The role of infection in signalling root resorption: A narrative review.

BACKGROUND: Root resorption consists of complex, multistep processes that involve cell signalling caused by inflammation and stromal cells, which promotes the secretion of receptor activator of nuclear factor κB ligand/ macrophage-colony stimulating factor (RANKL/M-CSF) resulting in a resorptive process. OBJECTIVE: The aim of this narrative review was to analyse the literature related to root resorption resulting from microbial infection and to comparing it with non-microbial infection. METHODS: An electronic literature search was performed using the PubMed database and applying keywords of articles published in English. Eligible papers were reviewed to reveal the descriptions of bone and root resorption processes. The abstracts were searched manually to identify articles about infection-stimulating bone and root resorption. RESULTS: Three main types of root resorption were identified, two associated with primary bacterial infection and one secondary to bacterial infection. These include external inflammatory resorption, internal inflammatory resorption and external cervical (invasive) resorption. DISCUSSION: The magnitude of cytokine involvement that promotes resorption and M-CSF/RANKL production depends on multiple factors, including pathogen virulence, site of infection and host genetic factors that activate the inflammation at the infection site. Two mechanisms activate the resorption mechanisms-the canonical and non-canonical pathways that can activate clastic cells independently of the RANKL/RANK canonical pathways. CONCLUSIONS: Two pathways of root resorption co-exist in the body. When resorption is caused by infection, chronic inflammation due to bacterial infection prolongs the secretions of pro-inflammatory cytokines that intensify root and bone resorption. The second pathway is bacterial independent of the non-infection root resorption that is part of the wound healing process, which is limited in time due to its innate ability.

Role of catalase in the elimination of residual hydrogen peroxide following tooth bleaching.

Hydrogen peroxide at high concentrations may cause damage to the tooth structure and to the surrounding periodontal tissues. The efficacy of catalase applied following intracoronal bleaching to eliminate residual hydrogen peroxide was examined and compared with prolonged water rinses. Extracted human premolars were treated endodontically and bleached with 30% hydrogen peroxide. Upon completion of the bleaching procedure, the teeth were treated with either catalase or water. Radicular hydrogen peroxide penetration was measured immediately after bleaching and following each catalase and/or water rinse. A correlation between the number of water rinses and the reduction in the radicular hydrogen peroxide penetration was found. Three cycles of 5-min water rinses and 1-h immersion of the teeth in water significantly reduced the residual hydrogen peroxide penetration. One treatment with catalase applied for 3 min totally eliminated the residual hydrogen peroxide. It is therefore suggested that catalase be used as an adjunct following intracoronal bleaching of nonvital teeth to effectively eliminate the residual hydrogen peroxide from the pulp chamber and from the surrounding periodontal tissues.

Incidence of four-rooted maxillary second molars: literature review and radiographic survey of 1,200 teeth.

A study of 1,200 teeth was carried out in order to determine the occurrence of four-rooted maxillary second molars. One-thousand untreated teeth were examined radiographically. Two-hundred teeth were evaluated radiographically following endodontic treatment. The results indicated that only 0.4% of the teeth presented with four separate roots. Endodontic therapy in such a tooth is described.

pH variation among materials used for intracoronal bleaching.

Intracoronal bleaching of pulpless teeth with 30% hydrogen peroxide may result in external cervical root resorption. One of several suggested etiological factors associated with this complication is the pH of the bleaching materials. Because the available data on the pH values of bleaching materials were conflicting, it was the purpose of this study to measure the pH of the materials commonly used for bleaching pulpless teeth. The pH of different concentrations of sodium perborate and 30% hydrogen peroxide, alone or in combination, were measured for a period of 14 days. Sodium perborate was confirmed to be alkaline, whereas 30% hydrogen peroxide was acidic. The pH of the materials when mixed together gradually changed from acidic to alkaline as the concentration of sodium perborate was increased. A thick clinical consistency mixture of both materials was alkaline, and its alkalinity increased with time. These results do not support the theory relating bleaching-induced root resorption to an acidic pH of the bleaching pastes.

A persistent oronasal sinus tract of endodontic origin.

Extraoral sinus tracts of endodontic origin may be confused with a wide variety of diseases. Although they may be located in a variety of sites on the face and neck, once diagnosed the treatment is relatively simple and successful. Endodontic therapy is the treatment of choice in these cases; however, periapical surgery may occasionally be required. A case of persistent oronasal sinus is described in which healing occurred only after surgical removal of the involved lesion.

Effect of bleaching agents on inorganic components of human dentin and cementum.

The effect of bleaching agents on the inorganic composition of human dentin and cementum was examined. Intact teeth were crushed, pulverized, and separated to dentin and cementum powders. The pulverized tissues were exposed to treatments with 30% H2O2, 3% H2O2, 2% sodium perborate in 30% H2O2, 2% sodium perborate in 3% H2O2, and 2% sodium perborate in bidistilled water for periods of 15 min and 1, 24, and 72 h. The degree of dissolution and the percentage of inorganic material for both dentin and cementum were measured. Thirty percent H2O2 and 2% sodium perborate in 30% H2O2 treatments significantly increased the solubility of dentin and cementum. The degree of dissolutions and the percentage of inorganic material remaining in the undissolved dentin and cementum increased with time progression. The greatest increase occurred with 30% H2O2 and 2% sodium perborate in 30% H2O2 after 24- and 72-h treatments. It is concluded that 30% hydrogen peroxide treatment may cause alteration in the chemical structure of the dentin and cementum making them more susceptible to degradation.

Effect of cementum defects on radicular penetration of 30% H2O2 during intracoronal bleaching.

Bleaching pulpless teeth with 30% hydrogen peroxide has been reported to cause external cervical root resorption. It has been hypothesized that H2O2 penetrating through open dentin tubules can initiate an inflammatory reaction which could result in root resorption. Extracted human premolars were treated endodontically and bleached intracoronally using the thermocatalytic technique. The teeth were divided into three groups; one group with no cementum defects at the cementoenamel junction, one group with artificial cementum defects at the cementoenamel junction, and another group with artificial cementum defects at the middle third of the root. The radicular penetration of 30% hydrogen peroxide in the three groups was assessed directly and compared using an in vitro model. Radicular penetration of hydrogen peroxide was found in all of the groups tested. The penetration of hydrogen peroxide was significantly higher in teeth with cementum defects at the cementoenamel junction than in those without defects.

Effect of bleaching agents on dentin permeability to Streptococcus faecalis.

Bacterial contamination of dentin may be a contributing factor in the development of bleaching-associated root resorption. In this study, the effect of commonly used bleaching agents on the permeability of dentin tubules to Streptococcus faecalis was evaluated. Sixty extracted bovine incisors were horizontally sectioned apically to the cementoenamel junction. In each tooth, a standard cavity was prepared, the pulp tissue extirpated, and remnants of soft tissue and smear layer were removed. Following rinsing and repeated autoclave sterilization, the teeth were divided into four groups, each treated with one of the following materials: 30% hydrogen peroxide, sodium perborate mixed with 30% hydrogen peroxide, sodium perborate mixed with distilled water, and distilled water alone that served as control. The bleaching agents were sealed in the teeth and incubated at 37 degrees C for 7, 14, and 21 days. At each time interval the bleaching agents were removed and the teeth incubated at 37 degrees C in brain heart infusion infected with S. faecalis. Histological sections were prepared, and the maximal bacterial penetration for each group was measured using a computerized morphometric system. Statistical analysis of the results revealed that teeth treated with either 30% hydrogen peroxide alone or in combination with sodium perborate were significantly more permeable to S. faecalis than those treated with sodium perborate mixed with water (p < 0.0001). Sodium perborate mixed with water did not cause an increase in dentin permeability to S. faecalis and was similar to the water control. In conclusion, it seems that bleaching agents containing hydrogen peroxide in high concentrations may increase bacterial penetration through dentinal tubules.

Incidence of interappointment emergency associated with endodontic therapy.

Endodontic interappointment emergency (EIE) occurs in a low incidence following treatment by qualified operators. The purpose of this study was to assess the incidence of EIE after treatment by undergraduate students and to examine its correlation with preoperative and operative parameters. Randomly selected 334 records were retrospectively surveyed for unscheduled emergency appointments following endodontic treatment by undergraduate students. Treatment included step-back canal preparation in multiple visits with formocresol interappointment dressing. The incidence of EIE was 4.2%, and unrelated to the patients' sex and age or to tooth location. It was significantly higher in nonvital than in vital teeth (p < 0.05), with the highest occurrence in nonvital teeth unassociated with periapical radiolucency. Clinically, EIE was associated with swelling in half of the cases. It is concluded that the incidence of EIE following treatment by undergraduate students is low and related to tooth vitality.

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).

Stafne's bone cavity in the anterior mandible: a possible diagnostic challenge.

Stafne was the first to report the presence of "bone cavities" in the angle of 35 mandibles. Such cavities generally appear in the area between the mandibular first molar and the mandibular angle, and are not considered rare. One of their primary radiological diagnostic features is the characteristic location below the mandibular canal. Stafne's bone cavity is relatively rare in the anterior mandible. The mandibular canal is not present in the anterior mandible. As a result, diagnosis in the anterior mandible may be missed. Needless treatment modalities such as endodontic treatment, bone trephining, and bone exploration may be conducted. The purpose of the present report is to describe a new case of Stafne's bone cavity in the anterior mandible and discuss the differential diagnosis process. The dental computerized tomography scan is suggested as the most suitable noninvasive diagnostic and follow-up modality for this bony configuration in the anterior mandible.

Prognosis of intracoronal bleaching with sodium perborate preparation in vitro: 1-year study.

Bleaching materials containing hydrogen peroxide have been used for treating discolored nonvital teeth but their use was occasionally associated with external root resorption. In a previous study it was found that the immediate results of bleaching teeth in vitro were equal for sodium perborate mixed with either water or hydrogen peroxide. The purpose of this study was to compare the bleaching prognosis of sodium perborate mixed with water or hydrogen peroxide over a 1-yr period. Extracted human teeth with intact crowns were discolored with human erythrocytes and bleached by sodium perborate mixed with either 30% hydrogen peroxide (group A), 3% hydrogen peroxide (group B), or water (group C). The bleaching materials were placed in the pulp chambers of the discolored teeth and sealed with IRM. They were replaced with fresh preparations after 3 and 7 days. After 14 days the coronal access cavities were sealed with composite resin and the teeth photographed with a color slide film under standardized conditions. The teeth were stored in artificial saliva for 1 yr and photographed after 3, 6, and 12 months. Two separate evaluators ranked the teeth by comparing them with the shades before and after bleaching. The bleaching success rates of the tested groups at each time interval were compared and analyzed statistically. It was found that after 1 yr all of the teeth in groups A and C maintained their shades. In 20% of the teeth in group B there was color regression. Statistically, these differences were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of different protective base materials on hydrogen peroxide leakage during intracoronal bleaching in vitro.

External root resorption may develop following intracoronal bleaching with hydrogen peroxide. The preventive effect of different base materials on the radicular penetration of H2O2 during intracoronal bleaching was assessed. Seventy-two bovine teeth and 20 human teeth were bleached with 30% H2O2. The bovine teeth were divided into four groups and the root canals filled with either IRM, zinc oxide-eugenol, composite resin, or glass ionomer. The radicular H2O2 penetration of each group at different layer thickness was compared. The experiment with the human teeth was performed in three stages. In the first stage no protective base was used. In the second stage IRM was placed to the cementoenamel junction level. In the third stage the IRM layer was removed 0.5 mm below the cementoenamel junction. None of the materials tested in the bovine teeth showed H2O2 penetration with a base thickness of 2 mm. When the base thickness was reduced to 1 mm, several teeth showed H2O2 penetration; however, there was no significant difference among the materials tested. When the base thickness was reduced to 0.5 mm, the H2O2 penetration in each group increased. A statistical difference was found between the composite and the glass ionomer (p < 0.05). The results for the human teeth showed that IRM layer placed at the cementoenamel junction level significantly reduced the radicular H2O2 penetration as compared with teeth where the IRM was either placed 0.5 mm below the cementoenamel junction or not placed at all (p < 0.01). It is therefore recommended that a protective base be placed to the cementoenamel junction level before intracoronal bleaching to prevent possible H2O2 hazards.

Dye leakage in retrofilled dog teeth and its correlation with radiographic healing.

In a previous study in beagle dogs, statistically significant differences in healing were observed radiographically 6 months after apicoectomy and retrofilling with amalgam and varnish, glass ionomer cement, or a composite resin. The purpose of this study was to compare the leakage of these retrofilling materials and to correlate leakage data with healing. After the dogs were sacrificed, 48 roots were extracted. Half of the roots had been irradiated with a CO2 laser on the bevelled root surface after retrofilling. The roots were coated with nail polish, except for their bevelled surface, and were suspended together with positive and negative controls in 2% methylene blue for 8 h. After the specimens were longitudinally split, they were ranked according to the severity of dye penetration, as observed with a dissecting microscope. The differences in dye leakage among the three retrofilling materials were not statistically significant. Consequently, dye leakage did not correlate with the previously assessed healing. Dye penetrated into the root through the bevelled root surface, regardless of CO2 laser exposure of that surface.

Effect of gutta-percha solvents on calcium and phosphorus levels of cut human dentin.

Fresh intact human teeth were cut and treated with 3 commonly used gutta-percha solvents: chloroform, xylene, and Endosolv-E. Treatment consisted of embedding the specimens of each group for 15 or 30 min in the test solution. After each time interval, the specimens were rinsed, dried, and prepared for surface energy dispersive spectrometric analysis. The calcium and phosphorus levels in each specimen were recorded and the differences between the test groups were statistically analyzed. The changes in the calcium and phosphorus levels following treatment with the gutta-percha solvents were minimal and statistically nonsignificant.

Effect of hydrogen peroxide and sodium perborate on the microhardness of human enamel and dentin.

The effect of 30% hydrogen peroxide and a paste of sodium perborate mixed with hydrogen peroxide at different temperatures and time intervals on the microhardness of human enamel and dentin was examined. Intact extracted human teeth were sectioned, embedded in acrylic resin, polished, and divided into four test groups related to surface treatment. The groups were 30% hydrogen peroxide at 37 degrees C, 30% hydrogen peroxide at 50 degrees C in an illuminated chamber, a paste of sodium perborate mixed with hydrogen peroxide at 37 degrees C, and a paste of sodium perborate mixed with hydrogen peroxide at 50 degrees C in an illuminated chamber. Teeth treated with distilled water at either 37 degrees C or 50 degrees C served as controls. The results indicated that treatment with 30% hydrogen peroxide reduced the microhardness of both enamel and dentin. This reduction was statistically significant after 5-min treatment for the dentin and after 15-min treatment for the enamel (p < 0.05). Treatment with sodium perborate mixed with hydrogen peroxide did not alter the microhardness of either the enamel or dentin at the tested temperatures and time intervals. It is therefore suggested that the use of high concentrations of hydrogen peroxide for bleaching purposes should be limited. Sodium perborate appears to be a less damaging bleaching agent.

Bypassing gutta-percha root fillings with an automated device.

Endodontic retreatment using Canal Finder K files and chloroform was performed in 106 gutta-percha-obturated, curved root canals, 71 in vitro and 35 in vivo. The minimum time taken to bypass the obturation in a single root canal was 3 s and the maximum time 95 s. The mean times were 19 and 27 s in the two in vitro groups and 32 s in the in vivo group. Eighty-nine percent of the root canals which had been obturated short were bypassed apically in vivo. Root canal curvature was well maintained in all but two root canals. In these two cases apical transportation occurred. Breakage of files occurred three times in vitro, but this did not prevent the completion of bypassing with new files. These results are attributed to the mode of action of the Canal Finder system, which makes it an efficient root canal pathfinder. The advantages of the suggested technique are discussed in light of the clinical considerations of endodontic retreatment.

Effect of gutta-percha solvents on surface microhardness of IRM fillings.

Eighty identical samples of IRM were prepared and embedded in acrylic resin. The samples were polished, rinsed, and divided into experimental groups and controls, 10 specimens each. Each experimental group was treated for 1 or 5 min with one of the following gutta-percha solvents: chloroform, xylene, or halothane. Sterile saline was used as a control. Treatment consisted of pipetting each solvent onto the external IRM surface. The specimens were then sealed in plastic assay tubes for the corresponding exposure periods. At each time period, surface microhardness of the samples was measured using a mini-load hardness tester with a 500 g load for 20 s. It was found that xylene and halothane caused significant reduction in surface microhardness of IRM after 5 min (p < 0.01). Chloroform caused significant reduction in surface microhardness of IRM after 1 min of treatment (p < 0.01). Chloroform caused total dissolution after 5 min of treatment. Saline caused only minor and nonsignificant changes in surface microhardness of IRM.

Bactericidal and cytotoxic effects of sodium hypochlorite and sodium dichloroisocyanurate solutions in vitro.

The antimicrobial and cytotoxic effects of sodium hypochlorite (NaOCl) and sodium dichloroisocyanurate (NaDCC) were evaluated and compared in vitro. The minimal inhibitory concentration and minimal bactericidal concentration of NaOCl and NaDCC were tested for Streptococcus sobrinus, Streptococcus salivarius, Enterococcus faecalis, and Streptococcus mutans. The cytotoxic effect was assessed by using human fibroblast tissue culture. Survival rate was assessed by a protein determination method. Results showed that the minimal inhibitory concentration and minimal bactericidal concentration values of NaOCl and NaDCC for the tested bacteria were in a similar range. NaDCC in concentrations higher than 0.02%, and NaOCl in concentrations higher than 0.01% were lethal to fibroblasts. In conclusion it seems that both agents were very effective in killing bacteria, and their cytotoxicity to fibroblasts in tissue culture was similar.

Histological characterization of bleaching-induced external root resorption in dogs.

External root resorption occasionally develops after intracoronal bleaching with hydrogen peroxide. In this study, an experimental model was established to study thermocatalytic bleaching-induced root resorption in dogs. Histological examination after 6 months revealed that 18% of the teeth had root resorption lesions. The lesions could be divided into three types. In type I, root excavations were associated with a dense inflammatory cell infiltrate. Type II lesions were characterized by granulation tissue formation. In type III, the lesions were filled with reparative cementum. The three types probably represent different phases of one process. Calcium hydroxide had no effect on the occurrence or type of resorption. The instability of hydrogen peroxide and the presence of inflammatory resorption lesions 6 months postoperatively suggest hydrogen peroxide-induced toxic radicals or denaturants as potential irritants.