Optimal Use of Physical Centric Relation Records for Digital Workflows.

Correctly articulated dental casts are essential for certain dental treatment. Articulation can be traditional: using a physical articulator; digital: using a physical articulator followed by 3D scanning, or virtual: using 3D scanning and software to articulate scans without initial physical articulation. This study compared the precision of traditional articulation, using physical centric relation records and an articulator and virtually, by digitally aligning scans of the casts and record. Articulated casts and centric relation records were obtained. 12 record pairs were recorded from the articulated casts. Virtual method: all records were scanned, unclamped, in a custom laboratory scanner. The casts were aligned to each scanned record to create virtual articulations. Traditional method: each record was used to physically articulate the casts. Each articulation was recorded using an intraoral scanner. The mean inter-arch separation between three key-points on each cast-pair were used to determine differences in occlusal separation in three anatomical directions, and precision of methods. Traditional articulations: standard deviations in key-point distance never exceeded 0.102mm. The virtual equivalent was 0.059mm. Statistically significant differences (p⟨0.05) between all anteroposterior separation distances were found between the methods, and in three of six lateral/vertical separations. Virtual articulation was significantly more precise than traditional articulation.

A Comparative study on the Effectiveness of Augmented Reality on Denture Tooth Selection.

One of the most difficult aspects of providing removable dentures, for both the patient and the dentist, is the tooth selection process. The aim of this study was to assess the effectiveness of augmented reality (AR) on patient experience of the tooth selection process. MATERIALS AND METHODS: 3D scanning of upper anterior teeth of various shapes and sizes allowed for the creation of a virtual library that were subsequently used to programme an AR software application, 'ToothPick'. Seventeen participants were recruited to a comparative study at Leeds Dental Institute, over two clinical appointments, to trial the app and complete a 10-question survey to assess the efficacy of AR simulation. The sample size response generated outcome variables for 'perceived usefulness' and 'perceived ease of use' from the perspectives of the patient, dentist and technician. RESULTS: By the second appointment, 86% of participants preferred the app over the conventional methods for selection of denture teeth due to increased ease of use and accuracy that AR simulation had in replicating the wax try-in. CONCLUSION: The sample population favoured the adoption of AR technology to select denture teeth from the perspective of both the patient and the clinician.

The LeVe CPAP System for Oxygen-Efficient CPAP Respiratory Support: Development and Pilot Evaluation.

Background: The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has placed a significant demand on healthcare providers (HCPs) to provide respiratory support for patients with moderate to severe symptoms. Continuous Positive Airway Pressure (CPAP) non-invasive ventilation can help patients with moderate symptoms to avoid the need for invasive ventilation in intensive care. However, existing CPAP systems can be complex (and thus expensive) or require high levels of oxygen, limiting their use in resource-stretched environments. Technical Development + Testing: The LeVe ("Light") CPAP system was developed using principles of frugal innovation to produce a solution of low complexity and high resource efficiency. The LeVe system exploits the air flow dynamics of electric fan blowers which are inherently suited to delivery of positive pressure at appropriate flow rates for CPAP. Laboratory evaluation demonstrated that performance of the LeVe system was equivalent to other commercially available systems used to deliver CPAP, achieving a 10 cm H2O target pressure within 2.4% RMS error and 50-70% FiO2 dependent with 10 L/min oxygen from a commercial concentrator. Pilot Evaluation: The LeVe CPAP system was tested to evaluate safety and acceptability in a group of ten healthy volunteers at Mengo Hospital in Kampala, Uganda. The study demonstrated that the system can be used safely without inducing hypoxia or hypercapnia and that its use was well-tolerated by users, with no adverse events reported. Conclusions: To provide respiratory support for the high patient numbers associated with the COVID-19 pandemic, healthcare providers require resource efficient solutions. We have shown that this can be achieved through frugal engineering of a CPAP ventilation system, in a system which is safe for use and well-tolerated in healthy volunteers. This approach may also benefit other respiratory conditions which often go unaddressed in Low and Middle Income Countries (LMICs) for want of context-appropriate technology designed for the limited oxygen resources available.

Full arch precision of six intraoral scanners in vitro.

PURPOSE: Intraoral scanners may offer an alternative to traditional impressions. That intraoral scanners produce precise scans is essential. Popular methods used to evaluate precision tend to rely on mean distance deviation between repeated scans. Mean value measurements may underestimate errors resulting in misleading conclusions and clinical decisions. This study investigated the precision of six intraoral scanners using the traditional method of measuring mean error, and a proposed method considering only the most extreme and clinically relevant aspects of a scan. METHODS: An edentulous model was scanned five times using six intraoral scanners. The repeated scans were aligned, uniformly trimmed and mean surface deviation measured across all 20 scan combinations within each scanner group. All scan combinations were then measured by arranging scan vertices from greatest to smallest unsigned distance from its compared scan and measuring the median value within the 1% of most greatly deviating points. Traditional mean deviation results and upper-bound deviations were compared. RESULTS: The upper-bound deviation within a scan reported errors up to two times greater than those found when measuring global mean distances. Results revealed clinically relevant errors of more than 0.3mm in scans produced by the Planmeca and Dentalwings scanners, findings not seen when measuring mean distance error of the complete scan. CONCLUSIONS: Upper-bound deviation of a cropped scan may provide a clinically useful metric for scanner precision. The Aadva, 3Shape, CEREC and TDS produced scans potentially appropriate for clinical use while Planmeca and Dentalwings produced deviations greater than 0.3mm when measuring the upper-bound deviation.

Precision of maxillo-mandibular registration with intraoral scanners in vitro.

PURPOSE: To compare the precision of maxillo-mandibular registration and resulting full arch occlusion produced by three intraoral scanners in vitro. METHODS: Six dental models (groups A-F) were scanned five times with intraoral scanners (CEREC, TRIOS, PLANMECA), producing both full arch and two buccal maxillo-mandibular scans. Total surface area of contact points (defined as regions within 0.1mm and all mesh penetrations) was measured, and the distances between four pairs of key points were compared, each two in the posterior and anterior. RESULTS: Total surface area of contact points varied significantly among scanners across all groups. CEREC produced the smallest contact surface areas (5.7-25.3mm2), while PLANMECA tended to produce the largest areas in each group (22.2-60.2mm2). Precision of scanners, as measured by the 95% CI range, varied from 0.1-0.9mm for posterior key points. For anterior key points the 95% CI range was smaller, particularly when multiple posterior teeth were still present (0.04-0.42mm). With progressive loss of posterior units (groups D-F), differences in the anterior occlusion among scanners became significant in five out of six groups (D-F left canines and D, F right canines, p<0.05). CONCLUSIONS: Maxillo-mandibular registrations from three intraoral scanners created significantly different surface areas of occlusal contact. Posterior occlusions revealed lower precision for all scanners than anterior. CEREC tended towards incorrect posterior open bites, whilst TRIOS was most consistent in reproducing occluding units.

The difference between registered natural head position and estimated natural head position in three dimensions.

This study determined the intra-rater and inter-rater reliability of re-orientating three-dimensional (3D) facial images into the estimated natural head position. Three-dimensional facial images of 15 pre-surgical class III orthognathic patients were obtained and automatically re-orientated into natural head position (RNHP) using a 3D stereophotogrammetry system and in-house software. Six clinicians were asked to estimate the NHP of these patients (ENHP); they re-estimated five randomly selected 3D images after a 2-week interval. The differences in yaw, roll, pitch, and chin position between RNHP and ENHP were measured. For intra-rater reliability, the intra-class correlation coefficient (ICC) values ranged from 0.55 to 0.77, representing moderate reliability for roll, yaw, pitch, and chin position, while for inter-rater reliability, the ICC values ranged from 0.38 to 0.58, indicating poor to moderate reliability. The median difference between ENHP and RNHP was small for roll and yaw, but larger for pitch. There was a tendency for the clinicians to estimate NHP with the chin tipped more posteriorly (6.3±5.2mm) compared to RNHP, reducing the severity of the skeletal deformity in the anterior-posterior direction.

Capturing differences in dental training using a virtual reality simulator.

Virtual reality simulators are becoming increasingly popular in dental schools across the world. But to what extent do these systems reflect actual dental ability? Addressing this question of construct validity is a fundamental step that is necessary before these systems can be fully integrated into a dental school's curriculum. In this study, we examined the sensitivity of the Simodont (a haptic virtual reality dental simulator) to differences in dental training experience. Two hundred and eighty-nine participants, with 1 (n = 92), 3 (n = 79), 4 (n = 57) and 5 (n = 61) years of dental training, performed a series of tasks upon their first exposure to the simulator. We found statistically significant differences between novice (Year 1) and experienced dental trainees (operationalised as 3 or more years of training), but no differences between performance of experienced trainees with varying levels of experience. This work represents a crucial first step in understanding the value of haptic virtual reality simulators in dental education.

An Investigation into the Trueness and Precision of Copy Denture Templates Produced by Rapid Prototyping and Conventional Means.

OBJECTIVE: To assess the trueness and precision of copy denture templates produced using traditional methods and 3D printing. MATERIAL AND METHODS: Six copies of a denture were made using: 1. Conventional technique with silicone putty in an impression tray (CT). 2. Conventional technique with no impression tray (CNT). 3. 3D scanning and printing (3D). Scan trueness and precision was investigated by scanning a denture six times and comparing five scans to the sixth. Then the scans of the six CT, CNT and 3D dentures were compared by aligning, in turn, the copies of each denture to the scanned original. Outcome measures were the mean surface-to-surface distance, standard deviation of that distance and the maximum distance. Student's unpaired t-tests with Bonferroni correction were used to analyse the results. RESULTS: The repeated scans of the original denture showed a scan trueness of 0.013mm (SD 0.002) and precision of 0.013mm (SD 0.002). Trueness: CT templates, 0.168mm (0.047), CNT templates 0.195mm (0.034) and 3D 0.103mm (0.021). Precision: CT templates 0.158mm (0.037), CNT 0.233mm (0.073), 3D 0.090mm (0.017). For each outcome measure the 3D templates demonstrated an improvement which was statistically significant (p⟨0.05). CONCLUSIONS: 3D printed copy denture templates reproduced the original with greater trueness and precision than conventional techniques.

Feedback and motor skill acquisition using a haptic dental simulator.

AIM: To investigate the effect of qualitatively different types of pedagogical feedback (FB) on the training, transfer and retention of basic manual dexterity dental skills using a virtual reality (VR) haptic dental simulator. METHODS: Sixty-three participants (M = 22.7 years; SD = 3.4 years), with no previous dental training, were randomly allocated to one of three groups (n = 21 each). Group 1 received device-only feedback during the training phase, that is the visual display of the simulator (DFB); Group 2 received verbal feedback from a qualified dental instructor (IFB); and Group 3 received a combination of instructor and device feedback (IDFB). Participants completed four tasks during which feedback was given according to group allocation as well as two skills transfer tests. Skill retention was examined immediately after training, at 1 week and at 1 month post-test. RESULTS: Statistically significant differences were found between the groups in overall performance (P < 0.001) and error (P = 0.006). Post hoc comparisons revealed the IDFB group produced substantially better performance and fewer errors in comparison with DFB and IFB training. This difference translated to improved performance in skill retention and generalisation of knowledge to novel tasks. CONCLUSION: These data indicate that the acquisition and retention of basic dental motor skills in novice trainees is best optimised through a combination of instructor and visual display (VR)-driven feedback. The results have implications for the utility and implementation of VR haptic technology in dental education.

Recurrent variceal haemorrhage managed with splenic vein stenting.

INTRODUCTION: Extrahepatic Portal Hypertension (EPH) is defined as extrahepatic hypertension of the portal venous system in the absence of liver cirrhosis. Isolated splenic vein stenosis/occlusion as one of the causes of extrahepatic portal hypertension is uncommon, comprising less than 5 % of all cases of portal hypertension. However, it is an increasingly recognised complication of both acute and chronic pancreatitis, and with the advent of more effective diagnostic methods, interventional radiological methods for its management are also becoming more effective. Often these would negate the need for invasive splenectomy surgery for the treatment of symptomatic hypersplenism and varices. METHODS: A case of a 38 year old gentleman, known to have Crohn's disease, presented with severe acute gallstone pancreatitis with necrosis of the pancreatic neck and body. His course was very complicated, requiring two laparotomies and various interventional drainages of variceal bleeds. As a result of non resolving recurrent variceal haemorrhage, it was decided to proceed with splenic vein stenting to relieve the consequences of splenic vein stenosis. A percutaneous transhepatic splenic vein stent was deployed. RESULTS: Immediate decompression of the varices was noted with no further haemmorrhage. CONCLUSION: There are little data to date on splenic vein stenting in the setting of EPH secondary to non-malignant pancreatic disease. We report a case managed successfully with splenic vein stenting and review the existing literature.

A review of percutaneous transhepatic biliary drainage at a tertiary referral centre.

AIM: To review percutaneous biliary drainage (PBD) procedures performed in Beaumont Hospital, Dublin, Ireland, over a 6-year period, to determine the 30-day morbidity and mortality. MATERIALS AND METHODS: A total of 119 patients undergoing 193 PBD procedures were identified over a 6 year period. Of the patients, 6.7% (eight patients) had stone disease, 63% (75 patients) had a malignancy, and the remainder were diagnosed with other conditions. Standard techniques of PBD and biliary stent insertion were applied, with 73 patients (61%) having same-day procedures and all undergoing gelfoam embolisation of percutaneous tracts. All patients received intravenous prophylactic antibiotics and intravenous hydration prior to PBD. RESULTS: The technical success rate was 97%, with a mean drop of 105 mmol/l between pre- and post-procedure bilirubin. Thirty-day mortality was 10.9% (13 deaths), with major and minor morbidities of 5% (six patients) and 7.6% (nine patients), respectively. Major complications included sepsis in two patients, major haemorrhage in two patients, and renal failure in two patients. Minor complications included infection in seven patients, bile leak causing self-limiting pain in one patient, and minor haemorrhage in one patient. CONCLUSION: The study confirms that PBD and stent insertion is a safe and effective technique in Beaumont Hospital, associated with an overall acceptable morbidity and mortality comparable with other studies.

Should prospective dental students be screened for colour vision deficits?

A perennial question in dental education is: what skills and aptitudes should be assessed in prospective dental students? Intellectual capacity and manual dexterity understandably rank highly, but are there minimum thresholds for visual perception that applicants need be able to demonstrate before they enter the profession? We have recently flagged this issue with regard to the thresholds of stereoscopic acuity required for a dentist when operating on teeth. In the present article, we highlight the issue of identifying a minimum acceptable level of colour vision.

How safe is internal iliac artery embolisation prior to EVAR? A 10-year retrospective review.

PURPOSE: Internal iliac artery (IIA) embolisation is commonly performed prior to endovascular aneurysm repair (EVAR) of aortoiliac aneurysms to prevent type 2 endoleaks via the internal iliac arteries. The safety of this procedure is controversial due to the high incidence of pelvic ischaemic complications. METHODS: We undertook a retrospective review of all patients undergoing IIA embolisation before EVAR from 2002 to 2012, to determine incidence of, and factors associated with pelvic ischaemia. RESULTS: Eight of 25 patients (32 %) experienced new-onset ischaemia, including erectile dysfunction (4 %), and buttock claudication (28 %) that persisted >6 months in only four patients (16 %). Both bilateral IIA embolisation and a shorter time interval to EVAR correlate with increased risk (p = 0.006 and p = 0.044). No co-morbidities or demographic factors were predictive. CONCLUSIONS: We conclude that IIA embolisation remains a beneficial procedure, however, to minimise the risk of buttock claudication we advise against both bilateral IIA embolisation and short time intervals between embolisation and subsequent EVAR.

A three dimensional view of stereopsis in dentistry.

Stereopsis and its role in dental practice has been a topic of debate in recent editions of this Journal. These discussions are particularly timely as they come at a point when virtual reality simulators are becoming increasingly popular in the education of tomorrow's dentists. The aim of this article is to discuss the lack of robust empirical evidence to ascertain the relationship (if any) between stereopsis and dentistry and to build a case for the need for further research to build a strong evidence base on the topic.

An in vitro study into the accuracy of a novel method for recording the mandibular transverse horizontal axis.

OBJECTIVES: To assess the accuracy of a novel, non-invasive method for determining the axis of rotation of articulated dental study casts. METHOD: A 3D structured light scanner was constructed using a projector and two CMOS cameras. Dental stone casts were arbitrarily mounted on an average value articulator. With the teeth together, sets of 10 scans were taken from three different viewpoints. Each scan captured approximately six upper teeth and six lower teeth. The teeth were then propped open, creating 10mm of incisal separation, and the three sets of 10 scans were repeated. From each pair of scans an axis of rotation was calculated using custom software. A total of 900 axes were created this way. The locations of these axes were plotted in sagittal planes located 57.5mm left and right of the midline to represent the position of the temporo-mandibular joints (TMJs). The accuracy of axis location was then assessed. RESULTS: The average radius of error of the individual axes, compared to the real axis, was 2.65 ± 1.01 mm. 61.3% of the axes lay within 3mm of the true axis, and 99.2% of the axes lay within 5mm of the true axis. CONCLUSIONS: The accuracy of this method is clinically acceptable. Further studies are required to confirm the accuracy of the virtual inter-occlusal records at the level of the dentition. Clinical studies are then indicated to determine whether the transverse horizontal axis on a patient can similarly be determined.

The voting rights of adults with intellectual disabilities: reflections on the arguments, and situation in Kenya and England and Wales.

Article 29 of the Convention on the Rights of Persons with Disabilities guarantees equality of political rights, including the right to vote and stand for election. The affirmation of these rights, first guaranteed by the Universal Declaration of Human Rights, raises an important question given the long-standing association between political rights and beliefs concerning the abilities of citizens to reason and act independently: how and to what degree can people identified as having intellectual disabilities participate in a defining act of the democratic process? Focused specifically on the right to vote, this paper addresses the question by (1) introducing the debates that have surrounded the voting rights of this population; and (2) reporting on recent attempts in Kenya, and in England and Wales, to promote voting by people with intellectual disabilities. It concludes by considering the effectiveness of the different approaches these countries have adopted.

Transcatheter embolisation of renal angiomyolipoma.

INTRODUCTION: Angiomyolipomas (AML) are rare benign renal tumours which are associated with aneurysms that can cause haemorrhage. Embolisation of AML greater than 4 cm with a variety of embolic agents is now the first-line treatment in these cases. METHODS: This was a retrospective analysis of all patients who underwent AML embolisation at Beaumont Hospital from 2000 to 2006 to review the efficacy of embolisation in the treatment of AMLs. RESULTS: There were six patients in total (n = 6). One patient (16%) had a background of tuberous sclerosis. Half of the patients presented acutely with bleeding and abdominal pain (50%) while the other half were found incidentally. There were no mortalities overall and three patients (50%) developed post embolisation syndrome. Five patients (83%) had a good response to embolisation with no further growth or regression of the AML. CONCLUSION: Embolisation is a safe and effective method for treating patients with AML.

Emergency percutaneous transcatheter embolisation of acute arterial haemorrhage.

AIMS: The purpose of this study was to review indications, source of haemorrhage, method of embolisation and clinical outcome in patients referred to Interventional Radiology for the emergency management of acute arterial haemorrhage. METHODS: Retrospective review of patients undergoing emergency percutaneous embolisation over 4 years. Clinical details, computed tomographic findings, embolisation procedure details and clinical outcome are outlined. RESULTS: Patients (n = 41) were included with various clinical indications for embolisation [haemoptysis (n = 8), iatrogenic (n = 7), traumatic pseudoaneurysm (n = 3), retroperitoneal bleed (n = 3), GI bleed (n = 6), splenic rupture (n = 1), renal laceration (n = 1), epistaxis (n = 12)]. Embolisation material consisted of coils, embospheres, glue, and covered stents. Technical success was achieved in 100% of cases. One patient died 2 days after embolisation secondary to myocardial infarction. CONCLUSION: Emergency arterial embolisation is a potentially life-saving treatment. Although it is technically challenging, indications are becoming increasingly varied and outcomes are more successful because of the availability of microcatheters and effective embolisation materials.