The subsurface lesion in erosive tooth wear.

OBJECTIVES: This study compared the surface change on natural and polished enamel exposed to a joint mechanical and chemical wear regimen. METHODS: Human enamel samples were randomly assigned to natural (n = 30) or polished (n = 30) groups, subjected to erosion (n = 10, 0.3% citric acid, 5 min), abrasion (n = 10, 30 s), or a combination (n = 10). Wear in the form of step height was measured with a non-contact profilometer, and surface changes were inspected with SEM on selected sections. Data was normalised and underwent repeated measures MANOVA, accounting for substrate and erosive challenge as independent variables, with Bonferroni correction for significant post hoc interactions. RESULTS: After four cycles, polished samples had mean step heights of 3.08 (0.40) µm after erosion and 4.08 (0.37) µm after erosion/abrasion. For natural samples, these measurements were 1.52 (0.22) µm and 3.62 (0.39) µm, respectively. Natural surfaces displayed less wear than polished surfaces under erosion-only conditions (p<0.0001), but the difference disappeared with added abrasion. SEM revealed a shallow subsurface layer for polished surfaces and natural ones undergoing only erosion. However, natural surfaces exposed to both erosion and abrasion showed deeper subsurface changes up to 50 µm. CONCLUSION: Natural enamel, when exposed to erosion alone, showed less wear and minimal subsurface alterations. But with added abrasion, natural enamel surfaces saw increased wear and notable subsurface changes compared to polished ones. CLINICAL SIGNIFICANCE: The pronounced subsurface lesions observed on eroded/abraded natural enamel surfaces highlight how combined wear challenges may accelerate tooth tissue loss.

Significance of predicted future liver remnant volume on liver failure risk after major hepatectomy: a case matched comparative study.

Introduction: Future liver remnant volume (FLRV), a risk factor for liver failure (PHLF) after major hepatectomy (MH), is not routinely measured. This study aimed to evaluate the association between FLRV and PHLF. Patients and methods: All patients undergoing MH (4 + segments) between 2011 and 2018 were identified from a prospectively maintained single-centre database. Perioperative data were collected for patients with PHLF, who were matched (1:2) with non-PHLF controls. FLRV and FLRV% (i.e., % of total liver volume) were calculated retrospectively from preoperative CT scans using Synapse-3D software, and compared between the PHLF and matched control groups. Results: Of 711 patients undergoing MH, PHLF occurred in 27 (3.8%), of whom 24 had preoperative CT scans available. These patients were matched to 48 non-PHLF controls, 98% of whom were classified as being at high risk of PHLF on preoperative risk scoring. FLRV% was significantly lower in the PHLF group, compared to matched controls (median: 28.7 vs. 35.2%, p = 0.010), with FLRV% < 30% in 58% and 29% of patients, respectively. Assessment of the ability of FLRV% to differentiate between PHLF and matched controls returned an area under the ROC curve of 0.69, and an optimal cut-off value of FLRV% < 31.5%, which yielded 79% sensitivity and 67% specificity. Conclusions: FLRV% is significantly predictive of PHLF after MH, with over half of patients with PHLF having FLRV% < 30%. In light of this, we propose that all patients should undergo risk stratification prior to MH, with the high risk patients additionally being assessed with CT volumetry.

The early wear susceptibility of cementum, enamel and dentine in vitro.

OBJECTIVES: To assess the differential early wear susceptibility of cementum, enamel and dentine at a micron level. METHODS: Whole human molar buccal surfaces incorporating natural enamel and cementum (n = 20) confirmed by imaging (digital microscopy: Keyence, VHX-7000 Milton Keynes, UK), were mounted, scanned (profilometry: XYRIS 4000, Taicaan, Southampton, UK), and allocated to receive erosion (citric acid, pH 2.7, 30 min (n = 10)) or erosion/abrasion challenges (3 cycles of (citric acid, pH 2.7, 10 min, 60 300 g linear abrasion strokes), n=10). Samples were polished and the experiment repeated on polished enamel, and polished coronal and radicular dentine within the same tooth. Profilometric wear data were obtained using superimposition: GeoMagic (3Dsystems, Darmstadt, Germany) and subtraction: MountainsMap (DigitalSurf, Besancon, France). Data were normal. A general linear model was used to assess differences between groups and substrates. RESULTS: The mean step height (SD) for natural enamel was 8.82 µm (2.53) for erosion and 11.48 µm (2.95) for erosion/abrasion. For natural cementum, the mean step height was 6.00 µm (2.29) for erosion and 4.67 µm (1.58) for erosion/abrasion. Dentine step heights ranged from 7.20 µm (1.53) for erosion and 9.79 µm (1.01) for erosion/abrasion with no statistical differences in dentine wear. Natural cementum surfaces had the lowest wear (p<0.001). Dentine had significantly less wear than natural enamel (p<0.02). CONCLUSIONS: Cementum surfaces demonstrated the most wear resistance, followed by dentine under erosion dominant conditions in this in vitro study. Further in-vivo investigations are needed to confirm the intraoral stability of cementum. CLINICAL SIGNIFICANCE: Cementum may be the least susceptible of dental substrates to wear and dentine does not wear at a faster rate than enamel under erosive conditions. This adds to our knowledge on the development of non-carious cervical lesions and questions whether wear rates will accelerate once dentine is exposed.

The interplay of saliva, erosion and attrition on enamel and dentine.

Purpose: This investigation aimed to compare the protective role of saliva against erosion and attrition challenges. Method: Polished enamel and dentine samples (n = 160) were prepared and randomly assigned to either the saliva or saliva-free group (n = 40 enamel and n = 40 dentine/group). Within each subgroup, they were allocated to four subgroups: negative control (deionized water exposure 10 min), erosion (0.3% citric acid 10 min), attrition (120 S of 300 g force), or combined erosion/attrition (0.3% citric acid 10 min then 120 S of 300 g force). Experimental cycles were repeated three times. Data analysis was performed using SPSS. Results: The mean and standard deviation (SD) of step heights produced by the attrition and erosion/attrition groups in enamel in the saliva-free group were 5.6 µm (2.4) and 13.4 µm (2.8), respectively, while they were 2.4 µm (3.8) and 12.9 µm (3.5) in the saliva group, with no significant difference between the saliva and saliva-free groups. For dentine, the corresponding step heights were 25.2 µm (5.5) and 35.9 µm (7.9) for the saliva-free group, but 21.8 µm (5.3) and 27.3 µm (6.4) for the saliva group (p < 0.001). Conclusion: There was a trend that saliva decreased wear, but this was only statistically significant for erosion/attrition dentine wear.

Impact of Frailty on Short-Term Outcomes After Laparoscopic and Open Hepatectomy.

BACKGROUND: Although laparoscopic hepatectomy (LH) is associated with improved short-term outcomes compared to open hepatectomy (OH), it is unknown whether frail patients also benefit from LH. The aim of this study was to evaluate the impact of frailty on post-operative outcomes after LH and OH. PATIENTS AND METHODS: Consecutive patients who underwent LH and OH between January 2011 and December 2018 were identified from a prospective database. Frailty was assessed using the modified Frailty Index (mFI), with patients scoring mFI ≥ 1 deemed to be frail. RESULTS: Of 1826 patients, 34.7% (N = 634) were frail and 18.6% (N = 340) were elderly (≥ 75 years). Frail patients had significantly higher 90-day mortality (6.6% vs. 2.9%, p < 0.001) and post-operative complications (36.3% vs. 26.1%, p < 0.001) than those who were not frail, effects that were independent of patient age on multivariate analysis. For those undergoing minor resections, the benefits of LH vs. OH were similar for frail and non-frail patients. Length of hospital stay was 53% longer in OH (vs. LH) in frail patients, compared to 58% longer in the subgroup of non-frail patients. CONCLUSIONS: Frailty is independently associated with inferior post-operative outcomes in patients undergoing hepatectomy. However, the benefits of laparoscopic (compared to open) hepatectomy are similar for frail and non-frail patients. Frailty should not be a contraindication to laparoscopic minor hepatectomy in carefully selected patients.

Outcomes of normothermic machine perfusion of liver grafts in repeat liver transplantation (NAPLES initiative).

BACKGROUND: Retransplantation candidates are disadvantaged owing to lack of good-quality liver grafts. Strategies that can facilitate transplantation of suboptimal grafts into retransplant candidates require investigation. The aim was to determine whether late liver retransplantation can be performed safely with suboptimal grafts, following normothermic machine perfusion. METHODS: A prospectively enrolled group of patients who required liver retransplantation received a suboptimal graft preserved via normothermic machine perfusion. This group was compared with both historical and contemporaneous cohorts of patient who received grafts preserved by cold storage. The primary outcome was 6-month graft and patient survival. RESULTS: The normothermic machine perfusion group comprised 26 patients. The historical (cold storage 1) and contemporaneous (cold storage 2) groups comprised 31 and 25 patients respectively. The 6-month graft survival rate did not differ between groups (cold storage 1, 27 of 31, cold storage 2, 22 of 25; normothermic machine perfusion, 22 of 26; P = 0.934). This was despite the normothermic machine perfusion group having significantly more steatotic grafts (8 of 31, 7 of 25, and 14 of 26 respectively; P = 0.006) and grafts previously declined by at least one other transplant centre (5 of 31, 9 of 25, and 21 of 26; P < 0.001). CONCLUSION: In liver retransplantation, normothermic machine perfusion can safely expand graft options without compromising short-term outcomes.

Liver transplantation is a life-saving procedure for many different diseases. In the UK, one in 10 patients awaiting transplant have had a previous liver transplant. These retransplant operations are complex, and the general belief is that a good-quality donor liver graft is required for best outcomes. However, there is a significant shortage of good-quality organs for liver transplantation, so many patients awaiting retransplantation spend longer on the waiting list. This study investigated whether a new technology, called normothermic machine perfusion, could be used to preserve lower-quality donor livers and have successful outcomes for patients undergoing retransplantation. Traditionally, good-quality livers are preserved in an ice box and the study compared the outcomes of these two different approaches. The aim was to prove that normothermic machine perfusion improves access to transplantation for this group of patients, without compromising outcomes. A group of patients who underwent retransplantation and received a lesser-quality liver preserved with normothermic machine perfusion was compared with two groups of patients who had received a transplant with traditional ice-box preservation. The complications, graft, and patient survival of the former group was compared with those in the latter two groups who underwent liver retransplantation with better-quality liver grafts. The rate of survival and adverse surgical outcomes were comparable between the groups of patients who received a liver preserved via traditional ice-box preservation, and those who received a lesser-quality liver preserved via normothermic machine perfusion. Normothermic machine perfusion can potentially expand the number of suitable donor livers available for retransplant candidates.

Superimposition of sequential scans to measure erosion on unpolished and curved human enamel.

OBJECTIVES: To determine if superimposition of sequential scans can discriminate between different fluorides at step heights less than 5 µm on natural human enamel surfaces. MATERIALS AND METHODS: Natural, unpolished, human enamel specimens (n = 60) were randomly assigned to one of three pre-treatment toothpaste slurries with a calcium silicate/fluoride, fluoride-only and a control. Baseline and post treatment scans, from a non-contacting profilometer with a 0.01 µm z-axis and <1 µm lateral scanning resolution were imported into superimposition software to define change in mean 3D step height and surface roughness following erosion in 0.3% citric acid for 15 min. Statistical analysis conducted with two-way repeated measures ANOVA and post-hoc Tukey's multiple comparisons. RESULTS: Confidence and resolution of superimposition and subtraction of repeated profiles from unpolished enamel revealed accuracy within 1-2 µm. The technique was able to discriminate between the fluorides demonstrating statistical differences in mean (SD) 3D step height (µm) of 1.96 (0.40) and 2.75 (0.49) (p = 0.0024). There was a statistically significant increase in surface roughness for all groups after 15 min erosion compared to baseline. But no statistically significant difference between the interventions after 15 min erosion but there was compared to no fluoride (p = 0.006). CONCLUSION: Superimposition and subtraction of profiles could discriminate between fluoride interventions, which showed statistical differences in enamel loss differences less than 3 µm. CLINICAL SIGNIFICANCE: This erosion model and data analysis workflow was able to distinguish differences between scans of 3 µm on unpolished enamel following the interaction with fluoride.

Severe Sepsis Mimicking Primary Nonfunction Following Liver Transplantation: Normothermic Machine Perfusion Is a Potential Environment for Bacterial Overgrowth and Transmission From Donor to Recipient. A Case Report.

Primary nonfunction (PNF) in the early postoperative period following liver transplantation is fatal if not managed appropriately with early retransplantation. Severe early allograft dysfunction can mimic PNF. The identification of treatable causative factors such as sepsis, hepatic artery, or portal vein thrombosis is essential to distinguish it from PNF, and their early management may avoid the need for retransplantation. In this article, we describe a case of sepsis-induced severe liver dysfunction from a contaminated graft perfused with normothermic machine perfusion (NMP), which presented in a manner similar to PNF. The implications of graft contamination are poorly described. To our knowledge, this is the first report of bacterial contamination of a graft that underwent NMP and subsequently caused severe sepsis in the recipient. The conditions created with NMP may be optimal for certain micro-organisms to thrive. The role of the liver in the immune system is complex as it provides an essential barrier to enterically derived portal venous pathogens and produces numerous acute phase proteins that augment the systemic immune response. Additionally, the liver is also known to restrain harmful and excessive systemic immune responses such as those that occur with the sepsis syndrome. The relationship between bacterial graft contamination, sepsis, and graft dysfunction may be multidirectional.

An investigation into the impact of tooth wear on the oral health related quality of life amongst adult dental patients in the United Kingdom, Malta and Australia.

OBJECTIVE: To investigate the relationship between levels of tooth wear scored using the Basic Erosive Wear Examination (BEWE) and the impact on the quality of life of adult dental patients. METHODS: BEWE assessments were performed on 319 new dentate adult patients attending the practices of 5 trained recruiters based in primary care in Malta (120), Australia (118) or the UK (81). Oral impacts on the quality of life were measured using a shortened form of the Oral Health Impact Profile (OHIP-26). Regression analysis were performed, adjusted for age, to estimate the relationship between the variables. Data were expressed as Confidence Intervals (95 % CI), p-values (values <0.05 were considered statistically significant) and adjusted R2 values. RESULTS: Overall, the sample had a mean age of 42.6 ±â€¯17.1 (range, 18-93 years), a mean cumulative BEWE score of 6.7 ±â€¯4.4 and a mean total OHIP-26 score of 1.84 ±â€¯0.59. For the cumulative sextant BEWE scores, 68.0 % of the participants scored ≤ 8, 24.5 % between 9 and 13 and 7.5 %, ≥ 14. A significant association was found between increasing BEWE score and the overall OHIP-26 total score (effect = 0.028; p = 0.002), implying a higher BEWE to be associated with a larger impact of oral conditions on daily life. CONCLUSION: Higher levels of tooth wear were significantly associated with a deteriorating oral-health related quality of life amongst the participants. CLINICAL RELEVANCE: When treatment planning for patients with tooth wear, it is appropriate to consider the psycho-social impact of the condition alongside other clinical findings.

Tooth wear and aging.

BACKGROUND: In an ageing population, tooth wear is likely to increase. It is increasing in prevalence in the younger population and a greater number of patients are retaining their teeth into old age. METHODS: This paper is a narrative review of the clinical presentation, the epidemiology and the restorative intervention for erosive tooth wear. The dilemmas in managing this common condition with the aging dentition in mind are described. The paper discusses evidence-based prevention methods and highlights how preventive intervention may be preferable over extensive restorative care and high maintenance needs. Patient wishes, expectations and commitment to treatment and maintenance require consideration during clinical decision making. CONCLUSION: Successful management of erosive tooth wear in an ageing population depends on effective diagnosis, preventive intervention and holistic advice regarding restorative intervention.

Prevalence, severity and explanatory factors of tooth wear in Arab populations.

OBJECTIVES: The aim of this study was to assess the prevalence and severity of tooth wear and related risk indicators in six Arab countries. METHODS: This multicenter, multinational cross-sectional study was conducted among 2924 participants between the ages of 18-35 years old from six Arab countries. Calibrated dentists assessed tooth wear using the Basic Erosive Wear Examination Index (BEWE). Participants were also asked to complete a questionnaire that assessed their dietary and oral health habits. Each participant was identified by the sextant with the highest BEWE score in the upper and lower jaws. RESULTS: Odds ratios were estimated for correlates of tooth wear anterior and posterior regions. Oman had the highest prevalence of BEWE score 3 (N = 255 (60.2%)). Overall, the highest BEWE score 3 was observed on the incisal edge of the upper anterior teeth (N = 602 (20.6%)) and in the lower left posterior region (sextant 6) on the occlusal surface (N = 466 (15.9%)). Correlates of severe tooth wear in both regions were eating or drinking more than six times per day, age and education. Drinking soft drinks "once a day" was significantly associated with severe tooth wear in the posterior region (OR: 1.3, 95% CI:1.05, 1.6). Brushing teeth more than twice a day was inversely associated with tooth wear in the anterior region (OR:0.75, 95% CI: 0.57,0.97). CONCLUSION: The prevalence of tooth wear in Arab populations is relatively high, specific preventive and therapeutic measures should be developed to target people at higher risk of this condition. CLINICAL SIGNIFICANCE: Tooth wear is now regarded as a significant oral health problems, dentists should advise their patients about dietary and oral health habits that can lead to severe tooth wear.

Cytoreductive surgery and HIPEC improve survival compared to palliative chemotherapy for biliary carcinoma with peritoneal metastasis: A multi-institutional cohort from PSOGI and BIG RENAPE groups.

BACKGROUND: Peritoneal metastasis from biliary carcinoma (PMC) is associated with poor prognosis when treated with chemotherapy. OBJECTIVE: To evaluate the impact on survival of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC), and compare with conventional palliative chemotherapy for patients with PMC. MATERIAL AND METHODS: A prospective multicenter international database was retrospectively searched to identify all patients with PMC treated with a potentially curative CRS/HIPEC (CRS/HIPEC group). The overall survival (OS) was compared to patients with PMC treated with palliative chemotherapy (systemic chemotherapy group). Survival was analyzed using Kaplan-Meier method and compared with Log-Rank test. RESULTS: Between 1995 and 2015, 34 patients were included in the surgical group, and compared to 21 in the systemic chemotherapy group. In the surgical group, median peritoneal cancer index was 9 (range 3-26), macroscopically complete resection was obtained for 25 patients (73%). There was more gallbladder localization in the surgical group compared to the chemotherapy group (35% vs. 18%, p = 0.001). Median OS was 21.4 and 9.3 months for surgical and chemotherapy group, respectively (p=0.007). Three-year overall survival was 30% and 10% for surgical and chemotherapy group, respectively. CONCLUSION: Treatment with CRS and HIPEC for biliary carcinoma with peritoneal metastasis is feasible and may provide survival benefit when compared to palliative chemotherapy.

In vitro evaluation of the early erosive lesion in polished and natural human enamel.

OBJECTIVE: This study evaluated the capability of profilometry, microhardness, Optical Coherence Tomography (OCT) and Tandem Scanning Confocal Microscopy (TSM) in characterising the early erosive lesion in polished and natural human enamel in vitro. METHODS: Polished (n=60) and natural (n=60) human enamel surfaces, were immersed and agitated in 0.3% citric acid erosion at 0s, 10s, 30s, 60s, 120s, and 300s (n=10). Changes in the surface were measured with 3D-step height change (µm), surface roughness (µm), surface microhardness (KHN), and images were assessed qualitatively with OCT and TSM. RESULTS: Mean (SD) 3D-step height change (µm) was measurable for polished enamel at: 60s (0.24±0.1), 120s (1.16±0.71), 300s (2.01±0.47; p<0.05); a step height change was not detectable on acid challenged natural enamel surfaces. Mean (SD) surface roughness (µm) of polished enamel was detected at 10s (0.270±0.013; p<0.05) and all erosion periods; and in natural enamel detected after 120s (0.830±0.125) and 300s (0.800±0.140; p<0.005). Polished enamel Mean (SD) microhardness (KHN) statistically significantly decreased at all time points (p<0.001); this was unmeasurable for natural enamel. Qualitative image analysis of both surface types indicated erosive change at the surface level, with progression after increasing erosion time. SIGNIFICANCE: The early erosive lesion in polished enamel could be characterised quantitatively surface roughness and microhardness and qualitatively using OCT and TSM; whilst in natural enamel only surface roughness could be utilised. Further investigation of early erosion in natural enamel is required to develop new more clinically relevant models.

Prevalence of gingival recession and study of associated related factors in young UK adults.

OBJECTIVES: To determine the prevalence of gingival recession (GR) and associations with dentine hypersensitivity (DH), erosive toothwear (BEWE), gingival bleeding (BOP) and periodontal pocketing (PPD) in young European adults. MATERIALS AND METHODS: This is a secondary analysis using data collected from 350 UK participants enrolled in a European cross sectional study of 3187 young adults. GR, BOP, PPD, DH (participant and clinician assessment) and BEWE were recorded. A questionnaire assessed demographics, oral hygiene and lifestyle habits. RESULTS: 349 participants completed the study. GR, BOP and PPD showed the same pattern of distribution, prevalence increasing from incisors to molars in upper and lower arches for buccal and palatal scores. Every participant exhibited recession affecting at least 1 tooth, 42% having a maximum recession of 4-8 mm. There was a significant and linear association demonstrating an increase in maximum recession with age. DH and BEWE produced a similar pattern to buccal periodontal indices, the premolars being most affected. Maximum recession correlated significantly with maximum DH (participant and Schiff), PPD, BOP, BEWE (scores of 2/3), BMI (≥25 kg/m2) and unsystematic brushing motion. 94% of the study population exhibited some BOP at one or more sites. 5% of the population had periodontal pocketing ≥4 mm, 46% had DH and 80% BEWE 2/3. CONCLUSION: Widespread recession and gingivitis with minimal periodontal disease was observed. Every participant exhibited at least one tooth with recession. Many teeth did not exhibit DH despite prevalent recession and severe erosive toothwear. Recession correlates to a number of oral and lifestyle variables. CLINICAL SIGNIFICANCE: Recession in young adults is multifactorial and highly prevalent. It can result in DH and consequential increase in demand for treatment relating to both pain and aesthetics. Further research is needed to understand the underlying aetiology to prevent recession occurring.

Randomised Controlled Clinical Trial Investigating The Impact of Implementation Planning on Behaviour Related to The Diet.

There is a perceived gap between dietary advice given by health practitioners and adherence to the advice by patients. We investigated whether a behaviour change technique (implementation-planning) was more effective than standard-of-care diet advice at reducing dietary acid intake using quantitative erosive tooth wear progression as an objective clinical outcome. This study was a randomised controlled, double-blind, single-centre clinical trial in the UK. Participants (n = 60) with high dietary acid intake (≥2 daily), were recruited and randomly assigned (1:1) to receive either implementation-planning or standard-of-care diet advice in a single clinical session. Questionnaires and impressions were taken at baseline and 6 months later. Dental casts were scanned using laser profilometry and superimposed using surface-matching software. Data were analysed per protocol and intention-to-treat using independent t-tests and Mann-Whitney tests. The intervention group reduced their dietary acid intake between meals to 1 intake per day compared to 2 intakes per day for the controls and demonstrated reduced dental hard tissue volume loss (-0.00 mm3 (SD = 0.01)) compared to controls (-0.07 mm3 (SD 0.17)), p = 0.049. This paper supports the use of implementation planning in clinical practice and presents a non-invasive method of intervention assessment in behaviour change. Larger trials are needed to confirm the generalisability of results.

Tooth wear risk assessment and care-planning in general dental practice.

Objective To assess charting, risk assessment and treatment-planning of tooth wear between recently qualified and experienced dentists in general dental practice.Design Service evaluation.Setting Multi-setting evaluation of three mixed NHS/Private general dental practices in North-East London.Methods The clinical notes of new patient examinations on dentate adults presenting from the 1 October 2016 to 31 December 2016 were audited collecting data on tooth wear charting, risk assessment and treatment planning. Data were analysed using descriptives, chi square and logistic regressions in SPSS. Significance was inferred at p <0.05.Results Foundation dentists and experienced dentists performed 85 and 200 new patient examinations, respectively, during the evaluation period. Tooth wear was charted for 48% of those attending foundation dentists and 5% of those attending experienced dentists. Diet was assessed in 50.6% of patients examined by foundation dentists and 1.0% of patients examined by experienced dentists. Foundation dentists were more likely to chart tooth wear, risk assess and preventively manage tooth wear compared to experienced dentists (p <0.001).Conclusion This service evaluation highlights that improvements are required in recording, risk assessing and preventive treatment planning of erosive tooth wear. Experienced dentists were less likely to risk assess tooth wear and less likely to provide preventive treatment. Experienced GDPs may benefit from re-training in this area.

The management of tooth wear with crowns and indirect restorations.

This manuscript summarises the reasons behind choosing indirect restorations in the treatment of tooth wear. The purpose of this article is to discuss the use of crowns as a restorative treatment option for tooth wear. There are also challenges with the use of composites as they can repeatedly fail and in these situations the indications for crowns for treatment of tooth wear is worthy of consideration. This article is part of a themed issue discussing the management of tooth wear.

Closed-loop intracranial stimulation alters movement timing in humans.

BACKGROUND: A prime objective driving the recent development of human neural prosthetics is to stimulate neural circuits in a manner time-locked to ongoing brain activity. The human supplementary motor area (SMA) is a particularly useful target for this objective because it displays characteristic neural activity just prior to voluntary movement. OBJECTIVE: Here, we tested a method that detected activity in the human SMA related to impending movement and then delivered cortical stimulation with intracranial electrodes to influence the timing of movement. METHODS: We conducted experiments in nine patients with electrodes implanted for epilepsy localization: five patients with SMA electrodes and four control patients with electrodes outside the SMA. In the first experiment, electrocorticographic (ECoG) recordings were used to localize the electrode of interest during a task involving bimanual finger movements. In the second experiment, a real-time sense-and-stimulate (SAS) system was implemented that delivered an electrical stimulus when pre-movement gamma power exceeded a threshold. RESULTS: Stimulation based on real-time detection of this supra-threshold activity resulted in significant slowing of motor behavior in all of the cases where stimulation was carried out in the SMA patients but in none of the patients where stimulation was performed at the control site. CONCLUSIONS: The neurophysiological correlates of impending movement can be used to trigger a closed loop stimulation device and influence ongoing motor behavior in a manner imperceptible to the subject. This is the first report of a human closed loop system designed to alter movement using direct cortical recordings and direct stimulation.

Precision of 655nm Confocal Laser Profilometry for 3D surface texture characterisation of natural human enamel undergoing dietary acid mediated erosive wear.

OBJECTIVES: To assess the precision of optical profilometry for characterising the 3D surface roughness of natural and polished human enamel in order to reliably quantify acid mediated surface roughness changes in human enamel. METHODS: Forty-two enamel samples were prepared from extracted human molars and either polished flat or left unmodified. To investigate precision, the variability of thirty repeated measurements of five areas of one polished and one natural enamel sample was assessed using 655nm Confocal Laser Profilometry. Remaining samples were subjected to forty-five minutes orange juice erosion and microstructural changes were analysed using Sa roughness change (µm) and qualitatively using surface/subsurface confocal microscopy. RESULTS: Enamel surface profilometry from the selected areas revealed maximal precision of 5nm for polished enamel and 23nm for natural enamel. After erosion, the polished enamel revealed a 48% increase in mean (SD) Sa roughness of 0.10 (0.07)µm (P<0.05), whereas in contrast the natural enamel revealed a 45% decrease in mean (SD) roughness of -0.32 (0.42)µm (P<0.05). These data were supported by qualitative confocal images of the surface/subsurface enamel. SIGNIFICANCE: This study demonstrates a method for precise surface texture measurement of natural human enamel. Measurement precision was superior for polished flat enamel in contrast to natural enamel however, natural enamel responds very differently to polished enamel when exposed to erosion challenges. Therefore, thus future studies characterising enamel surface changes following erosion on natural enamel may provide more clinically relevant responses in comparison to polished enamel.