A Retrospective Clinical Study with Regard to Survival and Success Rates of Zirconia Implants up to and after 7 Years of Loading Stefan Roehling, DDS;*† Henriette Woelfler, PhD;‡ Stefan Hicklin, DDS;§ Heinz Kniha, MD, DDS, PhD;¶ Michael Gahlert, DDS¶**

ABSTRACT Purpose: The study aims to retrospectively investigate the clinical performance of first-generation zirconia implants with a sandblasted surface up to and after 7 years of loading. Materials and Methods: Clinical records of patients treated with zirconia implants between 2004 and 2009 were screened. Consequently, adequate patients were invited to a clinical and radiographic investigation to classify each implant according to strict success criteria. Results: Seventy-one patients receiving 161 implants were available for the evaluation. Overall, 36 implants (22.4%) were lost due to early (n = 14) and late failures (n = 4) or fractures (n = 18). All surviving 125 implants fulfilled the success criteria. None of the investigated implants had a history of peri-implant infections. Mean values with regard to gingival index, plaque index, modified sulcus bleeding index, and probing depth were 0.03, 0.23, 0.59, and 2.80 mm, respectively. The radiographically evaluated mean crestal bone loss was 0.97 1 0.07 mm. Diameter-reduced implants (3.25 mm) showed lower survival (58.5%) compared with implants with a diameter of 4.0 mm (88.9%) and 5.0 mm (78.6%). The overall longitudinal survival rate was 77.3%. Conclusions: First-generation zirconia implants showed low overall survival and success rates. The evaluated clinical and radiographic parameters were consistent with healthy peri-implant tissues. Additionally, nonfractured failures were not associated with peri-implant infections. KEY WORDS: clinical study, implantology, implant survival, long-term study, long-term survival, retrospective, sandblasted, success rate, survival rate, zirconia

INTRODUCTION Implant therapy on partially or fully edentulous patients has become a science-based treatment modality in the clinical daily routine. The direct functional and structural connection/bonding of the implant’s surface with the surrounding bone tissue is the most important prerequisite for a successful osseointegration.1,2 Currently, the most often used material for the fabrication of dental implants is titanium.3 A recently published retrospective study investigated the clinical outcome of titanium implants with a moderately rough surface topography. A survival rate of 98.8% and a success rate of 97.0% after

*Resident oral surgery, PhD Candidate, Department of Oral and Cranio-Maxillofacial Surgery, Hightech Research Center, University Hospital Basel, University of Basel, Basel, Switzerland; †research fellow, Department of Periodontics, Health and Science Center at San Antonio, University of Texas, San Antonio, TX, USA; ‡professor for demography, University of Bamberg, Bamberg, Germany; §senior lecturer, Department for Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland; ¶ co-owner, Private Dental Clinic Dres. Kniha and Gahlert, Munich, Germany; **senior surgeon, staff scientist, Department of Oral and Cranio-Maxillofacial Surgery, Hightech Research Center, University Hospital Basel, University of Basel, Basel, Switzerland Corresponding Author: Dr. Stefan Roehling, Department of Oral and Cranio-Maxillofacial Surgery, Hightech Research Center, University Hospital Basel, University of Basel, Spitalstr. 21, 4031 Basel, Switzerland; e-mail: [email protected] The authors of the current study evaluated the presented data without any influence and support from industrial partners. All authors have no conflict of interest.

© 2015 Wiley Periodicals, Inc. DOI 10.1111/cid.12323

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a follow-up period of 10 years and more were reported, which confirmed the clinical long-term reliability of titanium implants.4 The development of strength oxide ceramics, such as alumina or zirconia, provided new metal-free treatment options for patients and clinicians. In comparison with other ceramics, zirconia has shown superior biomechanical properties such as high fracture toughness and bending strength.5 Since its introduction to dentistry in the beginning of the 1990s, zirconia has been used for all ceramic posts, as frameworks for all ceramic crowns and fixed dental prostheses (FDP), and for implant abutments.6 Currently, zirconia is the material of choice for the fabrication of ceramic dental implants.7 Due to its tooth-like color, it can be used for esthetically very demanding prosthetic reconstructions.8 Additionally, laboratory investigations have shown that zirconia implants might have the ability to withstand oral forces.9,10 Furthermore, it has been demonstrated that zirconia is very favorable for the formation of the epithelial attachments and the mucosal conditions,11 which can be seen as important prerequisites for preventing periimplant infections. Probably the most important advantage is the fact that several investigations have shown a significantly reduced bacterial adhesion on zirconia surfaces in comparison with titanium surfaces12,13 and also less inflammatory cells in the peri-implant soft tissue of zirconia in comparison with titanium or other metals.11,14 Histological results from animal investigations have shown that zirconia implants can directly integrate into osseous host tissue under nonloaded and even under loaded conditions.15–20 Analogue to titanium, it has been demonstrated that roughening of the implants’ surface also leads to an increased degree of bone-to-implant contact/osseointegration of zirconia dental implants21–26 and that micro-roughened zirconia implants show at least a comparable osseointegrative capacity compared with moderately rough titanium implants.22–26 With regard to the clinical application of zirconia dental implants, only very little evidence-based scientific data are available. In the literature, only a few studies are available that investigated the clinical outcome with different types of zirconia implants and the survival rates widely ranged between 0% and 98%.8,27 Furthermore, it was shown that the study design of most of the clinical studies that have been conducted so far showed considerable shortcomings and only low levels of evidence.28 It has been stated that “Well-conducted long-term studies

are urgently needed to permit a meaningful assessment of the survival or success rates of ZI (zirconia implants) and a statement concerning their application as an alternative to TI (titanium).”28 As modern zirconia implants with a micro-rough surface topography might have the potential to become an alternative to titanium for the fabrication of dental implants, and based on the fact that so far only very limited published data from clinical investigations are available, it is of great significance to get further sciencebased clinical results of commercially available zirconia dental implants. In a recently published retrospective study, it was demonstrated that commercially available firstgeneration zirconia implants with a sandblasted surface topography showed a survival probability of 82.4% up to and after 3 years of functional loading.29 Consequently, the aim of the present retrospective study was to evaluate the clinical performance of the same type of zirconia implants up to and after 7 years of functional loading. In contrast to the recently published study,29 more patients and implants have been investigated and besides the survival rates, also the success rates, the clinical parameters, and the peri-implant crestal bone remodeling have additionally been evaluated. MATERIALS AND METHODS The concept of the present study was approved by the Ethics Commission of the Ludwig-Maximilians Universität München (project number: 017-10). In this retrospective study, the records of all patients who have been treated in a private dental practice with first-generation monotype (i.e., the abutment for crown cementation is an inherent part of the implant body) zirconia Z-Look 3® dental implants (Z-Systems GmbH, Kiel, Germany) were checked. The currently investigated implant system has been commercially available in Germany since 2004. According to the manufacturer, the zirconia implants had a sandblasted surface topography however, no information with regard to qualitative or quantitative data was available. Fully edentulous as well as partially edentulous patients who received at least one monotype full-zirconia dental implant between October 2004 and November 2009 were included in the study. Subsequently, these patients were contacted and invited to participate in a clinical follow-up examination. All patients gave their written consent after being informed in detail about the objectives of the study.

Long-term Performance of Zirconia Implants Long-term Performance of Zirconia Implants 5473

All implant surgeries were performed according to science-based surgical principles30 and according to the specifications of the zirconia implant manufacturer. During the drilling of the implant bed, bone quality was assessed on the tactile perception of the drilling resistance and categorized into dense bone (D1), normal bone (D2, D3), and soft bone (D4).31 After placement, all implants were protected against premature loading with protective stents or protective dentures, which were manufactured before or immediately after surgery. The information regarding implant surgery (number, diameter, length and position of inserted implants, age, gender, risk factors, and bone quality) was extracted from the clinical records.

taken immediately after implant placement and at the last follow-up investigation were selected and analyzed as previously described.35 The nonstandardized digital panoramic images were analyzed using NIH ImageJ 1.33 (6 Bethesda, Maryland, USA) open software. When possible, the known implant length of each implant was used for calibration. When the implant length was not clearly visible, the known distance between the implant threads was used for calibration of each implant. With this calibration, the linear measurements were transformed into millimeters. The following parameter was evaluated: •

Distance from the Implant shoulder to the first visible Bone-to-implant contact (DIB) at two sites (mesial, distal) of the implant.35 The DIB value of each implant was calculated as the average of the mesial and distal value obtained. For each implant, the DIB was evaluated directly after implant placement (DIB1) and at the time point of the last follow-up investigation (DIB2). Additionally, the difference between DIB1 and DIB2 (DIB2 – DIB1) was calculated to identify the amount of crestal bone remodeling.

Clinical Examination At the follow-up examination, the patients were clinically examined and additionally, all implants and restorations were photographed. The following parameters were evaluated: • • • • • •

• •

Presence or absence of subjective complaints (pain, foreign body sensation, dysesthesia) Presence or absence of recurrent peri-implant infections with suppuration Presence or absence of implant mobility Gingival Index (GI) at four sites (vestibular, oral, mesial, distal) around the implant32 Modified Plaque Index (mPLI) at four sites around the implant33 Probing Depth (PD) measured in millimeters with a standard periodontal probe at four sites (vestibular, oral, mesial, distal) around the implant Modified Sulcus Bleeding Index (mBI) at two sites (vestibular, oral) of the implant33 Distance from the Implant shoulder to the mucosal Margin (DIM), measured in millimeters with a standard periodontal probe at two sites (vestibular, oral) of the implant.34 Only positive DIM values (visible implant shoulders) were recorded to identify incidence and occurrence of soft tissue recessions.

Radiographic Examination Radiographic analysis was performed on the basis of the digital panoramic radiographs that were taken in the course of the regular implant recall. For peri-implant bone loss analysis, the panoramic radiographs that were

Implant Success On the basis of the obtained clinical and radiographic data, each implant was classified as success or failure according to previously published success criteria by Buser and colleagues (Table 1).36 Patient Satisfaction In order to analyze the patients’ satisfaction and perception of the implant therapy, the patients who were clinically and radiographically followed up were asked to fill in a questionnaire based on the protocol described by Pjetursson and colleagues37 and Simonis and colleagues (Table 2).38

TABLE 1 Criteria of Success36 1 2 3 4 5

Absence of persistent subjective complaints such as pain, foreign body sensation, and/or dysesthesia Absence of a peri-implant infection with suppuration Absence of mobility Absence of a continuous radiolucency around the implant Possibility for restoration

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TABLE 2 Patient Questionnaire Questions

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Q11 Q12

Statements

“My crown/my bridge functions very well, and I can chew on it very well” “I feel more secure biting on my teeth/implant” “To speak, I can use my crown/bridge very well” “I am pleased with the aesthetic results” “I can clean my implants very well” “It is easier for me to clean my implants than to clean my teeth” “I need more time to clean my teeth/implant” “The tissues around the implants bleed less than around the teeth” “I got exactly what I expected” “I would like this treatment again, if needed” “I would recommend this treatment to a friend or relative, if indicated” “I found that the cost of the treatment was justified”

Statistical Analysis The time-dependent survival probability of the investigated implants was calculated according to Kaplan–Meier.39 The survival time is given through the date of implant placement until date of recurrence or recall, and represents the time passed without implant failure. Comparisons between survival times for varying diameter and age at implant placement were performed by a log-rank test. For all statistical analysis, a p value of

A Retrospective Clinical Study with Regard to Survival and Success Rates of Zirconia Implants up to and after 7 Years of Loading.

The study aims to retrospectively investigate the clinical performance of first-generation zirconia implants with a sandblasted surface up to and afte...
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