Study population
A total of 29 partially edentulous subjects were consecutively recruited from the Dental School of Medicine, Philipps-University, Marburg, Germany between April 2010 and April 2013 (Table
1). Subjects were excluded for the following reasons: history of systemic disease (e.g., cardiovascular diseases, diabetes mellitus, osteoporosis), pregnancy, untreated caries, current orthodontic treatment, continuous drug administration, and psychiatric disorders. Systemic diseases were assessed by an internist.
Table 1
Implants in study population
Patient | 24 | 5 |
Sex |
Female | 15 | 3 |
Male | 9 | 2 |
Age |
< 50 years | 2 | 2 |
> 50 years | 22 | 3 |
Implant system |
Nobelspeedy Replace RP | 49 | 17 |
Nobelspeedy Replace NP | 16 | 4 |
Nobel Replace Straight Groovy | 29 | 5 |
Nobelspeedy Groovy | 10 | 0 |
Topography |
Anterior maxilla | 26 | 12 |
Posterior maxilla | 36 | 10 |
Anterior mandible | 18 | 0 |
Posterior mandible | 24 | 4 |
Superstructure |
Single crowns | 52 | 4 |
Removable | 41 | 21 |
Fixed bridges | 11 | 0 |
Bone quality |
1 | 3 | – |
2 | 97 | 21 |
3 | 4 | 5 |
Degree of atrophy |
A | 41 | 12 |
B | 28 | 14 |
C | 35 | – |
All subjects were treated for periodontitis at the Dental School of Medicine, Philipps-University, Marburg, Germany. Periodontal treatment was followed by a 3-month recall schedule for 3 to 6 years. Each recall session comprised oral hygiene control with motivation and instruction, subgingival scaling, and root planing at tooth surfaces with probing depth (PDs) > 4 mm, and bleeding on probing (BOP). Preceding implant placement, non-retainable teeth were removed and subgingival scaling and root planing were performed for residual teeth where necessary. Six months after tooth removal, the residual teeth showed healthy periodontal tissue with PDs ≤ 3 mm and no BOP.
Periodontal disease was diagnosed according to the criteria of the American Academy of Periodontology [
16]. The clinical and radiological findings in the recall schedule before insertion of the implants were the basis to distinguish between generalized chronic periodontitis (GCP) and generalized aggressive periodontitis (GAP). Twenty-four subjects (9 males and 15 females; mean age, 63 years) with GCP displaying more than 30% of sites affected, with bone loss < 0.2 mm per year. Five subjects (two males and three females; mean age, 31 years) with GAP displaying more than 30% of sites affected, with bone loss > 0.2 mm per year.
Implant placement and prosthesis
At total, 130 implants with oxide-coated surfaces (Nobel Replace Straight Groovy; Nobel Speedy Groovy; Nobel Speedy Replace, Nobel Biocare, Zürich, Switzerland) were placed with a length of 10 to 15 mm and a diameter of 3.5 or 4 mm. In GCP subjects 104 implants were inserted, and in GAP subjects, 26 implants (Table
1).
In both groups, the bone quality and atrophy of the alveolar bone were classified during implant insertion according to Lekholm and Zarb [
17].
Second-stage surgery was performed in the maxilla after 6 months and in the mandible after 3 months. Implant placement and second-stage surgery were performed by a single periodontist (R.M.).
About 4 weeks after the final abutments were placed, GCP subjects were rehabilitated with single crowns, implant-supported bridges, or removable superstructures, according to the Marburg double crown system [
18] (Table
1). In GAP subjects, single crowns or removable superstructures (Marburg double crown system) were inserted. All prosthetic appliances were provided at the Dental School of Medicine, Philipps-University, Marburg, Germany. All crowns and bridges were cemented and solely porcelain-fused-to-metal restorations.
Clinical parameters
At each session, the Gingival Index (GI) [
19], Plaque Index (PI) [
20], PDs, BOP, gingival recession (GR), and clinical attachment level (CAL) were evaluated at four sites (mesial, distal, buccal, and lingual/palatinal) on the teeth and implants. The CAL was measured at the teeth from the cement-enamel junction to the base of the pocket. For implants, the upper edge of the corresponding final abutment served as the top reference point. Trauma to peri-implant tissue was avoided by waiting 1 year after implant placement before measuring probing depths.
The clinical examinations were performed by four examiners (all dentists, formally affiliated with the Dental School of Medicine, Philipps-University, Marburg, Germany) before study initiation, each examiner was calibrated for intra- and interexaminer reproducibility using duplicate measurements of a minimum of 50 sites in at least five subjects. The correlation coefficients were 0.90 to 0.99 for intraexaminer reproducibility and 0.91 to 0.95 for interexaminer reproducibility.
Radiographic examination
Standardized radiographs of the teeth and implants were taken by two persons using the parallel technique [
21]. These radiographs were obtained immediately after insertion of the superstructure (baseline for mucositis and peri-implantitis evaluation) and at 1, 3, and 5 years thereafter. The digitized radiographs were evaluated using a computer software (Planmeca Romexis Version 3.0.1, Planmeca, Helsinki, Finland). Bone loss was determined in relative terms at the mesial and distal tooth surfaces by measuring the distance from the CEJ to the apex. The distance from the marginal bone level to the upper edge of the implant was measured (in mm) at the mesial and distal implant surfaces and related to the implant thread. All radiographs were analyzed by an independent masked examiner.
Study follow-up schedule
All patients received a supportive periodontal therapy at the Dental School of Medicine, Philipps-University, Marburg, in the course of the observation period. The first clinical examination was 2 to 4 weeks before the non-retainable teeth were extracted. The periodontally healthy residual dentition and the implants were evaluated immediately after the superstructure was inserted. Subsequently, the subjects were followed up at 3-month intervals for 3 to 6 years. At each follow-up session, the clinical parameters were recorded and subjects were remotivated and reinstructed in effective oral hygiene. In addition, the teeth and implants were cleaned professionally. Supragingival deposits were removed, followed by polishing with rubber cups and polishing paste. Subgingival debridement was performed in the teeth and implants with PDs > 4 mm and BOP positive. In the teeth, conventional stainless-steel curettes and ultrasonic devices were used, whereas in implants, plastic curettes and polyether ether ketone-tips for the ultrasonic device were applied to avoid damage of the implant surface.
A functional analysis and medical history were performed at the beginning of the study and reviewed annually.
Cigarette smoking status was self-reported. Subjects were considered smokers if they had been smoking 10 or more cigarettes a day during the past 5 years [
22].
Statistical evaluations
Data analysis was performed with a computerized statistics package (SPSS 12.0.1 for Windows, SPSS). The examined patients were not included in any other publications.
Mean values for clinical and radiologic parameters were determined separately for the implants and the teeth, for both patient groups, and for every visit. Four visits were consolidated for analysis.
The probability of implant loss (implant survival) at a certain time was computed with reference to previously established criteria using a Kaplan-Meier survival curve.
The assessment of implant success, mucositis, and peri-implantitis was performed at the time of radiographic examination 1 year after insertion of the superstructure and 3 and 5 years thereafter.
The implant success rate was defined by the following parameters: no implant movement, no discomfort (pain, foreign body sensation etc.), PDs ≤ 5 mm without BOP, no continuous radiologic translucency surrounding implants, and annual peri-implant bone loss ≤ 0.2 mm 1 year after insertion of the superstructure [
23]. Implants that did not meet at least one criterion were considered a failure.
Peri-implant mucositis was defined as PDs ≥ 5 mm with BOP and no bone loss after the first year of loading. Peri-implantitis was defined as PDs > 5 mm with or without BOP and an annual bone loss of > 0.2 mm after the first year of loading.
All technical and surgical complications (e.g., fracture of the abutment screw or superstructure, compromised wound healing) were recorded.
The potential risk factors of gender, implant topography, implant length, type of superstructure, and bone quality and atrophy were analyzed for their correlation with the prevalence of mucositis, peri-implantitis, implant success, and survival. At first, the effect of each risk factor was tested with a univariate regression analysis. A multivariate analysis was performed for risk factors with P values of ≤ 0.05 in the univariate analysis. The extent of the effect of a risk factor was indicated with an odds ratio (OR), with a confidence interval (CI) of 95%.