Prospective observational cohort study of the change of the marginal bone crest in relation to the prosthetic abutment height and the peri-implant vertical mucosal thickness at implants positioned subcrestally

ORIGINAL ARTICLE Prospective observational cohort study of the change of the marginal bone crest in relation to the prosthetic abutment height and the peri-implant vertical mucosal thickness at implants positioned subcrestally Serafín Maza-Solano DDS | María Baus-Domínguez DDS | Manuel-María Romero-Ruíz DMD, PhD | Aida Gutiérrez-Corrales DDS, PhD | Daniel Torres-Lagares DDS, PhD | María- ´ Angeles Serrera-Figallo DDS, PhD Departamento de Estomatología, Facultad de Odontología, Universidad de Sevilla, Seville, Spain Correspondence María Baus-Domínguez and María- ´ Angeles Serrera-Figallo, Department of Stomatology, Faculty of Dentistry, University of Seville, C/Avicena S/N, 41009, Seville, Spain. Email: [email protected] and [email protected] Abstract Aim: To evaluate the influence on peri-implant crestal bone loss exerted by the vertical mucosal thickness and the abutment height over 12 months after placement of the restoration on subcrestal implants with change of platform, using a restoration abutment platform smaller than the implant platform. Materials and Methods: A total of 99 implants were rehabilitated in the maxillary and mandibular posterior regions. A total of 22 implants were rehabilitated in the maxilla and 77 implants in the mandible, using digitally designed customized abutments with Atlantis weborder software, from the commercial house Dentsply Sirona (Dentsply Sirona S.A., Barcelona, Spain), version 4.6.5, adapting the height to the vertical thickness of the mucosa. Clinical and radiographic monitoring begins during the surgical procedure of placement of the implant and ends 12 months afterwards. Crestal bone loss was evaluated through the Carestream ® CS8100 3D radiographic equipment. Results: In all cases, the greatest loss of marginal bone occurred between the day of surgery (Tx) and placement of the rehabilitation (To). The average bone loss between both times was greater when the abutment height and vertical mucosal thickness did not exceed 3 mm. Subsequently, bone loss slowed and stabilized at 12 months. Conclusions: The minimum abutment height and the vertical mucosal thickness are factors to take into account when minimizing peri-implant marginal bone loss, the abutment height having the greatest importance according to the clinical data obtained. Received: 28 December 2023 Revised: 18 April 2024 Accepted: 9 May 2024 DOI: 10.1111/cid.13347 This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. © 2024 The Author(s). Clinical Implant Dentistry and Related Research published by Wiley Periodicals LLC. Clin Implant Dent Relat Res. 2024;1–13. wileyonlinelibrary.com/journal/cid 1 KEYWORDS abutment height, biological width, dental implants, marginal bone loss, platform switching, thick mucosa, vertical mucosal thickness Summary Box What is know •Peri-implant bone loss is affected by multiple factors, notable among which are the height (vertical thickness) of the peri-implant mucosa and the design of the prosthetic restoration, including the transepithelial abutment height. What this study adds •The average bone loss between Tx and To was greater when the abutment height and vertical mucosal thickness did not exceed the 3 mm analyzed (0.97 mm with abutment heights under 3 and 0.70 mm with abutments over 3 mm; 0.84 mm with a vertical mucosal thickness under 3 and 0.60 mm with a vertical mucosal thickness over 3 mm). Subsequently, progressive stabilization of the marginal bone loss was observed up to 12 months. •Helping the clinician to know the influential factors in peri-implant marginal bone loss, to thereby facilitate decision making in implantological planning, surgery and rehabilitation. 1|INTRODUCTION The definition of success in implant treatment does not only depend on achieving osseointegration, but also on maintaining the periimplant health of the hard and soft tissues, 1 aesthetic results and the absence of complications. 2,3 A successful result requires minimal marginal bone loss over time to avoid pathogenic microflora causing inflammation and progressive bone resorption. 4 The study of factors affecting marginal bone levels around the implants has increased in importance in recent years, notably vertical mucosal thickness, healing abutment height and prosthetic abutment height. 5–8 These factors have been significantly associated with the risk of generating greater marginal bone resorption, being reported in numerous clinical trials on implants placed at crestal level. 5,9–14 Galindo et al. 11 demonstrated the key role of abutment height in maintenance of the peri-implant marginal bone, indicating that the abutment height may affect the crestal bone level, this being maintained when abutments over 2 mm high are used, also suggesting that early marginal bone resorption was more influenced by the characteristics of prosthetic rehabilitation than by the post-surgical bone remodeling process, which significantly increased up to 6 months after the functional load before stabilizing. 15 Various studies have indicated that there is less peri-implant bone loss when the abutment height is greater, because it leads to a greater vertical mismatch, resulting in a larger space for the growth of soft tissue and a greater distance with regard to the inflammatory area, leading to connection of the crown with the abutment, regardless of the rehabilitation being with a screwed or cemented prosthesis. 10,11,13,16 It is important to take into account the recently redefined concept of peri-implant phenotype, which encompasses the term “Peri-implant Supracrestal Tissue Height (STH),” 17 which is formed by the sulcus epithelium, junctional epithelium and supracrestal connective tissue. Thus, the STH is “short”if it is under 3 mm, and “high”when it exceeds 3 mm. According to the authors, if the abutment has a low height, pressure is caused to the soft tissue in an apical direction, which would cause greater bone loss. The restoration of these dimensions around dental implants may explain the greater quantity of bone loss around them in places with thin, soft tissue, 18 although slight bone loss after placement of the prosthesis is still considered a successful 19 and inevitable result due to the establishment of biological width. 20,21 In recent studies analyzing marginal bone loss using short and long abutments, with fine and thin mucosa, it was indicated that marginal bone loss during establishment of biological width was influenced by the height of abutments, regardless of the vertical mucosal thickness. 22 The null hypothesis stated in this study is that there are no differences in the evolution of the marginal crestal bone level for rehabilitated implants with abutments of different heights. Conversely, the alternative hypothesis is that there are differences in the evolution of the marginal crestal bone level for rehabilitated implants with abutments of different heights. On this basis of all of the above, the purpose of this study was to evaluate the changes caused at peri-implant bone level based on the prosthetic abutment height and vertical mucosal thickness over 12 months after the prosthetic loading. 2MAZA-SOLANO ET AL. 17088208, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/cid.13347 by Readcube (Labtiva Inc.), Wiley Online Library on [29/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 2|MATERIALS AND METHODS 2.1 |Study design This is a prospective observational cohort study approved by the Andalusian Biomedical Research Ethics Coordinating Committee (Code US-DTL-2022.1) that complies with all the guidelines of the World Medical Association Declaration of Helsinki: Ethical principles for medical research involving human subjects 23 and following the STROBE guidelines for cohort studies. All patients received an information sheet on the study and gave their explicit consent for participation in it, as well as for the surgical and rehabilitation procedure in question. 2.2 |Participants Partially edentulous patients were selected who needed treatment with implants for fixed prosthetic rehabilitation of the posterior maxilla and mandible, using for the study the teeth from the first premolar to the second molar. The inclusion criteria were the following: (a) patients over 18 years of age; (b) patients who did not have any contraindication for implant surgery; (c) patients with predisposition and capacity for complying with the study protocol explained to them and accepted through informed consent; (d) minimum bone crest of at least 5 mm wide and 8 mm high above the mandibular channel in the place where the implant was planned, following planning with Cone Bean Computer Tomography (CBCT); (e) without guided bone regeneration procedures before or during placement of the implant; (f) 6 months having passed since the extraction of the tooth corresponding to the place of implant insertion; (g) rehabilitations with 1, 2 and 3 implants; (h) good state of oral hygiene (PI <15%, BoP <15%); (i) sufficient primary stability of the implant (≥20 Ncm); (j) subcrestal placement of the implant (all implants were placed subcrestal, the depth of which depended on the initial vertical thickness of the patient's mucosa, as the aim was that later, during rehabilitation, the implants would have a prosthetic abutment (transepithelial abutment) at least 2.5 mm high). Patients with a history of head and/or neck radiotherapy, immunocompromised patients (HIV infection or chemotherapy in the last 5 years), patients with uncontrolled diabetes, currently or previously taking intravenous bisphosphonates, patients who are pregnant, have psychiatric, alcohol abuse or drug problems, patients who smoke more than 10 cigarettes per day or participants in other studies were excluded. All patients were selected consecutively between May 2019 and February 2021 and treated independently by two operators: one who carried out the surgical treatment consisting of the placement of the implant; and another who carried out the prosthetic treatment, consisting of the rehabilitation on this implant, and subsequent monitoring up to 12 months. This monitoring consisted of the collection of data from treatment with periapical x-rays and photographs taken on the day of implant placement (Tx), the day of prosthesis placement (To), the 1-month check-up (T1), the 3-month check-up (T2), the 6-month check-up (T3), and the 12-month check-up (T4) (Table 1). 2.3 |Surgical protocol All patients were administered local anesthesia Articaine, Epinephrine Hydrochloride (Artinibsa ® 40 mg/mL +0.01 mg/mL; Inibsa dental, Barcelona, Spain.), following application of intraoral anesthetic gel (Hurricaine ® 200 mg/g benzocaine oral gel; Laboratorios Clarben S.A., Madrid, Spain). A mid-crestal incision was made, preserving an adequate quantity of keratinised tissue on both vestibular and lingual sides. A full thickness buccal flap was elevated and the vertical mucosal thickness (distance between the marginal mucosa and the bone crest) of the undetached lingual flap was measured (Figure 1), with a 15 mm PUNC15 periodontal probe (G. Hartzell & Son; USA), at the center of the site planned for implant placement. Subsequently, the lingual flap was elevated, and the implant bed was prepared with copious irrigation of cold saline solution, following the manufacturer's recommendations for subcrestal placement. The Astra Tech osseospeed EV ® (Dentsply Sirona; Gmbh, Rodenbacher Chaussee, Hannau-Germany) internally connected straight implants were inserted below the level of the bone, minimum 1 mm subcrestal, always depending on the measurement of the vertical thickness of the mucosa to try to have an abutment height of at least 2 mm. The implants were immediately connected to closure or healing plugs, remaining in a subgingival position within the mucosa. The flaps were sutured with simple stitches, using sterile non-absorbable Supramid ® 4/0 (Aragó black TB15-CT 19 mm 3/8; Barcelona, Spain). Patients were prescribed post-surgical antibiotic therapy (Amoxicillin/Clavulanic Acid 875/125 g) three times a day for 7 days TABLE 1 Timeline and nomenclature of the study times. Time of the study Nomenclature Surgery Tx Prosthesis placement To 1-month check-up T1 3-month check-up T2 6-month check-up T3 12-month check-up T4 FIGURE 1 Measurement of vertical mucosal thickness with the periodontal probe (Linkevicius et al. 24 ). MAZA-SOLANO ET AL.3 17088208, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/cid.13347 by Readcube (Labtiva Inc.), Wiley Online Library on [29/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License and non-steroidal anti-inflammatory drugs such as dexketoprofen trometamol (Enantyum ® 25 mg), for 5 days if necessary. Each patient was issued a kit with a chlorhexidine digluconate +0.12% cetylpyridinium chloride mouthwash (GUM Sunstar Iberia; Barcelona, Spain), for rinsing after eating each daily meal, as well as a chlorhexidine digluconate +0.12% cetylpyridinium chloride toothpaste. All patients were instructed to follow a soft diet to minimize trauma to the implant site. The sutures were removed 14 days after surgery. Patients were instructed not to use removable prostheses during the whole healing period, and immediate loading was not carried out in any of the cases. After 2 months of submerged healing, a second surgery was performed to open the plugs, changing the closing screw for a higher one so that it was juxta-gingival or supragingival. The final impressions were taken 2 weeks after the second surgery, once the soft tissue around the healing screw had formed. 2.4 |Restorative protocol The height of the prosthetic abutments was chosen according to the vertical thickness of the soft tissue in the implant area, so that the margin of the abutment was 1 mm subgingival, also adapting it to the diameter resulting from the healing process after placing the healing plug. Individualized Atlantis ® (Dentsply Sirona; Aminogatan 1, Mölndal, Sweden) type abutments were used through digital scanning (Cerec ® , Dentsply Sirona) using IFLO (Atlantis ® System) type digital scanning abutments. After the digital scanning, the file obtained was sent to the WebOrder of the system (AtlantisWebOrder ® , Dentsply Sirona) to edit the individualized abutment. The editing was carried out respecting the thickness levels of the soft tissue, adapting them to the resulting situation after the healing period. After the functional and aesthetic test, cemented-screwed zirconia (Cercon ® xt ML; Dentsply Sirona, Hanau-Wolfgang, Germany) and vitrified ceramic (Ivoclair Vivadent AG; Schaan/Liechtenstein), restorations were placed. All were screwed at a torque force of 25 Ncm 2 , following the manufacturer's recommendation, and the crowns were cemented to their corresponding abutment with dual resin cement (Relyx Unicem 2 Automix Self-Adhesive Resin Cement ® ; Neuss-Germany) outside the mouth. Once placed in the mouth, the radiographic and photographic control protocol began. 2.5 |Radiographical measures Using Carestream ® CS8100 3D equipment, a total of six digital x-rays were taken for each implant using a long cone parallelism technique with a Rinn type device. A personalized bite template was created for each patient with Elite HD + ® (Zhermack, Rovigo, Italy) type heavy silicone for the area where the implant was going to be positioned, thereby reproducing the position of the Rinn type positioner for the rest of the study x-rays. After placement of the implant, a first x-ray was taken: baseline (Tx), the second after crown placement (To), the third, 1 month after crown placement (T1); the fourth, 3 months after crown placement (T2); the fifth, 6 months after crown placement (T3), and the sixth, 12 months after crown placement (T4) (Figure 2). Prior to surgery, the bone situation was examined to determine the volume of bone tissue available in three dimensions to house the implant, undertaking an orthopantomography and a CBCT scan. The distance between the implant platform and the bone crest was measured at each time interval at the distal and mesial points oftheimplant.Apositivevaluewasassignedwhenthebonecrest was coronal to the implant platform, and a negative value when the bone crest was apical to this platform. All x-rays were carried out by the same examiner: S.M.S. After taking the periapical radiograph, both examiners began to take measurements and record them in their own template individually and systematically. They used the same Carestream ® software version 7.0.3. on the same radiograph, using the measurement function provided by the software in order to mitigate possible errors derived from the possible collection of independent data. Measurements were taken from the implant platform to the most coronal portion of the bone crest. After measurements were made, the correlation between the equivalent variablesofbothexaminerswascalculated. For this purpose, Pearson's correlation was used for variables with normal distribution, and Spearman's correlation for variables that do not follow a normal distribution. The probability was very close to 0 in all cases (p<110–20) (Table 2). Similarly, and to ensure our results, the ICC (Intra-examiner Concordance Index) was calculated: ICC ¼MSbetweenMSwithim MSbetweenþk1ðÞMSwithim MSbetween is the mean of the sums of squares between groups. Mswithim is the mean of the sums of squares within groups. kis the number of measurements made by each examiner. ICC ¼1:5851384620:000514286 1:585138462þ141ðÞ0:000514286 ICC ¼1:584624176 1:593755684 ICC ≈0:994219 Since a value close to 1 indicates high inter-examiner agreement, this result suggests that the measurements made are consistent. 2.6 |Statistical analysis Bone level changes were measured, classifying all implants into two groups according to mucosal thickness (< or >3 mm) and into two groups according to prosthetic abutment height (< or >3 mm). 4MAZA-SOLANO ET AL. 17088208, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/cid.13347 by Readcube (Labtiva Inc.), Wiley Online Library on [29/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License A complete descriptive analysis of all variables was carried out. Given the time diversity between the implant placement and sample collection date, the operation is carried out on all subjects, excluding those with over 180 days between placement and sample collection. The normality of the numerical variables was determined using the Kolmogorov–Smirnov test. All numerical variables were normal, except ALTPIPRE, GROSVER, T0DISTAL, S1DISTAL, and S2AVERAGE. For crosses of categorical variables and numerical variables, ANOVA is applied for normally distributed variables and Mann– Whitney U(dichotomous) and Kruskal–Wallis (more than two categories) for the rest. Correlations between numerical variables were carried out using Pearson's correlation, given that the majority follow a normal distribution. However, for cases in which a variable whose distribution is not normal is involved, Spearman's correlation has been used. FIGURE 2 X-rays taken by patients: (A) baseline (Tx), (B) after crown placement (To), (C) 1 month after crown placement (T1), (D) 3 months after crown placement (T2), (E) 6 months after crown placement (T3), (F) 12 months after crown placement (T4). TABLE 2 Correlation between both examiners. Variables Examiner 1 Examiner 2 Correlation Average S.T. Average S.T. Pearson Spearman Mesial: Pillar height 3.41 0.71 3.41 0.71 1.000* Mesial: TX bone level surgery 2.01 0.72 2.06 0.74 0.983* Mesial: Placement Bone Level T0 1.33 1.09 1.34 1.10 0.985* Mesial: 1 month bone level T1 1.26 1.24 1.24 1.19 0.986* Mesial: 3 months bone level T2 1.17 1.06 1.16 1.07 0.988* Monthly: 6 months bone level T3 1.19 1.24 1.21 1.24 0.994* Monthly: 12 months bone level T4 1.38 1.19 1.38 1.18 0.966* Distal: Pillar height 3.05 0.80 3.05 0.80 1.000* Distal: TX bone level surgery 1.54 0.71 1.54 0.73 0.983* Distal: Bone level placement T0 0.65 0.94 0.71 0.96 0.923* Distal: 1 month bone level T1 0.50 0.98 0.49 0.99 0.990* Distal: 3 months bone level T2 0.55 0.89 0.55 0.91 0.984* Distal: 6 months bone level T3 0.64 0.82 0.65 0.84 0.992* Distal: 12 months bone level T4 0.79 0.79 0.80 0.78 0.987* *The probability is very close to 0 in all cases (p<110 20 ). MAZA-SOLANO ET AL.5 17088208, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/cid.13347 by Readcube (Labtiva Inc.), Wiley Online Library on [29/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License Statistical significance was established at p< 0.05. 3|RESULTS 3.1 |Number of participants and implants A total of 59 subjects were included, considering for the analysis the possibility of rehabilitating 1, 2 or 3 implants, with a total of 54 implants of 1 piece, 29 of 2 pieces, and 16 of 3 pieces. All cases analyzed reached an adequate level of osseointegration and a total of 22 implants were placed in the maxilla and 77 in the mandible. 3.2 |Changes of marginal bone level in cases with vertical mucosal thickness up to 3 mm In cases with equal vertical mucosal thickness less than 3 mm (82 patients), there was greater average marginal bone loss in the period between the day of surgery (Average Tx) and the day of placement of the rehabilitation (Average To), the average bone loss being 0.84 mm. That is, starting from a bone crest to implant neck distance of 1.69 (Average Tx), at the time of crown placement this distance had been reduced to 0.85 mm (Average To). In subsequent measurements, bone loss stabilized, reaching a bone crest to implant neck value of 0.80 mm at T1 (Average T1) with an average loss between To and T1 of 0.05 mm; a level of 0.70 mm at T2 (Average T2), with an average loss of 0.15 mm between To and T2; a level of 0.78 mm at T3 (Average T3), with average marginal bone loss between To and T3 of 0.07; and finally a level of 0.89 mm at T4 (Average T4), with an average marginal bone loss between To and T4 of 0.04, which reflects the marginal bone recovery that occurred from 6 months to 12 months after placement of the prosthesis. That is, bone loss was not only stabilized, but a slight recovery was observed from the sixth month after prosthetic loading (Table 3) (Figure 3). 3.3 |Changes of marginal bone level with 3 mm or more of vertical mucosal thickness When the vertical mucosal thickness is greater than or equal to 3 mm (17 patients), there was also greater mean marginal bone loss between the day of surgery (Average Tx) and the day of rehabilitation placement (Average To). The average difference was 0.60 mm. That is, starting from a bone crest to implant neck distance of 2.02 on the day of implant insertion (Average Tx), at the time of crown placement this distance had been reduced to 1.42 mm (Average To). The bone loss subsequently stabilized over time, and evolved until reaching a bone level of 1.24 mm at T1 (Average T1), with an average loss between To and T1 of 0.18 mm, and so on progressively until reaching a level of 1.21 mm on average at T4 (Average T4), with an average marginal bone loss between To and T4 of 0.21 mm, which reflects the marginal bone recovery that occurred in the later phases of the times analyzed (Table 2) (Figure 4). If we compare the results of both values of vertical mucosal thickness (greater or less than 3 mm) in terms of the bone loss obtained, we find that the marginal bone loss was more pronounced when the vertical mucosal thickness was less than 3 mm, the difference between Tx and To being 0.24 mm less bone loss when the vertical mucosal thickness was greater than when it was less than 3 mm. This difference was not significant. TABLE 3 Numerical data of bone evolution depending on vertical mucosal thickness. Variable Vertical mucosal thickness Sign. <3 mm >3 mm Average D.E. Average D.E. Mesial Tx 1.99 0.78 2.16 0.58 Distal Tx 1.38 0.59 1.87 0.78 <0.01 Average Tx 1.69 0.56 2.02 0.63 <0.05 Mesial To 1.15 1.01 1.72 1.39 <0.05 Distal To 0.54 0.78 1.11 0.98 <0.05 Average To 0.85 0.77 1.42 1.03 <0.05 Mesial T1 1.12 1.00 1.50 1.42 Distal T1 0.47 0.75 0.98 1.08 <0.05 Average T1 0.80 0.77 1.24 1.12 <0.05 Mesial T2 0.96 0.96 1.51 1.60 Quasi Distal T2 0.43 0.66 0.84 1.11 <0.05 Average T2 0.70 0.72 1.17 1.25 <0.05 Mesial T3 1.02 0.97 1.51 1.66 Distal T3 0.53 0.72 0.84 1.09 Average T3 0.78 0.77 1.17 1.27 Quasi Mesial T4 1.13 1.03 1.63 1.68 Distal T4 0.64 0.76 0.79 1.01 Average T4 0.89 0.81 1.21 1.20 FIGURE 3 Evolution of the bone level when the vertical mucosal thickness is under 3 mm. 6MAZA-SOLANO ET AL. 17088208, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/cid.13347 by Readcube (Labtiva Inc.), Wiley Online Library on [29/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 3.4 |Changes of marginal bone level with less than 3 mm abutment height With a prosthetic abutment height of less than 3 mm (47 rehabilitations), the greatest marginal bone loss occurred in the same way as described above, between the day of surgery (Tx) and the day of placement of the prosthetic rehabilitation (To), the loss being 0.97 mm between both times recorded. That is, starting from 1.57 mm bone height of the crest at Tx (Average Tx), it was reduced to a level of 0.60 mm bone height at To (Average To). Subsequently, there was a bone loss of 0.05 mm between To and T1 and of 0.15 mm between To and T2, reaching a measured bone crest height of 0.45 mm. Between To and T3, bone loss of 0.09 mm occurred, a slight recovery therefore being observed in this phase. Between To and T4 there was no bone loss, but instead a recovery of 0.01 mm (Table 4). There was a stabilization of marginal bone loss from To where bone loss was much slower until T2, and from there a slight recovery until T4 (Figure 5). 3.5 |Changes of marginal bone level with more than 3 mm abutment height With a prosthetic abutment height greater than 3 mm (52 rehabilitations), the greatest marginal bone loss also occurred between the day of surgery (Tx) and the day of placement of the prosthetic rehabilitation (To); specifically starting with a crestal height of 1.84 mm, there was a bone loss of 0.7 mm between Tx and To, reaching a crestal bone level of 1.14 mm at To. There was a bone loss of 0.08 mm between To and T1, reaching a crestal bone level of 1.06 mm at T1, and a marginal bone loss of 0.17 mm between To and T2, reaching a crestal bone level of 0.97 mm at T2. Between To and T3 there was a marginal bone loss of 0.10 mm, and between To and T4 there was a marginal bone loss of 0 mm, there being no loss in this last phase, as occurred previously. (Table 3). FIGURE 4 Evolution of the bone level when the vertical mucosal thickness is greater than 3 mm. TABLE 4 Numerical data of bone evolution depending on abutment height. Variable Abutment height (average of mesial and distal) Sign. <3 mm >3 mm Average D.E. Average D.E. Mesial Tx 1.73 0.69 2.19 0.73 <0.01 Distal Tx 1.41 0.66 1.49 0.64 Average Tx 1.57 0.56 1.84 0.57 <0.05 Mesial To 0.85 1.17 1.49 0.98 <0.01 Distal To 0.36 0.79 0.80 0.83 <0.05 Average To 0.60 0.82 1.14 0.79 <0.01 Mesial T1 0.81 1.14 1.40 0.98 <0.01 Distal T1 0.29 0.80 0.71 0.81 <0.05 Average T1 0.55 0.84 1.06 0.79 <0.01 Mesial T2 0.69 1.13 1.27 1.04 <0.01 Distal T2 0.20 0.78 0.67 0.70 <0.01 Average T2 0.45 0.82 0.97 0.80 <0.01 Mesial T3 0.74 1.14 1.32 1.05 <0.01 Distal T3 0.28 0.77 0.76 0.75 <0.01 Average T3 0.51 0.84 1.04 0.84 <0.01 Mesial T4 0.85 1.23 1.64 1.08 <0.05 Distal T4 0.37 0.85 0.84 0.73 <0.01 Average T4 0.61 0.91 1.14 0.82 <0.01 MAZA-SOLANO ET AL.7 17088208, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/cid.13347 by Readcube (Labtiva Inc.), Wiley Online Library on [29/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License The greatest marginal bone loss in terms of prosthetic abutment height occurred between surgery and the placement of the rehabilitation, but for abutments over 3 mm high, the difference in loss was less, because with abutments over 3 mm high there was an average marginal bone loss of 0.70 mm between Tx and To, while for abutments under 3 mm high the marginal bone loss was 0.97 mm between Tx and To. In both cases, there was subsequently a stabilization of the marginal bone loss (Figure 6). 3.6 |Correlations between the mucosa thickness/ abutment height and bone-level changes Regarding the correlations between the vertical thickness of the mucosa and the height of the rehabilitative abutment with respect to the bone level (mesial, distal, and medial), there was no significant correlation for the variable vertical thickness of the mucosa, but there was a negative correlation for the variable height of the abutment, as the significance value, where there was a statistically significant difference, was p< 0.05 and <0.01, indicating that the higher the height of the abutment, the greater the bone level (Table 5). Similarly, the correlations between the vertical thickness of the mucosa and the height of the rehabilitative abutment with respect to the degree of bone loss between the different moments of measurement from Tx and T0 only show significance by p-value <0.05 between T0 and T1 with a positive correlation (Table 6), since when the vertical thickness of the mucosa was greater, greater bone loss was obtained in this section. No further significant differences were reached. 4|DISCUSSION There are multiple factors that influence marginal bone loss around implants. The present study focuses mainly on prosthetic factors and soft tissue thickness, but it should not be forgotten that there are other very interesting factors to be taken into account, such as periodontal health and smoking. Several systematic reviews and clinical trials have suggested that implant failure and associated margin-al bone loss are greater in patients with a history of periodontitis. Microbiota-environmental factors have been identified in both situations, and recent analyses have shown that there are no significant differences between bacterial genera on implants and teeth in supragingival and subgingival biofilms. The diseased peri-implant and periodontal tissues shared a similar microbiota. Periodontal disease has been estimated to induce additional bone loss in implant installation FIGURE 5 Evolution of the bone level when the abutment height is under 3 mm. FIGURE 6 Evolution of the bone level when the abutment height is over 3 mm. TABLE 5 Correlations (original variables). Variables Vertical mucosal thickness a Abutment height (average) TX Mesial 0.013 0.148 TX Distal 0.152 0.222* TX Average 0.089 0.220* T0 Mesial 0.135 0.151 T0 Distal a 0.137 0.322** T0 Average 0.159 0.241* T1 Mesial 0.072 0.147 T1 Distal 0.145 0.342** T1 Average 0.097 0.263** T2 Mesial 0.117 0.153 T2 Distal 0.123 0.376** T2 Average 0.132 0.271** T3 Mesial 0.048 0.203* T3 Distal 0.069 0.410** T3 Average 0.070 0.315** T4 Mesial 0.095 0.219* T4 Distal a 0.049 0.424** T4 Average 0.091 0.320** a Spearman's correlation has been applied to correlations involving any of these variables, and Pearson's correlation has been applied to the rest. *The correlation is significant p< 0.05 (bilateral).**The correlation is significant p< 0.01 (bilateral). 8MAZA-SOLANO ET AL. 17088208, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/cid.13347 by Readcube (Labtiva Inc.), Wiley Online Library on [29/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License in periodontally diseased patients compared to periodontally healthy patients. There is evidence that patients with existing or ongoing periodontitis are more likely to experience implant failure and biological complications. 25,26 However, due to the high heterogeneity among studies and methodological variability, it is difficult to draw solid conclusions. Articles on chronic periodontitis showed an increased risk of implant failure, with ORs between 3.1 and 4.7 for affected patients. 26 Patients with a history of aggressive periodontitis can be worse off, with an increased risk of implant failure (OR =4.80), mucositis (OR =3.61), and peri-implantitis (OR =14.09). 27 However, other studies warn that smoking and a history of periodontitis are particularly influential in the late stages of implant failure. In a prospective study, it was shown that interproximal bone loss was significantly related to tobacco or alcohol use, increased plaque levels, and gingival inflammation. A subsequent retrospective study demonstrated lower survival rates and increased marginal bone loss in tobacco smokers with a history of treated and maintained periodontitis. 28 A recent systematic review stated that implant insertion in smokers resulted in higher failure rates, postoperative infections, and marginal bone loss. 29 In our study, we excluded all patients who smoked more than 10 cigarettes per day, as well as patients with poor oral hygiene (PI >15%, BoP >15%). Another of the multiple factors that influencing peri-implant marginal bone loss are prosthetic factors. It has been reported that early marginal bone loss is more influenced by the characteristics of the prosthetic rehabilitation than by the post-surgical bone remodeling process. 15 Other studies have indicated that changes in the crestal bone occur during the initial phase of healing, once the implant has been placed and loaded, 19,30 demonstrating that after implant surgery a remodeling occurred that was characterized by a reduction of bone dimensions, both horizontally and vertically. 31 In this study, a more acute peri-implant marginal bone loss occurred between surgery (Tx) and prosthesis placement (To), specifically of 0.84 mm when the vertical mucosal thickness was under 3 mm, 0.60 mm when the vertical mucosal thickness was greater than 3 mm, 0.96 mm when the abutment height is under 3 mm, and TABLE 6 Correlations (derived variables). Variables Vertical mucosal thickness a Abutment height (average) Difference TX—T0 Mesial 0.064 0.054 Difference TX—T0 Distal 0.023 0.118 Difference TX—T0 Average 0.063 0.094 Difference TX—T1 Mesial 0.014 0.047 Difference TX—T1 Distal 0.042 0.175 Difference TX—T1 Average 0.034 0.117 Difference TX—T2 Mesial 0.103 0.055 Difference TX—T2 Distal 0.056 0.190 Difference TX—T2 Average 0.096 0.127 Difference TX—T3 Mesial 0.030 0.110 Difference TX—T3 Distal 0.041 0.225* Difference TX—T3 Average 0.011 0.178 Difference TX—T4 Mesial 0.079 0.135 Difference TX—T4 Distal 0.076 0.212* Difference TX—T4 Average 0.010 0.191 Difference T0—T1 Mesial 0.225*0.014 Difference T0—T1 Distal a 0.073 0.113 Difference T0—T1 Average 0.165 0.060 Difference T0—T2 Mesial 0.013 0.007 Difference T0—T2 Distal a 0.042 0.069 Difference T0—T2 Average a 0.046 0.064 Difference T0—T3 Mesial 0.094 0.100 Difference T0—T3 Distal 0.114 0.145 Difference T0—T3 Average 0.131 0.138 Difference T0—T4 Mesial 0.026 0.124 Difference T0—T4 Distal 0.155 0.110 Difference T0—T4 Average 0.114 0.138 a In the correlations involving any of these variables, Spearman's correlation was applied, and Pearson's correlation was used for the rest. *The correlation is significant p< 0.05 (bilateral). MAZA-SOLANO ET AL.9 17088208, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/cid.13347 by Readcube (Labtiva Inc.), Wiley Online Library on [29/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License