Evaluation of the Quality of Undergraduate Full Veneer Crown Preparations at a UK Dental Teaching Hospital.

OBJECTIVES: To determine the quality of full veneer crown preparations produced by supervised undergraduate students at a UK dental teaching hospital. METHODS: One hundred and eighty-five scanned digital dies between October 2019 and March 2021 were obtained. Using cross-sections in four planes, the total angle of convergence, abutment height, margin design and margin depth were evaluated. Statistical comparisons were made by plane, location, material-type, tooth-type, and inter- and intra-arch positions. RESULTS: Across all preparations the mean total angle of convergence was 24.8° ± 11.7°. and mean abutment height was 3.6 mm ± 1.0 mm. Mandibular and molar teeth were significantly more tapered (P ⟨0.001) and exhibited significantly shorter abutment heights (P ⟨0.001). Chamfer margins were the most frequently observed and mean margin depths ranged from 0.49-1.06 mm. The compliance to recommended taught parameters were 28.1%, 42.7%, 34.1% and 6.5% for total angle of convergence, abutment height, margin design and margin depth, respectively. CONCLUSIONS: The findings from this study suggest that compliance to taught parameters is poor, especially for molar teeth, and demonstrates the use of digital software in guiding future research and teaching.

Antimicrobial Efficacy of Different Irrigant Solutions Using a Novel Biofilm Model: An In Vitro Confocal Laser Scanning Microscopy Experiment.

AIM: To determine the ability of different irrigation solutions to biomechanically remove Enterococcus faecalis biofilm from a novel artificial root canal model during chemomechanical preparation. METHODS: High resolution micro-computer-tomography scans of a mandibular molar's mesial root were used to produce 50 identical 3D-printed resin root canal models. These were cultured with E.faecalis over seven days to generate biofilm and subjected to chemomechanical preparation using: saline; 17% ethylenediaminetetraacetic acid (EDTA) or 2% sodium hypochlorite (NaOCl) alongside positive/negative controls (n = 10). Canals were prepared to 40/.06 taper, with 1 mL irrigation between instruments, followed by 5 mL penultimate rinse, 30 s ultrasonic activation and 5 mL final rinse. Residual biofilm volume (pixels) was determined following immunofluorescent staining and confocal-laser-scanning-microscopy imaging. Statistical comparisons were made using Kruskal-Wallis with post-hoc Dunn's tests (α ⟨0.05). RESULTS: In all canal thirds, the greatest biofilm removal was observed with NaOCl, followed by EDTA and saline. The latter had significantly higher E.faecalis counts than NaOCl and EDTA (P ⟨0.01). However, no statistical differences were found between EDTA and NaOCl or saline and positive controls (P ⟩0.05). CONCLUSIONS: Within limitations of this model, 17% EDTA was found to be as effective as 2% NaOCl at eradicating E.faecalis biofilm following chemomechanical preparation. Further investigations with multi-species biofilms are encouraged.

The influence of irrigant activation, concentration and contact time on sodium hypochlorite penetration into root dentine: an ex vivo experiment.

AIM: To establish whether irrigant activation techniques, namely manual dynamic activation (MDA), passive ultrasonic irrigation (PUI) and sonic irrigation (SI), improve the tubular penetration of sodium hypochlorite (NaOCl) into root dentine when compared with conventional needle irrigation (CNI). Secondly, investigate if increasing NaOCl concentration and/or contact time improves the performance of these techniques. METHODOLOGY: A total of 83 extracted human maxillary permanent canines were decoronated to 15 mm, and root canals prepared to a size 40, .10 taper. Root dentine was stained with crystal violet for 72 h and embedded in silicone. Eighty specimens were randomly distributed into 16 groups (n = 5) according to the irrigant activation technique, NaOCl concentration (2%; 5.25%) and irrigant contact time (10 min; 20 min). All activation techniques were used for 60 s in the last minute of irrigation. Additionally, three teeth were not exposed to NaOCl to confirm adequate dentine staining had occurred (i.e. negative control). All specimens were subsequently dissected, observed under a light microscope and NaOCl penetration depth (µm) determined by measuring the average width of bleached dentine using ImageJ software. Statistical comparisons were made with paired and unpaired t-tests, anovas followed by post hoc Tukey's and Dunnett's tests, and a general linear model (α < 0.05). RESULTS: Overall, NaOCl penetration ranged from 38.8 to 411.0 µm with MDA, PUI and SI consistently resulting in significantly greater tubular infiltration than CNI (P < 0.05). The deepest measurements in the coronal, middle and apical segments were all recorded in the MDA; 5.25%; 20 min group and the least in the CNI; 2%; 10 min group. Increasing either irrigant concentration or contact time resulted in significantly greater NaOCl penetration depths for all techniques and segments of the canal (P < 0.05). However, when irrigant concentration and contact time were increased together, a significant interaction effect between these two independent variables was observed on overall NaOCl penetration (P < 0.05). CONCLUSIONS: Agitating irrigants with MDA, PUI or SI, as well as using greater irrigant concentrations or contact times, potentiated NaOCl penetration into root dentine. However, longer durations of NaOCl exposure at lower concentrations resulted in similar depths of tubular penetration as those achieved at higher concentrations.

A systematic review of methods used to sample and analyse periradicular tissue fluid during root canal treatment.

AIM: The primary aim was to identify techniques used to sample and analyse periradicular tissue fluid (PTF) in permanent teeth diagnosed with apical disease during root canal treatment. Secondly, to identify the types of inflammatory mediators studied using this approach. METHODOLOGY: Data Sources: PubMed, EMBASE, Cochrane Library, Science Direct, Web of Science and OpenGrey. Eligibility Criteria: Clinical studies published until 1 June 2018 which utilized orthograde techniques to sample and analyse PTF were included. Cell culture, laboratory or animal studies and those concerned with investigating inflammatory mediator activity from within healthy or diseased pulp tissue, and not periradicular tissues, were excluded. Study appraisal and methods: In accordance with PRISMA guidelines, data were extracted on study characteristics, target mediators, sampling and assay techniques and the parameters associated with the PTF sampling and eluting protocol. A qualitative synthesis was conducted, and studies were critically appraised using a modified version of the Cochrane risk of bias tool. RESULTS: Study Characteristics: From 251 studies, 33 were eligible for inclusion. Sampling techniques included the use of paper points (n = 27), fine needle aspiration (n = 4) and filter strips (n = 2). Assay techniques included enzyme-linked immunosorbent assay (n = 18), quantitative polymerase chain reaction (n = 9), radioimmunoassay (n = 4), colorimetric assay (n = 2), immunofluorometric assay (n = 1) and cytometric bead array (n = 1). Forty-five different inflammatory mediators were targeted at the proteomic/metabolomic (n = 25) or transcriptomic level (n = 9). LIMITATIONS: Significant heterogeneity exists within the methodology, and only 5 studies disclosed unambiguous information about their PTF sampling and eluting protocols. CONCLUSIONS: Paper points and proteomic/metabolomic analysis are currently the preferred methods for studying and analysing PTF during root canal treatment. The most studied analytes were IL-1ß and TNF-α. IMPLICATIONS: Further research is required to develop an optimized PTF sampling and eluting protocol to overcome methodological heterogeneity, and future studies are advised to follow a standardized approach to reporting their methodology.

Efficacy of irrigant activation techniques in removing intracanal smear layer and debris from mature permanent teeth: a systematic review and meta-analysis.

AIMS: To establish whether irrigant activation techniques (IATs) result in greater intracanal smear layer and debris removal than conventional needle irrigation (CNI). METHODOLOGY: Six electronic databases were searched to identify scanning electron microscopy studies evaluating smear layer and/or debris removal following the use of manual dynamic activation (MDA), passive ultrasonic irrigation (PUI), sonic irrigation (SI) or apical negative pressure (ANP) IATs in mature permanent teeth. Meta-analyses were performed for each canal segment (coronal, middle, apical and apical 1 mm) in addition to subgroup analyses for individual IATs with respect to CNI. Outcomes were presented as standardized mean differences (SMD) alongside 95% confidence intervals (95% CI) and chi-squared analysis. RESULTS: From 252 citations, 16 studies were identified. The meta-analyses demonstrated significant improvements in coronal (SMD: 1.15, 95% CI: 0.72-1.57 / SMD: 0.54, 95% CI: 0.29-0.80), middle (SMD: 1.30, 95% CI: 0.59-2.53 / SMD: 0.8, 95% CI: 0.58-1.13) and apical thirds (SMD: 1.22, 95% CI: 0.83-1.62 / SMD: 1.86, 95% CI: 0.76-2.96) for smear layer and debris removal, respectively. In the apical 1 mm IATs improved cleanliness; however, differences were insignificant (SMD: 1.15, 95% CI: -0.47-2.77). Chi-squared analysis revealed heterogeneity scores of 79.3-92.8% and 0.0-93.5% for smear layer and debris removal, respectively. CONCLUSIONS: IATs improve intracanal cleanliness across a substantial portion of the canal, and therefore, their use is recommended throughout root canal preparation. However, current data is too heterogeneous to compare and identify superiority of an individual technique highlighting the need to standardize experimental protocols and develop a more representative research model to investigate the in vivo impact of IATs on clinical outcomes and periapical healing following root canal treatment.

A practitioner's guide to gutta-percha removal during endodontic retreatment.

Endodontic retreatment can be a challenging task that can result in many complications if not approached cautiously. Many of these difficulties revolve around regaining access to the pulp chamber through extensive coronal restorations and removing residual root filling material, the commonest being gutta-percha (GP), from within obturated canals. This can often be an untidy, time consuming process that places teeth at a greater risk of iatrogenic injury and inhibits the operator achieving the necessary chemical disinfection required to eliminate the persistent apical disease. Therefore the following article aims to aid practitioners, particularly those who are unfamiliar, with accessing and removing GP from endodontically treated teeth. The outlined systematic approach is accessible in general practice, where the vast majority of endodontic treatment is conducted, requires basic equipment and with the correct experience can be applied to both straight and curved canals. By overcoming this initial stage of retreatment, subsequent chemical disinfection, which is critical to success, can be carried out to a higher standard reducing risks of re-infection.

Effective anaesthesia of the acutely inflamed pulp: part 2. Clinical strategies.

Achieving profound pulpal anaesthesia in a mandibular molar diagnosed with irreversible pulpitis can be argued to be the most testing of dental anaesthetic challenges. Following discussion on the possible reasons for this occurrence in part 1, part 2 outlines the various local anaesthetic techniques that practitioners can use to overcome the acutely inflamed mandibular molar. They should then be able to apply these same principles to help anaesthetise any other tooth presenting with an acutely inflamed pulp. Techniques are discussed in detail along with key variables that have been associated with having an impact on the anaesthetic efficacy. This is to bring to light factors that can aid anaesthetic success as well as dispel common misnomers.

Effective anaesthesia of the acutely inflamed pulp: part 1. The acutely inflamed pulp.

Achieving profound pulpal anaesthesia in a mandibular molar diagnosed with irreversible pulpitis can be argued to be the most testing of dental anaesthetic challenges. This can be attributed to the technical complexities of conventional techniques and the presence of pulp pathosis. Reasons for why the latter influences the ability to attain pulpal anaesthesia is not yet fully understood, but its frequent occurrence is well documented. In light of overcoming this it has become common practice to prescribe antibiotics, refer onto secondary care or to even commence treatment without appropriately anaesthetising the tooth. Therefore, this two part series aims to help practitioners attain clinically acceptable pulpal anaesthesia in the most testing of scenarios; the acutely inflamed mandibular molar. They should then be able to apply these same principles to other teeth presenting with similar symptoms. This section outlines the clinical presentation and pathophysiology associated with an acutely inflamed pulp, defines what it is to attain pulpal anaesthesia and critically analyses theories as to why these teeth are up to eight times more difficult to anaesthetise than their healthy counterparts.

Elastohydrodynamic lubrication analysis of a functionally graded layered bearing surface, with particular reference to 'cushion form bearings' for artificial knee joints.

Elastohydrodynamic lubrication of a functionally graded layered (FGL) bearing surface, whose elastic modulus increases with depth from the bearing surface, was investigated in this study. The finite difference method was employed to solve the Reynolds equation, simultaneously with the elasticity equation of the bearing surface, under circular point contacts. The finite element method was adopted to solve the elasticity equation for the FGL bearing surface. The displacement coefficients thus obtained were used to calculate the elastic deformation of the bearing surface, required for the elastohydrodynamic lubrication analysis. Good agreement of the predicted film thickness and pressure distribution was obtained, between the present method and a previous study for a single layered bearing surface with a uniform elastic modulus. The general numerical methodology was then applied to an FGL bearing surface with both linear and exponential variations in elastic modulus, with particular reference to the 'cushion form bearing' for artificial knee joints. The predicted film thickness and pressure distribution were shown to be quite close to those obtained for a single layer under typical operating conditions representative of artificial knee joints, provided that the elastic modulus of the single layer was chosen to be the average elastic modulus of the graded layer.

Effect of corticosteroids on survival of children with acquired immunodeficiency syndrome and Pneumocystis carinii-related respiratory failure.

The medical records of patients with acquired immunodeficiency syndrome were reviewed to evaluate the effect of our adoption to the pediatric population of the National Institutes of Health recommendation for adjunctive corticosteroid therapy in adults with Pneumocystis carinii pneumonia. In 21 episodes of P. carinii-related respiratory failure, only adjunctive corticosteroids were associated with a significant improvement in survival to successful removal of the tracheal tube, from a historical rate of 11% to 91%.

Oestrogen-related changes in sex hormone binding globulin levels during normal and gonadotrophin-stimulated menstrual cycles.

Previous studies have identified no consistent change in sex hormone binding globulin (SHBG) levels during normal menstrual cycles. This is despite marked cyclical changes in plasma oestradiol concentration, and the observation that SHBG level increases in pregnancy, and after administration of exogenous gonadotrophin or synthetic oestrogens. The level of SHBG was measured in 19 normal females at 2 d intervals from day -8 to +10 where the preovulatory peak of oestradiol was designated as occurring on day 0. SHBG levels increased by a mean 15% +/- 4 (SEM) between the follicular and luteal phases (P less than 0.001) and this was due entirely to an increment between day 0 and +2. The change in SHBG levels was correlated with the change in oestradiol levels between days -8 and 0 (P less than 0.001). Fifty-six infertile patients were also studied. Twenty-seven received Pergonal alone whilst the other 29 received Pergonal after a preceding 5 d on Clomid. In both groups peak preovulatory oestradiol levels were greater than 3 times higher than in normal cycles. SHBG levels showed no change in the follicular phase but rose markedly during the luteal phase. These increases were significantly correlated with peak preovulatory oestradiol concentration but showed no relationship with mid-luteal progesterone concentration. We conclude that supranormal levels of oestradiol cause marked increases in SHBG binding capacity and increases in SHBG level of a lower order occur shortly after the preovulatory peak of oestradiol in the normal menstrual cycle.