Effect of Bone-related and Soft-tissue-related Variables on the Marginal Bone Loss of Platform-matched and Platform Switched Dental Implants

In this clinical trial the effect of the implant-abutment morphology (platform-switched vs platform matched) will be assessed in both soft tissue (soft tissue thickness) and hard tissue (marginal bone loss) outcomes. Several clinical predictors (initial implant position level, gingival biotype, abutment height and prosthetic emergence profile) will also be taken into account as modulating factors of the clinical outcome.

This prospective clinical trial is conducted at the Dental Clinic of the Faculty of Medicine of the University of Salamanca. The protocol was developed in accordance with the 1975 Declaration of Helsinki, and later approved by the Bioethics Committee of the University of Salamanca with the number (Ref:473/2020)

Before initiating any procedure, each patient received information about the study design and signed an informed consent. The subjects are recruited consecutively following the admission protocols of the Dental Clinic of the Faculty of Medicine of the University of Salamanca, Salamanca, Spain. The inclusion criteria are:

(1) Patients of legal age (\>18 years); (2) in need of at least one maxillary or mandibular dental implant to be inserted in mature bone (more than 4 months after tooth extraction) in the posterior area (premolars and molars); (3) with good oral hygiene (plaque and gingival index ≤ 25%). The exclusion criteria included clinical conditions that contraindicated implant surgery, (1) patients with immunological alterations, pregnant and lactating, (2) heavy smokers \> 20 cigarettes/day, (3) with the need for bone or soft tissue augmentations, (4) patients whose anatomy prevented the correct three-dimensional placement of the implant to perform prosthetically guided screwed restorations.

All implants were placed by an experienced implantologist following standard procedures and the manufacturer's recommendations. All implants were connected to a transmucosal abutment to heal in one-stage approach. Several variables were collected in this surgical phase (bone quality, implant stability, implant-bone level, mucosal thickness, keratinized mucosa width ...)

After 3 to 4 months of implant healing all the clinical parameters were reevaluated and the final impression will be used for the manufacturing of a porcelain-fused to metal screwed crowns.

Two types of data will be analyzed: Cross-sectional and longitudinal data. On the one hand, cross-sectional data included sociodemographic (sex and age), behavioral (smoking, oral hygiene..) clinical (antagonist, adjacent dentition, arch location, implant diameter and length, insertion torque values, bone density, implant-level...) and prosthetics (abutment and prosthetic profiles, interocclusal prosthetic space, cantilever lengths...).

On the other hand, the longitudinal variables were classified into 2 types, related to the gingival tissues and related to the surrounding bone. Regarding the gingival tissues these were the longitudinal variables assessed in different follow-up observations (at 3, 6 and 12 months): plaque and gingival index, keratinized mucosa width. Regarding the bone-related variables the implant stability by ISQ as well as the marginal bone position were also measured at 3, 6 and 12 months.

Eligibility Criteria:
Inclusion Criteria:

* Patients of legal age (\>18 years).
* With rehabilitation needs with 1 maxillary or mandibular implant in mature bone (more than 4 months after tooth extraction) in the posterior sector (premolars and molars).
* With good hygiene (plaque and gingival index ≤ 25%).

Exclusion Criteria:

* Medical conditions that contraindicated implant surgery.
* Patients with immunological alterations, pregnant and lactating.
* Heavy smokers \> 20 cigarettes/day,
* Requiring bone augmentations or of soft tissues.
* Patients whose anatomy prevented the correct three-dimensional placement of the implant to perform prosthetically guided screw-retained restorations.