Mineral trioxide aggregate and other bioactive endodontic cements: an updated overview - part II: other clinical applications and complications.

Mineral trioxide aggregate (MTA) is a dental material used extensively for vital pulp therapies (VPT), protecting scaffolds during regenerative endodontic procedures, apical barriers in teeth with necrotic pulps and open apices, perforation repairs as well as root canal filling and root-end filling during surgical endodontics. A number of bioactive endodontic cements (BECs) have recently been introduced to the market. Most of these materials have calcium and silicate in their compositions; however, bioactivity is a common property of these cements. These materials include the following: BioAggregate, Biodentine, BioRoot RCS, calcium-enriched mixture cement, Endo-CPM, Endocem, EndoSequence, EndoBinder, EndoSeal MTA, iRoot, MicroMega MTA, MTA Bio, MTA Fillapex, MTA Plus, Neo MTA Plus, Ortho MTA, Quick-Set, Retro MTA, Tech Biosealer, and TheraCal LC. It has been claimed that these materials have properties similar to those of MTA but without the drawbacks. In Part I of this review, the available information on the chemical composition of the materials listed above was reviewed and their applications for VPT was discussed. In this article, the clinical applications of MTA and other BECs will be reviewed for apexification, regenerative endodontics, perforation repair, root canal filling, root-end filling, restorative procedures, periodontal defects and treatment of vertical and horizontal root fractures. In addition, the literature regarding the possible drawbacks of these materials following their clinical applications is reviewed. These drawbacks include their discolouration potential, systemic effects and retreatability following use as a root filling material. Based on selected keywords, all publications were searched regarding the use of MTA as well as BECs for the relevant clinical applications. Numerous publications were found regarding the use of BECs for various endodontic applications. The majority of these investigations compared BECs with MTA. Despite promising results for some materials, the number of publications using BECs for various clinical applications was limited. Furthermore, most studies had several methodological shortcomings and low levels of evidence.

Mineral trioxide aggregate and other bioactive endodontic cements: an updated overview - part I: vital pulp therapy.

Mineral trioxide aggregate (MTA) is a bioactive endodontic cement (BEC) mainly comprised of calcium and silicate elements. The cement was introduced by Torabinejad in the 1990s and has been approved by the Food and Drug Administration to be used in the United States in 1997. A number of new BECs have also been introduced to the market, including BioAggregate, Biodentine, BioRoot RCS, calcium-enriched mixture cement, Endo-CPM, Endocem, EndoSequence, EndoBinder, EndoSeal MTA, iRoot, MicroMega MTA, MTA Bio, MTA Fillapex, MTA Plus, NeoMTA Plus, OrthoMTA, Quick-Set, RetroMTA, Tech Biosealer and TheraCal LC. It has been claimed that these materials have properties similar to those of MTA without its drawbacks. In this article, the chemical composition and the application of MTA and other BECs for vital pulp therapy (VPT), including indirect pulp cap, direct pulp cap, partial pulpotomy, pulpotomy and partial pulpectomy, have been reviewed and compared. Based on selected keywords, all papers regarding chemical composition and VPT applications of BECs had been reviewed. Most of the materials had calcium and silicate in their composition. Instead of referring to the cements based on their chemical compositions, we suggest the term 'bioactive endodontic cements (BECs)', which seems more appropriate for these materials because, in spite of differences in their chemical compositions, bioactivity is a common property for all of them. Numerous articles were found regarding use of BECs as VPT agents for indirect and direct pulp capping, partial pulpotomy and cervical pulpotomy. Most of these investigations used MTA for VPT. In most studies, newly introduced materials have been compared to MTA. Some of the BECs have shown promising results; however, the number of their studies compared to investigations on MTA is limited. Most studies had several methodological shortcomings. Future investigations with rigorous methods and materials are needed.

Effect of MTA particle size on periapical healing.

AIM: To examine the effect of reduction in MTA particle size on dento-alveolar and osseous healing in dogs. METHODOLOGY: Root canals of 24 mandibular premolars in four 2-year-old beagles were prepared and filled with gutta-percha and sealer. Two to four weeks later, during periapical surgery, the root-end cavity preparations in these teeth were filled with either grey ProRoot MTA or modified (reduced particle sizes with faster setting time) MTA. The animals were sacrificed 4 months later. Degrees of inflammation, type of inflammatory cells, fibrous connective tissue adjacent to the root-end filling materials, cementum formation over the resected roots and root-end filling materials and bone healing were examined. Data were analysed using the McNemar test. RESULTS: No significant differences in healing of periapical tissues were found when comparing ProRoot MTA to a modified MTA containing reduced particle sizes. CONCLUSION: Reducing the particle sizes of MTA did not impact its biological properties.

Osteoblast biocompatibility of mineral trioxide aggregate.

This study investigated the biocompatibility of variants of mineral trioxide aggregate (MTA), by culturing human MG63 osteosarcoma cells in the presence of materials, observing cytomorphology and cell growth, and then assaying cytokine expression from the cells. Reference materials were employed. Cell growth was quantified by preparing samples (n = 6) at 2, 4 and 7 days, for viewing by scanning electron microscopy and then scoring the amount of material that was covered by healthy cells. Subsequently, samples of culture media were tested using ELISA assays for expression of Interleukin (IL)-1alpha, IL-6, IL-8, IL-11 and macrophage colony stimulating factor (M-CSF). These assays were compared with controls where no material was present, and where media and fetal calf serum had not been exposed to cells. Results showed good cell growth on MTA. Expression of IL-6 from cells was only evident in the presence of MTA and Interpore 200. Interleukin-8 was expressed in high concentrations only in the presence of MTA. There was no evidence of expression of IL-1alpha or IL-11 with any material. Production of M-CSF was high for all materials. It appears that the variants of MTA are biocompatible and suitable for use in clinical trials.

Experimentally induced alterations in periapical tissues of the cat.

Ten cats were immunized with subcutaneous injections of keyhole limpet hemocyanin (KLH). After it was determined that the experimental animals had developed circulating antibodies to KLH, challenge doses of KLH were administered via the root canal system. The radiographic and histologic findings suggest that antigen-antibody complex reactions can occur in periapical tissues of teeth, and that they can play a role in the pathogenesis of periapical lesions. In contrast, no radiographic and histologic changes were noted in non-immunized cats.

Clinical applications of mineral trioxide aggregate.

An experimental material, mineral trioxide aggregate (MTA), has recently been investigated as a potential alternative restorative material to the presently used materials in endodontics. Several in vitro and in vivo studies have shown that MTA prevents microleakage, is biocompatible, and promotes regeneration of the original tissues when it is placed in contact with the dental pulp or periradicular tissues. This article describes the clinical procedures for application of MTA in capping of pulps with reversible pulpitis, apexification, repair of root perforations nonsurgically and surgically, as well as its use as a root-end filling material.

Effect of systemic doxycycline on alveolar bone loss after periradicular surgery.

Studies in the periodontic literature have shown an average of 0.5 mm to > 1.0 mm of bone loss after full thickness flap reflection. Similar literature has revealed that the tetracycline family of antibiotics can prevent bone loss. The purpose of this study was to observe the effect of systemic Doxycycline on crestal alveolar bone loss after periradicular surgery in beagle dogs. Five beagle dogs were used in two phases of this study. In the first phase (control sides), after reflecting full thickness flaps in one mandibular quadrant, notches were placed in the enamel of the third and fourth premolar teeth using a one-quarter round bur. Using magnification, measurements were taken from the reference notches to the height of the alveolar crest. After 8 wk, flaps were reflected in the same quadrant and measurements retaken, and the amount of bone loss was then measured. In the second phase (experimental sides), the same procedure was performed on the contralateral mandibular quadrant, but the dogs were placed on 4.4 mg/kg/day of Doxycycline for 10 days after reflections of full thickness flaps. After another 8 wk, the area was reflapped and measured. There was significantly (p < 0.01) less bone loss on the Doxycycline-treated side.

Effects of vacuuming on dye penetration patterns in root canals and glass tubes.

This study compared the dye leakage pattern of prepared root canals with that of glass tubes, with and without vacuuming. The apical 12 mm of 40 calcified root canals were prepared to tubes with a diameter of 0.5 mm. The coronal end of these canals and 40 glass tubes with similar diameters (12 mm x 0.5 mm) were closed with 2 mm of Cavit. Twenty samples from each group were left empty, and the rest (20) were filled with gutta-percha without sealer. Half of the samples of filled (10) and unfilled (10) specimens were then placed horizontally in 2% methylene blue dye. The other half (10) of the samples from each group were placed in a vacuum (25 mm Hg) and submerged in the dye. Leakage was then measured in millimeters and statistically analyzed using analysis of variance. The 20 empty glass tubes with or without vacuum leaked 17% or less of their lengths. The 20 glass tubes filled with gutta-percha averaged 70.5% leakage. Of those, the 10 glass tubes that were vacuumed had 100% leakage. Empty root canals exhibited mean leakage of 74% without vacuum and 91% of their length with vacuum. Canals filled with gutta-percha leaked a mean of 95.5% of their entire lengths without vacuum and 100% with vacuum (no significant difference). The results showed that filled and unfilled, prepared root canals leaked significantly more than their glass tube counterparts (p < 0.001), and vacuuming may not be necessary for dye leakage studies in filled root canals.

Wound healing after mucoperiosteal surgery in the cat.

The purpose of this study was to examine possible tissue-dependent differences in rate of healing after mucogingival flap surgery. After intrasulcular incision and a vertical-releasing incision distal to the maxillary and mandibular cuspids, buccal, full-thickness mucogingival flaps were raised in four quadrants of 10 adult cats. The triangular flaps were left open for 30 min and then repositioned and sutured. Tissue reactions were studied histologically after 1, 3, 7, 14, and 28 days of healing. Although new collagen occasionally was observed in the wound space in the free gingiva at 3 days, collagenous union between the cut dentogingival fibers and the flap seemed well established at 7 days. Flap reattachment to the denuded cortical bone was seen at 14 days in the region of the attached gingiva. In the region of the alveolar mucosa, however, residual coagulum and inflammatory reaction was present as late as at 28 days in several specimens. These observations indicate a marked difference in rate of healing among the different interfaces involved. These variations seem to be related to variations in size of the resulting wound space when a full-thickness mucoperiosteal flap is readapted over cervical root surfaces, alveolar bone crest, and denuded cortical bone, respectively.

Diagnosis and treatment of extracanal invasive resorption.

Extracanal invasive resorption is not a well-defined phenomenon. This article describes its clinical, radiographic, and histological characteristics. Treatment of affected teeth based on the location of the resorptive defect is also described.

Effect of preflaring on tactile detection of the apical constriction.

The efficacy of tactile detection of the apical constriction in flared and nonflared root canals was examined in 120 root canals of adult patients. In 68 nonflared (group 1) root canals, a #15 or #20 K-file was used to detect ("feel") the apical constriction. In 52 teeth (group 2), Hedstrom files, Gates Gliden drills #2 to #4, and ultrasonic files were used to enlarge the canal orifice and flare the coronal portion of the root canals before testing the apical constriction. After placing a #15 or #20 file in each root canal, a radiograph was taken, and the distance between the tip of the file and the radiographic apex was measured. The location of the file tip was classified into three categories: (a) within 1 mm short of the radiographic apex; (b) underextended, more than 1 mm short of the radiographic apex; and (c) overextended beyond the radiographic apex. In group 1 (nonflared), 32.3% of the root canals were classified in category a, as compared with 75.0% in group 2 (preflared). Over 26% of the root canals in group 1 and approximately 4% of the canals in group 2 were included in category b. Files inserted in preflared root canals had a significantly lower incidence of overextension than those placed in nonflared canals (21% versus 41%). The ability to determine the apical constriction by tactile sensation was significantly increased when the canals were preflared (p < 0.0001).

Investigation of mutagenicity of mineral trioxide aggregate and other commonly used root-end filling materials.

Little information is available regarding the mutagenicity of root-end filling materials. To study mutagenicity of Intermediate Restorative Material (IRM), Super-EBA, and a potential root-end filling material, mineral trioxide aggregate (MTA), strains of Salmonella typhimurium LT-2 (TA 98, R-factor strain and TA 1535, non-R-factor strains) were used in a standard Ames mutagenicity assay. Positive controls (S9 protein and benzo-(a)-pyrene and N-methyl-N'-nitro-N-nitrosoguanidine) operated properly. No increase in revertant bacteria colony counts occurred with any of the test materials. Based on these results, it seems that IRM, Super-EBA, and MTA are not mutagenic as measured by the Ames Test.

Concentrations of leukotriene B4 in symptomatic and asymptomatic periapical lesions.

Twelve periapical lesions from symptomatic and asymptomatic patients (six each) were obtained and immediately frozen in liquid nitrogen. Six pulps from unerupted third molars as well as chronically inflamed gingival tissues were also obtained, frozen, and used as negative and positive controls, respectively. The concentration of leukotriene (LT) B4 was determined by reverse phase high pressure liquid chromatography. Representative samples from each group were fixed in formalin, sectioned, and stained with hematoxylin and eosin. Extremely low levels of LTB4 were detected in the uninflamed pulpal samples in comparison to those found in chronically inflamed gingival tissues and periradicular lesions. A significant statistical difference was noted between concentrations of LTB4 in periapical lesions of symptomatic patients and those found in asymptomatic patients and samples of chronically inflamed gingival tissues (p < 0.05). In addition, a positive correlation was found between the presence of symptoms, the concentration of LTB4, and presence of polymorphonuclear leukocytes in symptomatic periapical lesions. The results show presence of high concentrations of LTB4 in symptomatic human periapical lesions.

An in vivo evaluation of Endex electronic apex locator.

Because of technical problems and hazards of radiation, dentists have desired alternative ways to determine the working length during root canal therapy. Attention has turned to electronic devices for measuring root canal length. Several such devices are now available. They show promise but their accuracy is hampered because moisture in the root canal can result in inaccurate responses. Recently, a new device, Endex, has been introduced, claiming ease of operation and accuracy in moist environments. Ten operators used the Endex to measure 185 root canal lengths (in 99 teeth). Endex measurements were compared with radiographic measurements. The Endex located the apical constriction accurately within +/- 0.5 mm in 89.64% of moist canals.

A comparison between two root end preparation techniques in human cadavers.

The purpose of this study was to compare ultrasonic and bur root end cavity preparations with regard to retention, cleanliness, and root canal parallelism. Twenty anterior teeth from human cadavers were instrumented and obturated with gutta-percha and sealer. After raising a full-thickness flap, the apices of the roots were exposed and beveled at a 45-degree angle. Half of the apical cavities were prepared with an appropriate sized Carr alloy tip energized by an Amadent Ultrasonic unit. The other half was prepared with an inverted cone bur in a slow-speed handpiece. The teeth were then extracted, sectioned longitudinally, photographed, and scanning electron micrographs examined. The ultrasonic cavities produced more parallel walls and deeper depths for retention. In addition, the ultrasonic tips followed the direction of the canals more closely than those prepared by burs. Scanning electron microscopic examination of the cavity wall showed presence of cleaner surfaces of root end cavities prepared by ultrasonic tips than those made with burs.

Absorbed radiation by various tissues during simulated endodontic radiography.

The amount of absorbed radiation by various organs was determined by placing lithium fluoride thermoluminescent chip dosimeters at selected anatomical sites in and on a human-like X-ray phantom and exposing them to radiation at 70- and 90-kV X-ray peaks during simulated endodontic radiography. The mean exposure dose was determined for each anatomical site. The results show that endodontic X-ray doses received by patients are low when compared with other radiographic procedures.

Healing of horizontal root fractures.

The roots of six anterior maxillary and mandibular teeth were intentionally fractured in three monkeys. The teeth were then rigidly splinted for 12 wk. The healing of the fractured roots was examined clinically, radiographically, and histologically for a period of 6 months. Five of six fracture sites healed by either dense connective tissue or mineralized hard tissue which appeared to enter the fracture sites from the periodontal ligament. The canal spaces in these teeth were reduced substantially by calcific deposits. The remaining pulp tissue appeared vital histologically, but with areas of odontoblastic layers absent. The fractured root which failed to heal showed presence of necrotic pulp in both apical and coronal segments and the fracture site was infiltrated by inflammatory cells.

Human saliva penetration of coronally unsealed obturated root canals.

Studies have shown significant coronal dye and bacterial leakage following exposure of sealed root canals to artificial and natural saliva. The purpose of this study was to determine the time needed for bacteria in natural saliva to contaminate the entire length of root canals obturated by lateral and vertical condensation techniques. Forty root canals were cleaned and shaped using a step-back technique. Thirty root canals were obturated with gutta-percha and root canal sealer using either lateral or vertical condensation techniques. Forty root canals were obturated without a root canal sealer and served as positive controls. After obturation, the coronal 3 mm of five root canals were sealed with sticky wax and served as negative controls. The coronal portions of the filling materials were placed in contact with human saliva and the number of days required for bacteria in saliva to penetrate the entire root canals were determined. No bacterial leakage occurred in the negative control group. Complete bacterial leakage occurred within 2 days in the positive control group. All root canals were recontaminated in less than 30 days. No statistical significant difference was found between the two methods of obturation.

The concentration of prostaglandin E2 in human periradicular lesions.

Prostaglandins (PG) have been implicated in the genesis of periapical lesions. Periapical specimens from patients with clinical signs and symptoms of chronic and acute apical periodontitis were obtained and immediately frozen in liquid nitrogen. Periradicular tissues from unerupted third molars were frozen and used as controls. The concentration of PGE2 was determined by radioimmunoassay. Low levels of PGE2 were found in the control tissues as compared with those detected in chronic and acute lesions. Significantly higher levels of PGE2 were found in acute lesions than those found in chronic lesions. The results show that acute lesions have higher concentrations of PGE2 than chronic lesions and confirm the role of prostaglandins in the pathogenesis of human periapical lesions.

Specificity of antibodies present in human periapical lesions.

Various classes of immunoglobulins have been found in human periapical lesions. The specificity of secreted antibodies against antigens egressing from the root canal system has yet to be thoroughly investigated. The purpose of this study was to test the specificity of antibodies present in human periapical lesions. Human periapical biopsies were removed and cultured as organ culture explants. Antibodies present in the lesions were extracted in the cell culture fluids. A modified enzyme-linked immunosorbent assay was used to determine the presence, type, and concentration of different classes of antibodies against a number of commonly found bacterial species present in the root canal system. The data show the presence of specific antibodies (IgG, IgM, and IgA) against all 16 microorganisms tested. Peptostreptococcus micros, Actinomyces israelii, Staphylococcus intermedius, and Fusobacterium nucleatum produced significantly high levels of IgG antibodies in these lesions.