To investigate the clinical behavior of two different resin-based restorative systems in extended Class II cavities in a controlled prospective split-mouth study over 12 years and to assess marginal quality under a SEM using epoxy replicas.
Thirty patients received 68 resin composite restorations (Solobond M + Grandio: n = 36; Syntac + Tetric Ceram: n = 32) by one dentist in a private practice. 35% of cavities revealed no enamel at the bottom of the proximal box, 48% of cavities provided <0.5 mm remaining proximal enamel. Restorations were examined according to modified USPHS criteria at baseline, and after six months, one, two, four, six, eight, 10, and 12 years. Expoxy replicas of 21 restoration pairs were analysed under a SEM at 200× magnification regarding marginal quality.
At the 12-years recall, 59 of the original 68 restorations in 27 of 30 patients were available (drop out 13%). Two restorations failed due to cusp fracture (Tetric Ceram) and marginal fracture (Grandio). The overall success rate of all restorations was 97.1% (Kaplan–Meier survival algorithm) with no differences between the two materials ( p = 0.923). After 144 months of clinical service, restorations in molars performed worse than in premolars regarding the integrity of restoration and tooth ( p < 0.05) being detected as wear, chippings, and cracks. Beyond the 4-year recall, marginal staining significantly increased. SEM evaluation of replicas revealed that perfect margin (49% baseline vs. 10% after 12 years), overhang (13% at baseline vs. 3% after 12 years), negative step formation (34% at baseline vs. 75% after 12 years), and marginal fractures (0% at baseline vs. 6% after 12 years) significantly changed during the evaluation period ( p < 0.001).
Extended direct resin composite restorations performed satisfactorily over 12 years of clinical service. SEM analysis delivered qualitative data regarding marginal deterioration over time.
Resin-based composites (RBC) are widely accepted as material of choice for directly restored posterior cavities . Compared to indirect restorations they can always be placed under minimally invasive conditions because no special preparation prerequisites exist . Survival was repeatedly reported to be acceptable with 1–3% average annual failure rates , however, technique sensitivity is still estimated to be substantial .
Due to the fact that many clinical trials are industry funded, the majority of reports just compared different products, and moreover, often limited observation times . However, also these studies can be of substantial interest when long-term data beyond the 10-years recall are collected. When appropriate RBCs have been applied correctly, these studies give a valuable insight regarding both fatigue and breakdown processes . This is even more true when additional instruments like SEM marginal quality assessment are performed , which have been rarely documented so far . Finally, the risk of bias due to industry funding was not given because the manufacturer did not affect any of the investigations like design or data analysis, this was completely in the hands of the authors. Moreover, funding was restricted to financial compensation of operator, patients, and travel costs.
The ratio between restorative in vivo and in vitro research has been less than 1:10 during the last decades which is also endorsed by the fact that once long-term data have been collected with substantial endeavor, the investigated material(s) may not be on the market anymore . Nevertheless, although both RBCs covered in the present study have suffered reformulations, it is still value for the reader because extended re-restorations of previously failed fillings in stress-bearing areas have been observed for a long time. Assuming that most of the early problems of RBC should have been solved over the years, and major milestone improvements may not happen anymore, today’s focus is more and more directed to different aspects such as, e.g. operator skills and finally patient risk factors like individual caries risk or bruxism .
Aim of the present clinical trial was to investigate the clinical behavior of two resin composites over an observation period of 12 years and to look deeper into marginal deterioration processes using an SEM replica technique. The null hypothesis was that there would be no difference between materials regarding both clinical outcome and SEM marginal quality.
Materials and methods
Prospective clinical trial
Patients selected for this study met the following criteria: (1) absence of pain from the tooth to be restored; (2) possible application of rubber dam during placement of restoration; (3) no further restorations planned in other posterior teeth; (4) good level of oral hygiene; (5) absence of any active periodontal and pulpal pathology; (6) restorations required in two different quadrants (split mouth design); (7) age 18–65; (8) no pregnancy.
The study was approved by an Ethics Committee (University Clinic Erlangen, Germany). All patients were required to give written informed consents before starting the study and agreed to participate in a recall program. Thirty patients (23 female, 7 male, mean age 32.9 (24–59) years) with a minimum of two fillings to be replaced in different quadrants received at least two different restorations in a random decision according to recommendations of the CONSORT statement . Sample size calculation was carried out according to previous clinical studies , occluding teeth were not excluded.
Thirty-six Grandio fillings were bonded using an etch-and-rinse technique using Solobond M (Voco, Cuxhaven, Germany) and 32 Tetric Ceram restorations were bonded with Syntac (Ivoclar Vivadent, Schaan, Principality of Liechtenstein). All fillings (only Class II, 52 MO/OD, 16 MOD or more surfaces (i.e. buccal or lingual), no complete cusp replacements) were re-restorations made by one dentist in a private practice (31 upper bicuspids, 12 upper molars, 14 lower bicuspids, 11 lower molars). Reasons for replacement were caries ( n = 19), insufficient esthetics ( n = 2), and secondary caries beneath amalgam restorations ( n = 47). For all teeth receiving restorations, current X-rays (within six months of the procedure) were present. After evaluating the radiographs, 53 cavities (78%) were treated as “caries profunda”. Twenty-four cavities (35%) revealed no enamel at the floor of the proximal box, while 33 cavities (49%) exhibited a proximal enamel width of <0.5 mm.
All fillings were inserted in permanent vital teeth without pain symptoms. The cavities were cut using coarse diamond burs under profuse water cooling (80 μm diamond, Komet, Lemgo, Germany), and finished with a 25 μm finishing diamond. Inner angles of the cavities were rounded and the margins were not beveled. After cleaning and drying under rubber dam isolation (Coltene/Whaledent Inc., Altstätten, Switzerland), adhesive procedures were performed with Solobond M (2-step etch-and-rinse adhesive) and Syntac (4-step etch-and-rinse adhesive). The resin composite materials were applied into the cavity in layers of approximately 2 mm thickness and adapted to the cavity walls with a plugger. Each layer was light cured for 40 s (Elipar Trilight, 3M ESPE, Seefeld, Germany). The occlusal region was modeled as exactly as possible under intraoral conditions, avoiding visible overhangs. The light-emission window was placed as close as possible to the cavity margins. The intensity of the light was checked periodically with a radiometer (Demetron Research Corp., Danburg, CT, USA) and was found to be constantly above 650 mW/cm 2 .
As soon as polymerization was completed, the surface of the restoration was controlled for defects and corrected when necessary. Visible overhangs were removed with a scaler and the rubber dam was removed. Contacts in centric and eccentric occlusion were controlled with foils (Roeko, Langenau, Germany) and adjusted with finishing diamonds (Komet Dental, Lemgo, Germany), shaped with flexible discs (3M Dental, St. Paul, USA), super-fine discs (3M Dental, St. Paul, USA) and polishing brushes (Hawe-Neos Dental, Bioggio, Switzerland).
At the initial recall (baseline, i.e. within 2 weeks), and after six months, one, two, four, six, eight, and 10 years, all restorations were assessed according to the modified United States Public Health Service (USPHS) criteria ( Table 1 ) by two independent investigators (dentists, both chairpersons) using loups with 3.5× magnification, mirrors, probes, bitewing radiographs, and intraoral photographs (Nikon D90, Sigma-Makro 105 mm) with and without occlusal contact points. Investigators were blinded, trained and calibrated through eight previous clinical studies and additional calibration sessions. Recall assessments were not performed by the clinician who initially placed the restorations.
|Modified criteria||Description||Analogous USPHS criteria|
|“Good”||Slight deviations from ideal performance, correction possible without damage to tooth or restoration||“Alpha”|
|“Sufficient”||Few defects, correction impossible without damage to tooth or restoration.
No negative effects expected
|“Insufficient”||Severe defects, prophylactic removal for prevention of severe failures||“Charlie”|
|“Poor”||Immediate replacement necessary||“Delta”|
Statistical appraisal was computed with SPSS for Windows XP 15.0 (SPSS Inc., Chicago, IL, USA). Statistical unit was one tooth, Kolmogorov Smirnov test revealed no normal distribution of values, so differences between restorative groups were evaluated using Mann–Whitney U -test, changes regarding different criteria over time were calculated with the Friedman test ( p = 0.05). Survival analysis was conducted using the Kaplan–Meier algorithm, additionally confidence intervals for both types of restorations were calculated.
In each recall, silicone impressions of restored teeth were taken (Dimension® Penta and Garant, 3M Oral Care, Germany, applied with syringes to get proximal parts recorded; and Minitray®, Hagen & Werken, Duisburg, Germany) and replica made using an epoxy resin (AlphaDie, Dürr-Dental, Rosbach, Germany). Inclusion criteria for SEM analysis were (1) no missed recall for continuous evaluation (max. 10% deviation), (2) impressions free of artifacts from every recall, (3) two restorations per patient (split-mouth), (4) both restorative systems evaluable in one patient. Inclusion criteria were fulfilled by 21 patients (i.e. 42 restorations, 21 of each material). Average observation time was 12.1 years. Localization of restored teeth were 19 upper premolars, 8 upper molars, 9 lower premolars, and 6 lower molars.
Replicas were mounted on specimen holders (Leit-C, Plano GMBH, Wetzlar, Germany) and then sputtered with gold at 20 mA for 75 s (Polaron SC 502 Sputter Coater, Quorum Technologies, Laughton East Sussex, UK). Replicas were assessed at 10×- and 200×-magnification at 12–16 kV under a SEM (Amray 1610 Turbo, KLA, Milpitas, CA, USA) using an overlap technique (Fiji-win32, fiji.sc/wiki/index.php/Downloads , and KHKs_iQuantiGap by Karl-Heinz Kunzelmann, LMU Munich, Germany). Semi-quantitative margin analysis was carried out using the criteria “perfect margin”, “overhang”, “positive step formation (restoration level higher than surrounding tooth)”, “negative step formation” (restoration level lower than surrounding tooth), “gap”, “fracture”, and “not judgeable” ( Fig. 1 ).
Statistical appraisal was computed with SPSS for Windows 15.0 (SPSS Inc., Chicago, IL, USA). Statistical unit was one specimen, Kolmogorov Smirnov test revealed no normal distribution of values, so differences between groups were evaluated using Mann–Whitney U -test, changes over time regarding all SEM criteria were calculated using the Friedman test ( p = 0.05).
At the 12-years recall, 59 of the original 68 restorations in 27 of 30 patients were available (drop out 13%), three patients involving six restorations did not show up anymore. Two restorations failed, this was either due to cusp fracture (Tetric Ceram) or due to marginal fracture (Grandio). The overall success rate of all restorations was 97.1% (Kaplan–Meier survival algorithm, Fig. 2 ). No differences could be calculated between the two tested materials (Log Rank, Mantel–Cox; p = 0.923, Table 2 ).
The results of the clinical investigation sessions are displayed in Tables 2–8 . The localization of the restoration in the upper or lower jaw did not reveal any significant differences at the 12-year evaluation ( p > 0.05; Mann–Whitney U test). After 12 years, no criteria showed significant differences between the type of restoration ( p > 0.05; Mann–Whitney U -test; Tables 2–4 and Fig. 3 ). However, after 144 months of clinical service, molar restorations performed worse than premolar fillings regarding both filling integrity and tooth integrity ( p < 0.05; Mann–Whitney U test; Tables 8a and 8b ). Main reasons for more degradation of molar restorations have been wear, chippings, and cracks after twelve years ( Table 8c ). In none of the cases, enamel cracks provoked clinical symptoms like hypersensitivity or spontaneous pain.
|Group||No.||Time of the last control [years]||Status||Cumulative rate of survival restoration at the time of control||Number of events||Number of remained restorations|
|Assessor||Standard error||Assessor||Standard error||Assessor||Standard error|
|Grandio||1||9333||Fracture of the restoration||0.971||0.028||1||34|
|2||9642||Caries independent of the restoration||.||.||1||33|
|Tetric Ceram||1||6608||Cusp fracture||0.969||0.031||1||31|