Mikako Hayashi

MTA for Obturation of Mandibular Central Incisors with Open Apices: Case Report

The case reported demonstrates dramatic healing of the periapical region of retreated root canals with open apices by the successful use of mineral trioxide aggregate (MTA). Unsuccessful conventional root canal therapy for the mandibular central incisors had been followed by surgical treatment. The severely damaged root canals were obturated using MTA in anticipation of the formation of artificial apical plugs. The treated teeth were asymptomatic, and radiographic examination demonstrated apparent regeneration of periradicular tissue 2 years after the obturation. MTA can be considered a very effective material to promote regeneration of apical tissue, even in teeth with large open apices.

Role of Mouse and Human Autophagy Proteins in IFN-γ–Induced Cell-Autonomous Responses against Toxoplasma gondii

IFN-γ mediates cellular innate immunity against an intracellular parasite, Toxoplasma gondii, by inducing immunity-related GTPases such as p47 IFN-γ–regulated GTPases (IRGs) and p65 guanylate-binding proteins (GBPs), which also participate in antibacterial responses via autophagy. An essential autophagy protein, Atg5, was previously shown to play a critical role in anti–T. gondii cell-autonomous immunity. However, the involvement of other autophagy proteins remains unknown. In this study, we show that essential autophagy proteins differentially participate in anti–T. gondii cellular immunity by recruiting IFN-γ–inducible GTPases. IFN-γ–induced suppression of T. gondii proliferation and recruitment of an IRG Irgb6 and GBPs are profoundly impaired in Atg7- or Atg16L1-deficient cells. In contrast, cells lacking other essential autophagy proteins, Atg9a and Atg14, are capable of mediating the anti–T. gondii response and recruiting Irgb6 and GBPs to the parasites. Although IFN-γ also stimulates anti–T. gondii cellular immunity in humans, whether this response requires GBPs and human autophagy proteins remains to be seen. To analyze the role of human ATG16L1 and GBPs in IFN-γ–mediated anti–T. gondii responses, human cells lacking ATG16L1 or GBPs were generated by the Cas9/CRISPR genome-editing technique. Although both ATG16L1 and GBPs are dispensable for IFN-γ–induced inhibition of T. gondii proliferation in the human cells, human ATG16L1 is also required for the recruitment of GBPs. Taken together, human ATG16L1 and mouse autophagy components Atg7 and Atg16L1, but not Atg9a and Atg14, participate in the IFN-γ–induced recruitment of the immunity-related GTPases to the intracellular pathogen.

Ways of enhancing pulp preservation by stepwise excavation—A systematic review

OBJECTIVES The best possible methods and materials in stepwise excavation for deep caries in permanent teeth were investigated. The review considers the questions from many aspects including clinical success, effects of reducing cariogenic bacteria, possibility of hardening softened dentin, and likelihood of generating tertiary dentin. DATA This systematic review includes the use of data from randomized controlled trials, controlled clinical trials as well as from case series in which pulp exposure resulted following the treatment and removal of deep caries. Only studies of caries in permanent teeth were considered. Those involving treatment of primary teeth were excluded. SOURCES An electronic search was conducted in the databases of MEDLINE and Igaku Chuo Zasshi (Japanese) from 1970 to 2008. The electronic search was supplemented by a manual search of the references lists of all the relevant studies. STUDY SELECTION The electronic and manual searches of journals retrieved a total of 266 English and 130 Japanese papers. According to the inclusion and exclusion criteria, 10 English and 3 Japanese studies were finally identified. CONCLUSION Our research suggests that stepwise excavation is effective for pulp preservation in extremely deep caries that do not show clinical symptoms of irreversible pulpitis. Calcium hydroxide, as well as antimicrobials and polycarboxylate cement combined with tannin-fluoride preparation, is effective in reducing bacteria and promoting remineralization of the carious dentin that remained after stepwise excavation. Further clinical trials with a high level of study design should be conducted to identify the best methods of removing carious dentin using stepwise excavation.

Prognosis of Intentional Replantation of Vertically Fractured Roots Reconstructed with Dentin-Bonded Resin

There is no particular treatment established to preserve vertically fractured teeth. We evaluated the long-term prognosis of the intentional replantation of 26 vertically fractured roots after reconstruction with 4-META/MMA-TBB dentin-bonded resin. Replanted teeth were evaluated according to clinical criteria and radiographic examinations for periods ranging from 4 to 76 months. Eighteen cases were functional and retained, with six fully successful; the others needed further observation. Eight cases failed to respond to treatment because of refracture, recurrence of gingival inflammation, or both. Longevity was calculated as 88.5% at 12 months after replantation, 69.2% at 36 months, and 59.3% at 60 months. All failures occurred in premolar and molar teeth. Longitudinal fractures extending more than 2/3 from the cervical portion toward the apex showed significantly shorter longevity compared with fractures within the 2/3 area (log-rank test, p = 0.02). Intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin may be considered for incisors as an alternative to extraction, although the long-term success is not optimal.

Clinical guidelines for treating caries in adults following a minimal intervention policy--evidence and consensus based report.

OBJECTIVES In 2002, FDI (World Dental Federation) published a policy advocating that caries be treated by minimal intervention (MI). This MI policy has been accepted worldwide and is taught in universities. But acceptance in general dental practice has been slower, especially in Japan where healthcare payment and practice favour drilling and filling. To help disseminate this MI policy into general practice, the Japanese Society of Conservative Dentistry developed an evidence-based clinical guideline for restoring carious permanent teeth in adult patients. METHODS The guideline was developed by a committee of nine university clinicians and a librarian. The committee selected the most frequent clinical questions in treating caries and used electronic databases to search and assess the best scientific evidence for each. Members then added their clinical experience and discussed to reach consensus on each question on treating caries with MI policy. Graded recommendations and guidance were made for each clinical question. The provisional guideline was strengthened after review and discussion with university researchers and general practitioners. RESULTS The guideline addresses the 16 most frequent clinical questions in treating adult caries, including restorative methods and how to tackle root caries. Recommendations for treatment using MI policy were developed using the best scientific evidence and consensus of experienced clinicians. CLINICAL SIGNIFICANCE The guideline offers a practical expert view of treating caries with the MI policy that incorporates the best scientific evidence, the latest techniques, the most preferable materials and the general consensus of expert clinicians.

Short-term evaluation of intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin.

The purpose of this study was to evaluate intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin. Twenty vertically fractured teeth were extracted intentionally and reconstructed with 4-META/MMA-TBB dentin-bonded resin. After reconstruction, the teeth were replanted into the original sockets. The replanted teeth were evaluated by clinical criteria and radiographic examination. The observation periods ranged between 4 and 45 months. Longevity was calculated by the Kaplan-Meier method, and factors that had significant influence on the longevity were analyzed with the Log rank test at a 95% level of confidence. From this short-term observation, 14 of 20 cases were functioned in the oral environment. Of these 14 cases, 6 could be considered truly successful and 8 cases needed further observation. The other six cases were total failures and were extracted. The longevity was calculated as 83.3% at 12 months and 36.3% at 24 months. Teeth with thin roots or with longitudinal fractures extending over 2/3 of the root from the cervical portion toward the apex showed significantly lower longevity. It was concluded that this method had the potential to preserve vertically fractured teeth.

Static and fatigue fracture resistances of pulpless teeth restored with post–cores

OBJECTIVES Superior restorative methods for effectively strengthening pulpless teeth need to be identified, since vertical root fractures of pulpless teeth are still a major problem in everyday clinical practice. The present study tested the null hypothesis that there were no differences in static and fatigue fracture resistances of pulpless teeth restored with different types of post-core systems. METHODS Extracted human premolars were restored with a combination of either a fiber post or metallic post and a composite resin core. Teeth with full crown preparations without post-core restorations served as a control. A 90 degrees vertical or 45 degrees oblique static compressive load was applied to restored teeth, and fracture loads and modes of fracture were recorded. Fatigue fracture tests were conducted by applying sinusoidal cyclic loads to restored teeth from vertical or oblique directions. Fatigue limits for each restoration were calculated using the staircase approach. RESULTS In both static and fatigue fracture testing under vertical or oblique loadings, the fracture loads of teeth restored with fiber posts were significantly greater than those of teeth restored with metallic posts. The fatigue limits of teeth restored with fiber and metallic posts were 112 kgf and 82 kgf respectively under vertical loadings and 26 kgf and 20 kgf under oblique loadings. SIGNIFICANCE The combination of a fiber post and a composite resin core showed superior fracture resistance against both static and fatigue loadings compared to restorations using a metallic post, and is therefore recommended in restoring pulpless teeth.

Cell Wall-Anchored Nuclease of Streptococcus sanguinis Contributes to Escape from Neutrophil Extracellular Trap-Mediated Bacteriocidal Activity

Streptococcus sanguinis, a member of the commensal mitis group of streptococci, is a primary colonizer of the tooth surface, and has been implicated in infectious complications including bacteremia and infective endocarditis. During disease progression, S. sanguinis may utilize various cell surface molecules to evade the host immune system to survive in blood. In the present study, we discovered a novel cell surface nuclease with a cell-wall anchor domain, termed SWAN (streptococcal wall-anchored nuclease), and investigated its contribution to bacterial resistance against the bacteriocidal activity of neutrophil extracellular traps (NETs). Recombinant SWAN protein (rSWAN) digested multiple forms of DNA including NET DNA and human RNA, which required both Mg2+ and Ca2+ for optimum activity. Furthermore, DNase activity of S. sanguinis was detected around growing colonies on agar plates containing DNA. In-frame deletion of the swan gene mostly reduced that activity. These findings indicated that SWAN is a major nuclease displayed on the surface, which was further confirmed by immuno-detection of SWAN in the cell wall fraction. The sensitivity of S. sanguinis to NET killing was reduced by swan gene deletion. Moreover, heterologous expression of the swan gene rendered a Lactococcus lactis strain more resistant to NET killing. Our results suggest that the SWAN nuclease on the bacterial surface contributes to survival in the potential situation of S. sanguinis encountering NETs during the course of disease progression.

Risk assessment of dental caries by using Classification and Regression Trees

OBJECTIVES Being able to predict an individuals risks of dental caries would offer a potentially huge natural step forward toward better oral heath. As things stand, preventive treatment against caries is mostly carried out without risk assessment because there is no proven way to analyse an individuals risk factors. The purpose of this study was to try to identify those patients with high and low risk of caries by using Classification and Regression Trees (CART). METHODS In this historical cohort study, data from 442 patients in a general practice who met the inclusion criteria were analysed. CART was applied to the data to seek a model for predicting caries by using the following parameters according to each patient: age, number of carious teeth, numbers of cariogenic bacteria, the secretion rate and buffer capacity of saliva, and compliance with a prevention programme. The risks of caries were presented by odds ratios. Multiple logistic regression analysis was performed to confirm the results obtained by CART. RESULTS CART identified high and low risk patients for primary caries with relative odds ratios of 0.41 (95%CI: 0.22-0.77, p = 0.0055) and 2.88 (95%CI: 1.49-5.59, p = 0.0018) according the numbers of cariogenic bacteria. High and low risk patients for secondary caries were also identified with the odds ratios of 0.07 (95%CI: 0.01-0.55, p = 0.00109) and 7.00 (95%CI: 3.50-13.98, p < 0.0001) according the numbers of bacteria and existing caries. CONCLUSIONS Cariogenic bacteria play a leading role in the incidence of caries. CART proved effective in identifying an individual patients risk of caries.

Effects of the tea catechin epigallocatechin gallate on Porphyromonas gingivalis biofilms.

The aim of this study was to investigate the effects of tea catechin epigallocatechin gallate (EGCg) on established biofilms and biofilm formation by Porphyromonas gingivalis, a major pathogen of periodontal disease.