Untitled Quiz

Course Objectives

• Students will be able to identify the geometric outlines of tooth crown surfaces and their physiological significance.
• Students will be able to list and explain factors affecting the periodontium.
• Students will be able to describe the temporomandibular joint, its components, and mastication muscles.
• Students will be able to list different mandibular movements and compensatory curves.
• Students will be able to describe the phases of permanent tooth development in the dental arch.
• Students will be able to identify the composition and function of saliva.
• Students will be able to define eruption, its phases, and movements in each phase.
• Students will be able to define and describe tooth shedding mechanisms, clinical considerations, and patterns of shedding in anterior and posterior teeth.

Tooth Eruption

• Tooth eruption is the movement of teeth from their developmental position to their functional position in the oral cavity.
• It involves both bodily and eccentric movements of teeth.
• The process begins at different times for the different types of deciduous and permanent teeth.

Terminology of Eruption

• Active Eruption: The actual movement of the tooth from the developmental site to its position in the dental arch.
• Passive Eruption: Tooth movement doesn't happen but instead, the gums recede.
• Clinical Crown: The portion of the tooth visible in the oral cavity.
• Anatomical Crown: The part of the tooth covered by enamel.

Histological Phases of Eruption

• Information will be discussed in various stages and subtopics regarding the pre-eruptive phase.

Phases of Eruption

• This section will cover when different phases start and end, as well as ongoing events and movement types during each phase.

Pre-eruptive Phase

• Begins during the early bell stage of tooth development.
• Ends with the beginning of root formation.
• Deciduous teeth initially have enough space for each tooth germ, but crowding occurs later due to rapid growth.
• The crowding is relieved by jaw growth in length, width, and height. This bodily movement allows teeth to move forward, backward, outward, and occlusally.

Movement of Deciduous Teeth

• Jaw growth in length moves anterior teeth forward and posterior teeth backward.
• Growth in width moves all teeth outward from the center.
• Jaw growth in height moves the teeth upwards.
• Bodily movement and eccentric growth are two types of movements in the pre-eruptive stage.
• Deciduous teeth initially have enough space for each tooth germ, but crowding occurs later due to rapid growth, and the crowding is relieved by the jaw growing in length, width, and height.

Premolars tooth germs

• First develop on the lingual aspect of their deciduous predecessors at the level of their occlusal surfaces and in the same bony crypt.
• The tooth germs occupy a more apical position as the predecessor teeth erupt and lie in their own bony crypts, and their positions are still lingually situated.
• By time, the primary molars have come into occlusion, and the crowns of the developing premolars occupy a position between the roots of the primary molars.

Permanent teeth without Deciduous Predecessors

• Maxillary permanent molars have occlusal surfaces facing downward and distally.
• Mandibular permanent molars have occlusal surfaces inclined mesially.
• The maxilla molars are in the tuberosity, facing distally, while mandibular molars are in the base of the ramus, facing mesially.
• They tilt to be upright with growth of the mandible.

Eruptive Phase

• Starts when the root formation begins.
• It ends when the tooth reaches occlusion.
• The clinically visible portion of the developing permanent teeth may cause discomfort or pain.
• Tooth growth may also lead to increased salivation, but no bleeding occurs.

Eruption Path of Succedaneous Teeth

• Gubernacular canal connects permanent teeth to the oral epithelium.
• Contains remnants of the dental lamina (Gubernacular cord).

Location of Gubernacular Canal

• Anteriorly, located lingual to primary anterior teeth.
• Posteriorly, located between the roots of primary molars.

Changes in Tissues Overlying Erupting Tooth

• Bone resorption, degeneration of connective tissue, and epithelial proliferation and fusion are crucial for tooth eruption.
• These processes form a central mass that degenerates into an epithelial-lined canal through which the tooth erupts without bleeding.

Osteoclasts Erode Jaw Bone

• Osteoclasts are crucial in the process of erupting adult teeth.
• Osteoclasts erode the jaw bone to make way for the erupting tooth.

Histogenesis of Dento-gingival Junction

• Desmolytic enzymes and epithelial plugs are involved. The final formation of the Dentogingival junction arises from reduced enamel epithelium.

Tooth Movement Phases

• Eruptive Phase: Characterized by root formation, supporting structures development (cementum, PDL, and bone) and formation of the dento-gingival junction.
• Post-eruptive Phase: Begins when the tooth reaches the occlusal plane. The tooth maintains position while the jaw grows, compensates for wear (axial movement, mesial drift). This phase ends at the end of the tooth's lifespan.
• Tooth movement types include axial (bodily, tilting), occlusal, and rotary.

Theories of Eruption Mechanism

• Root Formation Theory: Proliferating root impinges on a fixed base, creating an apically directed force that causes occlusal movement.
• Bone Remodeling Theory: Selective deposition and resorption of bone linked to tooth eruption. Though initially considered a cause of eruption, this remodeling process is now recognized as a byproduct of eruptive movements.

Dental Follicle Theory

• The dental follicle is important for tooth eruption.
• If the follicle is removed, no eruptive pathway forms.
• A replica of the germ will erupt and thus establish a pathway.

Periodontal Ligament Traction Theory

• Periodontal ligament cells and fibers pull the tooth into occlusion.
• Factors include fibroblast contractile properties, connection with collagen fibers, and oblique alignment of PDL collagen fibers.

Vascular Pressure Theory

• Local volume changes in periapical regions, potentially due to arterial pulse or swelling, can influence limited tooth movement.

Passive Eruption

• This phase can be categorized into First, Second, Third, and Fourth stages, that last until the tooth is lost. Gingival recession happens as part of passive eruption.

Stages of Passive Eruption

• Detailed explanation of the first, second, third, and fourth stages, including how the stages occur as the tooth is erupting.