Presentation on theme: "COMPONENTS OF A REMOVABLE PARTIAL DENTURE Dr. Waseem Bahjat Mushtaha Specialized in prosthodontics."— Presentation transcript:
COMPONENTS OF A REMOVABLE PARTIAL DENTURE Dr. Waseem Bahjat Mushtaha Specialized in prosthodontics
A removable partial denture will have some of the following components: I-Major connector 2-Minor connector 3-Rests 4-Direct retainers (clasps) 5-Indirect retainers 6- One or more denture bases and replacement teeth
I- MAJOR CONNECTORS The major connector connects the parts of the prosthesis located on one side of the arch with those on the opposite side. All other parts of the partial denture are attached to it either directly or indirectly.
Requirements of major connectors 1- Must be rigid to transmit stresses of mastication from one side of the arch to the other. 2- Must be properly located in relation to gingival and movable soft tissues. 3-must not impinge on the gingival margin. 4-provide an opportunity of positioning denture bases were needed 5-maintain patients comfort by covering little tissues, avoid. food trap and avoid bony and soft tissue prominence during insertion and removal
MAXILLARY MAJOR CONNECTORS Design specifications: I-The borders are placed a minimum of 6 mm from gingival margins or are positioned on the lingual surfaces of the teeth. 2-Reliefis normally not required under the major connector. 3- The posterior palatal bar or strap should be located as far posteriorly as possible without contacting the movable soft palate. 4-All borders should taper slightly towards the soft tissue. 5-Both anterior and posterior borders should cross the midline at right angles, never diagonally. 6- The thickness of the metal should be uniform throughout the palate.
7-The finished borders of the metal should be gently curved, never angular. 8- The metal should be smooth but not highly polished on the tissue side. ( to avoid delete fine details ) 9-All borders on the soft tissue should be beaded with the bead fading out near the gingival margin of the teeth.
TYPES OF MAXILLARY MAJOR CONNECTORS The term bar is used whenever the anteroposterior width of the major connector is less than 8 mm. If the anteroposterior width of the major connector is in the 8 to 12 mm range the term strap is applied. When more than 12 mm is covered the term palatal plate is used. If the entire palate is covered, the term complete palatal plate is used.
The following types of maxillary major connectors are used: 1-single palatal bar 2-anteroposterior, or double, palatal bar. 3-single palatal strap. 4-horseshoe, or U-shaped connector 5-closed horseshoe or anteroposterior palatal strap. 6-complete palatal plate
1- SINGLE PALATAL BAR Indications: In tooth- borne partial denture when second premolars and or first molars are missing. Design: I -It is a narrow half oval with its thickest point at the center. 2-It is gently curved and should not form a sharp angle at the junction with the denture base. 3-It should not be placed further anterior to the second premolar. This position is favorable for the tongue action. Disadvantages: l-For a single bar to maintain any degree of rigidity it should be bulky (less acceptable by the patient). 2-It drives little support from the bony palate because its narrow anteroposterior width. 3- Its use is limited to replace one ore two teeth on each side of the arc.
II-ANTEROPOSTERIOR PALATAL BAR Indications: 1 -It can be used in any class specially when the anterior and posterior abutments are widely separated. 2-When a patient objects a large amount of palatal coverage. 3- In patients with large palatal torus. Design: 1-The anterior bar is flat but narrower than the palatal strap. 2-The posterior bar is half oval similar to the single bar but less bulky. 3- The two bars are joined by flat longitudinal bars on each side palate
Advantages: 1-It is rigid because it lies at different planes. 2-It offers little tissue coverage. Disadvantages: The anteroposterior bars should not be considered as the first choice because of the following disadvantages: 1-Provides little support from the palate. 2- The anterior bar covers the rugae area and may interfere with phonetics and patient's comfort. 3-Because the bars are narrow, extra bulk is required for rigidity.
III- SINGLE PALATAL STRAP Indications: 1- In most maxillary tooth borne partial dentures when posterior teeth are missing. 2- In tooth-mucosa borne partial dentures when the extension base is short. Design: I-It consists of a wide, thin band of metal that crosses the palate. Its anterior border should be posterior to the rugae area and the posterior border should terminate short of the junction of the hard and soft palate. 2-Anteroposterior width is within the 8- I 2mm range. Advantages: 1- Rigid because it is wide and located in different planes. 2- It increases patient comfort because it is thin. 3-It provides support to the partial denture since it covers a relatively large area of the palate. Disadvantages: The patient may complaint from excessive palatal coverage.
IV- HORSESHOE OR U-SHAPED CONNECTOR Indication: 1-When several anterior teeth are being replaced. 2-In tooth-borne partial dentures with anterior and posterior teeth are missing. 3-When a hard midline suture or palatal torus cannot be covered.
Design: I-It consists of U-shaped thin band of metal of 6-8 mm In width. 2-The borders must be either 6mm away from the gingival margin or extend onto the lingual surfaces of the teeth. 3-The connector should be uniform in thickness, symmetric, and with curved and smooth borders Advantages: 1- It solves the problem of missing anterior teeth especially when there is deep anterior vertical overlap 2- It offers a definite advantage in the presence of hard median suture or large torus. Disadvantages: I-Tends to be less rigid than other connectors as a buccolingual movement may occur in the posterior area. 2-It covers the rugae area and interferes with phonetics and patient's comfort.
V- ANTEROPOSTERIOR PALATAL STRAP (CLOSED HORSESHOE) Indications: 1- In tooth borne, and mucosa borne partial dentures when replacement of anterior and posterior teeth is required. 2- When a palatal torus exists.
Design: 1- The anterior strap should be positioned as back as possible on the rugae area 2- The posterior strap should be placed as far back as possible on the hard palate. 3-The borders of the connector should be placed 6 mm away from the gingival margins or should extend above the height of contour of the teeth Advantages: I-It is rigid because it lies at to different planes. 2-lt provide good support to the partial denture. Disadvantages: May be not accepted by some patients due to multiple borders and coverage to the rugae area
VI-THE COMPLETE PALATAL PLATE Indications: 1-In long span bilateral tooth-mucosa borne partial denture with and without anterior teeth replacement. 2-Should be used whenever maximum tissue support is desired. 3-ln patients with palatal defects. 4-Maximum palatal coverage should be considered in the presence of poor residual ridge, periodontal disease, increased muscular force and poor bone indices. 5-In transitional partial denture.
Design: 1-The anterior border should be 6 mm away from the gingival margin. 2-Posterior borders are extended to the junction of movable and immovable soft palate. 3-The posterior border is beaded to prevent debris from collecting beneath the plate.
Advantages: 1-It offers maximum rigidity support and retention to the partial denture. 2-It is made in a uniform thin metal plate, which reproduce anatomic contour of the palate and feel natural to the patient. Disadvantages: 1-Often cannot be used in the presence of a palatal torus. 2-Complete palatal coverage may alter taste and tactile sensation.
Types of palatal plates I-Complete cast metal plate covering the entire palate. It may not be relined easily 2-Complete resin-plate, which can be relined or rebased 3-Combination of anterior metal with posterior resin area. The resin area may be relined or rebased
MANDIBULAR MAJOR CONNECTORS Design specifications: 1-The superior borders are placed at least 3 mm from the gingival margins. Where a 3mm distance from the gingival margins cannot be obtained the metal should extend onto the cingula of anterior teeth or onto the lingual surfaces of the posterior teeth. 2- The inferior border should not interfere with the soft tissue movement of the floor of the mouth. 3-Relief of the tissue surface of the major connector is required to prevent tissue impingement at rest or during function. 4-The metal should be highly polished on the tissue side to minimize plaque accumulation,
TYPES OF MANDIBULAR MAJOR CONNECTORS 1-Lingual bar. II-Sublingual bar. III- Double lingual bar. IV- Lingual plate. V-Labial bar.
I-Lingual bar Indication: It is the first choice major connector, should be used whenever the functional depth of the lingual vestibule equal or exceed 8 mm. Design: l-The bar should be half pear-shaped in cross section. Superior inferior dimension is 5 mm, and it is 2 mm in thickness. 2- The superior border of the bar should be located at least 3 mm from the gingival margins of all adjacent teeth. 3- The Inferior border may be placed at the functional depth of the lingual vestibule. 4-Relief of the tissue surface of the bar major connector is necessary.
Advanlages: 1- The simplest mandibular major connector with highest patient acceptance. 2-lt does not cover the teeth or the gingival tissues. Disadvantages: If it is not properly designed it may not be rigid
II-Sublingual bar Indications: When the lingual bar cannot be used because of a lack of functional depth of the lingual vestibule (depth of 5-7 mm). Design: 1-The sublingual bar is essentially a lingual bar rotated 45 degrees. 2- The superior border of the bar should be located at least 3 mm from the gingival margins of all adjacent teeth. Advantages: 1- It does not covers the teeth or tissues. 2-More rigid than a lingual bar in the horizontal plane. Disadvantages: A functional impression of the vestibule is required to accurately register the position and contour of the vestibule.
III-The double lingual bar Indications: 1- When indirect retention is required. 2- When periodontally affected teeth that require splinting are present. Design: 1 -It is made of two bars; cingulum bar (Kennedy bar) and the conventional lingual bar. A rigid minor connector at the embrasure between the canine and first premolars joins the two bars. Rests are placed at each end of the upper bar attached to the minor connector 2- The lower bar has the same design as a single lingual bar 3- The upper bar is scalloped, and half-oval in cross section (2-3 mm high, and 1 mm thick at its greatest diameter). Advantages: 1-Provides indirect retention. 2-Contributes to horizontal stabilization. 3-No gingival margin coverage. Disadvantages: I-Tongue annoyance. 2-Food impaction if the upper bar is not in intimate contact with the teeth
IV-Lingual plate Indications: 1-When the functional depth of the lingual vestibule (less than 5 mm) is not enough for bar placement, 2-When future loss of natural teeth is anticipated to facilitate addition of artificial teeth to the partial denture. 3- when splinting of anterior teeth is required. 4- When lingual tori are present.
Design: 1-It consists of a pear shaped lingual bar with a thin metal extending upward from the superior border of the bar onto the lingual surfaces of the teeth above the cingula and survey lines 2-ln extension base partial denture the lingual plates should have a rest on each side to prevent labial movement of the teeth. 3- There should be adequate blockout and relief of the soft tissue undercuts, undercuts in the proximal areas of the teeth, the free gingival margins and the pear shaped bar.
Advantages: 1-The most rigid mandibular major connector. 2- It gives indirect retention to the partial denture. 3-Deflect food from impacting on lingual tissues. 4-Provide resistance against horizontal or lateral forces. 5- Permits the replacement of lost tooth without remaking the partial denture. 6-Help in splinting and prevent super-eruption of the anterior teeth. Disadvantages: Covers more tooth and gingival tissues than other mandibular major connectors.
V-Labial bar Indications: 1- When the mandibular teeth are so severely inclined lingually as to prevent the use of lingual major connector. 2- When large lingual tori exist and their removal is containdicated. Design: 1- It is a half pear shaped bar, runs across the mucosa labial to the anterior teeth. 2-Labial vestibule should be adequate to allow the superior border to be place at leas 3mm below the free gingival margins. 3-Reliefis required beneath the bar. Advantages: It solves the problem of severely inclined teeth and avoids surgical intervention to remove a large torus. Disadvantages: 1-It tends to lack rigidity since it is considerably longer than a lingual bar. 2- The least comfortable mandibular major connector.
MINOR CONNECTORS Definition: A minor connector is a rigid component that links the major connector or base and other components of the partial denture such as rests, indirect retainers and clasps.
Functions: 1- Transmit forces to the abutment teeth. 2-Transfer the effect of retainers, rests and stabilizing components to the rest of the denture. Design specifications: 1-Should have sufficient thickness for rigidity. 2-Should exhibit minimal gingival coverage; the lingual minor connector should cross the gingival margins directly, joining the major connector at rounded right angle, 3-Slight relief is required when crossing the gingival margin especially in tooth-mucosa borne dentures. 4-Should be highly polished to minimize plaque accumulation. 5-Should be located at least 5mm from other vertical components