MFD Theme 2b Flashcards
what is epidemiology
the scientific method of studying diseases in populations.
orderly study of diseases and conditions where the group and not the individual is the unit of interest.
study of the distribution and determinants of disease frequency in human populations.
what are the examples of epidemiology in dentistry
measurement of dental disease in populations & subgroups
evaluation of the effectiveness of treatments
assessment of needs and demands within the community
what are the 3 components of epidemiology
- Distribution
- Frequency
- Determinants
what is the process of epidemiology
suspicion
formulation of hypothesis
hypothesis tested in epidemiological studies with comparison group
Collect and analyse- statistical association
Assess validity of any observed association
Does statistical association suggest a causal relationship?
how can you measure disease to investigate epidemiology
Can use indices
Importance of standardisation
Quantification of disease
Need to be objective rather than subjective
what is the Gold standard measure for 12 Dental Disease
Valid, reliable, objective, simple to investigate, reproducible, sensitive & acceptable to the patient (i.e. must not cause harm to the patient).
Is everything you measure a true measure of that disease or is it just a proxy
Reproducible for everyone by standardisation and calibration where possible
Must calibrate to the gold standard we all see the same thing
Sensitive- minute or major improvements in a condition
Acceptable to the patient e.g. periodontal probing (do not press too hard)
what are the types of study design
1) Descriptive – observational/ case-reports / case-series / cross-sectional
2) Analytic – observational (case-control/ cross-sectional) OR observational (clinical trials).
what are case studies/series used for
Highlighting interesting or novel cases / treatment
Recognition of new disease/outcome
Formulation of new hypotheses
what are the Disadvantages/weaknesses of case studies/series
- Cannot demonstrate valid statistical association
* Lack of appropriate comparison group can obscure a relationship or suggest an association where none exists
what is involved in a cross sectional survey
Observation of a defined population at a single point in time (or time interval)
Exposure and outcome are determined simultaneously
Used for measuring the prevalence of a disease/looking at potential risk factors or cause
Adult and children survey every year are a good example
Could be a period of time- still cross sectional
However cannot validate what you’ve been told
what are cross sectional surveys use for
Measure prevalence of a disease
look at potential risk factors or cause
what are the disadvantages of cross sectional surveys
- Can’t prove causality can only link potential association
- Confounders may be unequally distributed (a confounder is an unobserved exposure associated with the exposure of interest and is a potential cause of the outcome of interest)-
- Group sizes may be unequal
- Recall bias (recall something better that happened recently rather than long time ago)
what are cohort studies
Involves identification of two groups of patients
- one which received the exposure of interest
- one which did not
following these cohorts forward to assess the outcome of interest.
Prospective and work forwards
what are cohort studies used for
Measures the incidence of disease
Looking at causes of disease
Determining prognosis
Establishing timing and directionality of events
what are Disadvantages / weaknesses of cohort studies
Controls may be difficult to identify
Exposure may be linked to hidden confounder
Blinding is difficult- easy to know what group you’re in
For rare diseases large sample size is often necessary (very small % of people actually have the disease)
Cohort studies should be used for common diseases e.g caries, gingivitis
what are case-control studies
A study which involves identifying patients who have the outcome of interest (cases) and patients without the same outcome (controls), and looking back in time to see if they had the exposure of interest.
Look BACKWARDS in time – start with the disease and look back, unlike cohorts
Involves looking at their exposure to carcinogens/teratogens/wood-shavings
Looking then back at dental/medical records & occupations in order to try create a link between those who have the outcome
what are case control studies used for
Looking at potential causes of disease (suitable for rare diseases
what are Disadvantages/weaknesses of case control studies
Confounders e.g. if you don’t drink tap water, it doesn’t matter if its fluoridated
Selection of controls may be difficult
Recall and selection bias
Difficult to establish time relationships between exposure to the risk factor and development of the disease
difference between case-control study and a cohort study
Case control involves investigating individuals who have already been infected with a disease
Cohort involves individuals who are initially disease free before the trial
what are Randomised Controlled Trials (RCTs)
Exposure status is assigned by the researcher (preferably by random allocation)
Randomisation is the best way of reducing selection bias between 2 groups of participants.
Best RCTS have qualitative component along-side asking people how they feel
Used for evaluating the effectiveness of an intervention
what are Randomised Controlled Trials (RCTs) Disadvantages:
High costs
Ethical issues
Participant compliance – e.g. drop out
what is a systematic review definition
The evidence from a number of studies (can be RCTS) can be gathered together in one report which pools and analyses all available data to assess the strength of the evidence
Why conduct a systematic review?
Systematic reviews can end confusion / highlight where there is not enough evidence/yield new insights by combining findings from different studies
what is prevalence
The proportion of individuals in a population who have the disease of interest at a specific instant.
Prevalence provides an estimated of the probability (risk) that an individual will be ill at a point in time
what is the equation for prevalence
Prevalence = number of existing cases of a disease/total population
what is incidence
Quantifies the number of new cases of a disease that develop in a population at risk during a defined time period.
what is the equation for cumulative incidence
number of new cases of a disease during given time period /total population at risk
what is the equation for incidence rate
number of new cases of a disease during given time period/ total person-time of observation
what is an index
A numerical value describing the relative status of a population on a graduated scale with definite upper and lower limits designed to permit and facilitate comparison with other populations classified by the same criteria and methods’.
what are the uses of indices
To describe the prevalence of a disease/condition in a population and they can be
used to describe the severity of diseases/conditions.
To study and compare the health status of individuals and populations
To provide data for epidemiological studies
For planning oral health policy – OCDO use the data from epidemiological studies to plan the contract
To evaluate the success of preventive interventions
what are the desirable properties of Indices:
Equally sensitive across the scale, to clinically-relevant changes in disease severity and disease progression.
Simple to apply, objective, clear and unambiguous.
Should be valid (it should faithfully record the disease/condition it is presumed to identify). measure what it reports to measure
Should be reliable (it should be consistent and repeatable at different times, by the same examiner or group of examiners).
The measurements gained should be amenable to statistical analysis.
Should be acceptable to the participant (it should not be painful nor cause harm).
what is meant by validity
actually measures what test purports to measure
dont want to measure a proxy
what is meant by reliability
consistency and repeatability in the hands of an examiner or group of examiners
what is meant by chance
a possibility/probability of
something happening
an opportunity
subject to random variation
what is meant by bias
Inclination or prejudice in favour of a particular person, thing or viewpoint. To influence unfairly
A systematic error relating to the measurement of a variable
what is cofounding
An error in the interpretation of a measurement (even if the measurement is accurate!)
A confounder is prognostically linked to the outcome of interest and is unevenly distributed between the study groups
how can cofounding be managed
Randomise
Stratify
Match
Statistical analysis
what are Problems with the DMF/dmf Index
M’ and ‘F’ teeth are assumed to have been carious. Missing- could be hypodontia, could be knocked out in an incidence. Filled teeth could be fractured
Were past treatment decisions for preventive or restorative reasons?
Equal weight is given to ‘D’, ‘M’, ‘F’, yet the implications for dental health are different. Which ones worse?? We treat them the same.
‘F’ teeth score the same as ‘M’ teeth…so what’s the point in having decayed teeth restored?
DMF/dmf score is irreversible.
what are things that should be considered when looking at the epidemiology of periodontal disease
Who and how many are affected in the population?
What is the disease process?
Chronic progressive
Burst theories
What is the aetiology?
How can we manage the condition?
how is PD measured visually
- Description of tissues
- Radiographs
- Photographs
how is PD measured using indices
- Bleeding on probing
- Tooth mobility
- Periodontal pocket depths (loss of attachment)
- Furcation involvement
- Others……?
what is the epidemiology of oral cancer
The 14th most common cancer in the UK (in 2012).
Incidence of OC in the UK has increased by 34% over the last decade
OC mortality rates in the UK have risen by around 10% in the last decade
what are established risk factors for oral cancer
- Age, sex
- Smoking
- Alcohol
- Chewing tobacco
- Betel quid
- Diet
- Weakened immune system
- Sunlight
- Chemicals
what are Potential Risk Factors for oral cancer
- Viruses?
- Irritation?
- Family history?
- Mouthwash?
what should be considered in Malocclusion / Dentofacial Anomalies
- Minor dental cosmetic irregularity or significant dento-facial disfigurement?
- Perspective: patient / family / peers / clinician?
- Social and psychological influences
- Prioritisation for orthodontic treatment = ‘IOTN’
- Prioritises those who need NHS treatment
what is IOTN and why is it used
Index of Orthodontic Treatment Need
How to prioritise who receives limited resources according to NEED (not demand)
Higher scores = greater need
Attempts to address equity issues
• Dental Component
• Aesthetic Component
what are Selected indicators for fluoride monitoring programme
- d3mft/D3MFT (reduced in areas of fluoridation?)
- Dental fluorosis (evidence of fluorosis assoc. with F intake, TF score)
- Bone health (Hip fracture)
- Renal effects (Incidence of kidney stones)
- Mortality (all causes, a ‘catch-all’ measurement)
- Birth defects (Incidence of Down’s Syndrome)
- Cancer: (Bladder/osteosarcoma/overall cancer incidence rate
why do we measure DMFT
Introduced as a summary of cumulative caries experience
Measures number of teeth that are decayed, missing (due to caries) or filled
Usually used in epidemiological studies
what are limitations of DMFT
Doesn’t give age
Gives equal weight to missing, untreated caries or well restored teeth
No measurement of extent of caries- small/deep (un-restorable)
Doesn’t consider other disease processes other than caries – does not consider periodontal disease
No indication of teeth at risk- may have early carious lesions
Sealants or PRRs given same weighting as heavily restored teeth- really small carious lesion in the fissure of a molar would be given the same rating as a heavily restored tooth.
Rate of caries progression cannot be assessed
Does not represent current treatment need
Relies on patient recall – may not remember why a tooth was lost
how do you measure DMFT
Score a tooth as 1 if it is:
- Decayed
- missing (due to caries)
- filled
Score a tooth as 0 otherwise
A few notes:
- Provided 3rd molars are included, the score is out of 32
- Be consistent if you are including 8s or not
- Do not include teeth missing due to reasons other than caries, e.g: Unerupted, congenitally missing, extracted for orthodontic/periodontal reasons, knocked out through trauma
why do we measure plaque
Indicate extent of plaque coverage of teeth
Used in epidemiological studies but also useful resource for individual patient care- plaque scores worked out as a %
what does the plaque coverage index measure
number of surfaces with plaque present (plaque either present or absent
1.Divide each tooth into 6 areas:
2.Assess whether or not plaque is present on each surface
3.Calculate the percentage of surfaces present with visible
plaque.
what should not be done when measuring plaque coverage index
Do not score occlusal surfaces.
Do not quantify amount of plaque i.e. it’s either present or absent.
how is plaque index measured
Plaque index = number of surfaces/ total number of surfaces with plaque x 100%
what is the silness and loe plaque index
Used when we want to measure the amount of plaque present on each tooth surface.
Like the Plaque Coverage Index, ignore the occlusal surfaces.
how is the silness and loe index measured
0 – No plaque
1 – Film of plaque, visible only by removal on a probe
2 - Moderate accumulation of deposits visible with the naked eye
3 – Heavy accumulation of plaque
Can divide each tooth into 4 or 6 surfaces
For the clinical trial, we will use 6 surfaces
tell your nurse which teeth are missing before you chart
Then, read out the score for each surface working systematically around dentition like with the Plaque Coverage index
how is s&l plaque index calculated
Plaque index = Total S & L plaque score/ Total number of surfaces
what cross infection control should be remembered on clinic
Personal Protective Equipment (PPE)
Mask, Gloves, Safety Glasses
Hair tied back, bare below the elbow
Patient Protection
Safety glasses, bib
Effective Hand Hygiene
Clean and dirty zones
Disposal of equipment
what waste disposals are there and what goes in each
Domestic waste
-Paper towels, bits of paper etc.
Clinical waste
- All gloves
- Anything remotely clinical looking e.g. bits of gauze, cotton wool etc.
Instruments are not waste!
- Return to tray (not in sharps bin!)
- Dirty utility room
- Tidy up when finished
