One-year evaluation of two hybrid composites placed in a randomized-controlled clinical trial

d e n t a l m a t e r i a l s 3 0 ( 2 0 1 4 ) 824–838

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One-year evaluation of two hybrid composites placed in a randomized-controlled clinical trial Florian Beck a , Nicoleta Dumitrescu a , Franz König b , Alexandra Graf b , Peter Bauer b , Wolfgang Sperr a , Andreas Moritz a , Andreas Schedle a,∗ a

Central Research Unit and Department of Conservative Dentistry, Bernhard Gottlieb University Clinic of Dentistry, Vienna, Austria b Center for Medical Statistics, Informatics and Intelligent Systems, Medical University of Vienna, Vienna, Austria

a r t i c l e

i n f o

a b s t r a c t

Article history:

Objective. The aim of this prospective randomized-controlled clinical trial is to assess the

Received 24 October 2013

long-term performance of two direct composite resins in posterior teeth. This study provides

Received in revised form

a survey of the one-year results.

29 April 2014

Materials and methods. A total of 1805 restorations were placed by students in stress-bearing

Accepted 19 May 2014

Class I/II cavities (including cuspal-coverage) in molars and premolars in 456 patients. Clinical evaluation was performed at baseline and after one year using modified USPHS criteria. The restorations in each patient were performed either with Ceram X/Prime&Bond NT or

Keywords:

Tetric Ceram/Optibond Solo Plus.

Randomized controlled clinical trial

Results. After one year 528 fillings with Ceram X and 580 with Tetric Ceram were available

Resin composite

for evaluation of substance loss, contact point, color match, marginal staining, marginal

Total etch

adaptation, secondary caries and radiographic examination (if necessary). This represents

Class I restorations

a recall rate of 61.18% (279 patients). The failure rate per material was 5.3% in the Ceram X

Class II restorations

group and 6.1% in the Tetric Ceram group. Most of the failures were associated with marginal

Longevity

adaptation/integrity of the filling. A significant influence on the occurrence of a failure was observed for the number of treated teeth per patient, the age of the patient, the mesio-distal extension of the restoration and the tooth position. Gender, material, a previous root canal treatment, the bucco-lingual extension of the filling or cuspal-coverage did not significantly influence the failure rate. Patients attending the first recall were significantly older and had more fillings than patients not attending. Conclusions. In a group of Class I/II restorations (including cuspal-coverage), there was no significant difference in failure rates between ormocer-based and bis-GMA-based restorative systems after one year. A previous root canal treatment had no negative influence on the failure rate. A longer observation period is indicated to get clear evidence of the long-term performance of these composite resin systems. © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

∗ Corresponding author at: Central Research Unit and Department of Conservative Dentistry, Bernhard Gottlieb University Clinic of Dentistry, Medical University of Vienna, Sensengasse 2a, 1090 Vienna, Austria. Tel.: +43 1 40070 2626; fax: +43 1 40070 2609. E-mail address: [email protected] (A. Schedle). http://dx.doi.org/10.1016/j.dental.2014.05.006 0109-5641/© 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

d e n t a l m a t e r i a l s 3 0 ( 2 0 1 4 ) 824–838

1.

Introduction

Amalgam, which was the filling material of choice for direct posterior restorations for more than 100 years, is increasingly being replaced in favor of composite restorations. This tendency can be explained by growing concern in populations over possible mercury intoxication from amalgam and the rising demand for tooth-colored restorations [1–6]. Furthermore, composite filling materials, in contrast to amalgam, meet the criteria to allow for the use of “minimal invasive technique” in dentistry and to maintain a maximum of tooth tissue [7]. The patient demand for white filling materials is rising, and furthermore, composite materials such as packable resinbased composites and “bulk-fill” materials are being promoted as an alternative to amalgam in respect to their handling procedures [8–10]. The longevity of a dental restoration is influenced by material-, dentist- and patient-related factors. Patient-related factors include oral hygiene amongst others (dietary habits, preventive measures, compliance in recall, oral environment and systemic diseases, tooth-related factors, cooperation and parafunctional habits) [6]. There are numerous studies in which dental students have served partly or solely as a patient population [3,5,11–14]. As a matter of fact, the performance of restorations in dental students can greatly vary from that of socially deprived patients. The different dental awareness of oral hygiene and caries prevention is a possible reason [15]. In 1997, Roulet stated that “trial patients are very carefully selected, especially for good compliance” [1]. In recently published recommendations for conducting clinical trials, the authors call for study groups that represent a cross-section of the population [15]. According to Opdam et al., cross-sectional studies represent more daily practice, but they do not offer data on survival or failure rates [16]. Controlled longitudinal clinical studies do provide this information [6]. In most conducted clinical trials, the restorations are performed by experienced university dentists on selected patients, who are motivated to maintain good oral hygiene. Practice-settings can differ from that in controlled, clinical trials. Typically, university dentists dedicate more time to the placement of a composite filling compared with practice-settings. [16,17]. Several clinical trials published during the last several years only provide so-called short-term results (0–5 years) [6,18,19]. Long-term clinical trials are clearly needed, particularly when considering that failures in restorations should be subdivided into early (after weeks or months) and late failures (after several years of clinical function) [6,15]. Failures during the treatment procedures can be held primarily responsible for the early failures, whereas late failures are a result of tooth and/or restoration fracture, secondary caries and wear [6]. Furthermore, long-term data are necessary to evaluate the long-term costs of a restorative treatment. The longevity of a restoration can be regarded as an indicator of the success of a treatment procedure [20]. The failure rate among 17 clinical studies between 1996 and 2002 varied greatly from 0% to 45%. Studies lasting longer than 10 years had the highest failure rates. It could be demonstrated

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that short-term studies provided more favorable results, in addition to having smaller study populations [18]. According to van Dijken and Lindberg, the longevity of a restoration is predominantly dependent on the dentist’s qualification and the stress the oral cavity is exposed to [21]. The shortcomings of all of these studies (small study population, short-term results, selection of the study population in favor of oral hygiene) served as a basis for this present study. The aim of this study is to assess the long-term performance of two direct composite resins for posterior restorations placed in a randomized-controlled clinical trial (over 10 years). This feasibility study demonstrates if treatment of a high number of participants is feasible in the routine clinical student course. This study also examines if the failure rate of these composites will differ more than 10% after 10 years of clinical service using modified US Public Health Service (USPHS) scoring system [22]. This study provides the results after one year of clinical service.

2.

Materials and methods

2.1. Study design, patient selection and description of the study population The null hypothesis reflects that no difference will be determined between the restorations of Class I/II (including cuspal coverage) after an observation period of 10 years using two different composite materials (Table 1). The primary outcome of this study is the clinical service of restorations of Class I/II defects (occurrence of failure: yes/no). The following is recorded: restoration failure; if dentin or base was exposed; if contact point was missing (present periodontal inflammation); color and/or translucency beyond the normal range of tooth colors; marginal staining penetration in the direction of the pulp; marginal gap exhibiting the enamel–dentin junction; fractured, loose filling that is missing partly or completely and presence of caries (associated with the filling). This outcome is being assessed every year until 10 years after baseline (time of filling placement). The study population was recruited from patients of the Bernhard Gottlieb University Clinic of Dentistry during one year. Each patient, who has been in need of a direct posterior restoration, was offered participation in the study. As a benefit for the patients, the composite fillings were free of charge. The patients committed to attending the annual recall by participating in the study. To maintain a high recall rate, the patients were offered one free composite restoration in posterior teeth (in case of replacement) for every successfully attended recall. The patients can quit the study at every time without giving any reason. Prior to the restorative treatment, each patient provided written, informed consent to participate in the study. The patients had to meet the following inclusion criteria: (1) At least one permanent (pre-) molar in the posterior teeth with a natural antagonist (even third molar). (2) Patient’s age was over 18 years at the time of filling placement.

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Table 1 – Name and product details of the composites used in the study [49,55–58]. Product

Ceram X mono

Tetric Ceram

Manufacturer Classification

Dentsply DeTrey Ormocer-based/nanoceramic resin composite/nanohybrid

Matrix

Methacrylate modified polysiloxane (organically modified ceramic), dimethacrylate resin, fluorescent pigment, UV stabilizer, stabilizer, camphorquinone, ethyl-4(dimethylamino) benzoate, iron oxide pigments, titanium oxide pigments, aluminum sulfo silicate pigments Barium-aluminum-borosilicate-glass, methacrylate functionalized silicon dioxide nano filler

Filler

Filler content (%vol) Filler content (%wt) Glass filler size (mean-␮m) Nano particle size (mean-nm) Nano filler size (mean-nm) Shrinkage (%vol) Elastic modulus (MPa) Compressive strength (MPa) Flexural strength (MPa)

57 76 1.1–1.5 ∼2.3 10 2.3 8500 320 110

(3) Need for restoration with single (Class I) cavity and/or multi-surface (Class II) cavities.

The exclusion criteria were as follows:

(1) Teeth where sufficient isolation was not applicable. (2) Unfinished endodontic procedure/necessity of endodontic treatment. (3) Patients suffering from severe systemic disease or allergies to components of the composites and/or adhesives.

Root canal treated teeth were not considered as an exclusion criterion. The study design of this randomized-controlled clinical trial (RCT) was created according to the American Dental Association (ADA) guidelines for posterior restorations and recommendations of the CONSORT statement [23,24]. The trial is prospective, longitudinal, and single-blinded. Patients were randomized to one of the two treatment groups (Ceram X or Tetric Ceram). All of the restorations within one patient were performed using the same filling material. After inclusion in the trial, a randomization number was assigned to each patient. Randomized filling materials were kept in numbered sealed envelopes in accordance to allocation concealment. Corresponding envelopes (due to the assigned randomization number) were opened directly before preparation of the cavity for each patient. The envelopes were provided by the Institute of Medical Statistics of the Medical University of Vienna. As a randomization method, permutedblock randomization was performed using random blocks (with block size 2, 4, 6 or 8). A block size of, e.g., 4 means, that within the next four patients, two patients were randomized to Ceram X and two were randomized to Tetric Ceram.

2.2.

Ivoclar Vivadent Microhybrid composite resin Bis-GMA, UDMA, TEGDMA

Barium glass, ytterbium trifluoride, Ba-Al-fluorosilicate glass, silicon dioxide, spheroid mixed oxide 60 79 1 – – 3.03 9400 230 130

Clinical procedure

Dental students placed 1805 restorations in 726 premolars and 1079 molars in 456 patients during one year. University dentists, experienced in the field of adhesive dentistry, supervised the students during filling placement. Cavity preparation was performed using rounded, cylindrical 100-␮m grit diamond burs (Komet, Lemgo, Germany) under profuse water-cooling and was limited to the removal of caries to protect a maximum of tooth tissue. Caries and decayed tooth tissue was removed with rose-head burs (Komet, Lemgo, Germany). Lastly, all of the cavities were finished with 30-␮m grit diamond burs (Komet, Lemgo, Germany). The preparation was performed according to common practices for placing direct adhesive restorations in posterior teeth. Deep cavities, where direct/indirect pulp capping was necessary, were treated with calcium hydroxide (Dycal, Dentsply DeTrey, Germany). Proximal contacts were achieved using a metallic matrix (Automatrix, Dentsply Caulk, Milford, DE, USA) and wooden wedges (KerrHawe, Bioggio, Switzerland). Isolation from the blood, saliva and sulcular fluid was achieved using a suction device and cotton rolls. Operative procedures and restoration placement were performed under local anesthesia if necessary (Ultracain® , Sanovi-Aventis, Vienna, Austria), but no rubber-dam was used. Etching with 36% phosphoric acid (Conditioner 36, Dentsply DeTrey, Konstanz, Germany) and adhesive procedures were performed according to manufacturers’ instructions. OptiBond Solo Plus was used for restorations with Tetric Ceram, and Prime&Bond NT was applied in the case of Ceram X mono. Using the incremental technique, the cavities were filled with composite in layers of approximately 2-mm thickness, adapted with a plugger and each layer light cured for at least 20 s. Light-curing units had a power output of ≥500 mW/cm2 . Contacts in occlusion and articulation were controlled with articulating paper and adjusted where necessary. Occlusal and proximal finishing

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was achieved with yellow and gray polishing cups (KerrHawe, Bioggio, Switzerland), flexible discs and finishing strips (SofLex, 3M, St. Paul, MN, USA). A fluoride application (Elmex Fluid, GABA, Lörrach, Germany) completed the filling therapy.

2.3.

The evaluation of the restoration

The evaluation of the restorations was assessed according to modified United States Public Health Service (USPHS) criteria [22] (Table 2). Due to the large number of 456 patients, the initial evaluation at baseline was performed immediately after clinical procedure. The first recall was performed after one year. University dentists, specially trained in the field of adhesive dentistry, evaluated the fillings.

2.4.

Recall process

Every patient receives a written invitation two months before the annual recall appointment. If a response fails within four weeks, the patient is called by phone to arrange a new appointment. In cases where the patient does not wish to join the recall, she/he is questioned regarding the fillings directly on the phone. If a patient neither responds nor is available for a telephone call, a questionnaire will be sent asking the patient about the survival time of the fillings and the reasons for not joining the recall. Overall, four attempts (letter → call (2 times) → letter) will be performed to reach a patient until she/he is considered to be drop-out. Fig. 1 explains the recall procedure of this study as a flow chart.

2.5.

Flow diagram of study participants

See Fig. 2.

2.6.

Statistical analysis

To investigate the influence of several factors (material, age, sex, number of treated teeth at baseline, tooth position, root canal treatment at baseline, extension of the filling: mesiodistal, buccal/oral, cuspal coverage) on the occurrence of a failure (failure per filling) at the first recall (binary outcome yes vs. no), univariate generalized mixed models (with random factor patient) using GEEs (Generalized Estimating Equations) were performed for each potential influence factor. This model takes into account a potential correlation between the outcome of teeth within one patient (e.g., due to an insufficient oral hygiene of one patient). Furthermore, a multiple model was performed with all factors being significant in the univariate analyses. A failure (per filling) occurred if the filling had to be renewed or repaired, if a root canal treatment was necessary or the tooth (with the filling) was extracted as long as one year after baseline. Secondly, statistical analyses were repeated without patients observed by phone calls or questionnaires to account for potential bias. As a third type of analysis we investigated the influence of several factors determined at baseline (material, age, sex, number of root canal treatments, number of upper/lower (pre-) molar fillings and number of Class I/II fillings) on the occurrence of at least one failure (per patient). Therefore, first,

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univariate logistic regression models were performed for each of the potential influence factors. Furthermore, a multiple logistic regression model was performed with all factors being significant in the univariate analyses. Baseline values (“age”, “number of treated teeth”, “material” and “sex”) were compared between the patients attending and patients not attending the first recall using univariate tests (t-test or Chi-squared test). The significance level for all of the statistical analyses were set to ˛ = 0.05. To take into account the small number of patients to whom the modified USPHS criteria (Table 2) could not be applied properly for the reasons listed below, statistical analyses using a best/worst-case scenario were performed. • The tooth with the restoration was extracted, and the patient could not provide an explanatory reason. • The patient received a partial denture that interferes with the filling placed in the present study (inclusion criterion was a natural antagonist for the opponent of the restoration). • Replacement of the restoration (alio loco) without stating the reason. • The patient had a partial/complete denture in the opposite jaw (instead of a natural antagonist), but the filling was rated very good/acceptable, and there was no interference. • The natural antagonist was missing at the first recall. In the best-case analysis, restorations (placed in the present study) were excluded, which were unavailable for evaluation at the first recall, as mentioned above, meaning that these fillings were considered to have the same clinical behavior in regard to failures as the other observed fillings. In the worst-case analysis, all of these fillings, which were formerly excluded, were now rated as failure. For both the same statistical methods were applied. The characteristics of the restorations were reported using descriptive statistics. The statistical analyses were performed with SAS software (version 9.1, SAS Institute Inc., Cary, NC, USA). The ethics committee of the Medical University of Vienna approved this clinical trial (EC-No.: 277/2005).

3.

Results

3.1.

The results of the baseline evaluation (T0)

At baseline, the mean age of the patients was 33.96 (SD: 11.23) years. 456 patients received a total of 1805 fillings during one year. Treatment groups and gender specification are depicted in Table 3. A detailed analysis of all the fillings according to the variable “tooth position” reveals that in both the upper and lower jaw, molars were the most treated teeth: 46 in the group “Ceram X” (8.17%, n = 72) and 16 in the group “Tetric Ceram” (8.23%, n = 76). The number of fillings in premolars (PM) and molars (M) were as follows: upper PM (CX: 190/TC: 210), upper M (CX: 273/TC: 272), lower PM (CX:145/TC:181) and lower M (CX: 273/TC:261). Table 4 shows the results of the baseline evaluation.

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Table 2 – Modified USPHS criteria for the direct clinical evaluation [22]. No.

Criterion

1

Substance loss of the filling

2

Contact point

Score

Description

Methods of evaluation

A C

Excellent/acceptable Dentin or base exposed

Visual and probe Visual and probe

A

- Normal contact point - No contact point and no signs of periodontal irritations - No contact point and signs of periodontal irritations - Patient wants replacement of the filling

Floss

C

Floss

3

Color match

A C

Excellent/acceptable Color and/or translucency are beyond the normal range of tooth colors

Visual Visual

4

Marginal staining

A C

Excellent/acceptable Marginal staining penetrates in direction of the pulp

Visual Visual

5

Marginal adaptation/integrity of the filling

A C

Excellent/acceptable Marginal gap until the enamel–dentin junction Filling is fractured, loose, missing partly or completely

Visual and probe Visual and probe

Visual and probe and X-ray

B

No evidence of caries along the margin of the restoration. Caries is associated with the filling

0–10

Registration of pain

Visual analogue scale

A B

Excellent/acceptable Occlusal height to high: correction performed

Visual (articulating paper)

A D

Vital/non vital (root canal treatment at baseline) Non vital/hypersensitivity (vital at baseline)

D

6

Secondary caries

7

Pain (associated with the filling)

A



8

Occlusion

9

Testing of sensitivity

10

Percussion sensitivity

A D

Negative Positive

11

Radiographic examinationa

A D

No pathology Diagnosis: marginal gap/secondary caries, apical pathology

12

Replacement is required

A D

Not required Renewal necessary (if pain is the reason: mention if postoperative (hyper-) sensitivity persists for more than 4–8 weeks

13

Repair is necessary

A C

Not required Repair is necessary (stating the reason(s) and a detailed description)

14

Need for tooth extraction

A D

No Yes (reason: e.g., pulpitis, trauma, periodontal pathology or other reasons)

Visual and probe

Visual and probe and X-ray

Thermal testing (CO2 ice)

Mirror handle X-ray

Criteria 1–6 are according to the Ryge criteria [22]: Alpha (A), excellent/acceptable; Bravo (B), failure in case of caries; Charlie (C), failure/repair; Delta (D), failure/replacement. Criteria 7–14 are marked with an apostrophe indicating that they are not Ryge criteria – but the value of the score remains identical. a Radiographic examination was only performed in case of clinical symptoms (e.g., pain, swelling, etc.).

3.2.

The results of the first recall (T1)

The first recall was performed one year (T1: mean value: 1.08 years, SD: 0.24) after filling placement (T0 = baseline). Out of a total of 456 patients (baseline), 279 attended the first recall (recall rate: 61.18%). Treatment groups and gender specification of the first recall are depicted in Table 5. 93.77% (n = 1039) of the fillings were in function, 2.53% (n = 28) had to be renewed

and 1.71% (n = 19) had to be repaired. Tooth extractions and root canal treatments were necessary in 0.36% (n = 4) and 1.08% (n = 12) of the fillings, respectively (Table 6). The percentage of failure according to the ADA guidelines was 5.3% in the Ceram X group and 6.1% in the Tetric Ceram group. The distribution of tooth positions was: upper PM (CX: 112/TC: 136), upper M (CX: 160/TC: 161), lower PM (CX: 99/TC: 126) and lower M (CX: 157/TC: 157).

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Fig. 1 – Recall flow chart of the study.

In the univariate analysis, investigating the occurrence of a failure (failure per filling: yes/no), older patients showed a higher risk of failure one year after baseline (at T1, p = 0.0044). Significant results were also observed for the baseline variable “number of treated teeth” (p = 0.0210) and “filling extension: mesio-distal”. A significantly smaller risk of the occurrence of a failure was observed for Class I fillings as compared to Class II fillings (p = 0.0067). Furthermore, a significant

difference was observed between tooth positions. A significantly higher risk of failure was observed for “lower molars” than “upper molars” (p = 0.0207) and “lower premolars” (p = 0.0187). No significant difference was observed for “upper premolars” compared with “lower premolars”. It has to be noted that there were more Class I fillings for upper molars (40.9%) as compared to upper premolars (8.55%), lower molars (29.3%) and lower premolars (22.1%) (all p < 0.01). A significant

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Fig. 2 – Flow of participants through each stage of the study, modified based on CONSORT [24].

Table 3 – Distribution of sex, age and number of treated teeth of the study population (baseline). Baseline (T0)

Ceram X/Prime&Bond NT

Tetric Ceram/Optibond Solo Plus

Total

n

226

230

456

Sex (Unknown) Male Female

2 (0.88%) 99 (43.81%) 125 (55.31%)

1 (0.43%) 99 (43.04%) 130 (56.52%)

3 (0.66%) 198 (43.42%) 255 (55.92%)

Age Mean SD Median

33.92 10.88 30.29

34.00 11.58 30.72

33.96 11.23 30.47

Number of fillings per patient Mean SD Median Min Max

3.92 2.84 3.00 1.00 13.00

4.01 3.18 3.00 1.00 17.00

3.96 3.01 3.00 1.00 17.00

n represents number of patients contributing to summary statistics. Percentages are based on n (number of valid values).

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Table 4 – Results of the Baseline Evaluation. Baseline (T0)

Treatment groups Ceram X (t = 881)

Tetric Ceram (t = 924)

Total (t = 1805)

1. Root canal treatment Yes No t

97 (11.07%) 779 (88.93%) 876

104 (11.30%) 816 (88.70%) 920

201 (11.19%) 1595 (88.81%) 1796

2. Testing of sensitivity Yes No t

786 (89.73%) 90 (10.27%) 876

826 (89.88%) 93 (10.12%) 919

1612 (89.81%) 183 (10.19%) 1795

3. Status of sensibility Negative Positive t

98 (11.19%) 778 (88.81%) 876

104 (11.33%) 814 (88.67%) 918

202 (11.26%) 1592 (88.74%) 1794

4. Pulpitis like symptoms Yes No t

0 (0.00%) 867 (100.00%) 867

4 (0.44%) 910 (99.56%) 914

4 (0.22%) 1777 (99.78%) 1781

5. Radiographic exam. (X-ray) Yes No t

798 (91.30%) 76 (8.70%) 874

834 (91.45%) 78 (8.55%) 912

154 (8.62%) 1632 (91.38%) 1786

6. Radiographic exam.: no pathology Yes No t

92 (10.43%) 790 (89.57%) 882

100 (10.81%) 825 (89.19%) 925

192 (10.63%) 1615 (89.37%) 1807

7. Radiographic exam.: marginal gap Yes No t

317 (35.94%) 565 (64.06%) 882

344 (37.19%) 581 (62.81%) 925

661 (6.57%) 1146 (63.42%) 1807

8. Radiographic exam.: CAR Yes No t

364 (41.27%) 518 (58.73%) 882

382 (41.30%) 543 (58.70%) 925

746 (41.28%) 1061 (58.72%) 1807

9. Radiographic exam.: CAP Yes No t

3 (0.34%) 879 (99.66%) 882

9 (0.97%) 916 (99.03%) 925

12 (0.66%) 1795 (99.34%) 1807

10. Radiographic exam.: unclear diagnosis 1 (0.11%) Yes 881 (99.89%) No 882 t

2 (0.22%) 923 (99.78%) 925

3 (0.17%) 1804 (99.83%) 1807

11. Extension of the filling mo mod o o/c.trans.d od t

127 (15.64%) 230 (28.33%) 249 (30.67%) 4 (0.49%) 202 (24.88%) 812

162 (18.84%) 230 (26.74%) 242 (28.14%) 0 (0.00%) 226 (26.28%) 860

289 (17.28%) 460 (27.51%) 491 (29.37%) 4 (0.24%) 428 (25.60%) 1672

12. Extension buccal Yes No t

58 (6.58%) 824 (93.42%) 822

62 (6.70%) 863 (93.30%) 925

120 (6.64%) 1687 (93.36%) 1807

13. Extension oral (ling./palatine) Yes No t

77 (8.73%) 805 (91.27%) 882

85 (9.19%) 840 (90.81%) 925

162 (8.97%) 1645 (91.03%) 1807

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Table 4 (Continued ) Baseline (T0)

Treatment groups Ceram X (t = 881)

14. Cuspal-coverage 1 2 3 4 t

Tetric Ceram (t = 924)

Total (t = 1805)

45 (61.64%) 21 (28.77%) 3 (4.11%) 4 (5.48%) 73

47 (63.51%) 16 (21.62%) 7 (9.46%) 4 (5.41%) 74

92 (62.59%) 37 (25.17%) 10 (6.80%) 8 (5.44%) 147

15. Contact point Yes No t

621 (71.22%) 251 (28.78%) 872

696 (75.87%) 221 (24.13%) 917

1317 (73.60%) 472 (26.40%) 1789

16. Contact point – established Yes No t

211 (25.12%) 629 (74.88%) 840

183 (20.70%) 701 (79.30%) 884

394 (22.85%) 1330 (77.15%) 1724

17. Color match Excellent Charlie t

875 (100.00%) 0 (0.00%) 875

915 (99.56%) 4 (0.44%) 919

1790 (99.78%) 4 (0.22%) 1794

18. Occlusion Yes No n

857 (97.94%) 18 (2.06%) 875

909 (99.13%) 8 (0.87%) 917

1766 (99.55%) 26 (1.45%) 1792

19. Marginal adaptation Excellent t

875 (100%) 875

918 (100%) 918

1793 (100%) 1793

20. Radiographic exam. after restoration 10 (1.15%) Yes 862 (98.85%) No 872 t

12 (1.31%) 901 (98.69%) 913

22 (1.23%) 1763 (98.77%) 1785

21. Radiographic exam. after restoration: no pathology 3 (0.34%) Yes 879 (99.66%) No 882 t

5 (0.54%) 920 (99.46%) 925

8 (0.44%) 1799 (99.56%) 1807

22. Radiographic exam. after restoration: marginal gap 882 (100%) No 882 t

925 (100%) 925

1807 (100%) 1807

23. Radiographic exam. after restoration: unclear diagnosis 882 (100%) No 882 t

925 (100%) 925

1807 (100%) 1807

24. Restoration to be corrected Replacement Repair Not necessary t

0 (0.00%) 5 (0.57%) 869 (99.43%) 874

3 (0.33%) 5 (0.55%) 908 (99.13%) 916

3 (0.17%) 10 (0.56%) 1777 (99.27%) 1790

25. Successful restoration Yes No t

866 (98.41%) 14 (1.56%) 880

897 (97.61%) 22 (2.39%) 919

1763 (98.00%) 36 (2.00%) 1799

t represents number of teeth contributing to summary statistics. Percentages are based on t (number of valid values). Abbreviations: CAR, caries associated with restoration; CAP, chronic apical periodontitis; mo, mesio-occlusal; mod, mesio-occlusal-distal; o, occlusal; od, occlusal-distal; o/c.trans.d., occlusal distal crista transversa; NAD, no abnormality detected.

smaller number of Class I fillings were found in upper premolars as compared to lower premolars (p < 0.001) and lower molars (p < 0.001). No difference was found between lower molars and lower premolars. Age, the number of treated teeth,

tooth position and filling extension (mesio-distal) remained significant in the multiple analysis. No significant influence of the variables “material” (p = 0.6063), “sex” (p = 0.7865), “root canal treatment”

833

d e n t a l m a t e r i a l s 3 0 ( 2 0 1 4 ) 824–838

Table 5 – Characteristics of patients attending the first recall. First recall (T1) n

Ceram X/Prime&Bond NT

Tetric Ceram/Optibond Solo Plus

133

146

Total 279

Age Mean SD Median Min Max

35.72 10.17 32.80 19.33 71.29

35.56 12.33 32.73 18.13 85.00

35.63 11.77 32.80 18.13 85.00

Number of fillings per patient Mean SD Median Min Max

4.53 2.96 4.00 1.00 13.00

4.36 3.43 3.00 1.00 17.00

4.43 3.21 3.00 1.00 17.00

Sex Unknown Male Female

2 (1.50%) 58 (43.61%) 73 (54.89%)

1 (0.68%) 66 (45.21%) 79 (54.11%)

3 (1.08%) 124 (44.44%) 151 (54.48%)

108 (81.20%) 22 (16.54%) 3 (2.26%) 0 (0.00%)

117 (80.14%) 24 (16.44%) 4 (2.74%) 1 (0.68%)

225 (80.65%) 46 (16.49%) 7 (2.51%) 1 (0.36%)

Number of failures per patient 0 1 2 3

n represents the number of patients contributing to summary statistics. Percentages are based on n (number of valid values).

(p = 0.6454), “filling extension: buccal” (p = 0.4298), “filling extension: lingual/oral” (p = 0.1027) or “cuspal coverage” (p = 0.4970) on the occurrence of a failure was observed. For 27 patients the outcome after one year was observed by phone calls or questionnaires. Excluding these patients from the statistical analysis, only “filling extension: mesio-distal” remained significant. A significant smaller risk of a failure was found for Class I fillings as compared to Class II fillings. In contrast to the previous analyses, no significant differences between tooth positions and no significant influence of age was found. The results for tooth positions and age may therefore be interpreted carefully. In the univariate logistic regression analyses, the number of fillings per patient at baseline as well as the number of lower molar fillings and the number of Class II fillings at baseline had a significant influence on the occurrence of at least one failure at the first recall (failure per patient at T1: yes/no, regardless of how many failures; p = 0.0057, p = 0.0003, p = 0.007, respectively). The risk for the occurrence of at least one failure was higher if more fillings in total, more fillings in lower molars or more Class II fillings were placed per patient. No significant influence of the number of upper premolar/molar, lower premolar or Class I fillings was found. Furthermore, no influence of material, age or sex on the occurrence of at least one failure was found. Since there are a potential correlation between the number of fillings, Class II fillings and lower molar fillings, the multiple regression analysis was performed accounting for these three factors being significant in the univariate analysis (see Section 2.6). In this multiple analysis, only the number of lower molar fillings remained significant.

Furthermore, a comparison of patient specific variables between the patients attending and not attending the recall was performed. Patients attending the first recall were significantly older than patients not attending (mean: 36.63, SD: 11.77 vs. 31.33, SD: 9.77 years; t-test: p < 0.0001) and had a larger number of treated teeth (mean: 4.43, SD: 3.21 vs. 3.22, SD: 2.51 fillings; ttest: p < 0.0001). No significant influence of sex (p = 0.5137) and material (p = 0.2915) on the attendance to the first recall was observed. Table 6 summarizes the results of the first recall. The use of the best-case recall data set for the statistical analysis did not reveal any changes in the results.

4.

Discussion

This longitudinal, randomized-controlled clinical study investigates the longevity of two composite materials (Ceram X and Tetric Ceram) using modified USPHS criteria. During one year, patients visiting the Department of Restorative Dentistry at the University of Dentistry of Vienna were offered participation in this study, providing that Class I or II restoration in their posterior teeth were indicated (n = 456). No patient was excluded because of high caries risk, poor oral hygiene or parafunctional habits similar to Van Dijken and Lindberg, who examined their own clinic patients, Kiremitci et al., who examined patients from the Department of Conservative Dentistry from their university and da Rosa Rodolpho et al., who investigated the patients from their private practice [8,21,25].

834

Table 6 – Evaluation of the modified USPHS criteria – first recall (T1). First recall (T1)

Ceram X (n = 528) Excellent/ Repair good 100

Extractiona

RCTb

Excellent/ Repair good

Renewal

Extractiona

Total (n = 1108) RCTb

Excellent/ Repair good

Renewal

0

0

99.28

0.36

0.36

99.62

0.19

0.19

0

0.4

99.82

0.18

0

99.71

0.1

0.19

0

0

0

0

0

0

99.4

0

0.6

99.63

0

0.37

99.52

0

0.48

96.16

1.62

2.22

96.86

1.66

1.48

96.53

1.64

1.83

99.18

0

0.82

99.26

0

0.74

99.22

0

0.78

99.4

0

0.6

99.45

0

0.55

99.43

0

0.57

94.51

1.52

2.27

93.10

1.90

2.76

93.77

1.71

2.53

99.6 100

100

0.19

1.33

100

0.52

0.86

Extractiona

RCTb

0.36

1.08

d e n t a l m a t e r i a l s 3 0 ( 2 0 1 4 ) 824–838

Substance loss (n = 502/549/1051) Contact point (n = 499/553/1052) Color match (n = 505/549/1054) Marginal staining (n = 504/547/1051) Marginal adaptation/integrity of the filling (n = 495/541/1036) Secondary caries (n = 488/538/1026) Radiographic examination (n = 500/548/1048) Successful restorationc (n = 528/580/1108)

Renewal

Tetric Ceram (n = 580)

Percentages are based on n (number of valid values). Tooth was extracted. b Root canal treatment (RCT) was necessary. c For one TC filling (0.18) and five CX fillings (0.86), resulting in a total of six fillings (0.55), the success of the restoration could not be determined due to contradictory statements from patients. a

d e n t a l m a t e r i a l s 3 0 ( 2 0 1 4 ) 824–838

In many other studies, the patients were carefully selected for availability and the chance to attend the recall appointment, e.g., dental students and their relatives and/or staff of the dental clinic/university [3–5,11–14,26,27] or – in two studies – mainly police officers [28,29]. On the one hand, recruitment of these subjects helps to keep the drop-out during longitudinal studies as low as possible. On the other hand, the performance of a dental material might differ between dental students and “socially deprived subjects” exhibiting a different awareness of oral hygiene and caries preventive methods [15]. The recall rate of this study (61.18%) is lower than the rates of the aforementioned studies [3–5,11–14,26,27], where an evaluation of 90–100% of the patients after one year was achieved. In the present study, many of the patients were unavailable for contact (letter, telephone call) already in the first year because they moved elsewhere and did not provide any new address. Patients with a higher number of restored teeth have an increased risk for failure [16,19,30]. The results of the first recall confirm this and clearly demonstrate that patients with more treated teeth at baseline had a higher risk of at least one failure after one year. Based on this fact, it can be presumed that patients attending the first recall mainly had a worse dental condition than those not attending. The patients not attending the recall, who were presumed to be symptomfree, might contribute to the smaller recall rate compared with other studies. Furthermore, a low recall rate has a negative influence on the annual failure rate, if calculated according to the American Dental Association [23]. In a study by Schirrmeister et al., the failure rate of Ceram X increased from 2.7% in the first year to 3.2% in the second year without adding faulty fillings, only because of a decrease in the recall rate (86% vs. 72%) [31]. High recall rates are frequently achieved by a certain sort of patient selection and by not respecting the recommendations of Hickel et al., where a cross-section of the population is advocated. Otherwise, the outcome is only applicable to the selected patient population [15]. Another point to be mentioned is the size of study population: 456 patients in this study vs. 16–54 patients in some of the other mentioned studies [3–5,11–14,26,27]. It is evident that recalls can be more easily organized with small study populations. Most of the studies follow the prescribed minimum number of patients of 25, which is regulated in the ADA guidelines for restorative materials [32]. Long-term studies without patient selection in regard to availability for recall might result in higher drop-out rates. Drop-out should be as low as possible to enhance the validity and power of the study [21]. In study periods as long as five years, failures are primarily associated with fracture of the restoration [18], followed by secondary caries. A similar pattern can be observed in the present study, where most failures occurred due to marginal adaptation/integrity of the filling, followed by the necessity of a root canal treatment and secondary caries. After one year, eight restorations were evaluated Charlie (repair) and 11 Delta (replacement) in the treatment group Ceram X versus 9 Charlie and 8 Delta for Tetric Ceram due to failures in marginal adaptation or fracture of the restoration. In both of the groups, this type of failure was primarily

835

observed in fillings with a “mod” extension. One reason accounting for the occurrence of marginal gaps might be that the restorations were performed without a rubber dam – only cotton rolls and a suction device were used for isolation, simulating (private) practice settings, where most fillings are placed without rubber dam. According to Raskin et al., the longevity of the composite filling is not influenced by the isolation technique. These authors could not find any significant difference between isolation with and without rubber dam for composite fillings after 10 years [33]. Similarly, in a review by Brunthaler et al., no influence of the isolation technique on the failure rate was identified [18]. Alternatively, in this study, composite as a material was not indicated when adequate isolation was not achievable (cotton rolls, suction device). The different modifications of the USPHS criteria, which are in use, only allow for a very limited comparison of studies [15,22]. Therefore, Hickel et al. established common evaluation criteria for clinical studies for better comparison [15,34] such as the annual failure rate according to ADA criteria [23]. The failure rates after one year in this study are 5.3% (Ceram X) and 6.1% (Tetric Ceram). The brand of the composite used did not display any influence on the occurrence of a failure after one year (p = 0.6063). Our results are in the range of annual failure rates (0–9%) for direct composite restorations stated by Hickel and Manhart in a review of controlled prospective and retrospective studies [35]. In a more recent review by the same authors they indicated a lower failure rate for direct composites of 2.2% [6]. Manchorova et al. published a comparable failure rate to our study of 6.7% after 15 months. Their recall rate was similar (63.16%). Their failure rate was due to the partial loss of filling material in three cases [36]. Schirrmeister et al. [31] investigated the same composite material but used a different adhesive system (Ceram X/K0127 vs. Tetric Ceram/Syntac Classic). After one year, the recall rate was 86% (n = 37 of 43 patients). The failure rate was 2.7% for Ceram X and 0% for Tetric Ceram. None of the fillings was rated worse than Bravo according to Ryge’s modified evaluation criteria. Most of the changes from Alpha to Bravo were associated with the criterion “marginal integrity” (Ceram X: 8.3% vs. Tetric Ceram: 10.8%). In our study endodontically treated teeth were not excluded in contrast to many other studies [2–5,8,11–14,21,25,27–29,36–41]: 11% of all teeth had already a root canal treatment at baseline (T0). The root canal treatment at baseline had no significant influence (p = 0.6454) on the occurrence of a failure after one year. A study by Can Say et al. [42], who performed a very similar endodontic treatment compared to our study, investigated the clinical service of 39 Class II composite fillings (material: Filtek Z250, 3M Espe) in only endodontically treated teeth, without posts and crown coverage. The root canal treatment was performed as follows: shaping of the root canals according to the crown-down technique, frequent irrigation with sodium hypochlorite (NaOCl) and obturation using the cold lateral condensation technique (sealer: AH Plus, Dentsply DeTrey, Konstanz, Germany). After two years, only the criterion “marginal discoloration” displayed a significant change from Alpha to Bravo (modified USPHS criteria). Neither secondary caries nor periapical lesions were observed. The

836

d e n t a l m a t e r i a l s 3 0 ( 2 0 1 4 ) 824–838

authors attribute these favorable results to the short study period and the mechanical properties of Filtek Z250 as well as the good oral hygiene of the patients. In the present study, 12 fillings had to be endodontically treated after one year: seven in the Ceram X group and five from the Tetric Ceram group. Root canal treatment was the second reason for filling replacement. The reasons for root canal treatment were chronic apical periodontitis (seven fillings), irreversible pulpitis (three fillings) and non-vital tooth with (one filling)/without abscess (one filling). Two of the teeth, where root canal treatment became necessary, were treated with calcium hydroxide due to caries profunda at baseline. One tooth was previously endodontically treated and had to be re-treated (revision). The necessity of root canal treatment due to pulpitis-like symptoms has also been observed in other studies [12,31]. The third reason for failure was secondary caries (CX: n = 4, TC: n = 4). In a randomized, clinical trial over a period of seven years, secondary caries was accountable for 88% of all failures in composite restorations in posterior teeth [43]. In contrast to our study, filling fracture was the second most common reason. According to Mjör [44], the clinical diagnosis of “secondary caries” is the most common reason for the replacement of a restoration in the primary and permanent dentition. Van Dijken and Lindberg report that secondary caries is the main reason for a defective restoration, but its development may take years until clinical manifestation. Secondary caries is an important reason for middle- (18 months) and long-term failures (>24 months) [21]. The risk of at least one failure after one year increased with the number of treated teeth per patient in the present study (statistically significant). In addition, the extension of the filling, in favor of the smaller extensions (one surface vs. two or three surfaces, “od” vs. “mod“), had a significant influence on the occurrence of a failure. Furthermore, it could be demonstrated that lower molars were more likely to fail than the upper molars and lower premolars, whereas the comparison of the upper and lower premolars did not reveal any significant differences. A significant larger risk of at least one failure was also found for a larger number of Class II fillings at baseline. In the multiple regression analysis only the number of lower molar fillings was significant indicating that this may be the main factor influencing the occurrence of one failure. In other words: the fact that a lower molar was treated seems to have a higher influence on the occurrence of at least one failure than its cavity size (Class II respectively). A further division of Class II fillings into surfaces in lower molars showed: mod > mo > od. But this was not considered in statistics due to a too low number of cases. The findings of a 17-year clinical study were similar to our results [25] in that a significant difference between the lower premolars and molars could be demonstrated. The differences between Class I and II cavities as well as the survival curve of one, two and three surface fillings were statistically significant. The risk for a failure in Class II restorations was 2.8fold higher than for Class I restorations. Multi-surface fillings had a 3.3-fold higher risk and two-surface fillings a 2.3-fold higher risk for the occurrence of failure than one-surface fillings. Brunthaler et al. also observed a higher failure rate in Class II restorations [18]. Possible explanations for the better

clinical performance of composites in premolars compared with molars include the fact that the related cavities are generally smaller, occlusal forces are less strong and cavities are more easily accessible for adhesive restorations [45,46]. It should be noted that no failures occurred in composite fillings with 3-or 4-cuspal coverage after one year. However, these favorable results are most likely due to the very small number of cases (n = 8). Due to the high turnover rate of composite resins and adhesives, this study, like others, also faces the problem that Tetric Ceram is no longer available regarding the dental market after several years of clinical service [2–5,11,12,38,47]. At the time the study began, Tetric Ceram was considered as a type of gold standard and, therefore, was chosen for comparison with Ceram X [48]. Tetric EvoCeram has replaced Tetric Ceram [38]. Ceram X mono, which is still available on the dental market but in a modified version (Ceram X mono+ ), consists partly (∼12.5%) of methacrylate modified polysiloxane (generically assigned as organically modified ceramic or “ormocer”). The remaining half of the resin matrix of Ceram X consists of conventional dimethacrylate resins. Whereas the ormocer particles (named “nano ceramic particles” by the manufacturer) provide a polysiloxane backbone with a multitude of methacrylate groups bonded via silicon–carbon bonds. Though the nano-ceramic particles in Ceram X belong to the matrix, this composite also contains nano-fillers. However, the majority of fillers are conventional glass fillers (Table 1) [49]. The mechanical properties of dental composites are highly dependent on both concentration and particle size of the filler [50–52]. Both composites investigated in this study have comparable values regarding filler content (weight/volume) and glass filler size (Table 1). In vitro testing of the flexural strength of these composites have also shown similar results: Ceram X: 110 MPa [49] vs. Tetric Ceram: 126.14 [51]/134 ± 9 [53]/134.7 ± 11.0 MPa [54]. The higher values for Tetric Ceram may be partly explained due to the higher amount of inorganic fraction [50]. Ilie et al. demonstrated in vitro that filler volume did not significantly alter between nanohybrid and microhybrid composites and had the most influence on the mechanical properties. As the performance in vitro of both types of composites, nanohybrid and microhybrid, was similar, clinical advantages of one or the other are to be questioned [54]. The present study by its nature has some limitations. The number of fillings between the two treatment groups is not equally distributed, which could have influenced the results. However, the potential correlation between the outcome of teeth within one patient was accounted for in the statistical analysis (see Section 2.6). Despite the great effort to reach a very high number of participants in this study, the high drop-out (recall rate: 61.18%) already after one year has to be faced. Maybe, clinical studies aiming to represent a crosssection of the population and ignoring some kind of selection regarding availability are bound to high drop-out rates. There were patients with more than one filling (in one case up to 17) both in Ceram X and Tetric Ceram group. However the average number of fillings per patient was similar in both treatment groups (see Table 3). As the final size of the cavity was determined straight before filling placement (i.e. at baseline) and fillings within one patient were performed with

d e n t a l m a t e r i a l s 3 0 ( 2 0 1 4 ) 824–838

the same material, this consequently has led to the circumstance of mixed Class I and II fillings. A split-mouth design was not feasible in our clinical setting but should be considered in further studies. A further limitation of this study is that not all case report forms were filled out properly (they were insufficiently legible) by the students, which resulted in certain discrepancies regarding the different evaluation criteria (total number) used for the statistical analysis. As this study aims to be a feasibility study, it is worthwhile mentioning that a randomized-controlled clinical prospective study investigating the performance of composites can be conducted in the routine clinical process profiting from the high number of fillings placed during dental student training. The criterion “marginal adaptation/integrity of the filling” in the present study was adapted from the original Ryge criteria (a.k.a. USPHS criteria) [22]. Information regarding the reason for failure can be better obtained when separating this criterion into “fractures and loss of retention” and “marginal adaptation” [15]. The statistical analysis of this study was performed using a best-/worst-case scenario. This was performed to take into account the patient cases where an evaluation by the USPHS criteria was not applicable. For instance, a composite filling was missing at the recall because a general dentist had changed it to an inlay for unknown reason. As a best-case, this filling was not included for statistics but as a worst-case it was regarded as a failure and included. A best-/worst-case scenario for the statistical analysis takes into account those cases in an objective manner.

5.

Conclusion

Within the limitations of this study, it can be concluded that in a group of Class I/II and cuspal-coverage restorations, there was no significant difference in the failure rates between an ormocer-based nanohybrid (Ceram X) and a bis-GMA-based microhybrid (Tetric Ceram) restorative system after one year. A root canal treatment at baseline had no negative influence on the failure rate. A longer observation period is indicated to obtain clear evidence of the long-term performance of these composite resin systems.

Acknowledgments The authors would like to thank the Dentsply DeTrey GmbH for sponsoring the study (investigation number: 14.1058) and Dr. Andreas Grützner, Dentsply DeTrey GmbH, for his valuable contributions to the study design.

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