Prosthodontics

Lecture - 1- Dr. Ruaa

Introduction

Prosthetics: The art and science of supplying artificial

replacements for missing parts of the human body.

Prosthodontics: is the dental specialty pertaining to the diagnosis,

treatment planning, rehabilitation and maintenance of the oral

function, comfort, appearance and health of patients with clinical

conditions associated with missing or deficient teeth and/or

maxillofacial tissues using biocompatible substitutes.

Prosthesis: an artificial replacement of an absent part of the human

body or a therapeutic device to improve or alter function.

Dental prosthesis: Is an artificial replacement of a tooth or teeth

and/or associated structures.

Restoration: a broad term applied to any material or prosthesis that

restores or replaces lost tooth or associated structure.

Dental prosthesis:

1. Fixed dental prosthesis: prosthesis that can’t be removed from

the patient‘s mouth by the patient himself, either luted to the

natural teeth or dental implant (crown and bridge).

2. Removable dental prosthesis: prosthesis that can be removed

from the patient‘s mouth by the patient like a. Removable partial

denture, b.Removable complete denture.

Removable partial denture: a dental prosthesis that replaces one

or more (but not all) of natural teeth and adjacent tissues.

Complete denture: A removable dental prosthesis that replaces

the entire dentition and associated structures of the maxilla (upper

Jaw) or mandible (lower jaw) by artificial substitutes.

Objectives of Complete denture:

1. Restoration of function (mastication).

2. Restoration of esthetics (disturbed facial dimensions and

contours).

3. Correction of phonetics (speech) due to the loss of natural teeth.

4. Satisfaction, pleasing and comfort of the patient.

5. Preservation of the remaining tissues in health.

Parts of denture:

1. Denture surfaces:

• Denture occlusal surface:

The portion of the surface of a denture that makes contact with its

antagonist.

• Denture polished surface:

The portion of the denture surface that extends in an occlusal

direction from the border of the denture and include the palatal

surface. It is usually polished and includes the buccal and lingual

surfaces of the teeth.

• Basal or impression surface:

The part of a denture that rests on the foundation tissue and is

determined by the impression.

2. Denture base: part of the denture that rest on the foundation

tissues and to which teeth are attached. Including:-

1. Denture border: The margin of the denture base at the junction

of the polished surface and the impression surface.

2. Denture flange: The part of the denture base that extends from

the cervical ends of the teeth to the denture border.

Dental implant: a prosthetic device implanted into the oral tissue

beneath the mucosal and/or periosteal layer, on or within the bone

to provide retention and support for fixed or removable prosthesis.

General consideration in complete denture construction:

1. From the operator (dentist):

a. Sufficient degree of diagnostic skills.

b. Sound knowledge of biological and mechanical principles.

c. Certain degree of artistic ability to achieve good esthetic

requirements.

d. Careful manipulation of dental materials and devices.

2. From the patient:

a. Co-operation with the dentist.

b. Some understanding of the limitation of prosthetic restoration.

c. Patience during the construction, learning and adjustment of the

new prosthesis.

3. From the technician:

There should be co-operation between clinical and technical

Procedures.

❖ Dentulous (dentate) patient: patient who has all his natural teeth

in his arch.

❖ Edentulous patient: patient who extracts all of his teeth.

❖ Partially Edentulous patient: patient who extract some of his

teeth.

Prosthodontics

Second Grade

Lecture 2 Dr. Suha Saadi

Anatomical Landmarks

To obtain satisfied results in the prosthodontics treatment, the dentist must fully

understand the anatomy and physiology of the supporting and limiting structures

involved.

Dentures contact mucosa with a compressibility and movement that varies

between each arch, among areas within the arch, and among patients, so the landmarks

of each arch will act as positive guides to the limit of the impression and denture

extensions.

Maxillary Arch Anatomical Landmarks

1.Labial frenum 2.Labial vestibule 3.Canine eminence 4.Buccal frenum 5.Buccal

vestibule 6.Distobuccal sulcus 7.Hamular notch 8.Vibrating line 9.Fovea palatinae

10.Residual alveolar ridge 11.Incisive papilla 12.Maxillary tuberosity 13.Rugae area

14.Median palatal raphe & suture

Limiting structure:

1. Labial frenum.

2. Labial vestibule.

3. Buccal frenum.

4. Buccal vestibule.

5. Hamular notch.

6. Posterior palatal seal.

Supporting structures:

1. Hard palate.

2. Residual ridge.

3. Rugae.

4. Maxillary tuberosity.

Relief areas:

1. Incisive papilla.

2. Mid-palatine raphe.

3. Fovea palatine.

4. Cuspid eminence

5. Maxillary tori

Limiting structure:

1. Labial frenum:

It is a fibrous band covered by the mucous membrane extend from the labial aspect

of the residual ridge to the lip. It might be single or multiple, broad or narrow. It has

no muscles fibers. During impression making a v- shaped, deep notch (labial notch)

should be recorded to accommodate labial frenum.

2. Labial vestibule: It is the portion of the oral cavity which is bounded on one side by residual ridge

and on the other side by the lips and cheek. It runs from the buccal frenum on one side

to the other on the labial side of the ridge, and divided by the labial frenum into two

compartments right and left.

3. Buccal frenum:

Appears as single or multiple folds. It separates the labial and buccal vestibule, it

has attachments of the following muscles;

Levator anguli oris - attaches beneath the frenum

Orbicularis oris- pulls the frenum in a forward direction

Buccinator – pulls the frenum in a backward direction

These muscles influence the position of the buccal frenum hence it need wider

and shallower clearance on the buccal flange.

4. Buccal vestibule:

It is the space distal to the buccal frenum. It is bounded laterally by the cheek and

medially by the residual alveolar ridge. The area of the denture which will fill this space

is known as buccal flange. The stability and retention of the denture are greatly

enhanced if the vestibule’s space filled properly with the flange.

The size of buccal vestibule varies according to:

1-contraction of buccinators

2-position of the mandible

3-amount of bone loss in the maxilla.

Distobuccal sulcus: it is located in the buccal side of the maxillary tuberosity.

5. Hamular notch:

It is the depression between the maxillary tuberosity and the hamular process of

the medial pteregoid plate, it is soft area of loose areolar tissue. This tissue can be safely

displaced to achieve the posterior palatal seal.

6. Posterior palatal seal:

It is the soft tissue at or along the junction of the hard and soft palates on which

pressure within the physiological limits of the tissues can be applied by the denture to

aid in the retention of the denture. This is the area of the soft palate that contacts the

posterior surface of the denture, it prevents air entry between the denture base and soft

palate.

Supporting structures:

These areas are load bearing areas, they show minimal resorption even under

constant load, so the load should be concentrated over these areas which are:

1. Hard palate:

The anterior region of the palate is formed by the palatine shelves of the maxillary

bone, which meet at the center to form the median suture. While the posterior part of

the palate is formed by the horizontal plate of the palatine bone. The horizontal portion

of the hard palate lateral to the midline acts as the primary support area. While rugae

area acts as a secondary support area.

2. Residual ridge:

It is the portion of the alveolar ridge and its soft tissue covering which remains

following the removal of the teeth.

The submucosa over the ridge has adequate resiliency to support the denture. The

crest of the ridge may act as secondary stress bearing area. The posterolateral portion

of the residual ridge is a primary stress-bearing area.

3. Rugae:

These are mucosal folds located in the anterior portion of the palatal mucosa. They

act as secondary support area. These folds play an important role in the speech.

4. Maxillary tuberosity:

It is a bulbous extension of the residual ridge in the second and third molar region.

The posterior part of the ridge and the tuberosity areas are considered as one of the

most important areas of support because they are least likely to resorb.

Relief areas:

These areas resorb under load or it contain soft structure within it, so should be

relieved during denture construction.

1. Incisive papilla:

It is a midline structure situated behind the central incisors. It is the exit point of

the nasopalatine nerve and vessels. It should be relieved, if not the denture will

compress the vessels or nerves, leading to necrosis and paresthesia of anterior palate.

2. Mid-palatine raphe:

This is the median palatine suture covered by a thin submucosa. It should be

relieved during denture fabrication. This area is the most sensitive part of the palate to

pressure.

3. Fovea palatina:

The fovea is formed by coalescence of the ducts of several mucous glands. This

acts as arbitrary guide to locate the posterior border of the denture. The denture can

extend 1-2mm posterior to the fovea palatine. The secretion of the fovea spreads as a

thin film on the denture there by aid in retention.

4. Cuspid eminence:

It is a bony elevation on the residual alveolar ridge formed after extraction of the

canine. If not relieved under complete denture soreness will occur.

5. maxillary tori (torus palatinus):

It is an anomaly that may be seen in above mid palatal suture. It considered as a

hyperplastic growth of bony tissue. It varies in size and its treatment also differ

according to its size, from simple relief to surgical removal.

Prosthodontic

Second grade

Lecture 3 Dr. Suha Saadi

Mandibular Arch Anatomical landmarks

1.Labial frenum 2.Labial vestibule 3.Buccal frenum 4.Buccal vestibule 5.Buccal shelf

area 6.Retromolar pad 7.Alveololingual sulcus 8.Lingual frenum 9.Mylohyiod ridge

10.Residual alveolar ridge

limiting structure:

1. Labial frenum

2. Labial vestibule

3. Buccal frenum

4. Buccal vestibule

5. Lingual frenum

6. Alveololingual sulcus

7. Retromolar pad

Supporting structure:

1. Buccal shelf area

2. Residual alveolar ridge

Relief area:

1. Mental foramen

2. Mylohyiod ridge

3. Genial tubercles

4. Torus mandibularis

Limiting structures:

1. Labial frenum:

It is a fibrous band extend from mucous membrane of the lip to the residual

alveolar ridge. Unlike the maxillary frenum, it is active since it receives attachment

from orbicularis oris muscle. It is quit sensitive and active and needs enough clearance

in the denture.

2. Labial vestibule:

It is bounded anteriorly by the labial frenum, posteriorly by the buccal frenum,

laterally by the labial mucosa and medially by residual alveolar ridge. The length and

the thickness of the labial flange of the denture occupying this space is influencing lip

support and retention.

3. Buccal frenum:

It may be single or multiple. It is the fold of mucous membrane extending from

the mucous membrane of the buccal mucosa to buccal surface of the residual alveolar

ridge. It overlies the depressor anguli oris. The fibers of buccinator are attached to the

frenum. Sufficient allowance should be done to prevent displacement of the denture

during function.

4. Buccal vestibule:

It is bounded anteriorly by the buccal frenum, posteriorly by the massetric notch

area, medially by residual alveolar ridge and laterally by buccal mucosa and

buccinator.

This space is influenced by the action of masseter muscle. When the masseter

contracts, it will push inward against the buccinator, producing a bulge into the mouth.

This bulge recorded only when the masseter contracts. It is reproduced as anotch in the

denture flange called masseteric notch

Massetric notch: is the area buccal to the crest of the residual alveolar ridge in the

disto-buccal corner of the mandibular arch.

5. Lingual frenum:

It is a fold of mucous membrane can be observed when the tongue is elevated. It

overlies the genioglossus muscle. Thus lingual notch in the denture should be done to

prevent displacement of the denture or ulceration of the tissue.

A high lingual frenum is called a tongue tie. It should be corrected if it affects the

stability of the denture.

6. Alveololingual sulcus:

It is extended from the lingual frenum to the retromylohyiod curtain and bounded

externally by the residual ridge and internally by the tongue. This space is filled by the

lingual flange of the denture and can be divided into:

A. Anterior portion: It is extended from the lingual frenum to the premylohyoid

fossa. The flange will be shorter anteriorly and it should touch the mucosa of

the floor of the mouth when tip of the tongue touches the upper incisors.

B. Middle region: It is extended from the premylohyoid fossa to the distal end of

the mylohyoid ridge; here the mylohyoid muscle is important in determining

the contour of the lingual flange. The lingual flange should slope medially

toward the tongue. This slope helps in three ways:

1-the tongue rests over the flange stabilizing the denture.

2-provide a space for raising the floor of the mouth without displacing the denture.

3-the peripheral seal is maintained during the function.

C. Posterior region: Is the retromylohyoid space or fossa, it extends from the end

of mylohyoid ridge to retromylohyoid curtain, lies posterior to the mylohyiod

muscle. The lingual flange of the denture should fill the retromylohyoid fossa

properly. The denture flange in this region should turn laterally toward the

ramus of mandibule to full the fossa and complete the typical S-form of the

lingual flange of the lower denture.

7.Retromolar pad:

It is a pear shaped body at the distal end of the residual alveolar ridge. It forms

the posterior seal of the mandibular denture.

It has muscular and tendenous elements lying underneath which are: fibers of

temporalis, masseter, buccinators, the superior constrictor muscles of pharynx and

tendinous mandibular raphe. Because of muscular tendenous elements, the area

should not be subjected to pressure effect.

This pad helps in maintaining the occlusal plane and arranging the mandibular

posterior teeth. Notice that teeth should not be placed on the retromolar pad because it

will act as a dislodging factor with the forces being inclined anteriorly.

Supporting structure:

1.Buccal shelf area:

It is the area between the buccal fernum and anterior border of the masseter. Its

bounded by the crest of the ridge medially, the retromolar pad distally and laterally the

external oblique ridge.

It has a thick submucosa overlying a cortical plate. As it lies at right angle to the

occlusal forces, it serves as a primary stress-bearing area.

2.Residual alveolar ridge:

The bony process that remains after teeth loss is known as residual alveolar ridge

bone. The bone of crest of lower residual ridge being made of cancellous bone while

the slopes are of cortical bone. Therefore, the crest may not be favorable as a primary

stress bearing area for the lower denture and termed as the stress relief area.

Relief area:

1. Mental foramen:

It lies buccally between the first and second premolar region. It transmits the

terminal branches of the inferior alveolar nerve and the mental artery. Due to ridge

resorption it may lie close to the ridge thus it should be relieved to avoid pressure over

the nerve and vessel.

2. Mylohyiod ridge:

It runs along the lingual surface of the mandible. Anteriorly the ridge lies close to

the inferior border of the mandible while posteriorly it lies flush with the residual ridge.

The thin mucosa over the mylohyoid ridge may get traumatized and should be relieved.

The area under this ridge is an undercut.

3. Genial tubercles:

These are a pair of bony tubercles found anteriorly on the lingual side of the body

of the mandible. Due to resorption, it may become increasingly prominent making

denture usage difficult.

4. Torus mandibularis:

It is an abnormal bony prominence founded bilaterally on the lingual side near the

premolar region. It covered by a thin mucosa. It has to be relieved or surgically

removed as decided by its size and extent.

Prosthodontics

Lecture - 4- Dr. Ruaa hameed

Impression tray

Impression tray: It is a device that is used to carry, confine, and control

impression material while making an impression. During impression making, the

tray facilitates insertion & removal of the impression material from the patient's

mouth.

The impression tray consists of two main parts:

a) Body (floor and flanges).

b) Handle.

There is upper tray to make impression of the upper arch & lower tray to make

impression of the lower arch. The difference between them is that in the upper

tray, there is the palatal portion that’s called (vault) & in the lower tray there is

the lingual flange. The handle is an extension from the union of the floor & labial

flange in the middle region (midline), it's (L) in shape so that, it will not interfere

with lip during impression procedure.

Types of trays: (There are two main types)

1. Stock tray: Used for the primary impression.

2. Special tray (individual tray): Used for the final impression.

The stock trays: Impression trays serve to carry the impression material

to the mouth & support it in the correct position while it is hardening. This

type of the trays can be used for several patients & used for making

primary impression. They can be made of different materials such as

Aluminum, stainless-steel, Tin, Brass or Plastic, also can be made in a

variety of shapes and sizes to fit in different mouths.

-Types of stock trays (according to the presence of natural teeth):

1. Stock tray for dentulous patient.

2. Stock tray for edentulous patient.

*We can distinguish between these two types of trays by:

The stock trays for dentulous patient have long flanges with wide and flat

floor, while the other have short flanges with narrow and oval floor.

-Types of stock trays (according to the impression material):

a) Perforated stock tray (used with alginate impression material).

b) Non- perforated stock tray (used with impression compound).

Factors affect the selection of stock tray:

1- The type of material that used in the primary impression procedure.

E.g. with impression compound we use non-perforated stock tray

because

the material will be stick on the tray and with alginate impression

material we should use perforated stock tray.

2- Size of the arch.

3- Form of the arch (round, square or taper).

4- The stock tray must cover all the anatomical landmarks needed in

complete denture & this is the most important point.

5- The stock tray should give a sufficient space to impression material in

all direction (4-5 mm).

The Special tray (Individual or custom tray):

It is an individualized impression tray made on a cast recovered from the

primary impression (study cast). It is used for making final impression.

*The special tray is made by the operator from the primary cast of the patient so

it is superior to the best stock tray likely to be available.

Advantages of special trays:

1- Economy in impression material (the impression material required in

special tray is less than in stock tray).

2- More accurate impression.

3- The special tray provides even thickness of impression material. This

minimizes tissue displacement & dimensional changes of impression

material.

4- Easy to manipulate.

5- The special tray is more accurately adapted to the oral vestibules, this

helps in better retention of denture.

6- Comfortable for the patient because it is less bulky than the stock tray.

Types of special tray:

1- Spaced special tray (with or without stopper).

2- Closed fitted special tray.

Criteria for Special tray construction:

1- The impression tray must not impinge upon movable structures.

2- The borders must be under extended (2mm).

3- The posterior limits of the impression tray should be slightly

overextended to ensure inclusion of the posterior detail for development

of the post-dam area in upper tray.

4- The tray should be rigid & has a sufficient thickness so it will not

fracture during its use (2-3 mm).

5- The tray must have a handle for manipulation & the handle must not

interfere with functional movement of the oral structures.

6- The tray must be smooth on its exposed surfaces and should have no

sharp corner or edges which could injure the patient.

Techniques or methods for the construction of the special trays:

1. Finger adapted dough method.

2. Sprinkle-on method.

Finger adapted dough method:

In close fit special tray we used only separating medium on study cast then a

self-curing acrylic resin tray material is mixed & uniformly adapted over the cast,

the special tray should be about 2-3 mm in thickness. In the special tray with

stoppers we should have 4 stoppers, 2 anterior & 2 posterior on both sides; a

baseplate wax sheet of 1mm in thickness is placed on the cast & windows open

on the wax sheet in area of stoppers by removing the wax to make the stoppers &

then put a uniform layer of self-cure acrylic resin upon it. When we remove the

wax, there is a space with 4 stoppers which will stop the special tray in the mouth

of the patient & stop the pressure on the material during making the impression.

Acrylic resin handle is attached in the anterior region of the tray to facilitate

removal of the final impression.

Sprinkle- on acrylic technique:

This technique used for construction of individualized impression

tray. After painting of the study cast with separating medium, the powder

of the acrylic resin (polymer) place in a container with a perforated top &

place the liquid (monomer) in a dappen dish. Shake the polymer on the

border & other surface of the study cast then add the monomer from the

dappen to saturate the polymer & allow complete polymerization of the

special tray.

Prosthodontics

Lecture– 5- Dr.Ruaa

Complete denture impression

Dental Impression: It is an imprint or negative likeness of the hard tissues

(teeth) and/or soft tissues (edentulous areas & adjacent tissues) in the oral cavity.

Complete denture impression: It is a negative registration of the entire denture

bearing, stabilizing & seal area of either the maxilla or the mandible.

Objectives of making impression:

Complete denture impression procedures must provide five objectives:

1. Retention : that quality inherent in the dental prosthesis acting to resist the

forces of dislodgment along the path of placement.

2. Stability: the quality of a removable dental prosthesis to be firm, steady, or

constant, to resist displacement by functional horizontal or rotational stresses .

Resistance to horizontal displacement of a prosthesis

Retention must hold the denture in its position at rest while stability must resist

displacement by rocking when a force is applied to the artificial teeth over a

limited area.

3 .Support: It is the quality of prosthesis to resist displacement toward the

underlying (foundation) tissues. Increase the amount of area covered by the

denture lead to increase the support.

*The best support for the denture is the compact bone covered with fibrous

connective tissue.

4. Esthetics: Border thickness should be varied with the need of each patient in

accordance with extends of residual ridge loss (to restore facial contour).

5. Preservation of the residual alveolar ridge & soft tissues: It is physiologically

accepted that with the loss of the stimulation for the natural teeth the alveolar

ridge will be resorbed (atrophy). Prosthodontist should keep in mind the effect of

impression material & technique on the denture base & the effect of the denture

base on the continued health of both the soft & hard tissues of the jaws.

Primary impression: It is a negative likeness made for the purpose of diagnosis, treatment planning &

construction of special tray. It is the first impression made for the patient and

from which the study cast was produced, this impression is obtained by the stock

tray.

Tray selection: Trays used for primary impression making are called stock trays which are a

factory prepared and are available in a standard sizes. This standardized trays

will not adapted closely to patient arch so an approximate tray (size and form)

should be selected for each patient.

Consideration in tray selection:

Sufficient clearance between the tray and the tissues, the amount of

clearance depend on the type of impression material.

If the tray is too large, it will distort the tissues in the borders of the

impression and will push the cheeks away from the residual ridge.

If is too small, the border will collapse inward to the residual ridge.

The tray material should not react with the impression material and should

not distorted.

Generally all primary impressions have overextended borders.

For the upper stock tray, the posterior border of the tray should cover the

maxillary tuberosity & the hamular notch while anteriorly the tray should

include the alveolar ridge.

For the lower stock tray, posteriorly should cover the whole area of the

retromolar pad area & anteriorly should include the alveolar ridge.

Materials used for making primary impression:

1- Impression compound.

2- Alginate impression material.

3- Rubber base impression material.

Primary cast (study model or diagnostic cast): It is the cast formed from

the preliminary impression and used in diagnosis or fabrication of an

impression tray.

Production of study cast (primary cast(

The primary impression is poured (casted) in plaster (after beading & boxing) to

get the primary cast (study model) which is the positive reproduction of the oral

tissues.

Boxing: It is the enclosure of an impression to produce the desired size & form

of the cast’s base and preserve desired details.

Boxing impression can be used for primary & final impression of complete

denture.

Advantages of boxing:

1. To facilitate pouring of the impression with plaster or stone.

2. Produce the desired size & form of the cast’s base (adequate thickness of

the cast).

3. Preserve desired details & borders of the impression.

4. In the lower impression, the boxing procedure will facilitate the

reproduction of the lingual borders.

Materials used for boxing impression:

1. Beading wax: a strip of wax is attached all the way around the

outside of the impression approximately (1-2 mm) below the

border & sealed to it with a wax knife.

2. Boxing wax: a sheet of wax is used to made the vertical walls of the

box & it is attached around the outside of the beading wax strip so

that it does not alter the borders of the impression, the width of the

boxing wax is about 10-15 mm.

3. Base plate wax: a sheet of wax can be used to fill the tongue space

in the lower impression that is sealed just below the lingual border

of the impression.

Final or Secondary impression:

It is a negative likeness or registration of the entire denture bearing, stabilizing

and border seal area of the maxilla & mandible for the purpose of fabricating

prosthesis.

The final impression is made with special tray and it is used for making master

cast which must be poured with stone material.

Master cast (definitive or final cast): A replica of the residual ridge areas and\or

other structures that is used to fabricate a dental restoration or prosthesis.

Materials used for final impression:

1- Zinc-oxide eugenol impression material.

2- Alginate impression material.

3- Impression plaster.

4- Waxes.

5- Elastomeric impression material:

a- Polysulfide

b- Poly ether.

c- Silicon.

The techniques used for making final impression:

1- Mucostatic impression technique (non-pressure technique)

2- Muco-compression or Functional impression technique (pressure or closed

mouth technique).

3- Selective pressure impression technique.

Common faults in making dental impression:

1- Poor selection of the tray.

2- Insufficient impression material loaded in the tray.

3- Excessive impression material loaded in the tray.

4- Failure to press the tray properly in position (insufficient seating pressure

or excessive seating pressure).

5- Incorrect position of the tray.

6- Obstruction of the proper flow for the impression material by lips, cheek or

tongue.

1

Prosthodontics

Second Grade

Lecture 6 Dr. Suha Saadi

Record base

The accuracy of the maxillo-mandibular relation record is affected by:

1. the rigidity of denture base

2. the stability of denture base

3. the movability of the record base

4. The borders & the polished surfaces of the record bases should be smooth &

round aiding in patient comfort & relaxation.

5. The proper contouring of the occlusion rims for lip & cheek support allows

the muscles of facial expression to act in a normal manner.

Record base: an interim denture base used to support the

record rim material for recording maxillo-mandibular

records.

Requirements of the record base:

1. The record base must be rigid.

2. The record base must be accurate & stabile.

3. The borders of the record base should be developed in

the same manner as the borders of the finished denture.

4. All the surfaces of the record base that contact lips,

cheek & tongue should be smooth, round & polished.

5. The crest, labial and/or buccal slopes should be thin to

provide a sufficient space for the arrangement of teeth.

2

Materials used in the construction of the record bases:

1- Shellac record base.

2- Self curing acrylic resin.

3- Heat curing acrylic resin.

4- Light curing acrylic resin.

Requirements of occlusal rim:

1. The position should be in the anticipated position of the artificial teeth.

2. It must be securely attached to the base.

3. The occlusal surface must be smooth and flat.

4. It should be contoured to support the lip and cheeks accurately.

5. All the surfaces should be smooth.

Material used in construction of occlusion rim:

1. Waxes are used more frequently in the registrations and the arrangement of teeth.

a. Bite plate wax (ready-made occlusion rims)

b. Parafine wax or base plate sheet wax (hand-made occlusion rims)

2. Modeling compound

Record rim (occlusion rim): the occlusal surfaces

fabricated on a record base for the purpose of

making maxillo-mandibular relationship records

and arranging teeth.

3

Measurements of the maxillary occlusion rims:

1- They should be directly over the crest of the residual ridges.

2- The maxillary rim should have a slight labial inclination & the maxillary labial

surface should be (7 – 8) mm anteriorly to the line bisecting the incisive papillae.

3- The final wax rims width should be (4 mm) anteriorly then gradually become wider

posteriorly to be (7 mm).

4- The occlusal height of the maxillary rim should be (22 mm) from the labial flange

lateral to the labial frenum & (18 mm) from the Buccal flange in the tuberosity area.

5- The posteriors of the occlusion rim are cut in 30ᵒ angle to the occlusal plane.

Measurement of mandibular occlusion rims:

1- It should occupy the space over the crest of the residual ridge.

2- The mandibular rim should have a slight labial inclination.

3- The labio-lingual thickness (width) should be approximately (4 mm) anteriorly and

also increase posteriorly to be (7 mm) in the molars area.

4- The occlusal height should be (18 mm) from the flange lateral to the labial frenum

& should be with the level of acrylic base posteriorly.

4

Uses of occlusion rims:

1- Jaw relation determination which include:

a) Determination of the vertical dimension.

b) Determination of the horizontal (centric & eccentric) jaw relations.

2- Aid in the selection of teeth:

a) The position of midline can be determined and draw on the occlusion rim.

b) The canine lines (cuspid lines) are drawn on the rim at the corner of the mouth

on each side.

c) The height of the anterior teeth is determined by drawing the high lip line when

the patient smile, the whole length of the incisors should be seen on smiling.

d) The low lip line is a line drawn on the occlusion rim when the upper lip is relaxed

in this case 2mm of the anterior teeth should be seen.

3- Setting up of teeth.

4- Orientation of the occlusal plane.

5- Determine the shape of the arch.

6- Support to the facial muscles.

The best anatomic guides to aid in determining the proper contouring

of the anterior section of the upper & lower occlusion rims are:

1- The philtrum

2- The naso-labial sulcus

3- The commissure of the lips

4- The mento-labial sulcus

5

Occlusal plane

It's an imaginary surface which is related anatomically to the cranium and

theoretically attached the incisal edges of the incisors and the tips of the occluding

surfaces of posterior teeth.

The height of the occlusal plane should be 1-2 mm below the upper lip, this will

be different from patient to other. Generally, there are 1-2 mm showing from the

incisors in the average dentulous patient. In fact, each case should be considered

separately in relation to the height of the lip, age of the patient and the sex of the patient

e.g. for the patient that have long lip the height of the occlusal plane should be with the

border of the upper lip, while for the patient with short lip there should be more than 2

mm showing from upper lip. So each case should be considered separately for best

prognosis.

Fox Bite Plane

The anterior part of the wax rim should be parallel

to the inter-pupillary line (imaginary line running

between the centers of the 2 pupils of the eyes when

the patient is looking straight forward).

It is an appliance used to check the parallelism of the

wax occlusal rim anteriorly and posteriorly.

6

Posteriorly the occlusal plane starting from the

canine region backward should be parallel to the

(Camper’s line), this is a line running from the ala

of the nose to the superior border of the tragus of

the ear (Ala-tragus line).

1

Prosthodontics

Second grade

Lec 7 Dr. Suha Saadi

Temporomandibular Joint(TMJ)

Before studying the maxillo-mandibular relation, it is mandatory to know in depth

about the various movements possible between both jaws. Mandibular movements occur

around the TMJ, which is capable of making complex movements.

There are two basic mandibular movements:

1. Functional mandibular movements are natural and characteristic movements that

occur during mastication, speech and yawning.

2. Parafunctional movements are unnatural and non-characteristic movements like

clenching and bruxism.

Temporomandibular Joint TMJ

It is the articulation of the condylar process of the mandible and the intra-articular

disk with the mandibular fossa of the squamous portion of the temporal bone; it is a

Ginglymoarthrodial joint.

*Ginglymoarthrodial joint: any joint, such as the temporomandibular joint, capable of

both hinging and gliding articulation.

Parts of temporomandibular joint:

1. The mandibular or glenoid fossa.

2. The condyle or head of the mandible.

3. The articular disc or Meniscus which is found between the

condyle and the glenoid fossa. It divides the synovial joint or

TMJ into upper (superior) and lower (inferior) compartments.

4. Synovial (joint) cavities.

2

Movement in the upper joint compartment is mostly translational, whereas that in

the lower joint compartment is mostly rotational. The joint connects the mandibular

condyle to the articular fossa of the temporal bone with the temporomandibular disk

interposed.

The differences between the TMJ and the other Joints in the body are:

1. The TMJ has an articular disc which completely divides the joint spaces into upper

and lower joint compartments.

2. TMJ is Ginglymoarthrodial Joint.

a. Hinge action (rotation).

b. Slide action (transition).

3. The relationship of teeth affects the relationship of the articulating components.

4. The mandible is the only bone in the body hinged on both ends that is not capable of

independent movement at one end.

3

The muscles that control the movement of the mandible could be considered

in 3 groups:

1. Closing muscles: The masseter, temporalis and

medial pterygoid muscles supply the power for

pulling the mandible against the maxillae (elevating

and closing mandible).

2. Gliding muscles: The lateral pterygoid muscles

connect the mandible to the lateral pterygoid plate

and act to protrude the jaw or to move it laterally

(gliding).

3. Opening muscle: The muscles that depress the

mandible (open) consist of four groups,

suprahyoid muscles, platysma muscles,

infrahyoid muscles and lateral pterygoid

muscles.

4

The mandibular bone has specific relationships to the bones of the cranium. The

mandible is connected to the cranium at the two TMJ by the temporomandibular and

capsular ligaments. The sphenomandibular and stylomandibular ligaments also

connect the bones in such a way as to limit some motions of the mandible.

The function of the ligaments is to stabilize the joints by limiting the movements,

ligaments do not stretch but it could be elongated and the elongation of the ligament

could compromise normal joint function.

*Occlusion is one of the most important parts for the treatment of the patients with

complete dentures. The TMJs affect the dentures and likewise the dentures affect health

and function of the joints.

The ligaments that affect the

movement of the mandible are:

1. Temporomandibular and capsular ligaments.

2. Sphenomandibular ligament.

3. Stylomandibular ligament.

5

Mandibular axes

There are three axes around which the mandibular movements take place in

horizontal, sagittal and frontal planes. These axes include the followings:

1. Horizontal (hinge or transverse) axis:

An imaginary line passing through the two

condyles, around which the mandible may rotate

within the sagittal plane (During the opening and

closing (hinge) movement.

2. Sagittal axis of the mandible:

An imaginary anterio-posterior line around which

the mandible may rotate when view in the frontal

plane. It occurs when one condyle moves

downward with lateral extrusion.

3. Vertical axis of the mandible:

An imaginary line around which the mandible may

rotate through the horizontal plane. This movement

occurs when the mandible moves in lateral

extrusion.

Prosthodontics

Lecture -8- Dr. Rehab Aamer

Maxillo-Mandibular Relation

*Maxillo-mandibular relationship record: It is the registration of any positional relationship of the mandible relative to the maxilla. These records may be at any vertical, horizontal or lateral orientation. Types of jaw relation: A- Vertical jaw relation: 1- Vertical relation of rest position. 2- Vertical relation of occlusion. B- Horizontal jaw relation: 1- Centric jaw relation. 2- Eccentric jaw relation (Lateral jaw relation and Protrusive relation). A- Vertical jaw relation: *Vertical dimension: It is the distance between two selected points, one on a fixed (maxilla) member and one on a movable (mandible) member. In general the vertical measurements of the face could be recorded between any two arbitrary selected points which are usually located one above the mouth at the tip of nose and the other below the mouth at the tip of chin in the midline region.

*Rest position (physiological rest position): It is a postural position of mandible when an individual is resting comfortably in an upright position and the associated muscles are in a state of minimal contractility.

*Rest vertical dimension: It is the distance measured when the mandible is in the rest position. *Occlusal vertical dimension: It is the distance measured between two points when the occluding members are in contact. (Occluding teeth or occlusal rims are in contact). *Interocclusal distance (freeway space): It is the distance between the occluding surfaces of the maxillary and mandibular teeth when the mandible is in its physiological rest position. -The difference between the R.V.D. (Rest vertical dimension) and O.V.D. (occlusal vertical dimension) is the interocclusal distance (freeway space) and equal 2-4 mm. R.V.D. – O.V.D. = Inter occlusal distance (2-4 mm).

Importance of vertical dimension: 1. Functional roles include: (a-Mastication, b- Respiration, c- Deglutition, d- Phonetics).

2. Psychological role. 3. Esthetic role.

4. Comfortable role by maintenance health of tissue, mucosa, bone, muscles and T.M.J. (Temporomandibular joint). Consequences of incorrect vertical dimension: A- Increased vertical dimension: 1. Interference with speech. 2. Sensation of bulk (bulky denture). 3. Premature contact of upper and lower teeth. 4. Instability of dentures due to their excessive height. 5. Accelerated resorption of residual alveolar ridge. 6. Loss of biting power. 7. Clicking of teeth in speech and mastication. 8. Muscular fatigue. 9. Separated upper and lower lip with poor esthetics. 10. Apparent inability to open mouth widely. 11. Inharmonious facial proportion. 12. Excessive display of artificial teeth and gum. B- Decreased vertical dimension: 1. Presence of wrinkles and folds (not due to age). 2. Loss of biting power. 3. Muscular fatigue. 4. Neuralgia. 5. Pain in the region of TMJ. 6. Cheek biting. 7. Thin lipped appearance. 8. Decreased facial height with prominence of lower jaw and chin. 9. Angular cheilitis (inflammation of the lips) due to folding of the corner of the mouth.

Methods of recording vertical relation:

A- Methods of recording rest vertical dimension: *Since we are recording a physiological rest position, all the muscles affecting this record should be relaxed. Signs like tension, strain, and nervousness can alter the position of the mandible.

1. Facial measurements: Instruct the patient to sit

upright and relax, then ask the patient to wipe his lips with his tongue, to swallow and to drop his shoulders. When the mandible drops to rest position the measurement between the points of reference (nose and chin) is taken.

2. Tactile sensation: Instruct the patient to stand erect and open the jaws widely until strain is felt in the muscles. When this opening becomes uncomfortable ask him to close slowly until the jaws reach a comfortable relaxed position. Measure the distance between the reference points and compare it with the measurements made after swallowing.

3. Phonetics: The patient is asked to repeatedly

pronounce the letter "m" a certain number of times. When the lips touch, ask him to stop all jaw movement. At this time the measurement between the two reference points is taken.

4. Facial expression: The experienced dentist may notice the relaxed facial expression when the patient's jaws are at rest. In normally related jaws the upper and lower lips should have a slight contact in a single plane. Also the skin around the eyes and chin should be relaxed. It should not be stretched, shiny or excessively wrinkled.

5. Anatomical landmarks: The Willis guide is designed to measure the distance from the pupils of the eye to the corner of the mouth and the distance from anterior nasal spine to the lower border of the mandible, if both these distances are equal, the jaws are considered at rest.

6. Electromyographic method: Electromyography is a special device that measures the tone (activity) of the masticatory muscles, when the tone is at its minimum level, this means these muscles are in rest position and the jaws are at rest position too.

B- Methods of recording occlusal vertical dimension: 1. Methods of pre-extraction records. 2. Methods without pre-extraction records.

1. Methods of pre-extraction records:

These records are made before the patient extracts all the opposing teeth and loses his occlusal vertical dimension, these records are: a. Profile photographs: These photographs are made and enlarged to the same size of the patient’s head. They should be taken in maximum occlusion then the measurements of anatomical landmarks on the photographs are compared with the same landmarks on the face. These measurements can be compared when the artificial teeth are inside mouth. b. Profile silhouettes: A reproduction of the profile in silhouettes can be cut out in cardboard or contoured in wire. These can be repositioned on the face after vertical dimension is established at initial recording (occlusion rims) or when the artificial teeth are inside mouth.

c. Radiographs: The cephalometric profile radiographs and the radiographs of the condyles in the fossae are used to determine the vertical jaw relation but their use is limited due to the inaccuracy of the technique. d. Articulated casts: when the patient is dentulous, a maxillary and mandibular casts are made and mounted in centric relation on an articulator then after the extraction of teeth and the mounting of the edentulous casts on the articulator, the inter-arch measurements are compared. e. Facial measurements: Two tattoos are marked on the upper and lower halves of the face before extraction. The vertical dimension is measured at occlusion and recorded. This measurement is used after extraction. f. Measurements of former dentures: Patient's previous denture can be used to compare the measurements with measurements that made during the recording procedure. These measurements can be correlated with observation of the patient's face to determine the amount of change required. 2. Methods without pre-extraction records: A. Power point (by Boos): A metal plate is attached to the maxillary record base. A bimeter is attached to the mandibular record base. This bimeter has a gauge, which shows the amount of pressure acting on it. The record bases are inserted into the patient mouth and the patient is asked to bite on it at different degrees of jaw separation. When the highest value is reached, this is calledthe power point which represents the occlusal vertical dimension. B. Neuromuscular perception: A central bearing device attached to accurately adapted record bases permits the

patient to experience (through the neuromuscular perception) the different vertical relations. The central bearing screw is adjusted downward and upward until the height of the contact feels right to the patient and this represents the occlusal vertical dimension. C. Swallowing threshold: The theory behind this method is that when a person swallows, the teeth come in contact together with a very light contact at the beginning of swallowing cycle. This factor can be used as a guide to determine occlusal vertical dimension. The technique involves building cones of soft wax on the lower record base so that it will contact the upper occlusion rim with the jaws too wide open. The flow of saliva is stimulated by a piece of candy. The repeated action of swallowing the saliva will gradually reduce the height of the wax cones to allow the mandible to reach the level of occlusal vertical dimension. D. Phonetics: Phonetics methods are widely used to evaluate the proper vertical dimension of occlusion. During pronunciation of sounds like (ch, s and j) the upper and lower teeth reach their closest relation without contact.

Prosthodontics

Lecture -9 – Dr. Rehab

Horizontal Jaw Relation

Horizontal jaw relation: It is the relationship of the mandible to

the maxilla in the horizontal plane. It can also be described as

the relationship of the mandible to the maxilla in antero-

posterior and side to side direction.

- The horizontal jaw relations include:

1. Centric jaw relation.

2. Eccentric jaw relation.

a) Protruded or forward relation.

b) Right or left lateral relation.:

1. Centric jaw relation:

The “Glossary of Prosthodontic Terms” lists more than seven

different definitions of centric relation. Although these

definitions are somewhat different, all of them indicate that

centric relation is determined by the TMJ structures and not by

the dentition.

1. Centric relation: the maxillomandibular relationship in

which the condyles articulate with the thinnest avascular

portion of their respective disks with the complex in the

anterior-superior position against the slopes of the articular

eminencies.

This position is independent of tooth contact. This position is

clinically discernible when the mandible is directed superior

and anteriorly. It is restricted to a purely rotary movement

about the transverse horizontal axis (GPT-5)

2. “The most retruded physiologic relation of the mandible to

the maxilla to and from which the individual can make

lateral movements."

Centric occlusion: the occlusion of opposing teeth when

the mandible is in centric relation. This may or may not

coincide with the maximal intercuspal position.

Importance of centric jaw relation (significance):

1. It is a reference position from which the mandible can move

to any eccentric position and return back involuntarily.

2. It is learnable, repeatable and recordable position.

3. It is the start point for developing occlusion.

4. Functional movements like chewing and swallowing are

performed in this position, because it is the most unstrained

position.

5. It is a reliable jaw relation because it is bone to bone relation.

Methods of recording centric jaw relation:

1. Functional methods. 2. Graphic method. 3. Tactile or interocclusal check record method.

1. Functional Method or Chew-in Method

These methods utilize the functional movements of the jaws to record the centric relation. The patient is asked to perform border movements such as protrusive and lateral excursive movements in order to identify the most retruded position of the mandible. A. Needles-house method:

Four metal beads or styli are embedded into the

premolar and molar areas of the maxillary

occlusal rim.

The occlusal rims are inserted into the patient’s

mouth and asked the patient to close on the

occlusal rims and make protrusive, retrusive,

right and left lateral movements of the

mandible.

When the patient moves his mandible, the metal

styli on the maxillary occlusal rim will create a

marking on the mandibular occlusal rim. When

all the movements are made, a diamond-shaped

marking pattern is formed on the mandibular

occlusal rim.

The posterior most point of this diamond pattern indicates

the centric jaw relation.

B. Patterson’s method:

Here occlusal rims made of modelling wax are

used. A trench or trough is made along the length

of the mandibular occlusal rim.

A 1:1 mixture of pumice and dental plaster is loaded

into the trench. The mandibular movement generates

compensating curves in the plaster and pumice. When

the plaster and pumice are reduced to the predetermined

vertical dimension of occlusion, the patient is instructed

to retrude the mandible and the occlusion rims are

joined together.

2. Graphic Methods

The graphic methods record a tracing of mandibular movement in one

plane (horizontal plane). These movements in the horizontal plane

describe a figure known as the Gothic arch tracing also known as arrow

point tracing. The apex of the tracing is the centric relation position and

the two sides of the tracing originating at that point being the limits of

lateral movements. A needle point tracing made on a tracing table coated

with carbon or wax can be used to indicate the relative position of the

upper and lower jaw in the horizontal plane. Graphic methods are either

intra-oral or extra-oral depending upon the placement of the recording

device. The extra-oral is preferable to the intra-oral tracing because the

extra-oral is more accurate, more visible and larger in comparing with

intra-oral tracing.

3. Tactile sense or interocclusal check record method: In the interocclusal method the centric relation is recorded by placing a recording medium between the record bases when the jaws positioned at centric relation. The materials that are commonly used for interocclusal records include plaster, wax, zinc oxide eugenol paste, impression compound, silicon and polyether. The patient closes into the recording medium with the lower jaw in its most retruded position and stops the closure at

predetermined vertical relation. This method is simple because there are no mechanical devices used in the patient mouth and this method has the advantage of causing minimal displacement to the recording bases in relation to the supporting bone.

The following instructions can assist the patient in retruding

the mandible:

1. Instruct the patient by saying, “Let your jaw relax, pull it

back, and close slowly and easily on your back teeth.”

2. Instruct the patient by saying, “Get the feeling of pushing

your upper jaw out and closing your back teeth together.”

3. Instruct the patient to protrude and retrude the mandible

repeatedly while holding his or her fingers lightly against the

chin.

4. Instruct the patient to turn the tongue backward toward the

posterior border of the upper denture.

5. Instruct the patient to tap the occlusion rims or back teeth

together repeatedly.

6. Tilt the patient’s head back while the various exercises just

listed are carried out.

7. Palpate the temporal and masseter muscles to relax them.

2. Eccentric jaw relations: Any relationship between the

jaws other than centric relation, which include: a) Lateral

jaw relation: it is the relation of the mandible to the maxilla

when the lower jaw is in a position to either side of centric

relation. b) Protrusive jaw relation: it is the relation of the

mandible to the maxilla when the mandible is thrust

forward.

Methods of recording eccentric jaw relation:

The main reason in making an eccentric jaw relation is to

adjust the articulator to simulate the eccentric movement

(lateral and protrusive) of the mandible to maxilla and to

establish balanced occlusion. The records are made in the

same manner as for centric relation record and these

include the functional, graphic and interocclusal record for

protrusive and lateral movements. Interocclusal eccentric

records may be made on the occlusion rim before the teeth

are set up or on the posterior teeth at the try-in

appointment. When this record is made on Hanau

articulator, the following formula is used to obtain an

acceptable lateral inclination:

L = H/8+12

L = lateral condylar path (inclination in degrees).

H = horizontal condylar path (inclination in degrees) as

established by the protrusive relation record from the

patient.

Prosthodontics

Lecture – 10 Dr. Rehab Aamer

Dental Articulator

Definition:

It is a mechanical instrument that represents the temporomandibular joints and

contains jaw members to which the maxillary and the mandibular casts can be

attached to simulate some or all mandibular movements.

Functions:

1- It allows most of the prosthetic work to be done in the absence of the patient

(diagnosis, treatment planning, setting-up of teeth, development of balanced

articulation and waxing-up of dentures).

2- It maintains jaw relation record during setting-up of teeth.

3- It aids in denture remounting after processing for correction of the occlusal

disharmony.

Types of dental articulators:

1- Simple hinge articulators (CL I).

2- Average (mean) value or fixed condylar path articulators (CL II).

3- Adjustable condylar path articulators:

a- Semi-adjustable condylar path articulators (CL III).

b- Fully-adjustable condylar path articulators (CL IV).

1. Simple hinge articulator (plane line):

It consists of upper and lower members join together at a certain

distance by a screw which acts at the back. The screw can increase or decrease the

distance between the two members and permits only a hinge like movement.

Movements:

This type of articulators gives only opening and closing movements.

Records required:

a- Vertical dimension of occlusion.

b- Centric relation records.

Disadvantages:

These articulators do not represent the temporomandibular joints and the dynamic

mandibular movements.

2. Average (mean) value or fixed condylar path articulator:

The upper and the lower members of this articulator are joined together by two

joints represents the TMJ. The horizontal condylar path is fixed at a certain angle

that ranges from 30o - 40o which is the average of most patients.

Movements:

1- Opening and closing.

2- Protrusive movement at a fixed condylar path angle.

Records required:

a- Vertical dimension of occlusion.

b- Centric relation record.

c- Face-bow record: In some designs of these articulators, the upper cast

can be mounted by a face-bow transfer.

*When the articulator dose not accepts a face-bow record, the mounting

is made according to Bonwill triangle.

Bonwill found in mandibles that the inter-condyle distance as well as the

distance from each condyle to the contact point of the lower central

incisors was 4 inches (equilateral triangle). An anterior pointer is

attached to the incisal pin of the articulator to locate the tip of the

occlusion rim labially and thus to orients cast in relation on the Bonwill

triangle.

Disadvantages:

a- Most of these articulators do not accept face-bow record.

b- The condylar path moves to a fixed angle and it is successful in

patients whose condylar angle approximates that of the articulator.

c- No lateral movements.

3. Adjustable condylar path articulators:

This type of articulators differs from the fixed condylar path articulators in that it

has adjustable condylar path and adjustable incisal guidance. They can be

adjusted so that the movements of its jaw members closely resemble all movements

for each individual patient.

a- Semi-adjustable condylar path articulators:

In these articulators, the horizontal condylar path is adjusted by a

protrusive record obtained from the patient. The lateral condylar path inclination

is adjusted according to Hanau’s formula:

L= H/8+12.

(L) = the lateral condylar path. (H) = the horizontal condylar path.

Some semi-adjustable articulators are non-arcon, while others are

arcon. The term arcon is commonly used to indicate an instrument that has its

condyles on the lower member and the condylar guides on the upper member.

Non-arcon semi-adjustable articulator arcon semi-adjustable articulator

Movements:

1. Opening and closing.

2. Protrusive movement according to the horizontal condylar path

angle determined from the patient.

3. Lateral movement to the angle estimated from the Hanau’s formula.

4. Some types have Bennett movement (immediate side shift).

Records required:

a- Face-bow record to mount the upper cast.

b- Vertical dimension and centric relation to mount the lower cast.

c- Protrusive record to adjust the horizontal condylar path inclination

of the articulator.

Disadvantages:

1- The lateral condylar path angle is determined from the formula.

2- Most of these articulators have no Bennett movement.

b- Fully-adjustable condylar path articulators:

The fully-adjustable articulators differ from the semi-adjustable articulators in that

the lateral condylar path inclinations are

adjusted according to records taken from the patient.

Movements:

The same movements of the semi-adjustable articulators in addition

they have Bennett movement.

Records required:

a- Face-bow record to mount the upper cast.

b- Vertical dimension and centric relation to mount the lower cast.

c- Protrusive record to adjust the horizontal condylar path inclination.

d- Right lateral record to adjust the lateral condylar path inclination.

e- Left lateral record to adjust the right lateral condylar path

inclination.

Disadvantages:

Multiple records are required with the possibility of errors.

* The semi-adjustable articulators are usually enough for complete

denture construction.

Face-bow

The face-bow: It is a caliper like device that’s used to record the

relationship of the maxilla to the temporomandibular joints (or to the opening axis

of the jaws) and to orient the maxillary cast to the opening

axis of the articulator depending on this record.

The face-bow consists of:

1. U-shaped frame.

2. The condyle rods.

3. The fork.

Types of face-bow:

1- The kinematic (mandibular hinge axis locator) face-bow: It is used to

locate the kinematic (true or terminal) transverse hinge axis then

recording the relation of the upper jaw to that hinge axis and

transferring the relation to the articulator.

*The transverse hinge axis is an imaginary line in which the mandible

rotates during opening and closing.

2- The arbitrary face-bow:

It is used to record the position of the upper jaw in relation to the

hinge axis and transferring this relation to the articulator. The arbitrary

face-bow is oriented to an arbitrary hinge axis (within 5mm distance

from the true terminal hinge axis).

The ear face-bow is designed to utilize an arbitrary axis by fitting

into the external auditory meatus.