During the initial weeks following tooth extraction, a physiological process of disuse atrophy occurs, marked by an extensive erosion of the alveolar bone and partial invagination of the mucosa. Although the extent and severity of the tissue repair process varies according to unique local and systemic variables, it often results in some level of horizontal and vertical alveolar ridge decrease, primarily in the bucco-coronal region [1]. Traditional implant placement techniques need a period of several months or more for the proper bone regeneration after tooth extraction prior to replacing a dental implant [2]. Recently, the old approach has been progressively supplanted by a quicker protocol that involves immediate placing an implant in a fresh extraction socket and rapidly restoring it. Provisional restorations on a single implant in the aesthetic zone have been advised for achieving a satisfactory soft tissue shape and hard tissue stability [3]. Furthermore, this technique has been associated with a number of potential advantages, including decreased treatment time, fewer surgical operations, less traumatic surgery, and increased patient satisfaction [4].

Nowadays tooth replacement with a single implant-supported restoration is a predictable and successful treatment. However, a strict patient selection and operation planning is necessary [5]. The complex aesthetic region evaluation is critical for the successful outcome and patient’s satisfaction regarding the implant-supported restoration in the aesthetic zone. Clinicians must take into account a variety of elements that affect the aesthetic outcome, including tooth position, neighbouring tooth root position, periodontal biotype, tooth form, smile line, implant site anatomy, and implant location. Additionally, the criteria’s such as the anatomical confines of the implant site, periodontal health, and occlusal parameters must be evaluated prior to determining the aesthetic aspects of such artificial repair [6-7].

In order to simplify the assessment of the most important soft and hard tissue parameters, several classifications of extraction sockets morphology have been developed. Additionally it can collaborate and acquire information using a global summary of the extraction socket classification system [7]. Bonnet et al. [8] evaluated the effectiveness of immediate implant placement technique in terms of soft tissue contours in aesthetic areas with the use of the pink aesthetic score (PES). The soft tissue around the tooth to be extracted was scored according to the PES before the surgery and at least 1 year after the final prosthesis placement. It is important to note that this index was created for the single implant-supported restoration aesthetic outcome assessment. Consequently, the classification of extraction sockets and aesthetic indexes for the single implant-supported restoration can be a useful tool for successful outcomes and patient satisfaction.

The primary objective of the present systematic review is to test the hypothesis - the revision of the complexity of the extraction sockets morphology classifications will reveal the most important parameters for implant aesthetic and functional success in case of immediate dental implant placement in aesthetic zone. The secondary objective is to revise the most important parameters of aesthetic indexes created for implant-supported restoration in aesthetic zone.

Protocol and registration

The current systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement for reporting systematic reviews [9].

The local bioethics committee granted approval (No. BCE-OF-90) by the Department of Bioethics, Medical Academy Lithuanian University of Health Sciences, Lithuania.

Focus question

The focus question was developed according to the Patient, Intervention, Comparison, Outcome and Study Design (PICOS) framework as described in Table 1.

The focus question: The revision of the extraction sockets morphology classifications and aesthetic indexes created for implant-supported restoration in aesthetic zone, will reveal the most important parameters for implant aesthetic and functional success and patient satisfaction.

Information sources

Search was undertaken in MEDLINE (PubMed) and Cochrane Library in combination with hand-search of relevant journals was conducted. Due to the desire to discover more socket classifications and aesthetic indexes for comparison, filters were applied ensure that the studies to be included were published between January 2005 to February 2022, and the information sources were in English. Additional related publications were found by manually searching the reference list of the selected articles.

Search

A thorough electronic search was carried out according to the PRISMA guidelines to determine the relevant studies [9]. The primary search inquiries used were: [“Dental Implant“ OR “Implant failure“ OR “immediate implant”] AND [“Implant esthetic” OR “Esthetic zone” OR “Esthetic region” OR “Esthetic indexes”] AND [“extraction socket” OR “socket classification”].

Selection of studies

The titles of the identified reports were independently screened by two reviewers (R.S. and P.D.) based on the inclusion criteria. A third reviewer (G.J.) checked mistyping. The abstract was assessed when the title indicated that the study was relevant. Full-text analysis was obtained for those with obvious relevance. The reviewers compared results and resolved differences through discussion, consulting senior researcher (G.J.) when consensus could not be reached. Reviewers were calibrated and inter-rater reliability Cohen’s kappa coefficient (κ) values were calculated for title-abstract screening.

Types of publication

Human studies published in the English language were considered in the review. Letters, editorials, PhD theses, and abstracts were excluded.

Types of studies

The review included all human systematic reviews and research syntheses and prospective cohort studies published between 1 January 2005 and 1 February 2022 that reported on patient’s extraction socket morphology evaluation before immediate implantation, as well as aesthetic indexes for implant-supported restoration evaluation, in the aesthetic zone.

Type of population

Patients undergo immediate dental implant placement and aesthetic outcomes evaluation following an implant-supported restoration in the aesthetic zone.

Inclusion criteria

Articles were selected according to the following inclusion criteria:

Exclusion criteria

Articles were selected according to the consequent exclusion criteria:

Sequential search strategy

Following the preliminary literature search, all article titles were screened to eliminate irrelevant publications. Afterward, studies were excluded based on data obtained from the abstracts. The final stage of screening included reading the full text articles to authorize articles eligibility.

Data extraction

The data was extracted independently from studies in the form of variables, in accordance with the present review’s aims and themes that are described below. If the essential data was missing, the corresponding authors were contacted by electronic mail.

Data items

Following items were collected and arranged in the following fields:

Assessment of methodological quality

The Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Systematic Reviews and Research Syntheses [10] (Table 2) and the JBI Critical Appraisal Checklist for cohort studies [11] (Table 3) were used to assess the procedural quality of the studies that fulfilled the inclusion criteria.

Methodological quality was categorized as follows: “high risk of bias”, when the study scored up to 49% of positive answers; “moderate risk of bias”, when study scored between 50 and 69% of positive answers; “low risk of bias”, when study reached more than 70% of favourable answers.

Statistical analysis

Zotero 5.0 reference management software (www.zotero.org) was used for articles management. Meta-analysis was not performed due to heterogenic parameters and lack of data for meta-analysis. The level of agreement between the two raters in selecting abstracts and studies were measured using Cohen’s kappa coefficient (κ).

Study selection

The database search yielded one paper in the electronic Journal of Oral and Maxillofacial Research that was discovered through a manual search, 107 articles in Cochrane Library and 369 publications in MEDLINE (PubMed) databases. There were selected 10% of publications for Kappa calculation, based on title-abstract analysis. Inter-rater reliability Kappa of 0.84 was achieved. Figure 1 illustrates a summary of the article selection process using the PRISMA flow chart.

There were 44 articles remaining after 433 duplicates were removed. Seventeen articles were excluded due to not relevant titles and abstracts.

Next 15 full-text articles [1-6,12-20] were excluded because they did not fulfil the inclusion requirements. Therefore, this scientific literature review evaluated 12 articles (Figure 1).

Risk of bias assessment

The JBI Critical Appraisal Checklist for systematic reviews and research syntheses [10] and the JBI Critical Appraisal Checklist for cohort studies [11] were used to assess the procedural quality of the studies that fulfilled the inclusion criteria.

The results on risk of bias assessment of systematic reviews and research syntheses are summarized in Tables 2 and 3. The results on risk of bias assessment of cohort studies are summarised in Tables 3 and 5. All of the systematic reviews, research syntheses, and prospective studies in this systematic review have high quality and a low probability of bias, with methods that do not include addressing incomplete follow-up.

Characteristics of the studies included

The studies included in this review compared the extraction socket classifications and aesthetic indexes for implant-supported restoration in the aesthetic zone. Five systematic reviews and research syntheses [21-25] and seven prospective studies [7,26-31] were included for the final review. The analysis included 537 patients in all prospective studies. All studies included in this review were published during the last 17 years, written in the English language and performed only on humans.

Synthesis of results

Tables 6 and 7 presents systematization of data of included studies. Table 6 represents the classifications of extraction sockets based on soft and hard tissue parameters in the aesthetic zone. By this study, all the classifications are referring to soft and hard tissues parameters but only two [26,27] are referring to tissue health as well.

Present systematic literature review hypothesizes that the revision of the complexity of the extraction sockets morphology classifications and aesthetic indexes created for implant-supported restoration in the aesthetic zone evaluation, will reveal the most important parameters for implant aesthetic and functional success.

Extraction socket classifications

All extraction socket classifications are designed for the evaluation of soft and hard tissues immediately after tooth extraction, as bone or soft tissue damage may occur during the surgical procedure. Clinical visual evaluation and the use of a periodontal probe can provide an objective evaluation of the tissues of the extraction socket. The presence and location of bony structures have an effect on the soft-tissue shapes. On the other hand, new evidence suggests that peri-implant soft tissues are essential for maintaining peri-implant health [32].

Soft tissue

One of the most important parameters of soft tissue is the facial soft tissue and its variations. All authors of the extraction socket classifications [21-24,26,27] except of Steigmann et al. [25] distinguished this parameter. Some socket classifications describe soft tissue variations as “soft tissue level” [22], “buccal soft tissue deficiency” [23], “vertical soft tissue deficiency” [26] or “soft tissue damage” [27]. In general vertical soft tissue deficiency is vertical distance between the socket and adjacent teeth’s buccal mucosa tissues margin [26]. For defects bigger than 2 mm, Kazor et al. [33] is recommending soft tissue augmentation prior to implant insertion.

Juodzbalys et al. [26] distinguishes in his classification more detailed soft tissue parameters, such as soft tissue contour, the keratinized gingival width, mesial and distal papillae appearance and soft tissue quality. Soft tissue contour variations are characterized as vertical distance between the socket and adjacent teeth’s buccal gingival scallop margin. The soft tissue contour closely mimics that of adjacent natural teeth and is critical in achieving a final aesthetic restoration [33]. Juodzbalys et al. [26] indicated a defect threshold of 2 mm when soft tissue plastic is already recommended. The keratinized gingival width on the mid-buccal side of the socket helps close-fitting tissue adaptation and provides a connective tissue circumferential fibre system that resists mechanical stress [34]. A mean KG width ≥ 2 mm is optimal for an aesthetic restoration [26]. Mesial and distal papillae appearance is the most challenging aspect of getting an excellent aesthetic outcome is maintaining a soft-tissue shape with intact papillae [12]. Maintaining a space of no more than 6 mm between the contact point and the alveolar crest next to the implant has been proved to be required for obtaining an unbroken papilla [35]. Treatments for a missing papilla caused by a lack of vertical bone are extremely difficult to conduct. Soft tissue quality: pink colour and firm consistency with a normal contour Juodzbalys et al. [26] classified as adequate quality for optimal aesthetic result achievement.

Another important soft tissue parameter included in most socket classifications is the gingival biotype [21,24,26]. It is evident that thick and thin tissues respond to regenerative procedures or inflammation is different [36]. Juodzbalys et al. [26] gingival tissue biotype characterized by fibrotic gingival thickness as thick (≥ 2 mm), moderate (≥ 1 to < 2 mm), or thin (< 1 mm). Numerous clinical studies have shown that a thick biotype allows for better aesthetic and functional results [37-39].

A broad biotype is seen as advantageous, particularly in terms of gingival recession, the most prevalent cosmetic issue linked with dental implants. A thin biotype with decreased tissue density and ragged gingival structure is the least appealing. This biotype may necessitate gingival biotype improvement, such as connective tissue transplant [12].

For everlasting harmonious gingival borders, the elevation and density of facial bone are critical. Thus, before placing an implant, the quality and amount of facial bone should be examined. Gingival recession occurs when an implant is placed in an area with a facial bone deficiency.

Hard tissue

When assessing the condition of hard tissue, all classifications distinguish one essential parameter - “buccal bone plate level” or “labial plate vertical position” [21-27]. This parameter can be characterized as the distance between the tip of the extraction socket labial plate and the cementoenamel junction of the adjacent teeth. The more distant the position of the alveolus bony margin to the soft tissues, the greater the risk for gingival recession [40]. The significant or complete loss of the buccal bone plate could be one of the contraindications for placing the implant immediately after tooth extraction [41]. If the distance between the tip of the extraction socket labial plate and the cementoenamel junction of the adjacent teeth is > 3 to < 7 mm, a guided bone regeneration procedure often is required [26].

Facial bone thickness is the next important parameter included in most socket classifications [25,26,27]. To maintain the implant soft tissue profile and to ensure implant aesthetics, a minimal labial plate width of 2 mm is needed. A thinner labial plate increases the risk of bone resorption during the healing period [42]. It suggests the importance of CBCT acquisition before any immediate implant placement. Alveolar buccal plates were also found to be thinner than lingual plates in many cases, and this was likewise linked to greater resorption in immediate implantation. Therefore, the resorption pattern showed that always the buccal portion of the alveolar process will be resorbed first and the axis of alveolar process is changing the angle [17,18].

Two authors highlighted buccal bone “defects” [25] or “lesions” [26]. Juodzbalys et al. [26] mentioned that periodontal and traumatic bone lesions often jeopardize the success of immediate implant procedures. In implant sites, hard-tissue defects include intra-alveolar, dehiscence, fenestration, horizontal ridge, and vertical ridge flaws. If patient lose a tooth or have an infection in the root canal or a fracture in the bone in the area where the sinus floor meets maxilla prior to getting an implant, clinician need to address these issues before getting an implant.

A compromised extraction socket buccal angulation is defined as 5° to 30° [26]. When deciding where to place implants in the past, it was generally based on the amount of bone accessible. To ensure that the dental implant is placed in the correct position following a thorough prosthetic planning, bone augmentation techniques are employed nowadays. Because of advances in the production of bone replacements and more information regarding guided tissue regeneration treatments, implant placement has become prosthetically driven. Advanced reconstructive surgery, on the other hand, raises the possibility of problems and a loss of aesthetic appeal. As a result, attempts have been undertaken to perform non-invasive treatment of bone abnormalities in order to avoid complicated treatments [12].

Reduced alveolar bone breadth and iatrogenic fracture of the alveolus, which may occur before or during tooth extraction, are further causes of additional bone resorption. Pathology resulting from any infective process, including as periodontal and endodontic abscesses, cysts, and tumours, are further local issues to consider. The growth of fibrous tissue in the injured regions may increase the rate and type of resorption, preventing normal healing and osseous regeneration [5].

Prognostic value

Dentists have come to believe that endosseous osseointegrated dental implants are a benign and regular method of replacing missing teeth. Implant dentistry’s early focus was on osseointegration, and that focus remains the most important criteria of success in the field today. As a result, new criteria are increasingly being employed to evaluate implant success due to patient and clinician needs and the improved confidence of osseointegration. Peri-implant soft-tissue level, prosthesis level, and patient subjective judgments are examples of these criteria. Implant dentistry’s success or failure should be evaluated using these characteristics. Modern patients expect not just better function but also a normal look from their medical treatments. It is critical for implants placed in the aesthetic zone to consider aesthetics while planning their location [12].

Juodzbalys and Wang [7] explained that because all of these elements affect their long-term aesthetic stability, it is obvious that clinicians should study all soft and hard tissue characteristics and prosthetic components when considering aesthetics. The parameters included in aesthetic index proposed by Juodzbalys and Wang [7] are as follows: mesial and distal interproximal bone height, gingival tissue biotype, implant apico-coronal position and horizontal contour deficiency. It is important the relationship between bone level and interproximal bone height and aesthetics of peri-implant soft tissue. It is obvious that the bone should support soft tissue papillae. While the thick tissue biotype exhibited less peri-implant soft tissue recession, Chen et al. [19] found that there was a significant difference between the two. Additionally, buccal shoulder implants location had three times the amount of recession as implants with the same position in the lingual/palatal region [7].

Aesthetic indexes

All aesthetic indexes parameters are evaluated after dental implant osseointegration, soft tissue maturation and final prosthetic treatment. Although some parameters of periimplant tissues are similar to the evaluation parameters of the extraction socket, they cannot be interpreted in the same way. Soft tissue parameters in both cases can be evaluated visually and using periodontal probe. In contrast, for bone dimensions assessment X-ray methods are used to assess implant treatment outcome [7].

There should be a harmonious relationship between the peri-implant soft tissues and the neighbouring tooth mucosa, and a well-integrated crown on the implant. A number of researchers have proposed objective measures for peri-implant aesthetic outcome. The most important parameters included in all aesthetic indexes covering only aspects of mucosal appearance, are the length of the interdental papillae and the soft tissue contour variations and appearance [7,28-31]. Although superstructure is as important as mucosa in determining the quality of prosthesis repair, it should also be considered in terms of mucosal appearance [15].

An aesthetic index that is often used is the pink and white score. The PES was developed by Belser et al. [29] to assess seven soft tissue features surrounding single-tooth implant crowns. The suggested index white aesthetic score (WES) encompassed the overall tooth shape, contour and size of the clinical crown, colour, and translucency [29].

Restoring a lost tooth with implants has become a common and reliable procedure. Modern implant dentistry uses implant rehabilitation to help patients regain lost phonetic and masticatory function as well as to improve their smile structural and aesthetic appeal. Restorations supported by dental implants are designed to resemble natural teeth as closely as possible. Implant-supported restorations also need to match the neighbouring teeth symmetrically. For implant rehabilitation to be successful, the following are regarded essential: appropriate bone volume, good implant positioning, stable and healthy peri-implant soft tissues, and an aesthetically pleasing soft tissue shape. Implant dentistry has just recently begun to develop quantitative methods for evaluating aesthetic outcomes [7].

For example, Meijer et al. [28] proposed aesthetic index rating soft tissue labial margin, papillae, contour of the labial surface, colour and surface. The rate of the prosthetic crown by: width, length, labial convexity, colour/translucency, surface, mesio-distal dimension and position of the incisal edge. Belser et al. [29] proposed the PES snd WES score that was described before. Juodzbalys and Wang [7] in order to rate the appearance of anterior maxillary implant-supported restorations and the soft and hard tissues around them, introduced the complex aesthetic index (CEI) for these restorations. The three factors of this aesthetic index are: the soft tissue index (S), predictive index (P), and implant-supported restoration index (R). Variations in soft tissue shape, vertical deficit, colour and texture, and the presence of mesial and distal papillae are all examples of soft tissue features. Primary components examined by the P include: interproximal bone height in the mesial and distal regions, gingival tissue biotype, implant apico-coronal location, and lack of horizontal contour. R components include: an evaluation of implant-supported restoration colour and transparency, labial convexity at the abutment/implant junction, the implant/crown incisal edge position, the crown width/length ratio, the surface roughness and ridges in relation to the neighbouring and contralateral teeth [7]. The results demonstrated that the CEI could accurately predict eventual implant aesthetic values by including both soft and hard tissue assessments. For complicated and prognostic evaluation, the CEI index is the best choice. Hosseini and Gotfredsen [30] proposed the Copenhagen index score (CIS) index scoring 6 parameters: distal papilla, mesial papilla, mucosal discoloration, colour match, crown morphology and symmetry/harmony. Recently Tettamanti et al. [31] proposed the peri-implant and crown index (PICI) based on: papillae, zenith, root convexity, shape, colour and characterization.