Dental_anatomy_ppt_08.ppt - Dental Anatomy\/Occlusion Review for the NBDE Part I D.D.S Resident Presented by Brandon Fowler Grad Ortho Objective To try

Dental_anatomy_ppt_08.ppt - Dental Anatomy/Occlusion...

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Unformatted text preview: Dental Anatomy/Occlusion Review for the NBDE Part I D.D.S. Resident Presented by: Brandon Fowler, Grad Ortho Objective To try to touch on the wide range of topics for the dental anatomy part of Part I Boards. I feel pretty confident that if you listen to this and memorize the packet you will pass this section if not do really well on it. You are here to learn about teeth so this should be the easiest section. Who cares about the innervation of the middle finger? OVERVIEW What and How should you study Embryology Anomalies Pathology Angle’s Occlusion Arch Relationships 3W Diagram Jaw Movements Contacts/Contours Primary vs. Perm Eruption times TMJ Anatomy Muscles of Mastication Tooth Morphology Extremes/“Except for” How Well Do You Want to Score Specializing???? Need to score above 90 Should already be studying pretty hard Starting to focus on boards more and more General Dentistry Need to pass with 75 Should be starting to study Focus on preclinical and clinic 6 ½ Months of Torture Feb. 2-3 hours/day March 3-4 hours/day April 3-4 hours/ day May 5 hours/day and 4 hrs on weekends June 6-7 hours/day and 6 hrs on weekends July Every chance you get and all day weekends (16 hrs 8am – midnight) Aug All day everyday (skipped some class) What to study and how BRS Books, Dental Decks, USMLE Review, Kaplan Review, Microbiology Made Simple BRS: Anatomy, Physiology, Pathology, Microbiology, Dental Anatomy ORDER THAT I RECCOMMEND BRS, Decks (at least 2X), USMLE/ Kaplan, then Courseware questions last two weeks Overview 100 Questions Previously taken as the final 100 questions of the exam (second half of the day) but the exam format changed in 2007. On your exam, the questions will be randomized and found throughout all 400 questions. May have some overlapping questions from Oral Pathology, Anatomy etc, For example. TMJ anatomy, muscles of mastication, etc. Useful resources: Dental Decks, old exam questions, Brand’s Anatomy of Orofacial Structures, Kaplan Part I Review Book Helpful Hint #1 Write down everything on the dry erase board you are given! (ie. 3W Diagram, tooth relationships, mnemonics, eruption schedules, primary and permanent teeth #s) Example: Tooth Embryology 6th embryonic week = the oral (stratified squamous) epithelium begins thickening. This thickened oral epithelium is known as the dental lamina. 8th embryonic week = continued thickening in the dental lamina in 10 areas of the upper arch and 10 areas of the lower arch Tooth Embryology Bud stage = initial budding from the dental lamina at the 10 thickened areas in each arch (the first stage in the development of the enamel organ) Cap stage = consists of three components: outer enamel epithelium, inner enamel epithelium, and stellate reticulum Bell stage = fourth layer of epithelium, the stratum intermedium, appears between the IEE and the stellate reticulum. Two processes occur: (1) future form of the crown of the tooth is determined (2) changes in IEE lead to production of dentin and enamel starting with IEE cells becoming taller secretion of dentin matrix secretion of enamel matrix calcification of dentin calcification of enamel = IMPORTANT!!! Tooth Embryology Terminology: Dental papilla = forms the Dentin and Pulp of the tooth Dental sac = forms Some Alveolar bone, Cementum of the tooth, and the periodontal ligament (PDL) Hertwig’s epithelial root sheath = made up of OEE and IEE that determines the shape of the roots Guaranteed to have at least 3 questions on this Dental Anomalies/Abnormalities of Teeth This is not covered much in the dental decks but is tested often. Read the chapter on dental anomalies in Brand and know your definitions! Macrodontia = teeth are too large Microdontia = teeth are too small Hyperdontia = multiple or extra teeth (called supernumerary teeth.) Mesiodens is the most common supernumerary tooth. Hypodontia or Oligodontia = Missing one or a few teeth Anodontia = Complete Absence of teeth Gemination -- This condition manifests as a "twinning" of teeth, usually incisors. It is assumed that a single tooth germ that produces a "double crown" or a "double root." Tooth counting reveals a normal number of teeth. Fusion -- Fusion results when two adjacent tooth germs merge producing one tooth. The fused tooth crown is broader than non-fused adjacent teeth and thus resembles gemination. However, tooth counting reveals decreased numbers. (e.g. the central and lateral incisors fuse together) Dilaceration -- This condition is recognized on radiographic examination by a sharp bend of the roots; it produces a challenge if extraction is necessary. Concrescence -- In concresence, the roots of two adjacent teeth are joined by cementum. Here again, it may present a challenge on extraction. Dens Invaginatus -- this condition is commonly known as "dens in dente," a "tooth within a tooth." It commonly affects maxillary lateral incisor teeth and manifests as an invagination on the lingual surface that may reach the pulp. Hypercementosis – is the excessive deposition of secondary cementum often confined to the apical half of the root, but in some instances, may involve the entire root. In the majority of instances, it affects VITAL teeth. NOTE: The premolars are the teeth most frequently involved. On the dental decks – anything that says “NOTE” or “Remember” is a Board question Enamel Hypocalcification – A hereditary dental defect in which the enamel is soft and undercalcified in context yet normal in quantity. It is caused by the defective maturation of ameloblasts (there is a defect in the mineralization of the formed matrix). The teeth are chalky in consistency, the surfaces wear down rapidly. A yellow to brown stain appears as the underlying dentin is exposed. Enamel Hypoplasia – A developmental defect in which the enamel of the teeth is hard in context but thin and deficient in amount. It results from the incomplete formation of the enamel matrix with a deficiency in the cementing substance. Clinically, the affected enamel may be pitted and discolored. An infected primary tooth may cause disruption of the following permanent tooth. The resulting permanent crown is often called a "Turner's tooth.” More Pathology Enamel Pearl - small mass of excess enamel on the surface of teeth located APICALLY to the CEJ Enamel lamellae = cracks in the enamel caused by developmental problems or trauma Enamel tuft = small area of hypocalcified enamel seen at the DEJ and extending about one fourth to one third of the way through the enamel Enamel spindle = an odontoblastic process that ends up in the enamel Dentinogenesis Imperfecta Dentinogenesis imperfecta results from an inherited structural deficiency in collagen formation. Since dentin and bone is supported by a collagen framework, dentin affected by this disease is structurally defective. Several types of the condition are recognized. Type I – Dentin abnormality occurs in patients that have osteogenesis imperfecta (characterized by blue sclera or a history of bone fractures) Type II – Most Common, only the dentin abnormality exists with no bone involvement. Type III (Brandywine Type) – Like type II, only the dentin abnormality exists. Clinically, the condition is recognized by a characteristic tooth crown color called "opalescent dentin" caused by abnormal dentin shining through the overlying enamel. The underlying defective dentin is not able to adequately support the unaffected enamel - it often flakes off. Remember: The enamel in these teeth is structurally and chemically normal. Amelogenesis Imperfecta A hereditary ectodermal defect that results in an abnormal enamel formation. Several forms are recognized based on their pathogenesis and severity. Type I (Hypoplastic AI) – the enamel has not formed to full thickness (or in some cases may be completely absent) on newly erupted developing teeth. It results from defective formation of the enamel matrix. Type II (Hypocalcified AI) – the quantity of enamel is normal but the enamel is so soft that it can be removed during a cleaning. Results from the defective mineralization of the enamel matrix Type III (Hypomaturation AI) – The enamel can be pierced by an explorer tip under firm pressure and can be chipped away from the normal appearing dentin. It is characterized bu immature crystallites. REMEMBER: In all three types of AI, the Dentin, Pulp and Cementum are UNAFFECTED by the disease process itself (unlike dentinogenesis imperfecta.) This condition causes teeth to be unusually small, discolored, pitted or grooved, and prone to rapid wear and breakage. Clinically, affected enamel may be thinner than normal (generalized hypoplastic form), may be of normal thickness but lacks strength (hypocalcified form), or may be pitted (hypoplastic pitted form). Sample Test Question Easy A developmental abnormality characterized by the presence of fewer than the usual number of teeth is A. Anodontia. B. Oligodontia. C. Microdontia. D. Hyperdontia. E. Don’t care Answer: B – Remember it is usually a congenital condition of having fewer than the normal number of teeth. Also called Hypodontia. Sample Test Question Easy "Production of a 'double crown' or 'double' root from single tooth germ" is the definition of? A. Fusion. B. Gemination. C. Concrescence. D. Hyperplastic enamel. E. Amelogenesis imperfecta. Answer: B – Remember Gemination is the "twinning" of teeth from a single tooth germ. Sample Test Question Medium Which of the following is produced by an inherited defect in collagen synthesis? A. Cleft lip B. Cleft palate C. Dilaceration D. Amelogenesis imperfecta E. Dentinogenesis imperfecta er: E – Remember Dentinogenesis imperfecta (and osteogen fecta) are produced by inherited defects in collagen synthes Sample Test Question Hard Which type of amelogenesis imperfecta is characterized by having enamel so soft that it can be removed during a prophylaxis? A. Type I (Hypoplastic Amelogenesis Imperfecta) B. Type II (Hypocalcified Amelogenesis Imperfecta) C. Type III (Hypomaturation amelogenesis Imperfecta) Answer: B Classification of Human Occlusion (Angle’s Classification) Remember: The Mesiobuccal cusp of the Maxillary 1 Molar st serves as a reference point in identifying Angle’s Class I, II and III Occlusions. Class I – MOST COMMMON. The MB cusp of the Max 1st molar lines up approximately with the buccal groove of the mandibular 1st molar. The max central incisors overlap the mandibulars. The Max canine lies between the mandibular canine and 1st premolar. Class II – LESS COMMON. The MB cusp of the max 1st molar falls approximately between the mandibular 1st molar and the 2nd premolar. Class III – LEAST COMMON. The MB cusp of the max 1st molar falls approximately between the mandibular 1st molar and 2nd Dental Arch Relationships The maxillary arch is slightly LONGER (Approx. 128 mm) than the mandibular arch (Approx 126 mm) What does this mean? -Every maxillary tooth is more DISTAL than its opposing counterpart, therefore: 1) The only maxillary tooth with 1 opposing counterpart is the MAXILLARY THIRD MOLAR 2) The only mandibular tooth with 1 opposing counterpart is the MANDIBULAR CENTRAL INCISOR Dental Arch Relationships The maxillary arch is usually WIDER than the mandibular arch Therefore, Supporting (functional) cusps are MAXILLARY LINGUAL and MANDIBULAR BUCCAL cusps Guiding (nonfunctional, shearing cusps) are MAXILLARY BUCCAL and MANDIBULAR LINGUAL cusps. Remember the “BULL-Shit rule” – Non Supporting cusps are “BULL-shit” (Buccal Upper, Lingual Lower) Maxillary Cusps Buccal cusps: -Premolar cusps and the DB cusp of the maxillary molars overlap the embrasure between the counterpart and the tooth DISTAL to it, except for the maxillary 1st and 3rd molars (DB of maxillary 3rd molar only overlaps 1 tooth) -MB cusps of all maxillary molars overlap the counterpart’s FACIAL groove (MESIOFACIAL groove for 1st molar, central groove for 2nd and 3rd molars) -DB cusp of maxillary 1st molar overlaps the DISTOFACIAL groove of the mandibular 1st molar Lingual cusps: -2nd premolar cusp and the DL cusps of the maxillary molars contact the counterpart’s distal marginal ridge and the mesial marginal ridge of the tooth DISTAL to it, except for the 1st premolar & DL cusp of the max. 3rd molar (only contact 1 marginal ridge respectively) -ML cusps of maxillary molars contact the counterpart’s CENTRAL FOSSA Mandibular Cusps Buccal cusps: -Premolar cusps and MB cusps of mandibular molars contact the mesial marginal ridge of the counterpart and the distal marginal ridge of the tooth MESIAL to it -The DB cusps of the mandibular molars contact the counterpart’s CENTRAL FOSSA -The distal cusp of the mandibular 1st molar contacts the maxillary 1st molar’s DISTAL PIT Lingual cusps: -Premolar cusps and ML cusps of mandibular molars overlap the embrasure between the counterpart and the tooth MESIAL to it -The DL cusps of the mandibular molars overlap the counterpart’s LINGUAL GROOVE Question: Which cusps are represented by the arrows? Lingual Cusps of Maxilla Buccal Cusps of Mandible Useful Diagrams Use this often and mark the teeth that they are talking about with a dot so you don’t get mixed up They will try to trick you by using the tooth’s number instead of the name Ex: Sample Test Question In an ideal intercuspal relation, which of the following maxillary cusps will oppose the mesiofacial groove of the mandibular first molar? A. Facial cusp of the second premolar B. Mesiofacial cusp of the first molar C. Distofacial cusp of the first molar D. Mesiolingual cusp of the first molar E. Distolingual cusp of the first molar Correct Answer: B (Note: This is the definition of Angle’s Class I Occlusion!) Sample Test Question Which of the following occurs when the distofacial cusp of Tooth #19 moves through the facial groove from the central fossa of tooth #14? A. Direct lateral excursion to the left B. Direct lateral excursion to the right C. Direct protrusive mandibular excursion D. Lateral-protrusive excursion to the left E. Lateral-protrusive excursion to the right Answer: A Jaw Movements ONLY THE MANDIBULAR ARCH MOVES!!!!!!!!!!! A Laterotrusive movement, Working Movement, Bennett movement = the side that the mandible moves towards. (e.g. A right laterotrusive movement = the jaw moving to the right.) Non-working (mediotrusive, balancing) movement = NOT the side that the mandible moves towards. (e.g. During a Right laterotrusive movement, the left side of the pt’s jaw is the non-working side.) Protrusion = moving the mandible forward in an anteriorposterior plane Retrusion = moving the mandible backwards in an anterior-posterior plane Sample Test Question – Hard Which of the following describes the laterotrusive movement (Bennett angle)? A. It is the angle that is formed by the non-working condyle and the sagittal plane during lateral movements. B. It is the angle that is formed by the condyle and the horizontal plane during protrusive movements. C. It is the difference in condylar inclination between protrusive and lateral movements. D. It is the difference between the condylar and incisal inclinations. E. What? Posselt’s Envelope of Motion 1 = Maximum Protrusion (Protruded contact position) 2 = Edge to edge position of incisors 3 = Centric Occlusion (Maximum Intercuspation) 4 = Centric Relation (Retruded contact position) Dot = Rest position 5 = Chewing stroke 6 = Rotation (Terminal Hinge Axis opening) 7 = Translation 8 = Maximum opening Sample Test Question In the diagram of Posselt's envelope of motion, the position representing maximum opening is the A. most inferior point. B. most anterior point. C. most posterior point. D. most superior point. E. Not sure Answer: A Jaw Movement Diagrams Which way is the mandible moving? Are the teeth on the side that the mandible is moving towards, or are they not? Isolate the teeth in question! Working movement (Straight Arrows) Right lateral (working side) movement Right lateral (working side) movement NOTICE MAXILLARY ARCH DOES NOT MOVE!! (Think in terms of where the mandible is moving in relation to the maxillary arch) Nonworking movement (Slanted Arrows Left lateral (non-working) movement Right lateral (non-working) movement Protrusion Mesio-Distal Contacts (from facial view) Central Incisor Lateral Incisor Canin Premolars e Molars Maxillary IJ JJ JM JJ MM Mandibula r II II IM JJ MM IJ means the MESIAL contact is located in the incisal third (I) while the DISTAL contact is located at the junction (J) of the incisal/occlusal and middle thirds. M= middle of the tooth Sample Test Question When viewed from the facial, the distal contact of a mandibular lateral incisor is located A. in the cervical third. B. in the incisal third. C. in the middle third. D. at the junction of cervical and middle thirds. E. at the junction of middle and incisal thirds. Answer: B Facio-Lingual Contacts (from incisal/occlusal view) Facio-Lingual Contacts: 1) CENTERED faciolingually for all ANTERIOR teeth 2) SLIGHTLY BUCCAL of the middle third for all POSTERIOR teeth Facio-Lingual Embrasures: Every tooth has a wider LINGUAL embrasure than FACIAL embrasure EXCEPT for the lingual embrasure between the MAXILLARY 1st and 2nd MOLAR (less wide), and MANDIBULAR Anteriors Heights of Contour Located in the MIDDLE third of the crown on: LINGUAL surfaces of all posterior teeth (both maxillary & mandibular) Located in the CERVICAL third of the crown on: FACIAL surfaces of all posterior teeth, and FACIAL & LINGUAL surfaces of all anterior Heights of Contour C= cervical third M=Middle third Cent, Lat, K9, 1st Bi, 2nd Bi, 1st M, 2nd M, 3rd M Max F = C L= C Mand F= C L=C C C C C C C C C C C C C C C C MMMMMM M C C C C C C C MMMMMMM Primary vs. Permanent Teeth The crowns of the primary ANTERIOR teeth are wider mesiodistally and shorter inciso-cervically than their permanent succesors. (Short and fat like a baby) The crowns of the primary MOLARS are shorter and more narrow mesiodistally at the cervical third than the permanents. The root trunks of primary molars are also very short. The cervical ridge of enamel at the cervical third is much more prominent in primary teeth. The BUCCAL and LINGUAL surfaces of primary molars are flatter above the crest of contour than on permanent molars, giving the appearance of a narrower occlusal table. The enamel rods on primary teeth point OCCLUSALLY at the cervical third, compared to APICALLY for permanent teeth (which is why there is no need for a gingival bevel for a Class II amalgam on primary teeth). The roots of the primary are longer, more slender, and taper more rapidly than those of the permanent molars The pulp horns extend higher occlusally and the pulp chambers are proportionately larger in primary teeth. The primary teeth are LIGHTER in color than the permanent teeth. (Milk Teeth) The MESIAL CUSP RIDGE is longer than the distal cusp ridge in the PRIMARY MAXILLARY CANINE (the opposite is true for all other canines). Eruption of Teeth In both the maxillary and mandibular arches, the permanent incisor tooth buds lie lingual as well as apical (inferior) to the primary incisors. The result is a tendency for the mandibular permanent incisors to erupt somewhat lingually and in a slightly irregular position. All permanent teeth move occlusally and buccally while erupting. Primate Spaces The primate spaces are normally present from the time the teeth erupt. Developmental spaces between the incisors are often present from the beginning, but become somewhat larger as the child grows and the alveolar processes expand. Generalized spacing of the primary teeth is a requirement for proper alignment of the permanent incisors. This spacing is most frequently caused by the growth of the dental arches. In the Maxillary arch, the primate space is located between the lateral incisors and canines. In the Mandibular arch, the primate space is located between the canines and first molars. *** Spacing is normal throughout the anterior part of the primary dentition, but it is most noticeab...
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