Disturbances and defects in enamel development

Prenatal effects by exposing to amoxicillin on dental enamel in Wistar rats

Amoxicillin is an antibiotic widely prescribed; its most frequent side effects are gastrointestinal disorders and hypersensitivity reactions. Over the last 10 years studies have been published which suggest that amoxicillin may cause dental alterations similar to dental fluorosis. Never the less, the results are not conclusive, this is why it was planned the need to make controlled studies on test animals. Objectives: The purpose of this study was to determine the effect produced by amoxicillin prenatal administration on dental enamel in Wistar rats. Study Design: 12 pregnant adult rats were used distributed into five different groups: witness control (n=2) didn’t get any treatment; negative control (n=2) they were prescribed with saline solution; positive control (n=3) they were prescribed with tetracycline 130 mg/kg, and two groups (n=3 and n=2) treated with amoxicillin doses of 50 and 100 mg/kg respectively. The treatments were daily administered by mouth, from the 6th gestation day to the end of gestation. Twenty five days after they were born, the offspring were sacrificed with a sodium pentobarbital overdose, the mandible was dissected and the first lower molars were gotten. The samples were fixed in 10% formaldehyde solution and clinically and histologically observed to determine any enamel disorders. Results: hypomineralization was observed in every single sample of the tetracyclic and amoxicillin treated group 100 mg/kg, meanwhile only 50% from the group administered with 50 mg/kg amoxicillin showed this histological disorder. Conclusions: the side effect caused by amoxicillin on dental enamel was doses dependent.

Key words:Amoxicillin, dental enamel, hypomineralization, Wistar rats.

The macroscopic appearance and associated histological changes in the enamel organ of hypoplastic lesions of sheep incisor teeth resulting from induced parasitism

Twenty-one penned female sheep were infected with a high dose of nematodes (200,000 Trichostrongylus vitrinus and 25,000 Ostertagia circumcincta) during first incisor development when aged 7-8 months. Three sheep were infected with 200,000 T. vitrinus only; 10 sheep were untreated. Anorexia, lassitude and severe diarrhoea were seen in 14 of the infected sheep after 21-26 days. Anthelmintic was given to sheep showing undue distress to end the infection and to all remaining sheep on day 33. Animals were killed at 3 stages: during the infection, at intervals during later tooth development, and at the time of eruption of the incisor teeth, 7-8 months after the parasites were given. Hypoplasia of the labial enamel of 15 out of 19 teeth from sheep killed after recovery from the infection was classified according to the extent and depth as pits, grooves or larger areas of missing enamel with ledge-formation cervically. The amount of missing enamel related to the severity of the systemic disturbance which affected the secretory ameloblasts. During the period of active infection, some secretory ameloblasts showed vacuolization or were shorter than in controls; some cells were no longer adjacent to the organic matrix; some continued to function but abnormally and later became separated from the retained organic matrix by connective tissue. Cervically-placed ledges resulted either from the recovery and resumption of activity of some ameloblasts or from differentiation of new secretory cells after the infection ended.

Dental involvement in congenital chloride diarrhea

Dental involvement in a case of congenital chloride diarrhea (CCD) was studied using light microscopy of decalcified and undecalcified sections, microradiography and TEM. Mixed enamel lesions were found, involving gross hypoplasia at the cuspal level and hypocalcification occurring all over enamel. The hypocalcification resulted in the immature aspect of the prismatic enamel, porosities, amorphous areas, prominent incremental lines and round-ended crystallites. A marked hypocalcification suggests a temporary break of amelogenesis likely related to acute episodes of the disease. Globular calcifications were associated with enamel formation. Dentinal hypocalcification was conspicuous and diffuse all over dentine. A globular mineralization pattern was revealed by the tretracycline (TC) stain which was well preserved in decalcified sections, thus indicating that TC uptake is related to the organic matrix. It is unlikely that TC alone is responsible for the hypocalcified areas which extended widely beyond the TC-stained bands. It is suggested that TC uptake only adds to dental defects induced by the metabolic troubles of CCD.

A histological study of the short-term effects of fluoride on enamel and dentine formation in hamster tooth-germs in organ culture in vitro

First maxillary molars in early stages of secretory amelogenesis were exposed in vitro to fluoride (F-) concentrations ranging between 2.63 microM and 2.63 mM for up to 3 days. In contrast to the dentine papilla, which seemed unaffected by F- in concentrations up to 1.31 mM, the enamel organ was dose-dependently extremely sensitive for F-. Young ameloblasts which became secretory in vitro were in particular sensitive and did not secrete enamel adjacent to new, in vitro-formed dentine. Hypermineralization of the dentine at the enamel-dentine junction suggested that these ameloblasts still transport and deposit minerals. 52 microM was the lowest concentration of F- that inhibited deposition of enamel in the cervical-loop region. Ameloblasts, secretory at the time of exposure to F-, in concentrations of 52 microM up to 1.31 mM secreted an abnormal, amorphous, von-Kossa-negative enamel matrix. 1.31 mM of F- was the lowest concentration which induced the formation of a hypermineralized band in the pre-exposure enamel. 2.63 mM of F- was highly toxic for the enamel organ but had only moderate effects on the dentine papilla.

The production of developmental defects of enamel in the incisor teeth of penned sheep resulting from induced parasitism

Thirty-four sheep were infected with nematode parasites (Trichostrongylus spp. and Ostertagia circumcincta) during central incisor formation. The tooth enamel was examined for defects of mineralization at eruption and compared with that of 14 control sheep. The type and number of parasites given, the duration of the infection and the age of the sheep were varied. Sheep receiving high doses of parasites e.g. 200,000 T. vitrinus + 20,000 O. circumcincta showed severe systemic effects (debilitation, scouring and weight loss) which were of short duration (7-10 days) as the infections were terminated by anthelmintic treatment. Hypoplastic enamel (a break in continuity) was induced in all 5 sheep infected at 8 1/4-9 months of age and demarcated opacities (an alteration in the translucency) in 3 out of 4 sheep infected at 10 months of age. Sheep given 150,000 or 40,000 T. colubriformis showed less obvious systemic effects although the weight loss continued in some sheep for up to 54 days. Although opacities of the enamel in the form of parallel lines, sometimes with localized increase in width or with a diffuse opacity superimposed, were seen by microscopic examination (X 10) of teeth in this group, many of the teeth from the control sheep showed similar lesions. Only the hypoplastic lesions can be attributed with confidence to the experimental manipulations.

The eosinophilic and amyloid-like materials in adenomatoid odontogenic tumor

This paper is concerned with the relationship between eosinophilic material (EM) and amyloid-like material and adenomatoid odontogenic tumors. In duct-like structures between opposing rows of tall columnar cells, EM did not stain for amyloid. Under electron microscopy, EM was composed of fibrillar and granular materials, and the fibrillar material was not amyloid. Two different kinds of EM were found in solid cell masses. Lesions from cases 2, 3, 4 and part of case 1 contained small droplet-shaped EM and these EM did not stain for amyloid. Case 1 also contained EM that stained positively for amyloid. The structure of amyloid positive EM resembled developing enamel of human tooth germs. This material was tubular and finely granular. The tubular material resembled enamel matrix fibers rather then amyloid and the fine granular material was stippled. The cells surrounding EM appeared similar to ameloblasts between secretory and maturation stages.

Structural changes induced by tetracycline in secretory ameloblasts in young rats

The effects of tetracycline hydrochloride (TC) on secretory ameloblasts in mandibular incisors and first molars in young rats were investigated. The pathogenesis of the TC-induced changes was examined in light and electron microscopes 6, 12, 24 and 96 h after a single intraperitoneal injection of a high dose of TC (200 mg TC/kg body wt.) into 4-d-old animals. Secretory ameloblasts from non-injected animals served as controls. Cellular changes were observed in all teeth 6 h after injection. The changes increased with the postinjection period and after 96 h they were so severe that they were considered irreversible. The incipient changes of the ameloblasts comprised altered structure and location of the mitochondria, succeeded by dilated cisternae of endoplasmic reticulum arranged in short curled formations. Later on, distorted Golgi complexes were observed. Secretory granules appeared in various numbers in the Golgi zone and in the Tomes' processes. In severely affected ameloblasts the cell nuclei showed an increased content of chromatin. Autophagic vacuoles and extracellular membrane bound fragments with cellular remnants were frequent, indicating death of some of the ameloblasts. Areas of stippled secretory material were observed along the formative enamel front and in extracellular spaces between the ameloblasts. In the 96-h group calcified bodies with a varying content of crystals were scattered between the cells. Incisors and the molars displayed similar patterns of structural changes of the secretory ameloblasts; however, the changes developed earlier and became more severe in the molars.

Defects of enamel in sheep resulting from trauma during tooth development

Defects of enamel were produced by inserting an instrument into the tooth crypt of developing permanent incisor teeth in sheep. The activity of the labial ameloblasts was deduced from tooth length at the time of trauma. Missing enamel (hypoplasia) resulted when secretory ameloblasts were damaged. Opacities (hypocalcification) followed trauma to the cells in their maturation phase.