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MAJOR CONNECTORS. DEFINITION. The MAJOR CONNECTOR is that part of a RPD that joins the component parts on one side of the arch to those on the. Major Connectors. BDS III year. RPD Lecture. Timing- PM. Dr Deeksha Arya . Associate Professor. Department of prosthodontics. Components of a typical. Major Connectors IN RPD – Download as Powerpoint Presentation .ppt /.pptx), PDF File .pdf), Text File .txt) or view presentation slides online. DENTISTRY-.

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The major connector joins the components of a removable partial denture RPD on one side of the arch to those on the opposite side. This quality allows stresses that are applied to any portion of the partial denture to be effectively distributed over the entire supporting area.

Other components of the RPD can be effective only if the major connector is rigid. The greatest damage an RPD can produce is that which results from a flexible major connector.

The fact that dental technicians 3 and patients 4 do not prefer palatal plates, while dentists 5 prefer wide palatal strap or palatal plate major connectors because they distribute the force to wide surfaces, is quite interesting.

When the literature about force transmission at maxillary major connectors in free-end RPDs is examined, it is seen that quite different results are observed because of differences of major connectors in the type, shape, location, and the evaluation methods. Failure to provide rigid connection can result in uncontrolled and destructive forces on abutment teeth, mucosa, and bone.

Others 8 observe that anteroposterior bar- and U-shaped plate dentures yield better results when compared with palatal plate ones. Some studies show that anteroposterior bars are preferable to anteropalatal bars, U-shaped plates are preferable to palatal straps, 9 anteroposterior bars are preferable to anteropalatal bars, and palatal plates are preferable to posterior palatal bars. Most scientists prefer palatal plate major connectors. The force transmission in RPD designs with different major connectors has been analyzed by photoelasticity, 9 strain gauges, 9,10,14,15 brittle lacquer, 14 and holography.

Others 13 evaluated the elastic deformation on maxillary major connectors with different shapes and widths. One optical method in the medical and dental fields, photogrammetry, is becoming more popular for determining deformation properties in three dimensions. Major connectors must be rigid to have maximum efficacy. In this study, the deformation properties of four major connectors for maxillary Kennedy Class I RPDs were evaluated by a stereophotogrammetric method, and surface microcracks were observed by the fluorescence penetrant liquid inspection test under periodic loading conditions.

Proper guide planes and rest seats were prepared on these models, which were bilaterally edentulous distal to the first premolars. The wax models were cast in a hard aluminum alloy EtialEtibank. The wax spacer 1 mm thick was adapted to the entire edentulous portion of the maxillary metal model.

This master model with the spacer was then duplicated, and eight refractory casts were made. Two sets of four differently designed maxillary major connectors palatal plate, U-shaped plate, palatal strap, and anteroposterior bar were waxed.

The design consisted of circumferential buccal retentive clasp arms with mesial rests. Four mandibular frameworks were prepared so that they could be attached to the mandibular metal model. All castings were radiographed and found to be free of porosities and voids. When the mounting procedure was completed, two maxillary models could be mounted in an articulator against the same mandibular model to make a set.

Posterior plastic denture teeth simulating the teeth on the original standard models were selected and set. The RPDs were processed in conventional heat-activated acrylic resin denture base material Meliodent, Bayer.

A rigid plate including evenly spaced lines in 1-cm squares and photogrammetric control points of different heights, and a denture holder prepared from thermoplastic material were used to take photographs. The denture holder, including negative impressions of the occlusal tooth surfaces and allowing standard positioning of the dentures, was screwed onto the rigid plate Fig 1.

An SMK stereometric camera, designed for recording three-dimensional close-range objects in measureable form, 18 with Avipan glass film Agfa was used to photograph tissue surfaces. After making the first picture, the camera was moved mm to the left, and a second photo was taken to form a stereo pair of photographs.

Using the original relationship record, a pair of RPDs was used to mount the metal master models in the computerized hydraulic loading machine Dartec. The intaglio surface of the maxillary RPD from the same set was coated with a mix of elastomeric impression material Accuflex, GCseated on the metal master model, and allowed to set. The occlusal loading mean force of kg with a frequency of 4 Hz simulated vertical loading. Measurements were observed and recorded after three loading periods: Photographing procedures were carried out both before baseline and after each loading period, and the black-and-white film was developed with Kodak solution for the photogrammetric film process stereophotographs.


The film pairs mm apart were superimposed over each other by special analytic equipment Planicomp C, Carl Zeiss and changed to three-dimensional models. A computer program especially developed for this type of study was used. The X and Y coordinates were kept constant, and the Z axis heights were determined to make volume mm 3 calculations for the dentures. Figure 2 shows a representative perspective scene. These calculations were made for each period and for both the whole area and the special points Fig 3limiting each denture on the anterior and posterior borders.

As the special points are different for each major connector type, in the evaluation stage each major connector was analyzed by itself with respect to the characteristics of its special points. Also, the deformation characteristics of some special points having similar locations such as points 1 to 9 on the palatal plate and U-shaped plate designs; Figs 3a and 3b and Table 1 were investigated in different major connectors. In the photogrammetric part of the study, 1, coordinate points were used for calculating the whole area volume on three-dimensional models.

The data were analyzed using the repeated-measures analysis of variance ANOVADuncan’s multiple range test, the paired t test, and the independent t test. To detect the surface microcracks of the major connectors, fluorescence penetrant liquid Fluoreszierendes Eindringmittel was applied onto the surface of the dentures aftercycles. After 20 minutes, emulgator Hydrophiler Emulgator was applied for 5 minutes. After 5 minutes, processing material BT 70, Beta Proses was applied and left for 20 minutes.

Then, photographs were taken using the light of a W ultraviolet lamp Tiede. The palatal plate showed the most deformation. The effectiveness ranking of the major connector types in decreasing order of the amount of deformation were: The evaluation of difference between the points on the posterior median line and the special points that join the posterior margin to saddles showed significant differences for the palatal plate design on the left side and only after the first period; for the palatal strap design the difference was significant on the right side for all loading periods; and for the anteroposterior bar design the difference was significant on the right side at baseline and after the third loading period Table 1.

The evaluation of difference between the anterior points 10 and 11 and posterior points 7 and 8 corners that surround the circle Fig 3d on the median part of the anteroposterior bar design and the points on the median line points 9 and 6 showed that on the posterior part, there was a significant difference only for the left side after the first and second periods Table 1.

According to the independent t test results, there were no significant differences between the deformation amounts at nine special points points 1 to 9 on the palatal plate Fig 3a and the U-shaped plate Fig 3b that had same configuration on the anterior edge.

There were no microcracks on the surfaces of the U-shaped plate and anteroposterior bar major connectors Fig 4abut there were microcracks in both the palatal plate and palatal strap denture groups Fig 4b. In studies testing the elastic property of a metal object, biaxial hydraulic systems that simulate chewing are preferred. In these systems, the number of cycles that symbolize period change into 1, Values exceeding this produce significant flexure on partial denture frameworks, but the clinical reliability of these results is disputable.

This information was accepted as basic, and a load of kg was used for all dentures tested. Fig 4a Anteroposterior bar major connector that has no microcracks in the fluorescence liquid penetrant inspection test.

Fig 4b Microcracks arrow in the palatal strap major connector. In prosthetic dentistry, the amount of deformation of major connectors was first analyzed by the photogrammetric method used in this study. The statistical evaluation of the results of the photogrammetric study showed that deformation became evident generally aftercycles. The anterior median point had the least deformation in the U-shaped plate major connector.

This special point showed the highest deformation connectorw the palatal strap major connector. Right and left mesial rests showed the highest deformation in the palatal strap major connector. When the types of major connector were separately evaluated according to the difference of deformation between the posterior median point and the junction points of the posterior edge with saddles, no statistical difference was observed with the U-shaped plate major connector Table 1.

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For both palatal plate and anteroposterior bar major connectors, the results revealed differences in deformation amounts between these points. According to the results of the whole area, palatal plate dentures were deformed the most, and anteroposterior bar dentures were deformed the least among the dentures tested.

Palatal strap and U-shaped plate dentures were between these two groups in terms of deformation amounts. As the results of the photogrammetric and fluorescence penetrant liquid inspection test are congruent, it can be suggested that the results of both parts of this study ocnnectors each other. After microcrack evaluations, it was seen that there were microcracks in both the palatal plate and palatal strap major connector groups Fig 4b.

These results were in accordance with the photogrammetric evaluations, indicating that these two major connector designs had the highest deformation Table 2. In these type of major connectors, the wax plates over the palatal depth may be thinned by the finger pressure of the technician at the waxing stage. Therefore, during the waxing stage there must be no sudden changes in the sectional thickness, especially on the midpalatal depth, to avoid mahor thin places and protect the rigidity of the major connectors.

Flexibility allows forces to be concentrated on individual teeth or the edentulous ridge, causing damage to the periodontal support of the teeth, resorption of the bony ridge, and impingement and injury to the soft tissue beneath the major connector. But as a U-shaped plate major connector covers the inclined surfaces, it can only resist a very small part of the chewing majkr. At the same time, because of its anterior location, the cross-sectional area is not affected as much as in the palatal plate and palatal strap major connectors during the waxing stage; therefore, it is placed third in decreasing order of deformation amount.

The anteroposterior bar major connector, which had no microcracks Fig 4aspread the chewing force to a wide area because of its shape and structural property, maior showed the least deformation of the major connector types tested.

This result is concordant with the findings of other researchers. Major connectors must be rigid to perform their functions with maximum efficacy. This study investigated the deformation of four major connectors for maxillary Kennedy Class I removable partial dentures.

Major Connectors.

The designs were palatal plate, U-shaped plate, palatal strap, and anteroposterior bar. The deformation properties of major connectors were comparatively analyzed by two methods. In the photogrammetric part, a stereometric camera, Avipan glass films, and an analytic apparatus were used.

A computerized hydraulic machine was programmed to load the eight test dentures at 4-Hz frequency under a vertical load of kg and cohnectors maximum ofcycles. The fluorescence penetrant liquid inspection test was used to detect the surface microcracks. The anteroposterior bar msjor the least deformation. The other connectors, ranked in increasing order for the amount of deformation, were the U-shaped plate, the palatal strap, and the palatal plate.

There were comnectors microcracks in the U-shaped plate conbectors the anteroposterior bar designs. Anteroposterior bar major connectors showed the least deformation among the maxillary major connector types tested.

Microscopic cracks were seen in major connectors showing the highest degree of deformation and located at the depth of the hard palate. Int J Prosthodont ; References The major connector joins the components of a removable partial denture RPD on one side of the arch to those on the opposite side.

Stereophotogrammetric Method A rigid plate including evenly spaced conneectors in 1-cm squares and photogrammetric control points of different heights, and a denture holder prepared from thermoplastic material were used to take photographs.

Fig 2 Coordinate axes on a representative perspective for complete plate design. Fig 3a Special points that limit the major connectors at anterior and posterior edges for various designs: Fig 3b Limiting points on U-shaped plate. Fig 3c Limiting points on palatal strap.

Fig 3d Limiting points on anteroposterior bar.