|Year : 2014 | Volume
| Issue : 1 | Page : 17-21
Nonrigid semi-precision connectors for FPD
Ashfaq Yaqoob1, Nusrat Rasheed2, Junaid Ashraf3, Gowhar Yaqub4
1 Department of Prosthodontics, Government Dental College, Srinagar, Jammu and Kashmir, India
2 Makhdoomia Health Line Dental Centre, Srinagar, Jammu and Kashmir, India
3 Registrar, SKIMS Medical College, Srinagar, Jammu and Kashmir, India
4 Department of Health, Srinagar, Jammu and Kashmir, India
|Date of Web Publication||28-Apr-2014|
Makhdoomia Health Line Dental Centre, Natipora, Srinagar 190 015, Jammu and Kashmir
Source of Support: None, Conflict of Interest: None
In the practice of fixed prosthodontics, certain situations like pier abutments, tilted abutments pose problems with rigid connectors. If rigid connectors are used in this situation, the pier abutment will act as a fulcrum because of physiologic tooth movement, arch position of the abutment, and the retentive capacity of the retainers. A nonrigid connector may be preferred in fabrication of fixed partial denture (FPD) with pier abutment. In this prosthesis, the movement of the nonrigid connector is enough to prevent the pier abutment from serving as a fulcrum. This clinical report describes rehabilitation of a patient with FPD with pier abutment using semi-precision attachment. The technique used is simple, economical, and feasible in an ordinary laboratory set up.
Keywords: Matrix patrix, pier abutment, semi-precision attachment, tenon mortise
|How to cite this article:|
Yaqoob A, Rasheed N, Ashraf J, Yaqub G. Nonrigid semi-precision connectors for FPD. Dent Med Res 2014;2:17-21
| Introduction|| |
The use of rigid connectors (solder joints) between pontic and retainers is the preferred method for fabrication of most fixed partial dentures (FPDs).
In pier abutment FPDs, a rigid connector may not be an ideal choice due to: Difference in physiological tooth movement of different teeth. Curvature of the arch, the faciolingual movement of anterior tooth occurs at a considerable angle to the faciolingual movement of molar tooth. These movements can create stresses on the abutments in long-span prosthesis. Some means must be used to neutralize the effects of these forces. ,,,,,
Thus, use of nonrigid connector has been recommended to reduce this hazard.
A nonrigid connector, a stress breaking mechanical union of retainer and pontic, is usually recommended in such situation.
It is used in the form of key (tenon) attached to pontic and keyway (mortise) placed within the retainer.
The indications for the use of nonrigid connector in fixed prosthodontics are
- The existence of pier abutment, which promote a fulcrum-like situation that can cause the weakest of the terminal abutments to fail and may cause the intrusion of the pier abutment
- The existence of the malaligned abutment, where parallel preparation might result in devitalization. Such situation can be solved by the use of intracoronal attachments as connectors
- The presence of mobile teeth, which need to be splinted together with fixed prosthesis
- Long-span FPDs which can be distort due to shrinkage and pull of porcelain on thin sections of framework and thus, affect the fitting of the prosthesis on the teeth.
The four types of nonrigid connectors are
- Dovetail (key-keyway) or tenon-mortise type connectors
- Cross-pin and wing-type connector
- Split-type connector
- Loop-type connector.
It has been reported that rigid FPDs with pier abutments are associated with higher debonding rates than short-span prostheses. Thus, these restorations may result in marginal leakage and caries. Nonrigid connectors are suggested as a solution to these difficulties. 
This clinical report describes the prosthodontic management of an edentulous span on both sides of a pier abutment, with FPD having a nonrigid connector.
| Case Report|| |
A 27-year-old female patient reported to the Department of Prosthetic Dentistry with missing teeth #35 and # 37, and she had difficulty in chewing and esthetic problems. On examination, it was found that the patient had canine-guided occlusion bilaterally. Radiologically and clinically, the abutment teeth were having favorable criteria. After discussing all the treatment options and their pros and cons, it was decided to rehabilitate the case with five-unit FDP using nonrigid connectors on the distal aspect of pier abutment.
- Diagnostic casts were made [Figure 1]
- The tooth preparation of #34 was done for metal-ceramic FPD and nonrigid connector between the #36 and #38. The distal of the #36 was prepared to accommodate a nonrigid connector [Figure 2]
- Putty-wash impression (Aquasil, Dentsply, USA) was made for the preparation of the working model. It was poured in high-strength die stone (Kalabhai Karson Pvt Ltd, India). Interocclusal records were made using polyether paste (Ramitec, 3M ESPE, USA) [Figure 3]
- Provisional restoration was cemented [Figure 4]
- Die preparation was done [Figure 5]
- Cast was mounted on articulator with face bow transfer and was programmed using interocclusal records [Figure 6]
- Wax patterns for FPD with nonrigid connector were prepared. Initially, the anterior segment of first premolar and second premolar and first molar with the keyway (Mortise) on its distal aspect was fabricated. Followed by third and the second molars with key (tenon) on its mesial aspect was fabricated in wax and then casted. Tenon was made from plastic pieces taken from sterile disposable syringe [Figure 7]
- Wax pattern was fabricated and recess for the female was cut accordingly to fit the plastic tenon on distal aspect of pier abutment. Tenon was lubricated with petroleum jelly and then wax-up was completed for exact fit. Accurate alignment of mortise is crucial; it must be parallel to path of placement of distal retainer. This is accomplished with a dental surveyor (Williams Surveyor, Williams Dental Supply Co., Worcester, MA) [Figure 8]
- After casting, metal try-in of the individual units were done to verify proper seating. Then ceramic facing was added [Figure 9]
- At the time of cementation, mesial segment was placed first followed by cementation of distal segment [Figure 10] and [Figure 11].
| Discussion|| |
With rigid connectors, an occlusal load applied on the abutment tooth at one end of an FDP (mainly the molar retainer) with a pier abutment, the pier may act as a fulcrum. Tensile forces may then be generated between the retainer and abutment at the other end of the restoration (in the premolar retainer). Anterior or posterior abutments may experience extrusive force and the resultant tensile force at the retainer to abutment interface may lead to potential loss of retention for these restorations, thus resulting in marginal leakage, caries of abutment, and FDP failure. ,,,,, Nonrigid connector is usually recommended in such a situation.
There is a conflict in opinion on placement site of nonrigid connector. Markley  suggested placement on one of the terminal abutments and not at the pier abutment. Adams  suggested placing the connector at the distal side of pier, and if desired, adding one more at the distal side of the anterior retainer; while Gill  suggested placing it at one side or both sides of the pier.
Carl E Misch  recommended that in conventional fixed prostheses, the "male" portion of a nonrigid attachment usually is located on the mesial aspect of the posterior pontic; whereas, the "female" portion is in the distal aspect of the natural pier abutment tooth. This prevents mesial drift from unseating the attachment. However, an implant does not undergo mesial drifting, and the nonrigid connector location is more flexible. For a natural pier abutment between two implants, a stress breaker is not indicated.
Shillingburg et al.,  suggested placing the connector at the distal aspect of pier abutment. Since the long axis of the posterior teeth usually leans slightly in a mesial direction, vertically applied occlusal forces produce further movement in this direction. This would nullify the fulcrum effect and the patrix/male of the attachment would be seated firmly in place when pressure is applied distally to the pier. This position has been supported by finite element analysis study  done by Oruc et al. In this case, we have placed it on distal aspect of the pier.
The contraindications of using a nonrigid connector in a posterior five-unit FPD with a pier are as follows:
- Significant mobility of abutments
- If the span between the abutments is longer than one tooth
- If the distal retainer and pontic are opposed by a removable partial denture or an edentulous ridge, while the two anterior retainers are opposed by natural dentition, allowing the distal terminal abutment to supraerupt. ,
| Conclusion|| |
The bonhomie of rigid and nonrigid connectors can increase the life span of an abutment in five-unit FDPs as it transfers less stress on the abutments. Also, allowing physiologic tooth movement, it eliminates any hindrance as against a fixed restoration with all rigid connectors. A small amount of time spent can be a miracle in the long run. The selection of right type of connector is an important step when sorting treatment plan.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11]