Othman Benay
2021, OF12
EVALUATION OF OSSEOINTEGRATION OF
ZIRCONIA AND TITANIUM DENTAL IMPLANTS: A
LITERATURE REVIEW
Master’s Thesis
Supervisor DDS, PhD Gintaras Juodžbalys
2
FINAL MASTER‘S THESIS IS CONDUCTED AT THE DEPARTMENT OF
ORAL AND MAXILLOFACIAL SURGERY.
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LITERATURE REVIEW” 1. Is done by myself.
2. Has not been used at another university in Lithuania or abroad.
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(2021.04.19) (Othman Benay)
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LITHUANIAN UNIVERSITY OF HEALTH SCIENCES MEDICAL ACADEMY
FACULTY OF ODONTOLOGY
DEPARTMENT OF MAXILLOFACIAL SURGERY
EVALUATION OF OSSEOINTEGRATION OF ZIRCONIA AND TITANIUM DENTAL IMPLANTS: A LITERATURE REVIEW
Master’s Thesis
Kaunas, 2021
Gintaras Juodžbalys DDS, PhD, Professor
20-04-2021
Othman Benay OF12 5K
TABLE OF CONTENTS
1. SUMMARY ………... 8
2. INTRODUCTION ……… 9
3. SELECTION CRITERIA OF THE STUDIES: SEARCH METHODS AND STRATEGY ………..……….. 11
3.1. Protocol ……….……….……....………. 11
3.2. Information sources ……….………..………. 11
3.3. Process of screening of articles …………..………..……….. 12
3.4. Literature search strategy ..………...……….. 12
3.5. Types of publications ……….………...………. 12 3.6. Animal models ………...………. 12 3.7. Inclusion criteria ………...……… 12 3.8. Exclusion criteria ………...……….. 12 3.9. Data collection ………...……….. 12 3.10. Ethical approval ………...……….. 13 3.11. PICOS strategy ………...……… 13 3.12. Outcome variables ………...……….. 13 3.13. Data items ………...……….. 14 3.14. Synthesis of results ……….... 14
3.15. Risk of bias assessment ………...……….. 15
3.16. Statistical analysis ………. 16
4. SYSTEMIZATION AND ANALYSIS OF DATA ……… 17
4.1. Study characteristics ……… 17
4.2. Study selection ………. 17
4.3. Exclusion of studies ………. 17
4.4. Quality assessment of included studies ……….... 17
5. DISCUSSION ……… 22
6. CONCLUSIONS ………..……….. 24
7. PRACTICAL RECOMMENDATIONS ……….... 24
8 EVALUATION OF OSSEOINTEGRATION OF ZIRCONIA AND TITANIUM DENTAL
IMPLANTS: A LITERATURE REVIEW
1. SUMMARY
Introduction: This literature review aims to evaluate the osseointegration of zirconia and titanium dental implants and identify which one is the better material according to scientific research clinical studies.
Materials and methods: Electronic data bases (ScienceDirect, Pubmed and Google Scholar) were searched between 1st of January 2011 and 7th of March 2021 and according to the inclusion criteria, controlled clinical trials performed on animals were studied and evaluated.
Results: All of the dental implants demonstrated good biocompatibility and osseointegration when evaluating according to the primary and secondary outcomes. The primary outcome variables is the bone implant contact (BIC) and biocompatibility (if there are signs of inflammation or infections). The secondary outcome variables are peak torque value, peri-implant bone volume density and push-in test.
Conclusion: No significant difference was discovered between the titanium dental implants and the zirconia dental implants in terms of osseointegration and biocompatibility when looking at the parameters intended to represent those. However, long term studies are essential to be performed in order to confirm these results.
2. INTRODUCTION
Titanium have for a long time in the dental world, been the golden standard material of choice for fabrication of dental implants. Titanium implants does not exhibit great aesthetic properties, since they leave a greyish hue on the gingiva and considering it is a conductive metal, it can also create galvanic currents in the oral cavity. Titanium is very biocompatible, very long lasting and has very good osseointegrative properties. For those reasons, discovering another material that can outmatch this one is difficult [14].
The first use of titanium in medicine dates back all the way to 1940 in which it was used in animals to demonstrate its biocompatibility. Since then, a lot of research has been conducted to reveal its long term effect [15].
Zirconia implants however have according to literature more superior biological, aesthetic, mechanical and optical properties. It was discovered as a mineral in the late 1800 and roughly 70 years after that it started being used in the medical world. Initially, it was used in orthopaedic surgeries as a material for ball head hip joint replacement, artificial hips, finger and acoustic implant prosthesis [16]. However, nowadays zirconia has gotten higher demand as the material of choice for dental implants.
Zirconia is available in two forms; crystalline and amorphous. The crystalline form is soft, white, and ductile and the amorphous form is a bluish-black powder found in nature. The powder is taken, and is synthetically treated at higher temperatures and higher pressure to form homogenous implants. To get a more stable form of zirconia, Magnesia (MgO), Limestone (CaO) and Yttrium Oxide (Y2O3) are added to increase the crack resistance, fracture toughness and longevity of the implant [12].
Zirconia, as mentioned earlier has satisfying osseointegration and biocompatibility properties. Minimal local and systemic adverse reactions, good cell adhesion, excellent tissue response and minimal inflammation are just a few. Clinical trials, both in humans and in animals confirmed the formation of mature bone closely around the implant [7].
The word “osseointegration” is defined as “formation of a direct interface between an implant and bone, without intervening soft tissue. No scar tissue, cartilage or ligament fibers are present between the bone and implant surface. The direct contact of bone and implant surface can be verified microscopically” [18] therefore the major goals have to be achieved when inserting a dental implant in order to fixate the implant into the bone. Its fixation reflects on its stability. The more stable a dental implant is, the higher chances it is for it to last a longer period of time. There are many ways to enhance the osseointegration of dental implants that is used in modern dentistry, and that by different surface modifications. Some of the widely used ones includes acid etching, sand blasting, plasma spraying and recently modifying the surface by using Nano technology. Apart from the above mentioned, atraumatic insertion techniques should be used to successfully achieve osseointegration.
10 The osseointegration is primarily measured with Bone Implant Contact, better known as BIC. The BIC provides a percentage on how much of the implant surface is in full contact with the bone, the higher the percentage value, the higher the osseointegration. Therefore, the BIC will be the primary outcome of choice to evaluate the osseointegration in this literature review.
The biocompatibility of a dental implant is evaluated using radiographical, clinical and histological examinations. In the presence of inflammation, infection or any alternative form of reaction that suggests that the dental implant is rejected by the host indicates the implant is not biocompatible. It is highly of importance to choose a dental implant material that bears the desired advantages and minimum disadvantages. For this purpose, this comparison between the two most widely used dental implant materials; titanium and zirconia, has been conducted.
The aim of this systemic review is to compare Titanium implants to Zirconia implants using the existing literature and determine which one has the better osseointegration and if zirconia could be a viable replacement or option for titanium implants. The objectives are:
Electronic data base searching regarding the osseointegration of these implant materials. Evaluation of the osseointegration by primarily comparing Bone Implant Contact (BIC)
3. SELECTION CRITERIA OF THE STUDIES: SEARCH METHODS AND STRATEGY 3.1. Protocol
This literature review was following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [1], presented in Figure 1.
Figure 1. PRISMA flow-chart. 3.2. Information sources
Electronic searches for articles were conducted in English in PubMed, Science Direct and Google Scholar from 1st of January 2011 to 7th of March 2021.
12 3.3. Process of screening of articles
The screening process started with the electronic searches in the above mentioned sites. Thenceforth, titles and abstracts of the articles appearing as search results were analysed and articles got chosen depending on if they were related to the topic or not. In the third step, those full text articles selected was carefully read, evaluated and compared to the inclusion criteria.
3.4. Literature search strategy
These keywords were used as search terms when conducting literature search:
‘Osseointegration’ [All Fields] OR ‘Osseointegrated’ [All Fields] OR ‘Osseointegrating’ [All Fields] OR ‘Osseointegrate’ [All Fields] AND ‘Titanium’ [All Fields] AND ‘Zirconia’[All Fields] OR ‘Zirconium oxide’ [All Fields] AND ‘Dental implants’ [All Fields] OR ‘Implants’ [All Fields].
3.5. Types of publications
This systemic review include clinical trial studies done on animal test subjects. They are published between 1st of January 2011 and 7th of March 2021.
3.6. Animal models
The clinical studies was done on a variety of animals. Those were Sprague-Dawley rats [2], sheep [3], miniature pigs [4, 6], domestic pigs [5], New Zealand rabbits [8] and Goettinger mini pigs [9]. Therefore, all of those animals are included in this literature review.
3.7. Inclusion criteria
The studies that were included had to follow the following criteria: 1) Studies that compared the osseointegration zirconia and titanium dental implants; 2) Clinical trials on animals; 3) English articles; 4) Articles published since 2011; 5) Articles with available full text.
3.8. Exclusion criteria
The studies such were excluded are those that followed one or more of these criteria: 1) Systemic or literature reviews; 2) Articles older than 10 years; 3) In vitro studies.
3.9. Data collection
The following data was extracted from the included articles: 1) Author and publication year; 2) Study design; 3) Number and type of test subjects; 4) Number and types of implants placed; 5) Implant placement site; 6) Experimentation period.
3.10. Ethical approval
The Bioethics Committee of Lithuanian University of Health Sciences approved the conduction of this systematic review (No. BEC-OF-92).
3.11. PICOS strategy
The clinical questions were organized according to problem, intervention, control or comparison, outcome and study design, better known as PICOS strategy presented in Table 1. The following focus question was formed in accordance with the same strategy: Which of the two dental implants, titanium or zirconia implants, has the better osseointegration and biocompatibility with the evaluation of BIC, surrounding soft tissue reaction, P-I BVD and push-in test?
Acronym Definition Description
P Problem Does zirconia dental implants osseointegrate as good as or better than titanium dental implants?
I Intervention Placement of zirconia and titanium dental implants in animal test subjects that has similar physiological response as humans C Control or
comparison
Conventional titanium dental implants compared to zirconia dental implants
O Outcome The osseointegration between the different implants and the surrounding bone, and the biocompatibility of the implant with the
surrounding soft tissues S Study design Controlled animal clinical trials
F Focus
question
Which of the two dental implants, titanium or zirconia implants, has the better osseointegration and biocompatibility with the evaluation of BIC, surrounding soft tissue reaction, P-I BVD and
push-in test? Table 1. PICOS framework of the framed clinical question.
3.12. Outcome variables
The primary outcome variables is the bone implant contact (BIC) and biocompatibility (in presence of inflammations or infections). The secondary outcome variables are peri-implant bone volume density (P-I BVD) and push-in test.
14 3.13. Data items
The data that was collected from the included studies are arranged into the following order presented in Table 2.
Author/Year The author and the year of publication
Study Design Type of study
Test subjects Which animals, age, weight and quantity
Procedure How many implants were in each implant
Dental implants Which dental implant material was used and if the implant went through any surface treatment and if so which surface treatment,
and how many of those were placed? Clinical trial period The length of the clinical trials in terms of
weeks
Site of insertion Where the implants were inserted Biocompatibility Any signs of inflammations or infections Bone implant contact (BIC) The implant surface is in contact with the
bone, measured in percentage (%) Peri-implant bone volume density (P-I
BVD)
Measured in percentage (%)
Implant push-in test Push-in test values, measured in Newton (N) Failed implants Any failed implants, and how many
Final conclusion of the study Conclusion
3.14. Synthesis of results
Relevant data of interest on the previously stated variables presented in Table 2 were collected and organized into two tables presented in Table 5 and Table 6, divided into the same selected parameters.
3.15. Risk of bias assessment
The risk of bias assessment was performed according to the Systematic Review Centre for Laboratory animal Experimentation’s (SYRCLE) tool for assessing risk of bias (Rob) [9]. It is a tool especially made to for animal studies. The questions evaluated can be found in Table 3. Half of the items in this tool are in agreement with the Cochrane Risk of Bias tool; Q1, Q3, Q8, Q9 and Q10. The risk of bias assessment can be found in Table 4.
Question number
Type of bias Defined question
Q1 Selection bias: sequence generation
Was the allocation sequence adequately generated and applied?
Q2 Selection bias: baseline characteristics
Were the groups similar at baseline or were they adjusted for confounders in the analysis? Q3 Selection bias: allocation
concealment
Was the allocation adequately concealed? Q4 Performance bias: Random
housing
Were the animals randomly housed during the experiment?
Q5 Performance bias: Blinding Were the caregivers and/or investigators blinded from knowledge which intervention each animal
received during the experiment? Q6 Detection bias: Random
outcome assessment
Were animals selected at random for outcome assessment?
Q7 Detection bias: Blinding Was the outcome assessor blinded? Q8 Attrition bias: Incomplete
outcome data
Were incomplete outcome data adequately addressed?
Q9 Reporting bias: selective outcome reporting
Are reports of the study free of selective outcome reporting?
Q10 Other sources of bias Was the study apparently free of other problems that could result in high risk of bias? Table 3. SYRCLE’s tool for assessing RoB.
16 Authors/SYRCLE Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Kohal et al. 2013 [2] ? + + - ? + ? - + + Langhoff et al. 2008 [3] ? + ? - + + + + + + Stadlinger et al. 2010 [4] ? + + - + + + - + + Möller et al. 2012 [5] ? + ? - + + + + + + Kubasiewics-Ross et al. 2017 [6] ? + + - + + + + + + Wen et al. 2013 [8] ? + ? - + + - + + + Gahlert et al. 2010 [9] ? + + - + + + + + +
+: low risk ?: unclear risk -: high risk
3.16. Statistical analysis
No meta-analysis could be performed due to the heterogeneity between the studies. The reviewed researches consisted of various different study designs, control groups and different outcome variables.
4. SYSTEMIZATION AND ANALYSIS OF DATA 4.1. Study characteristics
The characteristics of the included studies are presented in Table 5 and Table 6. Three of the studies included [3, 4, 9] were older than 10 years since they were well executed and well documented. In total, 495 implants were placed in a variety of animals. Only a total of nine failed implants were recorded. The clinical trial periods ranged from 2 weeks up to 12 weeks.
4.2. Study selection
A total of 337 articles were screened, out of which 309 articles were excluded due to irrelevant titles and abstracts. The remaining 20 articles were assessed for eligibility based on the inclusion criteria. Then, a total of 13 articles were once more excluded by reasons presented in Figure 1. After a complete review, seven articles were included in this review [2-6, 8, 9]. Figure 1 shows the PRISMA flow-chart which illustrates publications identified, screened, assessed and included in this review.
4.3. Exclusion of studies
Nine studies were excluded after assessment of full-text articles with reasons [12, 13, 18-24]. Those were: 1) Comparative outcomes were irrelevant; 2) In-vitro studies; 3) Scientific reviews; 4) Systematic reviews; 5) Meta-analysis articles.
4.4. Quality assessment of the included studies
The quality assessment of the included studies are summarized in Table 4 and revealed good qualities based upon the scores.
18
Author/Year Study Design Test subjects (n)
Dental implants Procedure Clinical
trial period
Site of insertion
Kohal et al. 2013 [2]
Clinical trial 56 8-week-old male
Sprague-Dawley rats
28 zirconia implants with sandblasted and acid-etched surface (TZP-proc) 28 titanium implants with
an electrochemical anodized surface (TiUnite)
28 zirconia implant with a turned surface (TZP-A-m) 28 titanium implant with a
turned surface (Ti-m) Total: 112 implants
28 rats received one TZP-proc implant
and one TiUnite implant. The rest of the rats
(28) received one TZP-A-m and one
Ti-m.
2 weeks and 4 weeks
Randomly into the left and right femurs
Langhoff et al. 2008 [3]
Clinical trial 15 2-3 year old female sheep (average weight
68kg)
18 titanium implants with calcium phosphate surface 18 titanium implants with plasma anodized surface 18 titanium implants with collagen I and Chondroitin
Sulfate surface 18 titanium implants with
bisphosphonates surface
18 zirconia implants with sandblasted and
acid etched surface 21 titanium implants with sandblasted and partially etched surface
(Reference)
Total: 110 implants
7 implants per iliac bone (one implant
type was not evaluated in this
study)
2 weeks, 4 weeks and 8 weeks
The iliac bones of the pelvis.
Stadlinger et al. 2010 [4]
Clinical trial 7 one-year-old miniature pigs
14 one-piece zirconia implants with a sandblasted surface 7 titanium implants with a
sandblasted and acid-etched surface
Total: 21 implants
Each pig got 3 implants implanted
in their posterior part of their mandible; one submerged zirconia
implant, one non-submerged zirconia
implant and one submerged titanium
implant.
4 weeks Posterior part of the mandible; in the location of the previously extracted
premolar teeth
Möller et al. 2012 [5]
Clinical trial 8 adult female domestic pigs with an age of more than 18 months and an average weight of 94.5kg 32 zirconium implants 32 titanium implants with
a sandblasted and high temperature etched surface
Total: 64 implants
Each pig received 4 zirconium implants and 4 titanium implants 4 weeks and 12 weeks
The frontal skull
Kubasiewics-Ross et al.
2017 [6]
Clinical trial 12 16-month-old minipigs with an average weight
of 50-60kg
12 zirconia implants with blasted surface (M1)
Each pig received 5 implants (one of
each) in the mandible in the area
12 weeks Posterior part of the mandible; in the location of the previously extracted
premolar teeth Table 5. Data analysis of included studies.
12 zirconia implants with etched surface (M2) 12 zirconia implants with
blasted and acid etched surface (M3) 12 titanium standard implants with sandblasted
and acid etched surface (reference 1) 12 zirconia standard implants (reference 2) Total: 60 implants of the previously extracted permanent premolar teeth Wen et al. 2013 [8]
Clinical trial 28 12-months-old New Zealand female rabbits weighing between 3-4.5kg 48 SLActive titanium implants (Ti) 48 SLActive titanium-zirconium alloy implants
(TiZr) SLActive = implant surface is hydrophilic roughened, sand-blasted, large grit and acid-etched.
Total: 96 implants
14 of the rabbits were ovariectomized (OVX) and had a low calmcium diet
to induce osteoporosis. The
rest (14) of the rabbits had their ovaries lifted and
replaced back in their original position (SHAM). 2 rabbits from each group didn’t receive any implants and were used as control
3 weeks and 6 weeks
Each animal received 4 implants; one leg had Ti in the femur and TiZr in the tibia and the collateral leg had the
opposite.
Gahlert et al. 2010 [9]
Clinical trial 18 female Goettinger mini pigs with an average age of 23.7 months and a weight between 31-51kg
18 zirconia implants with acid etched surface 18 titanium implants with
sandblasted and acid etched surface (control)
Total: 32 implants
Each pig received one of each implant.
4 weeks, 8 weeks and 12 weeks
In the maxilla in the area of previously extracted canines and
incisors
20 Table 6. Continuation of data analysis of included studies.
Author/Year BIC (%) P-I PVD (%) Implant push-in
test (N)
Biocompatibility Failed implants Conclusion
Kohal et al. 2013 [2] TZP-proc: After 2 weeks: 17.6 After 4 weeks: 33.5 TiUnite: After 2 weeks: 36.2 After 4 weeks: 56.1 TZP-A-m: After 2 weeks: 30.9 After 4 weeks: 46.6 Ti-m: After 2 weeks: 23.2 After 4 weeks: 39.4 - TZP-proc: After 2 weeks: 25.8 After 4 weeks: 30.6 TiUnite: After 2 weeks: 26.5 After 4 weeks: 49.0 TZP-A-m: After 2 weeks: 18.9 After 4 weeks: 9.3 Ti-m: After 2 weeks: 18.8 After 4 weeks: 7.3 No sign of inflammation, infection or adverse reaction at the sites of all implantations
One 2-week Ti-m Two 4-week Ti-m
One 4-week TiUnite One 4-week TZP-proc Total: 5 implants Zirconia materials were as biocompatible as titanium. TZP-proc performed the worse than TiUnite. TZP-A-m perfomed better than Ti-m. Titanium implants
with surface treatment were better than Zirconia
implants with surface modification. In terms of implants without surface treatment, Zirconia performed better. Langhoff et al. 2008 [3] All titanium implant types: After 2 weeks: 59-62 4-8 weeks: 78-83 The plasma anodized surface treated implants however decreased with time (4-8 weeks) (58) The zirconia implant: After 2 weeks: 20% more than Reference (78) After 4 weeks: Improved more than reference (82) After 8 weeks: Decreased below the reference (74) - - No signs of infections or inflammations could be found at
the site of all implantations
- All implants had good biocompatibility and osseointegration compared to the reference implant. The zirconia implants are a viable option to the
titanium implants since they had very
similar BIC. Stadlinger et al. 2010 [4] Titanium implants: Mean: 53.08 Lower bound – Upper bound: 47.72-58.43 Zirconia submerged implants: Mean: 52.63 Lower bound – Upper bound: 41.53-63.74 Titanium implants: Mean: 74.36 Lower bound – Upper bound: 55.38-93.33 Zirconia submerged implants: Mean: 79.58 Lower bound – Upper bound: 47.59-111.57 - No inflammatory reactions were found at the site of
all implantations One sub-merged zirconia implant was lost. One non-merged zirconia implant was clinically mobile All implants showed good osseointegration and biocompatibility in
both soft and hard tissues. Submerged zirconia
implants had the better values compared to the
Zirconia non-submerged implants: Mean: 47.95 Lower bound – Upper bound: 40.36-55.54 Zirconia non-submerged implants: Mean: 62.54 Lower bound – Upper bound: 27.55-97.54 Total: 2 implants non-submerged zirconia implants Möller et al. 2012 [5] Zirconia implants: After 4 weeks: 59.3±4.6 After 12 weeks: 67.1±2.3 Titanium implants: After 4 weeks: 64.1±3.9 After 12 weeks: 73.6±3.2 - - No signs of infections could be seen during the observation period
and in the preparations
- The
osseointegration of the zirconia implant and the titanium implant were very
similar. These results show that zirconia implants are a viable option instead of titanium implants. Kubasiewics-Ross et al. 2017 [6] M1 = 39.72 M2 = 43.97 M3 = 40.63 Reference 1 = 27.77 Reference 2 = 49.63 - - No macroscopic or microscopic signs of cellular inflammation or implant rejection could be found in any of the test
groups
- Zirconia implants with modified surfaces has similar
osseointegration to titanium implants. These results show
that zirconia implants are viable
option
Wen et al. 2013 [8] Titanium implants: After 3 weeks: 37.1±14.3 After 6 weeks: 47.7±8.7 Titanium-Zirconium alloy implants: After 3 weeks: 37.6±10.9 After 6 weeks: 50.4±11 - - - - Ti-implants and TiZr-implants had very similar osseointegration. These results show
that TiZr-implants are a viable option to conventional titanium implants. Gahlert et al. 2010 [9] Titanium implants: After 4 weeks: 64.7±9.4 After 8 weeks: 79.2±1.7 After 12 weeks: 83.7±10.3 Zirconia implants: After 4 weeks: 70±14.5 After 8 weeks: 67.1±21.1 After 12 weeks: 68.3±22.8 Titanium implants: After 4 weeks: 61.1±6.2 After 8 weeks: 63.6±6.8 After 12 weeks: 68.2±5.8 Zirconia implants: After 4 weeks: 60.4±9.9 After 8 weeks: 65.4±13.8 After 12 weeks: 63.3±21.5 - Clinical inspection did not reveal any
signs of inflammation
1 titanium implant 1 zirconia implant (One animal died)
Total: 2 failed implants Both types of implants showed great osseointegration and biocompatibility.
The sample size was very limited
but we can conclude that both
types of implants are viable options as a dental implant
22 5. DISCUSSION
This literature review compared zirconia implants with titanium implants. More precisely it compared the osseointegration and the biocompatibility of these implants with the soft and hard tissues of the host. The different animal models that were used in these included studies and the sites of insertions chosen in each animal represented in one way or another the same physiological response as that of humans and had very similar structure to that of humans [2-6, 8, 9].
This literature review demonstrated that implants made out of zirconia and titanium bear quite similar properties in terms of osseointegration and biocompatibility since the BIC, the biocompatibility and the secondary outcome variables showed it. Acknowledging the biocompatibility, none of the implants generated any inflammatory or adverse reactions and none of the implants got rejected by the host [2-6, 8, 9].
Bone Implant Contact (BIC) is a method established in which a direct contact between the bone and the implant surface is measured by the help histomorphometric analysis. In a study Scarano et al. [26] compared BIC to implant stability and found that there is statistically significant correlation between them which suggests that the BIC values do accurately reflect on the implant stability.
The implants presented an enhanced response when surface treated. Most dental implants are sandblasted and acid etched before implantation which increases the surface area of the surface of the dental implant which in turn increases the bone implant contact [12].
The studies that were included in this literature review proved that zirconia implants is a very promising material and could be an alternative to titanium. Since zirconia has much more aesthetical properties and all the other parameters are very similar, zirconia could potentially replace the golden standard. Another reason why zirconia is much more aesthetic is due to it not showing a greyish hue on the vestibular soft tissues. However, that depends on the thickness of the tissue. It has been established that when the thickness is 3mm, you will not be able to detect the greyish hue caused by the titanium implant [13].
Since these studies were done in a very brief period of time, we cannot evaluate the long-term prognosis of both materials, yet many studies carried out that titanium bears much better long-term prognosis out of the two materials. Further studies will have to be conducted to compare the long-term prognosis of both materials.
These clinical trials possessed limited sample sizes, which could be considered a weakness since bigger sample size is desired to get a more précised study with more accurate results. Hence the results of these studies cannot be taken literally, more like an overview. Nevertheless, it is concluded that there was no distinct differences between the different implant materials.
The study conducted by Wen et al. [8] had titanium-zirconium (TiZr) alloy implants compared to titanium implants. The TiZr implants had 13-15% zirconia and although the BIC showed no significant differences between them and the titanium implants, there is literature [11] that found out that TiZr implants were 2.5 times greater in strength than titanium implants.
A study conducted by Koch et al. [25] compared the osseointegration of one-piece zirconia implants with titanium implants of identical design. The implants were inserted in dogs. After 4 months, the BIC was measured and the experiment concluded that the zirconia dental implants were capable of having similar BIC rates to titanium implants with the same surface modification. This study confirms the findings of this scientific analysis.
24 6. CONCLUSIONS
The aim of this literature review was to compare titanium implants to zirconia implants using the existing literature and determine which one exhibits the better osseointegration and if zirconia could be a viable replacement or option for titanium implants.
To conclude, this literature review compared zirconia dental implants with titanium dental implants in terms of osseointegration and biocompatibility. The osseointegration was measured using BIC as a primary outcome while the biocompatibility was determined if there was presence of any adverse reaction or inflammation around the implantation site or if there was any soft tissue negative response by the host.
This literature review suggests that significant difference was not detected between the titanium dental implants and the zirconia dental implants in terms of osseointegration and biocompatibility with the parameters intended to represent those.
7. PRACTICAL RECOMMENDATIONS
Further studies are required to investigate the long term stability of both dental implant types; titanium and zirconia since the studies included in this review did not examine it.
In order to acquire more accurate results, a larger sample size of implants is demanded since the studies reviewed had all smaller sample size.
8. REFERENCES
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