SYSTEMATIC REVIEW

Crestal bone loss and periimplant inflammatory parameters around zirconia implants: A systematic review Fahim Vohra, MRD RCS, MClinDent, MFDS, BDS,a Abdul Aziz Al-Kheraif, PhD,b Siti Mariam Ab Ghani, MClinDent,c Mohamed Ibrahim Abu Hassan, PhD,d Talal Alnassar, MDS,e and Fawad Javed, PhDf With recent advances in ABSTRACT implant dentistry, yttriumStatement of problem. Zirconia implants have been used for oral rehabilitation; however, evistabilized zirconia, a chemically dence of their ability to maintain crestal bone and periimplant soft tissue health is not clear. inert and biocompatible matePurpose. The purpose of this systematic review was to evaluate crestal bone loss (CBL) around rial, implants have been used zirconia dental implants and clinical periimplant inflammatory parameters. to rehabilitate partially and Material and methods. The focus question addressed was, “Do zirconia implants maintain crestal completely edentulous inbone levels and periimplant soft tissue health?” Databases were searched for articles from 1977 1,2 dividuals. In a recent prothrough September 2014 with different combinations of the following MeSH terms: “dental imspective clinical trial, Borgonovo plants,” “zirconium,” “alveolar bone loss,” “periodontal attachment loss,” “periodontal pocket,” et al3 reported comparable “periodontal index.” Letters to the editor, case reports, commentaries, review articles, and articles crestal bone loss (CBL) around published in languages other than English were excluded. zirconia (ZrO2) implants from Results. Thirteen clinical studies were included. In 8 of the studies, the CBL around zirconia implants baseline up to 4 years of followwas comparable between baseline and follow-up. In the other 5 studies, the CBL around zirconia up, with implant survival rates implants was significantly higher at follow-up. Among the studies that used titanium implants as of up to 100%. Similarly, Brull controls, 2 studies showed significantly higher CBL around zirconia implants, and in 1 study, the et al4 showed a mean CBL of CBL around zirconia and titanium implants was comparable. The reported implant survival rates for zirconia implants ranged between 67.6% and 100%. Eleven studies selectively reported the 0.1 mm around ZrO2 implants periimplant inflammatory parameters. at 3 years of follow-up with a mean implant survival rate Conclusions. Because of the variations in study design and methodology, it was difficult to reach a consensus regarding the efficacy of zirconia implants in maintaining crestal bone levels and peri(ISR) of 96.5%. implant soft tissue health. (J Prosthet Dent 2015;-:---) Although titanium (Ti) implants are commonly used to shown low bacterial adherence and low potential for replace missing teeth and have shown promising outperiimplant infection.10 Studies have also suggested that comes (implant survival rates up to 99.7%),5-7 the immune reactions as a result of sensitivities and allergies occurrence of complications (infection) such as periimto Ti implants could lead to biologic complications.11-13 plant mucositis and periimplantitis around Ti implants 8,9 Moreover, the bluish-gray appearance of Ti implant cannot be ignored. In comparison, ZrO2 implants have

Supported, partially, by the Research Centre, College of Applied Medical Sciences and the Deanship of Scientific Research at King Saud University, Riyadh, Saudi Arabia. a Assistant Professor, Department of Prosthetic Dental Sciences, College of Dentistry, King Saud University, Riyadh, Saudi Arabia. b Associate Professor and Chair, Dental Materials Research, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia. c Senior Lecturer and Head, Centre for Restorative Dentistry Studies, Faculty of Dentistry, University of Technology (MARA), Shah Alam, Malaysia. d Dean, Faculty of Dentistry, Department of Restorative Dentistry, University of Technology (MARA), Shah Alam, Malaysia. e Assistant Professor, Department of Prosthetic Dental Sciences, College of Dentistry, King Saud University, Riyadh, Saudi Arabia. f Research Associate, Eastman Institute for Oral Health, Division of General Dentistry, University of Rochester, Rochester, NY.

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MATERIAL AND METHODS The focused question addressed was, “Do zirconia dental implants maintain crestal bone levels and periimplant soft tissue health?” The following inclusion criteria were imposed: original studies, clinical studies with 12 months of follow-up, intervention recording crestal bone loss and periimplant inflammatory parameters around ZrO2 dental implants, and articles published only in English. Letters to the editor, historic reviews, commentaries, experimental (animal) studies, case-reports, and unpublished articles were excluded. In order to identify studies relevant to the focused question, the MEDLINE database, the EMBASE database, the Cochrane Central Register of Controlled Trials (CENTRAL), Scopus, and the Web of Knowledge and Google-Scholar databases were electronically searched. Databases were searched for articles from 1977 through September 2014 with the following Medical Subject Headings (MeSH) terms: (1) dental implantation, (2) dental implants, (3) zirconium, (4) alveolar bone loss, (5) periodontal attachment loss, (6) periodontal pocket, (7) periodontal index, (8) dental plaque index, and the THE JOURNAL OF PROSTHETIC DENTISTRY

Screening Eligibility

collars in areas of thin mucosa or mucosal recession compromises the esthetics of the definitive implant. These biologic and esthetic complications have led to the search for an alternative implant material to Ti. In a recent systematic review, Depprich et al14 showed that the implant survival rates of ZrO2 implants ranged between 74% and 98% for up to 56 months of follow-up. However, a possible risk of bias in the studies assessed by Depprich et al14 cannot be disregarded. It is well known that the maintenance of crestal bone levels plays an important role in the long-term survival and success of dental implants,15-17 as does an inflammation-free periimplant soft tissue environment.18,19 However, certain parameters such as plaque index (PLI), bleeding index (BI) bleeding on probing (BOP), periimplant pocket depth (PPD), and clinical attachment loss (CAL) were not addressed in the study.14 With this background, the purpose of the present study was to systematically review the crestal bone levels and clinical periimplant inflammatory parameters around ZrO2 dental implants.

Included

Although zirconia dental implants can osseointegrate and remain functionally stable, they cannot be considered as an alternate to traditional Ti implants because well-designed randomized controlled trials are unavailable.

Identification

Clinical Implications

Records identified through database searching (n = 50)

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Additional records identified through other sources (n = 5)

Records after duplicates removed (n = 55)

Records screened (n = 55)

Records excluded (n = 38)

Full-text articles assessed for eligibility (n = 17)

Full-text articles excluded, with reasons (n = 4)

Studies included in qualitative and quantitative synthesis (n = 13)

Studies included in quantitative synthesis (n = 13)

Figure 1. Literature search strategy using PRISMA flow diagram.

combinations 1 or 2 and 3; 1 or 2 and 3 and 4; 1 or 2 and 3 and 5; 1 or 2 and 3 and 5 or 6 or 7 or 8 ; and 1 or 2 and 3 and 4 and 5 or 6 or 7 or 8. Other relevant nonMeSH keywords were used in the search process to identify articles discussing periodontal inflammatory parameters around ZrO2 implants. These included “yttriastabilized zirconia implants,” “zirconia,” “inflammation,” “bleeding index” and “bleeding on probing,” and “periimplant pocket” and “clinical attachment loss.” The titles and abstracts of studies identified with the described protocol were screened by 3 authors (F.V., A.A.K., F.J.) and checked for agreement. The full texts of those studies judged by title and abstract to be relevant were read by authors (F.V., M.I.A., T.S.) and independently evaluated in accordance with the eligibility criteria. An additional hand search was performed in the reference lists of all full texts of all studies identified during the initial search. The tables of contents of Journal of Prosthetic Dentistry, Implant Dentistry, Clinical Oral Implant Research, Clinical Implant Dentistry and Related Research, Journal of Clinical Periodontology, and the European Journal of Oral Implantology were independently hand searched by 2 authors (F.V., T.S.) for relevant studies published up to September 2014. This was done to identify any studies missed in the previous step. The identified studies were then checked for disagreement after discussion among the authors. Kappa scores (Cohen kappa coefficient) were used to determine the level of agreement between the 2 reviewers.20,21 Articles available online in electronic form ahead of print were considered eligible for inclusion. Figure 1 summarizes the literature search strategy Vohra et al

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Table 1. Characteristics of studies that fulfilled eligibility criteria Author

Study Design

No. of Patients

Mean Age (y), range

Female, % (n)

Brull et al4

Retrospective

74

51 (18-72)

NA

Cionca et al27

Prospective

32

51.9 (24-75)

Payer et al32

Prospective

22

Osman et al30,a

Prospective

Siddiqi et al1,a

Study Groups

Follow-up (mo)

Outcome

Group 1: 55 1-piece ZrO2 implantsb Group 2: 66 2-piece ZrO2 implants

Up to 36

CBL around ZrO2 implants at baseline and follow-up was comparable (0.1 ±0.6 mm)

56.2 (18)

49 ZrO2 implants

Up to 24

CBL around implants at baseline and follow-up was comparable

46 (24-77)

40.9 (9)

Group 1: 16 ZrO2 implants Group 2: 15 Ti implants

Up to 24

Both ZrO2 and Ti implant showed significant CBL at follow-up, Ti: 1.43 ±0.67 vs. ZrO2 1.48 ±1.05 ZrO2 implant showed significantly higher CBL than Ti implants in mandible

19

62 (46-80)

21.0 (4)

Group 1: 73 ZrO2 implantsb Group 2: 56 Ti implantsb

Up to 12

CBL around ZrO2 implants at baseline and follow-up was comparable (0.42 mm ±0.40)

Prospective

22

62 (50-79)

18.1 (4)

Group 1: 68 Alveolar ZrO2 implantsb Group 3: 60 alveolar Ti implantsb

Up to 12

CBL around ZrO2 and Ti implants at baseline and follow-up was comparable

Borgonovo et al3

Prospective

13

60 (38-75)

7.6 (1)

35 ZrO2implantsb

Up to 48

CBL was comparable between baseline and follow-up

Kohal et al29

Prospective

28

55.7 (39-75)

39.2 (11)

56 ZrO2 implantsb

Up to 12

CBL was significantly higher than baseline. In 40% of subjects CBL was greater than 2 mm

Payer et al31

Prospective

20

44.4 (27-71)

45.0 (9)

20 ZrO2 implantsb

Up to 24

CBL was significantly higher at follow-up compared with baseline

Borgonova et al25

Prospective

6

NA

NA

14 ZrO2 implantsb

Up to 48

CBL was comparable between loading and follow-up

Borgonova et al24

Prospective

5

56.2 (50-65)

NA

29 ZrO2 implantsb

Up to 48

CBL (1.5 mm around one implant

Cannizzaro et al26

Prospective

40

38.5 (18-55)

57.5 (23)

Group 1: 20 non- occlusal ZrO2 implantsb Group 2: 20 occlusal ZrO2 implantsb

Up to 12

CBL was significantly higher at follow-up as compared to baseline in both test groups

CBL, crest bone loss; NA, not available; ZrO2, zirconia; Ti, titanium. a Implants supporting complete overdentures. b 1-piece implants.

according to the PRISMA guidelines. The research methodology of the present systematic review was adopted from previous published work, and the review pattern focused on summarizing the relevant data.22 The search yielded 55 studies. Overall, 42 studies were excluded (Appendix A, available online). In total, 13 studies were included and data analysis was performed (Fig. 1). RESULTS All the studies1,3,4,23-32 were performed either at universities or health care centers. The number of participants in the studies ranged between 5 and 74. Eleven studies1,3,4,23,24,26,27,29-32 reported the mean age of participants, which was between 38.5 years and 62 years (age range 18 to 80). Ten studies1,3,23,26-32 reported the percentage of female participants, which ranged between 6% and 57.5% (Table 1). In 3 studies,1,30,32 Ti implants were compared with ZrO2 implants. In 2 studies,4,26 smokers were included. In 5 studies,3,23,24,27,30 Vohra et al

individuals smoking more than 10 cigarettes daily were excluded. In all studies,1,3,4,22-31 CBL was measured using conventional 2- dimensional radiographs. The follow-up period ranged from 12 months to 48 months. The number of implants placed ranged between 14 and 150, with diameters between 3.5 mm and 6 mm and lengths between 6 mm and 16 mm. All implants had rough surfaces. In 11 studies,1,3,4,23-26,28-31 1-piece implants were used. In 3 studies,1,30,32 CBL and implant survival rates around ZrO2 implants were compared with Ti implants. In 3 studies,26,28,29 implants were placed using flapped and flapless surgical procedures. In 4 studies,4,26,28,29 implants were placed in fresh extraction sockets as well as in healed sites. In 6 studies,3,23-25,28,29 adjunct guided bone regeneration procedures were performed at the time of implant placement. In 2 studies,26,31 implants were loaded immediately after placement (Table 2). In summary, there was a lack of homogeneity in the assessment of periimplant inflammatory parameters THE JOURNAL OF PROSTHETIC DENTISTRY

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Table 2. Implant-related characteristics of included studies No. of Implants

Implant Dimensions (mm), W/L

Brull et al4

121

3.5->5/8-15

Cionca et al27

49

3.5-5.5/8-12

Healed sites

Conventional

Up to 24

ZrO2 implants: 1.5 mm)

ZrO2: 92.3

Cannizzaro et al26

40

3.5-6/10-15.5

Healed sites and extraction sockets

Immediate and delayed

Up to 12

Non occlusal ZrO2 implants At placement 0.08 (0.18) At follow-up: 0.97 (0.47) Occlusal ZrO2 implants At placement 0.11 (0.28) At follow-up: 0.83 (0.52)

Survival rates were comparable among the groups

Author

Implant Placed Healed sites and extraction sockets

Loading Protocol Conventional

Follow-up (mo) Up to 36

Mean CBL (mm), SD ZrO2 implants: 0.1 (0.6)

Implant Survival (%) ZrO2: 96.5

Conventional, loading at 3 months; immediate, loading same day as implant placement; early, loading within 6 weeks; delayed, loading at 6 months or later; NA, not available; mm, millimeters; ZrO2, zirconia; Ti: titanium; CBL, crestal bone loss; SD, standard deviation. a Implants were placed in edentulous maxilla and mandible. b CBL was distance from top of implant (head of ball) to first crestal bone contact at mesial and distal aspect of implant was measured.

(plaque index [PLI], bleeding index [BI], bleeding on probing [BOP], periimplant pocket depth [PPD], and clinical attachment loss [CAL]) among the studies that fulfilled our eligibility criteria.1,3,4,23-32 In 5 studies,23,24,27,31,32 plaque scores in participants with ZrO2 implants were expressed as a percentage of fullmouth sites, which ranged from 19% to 92%. However, in another 5 studies,1,3,25,28,29 PLI ranged between 0 and 0.29 (Loe and Silness plaque index score) around ZrO2 implants at follow-up. In 4 studies,1,25,28,29 BI was reported, which was 0.15 to 0.57 at follow-up. Five studies4,23,24,31,32 reported BOP, which ranged from 0.15% to 92%. The PPD around ZrO2 implants was reported in 9 studies1,3,4,23-25,27-29 and ranged from 1.8 to THE JOURNAL OF PROSTHETIC DENTISTRY

3.2 mm. CAL was reported in 2 studies28,29 and ranged from 2.84 mm to 3.24 mm at follow-up (12 months). Only 1 study1 reported the amount of keratinized mucosa around implants at baseline and follow-up, which was comparable. In 2 studies,26,30 not all periimplant inflammatory parameters were reported. These results are summarized in Table 3. In 8 studies,1,3,4,23-25,27,30 the CBL around ZrO2 implants was comparable between baseline (0.0 mm) and follow-up (0.66 to 7.82 mm) (up to 48 months). In 4 studies,26,28,29,31,32 the CBL around ZrO2 implants was significantly higher at follow-up (0.83 to 2.75mm) (up to 24 months) compared with baseline (0.08 to 0.16 mm). Among the studies1,30,32 that used Ti implants as controls, Vohra et al

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Table 3. Clinical periimplant parameters in included studies Author

PLI

BI

BOP (%)

PPD (mm)

CAL (mm)

Brull et al4

NA

NA

Implant: 4.1 Teeth: 7.2

Implant: 1.8 Teeth: 2.1

NA

Cionca et al27

At loading: 7% At 12 mo: 21%

At loading: 6% At 12 mo: 27%

NA

At loading: 3.1 ±0.6 At 12 mo: 3.2 +-0.7

NA

Payer et al32

ZrO2 implants At placement: 15.75% (2.72) 24 months: 19.38% (0.88) Ti implants At placement: 11.25% (3.67) 24 mo: 16.05% (8.29)

NA

ZrO2 implants At placement: 10.9 (5.63) 24 months: 9.1(4.34) Ti implants At placement: 9.0 (6.32) 24 mo: 7.4 (3.39)

NA

NA

Osman et al30

NA

NA

NA

NA

NA

Siddiqi et al1

ZrO2 implants At loading: 0.37 (0.45) 12 mo: 0.25 (0.33) Ti implants At loading: 0.58 (0.50) 1 mo: 0.71 (0.58)

At loading: 0.35 (0.44) 12 mo: 0.22 (0.32)

NA

At loading: 1.59 (0.61) 12 mo: 2.23 (0.69)

NA

Borgonova et al3

At loading: 1 At 48 mo: 0

NA

At loading: 1 At 48 mo: 0.15

At loading: 3.0 At 48 mo: 3.19

NA

Kohal et al29

At loading: 0.51 (0.49) At 12 mo: 0.09 (0.16)

At loading: 0.46 (0.55) At 12 mo: 0.15 (0.18)

NA

At loading: 2.85 (0.73) At 12 mo: 2.65 (0.62)

At loading: 3.14 At 12 mo: 3.24

Payer et al31

At loading: 27% (5.3) At 24 mo: 22% (6.4)

NA

At loading: 25 (5.6) At 24 mo: 15 (5.5)

NA

NA

Borgonova et al25

At 48 mo:0.29 (0.47)

At 48 mo: 0.57 (0.51)

NA

At 48 mo: 3.13 (0.87)

NA

Borgonova et al24

At 6 mo: 50%

NA

At 6 mo: 50

At 6 mo: 2.85 (1.85-2.1)

NA

Kohal et al28

At loading: 0.26 (0.35) At 12 mo: 0.11 (0.23)

At loading 0.36 (0.50) At 12 mo: 0.23 (0.32)

NA

At loading: 2.75 (0.75) At 12 mo: 2.34 (0.66)

At loading: 2.84 (1.19) 12 mo: 2.71 (0.75)

Borgonova et al23

At 12 mo: 92.3%

NA

At 12 mo: 92.3

At 12 mo: < 5mm

NA

Cannizzaro et al26

NA

NA

NA

NA

NA

PLI, plaque index; BI, bleeding index; BOP, bleeding on probing; PPD, periimplant probing depth; CAL, clinical attachment loss; NA, not available; Gp, group; mm, millimeters; ZrO2, zirconia; Ti, titanium.

2 studies1,30 showed significantly higher CBL around ZrO2 implants, and in 1 study,32 the CBL around ZrO2 and Ti implants was comparable. In the study by Kohal et al,28 the CBL was greater or equal to 2 mm in 34% of study participants. In the study by Borgonovo et al,23 more than 1.5 mm of CBL was found around 1 implant. In the study by Siddiqi et al,1 bone level was measured from the top of the implant (head of ball) to the first crestal bone contact at the mesial and distal aspect of the implant. In the studies by Payer et al31 and Borgonova et al,24 bone level was measured from the implant shoulder to the crest. The use of these modified bone level assessment techniques resulted in a baseline bone level in excess of zero. The survival rates for ZrO2 implants ranged between 67.6% and 100%. In 3 studies1,30,32 in which Ti implants were compared with ZrO2 implants, the survival rates were comparable. In the study by Siddiqi et al,1 the survival rate of ZrO2 implants was 67.6% and that of Ti implants was 66.7%. The follow-up period in the studies included ranged from 12 to 48 months.1,3,4,23-32 DISCUSSION One of the most frequently reported criteria for the success of conventional osseointegrated Ti implants is CBL of greater than 1.5 mm/year (with no radiographic Vohra et al

signs of pathology) during the first year of implant loading.33 Among the studies included in the present review,1,3,4,23-32 11 studies3,4,23-30,32 reported CBL of greater than 1.5 mm up to 4 years of follow- up. It is therefore speculated that crestal bone levels with ZrO2 and conventionally used Ti implants are comparable. However, in 93,4,23-29 of the 11 studies3,4,23-30,32 that reported CBL greater than 1.5 mm around ZrO2 implants, ZrO2 implants were not compared with Ti implants. In an attempt to clarify whether ZrO2 implants minimize CBL, these implants must be compared with Ti implants. From the studies included in the present systematic review, 3 studies1,30,32 compared CBL with ZrO2 and Ti implants. The results of the studies by Osman et al30 and Siddiqi et al1 reported increased CBL around ZrO2 implants compared with Ti implants, whereas, in the study by Payer et al,32 CBL was comparable around ZrO2 and Ti implants. This may be explained by the markedly varied methodologies of these studies. For example, in the studies by Osman et al30 and Siddiqi et al,1 ZrO2 and Ti implants were placed in edentulous jaws and were followed up for 12 months, whereas, in the study by Payer et al,32 implants were placed in partially dentate individuals and were followed up for 24 months. Moreover, the implant locations also varied among the studies. For instance, in the study by Payer et al,32 more than 75% of implants were placed in the mandible compared with THE JOURNAL OF PROSTHETIC DENTISTRY

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50% in the studies by both Osman et al30 and Siddiqi et al.1 Furthermore, in 2 studies,1,30 1-piece implants were used to support implant overdentures, but 2-piece implants were used to retain crowns and partially fixed dental prostheses in the study by Payer et al.32 One-piece implants may minimize bone loss by avoiding the implant abutment microgap and micromovements. Therefore, implant design, implant location, and coronal implant-supported restorations could have influenced the crestal bone levels around the implants reported in the studies comparing ZrO2 and Ti implants.1,30,32 Further long-term studies should focus on crestal bone levels around ZrO2 and Ti implants using standardized protocols. In the present review, 38% of studies26,28,29,31,32 showed significant CBL around ZrO2 implants at follow-up; however, in nearly 62% of the studies,1,3,4,2325,27,30 CBL around ZrO2 implants at baseline and follow-up was comparable. Multiple factors can explain the variability in these results. Alveolar bone remodeling is known to vary in immediate and conventionally placed implants.34-36 From the literature reviewed, in 326,28,30 of the 5 studies that showed significant bone loss around ZrO2 implants, the implants were placed in healed sites as well as fresh extraction sockets, making it difficult to estimate the precise amount of CBL that occurred around ZrO2 implants. Further studies focusing on ZrO2 implants placed in either healed sites or fresh extraction sockets are warranted to determine the extent of CBL around ZrO2 implants. Other factors that could have biased the outcomes of the reported studies include smoking and the use of guided bone regeneration. In the studies in which smokers were included,3,4,23,24,26,27,30 the duration of the habit was not reported. Smoking jeopardizes the outcome of the oral surgical procedure and increases CBL.37 In more than 45% of studies,3,2325,28,30 bone augmentation procedures were performed to enhance new bone formation around ZrO2 implants. This is a potential source of bias, in that new bone formation as a result of guided bone regenerative protocols would most likely mask the contribution of dental implants (regardless of their type, ZrO2 or Ti) in maintaining crestal bone heights.38,39 Assessing whether ZrO2 implants are able to maintain crestal bone levels in a manner similar to traditional Ti implants would have been possible if ZrO2 and Ti implants had been assessed exclusively in nonsmokers without the adjunct use of guided bone regeneration. The biologic response of periimplant soft tissue is favorable for ZrO2 implants because of the low bacterial adherence of ZrO2.10 With regard to clinical periimplant inflammatory parameters, periimplant inflammatory parameters remained uninvestigated in 2 studies.26,30 However, in the remaining studies,1,3,4,23-25,27-29,31,32 only selective clinical periimplant inflammatory parameters were THE JOURNAL OF PROSTHETIC DENTISTRY

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investigated. For example, in the study by Brull et al,4 BOP and PPD were assessed around ZrO2 implants, whereas PPD and BI remained uninvestigated in the study by Payer et al.32 Likewise, CAL (a critical factor in the assessment of periodontal/ periimplant disease) was assessed in only 2 studies.28,29,40 In order to assess the influence of ZrO2 on periimplant inflammatory parameters, studies with standardized protocols are required. CONCLUSIONS The variations in study design and methodology make a consensus difficult regarding the efficacy of ZrO2 implants in maintaining crestal bone levels and periimplant soft tissue health. Further long-term, randomized controlled trials with a standard methodology are needed. REFERENCES 1. Siddiqi A, Kieser JA, De Silva RK, Thomson WM, Duncan WJ. Soft and hard tissue response to zirconia versus titanium one-piece implants placed in alveolar and palatal sites: a randomized control trial. Clin Implant Dent Related Res. 23 Sep 2013. http://dx.doi.org/10.1111/cid.12159. [ePub Ahead of Print] 2. Pirker W, Wiedemann D, Lidauer A, Kocher AA. Immediate single stage truly anatomic zirconia implant in lower molar replacement: a case report with 2.5 years follow-up. Int J Oral Maxillofac Surg 2011;40:212-6. 3. Borgonovo AE, Censi R, Vavassori V, Dolci M, Calvo-Guirado JL, Delgado Ruiz RA, et al. Evaluation of the success criteria for zirconia dental implants: a four-year clinical and radiological study. Int J Dent. 26 August 2013. http://dx/ doi.org/10.1155/2013/463073. [ePub Ahead of Print] 4. Brull F, van Winklehoff AJ, Cune MS. Zirconia dental implants: a clinical, radiographic and microbiologic evaluation up to 3 years. Int J Oral Maxillofac Implants 2014;29:914-20. 5. Pjetursson BE, Thoma D, Jung R, Zwahlen M, Zembic A. A systematic review of the survival and complication rates of the implant-supported fixed dental prosthesis (FDPs) after a mean observation period of at least 5 years. Clin Oral Implants Res 2012;23:22-38. 6. Van Valzen FJ, Ofec R, Schulten EA, Ten Bruggenkate CM. 10-year survival rate and the incidence of the peri-implant disease of 374 titanium dental implants with a SLA surface: a prospective cohort study in 177 fully and partially edentulous patients. Clin Oral Implants Res. 5 November 2014. http://dx.doi.org/10.1111/clr.12499. [ePub Ahead of Print] 7. Guo Q, Lalji R, Le AV, Judge RB, Bailey D, Thomson W, et al. Survival rates and complication types for single implants provided at the Melbourne dental school. Aust Dent J. 27 October 2014. http://dx.doi.org/10.1111/adj.12248. [ePub Ahead of Print]. 8. Lindhe J, Myle J. Peri-implant diseases: consensus report of the sixth European Workshop on Periodontology. J Clin Periodontol 2008;35:282-5. 9. Mombelli A, Muller N, Cionca N. The epidemiology of peri-implantitis. Clin Oral Implants Res 2012;23:67-76. 10. Scarano A, Piattelli M, Caputi S, Favero GA, Piattelli A. Bacterial adhesion on commercially pure titanium and zirconium oxide disks: an in vivo human study. J Periodontol 2004;75:292-6. 11. Jacobi-Gresser E, Huesker K, Schutt S. Genetic and immunological markers predict titanium implant failure: a retrospective study. Int J Oral Maxillofac Surg 2013;42:537-43. 12. Sicilia A, Cuesta S, Coma G, Arregui I, Guisasola C, Ruiz E, et al. Titanium allergy in dental implant patients: a clinical study on 1500 consecutive patients. Clin Oral Implants Res 2008;19:823-35. 13. Javed F, Al-Hezaimi K, Almas K, Romanos GE. Is titanium sensitivity associated with allergic reactions in patients with dental implants? A systematic review. Clin Implant Dent Relat Res 2013;15:47-52. 14. Depprich R, Naujoks C, Ommerborn M, Schwarz F, Kubler NR, Handschel J. Current findings regarding zirconia implants. Clin Implant Dent Relat Res 2014;16:124-37. 15. Jimbo R, Albrektsson T. Long-term clinical success of minimally and moderately rough oral implants: a review of 71 studies with 5 years or more of follow-up. Implant Dent 2015;24:62-9. 16. Pozzi A, Mura P. Clinical and radiologic experience with moderately rough oxidized titanium implants: up to 10 years of retrospective follow-up. Int J Oral Maxillofac Implants 2014;29:152-61. 17. Rasperini G, Siciliano VI, Cafiero C, Salvi GE, Blasi A, Aglietta M. Crestal bone changes at teeth and implants in periodontally healthy and

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Corresponding author: Dr Fahim Vohra King Saud University PO Box 60169 Riyadh 11545 SAUDI ARABIA Email: [email protected] Copyright © 2015 by the Editorial Council for The Journal of Prosthetic Dentistry.

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