Tooth Crown and Root Anatomy Tena A. Phillips, DDS Assistant Professor Chattanooga State Community College Dental Hygiene Program

Transcription

1 Key Terms Tooth Crown and Root Anatomy Tena A. Phillips, DDS Assistant Professor Chattanooga State Community College Dental Hygiene Program Primary Dentition Permanent Dentition Mixed Dentition Quadrant Sextant Anterior Posterior Mastication Universal Numbering System Palmer Numbering System Federation Dentaire Internationale Mesial/Distal Buccal, Facial, Labial Lingual Occlusal Proximal Line angle Point angle Enamel Dentin Cementum Pulp Key Terms. Learning Objectives CEJ DEJ Anatomical Crown Clinical Crown Free gingiva Attached gingiva Mucogingival junction Mucosa Gingival sulcus Gingival margin Lobe Mammelon Cingulum Cusp of Carabelli Cusp Pit/Fissure Groove Fossa Sulcus Marginal ridge Transverse ridge Oblique ridge Define and correctly spell key terms Describe the differences between primary and permanent dentitions and approximate year of eruption for each tooth Describe the stages of tooth development Be able to utilize various numbering systems Know the surfaces of teeth and the jargon utilized in communicating with other professionals when discussing tooth surfaces and restorations. Be prepared to discuss line angles and point angles Compare and contrast anatomical differences among various teeth in the primary and permanent dentition. Be able to identify various teeth and list their probable universal tooth number Be prepared to discuss the cleaning techniques for various difficult to clean areas of teeth. Dentition Dental Anatomy Overview There are only two sets of teeth and three dentitions: Primary Permanent Mixed 1

2 Primary Dentition (Deciduous teeth or Baby Teeth) Permanent Dentition (Adult Teeth) Contains 20 teeth These teeth are called deciduous because they are lost and new teeth erupt. (like a deciduous tree that loses it s leaves in the winter) They erupt at different ages and are lost at different ages. Contains 32 teeth. Anterior and bicuspid (premolar) teeth are succedaneous, meaning they replace or succeed the primary teeth Molar teeth do not replace primary teeth in order to erupt Image courtesy of Image courtesy of Mixed Dentition (both primary and permanent teeth are present) Dental Arches Generally occurs between ages 6 and 12. Image courtesy of Dentagama.com Maxillary Arch (Upper) Mandibular Arch (Lower) Quadrants Sextants The mouth can be divided into 4 equal sections called quadrants. The oral cavity can also be divided into 6 equal parts called sextants. From Finkbeiner B, Johnson C: Comprehensive dental assisting, St Louis, 1995, Mosby From Finkbeiner B, Johnson C: Comprehensive dental assisting, St Louis, 1995, Mosby 2

3 Anterior vs. Posterior Anterior teeth include 6 teeth in the maxillary arch and 6 in the mandibular arch. 2 central incisors, 2 lateral incisors, 2 cuspids or canines Posterior teeth include bicuspids (premolars) and molars Functions of Teeth Mastication Teeth are designed for chewing or mastication. incisors cuspids bicuspids molars chisel-like cutting or incising Wedgelike cutting/ tearing Min. 2 cusps Tearing/ grinding 4-5 cusps grinding Functions of Teeth Other Tooth Numbering Systems Universal Appearance Speech Most widely used numbering system In the USA Growth of Jaws Image: denteractive.com Tooth Numbering System Palmer Tooth Numbering System International (FDI-Federation Dentaire Internationale A two digit system is used: The first digit indicates the quadrant The second digit indicates the number of the tooth in the quadrant. The numbers are pronounced separately. Used by many Pedodontists! 3

4 Tooth Development Tooth Development Chart Simplified Version Image: doctorspiller.com Image: devbiologist.org Parts of the Teeth Parts of the Periodontium Slideshare.net Image: acs.org. Surfaces of Teeth Teeth have 5 surfaces: Mesial (proximal) Toward midline Distal (proximal) Away from midline Buccal / Facial / Labial Toward cheek/lip Lingual / Palatal Toward the tongue or palate Occlusal / Incisal Chewing surface 4

5 Questions? Learn the Jargon This method of tooth notation is 1. Palmer 2. Universal 3. Federation Dentaire Internationale 4. None of the above Is there ever an instance when two mesial surfaces approximate each other? 1. Yes 2. No The line marks the mesial surface of & Is there ever an instance when two distal surfaces approximate each other? 1. Yes 2. No Teeth can be divided into thirds. Line and Point Angles of Teeth Line angle Formed by the junction of two surfaces Its name is derived from both surfaces Point angle Formed by the junction of three surfaces Its name is derived from these three surfaces. Line Angles Point Angles medical-dictionary.thefreedictionary.com medical-dictionary.thefreedictionary.com 5

6 Anatomical Landmarks of the Crown Developmental Lobes in Anterior Teeth Lobes are the primary centers of calcification and growth during tooth development. Each tooth develops from 4 or more lobes. The pulp chamber has pulp horns that correspond to these lobes. Images courtesy of pocketdentistry.com Mammelons Lingual of Maxillary Anterior Cingulum / Lingual Pit Medicineacademic.ru Images: slideshare.net Cusps Developmental Lobes in Posterior Teeth Cusps Canines and posterior teeth have one to five cusps Most cusps are named for the closest tooth surface or line angle Slideshare.net 6

7 Lobes of Anterior & Posterior Teeth Ridges: Marginal Ridges Marginal Ridges are elevations of forming the margin of the surface of the tooth. Anterior Posterior Ridges: Triangular Ridges: Transverse Transverse ridge is the union of two triangular ridges. Image: slideshare.net Quizlet.com Ridges: Oblique Oblique ridge is the union of two triangular ridges that are not straight across from each other Tubercle Small elevation that is formed entirely of enamel. It has no pulp horn. Image: studyblue.com Slideshare.net Cusp of Carabelli on Max Molar 7

8 Questions? Crown depressions Grooves/Fissures/Fossa/Pits/Sulcus Grooves are shallow depressions that separate cusps or primary parts of teeth Fissures are grooves that are deep and have not fully grown together. Fossa is a depression or concavity Lingual Central Triangular Pits are small depressions in the fossa Sulcus is a long depression Developmental Grooves Developmental Grooves Shallow groove or line between primary parts of the crown Supplemental Grooves Less distinct and do not mark the junction of primary parts Grooves, Pits and Fissures Teeth are constructed by the formation of lobes that merge to form the tooth. The cracks between the lobes are called grooves or fissures. A pit is formed where two fissures cross. Image: slideshare.net Pits and Fossa Sulcus 8

9 Questions? Developmental grooves are long, deep, linear depressions. 1. True 2. False The sulcus of a premolar or molar and the central groove are the same anatomical landmark. 1. True 2. False The unique feature of this molar is the 1. Transverse ridge of a lower left first molar 2. The oblique ridge of a maxillary right molar 3. The oblique ridge of a maxillary left molar 4. The transverse ridge of a maxillary right molar Permanent Dentition Dental Morphology of Individual Teeth Maxillary Right Central Incisors Maxillary Right Lateral Incisors Most often congenitally missing tooth in the mouth Smaller than maxillary central Often has a lingual pit Maxillary Central vs Maxillary Lateral Maxillary Right Canine (Cuspid) Cornerstone of the maxillary arch Longest root of all the teeth (except mandibular canine) Crown is pentagonal in shape Prominent labial ridge. Prominent cingulum and lingual ridge Single rooted with deviation most often to distal. 9

10 Maxillary Right 1 st Premolar (Bicuspid) Maxillary Right 2 nd Premolar (Bicuspid) Trapezoid shape Crown is narrower on the lingual Mesial concavity apical to the contact Buccal and lingual triangular ridges meet to form transverse ridge. Lingual cusp is offset to mesial and shorter than buccal Groove crosses mesial marginal ridge onto the mesial surface Often has bifurcated root which may deviate to the distal Less trapezoidal than max.1 st premolar Buccal and lingual cusps are in line with each other Buccal and lingual cusps are the same length Root is single Maxillary 1 st premolar vs Maxillary 2 nd premolar Maxillary Right 1 st Molar 1st 2nd Large well developed crown with oblique ridge with prominent lingual groove 4 cusps with a special 5 th cusp of carabelli Crown is trapezoidal in shape Three roots, 2 buccal & 1 palatal Maxillary Right 2 nd Molar Maxillary Right 3 rd Molar Anatomy is less pronounced than first molar and is smaller overall No cusp of carabelli, but lingual groove is present Distal cusps less developed Three roots that are less divergent and may be joined together 4 cusps with very small distal lingual cusp Crown may be Heart shaped Rhomboidal Peg Missing 3 roots may be completely converged and conical in shape Anatomy of crown and roots varies 10

11 Anatomical Variations of Maxillary 3 rd Molars Comparison of 1 st, 2 nd, & 3 rd Maxillary Molars Mandibular Right Central Incisor Mandibular Right Lateral Incisor Smallest tooth in the mouth M & D angles are sharp and almost at 90 degree angles Lingual is concave Root is straight Wider than mandibular central incisor Distal is curved more than mesial Mandibular Central vs Lateral Incisors Maxillary vs Mandibular Incisors 11

12 Mandibular Right Canine(Cuspid) Cornerstone of the mandibular arch Longest root of all the teeth Features less pronounced than upper cuspid Flat on the mesial and concave on the distal Mandibular Right 1 st Premolar (Bicuspid) Well formed buccal cusp slightly mesial to center of the crown Very small lingual cusp Small mesialingual groove that extends to mesial surface Diamond shaped or triangular from occlusal Often restore with snake eyes Single root, deep developmental groove on mesial Mandibular Right 2 nd Premolar (Bicuspid) Maxillary Premolars vs Mandibular Premolars May have one or two lingual cusps With 3 cusps, occlusal groove is Y-shaped Square in shape Single rooted intranet.tdmu.edu.ua Mandibular Right 1 st Molar Maxillary 1 st Molar vs Mandibular 1 st Molar 5 cusps 3 buccal, and two lingual Prominent buccal groove often with buccal pit 2 roots Mesial and Distal that are very divergent cowboy legs Maxillary 1 st molar Mandibular 1 st Molar 12

13 Mandibular Right 2 nd Molar Mandibular Right 3 rd Molar 4 cusps with prominent mesialingual cusp 2 roots that are not as divergent as first molar Anatomy is less pronounced. 4 cusps, two roots which may converge Root Morphology and the Dental Hygienist Why it is important to know! Bone Height and Periodontal Disease Healthy bone height is 1 mm apical to the CEJ. Periodontal disease causes bone loss exposing roots. Bifurcation and Trifurcation can be tricky to navigate when scaling and root planing Depression on Maxillary 1 st Premolar Mesial surface depression on root Can be difficult to scale and root plane 13

14 Depression on Mandibular Cuspid Mesial surface is convex and may be missed during scaling and root planing Depression on Mandibular Premolar Root Depresson on root is difficult to locate and clean Mandibular 1 st Molar Root Depression Radiographic Evidence of Calculus Mesial root has a deep concavity Very difficult to clean as bone is lost to perio disease 14