22-Year clinical evaluation of the performance of two posterior composites with different filler characteristics

Abstract

Objectives

This retrospective longitudinal study investigated the longevity of posterior restorations placed in a single general practice using 2 different composites in filler characteristics and material properties: P-50 APC (3M ESPE) with 70 vol.% inorganic filler loading (midfilled) and Herculite XR (Kerr) with 55 vol.% filler loading (minifilled).

Methods

Patient records were used for collecting data. Patients with at least 2 posterior composite restorations placed between 1986 and 1990, and still in the practice for regular check-up visits, were selected. 61 patients (20 male, 41 female, age 31.2–65.1) presenting 362 restorations (121 Class I, 241 Class II) placed using a closed sandwich technique were evaluated by 2 operators using the FDI criteria. Data were analyzed with Fisher’s exact test, Kaplan–Meier statistics, and Cox regression analysis ( p < 0.05).

Results

110 failures were detected. Similar survival rates for both composites were observed considering the full period of observation; better performance for the midfilled was detected considering the last 12 years. There was higher probability of failure in molars and for multi-surface restorations.

Significance

Both evaluated composites showed good clinical performance over 22 years with 1.5% (midfilled) and 2.2% (minifilled) annual failure rate. Superior longevity for the higher filler loaded composite (midfilled) was observed in the second part of the observation period with constant annual failure rate between 10 years and 20 years, whereas the minifilled material showed an increase in annual failure rate between 10 years and 20 years, suggesting that physical properties of the composite may have some impact on restoration longevity.

Introduction

Nowadays, resin composite is considered as a suitable direct posterior filling material showing an acceptable survival in clinical studies . Also in large sized restorations, composite can achieve comparable longevity to amalgam . Generally, hybrid composites can be considered as the best materials for posterior restorations since in clinical studies these materials mostly perform adequately . High failure rates on the short to median long term are seldom found in clinical studies for hybrid composites, with the exception of some novel materials that turned out to be not acceptable shortly after being brought on the market .

Meanwhile, considerable differences in properties exist among commercial composites. These differences are mainly related to differences in filler loading level, particle morphology and size . Based on the filler features, composite restoratives are currently classified as nanofilled, microfilled or micro/nanohybrid materials, with filler mass fractions varying from 42% to 85% . Hybrid composites can be also classified into minifilled composites, with average particle size <1 μm, and midifilled composites, with average particle size between 2 μm and 5 μm . The elastic modulus and other properties of these different types of composites have been shown to be fairly variable in in vitro studies . As large differences in clinical behavior of posterior composite restorations could not be demonstrated so far , it remains questionable whether differences in composite properties reported in laboratory tests have any relevance regarding the clinical survival of composite restorations.

A restriction in clinical studies is that observation times of longer than five years are hardly feasible in most prospective clinical trials, considering the expected population attrition rate. Alternatively, data on failed restorations obtained from cross-sectional studies are often used to establish the longevity of dental restorations in general practice, but this method has been shown to be highly unreliable . Therefore, retrospective clinical studies, dealing with larger patient groups, are more suitable to study survival of a considerable amount of restorations during a longer period of time . In the study of Opdam et al. the compared materials showed identical clinical performance after 5 years, but significantly different performance after 12 years. Therefore, it seems possible that differences in mechanical properties observed in vitro can have an effect in vivo , but only after a longer observation time. Since most clinical trials have observation times shorter than 10 years, differences in late failing behavior are not detected in those studies.

The purpose of this retrospective longitudinal study was to investigate the longevity of posterior restorations placed in a single general practice using two different composites in filler characteristics and material properties: P-50 APC (3M ESPE) with 70 vol.% inorganic filler loading (midfilled) and Herculite XR (Kerr) with 55 vol.% filler loading (minifilled). The hypothesis tested was that two composite materials with different filler loading and elastic modulus show comparable clinical performance after 22-years follow-up.

Materials and methods

Patients’ selection

For this study, the case reports of 80 adult patients were selected according to pre-determined inclusion criteria among the registers of a private practice dental office in Brazil (PARR), from a total of 920 patients who attended the dental office from January 1986 to December 1990. Patients that were selected for the study had a full dentition and normal occlusion, as verified by the clinical and radiographic registers, and had stayed in continuous clinical follow-up in the last 22 years including at least 1 annual recall. Moreover, they had received at least 2 composite restorations in posterior teeth between 1986 and 1990. A 17-year survival report of the same restoration group was published in 2006 . The restorations were placed using 2 resin composites with different material properties: P-50 APC (3M ESPE, St. Paul, MN, USA), a midifilled hybrid composite with inorganic filler loading of 70 vol.%; and Herculite XR (Kerr, Orange, CA, USA), a minifilled hybrid composite with inorganic filler loading of 55 vol.% . Some important material properties are shown in Table 1 .

Table 1
Characteristics of the resin composites evaluated. a
Material Classification b Filler Ra E CS VHN
MPS Vol.% A Vol.% B
Herculite XR Midifilled hybrid 1.0 55 57 0.12 16 397 74
P-50 APC Minifilled hybrid 2.1 70 77 0.48 25 395 159
MPS: mean particle size, Vol.% A : inorganic filler volume percentage as calculated by Willems et al. , Vol.% B : inorganic filler volume percentage as disclosed by the manufacturers, Ra: surface roughness (μm), E = elastic modulus (GPa), CS: compressive strength (MPa), and VHN: Vickers hardness (kg/mm 2 ).

a Based on Willems et al. and .

b Based on Bayne et al. .

The selected patients were invited by phone calls and letters to visit the practice for evaluation. Patients signed a written informed consent prior to start of the clinical evaluation, and 2 researchers (MSC and TAD) enrolled in the study carried out the examination. The study protocol was approved by the local Ethics Committee (022/2008). From the 80 patients that fulfilled the inclusion criteria to be evaluated, 19 did not accept the invitation. As a result, 61 patients (67.2% female and 32.8% male, age 31.2–65.1) agreed to participate in the study. These patients had 362 posterior composite restorations (range 1–17 restorations/patient, average 5.9/patient), as shown in Table 2 , distributed according to patients’ gender, age group and tooth/restoration type.

Table 2
Distribution of restorations evaluated according to patient gender, patient age group, tooth and class type.
Gender Class I Class II Grand Total
Female (age group) LM LPM UM UPM Total LM LPM UM UPM Total
28 20 21 8 77 34 35 43 48 160 237
31–40 3 1 2 6 3 3 3 6 15 21
41–50 13 13 14 8 48 23 17 17 20 77 125
51–60 8 4 3 15 6 13 22 22 63 78
>60 4 2 2 8 2 2 1 5 13
Male (age group) LM LPM UM UPM Total LM LPM UM UPM Total Grand Total
15 12 13 4 44 21 16 19 25 81 125
31–40 3 2 5 5 1 3 2 11 16
41–50 10 8 10 2 30 9 8 14 19 50 80
51–60 2 4 1 2 9 7 7 2 4 20 29
Grand total 43 32 34 12 121 55 51 62 73 241 362
LM: lower molar, LPM: lower pre-molar, UM: upper molar, and UPM: upper pre-molar.

Restorative procedures

One operator (PARR) had placed all restorations under rubber-dam isolation between 1986 and 1990. The patients received restorations of both materials, which were used in that period in the practice for Class I and II restorations without differences in indication. Cavities were prepared using diamond burs and low-speed steel burs were used to remove carious tissue. Preparations were restricted to carious tissue elimination, no bevels were made. Only in deep cavities the pulpal wall was covered with a thin layer of calcium hydroxide (Dycal; Dentsply, Petrópolis, RJ, Brazil). For all cavities, the dentin was covered with a layer of conventional glass–ionomer cement (Ketac-Fil; 3M ESPE).

After setting of the base-cement, all cavities were acid-etched using 35% phosphoric acid and the adhesive, belonging to the selected resin composite, was applied according to the manufacturers’ instructions: Scotchbond 2 (3M ESPE) for P-50 APC and XR Prime/XR Bond (Kerr) for Herculite XR. The composites were placed with an incremental technique; each increment was photoactivated for 40 s using a quartz–tungsten–halogen curing unit (Visilux; 3M ESPE). The restorations were finished using fine-grit diamonds and rubber points with aluminum oxide polishing paste. Aluminum oxide discs were used for proximal finishing. If necessary, abrasive finishing strips were used in the interproximal surfaces until the operator considered the restorations as clinically satisfying.

Evaluation and statistical procedures

The history of the restorations was initially investigated from the dental records. If a restoration had failed, either resulting in replacement or repair, this was considered as a failure and the data and reason for failure were recorded. The restorations were then clinically evaluated between September 2008 and October 2008 using an explorer and dental mirror, according to the FDI criteria. These criteria evaluated biological, esthetic and functional properties of the restorations and were described in detail previously . The 2 calibrated examiners, blinded to type of material, worked independently to perform the evaluation. The surfaces were dried with air stream before evaluation. In case the evaluators disagreed, they reached consensus in a new combined evaluation. Most patients in the practice had a complete bi-annual periapical radiographic exam, which was assessed by the examiners. Additional radiographs were only made when necessary to complement the clinical evaluation, in order to avoid unnecessary radiation exposure for the patients.

Statistical analysis was carried out using SPSS for Windows 19.0 statistical package (Chicago, IL, USA). Descriptive statistics were used to describe the frequency distributions of the evaluated criteria and the reasons for failure. Qualitative analysis based on the FDI criteria was analyzed independent for each one of the 15 clinical characteristics evaluated. Differences in these qualitative criteria between the 2 materials were analyzed using Fisher’s Exact test at p < 0.05. Survival curves were created by the Kaplan–Meier method. Moreover, a Cox regression was applied on the data to evaluate the influence of material, tooth type and number of surfaces on the results ( p < 0.05). To investigate if a different failure behavior existed in the last 10 years compared to the first period of service, Kaplan–Maier statistics as well as the Cox regression were carried out twice for these separate intervals.

Materials and methods

Patients’ selection

For this study, the case reports of 80 adult patients were selected according to pre-determined inclusion criteria among the registers of a private practice dental office in Brazil (PARR), from a total of 920 patients who attended the dental office from January 1986 to December 1990. Patients that were selected for the study had a full dentition and normal occlusion, as verified by the clinical and radiographic registers, and had stayed in continuous clinical follow-up in the last 22 years including at least 1 annual recall. Moreover, they had received at least 2 composite restorations in posterior teeth between 1986 and 1990. A 17-year survival report of the same restoration group was published in 2006 . The restorations were placed using 2 resin composites with different material properties: P-50 APC (3M ESPE, St. Paul, MN, USA), a midifilled hybrid composite with inorganic filler loading of 70 vol.%; and Herculite XR (Kerr, Orange, CA, USA), a minifilled hybrid composite with inorganic filler loading of 55 vol.% . Some important material properties are shown in Table 1 .

Table 1
Characteristics of the resin composites evaluated. a
Material Classification b Filler Ra E CS VHN
MPS Vol.% A Vol.% B
Herculite XR Midifilled hybrid 1.0 55 57 0.12 16 397 74
P-50 APC Minifilled hybrid 2.1 70 77 0.48 25 395 159
MPS: mean particle size, Vol.% A : inorganic filler volume percentage as calculated by Willems et al. , Vol.% B : inorganic filler volume percentage as disclosed by the manufacturers, Ra: surface roughness (μm), E = elastic modulus (GPa), CS: compressive strength (MPa), and VHN: Vickers hardness (kg/mm 2 ).

a Based on Willems et al. and .

b Based on Bayne et al. .

The selected patients were invited by phone calls and letters to visit the practice for evaluation. Patients signed a written informed consent prior to start of the clinical evaluation, and 2 researchers (MSC and TAD) enrolled in the study carried out the examination. The study protocol was approved by the local Ethics Committee (022/2008). From the 80 patients that fulfilled the inclusion criteria to be evaluated, 19 did not accept the invitation. As a result, 61 patients (67.2% female and 32.8% male, age 31.2–65.1) agreed to participate in the study. These patients had 362 posterior composite restorations (range 1–17 restorations/patient, average 5.9/patient), as shown in Table 2 , distributed according to patients’ gender, age group and tooth/restoration type.

Nov 28, 2017 | Posted by in Dental Materials | Comments Off on 22-Year clinical evaluation of the performance of two posterior composites with different filler characteristics
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