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Practice-based, clinical trial of a silorane-based composite resin system in posterior teeth SADJ September 2013, Vol 68 no 8 p358 - p363 N Malhotra1, ST Somashekar2, K Mala3, V Pai4, R Shenoy5
Abstract Introduction: Newer monomer systems have been introduced in an attempt to improve the success rate of direct composite restorations by minimising shrinkage Aims and Objectives: To evaluate the in vivo performance of a silorane-based resin composite system (FiltekTM Silorane,also known as P90), used together with a two-step self-etch bonding system (P90 System Adhesive, Self-Etch Primer and Bond), for the restoration of Class I and Class II cavities in human permanent posterior teeth. Materials and methods: A total of 53 restorations were completed and patients were recalled one year later. The restorations were assessed by two independent clinicians, using the Modified U.S. Public Health Service evaluation criteria for the following parameters: retention, colour match, marginal discolouration, secondary caries, anatomic form, marginal adaptation, surface texture, occlusal and interproximal contacts. Results: Of the 41 restorations assessed at the one year follow-up, 92.7% showed clinically acceptable scores for all the parameters evaluated. Cronbach's α values ranged from 0.72-1.00 showing a good inter-examiner agreement and reliability.
1. N Malhotra: MDS, PGDHHM. Reader, Department of Conservative Dentistry and Endodontics, I.T.S Dental College Hospital and Research Centre, Greater Noida, U.P, India. 2. ST Somashekar: BDS. Ex-Junior Resident, Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore, Manipal University, Karnataka. 3. K Mala: MDS. Professor, Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore, Manipal University, Karnataka. 4. V Pai: MDS. Professor, Department of Conservative Dentistry and Endodontics,Manipal College of Dental Sciences, Mangalore, Manipal University, Karnataka. 5. R Shenoy: MDS. Associate Professor, Dept. of Community and Preventive Dentistry, Manipal College of Dental Sciences, Mangalore, Manipal University, Karnataka. Corresponding author N Malhotra: Dept. of Conservative Dentistry and Endodontics, I.T.S Dental College Hospital & Research Centre 47, Knowledge Park - III, Distt., Gutam Budh Nagar, Greater Noida - 201308, Uttar Pradesh, India. Cell: (91 0824) 99583 17299, E-mail:
[email protected]
Acronyms RBC: Resin based Composites ROCP: Photo-ring-opening-cationic polymerisation UPHSS: U.S. Public Health Service System
Conclusion: Silorane-based composite, FiltekTM Silorane, when used in conjunction with the recommended adhesive system showed a clinically acceptable performance in posterior teeth restorations over a one year clinical service. Keywords: Clinical Trial, Silorane-based Composite, OneYear Follow-Up, USPHS
Introduction Currently, the rising demand for aesthetic dentistry has lead to a steady decline in the placement of amalgam restorations. Patients now desire aesthetic as well as functionally sound restorations, not only for the anteriors, but also for posterior teeth. Continuous evolution and development of resin-based composites (RBCs), has introduced options such as packables, flowables, whisker-reinforced, fibre-reinforced, nano-filled and indirect RBC’s1-3, which are currently available to restore the posterior dentition. These advances have allowed the RBC material to fulfill almost all the ideal requisites of a posterior restorative material. Although these restorative materials have been successfully used for more than 50 years, the vexatious issues of polymerisation shrinkage and associated stresses, still persist.4 The resultant volumetric contraction is reported to cause cusp deformation, micro-leakage, marginal staining, enamel fracture, secondary caries and post-operative sensitivity.1,5,6 Various strategies, techniques and materials have been developed to offset the negative effects of stresses generated during the volumetric shrinkage of RBCs.5 The most recent commercial addition in the materials category is Silorane resin-based composite or Siloranes.7 This hydrophobic resin8 system is derived by combining siloxanes and oxiranes, processed via a process of photo-ring-opening-cationic polymerisation (ROCP).6 This procedure gains space and counteracts the loss of volume, which occurs when the chemical bonds are formed, thus resulting in low polymerisation shrinkage.9 They have also been shown to exhibit mechanical properties, comparable to the conventional bis-
360 > research GMA/methacrylate-RBCs.9,10 Commercially, Silorane RBC is available as FiltekTM Silorane (known in the USA as FiltekTM P90, manufactured by 3M ESPE St Paul, U.S.A). This is a microhybrid composite, filled with fine quartz particles and radio-opaque yttrium fluoride. It is used together with P90 system adhesive, a two-step self-etching bonding system, consisting of a self-etch primer (hydrophilic) which bonds to teeth and an adhesive (hydrophobic), adhering to the resin. It is usually considered essential to evaluate the performance of any newly introduced material or technique in a dental practice situation. The importance of a clinically-based and/or practice-based research has been emphasised in dental literature.11,12 A variety of in vitro tests are available to provide valuable information regarding the service of a restorative material, but none of these can exactly replicate the in vivo conditions of an oral cavity. Clinical studies/trials apply objective, reliable and clinically relevant criteria to assess the quality and serviceability of the restoration. This is universally considered to be a standard protocol for evaluating a restorative material performance.13-16 The U.S. Public Health Service System (UPHSS), or the U.S. Public Health Service-Ryge Modified Criteria, are the most commonly used methods to evaluate the clinical performance for the RBCs.14,15,17,18 The characteristics taken into consideration to assess the restorations, at both the baseline and the subsequent follow-ups, include retention, recurrent caries, colour match, marginal discolouration, marginal integrity, anatomical form, surface texture, contact and surface staining. This paper reports on a clinical trial designed to evaluate the performance of a silorane resin-based composite system (FiltekTM Silorane), for restoring moderate sized Class I and Class II cavities in human pre-molar and permanent molars in a clinical dental practice. Follow-up data was collected after one year. The test hypothesis was that the silorane resin-based composite system would perform acceptably, following a one year period of clinical service.
Materials and methods A clinical trial was conducted to evaluate the performance of FiltekTM Silorane low shrink posterior restorative, used in conjunction with a two-step self-etching bonding system (P90 System Adhesive, Self-Etch Primer and Bond), for the restoration of moderate sized Class I and Class II cavities in adult posterior teeth. Subjects were randomly selected from among patients visiting the dental out-patient department (OPD). Ethics committee approval was obtained prior to the commencement of the clinical trial (Ref No: 09001) and written informed consent was obtained from each subject, prior to their being recruited to the study. The participants were free to withdraw from the study, without providing a reason, at any time during the trial and evaluation phase. Inclusion and exclusion criteria Included in the study were patients with: • Vital pre-molars and molars, requiring a new Class I or Class II restoration of moderate size as a result of primary carious lesions. For the purpose of the study, the restoration should not have extended more than one-third up on one or more cuspal slope, but with at least one margin of the proximal portion reaching into the interproximal embrasure; • Molar supported permanent dentitions, free of any clinically significant occlusal interferences; • A history of regular dental attendance and who were agreeable to return for the evaluation (assessment) appointment;
Teeth selected for the study were required to have: opposing tooth contacts, sufficient enamel and dentin with a remaining dentin thickness of at least two mm following cavity preparation, ( infrequent small areas where caries had penetrated further were accepted), were free of cracks/defects and signs of abnormal wear and where appropriate, shared sound proximal contacts with the adjacent teeth. In addition, the gingival tissue around the tooth to be restored was required to be sound and healthy.
•
Exclusion criteria applied for the study were as follows: • When restorations in the opposing or adjacent teeth required replacement or repair; • When the patient reported a history of any adverse reaction to the class of restorative materials used in the study; • Where there was evidence of occlusal parafunction and/ or pathological tooth wear; • When the patient was already participating in the clinical evaluation of other restorative materials involving posterior teeth. Where indicated, clinically appropriate radiographic and vitality assessments were performed. The sample comprised 34 subjects, 18 of whom were male and 16, female. A total of 53 restorations were placed. Operative procedure. One operator prepared and restored all the cavities. With few exceptions, the teeth were treated under local anesthesia and isolated using rubber dam. The cavities were prepared as conservatively as possible, using a new#245 bur for each tooth (BULK 100 FG Carbide 245S, SS White Burs, Inc., Lakewood, New Jersey). No bevels were placed at any of the cavo-surface angles, resulting in cavo-surface margins of approximately 90°. Gingival margins were extended apical to any remaining approximal contact areas. The internal line and point angles were rounded. Where indicated, a calcium hydroxide liner (Dycal, DENTSPLY Caulk, Milford, Delaware, U.S.A) was placed in the deep portions of the preparation and covered by a 1mm layer of resin-modified glass-ionomer sub-base (Fuji II LC, GC Corporation, Tokyo). Table 1 shows the distribution of the restorations according to tooth type and class of cavity. A wedged metal matrix system (Palodent® Sectional Matrix System, Dentsply, U.S.A) was used for the Class II restorations. Restorations were placed using FiltekTM Silorane and in accordance with the manufacturer’s directions. Shades were chosen as nearest to matching the colour of the natural tooth. Using a disposable applicator, one drop of the primer (LS Self Etch Primer, 3M ESPE) was applied to the entire surface of the cavity and agitated for 15 seconds on the cavity Table 1: Distribution of Silorane restorations in the study according to tooth type and class of restoration Tooth type
Class of restoration Class I
Class II
Molars
10
8
Premolars
1
7
20
3
-
4
Maxillary
Mandibular Molars Premolars
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surface, followed by curing with an Light-Emitting Diode (LED) curing unit (Elipar FreeLight, 3M ESPE, Seefeld, Germany) for 10 seconds. With a separate applicator, one drop of the bonding agent was applied to the entire area of the cavity and cured for 10 seconds, with the LED (Elipar FreeLight, 3M ESPE, Seefeld, Germany) The cavity was restored with composite in increments of 2mm, with each layer being cured, using LED for 20 seconds at a power rating of 500 mw/cm2 (measured using a portable Radiometer). Following this, the completed restoration was cured (Elipar FreeLight, 3M ESPE, Seefeld, Germany) for an additional 10 seconds from both the buccal and lingual surfaces and was finished using composite finishing burs (Composite Finishing Kit, Shofu Inc., Kyoto, Japan), polishing disks and strips (Sof-Lex, 3M, 3M ESPE, St. Paul, Minnesota, USA). The occlusion was evaluated for proper contact and high-points using articulating paper (MDM Corp., Delhi, India). Further adjustments were made using composite finishing burs. Finally, the restorations were polished, using Enhance polishing paste and polishing cup (Dentsply Caulk, Milford, Delaware, USA). Evaluation of the restorations Two experienced clinicians, who had not been involved in any way in the treatment, assessed the restoration independently at the one-year recall appointment. All the restorations were inspected and evaluated using the Modified U.S. Public Health Service (USPHS) criteria for the following parameters: • Retention • Colour match
• • • • • • • •
Marginal discoloration Secondary caries Anatomic form Marginal adaptation Surface texture Occlusal contacts Interproximal contacts Post-operative sensitivity
The Codes, Criteria and Evaluation Methods applied for the assessment of restorations are summarised in Table 2. When there was a disagreement during an evaluation, consensus opinion was reached by re-examining the restoration to obtain a joint agreement. At the recall appointment, impressions were taken with Impregum (Impregum™ Penta™, 3M ESPE AG, Seefeld, Germany) in preparation for die stone models to be poured for further evaluation of the anatomic form, marginal adaptation and surface texture following visual examination. At interview, the patients were also requested to report any post-operative sensitivity experienced, following placement of the restoration and/or during the ensuing period of one year, the evaluation period. Statistical analysis Descriptive analysis of the data recorded was performed using SPSS software (Version 16.0, SPSS, Chicago, Illinois, USA.). Inter-examiner reliability was tested using Cronbach's Alpha (α) statistic.
Table 2: Modified U.S. Public Health Service (USPHS) evaluation criteria applied in the study Clinical parameter Retention
Colour match
Marginal discolouration
Secondary caries
Anatomic form
Marginal adaptation
Surface texture
Occlusal contacts
Interproximal contacts
Postoperative sensitivity
Code
Criteria
Alpha
No loss of restorative material
Charlie
Any loss of restorative material
Alpha
Matches tooth
Bravo
Acceptable mismatch
Charlie
Unacceptable mismatch
Alpha
No discouloration
Bravo
Discolouration without axial penetration
Charlie
Discolouration with axial penetration
Alpha
No caries present
Charlie
Caries present
Alpha
Continuous
Bravo
Slight discontinuity, clinically acceptable
Charlie
Discontinuous, failure
Alpha
Closely adapted, no detectable margin
Bravo
Detectable margin, clinically acceptable
Charlie
Marginal crevice, clinical failure
Alpha
Enamel-like surface
Bravo
Surface rougher than enamel, clinically acceptable
Charlie
Surface unacceptably rough
Alpha
Contact is tight
Bravo
Contact is light
Charlie
No contact
Alpha
Contact is tight
Bravo
Contact is light
Charlie
No contact
Alpha
No Postoperative sensitivity
Charlie
Postoperative sensitivity present
Evaluation method Visual and probe Diestone replica
Visual
Visual
Visual and probe
Visual and probe Diestone replica
Visual and probe Diestone replica
Visual and probe Diestone replica
Visual (articulating paper)
Visual (dental floss)
Inter viewing the patient
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Table 3: Number of restorations reviewed after one year and recall rate (%) Baseline
One year
Recall rate
Class I
31
25
80.6%
Class II
22
16
72.7%
Molars
41
33
80.5%
Premolars
12
8
66.6%
Total
53
41
77.3%
Restoration class
Tooth type
Table 4: Summary of the clinical assessment of the P90 restorations at one year Clinical parameter
Score* Acceptable
Unacceptable
Alpha (%)
Bravo (%)
Charlie (%)
Retention
38 (92.7%)
-
3 (7.3%)
Colour match
11 (26.8%)
30 (73.2%)
-
Marginal discoloration
40 (97.6%)
1 (2.4%)
-
Secondary caries
41 (100%)
-
-
Anatomic form
31 (75.6%)
10 (24.4%)
-
Marginal adaptation
27 (65.9%)
14 (34.1%)
-
Surface texture
12 (29.3%)
29 (70.7%)
-
Occlusal contacts
39 (95.1%)
1 (2.4%)
1 (2.4%)
Interproximal contacts
12 (29.3%)
1 (2.4%)
2 (4.9%)
Postoperative sensitivity
39 (95.1%)
-
2 (4.9%)
*Scores defined in Table 2.
Results. The average age of the 34 subjects was 34yrs (range 16-52 yrs). At the one-year follow-up, 41 of the total number of 53 restorations were assessed for the clinical parameters summarised in Table 2 (26 patients). Recall rate (%) based on tooth type and class of restoration is summarised in Table 3. Of the eight patients who did not attend the one year follow up appointment, it was not possible to contact two, one refused to attend, two were unavailable and three failed to present at the appointment. Table 4 shows the results of clinical evaluation at the one year recall appointment. Cronbach's α values ranged from 0.72-1.00, showing a good inter-examiner agreement and reliability for all the tested clinical parameters, except for marginal discoloration where a moderate agreement was observed (Cronbach's α =0.56). The majority of the restorations (approx. 80%) achieved acceptable scores (either Alpha or Bravo), for the evaluation criteria. 100% Alpha scores for the assessed restorations were obtained for secondary caries, followed by marginal discoloration (97.6%), occlusal contacts (95.1%), post-operative sensitivity (95.1%) and retention (92.7%). Maximum Bravo scores were for colour match (73.2%) and surface texture (70.7%). Highest Charlie scores (unacceptable) were observed for the parameter of retention (7.3%). Of the assessed 41 restorations, three were fractured with loss of restorative material. In two cases the proximal portion of the restorations (on teeth 26, 25) were fractured and in one of the restorations (on tooth 16) the material was lost
(absent) from the palatal aspect. Two patients reported postoperative sensitivity during the follow-up period.
Discussion The reported recall rate of our study was 77.3% which is in accord with other clinical evaluations of RBC’s.13-15 The clinical performance of a newly introduced low-shrink commercial composite, FiltekTM Silorane, which is based on silorane-chemistry, was assessed in 41 Class I and Class II restorations at a one year recall. A good clinical performance was shown for all the parameters tested in the trial. Siloranes are based on photo-ring-opening-cationic polymerisation (ROCP), wherein the curing is initiated by an electron donor degrading the iodonium salt to an acidic cation to start the ring-opening polymerisation process.7,9 This leads to a decrease in volumetric shrinkage and an overall reduction in associated shrinkage stresses. Silorane-based composites show an average volumetric shrinkage of 0.9 vol% as opposed to 2-3 vol% for methacrylate-based composites.15 This may lead to superior adaptation, reduced cuspal deflection and deformation and less micro-leakage19-22, possibly resulting in reduction of residual stresses, marginal discolouration, incidence of secondary caries and post-operative sensitivity. As a result, the observed clinical performance of the FiltekTM Silorane restorations for all the tested parameters, may possibly be attributed to the inherent lowshrinkage characteristic of the silorane-based composites. The absence of an oxygen inhibition layer (hydrophobic resin), reduced water sorption and better chemical stability in an aqueous environment,7,8,23 can be the other contributing factors for the observed clinical scores at the one year recall appointment. The use of the recommended self-etch primer (LS Self Etch Primer, 3M ESPE) and the hydrophobic viscous bond coating resin for the bonding of FiltekTM Silorane, have also been shown to produce an intense inter-tubular decalcification with a 1.7-2.0µm thick hybrid layer, leading to clinically acceptable bond strengths7,24. The results are also in accord with a recently published study by Burke et al.25, wherein 97% of the restorations were rated optimal for anatomic form, 84% for marginal integrity, 77% for marginal discolouration. Ninety-three percent (93%) of the restorations were rated optimal for surface quality. In our study, comparable assessments were: restorations with acceptable rating for anatomic form at 75.6%, for marginal adaptation at 100%, for marginal discolouration at 97.6%, and for surface texture at 100%, along with an acceptable retention rating for 92.7% of the restorations. The modified USPHS criteria were used in this study for clinical assessment as they are easy to apply, reflect absolute differences with scores having direct clinical implications and are commonly followed in pilot and definitive studies for the evaluation of dental materials.26,27 Parameters recording Alpha and Bravo scores were considered as “clinically acceptable” and those having Charlie scores as “clinically unacceptable”.16,26 In confirmation, restorations having Alpha and Bravo scores required neither repair, nor replacement and the differences between the two scores were minor in degree.26 For all the tested parameters, the majority of the restorations showed Alpha scores. The maximum Bravo scores were observed for colour match (73.2%) and surface texture (70.7%). Currently, FiltekTM Silorane is commercially available in four shades only (A 2, A3, B2, C2). This limited availability may have led to the observed Bravo scores for the colour match. The surface texture of an RBC is determined
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by the size and distribution of filler and the composition of resin matrix.28,29 It is also influenced by the initial physicochemical interactions between an RBC and the finishing and polishing agents used, as well as the wear characteristics of the material (Siloranes), in both contact free areas and in the occlusal and functional contact areas. The reported Bravo scores for surface texture could be as a result of the interplay of all the above mentioned factors, under the influence of the prevailing conditions of the oral environment. Charlie score was observed in three of the restorations due to loss of restorative material, leading to post-operative sensitivity and loss of interproximal and occlusal contacts. This could be attributed to an improper case selection and/or cavity preparation design. A high degree of inter-examiner agreement (Cronbach's α=0.72-1.00) between the scores implies an unbiased assessment between examiners who were not involved with the placement of restorations.15 However a subjective bias cannot be completely excluded, as seen in case of marginal discolouration (Cronbach's α = 0.56).26 The results of the study indicate a good one year clinical performance of the tested RBC under general dental practice conditions. Such practice-based trials are considered to be more logical in the evaluation of the clinical performance of a material and the overall treatment effectiveness, as they provide “real world” information and strengthen the relevance of the results.12,13,30 Though such shortterm evaluations (i.e. one year) and followup data have limited validity and are of restricted value, they are useful in showing the early failures and sub-optimal performance of a material.16 As Silorane is a newly introduced restorative material, the literature available for this material is limited. The results obtained from this early study should be confirmed by subsequent follow-up investigations and in vivo studies on the long-term durability of the product.
Conclusion Results from this practice-based trial following one year of clinical service, indicate that Silorane composite, used in conjunction with the P90 self-etch adhesive system, showed a clinically acceptable performance when used to restore moderate sized Class I and Class II restorations in permanent dentition. Acknowledgement We extend our thanks to the manufacturers of FiltekTM P90 (Silorane) (3M ESPE), for supporting this research work and providing us with the test material.
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