In vivo recalcification of dentin demineralized by citric acid

Abstract— Acid-treatment of root surfaces as an adjunct to pcriodontal reconstructive may have deleterioujs effects on that part of the root which remains in a supragingival location after healing. The peresent experiment aimed to examine whether recalcification of such root surfaces may occur. Cylindrical blocks of root dentin were prepared from 10 premolar, treated with citric acid and mounted in acrylic specimen holders which worn in the mouth continuoulsy for 14 d by two test subjects. The specimens were then sectioned and microradiographs produced. The citric acid had produced a completely demineralized surface zone in the root dentin and the subject hard tissue showed a zone of partially reduced mineral content. Following exposure to the oral cavity, the demineralized surface layer appeared unchanged in width. The subjacent zone, however, had been reduced in width in all instances when compared with control specimens from the same teeth.     

Anti-bacterial effect of citric acid treatment of periodontally diseased root surfaces In vitro

Abstract This investigation examined whether citric acid may exert an anti-bacterial effect against plaque deposits present on root surfaces in vitro. Aerobic and anaerobic blood-agar plate cultures were prepared from plaque samples obtained from the proximal root surfaces of 20 periodontally diseased human teeth following extraction. Ten teeth were exposed to saturated citric acid (pH 1) for 3 min, followed by rinsing in sterile 0.85% saline and plaque samples were then obtained immediately adjacent to those sites sampled initially. Controls consisted of using sterile water instead of citric acid on a further five teeth. The numbers of colonies present on pre- and post-treatment culture plates were counted al 24 h. The results indicated that citric acid application reduced, in all instances, the numbers of colonies grown from post-exposure plaque samples as compared to pre-exposure samples. No colonies were detected in 55% of aerobic and 30% of anaerobic cultures of acid-treated root surface samples. For aerobic cultures, citric acid exposure reduced the number of colonies grown from >10⁴ to <100 in 95% of the root surfaces sampled, while for anaerobic cultures, reduction from >10⁴ to <100 was found in 80% of surfaces sampled. The findings indicate that citric acid exerts anti-bacterial activity against microbial plaque deposits present on periodontally diseased root surfaces in vitro.     

Pulpal response to topical application of citric acid to root dentin

Abstract The purpose of the present study was to investigate the pulpal reactions to citric acid (pH 1.0) applied for 3 min to exposed root dentin. We used 48 roots of 24 maxillary and mandibular third and fourth permanent premolars from dogs divided equally into experimental (citric acid) and control (saline) roots. Following surgical exposure of the buccal root surface and the removal of the cementum with a Gracey curette, citric acid or saline was applied on the exposed dentin. The pulpal reactions were histologically evaluated 1, 7 and 15 days postoperatively using hematoxylineosin stained sections. Results obtained from 43 specimens showed no difference in the pulpal response at any of the observation intervals between citric acid and saline-treated teeth.     

The effect of citric acid application on periodontally involved root surfaces. 1. An in vitro light microscopic study.

This study investigated the effect of citric acid application on periodontally involved root surfaces. Forty periodontally involved teeth were randomly divided into four groups of ten teeth each: no treatment, citric acid treatment, root planing alone, and root planing in conjunction with citric acid treatment. Ten nondiseased, untreated teeth served as controls. After treatment, each tooth was split along its long axis; half was examined under light microscopy and half under scanning electron microscopy (part II of the paper). Light microscopy revealed that the effects obtained by scaling and root planing were not altered after citric acid application. Moreover, the cementum layer was not entirely removed without careful and thorough planing of the root surface. Citric acid application alone had no effect on the diseased root surface. Citric acid did not penetrate the dentinal tubules, nor did it alter the collagen content of the roots obtained by scaling and root planing.     

Pulpal reactions to the application of citric acid to root-planed dentin in beagles

The purpose of this study was to examine histological reactions in the dental pulp incident to the application of citric acid to a root-planed tooth surface. Full thickness flaps were raised and the labial alveolar bone removed over maxillary and mandibular incisor roots in six beagles. The exposed root surfaces were subjected to either superficial or deep root planning. On either the right or left side in each dog, citric acid (pH 1) was applied to the root surfaces for 3 min. The flaps were then repositioned at their original level. Block sections of mandibular teeth were obtained at one week and of maxillary teeth at fifteen weeks after experimental procedures. Histological examination of the short-term specimens showed a reduced width of the predentin corresponding to the instrumented root surface, but no cellular reactions in the odontoblast layer or the pulp. At 15 weeks, varying amounts of reparative dentin had formed in all specimens. More reparative dentin had formed after deep root planing than after superficial, while the difference between acid-conditioned and non-acid conditioned teeth was nonsignificant. The results indicate that root planing may result in the formation of reparative dentin but does not cause inflammatory cellular reactions in the pulp. The application of citric acid to the root planed surface does not significantly change the character of the histological pulpal response.     

In vitro microleakage of dentin adhesives.

This in vitro study measured the microleakage of current dentin bonding agents and glass-ionomer bases. Freshly extracted human molars were prepared to a flat surface, and dentin adhesives and composite resins were applied in a plastic matrix. Samples were stored in water at 37 degrees C, thermocycled, stained with AgNO3, embedded in epoxy resin, and sectioned for evaluation of stain penetration at the composite resin/tooth interface. The reliability index of the dentin adhesives varied significantly between materials. The enamel control had essentially no microleakage, and the aluminum oxalate dentin adhesive on dentin had significantly less microleakage than other dentin adhesives tested. Present dentin adhesives were unable to prevent, but may reduce, microleakage.     

Effects of citric acid on diseased root surfaces

The effect of topically applied citric acid on periodontally diseased root surfaces was evaluated using the scanning (SEM) and transmission (TEM) electron microscopes. Results with the SEM indicate that acid application had no effect on specimens that had not been root planed. After application to root planed surfaces, however, the acid priduced a fiber-like surface with frequent depressions. TEM observations showed that the acid application produced a four micron wide demineralized zone, which was characterized by exposed collagen fibrils. These fibrils seemed to be continuous between the mineralized and demineralized zones of the root.
It appears that the relative success of the citric acid application in periodontal reattachment procedures is realted to the fact that the acid causes exposure of collagen fibrils in the dentin matrix, thus providing a suitable nidus for splicing with new fibrils during the healing process.     

Effect of citric acid treatment on the migration of epithelium on root surfaces in vitro

Explants of bovine gingival mucosa were cultured for four days on scaled and citric acid-conditioned root surfaces. Demineralization of the hard tissue with citric acid exposed the collagenous matrix of the root. Undemineralized islands were frequently seen among the collagen fibers of the treated roots. When cultured on scaled, control root surfaces, the epithelium migrated inwards between the connective tissue of the explant and the root surface. On citric acid-treated roots, epithelial migration in this direction was rare although it was possible. Citric acid treatment of the substratum directed the epithelium to migrate outwards from the explant. Only a few of the controls showed epithelial migration to the outward direction. The findings indicate that demineralization of the root surface has an influence on the direction in which the epithelium initially starts to migrate. An induced delay of epithelial migration between the gingival connective tissue and the hard tissue may be favorable for connective tissue attachment to the root surface.     

In vitro antibacterial effects of the dentin primer of Clearfil Protect Bond.

OBJECTIVES: This study aimed to investigate the antibacterial effects of the dentin primer of a commercially available self-etching adhesive system, Clearfil Protect Bond, which contains antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB). METHODS: Inhibitory effects against Streptococcus mutans, Lactobacillus casei, or Actinomyces naeslundii were examined by an agar-disc diffusion method using the Clearfil Protect Bond primer containing 5% MDPB and an acidic adhesion-promoting monomer MDP, the primer only with MDP, and the primer with 1% cetylpyridinium chloride. The minimum inhibitory/bactericidal concentrations (MIC/MBC) of each primer for the three bacterial species were determined by serial microdilution assays. For testing the bactericidal effects seen in dentin, the primer was applied to demineralized dentin blocks in which S. mutans had been impregnated, and numbers of viable bacteria were counted. RESULTS: For all three bacteria, the sizes of the inhibition zones produced by Clearfil Protect Bond primer were significantly greater than for the other primers (p<0.05, ANOVA and Scheffe's F-test). The MIC/MBC values of Clearfil Protect Bond primer were less than those of the primer without MDPB, and comparable to those of the primer containing cetylpyridinium chloride. No bacterial recovery was obtained after application of Clearfil Protect Bond primer to the bacteria-impregnated dentin, although the primer without MDPB showed some bactericidal effect. SIGNIFICANCE: Clearfil Protect Bond primer has strong antibacterial activity based upon MDPB against S. mutans, L. casei and A. naeslundii, and the capability to disinfect cavities containing residual bacteria.     

High resolution SEM evaluation of dentin etched with maleic and citric acid.

OBJECTIVES: This study evaluated the ultra-morphological effects of maleic and citric acid on human dentin by means of a field emission in-lens scanning electron microscope (FEISEM). Both acids were tested on human dentin at pH 0.7 and 1.4 in aqueous solutions. METHODS: Each of 12 dentin disks were divided into four groups and exposed to either maleic acid at pH 0.7, maleic acid at pH 1.4, citric acid at pH 0.7 and citric acid at pH 1.4. All samples were then fixed and dehydrated in a critical point drying apparatus. Observations were carried out by means of a FEISEM (JEOL 890) after coating with a carbon-platinum film. RESULTS: Both acids removed smear layer and partially removed smear plugs. Details of fine structures measuring from 5 to 15 nm were shown on the intertubular demineralized dentin. Maleic acid at pH 0.7 showed the highest depth of demineralization of all the tested samples; citric acid, showed a higher depth of demineralization values when tested at pH 1.4 than at pH 0.7. SIGNIFICANCE: The FEISEM reveals ultra-structural aspects of the demineralization process of the dentin tissue of the both acids tested. Differences related to the pH of the acids were found. Images obtained at high magnification clarify the dentin collagen structure of both peritubular and intertubular dentin. Small periodic structures associated with collagen fibrils were also imagined.     

In vitro study of remineralization of dentin: effects of ions on mineral induction by decalcified dentin matrix

We examined the effects of various ions on the mineralization of dentin matrix in vitro. Demineralized dentin matrix was incubated in a metastable calcium phosphate solution with or without silicate, fluoride, calcium, phosphate, magnesium or silver. Insoluble dentin matrix induced mineral formation after incubation for 10.2 h in the metastable solution without added ions. Silicate at 5 microM and fluoride at 40 microM significantly reduced the mineral induction time. At least 200 microM calcium or 100 microM phosphate was required to promote mineral induction. Conversely, magnesium and silver concentrations as low as 10 and 2 microM inhibited mineral induction. The mineral induced by each sample after incubation for 24 h was identified by its X-ray diffraction pattern as apatite. We concluded that silicate is a stronger inducer of remineralization of dentin matrix than fluoride, calcium or phosphate, and that magnesium and silver inhibit the induction of remineralization of dentin matrix.     

In vitro shear bond strength of dentin adhesives.

This in vitro study compared the shear bond strengths of current dentin adhesives. Freshly extracted human molars were prepared to a flat surface and treated with dentin adhesives and composite resin light polymerized in a plastic matrix. Completed samples were stored in 37 degrees C water and thermocycled 1,500 times. Samples were sheared at the tooth/composite resin interface using a wire loop. The reliability index varied significantly between materials. Large coefficients of variation were found for all dentin adhesives. One dentin adhesive was able to achieve a bond strength to dentin that was 47% of the control bond strength of enamel.     

Improving bond strength through acid etching of dentin and bonding to wet dentin surfaces.

A bonding system using moisture on the tooth surface can be an enormous benefit as obtaining dentin dryness in the mouth is nearly impossible. The author describes a system that bonds to both wet and dry surfaces.     

Root dentin morphology after different modes of citric acid and tetracycline hydrochloride conditioning.

The purpose of this study was to assess the effect of citric acid and tetracycline HCl application to dentin surfaces by a "passive dripping" or an "active burnishing" technique. Twenty dentin blocks were prepared from freshly extracted non-diseased human impacted third molars. The blocks were root planed and randomly assigned to two groups for treatment with either citric acid or tetracycline HCl. The duration of treatment was 30, 60, 120, or 240 seconds. Control blocks were treated with distilled water. After treatment the blocks were processed for observation and measurements in the scanning electron microscope (SEM). Application of either of the acid solutions resulted in removal of the smear layer. Measurements indicated a time dependent increase in the mean dentinal tubule orifice diameter ranging from 1.05 microns in control specimens to 3.18 microns after 4 minutes treatment (citric acid group). The increase in tubule diameter was significantly greater (P less than or equal to 0.01) for both citric acid treatment modalities than tetracycline HCl treatment. There was also a time dependent increase in the depth of penetration as measured by a trumpeting of the tubule profiles, and this penetration was significantly greater (P less than or equal to 0.01) after citric acid treatments. Passive or active application of the acids did not seem to have any major impact on the measurements or on the surface morphology. It was concluded that citric acid causes more extensive changes than tetracycline HCl and that the mode of application of the agent is probably not critical.     

Induction of cartilage and bone by dentin demineralized in citric acid

The capacity of a roll of dentin demineralized by either 0.6N HCl, pH 1 for 3 minutes or 3 hours, or by 3M (9N) citric acid, pH 1, for 3 minutes, to induce cartilage and bone when implanted in muscle, was investigated. Serial sections of specimens were examined 7, 10, 14. 17, and 21 days after implantation, and randomly selected sections analyzed histomorphometrically. Cartilage was induced on the internal aspect of the citric acid-demineralized dentin roll, but significantly less than that induced after demineralization with HCl. The quantity of bone deposited subsequently did not significantly exceed the amount of cartilage that preceded it in relation to any of the preparations used. The results suggest that citric acid-demineralized dentin induces chondrogenesis and osteogenesis when implanted in muscle, but does so less effectively than does HCl-demineralized dentin, and only within the confines of a microenvironment. It is therefore unlikely that citric acid demineralization of root surface results in induction of cementum by this mechanism.     

Effects of topical fluorides and citric acid on overglazed and autoglazed porcelain surfaces.

The effect of 1.23% acidulated phosphate fluoride, 0.40% stannous fluoride gels, and 2.00% citric acid solution on 150.00 overglazed and 150 autoglazed porcelain surfaces was measured using a profilometer. Application of 1.23% acidulated phosphate fluoride for periods of 16 and 32 minutes caused etching in both groups, but the autoglazed group was significantly more effected. In both groups increase in application time did not affect the amount of etching. No etching was detected in either group after the application of 0.40% stannous fluoride for 6 and 12 hours and 2.00% citric acid for 4 and 8 hours.     

Scanning electron microscopic studies of root dentin surfaces treated with citric acid, elastase, hyaluronidase, pronase and collagenase

The effect of topical application of various enzymes to citric acid-demineralized root surface dentin was evaluated using the scanning electron microscope. All of the enzyme treatments appeared to expose more collagen than demineralization alone. Collagenase application appeared to clear all ground substance from the collagen fibrils and may have hydrolyzed some of the fibrils themselves. The other enzymes appeared to clear partially the intercollagenous ground substance.     

In vitro yeast infection of human dentin

An in vitro model was developed for investigation of Candida albicans penetration into human dentinal tubules. The model consisted of a dentin disc mounted between two cuvettes that each had a circular opening facing the disc. The cuvettes were filled with Tryptic-Soy-Broth, and the pulpal side cuvette was inoculated with C. albicans and incubated at 37 degrees C in air until growth occurred in the uninoculated cuvette or up to 30 days. The system was also used with Enterococcus faecalis. Completely glue-covered dentin specimens served as negative controls. Brown & Brenn-stained histological preparations of the specimens were examined with light microscopy. The time needed before growth occurred in the uninoculated cuvette showed great variation with C. albicans, whereas E. faecalis penetrated within 1 to 5 days of incubation. Slight penetration both by hyphae and yeast cells was observed in specimens inoculated with C. albicans, whereas specimens inoculated with E. faecalis showed deep and effective penetration. This study demonstrates the penetration of dentin as a possible pathway of infection by C. albicans. However, dentin penetration by C. albicans was slow and limited in comparison with E. faecalis.