Contralateral Nodal Relapse in Well-lateralised Oral Cavity Cancers Treated Uniformly with Ipsilateral Surgery and Adjuvant Radiotherapy With or Without Concurrent Chemotherapy: a Retrospective Study

AIMS

To evaluate the incidence and pattern of contralateral nodal relapse (CLNR), contralateral nodal relapse-free survival (CLNRFS) and risk factors predicting CLNR in well-lateralised oral cavity cancers (OCC) treated with unilateral surgery and adjuvant ipsilateral radiotherapy with or without concurrent chemotherapy.

MATERIALS AND METHODS

Consecutive patients of well-lateralised OCC treated between 2012 and 2017 were included. The primary endpoint was incidence of CLNR and CLNRFS. Univariable and multivariable analyses were carried out to identify potential factors predicting CLNR.

RESULTS

Of the 208 eligible patients, 21 (10%) developed isolated CLNR at a median follow-up of 45 months. The incidence of CLNR was 21.3% in node-positive patients. CLNR was most common at level IB (61.9%) followed by level II. The 5-year CLNRFS and overall survival were 82.5% and 57.7%, respectively. Any positive ipsilateral lymph node (P = 0.001), two or more positive lymph nodes (P < 0.001), involvement of ipsilateral level IB (P = 0.002) or level II lymph node (P < 0.001), presence of extranodal extension (P < 0.001), lymphatic invasion (P = 0.015) and perineural invasion (P = 0.021) were significant factors for CLNR on univariable analysis. The presence of two or more positive lymph nodes (P < 0.001) was an independent prognostic factor for CLNR on multivariable analysis. CLNR increased significantly with each increasing lymph node number beyond two compared with node-negative patients.

CONCLUSION

The overall incidence of isolated CLNR is low in well-lateralised OCC. Patients with two or more positive lymph nodes have a higher risk of CLNR and may be considered for elective treatment of contralateral neck.

Challenges in the Sustainability of Brachytherapy Service in Contemporary Radiotherapy

Brachytherapy has a long history of delivering a highly conformal radiation dose to the target volume with sparing of adjacent normal tissue and has an irreplaceable role in certain cancers, such as cervical and prostate cancers. There have been futile attempts to replace brachytherapy with other radiation techniques. Despite that there are multifaceted challenges in preserving this dying art, from establishment, to a trained workforce, to maintenance of the equipment and source replacement costs. Here we focus on the challenges to access brachytherapy, the availability and distribution of care across the globe and appropriate training leading to proper implementation of the procedure. Brachytherapy holds a significant place in the treatment armamentarium of most common cancers, such as cervical, prostate, head and neck and skin cancers. However, there is an uneven distribution of brachytherapy facilities, not only across the globe, but also at a national level, with a larger proportion of facilities concentrated in certain regions, more so in low and low-middle income countries. The regions with the highest incidence of cervical cancer have the least access to brachytherapy facilities. Attempts to bridge the gap are essential and should be focused on uniform distribution and access to care, improving training of the workforce through specialised training programmes, reducing the cost of care, planning to reduce the recurring cost, generating evidence and research guidelines, renewing interest in brachytherapy through rebranding, use of social media and building an attainable long-term roadmap.

Non-surgical organ preservation in laryngeal and hypopharyngeal cancers: an audit from the clinic

BACKGROUND

There is increasing concern regarding efficacy of organ preservation protocol in laryngeal and hypopharyngeal cancers.

METHOD

This study retrospectively assessed disease-related and functional outcomes of 191 patients with non-metastatic laryngeal or hypopharyngeal squamous cell carcinoma treated with curative intent (radiotherapy with or without chemotherapy).

RESULTS

Seventy-six patients (39.8 per cent) had a primary cancer in the larynx, and 115 patients (60.2 per cent) had a primary cancer in the hypopharynx. The median follow up was 39 months. The 3-year time to progression, overall survival, local control and laryngectomy free survival was 56.2 per cent, 76.3 per cent, 73.2 per cent and 67.2 per cent, respectively. At the time of analysis, 83 patients (43.5 per cent) were alive and disease free at their last follow up and did not require tube feeding or tracheostomy. The laryngo-oesophageal dysfunction-free survival was 61 per cent at 3 years.

CONCLUSION

Organ conservation protocols remain the standard of treatment in appropriately selected patients with laryngeal and hypopharyngeal cancers.

Systematic review of response criteria and endpoints in autoimmune hepatitis by the International Autoimmune Hepatitis Group

BACKGROUND & AIMS

Autoimmune hepatitis (AIH) has been well characterised and codified through the development of diagnostic criteria. These criteria have been adapted and simplified and are widely used in clinical practice. However, there is a need to update and precisely define the criteria for both treatment response and treatment.

METHODS

A systematic review was performed and a modified Delphi consensus process was used to identify and redefine the response criteria in autoimmune hepatitis.

RESULTS

The consensus process initiated by the International Autoimmune Hepatitis Group proposes that the term 'complete biochemical response' defined as 'normalization of serum transaminases and IgG below the upper limit of normal' be adopted to include a time point at 6 months after initiation of treatment. An insufficient response by 6 months was a failure to meet the above definition. Non-response was defined as '<50% decrease of serum transaminases within 4 weeks after initiation of treatment'. Remission is defined as liver histology with a Hepatitis Activity Index <4/18. Intolerance to treatment was agreed to stand for 'any adverse event possibly related to treatment leading to potential drug discontinuation'.

CONCLUSIONS

These definitions provide a simple and reproducible framework to define treatment response and non-response, irrespective of the therapeutic intervention. A consensus on endpoints is urgently required to set a global standard for the reporting of study results and to enable inter-study comparisons. Future prospective database studies are needed to validate these endpoints.

LAY SUMMARY

Consensus among international experts on response criteria and endpoints in autoimmune hepatitis is lacking. A consensus on endpoints is urgently required to set a global standard for the reporting of study results and to enable the comparison of results between clinical trials. Therefore, the International Autoimmune Hepatitis Group (IAIHG) herein presents a statement on 5 agreed response criteria and endpoints: complete biochemical response, insufficient response, non-response, remission, and intolerance to treatment, which can be used to guide future reporting.

A211 INCIDENCE OF PRIMARY SCLEROSING CHOLANGITIS: A META-ANALYSIS OF POPULATION-BASED STUDIES

Background

Primary sclerosing cholangitis (PSC) is a chronic liver disease associated with significant morbidity, mortality and healthcare utilization. Understanding the incidence of PSC is important in defining the burden of disease and planning for allocation of healthcare resources.

Aims

To conduct a systematic review and meta-analysis of population-based studies of the incidence of PSC and to assess temporal trends of incidence overtime.

Methods

Medline and Embase (from inception to May 10, 2021) were systematically searched to identify studies via the following inclusion criteria: 1) original articles, 2) population-based study of defined geographic area, 3) reported the incidence of PSC or provided data to calculate the incidence of PSC. Studies that assessed specific populations (e.g., pediatric-only, IBD-only) or reported less than 1 year of data were excluded. Abstracts and full texts were reviewed for inclusion and data was extracted independently in duplicate by two individuals (JC, AM). Meta-analyses were performed to calculate overall and country-specific incidence rates (per 100,000 persons) with 95% confidence intervals (CI). Meta-regression calculated the Average Annual Percentage Change (AAPC) of PSC incidence rates overtime.

Results

The initial search returned 3,958 abstracts. After duplicates were removed, abstracts (3,443) were screened, and full texts were reviewed (317), 17 studies met the criteria for inclusion and underwent data extraction. Meta-analysis included 6 studies with annual data contributing to the calculation of AAPC. Studies originated from 10 countries from North America, Europe, and Oceania; however, no population-based studies were published in Asia, Africa, or Latin America (Figure 1). Overall, the incidence rates of PSC was 0.82 per 100,000 (95% CI: 0.62, 1.02) (Figure 1). Incidence rates of PSC were significantly increasing overtime (AAPC: 4.56%; 95% CI: 0.45, 8.68).

Conclusions

The incidence of PSC is low at 0.82 per 100,000 but has been significantly increasing over time. Future studies on the incidence of PSC should be directed at Asia, Africa of Latin America to assess the global epidemiology of PSC.

Figure 1: Pooled incidence rate estimates of PSC per 100,000 person-years at risk.

Funding Agencies

None

A202 IMPACT OF THE COVID-19 PANDEMIC ON THE EPIDEMIOLOGY OF ALCOHOL-RELATED HEPATITIS

Background

Alcohol-related hepatitis (AH) is the most severe form of alcohol-related liver disease, with rising incidence. Stay-at-home orders for the COVID-19 pandemic were associated with increased alcohol consumption. Online sales reported a 262% increase from March 2019 to 2020.

Aims

The purpose of this study was to track the epidemiology of hospitalizations for AH by sex before and after the COVID-19 pandemic. We hypothesized that AH would be more severe in females and younger individuals during the pandemic.

Methods

Using the Discharge Abstract Database, we identified all hospitalizations in Alberta with international classification of disease-10 codes for AH between March 2018 and September 2020. We merged this dataset with provincial laboratory data to identify all inpatient lab values. We calculated Model for End-Stage Liver Disease (MELD) and Maddrey scores and validated a laboratory-based algorithm for AH. Severe AH was defined as Maddrey score > 32. Onset of the pandemic was defined as March 2020. Stratified by pandemic onset, descriptive statistics were done with Chi-squared and Kruskal Wallis tests. Inpatient mortality was assessed as a primary outcome. Binomial regression was used to assess changes in frequency of admission for AH with the denominator as all cirrhosis-related admissions over the same time-period.

Results

We identified 991 hospitalizations for AH prior to the pandemic (n=381, 38.5% female) and 417 during the pandemic (n=144, 34.5% female). Hospitalizations for AH significantly increased during the pandemic (p = 0.04) (Figure 1). Median Maddrey score for females (30.5) before the pandemic was significantly higher than for males (22.9), p < 0.01. During the pandemic, median Maddrey for females (28.7) was higher than males 21.4, p = 0.07. Median age at admission was significantly lower for both males and females during the pandemic (age 44 and 41, respectively) as compared to prior (age 47 and 45, respectively) p < 0.05. There was no significant difference in MELD between sexes before (13.5 for females, 14.0 for males, p = 0.15) and during the pandemic (13.3 for females, 13.0 for males, p = 0.75). Additionally, there was no significant difference in mortality between sexes before (10.4% in females, 11.5% in males, p = 0.22) and after the pandemic (9.2% in females, 9.9% in males, p = 0.67).

Conclusions

Hospitalizations for AH rose during the pandemic and occurred at younger ages. There was no significant difference in disease severity or mortality before and during the pandemic. Overall, females have more severe AH than males. Public health efforts should continue to be made to educate about the harms of alcohol excess and offer community support. Future studies will expand the trend through multiple pandemic waves.

Funding Agencies

None

Post-cricoid and Upper Oesophagus Cancers Treated with Organ Preservation Using Intensity-modulated Image-guided Radiotherapy: a Phase II Prospective Study of Outcomes, Toxicity and Quality of Life

AIMS

To prospectively examine the outcomes, toxicity and quality of life (QoL) of patients with post-cricoid and upper oesophagus (PCUE) cancers treated with an organ-preservation approach of (chemo)-radiotherapy using intensity-modulated image-guided radiotherapy (IM-IGRT).

MATERIALS AND METHODS

This phase II prospective study was conducted at a tertiary cancer centre from February 2017 to January 2020. Forty patients with squamous cell carcinoma of PCUE of stage T1-3, N0-2, M0 were accrued. Gross exolaryngeal extension/dysfunctional larynx were major exclusion criteria. Patients received 63-66 Gy in once-daily fractions using volumetric modulated arc therapy with daily IGRT. Outcome measures included disease-related outcomes, patterns of failure, Radiation Therapy Oncology Group toxicities, feeding tube dependency and QoL.

RESULTS

The median follow-up was 22 months. Twenty-six (87.5%) patients had locoregionally advanced disease and 34 (85%) patients received (chemo)-radiotherapy. A complete response was observed in 26 (65%) patients. The 2-year locoregional control, event-free survival and cause-specific survival were 59.6%, 40.2% and 44.8%, respectively. The volume of primary tumour (GTVPvol) exceeding 28 cm³ had inferior overall survival (P = 0.005) on univariate analysis. Multivariable analysis showed GTVPvol and positron emission tomography-computed tomography maximum standardised uptake value to be independently predictive for event-free and overall survival. A feeding tube requirement at presentation was seen in 11 (27.5%) patients, whereas long-term feeding tube dependency at 6 months was seen in 10 (37%) patients. For QoL, a statistical improvement in pain, appetite loss and swallowing was observed over time.

CONCLUSION

Although the outcomes of PCUE cancers remain dismal, the use of state of the art diagnostic modalities, careful case selection and modern radiotherapy techniques improved outcomes as compared with before in this exclusive analysis of PCUE cancers.

A210 DECLINE IN HEPATITIS B QUANTITATIVE SURFACE ANTIGEN LEVELS IN CHRONIC HEPATITIS B PATIENTS ON TREATMENT WITH NUCLEOS(T)IDE ANALOGUES

Background

The Hepatitis B virus (HBV) affects over 250 million people worldwide and can lead to cirrhosis and hepatocellular carcinoma. HBV surface antigen (HBsAg) quantification is increasingly used to predict disease activity and treatment response. As there is no virologic cure, clinicians are seeking a “functional cure”, or HBsAg loss, as a guide to safely stopping nucleos(t)ide analogue therapy. Tenofovir Disoproxil Fumarate (TDF) and Entecavir (ETV) are first line therapy but require prolonged treatment to achieve HBsAg clearance.

Aims

To assess the association between nucleos(t)ide therapy and decline in quantitative HBsAg (qHBsAg) in patients with HBV from Calgary, Alberta.

Methods

A retrospective review of adult patients with chronic HBV, followed at the University of Calgary Liver Clinic, was conducted between January 2012 and October 2020. Patients were excluded if treatment was discontinued or changed, only had a single qHBsAg measurement, or were co-infected with hepatitis C virus, hepatitis delta virus, or HIV. Patients were stratified according to therapy with TDF, ETV, or no treatment. To identify associations between mean changes in qHBsAg by medication exposure, one-way ANOVAs and t-tests were performed. Results were reported as means and 95% confidence intervals (CI). The median time from initial qHBsAg to most-recent was calculated.

Results

187 patients were included in the final analysis (Table 1). 77 were excluded for being on more than one medication over the study period, 10 were excluded due to discontinuation of treatment, and 195 were excluded for single qHBsAg measurements. The mean qHBsAg decline was -750.04 IU/mL (95% CI -1311.58, -188.50) in the TDF group (n=45) and -309.20 IU/mL (95% CI -600.90, -17.50) in the ETV group (n=35) (p=0.20). In the no treatment group (n=107), the mean qHBsAg increased by 711.29 IU/mL (95% CI -600.78, 2023.80)(Figure 1). The median time from initial qHBsAg to most-recent was 980 days.

Conclusions

Quantitative HBsAg levels declined in patients on TDF and ETV, but increased in untreated patients. Although HBsAg levels showed a trend for greater decline in TDF-treated patients, results failed to reach statistical significance, and may be affected by overall treatment duration. Future studies will explore medication use as a time-varying covariate to identify how change in treatment influences changes in HBsAg over time.

Funding Agencies

None

A62 CANADIAN POPULATION-BASED EVALUATION OF THE NATURAL HISTORY OF PRIMARY BILIARY CHOLANGITIS OVER THE LAST DECADE

Background

Few studies have evaluated the epidemiology of primary biliary cirrhosis (PBC) in North America. Ursodeoxycholic acid (URSO) improves outcomes amongst PBC patients.

Aims

Therefore, we undertook this study to determine the epidemiology of PBC in Canada, and impact of URSO on clinical outcomes, two decades after URSO approval in North America.

Methods

We used our previously validated coding algorithm to identify PBC patients in population based administrative databases in the Calgary Health Zone (population ~1.5 million) from 2005–2015. Multiple sources of data including inpatient, ambulatory, physician billing, laboratory, and pharmaceutical were linked. Annual prevalence and incidence were estimated using Poisson regression. Age/sex adjusted rate ratios were calculated. We used Cox regression models to estimate: all-cause mortality, liver transplant and decompensated cirrhosis free survival. In our models, we adjusted for demographic and clinical variables including response to URSO.

Results

During the study period over 11 years, the overall annual age/sex adjusted PBC incidence was 29.5 cases per million (48.3 and 9.9 per million for women and men, respectively). The highest incidence rate was observed among women aged 60–79 (90.9 per million) with an incidence rate ratio of 10.4 (95%: 6.83–15.9) compared to those aged 20–39. While incidence rate remained stable, prevalence rate increased significantly from 242 to 343 cases/ million, between 2005 and 2015 (P&lt;0.01). Prevalence rate was highest at 965 cases/ million amongst women aged 60–79. We identified 299 incident PBC cases with a median follow up of 5.1 years (IQR 2.9–8.3). 87 (29.1%) of these incident cases developed decompensated cirrhosis or HCC, 10 patients (3.4%) underwent liver transplantation, and 44 (14.7%) patients died. The annual mortality rate was 2.9% (95%CI: 2.1- 3.8) compared to 3.4% (2.3–4.9%) a decade ago (P=0.04). The estimated 5-year survival rate was 87.6% (82.6- 91.3). Standardized mortality rate was 3.2 (95%CI: 2.2–4.1). Overall, 25% of our incident cohort were not prescribed URSO. Patients not prescribed URSO were more likely to be male, older age, have normal ALP and had decompensated cirrhosis at diagnosis (P&lt;0.01 for all). Among those who used URSO, response rate was 86%. Response to URSO was an independent predictor of reduced risk of decompensated cirrhosis and liver transplant, and higher survival (aHR: 0.46, 0.29–0.74).

Conclusions

PBC prevalence is increasing in this North American population. While mortality rate decreases in our PBC cohort, survival was suboptimal compared to the general population, mainly due to late presentation at diagnosis. Therefore, better surveillance and early detection of possible PBC patients in the primary care setting are essential to improve PBC outcomes.

Funding Agencies

None

A187 CHOLESTATIC LIVER DISEASE AND BRAIN DYSFUNCTION: ROLE OF THE ARYL HYDROCARBON RECEPTOR

Background

Cholestatic liver disease is associated with immune-mediated inflammatory liver injury. This disorder is also associated with brain dysfunction and behavioural changes, notably fatigue, depression and social withdrawal. The mechanisms leading to these central nervous system abnormalities are unknown, however, they are associated with neuroinflammation. Microglia and astrocytes are two glial populations that play key roles in neuroinflammation. Activated glia display morphological changes, secrete cytokines, and mediate electrophysiological changes, altering the normal functioning of the brain. The aryl hydrocarbon receptor (AhR) is a transcription factor involved in the immune response. AhR is present on glia and its’ activation has been shown to reduce neuroinflammation. The role of the AhR in cholestatic liver disease has yet to be examined.

Aims

To study the function of the AhR in a model of cholestic liver disease. We will test the hypothesis that activation of AhR in the brain will reduce neuroinflammation and behavioral deficits observed in cholestatic mice.

Methods

Male C57Bl/6J mice had cholestasis induced by bile duct ligation (BDL); comparisons were made to sham-operated controls. Mice were tested for social interaction with a 4-week old juvenile in their home cage and the number of social interaction attempts quantified. Next, mice were euthanized, brains were removed and processed for immunohistochemistry. Brain sections were stained for markers of microglia (IBA-1) and astrocytes (GFAP). Microglia were counted and astrocyte activation was qualitatively assessed. PCR was used to quantify gene expression of AhR and its downstream gene targets (eg. CYP1A1) in mice that recived treatment with beta-napthoflavone (BNF), an AhR agonist, or in vehicle treated controls.

Results

BDL mice made significantly fewer attempts to interact with the juvenile as compared to controls (P&lt;0.05). We also observed a significant increase in IBA-1 immunoreactive cell numbers in both the CA1 region of the hippocampus and the hypothalamic paraventricular nucleus (PVN, P&lt;0.05). BDL mice also displayed marked increases in GFAP+ staining in the PVN, but not the CA1, in contrast to sham controls. Lastly, we found that BNF significantly upregulated CYP1A1 (P&lt;0.05) in the liver and prefrontal cortex of mice. We are currently examining whether BNF can reduce neuroinflammation and improve decreased social interaction in cholestatic mice.

Conclusions

Cholestatic liver damage was associated with impaired social behavior. Further, glial activation, an indicator of neuroinflammation was increased in components of the limbic system associated with the response to stress, learning, and memory. Future experiments will address whether activation of the AhR will ameliorate neuroinflammation and behavioral changes observed in mice with cholestatic liver injury.

Funding Agencies

CCC, CIHR

Synthesis of stabilized hydroxyapatite nanosuspensions for enamel caries remineralization

BACKGROUND

The aim of this study was to develop and evaluate a method for synthesizing a stable suspension of hydroxyapatite nanoparticles and to test its efficacy for remineralizing carious enamel lesions.

METHODS

Hydroxyapatite (HA) particles were synthesized using wet chemistry. Synthesized particles were introduced into a high-pressure homogenizer (5-10 homogenization passes at 15 000 psi) in the presence of different stabilizers. Size and distribution of the resultant particles were determined using dynamic light scattering (DLS). The morphology and composition of the nanoparticles were determined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Subsequently, artificial lesions were treated with HA nanosuspension plus artificial saliva or a fluoride-containing artificial saliva only. Visual analysis and quantification of the lesion mineral density before and after remineralization were performed using microcomputed tomography.

RESULTS

DLS and SEM results confirmed the formation of nonagglomerated HA nanoparticles (20-40 nm) following high-pressure homogenization treatment. Quantitative evaluation of the lesions showed that remineralization of the lesion with hydroxyapatite nanosuspension led to a significantly higher level of mineral gain compared to the control group (P < 0.05).

CONCLUSION

High-pressure homogenization is an effective method for facile preparation of a stable suspension of hydroxyapatite nanoparticles. Treatment of artificial lesions with nonagglomerated spherical HA nanoparticles improves the remineralization of enamel lesion.

Human papillomavirus/p16 positive head and neck cancer in India: Prevalence, clinical impact, and influence of tobacco use

BACKGROUND

Limited data are available on the prevalence and prognostic significance of human papillomavirus (HPV) in squamous cell carcinoma of head and neck (SCCHN) in the Indian population.

AIM

The present study aimed to determine the prevalence of HPV and p16 in an Indian cohort of SCCHN and assess their correlation and influence of tobacco use on patient outcomes.

MATERIALS AND METHODS

The p16 and HPV status of 170 patients of SCCHN treated with curative chemoradiotherapy was determined using immunohistochemistry and polymerase chain reaction, respectively, and further correlated with their demographic characteristics. In addition, genotyping of HPV-positive samples was performed. Survival outcomes were analyzed and compared for both p16 positive (p16 +ve) and p16 negative (p16 -ve) population. The influence of tobacco use on outcomes was assessed.

RESULTS

p16 expression was observed in 20% (34/170) cases whereas HPV positivity was detected in 39.4% (67/170) of SCCHN patients with HPV16 being the most common (91%) subtype. About 73.5% patients were p16 +ve among the tobacco users in this cohort (83.5%). Interestingly, p16 positivity was significantly associated with nonusers of tobacco (P = 0.02) and younger females (P = 0.06). The p16 +ve and p16 -ve groups did not exhibit a significant difference in the 5-year cause-specific survival (CSS) (79% vs. 72.2%), disease-free survival (DFS) (78.3% vs. 68.3%, P = 0.5), and locoregional control (LRC) (82.2% vs. 71.5%, P = 0.4). However, the outcome analyses in tobacco nonusers revealed a definite large improvement in CSS (P = 0.08) and a trend toward improvement in DFS (P = 0.15) and LRC (P = 0.11) in the p16 +ve versus the p16 -ve groups.

CONCLUSION

The low prevalence of p16 positivity (20%) and dual HPV and p16 positivity (38.8%) in the studied Indian cohort indicates the low utility of p16 as a surrogate for HPV in the background of high tobacco burden. The outcomes are largely improved in a small subset of SCCHN cases comprising p16 +ve tobacco nonusers.

An unusual case of nephrotic syndrome

Nephrotic syndrome can be rarely due to inherited disorders of enzymes. One such variety is lecithin cholesterol acyltransferase deficiency. It leads to accumulation of unesterified cholesterol in the eye and other organs. We report a case of nephrotic syndrome with cloudy cornea and hypocholesterolemia with foam cells and lipid deposits on renal biopsy. Awareness about this rare disease may help in the early institution of specific measures to prevent progression to end-stage renal disease.

Bone metabolism induced by denture insertion in positron emission tomography

18F-fluoride positron emission tomography (PET) can identify subtle functional variation prior to the major structural change detectable by X-ray. This study aims to investigate the mechanobiological bone reaction around the abutment tooth and in the residual ridge, induced by insertion of removable partial denture (RPD) within two different groups of patients: patients without denture experience (Group 1) and patients with denture experience before (Group 2), using 18F-fluoride PET imaging technique. 18F-fluoride PET/computerised tomography (CT) scan was performed to examine the bone metabolic change in mandible before and after the RPD treatment. Region of interests (ROIs) were placed in alveolar bone around abutment tooth and in residual bone beneath the RPD. Standardised uptake value (SUV), reflecting the accumulation of 18F-fluoride, was measured for each ROI. In all subjects of Group 1, SUVs after insertion were higher than before in both alveolar bone and residual bone, while there was less significant change in SUV in subjects of Group 2. This study demonstrated using longitudinal 18F-fluoride PET scans to effectively examine the bone metabolic change in mandible induced by occlusal loading after RPD insertion. Using this technique, within the six subjects in this study, it was shown that bone metabolism around abutment tooth and residual ridge increased after RPD insertion in case of first-time denture user, while there was no big change in the patient with experience of denture before. This study revealed the effectiveness of applying PET to evaluate bone metabolic activity as mechanobiological reaction.

Mechanobiological Bone Reaction Quantified by Positron Emission Tomography

While nuclear medicine has been proven clinically effective for examination of the change in bone turnover as a result of stress injury, quantitative correlation between tracer uptake and mechanical stimulation in the human jawbone remains unclear. This study aimed to investigate the relationship between bone metabolism observed by 18F-fluoride positron emission tomography (PET) images and mechanical stimuli obtained by finite element analysis (FEA) in the residual ridge induced by the insertion of a removable partial denture (RPD). An 18F-fluoride PET/CT (computerized tomography) scan was performed to assess the change of bone metabolism in the residual ridge under the denture before and after RPD treatment. Corresponding patient-specific 3D finite element (FE) models were created from CT images. Boundary conditions were prescribed by the modeling of condylar contacts, and muscular forces were derived from the occlusal forces measured in vivo to generate mechanobiological reactions. Different mechanobiological stimuli, e.g., equivalent von Mises stress (VMS), equivalent strain (EQV), and strain energy density (SED), determined from nonlinear FEA, were quantified and compared with the standardized uptake values (SUVs) of PET. Application of increased occlusal force after RPD insertion induced higher mechanical stimuli in the residual bone. Accordingly, SUV increased in the region of residual ridge with higher mechanical stimuli. Thus, with SUV, a clear correlation was observed with VMS and SED in the cancellous bone, especially after RPD insertion (R2 > 0.8, P < 0.001). This study revealed a good correlation between bone metabolism and mechanical stimuli induced by RPD insertion. From this patient-specific study, it was shown that metabolic change detected by PET in the loaded bone, in a much shorter duration than conventional x-ray assessment, is associated with mechanical stimuli. The nondestructive nature of PET/CT scans and FEA could potentially provide a new method for clinical examination and monitoring of prosthetically driven bone remodeling.

Fluoride release, recharge and mechanical property stability of various fluoride-containing resin composites

AIM

To determine the fluoride release and recharge of three fluoride-containing resin composites when aged in deionized water (pH 6.5) and lactic acid (pH 4.0) and to assess mechanical properties of these composites following aging.

METHODS

Three fluoride-containing resin composites were analyzed in this study; a new giomer material named Beautifil II, Gradia Direct X, and Tetric EvoCeram. A glass ionomer cement, Fuji IX Extra, was also analyzed for comparison. Specimens were fabricated for two test groups: group 1 included 10 disc specimens initially aged 43 days in deionized water (five specimens) and lactic acid (five specimens). The fluoride release from these specimens was measured using a fluoride-specific electrode on nine specific test days during the aging period. Following 49 days of aging, each specimen was recharged in 5000 ppm neutral sodium fluoride solution for 5 minutes. Specimen recharge was then repeated on a weekly basis for 3 weeks. The subsequent fluoride rerelease was measured at 1, 3, and 7 days after each recharge episode. Group 2 included six disc specimens aged for 3 months in deionized water (three specimens) and lactic acid (three specimens). The hardness and elastic modulus of each specimen was measured using nano-indentation at intervals of 24 hours, 1 month, and 3 months after fabrication. Two-way factorial analysis of variance (ANOVA) and post-hoc (Tukey) testing was used to assess the influence of storage media (two levels) and composite type (three levels) on the fluoride release, fluoride rerelease, hardness, and elastic modulus of the assessed materials. The level of significance was set at p=0.05.

RESULTS

All three composites demonstrated fluoride release and recharge when aged in both deionized water and lactic acid. The cumulative fluoride released from Beautifil II into both media was substantially greater than the fluoride released from Gradia Direct X and Tetric EvoCeram after 43 days aging and was significantly (p<0.05, ANOVA, Tukey test) greater during several analysis periods. Beautifil II demonstrated the greatest recharge ability of the three composites over the 3-week recharge period in both media. Fuji IX Extra demonstrated a significantly (p<0.05) greater fluoride release and recharge compared with the three resin composites. The elastic modulus and hardness of the three composites did not decrease significantly (p<0.05) with fluoride release or fluid uptake over the 3-month aging period, in either media.

CONCLUSION

The three composites in the present study demonstrated fluoride release (Beautiful II > Gradia Direct X > Tetric EvoCeram) and fluoride recharge (Beautiful II > Gradia Direct X > Tetric EvoCeram). This capability raises the possibility of fluoride-containing composites exhibiting a lower incidence of recurrent caries than non fluoride–containing composites. The mechanical properties of each composite did not diminish with aging and fluoride release over the testing period.

Autoantibodies to GW bodies and other autoantigens in primary biliary cirrhosis

Autoantibodies to intracellular targets in mitochondria and nuclei are serological hallmarks of primary biliary cirrhosis (PBC). One of the most recently identified cellular targets of PBC autoantibodies is a novel cytoplasmic structure referred to as GW bodies [GWB, G (glycine) W (tryptophan)-containing bodies (GWB)]. GWB are indentified as discrete cytoplasmic domains that are involved in mRNA processing via the RNA interference (RNAi) pathway. Key components of GWB include the proteins GW182, Ago2, RNA-associated protein 55 (RAP55) and Ge-1/Hedls. The primary objective was to study the frequency and clinical association of antibodies directed to GWB components, in 109 PBC patients. Autoantibodies to mitochondrial antigen-pyruvate dehydrogenase complex (M2), branched-chain 2-oxo-acid dehydrogenase complex and 2-oxo glutarate dehydrogenase complex (3E-BPO), gp210, sp100, promyelocytic leukaemia cell antigen (PML) and liver kidney microsomal-1 antigen (LKM-1) were detected by a line immunoassay and antibodies to GWB (GW182, RAP55, Ge-1, GW2, GW3) and glutamate receptor interacting protein (GRIP)-associated protein-1 (GRASP-1), by an addressable laser bead immunoassay (ALBIA). The most common GWB autoantigen targets were: RAP55-28%, GW182-12%, GW2-2% and antibodies to GRASP-1-17%. By comparison, the frequency of reactivity to established PBC autoantigens was: gp210, 27%; sp100, 27% and PML, 17%. None of the autoantibodies were associated with differences in Mayo risk score or liver decompensation. This study is the first study to show that antibodies to RAP55, GW182 and GRASP-1 are the most common GWB targets in PBC.

Clinical trials in zirconia: a systematic review

Zirconia is unique in its polymorphic crystalline makeup, reported to be sensitive to manufacturing and handling processes, and there is debate about which processing method is least harmful to the final product. Currently, zirconia restorations are manufactured by either soft or hard-milling processes, with the manufacturer of each claiming advantages over the other. Chipping of the veneering porcelain is reported as a common problem and has been labelled as its main clinical setback. The objective of this systematic review is to report on the clinical success of zirconia-based restorations fabricated by both milling processes, in regard to framework fractures and veneering porcelain chipping. A comprehensive review of the literature was completed for in vivo trials on zirconia restorations in MEDLINE and PubMed between 1950 and 2009. A manual hand search of relevant dental journals was also completed. Seventeen clinical trials involving zirconia-based restorations were found, 13 were conducted on fixed partial dentures, two on single crowns and two on zirconia implant abutments, of which 11 were based on soft-milled zirconia and six on hard-milled zirconia. Chipping of the veneering porcelain was a common occurrence, and framework fracture was only observed in soft-milled zirconia. Based on the limited number of short-term in vivo studies, zirconia appears to be suitable for the fabrication of single crowns, and fixed partial dentures and implant abutments providing strict protocols during the manufacturing and delivery process are adhered to. Further long-term prospective studies are necessary to establish the best manufacturing process for zirconia-based restorations.

Clinical trials in zirconia: a systematic review

Zirconia is unique in its polymorphic crystalline makeup, reported to be sensitive to manufacturing and handling processes, and there is debate about which processing method is least harmful to the final product. Currently, zirconia restorations are manufactured by either soft or hard-milling processes, with the manufacturer of each claiming advantages over the other. Chipping of the veneering porcelain is reported as a common problem and has been labelled as its main clinical setback. The objective of this systematic review is to report on the clinical success of zirconia-based restorations fabricated by both milling processes, in regard to framework fractures and veneering porcelain chipping. A comprehensive review of the literature was completed for in vivo trials on zirconia restorations in MEDLINE and PubMed between 1950 and 2009. A manual hand search of relevant dental journals was also completed. Seventeen clinical trials involving zirconia-based restorations were found, 13 were conducted on fixed partial dentures, two on single crowns and two on zirconia implant abutments, of which 11 were based on soft-milled zirconia and six on hard-milled zirconia. Chipping of the veneering porcelain was a common occurrence, and framework fracture was only observed in soft-milled zirconia. Based on the limited number of short-term in vivo studies, zirconia appears to be suitable for the fabrication of single crowns, and fixed partial dentures and implant abutments providing strict protocols during the manufacturing and delivery process are adhered to. Further long-term prospective studies are necessary to establish the best manufacturing process for zirconia-based restorations.