To evaluate the effect of anodized dental implant surface on cumulative implant survival and success. A systematic review and meta-analysis

Abstract

Background:

There have been certain apprehensions regarding the use of surface-modified dental implants due to peri-implant infection and crestal bone loss over the years. Thus, this review aims to evaluate the long-term effect of anodized implant surface on cumulative implant survival (CSR) and success rates in relation to marginal bone loss (MBL).

Materials and Methods:

Systematic electronic search was done using two databases, PubMed and Embase to assess the potentially relevant records from January 2008 to October 2019. Publications reporting cumulative survival and success rates with anodized dental implants were identified. Screening for duplicate articles and extraction of data was carried out to formulate evidence tables. Meta-analysis was conducted following PRISMA guidelines.

Results:

Out of 217 observational clinical studies, 8 studies were selected based on predefined selection criteria. The summary estimate for the included studies for CSR was reported as 0.98 (95% confidence interval [CI]: 0.96; 0.99). The heterogeneity (I² = 37.3%) among these studies was found to be statistically nonsignificant (P = 0.1314). The mean values of MBL after the implant insertion were 0.84 mm at 0–1 year and 1.05mm by the end of follow-up period. This data were provided by five studies only. The mean difference of the analyzed studies came out to be 0.49 mm with a 95% CI (−0.22; 1.19). The heterogeneity (I² = 97%) for these studies was statistically significant with P < 0.01.

Conclusion:

The anodized dental implants have demonstrated long-term survival and success rates in terms of clinical outcomes.

INTRODUCTION

The achievable goal of modern dentistry is restoration and replacement of missing teeth in a functionally acceptable and esthetic manner. The rehabilitation of partially and completely edentulous patients with dental implants is a widely accepted and well-documented treatment protocol, which has become an indispensable part of today’s dentistry. Implant dentistry is unique in the fact that it has the ability to achieve the ideal restorative goal irrespective of the atrophy, disease, or injury of the stomatognathic system.[1] The use of implants in dentistry got recognized only after pioneer works conducted by Branemark in late 1969 on the concept of Osseointegration.[2] Osseointegration was defined as “A direct structural and functional connection between the ordered, living bone and the surface of a load-carrying implant without an intervening connective tissue layer”.[2] Bone to implant contact (BIC) is a key criterion, as it is the implant surface that has to be in direct contact with the vital bone for successful osseointegration, thus resulting in long-term success and survival of dental implants.[3] BIC may be affected by the factors such as surface texture and roughness, surface chemistry, wettability, and surface energy.[4]

Surface topography describes the various macroscopic and microscopic features of the dental implant surface. Surface modification of dental implants may be performed by diverse methodologies such as mechanical methods, physical methods, and chemical methods. Physical methods for surface modifications of dental implants are plasma spraying, sputtering, and ion deposition; these methods improve biological activity and mechanical properties, which include wear and corrosion resistance. Mechanical methods include techniques such as machining, polishing, and blasting which result in smooth or rough surfaces to enhance cell adhesion, proliferation, and differentiation.[3] Implant surfaces can also be modified by chemical agents such as acids or alkali, sol-gel treatment, chemical vapor deposition, and anodization. These modifications of Titanium (Ti) have been found to alter surface roughness and composition, improve wettability and surface energy of Ti implant surface.[5]

Implant surface roughness can be grouped as Macro roughness, Micro roughness, and Nano roughness. There are various studies depicting the effect of macro and micro-roughness on cells and tissues, mainly osteoblasts.[6,7,8,9,10] Nano meter-sized roughness can have influence on cell proliferation, cell migration, and differentiation. Grit blasting acid etching and anodization are commonly used methods for modifying Nano surface roughness.[11]

Anodized dental implants were first introduced in the year 2000 by the name TiUnite, by the Nobel Biocare, Sweden.[12] Anodized dental implants have also been described in the literature as Ti porous oxide, or anodized Ti surfaces implant.[13,14] Anodic oxidation creates a unique nanometric scale topography to withstand the shear forces by enabling bone apposition, thus maintaining an adequate BIC. It increases the thickness and roughness of Ti oxide layer from 17–200 nm as in conventional Ti implants to 600–1000nm. It also results in surface with micropores having a pore size of about 1.3–2.0 mm² and a moderate degree of surface roughness.[15] These implant surfaces have shown to promote cell adhesion, cell proliferation, and extracellular matrix deposition by human gingival fibroblasts. A further added advantage is that anodized implants do not facilitate enhanced biofilm formation despite increased surface roughness.[16]

To, the best of our knowledge, no meta-analysis has been carried out on both retrospective and prospective observational clinical studies, to assess the long-term success and survival of anodized dental implants. The current systematic review and meta-analysis were designed to evaluate the effect of anodized dental implant surface on Cumulative Implant survival (CSR) and success rates in relation to marginal bone loss (MBL).

MATERIALS AND METHODS

Search strategy

Three authors independently searched the data in the following databases, PubMed and EMBASE including all studies published from January 2008 to October 2019 by framing a search strategy [Appendix 1]. Extensive manual search was also conducted for appropriate literature in various dental journals.

Study selection

Literature published from January 2008 to October 2019 was included in the present study. In view of the recent data on the effect of anodized surface on implant survival and success, these trials were filtered from January 2008 to October 2019. The literature search was confined to the English language only. The study strategy was formulated using the Participants, Intervention, Comparators, and Outcomes criteria.

• P-Healthy patients where dental implants were placed.

• I-Surface modified Ti dental implants (Anodized implants)

• C-No comparator (Because the review intended to evaluate the cumulative implant survival and success rates on anodized implant surfaces.)

• O- Cumulative implant survival rate (CSR %) and success rate, relative to MBL for more than 5 years.

Implant survival is defined as, when the “implant is in function and stable with no evidence of peri-implant radiolucency and no suppuration or pain at the implant site or ongoing pathologic processes.”[17] Accordingly, implant success is defined as, in addition to the criteria for implant survival, “the MBL around the implant must not exceed a value of 1.5 mm during the 1^st year of implant placement and 0.2 mm yearly thereafter.”[17]

Registry protocol

The current study was registered with the “International Prospective Register of Systematic Reviews (PROSPERO)” an open assess database for systematic review under the registration number-CRD42019131672.

Inclusion and exclusion criteria

Human clinical studies (prospective or retrospective) with a minimum of 50 oxidized dental implants placed and their follow-up of more than or equal to 5 years were considered. In terms of outcome variables, studies assessing cumulative survival rate and MBL around the placed implants, and those published in dental internationally peer-reviewed journals in English language only were included. In vitro studies, animal studies, studies reporting incomplete data, case reports, randomized control trials, articles having a follow-up period of <5 years, studies with implant surface other than anodized surface, studies assessing histological outcomes, and studies published in language other than English only were excluded.

Extraction of data

Three authors independently screened all the included prospective and retrospective studies extracting the relevant data from each of the studies based on inclusion and exclusion criteria. Characteristics that were extracted from each article were, (1) last name of the first author (2) publication year (3) Design of study (4) Total number of patients involved (5) Total number of implants placed (6) Follow-up time (7) Failed implants (8) Cumulative survival rate in percentage (9) MBL in millimeters.

Quality assessment

For assessing the quality and risk of bias in this single-arm study a “Modified version of the Newcastle Ottawa Scale” was applied.[18] Originally, an 8-point scale, from which the questions pertaining to the control groups were not included in the questionnaire. The first two questions were designed to evaluate the selection of the study population, whereas the remaining three questions assessed the outcome quality of the studies. The following study aspects were evaluated such as the adequacy of case definition, representativeness of the cases, ascertainment of the exposure, the methodology of ascertainment of exposure for the cases and the nonresponse rate. As per the modification, a score of three or less was regarded as poor quality for single-arm study.

Data analysis

The analysis was done by using Metapackage in R programming v 3.5.1. To analyze the summary effect as pooled proportion of cumulative survival rate and mean difference of the studies for MBL at 95% confidence interval (CI), a forest plot was drawn for each of the outcome variables. To identify the possibility of publication bias among the included studies in the meta-analysis, funnel plot was drawn to represent both CSR and MBL. For exploring heterogeneity, Cochran Q and I² statistics were employed. I² statistics define the variation across the studies due to heterogeneity in terms of percentage, Tau2 quantifies the amount of heterogeneity present in the data.[19]

RESULTS

Study selection

The search strategy resulted in 217 potentially relevant papers from PubMed database, Embase, and manual search. Total articles after the elimination of duplicates were 110. These articles were later curtailed to 30 during initial screening, as the rest were animal studies, in vitro trials, randomized controlled trials (RCTs), case reports, and histological studies. Out of these 30 full-text articles, 22 studies were excluded as 12 studies had different implant surfaces and 10 had a follow-up of <5 years. After complete assessment, 8 articles fulfilled all the inclusion criteria for the analysis of the data. A detailed illustration of literature search has been outlined as a PRISMA Flowchart Moher et al. [Figure 1].[20]

Figure 1.

Flowchart illustrating different phases of a systematic review. RCT – Randomized control trails

Study characteristics

Out of the 8 studies which were included in this meta-analysis, 6 studies were described as prospective and 2 studies as retrospective. The duration of studies ranged from 5 years to 11 years. All the studies depicting case groups were combined for assessing the proportion of survival rate and success rate in terms of MBL, among the anodized implants placed in predominantly healthy sites.

The studies included 1756 implants ranging from 54 to 817 with a median of 112 placed in both maxilla and mandible, of which 52 implants failed during the follow-up period of 5–11 years. The number of patients varied from 22 to 490 with a median of 51. The age of subjects included in studies ranged from 20 years to 77 years. All the studies included anodized Ti-Unite implants. The number of the left to follow up (LFTU) patients was in a range of zero patients to 167 patients with a median of 10. The data for LFTU were categorized as deceased patients, patients moved to other places, and inactive patients who did not respond after contacting twice. Mean bone loss from implant insertion until complete follow-up was in the range of 0.13 mm (standared deviation [SD] 0.17) to 1.93 mm (SD 0.4). Detailed study characteristics are described in Tables 1 and 2.

Table 1.

Study characteristics of all the included studies for cumulative survival rate

Last name of first author, year of publication	Type of study	Purpose of study	Implant surfaces	Number of patients	Age range of patients (years)	Follow up time (years)	Total number of implants	Number of Successful Implants	Number of failed implants	CSR (%)	LFTU patients
Mura, 2012[21]	Retrospective	5 years clinical and radiological outcome of patients treated with replace select tapered Ti Unite implants	Ti Unite surface	56	21-76	5	79	79	0	100	8
Glauser, 2013[22]	Prospective	To document 7 years outcome of immediately loaded implants exhibiting an oxidized surface	Moderately rough oxidized surface	38	19-77	7	102	99	3	97.10	6
Francetti et al., 2014[23]	Prospective	Assess long term clinical outcome and periimplant bone level changes around oxidized implants supporting partial fixed rehabilitation	Oxidized microtextured surface	22	-	6	54	56	1	97.60	3
Östman et al., 2012[24]	Prospective	To evaluate the survival rate, marginal bone loss, and soft tissue conditions at surface modified titanium implants	Oxidized implants	46	-	10	121	120	1	99.20	0
Degidi et al., 2012[25]	Prospective	To assess the 10 years performance of Ti Unite implant supporting fixed prosthesis placed with immediate loading approach	Ti Unite surface	59	31-69	10	210	10	5	97.33	-
Pettersson and Sennerby 2015[26]	Retrospective	5 years outcome of replace select tapered implants	Oxidized surface	88	53-77	5	271	270	1	99.60	37
Becker et al., 2013[27]	Prospective	To evaluate the implant survival rate and crestal bone changes for porous oxide coated implants (Ti Unite implants)	Ti Unite surface	490	17-87	10	817	783	38	95.70	167
Glauser, 2016[28]	Prospective	To document 11 years outcome of immediately loaded implants exhibiting an oxidized surface	Moderately rough oxidized surface	38	19-77	11	102	99	3	97.10	12

LFTU – Left to follow up; CSR – Cumulative implant survival

Table 2.

Study characteristics of all the included studies for marginal bone loss

Last name of first author, year of publication	Type of study	Purpose of study	Number of implants	Follow up time (years)	Mean bone loss from implant insertion till follow up (mm)	SD	Mean marginal bone remodelling at implant insertion (mm)	SD
Mura, 2012[21]	Retrospective	5 years clinical and radiological outcome of patients treated with replace select tapered Ti Unite implants	79	5	0.56	1.98	0.75	1.59
Glauser, 2013[22]	Prospective	To document 7 years outcome of immediately loaded implants exhibiting an oxidized surface	102	7	1.51	1	1.16	0.85
Francetti et al., 2014[23]	Prospective	Assess long term clinical outcome and periimplant bone level changes around oxidized implants supporting partial fixed rehabilitation	54	6	0.76	0.47	-	-
Östman et al., 2012[24]	Prospective	To evaluate the survival rate, marginal bone loss, and soft tissue conditions at surface modified titanium implants	121	10	0.7	1.35	0.4	1.06
Degidi et al., 2012[25]	Prospective	To assess the 10 years performance of Ti Unite implant supporting fixed prosthesis placed with immediate loading approach	210	10	1.93	0.4	0.56	0.21
Pettersson and Sennerby 2015[26]	Retrospective	5 years outcome of replace select tapered implants	271	5	1.74	1.49	-	-
Becker et al., 2013[27]	Prospective	To evaluate the implant survival rate and crestal bone changes for porous oxide coated implants (Ti Unite implants)	817	10	0.13	0.17	-	-
Glauser, 2016[28]	Prospective	To document 11 years outcome of immediately loaded implants exhibiting an oxidized surface	102	11	1.66.	0.98	1.16	0.85

SD – Standard deviation

Publication bias

To address the possible publication bias we used Funnel Plot asymmetry. Analysis of funnel plot showed slight asymmetry, suggesting a minimal risk of publication bias [Figure 2].

Figure 2.

Publication Bias of the selected studies, the dots represents the individual studies

Synthesis of result

Forest plot was drawn [Figure 3] for the included studies using a random effect model, which included 1756 implants of which 52 were lost. The pooled effect sizes of the included studies for CSR were reported as 98% (95% CI: 0.96–0.99). Q and I² statistics quantify the heterogeneity among the studies, which comes out to be statistically nonsignificant since P value is 0.1314, and I² was 37.3%. Of the 8 analyzed articles complete information about MBL at follow-up was provided by all the articles, while a comparison between MBL after implant insertion at 0–1 year up to follow-up time was provided by only five studies. A forest plot of these five studies was drawn by plotting mean and SD between 0–1 years and at follow-up using the random effect model [Figure 4]. The mean difference of the analyzed studies came out to be 0.49 mm with a 95% CI [−0.22; 1.19]. A high heterogeneity value of I² = 97% was found. Heterogeneity was statistically significant at P < 0.01. These results indicate a high survival and success rate for anodized implants placed at different sites in the maxilla and mandible.

Figure 3.

Forest Plot showing the summary estimate for the included studies for cumulative survival rate (CSR). CI – Confidence interval, I² – Degree of heterogeneity, P – Probability value, Ʈ² – Between study variance

Figure 4.

Forest plot for marginal bone level assessment at 0–1 years and follow up period. CI – Confidence interval, I² – Degree of heterogeneity, P – Probability value, SD – Standard deviation, MD – Mean difference, Ʈ² – Between study variance

DISCUSSION

The current meta-analysis evaluates prospective and retrospective clinical studies on anodized dental implants placed in healthy sites with a minimum of 5 years follow-up. The articles published in the English language assessing cumulative survival rate (CSR) and success rates in terms of MBL were considered. Studies on implants other than anodized surfaces, in vitro studies, animal studies, case reports, RCT’s and studies with unclear documentation of CSR and MBL were excluded from the analysis. Based on the pre-defined inclusion and exclusion criteria, the present meta-analysis was limited to 8 studies, which had well-documented data on CSR and MBL following the placement of anodized dental implants.

In our study, the most important criteria for the implant survival were analyzed and discussed as the cumulative survival rate (CSR) in percent varying from 95.7% to 100%. Of the 1756 implants that were placed in the healthy sites, 52 implants failed during the follow-up period of 5–11 years, resulting in a CSR of 98%. These findings are in accordance with the proposed criteria by Albrektsson et al., who proposed a success rate of 85% to be achieved at the end of 5 years observational period and 80% by the end of a 10 years follow up period.[17] Mura, in their 5 years retrospective study on clinical outcomes using replace select tapered Ti-Unite implants reported a cumulative survival rate (CSR) of 100% after 5 years of follow-up period. These implants were placed in post extraction socket which was followed by immediate loading.[21] In another 7 years follow-up study of immediately loaded implants with the oxidized surface, Glauser reported cumulative survival rate of 97.1%. The majority of these implants were placed in posterior regions (88%) and in the soft bone quality (76%). Neither any biological or technical complications were detected nor did the plaque samples showed any characteristic discrepancy between the teeth and the implants.[22]

The second parameter that was evaluated by researchers was the success rate in terms of MBL. Comparison between MBL at baseline (0–1 year of follow-up) was provided by five studies comprising 614 implants. Based on the available data, the average MBL was 0.84 mm at the first year of implant placement and 1.05 mm by the end of follow-up period. The cumulative mean difference for the above analyzed studies came out to be 0.49 mm with 95% CI (−0.22; 1.19). These results are in accordance with the standard established norms, according to which the MBL should not exceed 1.5 mm in the first year followed by 0.1 mm in each subsequent year.[29] The findings in our study regarding MBL are in line with that reported by Glauzer, who documented an 11 years study of implants with an oxidized surface which were subjected to immediate occlusal loading. Mean marginal bone remodeling was 0.47 mm (SD 1.09) from the first year after implant placement to 11 years follow-up.[28] In another study by Östman et al., using surface-modified Ti dental implants, a mean MBL of 0.41 mm (SD 1.06) at 0–1 year and 0.7 mm (SD 1.35) during the follow up of 10 years was observed.[24]

In more than 60% of the cases, implant loss occurred before functional loading of the implant, which could be due to overheating of the implant bed or due to micro-movements caused after immediate loading. The subsequent cause of loss of implant was bone loss caused by infections or peri-implantitis. The present analysis reported complication rate of 2.96%, which was in a range similar to that reported by Snauwaert et al. In their study, the authors reported an early implant loss in 3.8% of cases due to biological complications, while late implant loss was reported in 2% of cases.[30]

This systematic review and meta-analysis were exclusively designed to assess the effect of anodized dental implant surface on cumulative implant survival and success rates. Rigorous attempts were made to assess the quality of included studies by adjusting the confounding variables and bias, also by following a strict protocol-driven study selection and data extraction methods. Limitations of this meta-analysis were that the search was restricted to the English language only for the feasibility of data extraction. Moreover, the included studies suffered from some degree of selection bias because the implants were either placed in a specialist clinic or in a university hospital set up. Furthermore, there were no specific details about the status of implants in the loss to follow-up patients.

CONCLUSION

In the light of the above results and discussion, anodized surface implants can be considered as a good treatment option as far as their long-term survival and success is concerned. However, large well-conducted clinical and animal trials with longer follow-up periods are necessary to further understand the long-term effect of anodized implants both clinically and histologically.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

APPENDIX

Appendix 1: Search strategy for Pubmed

Following MESH terms were used: (((((((((((((dental implant surface[MeSH Terms]) OR Prosthesis, Surgical Dental[MeSH Terms]) OR Prostheses, Surgical Dental[MeSH Terms]) OR Surgical Dental Prosthesis[MeSH Terms]) OR Surgical Dental Prostheses[MeSH Terms]) OR Dental Prosthesis, Surgical[MeSH Terms]) OR Dental Prostheses, Surgical[MeSH Terms]) OR Implant, Dental[MeSH Terms]) OR Dental Implant[MeSH Terms]) OR Implants, Dental[MeSH Terms]) OR implant surface[MeSH Terms])) OR (((((((((((dental implant surface[Title/Abstract]) OR Prosthesis, Surgical Dental[Title/Abstract]) OR Prostheses, Surgical Dental[Title/Abstract]) OR Surgical Dental Prosthesis[Title/Abstract]) OR Surgical Dental Prostheses[Title/Abstract]) OR Dental Prosthesis, Surgical[Title/Abstract]) OR Dental Prostheses, Surgical[Title/Abstract]) OR Implant, Dental[Title/Abstract]) OR Dental Implant[Title/Abstract]) OR Implants, Dental[Title/Abstract]) OR implant surface[Title/Abstract])) OR ((((((((((dental implant surface) OR Prosthesis, Surgical Dental) OR Prostheses, Surgical Dental) OR Surgical Dental Prosthesis) OR Surgical Dental Prostheses) OR Dental Prosthesis, Surgical) OR Dental Prostheses, Surgical) OR Implant, Dental) OR Dental Implant) OR Implants, Dental).

((((“Survival”[Mesh] OR “Mortality”[Mesh] OR “Survival Rate”[Mesh])) OR ((((((((((((((((Survival Rates, Cumulative[MeSH Terms]) OR Survival Rate, Cumulative[MeSH Terms]) OR Rates, Cumulative Survival[MeSH Terms]) OR Rate, Cumulative Survival[MeSH Terms]) OR Cumulative Survival Rates[MeSH Terms]) OR Cumulative Survival Rate[MeSH Terms]) OR Times, Mean Survival[MeSH Terms]) OR Time, Mean Survival[MeSH Terms]) OR Survival Times, Mean[MeSH Terms]) OR Survival Time, Mean[MeSH Terms]) OR Mean Survival Times[MeSH Terms]) OR Mean Survival Time[MeSH Terms]) OR Survival Rates[MeSH Terms]) OR Rates, Survival[MeSH Terms]) OR Rate, Survival[MeSH Terms]) OR survival[MeSH Terms]))) AND ((((((((((((((dental implant surface[MeSH Terms]) OR Prosthesis, Surgical Dental[MeSH Terms]) OR Prostheses, Surgical Dental[MeSH Terms]) OR Surgical Dental Prosthesis[MeSH Terms]) OR Surgical Dental Prostheses[MeSH Terms]) OR Dental Prosthesis, Surgical[MeSH Terms]) OR Dental Prostheses, Surgical[MeSH Terms]) OR Implant, Dental[MeSH Terms]) OR Dental Implant[MeSH Terms]) OR Implants, Dental[MeSH Terms]) OR implant surface[MeSH Terms])) OR (((((((((((dental implant surface[Title/Abstract]) OR Prosthesis, Surgical Dental[Title/Abstract]) OR Prostheses, Surgical Dental[Title/Abstract]) OR Surgical Dental Prosthesis[Title/Abstract]) OR Surgical Dental Prostheses[Title/Abstract]) OR Dental Prosthesis, Surgical[Title/Abstract]) OR Dental Prostheses, Surgical[Title/Abstract]) OR Implant, Dental[Title/Abstract]) OR Dental Implant[Title/Abstract]) OR Implants, Dental[Title/Abstract]) OR implant surface[Title/Abstract])) OR ((((((((((dental implant surface) OR Prosthesis, Surgical Dental) OR Prostheses, Surgical Dental) OR Surgical Dental Prosthesis) OR Surgical Dental Prostheses) OR Dental Prosthesis, Surgical) OR Dental Prostheses, Surgical) OR Implant, Dental) OR Dental Implant) OR Implants, Dental)).

Search Strategy for Embase

(‘tooth implant’/exp OR ‘tooth implant’) AND survival AND rate AND Success AND rate AND (‘dental alloy’/dd OR ‘dental material’/dd OR ‘titanium’/dd) AND (2008:py OR 2009:py OR 2010:py OR 2011:py OR 2012:py OR 2013:py OR 2014:py OR 2015:py OR 2016:py OR 2017:py OR 2018:py) AND (‘complication’/dm OR ‘edentulousness’/dm OR ‘periimplantitis’/dm OR ‘periodontal disease’/dm OR ‘prosthesis complication’/dm OR ‘screw loosening’/dm) AND (‘case control study’/de OR ‘clinical article’/de OR ‘clinical trial’/de OR ‘cohort analysis’/de OR ‘comparative study’/de OR ‘controlled clinical trial’/de OR ‘controlled study’/de OR ‘human’/de OR ‘longitudinal study’/de OR ‘major clinical study’/de OR ‘multicenter study’/de OR ‘observational study’/de OR ‘prospective study’/de OR ‘randomized controlled trial’/de OR ‘randomized controlled trial topic’/de OR ‘retrospective study’/de) AND (‘bone implant interface’/dv OR ‘dental device’/dv OR ‘endosseous implant’/dv OR ‘implant’/dv OR ‘implant-supported denture’/dv OR ‘narrow diameter implant’ OR ‘osseointegrated implant’/dv OR ‘overlay denture’/dv OR ‘single tooth implant’/dv OR ‘tooth implant’/dv OR ‘tooth prosthesis’/dv) AND (‘article’/it OR ‘article in press’/it).