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Authors are the souls of any journal, and deserve much respect. To publish a journal manuscripts are needed from authors. Authors have a great responsibility for producing facts of their work in terms of number and results truthfully and an individual honesty is expected from authors in this regards. Both ways its true "No authors-No manuscripts-No journals" and "No journals–No manuscripts–No authors". Reviewing a manuscript is also a very responsible and important task of any peer-reviewed journal and to be taken seriously. It needs knowledge on the subject, sincerity, honesty and determination. Although the process of reviewing a manuscript is a time consuming task butit is expected to give one's best remarks within the time frame of the journal.
Salient features of the JCDR: It is a biomedical, multidisciplinary (including all medical and dental specialities), e-journal, with wide scope and extensive author support. At the same time, a free text of manuscript is available in HTML and PDF format. There is fast growing authorship and readership with JCDR as this can be judged by the number of articles published in it i e; in Feb 2007 of its first issue, it contained 5 articles only, and now in its recent volume published in April 2011, it contained 67 manuscripts. This e-journal is fulfilling the commitments and objectives sincerely, (as stated by Editor-in-chief in his preface to first edition) i e; to encourage physicians through the internet, especially from the developing countries who witness a spectrum of disease and acquire a wealth of knowledge to publish their experiences to benefit the medical community in patients care. I also feel that many of us have work of substance, newer ideas, adequate clinical materials but poor in medical writing and hesitation to submit the work and need help. JCDR provides authors help in this regards.
Timely publication of journal: Publication of manuscripts and bringing out the issue in time is one of the positive aspects of JCDR and is possible with strong support team in terms of peer reviewers, proof reading, language check, computer operators, etc. This is one of the great reasons for authors to submit their work with JCDR. Another best part of JCDR is "Online first Publications" facilities available for the authors. This facility not only provides the prompt publications of the manuscripts but at the same time also early availability of the manuscripts for the readers.
Indexation and online availability: Indexation transforms the journal in some sense from its local ownership to the worldwide professional community and to the public.JCDR is indexed with Embase & EMbiology, Google Scholar, Index Copernicus, Chemical Abstracts Service, Journal seek Database, Indian Science Abstracts, to name few of them. Manuscriptspublished in JCDR are available on major search engines ie; google, yahoo, msn.
In the era of fast growing newer technologies, and in computer and internet friendly environment the manuscripts preparation, submission, review, revision, etc and all can be done and checked with a click from all corer of the world, at any time. Of course there is always a scope for improvement in every field and none is perfect. To progress, one needs to identify the areas of one's weakness and to strengthen them.
It is well said that "happy beginning is half done" and it fits perfectly with JCDR. It has grown considerably and I feel it has already grown up from its infancy to adolescence, achieving the status of standard online e-journal form Indian continent since its inception in Feb 2007. This had been made possible due to the efforts and the hard work put in it. The way the JCDR is improving with every new volume, with good quality original manuscripts, makes it a quality journal for readers. I must thank and congratulate Dr Hemant Jain, Editor-in-Chief JCDR and his team for their sincere efforts, dedication, and determination for making JCDR a fast growing journal.
Every one of us: authors, reviewers, editors, and publisher are responsible for enhancing the stature of the journal. I wish for a great success for JCDR."
Thanking you
With sincere regards
Dr. Rajendra Kumar Ghritlaharey, M.S., M. Ch., FAIS
Associate Professor,
Department of Paediatric Surgery, Gandhi Medical College & Associated
Kamla Nehru & Hamidia Hospitals Bhopal, Madhya Pradesh 462 001 (India)
E-mail: drrajendrak1@rediffmail.com
On May 11,2011
Dr. Shankar P.R.
"On looking back through my Gmail archives after being requested by the journal to write a short editorial about my experiences of publishing with the Journal of Clinical and Diagnostic Research (JCDR), I came across an e-mail from Dr. Hemant Jain, Editor, in March 2007, which introduced the new electronic journal. The main features of the journal which were outlined in the e-mail were extensive author support, cash rewards, the peer review process, and other salient features of the journal.
Over a span of over four years, we (I and my colleagues) have published around 25 articles in the journal. In this editorial, I plan to briefly discuss my experiences of publishing with JCDR and the strengths of the journal and to finally address the areas for improvement.
My experiences of publishing with JCDR: Overall, my experiences of publishing withJCDR have been positive. The best point about the journal is that it responds to queries from the author. This may seem to be simple and not too much to ask for, but unfortunately, many journals in the subcontinent and from many developing countries do not respond or they respond with a long delay to the queries from the authors 1. The reasons could be many, including lack of optimal secretarial and other support. Another problem with many journals is the slowness of the review process. Editorial processing and peer review can take anywhere between a year to two years with some journals. Also, some journals do not keep the contributors informed about the progress of the review process. Due to the long review process, the articles can lose their relevance and topicality. A major benefit with JCDR is the timeliness and promptness of its response. In Dr Jain's e-mail which was sent to me in 2007, before the introduction of the Pre-publishing system, he had stated that he had received my submission and that he would get back to me within seven days and he did!
Most of the manuscripts are published within 3 to 4 months of their submission if they are found to be suitable after the review process. JCDR is published bimonthly and the accepted articles were usually published in the next issue. Recently, due to the increased volume of the submissions, the review process has become slower and it ?? Section can take from 4 to 6 months for the articles to be reviewed. The journal has an extensive author support system and it has recently introduced a paid expedited review process. The journal also mentions the average time for processing the manuscript under different submission systems - regular submission and expedited review.
Strengths of the journal: The journal has an online first facility in which the accepted manuscripts may be published on the website before being included in a regular issue of the journal. This cuts down the time between their acceptance and the publication. The journal is indexed in many databases, though not in PubMed. The editorial board should now take steps to index the journal in PubMed. The journal has a system of notifying readers through e-mail when a new issue is released. Also, the articles are available in both the HTML and the PDF formats. I especially like the new and colorful page format of the journal. Also, the access statistics of the articles are available. The prepublication and the manuscript tracking system are also helpful for the authors.
Areas for improvement: In certain cases, I felt that the peer review process of the manuscripts was not up to international standards and that it should be strengthened. Also, the number of manuscripts in an issue is high and it may be difficult for readers to go through all of them. The journal can consider tightening of the peer review process and increasing the quality standards for the acceptance of the manuscripts. I faced occasional problems with the online manuscript submission (Pre-publishing) system, which have to be addressed.
Overall, the publishing process with JCDR has been smooth, quick and relatively hassle free and I can recommend other authors to consider the journal as an outlet for their work."
Dr. P. Ravi Shankar
KIST Medical College, P.O. Box 14142, Kathmandu, Nepal.
E-mail: ravi.dr.shankar@gmail.com
On April 2011 Anuradha
Dear team JCDR, I would like to thank you for the very professional and polite service provided by everyone at JCDR. While i have been in the field of writing and editing for sometime, this has been my first attempt in publishing a scientific paper.Thank you for hand-holding me through the process.
Dr. Anuradha
E-mail: anuradha2nittur@gmail.com
On Jan 2020
Original article / research
Full Version
A Three-dimensional Finite Element Analysis of Effect of Abutment Materials on Stress Distribution around Peri-implant Bone in Immediate and Delayed Loading Conditions
Correspondence Address :
Dr. Saumya Agarwal,
Postgraduate Trainee, Department of Prosthodontics and Crown and Bridge, Subharti Dental College, Meerut, Uttar Pradesh, India.
E-mail: saumya.aga13@gmail.com
Introduction: Osseointegration is important for successful dental implant treatments. Abutment materials affect the load transfer to the implant and surrounding bone thus determining the long term implant survival.
Aim: To perform stress analysis around peri-implant hard tissue with different abutment materials and their comparative evaluation in immediate and delayed loading conditions using finite element analysis.
Materials and Methods: An in-vitro experimental study was carried out at Department of Prosthodontics at Subharti Dental College Meerut, Uttar Pradesh in December 2021. on a root form titanium grade IV Implant, assembled with an abutment Ø4.0-0.5GH and this test model was three-dimensional (3D) scanned, reconstructed on computer-aided design software CREO. Six abutment groups: group 1- zirconia with Delayed Loading (DL), group 2- Polyether Ether Ketone (PEEK) with DL, group 3- Titanium grade Extra Low Interstitial (ELI) with DL, group 4- zirconia with Immediate Loading (IL), group 5- PEEK with IL, group 6- titanium grade ELI with IL, were loaded from vertical, horizontal and oblique direction. Von Mises and principal stress analysis was done on the implant and the peri-implant bone using the finite element method and the statistical analysis was done.
Results: For delayed loading group, highest stresses were generated in group 1 (462.88 MPa), followed by group 3 (413.72 MPa) and least in group 2 (319.38 MPa). For immediate loading, highest to lowest stresses were in group 4 (694.32 MPa), group 6 (620.58 MPa) and group 5 (479.07 MPa). The principal stress analysis showed significant difference between all groups in cancellous bone and cortical bone except between titanium and customised zirconia abutment in cortical bone in delayed loading (p=0.0846) and in immediate loading (p=0.1125).
Conclusion: Change in abutment materials significantly affects the stress generated in and around the implant thus more studies must be carried out to reach a consensus on the most optimal material encouraging least dissipation in peri-implant hard tissues.
Polyether ether ketone, Titanium, Zirconia
With the development of osseointegrated dental implants, a new era for oral rehabilitation began. Clinicians and researchers all over the world are interested in the high success rate and long term follow-up (over 20 years) of patients treated with osseointegrated dental implants (1). The existence of osseointegration is critical for successful dental implant treatments. Two procedures are included in Branemark’s protocol. The implant is put and submerged under a hermetically sutured mucosa in the first stage to allow for normal healing without the risk of bacteremia in the absence of any functional stimulation. The implant is then exposed, an abutment is affixed, and a restoration is placed on the abutment if osseointegration has happened (2). A one step surgical approach was developed to avoid the significant psychological, cosmetic, and functional handicaps associated with the four to six month healing period. Non submerged implants are used in this approach, and loading normally begins earlier than in Branemark techniques. Immediate loading is the term for this method (3). Progressive loading refers to the process of gradually loading an implant from one transition stage to the next in order to reduce the risk of early failure or marginal bone loss (3),(4),(5). At the start of prosthodontic treatments, progressive or gradual bone loading is critical, especially in less dense bone types. The implant’s gradual loading allows the bone to remodel and arrange in line with Wolff’s law, which stipulates that trabecular bone places and displaces itself in predictable patterns (6).
Digitalisation has introduced increasingly useful tools for the development of newer materials to achieve better clinical results in the biomedical sciences. Finite Element Analysis (FEA) is an engineering method to solve complicated mechanical problems by simulation of force upon a constructed or a scanned model (1),(2).
Past three decades have extensively employed FEA to evaluate the stresses acting upon the implant fixture and the peri-implant bone tissue. Successful dental implant therapy depends upon optimum load transfer from different directions to the surrounding bone. Key factors that influence it are:
1) Implant bone interface
2) Dimensions
3) Surface characteristics
4) Prosthetic design (1).
Various authors have evaluated the role of different abutment materials in the load transfer to the implant and surrounding bone in order to determine the most favourable material for the purpose of long-term implant survival (2),(3),(4),(5). Although a critical variable to these simulations must be the bone implant interface, most FEA models assume optimal osseointegration which does not necessarily occur in every clinical situation (5). With the world radically shifting towards immediate loading protocols, the imperfect bond between implant surface and the surrounding bone also must be evaluated. Consequently, the most favourable abutment choice and their relationship with the developing peri-implant stresses can be determined by calculated FEA simulations (7). The current study was done to address a more specific situation i.e., the behaviour of the different abutment materials in immediate and delayed loading separately which has not been evaluated so far. This will differentiate the preferred abutment material in specific loading condition.
The objective of the present study was the analysis of von Mises, maximum and minimum principal stress pattern in peri-implant bone, before and after osseointegration. Also, to ascertain the most suitable material under different loading conditions. The null hypothesis was:
(a) There is no difference in von Mises stress patterns produced by titanium, zirconia and PEEK in delayed and immediate loading conditions.
(b) There is no difference in maximum and minimum principal stress patterns produced by titanium, zirconia and PEEK in delayed and immediate loading conditions.
This in-vitro experimental study was carried out in the Department of Prosthodontics at Subharti Dental College Meerut, Uttar Pradesh in December 2021. In the preliminary step a root form Titanium grade IV Implant Ø 4.0-11.5L (Osstem TSIII SA fixture) was assembled with an abutment Ø4.0-0.5GH (Osstem Free Form ST) and this test model was 3D scanned using a 3D scanner (Artec Eva Lite [Table/Fig-1,2]. Preprocessing was done by generation of the 3D CAD model using CREO software. Thereafter the CAD model was imported into Ansys/Creo parametric Design Modeler.
To simulate biological entities the material properties were assigned to each part of the digitally reconstructed model of bone from reviewed literature (5),(7),(8),(9). Material properties of implant and the different abutment materials were sequentially entered to simulate their mechanical and biologic behaviour (Table/Fig 3) (5),(7),(8),(9). The bone was modelled as a cancellous core surrounded by a 1Â mm thick cortical bone layer. It was 18 mm in height, 16 mm in buccolingual width, and 20 mm in mesiodistal length (9).
Study Procedure
Both cortical and cancellous bone were treated as homogeneous, isotropic and linearly elastic materials (10). The implants were loaded statically under two conditions: before osseointegration (i.e., frictional interface between bone and implant) and after osseointegration (i.e., non frictional interface) (i.e., fully bonded interface between implant and bone). Stress and strain distributions were computed along the length of the bone implant contact (11). To obtain initial stability for the situation of immediate loading after implantation, it was modelled using non linear frictional contact elements, which allowed minor displacements between implant and bone. Under these conditions, the contact zone transfers pressure and tangential forces (i.e., friction), but no tension. The friction coefficient was set to 0.3 (11).
After assigning the material properties and defining load, meshing was verified before running the final analysis (Table/Fig 4). A total of 36529 elements and 7487 nodes were created (Table/Fig 5).
In each model, the implants were loaded as:
• Vertically in the top centre of abutment (200 N) (5).
• Obliquely at 300 from vertical from buccal aspect - (100 N) (5).
• Horizontally in buccolingual direction- (50N) (12).
The test models were divided into the six groups (Table/Fig 6).
The stress distribution in the implant and abutments was evaluated through the von Mises stress analysis, and the stress distribution in the peripheral bone was examined through the maximum and minimum principal stress analysis (Table/Fig 7) (5). After collecting the data, results were tabulated, statistically analysed and compared (Table/Fig 8),(Table/Fig 9).
Statistical Analysis
The results obtained were compiled, tabulated and subjected to z-test double sample proportion test for comparison between groups. For this purpose, Statistical Package for the Social Sciences (SPSS) software, version 24 was used on a computer (Windows (x86-64)). According to the study objectives, separate analysis of results was done in delayed loading and in immediate loading for all abutments in pairs and the p value was obtained for each pair by calculating the differences in the stress values among them. The same procedure was followed to evaluate both von Mises stresses in implant body and the principal stresses in peri-implant hard tissues. Another dimension to the study was added by obtaining the difference and significance of the same abutment material by comparing them in immediate and delayed loading.
The result of von Mises analysis showed the highest generated stresses in the customised zirconia abutment assembly (462.88 MPa) in the delayed loading condition, followed by titanium grade ELI (413.72Â MPa) abutment assembly and least in PEEK (319.38 MPa) customised abutment assembly (Table/Fig 10).
Similar results of stress patterns were obtained for the immediate loading condition where PEEK abutment transferred the lowest stress values in the fixture (Table/Fig 11). Highest stresses were generated in group 4 i.e. customised zirconia abutment assembly (694.32 MPa), followed by group 6 i.e., titanium grade ELI abutment assembly (620.58 MPa) and least in group 5 i.e., PEEK customised abutment assembly (479.07 MPa). The statistics for von Mises obtained according to z-test (double sample proportion test) showed a significant difference in all assemblies to reject the null hypothesis except when comparison was done between titanium grade ELI (abutment) and zirconia customised abutment which showed a non significant (p=0.0811 in DL and p=0.0618 in IL) difference among the two (Table/Fig 12).
The results of the maximum and minimum principal stress in cortical and cancellous bones showed varied values. For delayed loading, According to the results, in the cortical bone highest maximum and minimum stress values were obtained in group 2 i.e., PEEK customised abutment with titanium implant, followed by group 3 i.e., titanium grade ELI abutment and least value in group 1 i.e., zirconia customised abutment assembly. In the cancellous bone highest maximum and minimum stress values were obtained in group 1 followed by group 3 and least value in group 2 (Table/Fig 13).
In immediate loading, in the cortical bone highest maximum and minimum stress values were obtained in group 5 i.e., PEEK customised abutment with titanium implant. However, in the cancellous bone highest maximum and minimum stress values were obtained in group 4 followed by group 6 and least value in group 5 (Table/Fig 14).
The pairs of different assemblies in both cortical and cancellous bone in delayed loading condition were analysed for their maximum and minimum principal stress values (Table/Fig 15). There was no significant difference between group 1 and group 3 for the maximum principal stresses in cortical bone (p=0.0846). All other groups showed significant difference among them for the maximum and minimum principal stress generated in both cortical and cancellous bone.
Similar results were obtained for the immediate loading condition. There was no significant difference between group 4 (zirconia customised abutment in IL) and group 6 (titanium grade eli abutment in IL) for the maximum principal stresses in cortical bone. All other groups showed significant difference among them for the maximum and minimum principal stress generated in cortical and cancellous bone (Table/Fig 16).
It was observed that when individual abutments were compared in immediate and delayed loading conditions there was significant difference achieved for the von Mises values. The results are tabulated in (Table/Fig 17). On the contrary, the compressive and tensile stresses in the peripheral bone tissue was mostly non significant in the two loading conditions. As per the results of z-test, the stress in cortical bone for maximum principal stress in the PEEK abutment assembly had significantly higher stress dissipation during immediate loading. All other groups had no significant difference (Table/Fig 18).
In comparison to Two Dimensional (2D) models, a 3D FEA is an effective technique for standardising these characteristics and obtaining a consistent outcome (1). The geometry, quantity, length, diameter, and angulations of implants, as well as the position of the implant(s) in the arch, all influence load distribution on implants, according to Sahin S et al., (13).
The outcomes of the current study indicate that the implant abutment assembly of the exact dimensions embed in a homogenous bony structure and subjected to similar forces will create a unique spectrum of stress with a change in abutment material. Also, the same assemblies will exert more stress in the implant and surrounding bone in immediate loading of the implants (incomplete osseointegration) compared to the delayed loading (assuming complete osseointegration has occurred).
Çaglar A et al., concluded that zirconia implant produced the lowest stresses in both the implant and the cortical bone, while values of von Mises and compressive stresses were lower in zirconia abutment than the titanium abutment (14). Linkevicius T et al., carried out a systematic review in which data for titanium versus aluminium oxide showed no statistically significant differences in crestal bone loss (3). Lastly, human histological data indicated better reaction of zirconium than titanium but no controlled studies tested zirconium oxide abutments to titanium abutments. This FEA study tested both types in a controlled in-vitro simulation and established better reaction of zirconia abutments to peri-implant health.
El-anwar MI et al., stated there was no significant effect over stress and deformation values in cortical and spongy bone (2). The FEA results showed that the crown and implant receive lesser stress in order of decreasing abutment rigidity from alumina (530.67 MPa), zirconium (561.71 MPa) and titanium (624.83 MPa). This can be attributed to the fact that total stress and deformation increase upon the implant as the abutment material stiffness increases. A similar trend was observed in the current study, with increased abutment material rigidity, there was increased energy absorption in the implant material.
Kapoor S et al., in their study, applied 178N unidirectional axial and oblique stresses on angulated titanium and zirconia abutments (FEA) (15). The implant and adjacent bone were less stressed by zirconia abutments than by titanium abutments. The stress observed in the cortical bone was higher than that recorded in the cancellous bone. As a result, higher modulus of elasticity zirconia abutments will absorb more load and transmit less stress to the implant and peri-implant bone as is analogous to current study. Another study revealed, titanium and carbon fibre reinforced PEEK implants with angled abutments had a detrimental effect on bone as they generated more stresses under parafunctional loading and hence should be avoided (10). The biomechanical performance of one piece zirconia dental implant abutments in the peri-implant bone is superior to that of others. It distributes the applied load more efficiently, has a more homogenous stress distribution, and has less deformation than other materials as concluded by Shash M et al., (16).
Li ZY et al., observed that at 6,12,18, and 24 months following restoration, neither ceramic nor titanium abutments had a detrimental effect on peri-implant tissue (17). According to Kaleli N et al., stress values of zirconia customized abutments were higher than those of PEEK customized abutments. Changes in customized abutment material and restoration had minimal effect on distribution of stress in the peripheral bone and implant, according to their findings. It was observed, in comparison to most ceramic materials, resin matrix ceramics have a low elastic modulus (5). This dissimilarity may emerge as the restorative crown, cement layer, inner screw, and abutment are all involved in conveying masticatory stresses to implants and peripheral bone and these factors were not considered in the current study (5). Although, the zirconia abutments reduced the stress in implant body in both studies. Tretto PH et al., concluded that implants made of materials having a lower elastic modulus resulted in higher stress and strain in peri-implant bone tissue i.e., for PEEK and reinforced fibreglass composite (18). They also had a larger stress concentration in the implants.
A von Mises stress value should not exceed 550 MPa which is the yield strength of a titanium implant, as failure may occur if this value is exceeded (19). The highest value obtained as per this study was using zirconia abutment in the immediate loading group i.e., 694. 32 MPa which would lead to imminent failure. While in the delayed loading conditions all the values were within the acceptable range with PEEK emerging as the most conducive material.
Recently the use of PEEK as an implant material, framework material and as abutment has captured popular interest. Its compatible elastic modulus seems to reduce the stresses incurred on the peripheral bone (20). The titanium abutments are the most frequently used abutment choice for its safe load transfer and excellent biocompatibility (2). Least conducive material for immediate loading as an abutment material is zirconia which largely exceeds the maximum bearable stress generated in the implant as per the current study (19). Although it can be safely used after optimal osseointegration of the implant. No studies have compared the difference in stresses generated with these abutment groups for immediate and delayed loading. The immediate loading produces larger stresses affecting the longevity of the implant treatment. PEEK abutment produced significantly higher stress in cortical bone compared to titanium and zirconia. Titanium and zirconia did not show and significant difference when compared to each other for maximum principal stress in cortical bone in both immediate and delayed loading conditions. More studies are needed for evaluation of most favourable material.
Limitation(s)
Limitations of the present study include the static loading of the FEA models was not compared to a dynamic model with a range of elastic moduli for the fixture (1). The consequences of dynamic loading should be investigated further. Bone model was assumed to be homogeneous and isotropic that differs from reality.
Within the limitations of this study, it can be concluded that a change in abutment material does affect the stress generated in the implant and the peri-implant tissue. PEEK abutment showed significantly less von Mises stress in the implant body when compared to titanium and zirconia in both delayed and immediate loading condition. There was no superiority of one abutment material over another in terms of stress distribution on bone since PEEK was more optimal for cancellous bone and zirconia for cortical bone in both delayed and immediate loading conditions. All materials produced more stress on implant upon immediate loading, although the stress produced on bone were not significantly different in two loading conditions except for maximum principal stress in PEEK.
More research is needed to obtain a consensus on the most optimal abutment material for minimising stress in the implant body and peri-implant hard tissues. The pattern of stress transfer around different abutment materials must also be considered for future studies to explore the most favourable abutment for specific clinical situation.
DOI: 10.7860/JCDR/2022/55199.16523
Date of Submission: Jan 28, 2022
Date of Peer Review: Feb 16, 2022
Date of Acceptance: Apr 05, 2022
Date of Publishing: Jun 01, 2022
AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? Yes
• For any images presented appropriate consent has been obtained from the subjects. NA
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