Basic Oral Physiology for Technologists PDF

Oral physiology for technologists Dr. Mahmoud Saeed Chapter one: Mandible Age Changes Figure (1) shows the lateral surface anatomy of the human mandible, while (fig. 2) shows its medial surface. Figure 1 shows lateral surface anatomy of the human mandible. Figure 2 shows medial surface...

Oral physiology for technologists Dr. Mahmoud Saeed Chapter one: Mandible Age Changes Figure (1) shows the lateral surface anatomy of the human mandible, while (fig. 2) shows its medial surface. Figure 1 shows lateral surface anatomy of the human mandible. Figure 2 shows medial surface anatomy of the human mandible.  The mandible at different ages: 1- At birth: Figure 3 shows the mandible at birth. Description: The mandibular canal is of large size and runs near the lower border of the bone. The mental foramen is near the lower border of the bone. The mandibular angle is obtuse (175°). 2- At childhood: Figure 4 shows the mandible at childhood. Description: Growth of the alveolar part, to afford room for the roots of the teeth. The mandibular canal is situated just above the level of the mylohyoid line. The mental foramen is between roots of mandibular 1st & 2nd deciduous molars. The mandibular angle is about the fourth year it is 140°. 3- At adulthood: Figure 5 shows the mandile at adulthood. Description : The mandibular canal runs nearly parallel with the mylohyoid line. The mental foramen opens midway between the upper and lower borders of the bone. The mandibular angle ranges from 110° to 120°. At old age: Figure 6 shows the mandible of completely edentulous person at old age. Description: The bone becomes greatly reduced in size. With the loss of the teeth the alveolar process is absorbed, and, consequently, the chief part of the bone is below the oblique line. The mandibular canal & the mental foramen are both close to the alveolar border. The mandibular angle: The ramus is oblique in direction and the angle measures about 140°. Chapter two: Physiologic Tooth Form 1- Facial and lingual aspects of maxillary/mandibular teeth: Is trapezoidal in shape with the largest side is incisal / occlusal while the shortest side is cervical. The significance of the trapezoid shape. - Provides interproximal space for interproximal gingival tissue, vascular supply, and bony support. - Allows interproximal contacts among the adjacent teeth that protects the interproximal gingival tissue from trauma during mastication. - Allows each tooth to occlude with two opposing teeth except mandibular central incisor and maxillary third molar preventing over eruption. 2- Proximal aspects: a- Anterior teeth It is triangular. its base is cervical while the apex is incisal. The significance of the triangular shape: - Facilitates incising and cutting. - Wide base provides sufficient strength to the crown. b- Posterior maxillary teeth It is trapezoidal in shape. the largest side is cervical while the shortest side is occlusal. The significance of the trapezoid shape: - Facilitates forces distribution during mastication. - Facilitates self-cleansing process. c- Posterior mandibular teeth Rhomboidal in shape with lingual inclination. The significance of the rhomboidal shape: - Lingual inclination brings cusps of the lower posterior teeth to the proper position with the opposing posterior teeth. - It maintains the long axis of maxillary and mandibular teeth are parallel. Sequelae of faulty restoration 1- Faulty size of the contact area: a- Open contact area (fig. 7) leads to; - Food impaction. - Caries production and periodontal diseases. Figure 7 shows open contact area. b- Heavy contact area (fig. 8) leads to; - Changes the anatomy of the interdental col. - Production of an interproximal area with disabled cleansing. Figure 8 shows heavy contact area (red arrow) and correct one (green arrow). 2- Faulty location of the contact area (proximal contour): a- Too occlusal contact area leads to shallow occlusal embrasure and flat marginal ridge. b- Too gingival contact area leads to reduced gingival embrasure. c- Too buccal or lingual contact area leads to obliteration of the buccal or lingual embrasure (Fig. 9). Figure 9 shows different proximal contours. 3- Faulty embrasures: a- Small or absent embrasure leads to additional stress on teeth and supporting structures. b- Too large embrasures lead to little protection to the supporting structures and food enforcement into the interproximal spaces (Fig. 10). 4- Faulty marginal ridge: a- Reduced marginal ridge height leads to loss of contact with the opposing teeth and impaction of food debris interproximally. b- Thin marginal ridge changes the occlusal anatomy (shallow or deep fossa) and it is liable to fracture. c- One planed marginal ridge produces premature contact during occlusion and increase the depth of the adjacent fossa (Fig. 10). Figure 10 shows faulty embrasures and marginal ridges. 5- Faulty facial contour (cervical ridge): a- Normal facial contour. b- Over contoured restoration leads to food deflection from gingiva resulting in under stimulation of the supporting structure. c- Under contoured restoration leads to laceration of the gingival tissue (Fig. 11). Figure 11 shows normal facial contour (a), over facial contour (b), and under facial contour (c). Chapter Three: Physiologic Tooth Movements Physiologic tooth movements are classified into pre-eruptive, eruptive, and post-eruptive movements. Our concern here is the post-eruptive movement during which teeth can compensate occlusal wear and interproximal wear and accommodate the mandibular growth. 1- Accommodation of the mandibular growth (14-18y): The mandible moves down word when grows so the mandibular teeth and the maxillary teeth move towards the occlusal plane to keep occlusion. This teeth movement occurred because of bone deposition at the socket fundus and the alveolar crest. Bone deposition at the socket fundus allows teeth to move towards the occlusal plane while bone deposition at the alveolar crest prevents root exposure. 2- Compensation of occlusal wear: On the long run teeth crowns become shorter due to occlusal wear. So, teeth move towards the occlusal plane to compensate that wear. This movement differs from the previous one. Because it occurs as a result of cementum deposition at roots apices so, the cervical third of roots become exposed. Note: when the opposing teeth lost, over eruption occurred. 3- Compensation of interproximal wear: During mastication, teeth move a minor movement that leads to interproximal wear. So that all teeth move in the mesial direction to compensate that wear. There are two factors control that movement the first is the transeptal fibers and the second one is masticatory forces. Note: these two factors control mesial drift phenomena. Orthodontic movement Periodontal ligament tissue orchestrates orthodontic movement. Periodontal ligament becomes compressed at the side of tooth movement direction. This compression activates osteoclasts to resorb bone. However, in the opposite side periodontal ligament becomes in tension that activates osteoblasts to deposit bone (Fig. 12).