Chemical aspects on dental hard tissues in primary teeth from preterm infants

Rythén M, Sabel N, Dietz W, Robertson A, Norén JG. Chemical aspects on dental hard tissues in primary teeth from preterm infants. Eur J Oral Sci 2010; 118: 389–395. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci Preterm children with very low birth weight suffer from several neonatal and postnatal complications that may affect the mineralization of teeth. Clinical and morphological studies have shown enamel aberrations in teeth from preterm children. In this study, the chemical composition in enamel and dentin was compared in primary teeth from preterm children and full‐term children, and the relationship between the chemical composition and the morphological appearance was investigated. Enamel and dentin in 17 exfoliated primary teeth, from 14 children with a gestational age below 29 wk, were investigated and compared with 36 exfoliated primary teeth from full‐term children, using X‐ray microanalyses (XRMA). In comparison with the teeth from the controls, the teeth from preterm children had a higher relative value of carbon (C), a lower relative value of calcium (Ca), a lower ratio of calcium/phosphorus (Ca/P) and a lower ratio of Ca/C throughout the outer part of the enamel. In dentin, the relative values for P were higher, and Ca/P ratio was lower, at the dentin–pulp junction. The Ca/P ratio indicated normal hydroxyapatite in the crystals in enamel and dentin. The lower ratio of Ca/C in the bulk and outer part of the enamel indicated more porous enamel.     

Aspects on dental hard tissues in primary teeth from patients with Ehlers–Danlos syndrome

Background.  Ehlers–Danlos syndrome (EDS) is a rare hereditary condition affecting connective tissues and dental hard tissues.
Hypotheses.  Primary enamel and dentine from EDS patients were expected to differ from those of healthy subjects regarding morphology and chemical composition.
Design.  Forty-seven exfoliated primary teeth from 25 patients with EDS were investigated. Morphology was studied using a polarized light microscope, scanning electron microscope, and X-ray microanalysis. Comparisons were made with 36 primary teeth from 36 healthy patients.
Results.  Morphological analysis of enamel in EDS teeth showed a high frequency of postnatally hypomineralized enamel and postnatally located incremental lines, whereas dentine was normal in all patients. Chemical analysis could not reveal any differences between EDS and control patients except for lower content of C and a higher Ca/P ratio in the enamel in the EDS teeth, indicating porous enamel. Regarding dentine, EDS teeth had a lower content of C, and a higher content of Ca, P, and O. Ratios for Ca/C and Ca/O were also higher compared with controls.
Conclusions.  There are several aberrations of booth enamel and dentine in primary teeth from patients with EDS. These could explain the occurrence of both more dental caries and tooth fractures in patients with EDS.     

Microscopic structure of dental hard tissues in primary and permanent teeth from individuals with Prader-Willi syndrome

Objectivesevere tooth wear, in terms of both erosive wear and attrition, is a significant problem in individuals with Prader-Willi syndrome (PWS). The purpose of the present study was to describe the structure of enamel and dentine in primary and permanent teeth from individuals with PWS.Designthirty-two primary and 10 permanent teeth representing 16 individuals with PWS were investigated in the study. The enamel surface was studied using scanning electron microscopy (SEM). The microscopic structure of enamel and dentine was studied using SEM, microradiography and light microscopy.Resultsthe microscopic structure of enamel and dentine was found to be normal with the exception of a slight increase of interglobular dentine (IGD). Severe erosive defects were observed in primary teeth and also in permanent teeth with long exposure to the oral environment.Conclusionthe erosive enamel defects in individuals with PWS seem more related to the factors in the oral environment than to enamel structure which appeared normal. The occurrence of IGD indicate deficient mineralization but is probably of minor clinical significance. Gastro-oesophageal reflux is worthy of further investigation in individuals with Prader-Willi syndrome.     

Porosity of hard dental tissues

The examination of the porosity of hard dental tissues and the Zn-phosphate cement was carried out with the mercury-porosimeter (Carlo Erba, Italy mod. 2000) under the atmospheric pressure of 200 MPA. The accuracy of this method does not permit measurements of the porosity of enamel, more precisely the enamel surface cannot be permeated by mercury. The total volume of opened pores of the examined dentin was considerably high (28 cm3/gr); the main characteristics of dentin porosity are: the prevalence of macropores (2R 200 nm) of which 40% with the diameter between 400 and 2000 nm and 40% with the diameter between 6000 and 150,000 nm the presence of pores with diameter between 50 and 400 nm, and over 100,000 nm was minimal. The specific porosity of dentin was found to be 60% greater in relation to the porosity of cement. In the cement the diameter between 4000 and 30,000 nm was found in the majority of pores (about 52%) and the remaining 48% belonged to the macropore groups. The specific porosity of Zn-phosphate cement was found to be five times greater in relation to the specific porosity of dental cement (0.082 to 0.016 cm3/gr). However, the prevalence of these specimens was that of mezo pores.     

Operating illumination to differentiate dental hard tissues

This in vitro study was designed to evaluate the ability of fluorescent tubes and dental lights to help operators distinguish tissues (fissures), differentiate between tissues (at the dentinoenamel junction or between carious and sound dentin), and distinguish form of a tooth preparation (Class II and Class V cavities). Operators with "normal" color vision ranked the lights in order of preference for each type of specimen. In general, for the fluorescent illuminants, operators preferred lights with high color temperature values and high color rendering index values. A small group of color-blind observers indicated a preference for an illuminant of low color temperature and low color rendering index value. For dental lights, operators preferred a higher color temperature for examining fissures, the dentinoenamel junction, and the cavity preparation. No particular illuminant was preferred for distinguishing between carious and sound dentin. Many observers had difficulty in choosing a preferred dental luminaire.     

Studies on the relationship between dental plaque and the hard tissues of healthy and diseased teeth]

1. Dental plaques were detected in all the teeth under investigation, with the exception of impacted teeth. 2. The appearance of the plaques is regular. They occur chiefly in certain zones of the tooth crown and in retention areas. The film thickness ranges from 10 to 60 mum. 3. No alterations of the structure or of the primary texture of the hard tissues were observed on healthy and periodontally diseased teeth. The plaques infiltrate but slightly into the surface. 4. Carious teeth have a different appearance. The plaques infiltrate more or less deeply. They even penetrate into the macroscopically free zones of the enamel as well as of the dentine. The infiltrate is diffuse, especially in regions where the relationship between mineral and organic constituents is distrubed.     

Preparation of hard dental tissues by aeroabrasive method

The efficiency of aeroabrasive preparation (AAP) of teeth was evaluated by clinical methods and scanning electron microscopy. The authors conclude that the use of AAP should be confined to the treatment of surface and medium caries. Analgesia before AAP is obligatory, except cases with preparation of fissures for preventive hermetization. The use of AAP is absolutely contraindicated in cases of allergic reactions in the patient, dentist, or assistant. Methods for protection of the dentist, assistant, and patient during the use of AAP are discussed.     

Adsorption of antibiotic TA to dental hard tissues

Antibiotic TA (TA) is a wide-spectrum, bactericidal antibiotic produced by Myxococcus xanthus strain TA. It was previously demonstrated that TA binds tightly to soft tissues while retaining its bactericidal activity in the bound form. The present study was undertaken to investigate TA adsorption to dental hard tissues. Slabs of dental tissues that had been cut from periodontally-involved extracted human teeth were treated with TA and then washed in saline with shaking (saline being replaced every 15 minutes). After 30, 60, and 120 minutes of washing, 45, 39, and 27% of the input TA activities were retained on the slabs, respectively. The tooth-bound TA was released slowly into the aqueous medium in active form. Similar experiments with beta-lactam antibiotics resulted in no significant adhesion to the slabs. The study demonstrates that TA binds tightly to dental tissues while retaining its bactericidal properties.