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Complex Fixed and Implant Prosthodontics: Making Nearly Foolproof Impressions
G
ordon
J. C
h r is t e n s e n , d . d . s
.,
m .s
. d .,
p h .d .
COMPLEX FIXED AND IMPLANT PROSTHODONTICS: MAKING NEARLY FOOLPROOF IMPRESSIONS
ith im plant and fixed prosthodontics a m ajor need for aging populations, dentists m ust continue to improve their techniques in this area. Successful im pressions lead to successful prostheses. Are im pressions for complex fixed and im plant prostho dontics adequate throughout the U nited States? Discussions with any large dental lab oratory will verify th a t im pres sions are among the most inadequate of all dental procedures. Laboratories often receive im pressions for complex prostheses w ith incomplete m argins, im pression m aterial separated from the tray adhesive, prepared teeth touching the tray, air bubbles on im portant prepared teeth and other problems. I t’s possible to m ake im pressions for complex fixed or im plant prostheses th a t are predictably accurate and stable, and from which more th an 99 percent of the restorations may be expected to fit. Why isn’t it done more often? W hat simple technique can produce such impressions? CUSTOM TRAYS
Most dental schools promote custom trays for complex procedures, but m ost dentists
don’t use them. M anufacturers promote stock trays, and these trays seem to be state of the art. Are stock trays adequate for complex fixed and im plant prostheses? In my opinion, no. There are too m any variables w ith stock trays to provide predictable results for complex cases. D entists should simplify procedures and use custom trays for complex prostheses. Most practitioners th in k these trays are too expensive and require too much tim e. Wrong. Custom trays can be m ade quickly. Because they use about h alf as much impression m aterial as stock trays, custom trays are less expensive. Several good custom tray techniques are available today. One th a t optimizes the ideal tray characteristics uses lightcuring prosthodontic resins. These m aterials are readily available on the international m arket. M anufacturers include: Astron Dental; H eraeus Kulzer; Pro-Den Systems; and Dentsply York. In the U nited States, Dentsply’s Triad is most popular. Although the initial purchase of the system seems expensive, the total cost of a curing oven and a supply of tra y m aterial is about the sam e as one ill-fitting
crown. M aking a tra y requires only a few m inutes. If neces sary, it also can be modified in m inutes. W hen we consider the short am ount of auxiliary tim e needed to m ake the tra y and the reduced am ount of im pression m aterial, custommade, light-curing prostho dontic trays with the im pres sions cost the sam e or slightly less. WHEN TO USE CUSTOM TRAYS?
I prefer full-arch custom trays. I use them routinely for every situation involving three or more units. The technique for double-arch im pressions m ak ing upper and lower im pres sions and interocclusal records a t the same tim e is suggested for one or two u n its only (“Dayto-day fixed prosthodontics,” JADA 1992;123[ll]:91-2.). WHICH IMPRESSION MATERIAL.?
The five types of im pression m aterials available today are: ■■ polysulfide (usually brown rubberlike m aterial); ■■ condensation-reaction silicone (usually a paste and a liquid catalyst); **■ addition-réaction silicone (usually two pastes, and JADA, Vol. 123, December 1992
69
commonly auto-mix brands); ■■ polyether (two pastes and I some auto-m ix brands identifiable by a somewhat b itter taste); ™ hydrocolloid, reversible. U sing th e custom tray concept, b u t recognizing th a t m ost im pressions sent to I commercial laboratories in the I U nited S tates sit for 24 hours or more before pouring, addition1reaction silicone and polyether ! are the m ost accurate and stable. E ither type is an excellent, accurate, stable “stateof-the-art” m aterial for Dr. Christensen is use with founder and custom, light; c o-director of ! Clinical Research curing ; Associates, Provo, prosthodontic Utah, and a wellknown lecturer in the trays. j clinical practice of Popular, ! dentistry. He has his successful j master’s degree in restorative dentistry brands of and his doctorate in additioni education and | psychology. reaction silicone are: Exaflex, G.C. America; Express, 3M; Extrude, Kerr; Perm agum , ESPEPrem ier; Reprosil, Caulk; and m any others. Brands of polyether are: Impregum, ESPE-Prem ier; Perm adyne, ESPE-Prem ier; and Polyjel, Caulk. Any of the other three im pression m aterial types will work if certain time require
70
JADA, Vol. 123, December 1992
m ents are observed before pour ing (polysulfide and condensation-reaction silicone—pour before three hours—and hydro colloid—pour before 30 m inutes). Of course, hydro colloid requires water-cooled trays. HOW ARE CUSTOM LIGHT-CURING TRAYS MADE?
Each specific brand has slightly different directions, but this is the overall general technique: *■* A diagnostic cast is required. But a diagnostic cast should be made anyway for all situations involving three or more units. Diagnostic casts are excellent for patient education, m aking trays, m aking provisional restorations and a long-term legal record of the preoperative state. ■* Wax is placed on the cast. Two layers of base plate wax are placed on the locations not to be prepared, and three layers on the portion of the cast where teeth will be prepared. Occlusal stops are m ade by removing the wax from the cast in a t least three small places on the occlusal surfaces of the teeth for accurate reproducible seating of
the tray. ■“ Light-curing prosthodontic resin is adapted to the waxed cast. ■“ The resin is polymerized in the curing oven. “ The tra y is trimm ed. Auxiliary staff can make several trays a t the same time for upcoming planned prostheses. THE PAYOFF
Do you w ant complex fixed and im plant prostheses to fit almost every tim e? Of course. Using custom light-curing prosthodontic impression trays and a proved brand of additionreaction silicone or polyether will alm ost guarantee success. Added benefits are predict ability of results, re-pouring potential, long-term stability plus a bonus of lower cost. ■ The opinions expressed are those of the author and do not necessarily reflect those of the American Dental Association or its subsidiaries. Inform ation about the m anufacturers m ay be available from the author. N either the author nor th e American Dental Association has any commercial in terest in the products m entioned in this article.
ordon
J. C
h r is t e n s e n , d . d . s
.,
m .s
. d .,
p h .d .
COMPLEX FIXED AND IMPLANT PROSTHODONTICS: MAKING NEARLY FOOLPROOF IMPRESSIONS
ith im plant and fixed prosthodontics a m ajor need for aging populations, dentists m ust continue to improve their techniques in this area. Successful im pressions lead to successful prostheses. Are im pressions for complex fixed and im plant prostho dontics adequate throughout the U nited States? Discussions with any large dental lab oratory will verify th a t im pres sions are among the most inadequate of all dental procedures. Laboratories often receive im pressions for complex prostheses w ith incomplete m argins, im pression m aterial separated from the tray adhesive, prepared teeth touching the tray, air bubbles on im portant prepared teeth and other problems. I t’s possible to m ake im pressions for complex fixed or im plant prostheses th a t are predictably accurate and stable, and from which more th an 99 percent of the restorations may be expected to fit. Why isn’t it done more often? W hat simple technique can produce such impressions? CUSTOM TRAYS
Most dental schools promote custom trays for complex procedures, but m ost dentists
don’t use them. M anufacturers promote stock trays, and these trays seem to be state of the art. Are stock trays adequate for complex fixed and im plant prostheses? In my opinion, no. There are too m any variables w ith stock trays to provide predictable results for complex cases. D entists should simplify procedures and use custom trays for complex prostheses. Most practitioners th in k these trays are too expensive and require too much tim e. Wrong. Custom trays can be m ade quickly. Because they use about h alf as much impression m aterial as stock trays, custom trays are less expensive. Several good custom tray techniques are available today. One th a t optimizes the ideal tray characteristics uses lightcuring prosthodontic resins. These m aterials are readily available on the international m arket. M anufacturers include: Astron Dental; H eraeus Kulzer; Pro-Den Systems; and Dentsply York. In the U nited States, Dentsply’s Triad is most popular. Although the initial purchase of the system seems expensive, the total cost of a curing oven and a supply of tra y m aterial is about the sam e as one ill-fitting
crown. M aking a tra y requires only a few m inutes. If neces sary, it also can be modified in m inutes. W hen we consider the short am ount of auxiliary tim e needed to m ake the tra y and the reduced am ount of im pression m aterial, custommade, light-curing prostho dontic trays with the im pres sions cost the sam e or slightly less. WHEN TO USE CUSTOM TRAYS?
I prefer full-arch custom trays. I use them routinely for every situation involving three or more units. The technique for double-arch im pressions m ak ing upper and lower im pres sions and interocclusal records a t the same tim e is suggested for one or two u n its only (“Dayto-day fixed prosthodontics,” JADA 1992;123[ll]:91-2.). WHICH IMPRESSION MATERIAL.?
The five types of im pression m aterials available today are: ■■ polysulfide (usually brown rubberlike m aterial); ■■ condensation-reaction silicone (usually a paste and a liquid catalyst); **■ addition-réaction silicone (usually two pastes, and JADA, Vol. 123, December 1992
69
commonly auto-mix brands); ■■ polyether (two pastes and I some auto-m ix brands identifiable by a somewhat b itter taste); ™ hydrocolloid, reversible. U sing th e custom tray concept, b u t recognizing th a t m ost im pressions sent to I commercial laboratories in the I U nited S tates sit for 24 hours or more before pouring, addition1reaction silicone and polyether ! are the m ost accurate and stable. E ither type is an excellent, accurate, stable “stateof-the-art” m aterial for Dr. Christensen is use with founder and custom, light; c o-director of ! Clinical Research curing ; Associates, Provo, prosthodontic Utah, and a wellknown lecturer in the trays. j clinical practice of Popular, ! dentistry. He has his successful j master’s degree in restorative dentistry brands of and his doctorate in additioni education and | psychology. reaction silicone are: Exaflex, G.C. America; Express, 3M; Extrude, Kerr; Perm agum , ESPEPrem ier; Reprosil, Caulk; and m any others. Brands of polyether are: Impregum, ESPE-Prem ier; Perm adyne, ESPE-Prem ier; and Polyjel, Caulk. Any of the other three im pression m aterial types will work if certain time require
70
JADA, Vol. 123, December 1992
m ents are observed before pour ing (polysulfide and condensation-reaction silicone—pour before three hours—and hydro colloid—pour before 30 m inutes). Of course, hydro colloid requires water-cooled trays. HOW ARE CUSTOM LIGHT-CURING TRAYS MADE?
Each specific brand has slightly different directions, but this is the overall general technique: *■* A diagnostic cast is required. But a diagnostic cast should be made anyway for all situations involving three or more units. Diagnostic casts are excellent for patient education, m aking trays, m aking provisional restorations and a long-term legal record of the preoperative state. ■* Wax is placed on the cast. Two layers of base plate wax are placed on the locations not to be prepared, and three layers on the portion of the cast where teeth will be prepared. Occlusal stops are m ade by removing the wax from the cast in a t least three small places on the occlusal surfaces of the teeth for accurate reproducible seating of
the tray. ■“ Light-curing prosthodontic resin is adapted to the waxed cast. ■“ The resin is polymerized in the curing oven. “ The tra y is trimm ed. Auxiliary staff can make several trays a t the same time for upcoming planned prostheses. THE PAYOFF
Do you w ant complex fixed and im plant prostheses to fit almost every tim e? Of course. Using custom light-curing prosthodontic impression trays and a proved brand of additionreaction silicone or polyether will alm ost guarantee success. Added benefits are predict ability of results, re-pouring potential, long-term stability plus a bonus of lower cost. ■ The opinions expressed are those of the author and do not necessarily reflect those of the American Dental Association or its subsidiaries. Inform ation about the m anufacturers m ay be available from the author. N either the author nor th e American Dental Association has any commercial in terest in the products m entioned in this article.