gree of clinical acceptability, and Bravo (Ã), Charlie. (C), and Delta (D) were ..... Collins cr, Bryant RW, Hodge K-LV A elinÃL:al «valuation of posterior composite ...
Clinical evaluation of different posterior resin composite materials: A 7-year report Lezize Çebnem Türkün, DDS, PhDVBekir Oguz Aktener, DDS, PhDVMustafa Ale?, Objectives: The aim of this study was to investigate the clinical performance ot 120 posterior composite restorations placed in 38 patients after a period of 7 years. Metfiod and materials: Eighty-eighf Class I and 32 Class II restorations were made (93 molars and 27 premolars) using three different resin composite materials: Z100, Clearfil Ray-Posterior, and Prisma TPH, The restorations were evaluated using Ryge's criteria tor color match, marginal discoloration, marginal adaptation, secondary caries, surface texture, and anatomic fcrm at baseline, 1, 2, 5, and 7 years. Photographs and radiographs were taken at each recall period. Results: At 7-year recalls, 70 restorations were available for examination. Four restorations had failed due to secondary caries. Saliva sampling was performed to determine the leyel ot mutans streptococci and laotobaoilli for the four failed restorations at the last recall. No statistically significant differences were found among the materials in regard lo color match, anatomic form, and secondary caries, Clearfil Ray-Posterior had sfatistically significanfly rougher surface texture than the surrounding enamel compared fo fhe other resin composifes, Z10D showed more cavosurface margin discolorafion after 5 years fhan the other fwo resin composites. All materials had siighf marginai adaptation problems at fhe 7-year recall. There was no apparenf relationship between fhe levels of mutans streptococci and lactobadlli in saliva and the failed restorations. Conciusion: The three posterior composites tested had acceptable clinical pertormance after 7 years. (Quintessence Int 2003:34:418-426) Key words: lactobadlli, long-term clinical performance, mufans strepfococci, posferior resin composifes, Ryges criteria
ental resin composites, specifically advocated for use in posterior teeth, were introduced in the early 1980s and have become increasingly popular in restorative dentistry,' The introduction of the materials was surrounded by much speculation about their possible long-term performance. Therefore, few materials, if any, in the modern history of clinical dentistry have given rise to more investigations and publications than resin composites. Resin composite materials have been used successfully in anterior teeth for many years, whereas their use in the posterior region and particularly in molar teeth has been questioned,^'^ The reasons for concern have been in regard to polymerization shrinkage and
D
'Assistant Professor, Department of Resloralive Denlistry and EndodonliCE, School of Denfistry, Ege Universily, Izmir, Turkey. 'Professor, Deparlmenl of Resforative Dentistry and Endodonlics, School of Dentistry, Ege University, Izmir, Turkey ^Assistant Prolessor, Department of Basic and Industrial Microbiology, Faculty of Science, Ege University, Izmir, Turkey. Reprint requests: Dr L. §ebnem Türkün, Department of Restorative Dentistry and Endodcntics, School of Dentistry, Ege Universily, 035100 Izmir, Turkey, E-mail' sebnemturkunShotniaiLcom
418
their tendency to wear,"*-^ Studies have focused on material properties and operative procedures, and continuous research has resolved many material-related problems and has contributed to development. Caries is tiow reported to be the most common reason for clinical failure of these restorations,'-' but data related to patient factors are still limited. Many techniques and systems are available for tooth-colored composite restorations, and many in vitro tests have been designed to predict the durability of direct composite restorations in clinical service,'"-'' Even with carefully designed simulation of clinical circumstances, the conditions vary considerably from those in vivo. For example, the outward flow of fluids through the dentinal tubules, the surface tension, and the functional stresses caused by titastication can not be simulated with in vitro tests,'^ Clinical wear is a matter of not only inherent material factors and operative procedures but also patient factors influencing the oral environment. Observations with regard to dental wear have indicated that saliva secretion rate might influence the wear,'^ Another such factor may be an acidogenic oral environtnent due to a high intake of fermentable carbohydrates Volume 34, Number B, 2003
• Türkün et al
which cause a fall in saliva pH favoring the growth of aciduric microorganisms, such as lactobacilli and mutans streptococci,'» In recent years, there has been an emphasis on relatively short-term studies to provide an early prediction of the long-term clinical performance of posterior composites.i'^-i" Although some articles have presented findings for 5 years and longer,*'^-=' the increasing emphasis on short-term studies has been based on the observation that the indirect evaluation techniques will detect loss of anatomic form earlier than direct clinical techniques,-^ Longer-term studies are needed to identify the modes of failure,-' the possible reasons for these failures, and to compare the expected lifespan of posterior resin composite with that of amalgam restorations. Moreover, data on the long-term performance of direct resin composite restorations in posterior teeth arc important in extending current knowledge and understanding pertinent to the expanding use of tooth-colored restorative materials.-* Few studies on the use of composites in posterior teeth have reported findings over 10 or more years, limiting the information available on the potential performance determinants and modes of failure of restorations, of the materials, and of the composites in general.'"-^•^° Chnical trials require objective, reliable, and relevant criteria to assess the performance of restorations. The United States Public Health Service (USPHS) evaluation system, also known as Ryge's criteria,^' is the most commonly used direct method for quality control of restorations. It was designed to reflect differences in acceptability (yes/no) rather than in degrees of success. This report gives the 7-year clincal findings of three different posterior resin composites. It records the performance of 70 restorations with the failure of one posterior and two all-purpose resin composites in posterior teeth and explores the possible relationship between failure and salivary levels of mutans streptococci (ms) and lactobaciUi (lbc).
METHOD AND MATERIALS
Subjects Thirty-eight patients (25 females and 13 males) requiring posterior resin composite restorations were referred to fhe Department of Restorative Dentistry of the Dental School in Ege University (Izmir, Turkey), Only those who demonstrated good oral hygiene were included in the study. Written patient consent was obtained at the start of the project, and the protocol was approved by the Human Ethical Research Committee Quintessence International
TABLE 1 Properties of the resin composites ZIOO Composite type Resin type Filler type
Densified compaot-fille bis-GMA TEG-DMA Zirconium, silica
Cleartil Ray-Posterior
PnsmaTPH
Densitied compact-ülied bis-GMA TEG-DMA Quartz, colioidal siiica, banum glass 3-5 pm quartz (fine), 0.05 pm turned silica 1 0-2 4 |jm
Densitied midway-tilled bis-GMA UDMA Barium glass. silica
86
77
66
7t
57
21.030
26.435
13,644
130
114
77
448
408
383
Filler particle size distribution
0.6-1 .Opm ullratine
Filler particle size Filler content per weight (%) Filler content per volume (%] Young's elastio modulus (MFa) Vicker's hardness (kg/mm^) Compressive strength (MPa)
0.8 pm 85
t-3t]ni ultratine 3.5 pm
bis-GMA = bisphierol glycidyl methacryiate; UDMA = urethane dimelhacrylate. TEQ-OMA = triethyleneglycoldimethacrylaie
of Ege University (Izmir, Turkey), A total of 120 restorations were placed (88 Class I and 32 Class II} in 93 molars and 27 premolars. Seventy-five percent of premolar preparations were Class il, and 90% of molar preparations were Class I to balance the size of the restorations. No more than three teeth per patient were included in the study. Light-curing resin composites used to restore the teeth in the study were ZIOO (3M Dental), Clearfil RayPosterior (now marketed as Clearfil Photo Posterior, Kuraray), and Prisma TPH (Caulk/Dentsply), The properties of the materials are shown in Table 1. One hundred and twenty cavities were prepared, restored, and finished by the same operator who followed standard procedures and the manufacturers' recommendations. Vitality test scores of the teeth were recorded before any preparation. Adhesive preparation design and no margin bevelling was performed for any cavity. The Class I cavity preparations extended between one quarter and no more than one third of the way up one or more of the cuspal slopes. The proximal portion of the Class II cavity preparations extended into the interproximal embrasures. The restorations could be qualified as small to moderate, Prewedging with an anatomically contoured wooden wedge (Hawe Neos Dental) was made before Class II cavity preparation, Tbis procedure allowed slow separation and served as a guide to determine the proper height of the gingival floor. 419
• Türkün el al
TABLE 2 Ryge's (USPHS) direct evaluation criteria Criteria Color match
Te si procedure Visual inspection with mirror at 18 inches
Cavosurface Visuai margin inspection discoloration with mirror at 18 inches
Marginal adaptation (occlusal and proximai)
Secondary canes
Surface texture
Anatomic form (occiusal and proximal)
Visuai inspection with expiorer and mirror. if needed
Visual inspec fion with explorer. mirror, and radiographs Visual inspection with explorer and mirror. if needed
Visuai inspection with explorer and mirror. if needed
Score
A. The restoration matohes the adjacent tooth in color and transiuoenoy. B. Light mismatch in color, shade, or transiucency between the restoration and the adjacent tocth. C. The mismatch in coior and transiucency is cutside the acceptable range of toofh ccior and franslucency A No discoioration anywhere along Ihe margin between the restoration and the adjacent tool h. B. S i ig ht discoloration along the margin between the restoration and the adjacent tooth, CThe discoloration penetrated along the margin of the restorative material in a puipal direction, A. No visible evidence of a crevice along the margin. B, Visibie evidence ol a crevice along the margin into which the explorer will penetrate. C. The dentin or base is exposed. D, The restoration is fractured, mobile, Of missing, A. No evidence of canes. B. Evidence of canes along the marign cf fhe restoration.
A. The restoration surface is as smooth as surrounding enamel, B. The restoraticn surface is rougher than fhe surrounding enamel. C. There is a crevice and fracture on Ihe surface cf fhe restoration. A, The restoration is continuous with existing anatomic form, B, The restoration is discontinuous with existing anatomic form, but the material is nol sufficient to expose the dentin or base. C, Sufficient materiai iost to expose the denlin or base.
All dentina! surfaces were covered with a glassionomer base (Chemfil Superior, DcTrcy/Dcntsply) to protect pulpal tissues from possible chemicai irritation by either the acid-etching agent or the resin composite monomer. The matrix and wedge for all Class li preparations were standard, eommercial, precontoured, and translucent (Luclwedge, Hawe Neos Dental). All enamel margins, as well as cavosurface margins, were acid etched and then coated with the appropriate bonding agent of the resin composites tested. The resin composites were inserted using an incremental technique. The first increment, 1 to 1.5 mm 420
thick, was condensed in one corner of the proximal gingival floor and then cured with a visible light-curing unit (Dcgulux/Dcgussa) for 40 seconds, Tbe curing light was tested prior to each placement to ensure an output in excess of 400 W/mm^, The second increment was condensed in the opposite corner and cured on that side. Succeeding increments, 1,5 to 2 mm, were placed and sequentially cured until the proximal and occlusal contours were restored fully. After removal of the matrices for Class II restorations, the proximal limits were polymerized again for 20 seconds both lingually and buccally. The occlusal surfaces were finished under water spray cooling with flame diamond burs (No, 859 EF.314,014, Komet) to remove gross excess followed by a sbarply tapered, pointed, white polystone. Aluminum oxide disks (Sof-Lex Pop-on Discs, 3M Dental) were used for proximal finish, A smooth reflective surface was finally accomplished using an appropriate fine aluminum oxide paste (Prisma Gloss, DeTrey/Dentsply) applied with a rubber cup. Clinical evaluation All restorations were evaluated using the method developed by Ryge and Cvar'' and commonly known as USPHS criteria. Evaluation parameters included the following: color-matching ability, marginal adaptation, anatomic form, cavosurface marginal discoloration, secondary caries, and surface texture. For eacb of the criteria, Alfa (A) was used to indicate the highest degree of clinical acceptability, and Bravo (ß), Charlie (C), and Delta (D) were used to indicate progressively lessening degrees of clinical acecptahiiity (Table 2). Each restoration was evaluated by three clinicians trained in the technique and not involved with the treatment procedures. When there was disagreement during an evaluation, the ultimate decision was made by consensus of the three examiners, who were calihrated before the study by a joint examination of 20 composite restorations. Bitewing radiographs for secondary caries detection were taken, vitality tests were recorded, and color photographs were taken (Agfa Chrome RSX 50, AGFA) at baseline and at I-, 2-, 5-, and 7-year reealls. All restorations accorded a Charlie or Delta rating or found to have heen replaced at the 7-year review were regarded as having failed. Statistical analyses Changes in the parameters during the 7-year period were evaluated by Cochran Q and Friedman test using the Statistical Package for Social Science (SPSS) software program. The level of significance was set at P
106); and into three lactobacilli classes (CFU/mL saliva); low(< 104); medium (104 to 105); and high (> 105), Four patients had medium levels of ms (105 to 106), Three patients had low levels (< 104) of Ibc, and one had a medium level [104 to 105) of Ibc, There appeared to be no relation between the levels of ms and Ibc and failed restorations. The mean failure rate was 4,3% for ZIOO, 3,8% for Clearfil Ray-Posterior, and 9,5''/o for Prisma TPH, These failure rates were not statistically different from each other (P>,05),
Quintessence Internalionai
Fig 5b The sarna restorations at Itie 7-year recaii ¿unit; ucit;rioration occurred on the cavosurface margins ol the second premoiar. The othei composite remained unchanged.
Fig 6 Seven-year occlusal restorations of Cleariil Bay-Postenor in mandibular molars. The first molar had some deterioration in color but little evidence of marginal stain. The second molar had a secondary canes on the mesial part ot the restoration
DISCUSSION
The 7-year recall rate of 58,3''/(i has been recognized as acceptable for a clinical study of this type," Patients in this study were routine patients of a large university dental hospital serving a socioeconomically less advantaged part of a greater metropolitan area. The overall failure rate for three resin composites at 7 years (5,7%) correlates well with other long-term clinical trials'^--'^"-" in which the failure rates were between O»/o to 4O'»/o (Table 4), The clinical evaluation of the 70 available restorations revealed a 94,3^/0 success rate and only a small number of significant differences among the three composite materials. For each composite, secondary caries and marginal adaptation were the most common reasons for failure, Bayne et al'^ attributed 65% 423
• Türkün et al
TABLE 4 Long-term clinical studies and their failure rates Investigators
Restorations reviewed
Bay ne et a l " 899 Wilson and Norman" 932 Rowe™ 256 Barnes et al^s 33 932 LetzeP Geurtsen and 1200 Schoeler" Köhler et aP 63 Barnes et al^^ 33 Collins et al=5 330 Raskin et a l " Maira*
100
Gaengier et a P
194
30
Materiais tested 17 composites 1 composite 1 composite 1 composite t composite 1 composite
5
2 composites 1 com pos i le 3 composites and t amaigam t composite 3 composites and 2 amalgams 1 composite
of the posterior composite failures affer 5 years to caries and restoration fracture (SSf'/o due to caries, 30% due to fracture). Gaengier et aP'' found 16 failures over a 10-year period, of which 69''/o were attributed to fracture and 31''/o to recurrent caries. Wilder et al,'' who examined four different ultra violet light-cured posterior composites at 10 years, found no difference among the materials. Similarly, Collins et al-^ and Mair-'' found no significant differences among posterior composites tested at 8 and 10 years, Abdalla and Davidson'- compared tbe marginal integrity of in vivo and in vitro Class II composite restorations. Tbey concluded that in all cases, restorations placed following the application of a light-curing glass ionomer showed significantly less microleakage than those without such a base. It is possible tbese results can be explained by the glass-ionomer base acting as a cushion and stress breaker under tbe resin composite restoration,'^ In that way, the load is not directly transferred to the restoration margin, which helps to preserve marginal integrity. Also, the use of such a base reduces the bulk of the restoration and minimizes the polymerization and stress contractions. In the current study, none of the restorations were fractured, and the rate for secondary caries was very low for the three materials at 7 years. This may be attributed to the inseriion of a glass-ionomer base under all restorations. Raskin et aF' made a clinical evaluation of Occlusin posterior resin composite at 10 years and found that location. Class, and size of the restorations and method of isolation were not found to influence significantly fhe 10-year performance of the material. The current findings are in concordance with Raskin et aí.^ The surface of all Clearfll Ray-Posterior restorations, except one, was scored as slightly rougher than 424
Foliow-up (y]
Faiiure rate (%) 9.2
5
17
5
9
5
9,4
5
17
5
13
5
27.6
8
23
8
11.7
10
40
10
0
10
25,8
the adjacent enamel (score Bravo) after 1 year. The antagonist tooth of the only restoration scored Alfa was extracted five months after the restoration was placed. The slightly rough surface texture was perceptible only witb a sharp explorer, and none of the patients complained about the situation. This roughness could be attributed to the particle size and the use of quartz as a filler particle in this material. This has been noted in many other studies evaluating the clinical sucess of quartz-filled resin composites,^' The longevity of restorations is dependent upon many factors, including operator skill, the materials and techniques used, the criteria for replacement, patient compliance with oral hygiene advice, the oral environment and its contribution to the patient's susceptibility to caries, and possibly, the means by which the treatment is funded,^* In 1997, Mjör' investigated the reasons for replacement and the age of failed restorations in genera! dental practice. He found that the clinical diagnosis of secondary caries was the main reason for replacement of composite, amalgams, and glass-ionomer restorations. In the current study, four restorations had to be replaced because of secondary caries. The median longevities were found to be about 6 years for composites, almost 9 years for amalgams, and jusf over 3 years for glass-ionomer restorations in the same research. According to Burke et al,'* the average age of the restorations at the time of replacement or failure is 5.7 years for composites and 8,3 years for amalgams. In regard to the current findings, it can he anticipated that the time of replacement for posterior resin composites may be prolonged to more tban 7 years, Köhler et al,* Rasmusson et al,'^ Bentley et al,'^ ^j^¿ Köhler and Hagef" compared the clinical failure rate of Volume 34, Number 6, 2003
• Türiíün et ai
resin composite materials and the level of microorganisms in saliva and found signifieant high levels of mutans streptoeocei and lactobacilli in patients witb failed restorations. According to the current survery, tbe failed restorations were not influenced by tbe levels of mutans streptococci and lactobaciUi present in tbe saliva. The desh-e for esthetics and alternatives to amalgam are the two main reasons for plaeing tooth-colored posterior restorations. However, composites are more problematic than amalgam, since their application technique is much more difficult, complicated, and time consuming. Dentists should consider that placing a posterior composite requires approximately 2,5 times as much time as plaeing a similar amalgam,'""" In longterm clinical studies, the failure rates of resin composite materials are not inferior to those of amalgam restorations,""-^ With the wear behavior and clinical performance of modern, highly filied, small-particle hybrid composites, it is suggested that posterior composites may be the material of choice for Class I and moderate Class II restorations when the appropriate application techniques are employed.
CONCLUSIONS 1. The overall failure rate of the composite restorations in posterior teeth at 7 years was 5,7% (4.3''/o for ZIOO; 3.8% for Clearfil Ray-Posterior; 9,5% for Prisma TPH). 2. The main modes of failure of the composites were secondary caries and marginal adaptation problems, 3, Direct evaluation of the three materials using Ryge's criteria revealed few significant findings with no clinical influence. 4, The bactériologie samplings suggested that, in the current study, tbere was no connection between the levels of mutans streptococci and lactobacilli in saliva and failure rates.
ACKNOWLEDGMENTS The aulfiors would like to fhunk 3M Dental. Dentsply. and Kiiraray for their material supporl and Mr Altan Destici for the photographs.
REFERENCES 1 Christensen GJ, Acceptability cf alternatives for conservative restoration of posterior teeth. J Esthef Dent 1995;7: 228-232. 2 Qvist V Qvist J, Mjör IA. Placement and longevity of loothcoloured restorations in Denmark, Acta Odontol Scand 1990;48:305-3n.
Quintessenceinternational
3. Ferracane |L. Using posterior composites appropriately, J Am Dent Assoc 1992;123:53-58. 4. Jensen ME, Chan DCN, Polymerization shrinitagc and microleakage. In; Vanherle G, Smith DC (eds). Posterior Composite Resiti Dentai Restorative Materiais. Utveeht, The Netheriands: Szulc, 1985:243-262. 5. Feilzer AJ. de Gee AJ, Davidson CL. Curing contraction of composites and giass ionomer eements. [ Prosthet Dent 1988;59:29a-310. 6. Ress JS, Jaeobsen PH. The polymerisation shrinkage of composite resins. Dent Mater 1989;5;41-44, 7. Mjör IA. The reasons for replaeement and the age of faiied restorations in general practice. Ac:ta Odontol Seand 1997; 55:58-63. 8. Pesun IJ, Olson AK, Hodges JS, Anderson GC. In vivo evaiuation of the surface of posterior resin composite restorations: A pilot study. J Prosthet Dent 20Û0;84:353-359, 9. Kohier B, Rasmusson C-G, Odman P. A five-year ciinicai evaluation of ciass II composite resin restorations. J Dent 2000;28:111-116. 10. Rouiet JF, Seewaldt A, Noack MJ. Margin quality of ciass III and IV eomposites in vitro. Dent Mater 1991;7:179-185, 11. Burgoyne AR, Nieholls Jl, Brudvik JS. In vitro two-body wear of iniay-oniay composite resin restoratives, ] Prosthet Dentl991;65:206-214. 12. Abdalia Al, Davidson CL. Comparison of the marginal integrity of in vivo and in vitro ciass II composite restorations. JDent 1993;21:158-152. 13. Carlsson GE, Johansson A, Lundqvist S. Ocelusal wear. Acta Odontül Scand 1985:43:83-90, 14. Birkhed D, Heintze U, Salivary secretion rate, buffer capacity and pH. In: Tenovuo JO (ed¡. Human Saliva: Clinical Chemistry and Microbiology. Vol 1. Boca Raton, FL: CRC Press. 1989:25-73, 15. Leinfeider KF. Wilder AD Jr. Teixeira LC. Wear rates of posterior composite resins. J Am Dent .Assoc 1986 ;112:829-833, 16. Rasmusson CG, Köhler B. Odman P. A 3-year clinical evaluation ol two eomposite resins in elass 11 cavities Aeta Odontol Scand 1998;56:70-75 17 Geurtsen W, Schoeler U, A 4-year retrospective clinical study of ciass I and ciass II eomposite restorations, J Dent 1997;25:229-232. 18, Manhart J, Neuerer P. Scheibenbogen-Fuchsbrunner A, Hiekel R. Three-year eiinical evaiuation of direct and indirect composite restorations in posterior teeth. J Prosthet Dent 2000:84:289-296. 19, Bayne SC, Tayiao DF. Roberson TM, et al. Long-term clinical failures in posterior composites [abstract 32], J Dent Res 1989;68:185. 20, Rowe AHR, A five year study of the eiinical performance of a posterior eomposite resin restorative material, J Dent 1989;17:S6-S9, 21, Wiider AD, May KN. Bayne SC. Taylor DF, Leinfelder KP, Ten year eiinical analysis oí 4 UV eured posterior composites [abstract 33], J Dent Res 1989;68:186. 22, Barnes DM. Blank LW, Thompson VP, Holston AM, Gingell JC. A 5- and 8-year clinical evaluation of a posterior composite resin. Quintessence Int 1991,22:143-151. 23, Raskin A, Michotte-Theall B, Vreven J. Wilson NHF, Clinical evaluation of a posterior composite 10-year report, JDent 1999,27:13-19.
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24. Mair L. Ten-year clinical assessment of three posterior resin composites and two amalgams. Quintessence Int 1998;29; 483-490. 25. Collins cr, Bryant RW, Hodge K-LV A elinÍL:al «valuation of posterior composite resin restorations: 8-ycar findings. J Dent 1998:26:311-317, 26. Freilich MA, Goldberg A), Gilpatrick RO, Simonsen RJ. Direct and indirect evaluation of posterior composite restorations at three years. Dent Mater 1992;8:60-64. 27. Wilson NHF. The evaluation of materials' Relationship between laboratory investigations and clinical studies. Oper Dent 1990:15:14 9-155. 28 Wilson NHF. Long-term performance of resin-bonded tooth-coloured restorations. Transactions of Annual Meetings of fhe Academy of Dental Materials 1996;9 216-228. 29. EI-Mowafy OM, Lewis DW, Benmergui C, Levinton C. Meta-analysis on long-term clinical performance of posterior composite restorations. J Dent 1994;22:33-43. 30. Wilder AD Jr, Bayne SC, Heymann HO. Long-term clinical performance of direct posterior composites. Transactions of Annual Meetings of tbe Academy of Dental Materials 1996:9:151-169. 31. Ryge G, Cvar JF. Criteria for the Ciinieal Evaluation of Dental Restorative Materials. US Dental Health Center, publication 7902244. Government Printing Office, 1971. 32. Westergren G, Krasse B, Evaluation of a micromethod for determination of Streptococcus mutans and Lactobacilli infection. ] Clin Microbiol 1978:7:82-84. 33. Wiison NHF, Norman RD. Five-year findings of a muUiclinieai trial for a posterior composite. J Dent 1991;19:153-159.
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34. Letzel H. Survival rates and reasons for failure of posterior composite restorations in multicentre clinical trial. J Dent 1989;17:S10-S17. 35. Gaengler P, Hoyer I, Montag R. Clinical evaluation of posterior composite restorations: The 10-year report. J Adhes Dent 2001:3(21:185-194. 36. Krejci I, Lutz F, Iírejci D. The influence of different hase materials on marginal adaptation and wear of conventional class II composite resin restorations. Quintessence Int 1988:19:191-198. 37 Wendt SL Jr, Leinfelder KF. Clinical evaluation of Clearfil photoposterior: 3-year results. Am | Dent 1992;5(3):121-125. 38. Burlce FJT, Wilson NHF, Cheung SW, Mjör IA. influence of patient factors on age of restorations at failure and reasons for their placement and replacement. ] Dent 2001:29:317-324. 39. Benttey CD, Broderius CA, Drake CW, Crawford JJ. Relationship between saiivary levéis of mutans streptococei and restoration longevity. Caries Res 1990;24:298-300. 40. Köhler B, Hager B. Influenee of salivary ievels of mutans streptococci on colonization of crown margins: A longitudinai study. J Prosthet Dent 1993:69:524-528. 41. Leidal TL Accompiishments and expectation with posterior composite resins. In: Vanberle G, Smith DC (eds). Posterior Composite Resin Dental Restorative Materials. St Paul, MN: 3M Dental, 1985:541-547. 42. Mjör IA, Long-term eost of restorative tberapy using different materials, Scand J Dent Res 1992:100:60-65. 43. Mjör IA. Clinical Longevity of Amaigams and Composites. Direct Restorative Material's Longevity in First, Second, and Tbird World Countries. [Proceedings of tbe 73rd General Session of the Intemationai Assoeiation for Dental Research 28 June-1 July 1995, Singapore].
Volume 34, Number 6, 2003
