Dental Anatomy PDF

13 Lajneh Teejan Noor Hamadneh Siham Alarag  Occlusion ❖Definition occlusion: the act of closure or being closure (Concerned with the occlusal surfaces of the teeth) A static morphological tooth contact relationship. In...

13 Lajneh Teejan Noor Hamadneh Siham Alarag  Occlusion ❖Definition occlusion: the act of closure or being closure (Concerned with the occlusal surfaces of the teeth) A static morphological tooth contact relationship. Includes all factors concerned with the development and stability of the masticatory system and the use of teeth in oral motor behavior. Includes the integrated system of functional units involving teeth, jaws, joints and muscles of the head and neck. like TMJ (temporomandibular joint) When we say occlusion, it needs to include all the factors related to the development and stability of the orofacial complex or the masticatory complex. alignment of maxillary teeth ❖Physiology & occlusion alignment of mandibular teeth (only one jaw) In physiology we talked more about the alignment of teeth. Now, in occlusion we talk about the relationship between the two arches. Occlusion is very important to mastication ❖Concepts of occlusion: and other disciplines like orthodontics. 1-Balanced occlusion (ideal occlusion) (If no ideal occlusion = malocclusion) a- Bilateral contacts in all functional excursions. ‫ن‬ ‫ يستمر اإلطباق‬،‫لليمي‬ ‫السفىل‬ ‫ي‬ ‫ن‬ ‫ إذا تحرك الفك‬:‫بمعن‬ ،‫الجهتي ن يف كل المجاالت العملية‬ ‫ن‬ ‫(تالمس االسنان عىل‬ ‫ن‬ ‫ن‬ ‫ن‬.‫ يستمر اإلطباق عىل الجهتي اليمي واليسار‬،‫ وإذا تحرك الفك لليسار‬.‫اليمي واليسار‬ ‫ن‬ ‫الجهتي‬ ‫عىل‬ ‫ن‬ )‫الجهتي االمامية والخلفية‬ ‫وإذا تحرك الفك لألمام يستمر االطباق عىل‬ doctor’s words In all functional movements we need bilateral contact (Bilateral contact=equally distributed masticatory forces on both sides.) within the physiological range of functional movement, we should have as maximum teeth as possible in contact. (70% of people has normal occlusion)  b- Prevent tipping of the denture bases. the concept of balanced occlusion is used in cases of complete dentures, which is a treatment option in case of total teeth loss. (keeping them in place) c- Balanced occlusion does not necessarily exist in natural dentition because each tooth is a separate unit. (‫ الخ‬،‫داع لإلطباق عىل اليسار‬ ‫ن‬ ‫ ال ي‬،‫)اذا تحرك الفك لليمي‬ this concept is not needed to keep the teeth in place. (every tooth is individually anchored to the jaw, so they are fixed in the place and will not move during speech, chewing, etc) 2- Inter-cuspal position every (functional) cusp occludes in a specific fossa on the opposing tooth. Functional cusps: are the ones that contact fossae upon closure, and they are: - The Lingual cusps for upper posterior teeth. - The Buccal cusps for lower posterior teeth. Non-functional cusps: don’t contact opposing fossae, but they are still important: - There is a rule for non-functional cusps: B.U.L.L: buccal of upper, lingual of lower. 3- Centric occlusion: a position of maximal, bilateral, balanced contact between the cusps of the maxillary and mandibular arches. In dentistry, centric relation is the mandibular jaw position in which the head of the condyle is situated as far posterior and superior as it possibly can within the mandibular fossa/glenoid fossa. o These 3 concepts developed in relation to orthodontics, complete dentures and full mouth rehabilitation o None are completely applicable to natural dentition (each individual has a different occlusion that suites them) doctor’s words This is a picture of the occluding of the teeth. We always have this concept of occlusion in relation to orthodontics, especially in complete dentures or in full mouth rehabilitation. maxillary teeth It is not present in ideal occlusion. This is the relationship when they occlude in centric mandibular teeth occlusion. We have maximal intercuspation of all the teeth. ❖Overview of primary occlusion (primary) o Each tooth occludes with 2 teeth of the opposing jaw except: -Mandibular central incisor. (occludes only with upper incisor) -Maxillary second molar. (only with mandibular second molar) Extra info: Rule for maxillary teeth: each max. tooth occludes with the antagonist man. tooth + the man. tooth distal to it. For example: the max. central incisor normally occludes with the man. central incisor+ the man. lateral incisor. The max. canine occludes with the man. canine + (either the man. 1st premolar if we’re talking about permanent teeth, or the man. 1st molar for deciduous teeth). TRICK! Rule for mandibular teeth: each man. Tooth occludes with the antagonist max. tooth + the max. tooth mesial to it. For example: the man. Lateral incisor occludes with the max. lateral incisor + the max. central incisor. The man. 1st molar occludes with the max. 1st molar + (either the max. 2nd premolar for permanent dentition, or the max. canine for deciduous dentition). o Occlusion is supported and made more efficient after eruption of first permanent molars. (Cornerstones of the mouth = when they reach full eruption, we reach the full occlusion.) o Interdental spacing is important for future sufficiency of space in permanent teeth. (in the permanent teeth it is not normal, however it is normal in primary teeth because it is required to accommodate the larger permanent teeth) o The probability of crowding in permanent teeth is related to the amount of interdental spacing in primary dentition. (If we have crowded primary dentition, we will most likely have crowded permanent dentition) o Developmental spacing depends on the generalized spacing between the teeth and the primary spaces that are present according to the jaw sizes. ❖ Primary molar relationship Terminal plane relationship (end plane) It’s the relation that predicts the secondary teeth occlusion by looking to the primary. Terminal plane means the occlusion of the last tooth in the jaw (2nd molars) The anterior posterior molar relationship. o 3 types of terminal plane relationships: a-Flush (straight) when permanent teeth erupt there will be: It isn’t the best type of relationship because we might have a ◼ 56% - Class I Angle’s molar relationship (normal occ) somewhat high percentage of class ◼ 44% - Class II Angle’s molar relationship (malocclusion) II (malocclusion). b- Distal step (max more buccally located) It is worse than a flush relationship, because it ◼ 100% Class II Angle’s molar relationship (always malocclusion) will give CLASS II c- Mesial step (man more buccally located) the best relationship, ◼ greater probability for Class I Angle’s molar relationship Because it will give a greater probability for ◼ lesser probability for Class III Angle’s molar relationship Class I Angle’s relationship (normal occlusion). (normal) (mesial) (distal)  (primary) Factors influencing the effect of terminal plane relationship on Angle’s (secondary) molar relationship: a- Differential growth of the jaw (the skeleton) b- Forward growth of the mandible (it continues to grow until 18, (the condyle grows)) c- Sufficient Leeway space to accommodate a mesial shift of the permanent molars. Leeway space is the amount of space gained by the difference in the mesiodistal diameter between deciduous molars and premolars. Deciduous molars are replaced by permanent premolars. Deciduous molars mesiodistally diameter is larger than premolars so the difference is called (leeway space). the combined mesiodistal crown dimension of the primary canine, 1st and 2nd molars are larger than the combined mesiodistal crown dimension of the permanent canine, 1st and 2nd premolars. the amount of space gained by their difference is called the leeway space of nance. This arrangement will give us class I molar relationship. In maxilla the space is 0.9 mm in each quadrant making the total space 1.8 mm In mandible the space is 1.7 mm in each quadrant making the total space 3.4 mm (the primary man. molars are wider) We prefer excessive leeway space If we don’t have enough space, we will have unerupted premolars, or canines in the maxilla, or the second man. premolar. In summary there is a change in anterior posterior molar relationship which will affect the permanent occlusion. ❖Permanent occlusion: 1- Anteroposterior relationship (normal) ◼ Incisors: Class I, II, III )‫(رسم الدكتورة‬ (we like to correct it) ◼ Canine: Class I, II, III ◼ Molars: Angle’s Class I, II, III (anteroposteriorly) 2- Faciolingual relationship (buccolingually) ◼ Premolars (Maxillary teeth are bigger, broader. Which creates a slight overlap. ◼ Molars Gives us an interlocking occlusal relation between the jaws.) ❖Incisal relationship ▪ Class I (Normal occlusion) (overjet=overbite=2-3 mm) Palatal of max covers incisal 1/3 of labial man ▪ Class II (Malocclusion) (overbite > 2-3 mm) upper central covering more than 1/3 of the lower central incisor. 2 types of class II: type 1: Overbite increase and overjet increase. type 2: Overbite increases but overjet is normal. ▪ Class III (Malocclusion) (overbite < 2-3 mm) 2 types of class IIl: type 1: Edge to edge (overbite=overjet=0) type 2: Reverse overjet. ▪ Reverse overjet (happens but rare) mandibular incisors in front of maxillary ones. ▪ Overjet Normally (1-3mm) (horizontal relation) Overlap = overjet, overbite. ) (The buccolingual incisal ▪ Overbite Normally (1-4mm) (vertical relation) relationship in centric (4 deep overbite) occlusion) Deep bite is often present in primary dentition reverse If this overbite reaches the cingulum = we call it an increased overbite. Either moderate or very deep bite.  In this case overbite Here overbite increase excessively increases and overjet Central incisor retroclined and also so it is class II lateral incisor appears as if they are division 1 proclined. → it is class II division 2 (overjet is normal) ❖Canine relationship Maximal canine guidance helps you with non-functional movement, Not in centric movement. ▪ Class I (Normal occlusion) When the cusp tip of the maxillary canine occludes in the embrasure between mandibular canine& 1st premolar. ▪ Class II (malocclusion) Mesial to class l. the lower jaw is pulled backward. ▪ Class III (malocclusion) dcCII CIII Distal to class l. the lower jaw is pulled forward. The cusp tip of the maxillary canine is pulled backward behind the embrasure. ❖Molar relationship 1-Angle’s Class I: (Normal occlusion) -mesiobuccal cusp tip of maxillary first molar in line with the mesiobuccal groove of the mandibular first molar. 2- Angle’s Class II: (malocclusion) -mesiobuccal cusp tip of maxillary first molar is in Mesial/anterior relationship with the mesiobuccal groove of the mandibular first molar. -Mandible moved backward. -Class II has two divisions: type 1: incisor is proclined. (Dr said she won't ask type 2: incisor is retroclined. about these 2 divisions)  3- Angle’s Class III: (malocclusion) -mesiobuccal cusp tip of the maxillary first molar is in distal/posterior relationship with the mesiobuccal groove of the mandibular first molar. -The mandible is moved anteriorly ❖ Arch occlusal relationship All are in an anteroposterior relationship except 5(the premolars) and 7 (the molars) are Faciolingual relationships. ❖ Curves of occlusion (was discussed) 1- Curve of Spee (anteroposterior) When you look laterally on lateral section from outside. An imaginary occlusal line from anterior to posterior. 2- Curve of Wilson (mesiodistally) When you see from the coronal section mesiodistally. (between the two 6’s (first molars)) 3- Sphere of Monson (the doctor said she won’t talk about this one) ❖ Inclination & angulation of the roots of the teeth 1- The mandibular arch is wider than maxillary arch. That’s why the posterior maxillary teeth go outward, and the mandibular posterior teeth go inward (to meet each other). 2- Each tooth must be placed at the angle that best withstands the line of forces brought against it during function. 3- If the tooth is placed at a disadvantage, (in a way reduces the ability to withstand the forces), its longevity may be at risk. 4- Anterior teeth are placed at a disadvantage. They are more aesthetic than load carrier, That’s why we must not put any load on them. Disadvantage doesn't mean “wrong occlusion or artificial” so it’s normal and can exist is artificial denture and natural teeth. ❖ Antagonists Antagonist: a tooth in one jaw that articulates during mastication or occlusion with a tooth in the opposing jaw. 1- With the exception of mandibular incisors and maxillary third molars, each tooth contacts two antagonist teeth in the opposing arch. 2- Loss of one tooth keeps the adjacent tooth in contact with opposing antagonist. 3- Mesial or distal drifting into the space disturbs occlusal contact with antagonist teeth. Antagonists in permanent teeth. ❖ Centric stops Definition: The point where opposing teeth touch in centric occlusion. 1- Lingual cusp tips of maxillary posterior make contact with opposing fossae and marginal ridges of mandibular posterior teeth. 2- Buccal cusp tips of mandibular posterior make contact with opposing fossae and marginal ridges of maxillary posterior teeth. 3- Lingual cusps of maxillary posterior teeth and buccal cusps of mandibular posterior teeth are called “supporting cusps.” 4- Areas of occlusal contact that a supporting cusp make with opposing teeth in centric occlusion are “centric stops.” In centric occlusion when 32 teeth 5- The tip of that cusp is also a centric stop. occlude, we almost have 138 spots. 6- Knowledge of centric stops are important in restorative dentistry. Supporting/centric holding cusp Non-Supporting/ guiding cusp They guide the mandible in lateral movement not centric occlusion ❖ Movements away from centric occlusion (acentric) 1- Lateral movement: ▪ Working side: -Contact occurs between teeth. -The side where the mandible projects outward. -In complete denture it’s called (non-balancing side). ▪ Non-working side: -No contact between teeth (in denture we have contact). -The side where the mandible projects inward. -In complete denture it is called (balancing side). ▪ Movement in TMJ -working side (non-balancing) → condyle process moves downward, forward and laterally. -non-working side (balancing) → condyle process moves downward, forward and medially. ▪ Tooth guidance The movement of the mandible is guided by: -Canine guidance: movement of upper canine over the lower causes the guidance. -Group guidance: movement of upper premolar or canine A: right working side. over lower premolars or canine. B: centric occlusion -incisal guidance (intercuspal position). C: left non-working side 2- Protrusive movement: -Movement of mandible anteriorly. -Guided by the incisors (lower incisors move over the upper incisors). 3- Retrusive movement: -Movement of mandible posteriorly. -The most retrusive position is the centric occlusion in complete dentures..‫ اللهم انصرهم وثبت اقدامهم‬.‫اللهم انا نستودعك غزة وأهلها‬ ‫تمت كتابة هذا الشيت صدقة جارية عن روح والدة زميلنا عمرو رائد من دفعة تيجان‬ ‫دعواتكم لها بالرحمة والمغفرة‬