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Modifications of the Fluid Resin Technique
M o d if ic a tio n s o f t h e flu id r e s in
Simon Civjan, DDS, MS Eugene F. Huget, DDS, MS Laszlo B. de Simon, W ashington,
DC
Means to obtain adequate retention of acrylic teeth and improved detail of the basal surfaces of fluid resin dentures have been investigated. Im proved dentures can be obtained by grinding of the ridge laps of the teeth and by use of processing pressures of 30- to 40-lb gauge.
Technical details for the fabrication o f fluid resin dentures have been described adequately in the dental literature.1'4 Processing proce dures are rapid, simple, and relatively inex pensive. Evaluation of fluid acrylic resin den tures has revealed, however, certain recurring inadequacies.5 Acrylic teeth do not bond read ily to the base. Furthermore, counter-replica tion o f the surface detail of subjacent tissues is often poorly defined. The purpose of this study was to evaluate the effects of simple modifications in technique on retention o f acrylic teeth and on the refinement o f surface detail.
M aterials and m ethods U nless otherwise indicated, bond strength of acrylic teeth* to a fluid cold-curing acrylic resint was determined according to American Dental Association Specification N o. 15 for acrylic resin teeth.6 Three series of bond strength specimens were prepared. In the first series, the teeth were used without modification. Speci
te c h n iq u e
mens were cured in a pressure pot in the pres ence o f =1 inch of water under 15-lb gauge pressure for 30 minutes at each o f these water temperatures: 72 F (room temperature), 100 F , 150 F , and 212 F. Additional specimens were processed under 40-lb gauge pressure for 30 minutes at respective temperatures o f 100 F and 150 F. The acrylic teeth used in the second ser ies were painted with the fluid resin monomer before the monomer-polymer slurry was poured. The specimens were cured under 15-lb pressure for 30 minutes at 72 F or under 15-lb pressure for 90 minutes at 160 F, followed by 30 minutes at 212 F. In the third series, the glossy surfaces of the teeth were removed by grinding o f the ridge laps and occlusal portions with a carborun dum abrasive band. Care was exercised to main tain the normal ridge lap curvature and the oc clusal anatomy. The specimens were processed for 30 minutes under 15-lb pressure at either 72 F or 150 F. Additional specimens were cured 30 minutes under 40-lb pressure at 100 F. T w o sets o f specimens that were processed with a conventional heat-curing resint served as control specimens. One set was prepared with unmodified teeth, whereas for the other set the teeth were pretreated with the resin mon omer. The heat-cured control specimens were processed in gypsum molds 90 minutes at 160 F , followed by 30 minutes at 212 F. Specimens for microscopic examination of base-tooth interfaces (Fig 1) were prepared in this manner. About Vi-inch thick sections of base and acrylic tooth were cut from fluid resin dentures with a cut-off wheel mounted in a high speed lathe. One side o f each section was flat tened by manual polishing with abrasive papers. Final polishing o f this side was accomplished with a nylon cloth. The flat side of the section was placed against a polished and reflective metallic surface and the entire specimen was fixed to the supporting base with inlay wax. The mounted specimens were polished manually J A D A , V o l. 8 5 , J u l y 1 9 7 2 ■ 1 0 9
Fig 1 ■Preparation of specimens for microscopic examination
Fig 2 ■Modified stone casts used to evaluate counter-replica
of tooth-base interface. Left to right: denture section; plastic-
tion characteristics of denture bases.
mounted reflecting metal disk; mounted specimen.
with 240- through 600-grit abrasive papers until light, reflected from the surface of the polished metal, could be seen through both the tooth and base portions of the sections. The specimen sur faces then were cleaned and were etched by swabbing with glacial acetic acid. The junction areas of acrylic tooth and resin base material were examined under 100X with a metallurgical microscope. § Fluid resin experimental dentures were used to evaluate the effects o f processing pressures on the counter-replication of surface detail. Segments of plastic mesh were luted to the labial, buccal, and lingual portions of the eden tulous ridges of maxillary and mandibular stone casts, as well as to the crests of the ridges o f the mandibular casts and to the palatal areas o f the maxillary casts. The modified models were dup licated in stone (Fig 2) with use of silicone molds. Normal complements of posterior denture teeth with either 33° anatomic or monoplane cuspal angulations were attached directly to the result ant models with baseplate wax. The experimen tal dentures were waxed-up in sets on a Hanau articulator and were cured 30 minutes in glycer ine-based hydrocolloidH molds at 100 F under pressures o f 15-, 30-, and 40-lb gauge. The num ber of sets processed at each pressure was: 5 at
15 lb; 5 at 30 lb; 4 at 40 lb. The tissue sides o f the dentures were examined visually and ranked qualitatively as poor, fair, good, or excellent. The effects o f processing pressures on the oc cluding vertical dimension were assessed by measuring the displacement of the incisal pin of the articulator before occlusal adjustment. Heat-cured control dentures, consisting of three sets with posterior teeth with 33° cuspal angulations and five sets with monoplane pos terior teeth, were processed in gypsum molds 90 minutes at 160 F , followed by 30 minutes at 212 F.
R e su lts Bond strengths of acrylic teeth to the polymer ized fluid resin are presented in the Table. For unmodified teeth, increased curing tempera tures tended to improve bond strength. Regard less of curing temperatures that were used, spe cimens that were processed under 15-lb gauge pressure showed high standard deviations and did not meet the specification minimum require ments of 4,480 pounds per square inch (psi) for bond strength between acrylic teeth and the denture base. Increase of the processing pres sure to 40 lb or painting of the teeth with mono-
T able ■ B ond stren g th o f a c ry lic teeth to a flu id resin.* Unground teeth Processing temperature (F)
Processing pressure (lb)
72
15 15 40 15 15 15
No. specimens
Strength (psi)
7 9
2,000 ± 900t
2,700 ±1,900 8 2,200 ± 900 150 20 3,800 ± 1,800 212 4 4,100 ±2,600 160 and 212^: 13 4,100 + 2,100 'Heat-cured controls (Duraflow) by ADA Specification No. 15: 6,700 ± 100 psi. fStandard deviation. ^Specimens cured 90 minutes at 160 F and an additional 30 minutes at 212 F.
100 100
110«
J A D A , V o l. 8 5 , J u l y 1 9 7 2
Monomer-treated teeth
Ground teeth
No. specimens
Strength (psi)
No. specimens
Strength (psi)
4
1,200 ± 800f
6 0 6 6 0 0
4,700 ± 900t
0 0 0 0 6
1,300 ± 1,500
5,700 ± 500 4,500 ± 500
Fig 3 «Typical interface of fluid resin denture base and un ground surface of acrylic tooth. Specimen was at 100 F and 40-lb gauge pressure. Polymer beads are visible in denture base.
Fig 4 «Typical interface of fluid resin denture base and ground surface of acrylic tooth. Specimens were processed at 100 F and 40-lb gauge pressure.
mer did not improve bond strength significantly. Grinding of the ridge laps and occlusal surfaces produced significant improvement in bond strength. Average values for specimens pro cessed under 15-lb pressure at 72 F and 150 F were 4,700 and 4,500 psi, respectively (see Table). The experimental values, though slightly higher than the minimum specification strength, were significantly lower than those obtained for the heat-cured control specimens. Typical interfaces between acrylic teeth and fluid resin denture bases are shown in Figures 3 and 4. The base material appeared to be sepa rated from the unground tooth by a relatively wide (~20yu,m) debris-filled crevice (Fig 3). Spe cimens with unground monomer-treated teeth presented essentially the same appearance. A well-defined crevice was not detected between the ground denture tooth and the polymerized fluid resin base (Fig 4). Examination of the tissue sides o f fluid resin experimental dentures provided this qualitative information. A processing pressure of 15 lb gave poor to fair counter-replication o f the sur faces of the models on which the experimental dentures were waxed. Thirty- to 40-lb proces sing pressure resulted in good to excellent coun ter-replication (Fig 5). The effect of processing pressure on the oc cluding vertical dimension o f fluid resin den tures that were cured in hydrocolloid molds is shown in Fig 6. Average pin displacement showed that the dentures tended toward in creased vertical dimension before occlusal ad justment. This tendency was reduced when pro cessing pressures were elevated from 15 to 30 or 40 lb. Standard deviations indicated, how ever, that a number of fluid resin dentures ex hibited loss of occlusal contacts leading to over-
FlUID RESIN
+.0 2 0 f-
HEAT CURED (controls)
^ +.0 1 0 UJ
* o
z
15 Us
-.0 1 0 -
-
020-
30Lb 40Lb processing pressures + underdosed - overdosed
Fig 5 ■Effect of processing pressures on quality of basal sur
Fig 6 «Effect of processing techniques on articulator pin dis
faces of dentures.
placement before occlusal adjustment. Civjan— Huget—de Simon: FLUID RESIN TECHNIQUE ■ 111
closure, whereas none o f the control dentures were overclosed. Increase o f the processing pressure to 30 or 40 lb did not increase signifi cantly either the degree or incidence o f over closure. Similar results were obtained when nonanatomic teeth were used.
the ridge laps. Improved detail o f the basal sur faces of fluid resin dentures, fabricated in hydro colloid molds, can be obtained by use o f proces sing pressures o f 30 to 40 pounds. The increased pressures did not produce changes in either the degree or incidence o f overclosure in articulated dentures.
Discussion Bond strength data confirm Shepard’s4 observa tion that adequate retention o f acrylic teeth to fluid resin denture bases could be obtained by judicious grinding of the ridge laps. The photo micrographic findings support the quantitative data that demonstrate a two-fold increase in bond strength for specimens with ground teeth. Although pretreatment of the teeth with methyl methacrylate monomer did not increase bond strength, it is likely that sufficient surface mod ification could be produced by other solvents to promote bonding of acrylic teeth to the coldcuring fluid resin. Rupp, Bowen, and Paffenbarger7 have reported that exposure o f acrylic teeth for seven minutes to a mixture o f methy lene dichloride and methyl methacrylate mono mer or coating o f the teeth with poly(methyl methacrylate) dissolved in a methylene dichloride-methyl methacrylate mixture significantly improves bond strength of conventional coldcuring resin and acrylic teeth. The improved counter-replication of tissue surface that was observed when 30- to 40-lb pro cessing pressures were used is attributed to closer contact between the polymerizing resin slurry and the tissue surface of the stone cast. T hese processing pressures are readily obtain able and can be maintained safely with simple laboratory equipment described by Shepard.4
Sum m ary Adequate retention of acrylic teeth to fluid res in denture bases can be obtained by grinding of
1 1 2 ■ J A D A , V o l. 8 5 , J u l y 1 9 7 2
Commercial materials and equipment are identified in this report to specify the experimental procedure. Such identifica tion does not imply official recommendation or endorsement or that the equipment and materials are necessarily the best available for the purpose. Col Civjan, DC, USA, is chief of the division of dental mater ials, US Army Institute of Dental Research, Walter Reed Army Medical Center, Washington, DC, 20012. Lt Col Huget, DC, USA, is research dental officer and Mr. de Simon is physical science technician, division of dental materials, US Army Institute of Dental Research.
*Justi S-R Imperial Plastic Teeth. H.D. Justi Division, Williams Gold Refinig Co., Inc., Buffalo, NY. tPronto II, Vernon-Benshoff Co., Inc., Albany, NY iDuraflow, Product Research Laboratories, Inc., Cambridge, Mass. §Vickers 55 Microscope, Vickers Instruments, Inc., Malden, Mass. UPerflex, Howmet Corp., Chicago.
1. Mirza, F.D. Dimensional stability of acrylic resin dentures. Clinical evaluation. J Prosthet Dent 11:848 Sept-Oct 1961. 2. Winkler, S., and O ’Connor, J. Duplicate dentures in one hour. Dent Dig 70:76 Feb 1964. 3. Winkler, S. Pour technique for denture base processing. Dent Dig 73:200 May 1967. 4. Shepard, W.L. Denture bases processed from a fluid resin. J Prosthet Dent 19:561 June 1968. 5. Civjan, S., and others. Evaluation of a “fluid” denture base resin. Abstracted, IADR Program and Abstracts No 233, March 1968. 6. American Dental Association. Guide to dental materials and devices 1970-71, ed 5. Chicago, American Dental Associ ation, 1970, p 174. 7. Rupp, N.W.; Bowen, R .L.; and Paffenbarger, G.C. Bond ing cold-curing denture base acrylic resin to acrylic resin teeth. JADA 83:601 Sept 1971.
Simon Civjan, DDS, MS Eugene F. Huget, DDS, MS Laszlo B. de Simon, W ashington,
DC
Means to obtain adequate retention of acrylic teeth and improved detail of the basal surfaces of fluid resin dentures have been investigated. Im proved dentures can be obtained by grinding of the ridge laps of the teeth and by use of processing pressures of 30- to 40-lb gauge.
Technical details for the fabrication o f fluid resin dentures have been described adequately in the dental literature.1'4 Processing proce dures are rapid, simple, and relatively inex pensive. Evaluation of fluid acrylic resin den tures has revealed, however, certain recurring inadequacies.5 Acrylic teeth do not bond read ily to the base. Furthermore, counter-replica tion o f the surface detail of subjacent tissues is often poorly defined. The purpose of this study was to evaluate the effects of simple modifications in technique on retention o f acrylic teeth and on the refinement o f surface detail.
M aterials and m ethods U nless otherwise indicated, bond strength of acrylic teeth* to a fluid cold-curing acrylic resint was determined according to American Dental Association Specification N o. 15 for acrylic resin teeth.6 Three series of bond strength specimens were prepared. In the first series, the teeth were used without modification. Speci
te c h n iq u e
mens were cured in a pressure pot in the pres ence o f =1 inch of water under 15-lb gauge pressure for 30 minutes at each o f these water temperatures: 72 F (room temperature), 100 F , 150 F , and 212 F. Additional specimens were processed under 40-lb gauge pressure for 30 minutes at respective temperatures o f 100 F and 150 F. The acrylic teeth used in the second ser ies were painted with the fluid resin monomer before the monomer-polymer slurry was poured. The specimens were cured under 15-lb pressure for 30 minutes at 72 F or under 15-lb pressure for 90 minutes at 160 F, followed by 30 minutes at 212 F. In the third series, the glossy surfaces of the teeth were removed by grinding o f the ridge laps and occlusal portions with a carborun dum abrasive band. Care was exercised to main tain the normal ridge lap curvature and the oc clusal anatomy. The specimens were processed for 30 minutes under 15-lb pressure at either 72 F or 150 F. Additional specimens were cured 30 minutes under 40-lb pressure at 100 F. T w o sets o f specimens that were processed with a conventional heat-curing resint served as control specimens. One set was prepared with unmodified teeth, whereas for the other set the teeth were pretreated with the resin mon omer. The heat-cured control specimens were processed in gypsum molds 90 minutes at 160 F , followed by 30 minutes at 212 F. Specimens for microscopic examination of base-tooth interfaces (Fig 1) were prepared in this manner. About Vi-inch thick sections of base and acrylic tooth were cut from fluid resin dentures with a cut-off wheel mounted in a high speed lathe. One side o f each section was flat tened by manual polishing with abrasive papers. Final polishing o f this side was accomplished with a nylon cloth. The flat side of the section was placed against a polished and reflective metallic surface and the entire specimen was fixed to the supporting base with inlay wax. The mounted specimens were polished manually J A D A , V o l. 8 5 , J u l y 1 9 7 2 ■ 1 0 9
Fig 1 ■Preparation of specimens for microscopic examination
Fig 2 ■Modified stone casts used to evaluate counter-replica
of tooth-base interface. Left to right: denture section; plastic-
tion characteristics of denture bases.
mounted reflecting metal disk; mounted specimen.
with 240- through 600-grit abrasive papers until light, reflected from the surface of the polished metal, could be seen through both the tooth and base portions of the sections. The specimen sur faces then were cleaned and were etched by swabbing with glacial acetic acid. The junction areas of acrylic tooth and resin base material were examined under 100X with a metallurgical microscope. § Fluid resin experimental dentures were used to evaluate the effects o f processing pressures on the counter-replication of surface detail. Segments of plastic mesh were luted to the labial, buccal, and lingual portions of the eden tulous ridges of maxillary and mandibular stone casts, as well as to the crests of the ridges o f the mandibular casts and to the palatal areas o f the maxillary casts. The modified models were dup licated in stone (Fig 2) with use of silicone molds. Normal complements of posterior denture teeth with either 33° anatomic or monoplane cuspal angulations were attached directly to the result ant models with baseplate wax. The experimen tal dentures were waxed-up in sets on a Hanau articulator and were cured 30 minutes in glycer ine-based hydrocolloidH molds at 100 F under pressures o f 15-, 30-, and 40-lb gauge. The num ber of sets processed at each pressure was: 5 at
15 lb; 5 at 30 lb; 4 at 40 lb. The tissue sides o f the dentures were examined visually and ranked qualitatively as poor, fair, good, or excellent. The effects o f processing pressures on the oc cluding vertical dimension were assessed by measuring the displacement of the incisal pin of the articulator before occlusal adjustment. Heat-cured control dentures, consisting of three sets with posterior teeth with 33° cuspal angulations and five sets with monoplane pos terior teeth, were processed in gypsum molds 90 minutes at 160 F , followed by 30 minutes at 212 F.
R e su lts Bond strengths of acrylic teeth to the polymer ized fluid resin are presented in the Table. For unmodified teeth, increased curing tempera tures tended to improve bond strength. Regard less of curing temperatures that were used, spe cimens that were processed under 15-lb gauge pressure showed high standard deviations and did not meet the specification minimum require ments of 4,480 pounds per square inch (psi) for bond strength between acrylic teeth and the denture base. Increase of the processing pres sure to 40 lb or painting of the teeth with mono-
T able ■ B ond stren g th o f a c ry lic teeth to a flu id resin.* Unground teeth Processing temperature (F)
Processing pressure (lb)
72
15 15 40 15 15 15
No. specimens
Strength (psi)
7 9
2,000 ± 900t
2,700 ±1,900 8 2,200 ± 900 150 20 3,800 ± 1,800 212 4 4,100 ±2,600 160 and 212^: 13 4,100 + 2,100 'Heat-cured controls (Duraflow) by ADA Specification No. 15: 6,700 ± 100 psi. fStandard deviation. ^Specimens cured 90 minutes at 160 F and an additional 30 minutes at 212 F.
100 100
110«
J A D A , V o l. 8 5 , J u l y 1 9 7 2
Monomer-treated teeth
Ground teeth
No. specimens
Strength (psi)
No. specimens
Strength (psi)
4
1,200 ± 800f
6 0 6 6 0 0
4,700 ± 900t
0 0 0 0 6
1,300 ± 1,500
5,700 ± 500 4,500 ± 500
Fig 3 «Typical interface of fluid resin denture base and un ground surface of acrylic tooth. Specimen was at 100 F and 40-lb gauge pressure. Polymer beads are visible in denture base.
Fig 4 «Typical interface of fluid resin denture base and ground surface of acrylic tooth. Specimens were processed at 100 F and 40-lb gauge pressure.
mer did not improve bond strength significantly. Grinding of the ridge laps and occlusal surfaces produced significant improvement in bond strength. Average values for specimens pro cessed under 15-lb pressure at 72 F and 150 F were 4,700 and 4,500 psi, respectively (see Table). The experimental values, though slightly higher than the minimum specification strength, were significantly lower than those obtained for the heat-cured control specimens. Typical interfaces between acrylic teeth and fluid resin denture bases are shown in Figures 3 and 4. The base material appeared to be sepa rated from the unground tooth by a relatively wide (~20yu,m) debris-filled crevice (Fig 3). Spe cimens with unground monomer-treated teeth presented essentially the same appearance. A well-defined crevice was not detected between the ground denture tooth and the polymerized fluid resin base (Fig 4). Examination of the tissue sides o f fluid resin experimental dentures provided this qualitative information. A processing pressure of 15 lb gave poor to fair counter-replication o f the sur faces of the models on which the experimental dentures were waxed. Thirty- to 40-lb proces sing pressure resulted in good to excellent coun ter-replication (Fig 5). The effect of processing pressure on the oc cluding vertical dimension o f fluid resin den tures that were cured in hydrocolloid molds is shown in Fig 6. Average pin displacement showed that the dentures tended toward in creased vertical dimension before occlusal ad justment. This tendency was reduced when pro cessing pressures were elevated from 15 to 30 or 40 lb. Standard deviations indicated, how ever, that a number of fluid resin dentures ex hibited loss of occlusal contacts leading to over-
FlUID RESIN
+.0 2 0 f-
HEAT CURED (controls)
^ +.0 1 0 UJ
* o
z
15 Us
-.0 1 0 -
-
020-
30Lb 40Lb processing pressures + underdosed - overdosed
Fig 5 ■Effect of processing pressures on quality of basal sur
Fig 6 «Effect of processing techniques on articulator pin dis
faces of dentures.
placement before occlusal adjustment. Civjan— Huget—de Simon: FLUID RESIN TECHNIQUE ■ 111
closure, whereas none o f the control dentures were overclosed. Increase o f the processing pressure to 30 or 40 lb did not increase signifi cantly either the degree or incidence o f over closure. Similar results were obtained when nonanatomic teeth were used.
the ridge laps. Improved detail o f the basal sur faces of fluid resin dentures, fabricated in hydro colloid molds, can be obtained by use o f proces sing pressures o f 30 to 40 pounds. The increased pressures did not produce changes in either the degree or incidence o f overclosure in articulated dentures.
Discussion Bond strength data confirm Shepard’s4 observa tion that adequate retention o f acrylic teeth to fluid resin denture bases could be obtained by judicious grinding of the ridge laps. The photo micrographic findings support the quantitative data that demonstrate a two-fold increase in bond strength for specimens with ground teeth. Although pretreatment of the teeth with methyl methacrylate monomer did not increase bond strength, it is likely that sufficient surface mod ification could be produced by other solvents to promote bonding of acrylic teeth to the coldcuring fluid resin. Rupp, Bowen, and Paffenbarger7 have reported that exposure o f acrylic teeth for seven minutes to a mixture o f methy lene dichloride and methyl methacrylate mono mer or coating o f the teeth with poly(methyl methacrylate) dissolved in a methylene dichloride-methyl methacrylate mixture significantly improves bond strength of conventional coldcuring resin and acrylic teeth. The improved counter-replication of tissue surface that was observed when 30- to 40-lb pro cessing pressures were used is attributed to closer contact between the polymerizing resin slurry and the tissue surface of the stone cast. T hese processing pressures are readily obtain able and can be maintained safely with simple laboratory equipment described by Shepard.4
Sum m ary Adequate retention of acrylic teeth to fluid res in denture bases can be obtained by grinding of
1 1 2 ■ J A D A , V o l. 8 5 , J u l y 1 9 7 2
Commercial materials and equipment are identified in this report to specify the experimental procedure. Such identifica tion does not imply official recommendation or endorsement or that the equipment and materials are necessarily the best available for the purpose. Col Civjan, DC, USA, is chief of the division of dental mater ials, US Army Institute of Dental Research, Walter Reed Army Medical Center, Washington, DC, 20012. Lt Col Huget, DC, USA, is research dental officer and Mr. de Simon is physical science technician, division of dental materials, US Army Institute of Dental Research.
*Justi S-R Imperial Plastic Teeth. H.D. Justi Division, Williams Gold Refinig Co., Inc., Buffalo, NY. tPronto II, Vernon-Benshoff Co., Inc., Albany, NY iDuraflow, Product Research Laboratories, Inc., Cambridge, Mass. §Vickers 55 Microscope, Vickers Instruments, Inc., Malden, Mass. UPerflex, Howmet Corp., Chicago.
1. Mirza, F.D. Dimensional stability of acrylic resin dentures. Clinical evaluation. J Prosthet Dent 11:848 Sept-Oct 1961. 2. Winkler, S., and O ’Connor, J. Duplicate dentures in one hour. Dent Dig 70:76 Feb 1964. 3. Winkler, S. Pour technique for denture base processing. Dent Dig 73:200 May 1967. 4. Shepard, W.L. Denture bases processed from a fluid resin. J Prosthet Dent 19:561 June 1968. 5. Civjan, S., and others. Evaluation of a “fluid” denture base resin. Abstracted, IADR Program and Abstracts No 233, March 1968. 6. American Dental Association. Guide to dental materials and devices 1970-71, ed 5. Chicago, American Dental Associ ation, 1970, p 174. 7. Rupp, N.W.; Bowen, R .L.; and Paffenbarger, G.C. Bond ing cold-curing denture base acrylic resin to acrylic resin teeth. JADA 83:601 Sept 1971.