MANDIBULAR FIRST BICUSPID

Facial: The outline is very nearly symmetrical bilaterally, displaying a large, pointed buccal cusp. From it descends a large, well developed buccal ridge.

Lingual: This tooth has the smallest and most ill-defined lingual cusp of any of the premolars. A distinctive feature is the mesiolingual developmental groove

Proximal: The large buccal cusp tip is centered over the root tip, about at the long axis of this tooth. The very large buccal cusp and much reduced lingual cusp are very evident. You should keep in mind that the mesial marginal ridge is more cervical than the distal contact ridge; each anticipate the shape of their respective adjacent teeth.

Occlusal: The occlusal outline is diamond-shaped. The large buccal cusp dominates the occlusal surface. Marginal ridges are well developed and the mesiolingual developmental groove is consistently present. There are mesial and distal fossae with pits,

Contact Points: When viewed from the facial, each contact area/height of curvature is at about the same height.

Root Surface:-The root of the mandibular first bicuspid is usually single, but on occasion can be bifurcated (two roots).

MAXILLARY FIRST MOLAR

The first molars are also known as 6-year molars, because they erupt when a child is about 6 years

Facial Surface:-The facial surface has a facial groove that continues over from the occlusal surface, and runs down to the middle third of the facial surface.

Lingual Surface:-In a great many instances, there is a cusp on the lingual surface of the mesiolingual cusp. This is a fifth cusp called the cusp of Carabelli, which is in addition to the four cusps on the occlusal surface.

Proximal: In mesial perspective the mesiolingual cusp, mesial marginal ridge, and mesiobuccal cusp comprise the occlusal outline. In its distal aspect, the two distal cusps are clearly seen; however, the distal marginal ridge is somewhat shorter than the mesial one.

Occlusal Surface:- The tooth outline is somewhat rhomboidal with four distinct cusps. The cusp order according to size is: mesiolingual, mesiobuccal, distobuccal, and distolingual. The tips of the mesiolingual, mesiobuccal, and distobuccal cusps form the trigon, Cusp of Carabelli located on the mesiolingual cusp.

Contact Points; The mesial contact is above, but close to, the mesial marginal ridge. It is somewhat buccal to the center of the crown mesiodistally. The distal contact is similarly above the distal marginal ridge but is centered buccolingually.

Roots:-The maxillary first molar has three roots, which are named according to their locations mesiofacial, distofacial, and lingual (or palatal root). The lingual root is the largest.

Genetics and Environment: Introduction

The size of the teeth and the timing of the developing dentition and its eruption are genetically determined. Teeth are highly independent in their development. Also, teeth tend to develop along a genetically predetermined course.: tooth development and general physical development are rather independent of one another. Serious illness, nutritional deprivation, and trauma can significantly impact development of the teeth. This genetic independence (and their durability) gives teeth special importance in the study of evolution.

Teeth erupt full size and are ideal for study throughout life. Most important, age and sex can be recorded.

When teeth erupt into the oral cavity, a new set of factors influence tooth position. As the teeth come into function, genetic and environment determine tooth position.

In real life, however, girls shed deciduous teeth and receive their permanent teeth slightly earlier than boys, possibly reflecting the earlier physical maturation achieved by girls. Teeth are slightly larger in boys that in girls

Compensating curvatures of the individual teeth.

- the gentle curvature of the long axes of certain posterior teeth to exhibit a gentle curvature.

-These are probably analogous to the trabecular patterns seen in the femur and therefore reflect lines of stress experienced during function.

Posteruptive tooth movement.

These movements occur after eruption of the teeth into function in the oral cavity. These movements, known collectively as occlusomesial forces.

A. Continuous tooth eruption eruption of teeth after coming into occlusion. This process compensates for occlusal tooth wear.. Cementum deposition and progressive remodelling of the alveolar bone are the growth processes that provide for continuous tooth movement

B. Physiological mesial drift :Tthe tendency of permanent posterior teeth to migrate mesially in the dental arch both before and after they come into occlusion. Clinically, it compensates for proximal tooth wear.

(1) It describes the tendency of posterior teeth to move anteriorly.

(2) It applies to permanent teeth, not deciduous teeth.

(3) The distal tooth have the stronger is the tendency for drift.

(4) It compensates for proximal wear.

(5) In younger persons, teeth drift bodily; in older persons, they tip and rotate.

(6) Forces that cause it include occlusal forces, PDL contraction, and soft tissue pressures. There may be other more subtle factors as well.

Height  of Epithelial Attachment

The height of normal gingival tissue . mesiallv and distallv on approximating teeth, is directly dependent upon the height of the epithelial attachment on these teeth. Normal attachment follows the curvature of the cementoenamel junction if the teeth are jn proper, alignment and contact.

Cementum

Composition

a. Inorganic (50%)—calcium hydroxyapatite crystals.

b. Organic (50%)—water, proteins, and type I collagen.

c. Note: Compared to the other dental tissues, the composition of cementum is most similar to bone; however, unlike bone, cementum is avascular (i.e., no Haversian systems or other vessels are present).

Main function of cementum is to attach PDL fibers to the root surface.

Cementum is generally thickest at the root apex and in interradicular areas of multirooted 

Types of cementum

a. Acellular (primary) cementum

(1) A thin layer of cementum that surrounds the root, adjacent to the dentin.

(2) May be covered by a layer of cellular cementum, which most often occurs in the middle and apical root.

(3) It does not contain any cells.

b. Cellular (secondary) cementum

(1) A thicker, less-mineralized layer of cementum that is most prevalent along the apical root and in interradicular (furcal) areas of multirooted teeth.

(2) Contains cementocytes.

(3) Lacunae and canaliculi:

(a) Cementocytes (cementoblasts that become trapped in the extracellular matrix during cementogenesis) are observed in their entrapped spaces, known as lacunae.

(b) The processes of cementocytes extend through narrow channels called canaliculi.

(4) Microscopically, the best way to differentiate between acellular and cellular cementum is the presence of lacunae in cellular cementum.

SURFACES OF THE TEETH

Facial, Mesial, Distal, Lingual, and Incisal Surfaces

• The facial is the surface of a tooth that "faces" toward the lips or cheeks. When there is a requirement to be more specific, terms like labial and buccal are used. The labial is the surface of an anterior tooth that faces toward the lips. The buccal is the surface of a posterior tooth that faces toward the cheek.
• The mesial is the proximal surface closest to the midline of the arch. The distal is the opposite of mesial. The distal is the proximal surface oriented away from the midline of the arch.
• The lingual is the surface of an anterior or posterior tooth that faces toward the tongue. Incisal edges are narrow cutting edges found only in the anterior teeth (incisors). Incisors have one incisal edge
• Proximal Surfaces

A tooth has two proximal surfaces, one that is oriented toward the midline of the dental arch (mesial) and another that is oriented away from the midline of the arch (distal).