Fast densensitization of tooth roots by topically applied SnF2 and SrCl2 in dogs

Qualitative microanalysis of ions and ultrastructural changes in dentin exposed to laser irradiation and to metal salts solution

BACKGROUND AND OBJECTIVES

This study evaluated the ultrastructural changes in dentin after treatment with the Nd:YAG laser and/or metal salt solutions and verified the presence of Sn++, Sr++, and F- in dentin structure.

STUDY DESIGNS/MATERIALS AND METHODS

Sixty dentin disks were randomly divided into groups (n = 10): (I) control (no treatment), (II) Nd:YAG (1.5 W, 100 mJ, 15 Hz, 125 J/cm2), (III) 10% SnF2 aqueous solution for 30 minutes, (IV) Nd:YAG+10% SnF2 aqueous solution for 30 minutes, (V) 10% SrCl2 toothpaste for 30 minutes, (VI) Nd:YAG+10% SrCl2 toothpaste for 30 minutes. Then, all samples were prepared for scanning electron microscopy (SEM) and the samples from Groups I to IV for the energy dispersive X-ray microanalysis (EDX).

RESULTS

SEM evaluation revealed occluded dentinal tubules and a dentin surface altered by the laser irradiation. The EDX microanalysis revealed Sn++ at a depth of 250 microm in Group IV and not deeper than 100 microm in Group III. In Group V, Sr++ was not deeper than 50 microm, but it could be detected at a depth of 500 microm in Group VI. F- was found only in Group IV.

CONCLUSIONS

Ultrastructural changes caused by laser irradiation can increase dentin uptake of Sn++, Sr++, and F-.

Dentine hypersensitivity: a review

Dentine hypersensitivity is a relatively common pain condition. Local pulpal inflammation, traumatic oral hygiene and dietary habits have been considered in the etiology of dentine hypersensitivity. Dentine hypersensitivity is probably caused by a change in fluid flow in the dentinal tubules, which in turn excites the nerve endings located at the pulp-dentine border. Consequently, treatment success would depend on the prevention of fluid flow across the dentinal tubules (sodium fluoride, stannous fluoride, sodium monofluorophosphate, strontium chloride, sodium citrate, potassium oxalate, and resins/adhesives), or on the desensitization of the nerve endings located at the pulp-dentine border (potassium nitrate). Although a wide variety of treatment methods have been available, clinical data is characterized with ambiguity, warranting further research of the factors which could possibly be implicated in the occurrence of dentine hypersensitivity.

Dentine hypersensitivity: effect of interactions between metal salts, fluoride and chlorhexidine on the uptake by dentine

A large number of compounds may be applied to the teeth for preventive or therapeutic purposes, most notably in dentine hypersensitivity. The uptake of any one compound by tooth substances may clearly be affected by another to produce synergistic, additive or antagonistic effects. This study determined whether uptake interactions occurred between fluoride, chlorhexidine, strontium, tin and zinc. All compounds, in particular tin, showed considerable affinity for dentine. Fluoride reduced the uptake of zinc but not tin, strontium or chlorhexidine. Chlorhexidine increased the uptake of zinc, but not tin, strontium or fluoride. Zinc and tin decreased fluoride uptake but strontium had no such effect. Finally, chlorhexidine uptake was increased by zinc and tin but not by fluoride or strontium. Based on the theories proposed for the reaction of these various compounds with calcified tissues, explanations for the interactions can be made. The results appear relevant to some reported clinical effects of combinations of these compounds and indicate that such interactions may have advantageous or disadvantageous consequences depending on the basis for treatment.

Hypersensitive teeth. Part II: Treatment

If the hydrodynamic theory for pain transmission were accepted, occlusion of the patent dentinal tubules would appear to be essential for treatment efficacy. There are many compounds with seemingly varied chemical forms that have been shown to be effective. Their exact mode of action however, is not clearly defined because well-designed, nonbiased, and controlled comparison studies between agents are lacking. The various toothpastes may have ingredients that actually occlude patent tubules or they may cause secondary desensitization by irrational or abrasive action. In any pain study, the nature of the placebo effect and other psychogenic factors play a significant role. Fluoride preparation with and without iontophoresis has been shown to alter tubule structure and form microprecipitates. The natural desensitization process, although slow, is nature's protection, allowing dentinal sclerosis of secondary dentin formation. Although the resin-adhesive systems, especially the new light-cured dentin bonding agents, appear immediately to be effective, the effect on the pulp remains unknown. Perhaps a combination of iontophoresis with sodium fluoride and light-cured dentin bonding material may yield protection and desensitization at a high level of predictability. With the population trends toward a more geriatric society, further research, knowledge, and understanding of dentinal hypersensitivity is of paramount importance. The expected increase in longevity of the dentition suggests that dentin exposure and sensitivity will increase as a clinical problem. There is a clear time-age relationship involved in gingival recession, erosion and attrition of the teeth, and the need for periodontal surgical therapy. For total comprehensive care, patient comfort is important and should be provided along with sound periodontal health and ideal restorative function.

Fluoride levels in dentin after iontophoresis of 2% NaF

The fluoride in successive layers of dentin (from 3-6 micron were removed per etch) has been measured following topical or iontophoretic application of 2% aqueous sodium fluoride to coronal exposed dentin of freshly extracted human third molar teeth. The fluoride contents of the topical and iontophoresed first etches were, respectively, 12 and 22-31 times greater than that of control (untreated) teeth. Similarly, the fourth etches were 12 and 50-70 times greater, and the seventh (last sampled) etches were 5 and 28-41 times greater. There was no apparent change in acid solubility of the dentin as its fluoride content varied under the conditions of this study. This is the first report studying the fluoride content of extremely thin layers of dentin successively removed by acid etch and relating topical to iontophoretic uptake.

Dentine hypersensitivity--a review. Clinical and in vitro evaluation of treatment agents

A large number of compounds have been employed in the management of dentine hypersensitivity. The symptomatic nature of the condition and its variability poses many problems to any evaluation of effect. Several semi-quantitative methods of response have been used; however, at this time it is uncertain what advantages they hold over the patients' subjective assessment of improvement. A review of the clinical studies reveals that a positive result for every agent tested to date may be found. Nevertheless considerable placebo responses have been obtained and equivocal results are occasionally reported. The fluorides and metal salts, particularly of strontium, have been most studied when used either in solution or delivered in toothpaste formulations. For these compounds the literature contains considerable information concerning the reaction with dental hard tissues which can be extrapolated into hypotheses for the modes of action in relieving dentine hypersensitivity. Moreover, some in vitro studies provide useful information concerning the effects of certain compounds on dentine, and are consistent with the clinical data. Unfortunately, contradictory findings and anomalies between clinical and in vitro effects still prevent the development of a sound clinical basis for the treatment of the condition. Moreover, there is a need to recognise those factors which predispose to dentine exposure, if the prevention of the occurrence or re-occurrence of hypersensitivity is to be achieved.