Histopathology of Dentine Caries PDF

Histopathology of Enamel and Dentine Caries Oral and Dental Science Josh Hudson GDC Learning Outcomes: 1.1.2 Describe oral diseases and their relevance to prevention, diagnosis and treatment 1.1.4 Explain the aetiology and pathogenesis of oral disease 1.1.6 Describe relevant and appropri...

Histopathology of Enamel and Dentine Caries Oral and Dental Science Josh Hudson GDC Learning Outcomes: 1.1.2 Describe oral diseases and their relevance to prevention, diagnosis and treatment 1.1.4 Explain the aetiology and pathogenesis of oral disease 1.1.6 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their application to patient management  Pre-reading Susceptible tooth surface Caries ‘Aetiology of Dental Caries’ Lecture Time Plaque Bacteria Fermentable Carbohydrate Pre-reading ‘Histology of enamel and dentine’ Lectures Histopathology of Dentine Caries Learning Objectives: By the end of the session you will be able to;  Describe the clinical appearance of dentine caries  Describe the histology of dentine caries  Be able to identify and name the 4 zones of destruction in dentine caries  Be able to identify mechanisms that the dentine uses to protect itself and the pulp from assault Recap on Caries Aetiology As pH lowers, the tooth surface (hydroxyapatite) will demineralise and break down into its component ions. If the PH does not neutralise, this demineralisation over time will lead to caries. How do we know this is happening clinically? ICDAS Scores The international caries detection and assessment system ICDAS was developed for use in clinical research, clinical practice and for epidemiological purposes A clinical scoring system used to diagnose caries ICDAS allows detection of the caries process at every stage and characterisation of the carious activity of the lesion Developed due to inconsistencies in caries diagnosis Still however has an element of subjectivity ICDAS Scores Moderate Stage Caries Dark shadow from dentine with/without enamel Code 4 breakdown White or brown spot when wet Darkened area of intrinsic shadow (grey, blue, brown) ICDAS Scores Extensive Stage Caries A distinct cavity in opaque or discoloured enamel with visible dentine Code 5 Visible evidence of demineralisation (white or brown walls) ICDAS Scores Extensive Stage Caries An extensive cavity Visually able to see extension Code 6 into dentine Recap on the Structure of Dentine The mineral component of dentine is hydroxyapatite Organic material is collagen This is a vital tissue as the dentinal tubules are permeated with the cell process of the odontoblasts It therefore is able to defend itself from assault (alongside the pulp) We refer to this as the dentinal-pulp complex as the 2 tissues are intimately related So how does dentine caries progress through each stage to give these ICDAS scores? Macroscopic Dentine Caries – ICDAS Code 4 Progression from enamel to dentine demonstrates a change in the hardness of the substrate This causes a lateral spread of caries under the enamel This leads to grey shadowing This eventually leads to breakdown in the crown integrity  Macroscopic Dentine Caries – ICDAS Code 4 This is similar to the erosion of a cliff with bacteria being represented by the water Macroscopic Dentine Caries – ICDAS Code 5/6 As the enamel becomes further undermined it breaks away This leads to dentine exposure (ICDAS 5) and eventually an extensive cavity (ICDAS 6) The more destruction, the more difficult to restore Macroscopic Dentine Caries – ICDAS Code 5/6 Bacterial destruction makes the dentine softer This can be identified with a sharp probe but do not try this on the cavity floor (why not?) As the caries progresses, the surface becomes heavily infected dentine which can be ‘peeled away’ with an excavator. This is usually browner in colour Below this is less infected dentine which is harder How does this clinical appearance translate to histological appearance? Microscopic Dentine Caries Note this now shows as a ‘mushroom’ shape (different to enamel caries) This sample demonstrates the ‘undercutting’ of enamel as caries progresses along the ADJ through softer dentine  Microscopic Dentine Caries th The macroscopic appearance discussed matches to 4 key zones of the lesion. In addition, a 5 zone (tertiary dentine) is noted away from the lesion Microscopic Dentine Caries As these areas cannot be observed clinically, these can also be defined as caries ‘affected’ and ‘infected’ zones 1) Zone of destruction 5 43 2 1 2) Zone of penetration 3) Zone of demineralisation 6 4) Translucent dentine Affected vs Infected Dentine Zone of destruction Zone of penetration Zone of demineralisation Translucent zone  Zone 1 – Zone of Destruction The outermost, superficial, irreparable, necrotic area of destruction clinically as dark brown, soft and mushy 1) With rapid caries this may be soft and yellow 2) With slowly progressing caries is harder and browner 3) Mineral content is dissociated due to bacterial acid 4) Collagen matrix denatured by proteolytic enzymes 5) Bacterial load is very high 6) Dentinal tubule structure destroyed 7) This produces round areas of liquefaction termed ‘liquefaction foci’ within the tubules 8) Cracks then form at 90⁰ to the tubules and are termed transverse clefts Zone 1 – Zone of Destruction This represents caries infected dentine and needs to be removed which is easily done with an excavator 1. It cannot be repaired 2. Provides poor surface to bond 3. Inability to form a seal 4. Inadequate restoration support Zone 2 – Zone of penetration/bacterial invasion Within this zone the dentinal tubule structure still exists and liquefaction has not occurred The tubules are however invaded by bacteria These decalcify the dentine with acid They also dissolve proteins (proteolysis) This is also a layer of caries infected dentine Generally, most clinicians believe this needs to be removed and can be done so with a rose head bur. When would you not remove this zone? If not removed and sealed, if the restoration fails the bacteria will rapidly continue the process Zone 3 – Zone of demineralisation  Acid produced in the higher zones spreads down the un-occluded dentinal tubules  This acid easily demineralises the dentine  No bacteria are present in this area  This is the advancing front of the lesion  This may be very small (less than 1mm) Zone 3 – Zone of demineralisation  This may feel softer than sound dentine  This can be repaired by the dentine pulp complex  May be paler brown in appearance  This is considered caries affected dentine  Does not need to be removed Firm demineralised dentine that does not need to be removed Zone 4 – Translucent (Sclerotic) Zone This happens when acid initially starts to penetrate  The live odontoblast processes start to lay down calcification within the tubules making them hyper- mineralised  This leads to them becoming ‘plugged’ with mineral  This aims to slow acid and toxin penetration and protect the pulp Zone 4 – Translucent (Sclerotic) Zone  This may show radiographically as a whiter area below the caries  This is due to the hyper mineralisation  This area does not need to be removed Zone 5 – Tertiary Dentine Is not truly considered a zone as it is not within the lesion however it is a part of the process This is new dentine that is laid down at the pulp-dentine border away from PULP the lesion itself This is laid down to create more dentine between the pulp and the lesion to give the pulp protection Zone 5 – Tertiary Dentine This is produced when the pulp becomes mildly inflamed by advancing acid It has an irregular tubular structure and comes in 2 different types Reactionary Dentine 1) Deposited as a result of a mild irritant 2) Originates from surviving upregulated odontoblasts Reparative Dentine 1) Deposited as a result of a strong irritant 2) Local cell death in the odontoblast layer 3) Odontoblast like cells form which produce a much more irregular dentine structure Zone 5 – Tertiary Dentine  6 1. Zone of destruction 5 2. Zone of penetration 4 3. Zone of demineralisation 3 4. Translucent dentine 2 1 5. Tertiary dentine 6. Normal dentine Video for Review  This video summarises the process. Please view from 4:40 https://www.youtube.com/ watch?v=Y_o0ygwA6CI Thank You!