A review of various methods of tripodization in removable partial denture to introduce a simplified classification system

R Rohini; Aditi Mishra; Raghuwar Dayal Singh; Sunit Kumar Jurel; Pooran Chand

doi:10.4103/jorr.jorr_8_22

REVIEW ARTICLE

Year : 2022 | Volume : 14 | Issue : 2 | Page : 172-175

A review of various methods of tripodization in removable partial denture to introduce a simplified classification system

R Rohini, Aditi Mishra, Raghuwar Dayal Singh, Sunit Kumar Jurel, Pooran Chand
Department of Prosthodontics, King George's Medical University, Lucknow, Uttar Pradesh, India

Date of Submission	25-Feb-2022
Date of Decision	16-Apr-2022
Date of Acceptance	23-Apr-2022
Date of Web Publication	01-Jul-2022

Correspondence Address:
Raghuwar Dayal Singh
Department of Prosthodontics, King George's Medical University, Shahmeena Road, Chowk, Lucknow - 226 003, Uttar Pradesh
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jorr.jorr_8_22

Abstract

This article aims to present a newer and simplified classification of tripodization methods, which can help prosthodontists to choose a better method according to their ease and clinical expertise. This study was based on searching published scientific research. Data search was conducted via Medline via PubMed, Wiley Online library, Ebscohost, ScienceDirect, Research Gate as well as the Google Scholar till 2020 using the keywords – removable partial denture, method, tripodization. All the 21 selected articles were critically evaluated regarding the concepts and the techniques to introduce an innovative classification system for the various tripodization methods. The proposed classification system would help in appropriate selection of suitable tripodization method for every particular clinical situation in the process of removable partial denture fabrication.

Keywords: Classification, methods, removable partial denture, tripodization

How to cite this article:
Rohini R, Mishra A, Singh RD, Jurel SK, Chand P. A review of various methods of tripodization in removable partial denture to introduce a simplified classification system. J Oral Res Rev 2022;14:172-5

How to cite this URL:
Rohini R, Mishra A, Singh RD, Jurel SK, Chand P. A review of various methods of tripodization in removable partial denture to introduce a simplified classification system. J Oral Res Rev [serial online] 2022 [cited 2022 Aug 16];14:172-5. Available from: https://www.jorr.org/text.asp?2022/14/2/172/349718

Introduction

Various steps are involved in designing and fabrication of removable partial denture (RPD) framework, such as surveying diagnostic cast, designing the framework, mouth preparation, wax pattern fabrication on master cast, production of refractory cast, and laboratory framework fabrication procedures. Surveying is mainly done to record the favorable, unfavorable undercuts and favorable path of insertion.^[1] A judicious compromise in all such factors help determine the favorable path of insertion that will govern the orientation of cast, that is, in other words, the favorable tilt of the cast.

Tripodization/tripoding is the process of recording the selected, most favorable cast orientation for future reference.^[2] The idea of tripodisation was based on marking three points on cast. But disadvantage of these points was in reproduction of them to the same plane. To over come this various other methods have been introduced aiming to improve the accuracy and feasibility of the process.^[3],[4]

Wagner and Forgue^[5] had done a comparative study on the accuracy of three methods, viz., tripod marks on anatomic area, points or vertical lines on lateral areas of the artistic portion of the cast, and cemented pin method. Sayed et al.^[6] comparatively studied the accuracy of three techniques (tissue points, scoring lines, and cemented posts, used for reorientation of casts during surveying procedure.^[6] Sruthi et al. had reviewed various methods till 2016.^[7]

Material and Methods

An electronic literature search conducted through Medline via PubMed, Wiley Online library, Ebscohost, ScienceDirect, Research Gate as well as the Google Scholar for article published between 1973 and 2020, using the keywords, such as tripodization and RPD, tilt of cast and RPD, preservation of tilt, and reproduction of tilt and RPD, which resulted in 1838 articles, out of which 21 articles were selected and reviewed by eliminating repeats and applying the inclusion and exclusion criteria.

Results

All the 21 selected articles were reviewed regarding the concepts and the techniques behind the proposed tripodization methods, which were critically evaluated to present a new classification system as shown in [Figure 1].

Figure 1: Classification system for tripodization methods

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Discussion

There are various methods/techniques for the tripodization procedure, which can be broadly categorized as invasive (methods which alter any aspect of cast) or noninvasive as shown in [Figure 1]. Invasive methods are based on the idea that if a pin fixed at a particular point on a cast, it aids in reproducing its tilt. The cast can reproduce its tilt utilizing the relationship between the cemented pin and surveying arm.^[8] This was the ideology behind the cemented pin method. However, the disadvantage encountered using this was the inability to articulate the casts in case of rehabilitation of both arches simultaneously.^[5] To overcome the drawback associated with cemented pin, the idea of pin and sheath (a removable pin) was proposed, in which pin being the detachable part, was attached to sheath embedded in cast to reorient it and removed whenever the cast was to be articulated.^[9] Disadvantage of this method was, a custom-made device was necessary as it was not commercially premanufactured. This led to the idea of utilizing the easily available alternatives in working station such as dowel pins and sheath. Another modification based on similar principle is the use of direct and indirect implant impression coping and implant analog.^[10] It has an added advantage of securing two definitive casts, both original and the duplicated one, utilized for framework wax up. However, disadvantage of the idea was easy dislodgement of embedded analogue or insufficient length of component to obtain tripodization.^[11] Some authors proposed the use of cobalt samarium magnets with strong ferromagnetic fields and intrinsic coercivity to rearrange the cast to its favourable orientation with the surveyor with the advantage of automatic reseating, ease of placement and reorientation, and economic feasibility.^[12]

Noninvasive methods utilized the fundamental of mechanical instruments and indexing techniques. Indexing technique focuses on generating a template utilizing anatomical landmarks which will help in recording the tilt of the cast. Sarnat and Klugman designed a position recorder that would support impression compound index of occlusal surface.^[13] The position recorder device comprises a triangular plastic plate and a handpiece mandrel. The triangular plate covers the entire arch and has three retention holes. Later, Shakibamehr et al.^[14] fabricated templates of occlusal surface of teeth in autopolymerizing acrylic resin onto which the relationship with the surveying tool was recorded. The same occlusal index helps reorienting both diagnostic and the final master cast. Polymerization shrinkage of acrylic resin could be of great disadvantage of inaccuracy of the index; other drawbacks of this method include duplication errors between the study cast and the master cast and prerequisite for use of similar surveyor systems.^[14] Further methods were advocated so that greater surface area will be included in the index for a more precise reorientation of cast. Ansari proposed to use a “u”-shaped custom tray to make an impression of entire arch to be utilized as an index.^[15] This technique has the advantage of its applicability to both arches.^[15] Similarly, Afsal et al. used a putty index involving the tissue surface and not the dentulous portion of the cast, but dimensional changes over a period of time restrict its use. Advantages of this method include precise marking of points could be precluded, when edentulous space is predominant, it can be better utilized, and both study and master casts can be reoriented.^[16],[17]

Finally, there are mechanical and geometric instruments which work on the principle of recording the orientation of a cast by using measurements mathematically. The earliest of all was the method given by Kaloyannides. Tilt of the cast was established by a geometric method, mathematically measuring the position of determined plane in relation to horizontal plane. Shape of the cast, any wear, or fracture of the cast would neither affect tripodization nor the surveying process.^[18] Then, in 1980, Sykora used a new technique of tripodization and reorientation of cast using a MS Level unit by adjusting the angulation of the MS Level until the air bubble is exactly in the center of the cross-hair ring.^[19] Further, Steas developed a device consisting of three adjustable arms attached to a surveyor that contact the cast at three divergent points, which was later modified by Sajjan (2006)^[21] to alleviate the main disadvantage of locating points at a single plane.^[20],[21] CAT was another device that allowed measurement of cast orientation in the frontal and sagittal planes as precise as one degree. Cast reorientation with the VPS index was simplified since only two positions are being aligned, compared to three marks with the conventional methods. The CAT could orient duplicate casts with the same VPS index and is used independent of a surveyor. The only disadvantage was the additional cost of CAT device and VPS.^[22] Latest of all is the universal tool proposed by Gali and Lanka, a flat equilateral metal triangular plate of 3-mm thickness available in five different sizes housed with a hole to accommodate a corresponding Allen screw in the vertical rod registering the tilt by using a 3-plane device, defining the horizontal plane with simultaneous contact of all three points. The different sizes of the triangular plates enable a clinician to choose and customize the device for different clinical situations and can be reused similar to any other surveying tool.^[23] Lasers as evolving technology have also stepped in with their role in the process of tripoding.^[24]

Conclusions

The proposed classification system would help in appropriate selection of suitable tripodization method for every particular clinical situation in the process of RPD fabrication.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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