3. Dental charting. Signs of teeth. Clinical and anatomical features of teeth.

3. Dental charting. Signs of teeth. Clinical and anatomical features of teeth.

 

All of the teeth in the mouth together are referred to as the dentition [den TISH un]. Humans have two dentitions throughout life: one during childhood, called the primary dentition, and one that will hopefully last throughout adulthood, called the permanent (also known as secondary)  dentition. The teeth in the upper jawbones (called the maxillae [mak SIL ee]) collectively form an arch shape known as the maxillary [MACK si lair ee] arch, and those teeth in the lower jawbone (called the mandible) collectively form the mandibular [man DIB yoo ler] arch. Each arch can further be divided into the left and right halves (also known as left and right quadrants since each quadrant contains one fourth of all teeth in that dentition).

COMPLETE PRIMARY DENTITION

The complete primary dentition is normally present in a child from the ages of about two to six years. There are 20 teeth in the entire primary dentition (shown in Fig. 1): ten in the upper maxillary arch and ten in the lower mandibular arch. This dentition is also called the deciduous [de SIDJ oo us] dentition, referring to the fact that all of these teeth are eventually shed by age 12 or 13, being replaced sequentially by teeth of the permanent dentition. The complete primary dentition has five teeth in each quadrant. The primary teeth in each quadrant are further divided into three classes: incisors [in SI zerz], canines, and molars.

 

PRIMARY TEETH

 

Fig. 1 Maxillary and mandibular primary dentition.

 

Based on location, starting on either side of the midline between the right and left quadrants, the two front teeth in each quadrant of the primary dentition are incisors (I), followed by one canine (C), then two molars (M). Using these abbreviations for the classes of teeth, followed by a ratio composed of a top number representing the number of teeth in each upper quadrant and the bottom number representing the number of teeth in each lower quadrant, a  formula can be used to represent the teeth in the human  primary dentition as follows:

 

The classes of primary teeth containing more than one tooth per quadrant (incisors and molars) are subdivided into types within each class. Each type can also be identified by its location within the complete quadrant. The primary incisor closest to the midline separating the right and left quadrants is called a  central incisor. The incisor next to, or lateral to, the central incisor is called a lateral incisor. Next in each quadrant is a canine, followed by two types of molars: a first molar behind the canine and then a second molar.

 

COMPLETE PERMANENT DENTITION

The complete permanent (or secondary) dentition is present in the adult. It is composed of 32 teeth: 16 in the upper maxillary arch and 16 in the lower mandibular arch (shown in Fig. 2). The permanent dentition has eight teeth in each quadrant, which are divided into four classes: incisors, canines, premolars (PM; a new class for permanent teeth), and molars. Based on location, the two permanent front teeth in each  quadrant are incisors (I), followed by one canine (C), then two premolars (PM), and finally three molars (M). The  dental formula for the human permanent dentition is as follows:

 

The classes of permanent teeth containing more than one tooth per quadrant (namely, incisors, premolars, and molars) are subdivided into types within each class. Each type can be identified by location within the quadrant. As in the primary dentition, the permanent incisor closest to the midline between the right and the left quadrants is called a central incisor; the incisor next to, or lateral to, the central incisor is called a lateral incisor. Next in the arch is a canine, followed by a first premolar, then a second premolar. Continuing around toward the back in each quadrant are three molars: a first molar, a second molar, and finally a third molar (sometimes referred to as a wisdom tooth).

As noted by comparing the formulas for primary and permanent teeth, differences exist. Although central and lateral incisors and canines are similarly positioned in both dentitions, permanent dentitions have a new category of teeth called premolars, which are located between canines and molars. Premolars are positioned in the spaces left where the primary molars were located earlier in life. Behind the premolars, there are three instead of two molars.

 Two other terms are used to categorize or distinguish groups of teeth by their location: anterior and posterior teeth. Anterior teeth are those teeth in the front of the mouth, specifically, the incisors and the canines. Posterior teeth are those in the back of the mouth, specifically, the premolars and the molars.

 

PERMANENT TEETH

 

 

Fig. 2 Maxillary and mandibular permanent dentition.

 

 

 TERMINOLOGY USED TO DEFINE TOOTH

All teeth have surfaces that are named according to their usual alignment within the dental arch. Refer to Figure 6 when studying the terms to denote tooth surfaces.

 

 

 

Terms that identify outer surfaces (toward the cheeks or lips) of anterior or posterior teeth

The facial surface of a tooth is the surface toward the face, that is, the surface of a tooth in the mouth resting against or next to the cheeks or lips. Facial may be used to designate this surface of any tooth, anterior or posterior. Another name for the facial surface of  posterior teeth is buccal [BUCK k’l], located next to the cheek (labeled on tooth No. 3 in Fig. 6). It is incorrect to use this term when speaking about the incisors or canines because they do not approximate the cheeks. The facial surface of anterior teeth is properly called a labial [LAY bee al] surface, located next to the lips (labeled on tooth No. 6 in Fig. 6). This term should not be used when referring to the premolars or the molars.

 

Terms that identify inner surfaces (toward the tongue) of maxillary and mandibular teeth

The lingual [LIN gwal] surface is the surface of a maxillary or mandibular tooth nearest the tongue. In the maxillary arch, this surface can also be called the palatal surface due to its proximity with the palate (labeled on tooth No. 5 in Fig. 6)

Terms that differentiate biting surfaces of anterior and posterior teeth

The occlusal [ahk KLOO zal] surface is the chewing surface of a posterior tooth (labeled on tooth No. 2 in Fig. 6). Anterior teeth (incisors and canines) do not have an occlusal surface but do have a cutting incisal edge or ridge (labeled on tooth No. 8 in Fig. 6)

 

Terms that differentiate approximating surfaces of teeth

The proximal [PROCK se mal] surfaces are the sides of a tooth generally next to an adjacent tooth. Depending on whether the tooth surface faces toward the arch midline between the central incisors or away from the midline, it is either a mesial [MEE zi al] surface (closer to the midline) or a distal [DIS tal] surface (farther from the midline). Mesial and distal surfaces are labeled on tooth No. 1 in Figure 6. Note that the mesial surface of a tooth touches, or is closest to, the distal surface of an adjacent tooth EXCEPT between the central incisors where the mesial surface of one central incisor faces another mesial surface. Also, the distal surface of the last molar in each arch does not approximate another tooth. Proximal surfaces are not naturally cleaned by the action of the cheeks, lips and tongue when compared to most of the facial or lingual surfaces which are more self-cleansing.

Terms to denote tooth surface junctions or dimensions

The junction line where two tooth surfaces meet is called an external line angle. To name a line angle, combine the names of the two surfaces, but change the “al” ending of the first surface to an “o.” (A guideline has been suggested for the order used when combining terms. Use the following order: mesial is used first, then distal, facial, lingual, and lastly occlusal or incisal. Using this guide-line, it is better to say mesio-occlusal than occlusomesial, and it is better to say distolingual than linguodistal.)

 

 

 

Examples of external line angles of a molar crown include mesio-occlusal, mesiolingual, mesiofacial, distoocclusal, distolingual, distofacial, bucco-occlusal, and linguo-occlusal. Point angles are the junctions of three tooth surfaces at a point, such as a mesiobucco-occlusal point angle. Examples of these external line angles and point angles are seen in Figure 7.

To describe a dimension of a tooth, terms can be combined to denote the direction over which a dimension is taken. For example, the length of an incisor crown from the incisal edge to the cervical line is called the incisocervical dimension or the dimension incisocervically (Fig. 7). Other similar terms used to describe a crown dimension include mesiodistal, faciolingual or buccolingual, and occlusocervical. The length of a root could be described as its cervicoapical dimension.

 

TOOTH IDENTIFICATION SYSTEMS: UNIVERSAL, WORLD DENTAL FEDERATION (INTERNATIONAL), AND PALMER NUMBERING SYSTEMS

 

The making and filing of accurate dental records is an important task in any dental practice. To do so expeditiously, it is necessary to adopt a type of code or numbering system for teeth. Otherwise, for each tooth being charted, one must write something like “maxillary right second molar mesio-occlusodistal amalgam restoration with a buccal extension” (11 words, or 81 letters). Simplified by using the tooth notation systems (and other standard abbreviations to denote tooth restoration surfaces).

The Universal Numbering System was first suggested by Parreidt in 1882, and officially adopted by the American Dental Association in 1975. It is accepted by third-party providers and is endorsed by the American Society of Forensic Odontology. Basically, the Universal Numbering System uses No. 1 through 32 for the 32 teeth in the permanent dentition, starting with 1 for the maxillary right third molar, going around the arch to the maxillary left third molar as 16; dropping down on the same side, the left mandibular third molar becomes 17, and then the numbers increase around the lower arch to 32, which is the lower right third molar. This numbering system is used for each permanent tooth in the illustration in Figure 3.

For the 20 teeth in the primary dentition, 20 letters of the alphabet are used from A through T. The letter A represents the maxillary right second molar, sequentially around the arch and through the alphabet to J for the maxillary left second molar, then dropping down on the same side to K for the mandibular left second molar, and then clockwise around the lower arch to T for the mandibular right second molar. This system is used to identify each primary tooth in the illustration in Figure 4.

 

 

 

There are also two other numbering systems, the Palmer Tooth Notation System, and the World Dental Federation (International) System used in other countries. The World Dental Federation notation (also known as the Federation Dentaire Internationale or FDI System) uses two digits for each tooth, permanent or primary. The first digit denotes the quadrant (right or left) and arch (maxillary or mandibular) and dentition (permanent or primary) as follows:

 

 

PERMANENT DENTITION

1 = Permanent dentition, maxillary, right quadrant

2 = Permanent dentition, maxillary, left quadrant

3 = Permanent dentition, mandibular, left quadrant

4 = Permanent dentition, mandibular, right quadrant

PRIMARY DENTITION

5 = Primary dentition, maxillary, right quadrant

6 = Primary dentition, maxillary, left quadrant

7 = Primary dentition, mandibular, left quadrant

8 = Primary dentition, mandibular, right quadrant

 

 The second digit denotes the tooth position in each quadrant relative to the midline, from closest to the midline to farthest away. Therefore, the second digits 1 through 8 stand for the permanent central incisor (1) through the permanent third molar (8) and 1 through 5 stands for the primary central incisor (1) through the primary second molar (5). The adult tooth Numbers 1 to 8 within each quadrant (1 through 4) are illustrated in Figure 5.

 

 

Combining the first and second digits, numbers within the range 11 through 48 represent permanent teeth. For example, 48 is a permanent mandibular right third molar since the first digit, 4, indicates the mandibular right quadrant for a permanent tooth, and the second digit, 8, indicates the eighth tooth from the midline in that quadrant, namely, the third molar. Numbers within the range 51 through 85 represent primary teeth. For example, 51 is a primary maxillary right central incisor since the first digit, 5, indicates the maxillary right quadrant for a primary tooth, and the second digit, 1, indicates the first tooth from the midline in that quadrant, namely, the central incisor. If the Universal number for a tooth were 32, the World Dental Federatioumber would be 48.

The Palmer Notation System is used by many orthodontists and oral surgeons. It utilizes four different bracket shapes to denote each of the four quadrants. The specific bracket surrounds a number (or letter), which denotes the specific tooth within that quadrant. The specific brackets are designed to represent each of the four quadrants of the dentition, as if you were facing the patient as seen in Figure 5.

_   is upper right quadrant

_  is upper left quadrant

¯   is lower right quadrant

¯  is lower left quadrant

 

The permanent teeth in each quadrant are numbered from 1 (nearest to the arch midline) to 8 (farthest from the midline) as in the International System. For example, 1 is a central incisor, 2 is a lateral incisor, 3 is a canine, and so forth. The bracket shapes used to identify each quadrant as you are facing a patient, and the tooth numbers (1–8) within each quadrant, are illustrated in Figure 5. To identify a specific tooth, you place the number of the correct tooth within the bracket that indicates the correct quadrant. For example, the lower left central incisor would be ¯1, the lower left second premolar would be ¯5, and the upper right canine would be 3_ . For primary teeth, the same four brackets are used to denote the quadrants, but five letters of the alphabet A through E represent the primary teeth in each quadrant (with A being a central incisor, B a lateral incisor, C a canine, etc.). Comparing the Universal System with the Palmer System, the permanent maxillary right second molar would be No. 2  using the Universal System, but would be 7_ using the Palmer system.

 

 

 

 

 

Common used dental charting in Ukraine – this charting is similar to those described previously

In clinic doctors use to chart permanent dentition like this:

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

For temporary dentition in clinic doctors use Rome figures, for example:

V IV III II I I II III IV V

V IV III II I I II III IV V

According to the WHO permanent dentition is charted in this manner:

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

Temporary dentition according to WHO is charted:

55 54 53 52 51 61 62 63 64 65

85 84 83 82 81 71 72 73 74 75

 

Charting the teeth

The teeth present and absent, teeth unerupted or partially erupted, the presence of caries and other defects of the teeth and the restorations present are recorded on a chart.

The chart shows the buccal/labial, palatal/lingual, mesial, distal and occlusal surfaces of all the teeth

How to examine teeth

The teeth should be examined in a systematic manner, making sure that each surface of each tooth is carefully inspected. A probe is used to remove plaque from the fissures and to detect ledges and deficiencies in existing restorations. The probe should not be pressed firmly into the fissure pattern as this could damage demineralized enamel. Good eyesight and lighting are essential if caries is to be detected. It is also important that the teeth are examined dry and free from plaque as caries is more likely to be detected.

Types of Teeth

Central and lateral incisors – have a single root and chisel-shaped crown. Function: they cut food (mandibular incisors are moving blades against the maxillary incisors), enable articulate speech, help to support the lip and maintain an aesthetic appearance.

Canine – has a single root, conical-shaped crown. Function: to cut, pierce, or shear food; together with incisors support the lips and the facial muscles.

Premolar – has a single root, sometimes upper tooth has bifurcated root. Crown has two cusps. Function: function with molars  to masticate food and to maintain the vertical dimension of the face (between the nose and chin). First premolars assist the canines in shearing or cutting food morsels, and all premolars  support the corners of the mouth and cheeks to keep them from sagging.

Molar – upper teeth have three roots, lower teeth have two roots. Crown has 3-5 cusps on occlusal surface. Function: major role in the mastication of food (chewing and grinding to pulverize) and (b) are most important in maintaining the vertical dimension of the face (preventing the jaws from closing too far, which could reduce the vertical dimension between the chin and the nose, resulting in a protruding chin and a prematurely aged appearance). They are also (c) important in maintaining continuity within the dental arches, thus keeping other teeth in proper alignment. Further, molars have (d) at least a minor role in esthetics or keeping the cheeks normally full or supported.

Formula of the deciduous (temporary) teeth is 2102. Formula of the permanent teeth is 2123. It means that child before 6 years of age in each side of upper and lower jaw has 2 incisors, 1canine, no premolars and 2 molars. Permanent teeth include 2 incisors, 1canine, 2 premolars and 3 molars.

Morphological differences between primary and permanent teeth

There are numerous differences between the primary and permanent dentition, many of which give rise to considerations in relation to operative treatment. Essentially, primary teeth have:

■ A shorter crown.

■ A lighter colour.

■ Narrower occlusal surfaces.

■ Broader and flatter interproximal contact areas.

■ Thinner enamel and dentine.

■ Longer pulp horns, particularly the mesial buccal.

■ Relatively larger pulps.

■ Enamel prisms which run slightly occlusally at the cervical margin.

■ Curved roots (to accommodate the developing permanent successor).

■ Roots which have open apices.

■ More tortuous and irregular pulp canals.

■ An large quantity of accessory pulp canals at the furcation areas.

A. Primary mandibular molar. B. Permanent maxillary molar.

 

AGE TERMS OF ERUPTION FOR DECIDUOUS TEETH AND PERMANENT TEETH:

 Order of temporary teeth eruption:

• Incisors;

• First molars;

• Canines;

• Second molars.

Child should have 20 teeth till the end of the second year of life.

Order of permanent teeth eruption:

• First mandible molars;

• Medial incisors and first maxilla molars;

• Lateral incisors;

• First premolars;

• Canines;

• Second premolars;

• Second molars;

• Third molars (called “wisdom tooth”, are erupted iot all persons).

There are 32 permanent teeth. Mutual arrangement of superior and inferior dental arches during closing the mouth is called bite (occlusion). Physiological and pathologic occlusion are distinguished.

Table 1. Average dates of tooth development and eruption for the permanent dentition.

 

ANATOMICAL STRUCTURE OF THE PERMANENT TEETH

Various views of a newly erupted permanent maxillary incisor that showing its features.

A human bite has 32 permanent teeth: 4 incisors, 2 canines, 4 premolars, 6 molars (at all – 16 teeth) on every jaw. For many people third molars (wisdom teeth) does not erupt because of being rudiments, and then people have 28 teeth. Absence of wisdom teeth, and sometimes lateral incisor and second premolars is the sign of reduction of the tooth in jaw system that is predefined by the change of feed character of a modern human-being.

MAXILLA

Central incisor.

A tooth has a crown and one well developed cone-shaped root. Vestibular surface of crown is a little protuberant. On the lingual surface of the crown there is a small cusp, that with lateral edges reaches a cutting edge. Cutting edge is  a little relocated in distal direction and has a sharp medial angle. A root is straight, a little oblate and declined distal from the vertical axis of tooth. On a transversal section tooth cavity has an oval shape.

Lateral incisor.

 The corner of crown is sharp, sometimes looking like a knoll. The vestibular surface of crown is protuberant. A lingual surface is concaved and limited by the margins of crown. The lateral rollers of lingual surface often meet in a cervical area, forming a triangle, on the top of which is located a deepening in enamel – blind fossula (pit). A root is considerably oblate in mesio – distal direction. Longitudinal furrows are placed on the lateral surfaces of the root. The apical part of root is often declined in -palatal direction. The tooth cavity resembles the smaller shape of a tooth crown.

 

Canine.

 A canine has one massive cone-shaped straight root with an insignificant deviation of its apex in distal direction. On a transversal section a tooth has rounded or sometimes oval shape. The vestibular surface of crown is protuberant. On a lingual surface there is a longitudinal roller which divides its into two parts, from them lateral has a greater area. The longitudinal enamel rollers of both surfaces pass to the cutting cusp. The lateral edges of crown form two corners with a cutting edge, distal corner is more obtuse. A tooth has well expressed signs of corner, curvature of the crown, deviation of root. The cavity of tooth resembles the contours of crown and root.

First premolar

 Has the crown of prismatic shape, buccal and lingual surfaces, buccal side is protuberant. On an occlusal surface there are two cusps – buccal and palatal, from them buccal is considerably greater. Between cusps, a furrow is located .

A root is oblate, on its wide lateral surfaces there are deep longitudinal furrows which in the cervical region of the tooth starts to divide a root into two parts: buccal and palatal. A palatal root is developed better. The cavity of tooth resembles the shape of a crown. The buccal horn of the pulp is located nearer to surfaces. Root-canals- two: palatal and buccal.

Second premolar.

A crown has a prismatic shape. There are two cusps on occlusal surface, among them, the buccal cusp  is more developed. Cusps are separated between itself by a transversal furrow which passes on the center of occlusal surface. The buccal surface of a crown is greater, than lingual. Medіal part of vestibular surface of crown is less protuberant, comparatively with distal (reverse sign of crown curvature) . Root, more frequently is one, cone-shaped, straight, oblate, with wide lateral surfaces and narrow longitudinal furrows on it. Sometimes nearer to the apex, the root can be diverged in two apexes (in 15 % cases). The shape of tooth cavity resembles the shape of a crown. The buccal horn of pulp, comes forward more than palatal. Root-canals – can be two: buccal and palatal (approximately in 25% cases) or one.

First molar.

A. Maxillary first molar. B. Mandibular first molar.

Various views of a maxillary right first molar.

  The largest teeth of maxilla. A crown has the form of rectangle. A diamond-shaped occlusal surface has four cusps: two palatal and two, more developed, buccal. Among buccal cusps, the mesio-buccal is developed more than distal-buccal. Cusps are separated between itself by H-similar line. Near a medio-palatal cusp, the small arched furrow separates a small additional cusp which does not reach to the occlusal surface — tuberculum anomale of Carabelli.

The shape of tooth cavity resembles the shape of a crown. The buccal horns of pulp, especially mesio-buccal, come forward slightly. First molar has three roots, the palatal root is more massive, roundly and straight, two other, are shorter, oblate on each side and declined in distal direction. A mesio-buccal root is more developed, than distal-buccal.

Second molar.

Various views of a maxillary right second molar.

A crown has the shape of a cube. On an occlusal surface there are four cusps which are separated between itself  by X-like line. Buccal cusps are developed more than palatal. The tooth has 3 roots, and 3 root canals – 1 palatal and 2 buccal (mesial and distal)

Buccal views of maxillary right molars. A. First molar. B. Second molar. C. Third molar. Notice how the roots tend to lie closer together when the molars are farther distally. Third molar roots are often fused.

 A palatal root is massive, straight. Both of a buccal roots are – oblate, declined in distal direction, roots can have a few root-canals and apexes.

Various views of maxillary right third molars.

NB! The molars of upper jaw have 3 roots (palatal, mesial buccal and distal buccal) and 3 root canals (names are the same);

First premolar has 2 roots and 2 root canals (buccal and palatal);

Second premolar has 1 root and 1 root canal (in some cases can have 2 canals)

MANDIBLE

Central incisor.

 It is the smallest tooth of a permanent bite. Crown is a comparatively high, the vestibular surface is a little protuberant, lingual surface is concaved. On the cutting edge of a tooth crown which was newly erupt is well seen three small indentations. The corners of crown  has a little difference  from one another. On the vestibular surface of a teeth the cutting edge pass to the small longitudinal enamel rollers.

A root is comparatively short, oblate in mesio – distal direction, on a transversal section has an oval shape. Almost unnoticeable signs of crown curvature and deviation of root. At whole, the tooth cavity resembles its external shape. The apex of root can be inclined to the middle (mesіal) plane.

Lateral incisor

Is an insignificantly bigger than central incisor. Oblate in the area of cutting edge. On the vestibular surface of the tooth crown, which was newly erupted, a small longitudinal rollersare present, which ends on a cutting edge with the well-noted three indentations. A tooth has one straight root, oblate on each side, with longitudinal furrows on proximal surfaces, on a transversal section – has an oval shape. The apex of root is declined distal. Tooth cavity is narrow, with slit-like shape, a root-canal is narrow.

Canines.

Various views of a mandibular right canine.

  The structure of canine is similar to the canine of maxilla, but insignificantly, smaller. A crown, partly keeps a diamond-shaped form, however looks narrower, prolonged, vestibular surface is protuberant. There is a central cusp on a cutting edge. Medіal part of cutting edge is shorter, than distal.

Root is insignificantly  oblate on each side, on a transversal section the root has an oval shape. The apex of root is declined distal. The tooth cavity has a fusiform shape with most bulge in the area of tooth neck.

 

Labial (A) and lingual (B) views of permanent mandibular and maxillary canine.

First premolar.

Various views of a mandibular right first premolar.

 First premolar. A crown partly resembles the shape of canine, however on a transversal section does not have such rounded shape.

Second premolar.

Second premolar insignificantly greater, than first premolar, the occlusal surface of both premolars are identically. They are separated between itself by an enamel roller, on the edges of which the small deepening are located (fossulas).

Root, as a rule, is one, a little oblate, its lateral surfaces are smooth and shiny. The apex of root is declined  in distal direction.

Occlusal view of the mandibular right second  premolar: three-cusp and two-cusp types.

First molar.

Various views of a mandibular right first molar.

  A crown has a cube shape. On an occlusal surface – five cusps are located : three buccal and two- lingual. The cusps of occlusal surface is separated by Ж –similar line, longitudinal part of which achieves enamel rollers on the edge of crown. Transversal part of this surface can pass to the vestibular surface and be closed to its by the small deepening (by blind fossulas- pits).

Distal root is more straight and has one root-canal.  Mesial root is oblate, with deep longitudinal furrows on wide lateral surfaces, has two root-canals(medial buccal, medial lingual canals).

Second molar.

Various views of a mandibular right second molar.

 The crown of a second molar is a little smaller than the crown of the first molar. The shape of the crown is similar to such in first molar, and  amount of roots is the same. Cube shape – has a crown, insignificantly prolonged in mesio-distal direction, has four cusps on a occlusal surface — two buccal and two lingual. Longitudinal fissure on an occlusal surface is located nearer to the lingual edge. Transversal fissure can go out to the vestibular surface of a crown and be closed on its by a blind fossula- pit.

A tooth has two roots and 3 canals; distal root is straight, rounded or oval on a transversal section, medial root- large, oblate, there are small furrows on its lateral surfaces. The apex of root is directed distal.

Various views of the permanent mandibular right third molar.

 

Buccal views of mandibular right molars. A. First molar. B. Second molar. C.Third molar. Note that the roots are closer together and become shorter from the first molar to the third molar. Third molar roots are often fused.

NB! The molars of mandible have 2 roots (mesial and distal) and 3 root canals (mesial- lingual, mesial-buccal and distal) Every tooth has anatomic signs which help clinician to define it to a certain group of teeth. Foremost, they are: the shape of a crown, cutting edge or occlusal surface and amount of roots. The next ones are the signs of belonging of the tooth to the right or left side of jaw: signs of crown angle, crown curvature and deviation of root.

The sign of the crown angle  (A)– is – the mesial angle of the crown  is more sharp than the more obtuse distal angle of the crown.  This is especially pronounced for upper central and lateral incisor and for premolars.

The sign of the crown curvature (B) – is – the vestibular side of the tooth is more convex than the lingual side.

The sign of the root  deviation (C)- deviation of the longitudinal axis of the root from the midline of crowns for incisors and canines – in the lateral direction, for premolars and molars – in distal direction. The roots of front group of teeth are deviated from the midline to  lateral direction, the teeth of masticatory group are deviated – to distal direction.

 

Information was prepared by Levkiv M.O.