitewing radiographs are added to the panoramic films, the sensitivities are significantly below those of the full-mouth periapical and bitewing survey. In contrast, the sensitivities of all three radiographic surveys in the diagnosis of periodontal disease are quite high, ranging from 87% to 96%, so that differences are not clinically significant. However, specificities tended to be low for periodontal disease and high for caries. Thus, for dental caries and (to a lesser extent) periodontal disease, the panoramic radiograph was inferior to the full-mouth intraoral series in its ability to correctly detect evidence of the disease.