Transcript Seminar IV
Management of Caries Caries Advancement Enamel • Covers Anatomical Crown • Translucent • Enamel Rods (perpendicular to DEJ and tooth surface) • Requires a base of Dentin to withstand forces • Hardest substance in the human body • Incapable of repairing itself Histology of Enamel Enamel Composed of very tightly packed hydroxyapatite crystallites organized into long columnar rods (prisms). Each rod starts at DEJ and extends as a wavy continuous column to the surface of the crown. Unstained, 100x Dentin • Formed by Odontoblasts • Darker than Enamel, less translucent • Hydroxyapatite crystals and collagen type I Harder than bone, softer than enamel • Dentinal tubules Histology of Dentin Dentinal Tubules Unstained, 400x Dentinal tubules allow fluid movement, ion transport necessary for remineralization and apposition and perception of pain Chemistry # ENAMEL – 96% Inorganic (Mineral Hydroxyapatite) 2% Organic (Protein) 2% Water # DENTIN 68% Inorganic (Mineral Hydroxyapatite) 22% Organic (Collagen) 10% Water Primary Dentin • Type of Dentin formed before and shortly after eruption Secondary Dentin • Continuation of Primary Dentin (forms at slower rate as tooth ages and with structural irregularities) • Circumpulpal Dentin (laid down incrementally every day) • Tubules take different directional pattern Reparative Dentin • Formed in response to irritation (attrition, abrasion, erosion, trauma, caries, operative procedures, other irritants) • Confined to localized irritated area of Pulp Chamber • Defense reaction to an area of injury • Structurally and chemically different from Primary and Secondary Dentin Sclerotic Dentin • Results from aging or mild irritation • Tubular content is replaced by calcified material • Tubules are obliterated • Intertubular Dentin is smooth Dead Tracts • Regions of empty Tubules • Degeneration of Odontoblastic Processes • Pulp is not stimulated to form replacement Odontoblasts The Pulp • Pulp is the connective tissue situated within the rigid encasement of mineralized dentin • Functions of the Pulp # Formative # Repair # Nutrition # Sensory # Protection/Defensive Relationship Pulp - Dentin • Permeability of dentin regulates the rate of diffusion of irritants that initiate pulpal inflammation • Odontoblasts are arranged peripherally in direct contact with dentin matrix • This close relationship between the dentin and pulp create a functional unit called the PULPODENTINAL COMPLEX Dentinal Tubules • Extend through entire thickness of dentin from DEJ to the pulp • S-shaped in the crown, less S-shaped in the root, almost straight in the cervical aspect • Inverted cone shape with smallest dimensions at the DEJ and largest dimensions at the pulp Dentinal Tubules • Number of tubules increases from DEJ to pulp (15.000 vs 65.000/sq mm) • Because both the density and diameter of the tubules increase with dentin depth from the DEJ, the permeability of dentin is lowest at the DEJ and highest at the pulp • Axial dentin is more permeable than occlusal dentin Enamel Caries • Demineralization results in pores enlargement # roughness + loss of shine • Demineralization progresses # pores increase in size • Through large pores bacteria may invade subsurface Enamel Caries ENAMEL CARIES This shows enamel prisms which have been extensively demineralized revealing the microanatomy of the prisms and the interprismatic substance. This represents initial surface breakdown of enamel and is the next stage after the white spot lesion. Enamel Caries – clinical characteristics of „white spot” lesion # loss of normal translucency of enamel with a chalky white apperance, particularly when dehydrated # a fragile surface layer susceptible to damage from probing particularly in pits and fissures # increased porosity particularly of the subsurface, with increased potential for uptake of stain Enamel Caries – clinical characteristics of white spot lesion # reduced density of the subsurface that may be detectable radiographically or with transillumination # a potential for remineralization with an increased resistance to further acid challenge # the reversed lesion will either regain normal translucency or the chalky appearance may remain and take up stain Microscopically, several zones have been identified. 1. Translucent Zone 2. Dark Zone 3. Body of the Lesion 4. Surface Zone Zones of Incipient Lesion Zones of Incipient Lesion # Translucent Zone The deepest, structureless appearance (quinoline + polarized light) # Dark Zone doesn’t transmit polarized light (pores too small to absorb quinoline) Zones of Incipient Lesion # Body of the Lesion - The largest portion, the largest pore volume varying from 5% to 25% at the center - Bacteria may be present # Surface Zone - Relatively unaffected (saliva, fluoride), serves as a barrier to bacterial invasion Dentinal Caries # Caries produces a variety of responses in dentin: i) pain, ii) demineralization, iii) remineralization, iv) apposition # The level of dentinal reaction to caries can vary depending on clinical advancement (slowly-, moderate-, rapidly advancing lesions) and acid level. # The dentin can react to low and moderate intensity caries attacks as long as the pulp remains vital and has an adequate blood circulation Dentinal Caries Caries advancement in dentin proceeds through three changes: # Demineralization by weak organic acids # The organic material of the dentin, particularly collagen, degenerates and dissolves # The loss of structural integrity is followed by invasion of bacteria Dentinal Caries "Dentinal sclerosis" and "reparative dentin" slow down microbial invasion. # In the earliest stages of exposure to the microorganisms of dental caries, there is an effort to seal off the tubules, increased calcification # The result is a visible change known as „transparent dentin” or, better, "dentinal sclerosis." # In addition to this pulpal odontoblasts, stimulated by the advancing carious lesion, will rapidly deposit dentin. Dentinal Caries # The dentinal tubules in this new dentin are irregular, an arrangement that makes it less permeable to microorganisms. # Histologists cannot seem to decide what to call this newly-formed dentin; the terms "irregular dentin," "reparative dentin," "secondary dentin," and "tertiary dentin" all have been used. Dentinal Caries # Dentinal sclerosis and reparative dentin may be a successful deterrents if the carious lesion progresses slowly. # Usually, however, the dentinal tubules are invaded and the occupant odontoblast is killed in the process. Dentinal Caries Destruction of dentin exposes the pulp to bacterial invasion. # As microbial invasion progresses along the dentinal tubules, acid production decalcifies surrounding dentin causing a fusion of them. # As decalcification continues, clefts appear; they are oriented perpendicular to dentinal tubules and cross a number of them. Dentinal Caries # These clefts are responsible for the flaking observed by dentists as carious dentin is removed during cavity preparation. # At this point it is important to realize that carious dentin is loaded with microorganisms and that when the pulp chamber is finally reached, bacterial invasion of the dental pulp will ensue Dentinal Caries Dentin Caries Horizontal clefting is revealed here and this occurs at right angles to the dentinal tubules. The process of beading, coalescence, and clefting typifies the mode of progression of dentinal caries. Dentinal Caries Zones of Dentinal Caries Zone 1 Normal Dentin # The deepest area # Tubules with odontoblastic processes # No bacteria or crystals found Zones of Dentinal Caries Zone 2 Subtransparent Dentin • Demineralization of the intertubular dentin • Damage of the odontoblastic processes • Crystals in the tubule lumen Affected dentin • Remineralization is possible -Softened -Demineralized -No bacteria -Repair is possible Zone 3 Transparent Dentin • Carious dentin – softer • Loss of mineral from the intertubular dentin, many crystals in the lumen of the dentinal tubules • No bacteria, collagen remains intact Zones of Dentinal Caries Zone 4 Turbid Dentin – Zone of bacterial invasion – Widening and distortion of the dentinal t – Dentinal tubules filled out with bacteria – Collagen is irreversibly denatured Zone 5 Infected Dentin – Great numbers of bacteria filling the t – Granular material in the intertubular spa Infected dentin -Softened -Demineralized -Contaminated w/bacteria -Requires removal Zones of Dentinal Caries Sclerotic dentin (s.d.) # Result of remineralization of transparent dentin # In slowly advancing lesions # Shiny, dark, hard (hypermineralized) # Function – to wall off a lesion by sealing the tubules # S.d. shows ideal final excavation depth (natural barrier that blocks penetration of toxins and acids) Pathology of Dentin Dentin Caries This is a zone of infected tubules. Pathology of Dentin Dentine Caries In these frames, bacteria in the dentinal tubules are demonstrated by special stains.