Survival analysis of root-resected molars from 1 to 13.4 years: A retrospective cohort study.

STATEMENT OF PROBLEM: While root resective therapy may extend the longevity of a molar, data on patient selection and outcomes of root resection are scarce. PURPOSE: The purpose of this retrospective cohort study was to analyze the survival of root-resected molars and investigate factors affecting the decision and outcomes of the therapy. MATERIAL AND METHODS: Patient- and tooth-related data from participants who had received root resection between 1999 and 2022 were collected. Cox regression was used to build predictive models for time-to-tooth loss based on predictors-initial diagnoses (carious, endodontic, periodontal, or endodontic-periodontal lesions), the presence of a complete-coverage crown, and the location of the tooth in the arch (P<.001). RESULTS: Of 60 teeth, all from different participants, 31 molars were resected because of endodontic lesions. The failure rate was 35% with 21 teeth extracted. At 5 years, the survival probability was 0.58, considering all predictors. The survival of molars resected because of carious or endodontic lesions was significantly lower than those because of periodontal or endodontic-periodontal lesions (P<.05). The hazard ratio for tooth loss in the resected teeth was 15.6, 95% confidence interval (CI) (3.7 to 83.2) without complete-coverage crowns and 8.6, 95% CI (2.2 to 43.2) at the most posterior location. CONCLUSIONS: Root resection provided to manage a localized periodontal lesion had the highest prognosis. The absence of a crown and the location as the most posterior tooth in the arch were associated with poor survival following resection.

Clinical and microbiologic investigation of an expedited peri-implantitis dog model: an animal study.

BACKGROUND: Animal studies are pivotal in allowing experimentation to identify efficacious treatment protocols for resolution of peri-implantitis. The purpose of this investigation was to characterize an expedited dog peri-implantitis model clinically, radiographically, and microbiologically. METHODS: Eight hound dogs underwent extractions (week 0) and implant (3.3 × 8.5 mm) placement with simultaneous surgical defect creation and ligature placement for induction of peri-implantitis (week 10). Ligatures were replaced at 6 weeks (week 16) and removed after 9 weeks (week 19) when supporting bone loss involved approximately 50% of the peri-implant bone. Microbial samples from the defects and healthy control implant sites collected at week 19 were analyzed utilizing a microarray. Clinical measures of inflammation were obtained and radiographic bone loss was measured from periapical radiographs. Radiographic depth and width measurements of bony defect were repeated at weeks 10 (baseline), 16, and 19. Canonical analysis of principal coordinates was used to visualize overall differences in microbial abundance between peri-implantitis and healthy implants. RESULTS: This accelerated disease protocol led to intrabony defect creation with a mean depth and width of 4.3 mm and 3.5 mm, respectively after 9 weeks of ligature placement. Microbial identification revealed 59 total bacteria in peri-implant sites, 21 of which were only present in peri-implant sites as compared to healthy controls. Overall microbial beta diversity (microbial between-sample compositional diversity) differed between peri-implantitis and healthy implants (p = 0.009). CONCLUSIONS: Within the limitations of this study, this protocol led to expedited generation of peri-implant defects with a microbial profile indicative of a shift to disease and defect patterns conducive to regenerative treatment. However, the possibility of potential spontaneous resolution of lesions due to the lack of a chronicity interval as compared to chronic disease models need to be further clarified and considered during preclinical peri-implantitis model selection.

Prevalence of Teaching Apical Patency and Various Instrumentation and Obturation Techniques in United States Dental Schools: Two Decades Later.

INTRODUCTION: Maintaining apical patency has been advocated to minimize canal transportation, ledge formation, and loss of working length, despite increasing debris extrusion. A previous study in 1997 by Cailleteau and Mullaney reported 50% of United States dental schools taught patency. This present study aimed to evaluate recent trends in endodontic education in United States dental schools, in relation to the prevalence of maintaining apical patency and examining the primary methods of working length determination, instrumentation, obturation, and temporization. METHODS: A survey of 20 questions was distributed to 65 schools via e-mail and was available from July 2021 to September 2021. RESULTS: Seventy-three percent of the 46 responding schools reported that they teach patency, with 8% of this number reporting that they do so exclusively to endodontic residents. Notably, a significantly lower number of schools reported teaching patency exclusively to endodontic students compared with the Cailleteau and Mullaney study despite a significantly higher percentage of schools teaching patency overall. The most common method used to determine working length was an electronic apex locator at the 0.5 reading. Vortex Blue was the most commonly used file system used by both predoctoral and postdoctoral programs. Lateral condensation was the primary obturation technique taught in predoctoral programs, whereas warm vertical condensation was the primary obturation technique in postdoctoral programs. The study also found that 57% of schools reported using intraorifice barriers, and the most common temporary filling was glass ionomer. CONCLUSIONS: A greater portion of schools teaches patency compared with the previous study in 1997. The data collected in this survey may serve as a baseline for similar studies in the future regarding changes in endodontic education over time.

Comparison Study of Diagnosis and Treatment Planning for Dental Infections between Dental Students and Practitioners.

This study aimed to access the knowledge in diagnosing dental infections and the practice in treatment planning for the affected teeth among dental practitioners (DPs) and senior (final-year) students. A survey questionnaire containing two cases (Case A; periodontal abscess and Case B; periapical abscess) with four questions per case was delivered to potential participants. Fifty-nine DPs voluntarily participated in the survey. For senior students, the case study was a part of their course requirements; one of the two cases (either Case A or B) was randomly assigned to the 126 seniors. The distribution of responses was significantly different between the DP and senior groups except for the diagnosis of Case B (Fisher's exact test; p = 0.05). Only 31% of the participants diagnosed Case A as periodontal abscess; most of them selected periodontal surgery as the first treatment option. Despite a high agreement in diagnosing Case B, the choice of treatment was significantly different; the most frequent treatment option was extraction (51%) from the DP group and root canal retreatment (57%) from the senior group. The study revealed that the diagnosis of periodontal abscess was more challenging than that of periapical abscess among dental professionals.

Retrospective study on traumatic dental injuries in preschool children at Kyung Hee Dental Hospital, Seoul, South Korea.

The purpose of this study was to analyse the traumatic dental injuries (TDI) of Korean preschoolers by investigating the occurrence, type, area, cause, injured region, seasonal variation and the interval between injury and treatment. In this study, data from 1856 preschoolers aged 4 months to 6 years and 11 months (mean age : 3.6 +/- 1.6) were used, out of a total of 2761 patients who attended the Department of Pediatric Dentistry, Kyung Hee Dental Hospital for TDI between January 1998 and December 2007. All the data were statistically analysed using the anova and chi-square statics. Most of the patients were 1-2, 2-3 years old (24.5%, 25.4%) and boys were 1.67 times more likely to have TDI. The most common cause, location and seasonal variation of the trauma, were respectively falling (50.8%), at home (48.8%) and late spring. The treatment intervals usually occurred within a day. Most of the injuries involved single (47%) or double (38%) tooth/teeth. However, car accidents or sports trauma often involved multiple teeth. In both primary and permanent dentition, the most common teeth injured were maxillary central incisors (72.6%), and periodontal injury was caused by subluxation or concussion. Among the various types of hard tissue injuries, enamel fracture in the primary dentition (35.0%) and enamel-dentin fracture in the permanent dentition (45.8%) were the most common types.

Release of Growth Factors into Root Canal by Irrigations in Regenerative Endodontics.

INTRODUCTION: The aim of this study was to investigate the release of growth factors into root canal space after the irrigation procedure of regenerative endodontic procedure. METHODS: Sixty standardized root segments were prepared from extracted single-root teeth. Nail varnish was applied to all surfaces except the root canal surface. Root segments were irrigated with 1.5% NaOCl + 17% EDTA, 2.5% NaOCl + 17% EDTA, 17% EDTA, or deionized water. The profile of growth factors that were released after irrigation was studied by growth factor array. Enzyme-linked immunosorbent assay was used to validate the release of transforming growth factor (TGF)-ß1 and basic fibroblast growth factor (bFGF) at 4 hours, 1 day, and 3 days after irrigation. The final concentrations were calculated on the basis of the root canal volume measured by cone-beam computed tomography. Dental pulp stem cell migration on growth factors released from root segments was measured by using Transwell assay. RESULTS: Total of 11 of 41 growth factors were detected by growth factors array. Enzyme-linked immunosorbent assay showed that TGF-ß1 was released in all irrigation groups. Compared with the group with 17% EDTA (6.92 ± 4.49 ng/mL), the groups with 1.5% NaOCl + 17% EDTA and 2.5% NaOCl + 17% EDTA had significantly higher release of TGF-ß1 (69.04 ± 30.41 ng/mL and 59.26 ± 3.37 ng/mL, respectively), with a peak release at day 1. The release of bFGF was detected at a low level in all groups (0 ng/mL to 0.43 ± 0.22 ng/mL). Migration assay showed the growth factors released from root segments induced dental pulp stem cell migration. CONCLUSIONS: The root segment model in present study simulated clinical scenario and indicated that the current irrigation protocol released a significant amount of TGF-ß1 but not bFGF. The growth factors released into root canal space induced dental pulp stem cell migration.

Interfacial characteristics of Biodentine and MTA with dentine in simulated body fluid.

OBJECTIVES: Newer tricalcium silicate cements (TSC) may offer biocompatibility with improved working properties. This study aimed to evaluate: (1) the occurrence of mineral deposition at the interface between dentine and two TSC (ProRoot(®) MTA and Biodentine(®)) in simulated body fluid, and (2) to investigate the nature of interfacial layer. METHODS: Six root dentine segments of 1.5mm thickness were obtained from extracted human teeth and were instrumented with Gates-Glidden drills. The specimens were then randomly filled with either MTA or Biodentine. The specimens were placed in the simulated body fluid containing the same phosphate concentration as blood plasma. After 4 weeks, the specimens were examined with Scanning Electron Microscope (SEM) and Energy Disperse X-ray Spectroscopy (EDX) to measure the thickness of the interfacial layer and Ca/P ratio. Transmission Electron Microscope (TEM) and Selective Area Electron Diffraction (SAED) were conducted to examine the interface ultramicroscopically and to determine the nature of the crystalline structure within interfacial layer. RESULTS: The thickness of interfacial layer was significantly higher in the MTA group (14.5 µm vs 4.8 µm) (p<0.001). However, there was no significant difference between MTA and Biodentine in Ca/P ratio of interfacial layer (4.1 vs 2.7) (p>0.05). From TEM examination, amorphous calcium phosphate (ACP) was observed in the interface along with the surface of dentine. CONCLUSIONS: As an alternative to MTA, Biodentine displayed bioactivity by producing an interfacial layer on the root canal dentine even though its thickness was significantly lower than MTA. ACP was observed in the interfacial layer of both biomaterials. CLINICAL SIGNIFICANCE: Biodentine could be considered as an alternative to MTA due to comparable bioactivity which creates interfacial layer between root canal dentin and Biodentine.

Differential aggressiveness of ethylenediamine tetraacetic acid in causing canal wall erosion in the presence of sodium hypochlorite.

OBJECTIVE: This study tested the hypothesis that the use of ethylenediamine tetraacetic acid (EDTA) as a final irrigant causes canal wall erosion only after prolonged use of 5.25% sodium hypochlorite (NaOCl) as the initial irrigant. METHODS: Two irrigation protocols were employed: (1) 5.25% NaOCl as the initial irrigant for 10 min and 17% EDTA as the final irrigant for 2 min; and (2) 5.25% NaOCl for 60 min and 17% EDTA for 2 min. Flexural strengths of dentine beams prepared from human mid-coronal dentine were evaluated using a miniature three-point bending device after they were irrigated with either protocol. Transmission electron microscopy was used to examine the conditions of instrumented canal walls irrigated with either protocol after they were bonded with methacrylate resin-based sealers. RESULTS: Immersion of dentine beams in NaOCl for 60 min instead of 10 min prior to the use of EDTA resulted in a significant (p<0.001) decline in flexural strength. For both NaOCl initial rinsing times, a 2-min final irrigation with EDTA created similar 0.5 microm thick demineralisation fronts. However, extensive surface and subsurface erosion of radicular dentine was seen only when the dentine was immersed in NaOCl for 60 min. CONCLUSION: The apparent aggressiveness of EDTA in causing canal wall erosion is attributed to the prolonged use of NaOCl. The associated decline in dentine flexural strength has potential clinical relevance when thin pulp chamber dentine is immersed in NaOCl for lengthy periods during canal instrumentation. This may render root-treated teeth more prone to vertical fracture.

The effect of initial irrigation with two different sodium hypochlorite concentrations on the erosion of instrumented radicular dentin.

OBJECTIVE: This study evaluated the effects of different NaOCl concentrations and contact times on removal of the organic phase from mineralized dentin with and without the adjunctive use of EDTA, and the effect of NaOCl concentrations on canal wall erosion after the use of EDTA as the final active irrigant. METHODS: Dentin powders were immersed in 5.25% or 1.3% NaOCl for different contact periods and then rinsed with 17% EDTA for 2 min. Before and after the use of 17% EDTA as the final rinse, the NaOCl-treated dentin powders were examined using ATR-FT-IR spectroscopy to analyze the relative loss of organic and inorganic components. Scanning (SEM) and transmission electron microscopy (TEM) were used to examine the erosion of instrumented canal walls irrigated with 5.25% NaOCl/EDTA or 1.3% NaOCl/EDTA. RESULTS: Compared with 1.3% NaOCl, less intact collagen remained within the subsurface of the mineralized dentin powder after the use of 5.25% NaOCl, irrespective of subsequent rinsing with 17% EDTA. Canal wall erosion was apparent only under SEM when root canals were irrigated 5.25% NaOCl followed by 17% EDTA. Under TEM examination, subsurface erosion extended 10-15 microm beneath the sealer-bonded dentin surface after the use of 5.25% NaOCl for 20 min. CONCLUSION: The superficial destructive effect of NaOCl on mineralized dentin is irreversible and is present irrespective of whether EDTA is subsequently employed as the final active irrigant. The EDTA removes the collagen-depleted apatite phase to expose the underlying cause of destruction that is morphologically perceived as canal wall erosion.

Review of contemporary irrigant agitation techniques and devices.

INTRODUCTION: Effective irrigant delivery and agitation are prerequisites for successful endodontic treatment. METHODS: This article presents an overview of the irrigant agitation methods currently available and their debridement efficacy. RESULTS: Technological advances during the last decade have brought to fruition new agitation devices that rely on various mechanisms of irrigant transfer, soft tissue debridement, and, depending on treatment philosophy, removal of smear layers. These devices might be divided into the manual and machine-assisted agitation systems. Overall, they appear to have resulted in improved canal cleanliness when compared with conventional syringe needle irrigation. Despite the plethora of in vitro studies, no well-controlled study is available. This raises imperative concerns on the need for studies that could more effectively evaluate specific irrigation methods by using standardized debris or biofilm models. In addition, no evidence-based study is available to date that attempts to correlate the clinical efficacy of these devices with improved treatment outcomes. Thus, the question of whether these devices are really necessary remains unresolved. There also appears to be the need to refocus from a practice management perspective on how these devices are perceived by clinicians in terms of their practicality and ease of use. CONCLUSIONS: Understanding these fundamental issues is crucial for clinical scientists to improve the design and user-friendliness of future generations of irrigant agitation systems and for manufacturers' contentions that these systems play a pivotal role in contemporary endodontics.

The efficacy of different sealer removal protocols on bonding of self-etching adhesives to AH plus-contaminated dentin.

INTRODUCTION: Smearing of unset root canal sealers over the pulp chamber dentin may adversely affect bonding of self-etching adhesives and jeopardize their coronal sealing potential. This study examined the influence of different sealer removal protocols on the microtensile bond strengths of two self-etching adhesives to AH Plus-contaminated dentin. METHODS: Coronal dentin surfaces were prepared from extracted human third molars. In the positive control groups, these surfaces were not contaminated with sealer and were bonded with Clearfil SE Bond or Clearfil Tri-S Bond. For the experimental groups, dentin surfaces were contaminated with AH Plus and wiped with either dry cotton pellets, cotton pellets saturated with ethanol, or cotton pellets saturated with Endosolv R followed by rinsing the dissolved sealer with water prior to bonding with the two adhesives. Bonded specimens were sectioned into resin-dentin beams for microtensile bond strength evaluation. Additional specimens were prepared for transmission electron microscopy to examine the ultrastructure and nanoleakage within the hybrid layers. RESULTS: For both adhesives, microtensile bond strengths significantly declined when the sealer was removed with dry cotton pellets or cotton pellets saturated with ethanol. Only the Endosolv R/water sealer removal protocol restored tensile bond strengths to those of the uncontaminated positive controls without adversely affecting hybrid layer formation in intact dentin or increasing nanoleakage within the resin-dentin interfaces. CONCLUSION: The Endosolv R sealer removal protocol appears to be effective in preventing the deterioration of bond strengths of the two self-etching adhesives to AH Plus-contaminated dentin and warrants further clinical investigation.

Electrospun gelatin/polyurethane blended nanofibers for wound healing.

In this study, we prepared a blended nanofiber scaffold using synthetic and natural polymers, polyurethane (PU) and gelatin respectively, using the electrospinning method to prepare a material for wound dressing. In order to confirm the properties of this gelatin/PU blended nanofiber scaffold, we performed scanning electron microscopy, atomic force microscopy, attenuated total reflectance Fourier-transform infrared spectroscopy, thermal gravimetric analysis, contact angle, water uptake, mechanical property, recovery, and degradation tests, and cellular response. The results obtained indicate that the mean diameter of these nanofibers was uniformly electrospun and ranged from 0.4 to 2.1 microm. According to the results, when the amount of gelatin in the blended solution decreased, the contact angle increased and water uptake of the scaffold decreased concurrently. In the mechanical tests, the blended nanofibrous scaffolds were elastic, and elasticity increased as the total amount of PU increased. Moreover, as the total amount of gelatin increased, the cell proliferation increased with the same amount of culture time. Therefore, this gelatin/PU blended nanofiber scaffold has potential application for use as a wound dressing.

A maxillary second molar with 6 canals: a case report.

The first step in a successful endodontic treatment is to gain access to the pulp chamber and find all of the canals. To achieve this goal, practitioners need to be familiar with all possible variations of the root canal and have adequate information of the tooth needing treatment. The present case report describes an anatomical variant of the maxillary second molar with 6 canals, a variation that has not been previously reported. Helpful hints for detection of the unusual canal are presented, as well.