Treatment outcomes of regenerative endodontic procedures in nonvital mature permanent teeth: a retrospective study.

OBJECTIVES: This retrospective study was undertaken to clinically and radiographically evaluate the long-term outcomes of regenerative endodontic procedures (REPs) for nonvital mature permanent teeth, to analyze predictors influencing treatment outcomes. METHODS: Nonvital mature permanent teeth treated by REPs with a minimum follow-up period of 6 months were included from 2015 to 2017. Treatment outcomes were categorized as success and failure. The periapical status and lesion healing were assessed in terms of the periapical index (PAI) and the percentage changes in periapical radiolucency (PARL) area. The clinical and radiographic outcomes of REPs were assessed by Mann-Whitney test at different follow-up period. Kaplan-Meier curves and Univariate Cox regression analysis were conducted to assess the success and identify potential predictors affecting outcomes, respectively. RESULTS: A total of 37 mature teeth with an average follow-up of 4.3 years satisfied the criteria, and 89.2% of the teeth had a successful outcome. Significant differences in PAI scores were found between each period with respect to the baseline (p < .05). Among different periods, there was a significant difference between intervals of 3-6 months and 7-12 months (p = .039) and no significant difference between each interval of more than 12 months (p > .05). Eighty-seven percent of teeth with preoperative PARL presented completely healed. REPs significantly decreased the PARL area at the interval of 7-12 months compared to 3-6 months (p = .025), with no significant difference between each interval of more than 12 months (p > .05). No significant predictor was found for the success of outcome (p > .05). Thirteen teeth (35.1%) regained pulp sensibility, and 40.5% of the teeth exhibited intracanal calcification. CONCLUSIONS: Within the limitations of this study, REPs provided a high long-term success rate and promoted the resolution of PARL as a biologically-based alternative treatment option for nonvital mature teeth. CLINICAL RELEVANCE: REPs provide a high long-term success rate and promoted healing of apical periodontitis comparable with reported outcomes for root canal therapy of mature teeth.

Experts consensus on the procedure of dental operative microscope in endodontics and operative dentistry.

The dental operative microscope has been widely employed in the field of dentistry, particularly in endodontics and operative dentistry, resulting in significant advancements in the effectiveness of root canal therapy, endodontic surgery, and dental restoration. However, the improper use of this microscope continues to be common in clinical settings, primarily due to operators' insufficient understanding and proficiency in both the features and established operating procedures of this equipment. In October 2019, Professor Jingping Liang, Vice Chairman of the Society of Cariology and Endodontology, Chinese Stomatological Association, organized a consensus meeting with Chinese experts in endodontics and operative dentistry. The objective of this meeting was to establish a standard operation procedure for the dental operative microscope. Subsequently, a consensus was reached and officially issued. Over the span of about four years, the content of this consensus has been further developed and improved through practical experience.

Clinical and radiographic outcomes of regenerative endodontic procedures for traumatized permanent necrotic teeth with apical periodontitis and external root resorption.

AIM: This clinical study was undertaken to assess the effect of treatment with regenerative endodontic procedures (REPs) on 20 teeth with pulp necrosis, apical periodontitis, and external root resorption (ERR). METHODOLOGY: Teeth were treated with REPS utilizing the American Association of Endodontists (AAE) protocol. Quantitative assessment of changes in radiographic root area (RRA) were statistically analysed to assess changes in root dimensions after an average follow-up period of 3 years. RESULTS: All 20 teeth survived, 14 teeth (70%) were classified successful, and only 1 tooth (5%) failed throughout the study period. Based on the radiographic examination, all 20 teeth showed complete repair of the periapical lesions and arrested ERR. However, 5 teeth (25%) subsequently developed replacement resorption. The RRA between baseline and 3-year follow-up showed a significant difference for the total 20 teeth (p = .009). An analysis according to the trauma type and the extra-oral time showed the RRA increase was significantly different in the non-avulsion group (p = .015) and for the avulsion group with an extra-oral time less than 60 min (p = .029). The RRA increase was not statistically significant in the avulsion group of extra-oral time more than 60 min (p = .405). Nine teeth (45%) and 10 teeth (50%) responded to cold and electric pulp testing, respectively. CONCLUSIONS: Within the limitations of this study, the favourable outcomes of REPs were further confirmed for traumatized permanent necrotic teeth with ERR in terms of periapical lesion healed and a significant increase in RRA. The study contributes further evidence of the role of REPs in arresting ERR.

Comparing accuracy after guide access and microscope-assisted access for fiber post removal.

OBJECTIVES: This study compared the accuracy of the guide-supported and the microscope-assisted fiber post removal systems by using the extracted teeth. These new idea and theory can be used by clinicians to remove fiber posts. METHODS: Twenty-eight human extracted premolars were randomly divided into the guide and microscope groups. After root canal treatment and fiber post restoration, the fiber posts were removed by using a digital guide and via microscope-assisted ultrasonic instrument, respectively. Mimics 10.0 was used to measure the deviation, and the accuracy of the two fiber post removal systems were compared. RESULTS: In the guide group, the apical vertical deviation was 0.99 mm±0.52 mm, the apical horizontal deviation was 0.75 mm±0.19 mm, the angle deviation was 2.32°±0.64°, and the volume loss was 8.09 mm3±1.42 mm3. In the microscope group, the apical vertical deviation was 0.44 mm±0.23 mm, the apical horizontal deviation was 0.23 mm±0.07 mm, the angle deviation was 0.64°±0.31°, and the volume loss was 15.25 mm3±3.94 mm3. No significant difference was found in the apical vertical deviation between the two groups (P>0.05), whereas the apical horizontal deviation, the angle deviation, and the volume loss were significantly different between the two groups (P<0.05). CONCLUSIONS: The removal of fiber post supported by a digital guide helped reduce the volume loss of post-core restoration teeth, but its accuracy was lower than that of removal by using a microscope-assisted ultrasonic instrument.

Regenerative Endodontic Procedures for Traumatized Immature Permanent Teeth with Severe External Root Resorption and Root Perforation.

External root resorption (ERR) is often a complication of traumatic injury to the teeth. Traditionally, external inflammatory root resorption is treated with calcium hydroxide. The outcome of ERR, especially replacement resorption, is unpredictable. The purpose of the present case report was to describe regenerative endodontic procedures (REPs) for 1 replanted avulsed tooth with severe external root resorption and root perforation (tooth #9) and 1 extruded tooth (tooth #8). A 9-year-old girl was referred for the treatment of teeth #8 and #9 4 months after the initial trauma. Clinical examination showed that tooth #9 had a sinus tract present near the periapical area, was tender to percussion and palpation, and did not respond to pulp sensibility tests. Tooth #8 responded to pulp sensibility tests. Periapical radiographic and cone-beam computed tomographic examination showed that tooth #9 had a periapical radiolucent lesion and severe ERRs with a root perforation. Tooth #9 was diagnosed with a necrotic pulp and symptomatic apical periodontitis. Regenerative endodontic procedures (REPs) were initiated. Tooth #8 became nonresponsive to pulp sensibility tests and developed a periapical lesion 12 months after REPs of tooth #9 and was also treated with REPs. The clinical symptoms and apical lesions resolved for both teeth after REPs. The severe ERRs were arrested, and root perforation was repaired for tooth #9. Teeth #8 and #9 underwent canal obliteration by hard tissue formation after REPs and were in function at 18 months and 30 months, respectively. REPs may be used to manage traumatized immature permanent teeth with a necrotic pulp and apical periodontitis associated with severe ERR and root perforation.

Oxidative potential of ambient PM2.5 in Wuhan and its comparisons with eight areas of China.

Oxidative potential (OP) is a good indicator for assessing health risk associated with exposure to fine particulate matter (PM2.5, <2.5 µm in aerodynamic diameter). In this study, 24-h ambient PM2.5 samples were collected at three sampling sites throughout selected months of 2012 in Wuhan, Central China. Water soluble ions, metals, organic carbon (OC), elemental carbon (EC), levoglucosan, polycyclic aromatic hydrocarbons (PAHs), hopanes, and dicarboxylic acids were determined. The dithiothreitol (DTT) assay was used to characterize the oxidative potential of PM2.5. Linear regression analysis and principal component analysis (PCA) were used to link OP to the individual redox-active components originating from diverse emission sources. The OP results from the three sites in Wuhan, combined with the findings from eight other field studies of OP conducted in China, were compiled in order to compare the OP data in developed countries. The average, normalized OP levels for volume and mass at the three sampling sites in Wuhan were in the range of 1.8-8.2 nmol min-1 m-3 and 18.2-52.8 nmol min-1 mg-1, respectively. The differences in OP levels across sampling sites depended on the temporal and spatial differences in redox-active components of PM2.5. Results from linear regression and PCA showed that the redox-active components emitted from secondary inorganic aerosols as well as secondary organic aerosols were associated with the volume normalized OP in Wuhan. Two notable findings are illustrated by synthesizing the OP results observed at multi-sites across China. Of the nine field studies conducted in China, the lowest measured mass-normalized OP levels are significantly higher than the highest OP levels from field studies conducted in developed continents. China shares the same sources responsible for OP (e.g., secondary sources, fuel combustion, biomass burning, and dust emissions) with several other countries in developed continents.

A hybrid source apportionment strategy using positive matrix factorization (PMF) and molecular marker chemical mass balance (MM-CMB) models.

The molecular marker-based chemical mass balance (MM-CMB) method performs well in the source apportionment of organic carbon (OC) but has some difficulty with contributions from primary sources to inorganic secondary ions when apportioning PM2.5 (particles with aerodynamic diameter of 2.5 µm or less) sources. Positive matrix factorization (PMF) with the input of inorganic and organic tracers can properly estimate the contributions of primary and secondary sources to inorganic secondary ions; however, PMF is unable to apportion several PM2.5 sources with large fractions of organic carbon and few elemental compositions. In this study regarding data collected in 2011 and 2012 at three sites in Wuhan, China, the MM-CMB model was used to apportion OC in the PM2.5, and the PMF model was used to apportion the inorganic ions (sulfate, nitrate, and ammonia), dust, and EC. The source contributions of PM2.5 were estimated by reconstructing masses of bulk chemical components that had been apportioned to real-world sources using suitable source apportionment methods. Good performance of this hybrid source apportionment strategy was observed with ten resolved factors, explaining 70-80% of measured PM2.5 mass on average. The hybrid strategy takes the advantages of both models in PM2.5 source apportionment and yields unique source apportionment results for PM2.5 bulk chemical components, which could provide new information for optimizing air quality regulations for the emission abatement of target PM mass and compositions for countries around the world.

Factors affecting the length of fiber post and core structure: a literature review / 口腔疾病防治

@#An id eal balance between the post length within root and the coronal extension should exist. Some theories advocated the use of the longest post as possible as the apical seal is not disturbed. Others advocated that the post should be longer than the crown or that the post should be a certain fraction of the length of the root. The conventional post length has been equal to 2/3-3/4 of the root length from half a century ago. Most of these theories have emphasized the post length in order to achieve sufficient retention and rigidity for coronal restoration. However, dental materials are evolving.With the use of fiber post and resin cement, stress distribution and post retention are improved over conventional metal post and zinc phosphate or glass-ionomer cement. Therefore, with improved bonding strength of fiber post, the post length within root should be minimized to maintain sufficient coronal rigidity. Factors affecting fracture resistance balance of a post-and-core system include the amount of Ferrule height (FH), Post length in root (PLIR), Post length in bone (PLIB), Abutment height (AH), Core length (CL) and Post length out of bone (PLOB). In view of the factors mentioned above, this paper investigated the mechanical factorsin a post-and-core system with literature review.

[Contrasting study of erythritol and xylitol on Streptococcus mutans].

OBJECTIVE: To study the inhibitory effect of erythritol by contrast to xylitol on growth and acid production of Streptococcus mutans (S. mutans). METHODS: S. mutans were incubated respectively in 0.5%, 1%, 2%, 4%, 8%, 12%, 16% erythritol or xylitol culture medium under anaerobic conditions. The A and pH value of the mediums were measured at 0, 2, 4, 6, 8, 10, 12, 18, 24 hours, following the profile plots by SPSS. RESULTS: The data of A were higher in 0.5%, 1%, 2% erythritol culture medium than in xylitol culture medium at the same concentration, while lower in 8%, 12%, 16% erythritol culture medium than in xylitol culture medium at the same concentration. The data of pH were lower in 0.5%, 1%, 2% erythritol culture medium than in xylitol culture medium at the same concentration, while higer in 8%, 12%, 16% erythritol culture medium than in xylitol culture medium at the same concentration. It indicated that the growth and acid production of S. mutans were higer in 0.5%, 1%, 2% erythritol culture medium than in xylitol culture medium at the same concentration, while lower in 8%, 12%, 16% erythritol culture medium than in xylitol culture medium at the same concentration. CONCLUSION: Compared with xylitol, erythritol in low concentration has weaker effort on the growth and acid production of S. mutans, while having stronger effort in high concentration.