Prions disease / dental implant courses

Prions diseasePrions disease
-unraveling an enigma-unraveling an enigma
INDIAN DENTAL ACADEMY
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What are Prions ?What are Prions ?
 Prions -cellular proteinsPrions -cellular proteins (PrPc(PrPc) normally present in) normally present in
mammals in various tissues found in the outermammals in various tissues found in the outer
membrane of the nerve cells.membrane of the nerve cells.
 The pathogenic form also called asThe pathogenic form also called as ScrapieScrapie is ais a
modified proteinmodified protein PrPscPrPsc - normal PrPc is converted into- normal PrPc is converted into
PrPsc through a post translational process during whichPrPsc through a post translational process during which
it acquires a high beta-sheet contentit acquires a high beta-sheet content

Prions are infectious transmissible proteinaceousPrions are infectious transmissible proteinaceous
particles that lack nucleic acid and are composedparticles that lack nucleic acid and are composed
exclusively of a modified isoform of theexclusively of a modified isoform of the
noninfectious cellular prion protein (PrPc).noninfectious cellular prion protein (PrPc).
[S.B.Prusiner][S.B.Prusiner]

How do prions function?
The normal, innocuous protein (PrPc) can change its shape to a
harmful, disease-causing form (PrPsc). The conversion from PrPc
to PrPsc then proceeds via a chain-reaction leading to
accumulation of this abnormal protein in the nerve cells causing
generation of plaques of amyloid material.
PrPc
PrPsc

Brain damage from spongiformBrain damage from spongiform
encephalopathyencephalopathy
vacoule

Different parts of the brain affected by prionsDifferent parts of the brain affected by prions
 Cerebral cortex When the cerebralCerebral cortex When the cerebral
cortex is affected, the symptomscortex is affected, the symptoms
include loss of memory and mentalinclude loss of memory and mental
acuity, and sometimes also visualacuity, and sometimes also visual
impairment (CJD).impairment (CJD).
 Thalamus Damage to the thalamusThalamus Damage to the thalamus
may result in insomnia (FFI).may result in insomnia (FFI).
 Cerebellum Damage to theCerebellum Damage to the
cerebellum results in problems tocerebellum results in problems to
coordinate body movements andcoordinate body movements and
difficulties to walk (kuru, GSS).difficulties to walk (kuru, GSS).
 Brain stem In the mad cow diseaseBrain stem In the mad cow disease
(BSE), the brain stem is affected.(BSE), the brain stem is affected.

Chemical Treatment: Concentration PSTV Scrapie
(viroid) (prion)
NH2OH (hydroxylamine) 0.1-0.5mM + -
Psoralen (binds NA) 10-500µg/ml + -
Phenol Saturated - +
SDS 1-10% - +
Zn2+ 2mM + -
Urea 3-8M - +
Alkali pH 10 (-) +
KSCN 1M - +
Enzymatic Treatment: Concentration PSTV Scrapie
RNAse A 0.1-100µg/ml + -
DNAse 100µg/ml - -
Proteinase K 100µg/ml - +
Trypsin 100µg/ml - +

Prion diseasesPrion diseases
Prion diseases are known asPrion diseases are known as TransmissibleTransmissible
spongiform encephalopathies (TSEs)spongiform encephalopathies (TSEs)
- rapidly progressive invariably fatal neuro- rapidly progressive invariably fatal neuro
degenerative diseases .degenerative diseases .
- long incubation period- long incubation period
- neuropathology feature of multifocal- neuropathology feature of multifocal
spongiform changespongiform change
- neuronal loss- neuronal loss
- absence of inflammatory reaction .- absence of inflammatory reaction .

Prions diseasesPrions diseases
 AnimalsAnimals
 Bovine spongiform encephalopathy (BSE)Bovine spongiform encephalopathy (BSE)
 Scrapie in sheep and goatsScrapie in sheep and goats
 Transmissible mink encephalopathyTransmissible mink encephalopathy
 Chronic wasting disease of deer, elkChronic wasting disease of deer, elk
 HumansHumans
 Creutzfeldt-Jacob disease (CJD)Creutzfeldt-Jacob disease (CJD)

Prion diseasesPrion diseases
Characteristics of infectionCharacteristics of infection::
 Loss of motor controlLoss of motor control
 DementiaDementia
 ParalysisParalysis
 EncephalitisEncephalitis
 Widespread neuronal lossWidespread neuronal loss

 Are group of diseases divided intoAre group of diseases divided into
a. Sporadic CJDa. Sporadic CJD
b. Inherited CJD -b. Inherited CJD -
Gerstmann-Straussler-Scheinker synGerstmann-Straussler-Scheinker syn
Fatal familial insomnia.Fatal familial insomnia.
c. Acquired CJD -c. Acquired CJD -
Iatrogenic,Kuru,Variant CJD formIatrogenic,Kuru,Variant CJD form
Creutzfeldt - Jacob disease.Creutzfeldt - Jacob disease.

Prion diseases ….Prion diseases ….
 Ways of infection:Ways of infection:
 Horizontal transmissionHorizontal transmission
 Somatic mutation of the geneSomatic mutation of the gene
 Spontaneous transformation of the form PrPc intoSpontaneous transformation of the form PrPc into
the PrPsc isoformthe PrPsc isoform
 Exposure to infected tissueExposure to infected tissue
 IatrogenicIatrogenic
 IngestionIngestion

Oral manifestations and infected oralOral manifestations and infected oral
tissues.tissues.
 Oral manifestationOral manifestation
- dysphagia- dysphagia
- dysarthria- dysarthria
 VCJDVCJD
- oro facial dysesthesia or parasthesia- oro facial dysesthesia or parasthesia
- Lose of taste and smell- Lose of taste and smell

Infected tissuesInfected tissues
 Most frequently infected tissues.Most frequently infected tissues.
-Trigeminal ganglion-Trigeminal ganglion
-Tonsils-Tonsils
-Posterior third of tongue .-Posterior third of tongue .
To date infection has been demonstrated byTo date infection has been demonstrated by
human autopsies ,in pulp tissue, alveolar nerves ,human autopsies ,in pulp tissue, alveolar nerves ,
gingiva and salivary glands at very low levelsgingiva and salivary glands at very low levels
than the levels found in brain .than the levels found in brain .

DiagnosisDiagnosis
 The following provide details of investigationsThe following provide details of investigations
commonly performed –commonly performed –
 Lumbar punctureLumbar puncture – The presence of a specific protein– The presence of a specific protein
known as “14-3-3” in CSF may assist in diagnosing aknown as “14-3-3” in CSF may assist in diagnosing a
TSE.TSE.
 EEG –EEG – The EEG may become abnormal, characteristicThe EEG may become abnormal, characteristic
changes are associated with sporadic CJD.changes are associated with sporadic CJD.
 MRI ScanMRI Scan –– May show heightened signal in areas ofMay show heightened signal in areas of
the basal ganglia. The presence of a high signal in thethe basal ganglia. The presence of a high signal in the
putamen region supports a diagnosis of CJD.putamen region supports a diagnosis of CJD.

DiagnosisDiagnosis
 Tonsil BiopsyTonsil Biopsy – Abnormal prion protein has been– Abnormal prion protein has been
associated with the lymphoreticular tissue from patientsassociated with the lymphoreticular tissue from patients
with neuropathologically confirmed vCJDwith neuropathologically confirmed vCJD..
 Genetic testingGenetic testing – The familial types of TSE’s are– The familial types of TSE’s are
detectable from blood testing. Predictive testing,detectable from blood testing. Predictive testing,
however, should only be carried out with fully informedhowever, should only be carried out with fully informed
consent following specialist genetic counselling at aconsent following specialist genetic counselling at a
regional genetics centre.regional genetics centre.
 Brain biopsyBrain biopsy – The only way to diagnose CJD with– The only way to diagnose CJD with
certainty is by brain biopsy, however, a negative resultcertainty is by brain biopsy, however, a negative result
may occur if an unaffected part of the brain ismay occur if an unaffected part of the brain is
examined.examined.

 Experimental studies of intraperitoneal andExperimental studies of intraperitoneal and
intradental injecions of prions haveintradental injecions of prions have
demonstrated prions in oral tissues.(Ingrosso Ldemonstrated prions in oral tissues.(Ingrosso L
etal 1999 )etal 1999 )
 Highly insensitiveHighly insensitive
 Prions bind to steel surface (Flechsig E etal )Prions bind to steel surface (Flechsig E etal )

Evaluating risk in healthcareEvaluating risk in healthcare
environmentsenvironments
 Risk is dependent upon three considerationsRisk is dependent upon three considerations
-the probability that an individual has or will-the probability that an individual has or will
develop TSEsdevelop TSEs
-the level of infectivity in tissues or fluids of-the level of infectivity in tissues or fluids of
these individualsthese individuals
-the nature or route of the exposure to these-the nature or route of the exposure to these
tissues.tissues.

Categorization of patients by riskCategorization of patients by risk
Patient groupPatient group Risk factorRisk factor
Symptomatic patientsSymptomatic patients -patients who fulfill the diagnostic-patients who fulfill the diagnostic
criteria for definite, possible CJDcriteria for definite, possible CJD
or VCJDor VCJD
-patients with neurological-patients with neurological
diseases of unknown causediseases of unknown cause
Asymptomatic patientsAsymptomatic patients
at risk for familialat risk for familial
forms of CJD linked toforms of CJD linked to
genetic mutationsgenetic mutations
-individuals who have or have-individuals who have or have
had blood relatives affected byhad blood relatives affected by
CJDCJD
-individuals who have been-individuals who have been
shown by specific genetic testingshown by specific genetic testing
to be at high risk of CJD .to be at high risk of CJD .

Patient groupPatient group Risk criteriaRisk criteria
AsymptomaticAsymptomatic
patients potentially atpatients potentially at
risk because ofrisk because of
iatrogenic exposureiatrogenic exposure
-recipients of hormone derived-recipients of hormone derived
from human pituitary glandfrom human pituitary gland
-individuals who have received a-individuals who have received a
graft of dura matergraft of dura mater
-patients who have been identified-patients who have been identified
as potentially at risk because ofas potentially at risk because of
exposure to the instruments usedexposure to the instruments used
on ,or receipt of blood ,plasmaon ,or receipt of blood ,plasma
derivatives, organs or tissuesderivatives, organs or tissues
donated by a patient who went ondonated by a patient who went on
to develop CJD or VCJD.to develop CJD or VCJD.

Tissue infectivityTissue infectivity
infectivity categoryinfectivity category Tissues ,secretions andTissues ,secretions and
excretionsexcretions
High infectivityHigh infectivity Brain, spinal cord, eyeBrain, spinal cord, eye
Low infectivityLow infectivity CSF,kidney,liver,lung,lymphnodeCSF,kidney,liver,lung,lymphnode
s/spleen,placenta,pulps/spleen,placenta,pulp
tissue/alveolar nerves/tissue/alveolar nerves/
gingiva/salivary glands.gingiva/salivary glands.
No detectableNo detectable
infectivityinfectivity
Skeletomuscular system, skin,Skeletomuscular system, skin,
bloodblood

Route of exposureRoute of exposure
 Transcutaneous exposures including contactTranscutaneous exposures including contact
exposures to non intact skin or mucousexposures to non intact skin or mucous
membrane ,splashes to the eye and inoculationsmembrane ,splashes to the eye and inoculations
via needle or scalpel and other surgicalvia needle or scalpel and other surgical
instruments pose a greater potential risk.instruments pose a greater potential risk.

Prion inactivationPrion inactivation
Inactivation methodInactivation method Type of materialType of material
IncinerationIncineration Disposable materialDisposable material
Organic remainsOrganic remains
Instruments in contact withInstruments in contact with
highly infectious tissueshighly infectious tissues
Autoclave at 134-138Autoclave at 134-138 oo
C forC for
18mins or in 6-3 cycles18mins or in 6-3 cycles
+immerse all the+immerse all the
instruments in NaOHinstruments in NaOH22 oror
NaHCLNaHCL
Heat resistant instrumentsHeat resistant instruments
without contact with highlywithout contact with highly
infectious tissueinfectious tissue

Inactivation methodsInactivation methods Type of materialType of material
1N NaOH1N NaOH22 or 1N NaHCLor 1N NaHCL
for 1hr + rinsingfor 1hr + rinsing
Heat sensitive instrumentsHeat sensitive instruments
without contact with highlywithout contact with highly
infectious tissue, surfaces.infectious tissue, surfaces.
Formic acid 96%Formic acid 96%
1hr+biohazardous labeling1hr+biohazardous labeling
Histological samplesHistological samples

Precautions for surgicalPrecautions for surgical
proceduresprocedures
 Involve the minimum required numberInvolve the minimum required number
healthcare personnelhealthcare personnel
 Use single -use equipments likeUse single -use equipments like
gloves,mask,linens and covers.gloves,mask,linens and covers.
 Mask all non disposable equipmentsMask all non disposable equipments
 Maintain one way flow of instrumentsMaintain one way flow of instruments
 Mark samples with a biohazard labelMark samples with a biohazard label
 Clean all the surfaces.Clean all the surfaces.

General measures for cleaningGeneral measures for cleaning
instruments and environmentinstruments and environment
 Instruments should be kept moist until cleanedInstruments should be kept moist until cleaned
and decontaminated.and decontaminated.
 Instruments should be cleaned as soon asInstruments should be cleaned as soon as
possible after use to avoid drying of tissues,possible after use to avoid drying of tissues,
blood and body fluids onto the items.blood and body fluids onto the items.
 Avoid mixing of instrumentsAvoid mixing of instruments
 Cover work surface with disposable materialCover work surface with disposable material

 Finally patient should never use the normalFinally patient should never use the normal
spittoon but rather a receptacle that is thenspittoon but rather a receptacle that is then
incinerated.incinerated.
 Instruments such as endodontic files, broachesInstruments such as endodontic files, broaches
and carbide and diamond burs should never beand carbide and diamond burs should never be
re-used ,since their complete sterilization isre-used ,since their complete sterilization is
impossible.impossible.
 Patients with confirmed prion disease should bePatients with confirmed prion disease should be
scheduled at the end of the day to permit morescheduled at the end of the day to permit more
extensive cleaning and decontamination.extensive cleaning and decontamination.

 It is preferable to avoid activating waterlinesIt is preferable to avoid activating waterlines
because of the risk of retraction of prion in oralbecause of the risk of retraction of prion in oral
fluids.fluids.
 A stand alone suction unit with disposableA stand alone suction unit with disposable
reservoir rather than suction component ofreservoir rather than suction component of
dental chair should be used.dental chair should be used.
 To avoid environmental contamination, dentalTo avoid environmental contamination, dental
equipment should be adequately shielded usingequipment should be adequately shielded using
disposable ,impermeable cover sheets.disposable ,impermeable cover sheets.

ConclusionConclusion
 With evidence of prions in oral tissues and itsWith evidence of prions in oral tissues and its
infectious nature we as dentists must be able toinfectious nature we as dentists must be able to
evaluate at risk patients ofevaluate at risk patients of Creutzfeldt-JacobCreutzfeldt-Jacob
DiseaseDisease and take precautions during theand take precautions during the
treatment of such patients to avoid the crosstreatment of such patients to avoid the cross
contamination.contamination.

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