5

Maxillary major connectors

Dr.Shanai M.

Major connectors cross section are shaped as.

A BAR-SHAPED major connector is long, narrow, and thick. In cross section bars are ½ round, ½ oval or ½ pear in shape.

A STRAP or PLATE-SHAPED major connector is long, wide and thin. The width of a strap or plate varies from 6 - 8 mm to the entire length of the palate.

There are six maxillary major connector designs

Single palatal strap
Single palatal bar
Combination anterior and posterior palatal strap-type connector
Palatal plate-type connector
U-shaped palatal connector
Anterior-posterior palatal bars

single palatal strap

Used to connect bilateral tooth-supported prosthesis, even those with short edentulous spaces, particularly when the edentulous areas are located posteriorly. Such a connector can be made rigid without objectionable bulk and interference with tongue


Indications:
1.tooth supported cases where no other connector can be used as Class III or
Class III mod.1 P partially edentulous arch.

Contraindications:

1. Tooth-tissue supported RPD.
2. Palatial torus.
3. Extremely long tooth supported edentulous space (A-P major connector would be better because it would cover less palatal tissue.)
4. It should never be used in cases involving distal extensions or replacement of anterior teeth since it must be made to bulky for rigidity.

Advantages:

1. Very simple design.
2. Posterior border is well anterior to the hamular notch- vibrating line.
3. Anterior border is posterior to rugae
4. Very few metal-tissue edges.

Single palatal bar

The palatal bar is a narrow halve oval with its thickest point at the center. The bar is gently curved and should not form a sharp angle at its junction with denture base. The palatal bar should only be used in tooth supported cases where no other connector can be used.

Disadvantage

It is usually objectionable due to its bulk consequently, patients find the palatal bar uncomfortable.
It should never be used in cases involving distal extensions or replacement of anterior teeth since it must be made to bulky for rigidity.

Combination anterior and posterior palatal strap-type connector

The anterior-posterior palatal strap provides maximum rigidity and minimum bulk. The strength of this connector lies in the fact that the anterior and posterior sections are joined together by longitudinal connectors on either side
Anterior component is a flat strap located as far posteriorly as possible to avoid rugae coverage and tongue interference. Anterior border of this strap should be located just posterior to a rugae crest and positioned on the appropriate slopes of prominent rugae, therefore allowing it to blend with the contours of the anterior palate .
Posterior strap is thin, a minimum of 8 mm wide, and Is located as far posteriorly as possible, yet entirely on hard palate. It should be located at right angles to midline rather than obliquely.

Indications:

1. Class III or Class III mod 1 partially edentulous arch with a long span edentulous space(s).
2. Class I or class II partially edentulous arch where adequate support, retention, bracing, and direct-indirect retention may be obtained from contact of the denture base with the ridge and the contact of the frame work with the palate.
3. An inoperable palatal torus.
4. A RPD replacing anterior teeth.
Contraindication:
1. inoperable maxillary torus that extends posteriorly to soft palate (a broad U-shaped major connector is used).
2.Where the palatal opening will be less than 15 mm anteroposteriorly or mediolaterally.
3. Where support, retention, bracing, and direct-indirect retention from the palate is required.
4. Where a major connector with a simpler design may be used.


Palatal plate-type connector
The words palatal plate are used to designate any thin, broad, contoured palatal coverage used as a maxillary major connector and covering one half or more of the hard palate.
Anatomic replica palatal castings have uniform thickness and strength by reason of their corrugated contours.

Anatomic replica palatal major connector has several advantages:

1. Its Permits making of a uniformly thin metal plate that reproduces the anatomic contours of the patient’s own palate.
2. Its uniform thinness and the thermal conductivity of the metal are designed to make the palatal palate more readily acceptable to the tongue and underlying tissue
3. The corrugation in the anatomic replica add strength to the casting; thus permits fabrication of a thinner casting with adequate rigidity.
4. Intentional surface irregularities maintain the original uniform thickness of the plastic pattern (only electrolytic polishing is needed).
5. By feature of intimate contact, interfacial surface tension between metal and tissue provides the prosthesis with greater retention. (to resist the pull of sticky foods, the forces of gravity, coughing, sneezing etc.)

When the last remaining abutment tooth on either side of a class I arch is canine or first premolar, complete palatal coverage is strongly advised, especially when the residual ridges have undergone excessive vertical resorption. This may be accomplished in one of two ways :
A. Use a complete cast plate extending to junction of hard and soft palates
B. Use a cast major connector anteriorly, with retention posteriorly, for the attachment of an acrylic-resin denture base to the anatomic landmarks

U-shaped palatal connector

SYNONYMS: ANTERIOR PALATAL STRAP, HORSESHOE, OPEN RING, OPEN DOUGHNUT
From both the patients standpoint and a mechanical standpoint, the U-shaped palatal connector is the least desirable of maxillary major connectors. It should never be used arbitrarily.

INDICATIONS

in case of a large inoperable tori
When several anterior teeth are to be replaced.
In case of patients with exaggerated gag reflex.
When periodontically weakened anterior teeth need some stabilizing support.
A Class IV partially edentulous arch.
A Class III or Class III mod 1 P partially edentulous arch with an anterior edentulous space, where cross-arch force distribution is not important.
DISADVANTAGES
Its lack of rigidity allows lateral flexure under occlusal forces… induce torque or direct lateral force to abutment teeth.
Bulk to enhance rigidity results in increased thickness in areas that are a hindrance to the tongue.
The design fails to provide good support characteristics and may permit impingement of underlying tissue when subjected to occlusal loading

Anterior-posterior palatal bars

The antero-posterior palatal bar displays characteristics of palatal bar and palatal strap major connectors.
The anterior bar is relatively flat. Its cross-sectional shape is similar to that of a palatal strap. Borders of the anterior bar are positioned on the appropriate slopes of prominent rugae, thereby allowing it to blend with the contours of the anterior palate.




The posterior bar is a half oval, similar to the palatal bar major connector. the two bars are joined by flat longitudinal elements on each side of the palate. this configuration gives the effect of a circle and is considerably more rigid than any of the individual elements. the two bars, lying in different planes produce a structurally strong L-beam effect

Advantages

The main advantage of an antero-posterior palatal bar is its rigidity.
Minimizes soft tissue coverage, yet provides exceptional resistance to deformation.
Disadvantages
Uncomfortable
The bulk and contour of the connector may be bother some to the tongue and may interfere with phonetics.
As a general rule, the antero-posterior palatal bar should not be considered the first choice for maxillary major connector.it should be selected only after other choices have been considered and eliminated