G.Pongione, G.Gambarini, S.De Luca, G.Floridi, M.Bossù, M.De Luca
University of Rome "La Sapienza", Dental School

Dimensions of root canal filling condensers.

Abstract
The goal of this study was to evaluate and compare the morphology of some conventional root canal pluggers commonly used in clinical practice. Five sets of long-handled pluggers of the following five brands (Deppeler,Ransom & Randolph, Hu Friedy,Maillefer and Obtura) were selected and examined with a very accurate measuring device. Results show that conventional size designations often provide no useful clinical indications of dimensions and shape of conventional root canal pluggers. Moreover instruments with the same nominal size designation can be very different in diameter and taper among the various brands.A great choice of different pluggers is available,but their great dimensional disparity can also be misleading. To alleviate some of the above-mentioned problems a new system of sizing, which allows the user to know what the tip dimensions and taper are (ANSI/ADA Specification no.71 for root canal filling condensers) has recently been developped.

Introduction
Selection of appropriate size pluggers is a crucial factor for an effective compaction of the softened gutta-percha in the vertical condensation method (1,2). Usually three or four pluggers must be preselected to ensure their loose fit in the coronal, middle and apical thirds of the canal (3).

Insertion of the plugger to the proper length is not always an easy procedure,especially in filling curved canals(4).The use of severely tapered condensers in these cases is often ineffective,since their access to the apical portion of the root canal can be difficult or impossible.

Many authors (5-7) recommend enlarging the root canal space until a n.8 or n.9 Schilder plugger fits to within 5 mm. of the apical foramen.However this enlargment must be achieved safely,avoiding overzealous canal shaping , which may weaken the tooth structure , being very dangerous for long-term prognosis of the restored tooth(8,9).

All these observations suggest that the final root preparation,the dimensions and shape of pluggers and the use of gutta-percha points are all strictly related, and therefore condensation instruments must not be empirically selected (10)

A set of graded root canal pluggers is available from many manufacturers. However the majority are conventional instruments, with a nomenclature that provides no indication of their diameters and taper.The exception are I.S.O. sized pluggers and spreaders (11) . In a survey of endodontic hand- andfinger spreaders, conventional instruments with the same nominal size designation were found to differ markedly in diameter and taper among brands (12).In a previous study, we also noted that the taper of many root canal filling condensers is not always uniform(13). To overcome these problems a new ANSI/ADA Specification No.71 has recently been developped. The new specification gives useful information on diameters and taper of root canal filling condensers to the user (14).

The goal of this study was to evaluate and compare the morphology of some conventional root canal pluggers commonly used in clinical practice, hoping that knowledge of the real dimensions of these instruments may alleviate some of the problems currently encountered with their use.

Materials and methods
Five sets of long-handled pluggers of the following five brands (Deppeler, Ransom & Randolph, Hu Friedy,Maillefer and Obtura) were selected.Each brand was randomly designed by a character code(A,B,C,D,E,) and the following 37 instruments were examined:

Diameters and taper were evaluated with the aid of a gagetalker ,a computerized measuring device (Sylvac 50,Fowler) capable of measuring diameters with the accuracy of +/- 0.001 mm. It must be underlined that ISO standard 3630 (Part III) requires an accuracy of at least +/-0.002 mm. Diameters at D0(tip diameter),D3, D7, D12,5 and D16 were measured.Taper was calculated using the following formula:Taper= Difference of diameters / length between diameters (i.e. D16-D3 / 13)

In light of our previous study (13) we decided to verify the uniformity of taper by measurements before and after the critical D3 location.Test conditions and procedures followed ISO standard requirements.

Results
The results of the dimensional measurements are shown in table 1 and 2.Instruments with the same size designation and/or similar in diameters and shape were grouped altogether. Tapers are shown in table 3.

Discussion
It's remarkable to find how similar instruments can present different designations and,viceversa, how instruments with the same designation can be very different. For example A4 is much smaller than D4 or E4; on the contrary A9 shows larger diameters than B9 or C9, while it is very similar to B10 1/2 or E3.

Sometimes even instruments which are designated to be the same size are somewhat different. If we compare two brands (B and C),we note that the smallest sizes are very similar ,while the biggest ones differ markedly: B root canal pluggers exhibit a more pronounced taper and a bigger tip.

Tip diameters(Do) are usually not specified by the manufacturers. Only B pluggers exhibit the diameters designated at Do indented on the handle: the table n.3 shows the correspondence between size designations and tip diameters for those pluggers.Table 1 shows how B pluggers match these ideal dimensions.

A pluggers exhibit a one-digit number designation which seems to indicate D0 diameters by tenths of millimeters.On the contrary the one-digit number designation of pluggers D and E cannot be associated in any way to the actual D0 diameters.

The Specification No.71 with a new system of sizing ( a five-digit number which precisely indicate tip dimension and taper) is now available to overcome all these problems (14)

Taper is usually defined by a two digit number, representing the taper in thousandths of millimeters. (table 1 - 3). The higher the numerical value, the more tapered the instuments.Among the different brands ,B pluggers are the most tapered. C pluggers are the less tapered(table 3) .It's also interesting to note that smallest sizes are more tapered, intermediate sizes tend to be very similar to ISO sized pluggers,while the biggest ones are significantly less tapered than ISO sized pluggers .

Taper should be, but it is not , always uniform among the single instruments.The working ends (the measured tapers between D0 and D3) tend to be more tapered than the coronal portions of the pluggers. Only C pluggers exhibit an opposite relation (table 3).

Sometimes size inconsistencies can also be found: we marked this problem with an asterisk(*), which means that the instrument has dimensions and taper completely irregular. For example,except for Do dimensions, the size B 9 1/2 measurements are smaller than the size B :in this case the basic foundation of a graded series of instruments is not respected.

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