1
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Abstract
Over the past 3 years, the first bivalent protein degraders intentionally designed for targeted protein degradation (TPD) have advanced to clinical trials, with an initial focus on established targets. Most of these clinical candidates are designed for oral administration, and many discovery efforts appear to be similarly focused. As we look towards the future, we propose that an oral-centric discovery paradigm will overly constrain the chemical designs that are considered and limit the potential to drug novel targets. In this Perspective, we summarize the current state of the bivalent degrader modality and propose three categories of degrader designs, based on their likely route of administration and requirement for drug delivery technologies. We then describe a vision for how parenteral drug delivery, implemented early in research and supported by pharmacokinetic-pharmacodynamic modelling, can enable exploration of a broader drug design space, expand the scope of accessible targets and deliver on the promise of protein degraders as a therapeutic modality.
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Affiliation(s)
| | - Suman Luthra
- Discovery Pharmaceutical Sciences, Merck & Co., Inc., Boston, MA, USA
| | - Matthew F Brown
- Discovery Sciences, Worldwide Research, Development, and Medical, Pfizer Inc., Groton, CT, USA
| | - Derek W Bartlett
- Pharmacokinetics, Dynamics, & Metabolism, Worldwide Research, Development, and Medical, Pfizer Inc., San Diego, CA, USA
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2
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Abstract
Targeted protein degradation has emerged from the chemical biology toolbox as one of the most exciting areas for novel therapeutic development across the pharmaceutical industry. The ability to induce the degradation, and not just inhibition, of target proteins of interest (POIs) with high potency and selectivity is a particularly attractive property for a protein degrader therapeutic. However, the physicochemical properties and mechanism of action for protein degraders can lead to unique pharmacokinetic (PK) and pharmacodynamic (PD) properties relative to traditional small molecule drugs, requiring a shift in perspective for translational pharmacology. In this review, we provide practical insights for building the PK-PD understanding of protein degraders in the context of translational drug development through the use of quantitative mathematical frameworks and standard experimental assays. Published datasets describing protein degrader pharmacology are used to illustrate the applicability of these insights. The learnings are consolidated into a translational PK-PD roadmap for targeted protein degradation that can enable a systematic, rational design workflow for protein degrader therapeutics.
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Affiliation(s)
- Derek W Bartlett
- Pharmacokinetics, Dynamics, & Metabolism, Pfizer Worldwide Research, Development and Medical, Pfizer Inc, San Diego, CA, USA.
| | - Adam M Gilbert
- Discovery Sciences, Pfizer Worldwide Research, Development and Medical, Pfizer Inc, Groton, CT, USA
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3
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Abstract
Bispecific protein degraders (BPDs) engage the ubiquitin-proteasome system (UPS) to catalytically degrade intracellular proteins through the formation of ternary complexes with the target protein and E3 ubiquitin ligases. Here, we describe the development of a mechanistic modeling framework for BPDs that includes the reaction network governing ternary complex formation and degradation via the UPS. A critical element of the model framework is a multi-step process that results in a time delay between ternary complex formation and protein degradation, thereby balancing ternary complex stability against UPS degradation rates akin to the kinetic proofreading concept that has been proposed to explain the accuracy and specificity of biological processes including protein translation and T cell receptor signal transduction. Kinetic proofreading likely plays a central role in the cell's ability to regulate substrate recognition and degradation by the UPS, and the model presented here applies this concept in the context of a quantitative pharmacokinetic (PK)-pharmacodynamic (PD) framework to inform the design of potent and selective BPDs.
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Affiliation(s)
- Derek W Bartlett
- Pharmacokinetics, Dynamics, & Metabolism, Pfizer Worldwide Research and Development, Pfizer Inc., San Diego, CA, USA.
| | - Adam M Gilbert
- Discovery Sciences, Pfizer Worldwide Research and Development, Pfizer Inc., Groton, CT, USA
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4
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Guerrero YA, Desai D, Sullivan C, Kindt E, Spilker ME, Maurer TS, Solomon DE, Bartlett DW. A Microfluidic Perfusion Platform for In Vitro Analysis of Drug Pharmacokinetic-Pharmacodynamic (PK-PD) Relationships. AAPS J 2020; 22:53. [PMID: 32124093 DOI: 10.1208/s12248-020-0430-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 02/08/2020] [Indexed: 12/14/2022]
Abstract
Static in vitro cell culture studies cannot capture the dynamic concentration profiles of drugs, nutrients, and other factors that cells experience in physiological systems. This limits the confidence in the translational relevance of in vitro experiments and increases the reliance on empirical testing of exposure-response relationships and dose optimization in animal models during preclinical drug development, introducing additional challenges owing to species-specific differences in drug pharmacokinetics (PK) and pharmacodynamics (PD). Here, we describe the development of a microfluidic cell culture device that enables perfusion of cells under 2D or 3D culture conditions with temporally programmable concentration profiles. Proof-of-concept studies using doxorubicin and gemcitabine demonstrated the ability of the microfluidic PK-PD device to examine dose- and time-dependent effects of doxorubicin as well as schedule-dependent effects of doxorubicin and gemcitabine combination therapy on cell viability using both step-wise drug concentration profiles and species-specific (i.e., mouse, human) drug PK profiles. The results demonstrate the importance of including physiologically relevant dynamic drug exposure profiles during in vitro drug testing to more accurately mimic in vivo drug effects, thereby improving translatability across nonclinical studies and reducing the reliance on animal models during drug development.
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Affiliation(s)
- Yadir A Guerrero
- Neofluidics, 6650 Lusk Blvd, Suite 101, San Diego, California, 92121, USA
| | - Diti Desai
- Neofluidics, 6650 Lusk Blvd, Suite 101, San Diego, California, 92121, USA
| | - Connor Sullivan
- Neofluidics, 6650 Lusk Blvd, Suite 101, San Diego, California, 92121, USA
| | - Erick Kindt
- Pharmacokinetics, Dynamics, & Metabolism, Pfizer Worldwide Research and Development, Pfizer Inc., 10646 Science Center Drive, San Diego, California, 92121, USA
| | - Mary E Spilker
- Pharmacokinetics, Dynamics, & Metabolism, Pfizer Worldwide Research and Development, Pfizer Inc., 10646 Science Center Drive, San Diego, California, 92121, USA
| | - Tristan S Maurer
- Pharmacokinetics, Dynamics, & Metabolism, Pfizer Worldwide Research and Development, Cambridge, Massachusetts, 02139, USA
| | - Deepak E Solomon
- Neofluidics, 6650 Lusk Blvd, Suite 101, San Diego, California, 92121, USA.
| | - Derek W Bartlett
- Pharmacokinetics, Dynamics, & Metabolism, Pfizer Worldwide Research and Development, Pfizer Inc., 10646 Science Center Drive, San Diego, California, 92121, USA.
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5
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Bartlett DW, Wu A, Li X, Kraus M, Wang H, Kindt E. Development of an In Vivo Retrodialysis Calibration Method Using Stable Isotope Labeling to Monitor Metabolic Pathways in the Tumor Microenvironment via Microdialysis. J Pharm Sci 2019; 108:3124-3129. [DOI: 10.1016/j.xphs.2019.05.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 05/10/2019] [Accepted: 05/21/2019] [Indexed: 01/03/2023]
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6
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Affolter T, Llewellyn HP, Bartlett DW, Zong Q, Xia S, Torti V, Ji C. Inhibition of immune checkpoints PD-1, CTLA-4, and IDO1 coordinately induces immune-mediated liver injury in mice. PLoS One 2019; 14:e0217276. [PMID: 31112568 PMCID: PMC6528985 DOI: 10.1371/journal.pone.0217276] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 05/08/2019] [Indexed: 12/18/2022] Open
Abstract
Cancer cells harness immune checkpoints such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1) and indoleamine 2,3-dioxygenase 1 (IDO1) to evade immune control. Checkpoint inhibitors have demonstrated durable anti-tumor efficacy in human and preclinical models. Liver toxicity is one of the common immune-related adverse events associated with checkpoint inhibitors (CPIs) and its frequency and severity often increase significantly during CPI combination therapies. We aim to develop a mouse model to elucidate the immune mechanisms of CPI-associated liver toxicity. Co-administration of CTLA-4 blocking antibody, 9D9, and/or an IDO1 inhibitor, epacadostat in wild-type and PD-1-/- mice (to simulate the effect of PD1 blockade) synergistically induced liver injury and immune cell infiltration. Infiltrated cells were primarily composed of CD8+ T cells and positively associated with hepatocyte necrosis. Strikingly, sites of hepatocyte necrosis were frequently surrounded by clusters of mononuclear immune cells. CPI treatments resulted in increased expression of genes associated with hepatocyte cell death, leukocyte migration and T cell activation in the liver. In conclusion, blockade of immune checkpoints PD-1, CTLA-4, and IDO1 act synergistically to enhance T cell infiltration and activity in the liver, leading to hepatocyte death.
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Affiliation(s)
- Timothy Affolter
- Global Pathology, Pfizer Drug Safety Research and Development, La Jolla, California, United States of America
| | - Heather P. Llewellyn
- Global Pathology, Pfizer Drug Safety Research and Development, La Jolla, California, United States of America
| | - Derek W. Bartlett
- Medicine Design, Pfizer Worldwide Research and Development, La Jolla, California, United States of America
| | - Qing Zong
- Biomarkers, Pfizer Drug Safety Research and Development, La Jolla, California, United States of America
| | - Shuhua Xia
- Investigative Toxicology, Drug Safety Research and Development, Groton, Connecticut, United States of America
| | - Vince Torti
- General Toxicology, Drug Safety Research and Development La Jolla, California, United States of America
| | - Changhua Ji
- Global Pathology, Pfizer Drug Safety Research and Development, La Jolla, California, United States of America
- * E-mail:
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7
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O'Toole S, Pennington M, Varma S, Bartlett DW. The treatment need and associated cost of erosive tooth wear rehabilitation - a service evaluation within an NHS dental hospital. Br Dent J 2018; 224:957-961. [PMID: 29880974 DOI: 10.1038/sj.bdj.2018.444] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/22/2018] [Indexed: 11/09/2022]
Affiliation(s)
- S O'Toole
- King's College London Dental Institute, Department of Prosthodontics, London, United Kingdom
| | | | - S Varma
- Guys Hospital, Prosthodontics, London, United Kingdom
| | - D W Bartlett
- Kings College London Dental Institute, Prosthodontics, London, United Kingdom
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8
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Ming JE, Abrams RE, Bartlett DW, Tao M, Nguyen T, Surks H, Kudrycki K, Kadambi A, Friedrich CM, Djebli N, Goebel B, Koszycki A, Varshnaya M, Elassal J, Banerjee P, Sasiela WJ, Reed MJ, Barrett JS, Azer K. A Quantitative Systems Pharmacology Platform to Investigate the Impact of Alirocumab and Cholesterol-Lowering Therapies on Lipid Profiles and Plaque Characteristics. Gene Regul Syst Bio 2017; 11:1177625017710941. [PMID: 28804243 PMCID: PMC5484552 DOI: 10.1177/1177625017710941] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 04/17/2017] [Indexed: 12/20/2022]
Abstract
Reduction in low-density lipoprotein cholesterol (LDL-C) is associated with decreased risk for cardiovascular disease. Alirocumab, an antibody to proprotein convertase subtilisin/kexin type 9 (PCSK9), significantly reduces LDL-C. Here, we report development of a quantitative systems pharmacology (QSP) model integrating peripheral and liver cholesterol metabolism, as well as PCSK9 function, to examine the mechanisms of action of alirocumab and other lipid-lowering therapies, including statins. The model predicts changes in LDL-C and other lipids that are consistent with effects observed in clinical trials of single or combined treatments of alirocumab and other treatments. An exploratory model to examine the effects of lipid levels on plaque dynamics was also developed. The QSP platform, on further development and qualification, may support dose optimization and clinical trial design for PCSK9 inhibitors and lipid-modulating drugs. It may also improve our understanding of factors affecting therapeutic responses in different phenotypes of dyslipidemia and cardiovascular disease.
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Affiliation(s)
- Jeffrey E Ming
- Sanofi, Bridgewater, NJ, USA; Frankfurt Am Main, Germany, and Montpellier, France
| | - Ruth E Abrams
- Sanofi, Bridgewater, NJ, USA; Frankfurt Am Main, Germany, and Montpellier, France
| | | | - Mengdi Tao
- Sanofi, Bridgewater, NJ, USA; Frankfurt Am Main, Germany, and Montpellier, France
| | - Tu Nguyen
- Sanofi, Bridgewater, NJ, USA; Frankfurt Am Main, Germany, and Montpellier, France
| | - Howard Surks
- Sanofi, Bridgewater, NJ, USA; Frankfurt Am Main, Germany, and Montpellier, France
| | | | | | | | - Nassim Djebli
- Sanofi, Bridgewater, NJ, USA; Frankfurt Am Main, Germany, and Montpellier, France
| | - Britta Goebel
- Sanofi, Bridgewater, NJ, USA; Frankfurt Am Main, Germany, and Montpellier, France
| | - Alex Koszycki
- Sanofi, Bridgewater, NJ, USA; Frankfurt Am Main, Germany, and Montpellier, France
| | - Meera Varshnaya
- Sanofi, Bridgewater, NJ, USA; Frankfurt Am Main, Germany, and Montpellier, France
| | | | | | | | | | - Jeffrey S Barrett
- Sanofi, Bridgewater, NJ, USA; Frankfurt Am Main, Germany, and Montpellier, France
| | - Karim Azer
- Sanofi, Bridgewater, NJ, USA; Frankfurt Am Main, Germany, and Montpellier, France
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9
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O'Toole S, Bartlett DW, Moazzez R. Efficacy of sodium and stannous fluoride mouthrinses when used before single and multiple erosive challenges. Aust Dent J 2016; 61:497-501. [DOI: 10.1111/adj.12418] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/22/2016] [Indexed: 12/26/2022]
Affiliation(s)
- S O'Toole
- Prosthodontic Department; King's College London; London UK
| | - DW Bartlett
- Prosthodontic Department; King's College London; London UK
| | - R Moazzez
- Mucosal and Salivary Biology Division/Restorative Dentistry Department; King's College London; London UK
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10
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Viola-Villegas NT, Sevak KK, Carlin SD, Doran MG, Evans HW, Bartlett DW, Wu AM, Lewis JS. Noninvasive Imaging of PSMA in prostate tumors with (89)Zr-Labeled huJ591 engineered antibody fragments: the faster alternatives. Mol Pharm 2014; 11:3965-73. [PMID: 24779727 PMCID: PMC4224519 DOI: 10.1021/mp500164r] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Engineered antibody fragments offer faster delivery with retained tumor specificity and rapid clearance from nontumor tissues. Here, we demonstrate that positron emission tomography (PET) based detection of prostate specific membrane antigen (PSMA) in prostatic tumor models using engineered bivalent antibodies built on single chain fragments (scFv) derived from the intact antibody, huJ591, offers similar tumor delineating properties but with the advantage of rapid targeting and imaging. (89)Zr-radiolabeled huJ591 scFv (dimeric scFv-CH3; (89)Zr-Mb) and cysteine diabodies (dimeric scFv; (89)Zr-Cys-Db) demonstrated internalization and similar Kds (∼2 nM) compared to (89)Zr-huJ591 in PSMA(+) cells. Tissue distribution assays established the specificities of both (89)Zr-Mb and (89)Zr-Cys-Db for PSMA(+) xenografts (6.2 ± 2.5% ID/g and 10.2 ± 3.4% ID/g at 12 h p.i. respectively), while minimal accumulation in PSMA(-) tumors was observed. From the PET images, (89)Zr-Mb and (89)Zr-Cys-Db exhibited faster blood clearance than the parent huJ591 while tumor-to-muscle ratios for all probes show comparable values across all time points. Ex vivo autoradiography and histology assessed the distribution of the probes within the tumor. Imaging PSMA-expressing prostate tumors with smaller antibody fragments offers rapid tumor accumulation and accelerated clearance; hence, shortened wait periods between tracer administration and high-contrast tumor imaging and lower dose-related toxicity are potentially realized.
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Affiliation(s)
- Nerissa Therese Viola-Villegas
- Department of Radiology and the Program in Molecular Pharmacology and Chemistry, Memorial Sloan Kettering Cancer Center , 1275 York Avenue, New York, New York 10065, United States
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11
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Moazzez RV, Austin RS, Rojas-Serrano M, Carpenter G, Cotroneo E, Proctor G, Zaidel L, Bartlett DW. Comparison of the possible protective effect of the salivary pellicle of individuals with and without erosion. Caries Res 2013; 48:57-62. [PMID: 24217151 DOI: 10.1159/000352042] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Accepted: 05/14/2013] [Indexed: 11/19/2022] Open
Abstract
The acquired pellicle adheres to tooth surfaces and has been suggested to provide differing degrees of protection against acidic erosion. This study investigated whether pellicle formed on enamel blocks in patients suffering dietary dental erosion modified the effect of an in vitro simulated dietary challenge, in comparison with pellicle formed on enamel blocks in healthy subjects and to no-pellicle enamel samples. Sixty subjects recruited from dental erosion clinics were compared to healthy age-matched controls. Subjects wore a custom-made maxillary splint holding human enamel blocks for 1 h during which the acquired enamel pellicle was formed. Enamel blocks were removed from the splints and a simulated dietary erosive challenge of 10 min was performed. In addition the challenge was performed on 30 enamel samples without pellicle. Profilometry showed no statistical difference between samples from the erosion subjects with a mean step height of 1.74 µm (SD 0.88) and median roughness (Sa) of 0.39 µm (interquartile range, IQR 0.3-0.56) and the controls with 1.34 µm (SD 0.66) and 0.33 µm (IQR 0.27-0.38), respectively. The control samples without pellicle had Sa of 0.44 µm (IQR 0.36-0.69) and these differences were statistically significant compared to those from the healthy subjects (p = 0.002). Mean (SD) microhardness reduction with a 100-gram load for the erosion group was 113.5 (10) KHN, for healthy subjects was 93 (15.4) KHN and for the enamel samples without pellicle 139.6 (21.8) KHN and all groups were statistically different. The microhardness and roughness data suggested the pellicle influenced erosion under these study conditions.
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Affiliation(s)
- R V Moazzez
- Salivary Research Unit, King's College London Dental Institute, London, UK
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12
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Sano K, Nakajima T, Ali T, Bartlett DW, Wu AM, Kim I, Paik CH, Choyke PL, Kobayashi H. Activatable fluorescent cys-diabody conjugated with indocyanine green derivative: consideration of fluorescent catabolite kinetics on molecular imaging. J Biomed Opt 2013; 18:101304. [PMID: 23752742 PMCID: PMC3677842 DOI: 10.1117/1.jbo.18.10.101304] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 04/28/2013] [Accepted: 05/10/2013] [Indexed: 06/02/2023]
Abstract
Antibody fragments including diabodies have more desirable pharmacokinetic characteristics than whole antibodies. An activatable optical imaging probe based on a cys-diabody targeting prostate-specific membrane antigen conjugated with the near-infrared fluorophore, indocyanine green (ICG), was designed such that it can only be activated when bound to the tumor, leading to high signal-to-background ratios. We employed short polyethylene glycol (PEG) linkers between the ICG and the reactive functional group (Sulfo-OSu group), resulting in covalent conjugation of ICG to the cys-diabody, which led to lower dissociation of ICG from cys-diabody early after injection, reducing hepatic uptake. However, unexpectedly, high and long-term fluorescence was observed in the kidneys, liver, and blood pool more than 1 h after injection of the cys-diabody PEG-ICG conjugate. A biodistribution study using I125-labeled cys-diabody-ICG showed immediate uptake in the kidneys followed by a rapid decrease, while gastric activity increased due to released radioiodine during rapid cys-diabody-ICG catabolism in the kidneys. To avoid this catabolic pathway, it would be preferable to use antibody fragments large enough not to be filtered through glomerulus or to conjugate the fragments with fluorescent dyes that are readily excreted into urine when cleaved from the cys-diabody to achieve high tumor-specific detection.
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Affiliation(s)
- Kohei Sano
- National Institutes of Health, National Cancer Institute, Center for Cancer Research, Molecular Imaging Program, Bethesda, Maryland 20892
| | - Takahito Nakajima
- National Institutes of Health, National Cancer Institute, Center for Cancer Research, Molecular Imaging Program, Bethesda, Maryland 20892
| | - Towhid Ali
- National Institutes of Health, National Cancer Institute, Center for Cancer Research, Molecular Imaging Program, Bethesda, Maryland 20892
| | | | - Anna M. Wu
- University of California-Los Angeles, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, Los Angeles, California
| | - Insook Kim
- SAIC-Frederick Inc., Applied/Developmental Research Directorate, Frederick National Laboratory, Frederick, Maryland 21702
| | - Chang H. Paik
- National Institutes of Health, Nuclear Medicine Department, Warren G. Magnuson Clinical Center, Bethesda, Maryland 20892
| | - Peter L. Choyke
- National Institutes of Health, National Cancer Institute, Center for Cancer Research, Molecular Imaging Program, Bethesda, Maryland 20892
| | - Hisataka Kobayashi
- National Institutes of Health, National Cancer Institute, Center for Cancer Research, Molecular Imaging Program, Bethesda, Maryland 20892
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13
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Abstract
BACKGROUND A laboratory investigation was designed to test the hypothesis that acids increase the rate of wear caused by attrition on dentine. METHODS Dentine sections from 10 teeth were polished, cleaned in an ultrasonic bath and divided into 8 equally sized areas. The occlusal tip of a tooth, placed vertically in a wear machine and loaded at 150 N, was moved against each dentine section for 5000 return strokes with artificial saliva acting as a lubricant. Each dentine section was divided into 8 sections and half randomly immersed in a 1% citric acid solution (pH 2.3) for 20 minutes. The wear regime produced 8 wear scars in total per dentine sample. The volume of each wear scar was measured using a contacting digitizing profilometer. RESULTS A total of 80 wear scars were produced with 40 treated with acid and 40 acting as controls. The mean for wear volume of the dentine scars with acid was 4.84 μm(3) (1.38) and for the non-acid surface 2.95 μm(3) (0.86). This difference was statistically significant (p < 0.05). CONCLUSIONS These results support the hypothesis that acids increase the rate of wear caused by attrition on dentine.
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Affiliation(s)
- H Li
- Hangzhou Dental Hospital, Second Clinical Medical Institute, Zhejiang Chinese Medical University, Hangzhou, China.
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14
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Austin RS, Rodriguez JM, Dunne S, Moazzez R, Bartlett DW. The effect of increasing sodium fluoride concentrations on erosion and attrition of enamel and dentine in vitro. J Dent 2010; 38:782-7. [PMID: 20600557 DOI: 10.1016/j.jdent.2010.06.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 06/22/2010] [Accepted: 06/22/2010] [Indexed: 10/19/2022] Open
Abstract
OBJECTIVES To investigate the effect of an aqueous sodium fluoride solution of increasing concentration on erosion and attrition of enamel and dentine in vitro. METHODS Enamel and dentine sections from caries-free human third molars were polished flat and taped (exposing a 3 mm x 3 mm area) before being randomly allocated to 1 of 5 groups per substrate (n=10/gp): G1 (distilled water control); G2 (225 ppm NaF); G3 (1450 ppm NaF); G4 (5000 ppm NaF); G5 (19,000 ppm NaF). All specimens were subjected to 5, 10 and 15 cycles of experimental wear [1 cycle=artificial saliva (2h, pH 7.0)+erosion (0.3% citric acid, pH 3.2, 5 min)+fluoride/control (5 min)+attrition (60 linear strokes in artificial saliva from enamel antagonists loaded to 300 g)]. Following tape removal, step height (SH) in mum was measured using optical profilometry. RESULTS When the number of cycles increased the amount of tooth surface loss increased significantly in enamel and dentine after attrition and erosion and for dentine after attrition. Attrition and erosion resulted in greater surface loss than attrition alone after 15 cycles of experimental wear of enamel. 5000 ppm and 19,000 ppm sodium fluoride solutions had a protective effect on erosive and attritional enamel tooth wear in vitro, however no other groups showed significant differences. CONCLUSIONS The more intensive the fluoride regime the more protection was afforded to enamel from attrition and erosion. However, in this study no such protective effect was demonstrated for dentine.
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Affiliation(s)
- R S Austin
- Department of Primary Dental Care, King's College London Dental Institute, Caldecot Road, Denmark Hill, London SE5 9RW, United Kingdom.
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15
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Kreulen CM, Van 't Spijker A, Rodriguez JM, Bronkhorst EM, Creugers NHJ, Bartlett DW. Systematic Review of the Prevalence of Tooth Wear in Children and Adolescents. Caries Res 2010; 44:151-9. [PMID: 20389070 DOI: 10.1159/000308567] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 01/27/2010] [Indexed: 11/19/2022] Open
Affiliation(s)
- C M Kreulen
- Department of Oral Function and Prosthetic Dentistry, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. c.kreulen @ dent.umcn.nl
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16
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Bartlett DW, Colcher D, Raubitschek AA. Rapid and efficient production of radiolabeled antibody conjugates using vacuum diafiltration guided by mathematical modeling. Bioconjug Chem 2008; 19:1927-37. [PMID: 18720981 DOI: 10.1021/bc800223x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Increasing interest in the use of radiolabeled antibodies for cancer imaging and therapy drives the need for more efficient production of the antibody conjugates. Here, we illustrate a method for rapid and efficient production of radiolabeled antibody conjugates using vacuum diafiltration guided by mathematical modeling. We apply this technique to the production of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated antibodies at the milligram and gram production scale and achieve radiolabeling efficiencies >95% using In-111. Using vacuum diafiltration, antibody-chelate conjugation and purification can be accomplished within the same vessel, and the entire process can be completed in <24 h. Vacuum diafiltration also offers safer and gentler processing conditions by eliminating the need to keep the retentate vessel under positive pressure through applied gas pressure or shear-inducing restriction points in the retentate flow path. Experimental data and mathematical model calculations suggest there exists a weak binding affinity (approximately 10(4)M(-1)) between the charged chelate molecules (e.g., DOTA) and the antibodies that slows the removal of excess chelate during purification. By analyzing the radiolabeling efficiency as a function of the number of diavolumes, we demonstrate the importance of balancing the removal of free chelate with the introduction of metal contaminants from the diafiltration buffer and also illustrate how to optimize radiolabeling of antibody conjugates under a variety of operating conditions. This methodology is applicable to the production of antibody conjugates in general.
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Affiliation(s)
- Derek W Bartlett
- Division of Cancer Immunotherapeutics & Tumor Immunology, Beckman Research Institute and City of Hope National Medical Center, Duarte, California 91010, USA
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Bartlett DW, Davis ME. Impact of tumor-specific targeting and dosing schedule on tumor growth inhibition after intravenous administration of siRNA-containing nanoparticles. Biotechnol Bioeng 2008; 99:975-85. [PMID: 17929316 DOI: 10.1002/bit.21668] [Citation(s) in RCA: 135] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This study addresses issues of relevance for siRNA nanoparticle delivery by investigating the functional impact of tumor-specific targeting and dosing schedule. The investigations are performed using an experimental system involving a syngeneic mouse cancer model and a theoretical system based on our previously described mathematical model of siRNA delivery and function. A/J mice bearing subcutaneous Neuro2A tumors approximately 100 mm(3) in size were treated by intravenous injection with siRNA-containing nanoparticles formed with cyclodextrin-containing polycations (CDP). Three consecutive daily doses of transferrin (Tf)-targeted nanoparticles carrying 2.5 mg/kg of two different siRNA sequences targeting ribonucleotide reductase subunit M2 (RRM2) slowed tumor growth, whereas non-targeted nanoparticles were significantly less effective when given at the same dose. Furthermore, administration of the three doses on consecutive days or every 3 days did not lead to statistically significant differences in tumor growth delay. Mathematical model calculations of siRNA-mediated target protein knockdown and tumor growth inhibition are used to elucidate possible mechanisms to explain the observed effects and to provide guidelines for designing more effective siRNA-based treatment regimens regardless of delivery methodology and tumor type.
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Affiliation(s)
- Derek W Bartlett
- Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 210-41, Pasadena, California 91125, USA
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18
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Bartlett DW, Su H, Hildebrandt IJ, Weber WA, Davis ME. Impact of tumor-specific targeting on the biodistribution and efficacy of siRNA nanoparticles measured by multimodality in vivo imaging. Proc Natl Acad Sci U S A 2007; 104:15549-54. [PMID: 17875985 PMCID: PMC1978218 DOI: 10.1073/pnas.0707461104] [Citation(s) in RCA: 595] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Targeted delivery represents a promising approach for the development of safer and more effective therapeutics for oncology applications. Although macromolecules accumulate nonspecifically in tumors through the enhanced permeability and retention (EPR) effect, previous studies using nanoparticles to deliver chemotherapeutics or siRNA demonstrated that attachment of cell-specific targeting ligands to the surface of nanoparticles leads to enhanced potency relative to nontargeted formulations. Here, we use positron emission tomography (PET) and bioluminescent imaging to quantify the in vivo biodistribution and function of nanoparticles formed with cyclodextrin-containing polycations and siRNA. Conjugation of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid to the 5' end of the siRNA molecules allows labeling with (64)Cu for PET imaging. Bioluminescent imaging of mice bearing luciferase-expressing Neuro2A s.c. tumors before and after PET imaging enables correlation of functional efficacy with biodistribution data. Although both nontargeted and transferrin-targeted siRNA nanoparticles exhibit similar biodistribution and tumor localization by PET, transferrin-targeted siRNA nanoparticles reduce tumor luciferase activity by approximately 50% relative to nontargeted siRNA nanoparticles 1 d after injection. Compartmental modeling is used to show that the primary advantage of targeted nanoparticles is associated with processes involved in cellular uptake in tumor cells rather than overall tumor localization. Optimization of internalization may therefore be key for the development of effective nanoparticle-based targeted therapeutics.
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Affiliation(s)
- Derek W. Bartlett
- *Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, MC 210-41, Pasadena, CA 91125
| | - Helen Su
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, 650 Charles Young Drive, CHS AR-274, Los Angeles, CA 90095; and
| | - Isabel J. Hildebrandt
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, 650 Charles Young Drive, CHS AR-274, Los Angeles, CA 90095; and
| | - Wolfgang A. Weber
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, 650 Charles Young Drive, CHS AR-274, Los Angeles, CA 90095; and
- Division of Nuclear Medicine, University of Freiburg, Hugstetterstrasse 55, 79106 Freiburg, Germany
| | - Mark E. Davis
- *Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, MC 210-41, Pasadena, CA 91125
- To whom correspondence should be addressed. E-mail:
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19
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Sundaram G, Wilson R, Watson TF, Bartlett DW. Effect of resin coating on dentine compared to repeated topical applications of fluoride mouthwash after an abrasion and erosion wear regime. J Dent 2007; 35:814-8. [PMID: 17854969 DOI: 10.1016/j.jdent.2007.07.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Revised: 07/23/2007] [Accepted: 07/29/2007] [Indexed: 10/22/2022] Open
Abstract
OBJECTIVES The role of fluoride in preventing erosion and abrasion on dentine remains unclear. The aim of this study was to investigate the effect of repeated applications of a 0.05% fluoride mouthwash and an adhesive on wear of dentine using stainless steel discs reference points and a laser profilometer. METHODS Small stainless steel discs were bonded to 60 caries free extracted molars which had previously been sectioned horizontally. The teeth were equally divided and subjected to four modalities in an erosion and abrasion laboratory model. Step heights were measured from the metal discs using a non-contacting laser profilometer at 100, 500, 1000, 2500 and 5000 cycles. RESULTS The results after 5000 cycles showed that dentine coated with a dentine adhesive (0.015 microm, S.D. 0.090) had statistically less wear than fluoride (0.127 microm, S.D. 0.150), abrasion and erosion (0.182 microm, S.D. 0.150) or abrasion only (0.096 microm, S.D. 0.090) (p<0.001). CONCLUSION In conclusion dentine surfaces coated with a resin-based adhesive provided more protection against erosion and abrasion than a fluoride mouthrinse. There were no statistical differences between the modalities for cycles less than 5000.
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Affiliation(s)
- G Sundaram
- Restorative group, King's College London Dental Institute, Guy's Tower, London Bridge SE19RT, United Kingdom
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20
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Dadoun MP, Bartlett DW. The microhardness of bleached dentine and its bond strength to a dentine bonding agent. Eur J Prosthodont Restor Dent 2007; 15:131-134. [PMID: 17970321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The aim of this study was to measure the hardness of a bleached dentine surface and its bond strength to a dentine-bonding agent. Thirty teeth were randomly divided into a test and control group. The teeth were hemi-sectioned, the cut surfaces ground flat and the test surfaces bleached with a 10% aqueous solution of carbamide peroxide continuously for 4 days. Hardness was determined using a Vickers microhardness test. The bond between Coltene 'One Coat Bond' and bleached and unbleached dentine was evaluated by measuring shear bond strength using an Instron machine. The mean hardness of dentine before and after bleaching was 62.5 (10.2) and 53.6 (7.3) and this difference was statistically different (p<0.001). For the controls immersed in water the hardness was before 60.8 (standard deviation: 7.2) and after 59.6 (8.2) respectively. The mean shear bond strength for the unbleached was 5.5MPa (1.6) and for the bleached samples was 3.3MPa (1.8) and this difference was statistically significant (p<0.002). Under these study conditions the Vickers hardness and bond strength to dentine was reduced by bleaching.
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Affiliation(s)
- M P Dadoun
- Prosthodntics, Guy's, King's and St. Thomas' Dental Institute, King College, Guy's Tower, London
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21
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Abstract
Small interfering RNA (siRNA) molecules achieve sequence-specific gene silencing through the RNA interference (RNAi) mechanism. Here, live-cell and live-animal bioluminescent imaging (BLI) is used to directly compare luciferase knockdown by unmodified and nuclease-stabilized siRNAs in rapidly (HeLa) and slowly (CCD-1074Sk) dividing cells to reveal the impact of cell division and siRNA nuclease stability on the kinetics of siRNA-mediated gene silencing. Luciferase knockdown using unmodified siRNAs lasts approximately 1 week in HeLa cells and up to 1 month in CCD-1074Sk cells. There is a slight increase in the duration of luciferase knockdown by nuclease-stabilized siRNAs relative to unmodified siRNAs after cationic lipid transfection, but this difference is not observed after electroporation. In BALB/cJ mice, a fourfold increase in maximum luciferase knockdown is observed after hydrodynamic injection (HDI) of nuclease-stabilized siRNAs relative to unmodified siRNAs, yet the overall kinetics of the recovery after knockdown are nearly identical. By using a mathematical model of siRNA-mediated gene silencing, the trends observed in the experimental data can be duplicated by changing model parameters that affect the stability of the siRNAs before they reach the cytosolic compartment. Based on these findings, we hypothesize that the stabilization advantages of nuclease-stabilized siRNAs originate primarily from effects prior to and during internalization before the siRNAs can interact with the intracellular RNAi machinery.
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Affiliation(s)
- Derek W Bartlett
- Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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22
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Heidel JD, Liu JYC, Yen Y, Zhou B, Heale BSE, Rossi JJ, Bartlett DW, Davis ME. Potent siRNA inhibitors of ribonucleotide reductase subunit RRM2 reduce cell proliferation in vitro and in vivo. Clin Cancer Res 2007; 13:2207-15. [PMID: 17404105 DOI: 10.1158/1078-0432.ccr-06-2218] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
PURPOSE Ribonucleotide reductase (RR) is a therapeutic target for DNA replication-dependent diseases such as cancer. Here, a potent small interfering RNA (siRNA) duplex against the M2 subunit of RR (RRM2) is developed and shown to reduce the growth potential of cancer cells both in vitro and in vivo. EXPERIMENTAL DESIGN Three anti-RRM2 siRNAs were identified via computational methods, and the potency of these and additional "tiling" duplexes was analyzed in cultured cells via cotransfections using a RRM2-luciferase fusion construct. Knockdown of RRM2 by the best duplex candidates was confirmed directly by Western blotting. The effect of potent duplexes on cell growth was investigated by a real-time cell electronic sensing assay. Finally, duplex performance was tested in vivo in luciferase-expressing cells via whole animal bioluminescence imaging. RESULTS Moderate anti-RRM2 effects are observed from the three duplexes identified by computational methods. However, the tiling experiments yielded an extremely potent duplex (siR2B+5). This duplex achieves significant knockdown of RRM2 protein in cultured cells and has pronounced antiproliferative activity. S.c. tumors of cells that had been transfected with siR2B+5 preinjection grew slower than those of control cells. CONCLUSIONS An anti-RRM2 siRNA duplex is identified that exhibits significant antiproliferative activity in cancer cells of varying human type and species (mouse, rat, monkey); these findings suggest that this duplex is a promising candidate for therapeutic development.
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Affiliation(s)
- Jeremy D Heidel
- Calando Pharmaceuticals, Inc., California Institute of Technology, Pasadena, California 91107, USA.
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23
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Li H, Watson TF, Sherriff M, Curtis R, Bartlett DW. The Influence of Fluoride Varnish on the Attrition of Dentine. Caries Res 2007; 41:219-22. [PMID: 17426403 DOI: 10.1159/000099322] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2006] [Accepted: 11/24/2006] [Indexed: 11/19/2022] Open
Abstract
Previous investigations have shown the potential for fluoride to be protective in an abrasion/erosion laboratory model. The aim of this study was to investigate the effect of high concentrations of fluoride delivered in a varnish on attrition of dentine. Fifteen caries-free, intact lower third molar teeth were sectioned and the enamel removed by a water-cooled diamond disc. Polished dentine surfaces were divided into 8 areas, 4 of which were randomly covered with a high-concentration fluoride varnish for 24 h. The samples were subjected to 5,000 cycles of attrition bathed under artificial saliva. Microhardness testing adjacent to the wear scars showed no statistical difference between the fluoride-treated (71.42 KHN, SD 10.52) and control surfaces (72.66 KHN, SD 9.69). The volume of the wear scar was statistically greater for the fluoride-treated surface at 9.6 microm(3) (SD 4.92) and 8.13 microm(3) (SD 5.54) for the control areas (p = 0.029). The low pH of the fluoride varnish appears to have increased the amount of wear from attrition in this laboratory study.
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Affiliation(s)
- H Li
- Department of TMJ (Orthodontics), West China College of Stomatology, Sichuan University, Chengdu, China
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24
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Abstract
Nucleic acid-based therapeutics have the potential to provide potent and highly specific treatments for a variety of human ailments. However, systemic delivery continues to be a significant hurdle to success. Multifunctional nanoparticles are being investigated as systemic, nonviral delivery systems, and here, we describe the physicochemical and biological characterization of cyclodextrin-containing polycations (CDP) and their nanoparticles formed with nucleic acids including plasmid DNA (pDNA) and small interfering RNA (siRNA). These polycation/nucleic acid complexes can be tuned by formulation conditions to yield particles with sizes ranging from 60 to 150 nm, zeta potentials from 10 to 30 mV, and molecular weights from approximately 7 x 107 to 1 x 109 g mol-1 as determined by light scattering techniques. Inclusion complexes formed between adamantane (AD)-containing molecules and the beta-cyclodextrin molecules enable the modular attachment of poly(ethylene glycol) (AD-PEG) conjugates for steric stabilization and targeting ligands (AD-PEG-transferrin) for cell-specific targeting. A 70 nm particle can contain approximately 10 000 CDP polymer chains, approximately 2000 siRNA molecules, approximately 4000 AD-PEG5000 molecules, and approximately 100 AD-PEG5000-Tf molecules; this represents a significant payload of siRNA and a large ratio of siRNA to targeting ligand (20:1). The particles protect the nucleic acid payload from nuclease degradation, do not aggregate at physiological salt concentrations, and cause minimal erythrocyte aggregation and complement fixation at the concentrations typically used for in vivo application. Uptake of the nucleic acid-containing particles by HeLa cells is measured by flow cytometry and visualized by confocal microscopy. Competitive uptake experiments show that the transferrin-targeted particles display enhanced affinity for the transferrin receptor through avidity effects (multiligand binding). Functional efficacy of the delivered pDNA and siRNA is demonstrated through luciferase reporter protein expression and knockdown, respectively. The analysis of the CDP delivery vehicle provides insights that can be applied to the design of targeted nucleic acid delivery vehicles in general.
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Affiliation(s)
- Derek W Bartlett
- Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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25
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Abstract
The terms 'abfraction' and 'abrasion' describe the cause of lesions found along the cervical margins of teeth. Erosion, abrasion, and attrition have all been associated with their formation. Early research suggested that the cause of the V-shaped lesion was excessive horizontal toothbrushing. Abfraction is another possible etiology and involves occlusal stress, producing cervical cracks that predispose the surface to erosion and abrasion. This article critically reviews the literature on abrasion, erosion, and abrasion, and abfraction. The references were obtained by a MEDLINE search in March, 2005, and from this, hand searches were undertaken. From the literature, there is little evidence, apart from laboratory studies, to indicate that abfraction exists other than as a hypothetical component of cervical wear.
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Affiliation(s)
- D W Bartlett
- Department of Prosthodontics, Guy's Tower, St. Thomas' Street, London Bridge, London SE1 9RT, UK.
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26
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Abstract
Mathematical models can predict solute clearances and solute concentrations during renal replacement therapy. At present, however, most nephrologists cannot use these models because they require mathematical software. In this report, we describe models of solute transport by convection and diffusion adapted to run on the commonly available software program Excel for Macintosh computers and PCs running Windows. Two programs have been created that can be downloaded from http://www.stanford.edu/~twmeyer/ or http://dev.satellitehealth.com/research/journal.asp. The first, called 'Dr Addis Clearance Calculator', calculates clearance values from inputs including the blood flow Q(b), the hematocrit, the ultrafiltration rate Q(f), the dialysate flow rate Q(d), the reflection coefficient sigma and the mass transfer area coefficient K(o)A for the solute of interest, and the free fraction f if the solute is protein bound. Solute concentration profiles along the length of the artificial kidney are displayed graphically. The second program, called 'Dr Coplon Dialysis Simulator', calculates plasma solute concentrations from the clearance values obtained by the first program and from additional input values including the number of treatments per week, the duration of the treatments, and the solute's production rate and volumes of distribution. The program calculates the time-averaged solute concentration and provides a graphic display of the solute concentration profile through a week-long interval.
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Affiliation(s)
- J L Walther
- Department of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, California 94304, USA
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27
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Schluep T, Hwang J, Cheng J, Heidel JD, Bartlett DW, Hollister B, Davis ME. Preclinical efficacy of the camptothecin-polymer conjugate IT-101 in multiple cancer models. Clin Cancer Res 2006; 12:1606-14. [PMID: 16533788 DOI: 10.1158/1078-0432.ccr-05-1566] [Citation(s) in RCA: 180] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Preclinical efficacy of i.v. IT-101, a nanoparticulate conjugate of 20(S)-camptothecin and a cyclodextrin-based polymer, was investigated in several mouse xenografts. The effects of different multiple dosing schedules on tumor growth of LS174T colon carcinoma xenografts are elucidated. All multiple dosing schedules administered over 15 to 19 days resulted in enhanced efficacy compared with untreated or single-dose groups. Further improvements in antitumor efficacy were not observed when the dosing frequency was increased from three weekly doses to five doses at 4-day intervals or 5 days of daily dosing followed by 2 days without dosing repeated in three cycles using similar cumulative doses. This observation was attributed to the extended release characteristics of camptothecin from the polymer. Antitumor efficacy was further evaluated in mice bearing six different s.c. xenografts (LS174T and HT29 colorectal cancer, H1299 non-small-cell lung cancer, H69 small-cell lung cancer, Panc-1 pancreatic cancer, and MDA-MB-231 breast cancer) and one disseminated xenograft (TC71-luc Ewing's sarcoma). In all cases, a single treatment cycle of three weekly doses of IT-101 resulted in a significant antitumor effect. Complete tumor regression was observed in all animals bearing H1299 tumors and in the majority of animals with disseminated Ewing's sarcoma tumors. Importantly, IT-101 is effective in a number of tumors that are resistant to treatment with irinotecan (MDA-MB-231, Panc-1, and HT29), consistent with the hypothesis that polymeric drug conjugates may be able to overcome certain kinds of multidrug resistance. Taken together, these results indicate that IT-101 has good tolerability and antitumor activity against a wide range of tumors.
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28
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Abstract
Small interfering RNA (siRNA) molecules are potent effectors of post-transcriptional gene silencing. Using noninvasive bioluminescent imaging and a mathematical model of siRNA delivery and function, the effects of target-specific and treatment-specific parameters on siRNA-mediated gene silencing are monitored in cells stably expressing the firefly luciferase protein. In vitro, luciferase protein levels recover to pre-treatment values within <1 week in rapidly dividing cell lines, but take longer than 3 weeks to return to steady-state levels in nondividing fibroblasts. Similar results are observed in vivo, with knockdown lasting ∼10 days in subcutaneous tumors in A/J mice and 3–4 weeks in the nondividing hepatocytes of BALB/c mice. These data indicate that dilution due to cell division, and not intracellular siRNA half-life, governs the duration of gene silencing under these conditions. To demonstrate the practical use of the model in treatment design, model calculations are used to predict the dosing schedule required to maintain persistent silencing of target proteins with different half-lives in rapidly dividing or nondividing cells. The approach of bioluminescent imaging combined with mathematical modeling provides useful insights into siRNA function and may help expedite the translation of siRNA into clinically relevant therapeutics for disease treatment and management.
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Affiliation(s)
| | - Mark E. Davis
- To whom correspondence should be addressed. Tel: +1 626 395 4251; Fax: +1 626 568 8743;
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29
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Bartlett DW, Davis ME. 705. A Practical Approach to siRNA-Based Treatment Design Using Bioluminescent Imaging and Mathematical Modeling. Mol Ther 2006. [DOI: 10.1016/j.ymthe.2006.08.784] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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30
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Abstract
OBJECTIVE To assess the outcome of compliance of advice sent to patients and dentists about monitoring tooth wear in general practice. METHOD Postal questionnaires were sent to 70 patients and their dentists requesting information on the outcome of letters of advice sent to general dental practitioners regarding monitoring tooth wear with study casts. They also requested information about the reasons for the patients' referral, the outcome of treatment and whether study models had been taken. RESULTS Replies were received from 60 dentists (87%) and 53 patients (75%). Of these, 16 patients and 16 dentists had moved from their recorded address. Study casts were reported as having been taken by 23 dentists (38%) and reported by 18 patients (34%). The most common reason for referral was advice about monitoring the wear and the appearance of their teeth. CONCLUSIONS The compliance of the patients and dentists in monitoring tooth wear by using study casts in general practice was not successful. It raises issues regarding the value of consultant advice letters to this common clinical problem.
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31
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Hu-Lieskovan S, Heidel JD, Bartlett DW, Davis ME, Triche TJ. Sequence-specific knockdown of EWS-FLI1 by targeted, nonviral delivery of small interfering RNA inhibits tumor growth in a murine model of metastatic Ewing's sarcoma. Cancer Res 2005; 65:8984-92. [PMID: 16204072 DOI: 10.1158/0008-5472.can-05-0565] [Citation(s) in RCA: 391] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The development of effective, systemic therapies for metastatic cancer is highly desired. We show here that the systemic delivery of sequence-specific small interfering RNA (siRNA) against the EWS-FLI1 gene product by a targeted, nonviral delivery system dramatically inhibits tumor growth in a murine model of metastatic Ewing's sarcoma. The nonviral delivery system uses a cyclodextrin-containing polycation to bind and protect siRNA and transferrin as a targeting ligand for delivery to transferrin receptor-expressing tumor cells. Removal of the targeting ligand or the use of a control siRNA sequence eliminates the antitumor effects. Additionally, no abnormalities in interleukin-12 and IFN-alpha, liver and kidney function tests, complete blood counts, or pathology of major organs are observed from long-term, low-pressure, low-volume tail-vein administrations. These data provide strong evidence for the safety and efficacy of this targeted, nonviral siRNA delivery system.
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MESH Headings
- Animals
- Cell Growth Processes/genetics
- Cell Line, Tumor
- Disease Models, Animal
- Down-Regulation
- Female
- Gene Silencing
- Luciferases/biosynthesis
- Luciferases/genetics
- Mice
- Mice, Inbred C57BL
- Mice, Inbred NOD
- Mice, SCID
- Neoplasm Metastasis
- Oncogene Proteins, Fusion/antagonists & inhibitors
- Oncogene Proteins, Fusion/biosynthesis
- Oncogene Proteins, Fusion/genetics
- Proto-Oncogene Protein c-fli-1/antagonists & inhibitors
- Proto-Oncogene Protein c-fli-1/biosynthesis
- Proto-Oncogene Protein c-fli-1/genetics
- RNA, Small Interfering/administration & dosage
- RNA, Small Interfering/genetics
- RNA, Small Interfering/toxicity
- RNA-Binding Protein EWS
- Receptors, Transferrin/metabolism
- Sarcoma, Ewing/genetics
- Sarcoma, Ewing/metabolism
- Sarcoma, Ewing/pathology
- Sarcoma, Ewing/therapy
- Transduction, Genetic
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Affiliation(s)
- Siwen Hu-Lieskovan
- Department of Pathology, Children's Hospital Los Angeles, Los Angeles, California 90027, USA
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32
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Moazzez R, Anggiansah A, Bartlett DW. The association of acidic reflux above the upper oesophageal sphincter with palatal tooth wear. Caries Res 2005; 39:475-8. [PMID: 16251791 DOI: 10.1159/000088182] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2004] [Accepted: 02/16/2005] [Indexed: 11/19/2022] Open
Abstract
This case-controlled clinical study, conducted at a secondary care unit, compared pH measurement at 2 cm above the upper oesophageal sphincter (UOS) in 31 patients complaining of extra-oesophageal symptoms of reflux to 7 control subjects. Twenty-four-hour ambulatory pH measurements were recorded and analysed at 5 cm above the lower oesophageal sphincter (LOS) and 2 cm above the UOS. In reflux patients the proportion of supine time when pH at 5 cm above the LOS was <4 was significantly greater than in controls. The proportion of time when pH at 2 cm above the UOS was <5.5 was also significantly greater in patients than in controls. Palatal tooth wear observed in the patient group correlated with acid reflux at night. In this group of patients presenting with symptoms of reflux, gastric acid passed through the upper oesophageal sphincter and increased the potential for erosion.
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Affiliation(s)
- R Moazzez
- Department of Prosthodontics, GKT Dental Institute, London, UK.
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33
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Meyer TW, Leeper EC, Bartlett DW, Depner TA, Lit YZ, Robertson CR, Hostetter TH. Increasing Dialysate Flow and Dialyzer Mass Transfer Area Coefficient to Increase the Clearance of Protein-bound Solutes. J Am Soc Nephrol 2004; 15:1927-35. [PMID: 15213283 DOI: 10.1097/01.asn.0000131521.62256.f0] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Clinical hemodialysis systems achieve high single pass extraction of small solutes that are not bound to plasma proteins. But they clear protein-bound solutes much less effectively. This study examines the extent to which clearance of a protein-bound test solute is improved by increasing the dialyzer mass transfer area coefficient (KoA) and the dialysate flow rate (Qd). A reservoir containing test solutes and artificial plasma with albumin concentration approximately 4 g/dl was dialyzed with a standard clinical dialysate delivery system. The clearance of phenol red (ClPR) was compared with the clearances of urea and creatinine at a plasma flow rate (Qp) of 200 ml/min with varying values of KoA and Qd. ClPR increased from 11 +/- 2 ml/min to 23 +/- 2 ml/min when KoA for phenol red, KoAPR, was increased from 238 to 640 ml/min and Qd was increased from 286 +/- 6 ml/min to 734 +/- 9 ml/min. Increasing either KoAPR or Qd alone had lesser effects. Clearance values for phenol red were much lower than clearance values for the unbound solutes urea and creatinine, which ranged from 150 to 200 ml/min and were less affected by varying KoA and Qd. A mathematical model was developed to predict ClPR from values of Qp, Qd, the fraction of phenol red bound to albumin (94% +/- 1%) and KoAPR. The model accurately predicts the pattern of measured results and shows further that ClPR can be made to approach Qp only by very large increases in both KoAPR and Qd.
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Affiliation(s)
- Timothy W Meyer
- The Departments of Medicine, VA Palo Alto HCS and Stanford University, Palo Alto, California 94303, USA.
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34
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Azzopardi A, Bartlett DW, Watson TF, Sherriff M. The surface effects of erosion and abrasion on dentine with and without a protective layer. Br Dent J 2004; 196:351-4; discussion 339. [PMID: 15044992 DOI: 10.1038/sj.bdj.4811083] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2001] [Accepted: 04/03/2003] [Indexed: 11/08/2022]
Abstract
OBJECTIVE The aim of this in situ study was to investigate with four imaging modalities whether covering dentine with adhesive resins could protect against erosion from acids. The objectives were to observe and quantify the effects of acids and the soft tissues, especially the tongue, on dentine and the bonding agents using four assessment techniques: qualitative assessment with SEM, surface roughness and thickness of resin with the TSM and volume loss with the laser profilometer. DESIGN An in situ investigation using extracted dentine sections embedded in splints held on the palate of 10 volunteers. The dentine sections were protected by two resins and subjected to a tooth wear regime. RESULTS Both Seal and Protect and Opitbond Solo protected the tooth surfaces from a tooth wear regime. There were no statistical differences between the control surfaces and those protected with dentine bonding agents for resin thickness, roughness and profilometry. The appearance of the slabs under both confocal and SEM showed that the material remained in place despite a vigorous wear regime and therefore protected the tooth surface. CONCLUSIONS For patients with uncontrolled erosion or tooth wear, applying a dentine bonding agent to exposed dentine is a practical option to prevent further damage.
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Affiliation(s)
- A Azzopardi
- Research Assistant, Division of Conservative Dentistry, Guy's, King's and St Thomas' Dental Institute, King's College, London
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Abstract
OBJECTIVE Tooth wear is recognised as a common feature of European dentitions. However, little is known about its progression in susceptible patients. The aim of this study was to assess the degree and progression of tooth wear in patients by examining study casts taken of their teeth on two separate occasions. DESIGN Over 500 sets of study casts taken during an 18-year period from patients referred for a variety of restorative procedures, were examined at Guy's Dental Hospital. Of these, 34 cases were found to have consecutive models taken at two time intervals and these were used to assess the progression of tooth wear. Study models from 19 females and 16 males, with an average age of 26 years (range 18-60) at the time of their first presentation and were all examined by a single operator. The Smith and Knight tooth wear index was used to assess the degree of tooth wear at presentation and then at another time which was a median of 26 months (interquartile range 14 - 50 months) later. RESULTS The most common initial TWI score per surface was 1, with 54% of surfaces affected at the first assessment and 57% at the second. Score 2 was less common (14% at both assessments) and the scores for 3 and 4 combined were relatively uncommon with 5% of surfaces effected. Minimal progression of tooth wear was observed on study casts with only 7.3% of surfaces involved. CONCLUSION In this sample, tooth wear was a slow, minimally progressive process.
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Affiliation(s)
- D W Bartlett
- Division of Conservative Dentistry, Guy's, King's and St Thomas' Dental Institute, King's College, London.
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Abstract
The aim of this study was to compare the erosive effect of gastric juice and a carbonated drink on enamel and dentine by measuring release of calcium from 30 hemisectioned teeth in vitro. In addition, the titrable acidity (mL of 0.05 M sodium hydroxide required to neutralize) and pH of the fluids was estimated. The mean pH of the seven gastric acid samples was 2.92 (range 1.2-6.78) and mean titratable acidity 0.68 mL (range 0.03-1.64). Both the pH and the titratable acidity of the gastric juice varied between patients all of whom suffered from symptoms of reflux disease. The carbonated drink had a pH of 2.45 and a titratable acidity of 0.29 mL. The median amount of calcium released by the gastric acids from enamel was 69.6 microg L-1 (interquartile range 5.4-144) and 62.4 microg L-1 (2.2-125.3) from dentine. The carbonated drink released 18.7 microg L-1 (13.4-23.4) and 18.6 microg L-1 (11.9-35.3), respectively. The differences in calcium release by gastric juice and the carbonated drink were statistically significant for both enamel (P < 0.005) and dentine (P < 0.01). It is concluded that gastric juice has a greater potential, per unit time, for erosion than a carbonated drink.
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Affiliation(s)
- D W Bartlett
- Division of Conservative Dentistry, Guy's King's and St Thomas' Dental Institute, London, UK.
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Bartlett DW. Bleaching discoloured teeth. SADJ 2001; 56:468-73. [PMID: 11768355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
The bleaching of teeth has encountered some legislative problems over the past few years but it is now possible to use both vital and non-vital bleaching techniques in the UK. Hydrogen peroxide has a long history of use and would appear to be safe to use to change the appearance of discoloured teeth. It is conservative of tooth tissue and may delay the need for more invasive veneers and crowns. This article describes some of the methods of bleaching using hydrogen peroxide that are currently available.
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Affiliation(s)
- D W Bartlett
- Kings's College, School of Dentistry, Floor 25, Guy's Tower, London Bridge, London SEI 9RT
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Bartlett DW, Coward PY, Wilson R, Goodsman D, Darby J. Experiences and perceptions of vocational training reported by the 1999 cohort of vocational dental practitioners and their trainers in England and Wales. Br Dent J 2001; 191:265-70. [PMID: 11575763 DOI: 10.1038/sj.bdj.4801159a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE To assess the self-reported confidence of vocational dental practitioners (VDPs) in clinical procedures together with vocational trainers' perceptions of the VDPs confidence in the same procedures, immediately after qualification and towards the end of the vocational training year. DESIGN A questionnaire-based cohort study. SETTING A general practice study carried out in 1999. SUBJECTS Vocational Dental Practitioners and vocational trainers in England and Wales. METHOD VDPs and trainers were asked on a single occasion to grade the clinical confidence of the VDP at the beginning and near the end of vocational training as high, satisfactory or low. RESULTS Questionnaires were sent to 531 VDPs and 555 trainers; 82 per cent of VDPs and trainers responded. Approximately half the VDPs were male and 57 per cent were white, whilst 89 per cent of trainers were male and 81 per cent white. A large proportion of both VDPs and trainers reported low confidence in orthodontics, molar endodontics and surgical extractions at the start of the training year. Towards the end of training, both groups reported improved confidence levels in most clinical procedures. However, a higher proportion of trainers reported low confidence than their VDPs in most clinical procedures at both time points (p<0.001). VDPs appeared to gain most from experience and training in administration/management and interpersonal skills. CONCLUSION Vocational training appears to satisfy its aim to enhance clinical and administrative confidence.
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Affiliation(s)
- D W Bartlett
- Division of Conservative Dentistry, School of Dentistry, King's College, London
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Abstract
OBJECTIVES To develop a reproducible method to measure tooth wear and assess the protection given by dentine bonding agents in an erosive/abrasive wear regime. METHODS Seal and Protect (Dentsply, UK) and Optibond Solo (Kerr, UK) were each applied to 20 extracted teeth and subjected to 3000 cycles in a reciprocating erosion/abrasion wear machine. A further 20 teeth, without protection, were subjected to the same wear regime and were either brushed in water or immersed in acid. Impressions were taken by a standardised technique and were scanned with a non-contacting laser profilometer. The amount of erosion was measured at the same co-ordinates before and after erosion using 2mm diameter metal discs as reference points. RESULTS The amount of wear on Seal and Protect had a mean 24.8 microm (SD 57.4 microm) and for Solo it was 1.4 microm (24.5 microm), and this difference was statistically significant (p=0.02). There was no statistically significant difference in the wear measured on the teeth brushed in water or immersed in acid. The wear measured on the unprotected teeth was 243 microm (SD 120 microm) and was statistically significantly different to the protected surfaces (p=0.001). CONCLUSION Both Seal and Protect and Solo protected the teeth in this wear regime and the technique could be used clinically for patients with uncontrolled dental erosion.
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Affiliation(s)
- A Azzopardi
- Division of Conservative Dentistry, Guy's, King's and St Thomas' Dental Institute, Floor 25, Guy's Tower, King's College, London Bridge, SE1 9RT, London, UK
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Bartlett DW, Anggiansah A, Smith BG, Kidd EA. The role of regurgitation and other symptoms of reflux disease in palatal dental erosion; an audit project. Ann R Coll Surg Engl 2001; 83:226-8. [PMID: 11518367 PMCID: PMC2503387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023] Open
Affiliation(s)
- D W Bartlett
- Division of Conservative Dentistry, Guy's, King's and St Thomas' Dental Institute, London, UK.
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Abstract
Mesotrione is a new herbicide being developed for the selective pre- and post-emergence control of a wide range of broad-leaved and grass weeds in maize (Zea mays). It is a member of the benzoylcyclohexane-1,3-dione family of herbicides, which are chemically derived from a natural phytotoxin obtained from the Californian bottlebrush plant, Callistemon citrinus. The compound acts by competitive inhibition of the enzyme 4-hydroxyphenylpyruvate dioxygenase (HPPD), a component of the biochemical pathway that converts tyrosine to plastoquinone and alpha-tocopherol. Mesotrione is an extremely potent inhibitor of HPPD from Arabidopsis thaliana, with a Ki value of c 6-18 pM. It is rapidly taken up by weed species following foliar application, and is distributed within the plants by both acropetal and basipetal movement. Maize is tolerant to mesotrione as a consequence of selective metabolism by the crop plant. Slower uptake of mesotrione, relative to susceptible weed species, may also contribute to its utility as a selective herbicide for use in maize.
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Affiliation(s)
- G Mitchell
- Zeneca Agrochemicals, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6ET, UK.
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Abstract
Mesotrione is a new herbicide being developed for the selective pre- and post-emergence control of a wide range of broad-leaved and grass weeds in maize (Zea mays). It is a member of the benzoylcyclohexane-1,3-dione family of herbicides, which are chemically derived from a natural phytotoxin obtained from the Californian bottlebrush plant, Callistemon citrinus. The compound acts by competitive inhibition of the enzyme 4-hydroxyphenylpyruvate dioxygenase (HPPD), a component of the biochemical pathway that converts tyrosine to plastoquinone and alpha-tocopherol. Mesotrione is an extremely potent inhibitor of HPPD from Arabidopsis thaliana, with a Ki value of c 6-18 pM. It is rapidly taken up by weed species following foliar application, and is distributed within the plants by both acropetal and basipetal movement. Maize is tolerant to mesotrione as a consequence of selective metabolism by the crop plant. Slower uptake of mesotrione, relative to susceptible weed species, may also contribute to its utility as a selective herbicide for use in maize.
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Affiliation(s)
- G Mitchell
- Zeneca Agrochemicals, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6ET, UK.
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Azzopardi A, Bartlett DW, Watson TF, Smith BG. A literature review of the techniques to measure tooth wear and erosion. Eur J Prosthodont Restor Dent 2000; 8:93-7. [PMID: 11307566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
This paper reviews methods to measure tooth wear especially those more recently introduced as a result of improvements in technology. The review searched methods to measure tooth wear and dental erosion from large epidemiological investigations, in vitro and in vivo studies. There seems to be wide variation in techniques used to measure tooth wear and erosion. In vitro techniques may have little direct clinical relevance but can lead to new and more accurate clinical methods. In vivo studies have problems with reference points and accurate validation of the techniques. There is a need for a simple, reliable technique to quantify tooth wear due to erosion.
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Affiliation(s)
- A Azzopardi
- Division of Conservative Dentistry, Guy's, King's and St Thomas' Dental Institute, Guy's Tower, London Bridge SE1 9RT
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Abstract
OBJECTIVES To investigate the relationship between dental erosion, oral pH and drinking habit in a group of adolescents. METHODS Oral pH was measured simultaneously at the surface of four teeth in 11 patients, aged 10-16 years, with erosion and in 10 controls subjects without erosion using antimony electrodes. Measurements were made before, during and after drinking 330 ml of a carbonated drink. The method and timing of drinking the beverage, reported dietary intake of acidic foods and flow rate and buffering capacity of saliva were recorded. RESULTS The erosion patients reported drinking more carbonated drinks (p<0.01) and drinking directly from a can more frequently than the controls (p<0.05). They also drank twice as quickly (p<0.05). The pH at the buccal surface of a molar remained lower for longer in the erosion patients than in the patients without erosion (p<0.01), whilst the labial surface of the upper central incisor had a longer exposure to low pH in the controls subjects (p<0.05). CONCLUSION The pattern of oral pH differed between subjects with and without erosion after drinking an acidic beverage. This may be related to observed differences in drinking habit, which could have influenced the pattern of erosion in these subjects.
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Affiliation(s)
- R Moazzez
- Division of Conservative Dentistry, Guy's, King's and St Thomas' School of Dentistry, King's College, London, UK
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Abstract
OBJECTIVE The aim of this study was to measure lower esophageal sphincter pressure, sphincter length, and esophageal motility in patients with dental erosion and compare the results with measurements made in patients without gastroesophageal reflux or dental erosion. STUDY DESIGN Lower esophageal sphincter length and esophageal motility were measured in 39 patients (age range, 15-74 years) with dental erosion through use of static esophageal pressure monitoring; the data were compared with those from 10 control subjects (age range, 26-46 years) with nonparametric statistical tests. RESULTS Median lower esophageal sphincter pressure was 9 mmHg (range, 0-26 mmHg) in the patients with erosion and 9.5 mmHg (range, 0 -14 mmHg) in the controls; there was no statistically significant difference between the two subject groups. Similarly, there was no statistically significant difference in esophageal length between the subject groups. There was a statistically significant difference between the groups (P =.01) in the measurement of esophageal motility; the median value was 8% (range, 0% to 100%) in the patients with erosion and 0% (range, 0% to 18%) in the controls. CONCLUSIONS It appears that esophageal motility in patients with dental erosion is more likely to be associated with low amplitude changes than with sphincter pressure alone. Poor esophageal motility may therefore be a risk factor in regurgitation erosion.
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Affiliation(s)
- D W Bartlett
- Division of Conservative Dentistry, Guy's, Kings and St Thomas' Dental Institute, Kings College, UK
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Saksena R, Bartlett DW, Smith BG. The role of saliva in regurgitation erosion. Eur J Prosthodont Restor Dent 1999; 7:121-4. [PMID: 11314424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
It has been suggested that salivary characteristics are important in the progression of erosion. The aim of this investigation was to measure salivary parameters in 22 patients with erosion, 10 with normal (non-pathological) levels of reflux (Group I) and 12 with previously diagnosed pathological levels of gastro-oesophageal reflux (Group II). A further 10 subjects without evidence of erosion and no history of reflux disease acted as controls (Group III). No statistically significant differences in salivary flow rate, buffering power or the concentrations of calcium, phosphorus and fluoride were detected. The results suggest that variation in the characteristics of unstimulated and stimulated saliva collected during waking hours do not have a major role in erosion.
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Bartlett DW, Ide M. Dealing with sensitive teeth. Prim Dent Care 1999; 6:25-7. [PMID: 10752461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
Dental pain is extremely common in the UK and can severely reduce the quality of life when it is associated with eating, drinking or speech. Patients often present complaining of a short, sharp, stabbing pain from hot or cold air, foods or drinks: while this may be caused by tooth decay, failing fillings or cracks in teeth, a major cause is sensitivity from exposed dentine. Treatment varies from dietary control, desensitising toothpastes to protection with dentine-bonding agents and glass ionomers. In extreme cases elective devitalisation is necessary.
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Affiliation(s)
- D W Bartlett
- Department of Conservative Dentistry, UMDS Guy's, King's and St Thomas', London
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Bartlett DW, Coward PY, Nikkah C, Wilson RF. The prevalence of tooth wear in a cluster sample of adolescent schoolchildren and its relationship with potential explanatory factors. Br Dent J 1998; 184:125-9. [PMID: 9524373 DOI: 10.1038/sj.bdj.4809560] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
OBJECTIVE To assess the prevalence of tooth wear in adolescents and its relationship with diet, saliva and gastro-oesophageal reflux. DESIGN Single centre cluster sample epidemiological study. SETTING A school in London in the summer of 1996. SUBJECTS 11-14-year-old schoolchildren. MAIN OUTCOME MEASURES The Smith and Knight tooth wear index (TWI), salivary factors, diet and symptoms of gastro-oesophageal reflux were recorded for all subjects. RESULTS Results were obtained from 210 subjects. One subject refused to provide a saliva sample and 11 subjects provided insufficient saliva for analysis of buffering power (n = 198). 57% (95% confidence intervals 50.3-63.7%) of subjects had tooth wear on more than ten teeth and a median 12% (interquartile range 6-18%, 95% confidence intervals 8-14%) of surfaces were affected. However, dentine involvement was rare. The median intake of carbonated drinks was 2 cans (interquartile range 1-3) a day. However, there was no correlation with TWI (r = -0.09, P = 0.19). There was no relationship between tooth wear index (TWI) and salivary flow rate (r = -0.02, P = 0.78) or buffering capacity (r = -0.02, P = 0.76). A trend was observed for those with a reported history of regurgitation (n = 27) to have a higher maxillary TWI (median 8, interquartile range 2-13) compared with those who did not (5, 2-9, P = 0.06). CONCLUSIONS Tooth wear is common in adolescents and the relationship with dietary acid, salivary buffering and symptoms of gastro-oesophageal reflux is complex and requires further investigation.
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Affiliation(s)
- D W Bartlett
- Department of Conservative Dentistry, UMDS, Guy's Dental Hospital, London Bridge
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Abstract
Teeth are sometimes worn excessively by erosion (chemical damage), abrasion (physical damage) or attrition (wear between opposing teeth). The most important role of self-prescribed or physician-prescribed drugs is the management of conditions which cause regurgitation erosion.
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Affiliation(s)
- D W Bartlett
- Department of Conservative Dentistry, UMDS, Guy's Hospital, London, UK
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