|Year : 2017 | Volume
| Issue : 3 | Page : 136-139
The key to the management of pier abutment: An alternative approach
Ansu Kuruvila, Suja Joseph, Namratha L Jayalekshmi, Sujith K Menon
Department of Prosthodontics and Crown and Bridge, Pushpagiri College of Dental Sciences, Tiruvalla, Kerala, India
|Date of Web Publication||27-Jun-2017|
Department of Prosthodontics and Crown and Bridge, Pushpagiri College of Dental Sciences, Pushpagiri Medicity Campus, Perumthuruthy, Tiruvalla - 689 107, Kerala
Source of Support: None, Conflict of Interest: None
Pier abutment poses a challenge to prosthodontist. Rigid connectors are less than ideal treatment in case of these abutments. Nonrigid connectors have been recommended to reduce the forces as they provide a stress-breaking effect. This case report presents an alternative approach to the management of pier abutment. A 46-year-old female patient with missing teeth involving a pier abutment was rehabilitated with a fixed dental prosthesis with key-keyway connectors. An alternative method of orientation of the connector was used to benefit the patient.
Keywords: Key-keyway connector, nonrigid connector, pier abutment
|How to cite this article:|
Kuruvila A, Joseph S, Jayalekshmi NL, Menon SK. The key to the management of pier abutment: An alternative approach. J Int Oral Health 2017;9:136-9
|How to cite this URL:|
Kuruvila A, Joseph S, Jayalekshmi NL, Menon SK. The key to the management of pier abutment: An alternative approach. J Int Oral Health [serial online] 2017 [cited 2019 Aug 25];9:136-9. Available from: http://www.jioh.org/text.asp?2017/9/3/136/209053
| Introduction|| |
The preferred method of fabrication of most fixed partial dentures (FPDs) is rigid connectors between the pontic and retainers. However, completely rigid restoration is not indicated in all situations. For example, in case of pier abutment.
Pier abutment is an intermediate abutment for a fixed dental prosthesis. Moreover, an intermediate abutment is a natural tooth located between terminal abutments that serve to support a fixed/removable prosthesis. Pier abutment poses a challenge to prosthodontist. Restoration of pier abutments with rigid FPDs is associated with higher debonding rates than short-span prostheses. Thus, these restorations may result in marginal leakage and caries. Conversely, nonrigid connector functions as a stress breaker between retainer and pontic and have thus been recommended to diminish the forces instead of usual rigid connector. The movement in a nonrigid connector is enough to impede the transfer of stress from segment being loaded to the rest of the FPD. The most commonly used nonrigid connector comprises a T-shaped key (patrix/male) that is attached to the pontic and a dovetail keyway (matrix/female) placed within the retainer.,
| Case Report|| |
A 46-year-old female patient [Figure 1] reported to the Department of Prosthetic Dentistry with missing teeth #14 and #16, and was not happy with her appearance and had difficulty in chewing. On examination, it was found that the patient had canine-guided occlusion bilaterally. The patient had undergone root canal therapy on #15 due to pulpal involvement following caries. Clinical and radiological examination revealed healthy abutment teeth with favorable crown–root ratio. After discussing all the treatment options, prosthetic rehabilitation with a five-unit fixed dental prosthesis using nonrigid connectors on the distal aspect of pier abutment was planned. Plastic dovetail (Stern gold Attachments, Attleboro, MA, USA) was selected in this case. It had frictional retention, plastic pattern male and female, with built in paralleling mandrels.
- Tooth preparations were completed [Figure 2] and impression was taken with polyvinyl siloxane impression material
- Wax pattern was fabricated and recess for the female was cut accordingly to fit the plastic dovetail on mesial aspect of pontic [Figure 3]
- Surveying was done to determine the position/parallelism of plastic dovetail
- Plastic dovetail female was placed within the correct contour of the abutment tooth. Male pattern was removed from the female pattern, keeping inside of female pattern free of wax. Any extension of the female pattern above the occlusal of the abutment was left remaining
- After investing and casting, excess height of the female was reduced
- Male/patrix pattern was seated in the casted female. Casting of the male pattern was contemplated
- Now, matrix and patrix were assembled together [Figure 4]
- Metal try in [Figure 5]
- Porcelain fused to metal with buccal facing was done on #13–#16 and full metal restoration was done on #17. The prosthesis was cemented with glass ionomer cement [Figure 6], [Figure 7], [Figure 8], [Figure 9].
This approach improved the patient's mastication and esthetics and gave her a confident smile.
| Discussion|| |
Factors such as physiologic tooth movement, arch position of abutment, and retentive capacity of retainers make rigid connectors less than ideal treatment in case of pier abutments. Physiologic tooth movement in the buccolingual direction of different teeth ranges from 56 to 108 μ and apical movement/intrusion of 28 μ has been recorded for maxillary incisors. Due to the curvature of the arch, the faciolingual movement of an anterior tooth occurs at a substantial angle to the faciolingual movement of a molar. These movements in divergent directions can generate stresses in a long-span prosthesis that will be transmitted to retainers and their respective abutments teeth., Fulcrum like action of the middle abutment results in the transmission of forces to the terminal retainers, thus leading to the failure of the weaker retainer.
The position of the nonrigid connector in the five-unit pier-abutment restoration is critical. Nonrigid connector has been advocated by many and has suggested various locations such as terminal retainer, distal of the pier abutment, and one more at distal of anterior retainer at one side or both sides of pier abutment., Shillinburg , suggested nonrigid connector on the middle abutment as its location on either of the terminal abutments would result in the pontic's acting as a lever and middle abutment functioning as a fulcrum. Therefore, he  suggested placement of connector at the distal aspect of pier abutment and has been supported by finite element analysis study done by Oruc et al., A controlled study  showed that nearly 98% of the posterior teeth measured tilted mesially when subjected to occlusal forces. If the keyway of the connector is placed on the distal side of the middle abutment, any mesial movement tends to seat the key into the keyway more solidly. Placement of the keyway on the mesial side, however, causes the keyway to be unseated during its mesial movements. However, Savion et al. suggested that the possible etiology of debonding in pier abutments is due to the development of extrusive reactive forces at the anterior abutment and flexural forces in the posterior abutment. Moulding et al. gave an alternative method of orientation of nonrigid connectors in FPD to overcome space limitations which may require overreduction of the preparation or over contouring of the retainer to place to keyway within the retainer wall. Here, key is given on distal surface of the retainer and keyway on mesial surface of pontic. This method of alternative orientation was used in this case as it offers several advantages over disadvantages.
This offers many advantages such as:
- Conventional tooth abutment preparations with less reduction
- Suitable axial contours
- Simplified angulation and placement of the nonrigid connector with mesially inclined posterior abutment
- Improved esthetics with porcelain.
- Chances of key getting unseated from keyway on mesial movement of the abutment
- Fabrication of nonrigid connector is technique sensitive and requires increased laboratory time and
These, in turn, form the strength and limitation of the case. The alternative orientation of the key and keyway makes this case different as the key is given on distal surface of the retainer and keyway on mesial surface of pontic, whereas the commonly used nonrigid connector comprises a key that is attached to the pontic and keyway placed within the retainer.
The four types of nonrigid connectors , are as follows:
- Dovetail (key-keyway) or (tenon-mortise) connectors
- Loop connectors
- Split connectors
- Cross pin and wing connectors.
Nonrigid connectors are indicated in fixed prosthodontics in the following situations:
- Pier abutment, which acts as a fulcrum, causes failure of the weakest of the terminal abutments
- Malaligned abutment, where parallel preparation might result in devitalization. The use of intracoronal attachments as connectors is advocated
- Mobile teeth, which need to be splinted together with the fixed prosthesis. When multiple teeth are involved, interlocks can be used to cement smaller segments, thus deliver splinting effect
- Long-span FPDs, which can distort due to the contraction and pull of porcelain on thin sections of metal framework and thus, affect the fit of the prosthesis on the teeth
- When prognosis of the distal abutment is questionable and fabrication of the removable partial denture is the subsequent treatment step, nonrigid connector can resolve the problem of repeating restoration of remaining abutments
- It could be used in cases of osseointegrated implants.
Contraindication for nonrigid connector:,
- If the abutment presents significant mobility
- If the span between the abutments is longer than one tooth because the stresses transferred to the abutment tooth under soldered retainer would be destructive
- If the posterior retainer and pontic are opposed by a removable partial denture or an edentulous ridge while the two anterior retainers are opposed by natural dentition.
FPDs have been considered the standard of care before the advent of implant therapy. The long-term survival of FPDs has been reported to be 87% at 10 years and 69% at 15 years. Factors that predisposed to failure included nonvital anterior abutments and pier abutments. Hence, in such cases, dental implant can be a better alternative to the patient provided the patient is medically fit with good bone support and financially affordable.
| Conclusion|| |
Nonrigid connectors when used judiciously can protect the pier abutment from deleterious forces and thereby increase the life span of FPD. The current article strives to rekindle the awareness of utilizing this treatment modality which has shown a substantially promising track record in the past years.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]