Measures of Disease Frequency

Ratio

A fraction in which the numerator is not part of the denominator

Eg 1 Students of the Dental Faculty/ Students of the Colombo University

2 I.U.D/Live birth

Proportion

Numerator is a part of the denominator

Eg 1.Students of the Dental Faculty/ Students of Peradeniya University

2. I.U.D/All birth

Rate

Proportion in which change over time is considered. (but in practice often used interchangeably with proportion)

Prevalence-number of cases

1. Point prevalence

Proportion of individuals in a specified population at risk who have the disease of interest at a given point in time.

2. Period prevalence

Over a specified period of time (year,lifetime)

Incidence- number of new cases arising in a given period in a specified population

1. Incidence rate/density- concept of person

time. Eg- Ref example

2. Cumulative incidence- No of new cases of disease occurring over a specified period of time in a population at risk at the beginning of the interval.

Eg New cases of flu, bet March 09 and Mar 10/All

students as at 17/3/2009

Features of above measurements

Incidence-

Aetiology

Unit if analysis an event

Actively acquired diseases

May exceed 100%

Duration

Conveys information about the risk of contracting the disease

Prevalence-

More permanent states/conditions

Societal burden

Unit of analysis is person

Never exceed 100%

Indicate how widespread the disease is

Prevalence=Incidence x disease duration

Short duration conditions Eg Flu- Low prevalence, High incidence

Incidence Rate/Density

Best estimation of the true risk of acquiring a disease at any moment in time.Cumulative Incidence

Best estimation of how many people will eventually get the disease in an given population.

Kennedy's Classification for Removable Partial Dentures

• Kennedy’s Class I- Bilateral edentulous areas located posterior to the remaining natural teeth. Denture saddles that restore such edentulous areas are described as distal extension saddle.

• Kennedy’s Class II- A unilateral edentulous area located posterior to the remaining natural teeth.

• Kennedy’s Class III- A unilateral edentulous area with natural teeth remaining both anterior and posterior to it. Denture saddles that restore this type of edentulous area are said to be 'bounded saddles'.

• Kennedy’s Class IV- A single edentulous area located anterior to the remaining natural teeth.

Dental Caries: Definition

Dental caries is a disease of the calcified tissues of the teeth caused by the action of micro-organisms on fermentable carbohydrates. It is characterized by demineralization of the mineral portion of enamel and dentine followed by disintegration of their organic matrix.

Surgical Incisions and Flaps

The following fundamental rules apply to every surgical procedure, concerning the incision and flap: The incision must be carried out with a firm, continuous stroke, not interrupted strokes. During the incision, the scalpel should be in constant contact withbone. Repeated strokes at the same place,many times, impair wound healing. Flap design and incision should be carried out in such a way that injury of anatomic structures is avoided, such as: the mental neurovascular bundle, palatal vessels emerging from the greater palatine

foramen and incisive foramen, infraorbital nerve, lingual nerve, submandibular duct, parotid duct, hypoglossal venous plexus, buccal artery (of concern

when incision of an abscess of the pterygomandibular space is to be performed), facial nerve and facial artery and vein, which are of concern basically for the drainage of abscesses performed withextraoral incisions.

Vertical releasing incisions should begin approximately at the buccal vestibule and end at the interdental papillae of the gingiva. Envelope incisions and semilunar incisions, which are used in apicoectomies and removal of root tips, must be at least 0.5 cm from the gingival sulcus.

The elliptic incision, which is used for the excision

of various soft tissue lesions, comprises two convex incisions joined at an acute angle at each end, while the depth of the incision is such that there is no tension when the wound margins are coapted and sutured.

The width of the flap must be adequate, so that the operative field is easily accessible, without creating tension and trauma during manipulation.

The base of the flap must be broader than the free gingival margin, to ensure adequate blood supply and to promote healing.

The flap itself must be larger than the bone deficit so that the flap margins, when sutured, are resting on intact, healthy bone and not over missing or unhealthy

bone, thus preventing flap dehiscence and tearing.

The mucosa and periosteum must be reflected together. This is achieved (after a deep incision)when the elevator is continuously kept and pressed firmly against the bone.

When the incision is not made along the gingival sulcus, for esthetic reasons, and especially in people with broad smiles, the scar that will result must betaken into consideration, particularly on the labial surface of the front teeth.

During the surgical procedure, excessive pulling and crushing or folding of the flapmust be avoided, because the blood supply is compromised and healing is delayed.

Types of Flaps

Various types of flaps have been described in oral surgery, whose name is based mainly upon shape. The basic flap types are: trapezoidal, triangular, envelope, semilunar, flaps created by and incisions, and pedicle flaps.

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Pregnancy and Drugs in Dentistry

Pregnancy is a major event in any women’s life and is associated with physiological changes affecting especially the endocrine, cardiovascular and haematological changes.

Foetal development during the first 3 months of pregnancy is a complex process of organogenesis and the foetus is then especially at risk from developmental defects. The most critical period is the 3^rd to 8^th week, during differentiation. Most developmental defects are unknown aetiology but,in addition to hereditary influences, infections, alcohol, smoking and drugs can be implicated in some cases.

Drugs can have harmful effects on the embryo or fetus at any time during pregnancy. It is important to bear this in mind when prescribing for a woman of childbearing age or for men trying to father a child.

During the first trimester drugs can produce congenital malformations (teratogenesis), and the period of greatest risk is from the 3^rd to the 11^th week of pregnancy.

During the second and third trimesters drugs can affect the growth and functional development of the fetus or have toxic effects on fetal tissues. Drugs given shortly before term or during labour can have adverse effects on labour or on the neonate after delivery.

Drugs should be prescribed in pregnancy only if the expected benefit to the mother is thought to be greater than the risk to the fetus, and all drugs should be avoided if possible during the first trimester. Drugs which have been extensively used in pregnancy and appear to be usually safe should be prescribed in preference to new or untried drugs; and the smallest effective dose should be used.

Few drugs have been shown conclusively to be teratogenic in man, but no drug is safe beyond all doubt in early pregnancy. Screening procedures are available when there is a known risk of certain defects.

Absence of a drug from the list does not imply safety.

Drugs to avoid in pregnant mothers.

Inhalation anaesthesias

• Nitrous oxide-congenital anomalies

Analgesics

NSAID’s

• Persistent pulmonary hypertension, bleeding tendency, premature closure of ductus arteriosus
• Aspirin – possible abortion, premature closure of ductus arteriosus, persistent pulmonary hypertension, bleeding tendency.

Opioid analgesics

• Pentazocaine-foetal addiction and withdrawal syndromes
• Codeine – respiratory depression

Anaesthetics

• Prilocaine-methamoglobinaemia
• Cocaine- anlkyloglossia, risk of spontainious abortion,neonatal cerebral infraction,abruption placentae

Antibacterial drugs

• Tetracyclines – discoloured teeth and bone, altered bone growth
• Gentamicin-deafness
• Co-trimoxazole (trimethoprim+sulfamethoxazole)-haemolysis,teratogenicity,methamoglobinaemia
• Vancomycin-toxicity
• Metronidazole-May be mutagenic?

Antifungal drugs

• Acyclovir –teratogenicity
• Flucanazole-congenital anomalies

Antiepileptic drugs

• Carbamazapine – neural tube defects,vitamin K impairment and bleeding tendency
• Valpolate-neural tube defects
• Phenytoin-fetal phenytoin syndrome
• Diazepam-cleft lip /palate
• · Avoid regular use (risk of neonatal withdrawal symptoms); use only if clear indication such as seizure control (high doses during late pregnancy or labour may cause neonatal hypothermia, hypotonia and respiratory depression)

Antithyroid drugs

• Carbimazole – Goitre

Immunosuppressive drugs

• Thalidomide-phocomalia(upper parts of limbs are not developed)
• Corticosteroids – adrenal suppression,growth retardation

Anti coagulants

• Warfarin

· 1^st trimester-hypoplastic nasal bridge

· 2^nd trimester-CNS malformations

· 3^rd trimester-risk of bleeding