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Clinical performance of resin-retained fixed partial dentures bonded with a chemically active luting cement
SECTION EDITOR
Clinical p e r f o r m a n c e of r e s i n - r e t a i n e d fixed p a r t i a l d e n t u r e s b o n d e d w i t h a c h e m i c a l l y a c t i v e luting c e m e n t A. S. M. G i l m o u r , B D S , F D S R C S ( E d ) , a a n d A. A l i , B D S , F D S R C S ( E n g ) , D R D R C S ( E d ) , M R D R C S ( E d ) b
University of Wales College of Medicine, Dental School, Cardiff, United Kingdom A clinical study w a s u n d e r t a k e n to r e v i e w r e s i n - r e t a i n e d fixed partial d e n t u r e s bonded w i t h a c h e m i c a l l y a c t i v e luting c e m e n t during a 4 - y e a r period. One hundred t h i r t y - s e v e n fixed partial d e n t u r e s w e r e r e v i e w e d of w h i c h five had f a i l e d b e c a u s e of a nonbonding failure (esthetics, trauma, fracture) and 47 (36%) had failed after a bonding failure, of w h i c h 72% w e r e rebonded. The m e a n t i m e of failure w a s 10.9 months (SD 9.8). The failure rate a p p e a r e d to be affected by position, use of a rubber dam, and the fixed partial denture design, although no one factor r e a c h e d c o n v e n t i o n a l s t a t i s t i c a l significance. (J PROSTHET DENT 1995;73:569-73.)
J[~esin-retained fixed partial dentures (FPDs) have been provided in dental practice for approximately 20 years and have developed from the original Rochette designs of the 1970s I to the more recent use of chemically active luting resins. 2 The main advantages of such FPDs are reduced pulpal morbidity caused by minimal tooth preparation and reduced gingival problems resulting from supragingival placement of the margins. In addition, chairside time and laboratory costs are reduced when compared with conventional prostheses. Young and elderly patients in particular benefit from this restorative option. A number of clinical trials that involve these restorations have been carried out with varying degrees of reported success. 35 Most of the previous studies have reported a number of different retentive types of resin-retained FPDs; however, the aim of this study was to assess the efficacy of just one type of resin-retained FPD, which was bonded with a chemically active resin. MATERIAL
AND METHODS
The study was designed as a retrospective clinical evaluation of resin-retained FPDs used to restore edentulous spaces of patients in the Department of Conservative Dentistry, Dental School, Cardiff, and the Maxillofacial Unit, Morriston Hospital, Swansea. The study was conducted over a 4-year period and reviewed partial dentures that were bonded by staff members and by students. All FPDs were constructed from a nonprecious metal alloy (Bondiloy, Krupps, Essen, Germany) with the internal
aLecturer, Department of Conservative Dentistry. bConsultant, Maxillofacial Unit, Morriston Hospital, Swansea, United Kingdom. Copyright | 1995 by The Editorial Council of THE JOURNALOF PROSTHETIC DENTISTRY.
0022-3913/95/$3.00 + 0. 10/1/62715
JUNE 1995
surface air-abraded with 50 #m alumina and were subsequently bonded with the chemically active luting cement, Panavia Ex (Kurary, Osaka, Japan). Data
collection
Data collected included patients' personal details, status of the operator (staff or student), information on the type and amount of tooth preparation, design, and position of the FPD, date of prosthesis insertion, and whether rubber dam was used during the luting procedure. Two hundred sixty FPDs were placed in 238 patients between 1987 and 1990. All patients were recalled, but only 119 patients appeared at the recall appointments for a total of 137 FPDs. The FPDs were examined independently by both authors for (1) the presence or absence of debonded retainers, (2) the marginal integrity of the FPD--which included any associated caries, and (3) the esthetic appearance of the abutment teeth. In addition, the amount of plaque and the condition of the gingival and periodontal tissues were recorded. The method of recording the information followed that of Thompson and Wood.3 E x a m i n a t i o n criteria. The examination was carried out independently; however, when disagreement occurred, it was resolved after some discussion, and the data were recorded. Debond. If a complete bond was not present during visual examination, the tip of a probe was inserted between the retainer casting and the tooth to ensure that no opening existed between the two. Only moderate force was used during this examination. Marginal integrity. All exposed margins were assessed with a probe tip for voids or defects. An "alpha" score indicated a completely closed margin, whereas a "bravo" rating was used, if a defect or void was found anywhere on the margin. A "charlie" score was not used
THE JOURNAL OF PROSTHETIC DENTISTRY
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THE JOURNAL OF PROSTHETIC DENTISTRY
GILMOUR AND ALI
number
percentage
50
100
40
80
30
60
20
40
J
10
20
3
6
9
12
15
18
21
0 24
months
F i g . 1. Failures of FPDs versus time.
T a b l e I. Success and failure by position in mouth Failed
Time at failure (mo) m
Anterior/maxillary Posterior/maxillary Anterior/posterior/maxillary Anterior/mandibular Posterior/mandibular Total
N
N
%
x
SD
86 16 2 16 12 132
30 6 1 4 6 47
37 38 50 25 50 36
10.5 5.3 26 17 9.6 10.6
10.05 4.9 0 11 9.4 9.8
Rebonded
22 6 2 4 34 [72 %]
N, Number.
T a b l e II. Success and failure by use of rubber dam Failed Number
Yes No Unknown
66 54 12
Percent
N
%
50 41 9
23 23 1
35 43 8
because this score was classified as a debonding and was recorded elsewhere. Caries. Any obvious caries was noted, and appropriate restorative procedures were carried out. Esthetics, Grayness was the criterion assessed of the anterior abutments. A charlie rating was not clinically acceptable, a bravo score was recorded if slight grayness of the a b u t m e n t was observed b u t was clinically acceptable, and an alpha score was recorded if no grayness was evident. Comparisons were made with the contralateral teeth coloration.
570
Modified plaque index. This index of Silness and Loe 6 was recorded for each a b u t m e n t and the contralateral teeth. Gingival index. The gingival index described by Loe 7 again was recorded for each a b u t m e n t and the contralateral teeth. Probing depths. Probing depths were assessed in three positions around the a b u t m e n t tooth in relation to the bonded wing of the F P D and were also assessed in the contralateral teeth for comparison. The depth of the deepest pocket was used for test and controls and was recorded in one of three categories: less than 3 mm, 3 m m to 5 ram, and greater than 5 m m in depth. RESULTS Of the 260 FPDs placed in 238 patients, 137 were evaluated at recall for 119 patients. This n u m b e r represented a recall rate of 53 % of the original patient population. Five FPDs were not included in the data analysis because of failure caused by t r a u m a (one), esthetics (three), and porcelain fracture (one). Therefore the data represent debonding failure in the patients in the recall group only. The time
VOLUME 73 NUMBER 6
GILMOUR AND ALI
THE JOURNAL OF PROSTHETIC DENTISTRY
Table III. Success and failure by prosthesis design Failed
Fixed/fixed Cantilever Other
Rebonded
Number
Percent
N
%
N
%
81 43 8
61 33 6
33 12 2
41 28 25
21 6
64 50
in situ at recall of the remaining 132 F P D s was 12 to 47 months (mean 24.5 months).
Table IV. Mean plaque index (MPI) and gingival index (GI) score for test and contralateral side MPI
Fixed partial denture types As expected, most of the F P D s were positioned in the anterior/maxillary region (Table I), and the rest were divided equally among the other regions of the mouth. The anterior/posterior maxillary position included two F P D s t h a t spanned across the maxillary canine.
Operator
and tooth preparation
At the beginning of the study resin-retained F P D s were infrequently u n d e r t a k e n by students; thus most of the F P D s were inserted by staff members (109; 80 % ); students placed only 28 (20%). The d a t a on tooth preparation revealed that "wrap-around" preparations were most common and were usually accompanied by cingulum/occlusal rests as described by Simonsen et alp Few operators reported the use of guide planes, slots, or grooves to increase mechanical retention or resistance form.
Failures
Position. Overall the total number of failures was 47 (36 %). Variation in failure rate occurred between the anterior m a n d i b u l a r region (25 % ) and the posterior mandibular region (50%) (Table I). Seventy-two percent of the failed fixed partial dentures had been rebonded. The mean time of failure was 10.6 (SD = 9.8) months, and variation was seen in the a n t e r i o r / m a n d i b u l a r and posterior/maxillary regions. Closer examination revealed that 50 % of the failed F P D s debonded within the first 9 months and t h a t nearly 25% debonded within the first month (Fig. 1). Rubber dam. Rubber d a m was used in 50% of cases, and failures occurred less often in this group (Table II); the difference was not significant (x 2 0.461, df 1, p > 0.05). Design. M o s t of the F P D s were of the fixed-fixed design (61%) (Table III) with cantilever designs t h a t accounted for 33 %. Other designs included movable joints and a resin-retained F P D supported by a conventional crown with a slot-type attachment, but the numbers within this group were small. W h e n design was assessed, a higher incidence of failure was recorded in the fixed-fixed design compared with the cantilever design, but statistical analysis failed to demonstrate a significant difference (• df 1, p > 0.05). Rebonding of the fixed partial dentures after
J u ~ 1995
Test side Contralateral side
GI
x
SD
x
SD
1.04 0.84
0.77 0.65
1.14 0.94
0.61 0.60
failure was more often done in the fixed-fixed designed partial dentures.
Marginal
integrity
and caries
Few voids or defects (bravo scores) were observed around the margins of FPDs, although a significant proportion had excess resin luting cement, usually in a proximal position. This excess was removed at the time of recall. Caries was not evident on any of the successful F P D s but was present in five F P D s where debonding had occurred. This finding may indicate t h a t in these F P D s some marginal leakage had occurred before debonding. 9
Esthetics Grayness of the a b u t m e n t teeth was r a t e d bravo in 18% of anterior F P D s and alpha in the remaining prostheses.
Periodontal
indexes
The periodontal indexes collected at the recall visits indicated an increase in the amount of plaque found and a deterioration of the gingival condition in relation to the retainers when compared with the contralateral side (Table IV). By use of a two-sample t test these differences were found to be significant (mean plaque index test score versus mean plaque contralateral t test score 2.16, p < 0.05, df 214) (gingival index test score versus gingival index contralateral t test score 2.52, p < 0.05, df 221). The probing depth, however, was less than 3 mm for the test teeth and for the contralateral areas in all but one bridge where the test side measured less than 3 mm and the contralateral side measured 3 to 5 mm. DISCUSSION The main problem with a clinical study is the number of patients who return for the recall appointment. W i t h o u t an
571
THE
JOURNAL OF PROSTHETIC DENTISTRY
adequate recall rate, the d a t a analysis is at best problematic and may even be misleading. Therefore the d a t a presented in this study should be received cautiously in forming definitive conclusions. T h o m p s o n and Wood 3 suggested t h a t in such studies the population is self-selected and has a high proportion of patients returning who perceive a problem. Therefore it m a y be reasonable to assume t h a t the results are less favorable than would be expected, if the total population had been assessed. Other studies t h a t investigated the failure rate of resinretained F P D s carried out in the United Kingdom demonstrated similar results. Hussey et al.4 reported a total failure rate of 25%, whereas Kellett 1~ reported a failure rate of 32 %. Dunne and Millar n found in their study that 33 % of resin-bonded restorations debonded, of which 55 % were rebonded. In all of these studies a high incidence of early failure was noted; Hussey et al.4 reported that 31% of debonding occurred within 3 months, Kellett 1~t h a t 56.5 % occurred within 1.8 months, and Dunne and Millar u t h a t 46% debonded in the first 6 months. In this study 25% of the failed F P D s debonded within the first month and 50% within 9 months. This finding may be attributed partly to difficulties in bonding technique, with contamination of either the tooth or metal bonding surfaces occurring. If this is the case, it is likely t h a t such failures will be reduced dramatically as experience is gained and moisture control improves. Other studies such as t h a t of Creugers et al. 5 reported survival rates of 75% for anterior and 44% for posterior resin-retained F P D s in their 7.5-year survival study. T h e y also found t h a t the incidence of failure decreased with time, with 50% of failures occurring within the first 2 years of the study. Their survival rates were better than those reported in this study, which may be explained by the small n u m b e r of operators and the strict standardization of method used by Creugers et al.5 Most of the F P D s were positioned in the anterior/maxillary region with small numbers of F P D s elsewhere making definitive conclusion difficult. The posterior/mandibular F P D s appeared to have a higher incidence of failure than those from other sites. Creugers et al. 5 reported a higher failure rate in mandibular and maxillary posterior segments alike when compared with anterior positions. In this study the posterior/mandibular position had a higherthan-average failure rate, whereas posterior maxillary F P D s performed no worse t h a n average. Difficulties in moisture control, shorter clinical crowns, and tilting of teeth in the posterior/mandibular region m a y explain the a p p a r e n t poor performance of these FPDs. Anterior/mandibular F P D s a p p e a r e d to survive longer than average, with a failure rate of 25 % and a mean time of failure of 17 months. The a p p a r e n t success of anterior/mandibular F P D s may relate to easier isolation of this region during cementation or more favorable occlusal forces. The rubber dam was used in only 50 % of F P D placements. The results m a y suggest t h a t the use of the rubber dam improved the success rate, albeit to a small degree.
572
GILMOUR AND ALI
However, on 12 of the data-recording forms no information on rubber dam was completed (Table II). If it is assumed t h a t no rubber dam was placed in these cases, the failure rate when no rubber dam was used would be reduced from 43 % to 38%, a similar failure rate to t h a t when rubber dam was used. W h a t is not clear from these figures, however, is the effectiveness of the isolation when rubber dam was used. Hussey et al.4 found in their study t h a t the failure rate was reduced when a cantilever design was used, and this study would appear to confirm the finding. The possible problem of ingestion or inhalation of a debonded cantilever F P D caused Clyde and Boyd 12 to advocate the use of fixed-fixed partial dentures. No evidence exists to suggest t h a t this is any more of a problem than any other extracoronal restoration. In this study no preparation or only minimal preparation was u n d e r t a k e n for the FPDs. Creugers et al. 5 and Simon et al.13 suggested that in the anterior region minimal preparation m a y be acceptable. However, it has been shown that in the posterior region greater mechanical resistance is required and t h a t the use of slots is now recommended. 13 No use was made of slots to increase retention and resistance in this study, and this exclusion may have contributed to the generally poor results. Grayness of the a b u t m e n t teeth, in particular the upper incisor teeth, after placement of a resin-retained F P D would a p p e a r to be much less of a problem than in the early days of the technique. This study found only 18 % of FPDs with mild grayness of the a b u t m e n t teeth, and this improvement is most likely because of the use of an opaque luting cement. Significant changes were noticed in the periodontal condition around the a b u t m e n t s of the F P D s when compared with teeth on the contralateral side. It is appreciated t h a t toothbrushing habits can make significant differences between opposite sides of the mouth, but is believed t h a t this method was superior to comparing the assessments with those t a k e n before operation. In a large number of F P D s the preoperative gingivae m a y have been affected by the p r e s e n c e of a removable partial denture, thereby not allowing us to use this as an accurate baseline. This deterioration in the health of the gingival tissues was slight and may be explained by an overcontouring of the restorations caused by minimal preparation and also by inadequate removal of the composite luting cement after placement of some of the fixed partial dentures. REFERENCES 1. Rochette AL. Attachment of a splint to enamel of lower anterior teeth. J PROSTHET DENT 1973;30:418-23. 2. Omura I, Yamauchi J, Horade I, Wada T. Adhesive and mechanical properties of a new dental adhesive [Abstract]. J Dent Res 1984;63:233. 3. Thompson VP, Wood M. Design of bonded cast bridges: six years in retrospect. In: Gettleman L, Vrijhoef MMA, Uchiyama Y, eds. Proceedings of a symposium on adhesive prosthodontics; 1986 June 24; Amsterdam. Nijmegen: Eurosound Drukkerj B V, 1988:91-I05. 4. Hussey DL, Pagni C, Linden GJ. Performance of 400 adhesive bridges fitted in a restorative dentistry department. J Dent 1991;19:221-5.
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THE JOURNAL OF PROSTHETIC DENTISTRY
5. Creugers NHJ, Kayser AF, Van't Hof MA. A seven and a half year survival study of resin bonded bridges. J Dent Res 1992;11:1822-5. 6. Silness J, Loe H. Periodontal disease in pregnancy. II. Correlation between oral hygiene and periodontal condition. Acta Odontol Scand 1964;24:121-35. 7. Loe H. The Gingival Index, the Plaque Index, and the Retention Index system. J Periodontol 1967;38:610-6. 8. Simonsen R, Thompson VR, Barrack G. Etched cast restorations: clinical and laboratory techniques. Chicago: Quintessence, 1983. 9. Gilmour ASM. Resin bonded bridges: a note of caution. Br Dent J 1989;167:140-2. 10. Kellett M. The etched-retained metal restoration in hospital clinical use. Br Dent J 1987;163:259-62. 11. Dunne SM, Millar BJ. A longitudinal study of the clinical performance
of resin retained bonded bridges and splints. Br Dent J 1993;174:40511. 12. Clyde JS, Boyd T. The etched cast metal resin bonded (Maryland) bridge: a clinical review. J Dent 1988;16:22-6. 13. Simon JF, Gartrell RG, Grogono A. Improved retention of acid etched fixed partial dentures: a longitudinal study. J PROSTHET DENT 1992; 68:611-5. Reprint requests to: DR. ALAN GILMOUR DENTAL SCHOOL DEPARTMENT OF CONSERVATIVEDENTISTRY HEATH PARK CARDIFF CF4 4XY UNITED KINGDOM
The Glossary of Prosthodontic Terms, Sixth Edition The Glossary of Prosthodontic Terms is the ultimate resource for the professional. This document, a collection of words/terms and their special connotation in the art and science of prosthodontics, was created to provide a standard lexicon for the profession. The sixth edition of the Glossary (printed in the January 1994 issue of The Journal of Prosthetic Dentistry) is now available from Mosby in your choice of formats: 9 Reprints of the 72-page Glossary are available for $12 each. (For quantities of 25 or more, cost is $10 each.) 9 For $32, you may purchase the Glossary on disk. The disk can be used on any IBM or compatible computer, with a minimum of 640K RAM and DOS 3.1 or later.
The Glossary, which includes more than 2,500 entries, was prepared by The Academy of Prosthodontics under the auspices of Dr. Clifford W. VanBlarcom, chairman of the Academy's Nomenclature Committee. A total of 18 organizations participated in the development of the Glossary.
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JUNE 1995
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573
Clinical p e r f o r m a n c e of r e s i n - r e t a i n e d fixed p a r t i a l d e n t u r e s b o n d e d w i t h a c h e m i c a l l y a c t i v e luting c e m e n t A. S. M. G i l m o u r , B D S , F D S R C S ( E d ) , a a n d A. A l i , B D S , F D S R C S ( E n g ) , D R D R C S ( E d ) , M R D R C S ( E d ) b
University of Wales College of Medicine, Dental School, Cardiff, United Kingdom A clinical study w a s u n d e r t a k e n to r e v i e w r e s i n - r e t a i n e d fixed partial d e n t u r e s bonded w i t h a c h e m i c a l l y a c t i v e luting c e m e n t during a 4 - y e a r period. One hundred t h i r t y - s e v e n fixed partial d e n t u r e s w e r e r e v i e w e d of w h i c h five had f a i l e d b e c a u s e of a nonbonding failure (esthetics, trauma, fracture) and 47 (36%) had failed after a bonding failure, of w h i c h 72% w e r e rebonded. The m e a n t i m e of failure w a s 10.9 months (SD 9.8). The failure rate a p p e a r e d to be affected by position, use of a rubber dam, and the fixed partial denture design, although no one factor r e a c h e d c o n v e n t i o n a l s t a t i s t i c a l significance. (J PROSTHET DENT 1995;73:569-73.)
J[~esin-retained fixed partial dentures (FPDs) have been provided in dental practice for approximately 20 years and have developed from the original Rochette designs of the 1970s I to the more recent use of chemically active luting resins. 2 The main advantages of such FPDs are reduced pulpal morbidity caused by minimal tooth preparation and reduced gingival problems resulting from supragingival placement of the margins. In addition, chairside time and laboratory costs are reduced when compared with conventional prostheses. Young and elderly patients in particular benefit from this restorative option. A number of clinical trials that involve these restorations have been carried out with varying degrees of reported success. 35 Most of the previous studies have reported a number of different retentive types of resin-retained FPDs; however, the aim of this study was to assess the efficacy of just one type of resin-retained FPD, which was bonded with a chemically active resin. MATERIAL
AND METHODS
The study was designed as a retrospective clinical evaluation of resin-retained FPDs used to restore edentulous spaces of patients in the Department of Conservative Dentistry, Dental School, Cardiff, and the Maxillofacial Unit, Morriston Hospital, Swansea. The study was conducted over a 4-year period and reviewed partial dentures that were bonded by staff members and by students. All FPDs were constructed from a nonprecious metal alloy (Bondiloy, Krupps, Essen, Germany) with the internal
aLecturer, Department of Conservative Dentistry. bConsultant, Maxillofacial Unit, Morriston Hospital, Swansea, United Kingdom. Copyright | 1995 by The Editorial Council of THE JOURNALOF PROSTHETIC DENTISTRY.
0022-3913/95/$3.00 + 0. 10/1/62715
JUNE 1995
surface air-abraded with 50 #m alumina and were subsequently bonded with the chemically active luting cement, Panavia Ex (Kurary, Osaka, Japan). Data
collection
Data collected included patients' personal details, status of the operator (staff or student), information on the type and amount of tooth preparation, design, and position of the FPD, date of prosthesis insertion, and whether rubber dam was used during the luting procedure. Two hundred sixty FPDs were placed in 238 patients between 1987 and 1990. All patients were recalled, but only 119 patients appeared at the recall appointments for a total of 137 FPDs. The FPDs were examined independently by both authors for (1) the presence or absence of debonded retainers, (2) the marginal integrity of the FPD--which included any associated caries, and (3) the esthetic appearance of the abutment teeth. In addition, the amount of plaque and the condition of the gingival and periodontal tissues were recorded. The method of recording the information followed that of Thompson and Wood.3 E x a m i n a t i o n criteria. The examination was carried out independently; however, when disagreement occurred, it was resolved after some discussion, and the data were recorded. Debond. If a complete bond was not present during visual examination, the tip of a probe was inserted between the retainer casting and the tooth to ensure that no opening existed between the two. Only moderate force was used during this examination. Marginal integrity. All exposed margins were assessed with a probe tip for voids or defects. An "alpha" score indicated a completely closed margin, whereas a "bravo" rating was used, if a defect or void was found anywhere on the margin. A "charlie" score was not used
THE JOURNAL OF PROSTHETIC DENTISTRY
569
THE JOURNAL OF PROSTHETIC DENTISTRY
GILMOUR AND ALI
number
percentage
50
100
40
80
30
60
20
40
J
10
20
3
6
9
12
15
18
21
0 24
months
F i g . 1. Failures of FPDs versus time.
T a b l e I. Success and failure by position in mouth Failed
Time at failure (mo) m
Anterior/maxillary Posterior/maxillary Anterior/posterior/maxillary Anterior/mandibular Posterior/mandibular Total
N
N
%
x
SD
86 16 2 16 12 132
30 6 1 4 6 47
37 38 50 25 50 36
10.5 5.3 26 17 9.6 10.6
10.05 4.9 0 11 9.4 9.8
Rebonded
22 6 2 4 34 [72 %]
N, Number.
T a b l e II. Success and failure by use of rubber dam Failed Number
Yes No Unknown
66 54 12
Percent
N
%
50 41 9
23 23 1
35 43 8
because this score was classified as a debonding and was recorded elsewhere. Caries. Any obvious caries was noted, and appropriate restorative procedures were carried out. Esthetics, Grayness was the criterion assessed of the anterior abutments. A charlie rating was not clinically acceptable, a bravo score was recorded if slight grayness of the a b u t m e n t was observed b u t was clinically acceptable, and an alpha score was recorded if no grayness was evident. Comparisons were made with the contralateral teeth coloration.
570
Modified plaque index. This index of Silness and Loe 6 was recorded for each a b u t m e n t and the contralateral teeth. Gingival index. The gingival index described by Loe 7 again was recorded for each a b u t m e n t and the contralateral teeth. Probing depths. Probing depths were assessed in three positions around the a b u t m e n t tooth in relation to the bonded wing of the F P D and were also assessed in the contralateral teeth for comparison. The depth of the deepest pocket was used for test and controls and was recorded in one of three categories: less than 3 mm, 3 m m to 5 ram, and greater than 5 m m in depth. RESULTS Of the 260 FPDs placed in 238 patients, 137 were evaluated at recall for 119 patients. This n u m b e r represented a recall rate of 53 % of the original patient population. Five FPDs were not included in the data analysis because of failure caused by t r a u m a (one), esthetics (three), and porcelain fracture (one). Therefore the data represent debonding failure in the patients in the recall group only. The time
VOLUME 73 NUMBER 6
GILMOUR AND ALI
THE JOURNAL OF PROSTHETIC DENTISTRY
Table III. Success and failure by prosthesis design Failed
Fixed/fixed Cantilever Other
Rebonded
Number
Percent
N
%
N
%
81 43 8
61 33 6
33 12 2
41 28 25
21 6
64 50
in situ at recall of the remaining 132 F P D s was 12 to 47 months (mean 24.5 months).
Table IV. Mean plaque index (MPI) and gingival index (GI) score for test and contralateral side MPI
Fixed partial denture types As expected, most of the F P D s were positioned in the anterior/maxillary region (Table I), and the rest were divided equally among the other regions of the mouth. The anterior/posterior maxillary position included two F P D s t h a t spanned across the maxillary canine.
Operator
and tooth preparation
At the beginning of the study resin-retained F P D s were infrequently u n d e r t a k e n by students; thus most of the F P D s were inserted by staff members (109; 80 % ); students placed only 28 (20%). The d a t a on tooth preparation revealed that "wrap-around" preparations were most common and were usually accompanied by cingulum/occlusal rests as described by Simonsen et alp Few operators reported the use of guide planes, slots, or grooves to increase mechanical retention or resistance form.
Failures
Position. Overall the total number of failures was 47 (36 %). Variation in failure rate occurred between the anterior m a n d i b u l a r region (25 % ) and the posterior mandibular region (50%) (Table I). Seventy-two percent of the failed fixed partial dentures had been rebonded. The mean time of failure was 10.6 (SD = 9.8) months, and variation was seen in the a n t e r i o r / m a n d i b u l a r and posterior/maxillary regions. Closer examination revealed that 50 % of the failed F P D s debonded within the first 9 months and t h a t nearly 25% debonded within the first month (Fig. 1). Rubber dam. Rubber d a m was used in 50% of cases, and failures occurred less often in this group (Table II); the difference was not significant (x 2 0.461, df 1, p > 0.05). Design. M o s t of the F P D s were of the fixed-fixed design (61%) (Table III) with cantilever designs t h a t accounted for 33 %. Other designs included movable joints and a resin-retained F P D supported by a conventional crown with a slot-type attachment, but the numbers within this group were small. W h e n design was assessed, a higher incidence of failure was recorded in the fixed-fixed design compared with the cantilever design, but statistical analysis failed to demonstrate a significant difference (• df 1, p > 0.05). Rebonding of the fixed partial dentures after
J u ~ 1995
Test side Contralateral side
GI
x
SD
x
SD
1.04 0.84
0.77 0.65
1.14 0.94
0.61 0.60
failure was more often done in the fixed-fixed designed partial dentures.
Marginal
integrity
and caries
Few voids or defects (bravo scores) were observed around the margins of FPDs, although a significant proportion had excess resin luting cement, usually in a proximal position. This excess was removed at the time of recall. Caries was not evident on any of the successful F P D s but was present in five F P D s where debonding had occurred. This finding may indicate t h a t in these F P D s some marginal leakage had occurred before debonding. 9
Esthetics Grayness of the a b u t m e n t teeth was r a t e d bravo in 18% of anterior F P D s and alpha in the remaining prostheses.
Periodontal
indexes
The periodontal indexes collected at the recall visits indicated an increase in the amount of plaque found and a deterioration of the gingival condition in relation to the retainers when compared with the contralateral side (Table IV). By use of a two-sample t test these differences were found to be significant (mean plaque index test score versus mean plaque contralateral t test score 2.16, p < 0.05, df 214) (gingival index test score versus gingival index contralateral t test score 2.52, p < 0.05, df 221). The probing depth, however, was less than 3 mm for the test teeth and for the contralateral areas in all but one bridge where the test side measured less than 3 mm and the contralateral side measured 3 to 5 mm. DISCUSSION The main problem with a clinical study is the number of patients who return for the recall appointment. W i t h o u t an
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adequate recall rate, the d a t a analysis is at best problematic and may even be misleading. Therefore the d a t a presented in this study should be received cautiously in forming definitive conclusions. T h o m p s o n and Wood 3 suggested t h a t in such studies the population is self-selected and has a high proportion of patients returning who perceive a problem. Therefore it m a y be reasonable to assume t h a t the results are less favorable than would be expected, if the total population had been assessed. Other studies t h a t investigated the failure rate of resinretained F P D s carried out in the United Kingdom demonstrated similar results. Hussey et al.4 reported a total failure rate of 25%, whereas Kellett 1~ reported a failure rate of 32 %. Dunne and Millar n found in their study that 33 % of resin-bonded restorations debonded, of which 55 % were rebonded. In all of these studies a high incidence of early failure was noted; Hussey et al.4 reported that 31% of debonding occurred within 3 months, Kellett 1~t h a t 56.5 % occurred within 1.8 months, and Dunne and Millar u t h a t 46% debonded in the first 6 months. In this study 25% of the failed F P D s debonded within the first month and 50% within 9 months. This finding may be attributed partly to difficulties in bonding technique, with contamination of either the tooth or metal bonding surfaces occurring. If this is the case, it is likely t h a t such failures will be reduced dramatically as experience is gained and moisture control improves. Other studies such as t h a t of Creugers et al. 5 reported survival rates of 75% for anterior and 44% for posterior resin-retained F P D s in their 7.5-year survival study. T h e y also found t h a t the incidence of failure decreased with time, with 50% of failures occurring within the first 2 years of the study. Their survival rates were better than those reported in this study, which may be explained by the small n u m b e r of operators and the strict standardization of method used by Creugers et al.5 Most of the F P D s were positioned in the anterior/maxillary region with small numbers of F P D s elsewhere making definitive conclusion difficult. The posterior/mandibular F P D s appeared to have a higher incidence of failure than those from other sites. Creugers et al. 5 reported a higher failure rate in mandibular and maxillary posterior segments alike when compared with anterior positions. In this study the posterior/mandibular position had a higherthan-average failure rate, whereas posterior maxillary F P D s performed no worse t h a n average. Difficulties in moisture control, shorter clinical crowns, and tilting of teeth in the posterior/mandibular region m a y explain the a p p a r e n t poor performance of these FPDs. Anterior/mandibular F P D s a p p e a r e d to survive longer than average, with a failure rate of 25 % and a mean time of failure of 17 months. The a p p a r e n t success of anterior/mandibular F P D s may relate to easier isolation of this region during cementation or more favorable occlusal forces. The rubber dam was used in only 50 % of F P D placements. The results m a y suggest t h a t the use of the rubber dam improved the success rate, albeit to a small degree.
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However, on 12 of the data-recording forms no information on rubber dam was completed (Table II). If it is assumed t h a t no rubber dam was placed in these cases, the failure rate when no rubber dam was used would be reduced from 43 % to 38%, a similar failure rate to t h a t when rubber dam was used. W h a t is not clear from these figures, however, is the effectiveness of the isolation when rubber dam was used. Hussey et al.4 found in their study t h a t the failure rate was reduced when a cantilever design was used, and this study would appear to confirm the finding. The possible problem of ingestion or inhalation of a debonded cantilever F P D caused Clyde and Boyd 12 to advocate the use of fixed-fixed partial dentures. No evidence exists to suggest t h a t this is any more of a problem than any other extracoronal restoration. In this study no preparation or only minimal preparation was u n d e r t a k e n for the FPDs. Creugers et al. 5 and Simon et al.13 suggested that in the anterior region minimal preparation m a y be acceptable. However, it has been shown that in the posterior region greater mechanical resistance is required and t h a t the use of slots is now recommended. 13 No use was made of slots to increase retention and resistance in this study, and this exclusion may have contributed to the generally poor results. Grayness of the a b u t m e n t teeth, in particular the upper incisor teeth, after placement of a resin-retained F P D would a p p e a r to be much less of a problem than in the early days of the technique. This study found only 18 % of FPDs with mild grayness of the a b u t m e n t teeth, and this improvement is most likely because of the use of an opaque luting cement. Significant changes were noticed in the periodontal condition around the a b u t m e n t s of the F P D s when compared with teeth on the contralateral side. It is appreciated t h a t toothbrushing habits can make significant differences between opposite sides of the mouth, but is believed t h a t this method was superior to comparing the assessments with those t a k e n before operation. In a large number of F P D s the preoperative gingivae m a y have been affected by the p r e s e n c e of a removable partial denture, thereby not allowing us to use this as an accurate baseline. This deterioration in the health of the gingival tissues was slight and may be explained by an overcontouring of the restorations caused by minimal preparation and also by inadequate removal of the composite luting cement after placement of some of the fixed partial dentures. REFERENCES 1. Rochette AL. Attachment of a splint to enamel of lower anterior teeth. J PROSTHET DENT 1973;30:418-23. 2. Omura I, Yamauchi J, Horade I, Wada T. Adhesive and mechanical properties of a new dental adhesive [Abstract]. J Dent Res 1984;63:233. 3. Thompson VP, Wood M. Design of bonded cast bridges: six years in retrospect. In: Gettleman L, Vrijhoef MMA, Uchiyama Y, eds. Proceedings of a symposium on adhesive prosthodontics; 1986 June 24; Amsterdam. Nijmegen: Eurosound Drukkerj B V, 1988:91-I05. 4. Hussey DL, Pagni C, Linden GJ. Performance of 400 adhesive bridges fitted in a restorative dentistry department. J Dent 1991;19:221-5.
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5. Creugers NHJ, Kayser AF, Van't Hof MA. A seven and a half year survival study of resin bonded bridges. J Dent Res 1992;11:1822-5. 6. Silness J, Loe H. Periodontal disease in pregnancy. II. Correlation between oral hygiene and periodontal condition. Acta Odontol Scand 1964;24:121-35. 7. Loe H. The Gingival Index, the Plaque Index, and the Retention Index system. J Periodontol 1967;38:610-6. 8. Simonsen R, Thompson VR, Barrack G. Etched cast restorations: clinical and laboratory techniques. Chicago: Quintessence, 1983. 9. Gilmour ASM. Resin bonded bridges: a note of caution. Br Dent J 1989;167:140-2. 10. Kellett M. The etched-retained metal restoration in hospital clinical use. Br Dent J 1987;163:259-62. 11. Dunne SM, Millar BJ. A longitudinal study of the clinical performance
of resin retained bonded bridges and splints. Br Dent J 1993;174:40511. 12. Clyde JS, Boyd T. The etched cast metal resin bonded (Maryland) bridge: a clinical review. J Dent 1988;16:22-6. 13. Simon JF, Gartrell RG, Grogono A. Improved retention of acid etched fixed partial dentures: a longitudinal study. J PROSTHET DENT 1992; 68:611-5. Reprint requests to: DR. ALAN GILMOUR DENTAL SCHOOL DEPARTMENT OF CONSERVATIVEDENTISTRY HEATH PARK CARDIFF CF4 4XY UNITED KINGDOM
The Glossary of Prosthodontic Terms, Sixth Edition The Glossary of Prosthodontic Terms is the ultimate resource for the professional. This document, a collection of words/terms and their special connotation in the art and science of prosthodontics, was created to provide a standard lexicon for the profession. The sixth edition of the Glossary (printed in the January 1994 issue of The Journal of Prosthetic Dentistry) is now available from Mosby in your choice of formats: 9 Reprints of the 72-page Glossary are available for $12 each. (For quantities of 25 or more, cost is $10 each.) 9 For $32, you may purchase the Glossary on disk. The disk can be used on any IBM or compatible computer, with a minimum of 640K RAM and DOS 3.1 or later.
The Glossary, which includes more than 2,500 entries, was prepared by The Academy of Prosthodontics under the auspices of Dr. Clifford W. VanBlarcom, chairman of the Academy's Nomenclature Committee. A total of 18 organizations participated in the development of the Glossary.
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