Tissue Preservation in Immediate 1C Implants Using an Anatomical Prefabricated Healing Abutment (Aharct)

Immediate replacement of a severely damaged posterior tooth with a dental implant has demonstrated high long-term success rates while offering the advantages of shorter treatment time and fewer invasive procedures compared with delayed implant placement. Beyond successful osseointegration, preservation of healthy peri-implant soft tissue and development of an optimal emergence profile are critical determinants of long-term implant success, as they reduce food impaction and plaque accumulation, facilitate oral hygiene, and contribute to favorable esthetic and functional outcomes. Historically, conventional healing abutments have been used primarily during the uncovering phase to promote soft-tissue healing; however, their cylindrical design does not replicate the natural contour of the extracted tooth and provides limited support for peri-implant soft-tissue architecture. Consequently, clinicians often use temporary titanium abutments and composite resin to customize healing abutments, or fabricate provisional restorations to shape the soft tissues during healing.

Recent evidence suggests that customized healing abutments, which mimic the natural tooth morphology, particularly in the cervical third, may better preserve peri-implant soft tissue contours, maintain marginal bone height, reduce early loading of immediately placed implants, and facilitate the development of a natural prosthetic emergence profile. Conventional customization with composite resin on a temporary abutment is technique-sensitive, requires additional clinical time, and carries the risk of contamination of the extraction socket by excess composite material. Prefabricated scannable AHAs have been developed to overcome these limitations by conforming to the extraction socket anatomy, supporting the surrounding soft tissues to prevent collapse during healing, stabilizing the blood clot, preserving space for bone regeneration, and simultaneously functioning as scan bodies for digital impression workflows. In addition, AHAs accurately transfer the three-dimensional implant position, potentially reducing treatment time, minimizing complications associated with repeated component exchanges, improving patient comfort and satisfaction, and streamlining fabrication of the definitive implant-supported restoration.

Preliminary laboratory investigations, clinical case reports, and early prospective clinical studies support the feasibility of AHAs for soft tissue management and digital implant workflows. However, the current evidence remains limited, particularly regarding their effectiveness in preserving pre-extraction soft-tissue contours following immediate implant placement in posterior sites. Existing studies are characterized by relatively small sample sizes, heterogeneous methodologies, and limited longitudinal clinical data. Therefore, further clinical investigation is needed to determine whether scannable anatomical healing abutments provide measurable benefits over conventional approaches in preserving peri-implant soft-tissue architecture and optimizing the emergence profile prior to the fabrication of a definitive single-implant-supported crown. This study aims to compare the anatomical healing abutment's capacity to preserve preextraction soft tissue contours, with attention to the position of the mid-facial gingival margin, enabling the delivery of the final crown in a shorter treatment period without the need for further soft tissue conditioning. The findings of this study will address an important gap in the literature and contribute to evidence-based protocols for immediate implant therapy and digital restorative workflows.Despite these theoretical and practical advantages, the currently available scientific literature remains relatively limited. Existing investigations primarily consist of laboratory studies, technical reports, case series, retrospective analyses, and a limited number of prospective clinical investigations. Although preliminary findings suggest favorable soft tissue management, simplified digital workflows, and acceptable clinical outcomes, robust randomized controlled clinical trials directly comparing Anatomical Healing Abutments with conventional healing abutments remain scarce. The available literature is further limited by relatively small sample sizes, heterogeneous methodologies, short observation periods, and inconsistent outcome measures.

Additional randomized clinical investigations using standardized surgical protocols, digital outcome measurements, validated esthetic indices, radiographic analyses, patient-reported outcomes, and longitudinal follow-up are needed to establish evidence-based recommendations regarding their clinical effectiveness.

The present study has been designed to address this important knowledge gap. The primary purpose of this multicenter randomized controlled clinical trial is to determine whether a prefabricated scannable Anatomical Healing Abutment provides superior preservation of peri-implant soft tissue contours compared with a conventional titanium healing abutment following immediate implant placement in posterior extraction sites. Rather than focusing exclusively on implant survival, the investigation comprehensively evaluates biological, prosthetic, radiographic, esthetic, digital, patient-centered, and economic outcomes throughout one year of functional loading.

Specifically, the primary objective is to quantify three-dimensional peri-implant soft tissue volumetric changes by superimposing sequential intraoral digital scans obtained at predetermined clinical time points. Advanced metrology software will be used to calculate volumetric differences within predefined regions of interest, allowing highly precise longitudinal assessment of peri-implant soft tissue preservation. This methodology provides substantially greater sensitivity than conventional linear measurements alone and permits objective evaluation of subtle soft tissue changes occurring throughout healing.

In addition to the primary endpoint, numerous secondary outcome measures have been incorporated to provide a comprehensive assessment of treatment effectiveness. These include longitudinal evaluation of the mid-facial mucosal margin, keratinized mucosa width, Pink Esthetic Score, implant position accuracy, three-dimensional hard tissue remodeling, marginal bone level changes, implant survival, peri-implant tissue health, implant stability, biological complications, prosthetic complications, patient-reported oral health-related quality of life, patient satisfaction, and treatment cost-effectiveness. Collectively, these outcomes will provide a multidimensional assessment of clinical performance and permit evaluation of whether preservation of peri-implant anatomy translates into measurable improvements in esthetic, functional, and patient-centered outcomes.

The investigators hypothesize that participants receiving the Anatomical Healing Abutment will demonstrate superior preservation of peri-implant soft tissue volume throughout healing compared with participants treated using conventional healing abutments while maintaining comparable implant survival, safety, and peri-implant tissue health. If confirmed, these findings may support broader implementation of anatomically contoured healing abutments as part of contemporary immediate implant therapy and digital restorative workflows.

This investigation is designed as a prospective, multicenter, randomized, controlled, longitudinal clinical trial conducted at the University of Illinois Chicago College of Dentistry and the Indiana University School of Dentistry. Both institutions will follow an identical clinical protocol, standardized surgical procedures, calibrated examiner training, common eligibility criteria, and uniform methods for data collection and outcome assessment. Conducting the study at two academic institutions increases the generalizability of the findings while maintaining protocol standardization and high-quality clinical oversight. The study will be coordinated collaboratively by the Co-Principal Investigators at each institution, with centralized statistical analysis performed after completion of participant follow-up.

Thirty participants requiring immediate replacement of a hopeless posterior tooth will be enrolled. Eligible participants will be randomly assigned in a 1:1 allocation ratio to one of two treatment groups consisting of fifteen participants each. Randomization will occur immediately following implant placement using a computer-generated allocation sequence incorporated into the REDCap® randomization module. The allocation sequence will be prepared by the study statistician before initiation of enrollment, and no stratification factors will be applied. Participants will remain blinded to their treatment allocation throughout the study, whereas the treating clinicians cannot be blinded because of the visible differences between the healing abutment designs.

The intervention evaluated in the test group consists of the Straumann® Anatomical Healing Abutment, a commercially available, FDA-cleared, and CE-marked healing component manufactured from polyether ether ketone (PEEK). The device is specifically designed to reproduce the anatomical cervical contour of posterior teeth while simultaneously functioning as a digital scan body. Unlike conventional healing abutments, the Anatomical Healing Abutment is intended to support peri-implant soft tissue architecture immediately after implant placement, facilitate preservation of the emergence profile, and allow direct acquisition of digital implant impressions without removal of the healing abutment. Throughout the healing phase, the device remains connected to the implant until definitive prosthetic procedures are initiated.

Participants allocated to the control group will receive the Straumann® Conventional Titanium Healing Abutment. This commercially available healing component represents the current standard of care for transmucosal healing after implant placement. Although highly successful for protecting the implant platform during healing, the conventional healing abutment possesses a cylindrical emergence profile that does not reproduce natural tooth anatomy and therefore serves as the comparator intervention in this investigation. Aside from the healing abutment assigned by randomization, every other aspect of treatment will be identical between study groups.

Participant eligibility has been carefully defined to create a relatively homogeneous study population while minimizing factors known to influence implant healing and peri-implant tissue remodeling. Eligible participants will be adults between 20 and 75 years of age with American Society of Anesthesiologists (ASA) Physical Status Classification I or II who require immediate implant placement for a hopeless maxillary or mandibular posterior tooth. Subjects must be willing to provide written informed consent, comply with all study procedures, and attend every scheduled follow-up visit. Candidate teeth must present with intact or successfully restored adjacent teeth and satisfy both clinical and radiographic criteria for immediate implant placement.

To minimize potential confounding variables, participants with conditions known to adversely affect wound healing or implant success will be excluded. These exclusion criteria include poorly controlled diabetes mellitus, smoking, immunodeficiency, previous head and neck radiotherapy, use of antiresorptive medications, pregnancy, poor oral hygiene, active periodontal disease, acute endodontic infection, inadequate occlusal relationships, insufficient restorative space, unfavorable soft tissue phenotype, significant mucogingival recession, or inadequate alveolar bone morphology. Following preliminary clinical screening, all potential participants will undergo cone-beam computed tomography (CBCT) to confirm the presence of sufficient facial bone thickness, adequate apical bone height, and favorable interradicular anatomy before final enrollment.

After informed consent has been obtained, participants will undergo a comprehensive baseline evaluation that includes review of medical history, medication use, oral examination, digital imaging, periodontal assessment, and restorative planning. Preoperative CBCT imaging and intraoral optical scanning will be performed using standardized acquisition protocols. Digital implant planning will subsequently be completed using coDiagnostiX® software according to a prosthetically driven treatment philosophy. Virtual implant positioning will be based upon the planned definitive restoration rather than the existing extraction socket anatomy alone. Customized surgical guides will then be digitally designed and fabricated using three-dimensional printing technology to facilitate accurate implant placement during surgery. Importantly, every participant will undergo identical digital planning regardless of eventual treatment allocation, thereby ensuring that only the healing abutment differs between study groups.

At the surgical appointment, atraumatic tooth extraction will be performed under local anesthesia while preserving the integrity of the surrounding alveolar bone whenever possible. Following extraction, the socket will be thoroughly debrided, and the facial bone plate will be clinically inspected. If a major facial bone defect incompatible with the study protocol is identified after extraction, the participant will receive appropriate clinical treatment but will discontinue protocol-specific data collection while remaining eligible for intention-to-treat analysis, consistent with the study protocol. Participants with intact sockets or only minor facial bone defects will continue according to the planned immediate implant protocol.

Straumann® BLX or BLC Roxolid® SLActive® implants will be placed immediately into the extraction socket according to the digitally planned implant position. The residual gap between the implant and socket walls will be grafted using Bio-Oss Collagen® xenogeneic bone substitute and covered with a BioGide® resorbable collagen membrane to promote guided bone regeneration and support preservation of the peri-implant ridge. Implant primary stability will be assessed using insertion torque measurements and resonance frequency analysis with the Osstell® device. These measurements will provide objective baseline information regarding implant mechanical stability immediately after placement.

Immediately after implant placement and assessment of primary stability, randomization will be performed and the assigned healing abutment installed according to the manufacturer's instructions for use. The Anatomical Healing Abutment will be hand-tightened in participants assigned to the test group, whereas participants assigned to the control group will receive the Conventional Titanium Healing Abutment. Both devices will remain in place throughout the healing phase until prosthetic procedures begin approximately twelve weeks after implant placement. Standardized suturing techniques, postoperative radiographs, postoperative medications, and oral hygiene instructions will be identical for both treatment groups.

Postoperative management includes a standardized medication regimen consisting of systemic antibiotics, nonsteroidal anti-inflammatory medication, and chlorhexidine mouth rinse in accordance with routine implant treatment protocols. Participants will return approximately ten to twelve days after surgery for clinical evaluation and suture removal. During this visit, implant survival and early biological complications-including infection, delayed healing, sinus membrane perforation, or neurosensory disturbances-will be documented. These observations will contribute to the overall safety evaluation of both treatment approaches.

Approximately twelve weeks after implant placement, participants will undergo definitive digital impression procedures. This visit represents one of the principal differences between the two treatment groups. In the intervention group, digital impressions will be obtained directly from the Anatomical Healing Abutment because the device simultaneously functions as a scan body. In contrast, participants in the control group will require installation of a conventional scan body before intraoral scanning can be completed. At this appointment, secondary implant stability measurements, clinical soft tissue measurements, standardized radiographs, and digital scans used for three-dimensional soft tissue analyses will also be obtained. Custom titanium abutments will subsequently be designed digitally and manufactured using CAD/CAM technology, followed by fabrication of monolithic zirconia or lithium disilicate crowns according to standardized restorative procedures.

Delivery of the definitive implant-supported restoration serves as the baseline prosthetic evaluation for subsequent longitudinal follow-up. Before crown delivery, participants will undergo another comprehensive clinical examination, intraoral digital scanning, peri-implant soft tissue measurements, radiographic evaluation, and assessment of biological complications. Esthetic outcomes will be evaluated using the Pink Esthetic Score, while oral health-related quality of life will be measured using the validated Oral Health Impact Profile-14 questionnaire. Investigators will also record chairside treatment time, laboratory time, and direct treatment costs for subsequent cost-effectiveness analyses. The definitive custom abutment will then be torqued according to manufacturer recommendations, and the definitive crown will be cemented using standardized restorative procedures.

Longitudinal follow-up will continue at six months and twelve months after delivery of the definitive restoration. These evaluations are intended to determine whether any early benefits associated with preservation of peri-implant anatomy are maintained after functional loading. At each follow-up appointment, investigators will evaluate implant survival, peri-implant tissue health, biological and prosthetic complications, mucosal margin stability, keratinized mucosa width, patient satisfaction, oral health-related quality of life, Pink Esthetic Score, standardized radiographic bone levels, and additional intraoral digital scans for three-dimensional soft tissue analysis. At the twelve-month visit, an additional CBCT examination will also be obtained to quantify three-dimensional hard tissue remodeling using artificial intelligence-generated models and digital superimposition techniques.

The primary endpoint of this clinical investigation is the preservation of peri-implant soft tissue architecture following immediate implant placement. Rather than relying solely on conventional linear clinical measurements, the study employs three-dimensional digital metrology to objectively quantify volumetric changes in peri-implant soft tissues over time. Intraoral optical scans will be acquired at standardized time points, including before tooth extraction, at implant impression, at delivery of the definitive prosthesis, and at six- and twelve-month follow-up visits. These digital surface models will be imported into Geomagic® metrology software, where consecutive scans will be superimposed using validated best-fit registration techniques. Volumetric changes within predefined regions of interest surrounding the implant site will then be calculated as percentage volumetric variation, providing a highly reproducible and sensitive assessment of soft tissue preservation throughout healing and functional loading. This methodology allows subtle dimensional changes that may not be detected through conventional clinical measurements to be objectively quantified and compared between treatment groups.

To complement the primary endpoint, several secondary outcome measures have been incorporated to characterize biological, prosthetic, radiographic, esthetic, functional, patient-centered, and economic aspects of treatment. The position of the mid-facial mucosal margin will be measured longitudinally using standardized periodontal measurements referenced to adjacent natural teeth. Preservation of this landmark is clinically important because apical displacement of the mucosal margin may compromise emergence profile development and negatively affect esthetic integration of implant-supported restorations. Similarly, the width of keratinized mucosa surrounding the implant will be measured throughout the observation period because adequate keratinized tissue has been associated with improved plaque control, patient comfort during oral hygiene procedures, and maintenance of peri-implant tissue health.

Esthetic outcomes will be evaluated using the Pink Esthetic Score (PES), a validated index that assesses multiple components of peri-implant soft tissue appearance, including the presence and contour of the papillae, level and curvature of the facial mucosa, root convexity, tissue color, and texture. Although posterior implant restorations generally receive less esthetic scrutiny than anterior restorations, preservation of harmonious peri-implant soft tissue contours remains important for patient satisfaction, prosthetic emergence profile, and long-term biological stability. Inclusion of the PES permits standardized comparison of esthetic outcomes between the two treatment approaches.

The study also incorporates advanced digital assessment of implant placement accuracy. Virtual implant planning performed before surgery will be compared with the actual implant position obtained from postoperative cone-beam computed tomography. Using the Treatment Evaluation module within coDiagnostiX® software, investigators will calculate three-dimensional linear deviations at the implant platform and apex together with angular deviations between planned and actual implant positions. These analyses will help determine whether implant placement accuracy influences subsequent soft tissue preservation or restorative outcomes and will provide additional information regarding the precision of digitally guided implant surgery within the study population.

Three-dimensional hard tissue remodeling will also be evaluated using an innovative digital methodology. Artificial intelligence-generated models created from postoperative and twelve-month CBCT datasets will be exported as standardized STL files and analyzed through digital superimposition in Geomagic® software. Root-mean-square (RMS) calculations will quantify three-dimensional changes in peri-implant bone morphology over time. Unlike conventional linear radiographic measurements alone, this approach allows comprehensive assessment of spatial hard tissue remodeling surrounding the implant and may improve understanding of the relationship between preservation of bone architecture and maintenance of soft tissue contours.

Standardized customized digital periapical radiographs acquired using the paralleling technique will be used to evaluate marginal bone levels throughout the study. Customized positioning devices will ensure reproducible radiographic geometry at every follow-up examination, allowing accurate longitudinal measurement of crestal bone changes adjacent to the implant platform. Marginal bone stability remains one of the most widely accepted indicators of long-term implant success and therefore represents an important complementary outcome measure.

Implant survival will be evaluated throughout the investigation using established clinical criteria based on the continued asymptomatic presence of the implant in function. Implant stability will be assessed immediately after placement using insertion torque measurements and resonance frequency analysis expressed as Implant Stability Quotient (ISQ) values. Secondary implant stability will be reassessed before prosthetic rehabilitation using the same standardized methodology. Together, these measurements provide objective information regarding primary mechanical stability and subsequent biological osseointegration while permitting comparison between treatment groups.

Peri-implant tissue health will be carefully monitored during every follow-up visit. Investigators will document the presence or absence of peri-implant mucositis and peri-implantitis using contemporary diagnostic criteria. Biological complications including postoperative infection, delayed healing, sinus membrane perforation, neurosensory disturbances, graft-related complications, wound dehiscence, and other implant-associated adverse events will be systematically recorded throughout the study. Prosthetic complications-including screw loosening, component fracture, restoration fracture, crown debonding, wear, or other mechanical complications-will likewise be documented to determine whether preservation of peri-implant anatomy influences long-term prosthetic performance.

Patient-centered outcomes constitute another major component of the investigation. Although objective clinical measurements are essential for evaluating treatment effectiveness, patient perception of treatment success has become increasingly important in contemporary implant dentistry. Oral health-related quality of life will therefore be measured using the validated Oral Health Impact Profile-14 (OHIP-14) questionnaire, while overall satisfaction with treatment will be evaluated using a visual analog scale (VAS). These instruments will assess participants' perceptions regarding comfort, function, chewing ability, esthetics, oral health, and overall satisfaction with their implant-supported restoration. Inclusion of patient-reported outcome measures provides a more comprehensive evaluation of treatment success beyond traditional clinical parameters.

An additional distinguishing feature of the present investigation is its assessment of treatment efficiency and cost-effectiveness. Contemporary implant dentistry increasingly emphasizes not only biological success but also optimization of clinical efficiency and resource utilization. Chairside clinical time, laboratory production time, and direct treatment costs associated with each restorative workflow will therefore be prospectively recorded from implant placement through delivery of the definitive restoration. These data will permit cost-effectiveness analyses comparing the Anatomical Healing Abutment workflow with the conventional healing abutment approach and may provide valuable information regarding potential economic advantages associated with anatomically contoured, scannable healing abutments.

Participant safety will be monitored continuously throughout the investigation. Because both healing abutments evaluated in this study are commercially available, FDA-cleared, and CE-marked devices used strictly within their approved indications, no unique device-related risks beyond those associated with routine implant therapy are anticipated. Nevertheless, investigators will systematically monitor implant survival, peri-implant tissue health, implant stability, biological complications, prosthetic complications, radiographic bone changes, and all adverse events occurring during the study period. Appropriate clinical management will be provided whenever necessary, and all adverse events will be documented and reported in accordance with institutional review board requirements, Good Clinical Practice guidelines, and applicable regulatory policies.

Multiple measures have been incorporated into the study protocol to minimize bias and maximize data quality. Standardized eligibility criteria reduce clinical heterogeneity among enrolled participants. Identical implant systems, grafting materials, restorative materials, postoperative medications, and clinical procedures will be used for both treatment groups. Digital treatment planning, surgical guide fabrication, implant placement protocols, prosthetic fabrication, imaging acquisition parameters, and follow-up schedules have all been standardized across participating institutions. Investigators and research personnel will undergo calibration before participant enrollment to ensure consistent implementation of study procedures and outcome assessments. Study data will be entered into a secure REDCap® electronic data capture system using standardized case report forms, and quality assurance procedures will verify completeness and accuracy of collected information before statistical analysis.

The multicenter design represents an additional strength of the study. Conducting the investigation at two academic dental institutions increases external validity by evaluating the intervention in independent clinical environments while maintaining protocol standardization. Furthermore, inclusion of comprehensive digital imaging, objective three-dimensional metrology, validated esthetic indices, standardized radiographic analyses, patient-reported outcome measures, safety assessments, and economic evaluations provides one of the most comprehensive clinical assessments currently available for anatomically contoured healing abutments following immediate implant placement.

The study has been designed with a superiority framework based on the hypothesis that preservation of peri-implant anatomy through the use of an Anatomical Healing Abutment will produce significantly less three-dimensional soft tissue volume loss than treatment with a conventional cylindrical healing abutment. Longitudinal statistical analyses will evaluate treatment effects over time while accounting for repeated measurements within individual participants. This analytical approach will permit assessment not only of differences between treatment groups but also of temporal patterns of tissue remodeling during healing and functional loading.

The anticipated clinical significance of this investigation extends beyond evaluation of a single implant component. If the Anatomical Healing Abutment demonstrates superior preservation of peri-implant soft tissue architecture while maintaining equivalent implant survival, peri-implant health, safety, and prosthetic performance, the findings could influence future clinical protocols for immediate implant therapy. Improved preservation of soft tissue contours may reduce the need for customized provisional restorations, decrease the number of restorative appointments, simplify digital impression procedures, minimize manipulation of peri-implant tissues, improve treatment efficiency, and facilitate fabrication of definitive implant-supported restorations with more natural emergence profiles. Conversely, if no clinically meaningful differences are observed, clinicians will have high-quality evidence supporting continued use of conventional healing abutments in comparable clinical situations.

Ultimately, this randomized controlled clinical trial seeks to generate high-level evidence regarding the biological, prosthetic, digital, esthetic, patient-centered, and economic performance of prefabricated scannable Anatomical Healing Abutments used during immediate implant placement in posterior extraction sites. By integrating advanced three-dimensional digital technologies with standardized clinical methodology and comprehensive longitudinal follow-up, the study aims to address an important gap in the current scientific literature and contribute meaningful evidence for the development of evidence-based protocols in implant dentistry. The findings are expected to improve understanding of peri-implant tissue preservation, optimize restorative workflows, enhance patient care, and support informed clinical decision-making regarding the use of anatomically contoured healing abutmen