1st Year 1st Semester Final Exam Odontology Topic Notes AMIT DATTANI 2012 University of Debrecen Medical and Health Science Centre – Faculty of Dentistry 1 Odontology Final Exam Topic Notes 2012 (Edited) Amit Dattani "Education is our passport to the future, for tomorrow belongs to the people who prepare for it today." -Malcolm X
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1st Year 1st Semester Final Exam Odontology Topic Notes AMIT DATTANI 2012
University of Debrecen Medical and Health Science Centre – Faculty of Dentistry 1
Odontology
Final Exam Topic Notes 2012
(Edited)
Amit Dattani
"Education is our passport to the future, for tomorrow belongs to the people who prepare for it today."
-Malcolm X
1st Year 1st Semester Final Exam Odontology Topic Notes AMIT DATTANI 2012
University of Debrecen Medical and Health Science Centre – Faculty of Dentistry 2
Odontology Final Examination Topics 2012
Contents
1. Description of human dentition ............................................................................ 4
2. Definition and main parts of the tooth ................................................................. 8
3. Zsigmondy’s and the two-digit notations ............................................................11
4. Physical properties of the tooth surface .............................................................15
5. Attrition, abrasion and erosion of teeth. Degrees of degradation ..........................19
6. Tooth identifiers on the crown ................................................................................22
7. Tooth identifiers on the dental neck and root ....................................................25
8. The morphology of the maxilla............................................................................27
9. The morphology of the mandbile ........................................................................27
10. Development of the crown ....................................................................................32
11. Development of the root and formation of the periodontium .............................38
12. Phases of the tooth eruption .................................................................................41
13. Developmental dates of the teeth ........................................................................43
14. Description of permanent maxillary incisors .........................................................46
15. Description of permanent mandibular incisors .....................................................49
17. Description of permanent maxillary canine ..........................................................52
18. Description of permanent mandibular canine ......................................................53
19. Description of maxillary premolars .......................................................................55
20. Description of mandibular premolars ...................................................................57
21. Differentiation of premolars ..................................................................................59
22. Description of permanent maxillary molars ..........................................................60
1st Year 1st Semester Final Exam Odontology Topic Notes AMIT DATTANI 2012
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23. Description of permanent mandibular molars ......................................................66
24. Differentiation of molars .......................................................................................71
25. Morphology of maxillary deciduous teeth ............................................................73
26. Morphology of mandibular deciduous teeth ........................................................77
27. Physical and chemical properties of enamel .........................................................84
28. Enamel structure and formations..........................................................................84
29. Physical and chemical properties of dentine ........................................................87
30. Dentine structure and formations .........................................................................89
31. Structure of the pulp .............................................................................................92
32. Functions of the pulp .............................................................................................92
33. Description of soft tissues of the periodontium ....................................................95
34. Description of hard tissues of the periodontium ..................................................98
These notes have been constructed from:
B.G Jansen Van Rendsburg – Oral Biology
Wheeler’s Dental Anatomy, Physiology and Occlusion 8th ed
The official lectures of the University of Debrecen Dental Department
Shimon Dantsis (Alumini) Notes
Netter’s Atlas of Human Anatomy 4th ed
(I am not responsible for the reproduction of any material in any way or form in this study pack.)
Please note, as I am also human there could be some mistakes. If you find any please message me on facebook so I can rectify these. I would also appreciate your feedback.
I dedicate this to the students at the University of Debrecen.
--
Amit Dattani (4th Year Dental Student)
1st Year 1st Semester Final Exam Odontology Topic Notes AMIT DATTANI 2012
University of Debrecen Medical and Health Science Centre – Faculty of Dentistry 4
1. Description of human dentition
The Human Dentition is:
Diphyodont: Having two different sets of teeth through a life time, the deciduous
(Primary) teeth and the Permanent (Secondary) teeth.
Heterodont: Contains different teeth (Incisors, Canines, Premolars and Molars) which
differ in shape and properties in the same arch.
Primary Dentition
Consists of 20 teeth (5 in each quadrant)
o 1 Central Incisor
o 1 Lateral Incisor
o 1 Canine
o 2 Molars
(NO Premolars!)
Dental Formula:
= I2 + C1 + M2
(2 Incisors, 1 Canine, 2 Molars)
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Permanent Dentition
Consists of 32 teeth (8 in each quadrant) o 1 Central Incisor o 1 Lateral Incisor o 1 Canine o 2 Premolars o 3 Molars
The Incisors & Canine form the Anterior teeth
The Premolars & Molars form the Posterior teeth
Permanent teeth begin to erupt at 6 years of age and continue to erupt till 17-21 years of age.
Dental Formula:
= I2 + C1 + P2 + M3
(2 Incisors, 1 Canine, 2 Premolars, 3 Molars)
A mixed dentition refers to one that is composed of primary and permanent teeth (when the
permanent teeth are erupting, after the deciduous).
Arrangement of teeth:
Upper Arch- Maxillary (stays stationary)
Lower Arch- Mandibular (moveable)
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Each arch is separated into the Upper, Lower, Left and Right quadrants, separated by a
midline (an imaginary line dividing the central incisors).
Occlusion is when the maxillary and mandibular arches are in contact.
The upper teeth usually surround (on the front and both sides) the lower teeth in a normal
occlusion (contact between teeth).
The upper arch is larger than the lower arch.
Shape of the Dental Arches:
Primary:
Upper and Lower – Semicircular
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Permanent:
Upper – Semieliptical
Lower- Parabolic
Note: Canine is also called “cuspid” and a premolar is also called “bicuspid”
Role of teeth:
Primary role is Mastication
Play a role in Speech
Have an Aesthetic function
Definitions:
“Succedaneous”: The teeth of the permanent dentition that replace the primary teeth.
“Non-succedaneous”: Teeth that are not replaced by another type of teeth (Permanent Molars).
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2. Definition and main parts of the tooth
“Tooth” – Independent organ belonging to the masticatory mechanism, found in oral cavity.
They have 3 main roles being mastication, speech (phonetics) and aesthetics.
A tooth has 2 main parts:
-Crown
-Root
Separated by a Cervical line/dental neck
(Cervical Line: the Cemento-Enamel Junction (CEJ) between
the crown and the root)
Basic Anatomy of the tooth:
(learn by heart now and you will understand it later…trust me on this one)
IMPORTANT: Learn detailed anatomy of tooth on Page 243 in “Oral Biology Jansen Van
Rensburg” book.
Parts of the tooth explained:
Enamel: hard tissue covering the crown of the tooth (made by ameloblasts)
Dentine: hard tissue under the enamel crown (softer than enamel). Made from odontoblasts.
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Cementum: layer of calcified tissue covering the root (sofer than dentine)
Pulp Chamber: cavity where the pulp itself is located
Pulp: The central hollow chamber of a tooth, containing delicate connective tissues, nerves
and both blood and lymph vessels. It is lined peripherally by odontoblasts.
Root Canal: contains part of the pulp chamber
Gingiva: the gum surrounding the tooth
Periodontium: the surrounding tissues of the tooth which provide support for the tooth
Made of up hard and soft tissues
Hard:
Alveolar bone
Cementum
Soft:
Gingiva
Periodontal Ligaments (PDL)
The crown and root have different definitions anatomically and clinically:
Anatomical Crown: part of the tooth that is covered with enamel
Clinical Crown: part of the tooth that is exposed and visible in the oral cavity (above the gum
line)
Anatomical Root: part of the root that is covered with cementum
Clinical Root: part of the root that is located in the jaw
Surfaces of teeth: (Wheelers dental anatomy book page 10)
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Facial: the surface that faces the front (face)
Labial: facial surface of anterior teeth (Incisors and canine)
Buccal: facial surface of the posterior teeth (premolars and molars)
Lingual: surface that is closest to the tongue (only for lower jaw)
Palatal: surface that is closest to the tongue side (only for upper jaw)
Mesial: surface of the tooth that is closest to the midline (also called proximal surfaces)
Distal: surface of the tooth that is furthest away from the midline (also called proximal
surfaces)
EVERY tooth has these surfaces, and they have ONE of the following:
Incisial surface: biting surface for anterior teeth
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Occlusal surface: biting surface for posterior teeth
Interproximal surface: The spaces between the proximal surfaces
3. Zsigmondy’s and the two-digit notations
In total there are 3 different notification systems.
1. Zsigmondy / Palmer Notification - (Used in the UK)
2. Universal System (2 digit numbering) - (1-32 /A-T)
3. FDI (Federation Denature International) System (2 digit numbering) – quadrant and tooth
number.
These systems are used so dental offices, staff; insurance companies can better communicate
between each other regarding exact details of certain teeth.
Adolf Zsigmondy (Hungarian Dentist) developed the idea in 1861. (Also known as the Palmer
Notification System)
He divided the teeth into 4 quadrants and each tooth was given a sign according to its location
in the mouth.
Maxillary Right Maxillary Left
Mandibular Right Mandibular Left
The teeth in each quadrant are numbered from 1-8 for an adult (permanent dentition) and
roman numerals (I-V) for the deciduous dentition (milk teeth). Roman Numbers were changed
to letters A-E for the deciduous dentition. (Roman numerals were not computer friendly so
not used today, Roman numerals used in Zsigmondy system and letters in Palmer system).
Permanent Dentition:
Maxillary Right Maxillary Left
Mandibular Right Mandibular Left
Midline (between both Central Incisors)
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E.g.
8 = Upper Right 8 (3rd
Molar)
4 = Upper Left 4 (1st Premolar)
2 = Upper Left 2 (Lateral Incisor)
Deciduous Dentition:
E.g.
C = Upper Right Deciduous Canine
A = Lower Right Deciduous Central Incisor
Universal System
Secondary Dentition (permanent):
Uses numbers from 1-32
Maxillary 1-16
Mandibular 17-32
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Primary Dentition:
Users Letters from A-T
Maxillary A-J
Mandibular K-T
E.g.
16 = Upper Left 3rd
Molar
24 = Lower left Permanent Central Incisor
N= Lower Left Deciduous Lateral Incisor
T= Lower Right Deciduous 2nd
Molar
FDI System
This system uses 2 digit numbering. (This system is used in the University clinics)
The first digit represents the quadrant number
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The second digit represents the tooth number (starting from the midline)
Permanent Quadrant (mouth) Deciduous
1 Upper Right (of patient) 5
2 Upper Left 6
3 Lower Left 7
4 Lower Right 8
Quadrants:
Permanent:
Deciduous:
REMEMBER THE QUADRANTS AS A CLOCK FACE (GOING CLOCKWISE!)
E.g.
11 = Upper Right Permanent Central Incisor
18 = Upper Right 3rd
Molar
35 = Lower Left 2nd
Premolar
46 = Lower Right Permanent 1st Molar
54 = Upper Right Deciduous 1st Molar
75 = Lower Left Deciduous 2nd
Molar
REMEMBER THE QUADRANTS AS A CLOCK FACE (GOING CLOCKWISE!)
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4. Physical properties of the tooth surface
Strictly speaking this topic is asking about the physical properties of the tooth surfaces, but
the examiners always like to around the topic and will ask you about other properties too.
The tooth is covered by enamel, which is the outer most layer. (The tooth surface is covered
by enamel, dentine and cementum.)
The enamel surface is the hardest tissue in our body
Covers the outer surfaces of the tooth
It is of ectodermal origin
Density
~ 2.84-3.00 grams/ml
Density decreases from the surface to the amelodentinal junction (where the enamel
and dentine meet)
During tooth development the density of enamel increases progressively
Differences between Mandibular Central and Mandibular Lateral Incisor (topic 16)
Lateral is slightly larger than the Central
Incisive edge is longer mesiodistally
Distal side of Lateral is rotating lingually
Crown of lateral slopes down towards distal side
Difference between Maxillary and Mandibular Incisors (topic 16)
Maxillary have more pronounced lingual fossae
Maxillary have roots that are more rounded in cross-section
Mandibular have smoother lingual anatomy without grooves and pits
Mandibular crowns are smaller and narrower relative to length
Mandibular crowns are flatter mesially and distally than Maxillary
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17. Description of permanent maxillary canine
Maxillary Canine
Root 1
Root canal 1
Pulp horns 1
Cusps 1
Eruption 11-12 years
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Largest and strongest tooth in mouth
All surfaces are convex
Large pointed cusp, tips placed approximately centrally
Distal slope longer than mesial
Great bulk of dentine
Bulky cingulum
Root is almost triangular in cross-section
Root inclines distally
18. Description of permanent mandibular canine
Mandibular Canine
Root 1
Root canal 1 or 2
Pulp horns 1
Cusps 1
Eruption 9-10 years
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Single cusp not as pointed as in maxillary
Marginal ridge and cingulum less well developed
Crown tilts distally since mesial surface is a straight line
Well marked cingulum on lingual surface
Root possibly flattened Mesially and Distally
Vertical Mesial and Distal grooves may be present on root
Only canine that is capable of bifurcated root
Crown and root tends to lean distally
Differences between Maxillary and Mandibular Canines
Maxillary has larger pulp cavity than Mandibular
Mandibular crown is narrower mesiodistally
Mandibular cusp on incisive edge is less pointed
Cingula on Maxillary are larger and centred mesiodistally, mandibular are slightly to the distal
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19. Description of maxillary premolars
Maxillary 1st Premolar
Root 2 (Buccal & Palatal- curve distally)
Root canal 2 (one in each root)
Pulp horns 2
Cusps 2 sharply defined (buccal larger than Lingual)
Eruption 10-11 years
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Concave canine fossa on mesial surface of crown extending to pronounced longitudinal groove on mesial surface of root
Mesial surface of buccal cusp longer than distal Pulp tilts slightly mesially Occlusal outline more angular than maxillary 2nd Premolar Grooves form letter ‘H’ on the occlusal surface
Maxillary 2nd Premolar
Root 1 (flattened mesiodistally, curves distally)
Root canal 1
Pulp horns 2
Cusps 2 (nearly equal in size, buccal larger)
Eruption 10-12 years
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No canine fossa Oval Occlusal outline Mesial slope of buccal cusp shorter than distal slope Grooves form letter ‘H’ on the occlusal surface
20. Description of mandibular premolars
Mandibular 1st Premolar
Root 1 (curves distally)
Root canal 1
Pulp horns 2
Cusps 2 (sharply defined -buccal larger than lingual)
Eruption 10-12 years
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2 Occlusal fossae distal larger than mesial Buccal cusp located centrally to apex Lingual inclination of crown to root Buccal surface convex, lingual almost straight Circular Occlusal outline, flattened + grooved on mesiolingual surface Mesial longitudinal groove more marked than distal
Mandibular 2nd Premolar
Root 1 (curves distally with blunt apex)
Root canal 1 or 2
Pulp horns 2 or 3
Cusps 2 or 3 (Buccal larger)
Eruption 11-12 years
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Occlusal outline like square-ish Mesial marginal ridge higher than distal No longitudinal grooves present
21. Differentiation of premolars
Difference between Maxillary and Mandibular Premolars
Mandibular crowns tilts lingually, so lingual cusp tips may be lingual to root Outline of Mandibular is rhomboidal shape as Maxillary is trapezoidal Mandibular lingual cusps are relatively MUCH shorter than mandibular buccal cusps
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Difference between Maxillary 1st Premolars and Maxillary 2nd Premolars
Maxillary 1st premolars usually have a divided root as Maxillary 2nd premolars usually have only 1 root
Maxillary 1st premolar buccal cusp larger than Lingual cusp Maxillary 2nd premolar has NEARLY equal sized cusps (buccal and lingual) Maxillary 1st premolars buccal cusp is more pointed than Maxillary 2nd premolars buccal cusp Maxillary 1st premolars occlusal surface is asymmetrical with mesial marginal ridge as
Maxillary 2nd premolars being more symmetrical with no mesial marginal ridge. Distance between the two cusps maybe greater in difference in the 1st premolar
Difference between Mandibular 1st Premolars and Mandibular 2nd Premolars
Mandibular 1st premolar buccal cusp is more pointed than Mandibular 2nd premolar buccal cusp
Mandibular 1st premolar lingual cusp is small and non-functional as Mandibular 2nd premolar cusp is functional and relatively longer
Mandibular 1st premolars have a mesiolingual groove separating the mesial marginal ridge from the lingual cusp, not found on Mandibular 2nd premolars
22. Description of permanent maxillary molars
Maxillary 1st Molar
Root 3 (1 lingual and 2 buccal)
Root canal 3 or 4
Pulp horns 4
Cusps 5 (5th is tubercle of Carabelli-non functioning)
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Eruption 6-7 years
1st Year 1st Semester Final Exam Odontology Topic Notes AMIT DATTANI 2012
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Three well developed separate roots Palatal root longest and thickest, it develops away from 2 buccal roots Buccal roots tend to curve distally Rhomboidal occlusal outline Largest maxillary tooth Mesiopalatal cusp largest Distopalatal cusp smallest Buccal cusps more pointed than palatal Crown wider buccolingually than mesiodistally 5th cusp located on the lingual side of the mesiolingual cusp Mesiolingual cusp is the largest of the four functioning cusps Mesiobuccal root has 1 or 2 root canals
Maxillary 2nd Molar
Root 3 (slight distal inclination)
Root canal 3
Pulp horns 3 or 4
Cusps 4
Eruption 12-13 years
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Occlusal Palatal Buccal
Distal Mesial
Rhomboidal occlusal outline Distal cusps greatly reduced in size 3 roots less divergent Buccal roots same length, closer together Coalescence of roots more common than Maxillary 1st molar All roots same length as Maxillary 1st molar Roots more slender and lie closer together than Maxillary 1st Molar Prominent palatal and buccal developmental grooves
Maxillary 3rd Molar
1st Year 1st Semester Final Exam Odontology Topic Notes AMIT DATTANI 2012
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Root 3 (short, often fused and curve distally)
Root canal 1
Pulp horns 3
Cusps 3 -5 (1 lingual and 2 buccal)
Eruption 17-21 years
Occlusal Palatal Buccal
Distal Mesial
Triangular occlusal outline Largest cusp is Mesiopalatal Crown appears too big for (short and fused) roots
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1st Year 1st Semester Final Exam Odontology Topic Notes AMIT DATTANI 2012
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23. Description of permanent mandibular molars
Mandibular 1st Molar
Root 2 (1 mesial and 1 distal- curved distally)
Root canal 3
Pulp horns 5
Cusps 5 (3 buccal, 2 lingual)
Eruption 6-7 years
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Largest mandibular tooth Buccal aspect 3 cusps visible Lingual aspect 2 cusps visible Mesiobuccal cusp is largest Mesial root is the largest of the two Larger crown mesiodistally than buccolingually Oblong occlusal outline Crown is shorter distally than mesially
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Crown seems asymmetrical as buccal side longer than lingual side ‘S’ shape on occlusal surface
Rounded-square occlusal outline Lingual cusp higher than buccal Mesial cusp larger than distal Mesial root larger than distal Crown usually smaller than Mandibular 1st Molar
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Roots not as robust but maybe longer than Mandibular 1st Molar Distobuccal cusp is larger than that of the Mandibular 1st Molar Two buccal cusps of equal height Roots not as broad than of the Mandibular 1st molar ‘+’ shape on occlusal surface
Mandibular 3rd Molar
Root 2 (close together, sometimes fused, curved distally)
Root canal 3
Pulp horns 4
Cusps 4-6
Eruption 17-21 years
Mandibular 3rd Molar patterns (in the Right molar)
They can have between 4-6 cusps and the patterns are shown. (Left)
The 3rd molar can vary in shape and position – usually malformed All cusps are short and round Square occlusal outline
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Marked convex buccal surface inclined lingually Roots often underdeveloped, short and thick Roots acutely incline distally
24. Differentiation of molars
There can be a lot you can say about this topic due to the different characteristics shown by
each molar.
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You can start comparing the upper and lower molars and by mentioning the:
Number of roots in the upper and lower molars
The direction of the roots (mesio-distal or bucco-lingual)
The number of root canals in each moalr
You can then compare each molar individually e.g. 1st upper and 1
st lower molar, etc…
(Tip: if you learn the bullet point list on each tooth then this will be very easy!)
The tables below should be learnt extremely well.
Permanent Maxillary
Permanent Mandibular
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25. Morphology of maxillary deciduous teeth
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Maxillary Central Incisor (51,61)
Buccal:
Crown is longer mesiodistally than cervico-incisially
Slightly convex labial surface is smooth
Incisive edge is straight
Vertical development grooves are rarely seen
Root is long in comparison to the crown
Lingual:
Well developed marginal ridges
Cingulum is prominent
Root narrows lingually from a slightly flat labial surface
Cross section from cervical part of root is triangular shaped
Mesial and distal:
Both surfaces are similar
Mesial and distal outlines are wedge shaped
The length bucco-lingually and cervico-incisially are almost similar, only 1mm difference between them
Curvature of the cervical margin is prominently convex incisially (not as prominent in the secondary tooth).
Maxillary Lateral Incisor (52,62)
Outline of this tooth is similar to the central incisor (maxillary)
It has a SMALLER crown than the central incisor
Mesiodistal length is shorter than the cervico-incisial height
Distal incisive angle of the crown is more rounded
Root has similar outline to the central incisor
Maxillary Canine (53,63)
Buccal:
Cannot be compared to the incisor crowns, but root shape is similar
Crown is narrowed at the neck
Mesiodistal surfaces are prominently convex
Incisive edge is long and has a well developed cusp
Mesial slope of cusp is longer than the distal ridge
Root is long
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Lingual:
Prominent vertical enamel ridge
Central cingulum is seen with mesial and distal marginal ridges
Lingual tubercle on the cusp tip is an elongation of the lingual ridge connecting cingulum and cusp
Lingual fossa divides the mesiolingual and distolingual halves
Mesial and distal:
Outlines are similar to the incisor’s mesial and distal aspects, but the crown is more robust in its cervical third.
Maxillary 1st Molar (54, 64)
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Greatest length of the crown is between mesial and distal contact areas where the crown narrows cervically
Roots are thin, long and divergent (3 roots)
Three roots (2 buccal ,1 palatal)
Distal root is shorter than the mesial root
Division of roots is close to the cervical margin
Lingual root is the thickest
From occlusal view: the buccal surface of crown is longer than the lingual surface
2 main cusps: o Buccal o Lingual
Buccal cusp is an elongated ridge that may be partially divided into 2 or 3 smaller cusps by developmental grooves
Usually one prominent buccal developmental groove
Shallow central developmental groove present, but broad
Lingual cusp is usually divided into a large mesiolingual and smaller distolingual cusp by a distal developmental groove
The distal marginal ridge is small compared to the mesial marginal ridge.
Buccal surface of the crown shows a prominent bulge close to the cervical margin and opposite a mesiobuccal root
Cervical margin slopes in a gingival direction mesially on the buccal side, relatively straight lingually and shows a slight mesial and distal occlusal convexity.
Maxillary 2nd Molar (55,65)
Marked divergence of roots
Bulbous shape of crown
Narrowed cervical area
Short root stem
Primary second molar resembles the permanent second molar
Cusps and roots have a similar arrangement
Mesiolingual cusp is the largest and is connected to the distobuccal cusp by a low oblique ridge.
Large mesial fossa and smaller distal fossa
Tubercle of Carabelli is often present on the lingual surface of the mesiolingual cusp
Buccal cusps are almost equal size, separated by a buccal developmental groove
Occlusal surface has a central fossa with a central pit
Well developed triangualar mesial fossa with a mesial pit
Oblique ridge present in the distal triangualar fossa
Cervical line resembles the 1st molar (primary).
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26. Morphology of mandibular deciduous teeth
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Mandibular Central Incisor (71,81)
Buccal:
Relatively flat without developmental grooves
Mesial and distal sides become narrower cervically from the contact area
Crown is wide in comparison to cervico-incisially
Root is long and thin, narrows to a sharp apex
Incisive edge is straight
Lingual:
Cingulum and marginal ridges present
In middle and incisial third the lingual surface is flat or may have a lingual fossa
Crown and root narrow lingually
Mesial:
Typical outline of an incisor
Generally smaller tooth than upper incisor
Labio-lingually its 1 mm shorter than the upper incisor labio-lingually
Nearly flat root
Root narrows gradually apically
Cervical outline is similar to other incisors
Distal:
Outline is similar to mesial aspect of tooth
Cervical margin is less prominent in convexity incisially
Mandibular Lateral Incisor (72,82)
Similar to central incisor but slightly larger in all dimensions except labio-lingually
Cingulum maybe somewhat larger
Lingual surface is more concave than the maxillary lateral incisor
Incisive edge shows greater tendency to descent distal
Mandibular Canine (73,83)
Few differences between maxillary and mandibular canine, except for dimensions
Tooth is smaller, especially labio-lingually than the maxillary
Cervical convexities are less prominent (labially and lingually)
Striking difference is: longer distal cusp ridge compared to mesial cusp ridge (in contrast to the ridges of the maxillary canine)
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Mandibular 1st Molar (74,84)
Occlusal surface is elongated mesiodistally
4 cusps, relatively indistinct
This tooth does not resemble any other molar
Mesial surface descends nearly vertically from the contact area
Distal surface convexity is similar to other deciduous molars
Cervical margin opposite the mesial root descends apically
Cervical margin is straight on lingual surface, slight convexity towards occlusal direction on the mesial and distal surfaces
Buccal surface of crown shows prominent bulge near cervical line
2 roots, mesial and distal
Roots are long, thin and divergent
Occlusally, the mesiolingual cusp is the largest and is separated by a small distolingual cusp by a lingual developmental groove
Buccal developmental groove separates the two buccal cusps
Large distal fossa, central development groove (CDG) starts here
CDG passes between mesiolingual and mesiobuccal cusps and ends in a mesial pit, in the smaller triangualar fossa.
Mandibular 2nd Molar (75,85)
Apart from general differences, this tooth resembles the permanent lower 1st molar- same number and arrangement of cusps and roots
Crown in comparison to the 1st primary molar, shows a more bulbous shape by a mesio-cervical constriction (not descending in a straight line)
Much larger than the 1st primary molar
Mesial and distal roots are long, thin and divergent. Bifurcate close to cervical margin
Occlusal surface has 5 cusps, (3 buccal + 2 lingual)
3 buccal cusps are more or less same size as are the lingual cusps
Total mesiodistal buccal surface is longer than the length of the lingual surface
Irregular central developmental groove runs from a mesial pit in the mesial triangular fossa to the distal pit in the distal triangular fossa
Transverse developmental grooves separate the 3 buccal cusps and 2 lingual cusps
The mesial and distal grooves continue as the buccal developmental groove and the lingual separates the two lingual cusps
Cental pit is where the lingual and mesiobuccal grooves meet the central groove
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Articulation (occlusion) of the deciduous dentition
1. Mesial surfaces of upper and lower central incisors meet at midline of dental arch
2. Upper central incisors articulate with the lower central incisor and the mesial third of the lateral incisor. The incisive edges of the lower anterior teeth make contact with the lingual surface of the upper incisors.
3. Upper lateral incisor articulates with the lower lateral incisor and part of the lower canine mesially
4. Upper canine articulates with the remaining distal part of the lower canine crown and the mesial part of the 1st lower molar
5. The upper 1st molar articulates with the distal two-thirds of lower 1st molar and the mesial part of the 2nd lower molar
6. The upper 2nd moalr articulates with the remaining part of the lower 2nd molar and extends distally, beyond the distal surface of the lower 2nd molar
Mineralisation and eruption
Mineralisation begins at about 4 months of intra-uterine life
By 6 months all teeth are actively mineralised
Usually no teeth present in mouth at birth
Statistics only show an AVERAGE time of mineralisation, eruption etc… but cannot be used EXACTLY because no two individuals develop the same way.
Differences between the Deciduous and Permanent Teeth
1. Deciduous teeth are smaller overall than the permanent
2. Enamel of deciduous is whiter and more opaque, therefore, crown is a
lighter colour than permanent tooth
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3. Enamel of deciduous is more permeable and more easily worn down but
permeability is lessened when tooth resorption starts
4. Depth of enamel is thinner and more consistent in deciduous (0.5-1mm
thick) and is 2.5mm thick in permanent
5. Deciduous have a pronounced cervical margin, the enamel bulges at the CEJ
6. Deciduous anterior crowns are bulbous with a pronounced cingulum
7. Newly erupted deciduous crowns are more pointed than permanent
8. Deciduous roots are shorter, less strong and lighter in colour than
permanent
9. Deciduous:
Anterior roots are longer in proportion to crown
Posterior are more divergent to allow for developing permanent
successor, they flare out more from each other wider than crown
10. Permanent pulp chambers are larger and follow exterior morphological
shape of tooth, tendency of less dentine
11. Deciduous root canals are very fine
12. Deciduous teeth have a more constant morphology, with less variations
than permanent
13. Deciduous CEJ is less sinuous than permanent
14. Deciduous dentition has 20 teeth, permanent has 32 teeth
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27. Physical and chemical properties of enamel
(see topic 4 – enamel part)
28. Enamel structure and formations
Basic structural components are the enamel rods / prisms.
The enamel rods have a round head and a narrow tail. The heads are commonly directed
towards the incisal edge /towards cusps and the tail towards the necks.
The rods are composed of hexagonal hydroxyapatite crystals. Crystals have different
orientation (heads and tails) with respect to the Tomes Process.
Lines of Retzius:
Brown lines begin at the amelodentinal junction and reach the surface of the enamel. Each
line indicates amelogenesis. The first line surrounds the dentin tip. Lines of retzius form as a
result of disturbed mineralisation. The place where the lines meet the surface of enamel,
shallow grooves are seen, called perikymata.
Bands of Hunter-Schreger: Longitudinal cross-sections of enamel viewed by reflected light, appears as light and dark
bands, found in the inner part of enamel. It is caused by successive changes in direction,
followed by groups of enamel rods in the horizontal plane, which cause change in the angle of
light.
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Enamel Tufts: Small branching defects found only at the DEJ, projecting into the enamel, have no clinical significance.
Enamel Spindles: Dentinal tubules found within the enamel – more abundant in cusp tips. Arise when a single odontoblasts process invades the pre-ameloblast layer during dentin development.
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Enamel Lamellae: (Thin unmineralised structures) Primary: in unerupted teeth, due to shrinkage of enamel during final stages of amelogenesis Secondary: in post-eruptive phase, has the same appearance but as a result of occlusal trauma
Tomes process: Secretory surface of amelogenesis
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Amelogenesis occurs in the crown stage of tooth development, always AFTER dentin formation
2 main stages of Amelogenesis
1. Secretory stage- in which proteins and organic matrix form a partially mineralised enamel 2. Maturation stage – mineralisation is completed
Secretory:
Cells of inner enamel epithelium differentiate to form ameloblasts, release enamel proteins
Enamel matrix mineralised by enzyme, alkaline phosphate
Enamel formation continues outward, away from the dentin
After first layer, the tomes process is produced
Maturation:
Ameloblast stops producing enamel
Starts to transport proteins used to complete mineralisation
29. Physical and chemical properties of dentine
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Dentine forms the main bulk of the tooth, it is composed of: o 70% inorganic material (mainly hydroxyapatite) o 20% organic (mainly collage and lipids etc…) o 10% water
Softer than enamel but harder than cementum
Inner dentine is softer than outer dentine
Dentine has a tubular structure – therefore dentine has a higher permeability than enamel
Dentine has nerves and so is sensitive
Types of Dentine
Mantle dentine o First formed dentine – a the DEJ i.e. closest to enamel o Less mineralised than primary dentine
Primary dentine o Forms bulk of the tooth o Very regular tubular structure o When the root apex is closed (during formation) the primary dentine is finished
and secondary dentine starts formation
Secondary dentine o Formed after root formation o Formed slower than root formation o Less regular tubular structure than primary dentine o Its deposition reduces the pulp chamber
Tertiary dentine / reparative dentine o Deposited in reaction to noxious / traumatic stimuli e.g. caries, dental
procedures – it protects the pulp o Deposited in a localised area o Has a very few and irregular tubules
Predentine o Not completely mineralised layer 10-20um wide o Remains between odontoblasts and mineralised dentine o Contains a lot of organic matrix o After inorganic materials deposited (hydroxyapatite crystals) it becomes
mineralised to primary dentin o Predentine is mineralised in spherical forms,then the spherical forms fuse
together and predentine forms primary dentine
Physical properties
Main bulk of tooth
Living tissue with a tubular structure
Yellowish-white in permanent teeth
It is sensitive tissue, it contains very small nerve branches
It is elastic and permeable
Age affects permeability and hardness. o With age it becomes less permeable o With age hardness increases
Softer than enamel but is harder than cementum
Softer inner part of dentine
Dentine is a tooth germ in the bell stage
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Inner cell of dental papilla will differentiate into odontoblasts (dentine forming cells later)
Functions of dentine
Acts as a main (bulk) portion of a tooth
Protects the pulp
Supports enamel
30. Dentine structure and formations
The three main types of dentine are primary, secondary and tertiary (topic 29)
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Odontoblasts are dentine forming cells
A single cell layer covers the pulpal surface and can have different forms
They are functioning as living cells as long as the tooth is vital and when needed they react to stimulus in order to form tertiary dentine
Odontoblast processes are cytoplasmic extensions that enter the dental tubules. Each process has branches and it has a secretory function.
Dental tubules: are narrow parallel channels that do not follow a straight course. They have two curvatures, a primary and a secondary. “S” shaped curvature – primary, are layered. A secondary curvature can be seen under higher magnification. Some tubules can penetrate through the enamel (enamel spindles).
o Inside the tubules we can find odontoblasts processes and fluid o Around the tubules we can find two kinds of dentine:
1. Peritubular dentine:
o Which circles the tubules like a ring o Very hard o Highly mineralised o Absent in the pre-dentin and interglobular dentine o Its thickness increases with age
2. Intertubular dentine: o Found between tubules o Softer than peritubular dentine o It is built from a well organised collagen fiber network
Sometimes we can find small areas in the dentine, which are not fully mineralised. We can divide these into two groups:
Interglobular dentine: irregularly shaped structures near the ADJ (amelodentinal junction)
Granular layer of Tomes: near cementum, seen as dark areas, resulting from irregular loops of the dentinal tubules. (see image)
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We can see different lines on dentine:
Incremental lines due to daily formation of dentine, appears as light and dark bands
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1. Contour lines of Owen: different events of major changes in body metabolism, might cause hypomineralisation of the dentine
2. Neonatal lines (lines of Von Ebner): hypomineralisation line, can be seen only in milk teeth or permanent first molars
Dentine formation: dentinogenesis is the first identifiable stage in the crown stage and root development.
It must occur before enamel formation
The different stages result in different kinds of dentine formation
Odontoblasts differentiate from the dental papilla
31. Structure of the pulp
32. Functions of the pulp
The dental pulp consists of a delicate vascular connective tissue with specialised cells
The pulp is concerned with reactions of the tooth to stimuli
It has 5 main functions:
1. Inductive and formative function o Interacts with the inner enamel epithelium and leads to differentiation of
odontoblasts into dentine o …this leads on to the differentiation of ameloblasts to form enamel.
2. Reparative function o Acts as a method of protection to isolate the pulp from any kind of stimuli e.g. low
grade attrition 3. Defensive, or protective function
o Causes an inflammatory response in the pulp in reaction to acute irritation e.g. bacteria, deep cavity preparation or irritating filling.
4. Nutritive function o The blood nourishes dentine and enamel through odontoblasts
5. Sensory function o Stimuli causes pain which acts as a protective function
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General appearance and structure
The dental cavity within each tooth is occupied by the dental pulp, which is surrounded by dentine except for the apical foramen, which is surrounded by cementum.
The pulp chamber can be theoretically split into two parts, the coronal pulp and the radicular pulp (root pulp)
The pulp communicates with the periapical tissues (tissues around the root) through its foramen. The foramen consists of nerves, blood vessels and lymph vessels passing through.
It is normal to see more than one small accessory foramen that connects the root canal to the periapical tissues.
The shape of the dental pulp is somewhat similar to the shape of the tooth.
The pulp horns are located as small “pointed” parts of the pulp that are located beneath cusps
Pulp is composed of:
o Cells
Odontoblasts- found close to predentin
Cell free zone- layer of Weil, beneath the odontoblasts cant be seen in developing tooth
Cell rich zone- rich in capillary and nerve network
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Fibroblasts- are the most numerous cells of the pulp. Provides elasticity to the blood vessels.
o Blood vessels o Lymph vessels o Nerves o Thin collagenous fibers o …in a gelatinous ground substance
The pulp has a very rich blood supply; vessels enter and leave through the apical foramen.
Nerve supply
Both myelinated and unmyelinated nerve fibres are found in the dental pulp
Myelinated- are terminal branches of the trigeminal nerve. They can only register pain; they enter the root canals and branch out forming the plexus of Raschkow. They become unmyelinated as they reach the odontoblasts layer.
Unmyelinated - they are located in the walls of blood vessels and innervate the smooth muscle cells to regulate vasoconstriction.
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33. Description of soft tissues of the periodontium
As mentioned previously, the periodontium consists of:
1. Alveolar bone 2. Cementum 3. Gingiva 4. PDL
These tissues surround and support the tooth; all components except from the gingival arise in the dental follicle.
The soft tissues of these is the Gingiva and the PDL
Gingiva
Surrounds the teeth and is bound to the buccal and lingual plates of the alveolar process
It is pale pink in colour and can be coloured by natural pigmentation
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The part of the gingival closest to the cervical region is not directly attached to the tooth and is known as the free gingiva. In other cases it is known as attached gingiva.
Gingival fibers are collagen fibers that are found in the lamina propria and have an important role in maintaining and supporting the tooth. The fibers work as a functional unit, but they are arranged in 5 subgroups:
1. Dentogingiva – between the cementum and the lamina propria (beneath the junctional epithelium and marginal gingiva).
2. Dentoperiosteal – from the cementum into the periosteum (muscle) 3. Trans-septal – from the cementum and connect adjacent teeth in the arch 4. Alveologingival – from the bony alveolar crest to the lamina propria 5. Circular – run around the neck of the tooth and maintain a tight gingival collar
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The interdental gingiva contains all the fiver groups illustrated above and the trans-septal fibers
The gingiva is supplied by branches of the infraorbital, nasopalatine, buccal, mental, lingual and palatine arteries.
Periodontal Ligament
It is a connective tissue that binds the tooth to the alveolar bone. It communicates with the bone marrow of the alveolar process through vascular channels (volkmann’s canals). They have nerve fibers that respond to occlusal pressure. (Note: fibroblasts synthesise fibres that become the PDL)
It’s situated within a ‘ground substance’ mainly composed of glycosaminoglycans, glycoproteins, and glycolipids. Cells making up the PDL are fibroblasts, epithelial cell rests of Malassez, osteoblasts, Osteoclasts, cementoblasts, macrophages and undifferentiated mesenchymal cells. The collagen fibers pass from the cementum and pass through the periodontal space and are embedded into the alveolar bone as Sharpey’s fibers.
The ligament has a sensory, supportive and protective function to withstand the forces of mastication and other forces alike. They also resist light occlusal impacts and have slight mobility as a cushion.
The width of the periodontal space varies from 0.1mm - 0.4mm
The periodontal fibers
Collagen is the most important structural component of the periodontal ligament. There are 5 principle fibers of the periodontium:
1. Alveolar crest group – similar to tran-septal fibers 2. Horizontal group - run horizontally below the alveolar crest 3. Oblique group- most numerous fibers and are found just beneath the coronal level 4. Apical group – surrounding the root apex 5. Inter-radicular group – at the division of roots
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The periodontal fibers
The PDL are supplied by branches of the superior and inferior alveolar arteries, the apical region is supplied by branches of pulpal arteries of individual teeth.
34. Description of hard tissues of the periodontium
The hard tissues of the periodontium are cementum and alveolar bone
Cementum
Covers the root surface
Its colour is yellow
Softest between the dental mineralised tissues
Softer than enamel and dentine because it is less mineralised
Its chemical composition is similar to that of bone o 65% inorganic o 23% organic o 12% water
The main role of cementum is to serve as a medium in which the PDL can attach and stabilise the teeth
o 2 main types of cementum Acellular – lack of cellular components and covers the root surface Cellular – in the apical third of the tooth (last third)
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Cells of the cementum:
1. Cementocytes- are cementum cells, they are cementoblasts and are embedded in cementum during cementogenesis
2.
3. Cementoblasts – located on the surface of cementum and produce the matrix and fibers of cementum
4. Cementoclasts – break down cementum
In the cementum we can find intrinsic and extrinsic fibers, sharpey’s fibers (collagen fibers which are embedded into cementum and alveolar bone, they are extensions of the PDL).
Alveolar bone
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The alveolar process is that part of the jaw in which the teeth are found (tooth bearing). It is therefore composed of alveolar bone and supporting bone. The remaining jaw-bone is supporting the alveolar process as basal bone.
After eruption the bone is covered by a thick cortical bone and within it is spongy bone (also known as ‘Cancellous bone’).
Lamina dura – is a thin plate of alveolar bone, in the alveolar sockets that allows the passage of blood vessels to the periodontal ligament.
I hope my notes help you in passing and understanding Odontology.
Wishing you the very best in your career.
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Amit Dattani
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