## 4 Discussion  
The measurement of soft tissues is receiving greater attention in the evaluation of treatment results. The volumetric analysis of oral tissues has evolved from visual inspection to more advanced techniques such as CBCT and, more recently, intraoral scanners. These instruments have, to a large extent, replaced conventional dental impressions and have facilitated the CAD/CAM process in prosthodontic treatment, as well as in orthodontic planning. In the research sphere, this technique has attracted much attention as an objective volumetric measurement method for evaluating changes in both soft and hard tissues after surgery [13; 14; 15]. In the technique described above, the provisional crown plays a significant role by offering registered responses of the soft tissues and the emergence profile; these responses can be exactly reproduced in the final restoration in an analog [13] or digital [12] manner and remain stable over time. The physiological explanation for this increase in gingival tissue is that the healing of the tissues after BOPT preparation continues under the same wound-healing mechanisms [14]. In this sense, the first provisional made in the clinic with an angle of approximately 45\({}^{\circ}\) remained cemented for 8 weeks to attain complete maturation of the tissues. In this stage, new blood vessels are created, and fibroblasts and myofiblabasts of the degranulation tissue grow and occupy the space created by the rotatory curettage. Then, there is a contraction of the myofiblabasts around the tooth; furthermore, thanks to the conical dental preparation, a migration of the soft tissues towards the crown occurs (from the area of greatest diameter (apical) to the area of the smallest diameter (coronal)) [16; 17]. This stage has been described as one where tissue growth takes place via a transduction mechanism [18; 19]. The fibroblasts of the connective tissue detect mechanical stimuli (mastication, pressure from the provisional, labial pressure when speaking, etc.) in their extracellular matrix; these stimuli are then converted into chemical information that stimulates cellular growth and proliferation [18]. The clinical experience of BOPT reported in the literature has established that this technique increases the thickness of gingival tissue and enhances the stability of the soft tissue in the medium- and long-term compared to other classical preparations with finishing lines [5; 7; 8] (Figures 16-20). Figure 16: Retreatment of a fixed prosthesis with the BOPT technique. Initial pretreatment situation (Front view). Figure 17: Retreatment of a fixed prosthesis with the BOPT technique. Initial pretreatment situation (Lateral view). Figure 18: Gingiva after perioperative treatment with BOPT. Figure 19: Situation after treatment with BOPT (Front view). These conclusions are based on measurements that continue to be carried out and based on traditional methods, such as photographs, direct visual inspections, or exploration with a periodontal probe. Hence there are inherent limitations in the precision, practicality, and reduced clinical indications with current techniques. For example, [PERSON] [7] and [PERSON] [4] used a periodontal probe to measure the gingival thickness and affirmed that this technique is not exact; hence, the conclusions of this technique are based on methods that are imprecise and subjective. [PERSON] [16] developed a reproducible method to measure the apico-coronal margin migration over time applying calibration of a well-known landmark and digital photography without using a periodontal probe. Vestibulo-lingual tissue changes were also analyzed by different authors [20,21] using intraoral scanners and the superimposition of different STL files. These methods are considered reproducible techniques for measuring the thickness or volume in any research involving soft tissue evaluation [21]. This study describes a comparative analysis of an initial situation and its follow-up in terms of monitoring changes in volume.