JOURNAL OF ENDODONTICS I VOL 8, NO 2, FEBRUARY 1982

The use of rotary instruments as auxiliary aids to root

canal preparation of molars

M a r w a n A b o u - R a s s , DDS, MDS, PhD, a n d R o b e r t J. Jastrab, DDS

Recent endodontic studies have dis- cussed various methods of root canal preparation. Some of these studies have raised questions about the effec- tiveness of hand instrumentation. Gutierrez and Garcia ~ showed that endodontic instrumentation leaves areas of the root canal unprepared. Haga 2 showed that instrumentation to a size 0.35 file did not smooth the canal walls. Davis and others 3 and Laws" considered the elimination of morphologic aberrations an important criterion for satisfactory root canal preparation. Klayman and Brilliant 5 considered the completeness of the debridement another important crite- rion. Jungman and others 6 and Harty and Stock 7 studied the effectiveness of different endodontic instruments in producing roundness of the apical third of the canal, indicating the value of such roundness in root canal prepa- ration. The Giromatic handpiece was investigated by Frank," who found some merit in its use in special situa- tions. Harty and Stock 7 found no dif- ference between hand and Giromatic instrumentation. O'Connell and Bray- ton 9 concluded that hand instrumenta- tion was more effective than the Giro- matic handpiece in removing debris from the root canal. The shortcomings of hand instruments described in these studies, as well as the time factor and operator stress, have made many clini- cians consider the use of engine-driven

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rotary instruments as auxiliary aids to root canal preparation.

Clinical studies have shown the superiority of serial, or flared, prepa- rations over the traditional narrow, non-flared preparations. '~ Such prepa- ration design can be effectively achieved by the use of the Peeso rea- mer or the Gates-Glidden drill to wid- en the canal orifice and flare the cervical third of the root canal. Today, many endodontists are using such instruments in combination with hand instrumentation. This study is an investigation of the effect of these engine-driven rotary instruments on the quality of the root canal prepara- tion. Specifically, does the use of the no. I Peeso reamer or the no. 1 Gates- Glidden drill as auxiliary aids to hand instrumentation improve the quality of canal preparation with significant time saving?

M A T E R I A L S

A N D M E T H O D S

One hundred maxillary and man- dibular freshly extracted adult molars were used in this study. The teeth were divided into four groups as fol- lows:

Group 1: Twenty-five molars were prepared with hand instrumentation using K-type endodontic files. The mesiobuccal, mesiolingual, distobuc- cal, and distolingual roots were

enlarged to size no. 30 to 35 for curved roots, and 40 for straight roots at the apical stop level located 1 mm short of the radiographic apex. The distal and palatal canals were pre- pared to a size no. 55 file. The midroot and cervical thirds of the preparations were flared.

Group 2: Twenty-five molars were enlarged to a size no. 25 K-type file. A handpiece-mounted no. 1 Peeso rea- mer was used in an up-and-down direction just short of any root curva- ture or, if the canal was straight, to within 4 to 6 mm from the floor of the pulp chamber. The canals were then irrigated, and the preparations com- pleted to the desired size with K-type files sizes no. 30 to 35 for curved roots and 40 for straight mesiobuccal, mesiolingual, distobuccal, and disto- lingual roots, or to size no. 55 in the palatal and distal roots.

Group 3: Twenty-five molars were prepared in an identical manner to the teeth in group 2, except that a no. 1 Gates-Glidden handpiece-mounted drill was substituted for the no. 1 Peeso reamer.

Group 4: Twenty-five molars were prepared with rotary instrumentation (Giromatic handpieces and Giro- broaches). The mesiobuccal, mesiolin- gual, distobuccal, and distolingual roots were enlarged to sizes no. 30 to 35 (curved) and 40 (straight) roots. The distal and palatal canals were enlarged to size no. 55. One operator performed

JOURNAL OF ENDODONTICS I VOL 8, NO 2, FEBRUARY 1982

the preparation on all four groups. The length of time required for root

canal preparation and procedural errors were recorded for each tooth. When the root canal preparation was completed, all canals were irrigated and injected with silicone rubber according to a method developed by Sproles. u The prepared teeth were placed into a special vacuum bowl with the crown of the tooth protruding from the vacuum bowl cover. The tooth was luted into this position with beading wax to maintain the vacuum seal and silcone rubber Xanopren blue wa* injected into the access until the material emerged from the root end. At this time, the vacuum was closed and the specimen returned to its vial for 24 hours. The excess rubber was trimmed away and the tooth then placed in 40 ml of 35% nitric_ acid and then into a shaker-incubator until all tooth structure was r6moved (20 hours). The models were rinsed with water and alcohol. The decalcification process had no effect on the silicone model as shown through previous vali- dation studies by Sproles. 'I The sili- cone root canal filling models were photographed (1:1 ratio) from the angulated mesial, distal, and buccal view. All photographs were standard.

M E T H O D S O F

E V A L U A T I O N

A panel of seven endodontists exam- ined photographs of each silicone mod- el projected on a screen. The panelists did not know the type of instrumenta- tion ,used for each model. Each panel- ist reviewed the three photographic views of the same model according to the following criteria: --Apical preparation design, mea-

sured by the presence of a defined apical stop, roundness of the prepa-

ration, and a well-condensed apical third of the filling model.

--Aberration removal, measured by the absence of fins and small projec- tions in the model.

--Smoothness, measured by lack of roughness or voids in the walls of the filling models.

--Uniformity of the model, measured by homogeneity and the lack of bubbles, voids, or lacerations in the body of the filling model.

--Flow, measured by the continuous blending of the access cavity with the canal walls to the apical third level, and the lack of an abrupt change in direction of the different sections of the canal.

--Taper, measured by the conical shape of the canal model from the cervical zone to the apical third level (flare).

O v e r a l l q u a l i t y

The quality of the aforementioned six criteria in addition to a subjective and esthetic element reflected the per- sonal opinion of the evaluator.

The specific criteria and overall quality were rated by each endodontist on a four-point scale as follows: a score of A indicated superior; B, acceptable; C, average; and D, poor.

R E S U L T S

Time required to complete root canal instrumentation

The time needed to prepare the root canal in each group was recorded and ranged from 19.5 to 30 minutes (Table 1). Hand instrumentation proved to be the most time-consuming (30 min- utes). The Giromatic method was the fastest method (19.6 minutes). The combination of hand instruments and the Peeso reamer required 22.6 min- utes. The combination of hand instru-

ments and the Gates-Glidden drill required 28.0 minutes. The time dif- ferences between the groups were sta- tistically significant (chi-square).

Number of errors All four methods tend to force debris

through the apex or accumulate denti- hal chips at the apical stop area, resulting in underfill. Three canals in the hand instrumentation group were underfilled because of this error. Two canals in the combined hand/Gates- Glidden instrument were particularly fragile and five drills fractured. How- ever, the fracture site was at the hand- piece level, making it easy to remove the fractured instrument. Most errors in the technique using the Peeso rea- mer involved forcing debris through the apex. Preparation errors with the Giromatic method consisted of two apical perforations, three broken broaches, a high level of debris pack- ing, and loss of measurement length.

Specific quality Table 2 shows the percentage of

superior scores for all four groups on the specific criteria, that is, apical preparation, aberration removal, smoothness of walls, uniformity of preparation, flow of preparation, and taper of design.

Overall quality The panel rated the overall quality

of each root canal preparation on a rating scale of A, B, C, or D. Table 3 shows the results of the statistical anal- ysis of the data on 292 canals in 100 teeth. The use of the Peeso reamer as an aid to hand instrumentation produced the best results on both the specific and overall quality rat- ings (Fig 1). A combination of hand and Gates-Glidden instrumentation ranked second (Fig 2). Hand instru- mentation ranked third in quality (Fig 3), and Giromatic instrumentation ranked fourth (Fi~: 4).

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JOURNAL OF ENDODONTICS [ VOL 8, NO 2, FEBRUARY 1982

D I S C U S S I O N

This study on 100 molars (292 root canal preparations) indicates that combining hand instrumentat ion with use of the Peeso reamer results in an improved root canal preparation. It also saves time and reduces the error potential. Instrumentat ion of the canal with a K-type file to a size no. 25 provides room for the no. 1 Peeso reamer to prepare the cervical portion of the root canal without its being j ammed between canal walls, thereby providing access to prepare the apical third of the canal. Removal of the cervical constriction of the canal is important in preparing the canal mid- sections. This procedure also facili- tates the preparat ion of postspace, when indicated. In straight roots, the Peeso reamer can be inserted to a distance 4 to 6 mm from the floor of the pulp chamber. In curved roots, it should be introduced short of the cur- vature.

Careful use and attention is required in the use of the no. 1 Peeso reamer to reduce errors. Enlarging the cervical third facilitates subsequent instrumentation and reduces the possi- bility of ledging, debris packing, and instrument fracture. One disadvantage of any rotary instrument is the tenden- cy to fracture, which usually occurs when pressure is appl ied during cut- ting, when it is forced into a narrow canal, or if the instrument is fatigued by repeated use.

Clinical experience shows that most Peeso reamers fracture at the shank level, which presents no difficulty in removing the separated portion. If the cutting portion of Peeso reamer is separated, then it is bypassed and removed or considered par t of the final root canal filling. However, the no l Gates-Glidden drill is smaller, and when it fractures it is easier to bypass

Table 1 �9 Time of performance needed for root canal preparation.

Method Teeth Canals

Hand instrumentation 25 73 K-type files

Combined hand-Peeso-hand 25 73

Combined hand-Gates-Glidden-hand 25 73

Giromatic 25 73

X = 30 minu~ S = 3.68t R = 24.5-41:{ X = 22.6* S 3.9 t R = 15.5-29i~ x = 2 8 0 "

S = 3.9t :~ R = 23.15-37~

ii! S 2.9, R = 15.2-25i3;

*X = mean value.

tS = S tandard deviation.

*R = Range

Table 2 �9 Percentage of superior ratings (A scores) for all groups (the B, C, and D scores are not reported here).

Group Group Group Group Criterion 1 2 3 4

Apical design 21.7 55.2 44.3 13.1 Aberration removal 30.2 51.0 43.3 26.6 Smoothness of walls 10.8 53.1 35.7 4.8 Uniformity of preparation 27.8 48.1 36.7 7.5 Flow 33.6 55.2 45.6 8.0 Taper 27.5 41.2 34.7 5.8

Overall quality 25.7 53.6 42.1 3.6

Table 3 �9 Percentage of scores.

Criterion Scores Group 1 Group 2 Group 3 Group 4

A 25.9 50.8 39.6 7.6 B 41.6 39.4 40.8 36.0 C 29.3 9.6 18.8 47.8 D 3.2 0.2 0.8 8.6

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J O U R N A L OF E N D O D O N T I C S [ V O L 8, N O 2, FEBRUARY 1982

and remove. If the canal is enlarged to a size no. 25 to 30 before using the size no. 1 Peeso reamer, the possibility of fracture is reduced.

Over-cutting the circumference of the canal body or cutting in the danger zone of the root canal walls may cause stripping or perforation. Anticurva- ture filing should be maintained by preparing the thick walls of the root canal (buccal and lingual wall of the cervical third). 12

After using the no. 1 Peeso reamer, the canal should be thoroughly irri- gated and enlarged with files to the desired size. These files are more tac- tile and are effective in recapitulation, smoothing and refining the canal walls, and producing the desired taper. The operator should attempt to pre- pare the canal throughout its length and avoid producing two levels of canal preparation, which would result in the midroot and cervical thirds being more condensed than the apical third. The use"of the no. 2 or no. 3 Peeso reamer has shown a greater tendency to produce such results and is not recommended as an aid to root canal preparation.

The use of the Gates-Glidden instrument (group 3) also produced positive results. However, the no. 1 Gates-Glidden drill tends to fracture and gouge the canal walls, thereby producing less uniformity of the canal walls. The combination of hand and Peeso reamer or Gates-Glidden instrumentation was superior to hand or Giromatic instrumentation alone.

Hand instrumentation required the rnost~ time and ranked third in the overall and specific quality scores. This concurs with previous findings by Haga, 2 and Gutierrez and Garcia. 1

Most endodontic errors in the study occurred with the Giromatic group and included apical perforation (two eases) and instrument fracture (three

Fzg 7--Model of tooth with canals pre- pared with a combination of K-type files and no. I Peeso reamer.

Fig 3--Model of maxillary tooth z~ith ca- nals prepared exclusively with K-type

files.

cases). The Giromatic method re- quired the least time to prepare the canal, but this must be weighed

Fig 2--Model of tooth with canals pre- pared with a combination of K-type files and no. 1 Gates-Glidden drill.

Fig 4--Model of tooth z~ith canals pre- pared with the Giromatic method.

against the overall results. The results obtained on the Giromatic instrumen- tation a r e consistent with those of

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JOURNAL OF ENDODONTICS ] VOL 8, NO 2, FEBRUARY 1982

Klayman and Brilliant s and O'Con- nell and Brayton. 9 The Giromatic method preparations ranked poor on all rating scales. The preparations lacked flow and taper, and many mor- phologic aberrations were present.

S U M M A R Y

One hundred adult extracted molars (292 canals) were apportioned into four groups of 25 teeth each. Group 1 was prepared using K-type files. Group 2 was prepared to size no. 25 with K-type files, followed by a no. 1 Peeso reamer, which enlarged the cer- vical third. The canal preparation was then completed with K-type files. Group 3 was identical to group 2 except that a no. 1 Gates-Glidden drill was used instead of a no. 1 Peeso reamer. In group 4, canals were pre- pared with the Giromatic method. All teeth were enlarged to size no. 30 to 35 in curved roots and size 40 in straight roots, at the apical stop level.

Accurate silicone models were made of the preparations. A panel of seven endodontists rated the results accord- ing to the specific criteria of apical design, aberration removal, flow, ta- per, uniformity, and smoothness of preparation. The combination of K-type file and Peeso reamer or Gates-Glidden reamer preparations (groups 2 and 3) favorably met the foregoing criteria. Hand instrumenta- tion and the Giromatic technique pro- duced less favorable results.

C O N C L U S I O N S

Giromatic instrumentation of the root canal produced preparations that lacked uniformity, flow, taper, and removal of morphologic aberrations. The apical preparation design was irregular. The Giromatic method required least performance time and produced the most procedural errors, including apical perforations, ledges, and debris packing.

Hand instrumentation with K-type files was most time-consuming, inef- fective in removing canal aberrations, and produced canals lacking definition of apical preparation, taper, and flow. Few procedural errors were ob- served.

The use of the no. 1 Peeso reamer as an auxiliary aid in enlarging the cervi- cal third was effective in improving the quality of root canal preparation with significant time-saving advantages and minimal errors.

Substituting the Peeso reamer with a no. 1 Gates-Glidden drill produced similar results.

The authors thank Dr. S. Oglesby for his assistance in the statistical analysis, and Drs. I". Patonai, S. Namazikhah, M. Piccinino, D. Jobe, F. Tsutsui, and M. Jann, all of whom served as the evaluation panel.

Dr. Abou-Rass is associate professor and chairman, and I)r. Jastrab is clinical assistant professor, department of endodontics, School of l)entistry, University of Southern California. Requests for reprints should be directed to Dr. Abou-Rass, University of Southern California,

School of Dentistry, PO Box 77951, Los Angeles, 90007.

References

1. Gutierrez, J . l l . , and Garcia, J. Micro- scopic and macroscopic investigation on results of mechanical preparation of root canals. Oral Surg 25:108, 1968.

2. llaga, C.S. Microscopic measurements of root canal preparations fnllowing instrumenta. tion. J Br Endod Soc 2:41, 1968.

3. Davis, S.R.; Brayton, S.M.; and Golman, M. The morphology of the prepared root canal. A study utilizing injectable silicone. Oral Surg 34:642, 1972.

4. Laws, A.J. Preparation of root canals: an evaluation of mechanical aids. N Z Dent J 64:156, July 1968.

5. Klayman, S.M. and Brilliant, J.D. A comparison of the efficacy of serial preparation versus Girnmatic preparation. J Endod 1:334, 1975.

6. Jungman, C.L.; Uchin, R.A.; and Bucher, J.F. Efl'ect of instrumentation on the shape of the root canah J Endod 1:334, 1975.

7. Harty, F.J., and Stock, C.J. The Giromat- ic system compared with hand instrumentation in endodontics. Br Dent J 137:239 Sept 1974.

8. Frank, A.L. An evaluation of the Giromat- ic endodontic handpiece. Oral Surg 24:419, 1967.

9. O'Conell, David T.; and Brayton, S.M. Evaluation of root canal preparation with two automated endodontic handpieces. Oral Surg 39:298, 1975.

10. Coffae, K.P., and Brilliant, J.D. The effect of serial preparation on tissue removal in the root canals of extracted mandibular molars. J En&• 1:211, 1975.

11. Sproles, R.A. An anatomical investiga- tion of the coronal pulp chamber of molar teeth utilizing a silicone injection technique. Thesis. University of Southern California. 1975.

12. Ahou-Rass, M.; Frank, A.L.; Glick, D.tl. Anticurvature liling method to prepare the root canal. JADA 101 (5): 792-794, 1980.

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