Histopathology of Enamel Caries Lecture Notes 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 appropriate dent...

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 ‘Aetiology of Dental Caries’ Susceptible tooth surface Caries Lecture Time Plaque Bacteria Fermentable Carbohydrate Pre-reading ‘Histology of enamel and dentine’ Lectures Histopathology of Enamel Caries Learning Objectives: By the end of the session you will be able to; Describe the clinical appearance of enamel caries Describe the histology of enamel caries Be able to identify and name the 4 zones of destruction in enamel caries Be able to describe the clinical appearance of enamel caries in relation to its histopathology 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 Score The international ICDAS was A clinical scoring ICDAS allows Developed due to caries detection developed for use system used to detection of the inconsistencies in and assessment in clinical diagnose caries caries process at caries diagnosis system research, clinical every stage and practice and for characterisation epidemiological of the carious purposes activity of the lesion ICDAS Score Sound tooth No evidence of caries when tooth surface is wet No evidence when tooth surface is dry Tooth clinically sound Score 0 ICDAS Score Initial Stage Caries No evidence when tooth surface is wet After air drying first visual signs seen White spot and/or brown carious discolouration Code 1 ICDAS Score Initial Stage Caries Distinct visual changes in enamel Visible when wet and dry Code 2 ICDAS Score Moderate Stage Caries Localised enamel breakdown without visible dentine exposure Visible when wet and dry Prolonged drying reveals loss of enamel integrity Code 3 How does this apply to the histological appearance? Enamel Caries Microscopic Appearance SEM (scanning electron microscope) Enamel Caries Microscopic Appearance  Every carious process starts with the slight etching of the enamel surface  This occurs under the dental plaque  This occurs frequently and is reversible  The scan to the right shows healthy enamel adjacent to this ‘etched’ enamel Enamel Caries Microscopic Appearance  Under cariogenic circumstances the tooth will dissolve further resulting in microporosities in the enamel surface  These are typically located at prism boundaries (see earlier lectures) Enamel Caries Micro/macroscopic Appearance  The first clinical signs are white spots  These appear white because a greater proportion of incoming light is being scattered compared to the surrounding enamel  This is due to increased porosities as the mineral is lost.  The air (or electrolyte) in these porosities has a different refractive index to sound enamel Enamel Caries Micro/macroscopic Appearance  Where these porosities occur, white spot lesions can incorporate exogenous pigmentation. This can make the lesion appear brown.  This may suggest that a lesion has been present for a longer period of time however, does not guarantee this Established Enamel Caries Histology Established enamel caries (still within enamel, not extending into dentine) has 4 distinct zones Established Enamel Caries Histology Established Enamel Caries Histology These present as a ‘wedge’ shaped lesion with the point of the wedge towards the dentine in smooth surface caries and towards the enamel surface in pit and fissure caries Established Enamel Caries Histology In order to identify all histological zones, the samples need to be cleared using a clearing agent such as quinoline. This is used commonly as it has an identical refractive index to enamel The classical zones of enamel caries are then identified due to differences in the amount and size of porosities. They are identified using transmitted light microscopy Using different clearing mediums of varying optical refractive indices with transmitted light microscopy or polarised light microscopy, the size of the porosities and pore volume can be obtained  1. Surface Zone This is the outermost zone of the lesion Can also be referred to as the intact or pseudo-intact surface It has a relatively high mineral content Has a pore volume below 5% The reason the pore volume is lower than deeper areas of the lesion is due to its ability to remineralise. This occurs as this area is in contact with mineral ions in saliva/plaque on its surface  2. Body of the Lesion This is the zone below this surface zone and makes up the majority of the lesion. This is the area that is visible on conventional radiographs This demonstrates porosities of a large diameter Pore volume varies from 5-25% Appears translucent with striae of Retzius well marked  3. Dark Zone This is a thin layer below the main body of the lesion Termed the ‘dark zone’ as has small porosities which the clearing medium cannot enter and hence appears dark under light microscopy The pore volume is 2-4% Suggestion of some remineralisation in this area Possibly due to lipid and protein presence that may hamper the mineral precipitation  4. Translucent Zone This is the layer at the advancing edge of the lesion This is the initial area of destruction as part of the carious process This has a pore volume of 1% (sound enamel 0.1%) This is due to the early demineralisation Initial dissolution occurs along the gaps between rods Video for review  This video summarises the process. Please view from 4:40 https://www.youtube.com/ watch?v=Y_o0ygwA6CI Thank You!