Volumetric Evaluation of Gingival Augmentation Around Dental Implants
Condition: Atrophy of Gingiva
MeSH terms: Gingival Recession
Study type: Observational

Summary: 
      The goal of this observational prospective study is to objectively assess the dimensional
      (volume & linear variance) and clinical changes of vestibular gingival soft tissues upon
      treatment with laser-aided pouch roll augmentation technique and implant placement over a
      12-month follow-up. Twelve patients with 16 mild horizontal ridge deficiencies in different
      edentulous sites scheduled for implant placement were enrolled. Digital impressions were
      taken with an intra-oral laser scanner and software and analyzed before (day 0) and 12 months
      after laser-aided pouch roll augmentation surgery. The digital files were converted to STL
      format and superimposed to assess peri-implant volumetric and linear dimensional variations
      in selected regions of interest (ROI) by a 3D analysis software. Operator-assessed clinical
      periodontal parameters (probing depth PD, bleeding on probing BoP, plaque index PI) were
      recorded. Patient-reported outcome (pain, discomfort, treatment liking) and aesthetic result
      were evaluated by administration of appropriate questionnaires.
    

Detailed description: 
      Introduction Adequate soft tissue thickness at the vestibular aspect of dental implants are
      crucial for satisfactory implant engraftment and aesthetic outcome. To pursue this objective,
      numerous surgical procedures have been adopted to augment the peri-implant gingiva, including
      autologous soft tissue grafting, xenogeneic collagen matrix, acellular dermal matrix, and
      roll/pedicle flap techniques: however, the available data do not suffice to clearly indicate
      which technique yields the best results.

      The pouch roll techniques, originally proposed by Abrams in 1980 and subsequently improved,
      are particularly effective because they maintain vascularity of the grafted flap, which
      greatly facilitates its survival. Most of these procedures use a scalpel to shape the flap
      and remove the keratinized epithelial layer, but this conventional pouch roll technique is
      hampered by the fact that flap thickness must be no less than 3 mm and it is very difficult
      to perform hand scalpel gingival de-epithelization of the without damaging the underlying
      connective tissue, thereby causing bleeding and predisposing to scarring in the long term.
      More recently, laser-aided epithelial photoablation has been proposed as a possible solution
      to these issues. In fact, diode laser operating at 810 nm wavelength (λ) has been
      successfully used for selective de-epithelialization for several periodontal therapy
      purposes, e.g. palatal grafts for gingival recession defects, gingival hyperpigmentation,
      intra/extra pocket decontamination in chronic periodontitis and placement to second-stage
      surgery for buried implant exposure. Laser photoablation offers several advantages, namely
      excellent hemostasis that results in a dry surgical field and better view of the operative
      field, tissue surface sterilization and shallow penetration limited to the gingival
      epithelium with minimal injury and inflammation of the underlying lamina propria. On this
      ground, the investigators successfully combined diode laser photoablation (λ 810 nm) to
      conventional roll flap technique for mild vestibular ridge deficiencies: in a preliminary,
      limited series of patients (n=3) this improved method resulted in fast healing, satisfactory
      clinical and aesthetic results, rapid prosthetic restoration and no need for local or
      systemic analgesics. The present study aims on one hand at expanding the case series to
      consolidate the preliminary findings, on the other hand at evaluating another key clinical
      outcome parameter of this laser-aided roll flap procedure, namely the actual, objective
      gingival soft tissue augmentation over time. To this purpose, the volume of the treated
      regions, acquired by a digital intra-oral scanning, was measured and analyzed by appropriate
      3D software and compared before roll flap surgery and implant placement and upon 12-month
      follow-up. Post-operative discomfort and aesthetic satisfaction of the patients were also
      assessed.

      Material and methods

      Volumetric measurements and analysis - Volume changes of the vestibular gingiva before and
      after the laser-aided roll-flap augmentation were evaluated and compared on digital
      intra-oral scanning impressions taken with an intra-oral scanner (Dentsply Syrona, Rome,
      Italy) and 3D reconstruction software (Exocad, Darmstadt, Germany). To reduce possible
      deviations and ensure higher accuracy of 3D analysis, quadrant instead of full-arch scans
      were recorded. These were converted to standard tessellation language (STL) format. Pre and
      post-operative STL files were collected, aligned and superimposed by selecting 10
      reproducible anatomical points as landmarks prior to be analyzed with an appropriate software
      (Rhyno3D, Washington DC, USA). This software allowed: i) to demarcate an exact 3D region of
      interest (ROI), ii) to superimpose the same ROI taken at 2 time points, i.e. before surgery
      (day 0) and at 12-month follow-up, while to measure the volume of the 2 corresponding ROI and
      to objectively assess their differences at the different time points. Each selected ROI
      corresponded to a single or multiple implant site. According to previous studies, ROI in the
      single implant sites was demarcated on the vestibular gingival aspect using the following
      criteria:

        1. gingiva-to-implant margin (or coronal gingival ridge, if before implant placement) as
           horizontal coronal border;

        2. muco-gingival junction as horizontal apical border;

        3. two vertical lines, 2 mm aside the surgical flap incision and corresponding to the
           mid-point of the interdental papillas, as mesial and distal borders.

      Due to individual variations in oral anatomy, ROI were obviously different among the
      patients, but substantially identical in the same patient at successive time points. The
      software was set to a spatial resolution of ±50 nm between the STL files: in this way,
      negligible or no variations <50 nm in the merged STL file appeared green in a visual
      pseudo-color range. To assess reproducibility of the method, a trained blinded examiner
      (M.P.), performed 2 measurements at 1-week interval: intra-class correlation coefficient was
      0.87 (95% CI 0.82-0.91).

      In each patient, the 2 ROI volumes (cubic mm) measured at day 0 and 12 months were compared
      to evaluate the changes of the vestibular gingival soft tissue over time. Exocad software
      also allowed to determine the linear dimensional changes (LD), i.e. the linear distance (mm)
      between the 2 ROI surfaces measured at 1, 3 and 5 mm along a vertical midline traced between
      the gingival free margin and the muco-gingival junction, as previously reported.

      Clinical peri-implant parameters and calibration - At 12 months, a trained and blinded
      examiner (L.L.) evaluated PD and BoP (within 30 s after probing) at 6 sites per implant (3
      buccal, 3 palatal) and PI (yes/no, 4 sites per implant), using a conventional manual
      periodontal probe (PCP15, Hu-Friedy, Milan, Italy) with about a 0.3 N force. Operator
      calibration was considered satisfactory when the percent fitting between the first and second
      measurements taken at a 24-h gap was ≥ 90%.

      Primary outcome variables

        1. Objectively measurable volumetric changes (cubic mm) of the ROI regions between day 0
           and 12 months.

        2. Objectively measurable linear dimensional changes (LD, mm) of the ROI regions between
           day 0 and 12 months;

      Secondary outcome variables

        1. Changes in periodontal probing depth PD (mm)

        2. Changes in periodontal bleeding on probing BoP (yes/no),

        3. Changes in plaque index PI (yes/no)

        4. Subjective perception of discomfort and pain during surgery and the post-operative
           period, semi-quantitatively assessed by Visual Analogue Scale (VAS) questionnaires
           administered 5 h after surgery and each morning for the next 7 days (score: 0,no pain to
           10,extremely painful);

        5. analgesics taken (number);

        6. willingness to undergo the same treatment again (yes/no).

        7. Color and texture differences between peri-implant and natural gingiva at 12 months,
           subjectively evaluated by the patients at a mirror from speaking distance (visible/not
           visible).

      Operators - Laser-aided roll-flap technique was performed by a dental practitioner (M.G) with
      long-lasting expertise in periodontal surgery, implant dentistry and use of dental laser
      technology.

      Surgical treatments - The delivered laser-aided roll flap technique was performed as
      previously described. It consisted in the following steps:

        1. De-epithelialization of a vestibular gingival area, 2 mm larger than the cover screw
           diameter, using a λ 810-nm diode GaAlAs laser (4x4 Dental Laser System, General Project
           Ltd., Montespertoli, Florence, Italy) equipped with a ∅ 600-μm optical fiber and set as
           follows: pulse mode, frequency 8,000 Hz, pulse energy 69 μJ, pulse duration 18 μs,
           corresponding to 0.6 W

        2. mean power (peak 3.8 W) and 40 J/square cm irradiation energy. Photoablation was
           performed in fiber tip contact mode at a constant speed of about 2.5 mm/s under airflow
           cooling and thermographic feedback to prevent tissue over-heating and damage. The
           procedure was made under a high-resolution stereomicroscope (Extaro 300, Zeiss, Milan,
           Italy).

        3. Full-thickness U-shaped incision of the photoablated mucosa was made with the same λ
           810-nm diode laser set at pulse energy 22 μJ, peak power 3.14 W, frequency 20 kHz, pulse
           width 7 μs, in contact mode and equipped with a ∅ 300-μm optical fiber. The incision
           margins were extended to the vestibular gingiva for 2 to 3 mm to facilitate flap
           displacement.

        4. Elevation and rolling of the full-thickness flap into a vestibular pouch, no surgical
           sutures.

        5. Relieve or remove any soft tissue or bone interferences by adjusting the abutment or the
           tissues.

        6. Connection of titanium abutments or healing abutment to the implants. Overall time of
           the surgical procedure was measured, starting from the end of local anesthesia to
           connection of titanium abutment.

      Post-surgical instructions and prosthetic treatments - No local or systemic antibiotics,
      mouthwashes or toothpastes containing triclosan, chlorhexidine, or other disinfectants were
      prescribed. The patients were instructed to avoid brushing of the treated zone for about 6
      hours from surgery and then to perform normal oral hygiene.

      Prosthetic treatment including the application of a temporary crown and the final
      rehabilitation was performed according to a standard treatment plan.

      Statistical analysis - This was performed with Prism5 software (GraphPad, Boston, MA, USA).
      The ROI of each treated implant/tooth site was taken as unit of analysis. Differences in ROI
      volumes (mean ±SEM) measured before the treatment (day 0) and at 12-month follow-up were
      analysed statistically by Student's t test for paired values. A p value ≤0.05 was considered
      significant.
    

Intervention name(s): volumetric evaluation of gingival augmentation around dental implants
Intervention type(s): Other
Intervention description(s): objective volumetric and clinical assesment of vestibular gingival soft tissues changes upon treatment with laser-aided pouch roll augmentation technique and implant placement over a 12-month follow-up
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        12 partially edentulous patients (mean age 62; range 42-86; 9 males/5 females) requiring
        vestibular soft tissue augmentation at implant sites in second-stage surgery because of
        mild horizontal ridge deficiency were enrolled
      
Keywords: dental implants; roll flap; gingival augmentation; volume changes; linear dimensional changes; clinical periodontal parameters; patient-reported outcomes