Citric acid demineralization of cementum and dentin: the effect of the storage medium

The effect varied scanning electron microscopy desiccation techniques has on demineralized dentin

The study objective was to assess (a) the effect of a rubbing-application of ethylenediaminetetraacetic acid (EDTA) or citric acid (CA) has on the ultrastructure of surface dentin and (b) the effect of two scanning electron microscopy (SEM) desiccation preparation techniques have on the collagen surface produced. Treatment regions on proximal root surfaces of extracted human teeth were root planned to expose dentin. Cotton pellets soaked in either 30% CA or 24% EDTA solution were rubbed on the treatment region then processed for SEM using one of two desiccation techniques, that is, (a) critically point dried from liquid CO₂ (control) or (b) air-dried from tetramethylsilane (experimental). Specimens were coated with gold/palladium and viewed/photographed with an SEM. Specimens of the control groups displayed tufted fibrils (CA > EDTA) with many dentin tubules being partially obscured by overhanging fibrils. Air-dried specimens of both treatment groups displayed a flat intact monolayer devoid of a matted meshwork of fibrous collagen. Discrete fibril "sprigs," emanating from the surface monolayer, were characteristic of the EDTA group only. The rubbing-application of EDTA on dentin produces a tufted fibril surface somewhat similar to that produced by CA. Air-drying desiccation of both resulted in marked distortion with fibril collapse/coalescence of the tufted collagen matrix.

Evaluation of different therapeutic Carnoy's formulations on hard human tissues: A Raman microspectroscopy, microhardness, and scanning electron microscopy study

PURPOSE

To evaluate different therapeutic Carnoy's solution formulations on hard human tissues.

MATERIALS AND METHODS

An in vitro study was performed with human teeth (n = 36) and bone fragments (n = 18), randomly divided into two experimental groups (Group I = Carnoy solution with chloroform; Group II = Carnoy solution without chloroform) and a control group (saline solution). The groups were subdivided into pre-conditioning, post-conditioning, and post-conditioning with saline washing. Raman microspectroscopy, Knoop microhardness test, and scanning electron microscopy with energy dispersive X-ray spectroscopy were used.

RESULTS

There was demineralization of dental structures regarding mineral/matrix and carbonate/phosphate ratios (GI versus GII, p < 0.05). The presence of chloroform resulted in a statistically significant reduction of the teeth surface microhardness (p = 0.036), but not exceeding 0.01 μm. Both GI and GII showed significant structural changes by using scanning electron microscopy with energy dispersive X-ray spectroscopy.

CONCLUSION

Carnoy's solution altered the organic and inorganic matrix of the human calcified specimens analyzed in vitro, and its effect was more pronounced when chloroform was present.

The irradiation action on human dental tissue by X-rays and electrons--a nanoindenter study

It is known that ionizing radiation is used in medicine for Roentgen diagnostics and for radiation therapy. The radiation interacts with matter, in particular with biological one, essentially by scattering, photoelectric effect, Compton effect and pair production. To what extent the biological material is changed thereby, depends on the type and the amount of radiation energy, on the dose and on the tissue constitution. In modern radiation therapy two different kinds of radiation are used: high energy X-rays and electron radiation. In the case of head-neck tumors the general practice is an irradiation with high energy X-rays with absorbed dose to water up to 70 Gy. Teeth destruction has been identified as a side effect during irradiation. In addition, damage to the salivary glands is often observed which leads to a decrease or even the complete loss of the salivary secretion (xerostomia). This study shows how the different energy and radiation types damage the tooth tissue. The effects of both, high X-ray energy and high energy electrons, on the mechanical properties hardness and elasticity of the human dental tissue are measured by the nanoindentation technique. We compare these results with the effect of the irradiation of low X-ray energy on the dental tissue.

Effect of tumor therapeutic irradiation on the mechanical properties of teeth tissue

Tumor irradiation of the head-neck area is accompanied by the development of a so-called radiation caries in the treated patients. In spite of conservative therapeutic measures, the process results in tooth destruction. The present study investigated the effects of irradiation on the demineralization and remineralization of the dental tissue. For this purpose, retained third molars were prepared and assigned either to a test group, which was exposed to fractional irradiation up to 60 Gy, or to a non-irradiated control group. Irradiated and non-irradiated teeth were then demineralized using acidic hydroxyl-cellulose gel; afterwards the teeth were remineralized using either Bifluorid12 or elmex gelee. The nanoindentation technique was used to measure the mechanical properties, hardness and elasticity, of the teeth in each of the conditions. The values were compared to the non-irradiated control group. Irradiation decreased dramatically the mechanical parameters of enamel and dentine. In nonirradiated teeth, demineralization had nearly the same effects of irradiation on the mechanical properties. In irradiated teeth, the effects of demineralization were negligible in comparison to non-irradiated teeth. Remineralization with Bifluorid12 or elmex gelee led to a partial improvement of the mechanical properties of the teeth. The enamel was more positively affected by remineralization than the dentine.

Root resorption and its association with alterations in physical properties, mineral contents and resorption craters in human premolars following application of light and heavy controlled orthodontic forces

OBJECTIVES

To study the effect of different orthodontic force levels on cementum, investigating from the point of view of its physical properties, alterations in the mineral components, type and location of the resorption craters and the exploration in 3D of space.

DESIGN

In vivo human premolars subjected to heavy and light forces were employed for this study. After a period of movement they were analyzed for hardness and elasticity. Also, the mineral composition measuring Ca, P and F of the cementum root surface was investigated. A new method for volumetric analysis of resorption craters was developed.

RESULTS

There were no significant differences for hardness and elastic modulus between the light and heavy force groups and no significant effects for different tooth positions. Significant inter-individual variation in the Ca, P and F concentrations was noted. Force-related data showed that mean volume of the resorption crater in light-force group was 3.49-fold greater than the control group, and the heavy-force group 11.59-fold more than control group. The heavy force group had 3.31-fold greater total resorption volume then light force group. Buccal cervical and lingual apical regions demonstrated significantly more resorption craters than the other regions. The 2D measurements were strongly correlated to 3D measurements.

CONCLUSION

The application of light and heavy forces did not show any statistically significant differences in hardness and elastic modulus when compared with untreated teeth. The inconsistent increase or decrease of Ca, P and F contents between control and experimental teeth at sites of compression and tension were difficult to explain. There was more resorption by volume in the heavy force group as compared with the light group and controls. Our data also suggested that the high-pressure zones might be more susceptible to resorption after 28 days of force application.

Physical properties of root cementum: part 2. Effect of different storage methods

This study examined the effect of 5 disinfection and storage protocols over different time periods on the hardness and elastic modulus of human premolar cementum. The sample consisted of 20 first premolars, which were divided into 5 groups of 4 teeth and stored in 1 of the following ways: (1) Miltons solution (1% sodium hypochlorite) for 10 minutes, (2) Miltons solution for 24 hours, (3) 70% alcohol, (4) desiccation, or (5) Milli Q (deionized water, Millipore, Bedford, Mass). Teeth in groups 1 and 2 were initially stored in Milli Q, tested within 6 hours, placed in their respective media, and retested. Groups 3, 4, and 5 were tested within 6 hours, then at 1 month, 2 months, and 3 months after extraction. Group 5 was further studied at 9 months, and 2 teeth in Group 4 were tested at 4 months. The hardness and elastic modulus of cementum was tested with the Ultra-Micro Indentation System (UMIS-2000, Commonwealth Scientific Industrial Research Organization, Australia) on unprepared specimens mounted on a 3-dimensional jig assembly. The results showed that storage in Miltons solution for 10 minutes had no significant effect on the hardness or elastic modulus, whereas storage for 24 hours caused a significant decrease in the hardness of cementum (P =.03). Storage in 70% alcohol for up to 4 months and in Milli Q for up to 9 months had no significant effects. Desiccation caused a significant increase in both the hardness and the elastic modulus from baseline to 3 months (P =.02 and P =.04, respectively), with most changes occurring within the first month. It was concluded that Miltons solution for 10 minutes could be considered an appropriate method for disinfection and removal of periodontal ligament fragments; however, its use for 24 hours should be avoided. Seventy percent alcohol and Milli Q are better storage methods, and desiccation should be avoided.

[Scanning electron microscopy analysis on root surfaces before and after scalling and citric acid and EDTA conditioning: an "in vitro" study]

The most benefic root surface for periodontal regeneration has not been known. Looking for this surface this study used 14 human teeth prepared as testing corpus and treated with scaling and conditioning with citric acid and EDTA, and analysed in scanning electron microscopy. The health teeth surfaces showed regular grains representing broken periodontal ligament fibers by exodontics. The contaminated surfaces showed calculus masses, very porous, and resorption areas. When scalled with hand curettes the surfaces was covered by smear layer. The citric acid conditioning was efficient on smear layer removal, as well as the EDTA gel, and the EDTA liquid solution was not efficient on smear removal.

A study of attached and oriented human periodontal ligament cells to periodontally diseased cementum and dentin after demineralizing with neutral and low pH etching solution

BACKGROUND

This study aimed to evaluate quantitatively the migrated, attached, and oriented human periodontal ligament cells (HPLC) to periodontally diseased cementum and dentin after demineralization with low and neutral pH etching solution.

METHODS

Human teeth, extracted due to periodontal diseases, were scaled and root planed so that cementum remained on one longitudinal half of the root and dentin was exposed on the other half. Forty root slices of 200 microm thickness, obtained from the mid-third of these roots, were divided into four groups: group 1, demineralized with a saturated solution of citric acid (pH 1.20); group 2, with 24% EDTA (pH 7.04); group 3, with tetracycline HCl 100 mg/ml (pH 2.00); and group 4, only scaled and root planed (control). Root slices were placed over the confluent HPLC in 35 mm culture dishes and incubated. Phase contrast microscopic photographs of attached and oriented refractile HPLC to root surfaces were taken at days 1, 3, and 7. Quantitative analysis of attached and oriented HPLC from these photographs was done using special software.

RESULTS

The results showed no significant difference in the attachment and orientation index of HPLC to cementum compared to dentin in any method of demineralization at each time point (P >0.05), although there was a significantly higher cell attachment and orientation index to demineralized dentin with EDTA and citric acid than to non-etched dentin and to all 3 demineralized cementum surfaces compared to non-etched cementum (P<0.05).

CONCLUSIONS

EDTA and citric acid demineralization may enhance HPLC attachment and orientation to the root surface, and it is not always necessary to remove excessive cementum when the demineralizing procedure is used.