.pptx final year bds paedodontics kuhs syllabus

Final year bds

1. ORIENTATION JAW RELATION SANHA K V THIRD YEAR

2. CONTENTS INTRODUCTION ORINTATION JAW RELTION FACE BOW CONCLUSION REFERENCE

3. MAXILLOMANDIULAR RELATIONS AND RECORD MAXILLOMANDIBULAR RELATIONSHIP: Any spatial relationship of maxilla to the mandible; any one of the infinite relationship of the mandible to the maxilla (GPT8) MAXILLOMANDIBULAR RELATONSHIP RECORD: A registration of any positional relationship of the mandible relative to maxilla (GPT)

4. Maxillomandibular relations are classified into: 1. Orientation relation Establish the relationship of the maxilla into cranium 2. Vertical relation Establish the degree of jaw separation or vertical height of the face 3. Horizontal relation Establish the antero-posterior and side to side relationship the jaws

5. ORIENTATION JAW RELATION It is the first jaw relation to be recorded. It establishes the relationship of maxilla to the base of skull or cranium. It establishes the angle or tilt of the maxilla in three reference planes. To record the angulation of the maxilla, a plane should be formed with atleast two posterior reference point and one anterior reference point

6. FACEBOW A caliper like instrument used to record the spatial relationship of the maxillary arch to some anatomic reference point or points and then transfer this relationship to an articulator; it orients the dental cast in the same relationship to the opening axis of the articulator. Customarily the anatomic references are the mandibular condyles, transverse horizontal axis and one other selected anterior point; also called hinge bow (GPT8).

7. Types of facebow 1.Arbitrary facebow It determine the centre of rotation of condyle 2.Kinematic / hinge facebow It establishes the centre accurately

8. ARBITRARY FACEBOW DEFINITION: A device used to relate the maxillary cast to the condylar elements of an articulator using (average anatomic landmarks to estimate the position of the transverse horizontal axis on the face (GPI8). Also called 'average axis facebow’. It is the most commonly used facebow and is preferred for complete denture construction. The hinge axis (transverse horizontal axis) is approximately located. It positions the rods within 5 mm of the true centre of rotation of condyle. This method does not locate the true hinge axis, but the clinical impact of this inaccuracy is minimal and will lead to a mild error in the occlusion, which can be adjusted during insertion of the complete dentures.

9. Arbitrary facebows are classified into Earpiece type(ear bow): The external auditory meatus is considered as reference point to determine the centre of condylar rotation. The condyles are located at an approximate distance in front of the meatus and this is compensated for in the articulator by mounting the facebow behind the condylar centre. This type of facebow is easier to manipulate clinically

10. Facial type: The centre of condylar rotation is arbitrarily marked as 13 mm anterior to the middle of the tragus of the ear, on a line drawn from the outer canthus of the eye to the middle of the tragus of the ear - canthotragal line . The condylar rods of the facebow are placed on this point. This facebow is mounted by placing the condylar rods at the centre of the condyle in the articulator.

11. KINEMATIC FACEBOW DEFINITION: A facebow with adjustable caliper ends used to locate the transverse horizontal axis of the mandible (GPT8). It locates the true (exact) centre of condylar rotation or transverse horizontal axis. It is preferred in full mouth reconstructions. It usually requires a fully adjustable articulator. When we consider the rotation of any circular object, only the central point rotates, any other point within the circle will show translatory movement. Similarly in the condyle, the centre alone will display pure rotation. This principle used to determine the true centre of rotation using kinematic facebow.

12. The condylar rods are first positioned arbitrarily similar to facia type of facebow at a point 13 mm anterior to the auditory meatus on the canthotragal line. The patient is instructed to make opening and closing movements in CR. The opening should not be greater than 12 mm as then the condyle will then begin to translate instead of rotating. The position of the condylar rod is shifted around the arbitrary mark until it shows pure rotation. This is the centre of condylar rotation. This point is marked, the condylar rods are locked, the facebow assembly is removed and mounted on an appropriate articulator.

13. PARTS OF FACEBOW U-shaped frame Condylar rods Bite fork Locking devices Orbital pointer pin

14. U-SHAPED FRAME It is a U-shaped metallic frame, to which all the other components of the facebow are attached. It extends from the TMJ of one side to the TMJ of the other side, atleast 2–3 inches anterior to the face to avoid contact.

15. CONDYLAR RODS These are two calibrated metal extensions fitted on either side of the free end of the U-shaped frame that are placed on the determined centre of condyle. The calibrations on either side are equalized (to centre the facebow) and then locked.

16. BITE FORK It is a U-shaped rod which is attached to the maxillary occlusal rim while recording the orientation jaw relation. It is attached to the frame with the help of a metal rod called the ‘stem’. The bite fork should be inserted about 3 mm above the occlusal surface into the occlusal rim. Sometimes the bite fork is attached to the occlusal surface of the occlusal rim with the help of impression compound. This is done in order to preserve the occlusal rim.

17. LOCKING DEVICE There are three locking devices : Locking clamp for bite fork: It attaches the bite fork to the U-shaped frame. Locking clamp for orbital pointer pin: Locks the orbital pin onto the U-shaped rod. There is another locking screw for the condylar rods.

18. ORBITAL PLANE It helps in marking the anterior reference point. It is adjusted after marking the anterior reference point on the patient. This enables the transfer of the third reference point.

19. FACEBOW TRANSFER The procedure of transferring the orientation of the maxilla to the articulator involves: Facebow record Facebow mounting

20. Clinical procedure for recording orientation jaw relation (using facia type) The maxillary occlusal rim is inserted into the patient’s mouth and contoured and all the required guidelines are marked. A point 13 mm from tragus of the ear on the canthotragal line is marked on both sides. The bite fork is flamed and attached anteriorly to the maxillary occlusal rim, 3 mm above the incisal plane and parallel to the occlusal plane. The maxillary rim with the attached bite fork is inserted into the patient’s mouth. The parallelism and centring of the attached bite fork are verified. The U-frame is supported by two fingers and gently rotated and inserted into the stem of the bite fork in the patient’s mouth

21. The condylar rods are unlocked and the condylar heads are then placed in the patient’s right and left condylar centres on the previously marked points. The third point of reference (infraorbital notch) is palpated and the orbital pointer is set to the third point of reference. The condylar rod readings are equalized on both sides and the locking screws are tightened. Following this, the orbital pointer is also tightened in position. Once the entire apparatus is in position, the condylar rods, orbital pin and the bite fork are verified for any movement, alignment and parallelism. The contoured mandibular occlusal rim may be used during the transfer to stabilize the maxillary rim. The facebow record is removed from the patient by loosening only the condylar screws. The record is now ready to be mounted on the articulator. This completes the facebow transfer and then it is transferred to the articulator.

22. Mounting on the articulator The articulator is programmed first (zeroing of articulator): The incisal guide pin is set to correct jaw separation and the anterior stop screws are tightened first. Next the horizontal condylar inclination is set at 40° and the Bennett angle at 20°. The facebow record is now mounted on the articulator as follows: The condylar rods are attached to the auditory pins. The bite fork is stabilized on the tilting support bar provided and the orbital pin is made to coincide with the orbital axis plane indicator. The incisal pin is locked with its lock screw at zero on calibration and the incisal table is set horizontally The upper member of the articulator is swung open, plaster is mixed and placed on the cast and the upper member is closed , until the incisal pin fully touches the incisal table and upper mounting plate is covered with plaster. Excess plaster is trimmed once the plaster is set. Facebow is now removed by loosening all the locking devices.

23. INDICATIONS OF FACEBOW Balanced occlusion is desired. Vertical dimension is subject to change. If a facebow is not used, the maxillary cast is mounted arbitrarily on the articulator using the occlusal plane as a guide. https://youtu.be/kCbHTxgwZLc?si=4zTLCA9M6_PlOplT

24. CONCLUSION Failure to use the facebow may lead to errors in occlusion of the denture. These errors depend on the orientation of casts, interocclusal record and type of the teeth to be used. If cusp teeth are to be used or if the interocclusal records are made with the teeth out of contact, facebow record becomes essential. ⁠Hinge axis is a component of every masticatory movement of the mandible and therefore cannot be disregarded and this hinge axis should be accurately captured and transferred to the articulator. So it becomes a fine representative of the patient and biologically acceptable restoration is possible.

25. REFERENCE TEXTBOOK OF PROSTHODONTICS-V RANGARAJAN, TV PADMANABHAN