Resin-bonded
prostheses
for posterior
Flemming Isidor, DDS, PhD, DrOdont,a and Rie Stokholm, Physiology, Royal Dental College, Aarhus, Denmark
teeth DDSb
This study evaluated fixed partial dentures bonded with resin to dentin on posterior teeth with minimal tooth preparation. The patients included were missing at least one premolar or first molar. The abutment teeth next to the modification spaces were moderately restored with MOD or class II restorations on most of the teeth. A total of 20 patients with 23 fixed partial dentures were included in the study. After removal of existing restorations, the abutment teeth were prepared to eliminate undercuts on the perimeter of the preparations. Undercut areas within the preparation were not filled but were blocked out later in the laboratory. The fixed partial dentures employed inlays as retainers for a metal ceramic pontic. The metal framework was cast in a high noble gold alloy. The areas of the retainers to be bonded were treated with the Kulzer Silicoater method. Immediately before cementation, enamel was etched and exposed dentin was treated with Gluma. Kerr’s resin bonded bridge cement was used for cementation. Patients were recalled after periods of 1 week, 1 month, 6 months, 1 year, 2 years, and 4 years for evaluation. None of the restorations lost retention and no major adverse effects were observed in the 4-year follow-up period. (J PROSTHET DENT 1992;68:239-43.)
ost resin-retained fixed partial dentures (FPDs) have been made on nonrestored teeth, enhancing retention to the tooth surface by only slight preparation of the abutments.l This resulted in overcontoured retainers, and was often uncomfortable for the patient and produced plaque accumulation.l, 2 Typical tooth preparation for FPDs, when moderate destruction of tooth structure has occurred, has involved either radical reduction of the abutment teeth or basing out undercut areas before moderate tooth preparation.3 Because existing types of posterior resin-retained FPDs frequently become debonded, a more retentive, conservative retainer design is badly needed.4-8 This study evaluated resin-bonded FPDs bonded to dentin on moderately restored posterior teeth using minimal tooth preparation.
MATERIAL
AND
Fig.
1. Patient
missing second maxillary
premolar.
METHODS
This study included 20 patients (16 women and 4 men; average age: 40 years) treated with 23 FPDs. All patients were missing at least one premolar or first molar (Fig. 1). The neighboring teeth to the edentulous area were either moderately decayed (occlusal or one or two proximal surfaces) or were restored with a class II or MOD restoration (Fig. 2). The restorations were removed and the teeth were excavated, if necessary. Only a limited modification including elimination of undercut areas from the periphery of the aAssociate Professor, Department Stomatognathic Physiology. bAssistant Professor, Department Stomatognathic Physiology.
of Prosthetic Dentistry
and
of Prosthetic
and
10/l/38627
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Dentistry
Fig. 2. Same patient as in Fig. 1; first maxillary and molar have class II restorations.
premolar
ISlDOR
Fig. 3. Preparation for an FPD resin-bonded to dentin.
AND
STOKHOLM
Fig. 5. FPD from the buccal aspect after cementation, and cosmetic result.
Table
I.
Number of various retainers used Retainers
Class II MQD Canine-inlay Total
Fig. 4. FPD after silica coating of the bonding surfaces.
preparations was performed. Undercut areas within the preparations were allowed to remain (Fig. 3). Potentially sensitive areas of the preparations were protected with a CaOH2 paste (Dycal, L.D. Caulk Division, Dentsply, International Inc., Milford, Del.). Impressions were made using a silicone impression material (President, Coltene AG, Altsttitten, Switzerland). From the impressions, working casts were made and were mounted in a suitable articulator. The framework for the prosthesis was waxed and was cast in a noble metal alloy (Esteticor Royal, Cendre & Metaux SA, Biel-Bienne, Switzerland) and porcelain was applied to the pontic area (VITA VMK 68, VITA Zahnfabrik, H. Rauter GmbH & Co. KG, Bad Sackingen, Germany). The FPD employed two inlays (class II or MOD) as retainers (Table I) and a modified ridge lap pontic with a porcelain occlusal surface. It was then tried in the mouth. Necessary adjustments were made for occlusion and color and the bonding surfaces of the retainers were treated with the Kulzer Silicoater Method (Kulzer & Co. GmbH, Bereich Dental, Wehrheim/Ts., Germany) according to the manufacturer’s instruction to enhance retention of the resin luting material to the metal framework. The silicoating was
240
NO.
%
19
40 49 11 100
23 5 41
precededby air abrasionusing50 +rn aluminum oxide particles and a pressureof 3.6bar. After applying the pyrolytic silica (SiO,-C) layer and the Silane adhesionprimer, the bonding surfacesof 18of the frameworkswerecoveredwith a layer of Dentacolor Opaquer product (Kulzer) (Fig. 4), allowing the prosthesesto be tried in the mouth before cementation (seeDiscussionsection).
Cementation
procedure
All temporary restorative material (non-eugenolic)was completely removed. Potentially sensitive areas of the preparations were again isolated with a CaOHspaste (Dycal, L.D. Caulk, Dentsply International). The exposed enamelwasthen etched with a 35% phosphoric gel for 1 minute, followed by thorough cleaningwith water spray for 30 secondsand drying. The dentin wastreated with a dentin adhesive (Gluma, Bayer Dental, Leverkusen, Germany). The dentin was cleaned with the cleanserfor 30 seconds,flushedwith water, and dried. The bond of the Gluma systemwasthen applied for 30 secondsand wasdried with air pressurefor 10 seconds.All prostheseswere cemented with ResinBridge Bonding Cementmaterial (Kerr/Sybron, Romulus,Mich.) with the mixed resin placed on the preparations and the mixed composite resin placed on the framework. The framework wasthen seatedon the teeth, after which its placementwaschecked.Excessiuting agent wasscrapedaway when the curing wasalmost completed. After complete setting of the luting material, the occlusion was checked and, if necessary,adjusted.
AUGUST
1992
VOLUME
68
NUMBER
2
RESIN-BONDED
PROSTHESES
Table II. Average (x) Plaque Index (patient mean) and standard deviation (SD) for all tooth surfaces, proximal surfaces of abutments, and proximal surfaces of other teeth during first 2 years of observation Plaque All surfaces
Fig.
6. Occlusal
view of FPD after cementation.
1 wk 1 mo 6 mo 12 mo 24 mo
Index
Proximal surfaces of abutments
Other proximal surfaces
x
SD
x
SD
x
SD
0.7 0.6 0.6 0.4
0.3
0.7
0.5
0.2 0.2
0.8
0.5
0.9 0.8
0.3
0.2
0.6 0.5 0.4
0.4 0.4 0.4
0.4 0.2 0.3 0.3 0.2
0.3
0.7
0.5 0.3
Table III. Average (x) Gingival Index (patient mean) and standard deviation (SD) for all tooth surfaces, proximal surfaces of abutments, and proximal surfaces of other teeth during first 2 years of observation Gingival All surfaces
Fig.
7. Radiograph
of FPD after cementation.
Each prosthesis was checked 1 week after cementation (Figs. 5 through 7). A total of 4 years of observation was obtained. Clinical examinations were performed 1 month, 3 months, 6 months, 1 year, and 2 years after the cementation. The following parameters were assessed the first 2 years at these examinations: Plaque Index,g Gingival Index,lO tooth mobility,rl pocket depth recorded to the nearest higher full millimeter at four surfaces on each tooth, tooth caries, pulp vitality (electrometrically), and occlusal disturbances. The marginal bone level was measured on standard radiographs and bite-wing radiographs were taken 1 week, 1 year, and 2 years after cementation of the prosthesis. Furthermore, any subjective complaints, such as post-cementation pain or any other discomfort, were recorded.
RESULTS None of the prostheses lost retention in the 4 years of observation, and only minor problems were observed. The Plaque Index was decreasing throughout the observation period in all areas and the amount of plaque assessed at the proximal surfaces in relation to the abutment
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DENTISTRY
1 wk 1 mo 6 mo 12 mo 24 mo
Index
Proximal surfaces of retainers
Other proximal surfaces
x
SD
x
SD
x
SD
0.7 0.7
0.4 0.3
0.7
0.5
0.7
0.2 0.4
0.8
0.4 0.4 0.5
0.8
0.6 0.6
0.8 0.8
0.7
0.4
0.9
0.5
0.4 0.2 0.3 0.4 0.4
0.6 0.6 0.7
retainers was similar to that observed at other proximal surfaces (Table II). On the other hand, the Gingival Index was generally higher at proximal surfaces of the abutments compared with other proximal surfaces (Table III). The probing pocket depth was unchanged in the observation period, and furthermore there was no progression of marginal bone loss at the retainers. No recurrent caries was observed. Three abutments on three different patients gave postcementation pain for 2 to 4 weeks. After this period the symptoms disappeared. The only treatment performed in these cases was adjustment of occlusion. During the 4 years of observation, all abutments reacted positively on the electrometric pulp test and there were no radiographic signs of periapical periodontitis. On one pontic a superficial fracture of porcelain on the lingual surface occurred after 6 months of service. The remaining porcelain was smoothed and the prosthesis is still functioning with no patient discomfort. The main complication observed in the study was a distinct radiographic gap between the retainer and the preparation on five abutments (Fig. 8). Clinically, no gaps were
241
ISZDOR
Fig. 8. Radiograph shows distinct gap between retainer and preparation of a resin bonded-to-dentin FPD abutment. No gap could be detected clinically. detected in these areas, and no subjective recorded.
complaints
were
DISCUSSION In the present study, all prostheses were still in function with no debonding after 4 years. No serious adverse reaction has been observed. In other studies of resin-retained posterior FPDs, a less favorable finding of frequent debonding has been reported,4‘s~12,13 although other studies have reported posterior resin-bonded prostheses where none have lost retention between 5 and 40 months.7,14s15 Constructing the FPDs with inlays as retainers bonded to dentin, as used in the present study, is a favorable alternative to traditional resin-bonded prostheses. This approach can be applied on both unrestored and moderately restored teeth. Since only the potentially sensitive areas of the preparation were sealed with a CaOHspaste, the dentin bonding agent and the composite luting agent were applied directly on relatively large areas of dentin. Except for transient pain in three teeth, no adverse reaction was observed with this treatment. Furthermore, it should be appreciated that all abutments remained vital. By comparison, a recent studyl” reported that one or both of the abutments in 11.8% of all FPDs became devitalized during a mean service length of 35 months. The increased gingival inflammation associated with the retainers in this study has also been observed in other studies of resin-retained2:17 and conventional FPDs.ls In the present study this has resulted in neither periodontal breakdown nor tooth caries. The most annoying complication observed was the lack of complete seating after cementation of some of the FPDs covered with the layer of Dentacolor Opaquer material. The last five FPDs cemented in this series were given a silica coating (Silicoater) but without the opaquer layer ap-
242
ANDSTOKHOLM
plied. None of these FPDs lifted during the cementation procedure. The reason for using the Dentalcolor opaquer is that it makes handling of the silica-coated framework easier. According to the manufacturer’s recommendation, the Silicoated framework without the opaquer layer should be cemented within 20 minutes after coating. Furthermore, the framework must not be contaminated with grease or saliva, since this will deactivate the silane layer. This makes the Silicoater technique impractical unless the Dentacolor Opaquer material is applied. The air abrasion performed before silica coating should create sufficient space for the opaquer layer. The thickness of this layer varies, especially on grooves, where there is a tendency for pooling and thick layering. This is a problem, especially when the preparations have parallel or nearly parallel walls, as did the preparations in the present study. The lift during cementation that was observed can be avoided if the Dentacolor Opaquer material is not used or if another system of enhancing retention of the frame is employed. Investigation of such systems is in progress in our laboratory. REFERENCES 1. Saunders WP. Resin bonded bridgework: a review. J Dent 1989;17:‘25565. 2. Creugers NHJ, Snoek PA, Vogels ALM. Overcountering in resinbonded prostheses: plaque accumulation and gingival health. J PROSTHET D~~~1988;59:17-21. 3. Creugers NHJ, Snoek PA, van ‘t Hof MA, Kriyser AF. Clinical performance of resin-bonded bridges: a g-year prospective study. I. Design of the study and influence of experimental variables. J Oral Rehabil 1989;16:427-36. 4. Kellett M. The etch-retained metal restoration in hospital clinical use. Br Dent J 1987;163:259-62. 5. Marine110 CP, Kerschbaum T, Heinenberg B, et al. First experiences with resin-bonded bridges and splints-a cross-sectional retrospective study. Part II. J Oral Rehabil 1988;15:223-35. 6. Mohl G, Mehra R, Ford A. Clinical evaluation of etched-metal resin-bonded fixed partial dentures. 3 PROSTHET DENT 198&59: 403-4. 7. van der Veen H. Resin-bonded bridges, in vitro and in viva. Thesis. Groningen: Rijksuniversiteit Groningen, 1988:81-112. 8. Creugers NH, Snoek PA, van-%Hof MA, Kayser AF. Clinical performance of resin-bonded bridges: a 5-year prospective study. II. The influence of patient-dependent variables. J Oral Rehabil 1989;16: 521-7. 9. Silness J, LSe H. Periodontal disease in pregnancy. II. Correlation between oral hygiene and periodontal conditions. Acta Odontol Stand 1964;22:121-35. 10. LSe H, Silness J. Periodontal disease in pregnancy. I. Prevalence and severity. Acta Odontol Stand 1963;21:533-51. 11. Miller SC, Yudkoff I, OkunMN. The science of oral diagnosis. In: Miller SC, ed. Oral diagnosis and treat,ment. 3rd ed. New York McGraw-Hill Book Company, Inc, 1957:9. 12. Clyde JS, Boyd T. The etched cast metal resin-bonded (Maryland) bridge: a clinical review. J Dent 1988;16:22-6. 13. Priest GF, Donatelli HA. A four-year clinical evaluation of resin-bonded fixed partia1dentures.J PROSTHET DENT 1988;59:542-6. 14. Hudgins JL, Moon PC, Knap FJ. Particle-roughened resin-bonded retainers.J PROSTHET DENT 1985;53:471-6. 15. Probster L, Sets J. Clinical performance of silane-coated, resin-bonded fixed partial dentures with two different preparational concepts. Quintessence Int 1990;21:707-12.
AUGUST
1992
VOLUME
68
NUMBER
2
RESIN-BONDEDPROSTHESES
16. Cheung GS, Dimmer A, Mellor R, Gale M. A clinical evaluation of conventional bridgework. J Oral Rehabil 1990;17:131-6. 17. Freilich MA, Niekrash CE, Katz RV, Simonsen RJ. The effects of resin-bonded and conventional fixed partial dentures on the periodontium: restoration type evaluated. J Am Dent Assoc 1990;121:265-9. 18. Isidor F, Budtz-J$rgensen E. Periodontal conditions following treatment with distally extending cantilever bridges or removable partial dentures in elderly patients. A 5-year study. J Periodontol1990;61:21-6.
Three-dimensional finite element cantilever fixed partial denture Hania Yahia University
A. Awadalla, BDS, MDS,a Mohsen Azarbal, H. Ismail, DMD, PhD,C and Wael El-Ibiari, of Pittsburgh,
School
of Dental
Medicine,
Pittsburgh,
Reprint
requests to:
DR. FLEMMINC ISIDOR DEPARTMENT OF PROSTHETIC OGY ROYAL DENTAL COLLEGE VENNELYST BOULEVARD DK-8000, AARHUS C DENMARK
stress DMD, BSd
DENTISTRY
analysis
AND STOMATOGNATHIC
PHYSIOL
of a
MDS,b
Pa.
A three-dimensional mathematical model was generated, representing a three-unit cantilever fixed partial denture and its supporting mandibular structures. First and second premolars were used as abutments with one posterior cantilever pontic. A 5 lb vertical load was applied to the pontic. Vertical and horizontal stresses were analyzed by means of a three-dimensional finite element stress analysis technique. The results showed that a cantilever pontic creates considerable compressive stress on the abutment nearest to the pontic and produces tensile stress on the abutment farthest from the pontic. (J PROSTHET DENT 1992;68:243-8.)
R eplacement of missingposterior teeth in the absenceof distal abutments can be achieved by one of the following ways: (1) with removable partial dentures with distal extensionbases,(2) with fixed partial denturesusing implants as distal abutments, and (3) with fixed partial dentures with cantilever pontics. Conflicting opmionsexist regarding the useof cantilever fixed partial denturesto restore edentulousspaceswithout a distal abutment. The decision to use a cantilever fixed partial denture should be basedon a sound periodontal condition, good alveolar bone support, favorable toothto-tooth and arch-to-arch relationships, favorable root shape, a good crown-to-root ratio, and clinical experience.l This study evaluated stress distribution in the abutment teeth and their supporting alveolar bone in a mandibular posterior cantilever fixed partial denture using a three-dimensional finite element stress analysis technique. aGraduate Resident. bAssistant Professor, Department of Prosthodontics. CProfessor and Chairman, Department of Prosthodoutics. dEngineering Consultant. 10/l/37744
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OF PROSTHETIC
DENTISTRY
MATERIAL
AND
METHODS
In this study the finite elementstressanalysistechnique wasusedto evaluate the stressesin a mandibular posterior cantilever fixed partial denture. Two- and three-dimensional finite element stressanalyseshave beenusedextensively in dentistry. 2-gA three-dimensional stressanalysis technique is preferred over a two-dimensionalone because it is an actual representation of the stressbehavior in the supporting bone.7 A three-dimensionalmathematical model of the mandible was used in this study, representing the mandibular canine, first premolar, secondpremolar, and their supporting structures with a cantilever pontic and 7 mm of the edentulous ridge distal to the secondpremolar. A threeunit cantilever fixed partial denture was designedusing first and secondpremolarsasabutments and a first molar as a pontic. In making the finite element model, the anatomic form and dimensions,the modulusof elasticity, and Poisson’sratios equivalent to those structures being simulated were entered into the computer program. Components of the dental model were mandibular bone, periodontal ligaments,natural teeth, type 3 gold crowns,and full gold pontics. Both abutment teeth were restored with cast crowns, using type 3 gold with one cast gold cantilever pontic replacing the first molar.
243
prostheses
for posterior
Flemming Isidor, DDS, PhD, DrOdont,a and Rie Stokholm, Physiology, Royal Dental College, Aarhus, Denmark
teeth DDSb
This study evaluated fixed partial dentures bonded with resin to dentin on posterior teeth with minimal tooth preparation. The patients included were missing at least one premolar or first molar. The abutment teeth next to the modification spaces were moderately restored with MOD or class II restorations on most of the teeth. A total of 20 patients with 23 fixed partial dentures were included in the study. After removal of existing restorations, the abutment teeth were prepared to eliminate undercuts on the perimeter of the preparations. Undercut areas within the preparation were not filled but were blocked out later in the laboratory. The fixed partial dentures employed inlays as retainers for a metal ceramic pontic. The metal framework was cast in a high noble gold alloy. The areas of the retainers to be bonded were treated with the Kulzer Silicoater method. Immediately before cementation, enamel was etched and exposed dentin was treated with Gluma. Kerr’s resin bonded bridge cement was used for cementation. Patients were recalled after periods of 1 week, 1 month, 6 months, 1 year, 2 years, and 4 years for evaluation. None of the restorations lost retention and no major adverse effects were observed in the 4-year follow-up period. (J PROSTHET DENT 1992;68:239-43.)
ost resin-retained fixed partial dentures (FPDs) have been made on nonrestored teeth, enhancing retention to the tooth surface by only slight preparation of the abutments.l This resulted in overcontoured retainers, and was often uncomfortable for the patient and produced plaque accumulation.l, 2 Typical tooth preparation for FPDs, when moderate destruction of tooth structure has occurred, has involved either radical reduction of the abutment teeth or basing out undercut areas before moderate tooth preparation.3 Because existing types of posterior resin-retained FPDs frequently become debonded, a more retentive, conservative retainer design is badly needed.4-8 This study evaluated resin-bonded FPDs bonded to dentin on moderately restored posterior teeth using minimal tooth preparation.
MATERIAL
AND
Fig.
1. Patient
missing second maxillary
premolar.
METHODS
This study included 20 patients (16 women and 4 men; average age: 40 years) treated with 23 FPDs. All patients were missing at least one premolar or first molar (Fig. 1). The neighboring teeth to the edentulous area were either moderately decayed (occlusal or one or two proximal surfaces) or were restored with a class II or MOD restoration (Fig. 2). The restorations were removed and the teeth were excavated, if necessary. Only a limited modification including elimination of undercut areas from the periphery of the aAssociate Professor, Department Stomatognathic Physiology. bAssistant Professor, Department Stomatognathic Physiology.
of Prosthetic Dentistry
and
of Prosthetic
and
10/l/38627
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Dentistry
Fig. 2. Same patient as in Fig. 1; first maxillary and molar have class II restorations.
premolar
ISlDOR
Fig. 3. Preparation for an FPD resin-bonded to dentin.
AND
STOKHOLM
Fig. 5. FPD from the buccal aspect after cementation, and cosmetic result.
Table
I.
Number of various retainers used Retainers
Class II MQD Canine-inlay Total
Fig. 4. FPD after silica coating of the bonding surfaces.
preparations was performed. Undercut areas within the preparations were allowed to remain (Fig. 3). Potentially sensitive areas of the preparations were protected with a CaOH2 paste (Dycal, L.D. Caulk Division, Dentsply, International Inc., Milford, Del.). Impressions were made using a silicone impression material (President, Coltene AG, Altsttitten, Switzerland). From the impressions, working casts were made and were mounted in a suitable articulator. The framework for the prosthesis was waxed and was cast in a noble metal alloy (Esteticor Royal, Cendre & Metaux SA, Biel-Bienne, Switzerland) and porcelain was applied to the pontic area (VITA VMK 68, VITA Zahnfabrik, H. Rauter GmbH & Co. KG, Bad Sackingen, Germany). The FPD employed two inlays (class II or MOD) as retainers (Table I) and a modified ridge lap pontic with a porcelain occlusal surface. It was then tried in the mouth. Necessary adjustments were made for occlusion and color and the bonding surfaces of the retainers were treated with the Kulzer Silicoater Method (Kulzer & Co. GmbH, Bereich Dental, Wehrheim/Ts., Germany) according to the manufacturer’s instruction to enhance retention of the resin luting material to the metal framework. The silicoating was
240
NO.
%
19
40 49 11 100
23 5 41
precededby air abrasionusing50 +rn aluminum oxide particles and a pressureof 3.6bar. After applying the pyrolytic silica (SiO,-C) layer and the Silane adhesionprimer, the bonding surfacesof 18of the frameworkswerecoveredwith a layer of Dentacolor Opaquer product (Kulzer) (Fig. 4), allowing the prosthesesto be tried in the mouth before cementation (seeDiscussionsection).
Cementation
procedure
All temporary restorative material (non-eugenolic)was completely removed. Potentially sensitive areas of the preparations were again isolated with a CaOHspaste (Dycal, L.D. Caulk, Dentsply International). The exposed enamelwasthen etched with a 35% phosphoric gel for 1 minute, followed by thorough cleaningwith water spray for 30 secondsand drying. The dentin wastreated with a dentin adhesive (Gluma, Bayer Dental, Leverkusen, Germany). The dentin was cleaned with the cleanserfor 30 seconds,flushedwith water, and dried. The bond of the Gluma systemwasthen applied for 30 secondsand wasdried with air pressurefor 10 seconds.All prostheseswere cemented with ResinBridge Bonding Cementmaterial (Kerr/Sybron, Romulus,Mich.) with the mixed resin placed on the preparations and the mixed composite resin placed on the framework. The framework wasthen seatedon the teeth, after which its placementwaschecked.Excessiuting agent wasscrapedaway when the curing wasalmost completed. After complete setting of the luting material, the occlusion was checked and, if necessary,adjusted.
AUGUST
1992
VOLUME
68
NUMBER
2
RESIN-BONDED
PROSTHESES
Table II. Average (x) Plaque Index (patient mean) and standard deviation (SD) for all tooth surfaces, proximal surfaces of abutments, and proximal surfaces of other teeth during first 2 years of observation Plaque All surfaces
Fig.
6. Occlusal
view of FPD after cementation.
1 wk 1 mo 6 mo 12 mo 24 mo
Index
Proximal surfaces of abutments
Other proximal surfaces
x
SD
x
SD
x
SD
0.7 0.6 0.6 0.4
0.3
0.7
0.5
0.2 0.2
0.8
0.5
0.9 0.8
0.3
0.2
0.6 0.5 0.4
0.4 0.4 0.4
0.4 0.2 0.3 0.3 0.2
0.3
0.7
0.5 0.3
Table III. Average (x) Gingival Index (patient mean) and standard deviation (SD) for all tooth surfaces, proximal surfaces of abutments, and proximal surfaces of other teeth during first 2 years of observation Gingival All surfaces
Fig.
7. Radiograph
of FPD after cementation.
Each prosthesis was checked 1 week after cementation (Figs. 5 through 7). A total of 4 years of observation was obtained. Clinical examinations were performed 1 month, 3 months, 6 months, 1 year, and 2 years after the cementation. The following parameters were assessed the first 2 years at these examinations: Plaque Index,g Gingival Index,lO tooth mobility,rl pocket depth recorded to the nearest higher full millimeter at four surfaces on each tooth, tooth caries, pulp vitality (electrometrically), and occlusal disturbances. The marginal bone level was measured on standard radiographs and bite-wing radiographs were taken 1 week, 1 year, and 2 years after cementation of the prosthesis. Furthermore, any subjective complaints, such as post-cementation pain or any other discomfort, were recorded.
RESULTS None of the prostheses lost retention in the 4 years of observation, and only minor problems were observed. The Plaque Index was decreasing throughout the observation period in all areas and the amount of plaque assessed at the proximal surfaces in relation to the abutment
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OF PROSTHETIC
DENTISTRY
1 wk 1 mo 6 mo 12 mo 24 mo
Index
Proximal surfaces of retainers
Other proximal surfaces
x
SD
x
SD
x
SD
0.7 0.7
0.4 0.3
0.7
0.5
0.7
0.2 0.4
0.8
0.4 0.4 0.5
0.8
0.6 0.6
0.8 0.8
0.7
0.4
0.9
0.5
0.4 0.2 0.3 0.4 0.4
0.6 0.6 0.7
retainers was similar to that observed at other proximal surfaces (Table II). On the other hand, the Gingival Index was generally higher at proximal surfaces of the abutments compared with other proximal surfaces (Table III). The probing pocket depth was unchanged in the observation period, and furthermore there was no progression of marginal bone loss at the retainers. No recurrent caries was observed. Three abutments on three different patients gave postcementation pain for 2 to 4 weeks. After this period the symptoms disappeared. The only treatment performed in these cases was adjustment of occlusion. During the 4 years of observation, all abutments reacted positively on the electrometric pulp test and there were no radiographic signs of periapical periodontitis. On one pontic a superficial fracture of porcelain on the lingual surface occurred after 6 months of service. The remaining porcelain was smoothed and the prosthesis is still functioning with no patient discomfort. The main complication observed in the study was a distinct radiographic gap between the retainer and the preparation on five abutments (Fig. 8). Clinically, no gaps were
241
ISZDOR
Fig. 8. Radiograph shows distinct gap between retainer and preparation of a resin bonded-to-dentin FPD abutment. No gap could be detected clinically. detected in these areas, and no subjective recorded.
complaints
were
DISCUSSION In the present study, all prostheses were still in function with no debonding after 4 years. No serious adverse reaction has been observed. In other studies of resin-retained posterior FPDs, a less favorable finding of frequent debonding has been reported,4‘s~12,13 although other studies have reported posterior resin-bonded prostheses where none have lost retention between 5 and 40 months.7,14s15 Constructing the FPDs with inlays as retainers bonded to dentin, as used in the present study, is a favorable alternative to traditional resin-bonded prostheses. This approach can be applied on both unrestored and moderately restored teeth. Since only the potentially sensitive areas of the preparation were sealed with a CaOHspaste, the dentin bonding agent and the composite luting agent were applied directly on relatively large areas of dentin. Except for transient pain in three teeth, no adverse reaction was observed with this treatment. Furthermore, it should be appreciated that all abutments remained vital. By comparison, a recent studyl” reported that one or both of the abutments in 11.8% of all FPDs became devitalized during a mean service length of 35 months. The increased gingival inflammation associated with the retainers in this study has also been observed in other studies of resin-retained2:17 and conventional FPDs.ls In the present study this has resulted in neither periodontal breakdown nor tooth caries. The most annoying complication observed was the lack of complete seating after cementation of some of the FPDs covered with the layer of Dentacolor Opaquer material. The last five FPDs cemented in this series were given a silica coating (Silicoater) but without the opaquer layer ap-
242
ANDSTOKHOLM
plied. None of these FPDs lifted during the cementation procedure. The reason for using the Dentalcolor opaquer is that it makes handling of the silica-coated framework easier. According to the manufacturer’s recommendation, the Silicoated framework without the opaquer layer should be cemented within 20 minutes after coating. Furthermore, the framework must not be contaminated with grease or saliva, since this will deactivate the silane layer. This makes the Silicoater technique impractical unless the Dentacolor Opaquer material is applied. The air abrasion performed before silica coating should create sufficient space for the opaquer layer. The thickness of this layer varies, especially on grooves, where there is a tendency for pooling and thick layering. This is a problem, especially when the preparations have parallel or nearly parallel walls, as did the preparations in the present study. The lift during cementation that was observed can be avoided if the Dentacolor Opaquer material is not used or if another system of enhancing retention of the frame is employed. Investigation of such systems is in progress in our laboratory. REFERENCES 1. Saunders WP. Resin bonded bridgework: a review. J Dent 1989;17:‘25565. 2. Creugers NHJ, Snoek PA, Vogels ALM. Overcountering in resinbonded prostheses: plaque accumulation and gingival health. J PROSTHET D~~~1988;59:17-21. 3. Creugers NHJ, Snoek PA, van ‘t Hof MA, Kriyser AF. Clinical performance of resin-bonded bridges: a g-year prospective study. I. Design of the study and influence of experimental variables. J Oral Rehabil 1989;16:427-36. 4. Kellett M. The etch-retained metal restoration in hospital clinical use. Br Dent J 1987;163:259-62. 5. Marine110 CP, Kerschbaum T, Heinenberg B, et al. First experiences with resin-bonded bridges and splints-a cross-sectional retrospective study. Part II. J Oral Rehabil 1988;15:223-35. 6. Mohl G, Mehra R, Ford A. Clinical evaluation of etched-metal resin-bonded fixed partial dentures. 3 PROSTHET DENT 198&59: 403-4. 7. van der Veen H. Resin-bonded bridges, in vitro and in viva. Thesis. Groningen: Rijksuniversiteit Groningen, 1988:81-112. 8. Creugers NH, Snoek PA, van-%Hof MA, Kayser AF. Clinical performance of resin-bonded bridges: a 5-year prospective study. II. The influence of patient-dependent variables. J Oral Rehabil 1989;16: 521-7. 9. Silness J, LSe H. Periodontal disease in pregnancy. II. Correlation between oral hygiene and periodontal conditions. Acta Odontol Stand 1964;22:121-35. 10. LSe H, Silness J. Periodontal disease in pregnancy. I. Prevalence and severity. Acta Odontol Stand 1963;21:533-51. 11. Miller SC, Yudkoff I, OkunMN. The science of oral diagnosis. In: Miller SC, ed. Oral diagnosis and treat,ment. 3rd ed. New York McGraw-Hill Book Company, Inc, 1957:9. 12. Clyde JS, Boyd T. The etched cast metal resin-bonded (Maryland) bridge: a clinical review. J Dent 1988;16:22-6. 13. Priest GF, Donatelli HA. A four-year clinical evaluation of resin-bonded fixed partia1dentures.J PROSTHET DENT 1988;59:542-6. 14. Hudgins JL, Moon PC, Knap FJ. Particle-roughened resin-bonded retainers.J PROSTHET DENT 1985;53:471-6. 15. Probster L, Sets J. Clinical performance of silane-coated, resin-bonded fixed partial dentures with two different preparational concepts. Quintessence Int 1990;21:707-12.
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1992
VOLUME
68
NUMBER
2
RESIN-BONDEDPROSTHESES
16. Cheung GS, Dimmer A, Mellor R, Gale M. A clinical evaluation of conventional bridgework. J Oral Rehabil 1990;17:131-6. 17. Freilich MA, Niekrash CE, Katz RV, Simonsen RJ. The effects of resin-bonded and conventional fixed partial dentures on the periodontium: restoration type evaluated. J Am Dent Assoc 1990;121:265-9. 18. Isidor F, Budtz-J$rgensen E. Periodontal conditions following treatment with distally extending cantilever bridges or removable partial dentures in elderly patients. A 5-year study. J Periodontol1990;61:21-6.
Three-dimensional finite element cantilever fixed partial denture Hania Yahia University
A. Awadalla, BDS, MDS,a Mohsen Azarbal, H. Ismail, DMD, PhD,C and Wael El-Ibiari, of Pittsburgh,
School
of Dental
Medicine,
Pittsburgh,
Reprint
requests to:
DR. FLEMMINC ISIDOR DEPARTMENT OF PROSTHETIC OGY ROYAL DENTAL COLLEGE VENNELYST BOULEVARD DK-8000, AARHUS C DENMARK
stress DMD, BSd
DENTISTRY
analysis
AND STOMATOGNATHIC
PHYSIOL
of a
MDS,b
Pa.
A three-dimensional mathematical model was generated, representing a three-unit cantilever fixed partial denture and its supporting mandibular structures. First and second premolars were used as abutments with one posterior cantilever pontic. A 5 lb vertical load was applied to the pontic. Vertical and horizontal stresses were analyzed by means of a three-dimensional finite element stress analysis technique. The results showed that a cantilever pontic creates considerable compressive stress on the abutment nearest to the pontic and produces tensile stress on the abutment farthest from the pontic. (J PROSTHET DENT 1992;68:243-8.)
R eplacement of missingposterior teeth in the absenceof distal abutments can be achieved by one of the following ways: (1) with removable partial dentures with distal extensionbases,(2) with fixed partial denturesusing implants as distal abutments, and (3) with fixed partial dentures with cantilever pontics. Conflicting opmionsexist regarding the useof cantilever fixed partial denturesto restore edentulousspaceswithout a distal abutment. The decision to use a cantilever fixed partial denture should be basedon a sound periodontal condition, good alveolar bone support, favorable toothto-tooth and arch-to-arch relationships, favorable root shape, a good crown-to-root ratio, and clinical experience.l This study evaluated stress distribution in the abutment teeth and their supporting alveolar bone in a mandibular posterior cantilever fixed partial denture using a three-dimensional finite element stress analysis technique. aGraduate Resident. bAssistant Professor, Department of Prosthodontics. CProfessor and Chairman, Department of Prosthodoutics. dEngineering Consultant. 10/l/37744
THE JOURNAL
OF PROSTHETIC
DENTISTRY
MATERIAL
AND
METHODS
In this study the finite elementstressanalysistechnique wasusedto evaluate the stressesin a mandibular posterior cantilever fixed partial denture. Two- and three-dimensional finite element stressanalyseshave beenusedextensively in dentistry. 2-gA three-dimensional stressanalysis technique is preferred over a two-dimensionalone because it is an actual representation of the stressbehavior in the supporting bone.7 A three-dimensionalmathematical model of the mandible was used in this study, representing the mandibular canine, first premolar, secondpremolar, and their supporting structures with a cantilever pontic and 7 mm of the edentulous ridge distal to the secondpremolar. A threeunit cantilever fixed partial denture was designedusing first and secondpremolarsasabutments and a first molar as a pontic. In making the finite element model, the anatomic form and dimensions,the modulusof elasticity, and Poisson’sratios equivalent to those structures being simulated were entered into the computer program. Components of the dental model were mandibular bone, periodontal ligaments,natural teeth, type 3 gold crowns,and full gold pontics. Both abutment teeth were restored with cast crowns, using type 3 gold with one cast gold cantilever pontic replacing the first molar.
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