Effect of a Ca(OH)2 solution and a chlorhexidine based detergent on the microbial activity of human carious teeth.

Occlusar carious lesions from human molars, preserved in continuous humidity after extraction, were removed using conventional clinical techniques. Bacteriological samples were taken after rinsing the cavity with water only, after experimentally infecting the cavity and after treating uninfected cavities either with a saturated Ca(OH)2 solution or with a chlorhexidine based detergent. The samples were cultivated on blood agar plates aerobically and anaerobically. Cavities rinsed with water only showed very sparce bacterial growth. After experimental infection the growth was significant, but decreased radically after treatment with the test materials. In order to describe the effect of the two test materials on the microbial enzyme activity in infected dentin, cryostat sections of 10 micrometer were prepared from undermineralized carious dentin fragments excavated from freshly extracted human teeth. Conventional histochemical techniques were applied to demonstrate the aminopeptidase activity in the sections using N-L-leucyl-2-naphthylamide as a substrate. The aminopeptidase activity of carious dentin was inhibited totally with the Ca(OH)2 solution, whereas the chlorhexidine based detergent had no effect on the enzyme activity.     

Bacteria in experimentally infected cavity preparations

ABSTRACT— The presence of bacteria on cavity walls was assessed histologically following experimental infection by inserting soft carious human dentin or guttapercha temporary fillings in 40 monkey teeth. Eighty-five infected cavities which had been restored using zinc oxide-eugenol cement (34 teeth), Ca(OH)₂ (39 teeth) or amalgam (12 teeth) were also evaluated. Bacteria could regularly be demonstrated in cavities where soft carious human dentin had remained in the cavities for 82 d, but not, or only very rarely, in any of the other series. It was concluded that vital dentin has considerable resistance against infection and that cavity sterilization appears to be of questionable value.     

Bacteria in experimentally infected cavity preparations.

The presence of bacteria on cavity walls was assessed histologically following experimental infection by inserting soft carious human dentin or guttapercha temporary filings in 40 monkey teeth. Eighty-five infected cavities which had been restored using zinc oxide-eugenol cement (34 teeth), Ca(OH)2 (39 teeth) or amalgam (12 teeth) were also evaluated. Bacteria could regularly be demonstrated in cavities where soft carious human dentin had remained in the cavities for 82 d, but not, or only very rarely, in any of the other series. It was concluded that vital dentin has considerable resistance against infection and that cavity sterilization appears to be of questionable value.     

Tissue-dissolution capacity and dentin-disinfecting potential of calcium hydroxide mixed with irrigating solutions

OBJECTIVE: The goal of this study was to compare the tissue-dissolution potential and antibacterial effectiveness of a conventional Ca(OH)(2)/saline paste with equivalent Ca(OH)(2)/NaOCl and Ca(OH)(2)/chlorhexidine digluconate medications. STUDY DESIGN: Tissue specimens were obtained from freshly dissected pig palates. Tissue pieces of similar form and weight were incubated in air-tight containers with Ca(OH)(2) pastes or solutions proper for up to 7 days. Antimicrobial testing was performed in dentin blocks infected with Enterococcus faecalis. Medicated, sealed dentin specimens were incubated for 1 and 5 days, and bacterial growth was tested at different dentin depths. RESULTS: Up to day 4, the Ca(OH)(2)/irrigating solution mixtures dissolved tissue more effectively than the conventional Ca(OH)(2)/saline paste. After 7 days, however, no statistically significant differences were found between the saline and hypochlorite mixtures, but the Ca(OH)(2)/chlorhexidine medication was significantly less effective. Dentin block disinfection was quicker and more thorough with the Ca(OH)(2)/chlorhexidine or the Ca(OH)(2)/NaOCl than with the Ca(OH)(2)/saline paste. CONCLUSION: Ca(OH)(2)/irrigant mixtures under investigation appear more advantageous than the conventional Ca(OH)(2)/saline mixture, and merit further investigation in a clinical study.     

Antibacterial activity of Propolis versus conventional endodontic disinfectants against Enterococcus faecalis in infected dentinal tubules

Introduction

The antibacterial activity against Enterococcus faecalis of 2 propolis samples was investigated in a dentin block model, and their effectiveness was compared with that of established endodontic disinfectants, chlorhexidine (CHX) and calcium hydroxide [Ca(OH)₂].

Methods

Standardized dentin blocks were infected with E. faecalis ATCC 29212. The root canal space was filled with one of the ethanolic extracts of propolis (Artvin or Tekirda? mix [TM]), CHX 2%, Ca(OH)₂, or ethanol or phosphate-buffered saline for control. Canal dentin was sampled after 1 or 7 days by using a standard-size bur. The dentinal shavings were vortexed vigorously in phosphate-buffered saline, and aliquots were cultured on tryptone soy agar plates. Colonies were counted after 2 days of incubation. Statistical significance was set to 5%.

Results

All experimental agents significantly reduced the number of the cultivable bacteria. CHX was the most potent disinfectant at both times. Compared with the ethanol control, no significant reduction in the number of colonies was found for the propolis extracts at day 1; however, significant reduction was found at day 7. The 2 propolis samples were statistically similar to each other and to Ca(OH)₂, but the TM sample was also similar to CHX at day 7. This has been linked to the greater concentration of flavonoids, a group of antibacterially active compounds, in the TM sample as determined by gas chromatography-mass spectrometry analysis.

Conclusions

The antimicrobial activity of the propolis samples tested in this study was between Ca(OH)₂ and CHX. Both propolis samples were antimicrobially effective; however, their activity did not exceed CHX.     

High microbicidal effect of peroxynitric acid on biofilm-infected dentin in a root carious tooth model and verification of tissue safety

ObjectivesRoot-caries, which frequently occurs in elderly people, is more difficult to treat than caries in a tooth crown, especially in filling restorations. To overcome this difficulty, it is essential to find a strategy for sufficiently sterilizing the infected dentin; however, techniques for sterilizing carious pathogens inside the biofilm, called dental plaque, have not yet been established. Recently, dental applications of plasma sterilization technology have attracted attention. The mechanism of plasma sterilization became clear, and revealed that peroxynitric acid (PNA) is an effective sterilization substance. Highly concentrated PNA solutions can be chemically synthesized in large quantities without using plasma technology. We thought that the application of PNA solution could be a novel treatment for root caries, and examined the microbicidal effect and safety of PNA.MethodsA sterilization experiment was performed using an extracted tooth model infected with Streptococcus mutans. Subsequently, a biofilm of S. mutans and Candida albicans was formed on a plate or a dentin slice, and sterilization experiments were performed in comparison with chlorhexidine. Furthermore, a toxicity test of PNA was performed using an epithelial tissue model.ResultsIn the infection model, sterilization was achieved with a 22 mM PNA solution in only 10 s. In the biofilm model, a 22 mM PNA solution showed a higher microbicidal effect than 2.0% chlorhexidine. In the toxicity test, 2.0% chlorhexidine was toxic, but a 220 mM PNA solution showed no toxicity.ConclusionsPNA is an unprecedented disinfectant that has high microbicidal activity on biofilm and is safe for tissues.     

Application of DIAGNOdent as a guide for removing carious dentin with Er:YAG laser

OBJECTIVES: The purpose of this study was to investigate the DIAGNOdent values applicable as a guide for removal of outer layer of carious dentin with Er:YAG laser. METHODS: Carious dentin of human extracted molars was removed by bur with Caries Detector (Group 1: red stained dentin was left, Group 2: light pink stained dentin was left) and by Er:YAG laser with DIAGNOdent value as a guide (30>Group 3>21, 20>Group 4>11, 10>Group 5). The cavity floor dentin after removing carious dentin was examined using microradiograms, EPMA and SEM. RESULTS: The cavity floor dentin of group 1,3 showed the decreases in the degree of X-ray absorption. In group 2,4 and 5, decrease of Ca, P were not observed. The decrease of Mg was observed on the more superficial part of the cavity floor for group 3 than for group 4. CONCLUSIONS: When carious dentin was removed using Er:YAG laser, the carious dentin outer layer was ideally removed with DIAGNOdent values: 11-20. DIAGNOdent values: 11-20, could indicate the completion of outer layer removal of carious dentin with Er:YAG laser, but there are some problems that must be addressed before the clinical application.     

Mechanism of bioactive molecular extraction from mineralized dentin by calcium hydroxide and tricalcium silicate cement

Objectives

The objective of the present study was to elucidate the mechanism of bioactive molecule extraction from mineralized dentin by calcium hydroxide (Ca(OH)₂) and tricalcium silicate cements (TSC).

Physiological recalcification of carious dentin.

In order to confirm the ability of physiological recalcification of the human carious dentin, the first layer of carious dentin was removed from the symmetric cavities of bilateral pairs of human teeth, disclosing it by 0.5% basic fuchsin-propylene glycol solution staining. One of the pair teeth was immediately extracted and the other was left in the mouth after filling the cavity with polycarboxylate cement. The Ca content and hardness of the remaining second layer immediately and three months after the operation were compared by an electron probe microanalyzer and microhardness tester. They increased markedly after three months returning to the normal level from inside, proving physiological recalcification. A similar experiment was performed by using bilateral pairs of dog teeth with cavities having artificially decalcified dentin floor. After removing the fuchsin-stainable first layer, one of the pair was immediately extracted and the other was left in the mouth for three months after exposing or filling the cavity with various cements. As the Ca content was compared, a marked recalcification of the second layer of softened dentin was observed after three months returning to the normal level from the inside. The effect of different cavity treatment was slight.     

Antibacterial Effect and Bioactivity of Innovative and Currently Used Intracanal Medicaments in Regenerative Endodontics

IntroductionThe purpose of this study was to determine the antibacterial effect and bioactivity of triple antibiotic paste (TAP), calcium hydroxide (Ca[OH]₂), and calcium hypochlorite (Ca[OCl]₂).MethodsRoot canals were infected with 3-week-old Enterococcus faecalis biofilm and then medicated for 7 days with TAP, Ca(OH)₂, or Ca(OCl)₂ (n = 10/group). Untreated and uninfected canals were used as positive and negative controls. The antibacterial effect was determined using colony-forming units and a Live/Dead bacterial viability kit. Dental pulp stem cells were seeded on medicated dentin surfaces for 7 days. Sodium thiosulfate and various concentrations of ascorbic acid (1%, 5%, and 10%) were also used to neutralize the samples treated with Ca(OCl)₂ before cell seeding (n = 3 in triplicate). Cell viability and morphology were evaluated using a viability assay and Live/Dead cell analysis. Alkaline phosphatase (ALP) activity was also measured to determine the cells’ mineralization activity.ResultsAll medicaments decreased the initial bacterial load (P < .05). The highest bacterial reduction in the main canal and dentinal tubules was observed in the Ca(OCl)₂ group (P < .05). TAP- or Ca(OH)₂-treated dentin surface improved cell viability and ALP activity compared with the untreated dentin surface (P < .05), whereas Ca(OCl)₂ decreased cell viability and ALP activity (P < .05). Ten percent ascorbic acid neutralized the effect of Ca(OCl)₂ on the treated dentin surface, showing higher cell viability (P < .05) and similar ALP activity with the untreated dentin surface and the other groups (P > .05).ConclusionsCa(OCl)₂ medication improved root canal disinfection against E. faecalis biofilm compared with TAP and Ca(OH)₂. The adverse effects caused by Ca(OCl)₂ on cell viability and mineralization activity can be neutralized with 10% ascorbic acid.     

In vitro antimicrobial activity of various medication preparations on E. faecalis in root canal dentin

The purpose of this study was to evaluate the antimicrobial activity of several medication preparations in root canal dentin infected with Enterococcus faecalis. Roots of extracted bovine incisors were prepared to standardized cylindrical test specimens, 5 mm in height. The smear layer was removed and the samples were autoclaved and then incubated at 37 degrees C/5% CO2 for 24 h in brain-heart infusion (BHI) broth containing 7.0 x 10(4) colony forming units per ml of E. faecalis. The samples were washed in phosphate buffered saline and mounted to individual culture wells with sticky wax. Test medications were applied to fill the canal lumina; medication groups were: (a) sterile H2O (positive control); (b) a 10% mixture of 1.0 g Ca(OH)2 USP in 10 ml sterile H2O; (c) 10% Ca(OH)2 in 0.12% chlorhexidine gluconate (Peridex); (d) Peridex; and (e) uninoculated BHI (negative control). The samples were incubated at 37 degrees C/5% CO2 for 24 h. Dentin samples for quantitative microbiology were then obtained with consecutive sterile burs (ISO 029, 035, 042). All three experimental groups demonstrated significantly greater antimicrobial activity than the positive control (p < 0.001). Group 2 demonstrated significantly greater antimicrobial activity than Group 3 or Group 4 at all dentin depths (p < 0.05). These results suggest that 10% Ca(OH)2 may be more effective than Peridex or 10% Ca(OH)2 in Peridex for the elimination of E. faecalis from dentin tubules.     

Histological study of an acid red caries-disclosing dye

When 20 extracted teeth were examined histologically after using a 1.0% acid red caries-disclosing dye before excavation of carious dentin, 25% showed the presence of bacteria in the dentin. The use of a solution of 1.0% acid red in propylene glycol to identify infected dentin will greatly decrease but not completely eliminate the changes of viable bacteria remaining in a cavity preparation.     

Calcium hydroxide's association with different vehicles: In vitro action on some dentinal components

OBJECTIVE: Calcium hydroxide, Ca(OH)(2), is a common intracanal medicament. Ca(OH)(2) powder can be mixed with different vehicles and used as a paste for temporary intracanal treatment. The vehicle may influence the dissociation of calcium hydroxide into ions. We sought to evaluate the level of pH and to quantitatively estimate the release of proteins, hydroxyproline, and phosphorus from pieces of radicular dentin kept in different Ca(OH)(2) solutions. STUDY DESIGN: Twenty-eight extracted incisors were maintained for 35 days in Ca(OH)(2) aqueous solutions prepared in chlorhexidine digluconate, propylene glycol (PG), anesthetic solution, camphorated monochlorophenol (CMCP), and CMCP-PG. The control solution contained Ca(OH)(2) without vehicle. RESULTS: The pH values changed little during the experiment. The concentrations of proteins, hydroxyproline, and phosphorus rose for all the solutions under study. Statistical analysis of the data from the control and the experimental groups revealed an increase in the concentration of proteins when chlorhexidine, anesthetic solution, and PG were used; a rise in hydroxyproline levels when CMCP-PG, CMCP, and PG solutions were used; and an increase in phosphorus when PG and chlorhexidine vehicles were used. CONCLUSION: The test solutions with the root dentin remained alkaline. A release of proteins, hydroxyproline, and phosphorus was observed.     

Chlorhexidine increases the longevity of in vivo resin–dentin bonds

Ricci HA, Sanabe ME, de Souza Costa CA, Pashley DH, Hebling J. Chlorhexidine increases the longevity of in vivo resin–dentin bonds. Eur J Oral Sci 2010; 118: 411–416. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The aim of this study was to evaluate the mechanical stability of resin–dentin bonds produced in vivo in the presence of chlorhexidine. Children presenting at least one pair of contralateral primary molars with occlusal carious lesions were enrolled in the study. After cavity preparation and phosphoric acid etching, dentin was treated with 5 μl of either 2% chlorhexidine (control group) or deionized water (experimental group). Thirteen pairs of teeth were restored and were collected after physiological exfoliation. The periods in oral function after restoration were divided as follows: up to 30 d; and 1–5, 10–12, and 18–20 months. Beam‐shaped specimens (0.81 mm²) were obtained and subjected to microtensile bond‐strength testing. A significant decrease of the bond strength was observed in the control group starting at the 1–5 month period (30.6%), while in the experimental group this decrease started only after 10–12 months of function (26.3%). The use of chlorhexidine as an adjuvant to the adhesion to dentin did not produce any detrimental effect to the immediate bond strength and was capable of reducing the rate of resin–dentin bond degradation within the first few months after restoration.     

Partial caries removal in primary teeth: association of clinical parameters with microbiological status

The relationship between clinical characteristics of carious dentin and bacterial colonization after partial caries removal is not completely understood. The aim of this study was to compare microbial counts between categories of carious dentin color, consistency and humidity, and to evaluate the correlation between these characteristics and the presence of cariogenic microorganisms in deep cavities (2/3 or more of the dentin thickness) submitted to partial caries removal. Sixteen primary teeth were submitted to the removal of all carious tissue from the lateral walls of the cavity, whereas carious tissue of the pulp wall was removed superficially. Dentin in the pulp wall was classified according to color, consistency and humidity immediately after cavity preparation and 3-6 months after cavity sealing and a tissue sample was collected on the same occasion for microbiological evaluation. Before sealing, Streptococcus mutans (p = 0.033) and Lactobacillus spp. (p = 0.048) counts were higher in cavities with humid dentin compared to cavities with dry dentin. A negative correlation was observed between carious dentin consistency and S. mutans count during this phase (r(s) = -0.571; p = 0.020). Arrest of dentinal caries lesions was observed after sealing, which was characterized by a reduction of bacterial counts and changes in dentin color, consistency and humidity, irrespectively of baseline dentin characteristics. The clinical characteristics of carious dentin change after the period of cavity sealing and cannot be applied as absolute indicators to limit the excavation of carious dentin when minimally invasive techniques are used.     

An in vitro study of affected dentin as a risk factor for the development of secondary caries

The objective of the study was to investigate the association between the presence of residual caries (inner affected dentin) on the cavity walls of cavity preparations and the further development of secondary caries lesions. Two 2 x 5 x 2 mm cavities, one in the apical portion (A) and one in the cervical portion (C) of the root, were prepared on both the lingual (L) and buccal (B) surfaces of 18 extracted human roots. The apical cavities (AB and AL) were artificially demineralized for 30 min using a decalcifying solution, followed by staining with a caries detector dye and then excavation of irreversibly demineralized dentin, leaving behind a layer of inner carious dentin. The cervical cavities (CB and CL) remained intact with sound dentin on the cavity walls. All cavities were then restored with composite resin. Following restoration, lingual specimens (AL and CL) were completely covered by an acid-resistant varnish to prevent further demineralization. All specimens were then incubated in an in vitro microbial artificial mouth model for 3 days in order to develop secondary carious lesions. At the end of the study all specimens were processed for energy-dispersive X-ray analysis of Ca concentration adjacent to the border between dentin and restoration. Statistical analysis of Ca concentrations revealed that the presence of affected inner dentin does not increase the susceptibility to secondary caries. Therefore, it was concluded that conservative cavity preparations leaving behind affected dentin do not increase the risk of secondary caries development.     

Comparative assessment of time-related bioactive glass and calcium hydroxide effects on mechanical properties of human root dentin

Abstract – Suspensions of micro‐ or nanoparticulate SiO₂‐Na₂O‐CaO‐P₂O₅ bioactive glasses could potentially be used as dressings in traumatized front teeth with open apices as an alternative to Ca(OH)₂. These materials have a disinfecting capacity similar to Ca(OH)₂, but bear the advantage of bioactivity. However, because bioactive glasses initially act as alkaline biocides just as Ca(OH)₂ does, they may also negatively affect mechanical dentin properties over time. This was assessed in the current study using standardized human root dentin bars. Specimens were immersed in 1:20 (wt vol^?1) suspensions of nanometric bioactive glass 45S5 or calcium hydroxide for 1, 10, or 30 days. Control specimens were immersed in pure saline for 30 days (n = 20 per group). Subsequently, modulus of elasticity (E) and flexural strength (FS) of the specimens were determined. Results were compared between groups using one‐way anova and Scheffé’s post‐hoc test. Ca(OH)₂ caused a significant (P < 0.001) 35% drop in mean flexural strength values compared to the control treatment after 10 days. No further change was observed between 10 days and 30 days. Bioactive glass caused a 20% drop in mean flexural strength as compared to the control after 10 days. However, this difference did not reach statistical significance (P > 0.05). No effects of either material on dentin modulus of elasticity values were observed. It was concluded that the calcium hydroxide suspension affected the dentin more than the bioactive glass counterpart; however, the effect was self‐limiting and probably restricted to superficial dentin layers, as suggested by the mere decrease in flexural strength but not in modulus of elasticity values.     

Combined Effect of a Mixture of Silver Nanoparticles and Calcium Hydroxide against Enterococcus faecalis Biofilm

IntroductionThe aim of this study was to evaluate the antibiofilm effectiveness of calcium hydroxide (Ca[OH]₂) mixed with 0.02% silver nanoparticles (AgNPs) in comparison with 1 mg/mL triple antibiotic paste (TAP), Ca(OH)₂, and 0.02% AgNPs against Enterococcus faecalis using confocal laser scanning microscopy.MethodsNinety dentin disks were prepared, sterilized, and inoculated with E. faecalis to establish a 3-week-old biofilm model. The samples received 1 mg/mL TAP, a mixture of Ca(OH)₂ + 0.02% AgNPs, Ca(OH)₂, or 0.02% AgNPs (n = 20/group). Specimens in each group were equally subdivided into 2 groups and incubated for 2 and 4 weeks. Untreated dentin disks (n = 10) were exposed to sterile saline solution and acted as a positive control. Sterile dentin disks (n = 10) were incubated anaerobically in brain-heart infusion broth and served as a negative control. At the end of each observation period, the specimens were stained with LIVE/DEAD BacLight dye (Molecular Probes, Eugene, OR) and analyzed with confocal laser scanning microscopy to determine the proportion of dead cells in the biofilm. Statistical analysis was performed using the generalized linear model repeated measure and Tukey tests (P < .05).ResultsA significantly greater proportion of dead cells was observed in the samples treated with 1 mg/mL TAP (90.39% and 99.41%) and a mixture of Ca(OH)₂ + AgNPs (90.85% and 98.49%) than those in the samples treated with Ca(OH)₂ (76.14% and 91.71%) and AgNPs (62.83% and 88.07%) at 2 and 4 weeks, respectively. A significant difference in the antibiofilm effectiveness was observed among the groups (P < .05), except for 1 mg/mL TAP and the mixture of Ca(OH)₂ + AgNPs (P > .05). All medicaments showed a significant difference in antibiofilm efficacy at the 2 time points.ConclusionsThe mixture of Ca(OH)₂ + AgNPs showed a high antibiofilm effect and was not significantly different from 1 mg/mL TAP. Furthermore, long-term contact between intracanal medicaments and bacterial cells achieved significant antibiofilm efficacy.     

Inhibition of cultivable bacteria by chlorhexidine treatment of dentin lesions treated with the ART technique

The aim of this study was to examine the changes in the cultivable microflora of carious dentin before and after atraumatic restorative treatment (ART) and investigate the inhibitory effect of chlorhexidine-gluconate-based cavity disinfectant in the microflora. Using a split mouth design, 35 primary molar pairs with class II carious lesions in 35 patients (mean age 7.31+/-0.47 years) were selected. The total viable counts (TVC), Streptococcus mutans and lactobacilli were first measured in the center of the infected demineralized lesion and then from the hard dentine after caries removal by the ART technique. Chlorhexidine-gluconate (2%)-based cavity disinfectant was applied to one of the molar pairs and the other molar received no disinfectant treatment. Thereafter, all of the teeth were restored with glass ionomer cement (GIC). Cavities were reassessed after 6 months and again dentine samples were microbiologically investigated. Removal of carious dentine by ART significantly reduced TVC, S. mutans and lactobacilli. After 6 months, application of chlorhexidine exhibited a greater significant reduction in TVC (p=0.013), and a significant reduction in S. mutans compared to the nondisinfected group (p<0.001). A significant reduction in lactobacilli counts was observed in both groups after 6 months, but the difference between the disinfected and nondisinfected groups was not significant (p=0.056). ART was found to be effective in reducing the cultivable microflora and chlorhexidine-gluconate-based cavity disinfectant might serve as a suitable additional agent in inhibiting the residual bacteria in the dentine.     

Effect of Medicaments Used in Endodontic Regeneration Technique on the Chemical Structure of Human Immature Radicular Dentin: An In Vitro Study

IntroductionThe aim of this study was to investigate the effect of 3 intracanal medicaments used in pulp regeneration on the chemical structure of radicular dentin.MethodsHuman immature radicular dentin specimens were exposed to triple antibiotic paste (tripaste), double antibiotic paste (bipaste), calcium hydroxide [(Ca(OH)₂] paste, or deionized water (control) for 1, 2, or 4 weeks. After each time point, specimens were examined with attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy to analyze the relative loss of organic and inorganic components by using phosphate/amide I ratios. Data were analyzed by using analysis of variance followed by post hoc comparisons.ResultsPhosphate/amide ratios were significantly different between the 4 groups at all time points (P < .0001): Ca(OH)₂-treated dentin > untreated control dentin > bipaste-treated dentin > tripaste-treated dentin. For bipaste groups, 4-week treated dentin had significantly lower phosphate/amide I ratios than 1- and 2-week treated dentin (P < .05); however, phosphate/amide I ratios of 1- and 2-week treated dentin did not have a significant difference. For tripaste groups, 4-week treated dentin had a significantly higher phosphate/amide I ratio than 1- and 2-week treated dentin (P < .001), and phosphate/amide I ratio of 1-week treated dentin was significantly higher than that of 2-week treated dentin (P = .04). No significant time effect for Ca(OH)₂-treated dentin or untreated control dentin was found (P > .05).ConclusionsThe results suggested a superficial collagen degradation or demineralization of radicular dentin caused by Ca(OH)₂ or antibiotic pastes, respectively, after 1, 2, or 4 weeks of exposure.