Prostho Final Lec 3

7/30/2019 Prostho Final Lec 3

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Dental surveying

*Dental surveyor: - an instrument used in the fabrication of a removable

partial denture

*Retention: - ability to resist

dislodgment forces.vertical

*Support: - Support is the

principle that describes how wellthe underlying mucosa (oral tissues,including gums and the vestibules)

keeps the denture from moving

vertically towards the arch

*Stability:-the resistance of adenture to movement on its tissue

foundation on lateral force

*Biocompatible: - it will live in the

body without causing harm to it

*Where do I need to dosurveying?

1-We do it in primary cast, and

secondary cast mainly and I use it

for cr-co RPD

* Primary cast

- I need to determine the area which is parallel to the path of insertion

- try to find an area for retention to make a clasp...Area of undercut

- draw our initial design

- try to identify which teeth are need preparation inside the patient mouth

{i.e. a tooth does not have an undercut so one of the alteration that wemight do is ENAMEL DIMPLE}.


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-ENAMEL DIMPLE: a small depression on enamel so the clasp goes

there when we dont have a good undercut

*Secondary cast

- Draw the final design

- Contouring the block out material whichmade of wax

*Other uses of the surveyor


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-the technician may be using dental articulator to countering the wax

pattern of ceramic crowns.. for example I want the crown from the

beginning when it still wax to have a guide plane so before fabricating

that crown, the technician make sure that the proximal side is flat in the

same characteristic that it should planted inside the patient's mouth

-Maybe I may put an area for reciprocation or I may put an internal

attachment, or internal rest, or an external attachment

-How do I know that any one of these component are parallel to the other

component of the RPD? We have to use surveyorSo the surveyor is used for RPD but it may be used for other restorations

like crowns and bridges

*Internal rest is a tunnel in which the partial denture will go in and out

-What does an internal rest do for retention?

1-It provides retention by friction the part which goes in and out it will

enter in tight path so it aids in retention

2-It help in support because it directs the force into the long access of thetooth

3-It helps in stability because it prevents the RPD from moving laterally

4-In esthetic it helps us because we dont need to add any clasp so its

more esthetic to the patient

-Sometimes the technician has finished all ceramic crowns and he wants

to cut it back its not in the wax stage now, its in the final completed

crown stage so once again we can use the surveyor to make sure that thecut is parallel to the path of insertion he had decided.


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*Surveyor in Implantology

-When I make the implant inthe bone, later on over it I will

add another competent so Iwant the external component

to go in and out smoothly, so

the surveyor making sure that

each implant is parallel to the

other

-Also dental surveyor aids the

surgeon in placing the implant

in the bone, they place theacryl and make a holes on it and

make sure that each implant is

parallel to the other , so we use the surveyor to design the holes before

doing surgery

-Some time we use surveyor in complete denture fabrication when we

have undercuts to avoid these undercuts or sometimes to get benefit from

it like if we have premaxilla undercut (we can use it for extra retention)

-Foracrylic RPD (interim) do we need surveying? Yes, to find

appropriate under cut to place my stainless steel wire in an under cut, thisis the main use.-There are Different types of survivors but they all share the same basic


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-Some time we add to the surveyor, the hand piece and we can use 2

degree or 6 degree taper tool so we need to do surveying to do a perfect

partial denture


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*Path of insertion (POI) is opposite to the path of removal (POR)

*BUT Path of displacement (POD) is different from path of removal

(POR) . its not parallel to the path of removal

*path of displacement occurs in any direction while path of removal

occurs in one direction only (perpendicular on the occlusal plane).

-usually when sticky food is there then the path of displacement will be

perpendicular to the occlusal table so its called "PARALLEL

DISPLACMENT"

only when the table tilt is zero,*

this case the path of removal will bein

the same (in the same direction) with

the path of displacementboth of

them will be perpendicular on the

occlusal plane.


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*How do we do a surveying line?!

-First of all before drawing any surveying

line I might use the analyzing rod to identifythe maximum parallel surfaces also we need

to make sure that the undercut in the bothside are almost equal so triangles must be

equals if they are not then we tilt the cast

slightly.

- Then we draw a line using a graphite marker the graphite marker has a

lead sheet on it to protect it from breaking and we start rotating to draw

a line so we can have a true undercut area so we can place a clasp on it

-When we draw a line the graphite marker should also touch the margin

of the gingiva to determine the soft tissue undercut.

After that I began gauging the undercut: - all the area below the survey

line we need to select exactly the area where the undercut is present

-The undercut gauge has a horizontal arm

which goes 0.02 inch horizontally .Wewant to make sure that the vertical part and

the horizontal part of the undercut gauge

are touching in the same time

-What if the surveyor line is high (the tooth

is too much tilted so the maximum bulge of

the tooth is high and very close to the

occlusal table) so if I end my clasp just

below the surveyor line I may traumatizethe tooth.

-The best for a retentive arm of the clasp to be in the middle just between

the middle and gingival thirdSometime I dont have an undercut...

What is the solution...?

1-I could reverse may clasp and put my retentive arm on the lingual side

if there is a lingual undercut

2-Or I can take an undercut from an adjacent tooth using extending clasp


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3-Or I can use a double embrasure clasp to obtain the retention from the

other side

4-If I dont want to change my design, I could prepare an enamel dimple

asmall space in enamel just to end my clasp in it


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Kennedy class I

.two abutments

Kennedy class II mod 1 .three

abutments with two clasps at least on

the posterior abutments

Kennedy class III mod 1 .four

abutments with four clasps


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-if we have severe interference then we might solve this problem either

by block out or cover the severely tilted teeth by servied crown with

suitable rest seat and undercutif all of the previous solutions are not

useful then we choose to extract the tooth as last resort.


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This is the dots method. I fix cast in the

correct position I want. I then let the

carbon rod touch three points in a single

direction. When I take the cast home

and come back the next morning, and I

want to put it back, these three points

will not touch the surveying machine

until I tilt the cast to the exact same

position which was the original tilt.

These also can be lines. So if I draw linesin the tilted position, they will never

come back parallel to the cast unless I

put the cast in the same tilted position


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*Surveying diagnostic casts is an important step in the fabrication of

removable partial dentures (RPD). After a suitable path of insertion is

determined, the orientation of the cast needs to be recorded to allow

repositioning of the cast in the same orientation at subsequent times.

-The ability to accurately record, communicate, and reproduce cast

orientation is critical to the laboratory fabrication of an RPD framework

with the same path of insertion as that determined by the dentist.

-Conventional methods for recording cast position require marking the

cast in several areas to establish a plane of orientation. Tripodization is

accomplished by placing horizontal marks on 3 divergent anatomic areas

on the cast.

-These marks define a plane of orientation for repositioning the cast. The

scoring method involves making 3 vertical marks along the base of the

cast on the posterior and lateral areas.

- The analyzing rod of a surveyor is aligned with all 3 marks to reorientthe cast. Several devices have been described to facilitate the recording

and reproduction of cast orientation

-DR.Ansari described the use of a U-shaped plastic impression tray with

a vertical stylus attached to a surveyor. The tray was indexed to the

occlusal surface of a cast with silicone putty material.


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*MASTER CAST SURVEYING


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Documents

Prostho Final Lec 3