CD Midterm Exam Review ENK DMA Dental Anatomy PDF

Dental Anatomy Session Number One Nomenclature and Morphology COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE • Primary/Deciduous • Transitional/Mixed • Permanent/Succedaneous COLLEGE OF DENTAL MEDICINE Consisting of two distinct dentitions: • Primary/Deciduous/baby/milk teeth • Secondary/...

Dental Anatomy Session Number One Nomenclature and Morphology COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE • Primary/Deciduous • Transitional/Mixed • Permanent/Succedaneous COLLEGE OF DENTAL MEDICINE Consisting of two distinct dentitions: • Primary/Deciduous/baby/milk teeth • Secondary/Succedaneous/permanent/adult teeth Overview: formation of the primary dentition begins in utero and is completed at around 3 yrs of age. The first teeth in this dentition begin to erupt at around 6 mos of age and the last emerges around 28 mos. This dentition stays until the child is around 6 years of age when exfoliation begins. Around this time, the permanent dentition begins to erupt and the child enters a stage of mixed dentition or the transitional phase, where both primary and secondary teeth are present. This phase ends with the loss of the last baby tooth beginning the permanent dentition, which is completed around 14-15 years of age excluding third molars, which are completed from 18-25 years. Clinical pearl: The early mixed dentition phase (6-9 yo) is a time to recognize and intercept localized factors to prevent severe malocclusions later on! COLLEGE OF DENTAL MEDICINE Primary/Deciduous/Milk teeth • Begins forming at about 14 weeks in utero. • Continues forming until about 3 years of age. • First teeth erupt at about 6 months. • Last primary erupts about 28 months. • Transition to mixed dentition at about 6 years with the eruption of the first permanent molars. • All deciduous teeth are lost. • 10 teeth/arch = 20 total. COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE Mixed/Transitional Dentitition • Consisting of both primary and permanent teeth • Begins with the eruption of the first permanent teeth (incisors usually) • Ends with the exfoliation of the last primary tooth usually around age 12. • Usually around 6 years in duration. COLLEGEOFDENTALMEDICINE Shutterstock COLLEGE OF DENTAL MEDICINE Secondary/Succedaneous/Permanent Dentition Shutterstock • Begins around age 6 and lasts until 14 – 15 (except for 3rds which are completed at 1825 y) • Replace all primary teeth • Permanent premolars replace primary molar. There are no primary premolars. • Ends with eruption of second permanent molars and canines • 16 teeth/arch = 32 total COLLEGE OF DENTAL MEDICINE Maxillary arch To begin, we need to identify which arch we are referencing. We refer to any tooth in the maxillary or upper arch as a maxillary tooth and any tooth in the lower arch as a mandibular tooth. Shutterstock Mandibular arch COLLEGE OF DENTAL MEDICINE Just as we use directions to orient in the world, we use directional terms in the mouth. Each arch is divided by the median line, thus dividing the mouth into quadrants. Shutterstock Mesial: refers to those surfaces facing toward the median line. Distal: nearer the posterior of the mouth Facial/Labial/Buccal: Facing the cheeks, lips, face Lingual:facing the tongue Palatal: facing the palate COLLEGE OF DENTAL MEDICINE • Facial/labial/buccal Surface of a tooth resting against or next to the cheeks or lips; facial is used for any tooth. Labial for anterior and buccal for posterior. Proximal surface- the surface of a tooth touching another tooth or facing a space. • Mesial –toward the midline • Distal-away from the midline Working portion of tooth that contacts opposing teeth • Occlusal • Incisal Surface of a posterior tooth used for chewing Surface of an anterior tooth used for cutting ("edge" or "ridge") Lingual Surface of a maxillary or mandibular tooth closest to the tongue Palatal Surface of a maxillary tooth closest to the palate COLLEGE OF DENTAL MEDICINE Provide a quick way to accurately reference an individual tooth in communications to labs, specialists, other practitioners, etc. There are many numbering systems. We will discuss three commonly used systems: • Universal • Palmer Shutterstock • FDI COLLEGE OF DENTAL MEDICINE Atooth can be described by • Position of the tooth: e.g. Left maxillary first molar • Assigned number or letter: e.g. tooth #14 (universal system) shutterstock COLLEGE OF DENTAL MEDICINE Permanent teeth- numbering begins with upper right third molar and progresses to upper left third molar 1-16, then resumes from lower left to lower right 17-32. Primary teeth-uppercase letters starting with upper right second molar A-J then K-T for the lower, beginning with the lower left. Shutterstock COLLEGE OF DENTAL MEDICINE Adopted by WHO. Teeth are given both a quadrant and a tooth number. Quadrant numbers come first and proceed in clockwise order starting from the midline of the UR. Teeth numbers are the second number and start at the midline and progress posteriorly Permanent Teeth Upper Right Upper Left 18 17 16 15 14 13 12 11 21 22 23 24 25 26 27 28 48 47 46 45 44 43 42 41 31 32 33 34 35 36 37 38 Lower Right Lower Left Primary Teeth Upper Right Upper Left 55 54 53 52 51 61 62 63 64 65 85 84 83 82 81 71 72 73 74 75 Lower Right Lower Left COLLEGE OF DENTAL MEDICINE ThePalmer NumberingSystem The symbolic system in which the arches are divided 87654321 12345678 into quadrants, with each tooth type in the quadrant being assigned the same numeric symbol. 87654321 12345678 The upper right six year molar would be notated as: 6 And a lower left canine would be notated as: 3 EDCBAABCDE EDCBAABCDE COLLEGE OF DENTAL MEDICINE Aformula for describing all mammalian teeth where the denomination of each tooth is represented by the initial letter in its name and followed by the number of teeth in the upper quadrant/lower quadrant. These are the formulae for the human dentition. I 2/2 C 1/1 M 2/2= 10 Primary Dentition Primary dentition lacks premolars I – incisor C- canine P- premolar M-molar I 2/2 C 1/1 P 2/2 M 3/3= 16 Permanent Dentition Permanent premolars replace primary molars COLLEGE OF DENTAL MEDICINE Life Tip: Know how to name each tooth with all the systems and use the nomenclature interchangeably! COLLEGE OF DENTAL MEDICINE TheDentitionCanbeDescribedbysetsofTraits • Set traits or Dentition traits: distinguish primary from permanent dentitions • Arch Traits: distinguish maxillary from mandibular teeth • ClassTraits: Class traits distinguish the 4 categories of teeth—incisors, canines, premolars, molars into their functional classes. • Type Traits: distinguish teeth within a class- eg a lateral from a central incisor. COLLEGE OF DENTAL MEDICINE Life Tip: Know examples of each trait! COLLEGE OF DENTAL MEDICINE Anterior Incisors • Central • Lateral Canines Posterior Premolars (permanent teeth only) • 1st premolar • 2nd premolar Molars • 1st molars • 2nd molars • 3rd molars/wisdom teeth COLLEGE OF DENTAL MEDICINE Crown is covered by enamel Cementoenamel junction Root is covered by cementum Crown functions in chewing and speech. Root functions in retention and force dispersion Shutterstock COLLEGE OF DENTAL MEDICINE Ridges Any linear elevation on the surface of a tooth and is named according to location (buccal ridge, incisal ridge, marginal ridge) Triangular Ridge Aridge that slopes downward from a cusp tip toward the center of the occlusal surface. COLLEGE OF DENTAL MEDICINE Oblique Ridge Aridge that crosses the occlusal surface of maxillary molars at an angle/obliquely. Formed by the union of the triangular ridge of the DB cusp and the distal cusp ridge of the ML cusp. © 2022 Productivity Training Corporation. All rights reserved. COLLEGE OF DENTAL MEDICINE Transverse Ridge The union of two cusp ridges running transversely from buccal to lingual. COLLEGE OF DENTAL MEDICINE Marginal Ridges COLLEGE OF DENTAL MEDICINE Enamel is thick at the marginal ridge and loss of tooth structure in this area weakens teeth. We prep through the marginal ridge when accessing Class II decay. • Their primary purpose is to prevent lodging of food in the contact. • Failure to properly contour your marginal ridges causes failures. COLLEGE OF DENTAL MEDICINE • The crowns of the incisors and canines (anterior teeth) have four surfaces and a ridge. • The crowns of the premolars and molars have five surfaces. • Surfaces are named according to their positions and uses. Facial surface Proximal surface Lingual/palatal surface Incisal edge Shutterstock COLLEGE OF DENTAL MEDICINE Cusps An elevation on the crown that makes up a divisional portion of the occlusal surface. Each has a tip, marked in blue here. Shutterstock COLLEGE OF DENTAL MEDICINE Line angle is formed by the junction of two surfaces and it gets its name from the two surfaces it joins. COLLEGE OF DENTAL MEDICINE Life Tip: Know how to describe, identify, and label the features on a tooth! COLLEGE OF DENTAL MEDICINE Development and Eruption Session Number 2 COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE Overview: There are three dentitions in humans: Primary, Transitional/Mixed, and Permanent. Teeth begin developing in the jaws as early as six weeks in utero. The crowns develop first and after they are complete, eruption occurs. After eruption, the final phase of development, root completion occurs. Development occurs during three periods: • Prenatal • Perinatal • Post natal Chronologies are used to describe the timing of these events in a population. COLLEGE OF DENTAL MEDICINE Chronology of the Primary Dentition COLLEGE OF DENTAL MEDICINE Chronology-thestudywhich dealswith thetimingofvariousstagesoftooth development.Itstarts with the initiation of first tissue and ends with emergence into the oral cavity and its completion of calcification. COLLEGE OF DENTAL MEDICINE Features of the Primary Dentition Chronology • Begins forming at about 6-7 weeks in utero • Begins calcifying at about 13-14 weeks in utero • Primary dentition is completed at about 3.5 years of age • All teeth are exfoliated *Mandibular teeth tend to emerge before their maxillary counterparts COLLEGE OF DENTAL MEDICINE Pre Natal V Post Natal Pre-Natal Post-Natal • The first indications of tooth formation begin at 6-7 weeks in utero. • Eruption of the first primary teeth begin at about 6 months of age. • Calcification of primary teeth begins 13-16 weeks post fertilization. • Primary crown formation is complete by 11 months. Root formation is completed by 3.5 years. • By 18-20 weeks, all primary teeth have begun to calcify. COLLEGE OF DENTAL MEDICINE Eruption - The developmental process responsible for moving a tooth from its crypt (gross word) position through the bone into the oral cavity to its final position of occlusion with its antagonist. Emergence – the moment of appearance of any part of the cusp or crown through the gingiva. It is synonymous with the moment of eruption, which is often used as a clinical marker for eruption. COLLEGE OF DENTAL MEDICINE https://www.mouthhealthy.org/all-topics-a-z/eruptioncharts COLLEGE OF DENTAL MEDICINE 1. Central incisor- usually mandibular 1st 2. Lateral incisor 3. First molar-usually maxillary first 4.Canine 5. And second molar Clinical Pearl: Variability is common! Know common variations such as lateral before central or two groups emerging simultaneously. COLLEGE OF DENTAL MEDICINE Life Tip: Goals of chronology are to be able to say which teeth erupt in which sequence, identify the age of a patient, and to know what is coming next! COLLEGE OF DENTAL MEDICINE Chronologies of The Permanent Dentition COLLEGE OF DENTAL MEDICINE • Comprised of 32 teeth. • At birth, first molars are the only teeth which show evidence of calcification • Permanent dentition is completed at 14-16 years of age excepting third molars which are complete at 18-25 years. • First molars are generally the first to emerge followed by lower incisors. •Mandibular teeth tend to emerge before their maxillary counterparts. • Calcification of permanent teeth begins at birth • By 3 years, all but the third molars have begun to calcify. Third molars begin to calcify from 7-10 years. • Permanent crown formation takes up to 8 years except for third molars which can take up to 16. Root formation is largely complete by 16 years except third molars which can take up to 25 years to complete. COLLEGE OF DENTAL MEDICINE • Calcification of permanent teeth begins at birth • By 3 years, all but the third molars have begun to calcify. Third molars begin to calcify from 7-10 years. • Permanent crown formation takes up to 8 years except for third molars which can take up to 16. Root formation is largely complete by 16 years except third molars which can take up to 25 years to complete. COLLEGE OF DENTAL MEDICINE 1. First molar 2. Central incisor 3. Lateral incisor 4. First premolar 5. Mandibular Canine 6. Second premolar 7. Max. canines 8. Second molar Clinical Pearl: Variability is common! Know common variations such as lateral before central or two groups emerging simultaneously. COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE Why do you need to know? • • • • Determine Dental age Identify abnormalities in development Identify when disturbances in formation occurred Anomalies occur most commonly in 3rd molars (wisdom teeth), maxillary lateral incisors, and mandibular second premolars. • Restorative concerns and challenges • Extraction concerns COLLEGE OF DENTAL MEDICINE Tissuesof the tooth • Dental pulp- connective tissue organ. Contains artery, veins, lymphatic tissue, nerves • Primary function is to form dentin • Apical Foramen-opening at apex where nerve and blood supply pass • Cementoenamel junction- may occur in different configurations • Enamel overlaps cementum • End-to-end approximation • Absence of connection enamel and cementum so that dentin is exposed • CEJ is landmark for periodontal probing • Estimate the timing of enamel hypoplasia by measuring from CEJ to mid-point of defect. • ADF=ACF ( years of formation/crown height x distance of defect from CEJ) ADF- age at which hypoplasia occurred. ACF- age at which crown was completed COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE Developmental Anomalies • In the absence of permanent tooth, primary root may not fully resorb or resorb at all • When root resorption does not follow normal pattern and permanent tooth is present, it may be blocked out of arch • Retention of primary tooth can occur with altered resorption Clincal pearl: knowing your eruption and exfoliation sequence can help you spot potential issues early! COLLEGE OF DENTAL MEDICINE Dental Anatomy Session 3: The Primary Dentition COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE New Terms COLLEGE OF DENTAL MEDICINE Contrasts Between Primary and Permanent Teeth • Roots of primary molars are longer, more slender, and flare beyond outline of crowns to allow for developing permanent tooth. • Cervical ridges are very distinct and offer restorative challenges. • Slender cervical third in the mesiodistal dimension. • The buccal and lingual surfaces above the cervical ridge are flatter than in permanent teeth leading to a narrow occlusal surface, comparatively. • Primary teeth are whiter. COLLEGE OF DENTAL MEDICINE Function of Primary Teeth • Functions in chewing, speaking, swallowing. • Maintains space for permanent dentition. • Development of occlusion in the permanent dentition. COLLEGE OF DENTAL MEDICINE Pulp Chambers and Pulp Canals of Primary Teeth A. Enamel cap of primary molars is thinner with more uniform depth. B. Comparatively greater thickness of dentin over the pulpal wall at the occlusal fossa of primary molars. C. Pulp horns are high and dentinal thickness is limited especially in mandibular 2nd molars. D. Cervical ridges are distinct and more pronounced in primary teeth especially on buccal. E. Enamel rods at the cervix slope occlusally instead of gingivally. F. Primary molars have narrow neck. G. The roots of the primary teeth are longer and narrower in comparison with crown size. H. The roots of the primary molars flare out nearer the cervix. COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Maxillary Central Incisor Labial: M-D diameter of crown is greater than its Cervicoincisal length. (wider than it is tall) Lingual: well developed marginal ridges and cingulum. 10mm 16mm Pulp Canal Mesial/Distal: curvature of CEJless distinct than in perm. Incisal: straight. Looking down, labial surface is much broader and smoother. Primary teeth lack mammelons and have a very straight incisal edge. Pulp Horn 6mm COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Maxillary Lateral Incisor 5.6mm 15.8 mm Labial: distoincisal point angle of the crown are more rounded than central. 11.4 mm Mesial/ Distal: Larger curvature of CEJ mesially than distally, but less so than permanent. Labial Lingual Similar in all ways to central. Root is longer in proportion as compared to central. COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Maxillary Canine Labial: crown is more constricted and cervical and mesial and distal surfaces more convex. Long triangular shaped cusp. Root is long, slender and more than twice the crown length. Compared to permanent, cusp is longer and sharper. Lingual: merging enamel ridges: cingulum and M and D marginal ridges and incisal cups ridges. Tubercle at cusp tip. Shallow ML and DL fossae. Tooth tapers lingually and usually distally inclined above middle 1/3. 6.5mm 19 mm M Mesial/Distal: similar to incisors, but wider at cervical 1/3 of mesial evidencing function. Incisal: diamond shaped. Cusp tip is distal to the center of the crown and mesial cusp slope is longer than distal which intercuspates with the longer distal slope of the mandibular canine. 13.5 ML,DLFossae Labial Lingual COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Mandibular Central Incisor Labial: crown has flat face without developmental grooves. Mesial and distal sides of the crown are evenly tapered from the contact areas with narrowing at the cervix. Crown is wide in proportion to length compared to permanent. Heavy trunk resembles the permanent max lateral incisor. Root is long and tapered. Root is almost twice the crown length. Lingual: May have slight concavity called lingual fossa. Easily seen ridges and cingulum. Lingual narrower than facial. 5 mm 14mm 9 mm Mesial: Incisal ridge centered over center of the root and between the crest of curvature of the crown labially and lingually. Significant cervical bulges typical of primary incisors. Labiolingual measurement is only 1mm less than primary max central evidencing heavy function. Distal: Reverse of mesial. Curvature of DEJless pronounced. Often has a developmental depression. Incisal: Incisal ridge is straight and bisects the crown labiolingually. COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Mandibular Lateral Incisor 5 mm The primary mandibular lateral is similar, but larger, in all dimensions to the central except labiolingually, where the two are the same. The lingual surface may be more concave and there is tendency for incisal edge to slope toward distal. 15 mm 10 mm COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Mandibular Canine 6 mm Very similar to maxillary canine except in dimension. The crown is approximately 0,5mm shorter and the root at least 2mm shorter. The M-D measurement at the root trunk is greater. The most obvious differentiating trait is that the distal ridge slope is longer than the mesial slope where the opposite is true of the primary maxillary canine. 17.5 mm 11.5 mm COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Maxillary First Molar Buccal- M and D contact areas are widest, converging sharply to the cervix, which is 2mm less in width. It has a narrower appearance at the neck than its permanent counterpart. It is much smaller than the primary second molar. It is shaped like a premolar. Roots - Slender and long and widely spread. D root is much shorter than M. Bifurcation begins almost at the site of the CEJ.Characteristic of all primary molars. Very small root trunk compared to permanent teeth. Lingual – Similar to buccal. ML cusp is most prominent cusp. It is longest and sharpest. DLcusp is poorly defined, small, and rounded, if it exists. May have only one lingual cusp. 5.0 mm 15.2 mm 10 mm Mesial – Wider at cervical than occlusal. ML cups is longer and sharper than MB cusp. Pronounced convexity is evident on the buccal outline of the cervical third. Distal – Crown is narrower distally than mesially. Tapers markedly toward the distal. DBcuspislongandsharpandtheDLcuspispoorlydeveloped.Prominentbulge atcervicalthird. *What guesses can you make about the function of the larger sharper cusps? What is the relationship between cusp function and root size? COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Maxillary First Molar Occlusal - Crown outline converges lingually and also distally, but occlusal surface is almost a rectangle. Awell-defined buccal developmental groove divides (BDG) divides the MB and DB cusps. Supplemental grooves radiate from the pit in the Mesial Triangular Fossa (MTF), one to the buccal, one to the lingual and one toward the marginal ridge. Sometimes an oblique ridge is present. There is always a distal developmental groove (DDG). This tooth does not resemble its counterpart in the permanent dentition, but does resemble a premolar, even though the primary dentition does not have them. COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Maxillary Second Molar Buccal – Resembles first permanent maxillary molar but is smaller. Two welldefined buccal cusps with a buccal developmental groove between them. The crown is narrow a the cervix in comparison with its MD measurement. Much larger than that of the first primary molar with much longer and heavier roots. Cusps are of nearly equal size. Lingual - Three cusps: Mesiolingual cusp, the largest and most well developed, Distolingual cusp, and a third supplemental cusp which is apical to the ML cusp and is often called the cusp or tubercle of Carabelli. Mesial – Resembles permanent molars. ML cusp appears large. MV cusp is relatively short from this angle. CEJ nearly straight. MB root extends lingually far out beyond the crown outline. 11.7 mm 17.5 mm 5.7 mm COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Maxillary Second Molar Distal – Smaller than Mesial. CEJis mostly straight. All roots can be seen from this aspect. DB root is shorter and narrower than the other from this view. This surface shows the most centered bifurcation between these roots. Occlusal - Resembles permanent first maxillary molar. Somewhat rhomboidal with four well-developed cusps and a cusp of Carabelli. There is a central fossa containing the Central Pit (CP), a Mesial Triangular Fossa (MTF) just distal to the Mesial Marginal Ridge (MMR) with its Mesial Pit (MP),A well defined Central Groove (CG) connects the MTF with the CF.The Buccal Developmental Groove extends buccally from the central pit separating the triangular ridges. There is a prominent Oblique Ridge (OR) just mesial to the Distal Fossa (DF). The DFcontains the Distal Developmental Groove (DDG). COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Mandibular First Molar Occlusal– Rhomboidal.MB prominence visible. ML cusp may be seen as the largest and best developed of all the cuspsand has a broad flatsurfacelingually. The MB cusp has a well-defined triangular ridge on the occlusal which terminates in the center of the occlusal surface buccolingually at the Central Developmental Groove (CDG).TheLingual Developmental Groove (LDG)extends towardlingualfromthe CDGseparatingtheMLandDLcusps.UsuallytheLDGextends just to the junction of the lingual cusp ridges without crossing over to the lingual surface. Themandibular primary firstmolarisunique.It doesnotresembleanyoftheotherteethin either dentition. COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Mandibular First Molar Buccal – The mesial outline of the crown at the contact is nearly straight, dropping down from the marginal ridge to the cervix. The distal makes up for it and converges dramatically toward the cervix. The distal portion of the crowns is shorter than the mesial portion with the CEJdipping apically where it joins the M root. Two distinct buccal cusps with the being larger. The roots are long and slender and spread at apical ½. If the crown were to be bisected through the furcation, the tooth would be evenly divided, but the mesial portion would be almost twice as tall as the distal half with a root that is a third longer than the distal. Lingual - The crown and root converge to the lingual markedly on the mesial surface. Distally, the opposite is true. The DLcusp is rounded with a hint of developmental groove between this cusp and the ML cusp. The ML cusp is a distinguishing feature. It is almost centered lingually but also in line with the mesial root. The mesial marginal ridge is very well developed almost resembling a small cusp. Mesial – The most noticeable detail is the extreme curvature toward the buccal at the cervical third. 6 mm 9.8 mm 15.8 mm Which side is the mesial? COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Mandibular First Molar Mesial – The most noticeable detail is the extreme curvature toward the buccal at the cervical third. In this view, it otherwise resembles the mesial of the primary second mandibular molar and the mesial of the mandibular permanent molars. Cusps are over the root base and the lingual outline extends beyond the root base. The CEJslants upward buccollingually due to the larger MB cusp. Note the flattened buccal surface from the crest of curvature on the buccal surface at the cervical third to the tip of the MB cusp.All primary molars have flattened buccal surfaces in this segment. Distal – Differs from mesial surface. The CEJdoes not drop buccally. The length of the crown bucaly and lingually is more uniform and the CEJis nearly straight. The DB cusp and DLcusp are not as long or sharp as the mesial cusps. The distal marginal ridge is smaller and the distal root is rounder and shorter. COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Mandibular Second Molar B Buccal – From the buccal, the primary mandibular second molar is narrow at the cervical portion of the crown compared to its width at the level of the contact. The tooth is divided into three similarly sized cuspal portions by developmental grooves, which results in a straight buccal surface with a Mesiobuccal, a buccal, and a distobuccal cusp. The roots are slender and long and flare widely. The roots of this tooth may be twice as long as the crown. Lingual– Two lingual cusps of nearly equal size separated by short lingual groove. The cuspsare not as wide as the threebuccalcuspsso the lingual is narrowerthanthe buccal. Relatively straight CEJ. Crown extends over root more at distal. L The primary mandibular second molar resembles the permanent mandibular first molar. COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Mandibular Second Molar Mesial – Resembles the permanent first molar. Crest of contour on buccal is more prominent on the primary molar which constricts toward the occlusal as it flattens above the cervical ridge. The buccal cusp is over the root and the lingual is extended beyond it. The lingual cusp is higher than the buccal cusp. The CEJis regular but slightly upward slanted from buccal to lingual to compensate for larger buccal cusp. The mesial root is broad and flat with a blunt apex. M Distal – Differs from Mesial. CEJdoes not drop to buccal. Length of crown is more uniform buccally and lingually. The CEJis almost straight across. The DB cusp and the DLcusp are not as long or as sharp as the mesial cusps. The distal marginal ridge is not as straight or well defined as on the mesial. The distal root is rounder, shorter, and more tapered. COLLEGE OF DENTAL MEDICINE Tooth by Tooth Description Primary Mandibular Second Molar Occlusal-Fairly rectangular. Three similarly sized buccal cusps and two lingual. The tooth is slightly wider at the buccal. Welldefined triangular ridges extending from each cusp tip to the central groove. Compared to the permanent mandibular first molar, the MB, DB, and DB are almost equal in size and development. The D cusp of the permanent molar is smaller than the other two. Because of the small buccal cusps, the primary tooth crown is narrower buccolingually compared to its mesiodistal measurement, than it is in the permanent tooth. COLLEGE OF DENTAL MEDICINE Differences to note Primary crown is wider m-d than its cervcico-incisal dimension Primary teeth lack mammelons and have a very straight incisal edge The curvature of the CementoEnamel Junction (CEJ) is less distinct COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE Comparison of Main Features of Tooth Types Central Incisors COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE Impression Materials Yacoub Al Sakka, DDS COLLEGE OF DENTAL MEDICINE Purpose and Requirement (1) Sufficiently fluid to adapt to the oral tissues. (2) Viscous enough to be contained in a tray. (3) Able to transform (set) into a rubbery or rigid solid in the mouth in a reasonable time. (4) Resistant to distortion or tearing. (5) Dimensionally stable long enough (6) Biocompatible. (7) Cost-effective. Various materials are available for making a precision negative mold of soft and hard tissues. Main purpose is to duplicate the anatomical form of the oral tissue COLLEGE OF DENTAL MEDICINE Working and Setting Time • Working Time. • Setting Time. • Variables Dentsply Official website The working time begins at the start of mixing and ends just before the elastic properties develop. The setting time is the time elapsed from the beginning of mixing until the material has enough strength to be removed from the mouth without distortion. COLLEGE OF DENTAL MEDICINE Ratio, Mixing and Setting Time • Changes in W/P ratio will alter consistency, strength and quality. • Under/over mixing will affect strength of the set impression. • Setting rxn is chemical reaction. Changes with temperature differences The proportioning of the powder and water before mixing is critical to obtaining consistent results. Changes in the water-to-powder (W/P) ratio will alter the consistency and setting times of the mixed material and also the strength and quality of the impression. COLLEGE OF DENTAL MEDICINE Dental Biomaterials: Gypsum COLLEGEOF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE Gypsum(CaSO4•2H2O) • Calcium sulfate dihydrate • Naturally occuring mineral mined around the world • Supplied as fine hemihydrate (CaSO4 •½H2O) powders • Used in construction, soil conditioning, food additives, pharmaceuticals, medical devices • Dental applications • Study models for oral and maxillofacial structures • Auxiliary materials for dental laboratories for production of dental prostheses. COLLEGE OF DENTAL MEDICINE Model vs. Cast COLLEGE OF DENTAL MEDICINE Glossaryof Prosthodontic Terms (Journal of Prosthetic Dentistry) • model \mŏd ́ l \ n (1575): a facsimile used for display purposes; a miniature representation of something; an example for imitation or emulation • cast \kast\ n (14c): a life-size likeness of some desired form; it is formed from a material poured into a matrix or impression or from a CAM printed replica; comp, DENTAL CAST, DIAGNOSTIC CAST,FINALCAST,PRELIMINARYCAST,REFRACTORYCAST,REMOUNT CAST COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE Model Cast Arepresentationof the patient’s mouth/dentition that is not necessarilywithout inaccuracies used for planning and patient education An accurate representationof a patient’s mouth/dentition used for fabrication of a dental prothesis Typically made from plaster but can be stone Typically made from stone and not plaster COLLEGE OF DENTAL MEDICINE Properties of an ideal gypsum product for a dental purpose: • • • • • • Dimensional accuracy: the dimensional changes which occur during and after the setting of these model materials should be minimal in order to produce an accurate model or die. Fluid at the time it is poured into the impression so that fine detail can be recorded. Minimize the presence of surface voids on the set model by encouraging surface wetting. Strong to resist accidental fracture. Hard enough to resist abrasion during manufacturing of a dental prosthesis. Compatible with all the other materials with which it comes into contact. COLLEGE OF DENTAL MEDICINE The current ISO Standard identifies 5 types: Type 1: Dental plaster (impressions) Type 2: Dental plaster (models) Type 3: Dental stone (models, casts) Type 4: Dental “die” stone - high strength, low expansion Type 5: Dental “die” stone - high strength, high expansion COLLEGE OF DENTAL MEDICINE TypesofGypsumProducts Selection criteria depends on purpose and physical properties 1. Impression Plaster (Type I) • Plaster of Paris • Modifiers regulate the setting time and setting expansion • Rarely used for making dental impressions- better materials available 2. Model Plaster (Type II) • Laboratory type II plaster • Used to fill a flask used in denture construction • Natural white color to contrast with colored stone 3. Dental Stone (Type III) • Minimal 1-hour compressive strength of 20.0 MPa. • Used for cast construction in the fabrication of full dentures to fit soft tissue • A slight settingexpansion can be toleratedin casts that reproducesoft tissues but not teeth • Used to process dentures because the stone has enough strength for this purpose but low enough strength for separating the denture from the cast. COLLEGE OF DENTAL MEDICINE Typesof GypsumProducts 4. Dental Stone, High Strength (Type IV) • Die material requires strength, hardness, and minimal setting expansion. • Modified α-hemihydrate is used • Allows “ditching” of the margins with a sharp instrument • Surface hardness increases more rapidly than the compressive strength because the surface dries more rapidly. • The average dry surface hardness = 92 (Rockwell hardness) • Type III stone is 82 (Rockwell hardness) 5. Dental Stone, High Strength, High Expansion (Type V) • Strength is attained by lowering the W/P ratio • Setting expansion has been increased from a maximum of 0.16% to 0.30% • Rational - use of base metals that have a greater casting shrinkage than do the traditional noble-metal alloys • Avoid use for producing dies for inlays and onlays – too tight COLLEGE OF DENTAL MEDICINE Controlof the Setting Time 1. W/P ratio: • Volume of the water divided by the weight of the hemihydrate powder • Important determining the physical and mechanical properties of the final gypsum product • Higher W/P ratio decreases the number of nuclei per unit volume = longer setting time. • The amounts of water and hemihydrate should be gauged accurately by volume/weight 2. Spatulation • Longer and more rapid mixing of the gypsum will result in a shorter setting time. 3. Water Temperature • Increase in water temperature leads to an acceleration of a chemical setting reaction. 4. Chemical modifiers • to increase or decrease the setting time - retarders and accelerators • Accelerators • Potassium sulfate • Slurry water COLLEGE OF DENTAL MEDICINE Factors controlled by manufacturers: • The concentration of nucleating agents in the hemihydrate powder: a higher concentration of nucleating agent, produced by ageing or from unconverted calcium sulphate dihydrate, results in more rapid crystallization. • Addition of chemical accelerators or retarders to dental stones: Potassium sulphate is an accelerator which act by increasing the solubility of the hemihydrate. Borax is a widely used retarder, the mechanism by which it works is not clear. Factors controlled by the dentist: •Temperature variation has little effect on the setting time. Increasing the temperature accelerates the dissolution of hemihydrate but retards the crystallization of dihydrate. •Increasing the W/P ratio retards setting by decreasing the concentration of crystallization nuclei. •Increasing mixing time (and speed) accelerates setting by breaking up dihydrate crystals during the early stages of setting, producing more nuclei on which COLLEGEOFDENTALMEDICINE crystallization can be initiated. COLLEGE OF DENTAL MEDICINE Dental Anatomy The Embrasure and Protective Function COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE ToothFormin Protective Function • Proximal Contact areas – protect the interdental space from food impaction. • Interproximal areas – house the papilla • Embrasures (spillways) – allow for the escape of food, thus preventing impaction. • Height of Contour- allows for natural *cleansability and protects the surrounding gingiva • Curvature of CEJ – dependent on height of contact area and the buccolingual diameter of the crown. *Not a word, but look! We are using it and you know what it means! COLLEGE OF DENTAL MEDICINE Formin Protective FunctionIntra-arch Relationships • Proximal Contact area • Embrasures (spillways) • Interproximal space • Labial/Buccal contours at the cervical third (cervical ridge) • Lingual contours at the middle third of the crown COLLEGE OF DENTAL MEDICINE ProximalContact Area • The proximal contact is the location of positive contact of one tooth with another in their alignment in the dental arch. • Except for the terminal teeth (Posterior-most teeth in the arch) each tooth should have a mesial and a distal contact. • The teeth touch in contact areas, not in point contacts • In newly erupted teeth in young dentitions, contacts on curved surfaces approach point contacts. • Distal of canines and mesial of first premolar have the smallest contact. • In the posterior, contacts are broader and flatter. COLLEGE OF DENTAL MEDICINE Contact area TheProximalContact Outline form of interdental papilla Why is it important? • Prevents food impaction • Provides stability within the arch by means of combined anchorage. Think of a fence. • Prevents drifting within the arch • Disperses occlusal forces to neighboring teeth COLLEGE OF DENTAL MEDICINE Interproximal Contact Position • Contacts are observed from 2 views: • Buccal • Incisal • Black lines denote position of contact in facial lingual dimension. COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE Interproximal Contact Position From the Labial/facial aspect: Black lines denote position of contact cervico-incisally/occlusally. COLLEGEOFDENTALMEDICINE Start high and go low towards the posterior. COLLEGE OF DENTAL MEDICINE ProximalContactsof Anterior Teeth Contacts of Central Incisors The contact areas mesially on both central incisors are located at the incisal third of the crowns. Because the mesioincisal third of these teeth approaches a right angle, the incisal embrasure is very slight. Contacts of Central and Lateral Incisors The distal outline of the central incisor crown is rounded. The lateral incisor has a shorter crown and has a more rounded mesioincisal angle than the central incisor. Their contact opens up an embrasure space distal to the central incisors larger than the small one mesial to the central incisors. Aline bisecting the contact areas distal to the central incisor and mesial to the lateral incisor approaches the junction of the middle and incisal thirds of each crown. COLLEGE OF DENTAL MEDICINE Contactof Lateral andCanine • Lateral Incisor and Canine • The distal contact area on the lateral incisor is approximately at the middle third. The mesial contact area on the canine is at the junction of the incisal and middle thirds. The form of these teeth creates an embrasure that is more open. COLLEGE OF DENTAL MEDICINE Trendsof Proximal Contacts • Contacts of posterior teeth are generally located buccal to center when viewed from the occlusal. • Contacts move cervically from the anterior to the posterior. • Contacts are more cervical on the distal of a tooth than the mesial. • Contacts become broader toward the posterior. • From the facial/lingual aspect, incisal/occlusal embrasures increase in size from anterior to posterior, but the cervical embrasures decrease in size. COLLEGE OF DENTAL MEDICINE TheSpacesaround a ProximalContact The proximal contact is surrounded by embrasures. • V-shaped valley between the teeth formed by the contact area. • Embrasures are named according to their location: • Gingival embrasure/interproximal space • Where papilla resides • Floor of embrasure is alveolar bone • Incisal embrasure • Labial/Buccal embrasure • Lingual embrasure Incisal embrasure Level of contact area Gingival embrasure/interproximal space Labial embrasure Level of contact area Lingual embrasure COLLEGE OF DENTAL MEDICINE Embrasures What purpose do they serve? • The spaces that are coronal to the contact area serve as spillways for the escape of food during chewing. The diversion of food from the occlusal table reduces the forces that cause food impaction into the contact area. • Aid in self-cleansing by exposing surfaces to oral fluids and mechanical cleansing. • The spaces that are apical to the contact area are filled with the papilla. COLLEGE OF DENTAL MEDICINE ToothFormInfluencesEmbrasureShape Blunted papilla The effect of spacing on papilla form COLLEGE OF DENTAL MEDICINE TheProximalContact Is described in a buccal lingual and a cervicoincisal relation. The buccal lingual position can be observed from the occlusal aspect. The cervicoincisal position can be observed from the buccal aspect. Contact position is dependent on alignment of the teeth. COLLEGE OF DENTAL MEDICINE Height of Contour COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE HeightofContour • Also known as the crest of curvature. • Place of greatest contour (bulge) occluso-gingivally. • Found on buccal and lingual surfaces • Aid in protection and stimulation of the gingival tissue. • On Facial surfaces, HOCis located in cervical third. • Lingual surfaces – anterior teeth HOCis at cervical 1/3. In posterior teeth, HOCis in middle or occlusal 1/3 . COLLEGE OF DENTAL MEDICINE Curvature of the CEJ and Gingival Line • • • • • The CEJ does not change. Its curvature is related to the dimensions of the crown and the contact area. Curves toward apical on the facial and lingual surfaces. Curves incisally/occlusally on the proximal surfaces. The Curvature is more marked on the mesial. The curvature is greater on anterior teeth and decreases posteriorly. COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE Dental Anatomy Session Number 4 Form and Function COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE The Stomatognathic System Ellis and Throckmorton. Mandibular Condylar Process Fractures. JOral Maxillofac Surg 2005. COLLEGE OF DENTAL MEDICINE Relationof ToothFormtoFunction • Herbivorous Dentition • Form and alignment to allow for mastication of vegetation by lateral movement. • Shallow cusps • Omnivorous Dentition • Form and alignment capable of up and down and lateral movements • Differentiated cusp forms. • Carnivorous Dentition • Form and alignment to allow mastication of animals by up and down movements. • Very steep cusps. COLLEGE OF DENTAL MEDICINE Lobes • Each lobe represents a primary center of formation • All anterior teeth show traces of four lobes • Three labially: mesial, labial, distal • One (cingulum) lingually: lingual • Each labial lobe of the incisor terminates incisally in rounded eminences called mamelons. • Prominent in newly erupted incisors, but usually wear with use. • Primary teeth do not have mamelons. • Maxillary centrals incisors often have labial grooves, which are remnant of the fusion of three lobes. COLLEGE OF DENTAL MEDICINE More on lobes • In premolars they are mesial, buccal, distal, and lingual. • The mandibular second premolar often also has two lingual cusps. Its lobes are the mesial, buccal, distal, mesiolingual and distolingual. • Molar lobes are named the same as the cusps. The tip of each cusp represents the primary center of formation of each lobe. • Turbercles of enamel may be found in addition to the primary lobes. Remember the cusp of Carabelli! COLLEGE OF DENTAL MEDICINE AWholeLottaLobes A. Labial of maxillary incisor showing mesial, labial, and distal lobes separated by labial grooves. The lingual lobe/cingulum not pictured. B. And E. lobes marked 1. mesial, 2. buccal, 2. distal, 4. lingual. C. 1st mandibular molar. 1 dl cusp/lobe, 2ml cusp/lobe, 4. distobuccal cusp/lobe, 5. mesiobuccal cusp/lobe, the distal lobe is between 4 and 1. D. Maxillary molar lobes/cusp 1. Mesiobuccal, 2. Distobuccal, 3. Mesiolingual, 4. Distolingual, 5. Cusp of Carabelli! COLLEGE OF DENTAL MEDICINE • Functional cusps aka stamp cusps, working cusps, centric cusps- Lingual of maxillary teeth, buccal of mandibular teeth. These cusps occlude with a fossa on the enamel inclines on each side of the groove and not in the depth of the groove. This leaves a small v-shaped path of escape for food. Cusps V-shaped groove for escape of food • Guiding cusp aka non-functional or non-working cusps – buccal of maxillary teeth, lingual of mandibular teeth. COLLEGE OF DENTAL MEDICINE Fissures and Pits • Failure or compromised coalescence of the enamel of the developmental lobes results in a deep invagination in the groove area of the enamel surface and is termed fissure. Non-coalesced enamel at the deepest point of a fossa is termed pit. Fissures and/or pits represent non– self- cleansing areas where acidogenic biofilm accumulation may predispose the tooth to dental caries COLLEGE OF DENTAL MEDICINE Geometriesof CrownOutlines All aspects of each tooth crown except the incisal or occlusal will fit within one of three geometric figures: • Triangle • Trapezoid • Rhomboid Why should you care? Aside from helping us to understand the functional aspects of the teeth, these shape questions appear on the boards. COLLEGE OF DENTAL MEDICINE Geometriesof CrownOutlines Note that the teeth occlude in a cusp/fossa relationship which delivers the force down the long axis of the root! COLLEGE OF DENTAL MEDICINE Long Axis CusptoFossa Youcanseehowthelineofforceisapplieddown the long axis of the tooth. This is a guiding principle of restorative dentistry. COLLEGE OF DENTAL MEDICINE Fundamentalsof Form • Facial and Lingual surfaces are trapezoids. • The interproximal spaces accommodate gingival tissue. • Spacing between the roots allow for sufficient bony support, nutrition, and function. • Every crown must be in contact at some point with at least one adjacent tooth to help protect the gingiva from trauma during mastication. • Interproximal contacts ensure support and stability. • Each tooth in the dental arch has two antagonists in the opposing arch EXCEPTthe mandibular central incisor and the maxillary third molar. Gingiva goes here! COLLEGE OF DENTAL MEDICINE Mesial and Distal Aspectsof the Anterior Teeth Triangles • Awidebaseforthecrownforstrength. • Tapered labial and lingual outlines narrowing to a thin ridge for incising. • From the facial, these teeth are trapezoids. COLLEGE OF DENTAL MEDICINE Mesial and Distal of Maxillary Posterior Teeth Trapezoids • The longest side is the base of the crown as opposed to the occlusal in the labial or lingual view. • Because the crown is narrower at the occlusal, it can more easily penetrate food. • If the crown were as wide as the base of the crown, it would take much more force to penetrate, and would tend to crush. Think of a mallet vs. a spear. Which is more effective at piercing? COLLEGE OF DENTAL MEDICINE Mesial and Distal of the Mandibular Posterior Teeth Rhomboidal • Crowns inclined lingual to their root bases. • Force is delivered down long axis of teeth. • If mandibular crowns were not inclined lingually, they would not intercuspate properly, but clash with the opposing cusp. COLLEGE OF DENTAL MEDICINE Interproximal Form/Contacts • The contact point of adjacent teeth is called an interproximal contact. • The triangular space apical to the contact is the interproximal space and is normally filled by the papilla. • Deficient marginal ridges and improper contacts contribute to food impaction into this space. • The gingiva follows the curvature, but is not necessarily coincident with, the CEJ. This feature is known as the gingival line. • Lossofpapilladuetoincorrectmanagementoftheinterdental spaceisa significant esthetic concern in the anterior teeth. COLLEGE OF DENTAL MEDICINE OcclusalCurvature The incisal edges and occlusal surface when examined as a whole, does not make a flat occlusal plane. Rather, there is curvature both anterio-posteriorly and Buccolingually. The two curves together create a kind of sphere of space. Curve of Spee- Curvature anterioposteriorly Curve of Wilson- the curvature buccolingually COLLEGE OF DENTAL MEDICINE Dental Anatomy Mandibular Incisors Session Number COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE ThePermanentMandibularIncisors Overview • The mandibular incisors have the smallest mesiodistal dimensions of all the teeth. • The central incisor is somewhat smaller than the lateral incisor. • The mandibular incisors are similar in form and show little trace of developmental features (smoothest in the mouth). • The contact areas are near the incisal ridges mesially and distally. • The mandibular incisors show little variability in development. • Mandibular incisors vary greatly from their maxillary counterparts. • Mesial and distal views of crown inclination are different. • Labial surfaces are inclined lingually. • The incisal edge (after mamelons have worn) are labially inclined as opposed to lingual inclination of maxillary incisors so that the planes are parallel. COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE TheMandibularCentralIncisors LabialAspect • Incisal ridge is straight and at nearly a 90 degree angle to the long axis. • Mesial and distal sides taper evenly from contact area to narrow cervix. • Outline form of root continuous with crown. • Incisal third is flattened while middle third is convex. • Apical third of root tapers to point which is generally distally inclined. D M • Sharp mesial and distal incisal angles. • Greatest CEJ contour of all mandibular teeth. • Smoothest, smallest, and most symmetric tooth in the mo • Contact points are in the incisal 1/3. COLLEGE OF DENTAL MEDICINE TheMandibular Central Incisors LingualAspect • Lingual aspect is smooth with a slight concavity at the incisal third between the inconspicuous marginal ridges. • Sometimes, the marginal ridges become more pronounced toward the incisal edge. • The lingual surface flattens then becomes convex toward the cervical third. • Few if any developmental lines. • Root is distally inclined. • Regular and symmetric outline form. • Cingulum is centered on long axis. M D COLLEGE OF DENTAL MEDICINE TheMandibular Central Incisors Mesial Aspect • Curvature of cervical line curves about 1/3 incisally and is greater than on the distal. • Labial outline is slightly labially inclined as it moves from cervical line then inclines sharply to lingual at HOC. • Lingual outline • Incisal ridge is rounded or worn flat and its center is usually lingual to the center of the root. • The root outlines from mesial are straight with the crown outline tapering rapidly in the apical ½to a blunt or pointed root tip. COLLEGE OF DENTAL MEDICINE TheMandibularCentralIncisor Distal Aspect • The cervical line curves about 1mm less than on the mesial. • The developmental depression on the distal root may be more pronounced than on the mesial. • Also contains developmental groove. 1 root 3 pulp horns 1 or 2 root canals. 40% of centrals have bifurcation of root canal. COLLEGE OF DENTAL MEDICINE Mandibular Lateral Incisor Facial and Lingual Aspects Facial Lingual • Sharp Mesioincisal angle. The distoincisal angle is more rounded. • More prominent Distal marginal ridge than central incisor. • Root is more distally inclined. • Lateral incisors are wider than the centras in a mesiodistal dimension. • Discernable lingual fossa. Facial Lingual COLLEGE OF DENTAL MEDICINE Mandibular Lateral Incisor Incisal Aspect • Mesial incisal edge slopes gingivally. • Distolingual twist to the crown. • Cingulum sits distal to center. • Curve to the distal of the crown. COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE Mandibular Lateral Incisor Mesial Aspect Mesial Distal Root • • • • • • • Mesial • Longer and wider root than central. Root is elliptical in cross section. 1 root 3 pulp horns 1 root canal (most of the time) Root is distally inclined. 43% of mandibular laterals will have 2 canals! Deeper root depression. Distal COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE Occlusion Session Number 1 Occlusion/TMJ anatomy COLLEGE OF DENTAL MEDICINE Occlusion Definition: The way the teeth meet when the mandible and maxilla come together. Occlusion is part of an integrated system that includes the teeth, joints, and musculature of the head and neck in oral motor function. Also, it describes the relationship movements. between tooth contacts and mandibular COLLEGE OF DENTAL MEDICINE Concepts in Occlusion The muscles of mastication move the mandible. The condyles and anterior teeth guide the mandible and teeth through function. Teeth need to function in harmony with each other, and with the joints and muscles. • Tooth morphology determined by: • TMJ’s • Condylar guidance/angle of eminence – determines how steeply the mandible moves downward and forward, which affects cusp height. • Anterior Guidance • Lingual inclines of maxillary anterior teeth • Overbite • overjet • Tooth alignment within the arch and with the opposing teeth • Jaw alignment- angles classification COLLEGE OF DENTAL MEDICINE Determinants of Occlusal Morphology The occlusal anatomy of the teeth must function in cooperation with the structures that are controlling the movement of the mandible: TMJ’s – condylar guidance Anterior teeth - Overjet, overbite, contours of lingual surfaces of maxillary teeth. The teeth must fit into the harmony of the jaw movement and vice versa. The teeth approximate but do not touch during movement. The steepness of the articular eminence determines at what angle the mandible descends. The angle of the cusps must be in harmony with the angle of the eminence to avoid occlusal interference. Occlusal interference: undesirable tooth contacts that may interfere with centric closure or in function. More on this later. COLLEGE OF DENTAL MEDICINE Determinants of Occlusal Morphology Vertical Horizontal • Anterior guidance (variable) • Distance from the midline • Distance of cusp to the controlling factors (variable) • Mandibular lateral translation • Condylar guidance (fixed) • Plane of occlusion (variable) • Curve of Spee (variable) • Bennet Movement (fixed) • Immediate side shift or progressive side shift. (fixed) • Distance from working condyle • Intercondylar distance Vertical determinants determine cusp heights and . COLLEGEOF DENTALMEDICI Fossadepths. Horizontal determinants affect the location and direction of ridges and grooves on the occlusal surface. COLLEGE OF DENTAL MEDICINE Skeletal Relationships Relationship of the mandible to the maxilla Angle’sClassificationI, II, III Orthodontic classification of the relationship of the maxillary and mandibular first molars to each other. • Class I – the position of the dental arches is normal with first molars in occlusion where the MB cusp of the upper first permanent molar occludes with the sulcus between the mesial and distal buccal cuspsof the lower first permanent molar. • ClassII - The relationship of the dental arches is abnormal with all the mandibular teeth occluding distal to normal. • Class II division 1 – upper incisors are protruding. • Class II division 2 – upper incisors are lingually inclined. (Hello, Ricky Gervais and Kiersten Dunst.) • Class III – The relationship of the dental arches is abnormal with all mandibular teeth occluding mesial to normal. COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE Anterior Tooth Relationships COLLEGE OF DENTAL MEDICINE Anterior Tooth Relationships • Due to the labial inclination and the larger maxillary arch, the maxillary anterior teeth overlap the mandibular anterior teeth in both horizontally and vertically. • Light or no contact in MIP. • Spares them from heavy occlusal forces that could displace them further labially. • Do not need to be in contact as posterior teeth maintain VDO. • Do need to engage during protrusive and lateral movements to guide mandible. COLLEGE OF DENTAL MEDICINE Anterior Tooth Relationships Maxillary arch form tends to be larger than mandibular, so the maxillary teeth overlap the mandibular. Overjet is usually 2-3mm. Overbite is usually 2-3mm. Jets fly horizontally! COLLEGE OF DENTAL MEDICINE Contacts • Static occlusion describes the contact • Dynamic occlusion describes the contacts between the teeth when the mandible is not between the teeth when the mandible is moving, moving. such as during chewing, speaking, or swallowing. • The lines indicate contact during protrusive and are an example of dynamic contacts. The dots indicate contacts in MIP and are an example of static contacts. • Dynamic contacts reflect the presence or absence of guidance. • Movements: • Working side- The side that the mandible moves toward during movement. • Non-working- the side that the mandible moves away from. COLLEGE OF DENTAL MEDICINE ToothContact Anterior Guidance=PosteriorDisclusion Teeth meet in a cusp fossa relationship where ideally: • The teeth contact simultaneously and with equal intensity. The back teeth are in contact while the anterior may or may not be in contact. • The posterior teeth come apart as soon as the mandible leaves MIP. • AssoonasthemandibleleavesMIP,theanteriorteethcontactandguide the mandible, along with the condylar path. This is incisal guidance. • When the posterior teeth disclude, the powerful elevator muscles shut off. • This disclusion protects the anterior teeth from occlusal forces. COLLEGE OF DENTAL MEDICINE Determinants of Occlusion Controlling factors Determinants of Occlusion Posterior • TMJ – and the condylar path The closer a tooth is to a determinant, the greater it will be influenced by it. -Yoda Neuromuscular System Anterior • Teeth • Posterior teeth-vertical stops for closure and guide the mandible to maximum intercuspation. • Muscles and nerves. • Anterior teeth-guide the mandible in lateral excursive and protrusive movements. COLLEGE OF DENTAL MEDICINE Guidance Condylar Gu