Dental Materials Flashcards
Challenges of dental materials
Extremes of pH Temperature fluctuations Risk of corrosion or degradation Wet environment Mechanical loading Microbial colonisation Need for term funtion and aesthetics Contact with wide range of foreign substances
Barriers to innovation
Lack of clinical evidence base
Lack of clinical readiness
Technologies not yet fully optimised
Regulatory environment
Lack of investment in new technology development
Lack of recognisable/viable commercial opportunity
Patient/public/clinical scepticism
GDC Learning outcomes relating to dental materials
Underpinning Science
Evidence Based Dentistry
Foundations of Practice
Management and Leadership
Pros and cons of peer reviewed publications
PROS:
Peer reviewed - nothing published without scrutiny
Methods and data must be accurate/truthful
Generally accessible to healthcare workers
Generally include sufficient details as to be understandable/useful
CONS:
Quality of peer review may differ from journal to journal
Other sections may contain more opinion than fact. Risk of fraud
Public/GDPs/team may find key papers behind a pay wall
May contain extensive technical jargon
Types of evidence
Systematic review Randomised control trial Scientific paper International/national databases Clinical/senior peers judgement/opinion Manufacturers marketing materials
Classification of biomaterials
By material
By application
By tissue exposure
By risk
Classification by risk:
Important in context of medical devices regulations and safety testing, classified as class I (low), II (intermediate, a &b) and III (high), on basis of:
Type of exposure - surface/skin, indwelling, blood
Length of exposure - <24hrs, day, permanent
Testing biocompatibility:
In vitro evaluation - cell-free models, cell culture
In vivo evaluation (animals)
Clinical testing and trial (pre-market)
Post market surveillance (e.g. adverse reaction reporting project)
Biocompatibility tests are used as part of process leading to aware of CE mark
In vitro determination of biocompatibility
Adv vs disadv
ADVANTAGES: Rapid Cost-effective Reproducible Ethically straight forward/non-controversial
DISADVANTAGES:
Poor model of complex situation
In vivo
Adv vs disadv
ADVANTAGES:
Whole complex animal model
DISADVANTAGES: Expensive Intermediate reproducibility Ethical debate/controversy Not always reliable model of human body, tissue or disease
Post market surveillance
May provide early warning of hazards of side effects
Some adverse reactions are extremely rare and may only be caught by PMS
Strengthen evidence base for a use of a biomaterial or device as part of a treatment
Whilst no real disadvantages, implementation may be expensive
PMS is required by law as part of Medical Devices Directives
Clinical trial to determine biocompatibility
ADV and DISADV
ADVANTAGES
Real human use/clinical model
DISADVANTAGES
Expensive
Some ethical issues
Not always a good representation of real clinical practice e.g. is often performed by skilled/specialised clinicians, patients selected, etc
CAD/CAM
CAD - computer aided design
CAM - computer aided manufacturing
CAD/CAM process:
Data acquisition - CT, MRI, laser digitalising (i.e. IO scanners), US, X-ray
Data processing - segmentation, interpolation, CAD package
Manufacturing - subtractive or additive
Uses for CADCAM
Medical modelling Drilling and cutting guides Digital orthodontics Dental implants Partial denture frameworks
I/O scanners pros and cons
Pros: Patient comfort Dentist auto evaluation Reduced model time Favours clinic-lab communication
Cons: Cost investment Training Just surface registration Coating - new ones dont have coating which used to be uncomfortable for pt
Current literature lacks sufficient evidence to provide solid information re. use of IO scanners under clinical condition e.g. in 2017 only 4 studies reported on validity, repeatability and reproducibility of digital measurements
Risk reduction for adverse reactions
Pre-market testing and CE mark
Improved packaging
Non-contact operative techniques
Post market surveillance - via competent authority and via adverse reaction unit
Pre-market testing
Required by law for new biomaterials
Tests based on ISO 10993 guidelines
Exact tests determined by evaluation of risks associated with the material and its clinical application
Tests include cytotoxicity, haemolysis, irritation, systemic toxicity and genotoxicity
Manufacturers work with a notified body to satisfy a Competent Authority that a medical device e.g. dental biomaterial is safe
New devices are then awarded a CE mark for sale in Europe
Most developed nations operate a similar system e.g. FDA/SFDA
Post market surveillance
Provides ‘early warnings’ of previously unsuspected adverse reactions
Can be used to identify factors associated with particular adverse reactions
Permits continued safety monitoring throughout duration of a products use on the market
Clinicians and indeed the whole team are required by law to report suspected adverse reactions to MHRA
MHRA yellow card reporting
Dental amalgam
50% Hg by weight
Minority believe mercury in amalgam responsible for widespread disease
Alleged symptoms of Hg poisoning from amalgam: chronic fatigue, anxiety, depression, burning sensation, metal taste, muscle pain, headaches
Known clinical symptoms of Hg poisoning - NS symptoms e.g. tremor, gingivitis, blue discolouration mucosa, renal dysfunction «_space;chronic
Acute - GI symptoms, depression of resp, kidney dys, pain and death
Adverse reaction reporting findings - clinician at greater risk, increased exposure increased risk, adverse reactions to dental biomaterials generally uncommon and not serious, use of amalgam declining in western markets
Minimata convention - eliminate Hg from all industrial processes inc dent. Phase down use of alagam in Europe, hoping for elimination by 2030
