Survival and Complication Rates of Narrow-Diameter Implants Used for Immediate Provisional Restoration of the Mandibular Anterior Region: A Retrospective Study

Abstract

Implant placement in the mandibular anterior region is often limited by narrow alveolar ridge width, particularly in older or medically compromised patients, where bone grafting is contraindicated or undesirable. This area is also crucial for esthetics, necessitating immediate restoration after tooth loss. This retrospective study evaluates the short- and long-term survival and complication rates of narrow-diameter implants (NDIs) placed for immediate provisional restoration in the mandibular anterior region. This study includes 22 one-piece NDIs (Osstem, Korea) placed in 13 patients with narrow ridges, immediately restored with non-functional provisional prostheses. Clinical records and follow-up data throughout 2023 were reviewed. Marginal bone loss (MBL) was assessed using standardized periapical radiographs. A generalized linear mixed model was used to analyze the correlation between MBL and clinical variables. The implant survival rate was 100% (95% CI: 82.7–100) over an average follow-up period of 7 years. Biological and mechanical complication rates were 18.18% and 4.54%, respectively; patient-based complications occurred in 30.77% of cases. No statistically significant predictors of MBL were identified, although smoking showed a trend toward significance (p = 0.096; OR = 8.00; 95% CI: 0.69–92.70). NDIs may be a viable option for immediate provisional restoration in this region, although findings should be interpreted cautiously.

1. Introduction

Dental implant procedures have been established in modern dental practice as a common and universal treatment method for partially or completely edentulous patients. Notably, dental implants serve as a versatile treatment option, enabling the restoration of missing teeth and the improvement of overall oral health in terms of functional effectiveness, esthetics, and speech/pronunciation clarity. However, they have drawbacks, including higher treatment costs, discomfort from surgery, the need for a baseline health condition for which surgery can be performed, and the likelihood of requiring long-term treatment to ensure implant osseointegration and peri-implant osteogenesis. The implant procedure also requires optimal placement of the implants in terms of their thickness, length, and number, depending on the site of the missing teeth. However, in practice, optimal implantation is challenging due to practical difficulties, such as limitations in available bone height for implant placement and securing the labiolingual and mesiodistal space at the missing tooth.

The mandibular anterior region has several advantages over other areas for dental implant procedures, such as a lower risk of injury to critical anatomical structures and ease of securing a field of vision and access to instruments. However, the orbicularis oris and mentalis muscles are in close proximity, resulting in many cases of shallow vestibular depth, which poses a challenge when performing implant procedures with bone augmentation/grafting. In particular, the labiolingual bone width is typically narrow, making it difficult to place standard-diameter implants (SDIs). Additionally, achieving ideal implantation by maintaining a 1.5 mm distance from the adjacent teeth on both sides is usually impossible when one mandibular anterior tooth is lost. The average mesiodistal width [1] of the mandibular anterior tooth in the Korean population is 5.38 and 6.02 mm for the central and lateral incisors, respectively, in men, and 5.20 and 5.80 mm in women, which are smaller than those of Caucasians. Dental crowding can also occur in the mandibular anterior region if the patient’s existing dental arch is small or the tooth dimensions are relatively large, and the available bone width after extraction may be even smaller. A study on an external hex implant by Tarnow et al. [2] reported that severe saucerization occurred when failing to secure the implant tooth and inter-implant distances of 1.4 and 3 mm, respectively, indicating greater challenges for dentists performing implant placement in the mandibular anterior region with narrow bone widths. The major obstacles to implantation in the mandibular anterior region include the narrow labiolingual width of the residual bone, the concave shape of the bone on the labial side of the apical region, and the lingual artery located on the lingual side. Additionally, the bone width in the mandibular anterior region poses a major hurdle in the practice of dental implant placement among Koreans. The average bone width [3] in the mandibular anterior region in the Korean population is reportedly 5–6 mm. Furthermore, the average width of bone resorption [4] after extraction is 2.99 and 4.95 mm in the mandibular central and lateral incisors, respectively, resulting in an average bone width loss of 3.97 mm. Considering these factors, the average available bone width for implant placement after extraction in the mandibular anterior region is <2.5 mm.

Various surgical techniques, such as guided bone regeneration, the alveolar ridge split technique, and distraction osteogenesis, have been employed to overcome the challenges of narrow bone width in dental implant placement. However, issues such as postoperative complications, a prolonged treatment period, and additional costs may arise. Additionally, using these surgical techniques may increase the possibility of complications in patients with systemic diseases who have difficulty receiving dental treatment (e.g., patients with a medical history of undergoing head and neck radiation or those with a medication history of taking bone resorption inhibitors) [5].

SDIs typically have a diameter of ≥3.75 mm, while implants with smaller diameters of ≤3.5 mm are classified as narrow-diameter implants (NDIs) [6,7]. As previously described, using NDIs in the region of the lost mandibular central and lateral incisors with narrow bone width enables securing the minimum interdental distance with natural teeth and minimizes the need for additional surgical procedures, including bone augmentation/grafting, by preserving the marginal bone around the implant. Therefore, NDIs are widely used for implant restoration of the lost mandibular anterior regions. The mandibular anterior region has advantages for immediate provisional restoration when placing NDIs due to the relative ease of securing the initial stability of the implants, owing to the thick cortical bone and superior bone quality/density in the area. Provisional restorations using implants may be classified based on the timing of the provisional prosthesis installation and the level of masticatory performance, which should be carefully planned and implemented according to individual cases. Furthermore, in the mandibular anterior region, the possibility of immediate functional loading of the provisional prosthesis upon placement is crucial because teeth in this region serve important psychological functions for patients, such as esthetics and speech/pronunciation, in addition to the elemental functions of cutting or shearing food during mastication. Restoring the lost mandibular anterior region immediately is crucial, and the use of NDIs is particularly valuable in this process. However, most studies involving NDIs in the mandibular anterior region have focused on their use for supporting and retaining implant overdentures. There is a lack of research on the survival rate and complication rates of NDIs used for the immediate restoration of the lost mandibular anterior teeth, which prompted this study.

NDIs have biomechanical limitations, such as a high risk of fracture due to their small diameter, a reduced contact area between the bone and implant, and a higher possibility of stress concentration compared to SDIs. Therefore, various studies have been conducted to overcome these limitations. For example, earlier studies suggested that splinting implants adversely affects stress distribution [8], but a recent study has shown that splinting NDIs in the mandibular anterior region is beneficial for both stress distribution and marginal bone loss (MBL) [9]. Studies investigating various factors affecting the long-term survival rate of NDIs implanted in the mandibular anterior region are still ongoing.

In this study, to evaluate the predictable treatment outcomes of NDIs, the clinical records of one-piece NDIs (Osstem, Seoul, Republic of Korea) used for dental implant procedures in our facility from 2010 to date were assessed retrospectively. The purpose of this research is to investigate the survival and complication rates of NDIs in the mandibular anterior region and to evaluate their clinical utility.

2. Materials and Methods

The study was conducted in accordance with the Declaration of Helsinki, and was approved by the Institutional Review Board of Veterans Health Service Medical Center (protocol code 05368 and date of approval 18 January 2023). Participants who received NDIs before 2022 were enrolled; that is, patients whose implant prostheses had been subjected to loading for ≥1 year after implant placement. Informed consent was obtained from all participants involved in the study. The patients’ medical records were reviewed and updated when they revisited the hospital in 2023 for follow-up. The inclusion criteria were patients who underwent NDI placement in the mandibular anterior region at our institution before 2022 and received a provisional prosthesis on the day of implant placement (immediate prosthesis with non-functional loading) (Figure 1).

Specifically, the main data obtained from the clinical records were (1) age and sex, (2) history of systemic disease, (3) smoking status, (4) bone augmentation status, (5) period from extraction to implantation, (6) implantation date, (7) inspection date, (8) implant system and surface treatment, (9) fixture size (diameter-length), (10) installation site (11) initial stability (Ncm), (12) complications, (13) implant failure, (14) radiographic measurements on the degree of alveolar bone resorption (number of exposed screw threads), (15) times of provisional and final prosthesis installation, (16) occlusal supporting state at the time of final prosthesis delivery, (17) occlusal supporting state at the time of recent follow-up, (18) presence of oral malaise, (19) type of opposing teeth, (20) occlusal contact with the opposing teeth, and (21) period from implant placement to the follow-up inspection date. Since the survival rate of NDIs placed only in the mandibular anterior region alone was investigated, patients with NDIs placed in the mandibular premolar or molar teeth with significantly narrow labiolingual bone widths were excluded from the study.

The survival and complication rates of NDIs were calculated from data in the medical records. According to the 2008 International Congress of Oral Implantologists consensus criteria [10], the survival rate of an implant was evaluated based on whether the implant was still physically present in the mouth at the time of examination. To calculate complication rates, complications were classified into biological (such as implant MBL) and mechanical (such as prosthesis fracture) complications. The MBL was considered to have occurred when the bone was resorbed in the apex direction, based on the boundary between the machined and rough surfaces of the implant fixture. The correlations between peri-implant MBL were evaluated, which is the most representative complication of dental implants, and risk factors, such as smoking, fixture diameter, immediate placement status, occlusal supporting state, type of opposing teeth, and occlusal contact. MBL was measured using standardized periapical radiographs obtained with an XCP device and paralleling technique. Digital images were analyzed using the INFINITT PACS M6 software. MBL was quantified as the number of exposed screw threads from the implant’s alveolar crest to the most coronal bone contact (in this study, the root in the coronal direction and the root of the apical direction referred to as the ‘one thread of the implant’, based on the crest of the implant fixture). When mesial and distal thread exposure differed, the average value was used. All measurements were conducted independently by two calibrated and blinded examiners. Inter-examiner reliability was verified prior to analysis. A generalized linear mixed model (GLMM) was used to assess the association between MBL (dichotomized as presence/absence of ≥1 exposed thread) and potential predictors, including smoking status (yes/no), fixture diameter (continuous), immediate placement (yes/no), occlusal support (yes/no), opposing dentition type (categorical), and occlusal contact (yes/no). The GLMM accounted for clustering by patient. Odds ratios (ORs) and 95% confidence intervals (CIs) were reported. Statistical significance was defined as p < 0.05. The primary outcome of this study was the survival rate of immediately loaded one-piece NDIs in the mandibular anterior region over the follow-up period. Secondary outcomes included the incidence and types of biological and mechanical complications, and changes in MBL.

3. Results

A total of 22 NDIs were placed in 13 patients at our hospital before 2022. The participants comprised nine men and four women with an average age of 75.2 years. Most patients (n = 11) had systemic diseases, including hypertension, diabetes, and heart disease. Only two patients were smokers, and no parafunctional habits were observed in any participant. The average duration from extraction to implantation was 1.7 months, and immediate implantation was performed in most patients. All participants underwent immediate placement of provisional prostheses. These prostheses were fabricated in an infra-occlusion design to allow for non-functional loading. All implants used in this study were one-piece NDIs (Osstem, Korea). Of the 22 NDIs, 9 and 13 were MS (resorbable blasted media [RBM] surface treatment, with microthreads in the coronal part of the implant) and MS SA (sand-blasted, large-grit, acid-etched [SLA] surface treatment, without microthreads in the coronal part of the implant) implants, respectively (

Table 1. Success and complication rates of narrow-diameter implants in 13 patients.

Patients	Time Interval Between Tooth Extraction and Implant Placement (Months)	The Date of Provisional Prosthesis Placement Following Implant Placement	Insertion Site and Implant Type	Smoking	Occlusal Contact	Complications	Implant Failure
1	2	Immediate	#42 (MS)	No	No	No	No
2	6	Immediate	#32, 42 (MS)	Yes	Yes	MBL	No
3	0	Immediate	#32 (MS)	No	Yes	No	No
4	0	Immediate	#31, 42 (MS)	No	Yes	Porcelain chipping	No
5	0	Immediate	#42 (MS)	No	No	No	No
6	0	Immediate	#31, 42 (MS)	No	No	No	No
7	3	Immediate	#31, 42 (MS SA)	No	No	No	No
8	3	Immediate	#32, 42 (MS SA)	No	Yes	No	No
9	1	Immediate	#32, 42 (MS SA)	No	Yes	No	No
10	0	Immediate	#32, 42 (MS SA)	Yes	No	MBL	No
11	0	Immediate	#32, 41 (MS SA)	No	Yes	No	No
12	4	Immediate	#31, 42 (MS SA)	No	Yes	No	No
13	3	immediate	#42 (MS SA)	No	Yes	No	No

MBL, marginal bone loss.

).

The dimensions of the implant fixtures used were as follows: 8 (2.5 mm × 13 mm), 3 (3 mm × 11.5 mm), 10 (3 mm × 13 mm), and 1 (3 mm × 15 mm) implants. Additionally, the insertion sites were distributed as follows: 4, 6, 1, and 11 at #31, #32, #41, and #42, respectively, with most implants being placed at #42. As specified by the manufacturer, the pitch of the MS implant (RBM surface) microthread is approximately 0.8 mm, roughly half that of the macrothread. As a result, a single microthread exposure was equivalent to half a thread exposure during MBL measurement. MBL was observed in four implants, with exposed threads ranging from 3 to 6. The biological complication rate was 18.18% (4/22 implants), with a 95% CI of 6.0% to 38.0%. The mechanical complication rate was 4.54% (1/22 implants), with a 95% CI of 0.2% to 22.8%. Additionally, the patient-based complication rate was 30.77% (4/13 patients), with a 95% CI of 12.7% to 55.8%. All complications were minor, and no implants required removal. These CIs were calculated using the Wilson score method for binomial proportions to provide a more precise estimation of complication variability in this limited sample. The mean initial stability was 28.2 Ncm (SD: 3.1; range: 24–35 Ncm). No variable showed a statistically significant association with MBL. Smoking status demonstrated a trend toward significance (OR = 8.00; 95% CI: 0.69–92.70; not statistically significant, p = 0.096). Other variables, including fixture diameter and occlusal contact, showed no significant correlation with MBL (Figure 2 and Figure 3 and

Table 2. Correlation between smoking and marginal bone loss.

	Value	95% CI
		Lower Limit	Upper Limit
ORs for smoking	8.000	0.690	92.703
No bone resorption	1.778	0.0658	4.801
Bone resorption	0.222	0.430	1.138
Number of valid cases	22

CI, confidence interval; ORs, odds ratios.

).

The final implant prosthesis was installed on an average of 4.6 months after implant placement. The average period from implant placement to the most recent implant prosthesis inspection date was 7 years (Figure 4 and Figure 5). No NDIs were removed from the mouth, indicating a 100% survival rate (95% CI: 82.7–100%). However, there was statistical uncertainty owing to the small sample size. All complications involved minor events, and there were no major complications requiring removal of the implant fixture.

4. Discussion

The use of NDIs for immediate provisional restoration of the mandibular anterior region demonstrated good clinical outcomes, with a 100% survival rate over an average 7-year follow-up period, indicating that NDIs can be considered a reliable treatment option.

Dental implants are generally classified based on their diameter as narrow, standard/regular, and wide. According to the 2018 International Team for Implantology (ITI) consensus report [7], NDIs can be further classified into Category 1, with diameters < 2.5 mm; Category 2, with diameters ≥ 2.5 to <3.3 mm; and Category 3, with diameters ≥ 3.3 to ≤3.5 mm. The ITI consensus statements report survival rates of NDIs for each category as follows: 94.5% (SD ± 5%), 97.3% (SD ± 4%), and 97.7% (SD ± 2%), for Categories 1, 2, and 3, respectively. Based on the clinical recommendations from the consensus report, the use of NDIs offers the following advantages: (i) they can be used when maintaining adequate tooth-implant and inter-implant distances, which is important in areas with reduced mesiodistal width; (ii) they can reduce the need for lateral bone augmentation and the complexity involved; (iii) they enable a simultaneous process instead of a staged installation process for bone augmentation, and (iv) they increase prosthetic flexibility in certain clinical situations. Therefore, NDIs can be used in a versatile manner depending on the clinical practitioner’s assessment and choice.

Category 2 NDIs (2.5–3 mm) were used in this study. Considering the 2018 ITI consensus report, it can be inferred that the use of these NDIs was suitable for restoring the lost mandibular anterior region. Schiegnitz et al. [11] reported that the use of Category 1 NDIs was associated with statistically significant inferior outcomes compared with the use of SDIs. However, no significant difference in implant survival rates was reported between Category 2 and 3 NDIs and SDIs. Category 2 NDIs are most commonly used for the restoration of a single tooth in the anterior region with limited interdental space. Walter et al. [12] reported the results of a 1-year study on 41 NDIs with a diameter of 2.9 mm placed for single-tooth restoration in 41 patients. In that study, the implant survival rate was 92.7%. Consequently, they concluded that a 2.9 mm NDI was a safe and reliable treatment option for cases involving narrow interdental spacing. Considering the abovementioned studies, Category 2 NDIs can be considered appropriate for implant restoration of the lost mandibular anterior region with a narrow labiolingual bone width and interdental spacing.

Mauricio et al. [13] conducted a qualitative analysis of 17 studies and a meta-analysis of three studies that investigated the survival rate, success rate, and MBL of NDIs as the primary outcomes to determine whether NDIs provide adequate support for fixed dental prostheses (FDPs) and partially removable dental prostheses. In total, 1624 NDIs and 339 SDIs placed in 1060 patients were analyzed, with only 17 implant failures (implant loss) reported during follow-up periods ranging from 1 to 10 years. Their analysis revealed that FDPs supported by NDIs showed survival and success rates comparable to those supported by SDIs, and that MBL was actually lower with NDIs than with SDIs. Stuart et al. [14] reported that NDIs showed survival rates comparable to those of SDIs, and an annual evaluation showed that bone loss was less with NDIs than with SDIs. These findings demonstrate the relative advantage of NDIs over SDIs in terms of reducing bone loss after dental implant placement.

The high survival rates of NDIs in this study may be attributed to the anatomical structure of the mandibular anterior region, which allows for the placement of relatively long implants or, when necessary, deeper installation to ensure a sufficient level of initial stability [15]. In the stomatognathic system, a Class III lever system [16], the mandibular anterior region, located on the anterior side, is reportedly subject to a lower functional force than other parts of the mouth, with the functional force being closer to vertical force than lateral force. In our study, one-piece NDIs were used, with the abutment and fixture integrated into one piece, allowing for optimal distribution of functional force [17]. The NDIs were placed only when sufficient occlusal support was confirmed at the time of implantation, which also appears to have positively influenced the long-term outcomes [18]. Regarding the high survival rates observed despite immediate implant placement in the lost mandibular anterior regions, the fabrication of an immediate provisional prosthesis without functional loading also appears to have affected such outcomes [19].

A complication rate higher than the implant biological complication rates reported in previous studies was observed. This finding suggests that the effects of smoking on implant MBL was more pronounced for implants placed in the anterior region. Moreover, the mandibular anterior region has a relatively smaller distribution of blood vessels than other regions, which may have increased the likelihood of negative effects from a reduced blood supply or circulation owing to smoking. Smoking is likely to cause more severe dryness in the mouth, consequently increasing the risk of peri-implant mucositis or peri-implantitis. In a retrospective study [20], smokers were reported to have a 2.9-fold increased risk of developing peri-implantitis compared with non-smokers (OR = 2.939, 95% CI: 1.236–6.988), and that the mandibular anterior region had a 3.8-fold OR (OR = 3.842, 95% CI: 1.080–13.671) for peri-implantitis compared with the maxillary anterior region (the reference area). This risk was lower than the 6.6-fold risk observed in the mandibular molar region but was significantly higher than in other areas, such as the maxillary molar or maxillary anterior regions (OR = 1.974). Furthermore, that study stated that high functional loading and alveolar bone density may be associated with infection progression.

Maryod et al. [21] investigated the timing of NDI loading. One group (G1) with the immediate loading protocol for NDIs that were placed to support an overdenture in the mandibular anterior region showed a survival rate of 91.7%, while another group (G2) with the early loading protocol exhibited a survival rate of 96.7%. While MBL was higher in G1, no significant difference was reported between the groups, with both immediate and early loading protocols for NDIs showing good clinical outcomes. Jofre et al. [22] also reported on the failure risk associated with initial stability after the immediate loading of NDIs. The initial stability of 90 NDIs was 12.5 ± 7.8 Ncm on average, and the survival rate was 94.2% (85/90). This indicated that NDIs showed lower initial stability than SDIs, on average; however, this low initial stability did not appear to be a risk factor for implant failure.

All implants used in this study were one-piece NDIs. In a previous study [23], the reported survival rates of one-piece and two-piece implants varied from 94.7% to 100% and from 96.2% to 97.5%, respectively, showing that both implant systems had high success rates, with no statistically significant differences. No statistically significant difference was observed in the MBL between the two implant systems, that is, the survival and success rates between the systems did not significantly differ. Additionally, one-piece implants have the advantages of reducing the microgap and the time taken for the procedure, whereas two-piece implants have the advantage of flexibility in the design of the upper prosthesis. Therefore, an optimal implant system should be selected based on the patient’s condition and the practitioner’s preference.

In this study, 13 and 9 NDIs with SLA and RBM surface-treated implants were used, respectively, and their success rates were 100%. MBLs were observed in both implant types (RBM, 11.11%; SLA, 23.07%). According to Lee et al. [24], SLA surface implants showed the lowest risk of failure compared to RBM and hydroxyapatite (HA) surface-treated types. In their study, the implant complication rate was 0.57% for SLA surface implants, which was relatively lower than the rates for RBM (1.01%) and HA (0.63%) implants. Therefore, when evaluating survival and success rates of implants based solely on the surface treatment technique, implants with SLA surface treatment can be expected to show superior outcomes compared to those with RBM surface treatment.

The Osstem MS (RBM surface treatment) implants used in this study featured microthreads on the coronal part, whereas the MS SA (SLA surface treatment) implants had a fixture design without microthreads. Chang et al. [25] compared coronal bone healing of NDIs with microthreads (reverse-tapered NDIs) and those without microthreads (reverse-tapered NDIs). They reported that the presence of microthreads could increase the initial bone-implant contact; however, the microthreads did not significantly affect coronal bone healing after 8 weeks. Oh et al. [26] reported that microthreads had no significant effect on the survival rates or marginal bone resorption of implants.

Among the structural factors affecting the survival and success rates of implants, the surface treatment technique may have some influence; however, the presence or absence of microthreads can be considered to have minimal influence. Therefore, a lower MBL rate would be expected in MS SA implants (SLA surfaces without microthreads) than in MS implants (RBM surfaces with microthreads). In our study, a lower MBL rate was observed in the MS implants than in the MS SA implants, although not statistically significant. MBL only occurred in smokers, regardless of implant type. Compared with risk factors generally considered to affect the survival and success rates of implants (such as smoking and excessive occlusal contact), the implant surface treatment technique and the presence or absence of microthreads had a limited effect. Moreover, this study did not demonstrate a clear clinical advantage of SLA over RBM treatment in terms of survival or MBL. Thus, conclusions favoring one surface treatment over the other were not warranted.

In cases of narrow bone width, the placement of standard-diameter implants with bone grafting has been associated with high success rates and favorable long-term outcomes [27]. Standard diameter implants have a larger bone-to-implant contact surface compared with narrow diameter implants, which results in a mechanical advantage in stress distribution. However, owing to the characteristics of national merit recipients who visit the hospital, most of whom are older adult patients with systemic conditions, bone grafting procedures are more likely to result in complications such as increased discomfort, longer treatment periods, higher costs, and elevated risks [28]. One possible approach to addressing this issue is to consider using narrow-diameter implants that either do not require or significantly minimize bone grafting. Despite the advantages of NDI, it is essential to acknowledge that certain risks are inherent in its design.

While the NDIs were not used for fixed prostheses, those applied to mandibular implant overdentures are reported to be clinically stable [29,30]. Accordingly, to further contextualize our findings and enrich the discussion, several recent studies have been incorporated.

In a long-term study concerning maxillary narrow single-tooth implants placed in congenitally missing lateral incisors, exceptional outcomes were reported: over a 5-year loading period, no bone defects, pathological probing depths, or mechanical complications such as screw loosening or prosthetic fracture were observed [31]. These results parallel our findings in demonstrating that NDIs can deliver stable and predictable outcomes in anatomically challenging sites, even in the maxilla where bone quality is often less dense than that in the mandible.

In the context of removable overdenture treatments, Scarano et al. (2024) [32] examined patients fitted with mandibular overdentures retained by mini dental implants over a 12–16-year period. They reported significant improvements in patient-reported satisfaction, specifically in terms of comfort, retention, chewing, and speech (p < 0.05), with the most pronounced gains observed in retention and chewing abilities. The 10- and 15-year survival rates for the mini dental implants were both 97.9%, strongly reinforcing their reliability in removable prosthesis scenarios [32].

While our study focused on fixed, one-piece NDIs in the mandibular anterior region, the outcomes described in the above studies offer complementary perspectives. NDIs perform robustly across both jaws—in the esthetically demanding maxilla as well as the high-load mandible—suggesting broad clinical applicability. Fixed and removable applications of NDIs both yield predictably successful outcomes, and patient-centered measures, such as satisfaction and comfort, further support their therapeutic value beyond mere survival rates. The 100% survival rate observed in our study, maintained over an average 7-year tracking period, aligns well with these favorable outcomes reported in other anatomical contexts and prosthetic modalities.

Furthermore, recent evidence highlights the importance of patient-reported outcomes when assessing the long-term success of implant treatments. Wallin Bengtsson et al. (2025) reported consistently high levels of patient satisfaction and functionality 10–15 years after single implant placement [33]. Their findings emphasize that implant success should be evaluated not only by survival rates or stability of marginal bone, but also by how patients perceive esthetics, ease of functional rehabilitation, and oral hygiene maintenance. This perspective further supports our current findings: our retrospective study achieved a 100% survival rate, while the relatively low incidence of complications and the stable clinical performance observed over an average of 7 years translate into tangible patient-centered benefits, particularly in the mandibular anterior region where esthetics and phonetics are of paramount importance.

Overall, NDIs provided favorable long-term survival outcomes for immediate restoration in the mandibular anterior region. However, the small sample size and the study’s retrospective design limit the generalizability of our findings. The lack of a control group and potential unmeasured confounders further constrain interpretation of the observed trends. The p-value approaching significance for smoking and MBL underscores the need for caution in interpreting borderline findings without adequate power.

5. Conclusions

The clinical utility of NDIs with a diameter of ≤3.0 mm was evaluated through a short- and long-term retrospective study of NDIs used for immediate provisional restoration of the lost mandibular anterior region at our hospital. Future studies should include randomized controlled trials with larger sample sizes and clearly defined control groups to validate the current results and explore the mechanistic underpinnings of observed complications.