Alveolar Ridge Sequelae Due to Peri-implantitis: a Retrospective Observational Study
Condition: Dental Implant; Peri-Implantitis; Bone Remodeling
MeSH terms: Peri-Implantitis
Study type: Observational

Summary: 
      The scientific evidence available at present regarding the alterations suffered by the
      alveolar ridge after the explantation of implants that have been considered to be abandoned
      due to periimplantitis, as well as the remaining sequelae from said treatment, is scarce and
      inconclusive.

      Regarding this background, it is speculated that the different types of peri-implant defects
      present different bone remodeling and different sequelae after the explantation of the
      implants affected by peri-implantitis.

      Thus, it has been hypothesized that the peri-implant defect configuration has an influence on
      the radiographic bone alterations that occur after explantation.

      In order to test this hypothesis, a retrospective study has been designed as it follows:
      Patients who have undergone implant placement procedure and suffer from peri-implantitis will
      be consecutively included in the study. In addition, patients should present at least 2 CBCTs
      taken before and after explantation, 4-6 months apart. Linear measurements will be taken in
      order to assess dimensional changes of the alveolar ridge at 1, 3, 5 and 7 mm from the bone
      crest.
    

Detailed description: 
      Peri-implant diseases have been a growing problem for the last decades. A recent
      cross-sectional study conducted in the Spanish population has shown a prevalence of mucositis
      and peri-implantitis at the implant level of 27% and 20%, and of 27% and 18% at the patient
      level, respectively (Rodrigo et al. 2018). As the peri-implant disease progresses, it has
      been observed that it generates different types of defects around implants affected by this
      pathology. Recently, Monje et al. 2019, have classified these defects according to their
      morphology (infrabony defects, supracrestal/horizontal defects or combined defects) and
      according to the depth of the defect and total bone loss/total implant length (3-4mm/<25% of
      implant length, 4-5mm/≥25-50% of implant length, >6mm/>50% of implant length (Monje et al.
      2019).

      Bone remodeling, as well as the sequelae or morphological alterations suffered by the
      alveolar ridge after tooth extraction have been widely described in the literature (Amler et
      al. 1960, Evian et al. 1982, Cardaropoli et al. 2003). In an animal model, Araujo and
      coworkers described the alterations of the alveolar ridge following tooth extraction;
      observing that bone height reduction of the buccal plate was more pronounced than the
      lingual, and that vertical bone loss was always associated with horizontal bone loss (Araujo
      et al. 2005). In contrast, the evidence available nowadays regarding the alterations suffered
      by the alveolar ridge after the explantation of implants that have been considered to be
      removed due to peri-implantitis, as well as the remaining sequelae from said treatment, is
      scarce and inconclusive.

      Therefore, the the primary objective of this study will be to evaluate radiographically the
      influence of the peri-implant defect configuration on the radiographic bone alterations after
      implant explanation.

      In this sense, a retrospective observational study will be design. The protocol of which will
      be approved by the Ethics Committee of the University of Extremadura (Badajoz, Spain), and
      will follow the Declaration of Helsinki on human studies. In addition, this study will be
      reported in accordance with the Analysis Strenghtening the Reporting of Observational Studies
      in Epidemiology (STROBE) Statement .

      Patient recruitment will be obtained from a private practice exclusively dedicated to
      periodontics and implantology. Edentulous patients, either total or partial, who previously
      underwent implant placement procedure will be consecutively included in the study. A
      prerequisite for being eligible for the study was to have at least 2 CBCts, one taken before
      explantation in order to diagnose peri-implantitis; and the other taken after explantation.

      In order to define a peri-implantitis case, it will be based on the consensus report of
      Workgroup 4 of the 2017 World Workshop on the Classification of Periodontal and Peri-implant
      Diseases and Conditions (Berglundh et al., 2018), in which it was stated that, in the absence
      of baseline information, the diagnosis of peri-implantitis required: presence of bleeding
      and/or suppuration on gentle probing, probing depth ≥6 mm and bone level ≥3mm apical to the
      most coronal portion of the implant or at the rough-smooth interface in transmucosal
      implants.

      Once defined, several variables will be recorded, including both patient- and implant-related
      ones. The former will include age, gender, type of edentulism (total/partial), history of
      periodontal disease (mild, moderate or severe), tobacco smoking (heavy smoker >10
      cigarettes/day; light smoker <10 cigarettes/day, former smoker 0 cigarette/day or
      non-smoker), numbers of implant per patient, and keratinized mucosa (0, <2 or ≥2 mm).
      Implant-related variables will include position (mandible / maxilla / anterior / posterior),
      implant system (brand, diameter, length and type of connection), implant macrodesign
      (transmucosal/bone level), type of prosthesis (single/multiple; screw/cement-retained), as
      well as explantation method (trephine, tweezers, forceps or implant removal kit). In
      addition, whether regeneration was performed or not after explantation will be recorded, as
      well as the material used for it.

      For the radiographic assessment, images were acquired by CBCT i-CAT Model 17-19 (Imaging
      Sciences International LLC, Hatfield, PA, USA). The imaging parameters were set at a width
      and depth of 16 × 13 mm, 120 kVp, 20.27 mAs, scan time 14.7 seconds, resolution 0.25 voxel
      and a field of view (FOV), which varied based on the scanned region. Defect morphology and
      severity were determined using the OnDemand3D software (Cybermed, Seoul, Korea) by one
      previously calibrated examiner.

      Prior to the assessment of the different radiographic variables, two reference lines will be
      established: longitudinal axis of the implant and a perpendicular line to it tangent to a
      reference point (sinus floor in the maxilla and mandibular base in the mandible). Several
      parameters will be assessed before and after explantation in each implant, including:
      bone-to-implant contact (BIC) at 4 sites (mesial, distal, buccal, lingual), defined as the
      first contact between the bone and the implant surface, assessed from the most coronal part
      of the intraosseous component of the implant; bone plate thickness (BPT), assessed at buccal
      and lingual in mm. The reference point will be the bone crest and bone thickness will be
      recorded at 1, 3, 5 and 7 mm from the crest. In addition, ridge width (RW) will be also
      recorded at 1, 3, 5 and 7 mm from the bone crest. If there is any discrepancy between buccal
      and lingual bone crest, the most apical one will be chosen as the reference.

      In order to assess changes in bone crest height, the distance between the most coronal point
      of the bone crest (buccal and lingual) and the reference line tangent to a fixed reference
      point was calculated in mm.

      BPT and RW at 1, 3, 5 and 7 mm will be also assessed when the implant has been already
      explanted, recording the months that have passed from the explantation.

      For the characterization of the peri-implantitis defects, the defect morphology and severity
      classification by Monje and coworkers will be followed (Monje et al. 2019):

        -  Morphology:

             -  Class I: Infraosseous defect. Class Ia: Buccal dehiscence. Class Ib: 2-3 walls
                defect. Class Ic: Circumferential defect.

             -  Class II: Supracrestal/horizontal defect.

             -  Class III: Combined defect. Class IIIa: Buccal dehiscence + horizontal bone loss.
                Class IIIb: 2-3 walls defect + horizontal bone loss. Class IIIc: Circumferential
                defect + horizontal bone loss.

        -  Severity: based upon the defect depth from the implant neck and ratio of bone loss/total
           implant length

             -  Grade S: Slight: 3-4 mm/<25% of the implant length

             -  Grade M: Moderate 4-5 mm/ ≥25%-50% of the implant length

             -  Grade A: Advanced: >6 mm/>50% of the implant length

      Regarding the statistical analysis, the statistical package (SPSS 15.0, SPSS Inc., Chicago,
      IL, USA, STATISTICS, version 7.1StatSoft, Inc. will be used for this purpose. The Pearson
      correlation test will be applied for the assessment of confounding factors and Linear
      regression models based on generalized estimating equations (GEEs) will be used to analyze
      the differences in the mean values of the post-extraction bone changes during the 2 time
      phases. This model will consider the correlations of within-subject repeated measures.
    

Intervention name(s): CBCT measurements
Intervention type(s): Other
Intervention description(s): No intervention will be performed on patients for this study. Based on the CBCTs already done previously of the patients in the sample, linear measurements will be taken in order to assess dimensional changes of the alveolar ridge at 1, 3, 5 and 7 mm from the bone crest in the CBCTs taken before and after implant explantation, 4-6 months apart.
Observational model: Other
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        Patient recruitment will be obtained from a private practice exclusively dedicated to
        periodontics and implantology (Clinica CICOM, Badajoz, Spain). Edentulous patients, either
        total or partial, who previously underwent implant placement procedure and which suffer
        severe peri-implantitis will be consecutively included in the study.
      
Keywords: dental implant; dental implant failure; peri-implantitis; bone loss; bone remodeling; implant explantation