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Fluorescence and Fluorescence and photochemical reactions:photochemical reactions:

Lessons from teeth and tissuesLessons from teeth and tissuesLaurence J. WalshLaurence J. Walsh

School of Dentistry,School of Dentistry,The University of QueenslandThe University of Queensland

©© 20062006

CollaboratorsCollaborators

•• Dr Dr JelenaJelena VlacicVlacic•• Dr Dr FardadFardad ShakabaieShakabaie•• Dr Dr SrdjanSrdjan DiklichDiklich•• Dr Jackson LiuDr Jackson Liu•• Dr Philip BirdDr Philip Bird•• Dr Michael LeeDr Michael Lee

•• Prof Helena Prof Helena RubinzsteinRubinzstein--DunlopDunlop

•• Dr Paul MeredithDr Paul Meredith•• Dr Stephen Dr Stephen NighswaterNighswater--

RempelRempel

•• Vanessa HoppeVanessa Hoppe•• WimWim van van UumUum•• John ClarkeJohn Clarke•• Helen CliffordHelen Clifford

•• Prof Prof RaimundRaimund HibstHibst•• Dr Frank SchwarzDr Frank Schwarz•• Dr Peter Dr Peter VerheyenVerheyen

Dental cariesDental caries

54,000+ patient 54,000+ patient appointments per yearappointments per year

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XX--rays do not show early lesionsrays do not show early lesions

(Matthias Frentzen)

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LEFT: Integrated fluorescence scan of infected carious dentine fLEFT: Integrated fluorescence scan of infected carious dentine from extracted rom extracted teeth, with excitation at 655 nm. Peak emission occurs at 820teeth, with excitation at 655 nm. Peak emission occurs at 820--830 nm, with a minor 830 nm, with a minor peak at 835 nm.peak at 835 nm.

RIGHT: Similar scan of dental calculus, showing an identical patRIGHT: Similar scan of dental calculus, showing an identical pattern of fluorescence tern of fluorescence in the nearin the near--infrared region infrared region

Excitation 655 nmExcitation 655 nm

DiagnoDENTDiagnoDENT

Applications: Applications: Primary caries diagnosisPrimary caries diagnosis

Calculus detectionCalculus detectionBiofilm detectionBiofilm detection

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Sensitivity and SpecificitySensitivity and Specificity

TIPS project: smooth surfaces of TIPS project: smooth surfaces of deciduous canines and molar teethdeciduous canines and molar teeth(9,000 tooth surfaces followed over 3 years)(9,000 tooth surfaces followed over 3 years)

>5048-5045-4742-4439-4136-3833-3530-3227-2924-2621-2318-2015-1712-149-116-83-50-2

diagnodent values

70.0%

60.0%

50.0%

40.0%

30.0%

20.0%

10.0%

0.0%

Perc

ent

Demineralised - enamel onlySound

Condition of tooth surface

Sound surfaces, and white spot lesionsSound surfaces, and white spot lesions

90-9980-8970-7960-6950-5940-4930-3920-2910-190-9

diagnodent values

90.0%

80.0%

70.0%

60.0%

50.0%

40.0%

30.0%

20.0%

10.0%

0.0%

Perc

ent

Gross decay - opencavity

Decayed into dentine

Condition of toothsurface

Caries detection Caries detection during cavity preparationduring cavity preparation

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• 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 ReductionsMean Reductions in in DiagnoDENTDiagnoDENT readings: readings: changes in 30 cavity preparations changes in 30 cavity preparations at the centre of the cavity floorat the centre of the cavity floor

Mechanical caries removal 60%Mechanical caries removal 60%

Er:YAGEr:YAG laser caries removal 55%laser caries removal 55%

CarisolvCarisolv 57%57%

Average final readingon the cavity floor: 5

KaVo KEY3 Er:YAG laser

DiagnoDENTDiagnoDENT pen:pen:Proximal caries tip with Proximal caries tip with periscope capabilityperiscope capability•• Acoustic signalAcoustic signal•• Peak value score (large digits)Peak value score (large digits)•• Momentary score (small digits)Momentary score (small digits)

FISSURE PROXIMALFISSURE PROXIMAL

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Autopilot Autopilot Er:YAGEr:YAG systemsystem

Affected vs. infected dentine

RealReal--time QLF control during Er:YAG laser time QLF control during Er:YAG laser cavity preparation for radiation cariescavity preparation for radiation caries

Auto-pilot caries detection and removal (R. Hibst)

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Tunnel approach to “hidden” caries

Detection of calculus

Subgingival Calculus Components• Minerals: calcium phosphate

salts (dicalcium phosphate dihydrate, octacalciumphosphate, magnesium substituted tricalciumphosphate).

• Organic: Bacteria and their metabolites or by-products, including various amount of porphyrins (haemin and haemoglobin related molecules) and Protoporphyrin IX

F. Schwarz

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Clinical simulation Clinical simulation of calculus detectionof calculus detection

ReproducibilityReproducibility •• A dental calculus A dental calculus detection system could be detection system could be linked to:linked to:–– an ultrasonic an ultrasonic scalerscaler, , –– a particle beam (Vector), or a particle beam (Vector), or –– an an Er:YAGEr:YAG or Alexandrite or Alexandrite

laserlaserto give a combined to give a combined

diagnostic and treatment diagnostic and treatment device. device.

Feedback system

Optical filter

Electronical filter

Mom PeakFluorescence values

Er:YAG Laser

Fluorescence value > Threshold

Fire

(Dr. Robert Gall)

Calculus Removal with Feedback

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Lack of damage to root surface

F. Schwarz

Before Scaler LaserF. Schwarz

Photochemical applications

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.

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)

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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.

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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

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Tetracycline + iron pigments + bilirubin

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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

• Methylene blue– peak absorption 670 nm

Absorption spectra of blue dyes (100 ug/mL)A: Methylene blue; B:Toluidine blue; C: Trypan blue

SaveDent PAD unit (635nm, 100 mW)

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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 futureThe future