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MindMap Gallery 1. Dental anatomy and physiology - incisors, canines, and premolars
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1. Dental anatomy and physiology - incisors, canines, and premolars
An article about oral anatomy and physiology - incisors, canines and premolars mind map, with detailed introduction and comprehensive description. I hope it will be helpful to those who are interested!
Edited at 2023-12-04 10:15:47
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1. Dental anatomy and physiology - incisors, canines, and premolars
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Dental anatomy and physiology - incisors, canines, premolars
Permanent tooth shape
1. Incisor group
(1) Maxillary central incisors
Features: The incisors are the largest in volume and the mesiodistal diameter of the anterior teeth is the widest, located on both sides of the midline. The mesial surfaces of the left and right central incisors are opposite to each other.
1.Dental crown
(1) Labial surface: The labial surface is relatively flat, approximately trapezoidal, the incisal neck diameter is larger than the mesial and distal diameter, the mesial and incisal edges are straight, the distal edge is slightly protruding, the neck edge is arc-shaped, and two sides can be seen after 1/3 of the cut. A vertical groove develops, and the neck 1/3 slightly protrudes to form the high point of the labial surface. The mesial incisal angle formed by the intersection of the incisal edge and the mesial edge is approximately right-angled, and the distal incisal angle formed by the intersection of the incisal edge and the distal edge is slightly rounded, so that the left and right can be distinguished. When the tooth first erupted, three incisal nodules were visible on the incisal edge, which gradually became straightened due to functional wear. Lip surface shapes can be divided into three types: oval, pointed, square 72% 26% 2%
(2) Lingual surface: The lingual surface is similar in shape to the labial surface but slightly smaller in volume. The central depression forms a lingual fossa, surrounded by raised ridges. There is a lingual protuberance on the neck of the tooth, a mesial marginal ridge mesially, a distal marginal ridge distally, and an incisal ridge at the incisal end.
(3) Proximal surface: The mesial surface is like a triangle. The top is the incisal end and the bottom is the neck edge. It is V-shaped and is called the neck curve. The distance from the bottom of the curve to the lowest point of the neck edge is called the neck curvature. The middle contact area is in the 1/3 of the cut close to the cut corner. The distal surface is similar to the mesial surface but slightly shorter and rounded. The distal contact area is slightly farther from the incisal angle in the incisal 1/3, and the mesial neck curvature is larger than the distal neck curvature.
(4) Incisal ridge: The labial side is relatively flat, forming the incisal edge, and the lingual side is rounded to form the incisal ridge. When the incisal ridges of the maxillary and mandibular incisors are in contact, they can perform their cutting function. When viewed proximally, the incisal ridge is located on the labial side of the long axis of the tooth.
2.Tooth root:
It is a single root that is strong and straight. The labial side is wider than the lingual side. The transverse section of the root neck is rounded and triangular. The root gradually shrinks toward the apex, and the apex is straight or slightly distal. The root length is slightly longer than the crown length or the crown and root lengths are equal. There are also cases where the root length is shorter than the crown length (crown-to-root ratio 1:1.1~1.2)
(2) Maxillary lateral incisors
Features: Located distal to the maxillary central incisor, its shape is basically similar to the maxillary central incisor, but slightly smaller and narrower than the maxillary central incisor.
1.Dental Crown:
(1) Labial surface: Similar to the maxillary central incisor in trapezoidal shape, but the crown is narrow and rounded, and the development groove is not as obvious as the maxillary central incisor. The mesial edge is slightly longer, the mesial incisal angle is like an acute angle, and the distal edge is shorter than the maxillary central incisor. The incisal edges are connected in an arc, and the distal incisal angle is arc-shaped, so the incisal edge is obviously oblique to the distal aspect.
(2) Lingual surface: The marginal ridge is more obvious than that of the maxillary central incisor, and the lingual fossa is deep and narrow. Occasionally, there is a groove that crosses the distal part of the lingual protuberance and extends to the root neck to form a fissure, which is a prone site for caries.
(3) Proximal surface: slightly triangular, with the mesial and distal contact areas both in the incisal 1/3, slightly farther from the incisal angle than the central incisor, with the mesial contact area closer to the incisal angle and the distal contact area further from the incisal angle. The corners are slightly further away.
(4) Incisive ridge: The inclination to the distal lingual side is larger than that of the maxillary central incisor, and it seems to be continuous with the distal surface.
2.Tooth root:
It is also a single root, with the root length longer than the crown length, thinner and slightly longer than the root of the maxillary central incisor, and the cross section of the neck is oval. (Crown-to-root ratio 1:1.4)
(3) Mandibular central incisors
Features: The smallest tooth among the permanent teeth in the mouth, symmetrical in shape, the crown width of the mandibular central incisor is about 2/3 of the maxillary central incisor
1.Dental Crown:
(1) Labial surface: Smooth and flat like a trapezoid, the incisal neck diameter is significantly larger than the mesial and distal diameter, the mesial and distal edges are symmetrical, the mesial and distal incisal angles are approximately equal, and the incisal edge is straight and difficult to remove from the body. Distinguish between left and right.
(2) Lingual surface: The lingual surface fossa is shallow, the incisal ridge and mesiodistal marginal ridge are not obvious, and the lingual protuberance is small.
(3) Proximal surface: like a triangle, the mesial and distal contact areas are both in the 1/3 of the incisal surface and close to the incisal angle
(4) Incisive ridge: When viewed from the proximal surface, the incisal ridge is located on the long axis of the tooth or slightly on the lingual side.
2.Tooth root:
It is a narrow and flat single root, relatively straight, and the transverse section of 1/3 of the root is gourd-shaped. The elongated depression on the distal surface of the root is slightly deeper than the mesial surface, which can be used as a reference for identifying left and right.
(4) Mandibular lateral incisors
Characteristics: Similar to the mandibular central incisor, but larger in size than the mandibular central incisor.
1. The crown of the mandibular lateral incisor is slightly wider than that of the mandibular central incisor.
2. The incisal edge is slightly inclined distally, the mesial edge is straight, the distal edge is slightly protruding, and the distal incisal angle is rounder and blunter than the mesial incisal angle.
3. The lingual surface is similar to the mandibular central incisor.
4. The proximal surface is like a triangle, the mesial contact area is located at the 1/3 of the incisal angle and the distal contact area is at the 1/3 of the incisal surface slightly away from the incisal angle.
5. The tooth root is an oblate single root, slightly longer than the mandibular central incisor, and the root apex is slightly distal.
(5) The difference between maxillary central incisors and mandibular central incisors
1. The maxillary incisors have wide crowns and obvious developmental grooves, while the mandibular central incisors have narrow crowns and smooth labial surfaces with unobvious developmental grooves.
2. The lingual fossa of the maxillary incisors is deep and the lingual marginal ridge is obvious. The lingual fossa of the mandibular incisors is narrow and shallow, and the lingual marginal ridge is not obvious.
3. In proximal view, the incisal ridge of the maxillary incisor is located on the labial side of the long axis of the tooth, and the incisal ridge of the mandibular incisor is close to the long axis of the tooth or slightly lingual.
4. The roots of the maxillary incisors are straight and thick. The roots of the mandibular incisors are flat and narrow. The mesiodistal surface is sunken into a groove shape, and the transverse section of the middle root is like a gourd shape.
(6) Applied anatomy of incisor appearance
1. The maxillary central incisors are located in the front of the dental arch and are easily broken or lost due to trauma. The defects have a direct impact on pronunciation and facial appearance. During restorative treatment, the shape and color of artificial teeth should be coordinated with the facial shape and adjacent teeth.
2. The interproximal contact area of the incisors and the top of the lingual fossa of the maxillary lateral incisors are often prone to caries due to poor self-cleaning effect. However, the lingual side of the mandibular incisors is close to the opening of the submandibular gland duct, so the probability of caries occurrence is small. , but calculus deposition is prone to occur in the lingual neck.
3. Occasionally there are extra teeth between the maxillary central incisors, which should be extracted in time to avoid crowding of the teeth and disorder of the occlusal relationship. The maxillary lateral incisors often have mutations such as tapered lateral incisors, and there are also cases where the maxillary lateral incisors are congenitally missing.
4. The roots of the maxillary central incisors are straight and round, and rotational force can be used when extracting the teeth. The roots of the maxillary lateral incisors may be curved, and the teeth should be extracted carefully. The roots of the mandibular incisors are flat and narrow, so it is not appropriate to use rotational force during tooth extraction.
2. Canine group
(1) Maxillary canines
Characteristics: The tooth with the longest tooth body and root among all the teeth in the mouth.
1.Dental Crown:
(1) Labial surface: Like a round pentagon, the five sides are: cervical edge, mesial edge, mesial oblique edge, distal oblique edge, and distal edge. The neck edge is arc-shaped, the mesial edge is long, the mesial oblique edge is short, the distal oblique edge is long, and the distal edge is short. The mesial oblique edge is connected to the mesial edge to form a mesial incisal angle, and the distal oblique edge is connected to the distal edge to form a distal incisal angle. When the canine first erupts, the angle between the mesiodistal and oblique edges at the tip of the cusp is approximately 90°. In the middle of the labial surface, a protrusion extending from the top of the tooth cusp to 1/3 of the neck forms a labial axial ridge. There is a developmental groove on both sides of the labial axial ridge. This ridge divides the labial surface into a mesial labial slope and a distal labial slope. The high point of the labial surface is on the labial axial ridge at the junction of the middle 1/3 and the cervical 1/3.
(2) Lingual surface: similar in appearance to the labial surface, but slightly smaller. The mesial marginal ridge is longer and straighter than the distal marginal ridge, the mesial cusp ridge is shorter, the distal cusp ridge is longer, and the lingual surface is prominent. There is a longitudinal ridge extending from the tooth tip to the lingual protuberance called the lingual axial ridge. The lingual fossa is divided into a smaller mesial lingual fossa and a larger distal lingual fossa by the lingual axial ridge.
(3) Proximal surface: Triangular-like, protruding than the proximal surface of the incisors. The distal surface is more prominent and shorter than the mesial surface. The mesial contact area is closer to the mesial incisal angle, and the distal contact area is slightly farther from the distal incisal angle. (near means near, far means far)
(4) Cusp: composed of four ridges and four slopes. The four ridges are the mesial cusp ridge, the distal cusp ridge, the labial axial ridge, and the lingual axial ridge. The distal cusp ridge is larger than the mesial cusp ridge, and the cusp is more mesial. The four bevels are: mesial labial bevel, distal labial bevel, mesial lingual bevel and distal lingual bevel.
2.Tooth root:
It is a straight and thick single root, the labial and lingual diameter is larger than the mesio-distal diameter, and the cross section of the root neck is oval and triangular. The root length is approximately twice the crown length (crown-to-root ratio 1:2). Root apex slightly remote
(2) Mandibular canines
Characteristics: Similar in shape to the maxillary canines, it is narrower and thinner than the maxillary canines, so the tooth body appears elongated.
1.Dental Crown:
(1) Labial surface: narrow and long pentagon, the incisal diameter is significantly larger than the mesio-distal diameter, relatively flat, the cervical ridge, labial axial ridge and developmental groove are not as obvious as those of the maxillary canines. The mesial edge is the longest, approximately parallel to the long axis of the tooth, the distal edge is shorter, the mesial oblique edge is shorter, and the distal oblique edge is longer. The ratio of the two lengths is about 1:2. The mesial and distal oblique edges are The intersection angle is greater than 90°. When observing the mandibular canine from the labial surface, the mesial edge of the crown and root are connected approximately in a straight line.
(2) The lingual surface is smaller than the labial surface and slightly concave. The lingual axial ridge is not as obvious as the maxillary canines. The high point of the shape is at the lingual protuberance.
(3) The proximal surface is like a triangle. When viewing the mandibular canine from the proximal surface, the labial edges of the crown and root are connected to form an arc.
(4) The cusps are not as obvious as the maxillary canines, and the cusps are more obvious mesially.
2.Tooth root
It is an oblate and slender single root, and the cross section at 1/3 of the root neck is oblate. There is a shallow elongated depression on the mesiodistal root surface. The root tip is slightly remote.
(3) The difference between maxillary canines and mandibular canines
1. The maxillary canines are larger in size and have wider crowns, while the mandibular canines are smaller in size and have narrower and longer crowns.
2. The cervical crest, axial crest and lingual protuberance of the maxillary canine are obvious and the lingual fossa is deep. The cervical crest, axial crest and lingual protuberance of the mandibular canine are not obvious and the lingual fossa is shallow.
3. Labial view of the maxillary canine. The mesial edge of the crown and the mesial edge of the root are connected at a certain angle. The mesial edge of the crown and the mesial edge of the root of the mandibular canine are connected to form an approximately straight line.
4. The mesial oblique edge and the distal oblique edge of the maxillary canine intersect at approximately a right angle, and the mesial oblique edge and the distal oblique edge of the mandibular canine intersect at an obtuse angle.
5. The cusps of mandibular canines are more obviously skewed mesially than those of maxillary canines.
6. In the interproximal view, the labial edges of the crown and root of the maxillary canine are connected without forming an arc, while the labial edges of the crown and root of the mandibular canine are connected and almost form an arc.
7. The maxillary canine has a thick root, and the cross section of the neck is oval and triangular. The mandibular canine has a slender root, and the cross section of the neck is oblate.
(4) Applied anatomy of canines
1. The canines are located at the corners of the mouth. The roots are long and thick, can withstand large forces, and have the function of supporting the corners of the mouth. If the maxillary canines are missing, the upper corners of the mouth will collapse, affecting facial appearance.
2. Canine crowns are smooth on all sides, have good self-cleaning effect, and are less prone to caries.
3. Canine teeth have long roots and are stable in the alveolar socket. They are usually the teeth that remain the longest in the mouth. When repairing related missing teeth, this tooth is often chosen as the abutment tooth.
4. The root of the maxillary canine is a conical single root and relatively straight. Rotational force can be used during tooth extraction. The root of the mandibular canine is slightly oblate. During tooth extraction, a smaller rotational force can be used after loosening.
3. Premolar group (formerly known as bicuspid teeth)
(1) Maxillary first premolar
Characteristics: The largest teeth among the premolars, 4>5 in the upper jaw and 5<4 in the lower jaw.
1.Dental crown
(1) Buccal surface: similar to the labial surface of the canine, but the crown is shorter and smaller, the mesial edge of the neck is slightly concave, the distal edge is slightly protruding, the mesial oblique edge is longer than the distal oblique edge, so the buccal cusp is far away from the middle. The only buccal cusp in the premolars is distally oriented. There is a longitudinal buccal axis ridge in the middle of the buccal surface. Two developmental grooves can be seen on both sides of the ridge, namely the mesiobuccal developmental groove and the distal buccal developmental groove. The high point of the shape is on the cervical ridge in the 1/3 of the neck.
(2) Lingual surface: smaller than buccal surface, smooth and rounded, like an oval. The tip of the tongue is short, rounded and blunt, leaning towards the middle, with the highest point in the middle 1/3 of the tongue surface.
(3) Proximal surface: slightly like a quadrilateral, with a wider neck, the mesial surface is depressed near the neck, and there is a groove spanning from the 𬌗 surface across the mesial marginal ridge to 1/3 of the mesial surface, which is called the mesial groove, and the distal surface is called the mesial groove. The middle surface is more rounded and smooth. The mesial and distal contact areas are all on the buccal side of the border.
(4) Facial surface: The shape is a hexagon with a clear outline, the buccal side is wider than the lingual side, and the buccal and lingual diameter is larger than the mesial and distal diameter. The angle formed between the mesiobuccal canine cusp ridge and the mesial marginal ridge is approximately 90°, the angle formed between the distal buccal canine cusp ridge and the distal marginal ridge is approximately an acute angle, and the mesiodistal cusp ridge of the lingual tip is approximately 90°. It is connected to the mesial and distal marginal ridges in an almost semicircular arc.
Marginal ridge: It consists of the mesial marginal ridge, the distal marginal ridge, the buccal marginal ridge (composed of the mesiodistal cusp ridge of the buccal cusp) and the lingual marginal ridge (composed of the mesiodistal cusp ridge of the lingual cusp), of which the distal marginal ridge is longer than The mesial marginal ridge and the buccal marginal ridge are longer than the lingual marginal ridge.
Triangular ridge: The triangular ridge extending from the top of the buccal apex to the center of the 𬌗 surface is called the triangular ridge of the buccal apex. The triangular ridge extending from the top of the lingual apex to the center of the 𬌗 surface is called the lingual apex triangular ridge.
Teeth cusps: There are two cusps on the 𬌗 surface, the buccal and lingual cusps. The buccal cusp is long and sharp, the lingual cusp is short, round and blunt. The buccal cusp is far away from the middle and the tongue cusp is far away from the middle.
Fissures and gaps: The central fossa is formed under the central concave surface of the 𬌗 surface. In addition to the central fossa, there are also two small fossae. One is the approximately triangular mesial fossa located in the mesial marginal ridge, also known as the mesial triangular fossa. One is the approximately triangular distal fossa located in the distal marginal ridge, also known as the distal triangular fossa. There is a mesio-distal central sulcus at the bottom of the central fossa, and the point-like depressions formed at both ends are the mesio-distal points. From the mesio-distal points, the mesio-buccal grooves emerge from the mesio-buccal side and end in the mesial marginal ridge. The sulcus is also called the mesiobuccal triangular sulcus. The mesial gap also emits a sulcus across the mesial marginal ridge to the mesial surface, which is called the mesial sulcus. It is a unique anatomical landmark of the maxillary first premolar. The distobuccal sulcus originates from the distal point space to the distal buccal side and ends in the distal marginal ridge, also known as the distobuccal triangular sulcus.
2.Tooth root:
It is flatter and the buccolingual diameter is larger than the mesial and distal diameter. Most of them bifurcate into two buccal and lingual roots in the middle or apical 1/3 of the root (80% of the cases are bifurcated). The buccal root is longer than the lingual root. There is a groove-like depression in the tooth root from below the cervical edge to the root bifurcation. The groove on the distal surface is deeper than the mesial surface. If it is a single root, the groove length on its mesial surface accounts for most of the root length. The root tip is slightly remote.
(2) Maxillary second premolar
Features: Similar in shape to the maxillary first premolar
1. The crown is small and round, and the outline is not as obvious as the maxillary first premolar.
2. The buccal neck is wider than the maxillary first premolar, the developmental groove and axial crest are not obvious, and the buccal cusp is rounded, blunt, and mesial.
3. The size of the lingual surface and the buccal surface are similar or slightly smaller, and the difference is not as obvious as the maxillary first premolar. The tip of the tongue is rounded, blunt, and mesial.
4. Proximal surface: It is like a quadrilateral, with few depressions in the mesial neck, and a rare groove on the 𬌗 surface that crosses the mesial marginal ridge to the mesial surface. The mesial and distal contact areas are all on the buccal side of the proximal edge.
5. The facial contour is not as obvious as the maxillary first premolar, the corners are rounder and blunter, the buccal edge and the lingual edge are similar in width, and the cusps are rounder and blunter. The height and size of the buccal and lingual cusps are similar, and both buccal and lingual cusps are mesial. The central fossa is shallow, the central sulcus is short, the mesial and distal gaps are close to each other, and there is no groove on the 𬌗 surface across the mesial marginal ridge to the mesial surface.
6. The maxillary second premolar has many roots that are not bifurcated and are flat single roots. Double roots account for 5%
(3) Mandibular first premolar
Characteristics: The premolars are the smallest in size, and their buccolingual diameter is similar to the mesiodistal diameter, so the crown appears square and round.
1.Dental crown
(1) Buccal surface: Like the labial surface of the mandibular canine, the buccal cusp is long, sharp, and mesial. The buccal axial ridge is obvious at the 1/3 of the neck. The buccal axial ridge is crescent-shaped, with the highest point of the shape at the 1/3 of the neck.
(2) Lingual surface: shorter and smaller, about 1/2 of the buccal surface. The tip of the tongue is obviously smaller than the tip of the cheek, and the high point of the shape is located in the middle 1/3.
(3) Proximal surface: It is like a quadrilateral. When viewed from the proximal surface, the crown of the tooth is obviously tilted toward the lingual side, and the buccal cusp is located on the long axis of the tooth. The mesial and distal contact areas are all on the buccal side of the border.
(4) Facial surface: It is oval-shaped, and the buccal side is obviously wider than the lingual side. The biggest feature of the 𬌗face is that the cheek tip is long and the tongue tip is short, both tips are mesial. The triangular ridge of the buccal apex and the triangular ridge of the lingual apex are connected across the 𬌗 surface to form a transverse ridge, which is an important anatomical landmark of this tooth. The transverse crest divides the 𬌗 surface into a larger oblong distal fossa and a smaller triangular mesial fossa. The central sulcus between the mesial and distal points is divided into the mesial sulcus and the distal sulcus by the transverse ridge. The mesial sulcus spans the marginal ridge to the lingual surface and is called the mesiolingual sulcus.
2.Tooth root
It is a flat and elongated single root, wider on the buccal side than on the lingual side. There are often bifurcation marks at the root apex of the mesial surface, and the root apex is slightly distal.
(4) Mandibular second premolar
Features: Larger than the mandibular first premolar
1. Crown: The shape is square and round, the thickness, width and height of the crown are similar, and the buccal and lingual surfaces are approximately equal in size.
(1) Buccal surface: The neck is slightly wider than the mandibular first premolar, and the buccal axis ridge is rounded. The cheek tip is rounded and blunt, slightly mesial.
(2) Lingual surface: If there are two tongue tips, the tongue surface is wider than the buccal surface. There is a lingual communication between the two tongue tips. The mesial tongue tip is larger than the distal tongue tip. If there is one tongue tip, the tongue surface is smaller than the buccal tip. The tip of the tongue is mesial.
(3) Proximal surface: The mesial and distal contact areas are all on the buccal side of the border.
(4) 𬌗face: two types: ①Two-cusp type 𬌗face is oval, with one buccal tip and one lingual tip. Both tips are mesial. The development groove is mostly H-shaped or U-shaped. ②Tricuspid type: The surface is square and round, with one buccal tip and two lingual tips. The mesial tongue tip is larger than the distal tongue tip, and the development groove is mostly Y-shaped.
2.Tooth root:
It is an oblate single root with no bifurcation marks on the mesial surface and the root tip is slightly distal.
(5) The difference between maxillary premolars and mandibular premolars
1. For the crown of the maxillary premolar, the buccolingual diameter is larger than the mesiodistal diameter, and the crown appears flat, narrow, and long. For the crown of the mandibular premolar, the buccolingual diameter is similar to the mesiodistal diameter, and the crown is round.
2. The crown of the maxillary premolar is relatively straight, and the buccal and lingual cusps are located on both sides of the long axis of the tooth. The crown of the mandibular premolar is obviously tilted lingually, and the buccal cusp is close to or located on the long axis of the tooth.
(6) Applied anatomy of premolars
1. The pits and fissures on the 𬌗 surface of the premolars and their adjacent surfaces are prone to caries. When filling or repairing, attention should be paid to restoring their normal anatomical shape and the shape and position of the adjacent surface contact areas to avoid food impaction.
2. Since the first molar is more likely to be missing, the second premolar is often used as an abutment to repair the first molar.
3. Since the roots of the maxillary premolars are flat or have double roots, rotational force cannot be used during tooth extraction. Most of the mandibular molars have a single root, but because the root is flat and the root tip is often curved, rocking force is mainly used when extracting the tooth.
4. The maxillary premolars are close to the maxillary sinus, and apical infection may spread to the maxillary sinus. When removing the roots, you should avoid using push force to prevent the broken roots from entering the maxillary sinus.
5. Sometimes a small cusp can be seen in the central fossa of the 𬌗 surface of the premolar, which is called the central cusp or deformed central cusp. The pulp cavity is often exposed due to wear and tear, causing pulpitis or apical periodontitis. Deformed central cusps are more common in the first two premolars of the mandible.
6. Mandibular premolars are often used as a sign to find the mental foramen.
7. Premolars may be misaligned, translocated or have extra teeth.