ON THE SALIVARY MICROSCRYSTALLIZATION INDEX VARIATION IN PATIENTS WITH DENTAL EROSION LESIONS

Headnote

Abstract

The aim of this study was to evaluate the variation of salivary micro-crystallization saliva index (IMK) in patients with gastroesophageal reflux desease, after utilisation of a remineralization product.

Materials and method. Twelve patients suffering from gastroesophageal reflux were included in the study. Unstimulated saliva was collected in the same day and at the same hour for each patient. A total amount of 0.5 ml of unstimulated saliva was placed on a glass plate, dried for 30 min in a thermostate at +37°C, then analyzed on a Nikon Eclipse E 600 device. The images were saved and stored in a computer. The IMK index was determined using formula: IMK= none of the eye network points projected on crystals/ none of the eye network points projected on the entire saliva drop. All patients were subjected to dental hard tissues remineralization using Recaldent MI Paste (GC Corporation) for 3 weeks, after which the IMK index was determined for each patient. Results. The appearance of crystals formed by saliva precipitation on the plates corresponds to one of these aspects: dendrite-shaped crystals, camomile flower, multiple points, micronetwork, cube or egg-shaped forms. The mean values of the IMK index varied from 0.4 before treatment to 0.9 after remineralization with Recaldent MI Paste.

Conclusions. Recaldent MI Paste increased the remineralization capacity of saliva when applied to patients with gastroesophageal reflux disease.

Keywords: saliva, salivary micro-crystallization index, Recaldent MI Paste, remineralization

1. INTRODUCTION

Dental erosion (DE) is a noncarious dental lesion (NCDL) causing loss of the hard dental tissues (enamel, dentine and cement) following the action of various - behavioural, biological, chemical, mechanical - factors, acting simultaneously, without interference of any bacterial factor. The major pathogenic mechanism implied in the initiation and development of DE is represented by dissolution of hydroxiapatite and tissues demineralization, produced by a prolonged exposure to various extrinsic and intrinsic acids [1]. The most frequently implied extrinsic factors refer to: a high consumption of acid foods and beverages or citric juices, medication with acid pH, or professional exposure in acid environments [2-7]. Enamel dissolution starts when pH decreases under 5.5, whereas dentine dissolution starts when pH decreases under 6.0 [8-11].

The development, evolution and prognostic of DE depend on both frequency and time of acid exposure, and prevention strategies applied. The biological protective factors that can counteract the erosive ones are saliva and the acquired pellicle [12,13]. An efficient salivary support can stop demineralization. Many researches [14,15] recommend the use of remineralisation agents with calcium and fluoride ions. The synergistic action of these three elements appears as the most efficient [16,17]. The actual preventive strategies in DE management include: removal of causal factors, diet advices, oral health education and optimization of salivary parameters.

The mineral content and salivary mucins sustain the remineralisation ability of saliva. Mucins are salivary proteins with role in transepithelial migration of Na+, K+, Cl- ions, as well as in the bio-crystallization ability of saliva. The organic matrix of salivary mucins represents a support for the development of crystals growth. They influence the dimension, form of anorganic deposits and structure of crystals resulted after dehydration of the salivary drop [18,19].

The optical properties of these structures can suffer changes under the action of the external factors intervening in the crystallization process, or as a response to the internal changes in the organism. These saliva features proved to be especially useful in both diagnostic and research [20,21]. The morphological changes of saliva and its micro-crystallization properties can be used to detect the qualitative and quantitative deficiencies of salivary mucin composition, associated to various systemic diseases or intoxications.

Gastroesophageal reflux, (GERD), associated with gastric acid regurgitation and/or chronic vomiting, represents one of the intrinsic factors implied in the debut and development of dental erosions [22-25]. The remineralisation agents can influence the remineralisation potential of saliva and thus counteract the erosive effect specific to GERD patients. Recent studies have proved the anti-erosive effect of a paste with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) [26-29].

The aim of this study is to assess the variations of saliva remineralising potential using the IMK micro-crystallization index after the remineralisation therapy applied to GERD patients.

2. MATERIALS AND METHOD

The study group included 12 patients, recently diagnosed with GERD, without treatment, and dental erosions under treatment in the Dental Clinic of the "M.Kogalniceanu" UMPh of Iasi. The micro-crystallization saliva index (IMK) was assessed at baseline and after 3 weeks of local applications (2 times daily) with MI Paste Plus (GC Corporate), by using the RECALDENT(TM)* technogy, that contains CPPACPF (Casein Phospho Peptide-Amorphous Calcium Phosphate-Fluor). The fluoride content is 0.2% w/w (900 ppm).

The protocol for IMK assessment involves the following steps: unstimulated saliva was collected in a test glass at 12 a.m., after which 0.5 ml of saliva were applied on a microscope slide dried for 30 min (+37°C). The slides were assessed microscopically (with a Nikon Eclipse E 600 device). The digital images were archived with a specific software. The samples were collected at baseline and after 3 weeks of Recaldent MI Paste topical applications. After IMK calculation using a standardised formula, the results were classified into three categories: high, mean, low.

The basic criteria characterising the ability of the oral fluid to mineralise the dental tissues and to form crystals is the dimension of crystal structure, measured by IMK (micro-crystallization saliva index).

(ProQuest: ... denotes formula omitted.)

IMK = 0.6÷1 (high level of micro-crystallization);

IMK = 0.4÷0.6 (mean level of micro-crystallization);

IMK = 0÷0.4 (low level of micro-crystallization).

3. RESULTS

The categories of micro-crystallization are classified as: tree-fern, flake or camomile flower, multiple points, micronetwork, lenticular or cubic structures, banded structures, or combinations (fig.1a, b).

The mean IMK values varied between 0.4 at baseline and 0.9, respectively, after three weeks of treatment with MI Paste Plus (tab.1, fig. 2).

4. DISCUSSION

Continuous demineralisation and remineralisation processes occur on the surfaces of hard dental tissues. Demineralization is associated with the loss of calcium and phosphate ions from the hard dental tissues. The remineralisation mechanisms are stimulated by the presence of high levels of calcium and phosphate ions in saliva [31]. Leus P.A. proved the existence of a correlation between the remineralisation abilities of saliva and the type of structure resulting after the crystallization of saliva drop on a microscope slide [32-34].

For patients with high saliva remineralisation ability, in 93.5% of cases the micro-crystalization had a "tree-fern" aspect with the tendency of distribution from the center towards the external areas of the saliva drop. For patients with low saliva remineralisation ability, in 87% of cases the crystal structure was absent or diffuse, and the saliva contained a few crystals in the visual field, or aciform crystals distributed in the visual field or grouped in the peripheric areas of the saliva drop.

Understanding of these processes requests the analysis of enamel, which is a compact, dense, homogenuous structure built-up by prisms containing 97% calcium and phosphate ions. Each prism contains hundreds of crystals distributed in a specific network and representing different forms of apatite. These crystals have different solubility degrees, the less soluble one being hydroxyapatite. Saliva is a reservoir of calcium and phosphate ions when pH is maintained around 7.0. The remineralisation process decreases when pH decreases under 7.0, and is almost absent when pH = 5.5 (for enamel) and pH = 6.8 (for dentine). The demineralization processes damage and destroy the enamel prisms. The surface layer of enamel becomes more porous, and conditions are created to initiate incipient carious lesions or dental erosion [35,36]. The solution for these pathological changes calls for a regenerative approach, assuming the realization and use of materials containing phosphate calcium and fluoride, characterised by the ability to penetrate deeply into the dental tissues and to restore the affected structure.

In agreement with the results of other researches [14-17], the present study confirms the relation between a constant and efficient supply of minerals (calcium phosphate and fluoride) in saliva and bacterial plaque, and the increase of saliva remineralisation potential associated with arresting of the acid erosive effect. Tricalcium phosphate, amorphous calcium phosphate and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) can successfully carry out this role.

5. CONCLUSIONS

The remineralisation agent MI Paste Plus increases the remineralisation potential of saliva and may be recommended for preventing and counteracting the erosive effect of an acid environment in patients with dental erosions and RGE. The possibility to test the remineralisation ability of saliva, using IMK, represents an important tool for assessing the evolution and success of the treatment. The IMK index, a parameter expressing the remineralisation ability of saliva, can be assessed using a simple, accessible and inexpensive technology.

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