Fluorescence and photochemical reactions: Lessons from teeth and tissues Laurence J. Walsh School of Dentistry, The University of Queensland 2006 Collaborators Dr Jelena Vlacic Dr Fardad Shakabaie Dr Srdjan Diklich Dr Jackson Liu Dr Philip Bird Dr Michael Lee Prof Helena Rubinzstein- Dunlop Dr Paul Meredith Dr Stephen Nighswater- Rempel Vanessa Hoppe Wim van Uum John Clarke Helen Clifford Prof Raimund Hibst Dr Frank Schwarz Dr Peter Verheyen Dental caries 54,000+ patient appointments per year 1
X-rays do not show early lesions (Matthias Frentzen) 2
LEFT: Integrated fluorescence scan of infected carious dentine from f extracted teeth, with excitation at 655 nm. Peak emission occurs at 820-830 830 nm, with a minor peak at 835 nm. RIGHT: Similar scan of dental calculus, showing an identical pattern tern of fluorescence in the near-infrared region Excitation 655 nm DiagnoDENT Applications: Primary caries diagnosis Calculus detection Biofilm detection 3
Sensitivity and Specificity TIPS project: smooth surfaces of deciduous canines and molar teeth (9,000 tooth surfaces followed over 3 years) Sound surfaces, and white spot lesions 70.0% 60.0% Condition of tooth surface Sound Demineralised - enamel only 50.0% Percent 40.0% 30.0% 20.0% 10.0% 0.0% 0-2 3-5 6-8 9-11 12-14 15-17 18-20 21-23 24-26 27-29 30-32 33-35 36-38 39-41 42-44 45-47 48-50 >50 diagnodent values 90.0% 80.0% 70.0% Condition of tooth surface Decayed into dentine Gross decay - open cavity Percent 60.0% 50.0% 40.0% Caries detection during cavity preparation 30.0% 20.0% 10.0% 0.0% 0-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90-99 diagnodent values 4
Extracted teeth with frank cavitations sectioned through the areas of cavitation Stepwise caries removal using either hand and rotary instruments, Carisolv, or Er:YAG laser Assessed by Diagnodent, visual inspection, probing using a blunt probe, and staining using acid red dye. Mean Reductions in DiagnoDENT readings: changes in 30 cavity preparations at the centre of the cavity floor Mechanical caries removal 60% Er:YAG laser caries removal 55% Carisolv 57% Average final reading on the cavity floor: 5 KaVo KEY3 Er:YAG laser DiagnoDENT pen: Proximal caries tip with periscope capability Acoustic signal Peak value score (large digits) Momentary score (small digits) FISSURE PROXIMAL 5
Autopilot Er:YAG system Affected vs. infected dentine Real-time QLF control during Er:YAG laser cavity preparation for radiation caries Auto-pilot caries detection and removal (R. Hibst) 6
Tunnel approach to hidden caries Detection of calculus Subgingival Calculus Components F. Schwarz Minerals: calcium phosphate salts (dicalcium phosphate dihydrate, octacalcium phosphate, magnesium substituted tricalcium phosphate). Organic: Bacteria and their metabolites or by-products, including various amount of porphyrins (haemin and haemoglobin related molecules) and Protoporphyrin IX 7
Clinical simulation of calculus detection Reproducibility A dental calculus detection system could be linked to: an ultrasonic scaler, a particle beam (Vector), or an Er:YAG or Alexandrite laser to give a combined diagnostic and treatment device. Feedback system Calculus Removal with Feedback Er:YAG Laser (Dr. Robert Gall) Fire Fluorescence value > Threshold Optical filter Fluorescence values Mom Peak Electronical filter 8
F. Schwarz Lack of damage to root surface F. Schwarz Before Scaler Laser Photo-chemical whitening 510-534 nm light breaks down tetracycline compounds (AODTC) and other complex molecules to simpler compounds which are then susceptible to oxidation using H2O2. Photochemical applications Technology overview International patent WO 02/22097 (14.09.2000) (Peter Verheyen). Laser 525-545 nm range (e.g. 532 nm) Final H2O2 level 38-42% Buffers and bases (e.g. sodium carbonate) to give a final ph 8.5-10.5 (hydroxyl radicals) Thickening agent for gelling (fumed silica 95% w/w; 90-125 microns particle size) Coloured agent (red: Rhodamine B, 0.5% w/w) which absorbs at 532 nm Diode-laser pumped frequency doubled Nd:YAG laser (532 nm) 9
Rhodamine absorption Rhodamine photochemistry When RB is exposed to 532 nm light, it absorbs photons of energy with subsequent electronic transition to the singlet excited state. 1. Fluorescence (602 nm orange/red) 2. Heat 3. Intersystem crossover: the triplet excited state. The path is dictated by the environment, e.g. the ph. High ph created via carbonate buffer Once in the triplet excited state (which is a more stable species), the molecule may fall back to the ground state or undergo reactions with molecular oxygen, resulting in production of hydroxyl radicals, superoxide ions, peroxides, labile singlet oxygen or other reactive oxygen species. Thermal issues A portion of laser energy absorbed into the Rhodamine B dye is transferred into the bleaching gel in the form of thermal energy. This transfer results in controlled heating of the gel, and not the tooth, minimizing the possibility of thermal insult to the dental pulp. Superficial heating of the gel accelerates the breakdown of hydrogen peroxide, which further boosts the overall yield of oxygen free radicals over a given time. 10
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DOTCAM DOTCAM DOTCAM comparison Change in ratio of blue channel intensity KTP Smartbleach 33.71-37.56 OpusWhite 8.10-11.58 PolaNite NGVB 13.83-15.77 Using this objective method, greater whitening effects could be shown for photochemical laser bleaching (KTP laser/ Smartbleach) compared with photothermal laser bleaching (diode laser /OpusWhite). Cases unresponsive to conventional power bleaching Tetracycline: fluorescence under UVA light 12
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Tetracycline + iron pigments + bilirubin 14
Direct laser effects with 635 nm red light Toxic for Gram negative periodonto-pathogens because of endogenous porphyrins which photosensitize Modestly inhibits the growth of key Gram positive species S. mutans, S. sobrinus, L. acidophilus but does not kill them. Dyes for PAD Tolonium chloride (toluidine blue, TBO) peak absorption 633 nm Absorption spectra of blue dyes (100 ug/ml) A: Methylene blue; B:Toluidine blue; C: Trypan blue Methylene blue peak absorption 670 nm SaveDent PAD unit (635nm, 100 mw) 15
SaveDent PAD unit with PDT isotropic diffuser and E. faecalis in root canals Control - saline 1.66 X 10E6 bugs Control - TBO dye 50 ug/ml 8.4% kill Control laser only 635 nm SaveDent 120 sec 10.7% kill PAD 99.99% kill The future 16