A simplified method for making posts and cores

A simplified

method

for making

David J. Baraban, DAD.* Boston University, School of Graduate

posts and

Dentistry,

cores

Boston, Mass.

lh e restoration of endodontically treated pulpless teeth is a desirable dental procedure. A previous report listed the criteria for the retention of such teeth, and described their restoration by indirect techniques.l Recently, the “Para-post system”? was developed for fabricating a post and core by either a direct or indirect method. It provides for the placement of a prefabricated post, which fits a post preparation made by a drill corresponding in size to the post. To supplement retention and establish positive seating, a paralleling device is provided to aid in placing one or two pin channels in the root parallel to the post preparation. When the preparations have been completed, the dentist may select the direct or indirect technique for making the post and core. However, the direct technique is the principal advantage of the system. EQUIPMENT system” consists of a kit of color-coded instruments which The “Para-post correspond to the gauge of the drills. There are 3 gauges: 0.050 (color-coded red), 0.060 (black), and 0.070 (green) (Fig. 1) . Two additional sizes, 0.036 and 0.040, are available for use in teeth with small roots (in cross section). Corresponding to the size of each drill and similarly color coded are the following supplies which are used in this technique: 1. Posts of 4 materials: (a) gold, (b) st am . 1ess steel, (c) aluminum, and (d) plastic (Fig. 2). The posts are cylindrical, with parallel walls, to correspond in size and shape to the post preparations made by the Para-post drills. This insures good retention and positive seating. The gold post is intended for use in the direct technique, wherein the acrylic resin pattern is cast directly to the post. The steel post with its attached acrylic resin may be cemented into the root. The steel post may also be used to retain a temporary crown. *Professor TWhaledent,

of Prosthetic

Dentistry.

Inc., Brooklyn,

N. Y.

287

288

Baraban

Fig. 1. Para-post

.I. Pros. Dim. Septrmber,

drills:

(A) 0.050, (B) 0.060, (C) 0.070.

Fig. 2. A Para-post drill with corresponding posts, paralleling jig, and long-shanked 7 0.027 drill: (A) aluminum post; (B) gold post; (C) steel post; (D) plastic post; (E) post drill; (F) paralleling jig with 0.027 drill.

197!!

Method for

making posts and cores 289

Fig. 3. Para-post pins: (A) gold pins (note the serrations for venting and retention of cement; (B) aluminum pins; (C) plastic pins.

The gold and steel posts* are serrated throughout their entire length to enhance retention by cement. The serrations also provide retention for the acrylic resin pattern. In addition, a single vertical groove provides venting for the excess which aids in the seating of the post. The aluminum post is used for the retention of a temporary crown. The plastic post may be used in either the direct or indirect technique for fabricating the post and core. and (c) plastic (Fig. 3). 2. Pins of 3 materials : (a) gold, (b) a 1uminum, The gold pin is used with the gold post in the direct casting technique. The aluminum pin is used with the steel or aluminum Post to aid in retention. The aluminum pin may also be used for a temporary restoration. The plastic pin is used in the indirect technique. 3. A jig for the positioning of the pin channel (Fig. 2, F) . 4. A long-shanked 7 mm. 0.027 drill for pin channel preparation (Fig. 2, E) . A low-gear contra-angle+ should be used with the drills. The success of any technique depends upon proper case selection. The available *Designed by Dr. G. Courtade, New York, N. Y. j‘LAuto-chuck,” Whaledent, Inc., Brooklyn, N. Y.

290

Baraban

J . Pros. Dent. Swtrmber, 1970

Y

Fig. 4, A-F. (,4) ‘4 radiograph

of an cndodontically treated nmndibuIar left first premolar. The root canal had been sealed with gutta prrcha. .4 post space has been puxided. The copper band protects the root end. ji?) Contouring the root face with a diamond point; (C) the prepared root face; (D) the post preparation with a Para-post drill in an Autochuck handpiece; (E) a gold Para-post spated in preparation; (F) a radiograph of the Parapost seated in the preparation.

drills can be used in roots which permit preparation of a channel to the depth of at least one half the root canal length without danger of fracture or perforation. Thus, the decision to use this system must be predicated on a careful analysis, both clinically and radiographically, of the root morphology. In addition to the ability to house the Para-post, it is desirable, but not essential, that the root have sufficient tooth structure to allow for the insertion of an auxiliary pin. Gutta percha is the filling material of choice for the canal of a pulpless tooth

gclluue~ ‘3”

"

Method

for making

posts and cores

291

Fig. 4, G-L. (C) The paralleling jig is in the post preparation with 0.027 drill positioned to prepare the pin channel; (H) the Para-post and pin (arrow) seated in their respective preparations; (I) a contoured copper band is seated on the tooth. The post and pin are in position; (J) the copper band is filled with acrylic resin; (K) the acrylic resin mold after the removal of the copper band; (L) the acrylic resin core pattern preparation.

which is to receive a post. A silver point canal filling is difficult to follow to the desired depth with a bur and may be dislodged in the process. The three-dimensional technique with gutta percha affords complete apical sealing of the canal, and allows for the provision of a post space to the desired depth (Fig. 4, A) .2 Prior to making the post preparation, all irregular tooth structure should be removed. If an auxiliary pin is to be used, the root face should be prepared relatively flat. This will permit the disc of the paralleling ‘jig to rest on the underlying tooth structure (Fig. 4, B and C) .

292

Baraban

J. Pros. Dent. September, 1970

Fig. M-P. (M) The post and acrylic resin core pattern are ready to cast; (N) the tempora1 Y acrylic resin crown with an aluminum Para-post and pin; (0) the gold castin g s,:ated in th e preparation; (P) a radiograph of the finished restoration.

If the entire length of the canal has been filled, the gutta percha should be removed to the desired depth with Gates-Glidden drills. The No. 5 Gates-Glidden drill corresponds closely in size to the 0.050 Para-post drill (Fig. 4, B) . A minimum number of insertions and withdrawals of the Para-post drill will prevent widening the gauge of the post hole. If the canal is of wider gauge than the 0.050 drill, the larger sizes may be used with proper precautions to prevent fracture or perforation. When the post hole preparation has been completed, the corresponding gold post is fitted into the canal (Fig. 4, E) . It should seat freely and not move laterally. A radiograph will confirm the depth to which the post extends (Fig. 4, F). The post is then removed, and the corresponding paralleling jig placed in the post preparation to select the site(s) for the pin(s). The 0.027 long-shanked drill is

vo&~“,‘3”

Method for making posts and cores 293

then rotated through the pin hole in the disc and into the tooth structure about 2 mm. (Fig. 4, G) . The depth of the pin channel may be measured with an “Omnidepth” instrument.* The precious metal pin should fit snugly, with sufficient length extending out of the preparation to insure retention in the acrylic pattern (Fig. 4, H) . An annealed copper band is accurately fitted to encompass the prepared root and to the desired height of the preparation. The root preparation is dried and lubricated with a thin film of silicone lubricant. The gold post and pin are inserted in their channels and the copper band reseated (Fig. 4, I). Then a thin mix of a fine-grained acrylic resint is flowed into the copper band to the top (Fig. 4, J) . As the acrylic resin begins to set, it is firmly compressed within the band. The acrylic resin should set within 5 minutes. The band is severed with a bur and removed (Fig. 4, K) . The cylindrical block of acrylic resin is then prepared for the desired type of crown (Fig. 4, L) . Upon completion of the preparation, the pattern and the attached post and pin are removed from the tooth (Fig. 4, M) . It may be reseated to check for accuracy. Then it is sent to the laboratory to be cast in gold (Fig. 4, 0). If there is not enough dentin to receive an auxiliary pin, rotation of the post may be prevented by extending the canal in the direction of the greatest thickness of dentin. This may be done with a tapered diamond point to a depth of 2 mm. If the cervical portion of the canal is too wide to provide a snug fit of the post, the walls of the canal should be tapered and made free of undercuts (Fig. 5). The tapered cervical portion of the preparation is dried and lubricated. The post is seated and held in position, as a thin mix of acrylic is teased into the space. When the acrylic has set, the post will be firm. Then the post and acrylic resin are removed, the excess acrylic is trimmed, and the post is reseated. Then the core is fabricated with the copper band and acrylic resin technique. In this way a direct pattern for a post and core with good retention and positive seating is achieved. If the dentist desires to use the indirect technique, the plastic post and pin are substituted for the gold, and the copper band-compound impression technique may be used. However, as previously noted, the principal advantage of the Parapost system is the ease with which a direct pattern can be prepared. Therefore, its use with the indirect technique seems purposeless. TEMPORARY

CROWNS

For temporary crowns, the aluminum or steel post and aluminum pin are seated in their preparations, and a suitable polycarbonate crown is fitted. The post must permit occlusal clearance. If the aluminum post is used, it should be grooved with a disc at its exposed occlusal end, to provide retention for the acrylic resin. The desired shade of acrylic resin is mixed, placed within the crown form, and seated over the preparation. Gross excess material should be removed while still soft. When the acrylic resin has set, the temporary crown with the post and

*Whaledent, +Duralay,

Inc., Brooklyn, Reliance

Dental

N. Y. Mfg. Company,

Chicago,

Ill.

294

Baraban

Fig. 51, A-F. (A)

J. Pros. Dent. September, 19H)

Endodontically treated mandibular premolars. The cervical portions c)f the a snug fit of the Para-post; (B) Para-posts fitted nflOFtnls are too wide to accommodate (C) acrylic resin patterns of ce n prec :iscely with acrylic resin in the cervical preparation; (D) Para-posts reseated in the preparations, with ci01Iper FJ’eF ,a1:ations attached to Para-posts; ban ZlS fitted about gingival margins of the roots; (E) the copper bands are filled with a Cl:ylic 1; (F) Para-posts with their acrylic resin core patterns.

Method

for making

posts and cores

295

pin are removed, trimmed, and polished (Fig. 4, N). Prior to cementation, the acrylic resin is lubricated with a thin film of silicone lubricant to prevent the harmful effect of the eugenol in the temporary cement. If the cementing medium does not contain eugenol, this step is not necessary. The cement should be applied only to the cervical area of the temporary crown and not to the post or pin. It is undesirable to have cement in the post and pin holes at this time. The crown is then seated and the excess cement removed. A tapered preparation may be used instead of a pin to stabilize a post for a temporary crown (Fig. 5, G) . The temporary crown serves to maintain the adjacent and opposing tooth positions relative to the prepared root, as well as to preserve its gingival relationships. Although a short lapse of time between appointments may be intended, deleterious changes in tooth and tissue relationships may occur between visits.

Fig. 5, G-J. (G) Temporary acrylic resin crowns with a Para-post incorporated in the set:ond premolar crown to provide retention. The use of posts in both premolars was not nececrsary for this purpose. (H) Temporary crowns cemented in place; (I) the cast posts and c:ores are cemented in their respective preparations; (J) individual porcelain and gold crowns two weeks after cementation. Note the return to health of the gingival tissues.

296

Baraban

FITTING

AND

CEMENTING

THE POST AND

CORE

The casting, fabricated by the direct method, will require minimal adjustmcul_ Prior to seating the casting, the dentist must completely debride the preparation. \Vhen the accurate fit and design of the Para-post and core has been ascertaincci, it may be cemented in place. The cementing procedure must assure full seating of the casting without undue The preparation should be hydraulic pressure which may car~sc root fracture. dried thoroughly. A thin mix of zinc phosphate cement is carried into the channel(s) with a slowly revolving contra-angle-driven lentulo. Yext, the root face is covered with a thin film of ccmcnt. Then the casting is gently teased into the preparation until it is fully seated and held in place until the cement has begun to set. Whrn the set cement has been debrided, the procedures for fabricating the coronal restoration may be instituted. OTHER

APPLICATIONS

If an endodontically treated, single-rooted tooth has sufficiently well-supported coronal tooth structure remaining to allow for a crown preparation it may be reinforced by the insertion and cementation of a Para-post (Fig. 6) . The Para-post should extend apically at least one half of the length of the clinical root and incisally one half the length of the clinical crown. This procedure will reinforce the tooth against cross-sectional fracture and can be performed during the visit when the tooth is being prepared for a crown. In addition, in instances where time is a factor, the acrylic resin core on the Pam-post may be utilized as the final product. Such a post and core may be made and cemented in place in one visit. This will also permit making the final impression for the crown in the same visit. However, eugenol cement should not be used, because the acrylic resin core will be softened and destroyed by the eugenol.

Fig. 6. (Aj Endodontically treated maxillary Para-posts cemented in canal preparations. mained so that cores were not necessary.

central incisors with post spaces provided; Sufficient well-supported tooth structure

(&) re-

Volume 24 Number 3

Method

for

making

posts and cores

297

CONCLUSION The “Para-post system” provides the following advantages: 1. It affords a standardized procedure for the fabrication of posts and cores for single-rooted endodontically treated teeth. 2. The range of the gauges of the Para-post drills from 0.036 to 0.070 permits their use in most roots. 3. The equipment is advantageous for the direct technique. 4. It may be used for temporary crowns. 5. In selected cases the acrylic resin core and Para-post may be fabricated and cewted in place in one visit. 6. h lnay be used to reinforce an endodontically treated tooth for which a cast core is not i%ecessary.

References 1. Barattan, 1967. 2. Schildcr, 1967.

D. J.:

3?.: Filling

677 BEACON BOSTON,

The

Restoration

of Pulpless

Root Canals in Three

ST. MASS. 02215

Teeth,

Dimensions,

D. Clin.

North

D. Clin. North

America,

633-653,

America,

723-745,