Highlights
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In vitro radiotherapy seems not to impair the mechanical properties of composite resins.
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Post-bonding in vitro radiotherapy does not weaken bond strength of adhesive systems.
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Pre-bonding in vitro radiotherapy decreases bond strength of adhesive systems.
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Bond strength of adhesive systems need to be investigated after in vivo radiotherapy.
Abstract
Objectives
To analyze the evidence regarding the impact of head and neck radiotherapy (HNRT) on the mechanical behavior of composite resins and adhesive systems.
Methods
Searches were conducted on PubMed, Embase, Scopus and ISI Web of Science databases using “Radiotherapy”, “Composite resins” and “Adhesive systems” as keywords. Selected studies were written in English and assessed the mechanical behavior of composite resins and/or adhesive systems when bonding procedure was conducted before and/or after a maximum radiation dose ≥50 Gy, applied under in vitro or in vivo conditions.
Results
In total, 115 studies were found but only 16 were included, from which five evaluated the effect of in vitro HNRT on microhardness, wear resistance, diametral tensile and flexural strength of composite resins, showing no significant negative effect in most of reports. Regarding bond strength of adhesive systems, 11 studies were included from which five reported no meaningful negative effect when bonding procedure was conducted before simulated HNRT. Conversely, five studies showed that bond strength diminished when adhesive procedure was done after in vitro radiation therapy. Only two studies about dental adhesion were conducted after in vivo radiotherapy but the results were not conclusive.
Significance
The mechanical behavior of composite resins and adhesive systems seems not to be affected when in vitro HNRT is applied after bonding procedure. However, bond strength of adhesive systems tends to decrease when simulated radiotherapy is used immediately before bonding procedure. Studies assessing dentin bond strength after in-vivo HNRT were limited and controversial.
1
Introduction
Head and neck radiotherapy (HNRT) produces a series of toxicities on non-targeted healthy tissues surrounding the tumor, leading to hyposalivation, mucositis, trismus, osteoradionecrosis and radiation-related caries . The latter is marked by a rapid onset and a high potential for generalized dental destruction, affecting approximately 25% of the patients who concluded this treatment, which compromises the overall oral function and the quality of life of cancer survivors . As a consequence, there’s a strong recommendation for head and neck cancer patients to have their oral health monitored before, during and after radiotherapy.
In this context, contemporary protocols for oral conditioning in these patients include multiple dental restorations before and after HNRT . In both situations, the choice of restorative materials is currently based on personal clinical experience rather than scientific evidence . Due to the fact that dental restorations are in the same primary radiation field of the tumor, they would be also susceptible to the direct effects of HNRT. In fact, some in vitro studies have demonstrated a negative interaction between ionizing radiation doses and metallic dental materials, by increasing the original radiation dose due to their high density, atomic number and conductivity . In addition, it has been observed that mechanical properties and clinical survival of restorative dental materials such as conventional glass ionomer and resin-modified glass ionomer cements are severely affected in an indirect way by hiposalivation related to radiogenic damage of salivary glands .
On this regard, non-metallic and insoluble dental materials are desirable to restore teeth from head and neck cancer patients before and after radiotherapy. Composite resins meet all these features, in addition they have excellent optical properties, elastic modulus similar to enamel and dentin which allows a more homogeneous masticatory load distribution. Also, these dental materials show higher biocompatibility compared to metallic restorations, as well as acceptable clinical performance . Composite resins are used together with etch-and-rinse or self-etch adhesive systems, which permits a micromechanical, chemical or both approaches, promoting interaction with hard dental tissues . These issues are relevant during restorative dental treatment in head and neck cancer patients who underwent or will undergo radiation therapy. In both cases, healthy dental tissue need to be preserved as maximum as possible and adequate bond strength is desirable, avoiding restoration replacement after cancer treatment has begun. However, as previously demonstrated in other studies, even using the most conservative HNRT techniques, tumor surrounding maxillofacial tissues and some restorative dental materials are directly or indirectly affected .
On this sense, it is possible to suggest that surface and bulk micromechanical properties of composite resins as well as bond strength of adhesive systems could be affected by HNRT as it occurs in enamel and dentin, especially when high doses of ionizing radiation are applied . This phenomenon could impair tooth-restoration interaction, increasing the susceptibility to early restoration failure and radiation-related caries progression . Unfortunately, until now no consensus exists regarding the direct and indirect effects of HNRT on the mechanical performance of composite resins and adhesive systems. In addition, it is not possible to determine if dental restorative procedures should preferably be performed before or after this cancer treatment. Also, nothing has been discussed about the most suitable composite resins or bonding agents to be used in head and neck cancer patients. Therefore, the present systematic review was designed to analyze scientific evidence regarding the impact of in vitro and in vivo HNRT on the mechanical behavior of composite resins and adhesive systems to ultimately contribute for the development of specific protocols using adhesive dental materials for head and neck cancer patients, before and after radiotherapy.
2
Materials and methods
The present systematic review was conducted following the Guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) and no registration protocol was adopted. The research question was: Do in vitro and in vivo HNRT affect the mechanical behavior of composite resins and adhesive systems?
2.1
Eligibility criteria
2.1.1
Inclusion criteria
Studies published in English language that assessed the effects of HNRT on the mechanical properties of composite resins and/or bond strength of adhesive systems on dentin and/or enamel, independently if bonding procedure was done before and/or after radiotherapy ( in vitro or in vivo conditions).
2.1.2
Exclusion criteria
Studies using a maximum radiation dose below 50 Grays(Gy) or evaluating the effects of radiotherapy on the mechanical behavior of experimental composite resins/adhesive systems or different dental materials. In addition, studies that omitted relevant methodological information such as total radiation dose and radiotherapy modality (fractioned or non-fractioned protocol), were excluded, as well as other types of papers (letters from editors, congress abstracts, literature reviews, clinical studies and different topics).
2.2
Search strategy
Electronic and systematic searches of scientific studies that evaluated the effects of HNRT on the mechanical behavior of composite resins and adhesive systems bonding to tooth, were conducted without restriction in publication year (Last search February, 20th 2017). Medline/PubMed ( ), EMBASE ( https://www.embase.com/login ), Scopus ( ) and ISI Web of Science ( ) were screened. The following keywords were used: “Radiotherapy”, “Composite resins” and “Adhesive systems”, linked in independent strategies by the boolean operator “AND”. The process was repeated in each database to ensure that any relevant result was missed during the identification phase. Additional searches were conducted by reading reference lists from all selected studies to detect other potentially eligible reports that could meet the inclusion criteria. In addition, key authors/co-authors were identified among the included studies (considering the frequency of published papers regarding the impact of HNRT on the mechanical behavior of composite resins or adhesive systems). Therefore, extra database searches filtered by author/co-author name were also conducted.
2.3
Study selection
All titles were systematically organized in Microsoft Office Excel 2016 (Microsoft Corporation, Redmond, Washington, USA). They were verified and counted to exclude duplicated items. Later, titles and abstracts were screened and read completely for possible inclusion on the qualitative synthesis of this review. Then, studies were classified into the following categories: duplicated, other language, maximum radiation dose (<50 Gy), experimental dental materials/other dental materials, other and included studies. In the end, reports assessed for eligibility were downloaded from database in full text version and they were read in detail in PDF formatted files. Studies that omitted relevant methodological information were also excluded from the current review.
2.4
Data extraction
Methodological information extracted from selected studies was related to author, commercial reference (composite resin or adhesive system), classification, radiation dose (in Gy), radiotherapy modality (fractioned or non-fractioned protocol), radiation device/type of ionizing radiation, mechanical test and type of property. In addition, information regarding adhesive procedure sequence (before or after HNRT) and dental substrate (enamel, dentin or both) were also extracted from included studies that assessed the impact of radiotherapy on bond strength of adhesive systems. Means and standard deviations of each mechanical property tested in composite resins and bond strength values of adhesive systems in Megapascals (MPa) were extracted and tabulated (considering maximum radiation dose).
2.5
Risk of bias assessment
To assess the risk of bias in studies regarding mechanical properties of irradiated composite resins, an adaptation of an instrument presented in a systematic review was used . Eight methodological aspects were verified: randomization, sample size calculation, comparable groups, detailed information regarding mechanical test, manufacturer’s instructions, single operator, data regarding exposure protocol and operator blinded. For studies that evaluated bond strength of adhesive systems, the same instrument previously applied in a systematic review of in vitro studies was employed . Aspects such as randomization, sample size calculation, teeth free of caries, specimens with similar dimensions, failure mode evaluation, manufactureŕs instructions, single operator and operator blinded were checked. If each item was pointed out in the selected article, it was judged as “Yes” but if not mentioned as “No”. Finally, the risk of bias was classified in high, medium or low, according to the sum of “yes” as follows: From 1 to 3 (high risk), 4 to 5 (medium risk) and 6 to 8 (low risk).
2.6
Data analysis
There was homogeneity in the research purpose among the studies but a great variability in tested materials, mechanical tests, measurement units, radiotherapy devices and treatment modalities was detected. This made inappropriate to conduct a meta-analysis but a detailed qualitative synthesis of the results was performed. Data related to means and standard deviations from mechanical properties of composite resins and bond strength of adhesive systems were described. Also, mean difference (between irradiated and control group) and decrease/increase in percentage were calculated in individual studies. Finally, summary results regarding the total number of studies reporting HNRT effects were presented in a figure.
2
Materials and methods
The present systematic review was conducted following the Guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) and no registration protocol was adopted. The research question was: Do in vitro and in vivo HNRT affect the mechanical behavior of composite resins and adhesive systems?
2.1
Eligibility criteria
2.1.1
Inclusion criteria
Studies published in English language that assessed the effects of HNRT on the mechanical properties of composite resins and/or bond strength of adhesive systems on dentin and/or enamel, independently if bonding procedure was done before and/or after radiotherapy ( in vitro or in vivo conditions).
2.1.2
Exclusion criteria
Studies using a maximum radiation dose below 50 Grays(Gy) or evaluating the effects of radiotherapy on the mechanical behavior of experimental composite resins/adhesive systems or different dental materials. In addition, studies that omitted relevant methodological information such as total radiation dose and radiotherapy modality (fractioned or non-fractioned protocol), were excluded, as well as other types of papers (letters from editors, congress abstracts, literature reviews, clinical studies and different topics).
2.2
Search strategy
Electronic and systematic searches of scientific studies that evaluated the effects of HNRT on the mechanical behavior of composite resins and adhesive systems bonding to tooth, were conducted without restriction in publication year (Last search February, 20th 2017). Medline/PubMed ( ), EMBASE ( https://www.embase.com/login ), Scopus ( ) and ISI Web of Science ( ) were screened. The following keywords were used: “Radiotherapy”, “Composite resins” and “Adhesive systems”, linked in independent strategies by the boolean operator “AND”. The process was repeated in each database to ensure that any relevant result was missed during the identification phase. Additional searches were conducted by reading reference lists from all selected studies to detect other potentially eligible reports that could meet the inclusion criteria. In addition, key authors/co-authors were identified among the included studies (considering the frequency of published papers regarding the impact of HNRT on the mechanical behavior of composite resins or adhesive systems). Therefore, extra database searches filtered by author/co-author name were also conducted.
2.3
Study selection
All titles were systematically organized in Microsoft Office Excel 2016 (Microsoft Corporation, Redmond, Washington, USA). They were verified and counted to exclude duplicated items. Later, titles and abstracts were screened and read completely for possible inclusion on the qualitative synthesis of this review. Then, studies were classified into the following categories: duplicated, other language, maximum radiation dose (<50 Gy), experimental dental materials/other dental materials, other and included studies. In the end, reports assessed for eligibility were downloaded from database in full text version and they were read in detail in PDF formatted files. Studies that omitted relevant methodological information were also excluded from the current review.
2.4
Data extraction
Methodological information extracted from selected studies was related to author, commercial reference (composite resin or adhesive system), classification, radiation dose (in Gy), radiotherapy modality (fractioned or non-fractioned protocol), radiation device/type of ionizing radiation, mechanical test and type of property. In addition, information regarding adhesive procedure sequence (before or after HNRT) and dental substrate (enamel, dentin or both) were also extracted from included studies that assessed the impact of radiotherapy on bond strength of adhesive systems. Means and standard deviations of each mechanical property tested in composite resins and bond strength values of adhesive systems in Megapascals (MPa) were extracted and tabulated (considering maximum radiation dose).
2.5
Risk of bias assessment
To assess the risk of bias in studies regarding mechanical properties of irradiated composite resins, an adaptation of an instrument presented in a systematic review was used . Eight methodological aspects were verified: randomization, sample size calculation, comparable groups, detailed information regarding mechanical test, manufacturer’s instructions, single operator, data regarding exposure protocol and operator blinded. For studies that evaluated bond strength of adhesive systems, the same instrument previously applied in a systematic review of in vitro studies was employed . Aspects such as randomization, sample size calculation, teeth free of caries, specimens with similar dimensions, failure mode evaluation, manufactureŕs instructions, single operator and operator blinded were checked. If each item was pointed out in the selected article, it was judged as “Yes” but if not mentioned as “No”. Finally, the risk of bias was classified in high, medium or low, according to the sum of “yes” as follows: From 1 to 3 (high risk), 4 to 5 (medium risk) and 6 to 8 (low risk).
2.6
Data analysis
There was homogeneity in the research purpose among the studies but a great variability in tested materials, mechanical tests, measurement units, radiotherapy devices and treatment modalities was detected. This made inappropriate to conduct a meta-analysis but a detailed qualitative synthesis of the results was performed. Data related to means and standard deviations from mechanical properties of composite resins and bond strength of adhesive systems were described. Also, mean difference (between irradiated and control group) and decrease/increase in percentage were calculated in individual studies. Finally, summary results regarding the total number of studies reporting HNRT effects were presented in a figure.
3
Results
3.1
Search and study selection
Flow diagram that summarizes the selection process of studies is shown in Fig. 1 . In total, 115 studies were identified through search strategies on four databases. After the first review process, 52 studies were eliminated due to duplication. Later, 52 studies were excluded because they did not meet the inclusion criteria, remaining 11 studies. In addition, by reading reference list from selected studies, four new results were found and considered in the present systematic review. Three key authors/co-authors (Correr-Sobrinho L, Soares CJ and Dibo da Cruz A) were identified and complementary database searches resulted in one additional study. In the end, 16 studies meeting all the inclusion criteria were included from which five evaluated the effect of radiotherapy on surface and bulk micromechanical properties of composite resins and 11 studies on bond strength of adhesive systems .
3.2
Study characteristics
3.2.1
Mechanical properties of composite resins
Table 1 shows main methodological aspects from included studies about the impact of HNRT on the mechanical properties of composite resins. All investigations about this issue were conducted under in-vitro radiotherapy . Evaluated composite resins were macrofilled (Concise, 3M Company), microfilled (Silux plus, 3M Company), hybrid (P-50, 3M Company; Te Econom Plus, Ivoclar Vivadent) and microhybrid (Filtek Z250, 3M ESPE and Empress Direct, Ivoclar Vivadent). Maximum ionizing radiation dose applied to composite resin samples ranged from 60 to 80 Gy. Non-fractioned radiotherapy protocols (total dose applied in a single session) were used on four included studies . Conversely, a fractioned protocol (2 Gy daily applied for 35 days to complete a total radiation dose of 70 Gy) was reported in one study . Radiotherapy devices that emitted gamma radiation were used in three selected studies to expose composite resin samples . Mechanical tests were Vickers hardness, Knoop hardness, abrasion, diametral tensile strength and flexural strength.
| Author | Commercial reference (manufacturer) | Classification | Radiation doses in Gy | Radiotherapy modality | Radiotherapy device/type of ionizing radiation | Mechanical test (type of property) |
|---|---|---|---|---|---|---|
| von Fraunhofer et al. | Concise (3M Company, St. Paul, MN, USA) | Macrofilled | 0 | NFRT | Cobalt-60 source | VH (S) |
| P-50 (3M Company, St. Paul, MN, USA) | Hybrid | 2 | Gamma | DTS (B) | ||
| Silux plus (3M Company, St. Paul, MN, USA) | Microfilled | 5 | ||||
| Valux (3M Company, St. Paul, MN, USA) | Hybrid | 10 | ||||
| 20 | ||||||
| 50 | ||||||
| 80 | ||||||
| Curtis et al. | Concise (3M Company, St. Paul, MN, USA) | Macrofilled | 0 | NFRT | Cobalt-60 source | A (S) |
| P-50 (3M Company, St. Paul, MN, USA) | Hybrid | 2 | Gamma | |||
| Silux plus (3M Company, St. Paul, MN, USA) | Microfilled | 5 | ||||
| Valux (3M Company, St. Paul, MN, USA) | Hybrid | 10 | ||||
| 20 | ||||||
| 50 | ||||||
| 80 | ||||||
| Catelan et al. | Filtek Z250 (3M ESPE, St. Paul, MN, USA) | Microhybrid | 0 | NFRT | Alcyon II Cobalt therapy device (general electric, Buc, France) | FS (B) |
| 30 | Gamma | |||||
| 40 | ||||||
| 50 | ||||||
| 60 | ||||||
| Dibo da Cruz et al. | Filtek Z250 (3M/ESPE, St. Paul, MN, USA) | Microhybrid | 0 | NFRT | Clinac 600 linear accelerator (Varian Medical Systems, Palo Alto, CA, USA) | KH (S) |
| Fill Magic Flow (Vigodent SA, Rio de Janeiro, RJ, Brazil) | Flowable composite resin | 5 | X-rays | |||
| 35 | ||||||
| 70 | ||||||
| Hegde et al. | Te-Econom Plus (Ivoclar Vivadent, Schaan, Liechtenstein) | Hybrid | 0 | FRT | Electron beam irradiator | VH (S) |
| Empress Direct (Ivoclar Vivadent, Schaan, Liechtenstein) | Microhybrid | 70 | NR | |||
3.2.2
Bond strength of adhesive systems
Main methodological aspects from selected studies that assessed the impact of HNRT on the bond strength of adhesive systems are presented in Table 2 . Eleven studies were found, from which two were conducted under in vivo radiotherapy and nine studies used in vitro modality . The etch-and-rinse (Adper Single Bond 2, 3M ESPE) and the self-etch adhesive system (Clearfil SE Bond, Kuraray) were the most tested materials. Regarding maximum radiation dose applied to teeth, it varied from 60 to 70 Gy within studies that employed in vitro HNRT, generally applied by fractioned protocols (2 Gy daily, until achieving the total radiation dose). Conversely, in both studies conducted after in vivo radiotherapy, patients from whom teeth were extracted received more than 50 Gy in the cervicofacial region. With respect to dental tissues, bond strength of adhesive systems on enamel and dentin was evaluated in three and ten studies, respectively.
| Author | Commercial reference (manufacturer) | Classification | Radiation doses in Gy | Radiotherapy modality | Radiotherapy device/type of ionizing radiation | Bonding procedure sequence (before or after HNRT) | Mechanical test | Dental substrate |
|---|---|---|---|---|---|---|---|---|
| Gernhardt et al. a | Scotchbond 1 (3M Dental products, Loughborough, UK) | Etch-and-rinse | 0 | FRT | Clinac 600 C linear accelerator | After | TBS | Dentin |
| Solobond Plus (VOCO, Cuxhaven, Germany) | Etch-and-rinse | 60 | NR | |||||
| Prime & Bond 2.1 (DeTrey Dentsply, Dreieich, Germany) | Etch-and-rinse | |||||||
| Syntac (Vivadent, Schaan, Leichtenstein) | Etch-and-rinse | |||||||
| Bulucu et al. a | Prime & Bond NT (Dentsply/Caulk, Milford, DE, USA) | Etch-and-rinse | 0 | FRT | Co-60 photons (Theratronics, Theratron 780 C, Ontario, Canada) | Before and after | SBS | Dentin |
| Clearfil SE Bond (Kuraray Medical, Osaka, Japan) | Self-etch | 60 | NR | |||||
| Aggarwal a | All bond 2 system (Bisco) | Etch-and-rinse | 0 | FRT | X-rays with tube voltage 120 kVp, tube current 5 mA | Before and after | PO | Dentin |
| 60 | ||||||||
| Biscaro et al. a | Single Bond 2 | Etch-and-rinse | 0 | NFRT | Linear accelerator Clinac 6/100; (Varian Medical Systems; Palo Alto, CA, USA) | Before | μSBS | Dentin |
| (3M ESPE; St. Paul, MN, USA) | 5 | X-ray | ||||||
| Clearfil SE Bond (Kuraray—Osaka, Japan) | Self-etch | 35 | ||||||
| Adper Prompt (3M ESPE) | Self-etch | 70 | ||||||
| Dibo da Cruz et al. a | Etch-and-rinse | 0 | NFRT | Clinac 600 linear accelerator (Varian Medical Systems, Palo Alto, CA, USA) | Before | μSBS | Dentin | |
| Adper Single Bond Plus (3M/ESPE, Dental products, St. Paul, MN, USA) | 70 | X-ray | ||||||
| Clearfil SE Bond (Kuraray, Kurashiki, Japan) | Self-etch | |||||||
| Adper Prompt Self-Etch (3M/ESPE, Dental Products, St. Paul, MN, USA) | Self-etch | |||||||
| Naves et al. a | Adper Single Bond 2 (3M ESPE, St, Paul, MN, USA) | Etch-and-rinse | 0 | FRT | Theratron, Phoenix 60 cobalt radiotherapy treatment unit (Theratronics International, Ltd., Atomic Energy of Canada, Ltd., AECL Medical, Ottawa, ON, Canada) | Before and after | μTBS | Enamel and dentin |
| 60 | Gamma | |||||||
| Yadav and Yadav a | Single Bond (3M ESPE) | Etch-and-rinse | 0 | FRT | Low linear energy transfer (LET) | Before | μTBS | Dentin |
| 60 | X-ray | During | ||||||
| After | ||||||||
| Santin et al. a | Transbond XT primer bonding agent (3M Unitek, Monrovia, Calif) | Etch-and-rinse | 0 | FRT | RS 2000 (Rad Source Technologies, Suwanee, Ga) | After | μSBS | Enamel |
| 60 | X-ray | |||||||
| da Cunha et al. a | Adper Single Bond 2 (3M ESPE; Sumaré, SP, Brazil) | Etch-and-rinse | 0 | NFRT | Linear accelerator Mevatron MX2 6mV (Siemens Healthcare; Erlangen, Germany) | After | μSBS | Enamel and dentin |
| Universal Single Bond (3M ESPE; St. Paul, MN, USA) | Universal adhesive | 20 | X-ray | |||||
| 40 | ||||||||
| 70 | ||||||||
| Galetti et al. b | Single Bond 2 (3M ESPE, St. Paul, USA) | Etch-and-rinse | HNCP who received more than 60 Gy | FRT | NR | After | μTBS | Dentin |
| Easy Bond (3M ESPE, St. Paul, USA) | Self-etch | |||||||
| Clearfil SE Bond (Kuraray Noritake Dental Inc., Tokyo, Japan) | Self-etch | |||||||
| Bernard et al. b | Optibond FL (Kerr France, Créteil, France) | Etch-and-rinse | HNCP who received more than 50 Gy | FRT | NR | After | μTBS | Dentin |
| Optibond XTR | Self-etch | |||||||
| (Kerr France, Créteil, France) | ||||||||
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