Nontraumatic Final Impressions for Fixed Partial Dentures Jules M. Hoflan, AB,DDS* A nontraumatic, nonretraction impression technique is presented which uses the fabrication of an acrylic resin shell from an interocclusal wax impression. A crucial step in the procedure is obtaining the complete finish line of the preparation within the resin. This tray, which is filled with an elastomeric impression material, is combined with a triple tray of the same material to provide all the necessary relationships to construct a crown or coping. This procedure is especially efficient for multiple abutments during fixed partial denture construction. J Prosthod 1:61-64.Copyright o 1992 by the American College of Prosthodontists.
INDEX WORDS: dental impressions, nontraumatic acrylic resin shell impressions
T
he need for a nontraumatic, nonretractive impression procedure during fixed partial denture construction is well documented in the periodontal literature. Tarnow et all state that the rapid gingwal repair activated by the placement of subgingival crown margins results essentially in the form of recession and liniited gingival inflamation. However, significant crestal resorption of the labial plate was This can result in the creation ofa periodontal pocket and/or recession after the restoration is inserted. The resulting exposure of the crown margin can be esthetically disconcerting for both patient and dentist. This information also suggests that there is great need for nontraumatic methods of tooth prcparation and provisional restorations during rehabilitative procedures. Rue1 et a14 state "that on the basis of wound healing and gingival recession caused by the three methods of'tissue management during the impression phase, the copper band impression method was the least trauma ti^."^ These recent articles stimiilated a search of the prosthetic literature for a nontraumatic method for replicating fixcd partial denturc preparations. In 1965, Cannistraci5 published an article in which he presented a new approach to impression making for full coverage restorations."? His method uses an acrylic resin shell which serves as a tray for the: impression material. This article presents an updatc of his original idea accompanied with refinements of
*ilmrtanl Clinical Prujssor $Prosthetic Dentzsty, Columbia ITniuer-
sig School $Dental and Oral S u r g q , A h I'ork, AT. Address repint reqursts to: Jules :M. Hoffman,AB,DDS: Columbia Univemty School oJDental and Oral Surgqy, 670 W 168 St>Nrrui York, AY 10032. Copyiiht 8 1992 by theAmerican College ofPosthodontirtr 105!W41X/92/ 0101-001285.00/0
technique and the introduction of advanced materials. It combines the advantages of the less traumatic copper tube technique with the mechanical displacement of gingival tissue without any accompanying trauma and recession from the retraction cord.
Prerequisites First, an interocclusal wax impression of the unprepared teeth is needed and an intimate clinical knowledge of the basic tcchnique for the construction o f a nontraumatic, direct provisional acrylic resin restoration? Second, a nontraumatic preparation is needed to the gingival crest with a 45"bevel subgingivally no wider than 1 mm.q
Technique The standard procedure for preparing a porcelain-tometal crown is used with littlc or no gingival trauma. To produce an acrylic shell, the basic tcchnique for the construction of a direct acrylic resin provisional is followed (Figs I and 2). Because marginal accuracy is rarely accomplished with the first application of resin, a thin mix of acrylic resin is added to the dried but doughy resin, which is still soft, and then reinserted on the preparation. The initial acrylic resin acts as a plunger forcing the thin acrylic resin into the gingival crevice. Because the acrylic resin is confined in the wax, the additions have no other place to go except into the sulcus, thus capturing the finish line of the preparation. This stcp is crucial to this technique because if the finish line is not reproduccd in the acrylic resin, the impression may be
Journal cfPrasthodontics. T'ol I , N o 1 (Stperrib)),1992:pp 61-64
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Nontraumatic Impessionrfm Full Coverage
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I
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Sfptcmbtrr1992, Volume I , ,Vurnber 1
inaccurate in this area (Fig 3). After the Inass has cured, it is removed from the wax, dried, and inspected for accuracy. If the margin is shy at some area, it is possible to add some resin with a brush into the sulcus and then reseat the cured acrylic. The acrylic resin is removed from the wax, dried, and the margin is scribed with a 0.30 Rapidograph pcn (Koh-Noor Corp., Bloomsbury, NJ; Fig 4). The external excess of the acrylic resin at the margin is reduced with a heatless wheel leaving about % mm thickness of resin at the scribed line. The entire internal surface of the resin is now ground out with an acrylic bur so that at lcast 1 mm of resin is removcd up to but not encroaching on the scribed line of the margin. A resin shell is created which will s e n e as the tray for the impression (Fig 5). The resin shell is replaced on the preparation with pressure. The operator should see some blanching because the internal occlusal surface was relieved. Holding the shell in this position, additional acrylic is added with a brush to the external occlusal surface. The patient is instructed to close his or her mouth when the added acrylic resin has become doughy. The purpose of this addition is to have the patient close his or her mouth in centric occlusion with the gingiva blanched. This step provides minimal retraction of the gingiva in order to capture a slight amount of tooth structurc beyond the finish line. This proves the end of the prcparation. The margins are checked for accuracy and the interproximal contacts are slightly reduced to allow for some of the impression matcrial to register the proximal surfaces of the adjacent teeth. All surfaces of the resin shell are coated with the companion adhesive to the elastomeric material used (Fig fi). The adhesive also prevents moisture release and resultant distortion of the acrylic. This technique is suitable for use with any of thc polyethers, polysyloxanes silicones, or rubber bases. When the adhesive has dried, adequate material is squeezed on a pad for a full mouth custom or sectional triple tray. The material is mixed and the resin shell and triple tray are loaded. The teeth are dried, the resin
Figure 1. Armamentarium. Figure 2. Interocclusal was i~npressionbefore tooth preparation. (Reprintcd with permission.8) Figure 3. Cured resin with captured prcparation finishing lines. (Reprinted with permission?) Figure 4. Finishing line scribed with a Rapidograph pen. (Reprinted uith permission?) Figure 5. Relieved resin shell. Figure 6. Resin shell coated with adhesive. Figure 7. Final impression in triple tray. Figure 8. Final impression of three unit fixrd partial denture.
shell is inscrted on the tooth followed by the triple tray, and the patient is instructed to close his or her mouth. After sufficient time has been allowed for setting, the patient is instructed to open his or her mouth so that the counter is separated first. The preparation side is removed within the path of withdrawal by means of an instrument placed on the lingual side and a finger on the buccal aspect (Fig 7). The impression is dried and inspected for accuracy. If all thc preceding steps have been followed, the first take is usually successful. If it is incomplete, the inissing area is noted, the resin tray is removed from the shell and the triple tray. Acrylic resin is paintcd into the sulcus in the area of deficiency and replaced on the tooth until cured. The impression procedure is then repeated. The impression should he poured immediately to prevent any distortion of the acrylic shell. This technique can be used for multiple abutments and fixed partial denture impressions if the edentulous areas are first blocked out with any suitable resin and checked for occlusion before the intcrocclusal wax impression is made. This results in an acrylic resin bridge tray which is used to produce an accurate impression without retraction cord and the associated trauma (Fig 8). This procedure is not advised for preparations whose finishing lines are more than 2 mm subgingivally because of the difficulty in reproducing the margin in acrylic resin shell.
Summary A nontraumatic, nonretraction impression technique for fixed partial denturcs is dcscribcd using an acylic resin shell which is fabricated from an interocclusal wax impression. The crucial step is to accurately reproduce the finish line ofthe prepared teeth within the acrylic resin shell. The resin tray loaded with clastomcric impression material is placed on the prepared tooth along with a loaded triple tray which combines the relationship of the impression of the prepared tooth to its adjacent teeth and the occlusion all in one step. The advantage with this technique is minimal trauma to the gingival tissucs and minimal loss of crestal hone. The disadvantage is difficulty in obtaining a n acceptable impression when the finish linc is more than 2 mm below the gingival crest.
64
Xontraumatic Impressionsf0 Full Coverage
References 1. Tarnow D, Stahl SS, Magner A, et al: Human gingival attachment responses to subgingival crown placement.J Clin Periodunto1 1986;13:563-569 2. Lo< H; SilnessJ: Tissue reactions to string packs uscd in fixer1 rcstorations. J Prosthet Dent 19f23;13:318-323 3. Ingraham R: Rotary gingival rurrctage-A technique for tooth prcparation and managcmmt of the gingival sulcus for imprcssion taking. IntJ Pcriodont Rest Dent 1981;1:8-33 4. Rue1 J, Schuessler. P, Malamcnt K, et al: ERect of rrtraction proccdurcs on thr pcriodontium in humans. J Prosthet Dent 1980:44:508-515
Jukr hi'. Hornan
5. Cannistraci AJ: A new approach to impression taking for crown and bridge. Drnt Clin North Am 1965; ?*far:73-99 6. LaForgia .4: Cordlcss tissue retraction for impressions for fixed prosthesis.,J Prosthet Dent 1967;17:379-386 7. 1,aForgia A: Multiple abutmrnt impressions using vacuum adapted temporary sp1ints.J Prosthct Dent IY70;23:44-50 8. Hoffman JMir? Ruhiri M: Interocclusal wax impressionsfor me in proLisiona1 and associated fixed prosthodontic procedures. J Prosthet Dent 1989;62:395-400
9. Hoffman JM: Modern concepts in crown preparation: A review with special emphasis on periodontal health. hY State D m t J
1991;57:32-35
INDEX WORDS: dental impressions, nontraumatic acrylic resin shell impressions
T
he need for a nontraumatic, nonretractive impression procedure during fixed partial denture construction is well documented in the periodontal literature. Tarnow et all state that the rapid gingwal repair activated by the placement of subgingival crown margins results essentially in the form of recession and liniited gingival inflamation. However, significant crestal resorption of the labial plate was This can result in the creation ofa periodontal pocket and/or recession after the restoration is inserted. The resulting exposure of the crown margin can be esthetically disconcerting for both patient and dentist. This information also suggests that there is great need for nontraumatic methods of tooth prcparation and provisional restorations during rehabilitative procedures. Rue1 et a14 state "that on the basis of wound healing and gingival recession caused by the three methods of'tissue management during the impression phase, the copper band impression method was the least trauma ti^."^ These recent articles stimiilated a search of the prosthetic literature for a nontraumatic method for replicating fixcd partial denturc preparations. In 1965, Cannistraci5 published an article in which he presented a new approach to impression making for full coverage restorations."? His method uses an acrylic resin shell which serves as a tray for the: impression material. This article presents an updatc of his original idea accompanied with refinements of
*ilmrtanl Clinical Prujssor $Prosthetic Dentzsty, Columbia ITniuer-
sig School $Dental and Oral S u r g q , A h I'ork, AT. Address repint reqursts to: Jules :M. Hoffman,AB,DDS: Columbia Univemty School oJDental and Oral Surgqy, 670 W 168 St>Nrrui York, AY 10032. Copyiiht 8 1992 by theAmerican College ofPosthodontirtr 105!W41X/92/ 0101-001285.00/0
technique and the introduction of advanced materials. It combines the advantages of the less traumatic copper tube technique with the mechanical displacement of gingival tissue without any accompanying trauma and recession from the retraction cord.
Prerequisites First, an interocclusal wax impression of the unprepared teeth is needed and an intimate clinical knowledge of the basic tcchnique for the construction o f a nontraumatic, direct provisional acrylic resin restoration? Second, a nontraumatic preparation is needed to the gingival crest with a 45"bevel subgingivally no wider than 1 mm.q
Technique The standard procedure for preparing a porcelain-tometal crown is used with littlc or no gingival trauma. To produce an acrylic shell, the basic tcchnique for the construction of a direct acrylic resin provisional is followed (Figs I and 2). Because marginal accuracy is rarely accomplished with the first application of resin, a thin mix of acrylic resin is added to the dried but doughy resin, which is still soft, and then reinserted on the preparation. The initial acrylic resin acts as a plunger forcing the thin acrylic resin into the gingival crevice. Because the acrylic resin is confined in the wax, the additions have no other place to go except into the sulcus, thus capturing the finish line of the preparation. This stcp is crucial to this technique because if the finish line is not reproduccd in the acrylic resin, the impression may be
Journal cfPrasthodontics. T'ol I , N o 1 (Stperrib)),1992:pp 61-64
61
62
Nontraumatic Impessionrfm Full Coverage
0
Jules M.Ho&n
I
63
Sfptcmbtrr1992, Volume I , ,Vurnber 1
inaccurate in this area (Fig 3). After the Inass has cured, it is removed from the wax, dried, and inspected for accuracy. If the margin is shy at some area, it is possible to add some resin with a brush into the sulcus and then reseat the cured acrylic. The acrylic resin is removed from the wax, dried, and the margin is scribed with a 0.30 Rapidograph pcn (Koh-Noor Corp., Bloomsbury, NJ; Fig 4). The external excess of the acrylic resin at the margin is reduced with a heatless wheel leaving about % mm thickness of resin at the scribed line. The entire internal surface of the resin is now ground out with an acrylic bur so that at lcast 1 mm of resin is removcd up to but not encroaching on the scribed line of the margin. A resin shell is created which will s e n e as the tray for the impression (Fig 5). The resin shell is replaced on the preparation with pressure. The operator should see some blanching because the internal occlusal surface was relieved. Holding the shell in this position, additional acrylic is added with a brush to the external occlusal surface. The patient is instructed to close his or her mouth when the added acrylic resin has become doughy. The purpose of this addition is to have the patient close his or her mouth in centric occlusion with the gingiva blanched. This step provides minimal retraction of the gingiva in order to capture a slight amount of tooth structurc beyond the finish line. This proves the end of the prcparation. The margins are checked for accuracy and the interproximal contacts are slightly reduced to allow for some of the impression matcrial to register the proximal surfaces of the adjacent teeth. All surfaces of the resin shell are coated with the companion adhesive to the elastomeric material used (Fig fi). The adhesive also prevents moisture release and resultant distortion of the acrylic. This technique is suitable for use with any of thc polyethers, polysyloxanes silicones, or rubber bases. When the adhesive has dried, adequate material is squeezed on a pad for a full mouth custom or sectional triple tray. The material is mixed and the resin shell and triple tray are loaded. The teeth are dried, the resin
Figure 1. Armamentarium. Figure 2. Interocclusal was i~npressionbefore tooth preparation. (Reprintcd with permission.8) Figure 3. Cured resin with captured prcparation finishing lines. (Reprinted with permission?) Figure 4. Finishing line scribed with a Rapidograph pen. (Reprinted uith permission?) Figure 5. Relieved resin shell. Figure 6. Resin shell coated with adhesive. Figure 7. Final impression in triple tray. Figure 8. Final impression of three unit fixrd partial denture.
shell is inscrted on the tooth followed by the triple tray, and the patient is instructed to close his or her mouth. After sufficient time has been allowed for setting, the patient is instructed to open his or her mouth so that the counter is separated first. The preparation side is removed within the path of withdrawal by means of an instrument placed on the lingual side and a finger on the buccal aspect (Fig 7). The impression is dried and inspected for accuracy. If all thc preceding steps have been followed, the first take is usually successful. If it is incomplete, the inissing area is noted, the resin tray is removed from the shell and the triple tray. Acrylic resin is paintcd into the sulcus in the area of deficiency and replaced on the tooth until cured. The impression procedure is then repeated. The impression should he poured immediately to prevent any distortion of the acrylic shell. This technique can be used for multiple abutments and fixed partial denture impressions if the edentulous areas are first blocked out with any suitable resin and checked for occlusion before the intcrocclusal wax impression is made. This results in an acrylic resin bridge tray which is used to produce an accurate impression without retraction cord and the associated trauma (Fig 8). This procedure is not advised for preparations whose finishing lines are more than 2 mm subgingivally because of the difficulty in reproducing the margin in acrylic resin shell.
Summary A nontraumatic, nonretraction impression technique for fixed partial denturcs is dcscribcd using an acylic resin shell which is fabricated from an interocclusal wax impression. The crucial step is to accurately reproduce the finish line ofthe prepared teeth within the acrylic resin shell. The resin tray loaded with clastomcric impression material is placed on the prepared tooth along with a loaded triple tray which combines the relationship of the impression of the prepared tooth to its adjacent teeth and the occlusion all in one step. The advantage with this technique is minimal trauma to the gingival tissucs and minimal loss of crestal hone. The disadvantage is difficulty in obtaining a n acceptable impression when the finish linc is more than 2 mm below the gingival crest.
64
Xontraumatic Impressionsf0 Full Coverage
References 1. Tarnow D, Stahl SS, Magner A, et al: Human gingival attachment responses to subgingival crown placement.J Clin Periodunto1 1986;13:563-569 2. Lo< H; SilnessJ: Tissue reactions to string packs uscd in fixer1 rcstorations. J Prosthet Dent 19f23;13:318-323 3. Ingraham R: Rotary gingival rurrctage-A technique for tooth prcparation and managcmmt of the gingival sulcus for imprcssion taking. IntJ Pcriodont Rest Dent 1981;1:8-33 4. Rue1 J, Schuessler. P, Malamcnt K, et al: ERect of rrtraction proccdurcs on thr pcriodontium in humans. J Prosthet Dent 1980:44:508-515
Jukr hi'. Hornan
5. Cannistraci AJ: A new approach to impression taking for crown and bridge. Drnt Clin North Am 1965; ?*far:73-99 6. LaForgia .4: Cordlcss tissue retraction for impressions for fixed prosthesis.,J Prosthet Dent 1967;17:379-386 7. 1,aForgia A: Multiple abutmrnt impressions using vacuum adapted temporary sp1ints.J Prosthct Dent IY70;23:44-50 8. Hoffman JMir? Ruhiri M: Interocclusal wax impressionsfor me in proLisiona1 and associated fixed prosthodontic procedures. J Prosthet Dent 1989;62:395-400
9. Hoffman JM: Modern concepts in crown preparation: A review with special emphasis on periodontal health. hY State D m t J
1991;57:32-35
