Implant Placement Depth and Peri-Implant Tissue Outcomes

Influence of Implant Placement Depth (-2 mm vs -4 mm Subcrestal) on Peri-implant Tissue Conditions: a Randomized Clinical Trial Protocol

The primary aim of this randomized clinical trial is to evaluate the influence of subcrestal implant placement depth (-2 mm vs -4 mm) on peri-implant marginal bone level changes, including marginal bone loss and bone remodeling. Secondary outcomes include implant success, peri-implant probing depth (PPD), and bleeding on probing (BoP).

Partially edentulous patients requiring fixed implant-supported prosthetic rehabilitation with two implants in posterior maxillary or mandibular regions will be included. Implants will be placed subcrestally at either -2 mm or -4 mm from the bone crest, following a submerged healing protocol. Allocation to insertion depth will be randomized. Marginal bone level changes will be assessed using standardized periapical radiographs at second-stage surgery, prosthesis placement, and at 1, 3, 6, and 12 months after functional loading. PPD and BoP will be recorded at the same time points.

Study Overview

• Status: Not yet recruiting
• Conditions: Marginal Bone Loss; Dental Implant Placement; Soft Tissue Management in Subcrestal Dental Implants
• Intervention / Treatment: Procedure: Subcrestal Implant Placement with Transmucosal Abutment and One Abutment-One Time Protocol

• Study Type: Interventional
• Enrollment (Estimated): 80
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Juan Carlos Bernabeu Mira, DDS, MSc, PhD; Phone Number: +34 697348312; Email: juan.c.bernabeu@uv.es

Study Locations

• Spain
  • Valencia
    • Valencia, Valencia, Spain, 46003
      • University of Valencia
      • Contact: Juan Carlos Bernabeu Mira, DDS, MSc, PhD; Phone Number: +34 697348312; Email: juan.c.bernabeu@uv.es
      • Contact: David Peñarroha Oltra, DDS, MSc, PhD; Phone Number: +34 649952560; Email: david.penarrocha@uv.es

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Patients ≥18 years old with partial edentulism.
• Need for rehabilitation with fixed implant-supported prostheses in posterior regions.
• Availability of minimum bone height for implants ≥6 mm in length.
• Minimum bone width without the need for guided bone regeneration.
• Supracrestal soft tissue thickness ≥2 mm.
• Non-smokers or smokers of ≤10 cigarettes/day.
• Plaque index and bleeding on probing <20%.
• Probing depth ≤3 mm.
• Signed informed consent.

Exclusion Criteria:

• Systemic diseases contraindicating implant surgery.
• Treatment with intravenous bisphosphonates.
• Head and neck radiotherapy.
• Uncontrolled diabetes.
• Pregnancy or breastfeeding.
• Alcohol or drug use.
• Psychiatric disorders.
• Need for bone regeneration procedures.
• Inability to complete follow-up.
• Implant failure during the study period.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: -2 mm subcrestal implant placement with 2-mm slim transmucosal abutments; Participants in this group will receive implants placed 2 mm below the level of the alveolar bone crest. Implants will share the same design, surface characteristics, and prosthetic connection, including platform switching. Slim transmucosal abutments with a height of 2-mm will be placed according to the subcrestal depth to ensure an adequate transmucosal profile and a stable relationship between the implant, peri-implant soft tissues, and the prosthetic restoration	Procedure: Subcrestal Implant Placement with Transmucosal Abutment and One Abutment-One Time Protocol; Participants will receive bone-level dental implants placed subcrestally at either -2 mm or -4 mm below the bone crest in healed posterior sites of the maxilla or mandible, according to randomization. Implant placement will follow the manufacturer's drilling protocol, achieving a final insertion torque of at least 35 Ncm. A transmucosal abutment will be connected at the time of surgery, with height selected based on implant placement depth (2-3 mm for -2 mm placement and 4-5 mm for -4 mm placement). The abutment will be tightened to a final torque of at least 30 Ncm following a one abutment-one time protocol.
Experimental: -2 mm subcrestal implant placement with 3-mm slim transmucosal abutments; Participants in this group will receive implants placed 2 mm below the level of the alveolar bone crest. Implants will share the same design, surface characteristics, and prosthetic connection, including platform switching. Slim transmucosal abutments with a height of 3-mm will be placed according to the subcrestal depth to ensure an adequate transmucosal profile and a stable relationship between the implant, peri-implant soft tissues, and the prosthetic restoration.	Procedure: Subcrestal Implant Placement with Transmucosal Abutment and One Abutment-One Time Protocol; Participants will receive bone-level dental implants placed subcrestally at either -2 mm or -4 mm below the bone crest in healed posterior sites of the maxilla or mandible, according to randomization. Implant placement will follow the manufacturer's drilling protocol, achieving a final insertion torque of at least 35 Ncm. A transmucosal abutment will be connected at the time of surgery, with height selected based on implant placement depth (2-3 mm for -2 mm placement and 4-5 mm for -4 mm placement). The abutment will be tightened to a final torque of at least 30 Ncm following a one abutment-one time protocol.
Experimental: -4 mm subcrestal implant placement with 4-mm slim transmucosal abutments; Participants in this group will receive implants placed 4 mm below the level of the alveolar bone crest. Implants will share the same design, surface characteristics, and prosthetic connection, including platform switching. Slim transmucosal abutments with a height of 4-mm will be placed according to the subcrestal depth to ensure an adequate transmucosal profile and a stable relationship between the implant, peri-implant soft tissues, and the prosthetic restoration.	Procedure: Subcrestal Implant Placement with Transmucosal Abutment and One Abutment-One Time Protocol; Participants will receive bone-level dental implants placed subcrestally at either -2 mm or -4 mm below the bone crest in healed posterior sites of the maxilla or mandible, according to randomization. Implant placement will follow the manufacturer's drilling protocol, achieving a final insertion torque of at least 35 Ncm. A transmucosal abutment will be connected at the time of surgery, with height selected based on implant placement depth (2-3 mm for -2 mm placement and 4-5 mm for -4 mm placement). The abutment will be tightened to a final torque of at least 30 Ncm following a one abutment-one time protocol.
Experimental: -4 mm subcrestal implant placement with 5-mm slim transmucosal abutments; Participants in this group will receive implants placed 4 mm below the level of the alveolar bone crest. Implants will share the same design, surface characteristics, and prosthetic connection, including platform switching. Slim transmucosal abutments with a height of 5-mm will be placed according to the subcrestal depth to ensure an adequate transmucosal profile and a stable relationship between the implant, peri-implant soft tissues, and the prosthetic restoration.	Procedure: Subcrestal Implant Placement with Transmucosal Abutment and One Abutment-One Time Protocol; Participants will receive bone-level dental implants placed subcrestally at either -2 mm or -4 mm below the bone crest in healed posterior sites of the maxilla or mandible, according to randomization. Implant placement will follow the manufacturer's drilling protocol, achieving a final insertion torque of at least 35 Ncm. A transmucosal abutment will be connected at the time of surgery, with height selected based on implant placement depth (2-3 mm for -2 mm placement and 4-5 mm for -4 mm placement). The abutment will be tightened to a final torque of at least 30 Ncm following a one abutment-one time protocol.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in peri-implant marginal bone level (mm)	Parallelized periapical radiographs will be obtained and a calibrated digital tool will be used to determine the vertical distance from the implant-abutment junction to the most coronal bone-to-implant contact on the mesial and distal sides. Unit of measure: Milimeters (mm)	From abutment placement (baseline time [TB]), 1 month post (T1), and at 3 (T3) (prosthetic loading) , 6 (T6), and 12 (T12) months after definitive prosthesis placement.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Peri-implant probing depth (mm)	Peri-implant soft tissue condition will be assessed by recording PPD using a periodontal probe at six surfaces per implant (mesiobuccal, midbuccal, distobuccal, and the corresponding lingual/palatal sites) to calculate the mean of every implant. Unit of measure: Milimeters (mm)	1 month post-op (T1), and at months 3 (T3) (prosthetic loading) , 6 (T6), and 12 (T12) after definitive prosthesis placement.
Bleeding on probing (presence/absence)	Bleeding on probing will be measured by gently passing a periodontal probe (using ~20-25g of force) to the base of the sulcus/pocket of the prosthesis at six surfaces per implant (mesiobuccal, midbuccal, distobuccal, and the corresponding lingual/palatal sites), then waiting 30 seconds to observe bleeding. It will be recorded as a dichotomous score (yes/no). Unit of measure: Percentage of sites showing bleeding per implant.	1 month post-op (T1), and at months 3 (T3) (prosthetic loading) , 6 (T6), and 12 (T12) after definitive prosthesis placement.
Implant success	Assessment of the implants will be performed by categorizing them into: success (optimal health), satisfactory survival, compromised survival, or failure.	From the time of surgery through the end of the 12-month follow-up period after definitive prosthesis placement.

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Baseline characteristics	Baseline variables will be collected for descriptive purposes and will not be combined into a single outcome measure. These include: age (years); sex (male/female); smoking habit (non-smoker or ≤10 cigarettes/day); brushing frequency (0, 1-2, or 3 times/day); edentulism type (interdental or free end); periodontal phenotype (thin or thick); antagonist type (natural teeth, tooth-supported bridge, implant-supported prosthesis, or removable prosthesis); cause of tooth loss (caries, periodontitis, or fracture); implant location (arch and quadrant); and soft tissue thickness (mm).	At enrollment time.

Collaborators and Investigators

• Sponsor: University of Valencia
• Investigators: Principal Investigator: Ana Verónica Blanco Besteiro, DDS, MSc and PhD candidate, University of Valencia

Study record dates

Study Major Dates

• Study Start (Estimated): May 15, 2026
• Primary Completion (Estimated): November 20, 2026
• Study Completion (Estimated): July 20, 2027

Study Registration Dates

• First Submitted: April 7, 2026
• First Submitted That Met QC Criteria: April 14, 2026
• First Posted (Actual): April 17, 2026

Study Record Updates

• Last Update Posted (Actual): April 17, 2026
• Last Update Submitted That Met QC Criteria: April 14, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Dental implant; Marginal bone loss; Subcrestal placement; Insertion depth
• Other Study ID Numbers: UV-INV-ETICA-3792383

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: The plan to share individual participant data (IPD) has not yet been determined.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No