Dental Education Hub

Category: Dental Anatomy

Dental anatomy or tooth morphology is the study of the development, function, morphology, and identification of each tooth in the human dentition.
This section comprehensively explains the introduction to the types of human dentition, the tooth numbering systems, morphology and variations of individual deciduous and permanent teeth, and dental occlusion.
In each blog, in addition to the textual information at the end, the blog is supported by a video lecture and practical demonstration of the subject that makes this content interesting for you.

  • Maxillary First Premolar: Dental Morphology Made Easy

    Maxillary First Premolar: Dental Morphology Made Easy

    The maxillary first premolar is the first posterior tooth in the maxillary dental arch. There are four premolars in the maxillary dental arch two in each quadrant. The term premolar is used for these teeth because these teeth are anterior to the permanent molars. The maxillary first premolar has two cusps one buccal and one palatal cusp. The number of roots is two one buccal and one palatal root. The other premolars maxillary and mandibular usually have a single root. The first premolar because of its morphology and position in the dental arch assist canine in the tearing function and molars in the grinding function. The first premolar has succeeded the deciduous maxillary first molar tooth.

    Development and Eruption of Maxillary First Premolar

    Following is a summary of the chronology of development and eruption of the maxillary first premolar.

    • Beginning of calcification of first premolar: 1 ½ year
    • Crown completion of first premolar: 5 – 6 years
    • Eruption of the maxillary first premolar: 10 -11 years
    • Root completion of the first premolar: 12 – 13 years

    Buccal Aspect

    • The maxillary first premolar resembles canine from the buccal aspect.
    • The curvature of the cervical line or cementoenamel junction is less as compared to the teeth that are present anterior to the maxillary first premolar.
    • Two cuspal slopes are associated with the buccal cusp those are the mesial cuspal slope and the distal cuspal slope. The mesial cuspal slope of the maxillary first premolar is longer as compared to the distal cuspal slope.
    • The buccal cusp is longer and pointed and the only visible cusp from the buccal aspect.
    • There are two developmental depressions on the buccal aspect. Mesiobuccal and distobuccal developmental depressions. In between these developmental depressions, a ridge called buccal ridge is present.
    • The buccal root is long and cone shape and bears some resemblance with the canine root. The length of the buccal root is less than the root length of the maxillary canine. The buccal root in the apical one-third portion slightly curves in a distal direction.
    • The mesial outline of the crown is slightly concave while the distal outline is straight.

    Lingual Aspect

    • The crown is narrow mesiodistally as compared to the buccal aspect.
    • Due to this reduced mesiodistal dimension of the crown on the lingual aspect part of the mesial and distal aspects of the crown is visible from the lingual aspect.
    • The lingual cusp is shorter in height as compared to the buccal cusp. Therefore, the buccal cusp along with the cuspal slopes is visible from the lingual aspect.
    •  The lingual root is also cone shape, smooth, and convex with no developmental depressions.
    • The crown is smooth and spheroidal from the lingual aspect and the lingual cusp tip is pointed.

    Mesial Aspect

    • The buccal and lingual cusp tips are within the confines of the root trunk.
    • The curvature of the cervical line is towards the crown but this curvature is less as compared to the curvature of the cervical line present on the mesial aspects of anterior teeth.
    • The mesial marginal ridge of the maxillary first premolar has a developmental groove. This developmental groove serves as an identification of the mesial surface of the tooth. 
    • A developmental depression is present on the mesial surface of the crown below the contact area and extends onto the root surface.
    • The developmental depression on the mesial marginal ridge and the concavity present on the mesial surface of the tooth helps in the identification of the maxillary first premolar even when the tooth has a single root.

    Distal Aspect

    • The distal aspect of the crown of the maxillary first premolar is smooth with no developmental groove or depression.
    • The curvature of the cervical line on the distal aspect of the crown is less as compared to the mesial aspect of the crown.
    • The distal marginal ridge is smooth with no developmental depression.
    • The maxillary first premolar has the largest root trunk.

    Occlusal Aspect

    • The occlusal surface of the maxillary first premolar is hexagonal.
    • The crown is wide mesiodistally on the buccal aspect as compared to the lingual aspect where the mesiodistal dimensions are less.
    • Overall the buccolingual dimension is more as compared to the mesiodistal dimension of the crown.
    •  The central developmental groove divides the crown into buccal and lingual halves.
    • There are some accessory or supplementary grooves that join the central developmental groove such as mesiobuccal developmental groove, distobuccal developmental groove, mesiolingual, and distolingual developmental grooves.
    • Two triangular depressions are present adjacent to the mesial and the distal marginal ridges. These triangular depressions are named the mesial and the distal triangular fossa.  
    • A ridge descent from the cusp tip towards the center of the occlusal surface and this ridge is named the buccal triangular ridge.
    • Similar to the buccal triangular ridge a liner elevation arises from the lingual cusp tip and terminates in the center of the occlusal surface and this ridge is named the lingual triangular ridge. The lingual triangular ridge is less prominent as compared to the buccal triangular ridge.
    • The buccal and the lingual triangular ridges form the transverse ridge.

    Maxillary First Premolar Dental Morphology Video Lecture

    Demonstration of Maxillary First Premolar Morphology on tooth models

  • Permanent Mandibular Canine: Dental Morphology made Easy

    Permanent Mandibular Canine: Dental Morphology made Easy

    The permanent mandibular canine is similar morphologically to the maxillary canine. However, the mandibular canines have overall smaller dimensions and the tooth landmarks are also not very well developed like a permanent maxillary canine.  In the permanent dental arch mesial to the mandibular canine mandibular lateral incisor is present and distal to the canine the mandibular first premolar is positioned. Like the maxillary canines, these teeth have a tearing function.

    Development and Emergence of Permanent Mandibular Canine

    Following is a summary of the development and emergence of the permanent mandibular canine.

    • Beginning of calcification of permanent mandibular canine: 4-5 months
    • Completion of the crown of mandibular canine: 6-7 years
    • Eruption of mandibular canine: 9-10 years
    • Completion of the root of mandibular canine: 12-14 years

    Labial Aspect

    • The mesiodistal dimension of the mandibular canine is slightly less as compared to the permanent maxillary canine.
    • Due to fewer mesiodistal dimensions, the crown of the mandibular canine appears longer as compared to the maxillary canine.
    • The mesial contact area of the mandibular canine is more towards the incisal aspect of the tooth. whereas the distal contact area is more towards the incisal and middle third.
    • The cusp tip is sharp and two ridges descend from the cusp tip. The mesial cuspal ridge is shorter as compared to the distal cuspal ridge.
    • The mesial outline of the crown of the mandibular canine is in line with the mesial outline of the root.
    • The distal outline of the crown of the mandibular canine is slightly rounded.
    • There are two developmental depressions on the labial surface of the crown. They are named mesial and distal developmental depressions. These developmental depressions are not as prominent as the developmental depressions present on the maxillary canine.
    • A labial ridge is present on the mandibular canine but it is not well developed like the labial ridge of the maxillary canine.
    • The cervical line or the cementoenamel junction has a curvature towards the root apex.
    • The root is single and terminates as a sharp-pointed root apex. In the apical third of the root, there is a slight curvature towards the distal aspect.

    Lingual Aspect

    • In the mandibular canine, the cingulum is smooth and is not very well developed.
    • The mesial and distal marginal ridges are less prominent.
    • The lingual ridge that is dividing the lingual fossa into two halves is also less distinct.
    • Due to less development of ridges, the mesial and distal lingual fossae are shallow and the lingual surface is smooth as compared to the maxillary canine.
    • The mesiodistal dimension of the root on the lingual aspect is little more than half of the dimensions of the labial surface. Due to this parts of the mesial and distal surface of the root is visible.
    • The cervical line shows more curvature towards the root apex with a slight distal offset.

    Mesial Aspect

    • The incisal portion of the permanent mandibular canine is thinner labiolingually.
    • The cusp tip is centered over the root.
    • The cingulum is also not very well developed as compared to the maxillary canine.
    • The cervical line curves more towards the incisal surface.
    • The root surface is smooth or sometimes a shallow developmental depression is present. The root apex is more pointed.

    Distal Aspect

    • The distal aspect is similar to the mesial surface with very few differences that are described below.
    • The tooth appears slightly smaller from the distal aspect.
    • The cervical line also curves towards the incisal surface but the extent of the curvature is less.
    • A shallow developmental depression is present on the root surface.

    Incisal Aspect

    • The cusp tip and the mesial cusp ridge are more inclined lingually as compared to the maxillary canine.
    • The mesiodistal dimension is less as compared to the labiolingual dimension.
    • The cingulum of the mandibular canine is more offset towards the distal aspect.

    Variation in the morphology of Mandibular canine

    The permanent mandibular canine usually has one root. However, in some cases, two roots may be seen in some extracted mandibular canines. Among the two roots of the mandibular canine one root is present on the labial side and the second root is present on the lingual side.

    Lecture of Permanent Mandibular Canine

    Demonstration of Permanent Mandibular Canine on Tooth Models

  • Permanent Maxillary Canine

    Permanent Maxillary Canine

    The Permanent Maxillary Canine is the pointed teeth. These teeth are the third teeth from the midline on each side of the maxillary dental arch. The canines are known as the cornerstone of dental arches. The canines are the most stable teeth in the dental arch because these teeth have the longest root. The canines have a tearing function.

    Development and Emergence of Permanent Maxillary Canine

    Following is a summary of the timeline of development and eruption of the permanent maxillary canine.

    • Beginning of maxillary canine calcification: 3-4 months
    • Completion of the maxillary canine crown: 6-7 years
    • Eruption of permanent canine: 11-12 years
    • Root completion of maxillary canine: 13- 15 years

    Labial Aspect of Permanent Maxillary Canine

    • The general crown form of the maxillary permanent canine is pentagonal (five sides and five angles).
    • The permanent maxillary canine is in contact with the mesial surface with the permanent maxillary lateral incisor. The mesial contact area is at the junction of the middle and the incisal third.
    • The maxillary canine on the distal surface is in contact with the maxillary first premolar. The distal contact area of the tooth is at the middle third of the crown.
    • The crown and the root of the maxillary canine are narrow mesiodistally (1mm difference) as compared to the permanent maxillary central incisor.
    • The cusp tip of the tooth is pointed and it is nearly on a line with the center of the root.
    • The mesial outline of the maxillary canine is convex while the distal outline is slightly concave.
    • The cervical line or the cementoenamel junction curvature is convex with curvature towards the root apex.
    • The pointed cusp tip of the canine has two slopes those are the mesial cuspal slope and the distal cuspal slope.
    • The mesial cuspal slope of the maxillary canine is shorter as compared to the distal cuspal slope.
    • A prominent labial ridge is present that starts from the tip of the cusp and terminates to the cervical area of the crown. This prominent labial ridge is a result of the over development of the middle labial lobe of the canine.
    • The maxillary canine has the longest root of any other tooth in the oral cavity.
    • The root of the maxillary canine is conical with a bluntly pointed root apex.
    • A slight curvature is present in the root of the maxillary canine in the apical third region usually towards the distal side.

    Palatal Aspect

    • The crown and the root both are narrow mesiodistally as compared to the labial aspect. Therefore, part of the mesial and distal surfaces of both crown and root are visible from the palatal aspect.
    • The mesial and distal marginal ridges of the maxillary canine are very well developed.
    • The cingulum is present at the cervical third of the crown and it is well developed. In some cases, the cingulum appears like a pointed cusp.
    • The curvature of the cervical line is more on the palatal surface as compared to the labial surface.
    • A linear elevation is present that extends from the cingulum to the tip of the maxillary canine and this ridge is refereed as a lingual ridge.
    • This lingual ridge divides the lingual fossa into the two fossae that are named mesial and distal lingual fossae.

    Mesial Aspect of Permanent Maxillary Canine

    • The crown and the root have greater bulk and labiolingual measurement as compared to other anterior teeth.
    • The maxillary crown outline from the mesial and distal aspect is wedge shape.
    • The labial outline of the maxillary canine is more convex as compared to the other anterior teeth.
    • The lingual outline of the crown is convex in the cervical area because of the cingulum and concave in the middle and incisal third.
    • The root outline is conical with a bluntly pointed root apex. In the apical third region, the root may slightly curve towards the labial aspect.

    Distal Aspect

    • The curvature of the cervical line is towards the incisal aspect similar to that of the mesial surface. However, the extent of this curvature is less on the distal side as compared to the mesial curvature of the cervical line.
    • The distal marginal ridge is heavier and irregular as compared to the mesial marginal ridge of the canine.
    • A prominent developmental depression is present on the distal aspect of the root.

    Incisal Aspect of Permanent Maxillary Canine

      • The crown outline of the permanent maxillary canine from the incisal surface is of diamond shape.
      • There is a greater labiolingual dimension as compared to the mesiodistal dimension.
      • The ridge of the middle labial lobe is noticeable from the incisal aspect of the canine.
      • The cingulum makes up the lingual third of the crown and is slightly offset towards the distal aspect.

    Lecture of Permanent Maxillary Canine Morphology

    Demonstration of Permanent Maxillary Canine Morphology on tooth models

  • Permanent Mandibular Lateral Incisor

    Permanent Mandibular Lateral Incisor

    In the mandibular arch, the permanent mandibular lateral incisor is the second tooth from the midline. The mandibular incisor has several unique features. This tooth is wider mesiodistally as compared to the mandibular central incisor. The opposite is true for the maxillary incisors where the maxillary central incisor is larger as compared to the lateral incisor. The mandibular lateral incisor is asymmetrical therefore it is easy to identify right and left mandibular lateral incisors as compared to central incisors that are more symmetrical and therefore difficult to distinguish right incisor from the left.  

    Development and Emergence of the Permanent Mandibular Lateral Incisor

    The calcification of the mandibular lateral incisor begins around the age of 3-4 months. The crown of the tooth is completed by the age of 4-5 years. The mandibular lateral incisor emerges into the oral cavity by the age of 7-8 years. The root of mandibular lateral incisor is completed by the age of 10 years.  

    Labial Aspect

    The permanent mandibular lateral incisor though it resembles the mandibular central incisor. However, it is slightly larger in all dimensions and the crown is asymmetrical. Few developmental lines are present on the labial surface of the tooth and those are not very prominent.  The mesioincisal angle is sharp and the distoincisal angle is more rounded.

     Lingual Aspect

    The tooth slightly converges towards the lingual side. Therefore, part of the mesial and distal surfaces of both the crown and root are visible from the lingual aspect. The tooth sometimes looks similar to the maxillary lateral incisor from this aspect. However, the tooth can be easily differentiated from the maxillary lateral incisor because of its smaller size and less development of marginal ridges.

    Mesial Aspect

    The mesial aspect of the crown is longer than the distal aspect. The mesial surface of the crown is smooth with no developmental depression. The root has a shallow developmental depression.

    Distal Aspect

    The distal aspect of the crown is smaller because of the slope of the incisal ridge in a distal direction. Due to this slope of the incisal ridge, the distal contact area is located more towards the cervical area as compared to the mesial contact area. The distal surface of the root has a developmental depression that is more pronounced. The curvature of the cervical line is nearly the same as of the mesial aspect.

    Incisal Aspect

    The incisal edge of the permanent mandibular lateral incisor is curved and follows the curvature of the dental arch.

    Lecture of Permanent Mandibular Lateral Incisor

    Demonstration of Permanent Mandibular Lateral Incisor on Models

  • Permanent Mandibular Central Incisor

    Permanent Mandibular Central Incisor

    Several unique features are associated with the permanent mandibular central incisor. The mesioincisal and the distoincisal angles are sharp and the mesial and the distal outlines of the crown are straight contrary to the other incisors. Another unique feature is that the mandibular central incisor is the smallest tooth in the dental arch. The maxillary third molars and central incisors have only one opposing teeth the rest of the teeth come in contact with two teeth of the opposing dental arch.

    Development and Eruption of Permanent Mandibular Central Incisor

    The calcification of the permanent mandibular central incisor begins at the age of 3-4 months. The crown is completed by the age of 4-5 years. The tooth emerges into the oral cavity around the age of 6-7 years by replacing the deciduous mandibular central incisor. The root of the mandibular central incisor is completed by the age of 9 years.

    Labial Aspect

    The crown from the labial aspect has very faint developmental lines. The incisal ridge of the newly erupted mandibular central incisor has three rounded protuberances called mamelons. The incisal ridge of the tooth is straight and nearly at a right angle to a line bisecting the crown and the root. The mesial and distal outlines of the crown are straight and then evenly taper from the contact area to the cervical portion of the crown. As compared to other incisors the root of the mandibular central incisor is narrower mesiodistally and in the apical one-third, the root ends as a pointed apex usually pointing towards the distal side.

    Lingual Aspect

    The marginal ridges and the cingulum of the permanent mandibular central incisor are not very well developed therefore the lingual fossa is smooth and very shallow as compared to other anterior teeth. The mandibular central incisor is among the few teeth that show very few developmental grooves and lines. The lingual surface of the tooth also shows a symmetrical outline. The crown and the root of the tooth taper towards the lingual aspect therefore part of the proximal surfaces of the crown and root are visible from the lingual aspect.

    Mesial Aspect

    The crown from both the mesial and the distal aspect appears wedge shape. The incisal ridge is present slightly lingual to the root apex. The curvature of the cervical line on the mesial aspect is quite marked approximate curvature is one-third of the crown length. The mesial surface of the root is flat with a shallow developmental depression on the root surface.

    Distal Aspect

    As the crown is symmetrical from the mesial and distal surfaces. Therefore, very few differences are there between the mesial and distal aspects. The curvature of the cementoenamel junction is less as compared to the mesial aspect. The developmental depression on the root surface is more prominent in the distal aspect.

    Incisal Aspect

    The permanent mandibular central incisor is also symmetrical from the incisal aspect. The mesial part of the crown is similar to the distal part of the crown. The incisal ridge of the tooth is almost straight and is right angle to a line crossing the crown labiolingually. The labiolingual dimensions of the crown are greater as compared to the mesiodistal dimension. The labial surface of the crown is wider mesiodistally as compared to the lingual surface where there is a crown and root convergence. More of the labial surface of the crown is visible as compared to the lingual surface because of the convexity of the crown on the labial surface.

    Variation and Anomalies

    As compared to other teeth variations and anomalies are very rare in the case of the mandibular central incisors.

    Lecture of Permanent Mandibular Central Incisor

    Demonstration of Permanent Mandibular Central Incisor on Models

  • Permanent Maxillary Lateral Incisor

    Permanent Maxillary Lateral Incisor

    The permanent Maxillary lateral incisors are the second tooth from the midline. The maxillary lateral incisor performs the cutting function and supplements the permanent maxillary central incisor during mastication and speech. The maxillary lateral incisor bears some resemblance with the maxillary central incisor. The overall dimensions of the maxillary lateral incisor are slightly smaller as compared to the maxillary central incisor.

    Development and Eruption of Permanent Maxillary Lateral Incisor

    The calcification of the permanent maxillary lateral incisor begins when the child is 10-12 months old. The crown of this tooth is completed by the age of 4-5 years. The tooth emerges into the oral cavity by the age of 8-9 years by replacing the deciduous maxillary lateral incisor and the root is completed by the age of 11 years.

    Labial Aspect

    The incisal ridge is more rounded as compared to the maxillary central incisor. Similarly, the mesial and the distal incisal angles are also more rounded in comparison with the incisal angles of the permanent maxillary central incisor. The distal incisal angle is more rounded as compared to the mesial incisal angle of the lateral incisor. The mesial outline of the crown is more rounded as compared to the mesial outline of the central incisor. The distal outline of the tooth is even more rounded as compared to a mesial outline of the same tooth and with the distal outline of the central incisor.

    In most anatomical forms, the crown of the tooth is more convex in comparison with the maxillary central incisor. The tooth is slightly narrower (2-3mm) mesiodistally and cervicoincisally as compare to the maxillary central incisor. The root length is greater in proportion to the length of the crown. The root is cone shape and in the apical one-third of the root curves in a distal direction and terminate as a pointed root apex.

    Lingual Aspect

    The mesial and the distal marginal ridges are well developed and the cingulum is also prominent. In between the ridges and the cingulum, a concavity is present called lingual fossa. Due to well-developed ridges and the cingulum, the lingual fossa on the lateral incisor is more concave as compared to the permanent maxillary central incisor. Like the Permanent maxillary central incisor, the crown and the root of the maxillary lateral incisor also tapers towards the lingual aspect. Due to this taper part of the mesial and the distal surfaces of the crown and the root is visible from the lingual aspect.

    Mesial Aspect

    In the mesial aspect, the crown of the maxillary lateral incisor appears similar to a small central incisor. The crown of the lateral incisor is slightly shorter as compared to the central incisor and the root appears longer. The incisal ridge of the tooth appears thicker as compared to the central incisor. The curvature of the cervical line is towards the incisor ridge. 

    Distal Aspect

    The labiolingual width of the crown is slightly more on the distal aspect because of the curvature of the crown portion of the tooth. The curvature of the cervical line is also towards the incisal ridge but the extent of the curvature is less as compared to the mesial surface.  A developmental groove is present on the distal surface of the root.

    Incisal Aspect

    In the dental arch, the tooth is positioned in between the maxillary central incisor and the canine. Therefore, the tooth sometimes resembles the central incisor and canine. The labiolingual dimension of the tooth is greater as compared to the mesiodistal dimension. From the incisal aspect of the tooth, it appears more convex with more rounded surfaces as compared to the central incisor.

    Variation and Anomalies

    After the third molars which are the most variable teeth. The maxillary lateral incisors are the second most variable tooth in the dental arch. One of the most common anomalies associated with this tooth is a smaller than usual and pointed tooth called the peg shape lateral incisor. In some cases, the maxillary lateral incisors are congenitally (by birth) missing. In this case, the permanent maxillary central incisors are in contact with the maxillary canines. An additional developmental groove is presently extending from the cingulum to the root surface. Sometimes instead of the cingulum which is a rounded convexity, a large pointed structure called tubercle is present.

    Lecture of Permanent Maxillary Lateral Incisor

    Demonstration of Permanent Maxillary Lateral Incisor on Models

  • Permanent Maxillary Central Incisor

    Permanent Maxillary Central Incisor

    In our day-to-day conversation with friends and colleagues the teeth that we most commonly notice are the Permanent Maxillary Central incisor. Permanent Maxillary Central Incisors are the most prominent teeth among all the anterior teeth because of their position in the dental arch and greater mesiodistal dimension. The mesial surfaces of both the right and the left maxillary central incisor are in contact with each other. Like other incisors, the maxillary central incisor crown is wedge shape and has a single conical root.

    Development and Eruption of Permanent Maxillary Central Incisor

    The first time you will be able to see developing permanent maxillary central Incisors on a radiograph when the baby is 3-4 months old (initiation of calcification). The complete crown formation (enamel completion) occurs by the age of 4-5 years. The tooth emerges into the oral cavity by the age of 7-8 years by replacing the deciduous maxillary central incisor. The root of the permanent maxillary central incisor is completed by the age of 10 years. One tip to remember the root completion is the addition of 2-3 years into the age of eruption.

    Labial Aspect of Permanent Maxillary Central Incisor

    The incisor surface of the newly erupted maxillary central incisor contains three rounded protuberances called mamelons. These mamelons are lost later by the normal process of attrition. The crown has a smooth convex labial surface with faint developmental depressions. The developmental depression on the labial surface is mesial developmental depression, distal developmental depression, and imbrication lines.  The mesial outline of the crown is straight and it forms a ninety-degree angle with the incisal ridge. The distal outline of the crown is convex and it forms a more rounded angle with the incisal ridge. The cervical line or the cementoenamel junction (CEJ) has a semicircular outline with curvature towards the root apex. The root of the maxillary central incisor is cone shape with a blunt root apex.

    Palatal Aspect

    The crown of the Permanent maxillary central incisor from the palatal aspect is rather irregular. The incisal and the middle portion of the crown are concave because of the presence of lingual fossa. The Palatal fossa sometimes referred to as the lingual fossa is surrounded by the incisal ridge, mesially and distally by the mesial and the distal marginal ridges, and in the cervical area by the cingulum.   The cervical portion of the crown is convex because of the presence of the cingulum. The root is conical and narrower on the palatal aspect because of this convergence of the root in cross-section the root appears triangular.

    Mesial Aspect of Permanent Maxillary Central Incisor

    The maxillary central incisor from the mesial aspect appears wedge or triangular shape. The base of the triangle is towards the cervical portion of the crown while the apex is towards the incisal ridge. The incisal ridge of the tooth is in line with the apex of the root. The labial outline of the crown is slightly convex. The Palatal outline of the crown is convex in the region of the cingulum and concave at the marginal ridge. The curvature of the cervical line (cementoenamel junction) is towards the incisal aspect. The Maxillary central incisor has the greatest curvature of the cervical line on the mesial aspect than any other tooth. The root from the mesial aspect is smooth and conical with a blunt root apex.

    Distal Aspect

    The crown appears thicker from the distal aspect and it is because of the position of the crown over the root base to adapt to the curvature of the maxillary dental arch. This feature is more prominent in the maxillary lateral incisor. The curvature of the cementoenamel junction (CEJ) is towards the incisal ridge. The curvature of the cementoenamel junction is less if you compare it with the curvature of the cervical line present on the mesial surface of the tooth. Sometimes a developmental depression is present on the distal surface of the root.

    Incisal Aspect of Permanent Maxillary Central Incisor

    The incisal aspect of the tooth is broader mesiodistally on the labial aspect. The incisal and the middle portion of the crown labially is flat while the cervical portion of the tooth on the labial aspect is more convex.  The crown tapers towards the lingual aspect and the cingulum makes the cervical portion of the crown lingually. Overall the crown from the incisal aspect has a triangular outline and the labiolingual dimensions are greater than the mesiodistal dimensions.

    Variation and Anomalies

    Sometimes the mesial and the distal marginal ridges and cingulum are more well developed and form a variation called ‘Shovel Shape Incisor’. Sometimes the size of the crown is larger than normal. A rare anomaly associated with this tooth is the small root.

    Lecture of Permanent Maxillary Central Incisor

    Permanent Maxillary Central Incisor on Models

  • Dentin Hypersensitivity and its Etiology

    Dentin Hypersensitivity and its Etiology

    Did you know that dentin hypersensitivity is among the most frequent complaint of patients? At the same time, dental practitioners least understand it as the little emphasis is given to this important yet common dental condition. This blog will provide a basic guideline that will help you better understand key concepts, etiology, and theories of dentin hypersensitivity.

    The dentin hypersensitivity is associated with a short sharp pain that arises from the exposed dentin and occurs in response to various stimuli such as tactile, chemical, thermal, and osmotic stimuli. The terms‘ dentin sensitivity’ and ‘dentin hypersensitivity’ are used interchangeably in the literature, but dentin hypersensitivity is more accurate. Other terms that are less commonly used to describe the hypersensitive dentin in the literature are cervical hypersensitivity, root hypersensitivity, and cementum hypersensitivity.

    The dentin hypersensitivity has a detrimental effect on the quality of life of an individual as it affects the physical and psychological well-being of the patient. The dentin hypersensitivity also affects the selection of diet and makes oral hygiene maintenance difficult.

    The hypersensitive dentin is a commonly encountered and least understood dental complaint, and its incidence is reported between 10% to 15%. This problem mostly affects young adult females between 20-40 years of age. The tooth surfaces commonly associated with dentin hypersensitivity are the labial surfaces of canines and buccal surfaces of premolars, especially in the dentition with gingival recession.

    In the hypersensitive dentin, the exposed dentinal tubules are patent. In some cases, where the exposed dentin is not hypersensitive, there is a more like a hood that the dentinal tubules are occluded with the deposition of sclerotic dentin.

    Etiology of Dentin Hypersensitivity

    It is important to understand that dentin hypersensitivity is not a disease but a symptom of one or a combination of the following underlying causes.

    Gingival recession

    There are numerous causes of gingival recession. One of the reasons for the gingival recession is the overzealous brushing of teeth. The gingival recession of this kind is typically present on the labial and buccal gingiva of the canines and premolars.

    Attrition

    It is a form of tooth tissue loss that involves the incisal and the occlusal surfaces of teeth. It is mostly seen in individuals with a history of night grinding of teeth (bruxism). These patients are likely to show the symptoms of dentin hypersensitivity.

    Abrasion

    An abrasion is a tooth surface loss that occurs because of tooth brushing with a hard toothbrush, improper tooth brushing technique, or using toothpaste or tooth cleaning powder with a higher abrasive. Abrasion of the enamel due to the over-enthusiastic brushing of teeth is one of the causes of hypersensitive dentin.

    Erosion

    Erosion is a form of tooth surface loss caused by the intrinsic acids (gastric acid due to gastroesophageal reflux disease) or extrinsic acids (overconsumption of citrus fruit juices and drinks) that may result in hypersensitive dentin.

    After dental treatment

    After dental procedures such as periodontal surgery, tooth whitening, scaling, and polishing, there is dentin hypersensitivity in some patients.

    Internal or external resorptions

    Normally the dentine is resorbed during the exfoliation of deciduous teeth. Dentine in permanent teeth is normally stable throughout life. The pathological dentin resorption may be initiated from two surfaces: from the dental pulpal surface, known as internal dentin resorption, or from the surface of the root, known as external dentin resorption. Mostly the causes of this internal and external resorption are unknown, but tooth hypersensitivity may be the earliest symptom.

    Theories of Dentin Sensitivity

    The following three theories have been proposed to explain the dentin sensitivity.

    Direct Innervation theory

    This theory of dentin sensitivity suggests that “Dentinal tubules contain nerve endings that respond to the external stimulus.”
    Several arguments are against direct innervation theory. The specialized histological sections of dentin also confirm that the nerves within the dentinal tubules appear absent in the dentin’s outer part near the dentin enamel junction (DEJ). While in the inner part of the dentin that is towards the dental pulp, very few tubules have nerve endings. Besides, the application of local anesthesia on the exposed dentin does not eliminate the dentin hypersensitivity.

    Transduction theory

     The transduction theory of dentin sensitivity is also known as odontoblast receptor theory. According to this theory of dentin sensitivity “Odontoblasts serve as a receptor and are connected to the nerve endings that are present in the dental pulp”.

    The transduction theory is also not widely recognized because there is no physiological evidence that shows that the odontoblast process is similar to nerve fiber and can conduct the impulses towards the dental pulp. In addition to that, odontoblast processes in most of the tubules are not extended to the dentin- enamel junction (DEJ) and in the majority of the dentinal tubules and the odontoblasts are not connected synaptically with the nerve fibers.

    Hydrodynamic theory

    The hydrodynamic or the fluid movement theory states that” when a stimulus is applied to the dentin it causes fluid movement through the dentinal tubules. This movement of fluid causes depolarization of the nerve endings that are present in the inner part of dentinal tubules and the cell-free zone of dental pulp just below the odontoblastic zone”.

    The fluid movement theory is the most widely accepted theory that explains dentin hypersensitivity. Several findings support the hydrodynamic theory for example when the cavity is prepared small drops of fluid can be seen on the floor of the cavity. The hydrodynamic theory also explains why the application of local anesthesia at the site of exposed dentin fails to block the dentin hypersensitivity.

    Treatment of Dentin Hypersensitivity

    The correct patient history and intraoral examination are important for the diagnosis of any disease or condition and the same is true for dentin hypersensitivity. As dentin hypersensitivity present similar to several conditions such as dental caries, cracked teeth, and irreversible pulpitis. Therefore, the detailed patient history, nature of pain, factors that increase or reduce the pain are important with the intraoral examination to confirm the diagnosis.

    Treatment of dentin hypersensitivity is a complex process and involves several steps such as behavioral modifications, patent education, removing the causative or etiological factors that are associated with hypersensitive dentin, home, and dental office treatments.

     Exposed dentin treatment aims to reduce or eliminate the sensitivity of the exposed dentin. The dental products that are commonly suggested occlude the open dentinal tubules that are desensitizing toothpaste, mouthwashes, and topical agents. These products usually contain calcium phosphate and fluoride ions, silver diamine fluoride (SDF), or a mixture of arginine, calcium carbonate, and fluoride. Recently the use of bioactive glass in the toothpaste has been suggested for hypersensitive dentin treatment as it occludes the open dentin tubules.

    Dentin Hypersensitivity | Video Explanation

    Dentin Hypersensitivity
  • Easy Dental terminology Guide for Students

    Easy Dental terminology Guide for Students

    Dental anatomy is defined as studying the formation, morphology, functions, and identification of each tooth in the dental arch. It also includes the study of the relationship of the adjacent teeth in the same dental turn and with the teeth of the opposing dental arch.

    To have a firm understanding of dentistry and dental anatomy, it is essential to have a clear understanding of the structure of a human tooth, surfaces of teeth, and basic dental terminologies used frequently during tooth anatomy study. In addition to that, these terms are essential as they will be used throughout individual dental professional and research careers.

    The following paragraphs will provide you with an understanding of those standard dental terms.

    Cusp

    It is a pronounced elevation or a mound on the occlusal surface of a posterior tooth. The cusp on the deciduous teeth is more pointed and sharp than the permanent ones. The occlusal surfaces of the teeth may have two to five cusps.

    Premolars usually have two cusps (one buccal cusp and one lingual or palatal cusp). The mandibular second premolar has three cusps (one buccal and two lingual cusps).  Therefore, the term bicuspid is not correct for the premolars.

    Maxillary molars crowns may have three to five cusps. When the number of cusps is four, the three cusps are larger (mesiobuccal, mesiopalatal, and distobuccal cusps) and the smallest cusp is the distopalatal cusp. In maxillary second and the third molars sometimes the distoplatal cusp is not present and the tooth is of three cusp type. In the maxillary first molar sometime a small cusp or tubercle is present on the palatal surface of the mesiopalatal cusp. This small fifth cusp is referred to as cusp of Carabelli or Carabelli’s tubercle.

    Mandibular molars have four to five cusps. The mandibular second and third molars usually have four cusps. There are two buccal cusps (mesiobuccal and the distobuccal) and two palatal cusps (mesiopalatal and distopalatal). However, the permanent mandibular first molars usually have five cusps. The five cusps in the mandibular first molar are distributed as three buccal cusps (mesiobuccal, distobuccal, and distal) and two lingual cusps (mesiolingual and distolingual).

    Tubercles

    The tubercle is a small elevation on the crown surface produced due to the extra formation of enamel. In the posterior teeth, the tubercles are associated with marginal ridges of premolars known as an accessory marginal tubercle. In the anterior teeth, the tubercles are associated with the palatal surface of permanent maxillary permanent lateral incisors and canines.

    Cingulum

    The cingulum is a large rounded eminence on the cervical third of the Palatal or lingual surface of all deciduous and permanent anterior teeth.

    Ridge

    A ridge is a linear elevation present on any of the tooth surface.

    Marginal ridges are present on both the anterior and the posterior teeth.  Marginal ridges on the anterior teeth are found at the mesial and distal terminations of the lingual or palatal surfaces. In the posterior teeth, the Marginal ridges are found at the mesial and distal terminations of the occlusal surface. In the posterior teeth, these marginal ridges connect the buccal and the palatal or lingual cusps.

    Triangular ridges are the linear ridges that are descending from the tips of cusps of posterior teeth toward the central area of the occlusal surface.

    Transverse ridge is a union of the two triangular ridges, which transversely cross the occlusal surface on a posterior tooth to merge. These transverse ridges divide the occlusal surface into mesial and distal occlusal fossae.

    Oblique ridge crosses the occlusal surface of most maxillary molars in an oblique direction. The oblique ridge divides the occlusal surface into two prominent compartments. The most prominent oblique ridge is present on the occlusal surface of the permanent maxillary first molar. In the maxillary first molar, the oblique ridge crosses the occlusal surface from mesiopalatal cusp to the distobuccal cusp.

    Mamelons

    These are the small rounded protuberances present on the incisal ridges of the newly erupted incisor teeth. These mamelons are lost by normal physiological wear as the teeth come in contact with the teeth of the opposing dental arch.

    The presence of mamelons in an adult dentition indicates that the opposing teeth are not in contact during function (open bite).   The mamelons are present on the permanent teeth only.  In the primary incisor teeth, the mamelons are not present.

    Fossa

    The fossa is an irregular depression or concavity present on the crown of a tooth.

    Lingual or Palatal Fossa is a large, shallow fossa present on the lingual or palatal surface of anterior teeth. In some teeth such as maxillary canines, the palatal fossa is divided into two fossae due to palatal ridge into mesiopalatal and distopalatal fossae.

    Occlusal  Fossa Posterior teeth exhibit two or more fossae of varying size and shape on the occlusal surface of the tooth. The ridges further divide the occlusal fossa into smaller fossae according to their location on the occlusal surfaces. For example, on the occlusal surface of the permanent mandibular first molar, the central, mesial triangular, and distal triangular fossa are present.

    Groove

    Groove denotes the union of the primary parts of the crown of a tooth. There are fine developmental grooves present on the anterior teeth. The posterior teeth have many developmental grooves, mainly present on the occlusal surface. The central developmental groove on the center of the tooth surface running mesiodistally is the developmental groove. The accessory grooves arise from the central developmental groove.

    Pit

    The pit is a small, depressed area where developmental grooves often join or terminate. A pit is also present in the deepest portion of the fossa. Some of the names of the pits that are present on the occlusal surface of a permanent mandibular first molar are the central pit, mesial, and distal pits. In the anterior teeth, the palatal surface of the permanent maxillary lateral incisors most commonly has a pit. These landmarks (pit and fissure) are among the problematic area of the tooth to clean, and food accumulation in these areas may result in the initiation of the dental caries process.

    Dental Terminology Guide

  • Structure of Human teeth and their Functions

    Structure of Human teeth and their Functions

    Introduction

    Humans have two sets of dentition the deciduous dentition and the permanent dentition. The complete deciduous dentition comprises of 20 teeth and the permanent dentition comprises of 32 teeth.

    Parts of Human Tooth

    Each tooth is comprised of two parts the crown and the root.

    1. Crown: It is the portion of the tooth covered by enamel. The crown of anterior teeth has an incisal ridge while the posterior teeth have an occlusal surface having cusps.
    2. Root: The root is embedded inside the alveolar socket and is covered by cementum. Anterior teeth usually have a single root while the posterior teeth have one root (maxillary second premolar, mandibular first premolar, and second premolar), two roots (maxillary first premolar, mandibular molars) or three roots (maxillary molars).

         Parts of Human Tooth

    Tissues of Human Tooth

    Human tooth comprises of the following four tissues

    1. Enamel
    2. Dentin
    3. Cementum
    4. Dental Pulp

    The first three tissues are the hard tissues or mineralized tissues of the tooth. while the dental pulp is the soft tissue. The following sections briefly describe each of these tissues of the tooth.

    Structure of Human tooth (A= Enamel, B= Dentin C=Pulp, and D= Cementum)

     Enamel

    Enamel covers the crown portion of the human tooth. Enamel is the hardest tissue of the human body. It is derived from the ectoderm.  The enamel thickness varies for example near the incisal edge and the cusp tips the thickness of the enamel is more as compared to enamel thickness near the cementoenamel junction (CEJ). The enamel structure comprises of highly ordered structure in form of rods and inter rods.

    The Enamel forming cells are known as ameloblasts and the ameloblasts they reduce in size when the enamel formation is complete and are lost when the tooth emerges into the oral cavity. Therefore, enamel lacks regenerative potential. However, remineralization of the very small demineralization lesions occurs with the help of saliva and toothpaste that are rich in fluoride and calcium.

    Dentin

    The hard tissue that forms the bulk of the tooth is dentin. The color of dentin is yellowish-white, and it is avascular hard tissue. The dentine is composed of apatite crystals and the organic component is collagen. It is resilient tissue and it supports and prevents fracture of the overlying enamel.

    The cells that form dentin are known as odontoblasts and these cells originate from the ectomesenchyme. The structure of dentin comprises of dentinal tubules that transverse the dentin thickness. These dentinal tubules contain the odontoblast cells process.  The odontoblasts they continue their function of dentin formation throughout life. After root formation is complete the dentin formation it continues at a slower pace. The dentin has regenerative potential as the formative cells deposit new dentin in response to a stimulus. In addition to that, the dental pulp has stem cells that can differentiate into odontoblast like cells and deposit the dentin matrix.

     Cementum

    Cementum is a mineralized tissue that covers the root surface of the tooth and covers the root dentin. The cementum and the root dentin are firmly interlocked with each other and form the cementodentinal junction. Another junction that is formed by the union of enamel and cementum at the neck of the tooth is a cementoenamel junction (CEJ) or cervical line.

    Cementum has some similarities with the bone the main difference is that cementum is an avascular tissue.  The formative cells of the cementum are called cementoblasts. The cementoblasts are differentiated from the dental follicular cells. During cementum formation the cells of the cementum they become entrapped into the cementum matrix and are called cementocytes. Natural repair and regeneration are possible in cementum.   The cementum matrix anchors the periodontal ligament fibers (PDL) and those PDL fibers on the other end are inserted into bone or the gingiva. A fibrous joint is formed as a result known as gomphosis.

    Cementum is the main component of the periodontium (supporting tissues of the tooth) other components of periodontium are periodontal ligaments, gingiva, and the alveolar bone.

    Components of periodontium (A= Cementum, B= Gingiva, C= Periodontal ligaments and, D= Alveolar bone)

    Table: Summary of the hard tissues of the Human tooth

      Enamel Dentine Cementum
    Composition 96%mineral comprises of hydroxyapatite, 3%organic material comprises of enamel proteins amelogenins and non-amelogenins enamelinsand tuftelins and 1%water 70% mineral comprises of hydroxyapatite, 20% organic component mainly type I collagen, glycosaminoglycansand phosphoproteins and 10% Water 50% inorganic component,35% organic material and12% of water
    Formative cells Ameloblasts Odontoblasts Cementoblasts
    Formative cells life span Reduce in size and lost when a tooth emerges into the oral cavity For the life of human tooth Most likely for the life of human tooth
    Regeneration No Yes Yes
    Degradative or Resorptive cells Not known Odontoclasts Cementoclasts and Odontoclasts
           

    Dental Pulp

    The dental pulp is the soft connective tissue present in the center of the tooth surrounded by dentin. The cavity in which dental pulp is present is called the pulp cavity. The pulp cavity consists of two components pulp chamber and the root canal.  The dental pulp comprises a mass of connective tissue cells, collagen fibers (mainly type 1 collagen), blood vessels, nerves, and lymphatics. The pulp cavity communicates with the exterior of the tooth at the root apex through the apical foramen. The nerve and blood vessels enter and leave the tooth at the apical foramen.  The size of the pulp chamber and the pulp canal reduces with age because of the deposition of dentin.

    The dental pulp has a rich blood supply and provides nutrition to the avascular dentin. The pulp and dentin are interrelated with each other as they originate from the same ectomesenchymal cells and therefore referred to as dentin pulp complex.

    The dental pulp performs the following important functions that help in maintaining the vitality and the function of a human tooth.

    1. Formative: The dental pulp constitutes of numerous cells. The most prominent cells among those are the odontoblasts. The cell body of the odontoblasts is inside the dental pulp and cell processes are within the dentin inside the dentinal tubules. These cells are capable of the formation of dentin throughout life.
    2. Nutritive: dentin is an avascular tissue and the dental pulp has a rich blood supply that provides nourishment to the dentin and the dentin forming cells.  
    3. Protective: The dental pulp contains unmyelinated and myelinated nerves that form a network of nerves called Raschkow’s plexus present below the odontoblasts and it helps in dentin sensitivity.
    4. Reparative: dental pulp helps in the formation of new dentin in response to noxious stimuli to protect the vitality of the tooth. This reparative function is performed either by the same odontoblasts that form the rest of the dentin or by the newly differentiated odontoblast like cells.

    The tissues of the tooth (enamel, dentin, and cementum) they are hard and resilient tissues and are capable to withstand the destructive processes. Therefore, these tissues are used by forensic science experts for identification purposes.

    Functions of Human Tooth

    The human teeth perform the following functions.

    1. Mastication: when the food enters into the oral cavity the process of digestion begins. The saliva helps in the initial chemical digestion of food. The mechanical digestion also starts in the oral cavity as the teeth grind the food into small particles. This process is known as mastication. The human dentition has three-tooth forms incisiform teeth (central and lateral incisors), caniniform teeth (canines), and molariform teeth (premolars and molars). Each of these tooth families performs their function, for example, incisiform teeth perform cutting function, caniniform teeth perform the tearing function, and molariform teeth perform the grinding function.   
    2. Phonetics: Teeth together with the tongue is important for proper pronunciation of words.
    3. Esthetics: Teeth maintain the position of the facial muscles and prevent sinking in of the facial muscles. Additionally, teeth together with the alveolar bone maintain the lower facial height.
    4. Space maintainer: Teeth prevent the over eruption or abnormal migration of the adjacent or the opposing teeth.
    5. Defense: The animals use their teeth as a weapon of attack and defense. However, human rarely uses their teeth for attack or defense purpose. 

    Structure of Human Tooth