Students' experience and perceptions of undergraduate endodontic education in New Zealand.

This study investigated the clinical experience and perceptions of New Zealand graduating dental students (2019 and 2020) towards endodontic teaching and their clinical learning outcomes using an online survey and clinical scenarios. Quantitative data were analysed using SPSS software, and qualitative data were analysed thematically. Responses were similar for both cohorts (response rates 74%, 2019; 73%, 2020). Endodontic teaching was valuable and interesting but difficult compared with other disciplines. Molar endodontics, finding canals and managing posture were challenging. Students felt more confident and less anxious when supervised by clinicians experienced in endodontics. Time management was the most anxiety-inducing factor and significantly related to clinical experience (p < 0.001). Overall, students appropriately applied knowledge in most areas of endodontics while holistic problem-solving in complex scenarios was variable. Maximising clinical experience and supervision from teachers experienced in endodontics are important for learning, improving confidence and reducing anxiety.

The effects of chelation on the intratubular penetration depth of mineral trioxide aggregate.

The penetration depth and extent of mineral trioxide aggregate (MTA) crystallisation into dentinal tubules at 2, 4 and 6 weeks after chelation and MTA obturation were investigated. Standardised 12 mm human root specimens (45) were prepared with NiTi rotary files using 4% NaOCl irrigation. They were randomly allocated to three irrigants (n = 15: 4% NaOCl, 15% ethylenediaminetetraacetic acid or Edgemix) and obturated with sodium fluorescein tagged ProRoot MTA. One millimetre thick apical, middle and coronal sections were examined using confocal laser scanning microscopy to determine MTA penetration depth and area. Depths varied from 352 to 1821 µm at 6 weeks depending on section level and were unaffected by chelation. No differences (p > 0.05) were found in mean maximum penetration depth or dentine area (%) between the 3 irrigants at all time intervals. MTA mineralisation penetrated up to 90% of dentinal tubules and can extend to the cementum in roots with patent, non-infected tubules.

De novo-designed transmembrane domains tune engineered receptor functions.

De novo-designed receptor transmembrane domains (TMDs) present opportunities for precise control of cellular receptor functions. We developed a de novo design strategy for generating programmed membrane proteins (proMPs): single-pass α-helical TMDs that self-assemble through computationally defined and crystallographically validated interfaces. We used these proMPs to program specific oligomeric interactions into a chimeric antigen receptor (CAR) that we expressed in mouse primary T cells and found that both in vitro CAR T cell cytokine release and in vivo antitumor activity scaled linearly with the oligomeric state encoded by the receptor TMD, from monomers up to tetramers. All programmed CARs stimulated substantially lower T cell cytokine release relative to the commonly used CD28 TMD, which we show elevated cytokine release through lateral recruitment of the endogenous T cell costimulatory receptor CD28. Precise design using orthogonal and modular TMDs thus provides a new way to program receptor structure and predictably tune activity for basic or applied synthetic biology.

T Cell Activation Machinery: Form and Function in Natural and Engineered Immune Receptors.

The impressive success of chimeric antigen receptor (CAR)-T cell therapies in treating advanced B-cell malignancies has spurred a frenzy of activity aimed at developing CAR-T therapies for other cancers, particularly solid tumors, and optimizing engineered T cells for maximum clinical benefit in many different disease contexts. A rapidly growing body of design work is examining every modular component of traditional single-chain CARs as well as expanding out into many new and innovative engineered immunoreceptor designs that depart from this template. New approaches to immune cell and receptor engineering are being reported with rapidly increasing frequency, and many recent high-quality reviews (including one in this special issue) provide comprehensive coverage of the history and current state of the art in CAR-T and related cellular immunotherapies. In this review, we step back to examine our current understanding of the structure-function relationships in natural and engineered lymphocyte-activating receptors, with an eye towards evaluating how well the current-generation CAR designs recapitulate the most desirable features of their natural counterparts. We identify key areas that we believe are under-studied and therefore represent opportunities to further improve our grasp of form and function in natural and engineered receptors and to rationally design better therapeutics.

Bonding strengths to porcelain: An in vitro study of ultrasonic and conventional tooth preparation and etching.

OBJECTIVE: To compare the bond strength of porcelain to enamel and dentin preparations finished with either ultrasonic instruments or diamond burs, with or without acid etching. MATERIALS AND METHODS: A total of 140 extracted bovine incisor teeth were divided into two groups, enamel and dentin. A split tooth model was employed: each tooth having a randomly allocated combination of diamond burs, ultrasonic instrument, etching, and no etching treatments on their labial surface. Lithium disilicate glass ceramic specimens were bonded to the prepared surfaces and tensile testing was carried out. Force was applied to failure, and linear mixed models were used to analyze the data. RESULTS: Etching increased the bond strength of the dentin samples by 7.63 MPa (P < 0.001). When bonding to dentin, ultrasonic instrument preparation produced a 2.88 MPa greater bond strength compared to burs (P < 0.001). CONCLUSION: Ultrasonic preparation produced greater bond strengths compared to rotary instruments. Etching improved the bond strength of all preparations, with enamel having consistently greater bonding values than dentin.

Lubrication during root canal treatment.

Lubrication is involved in all root canal treatment phases, from dental dam placement to canal obturation. Most often associated with instrumentation, lubrication is required to facilitate the mechanical action of hand/rotary files and to help emulsify and suspend the debris produced. Aqueous irrigation solutions such as sodium hypochlorite and ethylenediaminetetraacetic acid (EDTA) should be regarded as lubricants, but paste-type substances are marketed specifically for this purpose. As more patients demand the retention of challenging teeth with narrow and curved root canals, the importance of lubrication in all aspects of root canal treatment must be acknowledged.

The effect of different geometric shapes and angles on the fracture strength of IPS e.max computer-aided designed ceramic onlays: An in vitro study.

STATEMENT OF PROBLEM: The current ceramic onlay preparation techniques for cuspal areas involve the reduction of cusps following the cuspal anatomy and the removal of all sharp angulations. However, there is little research literature studying the effect of occlusal preparation angles. Furthermore, there is no recent literature on the effect of angulations on IPS e.max computer-aided designed (CAD) (e.max) ceramic onlays. PURPOSE: The purpose of this study is to investigate the effect of geometric cuspal angulation and different internal preparation angles on the fracture strength of e.max CAD ceramic onlays. MATERIALS AND METHODS: Sharp (33° and 22°) and round (33° and 22°) preparations were tested, each group having 10 specimens. e.max ceramic onlays were milled, sintered, glazed, and then bonded onto geometric tooth models. Fracture strength was measured at the initial fracture with a universal testing machine. The load was applied laterally to the central fossa (2-point contact) and vertically to the cusp peak (1-point contact). RESULTS: A reduced cuspal angulation of 22° resulted in a stronger ceramic onlay than a 33° angulation when laterally loaded (P = 0.001). The presence of sharp angles weakened the ceramic significantly for both the 22° preparation (P = 0.0013) and 33° preparation (P = 0.0304). CONCLUSION: This in vitro study found that preparation angles of 22° resulted in superior fracture strength during central fossa loading and that rounding the preparation resulted in significantly higher fracture strength when a cusp peak load was applied. When the cusp tip loading is applied, the preparation angle does not appear to influence the fracture strength.

Crack Formation Following Root-End Preparation in Roots with the Butterfly Effect.

OBJECTIVE: To investigate apical cracks in roots that exhibit the butterfly effect and that have undergone apical resection and ultrasonic root-end cavity preparation. The effect of the obturation material was also studied. METHODS: Forty extracted single-rooted teeth were decoronated at the cemento-enamel junction. Roots were viewed under a light microscope and coded according to the presence or absence of the butterfly effect. Canals were prepared using ProTaper Next instruments to size X3 and assigned to two obturation groups (gutta-percha and AH Plus, and ProRoot MTA alone). Each contained twenty roots (10 with the butterfly effect and 10 without the butterfly effect). Roots were resected perpendicular to their long axis, 3 mm from the apex, and cavities were cut using ultrasonic retrotips. Resin replicas were used for crack imaging from scanning electron micrographs. Statistical analyses were performed using Stata 13.1 (StataCorp, College Station, TX, USA). RESULTS: Cracks occurred more frequently in teeth with the butterfly effect (80%), with this difference being significant (P=0.001). Most cracks (73%) ran buccolingually. Teeth obturated with MTA developed fewer cracks compared to those obturated with GP and sealer. CONCLUSION: Root-ends with the butterfly effect had a significantly higher number of buccolingual cracks following resection and ultrasonic root-end preparation. This might explain the development of some vertical root fractures, which usually run buccolingually. Canal obturation with MTA may be protective.

Sealer penetration and adaptation in root canals with the butterfly effect.

The butterfly effect is a phenomenon seen in some roots and is related to density of dentinal tubules. The aim was to investigate penetration depth and adaptation quality of root canal sealers and ProRoot MTA into bucco-lingual and mesio-distal aspects of roots with and without the effect. One hundred and twenty teeth were decoronated at the cemento-enamel junction. Canals were prepared and assigned to obturation groups: gutta-percha with a sealer (AH Plus, EndoREZ, Kerr Pulp Canal Sealer, MTA Fillapex) or ProRoot MTA alone (each containing 10 butterfly and 10 non-butterfly roots). Root sectioning yielded coronal and middle samples. Confocal laser scanning and scanning electron microscopy were used to assess penetration and adaptation. Teeth with the effect had greater mean penetration bucco-lingually (766 µm) than mesio-distally (184 µm, P = 0.003). Coronal sections had greater penetration (430 µm) compared with middle (247 µm, P = 0.006). In conclusion, greater penetration in roots with the effect may improve treatment outcomes.

Proposed new industry code on unhealthy food marketing to children and young people: will it make a difference?

Reducing the exposure of children and young people to the marketing of unhealthy foods is a core strategy for reducing the high overweight and obesity prevalence in this population. The Advertising Standards Authority (ASA) has recently reviewed its self-regulatory codes and proposed a revised single code on advertising to children. This article evaluates the proposed code against eight criteria for an effective code, which were included in a submission to the ASA review process from over 70 New Zealand health professors. The evaluation found that the proposed code largely represents no change or uncertain change from the existing codes, and cannot be expected to provide substantial protection for children and young people from the marketing of unhealthy foods. Government regulations will be needed to achieve this important outcome.

Eyesight: a study of the staff of a dental school.

OBJECTIVES/AIMS: The aim was to investigate the vision of all 90 dentally qualified staff at a dental school. MATERIALS AND METHODS: Ethical approval was obtained and a questionnaire-based survey conducted. Data were screened and analysed using Stata 13.1. The χ2 and Fisher's Exact tests were used to test for significance with an alpha level of 0.05. RESULTS: The participation rate was 95.6%. Most of the teachers (92%) considered their eyesight was satisfactory to practice dentistry. Of the 97% who had been tested at some stage, 15% had their eye examination due to sight deterioration with 22% needing correction. Almost two-thirds were myopic and a third were hyperopic. Forty-nine per cent wore spectacles only, with about a quarter of this group alternating between spectacles and contact lenses. Of those with corrected vision, 80% followed their optometrist's recall advice. Four participants reported that they were colour blind. While 4% had had laser-eye surgery, a further 27% were interested in this. Magnification was used by 72% with no significant differences between genders, age of staff member, place of qualification or registration status. Most of the staff (81%) thought that screening of dental student's eyesight should be mandatory, and regular eye examinations as a condition of dental practice was supported by 67%. DISCUSSION: The number of teachers reporting recent vision tests was encouraging; nevertheless, a worrying 8% surveyed were unsure if their eyesight was satisfactory for work. The commonest vision problem was myopia, with almost half of the teachers wearing spectacles. It is clear that visual standards for dentistry would be helpful. Magnification use was high, with many non-users indicating their intention to buy loupes. CONCLUSIONS: Within the limits of this study the teachers were conscientious regarding their eye care, irrespective of their training and age. There was strong support for the mandatory testing of vision for all dentists and especially dental students.

Electronic apex locators may be better at determining endodontic working length than radiographs and could reduce patient radiation exposure.

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Clinical efficacy of electronic apex locators: Systematic review. Martins JNR, Marques M, Mata A, Carames J.J Endod 2014;40(6):759-77. REVIEWER: Nicholas Chandler, BDS, MSc, PhD, LDSRCS, MRACDS (Endo), FDSRCPS, FDSRCSEd, FFDRCSI PURPOSE/QUESTION: The authors conducted a systematic review to compare radiographic and electronic methods of determining endodontic working length. SOURCE OF FUNDING: The authors reported no external funding sources. TYPE OF STUDY/DESIGN: Systematic review LEVEL OF EVIDENCE: Level 2: Limited-quality patient-oriented evidence STRENGTH OF THE RECOMMENDATION GRADE: Grade B: Limited-quality patient-oriented evidence.

Effectiveness of Disposable (Single-use) Tips for Dental Air-water Syringes.

BACKGROUND: Single-use dental syringe (SUS) tips eliminate cross-infection risks. Many dental materials are moisture sensitive; therefore bonding could be affected by remaining moisture from SUS tips. METHODS: An air-water syringe was calibrated to 50 PSI and the air pressure measured. SUS tips were then attached and pressure re-measured. Seven tips were tested; moisture content and spray pattern were investigated. Ethical approval was granted. Twenty third molar teeth were sectioned, stored in phosphate buffered saline and randomly allocated into groups with a SUS tip. They were mounted in acrylic and polished. Specimens were dried with a tip under standardised conditions, treated using a 3-step etch-prime-bond technique, then had a post bonded perpendicular to the dentine surface. The force to detach them was measured. Data were analysed using one-way analysis of variance (ANOVA) and Chi-squared tests. RESULTS: The difference in output pressure between groups proved significant (p < 0.001). Tensile force at failure was significantly different between groups (p = 0.19). CONCLUSIONS: The pressure output of the syringe and bond strength are influenced by the SUS tip.

Root canal treatment and prevalence of apical periodontitis in a nigerian adult subpopulation: a radiographic study.

PURPOSE: To evaluate the frequency, distribution and quality of root canal treatment in an adult Nigerian subpopulation and to determine the prevalence of apical periodontitis. MATERIALS AND METHODS: The periapical status and length of root fillings of 756 patients attending Obafemi Awolowo University Teaching Hospital, Ile-Ife, Nigeria for the first time were evaluated using full mouth periapical radiographs. The length of the root canal filling was considered 'adequate' if it was ≤ 2 mm from the radiographic apex, 'under-filled' if it was > 2 mm short of the apex, and 'overfilled' if filling material extended beyond the radiographic apex. Periapical status was assessed using the periapical index (PAI) with teeth classified as having apical periodontitis if the score was over 2. RESULTS: Overall, 61.2% of the patients had root-filled teeth and 67.2% featured apical periodontitis. Of the 21,468 teeth examined, 12.2% had been root filled, and of these 41% exhibited apical periodontitis. The prevalence of root-filled teeth was higher in the younger patients, while the prevalence of apical periodontitis in root-filled teeth was similar between age groups. Root-treated teeth that were overfilled or were mandibular incisors had the highest prevalence of apical disease. Overfilled teeth were more prone to developing an apical radiolucency than were under-filled teeth (P < 0.001 and P < 0.05, respectively). CONCLUSIONS: The prevalences of endodontically treated teeth and apical periodontitis were within the range reported for other countries; however, a very large number of patients required treatment or retreatment.

Undergraduate endodontic teaching in New Zealand: students' experience, perceptions and self-confidence levels.

The aim was to investigate undergraduate students' experiences, perceptions of future practice and self-rated confidence levels across endodontic tasks. After ethical approval, a survey involved all fourth and fifth year students. Quantitative data were analysed in SPSS version 20.0. Qualitative data were analysed using a general inductive approach. The participation rate was 84% (n = 136 of 162). The mean number of canals completed was 2.6 by fourth years and 10.4 by fifth years. Maxillary premolars were the most common first tooth treated. Pulpal factors and root morphology were the most common reasons for experiencing difficulty. Self-rated confidence levels were lower for the more junior students and complex procedures. Students felt that an increased use of extracted natural teeth would be beneficial in their pre-clinical practice. A high level of interest was shown in future specialisation in endodontics. Students may benefit from further didactic teaching or pre-clinical instruction in selected topics.

Antibacterial properties of root canal lubricants: a comparison with commonly used irrigants.

The aim was to assess in vitro the antibacterial activity of 10 root canal lubricants. K-Y Jelly personal lubricant, RC-Prep, File-Eze, File-Rite, EndoPrep Gel, Endosure Prep Crème 15%, Prep-Rite, Glyde, SlickGel ES and Alpha Glide were selected and compared in their antimicrobial properties to seven irrigants. Serial dilutions of each agent in tryptic soy broth were inoculated with either Enterococcus faecalis or Pseudomonas aeruginosa and incubated at 37C for 24 h. During incubation bacterial growth was measured by optical density (A(600)), and samples removed for cultivation on tryptic soy broth agar. Against both test bacteria after 1 h incubation, six lubricants recorded minimum bactericidal concentrations ranging from 1/10 to 1/80, whereas the inhibitory activity of the irrigants ranged from 1/20 to 1/640. Under these conditions, several lubricants exhibited antimicrobial activity comparable with some irrigants. Three irrigants, Consepsis (containing chlorhexidine), Endosure EDTA/C (containing cetrimide) and EndoPrep Solution (containing cetrimide), showed superior antibacterial action to lubricants against both species. The irrigants containing ethylenediamine tetraacetic acid and cetrimide were the most effective against both bacterial species at all time intervals. Antimicrobial activity of the lubricants did not correlate to pH values, which ranged from 2.9 to 10.3. Root canal lubricants have antibacterial properties that may help to disinfect canals.

Investigation of dentin hardness in roots exhibiting the butterfly effect.

INTRODUCTION: Most vertical root fractures occur in root canal treated teeth, and they usually run in a buccolingual direction. The butterfly effect is an optical phenomenon seen in some sections of tooth roots. The aim was to investigate the microhardness of dentin in mesiodistal and buccolingual cross sections of roots exhibiting the effect. METHODS: Thirty extracted single-rooted teeth were allocated according to patient age: group 1, 15-24 years; group 2, 25-44 years; and group 3, 45 years and older. Roots were embedded in acrylic and cut into ten 1-mm-thick cross sections. Sections were viewed under a light microscope and coded (1 or 2) according to presence or absence of the butterfly effect. A root scored 20 when all levels featured the butterfly appearance. The 2 teeth with the highest score from each group and 2 control teeth with the minimum score (10) were selected. Two adjacent, consecutive cross sections were chosen from the middle of the roots. Vickers microhardness testing was carried out on the dentin walls. RESULTS: Mean hardness scores were highest mesiodistally (83.7 kgf/mm(2)) and lowest buccolingually (56.4 kgf/mm(2)), a significant difference (P = .028). This trend was found across all age groups. CONCLUSIONS: Root sections with the butterfly effect are harder mesiodistally. This might explain the high prevalence of vertical root fractures that run buccolingually.

Crack formation on resected root surfaces subjected to conventional, ultrasonic, and laser root-end cavity preparation.

OBJECTIVE: The aim of this study was to evaluate cracks on root ends following resection and cavity preparation with a laser and two established techniques. BACKGROUND DATA: If root canal treatment of a tooth fails, an apicoectomy operation may be indicated. Three millimeters of the root tip is resected and a cavity of similar depth with parallel walls is cut to receive a root-end filling. MATERIALS AND METHODS: Sixty extracted human maxillary anterior teeth were used. Their root canals were prepared with rotary instruments, and they were filled with gutta-percha. Twenty teeth were resected with tungsten carbide fissure burs, and their root-end cavities cut with tungsten carbide round burs at a slow speed (Group 1). The other 40 teeth were resected with an Er:YAG laser, and root-end cavities were made with the same laser (Group 2), or with an ultrasonically-powered zirconium nitride coated retrotip (Group 3). The number and types of cracks on the resected surfaces were assessed using a stereomicroscope before and after cavity preparation. RESULTS: Cracking was not significantly different between the more conventional group and the laser groups after resections (p>0.05) or following cavity preparation (p>0.05). CONCLUSIONS: In this in vitro study, the laser resection and root-end preparation technique did not influence the number or type of cracks formed on the root surfaces.

Accuracy of the Dentaport ZX apex locator for working length determination when retreating molar root canals.

The aim of this study was to evaluate the accuracy of the Dentaport ZX apex locator for working length determination during root canal retreatment of mandibular molars. Fifteen extracted mandibular first molars with separate mesial canals and apical foraminae and one distal canal were selected. The mesiobuccal and distal canals were investigated; the length with the file tip at the major diameter was defined as the tooth length (TL). The canals were prepared with ProTaper files to 1 mm short of this and filled with gutta-percha and AH Plus sealer. One week later, the root fillings were removed using ProTaper retreatment files. Tooth length was remeasured and recorded as the retreatment tooth length (RTL). Then electronic measurements were taken at the major (electronic apex locator (EAL) major) and minor (EAL minor) foraminae as suggested by the instrument display. These lengths were compared with RTL and measurements 0.5 and 1 mm short of this distance. For both canals, no significant difference was found between RTL and EAL major, and 0.5 mm short of RTL and EAL minor (P > 0.05). There were significant differences found between all other readings. The Dentaport ZX could not detect the minor foramen accurately but was able to indicate the major foramen in molars undergoing a root canal retreatment procedure.

Dentists make larger holes in teeth than they need to if the teeth present a visual illusion of size.

BACKGROUND: Health care depends, in part, on the ability of a practitioner to see signs of disease and to see how to treat it. Visual illusions, therefore, could affect health care. Yet there is very little prospective evidence that illusions can influence treatment. We sought such evidence. METHODS AND RESULTS: We simulated treatment using dentistry as a model system. We supplied eight, practicing, specialist dentists, endodontists, with at least 21 isolated teeth each, randomly sampled from a much larger sample of teeth they were likely to encounter. Teeth contained holes and we asked the endodontists to cut cavities in preparation for filling. Each tooth presented a more or less potent version of a visual illusion of size, the Delboeuf illusion, that made the holes appear smaller than they were. Endodontists and the persons measuring the cavities were blind to the parameters of the illusion. We found that the size of cavity endodontists made was linearly related to the potency of the Delboeuf illusion (p<.01) with an effect size (Cohen's d) of 1.41. When the illusion made the holes appear smaller, the endodontists made cavities larger than needed. CONCLUSIONS: The visual context in which treatment takes place can influence the treatment. Undesirable effects of visual illusions could be counteracted by a health practitioner's being aware of them and by using measurement.