Comparative analysis of the particle size and shape of commercially available mineral trioxide aggregates and Portland cement: a study with a flow particle image analyzer.

The aim of this study is to characterize the particle size distribution and circularity of various Mineral Trioxide Aggregates (MTA) (ProRoot MTA/ MTA Angelus/Gray and White) and Portland cements with effective size ranges of 1.5-160 microm using a flow particle analyzer (Sysmex FPIA-3000, Kobe, Japan). Cumulative percentage of particles between 6 and 10 microm were, 65, 73, 48, 53, and 70 %, for Gray ProRoot MTA, White ProRoot MTA, Gray MTA Angelus, White MTA Angelus, and Portland cement, respectively. ProRoot MTA contains fewer large particles than MTA Angelus. MTA Angelus contains a higher number of small particles than ProRoot MTA. White MTA contains smaller particles with a narrower range of size distribution than Gray MTA. MTA Angelus particles have relatively low circularity and wide size distribution and are less homogeneous than ProRoot MTA.

Apical anatomy in mesial and mesiobuccal roots of permanent first molars.

The purpose of this in vitro study was to investigate the canal configuration types, and the prevalence and location of anatomical variations in the mesiobuccal (MB) and mesial roots of permanent maxillary and mandibular first molars after instrumentation. The number and the type of canals were determined before instrumentation using conventional methods. All root canals from the 47 MB roots and 42 mesial roots were then instrumented to size #30 with ProFile .04 taper rotary instruments in a crown-down method and then filled with a single gutta-percha cone and sealer. Transverse 1 mm-thick cross-sections at 2, 3, 4, and 5 mm from the apex were obtained, stained and examined using a stereomicroscope. The canal configuration types and the prevalence and location of isthmi and accessory canals in roots with two canals were evaluated. The prevalence of two canals was 80.8% in the maxillary MB roots and 95.2% in the mandibular mesial roots. There were six types of canal configurations in the instrumented root apices. The prevalence of anatomical variations was highest at the apical 4 mm level, and was more frequent in mandibular first molars, and in roots with Weine type III canal. chi test showed that the prevalence of the anatomical variations was statistically higher in the maxillary MB roots with Weine type III canals than in those with Weine type II canals (p < 0.05). Different canal configurations were often found at different levels in the same root. The results indicate that anatomical variations persist following instrumentation of roots with two canals in first molars. These anatomical variations should be considered during surgical or nonsurgical endodontic procedures of the permanent first molars.

An effective method of inactivating chlorhexidine.

OBJECTIVE: The purpose of this study was to find an effective inactivating agent for chlorhexidine that would facilitate removal of all residual antimicrobial effect, which may cause false-negative results during microbiologic culturing. STUDY DESIGN: L-alpha-lecithin, Tween 80, and sodium thiosulfate were used in different proportions to prepare 6 potential inactivating solutions. Nine mL of each inactivating solution was mixed with 1 mL of 2% chlorhexidine solution. After 5 minutes of equilibration, 0.1 mL of bacterial cell suspension containing 2 x 10(4) viable cell of Enterococcus faecalis was added to the mixture. At 10 and 60 minutes, 0.1-mL aliquots were withdrawn and spread over blood agar plates and incubated at 37 degrees C for 72 hours. The number of colony-forming units on the blood agar plates was determined and recorded. RESULTS: The combination of 3% Tween 80 and 0.3% L-alpha-lecithin was found to be the most effective inactivating agent, allowing full recovery of the test organisms in the presence of chlorhexidine. CONCLUSION: The present study demonstrated a method to predictably inactivate chlorhexidine.

The effect of chlorhexidine as an endodontic disinfectant.

OBJECTIVE: The purpose of this study was to establish whether addition of a 2% chlorhexidine rinse to a conventional treatment protocol enhances the rate of the successful disinfection of the root canal system in vivo. STUDY DESIGN: Twenty-four teeth with infected necrotic pulps and resorbing apical periodontitis were treated with a conventional technique in which 1% NaOCl as irrigant was used. Half of the cases received an additional rinse with 2% chlorhexidine. Prereduced thioglycollate medium was used to take cultures that were incubated for 4 weeks. RESULTS: Cultivable bacteria were retrieved at the conclusion of the first visit in 1 out of 12 chlorhexidine cases whereas in the control group 7 out of 12 cases showed growth. This difference was significant (P < .05). CONCLUSION: The findings are clinically important.

Endodontic infection: some biologic and treatment factors associated with outcome.

OBJECTIVE: We sought to investigate the simultaneous effect of apical periodontitis, instrumentation level, and density of root canal filling on endodontic treatment outcome. METHODS: For this study, 200 endodontically treated teeth with 441 roots were used. A follow-up examination was conducted 4 +/- 0.5 years postoperatively. Data were subjected to univariate and multivariate analysis. RESULTS: Periapical pathosis had the strongest effect on treatment outcome (P <.0001). The instrumentation level (mean +/- SEM of the working length) for successfully treated teeth/roots with normal preoperative pulp and periapex was farther away from the radiographic apex (1.23 +/- 0.13 mm) than for teeth/roots with an unsuccessful outcome (0.20 +/- 0.09 mm; P <.005). However, successfully treated teeth/roots with pulp necrosis and apical periodontitis had working length levels closer to the radiographic apex (0.55 +/- 0.12 mm) than did teeth/roots with unsuccessful outcomes (1.73 +/- 0.30 mm; P<.001). In teeth/roots with apical periodontitis, a millimeter loss in working length increased the chance of treatment failure by 14%. The risk of failure was higher for a fair/poor density of obturation than for a good density for all diagnoses of periradicular status. CONCLUSION: Diseased periapex, level of working length relative to the radiographic apex, and fair/poor density all affect the outcome of endodontic treatment.

Direct contact between enamel matrix derivative (EMD) and osteoblasts is not required for EMD-induced cell proliferation.

OBJECTIVE: The purpose of this study was to determine whether the effect of enamel matrix derivative (EMD) on osteoblast proliferation is dependent on direct contact between EMD and the cells. STUDY DESIGN: MC3T3-E1 cells were seeded onto 6-well culture plates at an initial density of 5000/cm(2) in Dulbecco's modified eagle medium (DMEM) with 10% fetal bovine serum (FBS). Serum was removed from the culture medium after 24 hours with or without the addition of EMD. Four groups were evaluated: group 1, DMEM only; group 2, DMEM with 100 microg/mL EMD directly added to the culture medium; group 3, DMEM with a culture plate insert (30-mm diameter; 0.4-microm pore size) only; group 4, DMEM with 100 microg/mL EMD added onto a culture plate insert. The porous membrane of the insert prevented direct contact between EMD and the cells. After 3-day incubation, cell morphology was examined and the total cell number per well was counted and analyzed using 1-way ANOVA. RESULTS: EMD formed precipitated aggregates on the membrane of the culture insert with the same appearance as when it was added directly to the medium. The culture plate insert alone did not cause any changes in cell morphology or proliferation. The addition of EMD significantly increased cell number regardless the presence of the culture plate insert. CONCLUSION: This study suggests that direct contact between EMD and osteoblasts is not required to induce cell proliferation. Soluble peptides released from EMD may contribute to the stimulating effects of EMD on cell proliferation.

Smear layer production by 3 rotary reamers with different cutting blade designs in straight root canals: a scanning electron microscopic study.

OBJECTIVES: The design of the cutting blade of rotary instruments may affect the outcome of root canal instrumentation in terms of cleanliness. The aim of this scanning electron microscopic study was to compare the quality and amount of smear layer generated in the apical third of straight root canals by 2 rotary nickel-titanium reamers and 1 rotary steel reamer with different cutting blade designs. STUDY DESIGN: Seventy intact, single-rooted human mandibular premolars with straight, fully developed roots were selected for this study. Before instrumentation, the cervical portion of all teeth was removed by using a microtome (Isomet), leaving 13-mm-long roots. Automated preparation was performed with ProFile (n = 20) and Hero 642 (n = 20) reamers by using the crown-down technique and with a stainless steel engine reamer (Mani; n = 20) by using a reaming motion. All root canals were instrumented to No. 40. A control group (pulp extirpation with barbed broaches; n = 10) was also included. Irrigation with 3 mL of a 1% sodium hypochlorite (NaOCl) solution was performed after each instrumentation. After the instrumentation, each root was split longitudinally, and a scanning electron microscope was used to examine the selected areas of the canal walls at the apical third from 2 different perspectives. A 4-category scoring system for smear layer was used, and the resulting scores were statistically analyzed. RESULTS: The least smear layer remained in the Hero 642 group at the selected apical third of straight root canals (P < .05). However, all instruments left a smear layer. The surface texture of the smear layer, in addition to the depth and the frequency of packed materials into the dentinal tubules, varied with instrument type. CONCLUSION: These data revealed that the design of the cutting blade of rotary instruments can affect root canal cleanliness in straight root canals. This information may be useful in the selection of nickel-titanium rotary reamers.

Emdogain promotes osteoblast proliferation and differentiation and stimulates osteoprotegerin expression.

PURPOSE: The purpose of this study was to investigate the effects of EMD on the growth and differentiation of osteoblastic cells (MC3T3-E1) and on the expression of osteoprotegerin (OPG), a key cytokine that inhibits osteoclastogenesis and osteoclast function. STUDY DESIGN: MC3T3-E1 cells were treated with 100 microg/mL EMD in serum-free medium for 1, 2, 3, 5, and 7 days, or in 2% fetal bovine serum (FBS) for 3 weeks. Cells incubated without EMD served as negative control. At the end of each incubation period, cell numbers were counted and total cellular mRNA was extracted. Northern blot analysis and RT-PCR were performed to determine the mRNA levels of core binding factor alpha (Cbfa1), collagen alpha1 (I), bone sialoprotein (BSP), osteocalcin (OC), insulin-like growth factor I (IGF-I), and OPG. Alkaline phosphatase (ALP) activity was also determined and compared between treatment and control groups. RESULTS: A marked increase in cell numbers was observed in EMD-treated groups from day 2 to day 7 (P < .01). mRNA expression of collagen alpha1 (I), BSP, OC, OPG, and IGF-I were up-regulated in cells treated with EMD. ALP activity was significantly increased by EMD treatment after 3-week culture under differentiating conditions (P < .05). The expression of Cbfa1 was not affected by EMD treatment from day 1 to day 5; the levels were elevated after culturing for 3 weeks in EMD-treated cells. CONCLUSIONS: EMD promotes both proliferation and differentiation of MC3T3-E1 cells and indirectly inhibits osteoclastogenesis and osteoclast function by stimulating the expression of OPG.

Cell and tissue reactions to mineral trioxide aggregate and Portland cement.

OBJECTIVE: Mineral trioxide aggregate (MTA) is being widely used for root-end fillings, pulp capping, perforation repairs, and other endodontic procedures. MTA and Portland cement (PC) have many similar physical, chemical, and biologic properties. PC cement has shown promising potential as an endodontic material in several studies in vitro and in vivo. The purpose of this study was to compare the cytotoxic effect in vitro and the tissue reaction of MTA and Portland cement in bone implantation in the mandibles of guinea pigs. STUDY DESIGN: Millipore culture plate inserts with freshly mixed or set material were placed into the culture plates with already attached L929 cells. After an incubation period of 3 days, the cell morphology and cell counts were studied. Adult male guinea pigs under strict asepsis were anesthetized, during which a submandibular incision was made to expose the symphysis of the mandible. Bilateral bone cavities were prepared and Teflon applicators with freshly mixed materials were inserted into the bone cavities. Each animal received 2 implants, one filled with ProRoot and 1 with PC. The animals were killed after 2 or 12 weeks, and the tissues were processed for histologic evaluation by means of light microscopy. RESULTS: There was no difference in cell reactions in vitro. Bone healing and minimal inflammatory response adjacent to ProRoot and PC implants were observed in both experimental periods, suggesting that both materials are well tolerated. CONCLUSIONS: MTA and PC show comparative biocompatibility when evaluated in vitro and in vivo. The results suggest that PC has the potential to be used as a less expensive root-end filling material.

Effects of root-end filling materials on fibroblasts and macrophages in vitro.

OBJECTIVE: The aim of this study was to investigate the effects of 4 root-end filling materials (mineral trioxide aggregate [MTA], intermediate restorative material [IRM], amalgam, and Retroplast) on cell growth, cell morphology, and cytokine (interleukin [IL]1beta and IL-6) production in mouse fibroblasts and macrophages. STUDY DESIGN: Millipore culture plate inserts with freshly mixed or set root-end filling material were placed into 6-well cell culture plates with already attached mouse fibroblasts or macrophages. Cells cultured with only the Millipore culture plate inserts served as a control. After a 3-day incubation, cell morphology was examined, and the total cell number per well was counted and analyzed by using 1-way analysis of variance. For cytokine assay, mouse macrophages were incubated in 24-well flat-bottom plates with set root-end filling material disks in the bottom. Cells cultured without the material disks served as negative controls, and cells cultured with lipopolysaccharides served as positive controls. After 24-hour incubation, culture media were collected for cytokine assay by using enzyme-linked immunosorbent assay. RESULTS: All root-end filling materials inhibited the cell growth of mouse fibroblasts and macrophages. There was no growth in the originally seeded cells in the fresh IRM, the fresh Retroplast, and the set IRM group. There was no difference between MTA and amalgam for cell growth either in the fresh material groups or in the set material groups. The total cell number in the set Retroplast group was significantly less than that in the set MTA group. Morphologically, MTA was characterized by denatured medium proteins and dead cells adjacent to the material, which were observed only in the fresh MTA group. There was no detected cytokine production in any of the tested material groups. CONCLUSION: All root-end filling materials inhibited cell growth, and none induced IL-1beta and IL-6 production.

To do a "root canal".

Endodontic treatment is often referred to as "a root canal". This article discusses the need to be more refined and descriptive in the selection of treatment alternatives. The pathological involvement of teeth needing endodontic treatment varies significantly from superficial pulp inflammation to pulp necrosis and infection, often complicated with a periradicular osteolytic process. This diversity should lead to a variety of treatment modalities based on the severity of the disease. Failure to do so and use a one-size-fits-all approach--"a root canal"--is an oversimplification and a disservice to the patient and the profession.

Is hard tissue formation in the dental pulp after the death of the primary odontoblasts a regenerative or a reparative process?

OBJECTIVES: Conceptually, two types of tertiary dentine may be produced in response to caries and environmental irritations: "reactionary dentine" that is secreted by existing primary odontoblasts and "reparative dentine", formed after the death of the odontoblasts by proliferation and differentiation of progenitor cells into odontoblast-like cells. Because histologic evidence for tubular dentine generated by newly differentiated odontoblast-like cells is lacking in human teeth, the present study examined pulpal cellular changes associated with caries/restorations, in the presence or absence of pulpal exposures. METHODS: Ninety-six extracted human teeth were histologically processed and serial sectioned for light microscopy: 65 contained untreated enamel/dentine caries; 20 were heavily restored and 11 had carious exposures managed by direct pulp-capping. RESULTS: Sparsely distributed, irregularly arranged dentinal tubules were identified from the tertiary dentine formed in teeth with unexposed medium/deep caries and in restored teeth; those tubules were continuous with the tubules of secondary dentine; in some cases, tubules were absent. The palisade odontoblast layer was reduced to a single layer of flattened cells. In direct pulp-capping of pulp exposures, the defects were repaired by the deposition of an amorphous dystrophic calcified tissue that resembled pulp stones more than dentine, sometimes entrapping pulpal remnants. This atubular hard tissue was lined by fibroblasts and collagen fibrils. CONCLUSIONS: Histological evidence from the present study indicates that reparative dentinogenesis cannot be considered as a regenerative process since the so-formed hard tissue lacks tubular features characteristic of genuine dentine. Rather, this process represents a repair response that produces calcified scar tissues by pulpal fibroblasts. CLINICAL SIGNIFICANCE: Formation of hard tissue in the dental pulp after the death of the primary odontoblasts has often been regarded by clinicians as regeneration of dentine. If the objective of the clinical procedures involved is to induce healing, reduce dentine hypersensitivity, or minimise future bacteria exposure, such procedures may be regarded as clinical success. However, current clinical treatment procedures are not adept at regenerating physiological dentne because the tissues formed in the dental pulp are more likely the result of repair responses via the formation of calcified scar tissues.

A prospective cohort study of endodontic treatments of 1,369 root canals: results after 5 years.

OBJECTIVE: The purpose of this prospective study was: 1) to follow-up a large number of endodontic treatments performed by a single operator, periodically checked over a 5-year period; and 2) to correlate outcome to a number of clinical variables. STUDY DESIGN: This prospective study included all consecutive cases during the selected time period. All cases were followed regularly for a 5-year period. At the 5-year end point of the study, 470 patients with 816 treated teeth and with 1,369 treated root canals were available for evaluation. RESULTS: The overall rate of success among the 816 teeth/1,369 root canals available for evaluation was 88.6%/90.3%. The success rate for 435 teeth/793 root canals undergoing vital pulp therapy was 91.5%/93.1%. Teeth/root canals with necrotic pulp but without detectable periapical bone lesion were successfully treated in 89.5%/92.3%. If the pulp necrosis was complicated by apical periodontitis, the success rate fell to 82.7% for the teeth and 84.1% for the root canals (P = .037). Teeth with periapical lesion <5 mm had a success rate of 86.6%, and in cases where the lesion was ≥ 5 mm the rate of success was 78.2%. CONCLUSIONS: More severe disease conditions negatively affects outcome. An optimal working length was identified. Excess of root canal filling material decreases success. Infected pulp space should be treated with an effective intracanal dressing. The quality of the coronal restoration or the placement of intracanal post retentions does not affect treatment outcome.

Influence of a passive sonic irrigation system on the elimination of bacteria from root canal systems: a clinical study.

INTRODUCTION: The present investigation evaluated the ability of a new passive sonic irrigation (sonic group) system (EndoActivator) to eliminate cultivable bacteria from root canals in vivo and compared it with that of standard syringe irrigation (control group). METHODS: Data were obtained by using bacteriologic sampling of root canals treated by endodontic residents. Sampling results from 1 session of treatment were then compared with results obtained after intervisit calcium hydroxide disinfection and a second session of treatment. RESULTS: There was no significant difference in the ability of sonic group and control group to eliminate cultivable bacteria from root canals (P > .05). A second session and intervisit calcium hydroxide disinfection were able to eliminate cultivable bacteria from significantly more teeth than a single session of treatment (P < .05). CONCLUSIONS: These in vivo results strengthen the case for a multi-visit approach to the treatment of apical periodontitis.

Cytotoxicity evaluation of endosequence root repair material.

OBJECTIVE: The purpose of this study was to evaluate the cytotoxicity of EndoSequence Root Repair Material (Brasseler USA, Savannah, GA) and compare it with gray and white MTA. STUDY DESIGN: Samples of 2 mg freshly mixed or set gray MTA (GMTA), white MTA (WMTA), EndoSequence Root Repair Material (ERRM), and AH26 were eluted with 300, 600, and 1,000 microL cell culture medium for 24 and 72 hours. L929 cells were seeded into 96-well plates at 3 x 10(4) cells/well and incubated with 100 microL elute from each elute group. Cells cultured only with culture medium served as negative control. AH26 was used as positive control. After 24 hours' incubation, cell cytotoxicity was evaluated by MTT assay. Cell viability was calculated as percentage of the control group. The results were analyzed with 1-way analysis of variance. RESULTS: For both set and fresh samples, there were no significant cell viability differences among GMTA, WMTA, and ERRM. Cell viability in the AH26 group was less than in all of the other 3 materials. CONCLUSION: This study suggests that ERRM may have cell viability similar to GMTA and WMTA in both set and fresh conditions.

Chronologic comparison of root dentin moisture in extracted human teeth stored in formalin, sodium azide, and distilled water.

This study quantified in vitro the root dentin moisture when 10% formalin (group A), 3% sodium azide (group B), and distilled water (group C) were used as teeth storage media. The root dentin moisture of 66 extracted human mandibular single-rooted teeth was measured at baseline (day 0) and at 1, 3, 7, and 14 days using a digital grain moisture meter. The baseline dentin moisture value was used as covariate in the generalized estimating equation (GEE) analysis. The mean dentin moisture values (%) +/- SD on days 0, 1, 3, 7, and 14 were, respectively: 10.6 +/- 0.64, 14.3 +/- 0.71, 14.6 +/- 0.84, 14.4 +/- 0.64, and 14.7 +/- 0.75 in group A; 11.4 +/- 0.94, 14.6 +/- 0.95, 14.6 +/- 0.76, 14.6 +/- 0.93, and 14.8 +/- 0.81 in group B; and 10.2 +/- 0.95, 12.8 +/- 0.90, 13.3 +/- 0.95, 13.0 +/- 0.91, and 13.2 +/- 0.89 in group C. The dentin moisture increased in all 3 groups; however, there was no overall significant difference in moisture between the formalin and sodium azide groups.

Wound healing of apical tissues after root canal therapy: a long-term clinical, radiographic, and histopathologic observation study.

OBJECTIVE: The purpose of this study was to evaluate the pulp healing process and the dentin-cementum complex in 51 endodontically treated human teeth after long observation periods and to correlate histologic observations with conventional periapical radiographic findings. STUDY DESIGN: Specimens were obtained from the extraction of 77 treated teeth, which were deemed to be unrestorable, with no evidence of periapical bone lesion at the follow-up. After stringent evaluation of the radiographs, 51 cases that 3 independent evaluators assessed as having normal periapical conditions were selected. The specimens were histologically evaluated using serial sections. RESULTS: In the majority of the cases, complete healing was observed, with no signs of acute or chronic inflammatory processes in the remaining apical tissue or periodontal tissue fragments. Some cases showed moderate inflammation in the root canal tissue. Narrowing of the apical root canal by cementum was a common finding in most cases, but total closure was not observed. Debris intermixed with necrotic tissue and sealer particles was a common finding in the pulp stump. Bacteria were present in the coronal portion of the root in almost all cases, but in only 1 case could bacteria be demonstrated in the coronal and apical portions of the root. CONCLUSIONS: Apical tissue of properly treated teeth with no signs of periapical changes is only rarely significantly inflamed. When the tissue is inflamed, microbial causes can always be demonstrated. Despite the presence of microorganisms coronally in nearly all cases, apical tissue is seldom affected.

Root dentin body moisture changes caused by ascorbic acid.

OBJECTIVES: To quantify in vitro the root dentin moisture (DM) when soaked in 10% ascorbic acid solution (Group A) and distilled water (Group B) for up to 14 days. METHODS: Forty-four extracted human mandibular single-rooted teeth were sectioned perpendicular to the long axis at the CEJ to access the root dentin. The samples were divided into Groups A and B. Baseline (day 0) DM was measured using a digital grain moisture meter. One sample was placed in each tube, which was then filled with solution. All tubes were kept at 37 degrees C and 100% humidity. DM was measured after 1, 3, 7, and 14 days. The baseline DM value was used as a covariate in the generalized estimating equation (GEE) analysis to account for the difference in the baseline DM between the two groups. RESULTS: The mean DM (%) values+/-standard deviation on days 0, 1, 3, 7, and 14 were 11.4+/-1.08, 17.1+/-0.87, 18.2+/-0.76, 18.4+/-0.77, and 17.9+/-0.90 in Group A, and 10.2+/-0.95, 12.8+/-0.90, 13.3+/-0.95, 13.0+/-0.91, and 13.2+/-0.89 in Group B, respectively. Group A had significantly higher baseline DM than Group B (p=0.006). After adjusting for differences in the baseline, the GEE analysis indicated that, on average, Group A had a significantly higher increase in DM than Group B, with means+/-standard deviation of 4.35+/-0.26. CONCLUSIONS: The moisture increase in the ascorbic acid group was greater than that in the distilled water group. Soaking root dentin in the unreplenished ascorbic acid solution or distilled water beyond 3 days did not further increase DM.