Pulp Irritants Lec 7 PDF

Pulp Irritant Lec 7 _____________________________________________________ The dental pulp may be exposed to a number of irritants that are noxious to the health of the pulp and jeopardize the functions of the pulp. Irritants can be classified as being short-term, long-term or due to trauma. Each typ...

Pulp Irritant Lec 7 _____________________________________________________ The dental pulp may be exposed to a number of irritants that are noxious to the health of the pulp and jeopardize the functions of the pulp. Irritants can be classified as being short-term, long-term or due to trauma. Each type of irritant or injury will have a different effect on the pulp in general, the effects will be acute inflammation, chronic inflammation or necrosis. Short-term irritants will usually cause acute inflammation which will then be followed by resolution of the inflammation and repair of the tissue since the irritant does not persist or is no longer occurring. Common examples of short-term irritants are the cutting or drying of cavities during tooth preparation and traumatic injuries that have not displaced the tooth so the apical blood supply has not been disrupted. In contrast, typical long-term irritants are dental caries, restorations breaking down, cracks, erosion and chemical substances which all lead to the loss of tooth structure. Long-term irritation will cause chronic inflammation of the pulp and, if left for long enough, pulp necrosis which will then be followed by infection of the pulp space. Trauma that causes displacement (luxation or avulsion) of the teeth will result in severing of the apical blood vessels. In teeth with fully developed roots, these blood vessels will often not be able to heal and revascularize the pulp. Therefore, in these cases, the response of the pulp to the injury is immediate necrosis. Subsequently, the necrotic pulp may become infected. The pulp irritants can be classified according to the cause of irritant: I. Microbial II. Physical III. Irradiation IV. Chemical 1- Microbial Irritant: This includes a- caries which is the most prevalent irritant. b- Periodontal disease. c- Contamination of an exposure of the pulp by microorganisms. d- Infection through the apical foramen. (This is very rare), could be systemic such as tuberculosis, leprosy, actinomycosis e- Bacterial microleakage : Microorganisms present in dental caries are the main source of irritation of dental pulp and periradicular tissues such as; streptococci, lactobacilli and actinomyces The population of microorganisms decreases to few or none in the deepest layers of carious dentin. The response of pulp to bacteria depends on factors, such as: 1- The speed of bacterial ingress and the speed of progress of caries, which can be slow, rapid or completely inactive (caries tends to be an intermittent process, with periods of rapid activity alternating with periods of quiescence). Fortunately, the healthy pulp responds by depositing a layer of reparative dentine over its pulp surface, thus walling it off. 2- The pulp response is also related to the thickness and degree of calcification of the remaining dentine, since dentine permeability can be reduced by dentinal sclerosis and reparative dentine formation. 3- If the distance between the caries and the pulp is 1 mm or more, pulp inflammation may be negligible. When the caries reaches within 0.5mm of the pulp, there is a significant increase in the extent of inflammation, but the pulp becomes acutely inflamed only when the reparative dentine is invaded by irritants such as bacteria or their toxins. After pulp exposure, bacteria colonies are persist at the site of necrosis. Pulp tissue may remain inflamed for long period of time and may undergo eventually or rapid necrosis this depend on several factors: 1. Virulence of bacteria 2. The host resistance. 3. The amount of circulation. 4. Lymph drainage. II-Physical irritant: 1- Mechanical A- Tooth preparation (caries removal or crown preparation). Pulp trauma results when the pulp is closely approached or the dentin is extensively removed. Over cutting during cavity preparation, whether a pulp is exposed or not is one of the greatest damages to the pulp. Not only the depth of cavity affects the pulp, but also the width of the cavity has the same important. Pulpal damage is roughly proportional to the amount of tooth structure removed as well as to the depth of removal. A full crown preparation damages every single coronal odontoblast (cutting of more surface area leads to more damage). B-Orthodontic movement: The force of movement during orthodontic treatment creates disturbance in the circulation of the pulp that is similar to those found in periodontally involved teeth. If the force beyond the limitation of physiologic tolerance, blood vessels in the periodontal ligaments may rupture with resultant hemorrhage which leads to loss of the nutritional supply to some pulp cells. If a hemorrhage occurs from larger vessels of the pulp the entire pulp become necrotic. In addition, orthodontic movement may initiate resorption of the apex, usually without a change in vitality. C-Tooth fracture (acute trauma): Which occurs by either direct trauma to the tooth or indirect trauma to the jaw, in addition sever occlusal pressure to tooth with large filling can cause fracture. Sometimes, fracture is related to the bacterial invasion that follows the accident. Untreated bacterial invasions will decrease any possibility of sustained vitality. If fracture occurs through the root, this will lead to disrupt the vascular supply that injured coronal pulp often loses its vitality. D-Abrasion (chronic trauma): Is abnormal tooth surface loss resulting from direct frictional forces between the teeth and external object or from frictional forces between contacting teeth in the presence of an abrasive medium such wear is caused by improper brushing or other habits such as holding a pipe between the teeth , tobacco chewing and chewing on hard objects such pen or pencils. Tooth brush abrasion is the most common example and it’s usually seen as sharp wedge-shaped notch in the gingival portion of the facial aspect of teeth. E-Attrition: Is a mechanical wear of the incisal or occlusal surfaces due to functional or parafunctional movements of the mandible (tooth grinding or bruxism). Pulp death or inflammation related to the incisal wear is seldom, pulp has ability to lay down dentin, but when a severely worn tooth occur (i.e. attrition exceed the rate of deposition of reparative dentin) the pulp becomes necrotic with an observable incisal opening into the pulp chamber. It is important to determine and eliminate the underlying cause (abrasion or attrition) in order to achieve effective treatment. If the tooth is hypersensitive so we can relief that by topical fluoride, fluoride rinse, dentinal bonding agents, or restoration. 2- Thermal: During any tooth preparation, heat will generate and this causes dehydration to dentine and aspiration of moisture through dentinal tubules. Therefore water should be directed onto the tooth to prevent any damage due to heat generation. Thermal irritation affected by type of bur, speed, pressure, way of use (intermittent), width and depth of the cavity III-Irradiation irritant: The pulps of the teeth are notably affected in patient who is exposed to deep radiation therapy for malignant growth in head and neck region. In time, odontoblasts cell and other cells will become necrotic, the salivary gland will be affected and resulting in decreasing of salivary flow. In this case, endodontic treatment can be carried out. IV- Chemical irritant: 1-Cleansing agents: These materials (such as chelating agents and dentine conditioner) are used to reduce microorganisms on the cut surface of dentin, and to remove the smear layer that remains on the dentin after cavity preparation. When we remove this smear layer a liner or cement would adapt better to the cut surface of dentin. Cleansing agents contain either an acid or a chelating agent such as ethylenediamine-tetraacetic acid (EDTA). The incidence of pulpal inflammation increased when cavities were treated with an acid cleansing agent before being filled. Acid cleansing agents greatly increase the permeability of dentinal tubules thus enhancing penetration of the dentin by irritating substances. 2-Erosion: Erosion is the superficial loss of dental hard tissue due to chemical process not involving bacteria. The clinical appearance may vary. Erosion (demineralization of superficial hard tissues) is evident in the facial or lingual surfaces tooth structure. In these cases, the dental lesions generally present a rounded, cupped-out defect initially confined to the enamel, if left untreated, the loss of tooth structure due to the chemical attack will accelerate once dentin has been reached, and deeper pattern of destruction will be seen. The causes of erosion are: 1- Extrinsic factors a- industrial acids: Can be carried in gaseous form in the air in heavily polluted areas and may cause demineralization of the labial surface of anterior teeth. b- Variety of food and drink of acidic nature with frequent ingestion may cause problems e.g. low PH cola drinks (including diet cola), fruits juices may cause erosion. c- Certain medications Alack of gastric acid may be compensated for by the oral administration of concentrated hydrochloric acid with advice that it should be taken through a straw or glass tube. Erosion on the lingual surface of the upper teeth is evidence of this problem. 2- Intrinsic factors Such as gastric acids, are the most common causes. Chronic vomiting will affect the palatal surface of the upper teeth. 3-Filling and lining materials: Certain filling and lining materials could cause irritation of the pulp tissue, such as silicate filling material and acrylic filling material. 1- Silicate filling material: is extremely damaging to pulp tissue especially when they are used without liners. It’s rarely used as a restorative material today. 2- Composite filling materials: The source of irritation are: -irritation caused by dentin conditioning and smear layer removal, -monomer of matrix and undercuring,, placement of an unfilled bonding resin against deeply etched dentine because of the release and diffusion through dentine of toxic chemicals from the resin, pulpal damage will result if placed directly on pulp floor.