Triangular Versus Circular Implant Neck Design and Their Effect on Marginal Bone Loss: a Systematic Review

Objectives: This literature review evaluates the differences between triangular and circular neck designs and their influences on marginal bone remodelling as well as peri-implant hard and soft tissue health. The primary aim was to compare implant survival and hard-tissue outcomes (peri-implant bone level, implant stability quotient and insertion torque). The secondary aim was to compare soft-tissue outcomes (probing depth, bleeding on probing, plaque index and full-mouth plaque score).

Material and Methods: The literature review followed PRISMA statement and used a PICOS-based focus question. An extensive search was conducted in MEDLINE (PubMed), Embase, Cochrane Library and Web of Science for studies published between December 1, 2015, and December 1, 2025. Inclusion criteria focused on human adult clinical studies, triangular vs circular neck implants, ≥ 3 months follow-up, and reporting at least one relevant clinical/radiographic parameter. Study risk of bias was assessed using the Joanna Briggs Institute Checklists.

Results: From 2999 identified records, 5 studies were included, comprising a total of 86 patients with follow-up ranging from 3 to 60 months. All studies compared triangular and circular neck implants. Implant survival was 100% in all studies. No significant differences were found in insertion torque, implant stability quotient and soft-tissue parameters. Two studies reported significantly lower (P ≤ 0.05) peri-implant bone level with triangular neck implants, while others found no significant differences.

Conclusions: The results indicate that triangular and circular implant neck designs demonstrate comparable clinical performance, with no clear differences in implant survival, insertion torque, implant stability quotient, and in soft-tissue outcomes. Peri-implant bone level may be lower with triangular neck implants in some settings, but findings are inconsistent across studies and limited.

J Oral Maxillofac Res 2026;17(2):e3

doi: 10.5037/jomr.2026.17203

Accepted for publication: 29 June 2026

Keywords: alveolar bone loss; dental implants; endosseous dental implantation; peri-implant endosseous healing.

INTRODUCTION

Dental implants have become the primary method for replacing missing teeth and restoring oral function and aesthetics [1]. They have demonstrated very high success rates, particularly due to osseointegration, first described by Brånemark [2]. He defined a direct structural and functional connection between the implant surface and the surrounding living bone without the interposition of soft tissue [2].

The stability and high success rates of dental implants depend on the integration of the skill of the surgeon and the implant characteristics, such as material, surface properties, implant design, etc. To ensure proper function and aesthetics, implants must maintain the health of the hard and soft tissues after osseointegration has been achieved [3].

Since its first development, there have been several innovations in implant characteristics, including shape, material, size, location, and various surgical techniques. These changes improved implant survival rates and the stability of the hard and soft tissues surrounding the implant [4]. Among these developments, particular attention has recently been directed toward the geometry and design of the implant neck because of their influence on osseointegration, marginal bone preservation, and peri-implant soft tissue stability [5].

The implant neck serves as the interface between the prosthesis and the implant body and is considered an important design feature influencing load distribution and the stability of peri-implant hard and soft tissues [6].

The conventional circular implant neck remains the most commonly used design across most implant systems. Recently, MIS Implants Technologies Ltd. (Bar Lev Industrial Park, Misgav, Israel) introduced an implant system featuring a triangular coronal neck configuration - MIS^® V3 (MIS Implants Technologies Ltd.), which differs from the traditional circular design (i.e. MIS^® C1 [MIS Implants Technologies Ltd.]) [7]. This triangular geometry creates three primary areas of contact with the crestal bone while intentionally leaving small spaces between portions of the implant neck and the surrounding cortical bone, thereby reducing uniform circumferential compression at the crestal level. These micro-gaps, estimated to be approximately 0.1 to 0.3 mm, are intended to redistribute compressive forces from continuous circumferential pressure to localized mechanical anchorage, allowing adequate primary stability while potentially limiting excessive stress on the crestal bone during insertion and early healing. When the flat surface of the triangular neck is oriented toward the buccal aspect, compression of the thin buccal cortical plate may also be reduced, which could contribute to improved preservation of marginal bone height [8]. During healing, these small spaces have been reported to become gradually filled with newly formed bone, with radiographic observations indicating bone formation around the coronal portion after several months of function [7]. In addition, the implant incorporates micro-rings at the neck region intended to enhance bone-to-implant contact at the crestal level [9]. However, the clinical advantages of triangular-neck implant designs compared with conventional circular-neck implants remain uncertain.

Therefore, the primary objective of the present literature review is to compare the effect of triangular neck design and conventional circular neck design on the implant survival rate and hard tissue parameters such as peri-implant bone level, implant stability quotient and insertion torque. The secondary objective is to evaluate the peri-implant soft tissue parameters, such as probing depth, bleeding on probing, plaque index and full-mouth plaque score.

MATERIAL AND METHODS

Protocol and registration

This systematic literature review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement for reporting systematic reviews [10].

It was registered in International Prospective Register of Systematic Reviews (PROSPERO), register under the number CRD420261320344.

The protocol can be accessed at: https://www.crd.york.ac.uk/PROSPERO/view/CRD420261320344

Focus question

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

Focus question: “In adults receiving dental implants, does a triangular neck design compared with a conventional circular neck design result in differences in peri-implant bone level (PIBL), implant stability, and peri-implant soft tissue health?”

Types of publication

This article contains studies which include only humans that are published in English. Systematic reviews, case studies, meta-analysis, letters and abstracts lacking full-text were excluded.

Information sources

The information source was the MEDLINE (PubMed), Embase, Cochrane Library, and Web of Science.

Types of studies

This review included randomized controlled and cohort studies published from December 1, 2015, to December 1, 2025.

Population

Adults ≥ 18 years undergoing dental implants placement.

Search strategy

According to the PRISMA guidelines [10] research articles were found using search databases such as MEDLINE (PubMed), Embase, Cochrane Library, and Web of Science published between December 1, 2015, and December 1, 2025. The keyword combinations used are shown in Table 2.

Inclusion criteria

• Full-text articles written in English and published between December 1, 2015, and December 1, 2025.

• Human clinical studies enrolling adult patients (≥ 18 years) undergoing dental implant therapy in healed ridges of the maxilla or mandible, ≥ 12 weeks post-extraction.

• Interventions assessing triangular cross-section implant necks (MIS^® V3) compared with conventional circular implant necks (MIS^® C1).

• Minimum follow-up of 3 months after implant placement or after functional loading.

• Studies reporting at least one peri-implant clinical or radiographic parameter, including PIBL, PD, BOP, PI, implant stability (insertion torque or implant stability quotient [ISQ]) or FMPS.

• Study designs limited to randomized controlled trials, prospective or retrospective cohort studies, or split-mouth clinical trials with a minimum patient sample size of 10.

Exclusion criteria

• Non-clinical studies (animal models, in vitro, cadaveric).

• Case reports, narrative reviews, systematic reviews, or expert opinions.

• Patients with uncontrolled systemic conditions, heavy smoking (> 10 cigarettes/day), or pregnancy.

• Abstract-only publications, conference proceedings, or articles not available in full text.

Data extraction

The data was taken out individually from studies, based on the tasks and objectives of this study.

The specific data items obtained are described in detail below.

Selection process of articles

This review’s research was done in multiple phases by two reviewers (D.S. and H.A.). Finding articles using the predetermined keywords was the first step (Table 2). Based on the titles and abstracts, all subsequent database duplications were removed. Publications were assessed for relevance and adherence to selection criteria following full-text analysis. Only articles that met these requirements were included in present literature review. Reviewers independently verified the results, and disagreements were resolved through discussion. No third reviewer was involved. Reviewers were calibrated by calculating Cohen’s kappa coefficient (κ) values to ensure inter-rater reliability of abstracts in a sample of 10% of publications.

Data items

The following parameters were extracted when available: First author and publication year, study design, number of patients, mean age (or range), male/female ratio, duration of the follow-up, total number of implants placed, implant site of placement (maxilla/mandible, anterior/posterior), implant survival (%), insertion torque at placement (Ncm), ISQ values (longest follow-up), PIBL (mm), probing depth (PD, mm), plaque index (PI, %/Silness and Löe), full-mouth plaque score (FMPS, %), bleeding on probing (BOP, %).

Risk of bias across studies

The Joanna Briggs Institute (JBI) Critical Appraisal Checklist for randomized controlled trials and cohort studies [11] were used to evaluate the procedural quality of the studies that met the requirements for inclusion criteria. Tables 3 and 4 provide specific questions that were assessed. In the checklist, every criterion was given a rating of “yes“, “no“, “unclear“, or “not applicable“. Methodological quality was categorized as follows: “low risk of bias” when the study reached more than 70% of favourable answers; “moderate risk of bias” when the study scored between 50 and 69% of positive answers; “high risk of bias”, when the study scored up to 49% of positive answers.

Synthesis of results

The items and data were gathered and organized in tables after the pertinent information had been obtained from the articles. According to the characteristics of included articles the following items were identified: the study, year of publication, follow-up, type of research, total number of patients and in each group, average ages and male to female ratio in test and control group separately. Furthermore the data items were arranged by specifying the study, total number of implants placed, duration of the follow-up, implant site of placement, implant survival, insertion torque, ISQ, PIBL, PD, PI, FMPS and BOP in test group (MIS^® V3 implant) and control (MIS^® C1 implant) group.

Statistical analysis

Mendeley^® Reference Manager version 2.110.2 (Elsevier; London, UK [www.mendeley.com]) was used to organize, store, and cite the articles. A meta-analysis was not performed because the articles were heterogenic (different study design, anatomical location, follow-up duration, data items, implant dimensions and loading protocol).

The level of agreement between the two raters in selecting abstracts and studies were measured using Cohen’s kappa coefficient (κ).

RESULTS

Study selection and exclusion

A total of 2999 records were initially identified (Figure 1). After removing 260 duplicate records, 2739 articles remained for screening. Six hundred and eighty records excluded due to more than 10 years old, which leave 2059 records sought for retrieval. Following the title and abstract screening, 2049 were excluded as they were irrelevant to the topic. As a result, 10 full-text articles were assessed for eligibility. The level of agreement between the two researchers (D.S. and H.A.) in selecting abstracts was measured at κ = 0.9.

Study exclusion

After analysing the full-text articles, 5 were excluded for the following reasons: two didn’t compare between triangular and circular implant neck design [12,13], one study was an animal experiment [14] and two were case series [8,15]. Finally, five studies met all criteria and were included in this literature review [16-20].

Quality assessment of the included studies

The quality of methodological studies was evaluated using The JBI Critical Appraisal Checklist for randomized controlled trials and for cohort studies. The evaluations for each study are presented in Tables 5 and 6. Eshkol‐Yogev et al. [16] was in “moderate risk of bias”. All other four articles [17-20] were in “low risk of bias”.

Study characteristics

The main characteristics of the studies are summarized in Table 7. The included studies consisted of 4 randomized controlled clinical trials [16-19] and one cohort study [20]. A total of 86 patients were included with follow-up duration selected for analysis. The results of the included studies are presented in Table 7.

Follow-up

This literature review chose all reported follow-up periods of at least 3 months to assess both short- and long-term outcomes (Table 7). Eshkol‐Yogev et al. [16] had the shortest follow-up period of 3 months. Li Manni et al. [17] and Tokuc and Kan [18] reported a follow-up period of 12 month, which were subsequently continued and reported with longer-term follow-up in later publications by Hurtgen et al. [19] and Tokuc and Kan [20], respectively. Hurtgen et al. [19], which is a follow-up study of Li Manni et al. [17] had follow-up periods of 36 and 60 months. Tokuc and Kan [20] reported a follow-up of 60 months.

Type of implant

Regarding implant type, all five included studies [16-20] used both MIS^® V3 (test) and MIS^® C1 (control) dental implants to evaluate differences in clinical outcomes related to implant neck design, with a total of 106 implants placed across the included studies (Table 8).

Site of dental implant placement

All five studies [16-20] reported the precise location of the dental implant placement region. Three studies [16,17,19] reported that the implants were placed in the posterior maxilla. Tokuc and Kan [18,20] reported implant placement in the anterior region of the mandible (Table 8).

Implant survival

In all five studies [16-20] the implant survival rates were absolute with 100% (Table 8).

Insertion torque

The insertion torque was mentioned in all five articles in the current review.

Eshkol‐Yogev et al. [16], reported that the insertion torque in test group is 45 Ncm with the range of 18 to 80 Ncm, compared to control group with 50 Ncm, with range of 45 to 50 Ncm (P ≥ 0.05). Li Manni et al. [17] and Hurtgen et al. [19] just mentioned that the surgeons did not exceed an insertion torque higher than 45 Ncm in both control and test group. Tokuc and Kan [18] showed insertion torque of 40.5 (SD 10.37) Ncm in the test group and 39.25 (SD 9.77) Ncm in the control group with the range of 25 to 50 Ncm in both groups (P = 0.075), while Tokuc and Kan [20] reported insertion torque of 38.8 (SD 13.1) Ncm and 40 (SD 9.4) Ncm in test and control group respectively, with the range of 25 to 50 Ncm (P = 0.888).

Implant stability quotient

ISQ was reported in just two studies [16,18] from five articles participating in the current study. Eshkol‐Yogev et al. [16] showed that the ISQ in the test group was 74.4 (SD 6), while in control group was 77.6 (SD 3.6) at the follow-up of 3 months (P = 0.097). Tokuc and Kan [18], reported ISQ of 77.1 (SD 5.42) in the test group, compared to control group with 78.4 (SD 6.96) at 8-week follow-up (P = 0.2).

Peri-implant bone level

PIBL parameter was presented in all five studies [16-20] in this literature review (Table 8). Three out of five articles showed lower values of PIBL in test group compared to control group in follow-up of 12 months [17,18] and 60 months [19]. Li Manni et al. [17] found that the PIBL in test group was lower with 0.22 (SD 0.3) mm compared to control group with 0.42 (SD 0.67) mm (P = 0.25). Tokuc and Kan [18] reported that PIBL in test group was 0.58 (SD 0.36) mm, while control group with MBL of 0.91 (SD 0.59) mm (P < 0.01). In addition, Tokuc and Kan [20] revealed PIBL of 0.71 (SD 0.69) mm in test group, while control group with 1.03 (SD 0.86) mm, at the follow-up of 60 months (P < 0.01). Eshkol‐Yogev et al. [16] reported very similar PIBL in test and control groups in shorter follow-up. After 3 months of follow-up, the test group reveal 0.5 (SD 0.4) mm of PIBL and control group with 0.5 (SD 0.7) mm (P = 0.1). Nevertheless, Hurtgen et al. [19], showed slight elevation of PIBL in test group compared to control group. At follow-up of 36 months showed PIBL of 0.39 (SD 0.42) in test group and 0.23 (SD 0.43) mm in control group (P = 1.00). Subsequently, at follow-up of 60 months reported 0.38 (SD 0.39) mm PIBL in test group compared to control group with 0.29 (SD 0.58) mm (P = 0.49).

Probing depth

Out of the five studies, only three [18-20] had information regarding PD (Table 8). Tokuc and Kan [18] found a PD of 1.67 (SD 0.95) mm in test group and 1.61 (SD 0.98) mm in control group (P = 0.886). Tokuc and Kan [20] reported very similar values of PD in test and control groups with 1.85 (SD 0.8) mm and 1.84 (SD 0.83) mm, respectively (P = 0.839). Hurtgen et al. [19] demonstrated a PD of 2.88 (SD 0.56) mm in test group compared to control group with 3.05 (SD 0.7) mm in a follow-up of 36 months (P = 0.53). Additionally, at the follow-up of 60 months reported PD of 3.32 (SD 0.531) mm in the test group compared to 3.36 (SD 0.531) mm in control group (P = 0.83).

Plaque index

PI parameters were presented in three studies out of five participating in this literature review (Table 8). PI was reported only in Tokuc and Kan [18,20] studies using the Silness and Löe scale (0 - 3) while in Hurtgen et al. [19] reported PI in percentages. Tokuc and Kan [18] revealed that the PI in test group was 0.47 (SD 0.82), while in the control group was 0.52 (SD 0.83) (P = 0.59). Tokuc and Kan [20] showed 0.44 (SD 0.54) mm in test group and 0.39 (SD 0.51) mm in control group (P = 0.719). Hurtgen et al. [19] showed that PI was 19.44 (SD 25.46)% in test group, while control group with 18.18 (SD 27.34)% at follow-up of 36 months (P = 0.91). At the follow-up of 60 months PI in test group was 19.7 (SD 26.69)%, compared to control group with 30.95 (SD 32.59)% (P = 0.36).

Full mouth plaque score

The FMPS was mentioned on two out of five studies [17,19] (Table 8). Li Manni et al. [17] revealed that the FMPS in test group was 7.91 (SD 8.31)%, while control group with 6.35 (SD 6.29)% (P = 0.54). Hurtgen et al. [19] showed that the FMPS for the test group was 15.28 (SD 16.37)% and 26.16 (SD 21)% in control group at follow-up of 36 months (P = 0.17). In addition, test group was 20.37 (SD 15.04)%, compared to 30 (SD 23.03)% for the control group at the follow-up of 60 months (P = 0.24).

Bleeding on probing

BOP was presented in two out of the five included studies (Table 8). Li Manni et al. [17] that checked the BOP in follow-up 1 year, showed a decrease in BOP percentage in the test group, with 17.6%, compared to 29.4% in the control group (P = 0.42). Hurtgen et al. [19] showed BOP of 33.3% in test group and 16.7% in control group at the follow-up of 36 months (P = 0.64). In contrast, at 60 months follow-up of the study, Hurtgen et al. [19] reported elevation of BOP percentage in both groups, especially in a test group with 100%. The control group showed 64.3% of BOP (P = 0.08).

DISCUSSION

This literature review analysed the effect of triangular versus circular implant neck designs on peri-implant hard and soft tissues. Five [16-20] studies were evaluated and include a test group with triangular cross-section neck implant design (MIS^® V3) and a control group with conventional circular cross-section neck dental implants (MIS^® C1). A comparative clinical evaluation of implant survival rate and hard tissue parameters such as PIBL, ISQ and Insertion torque, as well as peri-implant soft tissue parameters such as PD, BOP, PI, FMPS, was conducted to evaluate the differences between the two groups.

The results of this review demonstrate that there are no significant (P > 0.05) differences in most of the parameters between implants with triangular neck design compared to circular neck design. All five included studies [16-20] revealed that the survival rate of implants were 100%, regardless implant neck design. These results indicate that both triangular and circular neck design are clinically trustworthy treatment options. This aligns perfectly with Giralt-Hernando et al. [21] and Montemezzi et al. [12] that showed high survival rate of 97.5% in a 1-year follow-up for triangular-neck implants and 96.72% survival rate in two-years follow-up for circular neck design respectively. In contrast, Porta-Ferrer et al. [22] reported lower survival rate of 88.9% for both groups in a 1-year follow-up. Overall, these findings suggest that both triangular and round implant neck designs are correlated with similar clinical efficacy and high short-term survival rate.

Similarly, the insertion torque has not statistically significant different (P > 0.05) between triangular and circular implant neck designs, according to all five articles [16-20]. In addition, no significant different (P > 0.05) was found ISQ by Eshkol‐Yogev et al. [16] and Tokuc and Kan [18] (with follow-up of 8 weeks). These finding is comparable with previous clinical and biomechanical studies which predominantly determined that the main factors influencing primary stability, subsequent insertion torque and ISQ are bone density, thread design, taper and implant body geometry rather than implant neck design. O’Sullivan et al. [23] reported that insertion torque has significant association with bone density and implant macro-design, indicating that other design features, such as cervical designs, may play a less dominant role. They found that implants placed in type 4 bone showed significantly lower insertion torque compared with those placed in bone type 2 and 3 for standard implants.

Furthermore, two studies included in this review, written by Tokuc and Kan [18,20] showed a significant peri-implant bone loss (PIBL) in test group with a triangular neck design compared to circular neck design, at the 12 and 60 months of follow-up respectively. In contrast, no significant different (P > 0.05) was found in PIBL between test group and control group, in three out of five articles included in this review [16,17,19] (Table 8). A 12-month randomized clinical trial with immediate implant placement by Porta-Ferrer et al. [22] is consistent with these results in the article. Porta-Ferrer et al. [22] argue that although a triangular implant neck reduces the crestal compression, this feature does not translate into a greater benefit in preserving marginal bone in the short term over a round implant neck. In addition, Giralt-Hernando et al. [21] reported low and acceptable marginal bone loss around triangular neck design at 1 year follow-up, but did not compare it to conventional round neck design. They found that the mean marginal bone loss for triangular neck design was 0.51 (SD 0.44) mm, closely comparable to the results of the articles participating in this review.

BOP was presented in two articles [17,19], that were included in this literature review. Li Manni et al. [17] reveal that at the follow-up of 12 months the BOP in test group was lower than in control group. In contrast, Hurtgen et al. [19] showed a higher percentage of BOP, at a follow-up of 3 and 5 years, for the test group compared to the control group. Even though the percentage values obtained for BOP in the two articles were different between the test and control group, there was no significant differences (P > 0.05) in BOP between triangular neck design and circular neck design in both articles. These finding also aligned with the study by Porta-Ferrer et al. [22] that showed no significant differences in MBL, PD and BOP (P > 0.05), which indicates that peri-implant mucositis is not primarily influenced by the design of the implant neck. Furthermore, BOP known as a clinical indicator of peri-implant mucositis. According to Rokaya at el. [24], the main cause for peri-implant mucositis induced by plaque accumulation, which is increased by surface roughness of the implant, residual cement, micro-gap contamination at the implant-abutment interface and prosthetic contour. Therefore, knowing that BOP reflects plaque-induced inflammation, it is unlikely that changing the implant neck design from circular to triangular alone will significantly affect the BOP tendency.

Regarding PD, both Tokuc and Kan [18,20] at the follow up of 1 and 5 years, and Hurtgen et al. [19] at the follow up of 3 and 5 years, observed no significant differences (P = 0.53 and P = 0.83 respectively) between the test and control groups (Table 8). Porta-Ferrer et al. [22] aligns also with these outcomes and showed no significant differences (P > 0.05) in PD at 12 months of follow-up. They found that PD values increased in both groups during peri-implant bone healing after immediate implant placement. At 12 months, PD values were similar and within normal limits. They concluded that implant neck design does not affect peri-implant soft tissue PD. Additionally, according to Berglundh et al. [25] peri-implant PD mainly reflects the inflammatory condition of the mucosa, and level of the marginal bone rather than implant macro-geometry. Therefore, in the absence of significant differences in BOP and MBL, it is biologically plausible that triangular neck and circular neck designs will not demonstrate clinically significant differences in PD.

A similar pattern was observed when evaluating the PI. Three studies, Tokuc and Kan [18,20] and Hurtgen et al. [19] showed no significant differences (P > 0.05) between the triangular neck design in test group and circular neck design in control group. Additionally, both Li Manni et al. [17] with follow-up of 12 months and Hurtgen et al. [19] with longer follow-up of 3 and 5 years observed no significant difference (P > 0.05) in FMPS between test and control groups. Although there is no conclusive proof that there is no relationship between implant neck macro-geometry and plaque retention, Bollen et al. [26] found that plaque accumulation around the implant is mainly influenced by surface roughness. They reported that surface roughness above a critical threshold (~ 0.2 μm) show increased plaque retention. Moreover, O’Mahony et al. [27] reported that the main factors that contributing to plaque accumulation are the size of the micro gap between implant or abutment component, surface roughness, threaded surface of the implant, while no evidence was reported to suggest that implant neck geometry influences plaque retention.

Limitations

Although the included studies offer valuable insights about the differences between triangular neck design and circular neck design on peri-implant soft and hard tissues, certain limitations must be considered.

First, triangular implant necks are a relatively new invention, and therefore there are only few studies comparing triangular implant neck design to the conventional circular neck design. We included only five articles in this review, and a few additional articles not included in the same article could corroborate our results. This limits the strength and reliability of the conclusions. Second, another limitation is the small sample size of the included studies. Although all articles are prospective cohort studies, the number of participants in each trial is relatively small, which reduces the statistical power to detect small but clinically significant differences between triangular and circular implant neck designs. Consequently, the lack of statistically significant differences in most of the parameters evaluated should be interpreted with caution, as true differences may exist but remain undetected due to insufficient sample size.

Another important limitation of this literature review is the lack of clinical and radiographic outcomes for some of the parameters in the included studies in this review. Not all studies reported the same parameters, such as insertion torque PD, ISQ, PI, FMPS that were compared between only two articles. Direct comparison between studies was further complicated by the fact that outcome measures were reported using various units of measurement, with some parameters being presented as percentages and others using mean values or ordinal measures. Potential distinctions between triangular and circular neck implant designs may be obscured by this lack of consistency in outcome selection, measurement, and reporting, which also restricts the capacity to thoroughly synthesize data.

Additionally, two articles [17,18] included in this literature review represent the primary studies while the other two [19,20] are extended follow-up reports of the same cohorts. These include the same patients and examine outcomes over different follow-up periods. Li Mani et al. [17] and Tokuc and Kan [18] examined the impact on peri-implant hard and soft tissue at 12 months follow-up, while Hurtgen et al. [19] Tokuc and Kan [20] evaluated the impact on peri-implant hard and soft tissue at 5 years follow-up. Additionally, Hurtgen et al. [19] also reported outcomes at a 3 year follow-up. Although both publications offer useful insights into both short- and long-term clinical performance, using overlapping patient populations weakens the data’s independence and could result in an overrepresentation of findings from a single cohort in the results interpretation.

Furthermore, another limitation relates to the assessment of ISQ in the study by Tokuc and Kan [17], in which ISQ was reported only at an 8-week follow-up, rather than at the 12-month follow-up used for other outcome parameters. This follow-up timing discrepancy may limit the direct comparison with other studies and could influence the interpretation of implant stability outcomes, as ISQ values are known to change during the early phases of osseointegration.

Another limitation of the included studies is the reduction in the number of patients at the follow-up visits. In both Hurtgen et al. [19] and Tokuc and Kan [18,20], the sample size decreased at successive follow-up periods. Li Mani et al. [17] initiated the study at follow-up of 1 year with 34 patients (17 patients in each group). However, Hurtgen et al. [19] reported that the number of patients decreased to 26 patients (13 in each group) at the follow-up of 3 years and further declined to 25 patients (11 in test group and 14 in control group) at the follow-up of 5 years. Correspondingly, Tokuc and Kan [18] began the study with 20 patients at the follow-up of 1 year, but then Tokuc and Kan [20] indicated 19 patients during 5 year follow-up. The statistical power of the long-term analyses may have been lowered due to attrition bias brought forth by this sample size reduction.

In addition, Eshkol‐Yogev et al. [16] reported early stability outcome such as ISQ, insertion stability and PIBL after implant placement at the follow-up of 3 months, while others [17-20] indicated post-loading clinical and radiographic outcomes. This limits direct comparison between early stability findings and long-term functional outcomes.

Future research should prioritize rigorously designed longitudinal studies with standardized methodologies to validate these associations, reduce bias, increase the sample size and the parameter included to better clarify the differences between triangular and circular implant neck design and the impact on peri-implant tissues.

CONCLUSIONS

Present study revealed no significant differences in implant survival rate and hard tissue parameters such as implant stability quotient and insertion torque. Although two [18,20] of the five studies included in this review reported a decrease in peri-implant bone level. However, this finding was not observed in the other studies that showed no significant difference in peri-implant bone level between triangular and circular implant neck designs.

No significant differences were reported in peri-implant soft tissue parameters, such as probing depth, bleeding on probing, plaque index and full-mouth plaque score.

ACKNOWLEDGMENTS AND DISCLOSURE STATEMENTS

The authors report no conflict of interest related to this study.

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