1. CUSP : A cusp is an elevation or mount on the crown portion of a tooth making up a divisional part of the occlusal surface. It is found on cuspids and on the chewing surfaces of bicuspids and molars. Canine has ‘one’ cusp and premolars have ‘two’ cusps, so named as ‘cuspid’ and ‘bicuspids’ respectively. Cusp has all histological components of a crown such as enamel, dentin and pulp.
- Parts of a cusp: Basically a pyramid/cone and has the following:
• Two cusp slopes or cusp ridge slopes: These are inclined surfaces that form an
angle at the tip and are named as mesial and distal cusp slopes or cusp arms
• One cusp tip
• Labial/buccal/lingual ridge: Anyone for the respective cusp
• Triangular ridge only in occlusal surface of posteriors.
2. TUBERCLE : A tubercle is a smaller elevation on some portion of the crown produced by an extra formation of enamel. For example, tubercle of Carabelli present on the palatal aspect of
mesiopalatal cusp of permanent maxillary first molar and maxillary deciduous 2nd molar. Tubercle of Carabelli is a small additional cusp.
3. CINGULUM : A cingulum (Latin word for “girdle”) is the lingual lobe of an anterior tooth. It makes up the bulk of the cervical third of the lingual surface. Its convexity mesiodistally resembles a girdle encircling the lingual surface at the cervical third. It makes up the bulk of the cervical part of the lingual surface of anteriors. It is prominent in permanent than in deciduous teeth and also in maxillary than mandibular teeth.
4. RIDGE : A ridge is any linear elevation on the surface of a tooth and is named according to its location(e.g., buccal ridge, incisal ridge, marginal ridge).
- Types of ridge: there are various types of ridges seen in different teeth and are named accordingly on the surface in which they are situated.
- Labial ridge : It is the ridge seen on labial surface.
- Buccal ridge : It is the ridge seen on buccal surface.
- Lingual ridge : The ridge present on the lingual surface.
- Marginal ridge : Rounded borders of the enamel that form the mesial and distal margins of the occlusal developmental grooves, supplemental groove, developmental groove, triangular ridge.
- Triangular ridge : It runs (descends/inclines) from cusp tip up to the center of the occlusal surface.
- Transverse ridge: This ridge is formed by union of buccal and lingual triangular ridges that crosses the surface of a posterior tooth in transverse (buccolingual) direction.
- Oblique ridge: It is formed by union of triangular ridges of the mesiopalatal and the distobuccal cusps, in oblique direction.
- Cervical ridge: It runs mesiodistally at cervical 1/3rd buccal surface of the crown, present on all deciduous teeth and only on permanent molars.
5. FOSSA : A fossa is an irregular depression or concavity, present on a surface of the crown of a tooth (plural of fossa—‘fossae’) .
Types of fossa :
- Lingual Fossa : An Irregular, shallow depression found on the lingual surfaces.
- Triangular Fossa : Situated next to mesial and distal marginal ridges.
- Cental Fossa : Centrally located depression found on the occlusal surface.
6. SULCUS : A long depression or valley in the surface of at between ridges and cusps, the inclines of which meet at an angle. A sulcus has a developmental groove at the junction of its inclines. (The term sulcus should not be confused with the term groove )
7. PITS : Pits are small pinpoint depressions located at the junction of developmental grooves or at terminals of those grooves , central pit is a term used to describe a landmark in the central fossa of molars where developmental grooves join. A small defect in the enamel of crown of the tooth,
usually present at the junction of four formative lobes of a developing tooth.
- Buccal pit : is terminal part of buccal developmental groove
- Lingual pit :is terminal part of lingual developmental groove.
8. LOBE : It is one of the primary sections of formation in the development of the crown. In simple
terms ‘Lobe is one of the primary divisions of a crown’ and is usually separated by developmental grooves.
9. EMBRASURES : Embrassure is a potential ‘V’ shaped space that surrounds the contact areas and
narrowed at contact area, widening towards facial, lingual and occlusal surfaces. When two teeth in the same arch are in contact, their curvatures adjacent to the contact areas form spillway spaces which help in escape of food during mastication and prevent food impaction.
- Types of Embrasures are as follows:
• Labial/Buccal Embrasures termed as ‘Facial Embrasures’
• Lingual/palatal Embrasures
• Gingival Embrasures
Lingual/palatal embrasure is larger than others. This is because most teeth converge lingually.
11. MAMELONS : These are three rounded protuberances/projections which are present on the incisal ridges of newly erupted incisor tooth. Mamelons are found predominantly in permanent and also in maxillary than in mandibular incisors. These projections wear away soon after eruption due to masticatory forces.
They are three in number which are mesial, middle and distal named according to the lobe. Mesial is the largest and middle is the smallest.
Normally, it is pronounced as ‘point’ in anteriors as the contact is not wider as in case of posteriors.
14. DIASTEMA :
It is the space between two adjacent teeth that don’t contact with each other which are supposed to be present normally.