Dental implants have become a cornerstone in modern prosthodontics for restoring edentulous spaces due to their high success rates and predictable outcomes. The long-term stability and functionality of implant-supported restorations depend significantly on both biological integration and prosthetic considerations. Among these, abutment design—whether single-use (definitive) or multiple-use (intermediate or healing abutments)—plays a crucial role in determining clinical outcomes such as marginal bone loss, peri-implant soft tissue response, and prosthetic longevity [1].

Single abutment protocols, also known as “one abutment, one time,” involve placing a definitive abutment at the time of implant surgery or uncovery, which remains undisturbed throughout the prosthetic phase. This technique minimizes repeated disconnection and reconnection, thereby preserving the integrity of the soft tissue seal and reducing bacterial infiltration [2]. In contrast, the multiple abutment protocol involves sequential replacement of healing abutments and prosthetic components during different stages of impression making, framework try-in, and delivery. While this method may offer flexibility for restorative procedures, it introduces microgaps and micromovements that could compromise peri-implant tissues [3].

Several clinical and radiographic studies have indicated that repeated manipulation of abutments disrupts the peri-implant mucosal barrier and may lead to increased marginal bone resorption [4]. Histological evidence supports the hypothesis that maintaining a stable abutment connection helps in the establishment of a stable biological width, thereby ensuring long-term tissue stability [5]. Furthermore, inflammatory mediators, such as interleukins and prostaglandins, have been found to be elevated in peri-implant crevicular fluid of implants subjected to multiple abutment changes, suggesting a higher inflammatory burden [6].

The mechanical consequences of abutment selection also bear significant consideration. Microgaps created during multiple abutment exchanges have been shown to allow microbial penetration, which in turn can trigger peri-implantitis and mechanical complications such as screw loosening or abutment fracture [7]. Finite element analysis has further revealed increased stress distribution around implants with multiple abutments due to cumulative mechanical alterations [8].

However, the clinical evidence remains divided. While some studies demonstrate reduced bone loss and better esthetic outcomes with single abutments, others report no significant difference in implant survival or patient satisfaction when compared with multiple abutment use [9]. Variability in patient-related factors, implant systems, abutment materials, and surgical techniques contribute to this disparity. Therefore, a well-controlled comparative clinical analysis is essential to evaluate the true impact of abutment selection on peri-implant outcomes.

This original research aims to assess the efficacy of single versus multiple abutments in implant-supported restorations, focusing on parameters such as marginal bone level changes, soft tissue response, and overall prosthetic success. By analyzing these outcomes, this study seeks to provide evidence-based recommendations to optimize abutment protocols and enhance long-term success in implant dentistry [10].

This prospective, randomized clinical study was conducted in the Department of Prosthodontics and Implantology at a tertiary care dental. Ethical clearance was obtained from the Institutional Ethics Committee., and written informed consent was secured from all participants prior to their inclusion.

Study Population

A total of 40 partially edentulous patients aged between 25 and 60 years, requiring single-tooth implant placement in the posterior mandibular or maxillary region, were recruited. Patients were selected based on the following

Inclusion criteria:

• Good systemic health (ASA I or II)
• Adequate bone volume (verified by CBCT) without the need for grafting
• Thick gingival biotype
• Sufficient inter-arch space for prosthetic rehabilitation

Exclusion criteria included:

• Poor oral hygiene (Plaque Index >2)
• Active periodontal disease
• Systemic conditions such as uncontrolled diabetes or immunosuppression
• History of bruxism or parafunctional habits
• Smoking or tobacco use

Study Design and Group Allocation

Participants were randomly allocated into two equal groups (n=20 each) using a computer-generated randomization sequence:

• Group A (Single Abutment Group): Patients received definitive abutments at the time of second-stage surgery (implant uncovery), which were not removed thereafter.
• Group B (Multiple Abutment Group): Patients received healing abutments followed by temporary and final abutment replacements at different stages of prosthetic fabrication.

All implants used were titanium screw-type implants with a diameter of 3.5–4.5 mm and a length of 10–12 mm (Nobel Biocare™ or equivalent system), placed using a standardized two-stage surgical protocol under local anesthesia. Implant placement followed the manufacturer's drilling sequence and torque recommendations (35–45 Ncm). A healing period of 3 months (mandible) and 4 months (maxilla) was observed before the prosthetic phase.

Prosthetic Protocol

For both groups, impressions were made using an open-tray technique with polyether material. Screw-retained metal-ceramic crowns were fabricated using CAD/CAM workflows. Occlusion was carefully adjusted to avoid premature contacts and lateral interferences.

Outcome Measures

Primary outcome:

• Marginal bone level changes, assessed radiographically at baseline (crown insertion), 3 months, and 6 months using standardized periapical radiographs and analyzed using ImageJ software calibrated for pixel-to-mm conversion.

Secondary outcomes:

• Peri-implant soft tissue health, including modified plaque index, bleeding on probing, and probing depth
• Patient satisfaction, evaluated using a Visual Analogue Scale (VAS) questionnaire (0–10 scale) at the 6-month follow-up

Statistical Analysis

All data were entered into SPSS software version 26.0 (IBM Corp., Armonk, NY). Descriptive statistics were computed for all variables. Intergroup comparison of marginal bone loss and clinical parameters was performed using the independent t-test for parametric data and Mann–Whitney U test for non-parametric variables. A p-value <0.05 was considered statistically significant.

Table 1: Marginal Bone Loss

The mean marginal bone loss observed in the Single Abutment group (Group A) was 0.81 ± 0.20 mm, which was significantly lower than the 1.20 ± 0.25 mm reported in the Multiple Abutment group (Group B). The difference between the groups was statistically significant (p < 0.001), indicating that maintaining a single abutment throughout the prosthetic phase may be effective in preserving peri-implant bone. This supports the hypothesis that repeated disconnection of abutments disrupts the mucosal seal and exacerbates crestal bone resorption.

Table 2: Probing Depth Comparison

The mean peri-implant probing depth was significantly lower in Group A (2.01 ± 0.29 mm) compared to Group B (2.63 ± 0.36 mm), with a statistically significant difference (p < 0.001). These findings suggest improved soft tissue stability and reduced peri-implant inflammation around single-use abutments. The greater probing depth in Group B could be attributed to inflammatory changes due to microgap formation and repeated abutment manipulation.

Table 3: Bleeding Index

Group A demonstrated a mean bleeding index of 0.49 ± 0.19, whereas Group B recorded a higher mean value of 0.91 ± 0.27. The intergroup difference was statistically significant (p < 0.001), highlighting better peri-implant soft tissue health in the single abutment protocol. The increased bleeding tendency in the multiple abutment group may reflect elevated inflammatory activity associated with the breakdown of the mucosal barrier.

Table 4: Patient Satisfaction (VAS)

Patients in the Single Abutment group reported higher overall satisfaction scores with a mean VAS of 8.92 ± 0.73, compared to 7.84 ± 0.70 in the Multiple Abutment group. This difference was statistically significant (p < 0.001), suggesting that single abutment protocols not only improve clinical outcomes but also enhance patient-reported quality of life. Factors contributing to this may include fewer appointments, reduced discomfort, and better esthetic results.

Table 1: Comparison of Marginal Bone Loss between Groups

Table 2: Comparison of Probing Depth between Groups

Table 3: Comparison of Bleeding Index between Groups

Table 4: Patient Satisfaction (VAS Score)

The present study aimed to evaluate and compare the clinical efficacy of single-use versus multiple-use abutment protocols in implant-supported prosthetic rehabilitation. The results demonstrated that the single abutment protocol significantly outperformed the multiple abutment protocol in terms of marginal bone preservation, peri-implant soft tissue health, and overall patient satisfaction. These findings align with the growing body of evidence advocating for minimal manipulation of abutments to promote peri-implant stability [11].

One of the most critical indicators of implant success is the maintenance of crestal bone levels. In this study, the mean marginal bone loss was significantly lower in the single abutment group compared to the multiple abutment group. This result supports the theory that the repeated disconnection and reconnection of healing and prosthetic abutments disrupts the soft tissue seal around the implant, facilitating microbial penetration and inflammatory responses that ultimately lead to bone loss [12]. The concept of the "one abutment, one time" protocol has been proposed to mitigate this risk by preserving the biological seal established during the initial phase of soft tissue healing [13].

Histologic studies have confirmed that stable abutment connections promote the formation of a stable epithelial and connective tissue interface around the implant collar. When this interface is violated by repeated abutment changes, the healing process is interrupted, and the re-establishment of the junctional epithelium begins anew each time, which may lead to a cumulative loss of crestal bone [14]. Moreover, the mechanical microgaps created during frequent abutment changes may allow for bacterial infiltration, which has been associated with increased peri-implant mucositis and progressive bone resorption [15].

In the current study, probing depth and bleeding on probing were also significantly better in the single abutment group. These soft tissue parameters are closely linked to inflammatory activity and correlate with peri-implant disease progression. The lower probing depths observed in the single abutment group may be attributed to a more stable peri-implant mucosal barrier, which acts as a protective mechanism against inflammatory insult [16]. Additionally, reduced bleeding indices in this group indicate better tissue response and less irritation during clinical examination, reinforcing the advantage of minimizing abutment handling.

Interestingly, patient satisfaction scores measured via the Visual Analogue Scale (VAS) were also significantly higher in the single abutment group. Factors such as fewer clinical visits, reduced soft tissue trauma, and more predictable esthetic outcomes may have contributed to this enhanced patient-reported outcome. Prior research has shown that simplified restorative protocols with fewer components often lead to reduced chairside time and lower procedural discomfort, which positively influences patient perception [17].

While some previous studies have reported no significant differences in long-term implant survival between the two protocols, it is important to note that survival alone does not equate to success. The biological and mechanical stability of peri-implant tissues, along with patient satisfaction, are equally critical endpoints for evaluating treatment efficacy [18]. In this context, the single abutment protocol appears to offer superior performance across multiple dimensions of clinical relevance.

The findings of this study are consistent with recent systematic reviews and clinical trials that have demonstrated a clear benefit of single abutment use in preserving bone and soft tissue. These studies have emphasized the importance of maintaining the integrity of the peri-implant seal and reducing bacterial colonization through fewer manipulations of the transmucosal component [19]. However, it is worth acknowledging that the success of either protocol may also depend on other variables such as the implant system used, precision of the prosthetic fit, occlusal load distribution, and the patient's oral hygiene compliance.

This study’s strength lies in its prospective design, standardized surgical and prosthetic protocols, and clearly defined clinical endpoints. However, some limitations must be addressed. The follow-up period was limited to six months post-prosthesis delivery, which may not capture long-term complications or differences in implant survival. Additionally, radiographic measurements were confined to two-dimensional periapical imaging, which, while standardized, may not reflect volumetric bone changes as precisely as cone-beam computed tomography. Future research with larger sample sizes, longer follow-up, and three-dimensional imaging is warranted to validate these findings and assess long-term outcomes [20].

Within the limitations of this study, it can be concluded that the use of a single definitive abutment in implant-supported prostheses offers superior clinical outcomes compared to multiple abutment changes. The single abutment protocol resulted in significantly reduced marginal bone loss, better peri-implant soft tissue health, and higher patient satisfaction. These findings support the "one abutment, one time" concept as a biologically and prosthetically favorable approach. Clinicians should consider minimizing abutment manipulation during prosthetic procedures to enhance the longevity and predictability of implant therapy.

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