|Year : 2012 | Volume
| Issue : 3 | Page : 190-193
Non-rigid connector in fixed partial dentures with pier abutment: An enigma simplified
Prince Kumar1, Vishal Singh2, Roshni Goel3, Harkanwal P Singh4
1 Department of Prosthodontics and Oral Implantology, Shree Bankey Bihari Dental College and Research Centre, Ghaziabad, India
2 Department of Prosthodontics and Oral Implantology, Dental College, Azamgarh, Uttar Pradesh, India
3 Department of Conservative Dentistry and Endodontics, IDST Dental College, Modinagar, Ghaziabad, India
4 Department of Oral Pathology, Swami Devi Dyal Hospital and Dental College, Panchkula, Haryana, India
|Date of Web Publication||26-Dec-2012|
Department of Prosthodontics and Oral Implantology, Shree Bankey Bihari Dental College and Research Centre, Masuri, N. H. 24, Ghaziabad,Uttar Pradesh
Source of Support: None, Conflict of Interest: None
In the fixed partial denture (FPD) prosthesis with rigid connectors, forces of mastication are transmitted to the terminal retainers, which make the middle abutment act as a class I lever fulcrum. This techno-clinical cycle often causes failure of the fixed partial dentures. To overcome this dilemma, a non-rigid connector may be incorporated on the distal aspect of the middle (pier) abutment. The non-rigid connector counterbalances the effects of these forces of leverage. This clinical report presents the use of a non-rigid connector in a long-span, five-unit FPD, replacing two missing teeth with an intermediate pier abutment.
Keywords: Connector, non-rigid connector, pier abutment, stress concentration
|How to cite this article:|
Kumar P, Singh V, Goel R, Singh HP. Non-rigid connector in fixed partial dentures with pier abutment: An enigma simplified. Int J Health Allied Sci 2012;1:190-3
|How to cite this URL:|
Kumar P, Singh V, Goel R, Singh HP. Non-rigid connector in fixed partial dentures with pier abutment: An enigma simplified. Int J Health Allied Sci [serial online] 2012 [cited 2019 May 20];1:190-3. Available from: http://www.ijhas.in/text.asp?2012/1/3/190/105086
| Introduction|| |
According to the Glossary of Prosthodontic terms, a connector is the portion of a fixed partial denture that unites the retainer(s) and pontic(s) or it is the component of a fixed partial denture prosthesis that joins the individual retainers and pontics together. The durability and performance of a Fixed Partial Denture largely depends on the type of occlusal relationship, area of missing teeth, distribution of stress, alveolar bone loss and condition of the periodontium.  Furthermore, the excessive flexing of a long-span FPD varies with the cube of the length of the edentulous span, which can lead to material failure of the prosthesis or an unfavorable response. Therefore, depending on the clinical condition and the patient demand, the clinician must be very cautious in selecting the type of connector for fixed prosthodontic treatment. Although, the rigid connectors are most commonly used, there are certain special circumstances where a non-rigid connector is required such as: 
This clinical report describes the use of a non-rigid connector in a long-span, five-unit FPD, replacing two missing teeth, with an intermediate pier abutment. Fixed prosthodontic rehabilitation with a non-rigid connector yielded a satisfactory result.
- Long-standing abutment (pier abutment) with edentulous spaces on either side that allow physiological tooth movement and relieve stress
- When it is impossible to prepare two abutments with a common path for the placement
- When prognosis of an abutment is uncertain; in such cases if the abutment fails only a portion of FPD needs to be remade
- In the mandibular arch, with an FPD consisting of anterior and posterior segments, a non-rigid connector is indicated, as the mandible flexes mediolaterally during the opening and closing strokes
| Case Report|| |
A 41-year-old male patient reported to the dental office with a chief complaint of difficulty in chewing, due to missing teeth on the left side. The medical history was found to be noncontributory. Intraoral examination revealed a missing left first premolar and first molar of the mandibular arch [Figure 1] and [Figure 2]. Initially, the patient was given an interim acrylic partial denture, with metal clasps, but she was not satisfied and was enthusiastic for a definitive fixed restoration of the same. Depending upon the patient's desire, her compliance toward the maintenance of oral hygiene, and the radiological status of the bone around the abutments, a definitive restoration with FPD of a non-rigid type design was decided on. The non-rigid connector design assembly consisted of, (a) a T-shaped extension key or a Tenon attached to the distal side of the retainer of the pier abutment (mandibular left second premolar), and (b) a Dove tail or keyway receptacle (Mortise) placed within the contours of the distal pontic (mandibular left first molar).
|Figure 2: Intraoral occlusal view of mandibular arch showing pier abutment|
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The step-by-step procedure was as follows:
- Primary impressions were made with an irreversible hydrocolloid material (Alginate, Dentsply, India) and diagnostic casts were obtained.
- Orientation jaw relation was recorded using a Face bow (Hanau Spring Bow™) and the primary casts were mounted on a Hanau™ semi-adjustable articulator, in centric occlusion (by Face bow transfer and wax interocclusal record). Mock tooth preparation was completed on the articulated casts to fabricate provisional restoration.
- The tooth preparation for the abutments was completed with certain special considerations as they were rotated following which a shoulder finish line was prepared at the gingival level. To accommodate the space for mortis, 0.75 to 1 mm of an extra amount of preparation was done on the distal aspect of the pier abutment. Gingival retraction was achieved with the application of Expasyl™ (Kerr, Orange, CA), a temporary retraction paste, for two minutes. The final impression was made with light and heavy-body consistency of poly vinyl siloxane, using the dual impression technique using a custom acrylic tray.
- Tray adhesive was applied over the special tray and a medium viscosity elastomer was loaded into the tray.A low viscosity elastomer was syringed over the prepared tooth surface and the tray with the impression material was seated over the prepared tooth surface. On the same day, provisional acrylic resin bridges were cemented using Relyx Temp™ Non Eugenol temporary cement (Dentsply, India) until the fabrication of final prosthesis was completed. The non-rigid connector design to be incorporated was first prepared in a wax pattern (custom-made).
- The incorporated design of a non-rigid connector consists of a mortise (female component) prepared within the contours of the retainer and a tenon (male component: 0.7 mm in width) attached to the pontic. The accurate alignment of the mortise is very critical; it must be parallel to the path of placement of the distal retainer. This is accomplished with a dental surveyor.
- After casting, a metal try-in of the individual units was performed, to confirm a proper seating of the framework [Figure 3]a-c. Subsequently, ceramic was added by the conventional layering technique [Figure 4]a-c.
- At the time of cementation, the mesial unit segment was placed first, followed by cementation of the distal segment. No cement should be placed in the keyway [Figure 5]a and b, [Figure 6] and [Figure 7].
|Figure 3: (a‑c) Intraoral view: Note the tooth preparation and metal trial with tenon and mortise components|
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|Figure 4: (a‑c) Non‑rigid connector, pier abutment, and final prosthesis on the master cast|
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|Figure 5: (a-b) Intraoral view of final prosthesis (cemented in two parts)|
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| Discussion and Summary|| |
The size, shape, location, design, occlusion, periodontal status, and selection of a precise connector play an imperative role in the long-term success of an FPD.  Overload, leverage, torque, and flexing that induce abnormal stress concentration are certain biomechanical factors that need a healthy technical consideration and analysis prior to the designing of components for an FPD. Connector size, shape, and position influence the success of FPD. Rigid and non-rigid connector designs have disparate effects on stress distribution and equilibration in a fixed partial denture with pier abutment.  Thus, restoration of two missing teeth with an intermediate pier abutment, with rigid connector FPDs, would result in the failure of prosthesis in the form of a fracture (most common). In masticatory and parafunctional activity the occlusal load on the pier abutment acts as a class I lever. Moreover, high stress concentration may be reported at pier abutments and at the cervical dentin near the edentulous ridge, resulting in excessive displacement at the terminal abutments. This factor plays an important role in the potential for failure in long-span FPD. The predictable use of a non-rigid connector assists in compensating the difference in resistance and retention form between the abutments. Bothelo and Dyson have shown that rigid FPDs with pier abutment are associated with higher debonding rates than a short-span prosthesis, and may result in microleakage and recurrent caries. 
Oruc et al., in 2008, conducted a stress analysis study and showed that when a non-rigid connector was incorporated distal to the pier abutment, the area of stress concentration in the pier abutment reduced. , They concluded that non-rigid connectors were a definite solution for such clinical conditions. Apart from these advantages, fabrication of the prosthesis with non-rigid connectors required more laboratory time and expense. Moreover the construction of a temporary bridge was more difficult, as abutment of the teeth was tilted. If the posterior abutment and pontic were either unopposed or opposed by a removable partial denture, and if the three anterior units were opposed by natural teeth, the key and the posterior units that were subjected to little or no occlusal forces might supraerupt.Therefore, accurate planning of the design philosophy was critical for the reflexive fit of non-rigid connectors, which prevented the leverage effect to a large extent and imparted it to the long-term success of the long-span FPD with pier abutments.
| Acknowledgment|| |
The Author would like to thank the patient for providing consent to use her photograph in this article.
| References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]