Comparison of mineral trioxide aggregate and calcium hydroxide for apexification of immature permanent teeth: A systematic review and meta-analysis.

BACKGROUND/PURPOSE: Calcium hydroxide and mineral trioxide aggregate (MTA) are used for inducing a calcific barrier at an open tooth root (apexification). The purpose of this study was to compare the efficacy of calcium hydroxide and MTA for apexification of immature permanent teeth. METHODS: Medline, Cochrane, EMBASE, and Google Scholar were searched until November 24, 2015, using the keywords apexification, permanent teeth, MTA, and calcium hydroxide. RESULTS: Of 216 studies identified, four studies were included. There were no differences in the clinical success rate [pooled odds ratio (OR) = 3.03, 95% confidence interval (CI): 0.42-21.72, p = 0.271], radiographic success rate (pooled OR = 4.30, 95% CI: 0.45-41.36, p = 0.206), or apical barrier formation rate (pooled OR = 1.71, 95% CI: 0.59-4.96, p = 0.322) between calcium hydroxide and MTA groups. The time required for apical barrier formation was significantly less in the MTA group (pooled difference in means = -3.58, 95% CI: from -4.91 to -2.25, p < 0.001). CONCLUSION: While both materials provide similar success rates, the shorter treatment time with MTA may translate into higher overall success rates because of better patient compliance.

Effect of sodium fluoride, ampicillin, and chlorhexidine on Streptococcus mutans biofilm detachment.

We examined the effect of three clinically used antimicrobials on Streptococcus mutans UA159 biofilm detachment under flow conditions. Sodium fluoride (NaF) and chlorhexidine at MIC levels promoted biofilm detachment and inhibited detachment when concentrations were higher than the MIC and reduced detached-cell viability only at high concentrations. Ampicillin at all concentrations tested inhibited detachment and reduced the percentage of viable biofilm-detached cells. All the three antimicrobial treatments reduced biofilm live/dead cell ratios.

Guidelines on the Prevention and Control of Disease in Dental Practice during the Coronavirus Outbreak.

Coronavirus disease 2019 has become a worldwide pandemic that is seriously jeopardising people's health. The National Health Commission and regional health administrations have issued regulations on the prevention and control of coronavirus disease 2019. Dentistry involves many invasive treatments, which differentiates it from other forms of medical practice. The following guidelines were produced by experts from the Stomatological Healthcare Service branch of the Chinese Stomatological Association to prevent the spread of coronavirus disease 2019 in dental clinics. The guidelines are in accordance with the relevant laws and documents from the health administration and range from technical guidelines to advice on how dental treatment should be conducted. Dental institutions can take these suggestions as a reference, based on the current local epidemic situation. It is anticipated that the guidelines will help dental institutions of different sizes to prevent the spread of the epidemic.

Adenovirus-mediated recombinant human bone morphogenetic protein-7 expression promotes differentiation of human dental pulp cells.

Recombinant human bone morphogenetic protein-7 (BMP-7) has been shown to stimulate new reparative dentin formation in animal models. However, little is known about whether BMP-7 could promote the odontoblast-like differentiation and the formation of mineralized nodules in human dental pulp cells. Here, we reported that the infection with adenovirus-BMP-7 (Ad-BMP-7), a BMP-7-expressing adenoviral vector, induced the expression of BMP-7 in primarily cultured human dental pulp cells in the long term with little effect on their proliferation and viability. Importantly, BMP-7 expression significantly increased alkaline phosphatase activity and induced the dentin sialophosphoprotein expression in a dose- and time-dependent manner, suggesting that BMP-7 promoted the odontoblast differentiation. Furthermore, BMP-7 expression stimulated the formation of many mineralized dentin-like calcified nodules. Our data suggest that Ad-BMP-7-mediated BMP-7 expression can promote the differentiation of human pulp cells into odontoblast-like cells and mineralization in vitro, which may provide insight for the design of new gene therapy for the pulp capping in the clinic.

[Immunohistochemical study of the expression of HGF in rat's reparative dentinogenesis].

OBJECTIVE: To investigate the role of hepatocyte growth factor (HGF) in rat's reparative dentinogenesis. METHODS: Reparative dentinogenesis was induced by preparing cavity on the first molar of SD rat. The teeth were collected on the 3rd, 15th, 30th day after the preparation of cavity, respectively. The healthy pulp was used as control. The expression of HGF in different stages of reparative dentinogenesis was detected by immunohistochemical method. The levels of HGF expression were quantitated by measurement of integral optical density (IOD). RESULTS: On the 3th day after cavity preparation, strong expression of HGF in the odontoblast layers and the cytoplasts of dental pulp cells was noted; the IOD value was 8.995+/-0.943. On the 15th day, positive expression of HGF was observed, the IOD value (5.624+/-0.951) was lower than that on the 3th day (P< 0.01). On the 30th day, the HGF expression (IOD 4.073+/-0.127) was found to be weak and similar to the control (IOD 4.279+/-0.348) (P>0.05). CONCLUSION: HGF may play an important role in the early stages of dental pulp repair.

[Effect of root canal curvature on canal length measurement on digital image of human lower mandibular permanent incisor].

OBJECTIVE: To investigate the effect of canal curvature on measured precision in canal length of human lower mandibular permanent incisors imaged by direct digital radiograph. METHODS: With Trophy digital X-ray system, 299 Chinese lower mandibular permanent incisors were selected to take the direct digital X-ray photography in both facial to lingual (L-T) and proximal directions (M-D). Two operators familiar with endodontic knowledge estimated the canal length by means of on-screen DDR with 2-and 3-click measurements. RESULTS: The true canal length of Chinese lower mandibular permanent incisors was (19. 54 +/- 1.62) mm. The tooth root canal length on digital image was overestimated with 3-click measurement (P < 0.05), and the canal length with 2-click measurement was almost similar to the true canal length from the facial-lingual direction X-ray photography (P > 0.05). The less than 1 mm difference between the estimated canal and the true canal length was above 95%. The canal length was underestimated with 2-click measurement as the curvature severity increased. CONCLUSION: Direct digital radiography system is applicable to estimate the canal length in clinic as the accuracy is very good. The curved canal length should be estimated with 3-click measurement.

Effect of Canal Anastomosis on Periapical Fluid Pressure Build-up during Needle Irrigation in Single Roots with Double Canals using a Polycarbonate Model.

Sodium hypochlorite is an effective irrigant for chemical debridement of root canals. However, increasing the intracanal pressure during irrigant delivery may result in irrigant extrusion into the bone and soft tissues surrounding the tooth. Because clinicians often encounter teeth with intracanal communications, the objective of the present study was to examine the effects of canal anastomosis on the generation of periapical fluid pressure at different fluid flow rates and insertion depths. Two similar polycarbonate models were used to simulate a single root with double canals, one containing, and the other without communicating channels between the canals. For both models, periapical pressure increased with increasing irrigant flow rates and insertion depths of a 30-gauge side-venting needle. In the presence of communicating channels, the magnitude of pressure build-up decreased by almost 90% irrespective of the fluid flow rate or needle insertion depth. Pressure reduction in anastomoses-containing roots provides an explanation why pressure generation in single roots is considerably higher. Nevertheless, it is still possible in teeth with canal anastomoses for pressure exceeding the intraosseous pressure to be generated when the fluid flow rate is sufficiently high and when the needle tip is close to the apical terminus.

Potential applications of antimicrobial peptides and their mimics in combating caries and pulpal infections.

Antimicrobial peptides (AMPs) are short cationic host-defense molecules that provide the early stage of protection against invading microbes. They also have important modulatory roles and act as a bridge between innate and acquired immunity. The types and functions of oral AMPs were reviewed and experimental reports on the use of natural AMPs and their synthetic mimics in caries and pulpal infections were discussed. Natural AMPs in the oral cavity, predominantly defensins, cathelicidins and histatins, possess antimicrobial activities against oral pathogens and biofilms. Incomplete debridement of microorganisms in root canal space may precipitate an exacerbated immune response that results in periradicular bone resorption. Because of their immunomodulatory and wound healing potentials, AMPs stimulate pro-inflammatory cytokine production, recruit host defense cells and regulate immuno-inflammatory responses in the vicinity of the pulp and periapex. Recent rapid advances in the development of synthetic AMP mimics offer exciting opportunities for new therapeutic initiatives in root canal treatment and regenerative endodontics. STATEMENT OF SIGNIFICANCE: Identification of new therapeutic strategies to combat antibiotic-resistant pathogens and biofilm-associated infections continues to be one of the major challenges in modern medicine. Despite the presence of commercialization hurdles and scientific challenges, interests in using antimicrobial peptides as therapeutic alternatives and adjuvants to combat pathogenic biofilms have never been foreshortened. Not only do these cationic peptides possess rapid killing ability, their multi-modal mechanisms of action render them advantageous in targeting different biofilm sub-populations. These factors, together with adjunctive bioactive functions such as immunomodulation and wound healing enhancement, render AMPs or their synthetic mimics exciting candidates to be considered as adjuncts in the treatment of caries, infected pulps and root canals.

Expression of toll like receptor 4 in normal human odontoblasts and dental pulp tissue.

The aim of the study was to determine the expression of TLR4 in odontoblasts and the dental pulp. Odontoblasts and pulp tissues were collected from freshly extracted human wisdom teeth. Reverse transcription-polymerase chain reaction and Western blotting were performed to detect TLR4 mRNA and protein expression, respectively. Immunohistochemical staining was used to determine the distribution of TLR4 in odontoblasts and the pulp. Scanning electron microscopy (SEM) was applied to observe the morphology of odontoblasts. It was demonstrated that TLR4 mRNA and protein expressions were both present in cells of odontoblast layer and pulp tissues and that TLR4 expression was distributed in odontoblasts and some pulpal vascular endothelial cells. SEM revealed the integrity of the odontoblast cell-layer and the well-preserved morphology of individual odontoblast cells. These findings suggest that TLR4 expressed in odontoblasts may play an important role in the dental immune defense.

Synthesis and characterization of dimethacrylate monomer with high molecular weight for root canal filling materials.

A new dimethacrylate monomer 9,9'-bis[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)phenyl] fluorene (3) with a molecular weight of 634 was synthesized in 51.4% yield by addition of a glycidyl ether group to 9,9'-bis(4-hydroxyphenyl) fluorene (1) by the reaction of compound 1 with epichlorohydrin, and then introducing the methacrylate moiety by the reaction of the epoxy group with methacrylic acid. The structure of monomer 3 was confirmed by FT-IR, (1)H-NMR, mass spectra and elemental analysis.

Cetylpyridinium chloride mouth rinses alleviate experimental gingivitis by inhibiting dental plaque maturation.

Oral rinses containing chemotherapeutic agents, such as cetylpyridinium chloride (CPC), can alleviate plaque-induced gingival infections, but how oral microbiota respond to these treatments in human population remains poorly understood. Via a double-blinded, randomised controlled trial of 91 subjects, the impact of CPC-containing oral rinses on supragingival plaque was investigated in experimental gingivitis, where the subjects, after a 21-day period of dental prophylaxis to achieve healthy gingivae, received either CPC rinses or water for 21 days. Within-subject temporal dynamics of plaque microbiota and symptoms of gingivitis were profiled via 16S ribosomal DNA gene pyrosequencing and assessment with the Mazza gingival index. Cetylpyridinium chloride conferred gingival benefits, as progression of gingival inflammation resulting from a lack of dental hygiene was significantly slower in the mouth rinse group than in the water group due to inhibition of 17 gingivitis-enriched bacterial genera. Tracking of plaque α and ß diversity revealed that CPC treatment prevents acquisition of new taxa that would otherwise accumulate but maintains the original biodiversity of healthy plaques. Furthermore, CPC rinses reduced the size, local connectivity and microbiota-wide connectivity of the bacterial correlation network, particularly for nodes representing gingivitis-enriched taxa. The findings of this study provide mechanistic insights into the impact of oral rinses on the progression and maturation of dental plaque in the natural human population.

Physiological properties of Streptococcus mutans UA159 biofilm-detached cells.

Biofilm detachment is a physiologically regulated process that facilitates the release of cells to colonize new sites and cause infections. Streptococcus mutans is one of the major inhabitants of cariogenic dental plaque biofilm. This study tested the hypothesis that S. mutans biofilm-detached cells exhibit distinct physiological properties compared with their sessile and planktonic counterparts. Biofilm-detached cells showed a longer generation time of 2.85 h compared with planktonic cells (2.06 h), but had higher phosphotransferase activity for sucrose and mannose (P < 0.05). Compared with planktonic cells, they showed higher chlorhexidine (CHX) resistance and fourfold more adherent (P < 0.05). Increased mutacin IV production in biofilm-detached cells was noted by a larger inhibition zone against Streptococcus gordonii (31.07 ± 1.62 mm vs. 25.2 ± 1.74 mm by planktonic cells; P < 0.05). The expressions of genes associated with biofilm formation (gtfC and comDE) and mutacin (nlmA) were higher compared with planktonic cells (P < 0.05). In many properties, biofilm-detached cells shared similarity with sessile cells except for a higher phosphotransferase activity for sucrose, glucose, and mannose, increased resistance to CHX, and elevated expression of gtfC-, comDE-, and acidurity-related gene aptD (P < 0.05). Based on data obtained, the S. mutans biofilm-detached cells are partially distinct in various physiological properties compared with their planktonic and sessile counterparts.

[Expression of wingless-type MMTV integration site family member 3 in rat dental follicle tissues and cells undergoing osteogenic differentiation].

OBJECTIVE: To investigate the expression of wingless-type MMTV integration site family, member 3 (Wnt3) in rat dental follicles and its protein level in dental follicle cells (DFC) undergoing osteogenic induction and to discuss the effects of Wnt3 on the differentiation of DFC. METHODS: Rats at postnatal days 1, 3, 5, 7, 9, 11 and 13 were executed, then the mandibles were immediately removed and immunohistochemistry was performed to detect the expression of Wnt3 in dental follicles of postnatal rats. The expression and distribution of Wnt3 in DFC were determined by immunofluorescence. Alizarin red-S staining was performed to assess the mineralization of DFC. Western blotting was used to evaluate Wnt3 and ß-catenin protein levels after stimulated by osteogenic medium for 1, 2 and 3 weeks, respectively. RESULTS: Immunohistochemistry revealed that the expression of Wnt3 in rat dental follicles began at day 5 and sustained to day 13. On day 1 and 3, the expression of Wnt3 in dental follicles was negative.Wnt3 was expressed in the cytoplasm of DFC. Alizarin red-S staining indicated that the osteogenic medium stimulated the differentiation of DFC into osteoblastic lineage.Western blotting demonstrated that the Wnt3 protein levels were significantly up-regulated after stimulated with osteogenic medium for 1 weeks compared with the control (2.60 ± 0.04 vs.1.00 ± 0.00, P < 0.05). Then the levels of Wnt3 protein were declined, and at the 3rd week, no significant difference was observed between osteo-induced group and the control (1.00 ± 0.05 vs.1.00 ± 0.00, P > 0.05). The levels of ß-catenin were increased in osteo-induced groups compared with the control (1.95 ± 0.05 vs.1.00 ± 0.00, P < 0.05; 9.77 ± 0.65 vs.1.00 ± 0.00, P < 0.05;1.75 ± 0.21 vs.1.00 ± 0.00, P < 0.05). Furthermore, the expression of ß-catenin reached to a peak on the 2nd week (9.77 ± 0.65), and then declined. CONCLUSIONS: Wnt3 was expressed in the rat dental follicles both in vivo and in vitro and up-regulated during early phase of osteoblast differentiation in DFC.Wnt3 may be involved in early phase of osteoblast differentiation.

Effect of sodium ascorbate on degree of conversion and bond strength of RealSeal SE to sodium hypochlorite treated root dentin.

The aim of this study was to investigate the effect of sodium ascorbate (Sa) on degree of conversion (DC) and bond strength (BS) of RealSeal SE to sodium hypochlorite (NaOCl) treated root dentin. Two hundreds simulated canals were prepared and irrigated with Distilled water(DW), 1.3% NaOCl (1.3% N), 5.2% NaOCl (5.2% N), MTAD, 17% EDTA (EDTA), 10% Sa, 1.3% NaOCl/MTAD (N-M), 1.3% NaOCl/Sa/MTAD(N-Sa-M), 5.2% NaOCl/EDTA(N-E), and 5.2% NaOCl/Sa/EDTA (N-Sa-E) respectively. They were subsequently bulk filled with RealSeal SE and analyzed with micro-Raman spectroscopy and universal testing machine for DC and BS respectively. One-way ANOVA and post hoc Tukey's test showed DC of 1.3% N, 5.2% N, N-M and N-E were significantly lower (p<0.01) than other six groups. BS of DW, Sa, N-M were significantly lower than 1.3% N, 5.2% N, MTAD, EDTA, N-Sa-M and N-E (p<0.01), and group N-Sa-E achieved the highest BS among all groups (p<0.01). NaOCl negatively affected DC and BS of RealSeal SE, which could be reversed with 10% Sa.

Bacteriocin immunity proteins play a role in quorum-sensing system regulated antimicrobial sensitivity of Streptococcus mutans UA159.

OBJECTIVE: Antimicrobial sensitivity of Streptococcus mutans can be modulated by putative bacteriocin immunity proteins. Bacteria use a quorum sensing (QS) system to regulate physiological activities including bacteriocin production, antimicrobial response, and biofilm formation. QS system of S. mutans is dependent on competence stimulating peptide (CSP), whose precursor is encoded by comC. However, whether bacteriocin immunity proteins play a role in QS system regulated S. mutans antimicrobial sensitivity is still unknown. We hypothesize that bacteriocin immunity proteins encoded by immA and immB play roles in QS regulated antimicrobial sensitivity in S. mutans UA159. DESIGN: In this study, sensitivity of S. mutans UA 159 comC mutant in planktonic and biofilm states to clinically used antimicrobials was investigated by the plate count method and confocal laser scanning microscopy. The effect of immA and immB inactivation on S. mutans antimicrobial sensitivity was studied. The expression of immA and immB in S. mutans comC mutant before and after chlorhexidine (CHX) treatment was also examined. RESULTS: It was found that comC, immA and immB mutation resulted in enhanced antimicrobial sensitivity to sodium fluoride (NaF), CHX and ampicillin (AMP) in planktonic states. After 2% CHX treatment, the live/dead cell ratio in comC mutant and wild strain biofilms decreased 67% and 39% (P<0.05). The expression of immA and immB was up-regulated in wild strain after CHX treatment, while the up-regulation of immB was largely inhibited in comC mutant (P<0.05). CONCLUSIONS: These findings suggest that the effect of S. mutans UA159 comC mutation on antimicrobial sensitivity can be due, in part, to attenuation of the expression of the bacteriocin immunity proteins related genes.

[The expression and modulatory role of reprogramming markers on the in vivo regeneration of dental pulp and periodontal ligament tissue after injury].

PURPOSE: The purpose of this study was to investigate the expression of reprogramming markers including Oct-4, Sox2 and c-Myc in rat dental pulp and periodontal ligament tissues undergoing tissue regeneration after injury. METHODS: Lewis rat model with dental pulp and periodontal ligament injury was created. HE staining was applied to investigate the structure of newly formed dentin-pulp complex and periodontium. The distribution of Oct-4, Sox2 and c-Myc was determined by immunofluorescent staining. RESULTS: HE staining showed that newly formed dentin-pulp complex and periodontium was constructed 4 weeks after injury. Immunofluorescent staining revealed Oct-4, Sox2 and c-Myc signal was activated in the newly formed dental pulp and periodontal ligament tissue after injury compared with the normal ones. Oct-4 and Sox2 showed similar expression pattern. CONCLUSIONS: Oct-4, Sox2 and c-Myc signaling may play an important modulatory role in the dental tissue regeneration after injury. Oct-4 and Sox2 may have operative interaction whereas c-Myc may play independent role during this process.

Remineralization of artificial dentinal caries lesions by biomimetically modified mineral trioxide aggregate.

Fluoride-releasing restorative materials are available for remineralization of enamel and root caries. However, remineralization of dentin is more difficult than remineralization of enamel due to the paucity of apatite seed crystallites along the lesion surface for heterogeneous crystal growth. Extracellular matrix proteins play critical roles in controlling apatite nucleation/growth in collagenous tissues. This study examined the remineralization efficacy of mineral trioxide aggregate (MTA) in phosphate-containing simulated body fluid (SBF) by incorporating polyacrylic acid and sodium tripolyphosphate as biomimetic analogs of matrix proteins for remineralizing caries-like dentin. Artificial caries-like dentin lesions incubated in SBF were remineralized over a 6 week period using MTA alone or MTA containing biomimetic analogs in the absence or presence of dentin adhesive application. Lesion depths and integrated mineral loss were monitored with microcomputed tomography. The ultrastructure of baseline and remineralized lesions was examined by transmission electron microscopy. Dentin remineralization was best achieved using MTA containing biomimetic analogs regardless of whether an adhesive was applied; dentinal tubules within the remineralized dentin were occluded by apatite. It is concluded that the version of MTA employed in this study may be doped with biomimetic analogs for remineralization of unbonded and bonded artificial caries-like lesions in the presence of SBF.

[Application and prospect on the resin-dentin adhesion in the root canal therapy].

The application of adhesive root canal filling materials is the tendency in root canal obturation. The orientation is to develop the adhesive core material and sealer making a whole structure. In this review, we summarized the researches on the resin-dentin adhesion in the root canal obturation.

[Effects of immA and immB coding putative bacteriocin immunity proteins on the antimicrobial sensitivity in planktonic Streptococcus mutans and biofilm formation].

OBJECTIVE: To investigate the effects of putative bacteriocin immunity proteins on the growth mode of Streptococcus mutans (Sm). To observe the differences of antimicrobial sensitivity in planktonic Sm wild-type strains and mutant strains caused by the inactivation of bacteriocin immunity proteins and their influence on the biofilm formation. METHODS: Sm wild-type strains (WT) and its knockout mutants defective in immA and immB (ΔimmA(-) and ΔimmB(-) mutants) coding putative bacteriocin immunity proteins were cultured in brain heart infusion (BHI) and selected by erythromycin at the concentration of 10 mg/L. Optical density was detected by spectrophotometer every hour and growth curve was drawn. WT, ΔimmA(-) and ΔimmB(-) mutants were treated with ampicillin (0.04, 0.05, 0.06, 0.07, 0.08 mg/L), sodium fluoride (50, 100, 150, 200, 250 mg/L) and sodium hypochlorite (0.078%, 0.156%, 0.313%, 0.625%, 1.250%) for 24 hours. Optical density was detected by multifunctional micro plate reader. WT and the mutants were cultured in MBEC(TM) P&G Assay for 24 hours. The minimum biofilm eradication concentration (MBEC) of chlorhexidine against Sm was determined by serial dilution method. Confocal laser scanning microscopy (CLSM) was used to visualize the biofilm architecture, depth and ratio of live to dead bacteria. RESULTS: Growth curve showed that it took about 3 hours to reach exponential phase and about 7 hours to stationary phase for WT, while 4 hours to exponential phase and 8 hours to stationary phase for mutants. Optical density of mutants were lower than WT in the presence of various antimicrobial agents (P < 0.01). In 0.06 mg/L ampicillin group, optical density value of WT, ΔimmA(-) and ΔimmB(-) mutants were 0.334 ± 0.016, 0.027 ± 0.016 and 0.047 ± 0.018. In 150 mg/L sodium fluoride group, optical density value of WT and mutants were 0.254 ± 0.018, 0.129 ± 0.011 and 0.167 ± 0.010. In 0.313% sodium hypochlorite group, optical density value of WT and mutants were 0.467 ± 0.008, 0.017 ± 0.006 and 0.050 ± 0.006. The MBEC of chlorhexidine against Sm WT, ΔimmA(-) and ΔimmB(-) mutants were 6.25, 1.57, and 3.13 mg/L. The results by CLSM showed a noticeable difference in biofilm architecture. The depth of WT biofilm was higher than the mutants biofilm (P < 0.01). The ratio of live to dead bacteria of WT biofilm was higher than ΔimmA(-) mutants in all layers (P < 0.05) and ΔimmB(-) mutants in the outer and intermedium layer (P < 0.01). There is no significant different between the inner layers of WT and ΔimmB(-) mutants (P = 0.191). CONCLUSIONS: Putative bacteriocin immunity proteins have influence on the growth mode of Sm. The antimicrobial sensitivity of planktonic Sm can be up-regulated by the inactivation of immA or immB. The MBEC of chlorhexidine against ΔimmA(-) and ΔimmB(-) mutants is lower than WT. The inactivation of immA or immB affects the biofilm formation.

[Macrophage migration-inhibitory factors expression and its effects on proliferation in human dental pulps].

OBJECTIVE: To investigate the expression of macrophage migration-inhibitory factors (MIF) in clinically healthy and inflamed human pulp tissues and the effects of rhMIF on the proliferation of human dental pulp cells (HDPC). METHODS: Immunohistochemistry was used to detect the localization of MIF expression in clinically healthy pulp and inflamed pulp tissues. Quantitative real-time polymerase chain reaction (PCR) was performed to evaluate the mRNA levels of MIF in pulp specimens. In addition, the culture supernatants of HDPC were collected after HDPC was stimulated by lipopolysaccharide (LPS) for 24 h, and then the MIF levels were assayed by quantitative sandwich enzyme-linked immunosorbent assay. Meanwhile, the effects of rhMIF on the proliferation of HDPC at different concentrations for 24 and 48 h were observed by cell counting kit-8 (CCK-8). RESULTS: MIF was mainly distributed in odontoblasts of healthy pulp tissue, however, in inflamed pulp tissue, it was widely detected in fibroblasts, inflammatory infiltrates and endothelial cells as well as odontoblasts. Quantitative real-time PCR showed that there was no significant difference in MIF mRNA levels between inflamed pulps and healthy pulps (P > 0.05). Additionally, the secretion of MIF was significantly increased by stimulation with LPS at the concentration of 0.1 and 1.0 mg/L [(1772.58 ± 495.05), (1692.58 ± 337.45) ng/L] (P < 0.05), and the concentration was (1048.53 ± 161.81) ng/L in control group. rhMIF stimulated the HDPC's proliferation at the concentration of 10, 30, 60 µg/L for 24 and 48 h. CONCLUSIONS: MIF was expressed in pulp tissue and its expression was increased after stimulation by LPS. rhMIF increased the proliferation of HDPC. These results suggest that MIF may be involved in the process of pulpal inflammation.