Dental Anatomy PDF 2024

12 Lajneh Teejan Lajneh Wisdom Siham Al-Arag  Physiology of Permanent Dentition “From chapter 5 of wheeler's book” ▪ The phrase (form follows function) means that, due to the evolutionary process, the morphological features of the teeth are fitted to the activities of thi...

12 Lajneh Teejan Lajneh Wisdom Siham Al-Arag  Physiology of Permanent Dentition “From chapter 5 of wheeler's book” ▪ The phrase (form follows function) means that, due to the evolutionary process, the morphological features of the teeth are fitted to the activities of this part. -The concept of form and function explains the interrelation of the shape of some part and its function. In dentistry, this is applied to the entire masticatory system, which acts as a highly coordinated functional unit it’s called multi-functional unit of orofacial. Form of each component of the masticatory system is closely related to its individual functions and to that of the whole system including: mastication, deglutition, phonetics (responsible for the sound) , aesthetics and maintenance ( for supporting tissue ). The primary function of teeth : Is to prepare food for swallowing and to Facilitate digestion. Adapted Form → Different types of teeth with their respective form are adapted to incise, shear and grind food, for example I, PM and M Adapted alignment→ protect the supporting periodontal tissues against trauma during mastication, facilitate the jaw movements, speech and enhance aesthetic appearance of face. ‘’Alignment’’ means upper & lower teeth have normally a curve, how much spacing between teeth, how much they go from 8 or 7 on right side to the other 8 or 7 on the left side, we can draw a line - In order to understand the form and function of teeth, we must consider these aspects one by one: 1- SIZE OF CROWN AND ROOT Crown and root should be proportional to each other and to the jaw size. Size and shape of roots →reflect function of respective teeth, ▪ e.g , canine teeth located at the corners of the mouth → longest roots ,also extra size and length of the canine root ensures enough anchorage and support for bear shear forces. Maxillary and mandibular molars that perform most part of trituration of food → need multiple roots to withstand the masticatory forces. Trifurcated roots of maxillary molars give a tripod arrangement in the alveolar bone (1 palatally & 2buccally) that provides great anchorage.  Developmental depressions on the lateral surfaces of the root anchorage in the alveolar bone. (increases surface area of contact Between root and alveolar bone) A- Canine B- Trifurcated upper 6 2- TOOTH FORM AND JAW MOVEMENTS Incisal and occlusal forms of the teeth have a direct influence on the jaw movements, relation of tooth form and jaw relation can be understood by comparing human jaw movements animal’s jaw. (e.g dogs ,wolves) -Animals have equal sized jaws while in humans, maxillary and mandibular jaws are not perfectly equal sized→ maxillary arch (bigger) overlaps the mandibular arch Labially and buccally in horizontal plane, it’s called ( interlocking jaws ) (interlocking jaws = maxilla overlaps mandible) increasing complexity of jaw movement is associated with increasing complexity of occlusal anatomy of teeth. TMJ (high complex joint has hinge and rotation movement) is specialized in humans and occlusal anatomy of teeth is complex. Interlocking jaws, conical form of only canine teeth and non-equal sized of jaws contribute to high complexity of TMJ movements: -high complexity of occlusal anatomy surface -prognathic jaws -prominent canines limit lateral jaw movements 3-INTERPROXIMAL SPACES When viewed from facial or lingual aspects, we can see teeth are narrower at cervix mesio-distally than they are towards the Occlusal surfaces→ this arrangement creates triangular/pyramidal shaped Space between the approximating teeth just cervical to the contact areas. -The base of the triangle is at the alveolar process between the adjacent teeth; --The sides of the triangle are formed by the proximal surfaces of the teeth -The apex of the triangle is at the contact area of the two teeth. ▪ Function of interproximal spaces: accommodate and protect interproximal gingival tissue. ▪ The gingival tissue that fills the interproximal space is called the gingival papilla/interdental papilla (it is a projection or elevation) ▪ Papilla of anterior teeth is pyramidal ///Papilla of posterior teeth is more broad The part of interdental gingival tissue that Lies below the contact area and extends facio-lingually is called The Col → junction between facial and lingual papilla The col is only present in posterior teeth PM &M Anterior teeth don’t have gingival col because two Papilla meet at one point. 4- PROXIMAL CONTACT AREAS (tight contacts between adjacent teeth) Contacts area vs contacts points Each tooth has two contact areas, the Mesial and the distal, the mesial contact area of one tooth faces the Distal contact area of the adjoining tooth located mesial to it, Except: ▪ last molar → 3rd molar or 2nd molar (when 3rd molar is absent), is in contact only with the tooth mesial to it. (doesn’t have distal contact area) ▪ the maxillary and mandibular central incisors are the only teeth that have their mesial Surfaces facing each other (mesial-mesial contact) Proper contact relations and combined anchorage of al teeth ensure: -whole dental arch function as one unit -masticatory forces are well developed -occlusal stability -prevent food impaction  -protect interproximal gingiva Position of contact areas depend on the type and form of the crown and alignment of teeth. Position of contact areas can be examined from two views: 1- Incisal/Occlusal view: It shows the relative position of the contact areas labiolingually/buccolingually , and are smaller in anterior teeth. 2- Facial (labial/buccal) view: It gives the relative position of the contact areas cervicoincisally/cervico-occlusally. Upper Lower As we move posteriorly 1-less length of crown 2-contact area become more cervically positioned from midline Distal Contact area always more cervically placed compared to mesial 2 exceptions: a- Mandibular 4 (first Premolar) → mesial contact area more cervically located (opposite of other teeth) b- Lower central incisors have identical mesial and distal contact points → at same level ‫سال َمةَ فيها تَركُ ما فيها‬ َ ‫إِنَّ ال‬ َ ‫على الدُنيا َوقَد‬ ‫ع ِل َمت‬ َ ‫َفس تَبكي‬ ُ ‫الن‬ ِ ‫ِإ اال الَّتي كانَ قَب َل ال َمو‬ ‫ت بانيها‬ ‫ت يَسكُنُها‬ ِ ‫دار لِل َمرءِ بَعدَ ال َمو‬ َ ‫ال‬ ‫خاب بانيها‬ َ ‫َوإِن بَناها بَش ٍ اَر‬ ‫طاب َمس َكنُها‬ َ ٍ ‫فَإِن بَناها بِخ‬ ‫َير‬ ‫ علي بن أبي طالب رضي هللا عنه‬- 5- EMBRASURES/ SPILLWAY It is the V shaped or triangular space between 2 adjacent teeth from incisal or occlusal aspect, narrower at contact area widest from toward incisal edge. Functions of Embrasures 1-The embrasures provide a spillway for the escape of food during mastication. 2-They reduce forces imparted on teeth during reduction of any hard food material. 3-They prevent food from being forced through the contact area 4-They make the tooth self-cleansing through saliva 5-Embrasures and contact areas protect the gingiva from undue trauma 6-FACIAL AND LINGUAL CONTOURS 7-CURVATURES OF CERVICAL LINE: mesial and distal a- In all teeth, the extent of the curvature is greater mesially than distally. b- General, the curvature of cervical line on distal surface is 1mm less than that of the mesial surface of the tooth. c- In both arches ,the anterior teeth exhibit greater CEJ curvature than posteriors The cervical line curvature is maximum at mesial of central incisor 3.5 mm, from here it diminishes gradually to 0.0 mm at the molars, where there is no curvature at all. 8-Imaginary occlusal curves (A )Curve of Spee (Anteroposterior Curve):from lateral aspect both upper and lower occluding (B)Curve of Wilson (Side-to-Side Curve): coronal view, from mesial to distal *Note: Clinical Significance are not included in the exam 9- GEOMETRIES OF CROWN OUTLINES All the aspects of tooth crowns except the Incisal/occlusal aspects can be outlined schematically within three geometric figures namely a triangle, trapezoid, and rhomboid. 1- Triangular outline : All maxillary and mandibular anterior teeth -mesial aspect -distal aspect 2- Trapezoid outline Trapezoid with longest uneven side towards incisal/Occlusal surface -facial and lingual aspects of all teeth (anterior and posteriors of both jaws) Trapezoid with shortest uneven side toward incisal/Occlusal surface -Proximal (mesial and distal) aspects of maxillary posterior teeth 3- Rhomboid outline Proximal (mesial and distal) aspects of mandibular posterior teeth ‫تمت كتابة هذا الشيت صدقة جارية عن روح والدة زميلنا عمرو رائد من دفعة تيجا ن‬ ‫دعواتكم لها بالرحمة والمغفرة‬ Thank you