Occlusion-operative & Orthodontics Exercises

Intercuspal contact refers to the contact between the cusp, fossa, and marginal ridge of opposing teeth. This means that when the upper and lower teeth come together, the cusps (the pointed parts of the teeth) fit into the grooves or fossa of the opposing teeth, and the marginal ridges (the raised edges of the teeth) make contact. This contact is important for proper occlusion and function of the teeth during biting and chewing. Therefore, the statement that intercuspal contact is the contact between the cusp, fossa, and marginal ridge of opposing teeth is true.

The given statement is false. Protrusive jaw movement refers to the forward movement of the lower jaw. This is not the rest position of the jaw, but rather an active movement that occurs during activities such as chewing or speaking. The rest position of the jaw is when it is in a relaxed and closed position, with the upper and lower teeth slightly apart.

The correct answer is molars because they are the largest and strongest teeth in the mouth, designed for grinding and chewing food. They have a larger surface area and more contact points with other teeth compared to premolars, anterior teeth, and canines. Therefore, molars have the highest percentage of contact with other teeth during chewing and biting.

The statement is false because maximum intercuspation actually occurs with heavy bite force when the number and area of tooth contact is greater, not less, than light tooth contact.

The given statement is true. A group function refers to an occlusal arrangement where the force generated during lateral movement of the jaw is distributed among at least two pairs of teeth on the working side. This distribution of occlusal load helps to minimize excessive force on individual teeth and promotes a more balanced and stable occlusion.

In crossbite occlusal contact relationship, the working cups refer to the lower lingual cusps and the upper buccal cusps. This means that during the chewing or grinding process, the lower teeth make contact with the inner side of the upper teeth. This is a correct statement as it accurately describes the occlusal contact relationship in crossbite.

The correct answer is "Flat or nearly flat." In normal occlusion, the occlusion plane should be flat or nearly flat. This means that the biting surfaces of the upper and lower teeth should align evenly, without any significant curves or deviations. This allows for proper distribution of forces during biting and chewing, ensuring a balanced and stable bite.

Balanced occlusion refers to the equal distribution of forces on the teeth during biting and chewing. While it may be suitable for dentures or artificial teeth, it is not considered ideal for natural dentitions. Natural dentitions have individual variations in tooth morphology, alignment, and occlusal relationships, which may not be fully accommodated by balanced occlusion. Therefore, it is true that balanced occlusion is not suitable for natural dentitions.

Andrews believes that the mandibular curve of Spee should not exceed a depth of 1.5 mm. This means that the curvature of the lower jaw should not be too pronounced, as it could lead to malocclusion or misalignment of the teeth. A depth of 1.5 mm ensures a proper balance and alignment of the teeth, promoting optimal function and stability in the bite.

The correct answer is contact between the cusp tip to fossa and marginal ridge of opposing tooth. This means that during intercuspal contact, the cusp tip of one tooth comes into contact with the fossa (depression) of the opposing tooth, while the marginal ridge (raised edge) of the opposing tooth also makes contact. This type of contact ensures stability and proper alignment of the teeth during biting and chewing.

The Curve of Wilson is not a key of normal occlusion. Normal occlusion refers to the proper alignment of the teeth in the upper and lower jaws. The key factors of normal occlusion include the molar inter arch relationship, rotation, and tight contacts. The Curve of Wilson, on the other hand, is a concept that describes the curvature of the occlusal plane from the posterior teeth in a mesial to distal direction. While it is an important consideration in dental occlusion, it is not considered a key factor in determining normal occlusion.

Torque is the force that causes rotation around an axis, and in dentistry, it refers to the force applied to a tooth during orthodontic treatment. In this context, when the gingival portion of the long axis of the crown is buccal (towards the cheek) to the incisal portion (towards the biting edge), the torque is considered negative. Conversely, when the gingival portion is lingual (towards the tongue) to the incisal portion, the torque is considered positive. Therefore, the statement that torque is positive when the gingival portion is buccal to the incisal portion is incorrect.

The statement is true because primary occlusal contact refers to the initial contact between the lower buccal cusps (the raised areas on the outer surface of the lower teeth) and the upper fossa (the concave depression on the chewing surface of the upper teeth). This contact is essential for proper alignment and function of the teeth during chewing and biting.

The correction of balancing side does not influence the selection of restorative materials. Restorative materials are chosen based on factors such as the number and position of occlusal contacts, the force of the occlusion load, and the manner of occlusion of opposing teeth in excursive function. Balancing side correction refers to adjusting the occlusion on the non-working side of the mouth, which is not directly related to the selection of restorative materials.

The statement is false because the cusp to marginal ridge relationship actually has multiple point contact, while the cusp to fossa relationship only has two point contact.

The functional cusp of the upper tooth being buccal and the lower tooth being lingual is true, not false. This is because during the chewing process, the upper teeth have buccal cusps that occlude with the lingual cusps of the lower teeth, creating a functional biting surface.

The digastric muscle is responsible for opening the jaw. It is a double-bellied muscle that is located in the lower part of the face and connects the mandible (lower jaw) to the base of the skull. When the digastric muscle contracts, it pulls the mandible downwards, allowing for jaw opening. The other muscles listed, such as the masseter, temporalis, and medial pterygoid muscles, are involved in jaw closing and chewing movements rather than jaw opening.

The statement "Should be NON Balanced occlusion" is not suitable for complete dentures because balanced occlusion is necessary for proper functioning of the dentures. Balanced occlusion ensures even distribution of forces during chewing and helps prevent dislodgement of the dentures. Therefore, the statement suggesting non-balanced occlusion is not suitable.

Crown angulation refers to the alignment of the long axis of the crown, not the entire tooth. In normal occlusion, the gingival portion of the long axis of the crown is distal to the incisal portion. A positive reading is given when the gingival portion of the long axis of the crown is mesial to the incisal portion, indicating abnormal angulation. Therefore, the statement that positive reading is given when the gingival portion of the long axis of the crown is mesial to the incisal portion is NOT TRUE.

The statement is false. In dentistry, the maximal intercuspal position refers to the position where the teeth come together in maximum intercuspation or contact. Centric relation, on the other hand, is the most retruded, unstrained, and repeatable position of the mandible in relation to the maxilla. Therefore, the maximal intercuspal position is not slightly posterior to centric relation, but rather coincides with it.

The correct answer is stating that the mesiolingual cusp of the maxillary first molar was seated in the central fossa of the mandibular first molar. This means that the cusps of the upper molar are aligned with the depressions or grooves of the lower molar, which is a characteristic of normal occlusion. This alignment allows for proper chewing and biting function.

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The presence of a diastema between 8-12 years old is not a normal feature of adult occlusion. A diastema refers to a gap or space between two teeth, and it is more common in children during the mixed dentition stage when the permanent teeth are erupting. As the adult dentition develops, the teeth should come into contact with each other, closing any diastemas. Therefore, the presence of a diastema between 8-12 years old would not be considered a normal feature of adult occlusion.

The correct answer is retroclined upper anterior. In class II.2 occlusion, the upper anterior teeth are positioned in a retroclined manner, meaning they are tilted backwards. This causes the incisal edges of the lower incisors to occlude with the middle third of the palatal aspect of the upper teeth. The maxillary incisors can either be proclined or normally inclined, and the mandible is positioned in a forward position.

A horizontal force that is inclined to the long axis of the tooth for a long period of time can cause occlusal traumatism. This means that excessive or prolonged horizontal forces applied to the tooth can lead to damage or injury to the tooth and surrounding structures.

Centric relation is not the intercuspal contact when the jaw and condyles are in centric occlusion. Centric relation refers to the position of the mandible in the temporomandibular joint when the condyles are in their most superior and posterior position within the glenoid fossa. It is a reproducible and consistent position used as a reference point for various dental treatments. Centric occlusion, on the other hand, refers to the maximum intercuspal position of the mandible. Therefore, the given statement is false.

The explanation for the given correct answer is that the first statement, "Up hill of the cusp is refer to outer incline extends from cusp tip to outer surface of tooth," is false because the term "uphill of the cusp" actually refers to the inner incline of the cusp, not the outer incline. On the other hand, the second statement, "stabilizing contact refers to contact between upper lingual cusp and lower fossa," is true because stabilizing contact does indeed occur between the upper lingual cusp and the lower fossa.

A deep curve of spee refers to the curvature of the occlusal plane in the mouth. This curve can cause the upper teeth to occupy a more contained area, making normal occlusion (proper alignment of the upper and lower teeth) difficult. However, the upper first premolar is an exception to this because it is positioned in such a way that it can still achieve normal occlusion despite the deep curve of spee.

The absence of missing teeth will not increase the posterior guidance. Posterior guidance refers to the way the teeth come together during chewing or biting. The presence of missing teeth can affect the alignment and stability of the remaining teeth, leading to changes in the posterior guidance. However, the absence of missing teeth would not have any impact on the posterior guidance.

The occlusal examination is a process that evaluates the contact and alignment of the teeth in the upper and lower jaws. Limited interarch space refers to a condition where there is insufficient space between the upper and lower teeth. This factor should be considered during occlusal examination as it can affect the overall alignment and function of the teeth. Therefore, limited interarch space should not be excluded from the course of occlusal examination.