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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 7  |  Issue : 3  |  Page : 130-136

One-year clinical evaluation of nanohybrid resin composite in the restoration of occlusal and proximo-occlusal cavities in Nigeria


1 Department of Restorative Dentistry, Lagos State University Teaching Hospital, Ikeja, Nigeria
2 Department of Restorative Dentistry, College of Medicine, Lagos State University, Ikeja, Nigeria
3 Department of Restorative Dentistry, College of Medicine, University of Lagos, Akoka, Nigeria
4 Department of Restorative Dentistry, General Hospital, Odan, Lagos, Nigeria
5 Department of Preventive Dentistry, College of Medicine, Lagos State University, Ikeja, Nigeria

Date of Web Publication15-Sep-2017

Correspondence Address:
Afolabi Oyapero
Department of Preventive Dentistry, Faculty of Dentistry, College of Medicine, Lagos State University, P.O. Box 21266, Ikeja, Lagos
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/AIHB.AIHB_38_17

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  Abstract 


Background: This study aimed to evaluate the clinical performance of nanocomposites in a Nigerian adult population. Resin composites are becoming the preferred direct restorative material in restoring occlusal and proximo-occlusal cavities due to their aesthetic properties and good clinical service. Materials and Methods: This was a clinical study evaluating the clinical performance of a nanohybrid resin composite in the restoration of occlusal and proximo-occlusal cavities in Nigerian adults. This study was done in the Conservative Dentistry Clinic of the Lagos State University Teaching Hospital, Ikeja, from April 2014 to September 2015. The restorations were evaluated immediately at baseline, 3, 6 and 12 months postoperatively for colour match, marginal discolouration, surface roughness, anatomical form, marginal adaptation, retention, post-operative sensitivity and secondary caries using the modified USPHS criteria. Statistical analysis was performed using Fisher's exact test and a 5% level of significance was considered statistically significant. Results: Males had more proximo-occlusal (26.7) than occlusal (6.7) cavities while the females (43.3) had more occlusal cavities. The nanohybrid occlusal restorations had 100% alpha scores at baseline for anatomical form which dropped to 93.3% at 12 months with 6.7% of the restorations scoring Bravo, whereas all nanohybrid proximo-occlusal restorations had 100% alpha scores from baseline to the 12-month review. All occlusal and proximo-occlusal restorations evaluated for surface texture and marginal adaptation had alpha scores at baseline which dropped to 93.3% at 12 months. Conversely, all nanohybrid occlusal and proximo-occlusal restorations scored 100% for colour match and retention, sensitivity and secondary caries from baseline to 12 months. Conclusion: The clinical performance of natural elegance nanohybrid resin composite (Henry Schein®) was satisfactory in the restoration of occlusal and proximo-occlusal cavities in Nigerian adults over a 1 year evaluation period.

Keywords: Nanohybrid, occlusal, proximo-occlusal, resin composite, restoration


How to cite this article:
Enone LL, Awotile AO, Adegbulugbe CI, Agbaje LO, Odogun LA, Oyapero A. One-year clinical evaluation of nanohybrid resin composite in the restoration of occlusal and proximo-occlusal cavities in Nigeria. Adv Hum Biol 2017;7:130-6

How to cite this URL:
Enone LL, Awotile AO, Adegbulugbe CI, Agbaje LO, Odogun LA, Oyapero A. One-year clinical evaluation of nanohybrid resin composite in the restoration of occlusal and proximo-occlusal cavities in Nigeria. Adv Hum Biol [serial online] 2017 [cited 2020 Apr 7];7:130-6. Available from: http://www.aihbonline.com/text.asp?2017/7/3/130/214894




  Introduction Top


Dental caries is a localised destruction of susceptible dental hard tissues, occurring over time as a result of acid by-products from bacterial fermentation of dietary carbohydrates.[1],[2] It is a dynamic process resulting from many cycles of demineralisation and remineralisation.[3] It is a slowly progressing chronic disease that can clinically affect the pits and fissures, which are the most susceptible sites, as well as smooth surfaces and the root surfaces, and commonly occurs in posterior teeth.[4] Despite advances in the diagnosis, prevention and control of dental caries, it still remains a clinically significant oral disease.[5] A shift towards a largely preventive approach to caries management with emphasis on the restoration and the retention of aesthetically pleasing functional teeth has resulted in a decline in the extraction of carious posterior teeth.[6],[7]

The objective of placing a restoration should be to improve the appearance of the tooth and to make the tooth cleansable. This may be achieved using a dental material that will replace lost tooth structure functionally and aesthetically both initially and over time.[5] Several restorative materials and techniques are available for restoring posterior teeth affected by caries.[8] For more than a century, dental amalgam has been the most commonly used material for restoring occlusal and proximo-occlusal cavities due to its strength, relative ease of clinical handling and low cost. There is, however, a decline in its use due to the increased demand for aesthetic restorative materials and controversies concerning the perceived health effects of mercury from the restoration.[9],[10] The general concern for the negative impacts of mercury on people's health led to renewed efforts to eliminate mercury use by adopting and signing of the Minamata Treaty in Japan in 2013.[11] The treaty mandated every signatory to phase down and control the use of mercury with a moratorium time line of about 10 years and the use of alternative materials such as composite resins, glass ionomer cements, ceramics and gold alloys.

Resin composites are becoming the preferred direct restorative material in restoring occlusal and proximo-occlusal cavities due to their aesthetic properties and good clinical service.[12] The longevity of resin composite restorations is influenced by a number of factors such as location, type and size of the cavity, the technique of the operator, age and caries prevalence of the patient. Recent reports have shown satisfactory survival rates for posterior composite restorations.[12] Furthermore, incorporating reduced filler particle sizes into resin composites and the resultant increase in filler loading were aimed at producing materials that will satisfy the requirements of dental composites such as excellent aesthetic and mechanical properties.[13] This led to the application of nanotechnology in dental resin composites. When applied to resin composites, it aims at producing materials with improved mechanical and aesthetic features attributed to the reduced filler size i.e., nanoparticles and wide distribution of the fillers.[14] The inherent filler properties of nanocomposites are maximised while retaining excellent clinical handling properties and at the same time minimising the amount of organic resin matrix, thus producing composites with greatly improved mechanical properties.[15]

Innovations in resin composites have increased its acceptance in the restoration of posterior teeth. Nowadays, they are considered as suitable direct posterior filling materials and they have shown acceptable survival in clinical studies.[16],[17],[18] Nanohybrid resin composites showed good clinical performance in a 6-year evaluation, which is comparable to that of a well-established conventional hybrid resin composite.[18] Kramer et al.[19] found no difference in the clinical behaviour of a nanohybrid composite compared with a fine hybrid resin composite in the restoration of proximo-occlusal cavities. Both materials performed satisfactorily over a 4-year follow-up period.

However, little is known of the clinical performance of nanocomposites in the Nigerian environment. Therefore, evaluating the clinical performance of nanohybrid resin composites will determine their suitability in the restoration of posterior teeth in Nigerian adults, especially in the light of differences in diet and high masticatory activity compared to Caucasian environments where most studies have been carried out. This study aimed to evaluate the clinical performance of nanocomposites in a Nigerian adult population.


  Materials and Methods Top


Study design and location

This was a clinical study evaluating the clinical performance of a nanohybrid resin composite in the restoration of occlusal and proximo-occlusal cavities in Nigerian adults. This study was carried out in the Conservation Clinic of the Restorative Dentistry Department of the Lagos State University Teaching Hospital, Ikeja, Lagos State, from April 2014 to September 2015. The study participants were enlisted from the patients referred for the restoration of occlusal or proximo-occlusal cavities at the clinic.

Sample size determination

The sample size for this study[20] was determined using a formula for clinical studies. The sample was increased to thirty restorations. This was considered satisfactory and in line with the American Dental Association's recommendations for clinical studies on enamel and dentine adhesive materials[21],[22] and also to accommodate patient attrition at follow-up periods.

Inclusion criteria

Patients aged 16 years and above with at least two occlusal or two proximo-occlusal cavities involving molars or premolars not extending beyond two-thirds of dentine thickness radiographically were included in this study. They also had moderate-sized cavities with bucco-lingual width not more than two-thirds of the intercuspal slopes and all teeth selected were devoid of pain, suggestive of irreversible pulpitis.

Exclusion criteria

Patients with tooth wear, those with parafunctional habits and those who could not maintain an acceptable oral hygiene (oral hygiene index-simplified >3) were excluded from the study.

Ethical approval/informed consent

Approval for the study was obtained from the Health Research and Ethics Committee of the Lagos State University Teaching Hospital, Ikeja. A written informed consent was also obtained from all participants and each participant was given detailed information and explanation of the study, especially about their availability for the follow-up periods of 3, 6 and 12 months. Every participant was given opportunities to ask questions about the study and suitable explanations were given prior to commencement of the study.

Methodology

Fifteen participants, each with 1 occlusal and 1 proximo-occlusal cavities requiring restorations who had met the inclusion criteria, were selected for the study. The teeth were restored with natural elegance nanohybrid resin composite (Henry Schein®). Shade selection was done in natural light before the restorative procedure while the teeth were moist. The teeth were treated under local anaesthesia (2% xylocaine HCl 1:80,000) and isolated with a rubber dam (UnoDent®). Carious lesions were excavated and the cavities were prepared with diamond round and straight fissure burs (UnoDent®) running at fast speed and cooled with water. Cavity preparations were determined by the size and extent of the carious lesions and were not unjustifiably extended into sound tooth tissues. The cavity margins in proximal cavities were bevelled as recommended by the manufacturer to improve enamel adhesion. Sectional metal matrix band and retainer (Flexi clamp®) and Hawe Sycamore interdental wedges (Kerr®) were used in the case of proximo-occlusal cavities. Pulpal protection was not indicated in any tooth. The cavities were etched by the etch and rinse technique with 37% phosphoric acid (Henry Schein®) for 15 s and then rinsed out carefully and air-dried for about 5 s as instructed by the manufacturer. Universal enamel and dentine bonding agent (Henry Schein®) was applied with an applicator brush and cured for 20 s as stated by the manufacturer. The composite restorative material was placed in the cavities using the oblique incremental method. In proximo-occlusal cavities, the first layer was placed on the gingival wall while the second increment was placed obliquely, contacting both buccal and axial walls and the first increment while a third increment was placed buccolingually. The final increment was placed occlusally to restore the occluso-proximal anatomical form. Each increment of composite, not exceeding 2 mm, was cured using ultra-light-emitting diode curing light (Rolence®) with 390–480 nm output for 40 s according to the manufacturer's instructions and additional curing was done buccally and lingually for 20 s after removing the matrix band and retainer. Finishing to reproduce the occlusal morphology was done with tapered white polystone finishing burs (Shofu®) intraproximally with dual purpose finishing strips (Henry Schein®). Polishing was carried out with polishing paste (Henry Schein®) and rubber cup (Shofu®) using a slow hand piece running at slow speed under irrigation immediately after placement of restorations.

Clinical evaluation and follow-up

All restorations were evaluated immediately at baseline, at 3, 6 and 12 months for retention, colour match, marginal integrity, anatomic form, marginal discolouration, surface texture and post-operative sensitivity. The clinical evaluation was done by a blinded trained examiner using the modified USPHS criteria by Cvar and Ryge in 1971[23] and adapted by Wilson et al.[24] The ratings included alpha for satisfactory restoration; Bravo for defect present but restoration is clinically acceptable and does not require replacement and Charlie and Delta for clinical failure of the restoration and that requires immediate attention. The clinical evaluation was done using loops with ×4 magnification (Lactona®), a dental mirror and a probe. Bitewing radiographs were taken at 6- and 12-month follow-up period for detection of secondary caries. Clinical photographs of restorations were also taken at each recall visit.

Data analysis

Data were entered and analysed with the Statistical Packages for Social Sciences version 20.0 (Chicago, IL). Descriptive statistics such as mean, range and standard deviation were used to present quantitative variables while categorical variables were summarised with percentages. Charts were also used for data presentation. Clinical performance of the resin composite materials was evaluated using Fisher's exact test. Categorical variables such as type of cavity and tooth type were also analysed using the Fisher's exact test. A 5% level of significance was considered statistically significant.


  Results Top


The study involved 15 patients, consisting of ten (66.7%) females and five (33.3%) males. Eighteen patients (60%) were aged between 20 and 39 years, nine (30%) patients were above 40 years while three (10%) patients were <20 years [Figure 1]. Recall rate was 100% as all patients were available for the follow-up periods. Males had more proximo-occlusal (26.7) than occlusal (6.7) cavities while the females (43.3) had more occlusal cavities [Table 1]. Eighteen (60%) maxillary teeth were restored compared to 12 (40%) mandibular teeth [Table 2]. Of this number, more molars i.e., 11 (36.7%) had occlusal cavities than premolars i.e., 4 (13.3%). Likewise, more molars i.e., 8 (26.7%) had proximo-occlusal cavities compared to premolars i.e., 7 (23.3%) [Table 3].
Figure 1: Histogram showing the age distribution of the participants.

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Table 1: Relationship between the types of cavities and gender of the participants

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Table 2: Location of carious teeth

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Table 3: Tooth-type distribution of occlusal and proximo-occlusal cavities

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Evaluation of the aesthetic parameters of restorations

All occlusal restorations evaluated for surface texture had alpha scores at baseline which dropped to 93.3% at 12 months, whereas the proximo-occlusal restorations maintained 100% alpha scores till 12 months. The nanohybrid occlusal and proximo-occlusal restorations had 100% alpha scores at baseline for anatomical form till the 6th month, which dropped to 93.3% at 12 months with 6.7% of the restorations scoring Bravo [Table 4] and [Table 5]. With respect to colour match and marginal discolouration, a 100% alpha score was recorded for the nanohybrid occlusal and proximo-occlusal restorations, respectively [Table 4] and [Table 5].
Table 4: Aesthetic parameters of nanohybrid occlusal composite restorations (n=15)

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Table 5: Aesthetic parameters of nanohybrid proximo-occlusal composite restorations (n=15)

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Evaluation of the functional parameters of restorations

The nanohybrid occlusal and proximo-occlusal restorations recorded 93.3% alpha scores and 6.7% Bravo scores at 12 months, respectively, for marginal adaptation. Conversely, all nanohybrid occlusal and proximo-occlusal restorations scored 100% for retention from baseline to 12 months [Table 6].
Table 6: Functional parameters of nanohybrid occlusal and proximo-occlusal composite restorations (n=15)

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Evaluation of the biological parameters of restorations

No Bravo scores for post-operative sensitivity was recorded for the occlusal restorations (100% alpha scores). However, 6.7% of nanohybrid proximo-occlusal restorations scored Bravo, dropping the alpha scores to 93.3%. No secondary caries was detected in all nanohybrid occlusal and proximo-occlusal composite restorations and they had 100% alpha scores from baseline to 12 months [Table 7].
Table 7: Biological parameters of nanohybrid occlusal and proximo-occlusal composite restorations (n=15)

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  Discussion Top


There is an increased interest in tooth-coloured restorative materials, especially due to the ongoing phase down of amalgam as a dental restorative material. This justifies the need for further evaluation of the clinical performance of resin composites in restoring posterior teeth in our local environment. Nanocomposites are available as nanofills which consist of both nanomer and nanocluster particles and nanohybrids which contain milled glass fillers and discrete nanoparticles (40–50 nm); with the nanofillers in a pre-polymerised filler form.[20],[25] Nanohybrids consist of filler particles with different sizes including large filler particles. The presence of varying particle sizes allows for a homogeneous filler distribution within the matrix, because the nanofillers take up the spaces between the larger particles perfectly. Therefore, the filler loading can be compared to that of the conventional hybrid resin composites.

In the present study, all the nanohybrid restorations maintained 100% alpha scores for marginal discolouration throughout the evaluation period. This was in agreement with another researches,[26] where 100% alpha scores were recorded from baseline to 12 months. Surface roughness was, however, observed on one nanohybrid composite restorations at 12 months. This may be due to the friction with food and opposing teeth during mastication.[8] Studies[20],[25] have shown that resin composites with nanoparticles are characterised by low incidences of roughness and wear after finishing and polishing as well as on recall when compared with other classes of dental composites. Unlike other hybrid resin composites, large filler particles cannot be separated from the resin matrix of nanohybrids and only poorly attached nanoclusters are separated during abrasion, thus retaining a well-polished surface.[27] The particles separated from the surface form nanosized defects which are invisible to the naked eye.[7] Other studies[20],[25] show equal or better polishability for nanofiller-containing composites due to the smaller filler particle size and lower degree of filler.

Loss of anatomical form can be a clinical manifestation of wear[28] and this can occur occlusally during mastication, and the type of diet is an important factor.[29] The Bravo score for anatomical form was only recorded from one occlusal nanohybrid restoration. None of the proximo-occlusal restorations had Bravo scores for anatomical form. This may be due to the greater masticatory forces on occlusal surfaces of posterior teeth resulting in an increased susceptibility of the restorations to wear. Loss of anatomical form for the restorations may be expected due to the more fibrous African (Nigerian) diet as compared to the soft refined European diet. Arhun et al.[30] in a European setting similarly recorded 100% alpha scores for nanohybrid restorations after 12 months with only one restoration scoring Bravo at 3 years.

From this study, it can be demonstrated that nanohybrid resin composite restorations demonstrated good colour stability over the study period of 12 months. Two nanohybrid restorations, however, scored Bravo at 12 months for marginal adaptation. This was similar to findings obtained by other researchers[31],[32] on marginal integrity at 12-month evaluation. However, Kiremitci et al.[33] did not record any Bravo scores at 12 months while Attia et al.[34] recorded Bravo scores for marginal integrity from 6 months. Alterations in marginal adaptation and observed marginal discolouration of composite restorations could occur as a result of degradation of the resin/bond interface as the monomers in adhesive materials can absorb water and chemicals from the environment which weakens the resin/dentin bond over time. Similarly, a crevice along the marginal interface may result from the fracture of overlapping surplus restorative material at the margins. Polymerisation shrinkage stress, cavity size/shape and C-factor could also influence the marginal features of composite restorations.[35]

All restorations maintained good retention with alpha scores throughout the 12-month evaluation period as similarly recorded in some studies.[12],[35] Resin composite restorations have been shown to perform favourably in posterior teeth, with annual failure rates of 1%–3%.[36] The main reasons for failure observed from clinical trials are still secondary caries and fracture of the tooth or restoration. Failure of posterior restorations due to wear is declining, and it is observed more in patients with bruxing and clenching habits,[36] in those who chew highly abrasive diets as well as in those with increased masticatory activity as seen in Nigerians.[29] Success and longevity of restorations is similarly dependent on factors such as patient's oral hygiene, presence of parafunctional habits, choice of material and the skill of the clinician.[36]

Post-operative sensitivity in this study was only recorded at 12 months with only one out of 30 (3.3%) restorations scoring Bravo. Some studies have recorded no post-operative sensitivity throughout the evaluation period[17] while others[37] recorded Bravo scores for post-operative sensitivity. Several factors have been attributed for post-operative sensitivity following placement of composite restorations. These include dentin etching and bacterial penetration of the pulp, occlusal discrepancies, deformation of cusps by shrinkage stress and deformation of the restoration by occlusal forces.[38] Secondary caries was, however, not detected clinically or radiographically for any of the nanohybrid occlusal and proximo-occlusal restorations as recorded by Shi et al.[38] but this contrasts with findings by Gonsalves et al.[39] Clinical studies have demonstrated that bulk fracture and secondary caries are leading causes of failure of posterior resin composite restorations.[36] Demarco et al.[12] ascribed the formation of secondary caries not only to the material itself but also to the clinical environment, caries experience and different handling characteristics. The technique of incremental placement of resin composites which reduces the shrinkage stress and microleakage at the adhesive interface and the good oral hygiene status of the enlisted individuals may be responsible for this finding.[35]


  Conclusion Top


All evaluated occlusal restorations had alpha scores for surface texture at baseline which dropped to 93.3% at 12 months, while the proximo-occlusal restorations maintained 100% alpha scores till 12 months. All restorations, however, recorded 93.3% alpha scores and 6.7% Bravo scores at 12 months for marginal adaptation. Conversely, all nanohybrid occlusal and proximo-occlusal restorations scored 100% for retention from baseline to 12 months. No Bravo scores for post-operative sensitivity was recorded for the occlusal restorations (100% alpha scores). However, 6.7% of nanohybrid proximo-occlusal restorations scored Bravo, dropping the alpha scores to 93.3%. No secondary caries was detected in all nanohybrid occlusal and proximo-occlusal composite restorations and they had 100% alpha scores from baseline to 12 months. The clinical performance of natural elegance nanohybrid resin composite (Henry Schein®) thus appears satisfactory in the restoration of occlusal and proximo-occlusal cavities in Nigerian adults over a 1-year evaluation period. Other clinical studies, especially those with a longer period of evaluation, are however still required to complement these findings.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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Abstract
Introduction
Materials and Me...
Results
Discussion
Conclusion
References
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