Endoscience PDF

1 Rawan Asrawi Batool Al-Harthi Ibrahim Abu Tahun 1|Page  Endoscience Endodontics is from the Greek word (Endodontia) that means working inside or within the tooth so Endodontics is a branch of dentistry that deals with...

1 Rawan Asrawi Batool Al-Harthi Ibrahim Abu Tahun 1|Page  Endoscience Endodontics is from the Greek word (Endodontia) that means working inside or within the tooth so Endodontics is a branch of dentistry that deals with the cause, diagnosis, prevention and treatment of the diseases of dental pulp and peri-radicular tissues. Dental Pulp is a complex tissue that white tiny can have huge consequences in terms of pain disease and overall oral health. Also, pulp acts a security and alarm system for the tooth especially when the pulp is challenged. The pulp tissue and it’s interaction with other tissues plays central role in both local and Reference books for the study systemic health. of dental pulp. Pulp biology What is pulp? It’s origin is from Latin word pulpa which is any soft, moist, and slightly shapeless mass of material such as the soft, juicy, edible part of a fruit. It is also the pith of the stem of a plant or the soft or fleshly part of an animal body. In arabic we said: ‫لب الثمرة أو لباب الورق‬ -Dental pulp in science and medicine refers to the soft innermost part of the tooth containing nerves and blood vessels. -Pulp is unmineralized oral tissue composed of soft connective tissue, vascular, lymphatic and nervous elements that occupies the central pulp cavity of each tooth by either weight or volume. Majority of the pulp (75-80%) is water. There is no inorganic component in normal dental pulp (aside from the presence of pulp stones which are pathologically found within the pulp cavity of aging teeth). -when your patient is having pain, you go inside the tooth and takeout the nerve to make him feel better. Some people refer to the pulp as the nerve because pain emanates from it (‫) منه ينبعث االلم‬.Also inside pulp we will find blood vessels and packing cells, so the term pulp is the correct term. -Dental pulp may be removed from the root canal in one piece. In an examination it’s found to be a pink firm cohesive unit, rich in fluid and highly vascular maintaining its original shape. Why this is possible? Because pulp is principally composed of a gelatin like material called ground substance, embedded in the stroma are the cells, blood vessels and nerve fibers that all together make the loose connective tissue which is categorized as the dental pulp organ. -Dental pulp is a part of pulp-dentin complex, what we called endodontium. Having similar background which is the dental papilla, developmentally and functionally Pulp and dentine are closely related and therefore they considered as a complex. Although dentin and pulp have different structures and compositions there is a great deal of evidence that once formed they react to stimuli as a functional unit. 2|Page Architecture of the pulp: 1-peripheral zone or odontogenic zone. 2-pulp core or the central zone (more centrally located). They have four layers from innermost to outermost: (let's go back to oral histo) 1-The central zone or the central region of the coronal and radicular pulp which contains the large nerve trunks and blood vessels that begin to arborize toward the pulpal peripheral areas. 2-The cell rich zone that contains fibroblasts and undifferentiated mesenchymal stem cells. The most important thing about this zone that it serves as a reservoir for replacement of the destroyed odontoblasts. Although, most frequently it is observed in the coronal pulp, this zone also exist in the radicular pulp. 3-The cell free zone or cell poor zone (also zone of weil), which abounds in nerve fibers that have lost their outer wrappings (their myelin sheets). These terminal naked nerves are sepicific receptors of pain. Many of them enter the odontoblastic zone. While some of them terminate in tubules near pre-dentine and inner mature dentine to form subodontoblastic nerve plexus of Rashckow which is separated from odontoblast by cell free zone of weil. And it is located central to the cell free zone. 4-Odontoblastic layer (outermost layer) which contains odontoblasts adjacent to the predentine and mature dentine (their cell bodies in the pulp and cell process in the dental tubules). This layer is very important because when odontoblasts are irradiated or injured they contribute to one or more defense functions of the pulpal dentinal complex. Defense Functions: 1. Tubular sclerosis 2. Irritation or reparative dentine formation 3. Inflammation of underlying connective tissue. Structural element of dental pulp: components of dental pulp are basically the same as in loose connective tissue anywhere else in the body. It consists of cells, intercellular substance and intercellular fluid.  Cellular elements: 1-formative cells: The principle cells of the pulp are fibroblast and odontoblasts. 2-defensive cells: like plasma cells and mast cells 3-progenitor cells (dental pulp stem cells) : multi-potent stem cells, that have the potential to differentiate into a variety of cell types (forming other types of formative or defensive cells). This is important in the future of dental practice and dental treatments. It has been recently documented in studies the Regenerative capacity of dental pulp stem cells. 3|Page Functions of dental pulp; The dental pulp ascribes the 4 basic functions for all loose connective tissue: 1-formation of dentine: it’s the primary task of the pulp in both sequence and importance to provide vitality to the tooth, it forms dentine and it continues to do so throughout the life of the tooth until the main form of the tooth crown and root is created. Then this process slows and eventually it might be to complete halt. 2- protection function: Also formation of new dentine is a defensive measure against any harmful, physical, chemical and microbial irritants that might affect the pulp by creation of a new dentine in the face of irritants to minimize pulpal exposure and to enable the vital pulp partially to compensate for loss enamel or dentine caused by mechanical trauma or by disease. Tertiary dentine: is the defensive form of dentine. 3-nutrition: aiming to maintain the vitality of dentine, by providing oxygen and nutrients to the odontoblasts and their processes as well as continuing source of dentinal fluid this will maintain the vitality of dentine. Also, it keeps the organic components of the surrounding minimized tissue supplied with nutrition hopefully, it helps to prevent the tooth from becoming brittle and exposed to fracture. 4-sensory function: Like any other connective tissue, dental pulp requires a nerve supply to provide its primary, but related function which are vasomotor and defense. Some special characteristics of the pulp; that needs consideration: 1)A Low compliance environment At periphery there is a layer of highly sophisticated cells (odontoblastic layer) so the pulp is enclosed in rigid mineralized tissue. The ability of a pulp to increase in volume during episodes of vasodilation as in case of inflammation is quite restricted, and that’s why pulpal pain is very severe pain. So in the case of a pulp, we are dealing with a low compliance system which perform regulation of blood flow is of critical importance and this explains why relatively minor pathological events like inflammation that cause swelling elsewhere in the body lead in our case in the pulp to a compression on the pulp and resulting in severe pain. Ground substance is the environment that promotes life of the cells of the pulp; it is act as a median to transport nutrients to cells and metabolites of the cells to the blood vessels and lymphatic channels. It also acts as a barrier against the spread of microorganisms and toxic products. -Any changes in the nature or quality of ground substance will directly influence the inflammatory response or modulate retrogressive or what we call aging changes and this will decrease the ability of the dental pulp to response to injury and repair itself. -Chemical mediators such as edema and heat may alter the quality of the ground substance and they will lead to a vascular stasis and ischemia, also may result in local cellular death of the pulp. 2) A Microcirculatory System: No true arteries or veins enter or leave the pulp, so the circulatory system of pulp is a microcirculatory system whose largest components are arterioles or venules. 4|Page Metabolism of the dental pulp: -The rate of oxygen consumption in the pulp is low compared to most other tissue. The nerve fibers of the pulp are relatively resistant to necrosis and they are more resistant than other tissues to autolysis, and this will allow the pulp to function under varying degrees of ischemia this could explain how the pulp manages to withstand periods of vasoconstriction resulting from use of anesthesia employing epinephrine containing local anesthetic agents. -Long list of materials such as Eugenol, Zinc Oxide Eugenol, calcium hydroxide and silver amalgam have been shown that they inhibit oxygen consumption by pulp tissue, indicating that these agents capable of depressing the metabolic activity of pulp cells. Another thing is the application of orthodontic forces applied to human premolar for 3 days it was found to result in 27% reduction in respiratory activity of the pulp. -Any dentist who is manipulating dentine they should know about pulp biology because it is the scientific basis upon which we build the entire science of dental therapy as well as diagnosis and treatment planning. From embryonic point of view: -Importance of bell stage: during bell stage and we have odontogenesis that trigger amelogenesis and we end up having the epithelial root sheath. This is epithelial cells that descend down, so dentine formation starts to take place, and we end up having root formation which will complete its formation a couple of years once the tooth erupts. - Odontoblasts are basically depositing dentine and as they are walking their way down, dentinal space or pulpal space starts to get smaller, odontoblasts start to get crunched down and they get packed into each other and they are lining dentine and end up forming the dentinal tubules. -Those tubules are running along from dentino-enamel junction all the way to the pulpal surface and they are conical in shape (ultra-structurally). -if u take a histological section at the DEJ, look at the dentin in a square area, u have basically around 1% density of the surface of the dentin with diameter of tubules around 1 micron or less , at the enamel level there are approximately 76000 dental tubules per 1 mm2 of dentin - If we go all the way up at the pulp surface and take a histological cross section at the pulp area , we will find 40-50% of surface of the dentine occupied by these tubules (density of tubules increases toward the dental pulp). This is important because it’s mean when we go deeper or closer to the pulp: dentine increases its permeability so there will be leakage through dentine to the pulp. And this is why we have higher chance of infection and sensitivity the deeper we go toward the pulp from decay or deep restoration. Dentin-pulp complex: The Body of odontoblasts lies in the pulp. Odontoblasts processes are extended into the dentinal tubules and then a nerve fiber goes inside here and that gives innervation to the dentine, nerve fibers do not exist in every tubule, and send them to penetrate the dentin for a few micro meters that’s what creates the dentine-pulp complex and the reason why dentine has sensitivity. 5|Page Tubular nature of dentine: -The closer we get to the apex, dentinal tubules get amorphous which means that the upper half or the coronal half of root has dentinal tubules, but the apical half specifically the apical 1/3 of the root has amorphous dentine (no tubules). -this is very important due to tubular nature of dentine permits fluid movement to occur within the tubule when a stimulus is applied the odontoblastic processes are bathed by intercellular fluid from dental pulp or dentinal lymph. -any rapid increase in the rate of the outward flow of fluids is what triggers the nerve inside the dental tubule and that in term trigger sharp shooting pain to the patient that’s actually the mechanism of dental sensitivity and why if we run our explorer over live dentine after we cut dentine, patient will actually have a sensation. -Fluid movement in dentinal tubules due to the nature occurs when tubules are stimulated and this is very important and will be discussed later. -If you cut the tooth for crown preparation and let your tooth sit there after a while, you will get a phenomenon called dentinal sweating (feeling that the crown is full of fluid). This is basically the flushing of dentinal tubules with interstitial fluid and this is very important because it keeps it clean and prevents contamination of the pulp. Intrapulpal pressure: -the results of basic studies on both animals and humans: Pulpal pain is pressure mediated:  dental pulp pressure shows rhythmic changes coincidence with heart beats.  pulp pressure exhibits a close relationship with the blood flow to and from the dental pulp.  that pulp pressure is affected by vasoactive drugs and Directly correlated to temperature fluctuations. As a conclusion: pulpal pain is pressure mediated, so normal intrapulpal pressure has been measured at an average around 10 mmHg varies with each arterial pulse wave, a slight inflammatory response that raise the intrapulpal pressure to 13 mmHg might be a reversible response. However, the pressure 35 mmHg indicates an irreversible state - generally believed that increasing the pressure within the dental pulp induces pain while conversely elimination of increase pulpal pressure by removing inflamed or necrotic pulp tissue inside the root canal, this is accepted as a reasonable dental treatment to relieve symptoms of pulpal disease because you remove infection and bacteria the patient will feel comfortable. A unique sensory organ: The pulp is covered with a protective layer of dentine which is covered with enamel, so pulp might be expected to be quite unresponsive to stimulation, but despite. The low thermal conductivity of the dentine Pulp is undeniably sensitive to thermal stimuli, like ice cream and warm drinks. -So pulp is sensitive to thermal changes, even though its covered with low-conductive dentine. 6|Page Mechanism of dental and pulp pain: Pain is a complex phenomenon and it has both physiological and psychological components of perception and reaction to pain and it is influenced by drugs, emotions and it varies from patient to patient What happens here that the neurons relay the impulse to the thalamus where it is received as pain and this information is carried to a higher brain center (cerebral cortex) which is the information processing center and localized pain How do stimuli such as heat, cold, mechanical pressure and dehydration stimulate the sensory receptors of the pulp when they are applied to the outer dentin? It has been suggested by Brannsrom’s that; when dentine is heated or cooled, there will be a rapid movement of fluid in dentinal tubule that will mechanically deform the nerve fibers resulting in physical changes within dentine that provides energy to excite the sensory structures (nerve terminals) in the pulp-dentine junction, and this Theory is called (dentine sensitivity theory) (Brannsrom’s theory) Hydrodynamic theory of dentine sensitivity Relationship between thermal fluctuation and intrapulpal pressure: 1) Heat stimulation: - Heat causes vasodilation and subsequent increase in intra-pulpal pressure so if the pulp is intact there is a specific pulpal temperature that must be reached before there is pain from heat so application of heat to normal teeth (intact teeth) gives a delayed response while if the tooth inflamed already increased intra-pulpal pressure exists so we should expect an immediate painful response to gradual or sudden heat increase (More vasodilation causes more intra pulpal pressure = more pain). 2) Cold stimulation: normal or intact pulp: response to cold is immediate, why? Because cold decreases the Intrapulpal pressure leading to strong capillary forces (vasoconstriction), and it has to do with the intratubular fluid movement. -Pain from cold is due to a sudden activation of sensory units as a result of the quick contraction of enamel; because there is a difference in the coefficient of expansion between enamel and dentin that will produce a jarring at the DEJ. What happens if enamel is absent? (due to fracture or caries or at the cervical area the response is due to direct effect of cold on poorly insulated nerve endings, such painful response may also due to the movement of fluid in the tubules because the coefficient of expansion of fluid is greater than that of the tubule wall and this will cause pain and trigger the nerve fibers in the region. -If the cold stimulation is maintained: the pain originally provoked will subside because of the adaptation will occur (as in eating ice cream the first bite is painful then your nerves adapt) -What is more important is in advanced acute pulpitis (the only case where cold relieves the pain immediately),Because we have coronal necrosis present in varying degrees, the cold here will not 7|Page exacerbate painful response, in contrast it will relieve the patient’s symptoms immediately, why? Because the cold causes vasoconstriction so it will reduce the blood volume and this will lower the Intrapulpal pressure to a sub-threshold level and that’s why removal of the cold will result in the return of pain within 30 to 60 seconds as the intrapulpal pressure returns to its original sub-threshold level Heat and cold are two different diagnostic tools: A painful response to cold is faster than heat, because the faster movement of the inter tubular fluid to contractive stimuli (cold) than to expansive stimuli (heat) ,So as a conclusion on this issue heat and cold represent two different phenomena Free nerve endings of the CNS: -They are responsible for sensation in the pulp. - Free nerve endings are ubiquitous because they are the only nerve endings found in the cornea, ear drum and dental pulp (they are the simplest sensory nerve endings). These are devoid of any auxiliary structures this means that they have neither specifity nor sensitivity , regardless of the source of stimulation (if it is heat, cold, etc.) they can only register pain no matter what the applied stimulus may be because they lack adequate proprioceptive fibers that allow them to localize pain Distribution of neural elements: There is about 2-3 thousand nerve endings will enter the pulp of the teeth, what is the type of these nerves? There are 2 main types: A & C fibers A fibers divided into: A delta fibers : (rapid and sharp pain sensation) - the most numerous (90% of alpha fibers) - are primarily nociceptors (they create sharp shooting pain associated with the tooth pain or with pulpal pain). A beta fibers: The cold sensitivity is triggered by alpha delta fibers - Only 10% of alpha fibers - Are primarily mechanoreceptors (They are proprioceptors) **From this distribution from 90% to 10%, the dental pulp is primarily a nociceptive kind of organ. This can explain why patient has difficulties in localizing the pain that coming from pulp When the inflammation starts to C fibers – the pulp proper: (involved in slow pain) spread deeper it ends up in the pulp proper where c fibbers get - stay at the middle or in the center of the pulp although they may branch out. involved and the patient will end - responsible for heat sensitivity up having heat sensitivity *Now it starts to make sense why pulpitis starts first with cold sensitivity and then at later stages it moves on to heat sensitivity. - As you know as the pathway progresses, alpha delta fibers which are located at periphery are first get involved in the inflammation and as the inflammation starts to spread deeper into pulp tissue and ends up with pulp center, now the C fibers end up getting involved so patient ends up having heat sensitivity. 8|Page Subodontobastic Plexus of Raschkow: is formed from peripheral nerves fibers (A delta), and these fibers are located at the periphery so they will die first because they are located closer to the outer surface of the tooth. Also, it's the last major structure developed in the tooth, it's usually until after tooth eruption. Clinical tests: Electric pulp test: Why they tend to be unreliable specially in young patient? (we are talking about electric pulp testing which is used to assist the vitality of tooth whether the tooth is vital or not) - Why it is unreliable? Unfortunately Because the pulp alpha delta fibers respond to electric pulp testing, conventional electric pulp tester probably lacks the ability to stimulate the C fibers deep in the pulp and this may explain why it is possible for a tooth that fails to respond to pulp test, it gives a negative response, but when we start introducing our files into root canal it is sensitive to edontodontic instrumentation. - The fact is that subodontoblastic nerve plexuses are the last major structure to develop in tooth from patients 15 to 17 years’ old and this should make us very cautious when we perform electric pulp testing on very young patients. Percussion test: (from arak u can skip it) Here we use a mirror for this purpose. Actually inflammation should reach the periodontal ligament because nociceptive fibers are localized only at the periodontal ligament. So response to percussion test or pain to percussion test means that inflammation and infection has reached the periapical region.  Biting response: -What happens to patient when we ask him to bite on his teeth? if there is pain, we are having patient biting into a tooth sloth and this will result in cuspal deflection due to occlusal forces. - What is the sequent of this occlusal forces or this deflection? Movement of fluid which is translated into the same issue of movement of fluid in dentinal tubules. When there is a crack in the tooth we should know that this will allow opening and closing of crack which will increase the fluid movement in turn this will create sharp pain. 9|Page  if we have a leaking restoration: The margin ends up acting like a crack in these cases and again and again, fluid movement in dentinal tubules which actually according to Brannstorm’s Theory of dentine hypersensitivity will induce pain. ‫ ووفقنا لما‬،‫ اللهم يسّر لنا كل عسير‬.‫ واجعله عام خير وبركة‬،‫ اللهم بارك لنا في هذا العام الدراسي‬،‫ والعمل الصالح‬،‫اللهم ارزقنا العلم النافع‬.‫تحب وترضى‬ THE END OF SHEET #1 10 | P a g e