Influence of Biologically Oriented Preparation Technique on Peri-Implant Tissues; Prospective Randomized Clinical Trial with Three-Year Follow-Up. Part II: Soft Tissues

Abstract

Purpose: The objective of this prospective randomized clinical trial (RCT) was to analyze and compare the clinical behavior of three types of prosthesis supported by single implants in the posterior region after three years of functional loading. Materials and methods: Seventy-five implants were divided into three groups according to the type of prosthetic restoration: screw-retained crown (group GS); cemented crown without finishing line (biologically oriented preparation technique) (group GBOPT); and conventional cemented crown with finishing line (group GCC). After three years in function, clinical parameters (presence of keratinized mucosa, probing depths, bleeding on probing, and radiographic bone loss) were compared between the three experimental groups. The possible correlation between soft tissue clinical parameters and bone loss was also analyzed. Results: Statistical analysis found significant differences in clinical parameters between the different types of crown, with the cemented restoration without finishing line (BOPT) presenting fewer complications and better peri-implant health outcomes including: significantly different KMW data (mm), with significant differences between groups GBOPT and GCC (p < 0.001, Kruskal-Wallis test), with GBOPT obtaining larger quantities of keratinized mucosa (KM); statistically significant differences in probing depth (PD) values between groups GBOPT and GCC (p = 0.010, Kruskal-Wallis test); significant differences in bleeding on probing (BOP) between groups GBOPT and GCC (p = 0.018, Chi² test) in favor of GBOPT. Conclusions: Soft tissue behavior around implants is related to the type of prosthetic restoration used, with cemented prostheses with BOPT presenting better peri-implant soft tissue behavior.

Keywords: BOPT; bone loss and clinical parameters; cemented; complications; implant-supported prosthesis; screw-retained; soft tissues.

Figure 1

Moment of transepithelial abutment placement. (A) Abutment for conventional cemented prosthesis with horizontal finishing line; (B) Abutment for cemented prosthesis without finishing line or biologically oriented preparation technique (BOPT).

Figure 2

Three restoration types. (A): screw-retained crown (GS); (B): cemented without finishing line (GBOPT); (C): conventional cementation with finishing line (GCC).

Figure 3

Width of keratinized mucosa (KMW) measurements, placing the probe parallel to the longitudinal axis of the implant.

Figure 4

Healed mucosa without inflammation showing healthy peri-implant tissue. (A). Screw-retained crown (group GS). (B). Cemented BOPT crown (group GBOPT). (C). Conventional cemented crown (group GCC).

Figure 5

Box Plot: keratinized mucosa width (mm) in each group.

Figure 6

Box Plot: keratinized tissue width (mm) in relation to prosthetic type (screw-retained vs. cemented).

Figure 7

Box Plot: probing depth (mm) in each group.

Figure 8

Box plot showing probing depth values (mm) in relation to prosthesis type (screw-retained vs. Cemented).

Figure 9

Case presenting bleeding on probing in a patient with at least 2 mm keratinized mucosa prior to treatment.

Figure 10

Restoration presenting inflammation in the surrounding peri-implant tissue.

Figure 11

Correlation between keratinized mucosa width and peri-implant bone loss in each group.

Figure 12

Correlation between keratinized mucosa width, probing depth, and peri-implant bone loss in each group.

Figure 13

Correlation between the presence of bleeding on probing and bone loss in each group.