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Abutment Preparation and Impression Technic for Full Coverage
L. A . W einberg,* D .D .S., M .S ., N ew York
Abutment Preparation and Impression Technic for Full Coverage
In this report technics are presented for full coverage abutment preparation, com pound tube impressions and copper plat ing, which consistently have produced excellent results for the author. Each den tist, how ever, must experim ent with dif feren t m ethods until he finds the best combination in his own hands.
Full coverage preparation and impression technics are varied to suit the needs and skill o f the operator; this report describes a m ethod that consistently produces the best results for me.
A R M A M E N T A R IU M
An ultra-speed instrument over 125,000 rpm is necessary in m od em day technol ogy. I prefer a Page-Chayes instrument (with a steel chuck) because it has a positive drive and selective speeds. Often, slower speeds are necessary to obtain the proper feel and control for exact m ar ginal placem ent and con tou r; this is a matter o f personal preference. Oral evacuation, with a modern system designed for this purpose, is essential to an efficient prosthodontic practice. It is vital to the dentist as well as the patient, in order to relieve mental fatigue associ ated with inefficient operations.
T R E A T M E N T O B J E C T IV E : A B U T M E N T PR E P A R A T IO N
T h e treatment objective in full coverage abutment preparation is to reduce the tooth structure sufficiently to facilitate the placem ent o f a properly contoured restoration with excellent marginal adap tation and occlusion. T his must be ac complished with minimal pulpal and soft tissue damage. T h e marginal placement and relationship to the gingiva have been discussed previously.1
E N A M E L S T R IP P IN G
A distinction should be made between en amel stripping and dentin preparation. Needless pulpal irritation is produced and time consumed in wearing away the en amel from the outside. T h e enamel is stripped off the occlusal, buccal and lin gual surfaces with a large Leff stone in a straight handpiece at 20,000 rpm. T he instrument is placed on the occlusal sur face for cutting into the dentinoenamel
52/514 • THE JO U RN A L OF THE AMERICAN DENTAL ASSOCIATION
ENAMEL STRIPPING DENTIN FIG. I
FIG. 2
ENAMEL
701 IN D-E JUNCTION
LABIAL GROOVE 701
FIG.4
THIN ENAMEL WALL
F ig . I • Enam el s tr ip p in g . L a rg e Leff sto ne is p la c e d on o c c lu sa l s u rfa c e a n d cuts in to c e m e n to e n a m e l ¡unction. It is m o v e d m e sially to keep w a te r s p r a y on c u t tin g su rfa c e Fig. 2 • En am el s t r ip p in g o f b u c c a l a n d lin gu a l su rfac e s. B ucca l a n d lin gu a l enam el re d u ce d , w h ich results in s g u a r e p re p a ra tio n with o n ly m esial a n d d ista l en a m el in ta c t
su rfa c e s are
Fig. 3 • B uccal g r o o v e . 701 c a r b id e cro ssc u t b u r cuts b u c c a l g r o o v e u p to fre e m a rg in o f g in g iv a a n d n ot b e lo w ; I mm. sh o u ld e r is c re a te d at g in g iv a l su rfa c e Fig. 4 • In te rp ro x im a l su rfa c e re d u ction . 701 b u r c o n tin u e s in d e n tin o e n a m e l ¡unction t h r o u g h interp ro xim al s u rfa c e le a v in g thin en am e l wall p ro te c t in g a d ja c e n t to o th
junction and moved mesially to keep water spray on the cutting surface (Fig. 1) . The combination of high speed and a concentric stone and handpiece limits vibration. The buccal and lingual surfaces are reduced in the same fashion, which re sults in a square preparation with only the mesial and distal enamel intact (Fig. 2 ). A B U T M E N T P R E P A R A T IO N
A new 701 carbide crosscut bur in the in strument o f the operator’ s choice is placed on the midline of the labial surface up to the free margin o f the gingiva and not below. The instrument is applied pulpally
until a groove is cut producing a 1 mm. shoulder (Fig. 3) at the gingival margin. The depth of the cut is controlled to pro duce a finish line or a shoulder as desired. The handpiece is moved mesially in a definite stroke, rather than a brushing action, creating the shoulder as it goes along. Discipline is necessary to raise the instrument occlusally to follow the con tour of the gingiva interproximally. U n less this is done, the shoulder disappears, and the margins become much too sub gingival. IN T E R P R O X IM A L R E D U C T IO N
The 701 bur continues in the dentino enamel junction through the interproxi-
W EINBERG . . . VOLUME 67, OCTOBER 1963 • 53/515
mal surface leaving a thin enamel wall protecting the adjacent tooth (Fig. 4 ). If the instrument is held upright, parallel with the long axis of the tooth, a thinner bur seldom is required. This procedure is repeated for the distal surface and joined on the lingual surface to produce a prep aration with the finish line up to but not below the free margin of the gingiva. SU B G IN G IV A L S H O U L D E R
Only on the maxillary anterior teeth from bicuspid to bicuspid is it necessary to drop
FIG.6
5
DIAMOND FIG. 8
the shoulder below the gingiva. When necessary it should be limited to 0.75 mm. ; most often it is too deep rather than too shallow. This should be done after the interproximal surface has been pre pared to prevent the problem of the “ dis appearing shoulder.” If this procedure is not followed, the labial subgingival shoul der is carried interproximally much more apically than it should be. The result is the permanent dissection of transseptal periodontal fibers with the apical migra tion of epithelial attachment and subse quent bone reduction.
BARREL 9
SLEEVE PREPARED
10
DEPTH
Fig. 5 • P re p a ra tio n r e sh a p in g . Thin, ta p e re d , ro u g h d ia m o n d sto n e is p la c e d u p t o sho u ld e r, m o v e d c irc u la rly to p ro d u c e p r o p e r t a p e r a n d re d u ctio n Fig. 6 • O c c lu s a l re d u ctio n . B a rre l-sh a p e d sto n e is p la c e d on o c c lu s a l s u rfa c e to re d u c e central, b u c c a l a n d lin gu a l g r o o v e areas. Even 1.5 mm. c le a ra n c e can b e a c c o m p lis h e d e a sily w ith o u t o v e rre d u c tio n Fig. 7 • P re p a ra tio n refine m e nt. O c c lu sa l a s p e c t o f p re p a ra tio n m ust b e ro u n d e d in o rd e r t o re d u ce the b u c c o lin g u a l w idth a n d to p ro v id e eve n thickn ess o f m ate ria l w ith p ro p e r c o n t o u r F ig. 8 • M o d if ie d d ia m o n d stone. G o ld sleeve sh o u ld exte nd 0.75 m m. b e y o n d s h o u ld e r on p re p a re d tooth structure. M o d if ie d d ia m o n d sto ne has b ee n d e v ise d f o r this p u rp o se . T h in n e st ta p e re d d ia m o n d sto ne a v a ila b le is c o v e re d with fine layer o f D u r a la y (p a in te d o n ) to w ithin 1.5 m m . o f end F ig. 9 • C o n t r o lle d s u b g in g iv a l d ep th. S le e v e is p re p a re d b y m o v in g sto n e a ro u n d s h o u ld e r with h a n d p ie c e re v o lv in g a t m e d iu m sp e e d to in cre a se o p e r a t o r 's sen se o f " f e e l " ; new finish line is c re a te d 0.75 mm. b e lo w s h o u ld e r Fig. 10 • D e p th g a u g e . M o d if ie d d ia m o n d s to n e 's 1.5 mm. c u ttin g tip acts as a d e p t h g a u g e w hen c o m p a r e d t o fre e m a rg in o f g in g iv a
54/516 • THE JO URN AL OF THE AMERICAN DENTAL ASSOCIATION
POLISHING STONE
ABRASIVE WHEEL FIG.lt
FIG.
SHARP LINE ANGLE SQUARE SHOULDER 3/4m m . SLEEVE
RUBBER
Fig. I I • A b u t m e n t fin ish in g . P re p a ra tio n is sm o o th e d b y c ir cu la r m o v e m e n t sim ila r to re d u c tio n s ta g e with ta p e r e d fin ish in g sto n e ; final p re p a ra tio n will be sm o o th with s h a rp p u lp a l line an gle , sq u a re s h o u ld e r and a 0.75 mm. sleeve p re p a re d p a st sh o u ld e r Fig. 12 • Final sm o o th in g . O c clusal p o rtio n is sm o o th e d and ro u n d e d with a b ra siv e ru b b e r w heel at slow sp e e d
O C C L U S A L R E D U C T IO N
P R E P A R A T IO N R E S H A P IN G
A thin, tapered rough diamond stone is placed up to the shoulder and moved cir cularly to produce the proper taper and reduction (Fig. 5 ). When a finish line is the preparation of choice, it is refined and dropped 0.5 mm. below the free margin of the gingiva with the diamond stone.
One of the consistent errors in abutment preparation is the lack of sufficient and properly contoured occlusal surface re duction. A barrel-shaped stone is placed on the occlusal surface to reduce the cen tral, buccal and lingual groove areas (Fig. 6 ). An even 1.5 mm. clearance can
ONE SIZE LAR G ER BAND
TIGHT BAND
Fig. 13 Fig. 14 in usual Fig. 15
FIG. 13
FIG. 14
FIG. 15
FIG. ¡6
• B an d sele ction . T ig h te st • B an d m o d ific a tio n . N e xt w ay; I mm. cuts are m a d e • Firm p e rip h e ry . T a b s are
c o n to u re d a n n e a le d b a n d is fitted to tooth la rg e r size then is used fo r im p re ssio n . B an d is c o n to u re d p ro p e rly on o p p o s it e en d all a ro u n d b a n d with scisso rs b e n t b a ck a g a in s t b a n d fo rm in g firm p e rip h e ry fo r se a tin g
Fig. 16 • B an d c o n to u rin g . C o n t o u r e d e n d then is b e n t in w a rd with Peso plie rs a ro u n d entire p e rip h e ry
W EINBERG . . . VOLUME 67, OCTOBER 1963 • 55/517
be accomplished easily without fear of overreduction. P R E P A R A T IO N R E F IN E M E N T
T he occlusal aspect o f the preparation must be rounded in order to reduce the buccolingual width and to provide an even thickness o f material with the proper contour (Fig. 7 ). W hen a veneer restoration is used, this step is essential to prevent bulky, m alcontoured restora tions; the technician must be provided with sufficient space to produce the de sired result. PO R C E L A IN J A C K E T P R E P A R A T IO N S
Porcelain jackets require a full shoulder completely around the tooth ; whenever possible it should be 1 mm. wide. T he finish line is often rough with unsup ported enamel. Since the porcelain will butt against the tooth structure, it is es sential to refine this area. T h e pulpal line angle should be w ell-defined; sharp hand instruments (hoes) facilitate accentuat ing this line angle, reducing unsupported enamel and smoothing the finish line it self. T h e result is a smooth 1 mm . shoul der at right angles to the pulpal wall. PR E P A R A TIO N F O R V E N E E R SLEE V E
W hen veneer restorations are required, a gold sleeve should be constructed to ex tend 0.75 mm. beyond the shoulder. In order to prevent overhanging margins, interferences in proper seating, excess bulk and gingival irritation, this tooth structure past the shoulder must be pre pared. A m odified diam ond stone has been devised for this purpose. T h e thin nest tapered diam ond stone available is covered with a fine layer o f Duralay (painted on ) to within 1.5 mm. o f the end (Fig. 8 ). Controlled Subgingival D epth • T he sleeve is prepared by m oving the stone
around the shoulder with the handpiece revolving at medium speed to increase the operator’s sense o f “ fe e l;'’ a new fin ish line is created 0.75 mm. below the shoulder (Fig. 9 ) . T h e Duralay prevents any accidental removal o f the coronal tooth structure; even more important, the 1.5 mm. cutting tip acts as a depth gauge when com pared with the free mar gin o f the gingiva (Fig. 10). Preparation Finishing • T h e smoothing and finishing o f a preparation with sand paper disks easily produce undercuts or unwanted reduction. T h e white tapered mounted polishing stone, as it is m anu factured, is too wide for most regions; it can be reduced by rotating it in the hand piece while applying a diam ond stone. T h e preparation is smoothed by circu lar m ovem ent similar to the reduction stage; the final preparation will be smooth with a sharp pulpal line angle, square shoulder and 0.75 mm. sleeve pre pared past the shoulder (Fig. 11). T he occlusal portion is smoothed and rounded with an abrasive rubber wheel ( Jelenko W hiz wheel) at slow speed (Fig. 12). E L A S T IC IM P R E S S IO N M A T E R IA L S
In the final analysis the impression tech nic that consistently produces the best results with the least tissue trauma will be selected. It should also be emphasized that the type o f working m odel produced, in relation to its facility o f laboratory handling, is also an extremely important factor often eliminated in discussions of the merits o f one system over another. T h e type o f working m odel can also affect the m ethod o f centric relation transfer. Ingenious combinations o f m a terials and m ethods by gifted operators seem to eliminate this problem. S O F T T IS S U E M A N IP U L A T IO N
In most posterior regions o f the mouth, the preparation should go up to the free margin o f the gingiva and only slightly
56/518 • THE JO URN AL OF THE AM ERICAN DENTAL ASSOCIATION
HARD PLUNGER BAND SEATED FIG, 17 SEAR
SOFT
COMPOUND
F ig. 17 • Im p re ssio n tech n ic. T ig h t fit with m o d ifie d b a n d is just as critica l as with u n m o d ifie d b a nd s. D rie d b a n d is filled with so fte n e d b ro w n stick c o m p o u n d with s lig h t excess (a b o u t 2 m m .) to fo rm a h a rd p lu n g e r. S o fte n e d c o m p o u n d is se a re d t o c o n to u re d e d g e s of b a n d Fig. 18 • S e a t in g . C o m p o u n d is re h e a te d w ith o u t s o fte n in g h a rd c o m p o u n d p lu n g e r ; b a n d is se a te d o n a b u tm e n t w ith fin g e rn a il p re ssu re F ig . 19 • C o m p re ss io n . B an d is m a in ta in e d in p o sitio n w h ile th u m b c o m p re sse s c o ld p lu n g e r F ig. 20 • C r o s s sectio n. R e su ltin g im p re ssio n c o n ta in s fine d e ta ils o f g in g iv a l r e g io n w h ich in clu d e s finish line a n d b e lo w
below. The manipulation of the gingiva in these regions for a good elastic impres sion is not an insurmountable problem; however, in the critical upper anterior re gion the margins are subgingival from 1 to 1.5 mm. Gingival retraction does pose a problem when sufficient marginal exposure is induced for a proper impres sion; soft tissue injury results. The gingival reaction to injury in this critical region often is recession because o f the thinness of the tissue. Any impres sion will injure the gingiva which, of course, includes the compound tube im pression. It is a question of degree and the individual preference of the operator.
O f the elastic impression materials I prefer rubber; I find it invaluable for inlays and for partial, immediate and some complete denture impressions. C O M P O U N D T U B E IM P R E S S IO N
For full coverage preparations I prefer compound tube impressions. The object of this technic is to reproduce the margins and the regions below in the compound. Band Selection • The tightest fitting con toured annealed band is fitted to the tooth (Fig. 13). The next larger size is used for the impression (Fig. 14). It is
WEINBERG . . . VOLUME 67, OCTOBER 1963 • 57/519
METALIZED CHIMNEY
2mm. CHIMNEY
28 GAUGE WAX
FIG. 22
FIG. 21
UNMETALIZED 6mm. WAX CHIMNEY
FIG. 24
LOOSE FAST CURE ACRYLIC
FIG. 23
F ig . 21 • C o p p e r p la tin g . U su a l 28 g a u g e wax c h im n e y is a d a p te d clo se to b a n d a fte r it is a tta c h e d p ro p e r ly t o ca th o d e . It is trim m e d to w ithin 2 m m . o f b a n d F ig. 22 • M e ta liz e d ch im n e y. 2 m m . wax c h im n e y is m etalize d with im p re ssio n F ig . 23 • U n m e ta lize d ch im n e y. O v e r m etalize d 2 mm. c h im n e y a n o th e r la y e r o f 2 8 g a u g e wax is a d a p t e d in usual w a y a n d left u nm etalized F ig. 2 4 • C o p p e r p la tin g . A f t e r c o p p e r p la tin g, a c ry lic resin h a n d le is p o u re d
vital to the success o f this technic to get exactly one size larger. Haphazard selec tion will result in gross gingival bulk with fracture of the compound and poor mar ginal delineation. Band Modification • The annealed band is properly contoured in the usual way and smoothed; 1 mm. cuts are made around opposite end of the band with scissors (Fig. 14). These tabs are bent back against the band, forming a finn periph ery for seating (Fig. 15). The contoured end is bent slightly inward with Peso pli ers around the entire periphery (Fig. 16). This serves as a lock for the compound and allows a bulk o f material to record the finish line and below the finish line completely.
Band Fit • A tight fit with the modified band is just as critical as with straight bands. A little experience will indicate quickly how much to bend in while con touring the band. Trial seating with soft utility wax also helps. Impression Technic • The dried band is filled with softened brown stick com pound with a slight excess (about 2 mm.) to form a plunger (Fig. 17). The softened compound is seared to the contoured edges of the band. The compound is reheated without softening the hard com pound plunger; then fingernail pressure is used to seat it on the abutment (Fig. 18). The band is maintained in position while the thumb compresses the cold plunger (Fig. 19). The impression is
58/520 • THE JO URN AL OF THE AMERICAN DENTAL ASSOCIATION
cooled with tepid water; all excess com pound is removed subgingivally and occlusally. Results • The impression is removed with the aid of Baade pliers in the long axis of the tooth; one hand is placed across the occlusal table to prevent injury to the opposing teeth. The resulting impression contains fine details of the gingival region including the finish line and below (Fig.
END OF BAND mm. METAL PROTECTDN SKIRT GRANULAR COPPER
20 ).
FIG. 25 Copper Plating • The band should be copper plated with an improved technic. The usual 28 gauge wax chimney is adapted close to the band after it is prop erly attached to the cathode (Fig. 21). The wax is trimmed to within 2 mm. of the band; it is metalized with the impres sion (Fig. 22). Over this metalized 2 mm. chimney another layer of 28 gauge wax is adapted in the usual way and left unmetalized (Fig. 2 3). After copper plating, an acrylic resin handle is poured (Fig. 24). The metal ized 2 mm. chimney plates a copper protection skirt, thus extending the area the technician must trim to 2 mm.
Fig. 25 • Results. M e ta liz e d 2 m m . c h im n e y p lates c o p p e r skirt e x te n d in g t o 2 mm. a re a s w h ich t e c h nician m ust trim a w a y from vita l a re a s o f the im p re ssio n
away from the vital sion (Fig. 25). An stone does not ruin mise the results. 57 West
parts of the impres accidental slip of a the die or compro Fifty-Seventh Street
instructor, department of graduate and postgraduate prosthodontics, New York University College of Dentistry. I. Weinberg, L. A. Esthetics and the gingivae in full coverage. J. Pros. Den. 10:737 July-Aug. I960.
Abutment Preparation and Impression Technic for Full Coverage
In this report technics are presented for full coverage abutment preparation, com pound tube impressions and copper plat ing, which consistently have produced excellent results for the author. Each den tist, how ever, must experim ent with dif feren t m ethods until he finds the best combination in his own hands.
Full coverage preparation and impression technics are varied to suit the needs and skill o f the operator; this report describes a m ethod that consistently produces the best results for me.
A R M A M E N T A R IU M
An ultra-speed instrument over 125,000 rpm is necessary in m od em day technol ogy. I prefer a Page-Chayes instrument (with a steel chuck) because it has a positive drive and selective speeds. Often, slower speeds are necessary to obtain the proper feel and control for exact m ar ginal placem ent and con tou r; this is a matter o f personal preference. Oral evacuation, with a modern system designed for this purpose, is essential to an efficient prosthodontic practice. It is vital to the dentist as well as the patient, in order to relieve mental fatigue associ ated with inefficient operations.
T R E A T M E N T O B J E C T IV E : A B U T M E N T PR E P A R A T IO N
T h e treatment objective in full coverage abutment preparation is to reduce the tooth structure sufficiently to facilitate the placem ent o f a properly contoured restoration with excellent marginal adap tation and occlusion. T his must be ac complished with minimal pulpal and soft tissue damage. T h e marginal placement and relationship to the gingiva have been discussed previously.1
E N A M E L S T R IP P IN G
A distinction should be made between en amel stripping and dentin preparation. Needless pulpal irritation is produced and time consumed in wearing away the en amel from the outside. T h e enamel is stripped off the occlusal, buccal and lin gual surfaces with a large Leff stone in a straight handpiece at 20,000 rpm. T he instrument is placed on the occlusal sur face for cutting into the dentinoenamel
52/514 • THE JO U RN A L OF THE AMERICAN DENTAL ASSOCIATION
ENAMEL STRIPPING DENTIN FIG. I
FIG. 2
ENAMEL
701 IN D-E JUNCTION
LABIAL GROOVE 701
FIG.4
THIN ENAMEL WALL
F ig . I • Enam el s tr ip p in g . L a rg e Leff sto ne is p la c e d on o c c lu sa l s u rfa c e a n d cuts in to c e m e n to e n a m e l ¡unction. It is m o v e d m e sially to keep w a te r s p r a y on c u t tin g su rfa c e Fig. 2 • En am el s t r ip p in g o f b u c c a l a n d lin gu a l su rfac e s. B ucca l a n d lin gu a l enam el re d u ce d , w h ich results in s g u a r e p re p a ra tio n with o n ly m esial a n d d ista l en a m el in ta c t
su rfa c e s are
Fig. 3 • B uccal g r o o v e . 701 c a r b id e cro ssc u t b u r cuts b u c c a l g r o o v e u p to fre e m a rg in o f g in g iv a a n d n ot b e lo w ; I mm. sh o u ld e r is c re a te d at g in g iv a l su rfa c e Fig. 4 • In te rp ro x im a l su rfa c e re d u ction . 701 b u r c o n tin u e s in d e n tin o e n a m e l ¡unction t h r o u g h interp ro xim al s u rfa c e le a v in g thin en am e l wall p ro te c t in g a d ja c e n t to o th
junction and moved mesially to keep water spray on the cutting surface (Fig. 1) . The combination of high speed and a concentric stone and handpiece limits vibration. The buccal and lingual surfaces are reduced in the same fashion, which re sults in a square preparation with only the mesial and distal enamel intact (Fig. 2 ). A B U T M E N T P R E P A R A T IO N
A new 701 carbide crosscut bur in the in strument o f the operator’ s choice is placed on the midline of the labial surface up to the free margin o f the gingiva and not below. The instrument is applied pulpally
until a groove is cut producing a 1 mm. shoulder (Fig. 3) at the gingival margin. The depth of the cut is controlled to pro duce a finish line or a shoulder as desired. The handpiece is moved mesially in a definite stroke, rather than a brushing action, creating the shoulder as it goes along. Discipline is necessary to raise the instrument occlusally to follow the con tour of the gingiva interproximally. U n less this is done, the shoulder disappears, and the margins become much too sub gingival. IN T E R P R O X IM A L R E D U C T IO N
The 701 bur continues in the dentino enamel junction through the interproxi-
W EINBERG . . . VOLUME 67, OCTOBER 1963 • 53/515
mal surface leaving a thin enamel wall protecting the adjacent tooth (Fig. 4 ). If the instrument is held upright, parallel with the long axis of the tooth, a thinner bur seldom is required. This procedure is repeated for the distal surface and joined on the lingual surface to produce a prep aration with the finish line up to but not below the free margin of the gingiva. SU B G IN G IV A L S H O U L D E R
Only on the maxillary anterior teeth from bicuspid to bicuspid is it necessary to drop
FIG.6
5
DIAMOND FIG. 8
the shoulder below the gingiva. When necessary it should be limited to 0.75 mm. ; most often it is too deep rather than too shallow. This should be done after the interproximal surface has been pre pared to prevent the problem of the “ dis appearing shoulder.” If this procedure is not followed, the labial subgingival shoul der is carried interproximally much more apically than it should be. The result is the permanent dissection of transseptal periodontal fibers with the apical migra tion of epithelial attachment and subse quent bone reduction.
BARREL 9
SLEEVE PREPARED
10
DEPTH
Fig. 5 • P re p a ra tio n r e sh a p in g . Thin, ta p e re d , ro u g h d ia m o n d sto n e is p la c e d u p t o sho u ld e r, m o v e d c irc u la rly to p ro d u c e p r o p e r t a p e r a n d re d u ctio n Fig. 6 • O c c lu s a l re d u ctio n . B a rre l-sh a p e d sto n e is p la c e d on o c c lu s a l s u rfa c e to re d u c e central, b u c c a l a n d lin gu a l g r o o v e areas. Even 1.5 mm. c le a ra n c e can b e a c c o m p lis h e d e a sily w ith o u t o v e rre d u c tio n Fig. 7 • P re p a ra tio n refine m e nt. O c c lu sa l a s p e c t o f p re p a ra tio n m ust b e ro u n d e d in o rd e r t o re d u ce the b u c c o lin g u a l w idth a n d to p ro v id e eve n thickn ess o f m ate ria l w ith p ro p e r c o n t o u r F ig. 8 • M o d if ie d d ia m o n d stone. G o ld sleeve sh o u ld exte nd 0.75 m m. b e y o n d s h o u ld e r on p re p a re d tooth structure. M o d if ie d d ia m o n d sto ne has b ee n d e v ise d f o r this p u rp o se . T h in n e st ta p e re d d ia m o n d sto ne a v a ila b le is c o v e re d with fine layer o f D u r a la y (p a in te d o n ) to w ithin 1.5 m m . o f end F ig. 9 • C o n t r o lle d s u b g in g iv a l d ep th. S le e v e is p re p a re d b y m o v in g sto n e a ro u n d s h o u ld e r with h a n d p ie c e re v o lv in g a t m e d iu m sp e e d to in cre a se o p e r a t o r 's sen se o f " f e e l " ; new finish line is c re a te d 0.75 mm. b e lo w s h o u ld e r Fig. 10 • D e p th g a u g e . M o d if ie d d ia m o n d s to n e 's 1.5 mm. c u ttin g tip acts as a d e p t h g a u g e w hen c o m p a r e d t o fre e m a rg in o f g in g iv a
54/516 • THE JO URN AL OF THE AMERICAN DENTAL ASSOCIATION
POLISHING STONE
ABRASIVE WHEEL FIG.lt
FIG.
SHARP LINE ANGLE SQUARE SHOULDER 3/4m m . SLEEVE
RUBBER
Fig. I I • A b u t m e n t fin ish in g . P re p a ra tio n is sm o o th e d b y c ir cu la r m o v e m e n t sim ila r to re d u c tio n s ta g e with ta p e r e d fin ish in g sto n e ; final p re p a ra tio n will be sm o o th with s h a rp p u lp a l line an gle , sq u a re s h o u ld e r and a 0.75 mm. sleeve p re p a re d p a st sh o u ld e r Fig. 12 • Final sm o o th in g . O c clusal p o rtio n is sm o o th e d and ro u n d e d with a b ra siv e ru b b e r w heel at slow sp e e d
O C C L U S A L R E D U C T IO N
P R E P A R A T IO N R E S H A P IN G
A thin, tapered rough diamond stone is placed up to the shoulder and moved cir cularly to produce the proper taper and reduction (Fig. 5 ). When a finish line is the preparation of choice, it is refined and dropped 0.5 mm. below the free margin of the gingiva with the diamond stone.
One of the consistent errors in abutment preparation is the lack of sufficient and properly contoured occlusal surface re duction. A barrel-shaped stone is placed on the occlusal surface to reduce the cen tral, buccal and lingual groove areas (Fig. 6 ). An even 1.5 mm. clearance can
ONE SIZE LAR G ER BAND
TIGHT BAND
Fig. 13 Fig. 14 in usual Fig. 15
FIG. 13
FIG. 14
FIG. 15
FIG. ¡6
• B an d sele ction . T ig h te st • B an d m o d ific a tio n . N e xt w ay; I mm. cuts are m a d e • Firm p e rip h e ry . T a b s are
c o n to u re d a n n e a le d b a n d is fitted to tooth la rg e r size then is used fo r im p re ssio n . B an d is c o n to u re d p ro p e rly on o p p o s it e en d all a ro u n d b a n d with scisso rs b e n t b a ck a g a in s t b a n d fo rm in g firm p e rip h e ry fo r se a tin g
Fig. 16 • B an d c o n to u rin g . C o n t o u r e d e n d then is b e n t in w a rd with Peso plie rs a ro u n d entire p e rip h e ry
W EINBERG . . . VOLUME 67, OCTOBER 1963 • 55/517
be accomplished easily without fear of overreduction. P R E P A R A T IO N R E F IN E M E N T
T he occlusal aspect o f the preparation must be rounded in order to reduce the buccolingual width and to provide an even thickness o f material with the proper contour (Fig. 7 ). W hen a veneer restoration is used, this step is essential to prevent bulky, m alcontoured restora tions; the technician must be provided with sufficient space to produce the de sired result. PO R C E L A IN J A C K E T P R E P A R A T IO N S
Porcelain jackets require a full shoulder completely around the tooth ; whenever possible it should be 1 mm. wide. T he finish line is often rough with unsup ported enamel. Since the porcelain will butt against the tooth structure, it is es sential to refine this area. T h e pulpal line angle should be w ell-defined; sharp hand instruments (hoes) facilitate accentuat ing this line angle, reducing unsupported enamel and smoothing the finish line it self. T h e result is a smooth 1 mm . shoul der at right angles to the pulpal wall. PR E P A R A TIO N F O R V E N E E R SLEE V E
W hen veneer restorations are required, a gold sleeve should be constructed to ex tend 0.75 mm. beyond the shoulder. In order to prevent overhanging margins, interferences in proper seating, excess bulk and gingival irritation, this tooth structure past the shoulder must be pre pared. A m odified diam ond stone has been devised for this purpose. T h e thin nest tapered diam ond stone available is covered with a fine layer o f Duralay (painted on ) to within 1.5 mm. o f the end (Fig. 8 ). Controlled Subgingival D epth • T he sleeve is prepared by m oving the stone
around the shoulder with the handpiece revolving at medium speed to increase the operator’s sense o f “ fe e l;'’ a new fin ish line is created 0.75 mm. below the shoulder (Fig. 9 ) . T h e Duralay prevents any accidental removal o f the coronal tooth structure; even more important, the 1.5 mm. cutting tip acts as a depth gauge when com pared with the free mar gin o f the gingiva (Fig. 10). Preparation Finishing • T h e smoothing and finishing o f a preparation with sand paper disks easily produce undercuts or unwanted reduction. T h e white tapered mounted polishing stone, as it is m anu factured, is too wide for most regions; it can be reduced by rotating it in the hand piece while applying a diam ond stone. T h e preparation is smoothed by circu lar m ovem ent similar to the reduction stage; the final preparation will be smooth with a sharp pulpal line angle, square shoulder and 0.75 mm. sleeve pre pared past the shoulder (Fig. 11). T he occlusal portion is smoothed and rounded with an abrasive rubber wheel ( Jelenko W hiz wheel) at slow speed (Fig. 12). E L A S T IC IM P R E S S IO N M A T E R IA L S
In the final analysis the impression tech nic that consistently produces the best results with the least tissue trauma will be selected. It should also be emphasized that the type o f working m odel produced, in relation to its facility o f laboratory handling, is also an extremely important factor often eliminated in discussions of the merits o f one system over another. T h e type o f working m odel can also affect the m ethod o f centric relation transfer. Ingenious combinations o f m a terials and m ethods by gifted operators seem to eliminate this problem. S O F T T IS S U E M A N IP U L A T IO N
In most posterior regions o f the mouth, the preparation should go up to the free margin o f the gingiva and only slightly
56/518 • THE JO URN AL OF THE AM ERICAN DENTAL ASSOCIATION
HARD PLUNGER BAND SEATED FIG, 17 SEAR
SOFT
COMPOUND
F ig. 17 • Im p re ssio n tech n ic. T ig h t fit with m o d ifie d b a n d is just as critica l as with u n m o d ifie d b a nd s. D rie d b a n d is filled with so fte n e d b ro w n stick c o m p o u n d with s lig h t excess (a b o u t 2 m m .) to fo rm a h a rd p lu n g e r. S o fte n e d c o m p o u n d is se a re d t o c o n to u re d e d g e s of b a n d Fig. 18 • S e a t in g . C o m p o u n d is re h e a te d w ith o u t s o fte n in g h a rd c o m p o u n d p lu n g e r ; b a n d is se a te d o n a b u tm e n t w ith fin g e rn a il p re ssu re F ig . 19 • C o m p re ss io n . B an d is m a in ta in e d in p o sitio n w h ile th u m b c o m p re sse s c o ld p lu n g e r F ig. 20 • C r o s s sectio n. R e su ltin g im p re ssio n c o n ta in s fine d e ta ils o f g in g iv a l r e g io n w h ich in clu d e s finish line a n d b e lo w
below. The manipulation of the gingiva in these regions for a good elastic impres sion is not an insurmountable problem; however, in the critical upper anterior re gion the margins are subgingival from 1 to 1.5 mm. Gingival retraction does pose a problem when sufficient marginal exposure is induced for a proper impres sion; soft tissue injury results. The gingival reaction to injury in this critical region often is recession because o f the thinness of the tissue. Any impres sion will injure the gingiva which, of course, includes the compound tube im pression. It is a question of degree and the individual preference of the operator.
O f the elastic impression materials I prefer rubber; I find it invaluable for inlays and for partial, immediate and some complete denture impressions. C O M P O U N D T U B E IM P R E S S IO N
For full coverage preparations I prefer compound tube impressions. The object of this technic is to reproduce the margins and the regions below in the compound. Band Selection • The tightest fitting con toured annealed band is fitted to the tooth (Fig. 13). The next larger size is used for the impression (Fig. 14). It is
WEINBERG . . . VOLUME 67, OCTOBER 1963 • 57/519
METALIZED CHIMNEY
2mm. CHIMNEY
28 GAUGE WAX
FIG. 22
FIG. 21
UNMETALIZED 6mm. WAX CHIMNEY
FIG. 24
LOOSE FAST CURE ACRYLIC
FIG. 23
F ig . 21 • C o p p e r p la tin g . U su a l 28 g a u g e wax c h im n e y is a d a p te d clo se to b a n d a fte r it is a tta c h e d p ro p e r ly t o ca th o d e . It is trim m e d to w ithin 2 m m . o f b a n d F ig. 22 • M e ta liz e d ch im n e y. 2 m m . wax c h im n e y is m etalize d with im p re ssio n F ig . 23 • U n m e ta lize d ch im n e y. O v e r m etalize d 2 mm. c h im n e y a n o th e r la y e r o f 2 8 g a u g e wax is a d a p t e d in usual w a y a n d left u nm etalized F ig. 2 4 • C o p p e r p la tin g . A f t e r c o p p e r p la tin g, a c ry lic resin h a n d le is p o u re d
vital to the success o f this technic to get exactly one size larger. Haphazard selec tion will result in gross gingival bulk with fracture of the compound and poor mar ginal delineation. Band Modification • The annealed band is properly contoured in the usual way and smoothed; 1 mm. cuts are made around opposite end of the band with scissors (Fig. 14). These tabs are bent back against the band, forming a finn periph ery for seating (Fig. 15). The contoured end is bent slightly inward with Peso pli ers around the entire periphery (Fig. 16). This serves as a lock for the compound and allows a bulk o f material to record the finish line and below the finish line completely.
Band Fit • A tight fit with the modified band is just as critical as with straight bands. A little experience will indicate quickly how much to bend in while con touring the band. Trial seating with soft utility wax also helps. Impression Technic • The dried band is filled with softened brown stick com pound with a slight excess (about 2 mm.) to form a plunger (Fig. 17). The softened compound is seared to the contoured edges of the band. The compound is reheated without softening the hard com pound plunger; then fingernail pressure is used to seat it on the abutment (Fig. 18). The band is maintained in position while the thumb compresses the cold plunger (Fig. 19). The impression is
58/520 • THE JO URN AL OF THE AMERICAN DENTAL ASSOCIATION
cooled with tepid water; all excess com pound is removed subgingivally and occlusally. Results • The impression is removed with the aid of Baade pliers in the long axis of the tooth; one hand is placed across the occlusal table to prevent injury to the opposing teeth. The resulting impression contains fine details of the gingival region including the finish line and below (Fig.
END OF BAND mm. METAL PROTECTDN SKIRT GRANULAR COPPER
20 ).
FIG. 25 Copper Plating • The band should be copper plated with an improved technic. The usual 28 gauge wax chimney is adapted close to the band after it is prop erly attached to the cathode (Fig. 21). The wax is trimmed to within 2 mm. of the band; it is metalized with the impres sion (Fig. 22). Over this metalized 2 mm. chimney another layer of 28 gauge wax is adapted in the usual way and left unmetalized (Fig. 2 3). After copper plating, an acrylic resin handle is poured (Fig. 24). The metal ized 2 mm. chimney plates a copper protection skirt, thus extending the area the technician must trim to 2 mm.
Fig. 25 • Results. M e ta liz e d 2 m m . c h im n e y p lates c o p p e r skirt e x te n d in g t o 2 mm. a re a s w h ich t e c h nician m ust trim a w a y from vita l a re a s o f the im p re ssio n
away from the vital sion (Fig. 25). An stone does not ruin mise the results. 57 West
parts of the impres accidental slip of a the die or compro Fifty-Seventh Street
instructor, department of graduate and postgraduate prosthodontics, New York University College of Dentistry. I. Weinberg, L. A. Esthetics and the gingivae in full coverage. J. Pros. Den. 10:737 July-Aug. I960.