Correlation of Two Functions in Dental Restoration

Correlation of Two Functions in Dental Restoration

1. Centric Relation (CR) and Maximum Intercuspation (CO)

• CO position is usually located 1-2 mm anterior to the CR position, the distance is usually 1 mm.

• CO position is often the position of maximum intercuspation between the maxillary (Ht) and mandibular (Hd) arches.

• CR is defined when the mandible is in the most posterior position and there is no muscle tension.

2. Vertical Dimension

• Vertical dimension is the height of the lower facial plane.

• The vertical dimension at physiological rest is denoted as VDR.

• The free space between VDR and VDO is about 2mm.

3. Baseplate and Occlusal Rim

• The anterior baseplate and occlusal rim play an aesthetic role.

• The posterior baseplate and occlusal rim play a functional role.

4. External Surface of the Occlusal Rim

• The anterior border of the occlusal rim should not be excessively thick to avoid deformation of the labial vestibule and incorrect lip support.

• The angle between the philtrum and the nasal column should be approximately 90 degrees for appropriate lip support.

• This angle is less than 90 degrees in Class 2 occlusion.

• An angle greater than 90 degrees in Class 3 occlusion and maxillary retrusion is observed.

5. Canine Eminence

• Canine eminence is an important anatomical landmark, being the anterior component of the occlusal rim.

• The external surface of the occlusal rim lies 7mm lateral to the canine eminence.

6. Lip Index

• The lip index is determined by taking the anterior border of the occlusal rim with alginate.

7. External Appearance of the Upper Lip

• Evaluate the length of the maxillary incisors visible in the resting position and while smiling.

• Evaluate the smile line.

8. Exposure of the Maxillary Central Incisors While Smiling

• The exposure of the maxillary central incisors while smiling is about 1.91 mm for men and 3.41 mm for women in the physiological resting position.

9. External Appearance of the Lower Lip

• Evaluate the inner-outer position of the maxillary central incisor edge.

• Evaluate the curvature of the incisal plane.

10. Speech

• When pronouncing “Fe-Ve,” the free border of the lower lip should be close to the occlusal rim.

• When smiling, the curvature of the incisal plane is similar to the curvature of the upper lip.

• When the jaws are at rest, the height of the occlusal rim is at the level of the red lip line.

• The maxillary incisal plane is parallel to the line connecting the two pupils (using the fox ruler).

11. Marking

• Marking between the maxillary incisors and the corresponding occlusal rim is aligned with the symmetry axis of the face.

• Lower a vertical line from the wing of the nose, corresponding to the future canine position.

• Request the patient to smile and draw the smile line corresponding to the future canine neck position.

12. Accuracy of the Occlusal Plane

• The accuracy of the occlusal plane should be level with the back of the tongue in the resting position.

• The level of the occlusal plane should be determined when using the letters ‘e’ and ‘o’.

• When pronouncing the letter ‘e,’ the tongue should lie above the occlusal plane.

• When pronouncing the letter ‘o,’ the tongue should lie above the occlusal plane.

• The posterior occlusal rim is parallel to the Camper’s plane.

13. Adjusting the Occlusal Rim

• Adjust the direction and volume of the mandibular occlusal rim so that the tongue is not obstructed horizontally and anteroposteriorly.

• Adjust the maxillary baseplate occlusal rim according to the mandibular baseplate occlusal rim.

14. Vertical Dimension of Occlusion

• The vertical dimension of occlusion is considered appropriate when:

• There is a free space without intercuspation.

• When testing the pronunciation of “x,” the occlusal rims touch each other.

• When testing swallowing, the occlusal rims touch each other.

15. CR

• CR is the most posterior position of the condyle, without muscle tension.

• CR is the most posterior correlation of the Hd with the Ht in the vertical dimension.

• At the CR position, the Ht and Hd move easily laterally when the condyle is in the most posterior position.

• CR should be used when the entire occlusion is restored.

16. CO

• CO is the maximum intercuspation of the teeth.

17. Determining CR Position

• Determine the CR position by:

• Recording the Gothic arch image.

• Recording function.

• Static measurement.

• Using cepha films.

18. Recording Centric Relation

• Using a baseplate with wax for recording centric relation:

• The maxillary occlusal rim has been completed with the restored chewing surface.

• The Hd is moved back to the most posterior position, without muscle spasms.

• Gradually shape the mandibular wax occlusal rim to the correct vertical dimension of occlusion.

• Mark the occlusal rim with landmarks: the midpoint between the two central incisors and posterior to the canine area while the patient is biting in centric relation.

• Fix the occlusion in centric relation.

19. Balanced Occlusion

• To achieve balanced occlusion, the reference points on the lateral side should not be different.

20. Fixing the Occlusion in Centric Relation

• Steps to fix the occlusion in centric relation:

• Apply vaseline for isolation.

• Reduce the HD by 1 mm opposite the grooves of the HT.

• HT: carve a diverging V-shaped groove on the chewing surface, posterior to the line drawn at the canine.

• Apply aluminum wax.

• Place the baseplate and occlusal rim in the patient’s mouth, hold the occlusal rims when the jaw recedes without pushing.

21. Ideal Conditions for Determining Centric Relation

• Patient sits comfortably with the head upright.

• Complete the vertical dimension of occlusion.

• Ensure close contact of the middle part of the two bite blocks, the chewing surface of the maxillary and mandibular occlusal rims should be completely flat.

• Ensure contact between the two temporary baseplates and the supporting area.

• The pressure applied to the baseplate during the centric relation determination stage should be consistent with the pressure during the impression taking stage.

22. Methods to Help the Mandible Move to Centric Relation

• Methods to help the mandible move to centric relation:

• Fatigue the external pterygoid muscles: bring the Hd forward for 45-60 seconds.

• Tense the horizontal fibers of the temporalis muscle.

• Swallow.

• Guide the Hd backward with the doctor’s help by applying a quick, strong push to the patient’s chin.

• Create a biting reflex in the molar area by placing two index fingers on the occlusal rim or the outer surface of the occlusal rim and instruct the patient to close their mouth.

23. Swallowing Reflex

• The swallowing reflex includes the activity of:

• Tongue muscles.

• Pharyngeal constrictor muscles.

• Cheek and lip muscles.

• The swallowing reflex helps the Hd move backward.

24. Horizontal Fibers of the Temporalis Muscle

• The horizontal fibers of the temporalis muscle do not contract spontaneously.

• The horizontal fibers of the temporalis muscle do not participate in the stage of lifting and moving the Hd backward.

25. Transferring the Mandible to the Articulator

• The height of the incisal pin increases by 1 mm and the articulator is flipped.

• The occlusal rims are joined together and connected by 4 points using wax.

Note:

• This article is compiled from the information provided.

• Technical terms may be further explained to suit the context.

• The application of this knowledge should be performed by individuals with expertise and experience in the field of dentistry.