Dental Anatomy PDF

Dental anatomy, Physiology and Occlusion Introduction Tooth morphology is the subject which deals with the external and internal structure, morphology, function, eruption and shedding of all teeth in the Mouth. Importance of Dental anatomy study The practitioner has to have knowledge of the mo...

Dental anatomy, Physiology and Occlusion Introduction Tooth morphology is the subject which deals with the external and internal structure, morphology, function, eruption and shedding of all teeth in the Mouth. Importance of Dental anatomy study The practitioner has to have knowledge of the morphology, occlusion, esthetics,Phonetics, and functions of these teeth to be able to differentiate between normal & abnormal cases to reach the correct diagnosis and undertake the appropriate treatment.  THE SURFACE FORM OF THE ORAL CAVITY LIP GINGIVA TEETH ROOF OF THE PALATE MOUTH CHEEK FLOOR OF THE TONGUE MOUTH PALATINE UVULA TONSILS GINGIVA Dental Anatomy Includes 1- The dentition : refers to all the teeth present in upper & lower jaws. 2- The External Morphology And Internal Composition Of Teeth. 3- The Relationship Of The Teeth To Each Other And To The Skull Bone.  TEETH -Teeth Are Arranged In The Oral cavity In Two Arches Called The Dental Arches One Lower And One Upper. -The Upper Arch Is Called The Maxilla The Teeth In This Arch Are Called Upper Or Maxillary Teeth. -The Lower Arch Is Called The Mandible The Teeth In This Arch Are Called Lower Or Mandibular Teeth. -Each Dental Arch Has A Midline That Divides The Arch Into Two Approximately Equal Right And Left Segments Named As Quadrant. -There Are Four Quadrants In The Entire Oral Cavity.  Classes of teeth Anterior teeth Incisors and Canines Posterior teeth Premolars and Molars (cheek teeth)  In The Oral Cavity There Are Four 2 1 Classes Of Teeth That Includes: 1-Incisors: 3 - There is two incisors The central incisor and The lateral incisor. 4 2-Canines: -There is one canine in each quadrant. 3-Premolars: -There are two in each quadrant. First and second premolars. 4-Molars: -There are three in each quadrant. They are the first molar, the second molar and the third molar. -The incisors and canines are considered anterior teeth since they are closer to the midline. - Molars and premolars are considered posterior teeth since they are farther from the midline.  Dental traits - Set traits : distinguish deciduous teeth from permanent. - Arch traits : maxillary and mandibular teeth. - Class traits :distinguish four classes of teeth according to function (Incisors, canines, premolars and molars( - Type traits : differentiate teeth within the same class as differences between (central and lateral incisor, 1 st & 2 nd premolars or between 1 , st 2 nd & 3 rd molars )  Dentition Periods clinically Humans have two dentitions 1-The primary dentition: (deciduous ) (Baby) (Milk) (Lacteal) (Temporary) at the age of ( 6m – 6y) 20 teeth. 10 maxillary and 10 mandibular. 5 teeth are present in each quadrant. 2 incisors. 1 canine. and 2 molars. The mixed dentition ( transitional Period ): at the age (6 y -12 y) and is called (Ugly-Duckling stage) The mixed dentition period is often a difficult time for the young child because of missing teeth, teeth of different colors and sizes, crowding of the teeth, and malposed teeth. 2-The permanent dentition: (secondary, adult or succedaneous ) 32 teeth, 16 maxillary and 16 mandibular. 8 teeth in each quadrant are Present. 2 incisors. 1 canine. 2 premolars. and 3 molars. The permanent molars are not preceeded with deciduous teeth so they may be termed as non- succedaneous teeth.  Deciduous Mixed Primary dentition Mixed dentition 6m-6y Permanent 6 y -12 y Shedding: It is the physiological loss of the deciduous teeth and their subsequent replacement by permanent teeth. Permanent dentition 12 y and up  X – Ray Showing 1- Primary dentition 2- Mixed dentition (6 m - 6 y ) (6 y - 12 y) 3- Permanent dentition (12 y and up)  Functions of teeth 1- Mastication : It is the most important function of the teeth. The teeth are designed to perform this function. Incisors Canine Premolars Molars Chisel like Wedge like At least two Multiple projections Cutting or Cutting and projections (cusps) incising tearing (cusps). Grinding Tearing and grinding  2- Appearance: Aesthetics - Well arranged clean teeth with proper alignment give nice appearance to the face. Teeth give support to the facial expressions. 3- Speech: Phonation Teeth are important for clear pronunciation and for production of sound. 4- Growth of jaws: Teeth play a role in the growth of the jaws in some periods of life. 5- Maintain the vertical dimension of the face. 6- Protection: in the case of some animals (biting). 7- Para- masticatory functions of teeth: use of teeth as tools.  Human Dental Formula Expresses number and type of teeth per side Primary teeth 2 1 2 I ---- C ---- M --- = 10 2 1 2 Permanent teeth 2 1 2 3 I ---- C ---- P --- M ---- = 16 2 1 2 3  Summary Humans have two dentitions 1-The primary dentition: (deciduous ) 20 teeth. 10 maxillary and 10 mandibular. 5 teeth are present in each quadrant. 2 incisors, 1 canine and 2 molars. The dental formula is: 2 1 2 I --- C ---- M ---- = 10 2 1 2 2-The permanent dentition: (secondary, adult or succedaneous ) 32 teeth, 16 maxillary and 16 mandibular, 8 teeth in each quadrant are present, 2 incisors, 1 canine, 2 premolars and 3 molars. The dental formula is : 2 1 2 3 I ---- C ---- P --- M ---- = 16 2 1 2 3 The permanent molars are not preceeded with deciduous teeth so they may be termed as non-succedaneous teeth. Tooth numbering systems 1) Palmer Notation System: (1861) It is the most widely used system it represents the four quadrants of the dentition as if you facing patient. In upper right In upper left In lower right In lower left The permanent teeth are numbered from 1-8 on each side from the midline. Upper right Upper left 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 Lower right Lower left The deciduous teeth are lettered from A-E on each side from the midline. Upper right Upper left E D C B A A B C D E E D C B A A B C D E Lower right Lower left 2) The two digit system (F.D.I) (1971) The teeth are designed by using two-digit system: a. The first digit of the code is located at the left side of the number and indicates the quadrant. In the permanent dentition. In the deciduous dentition. U.R. 1 2 U.L. U.R. 5 6 U.L L.R. 4 3 L. L. L.R. 8 7 L.L. b- The second digit is located at the right side of the number and indicates the number of the tooth in the quadrant. The two digits should be pronounced separately. The permanent teeth are numbered from 1-8 from the midline. The deciduous teeth are numbered from 1-5 from the midline. Permanent teeth 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 Deciduous teeth 55 54 53 52 51 61 62 63 64 65 85 84 83 82 81 71 72 73 74 75  3)The universal numbering system (American numbering system)(A.D.A) system:. The number is always preceded by the sign # to designate that the system is used for universal system. Permanent teeth (1 – 32) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 Deciduous teeth (A - T) A B C D E F G H I J T S R Q P O N M L K 4- Dane (Hederup system): symbols as (+) & (-) are used 8 + 7 + 6 + 5 + 4 + 3 + 2 +1+ +1+ 2 + 3 + 4 + 5 + 6 + 7 + 8 Permanent dentition: R 8 − 7 − 6 − 5 − 4 − 3 − 2 −1− ‫׀‬ −1− 2 − 3 − 4 − 5 − 6 − 7 − 8 L 05 + 04 + 03 + 02 + 01 + ‫׀‬ + 01 + 02 + 03 + 04 + 05 - Deciduous dentition: R L 05 − 04 − 03 − 02 − 01 − − 01 − 02 − 03 − 04 − 05  Parts of tooth 1- Macro-anatomy of the tooth Each tooth has Four anatomical parts: Enamel I.Crown Cementum II.The Neck: cervical line or cemento-enamel junction (CEJ). II.Root (s) IV. Pulp cavity Anatomical And Clinical Crown And Root Clinical Anatomical Crown Crown Clinical Root Anatomical Root Anatomical And Clinical Crown And Root Gingival Recession Gingival Recession Anatomical crown Clinical Crown Part of the Anatomical root Anatomical And Clinical Crown And Root C.C. CROWN A.C. C.R. ROOT A.R. Newly Erupted Teeth CROWN A.C. C.C A.R. ROOT C.R. Gingival Recession Dental tissues 2- Micro-anatomy of the tooth -Three calcified tissues: Enamel (hardest tissue) Dentin Cementum + One soft specialized connective tissue: Cementum Pulp. Periodontal Ligament  Junctions Of Tooth Tissues There Are Three Sites Of Junction Enamel DEJ 1- Cemento-enamel junction (CEJ): CEJ Dentin 2- Dentino-enamel junction Pulp (DEJ): 3- Dentino-cemental junction (DCJ): DCJ Cementum  The Teeth and Investing Structures Enamel PDL Dentin alveolar bone Cementum oral mucosa Pulp gingiva saliva TMJ Enamel: Covers, Most Mineralized, Yellowish White. Cementum: Covers, Medium For The Attachment, Dull Yellow, Thickness. Dentin: Surrounds The Pulp Cavities, Underlying The Enamel And The Cementum, Yellow. Pulp: Housed In The Pulp Cavity, Soft Tissue, Supply.  The Pulp Consists Of Two Parts 1 –Coronal pulp : Pulp Pulp chamber + pulp Horn horns 2 – Radicular pulp : Root canal + apical foramen+ accessory canals Note: Many roots m ay be formed with more than one canal, which may end in a common foramen.  The Periodontium Is The Investing And Supporting Attachment System Of Teeth. It consists of: Two Soft Tissues Two Hard Tissues 1- Gingiva 1- Cementum The Oral Mucous Covers The Anatomical Membrane, Which Covers Root Of The Tooth The Neck Of The Tooth And Part Of The Alveolar Bone. 2- Periodontal Ligament 2- Alveolar Bone Strong Ligament that Attaches The Bone Of The Jaw That The Tooth To The Alveolar Bone Surrounds The Root Of The Tooth  Tooth Surfaces Each Tooth Has Five Surfaces Like A Box With 4 Sides And A Roof. MASTICATORY LINGUAL DISTAL MESIAL FACIAL FACIAL LABIAL OR BUCCAL TOWARDS TOWARDS THE LIP THE CHEEK FOR FOR ANTERIOR POSTERIOR TEETH TEETH FACIAL  LINGUAL PALATAL OR LINGUAL TOWARDS TOWARDS THE THE PALATE TONGUE FOR MAXILLARY FOR MANDIBULAR TEETH LINGUAL TEETH  PROXIMAL MESIAL & D I S TA L TOWARDS THE MIDLINE AWAY FROM THE MIDLINE MESIAL FOR ALL THE DISTAL TEETH  MIDLINE M M D D M = MESIAL SURFACES D = DISTAL SURFACES  MASTICATORY INCISAL OR OCCLUSAL MASTICATORY FOR ANTERIOR TEETH FOR POSTERIOR TEETH The Surfaces Are Identified By The Relationship To Other Orofacial Structures M M Proximal MIDLINE D D Anterior surfaces teeth for all the Distal surface teeth Mandibular Maxillary teeth PALATE teeth Posterior TONGUE teeth CHEEK (buccal) Posterior teeth LIP Anterior teeth  So The Tooth Surfaces Are: A- Facial. B- Lingual. C- proximal. Distal surface D- Masticatory. E- Apical  Division Into Thirds For descriptive purposes ( to locate the anatomical landmarks ): - Crown surfaces could be divided horizontally or vertically into three portions or thirds, - The root could be divided into thirds horizontally, while vertically into halves by the root axis line { labial (buccal) & lingual and/or mesial & distal }.  Mesial Middle Middle Distal Lingual Labial Incisal Middle Cervical Cervical Cervical Mesial half Labial half Middle Distal half Lingual half Middle Apical Apical  Line And Point Angles Line Point angle angle  Line And Point Angles Line angle: It’s name is derived from both surfaces (6 in anterior teeth and 8 in posterior teeth) Point angle: 4 for anterior and posterior teeth.  Note: Incisal ridge Note: The anterior teeth have fewer line angles because the meeting of the mesial and distal line surfaces with incisal ridge are rounded , so the mesio-incisal and disto-incisal line angles are practically not exist.. Incisal Edge Line And Point Angles Of The Anterior Teeth Line And Point Angles Of The Posterior Teeth Anatomical landmarks of the crown A - Crown Elevations B- Crown Depression  A - Crown Elevations 1- Lobe It is one of the primary centers of calcification and growth formed during the crown development. Each tooth begins to develop from four lobes or more. -- All anterior teeth and premolars are formed from 4 lobes except - the mandibular 2nd premolar (3 cups type) formed from 5 lobes (3 buccal and 2 lingual). -All molars formed from 4 lobes (2 buccal and 2 lingual) except the mandibular 1st molar formed from 5 lobes. 1 2 3 4 5 THE MATURE FORMS OF LOBES ARE: 1.Cusps 2.Cingulum 3. Mamelones  2-Cusps They are pyramidal projections on the incisal portion of the canine and on the occlusal surfaces of the premolars and molars teeth.  * Cusp slopes the inclined surfaces, meet at an angle with the cusp tip. also known as cusp arms. * Contact a point or area where one tooth is in contact its neighbor  3.Cingulum It is the enlargement or bulge on the cervical third of lingual surface of the crown in anterior teeth (incisors and canines). It is also called the lingo-cervical ridge  4. Mamelones They are three small round projections of enamel present in the incisal third of newly erupted permanent incisors. After normal use, eventually the mamelones wear down into a flat edge.  5- Tubercle It is a small elevation. It is produced by excessive formation of enamel. Tubercle is noticed at the palatal surface of E & 6 and sometimes at the lingual surface of incisors over the cingulum. B D M P Tubercle differs from cusp as it is formed of enamel only while cusp is formed of pulp horn covered by dentin and enamel  6-Enamel pearl Are very small droplets of enamel present on dentin of the root mostly on the furcation area of permanent molars  7- Ridge It is a linear elevation on the different surfaces of the crown. A- Ridges on the facial surface (Labial and Buccal) B- Ridges on the lingual surface C- Ridges on the occlusal surface of posterior teeth A- Ridges on the facial surface (Labial and Buccal) 1-Labial Ridge: Found on the labial surfaces of canines. It is the result of greater development of middle labial lobe. 2-Buccal Ridge: Usually found on the buccal surfaces of the premolars. It is the result of greater development of middle buccal lobe. 3-Cervical Ridge: It is found on the cervical one third of the facial surfaces of all the teeth. Cervical ridge are Well developed in deciduous teeth and more pronunced in the (D) followed by (E). B- Ridges on the lingual surface 1.Incisal Ridge: Linear elevation in lingual surface of incisor 2. Lingual Cusp Ridge: Cusp Slopes Or Cusp Arms NOTE: Usually distal cusp slope is longer than mesial cusp slope in all teeth except C and 4 where the mesial cusp slope is longer DCR MCR than the distal  3.Lingual Ridge: Linear elevation in lingual surface of canine 4.Marginal Ridge: DMR MMR C- Ridges on the occlusal surface of posterior teeth 1.Marginal Ridges MESIAL MARGINAL RIDGE DISTAL MARGINAL RIDGE 2.Triangular Ridges: it descend from the cusp tip of posterior teeth toward The central part of occlusal surface All posterior tooth cusps have a triangular ridge, except the mesiolingual cusp on maxillary molars which has two triangular ridges  3.Transverse ridge the union of directly opposing triangular ridge 4.Oblique Ridge: the union of non opposing triangular ridges of buccal and lingual cusps Found on (E 6 7 may be D, 8) Remember that all teeth either anterior or posterior have cervical ridge and two marginal ridges (mesial and distal one).  B- Crown Depression I- LINER DEPRESSIONS 1- DEVELOPMENTAL GROOVE: It is narrow, shallow and sharply defined short or long, denoting union of primary lobes in occlusal and may extend buccaly and lingually  2- SUPPLEMENTAL GROOVES: They are small, irregularly placed, Found usually on occlusal surfaces. They do not denote union of primary lobes. The third molars followed by second permanent molars are characterized by high number of supplemental grooves _ 6 6 _ 7 7 _ 8 8 3- FISSURE: It is found in the bottom of developmental groove. Results from incomplete union of the primary lobes. It is a fault in enamel. Cusp tip Cusp tip Enamel Developmental Dentin groove Fissure 4- SULCUS: It is a broad depression or valley on the occlusal surfaces of posterior teeth. Its inclines meet in a developmental groove and extend to the cusp tips. Cusp tip Cusp tip Enamel Developmental Dentin groove Fissure  II- CIRCUMSCRIBED DEPRESSIONS 1- FOSSA: It is a small depression or concavity found in Anterior in lingual surface Posterior in occlusal surface. a- LINGUAL FOSSA b- MESIAL AND DISTAL TRIANGULAR FOSSA c- CENTRAL FOSSA a- LINGUAL FOSSA: Found on the lingual surfaces of anterior teeth. b- MESIAL AND DISTAL TRIANGULAR FOSSA: Found on the occlusal surfaces of posterior teeth mesial and distal to the marginal ridges. MTF DTF MMR DMR c- CENTRAL FOSSA Found on occlusal surfaces of molars. They are formed by the converging of ridges terminating at a central point where there is the junction of grooves. CF MTF DTF CP 2- PITS a- TRUE PITS: These are small pinpoint depression. present at the junction / or at the ends of the developmental grooves They may be found at the bottom of the central fossa (central pit) or at the bottom of the mesial and distal triangular fossae (mesial and distal pits). c.p. d.p. m.p. b- FAULTY PIT Usually develops as a result of incomplete formation of enamel. It is located at the end of the buccal developmental grooves of the lower molars or palatal developmental grooves of the upper molars. p.p. b.p.  Other landmarks in human teeth Interproximal space: The triangular space normally filled by the gingival papillae. Embrasures: curvatures adjacent to the contact areas form spillway spaces called embrasures.  Apex of root: tip end of the root Cervix: it is the middle part of the tooth consisting of adjoining parts of the crown and the root near the cemento-enamel junction. Cervical line: it is a thin and shallow linear depression dividing the anatomical crown and root. Root apex SOCKET: It is the bony space in the alveolar bone containing the roots of erupted tooth. CRYPT: It is the bony space in the alveolar bone containing the developing unerupted tooth(tooth germ) CRYPT: Teeth May Be Divided According To The Number Of Roots Single rooted teeth Multirooted teeth The undivided portion of the root is called: Root Trunk. - All anterior teeth and premolars except maxillary 1 st premolar having one root. -- All mandibular molars and maxillary 1 st premolar have two roots. -- All maxillary molars have three roots.  OTHER TERMS SELF CLEANSING SURFACES: Those surfaces of the teeth that are cleaned by the normal functional action of the tongue, lips, cheeks and lubricated by mouth fluids. Facial Lingual Incisal Occlusal CALCIFICATION: The organic framework of a tooth becomes hard by depossition of calcium and phosphorous salts brought in by small blood vessels. Organic Hard Tissues Framework Life history of the tooth  Life history of the tooth 1- Developmental stages Dental lamina and bud stage (initiation) Cap stage bell stage 2- Apposition 3- Early root formation 4- Eruption 5- Root completion 6- Attrition 7- Shedding of deciduous teeth Chronology of the human teeth Deciduous teeth  Chronology of the human teeth Deciduous teeth Enamel Beginning of Eruption Root Beginning of Shedding organ calcification completion Root resorption appearance A 7 W.I.U 4 M.I.U 7 M 1.5 Y 4Y 7Y A 6 M 7 W.I.U 4.5 M.I.U 8 M 2 Y 5Y 8Y B B 7 M 1.5 Y 8 W.I.U 5 M.I.U 18 M 3Y 8Y 11 Y C 16 M 9 Y C 8 W.I.U 5 M.I.U 14 M 2.5 Y 6Y 10 Y D D 12 M 9 Y 9 W.I.U 6 M.I.U 24 M 3Y 7Y 10 Y E 20 M E  Appearance of enamel organ 7-9 w.i.u. Beginning of calcification from 4-6 m.i.u. Crown completed from 4-10 m. Eruption. The teeth erupt when ⅓ to ½ of their root length are formed and calcified. ❑ in pairs ❑ mandibular before the maxillary. ❑ The 1 st erupted tooth is the mandibular central incisors at 6 m. ❑ Earlier in girls. ❑ Deciduous canines erupt after 1 st molar. ❑ At 2.5-3 years all the deciduous teeth have been erupted. ❑ Sequence of eruption: for both arches A, B, D, C and E  Root completion: after eruption by about 1 year. For All deciduous teeth root completion from 1.5-3 years. Beginning of root resorption: after root completion by about 3 - 4 years (4-7years). Shedding: the time consumed from beginning of resorption till tooth exfoliation is 3- 3.5 y (7-11 year). The last shedded tooth is the upper canine (11 y).  Permanent teeth Permanent Enamel organ Beginning of Crown Eruption Root teeth appearance calcification completed completion 1 5 M.I.U 3-4 M 4-5 Y 7-8 Y 10 Y 1 6-7 Y 9Y 2 5 M.I.U 10 M 4-5 Y 8-9 Y 11 Y 2 3-4 M 7-8 Y 10 Y 8 M.I.U 4-5 M 6-7 Y 11-12 Y 14-15 Y 3 3 9-10 Y 12-14 Y 7 M.I.U 1.5- 2 Y 5-6 Y 10-11 Y 12-13 Y 4 4 3-5 Y 10-12 Y 8 M.I.U 2-2.5 Y 6-7 Y 10-12 Y 13-15 Y 5 5 8 M.I.U 11-12 Y 4 M.I.U At birth 3-4 Y 6-7 Y 9-10 Y 6 6 2.5-3 Y 7 1Y 2.5-3 y 7-8 Y 12-13 Y 14-16 Y 7 11-13 Y 8 4Y 7-9 Y 12-16 Y 17-21 Y 18-25 Y 8 8-11 Y  Appearance of enamel organ 4-8 m.i.u 7 at about 1 year and 8 except at 4 years. 7 8 Beginning of calcification. Maxillary teeth calcify before mandibular. 1st molar at birth, anteriors 3-5 m except 2 at 10 m. premolars and 2 nd molar 1.5- 2.5 year. 3rd molar 8-10 year. Crown completion from 3-8 y except 3rd molar at 12-16 year. Eruption. mandibular teeth before the maxillary except the maxillary premolars erupt before the mandibular ones by about 1 year. The 1 st erupted tooth is the mandibular 1 st molar at 6 y.  Sequence of eruption Root completion: this occurs after tooth eruption by about 3 year. All teeth 10-15 y, 2nd molar 14-16 3rd molar 18-25  Dentition at different ages Condition of teeth at birth Non erupted (amount of calcified tissue) Erupted No A ½ the crown No B ↓than ½ of the crown No C Tip of the cusp No D Occlusal ⅓ No E Cusp tips ❖ Permanent Mesiolingual cusp No 6  Condition of teeth at 6 months Non erupted (amount of calcified tissue) Erupted ✓ A ⅓ root  B Crown and small portion of root  C Parts of the crown  D Parts of the crown  E Parts of the crown ❖ Permanent _ Occulsal ⅓  6 Incisal ⅓  1,2 Tip of the cusp  3  Condition of teeth at 3 years - Maxillary and mandibular deciduous teeth are erupted and are in occlusion. Non erupted (amount of calcified tissue) Erupted A Root completed ✓ B Root completed ✓ C Root completed ✓ D Root completed ✓ E Root completed ✓ ❖ Permanent 6 Crown  No 1, 2 ↑ than ½ crown  No 3 ½ crown  No 4,5 Small parts of the crown  No 7 Separate cusps  No  Condition of teeth at 6 years Non erupted (amount of calcified tissue) Erupted A → Shedded ---- ✓ B Show amount of root resorption ✓ C Show amount of root resorption ✓ D Show amount of root resorption ✓ E Not Show any root resorption ❖Permanent ✓ 6 ⅓ root ✓ 1 ⅓ root  2 ↓ than ⅓ root  3 Crown completed 4,5  Crown completed  7 Crown not completed  Condition of teeth at 9 years Non erupted (amount of calcified tissue) Erupted ---- A → Shedded ---- B → Shedded ---- C → Shedded only lower (upper at 11y) ---- D → Shedded ✓ E Most of the roots are resorbed ❖ Permanent ✓ 6 Root completed ✓ 1 Root completed ✓ 2 Most root is completed ✓ 3 ⅓ root (upper 10-12 y)  4,5 ↓ than ⅓ root  7 Crown completed  8 Separate cusps  Condition of teeth at 12 years All deciduous teeth are shedded. All permanent teeth are erupted except 8 all have completed roots except 7 8