Narrow-diameter implants versus regular-diameter implants for rehabilitation of the anterior region: a systematic review and meta-analysis

A One-Year Randomized Controlled Clinical Trial of Three Types of Narrow-Diameter Implants for Fixed Partial Implant-Supported Prosthesis in the Mandibular Incisor Area

Narrow-diameter implants (NDI) serve as a solution for treating limited bone volume in the anterior mandible. This study aimed to evaluate the one-year clinical outcomes of various NDIs in the mandibular incisor area after immediate loading in partially edentulous patients. This single-center, prospective, single-blinded, randomized controlled trial study included 21 patients, with 7 patients in each of the following groups: control (BLT NC SLActive®; Straumann), experimental group 1 (CMI IS-III Active® S-Narrow; Neobiotech), and experimental group 2 (CMI IS-III Active® Narrow; Neobiotech). Using full digital flow, two fixtures were placed in each patient and immediately provisionalized on the day of surgery. Evaluations encompassed periapical radiographs, implant stability quotient (ISQ), implant stability test (IST) readings, per-implant soft tissue health, patient satisfaction surveys, and esthetic score assessments. Definitive prostheses were delivered twelve weeks post-surgery (CRiS, number: KCT0007300). Following exclusions due to low stability values (n = 2), fixture failure (n = 5), and voluntary withdrawal (n = 1), the implant success rate for patients completing all clinical protocols stood at 100%. The resulting patient failure rates in the control, experimental group 1, and experimental group 2 were 50.0%, 42.9%, and 14.3%, respectively. There were no significant differences between the groups in terms of marginal bone loss, soft tissue health, patient satisfaction, and esthetic scores. Narrow implants showed superior clinical outcomes, followed by S-Narrow and Straumann implants. Calculated one-year survival rates at the implant level were 66.7% for the control group, 85.7% for experimental group 1, and 100% for experimental group 2. All three types of NDIs showed acceptable clinical and radiographic results during the year-long observation period.

Clinical outcomes of narrow- and regular-diameter implants with bone augmentation in the anterior maxilla: a systematic review and meta-analysis

OBJECTIVES

To evaluate the clinical outcomes of narrow-diameter implants (NDIs) and regular-diameter implants (RDIs) with bone augmentation in the anterior maxilla, with implant survival rate (ISR) as the primary outcome. Additionally, secondary outcomes such as peri-implant marginal bone loss (MBL), pocket probing depth (PPD), mechanical complications, and biological complications were also considered.

MATERIALS AND METHODS

A thorough literature search was performed to identify randomized controlled trials and cohort studies comparing outcomes of NDIs and RDIs with bone augmentation in the anterior maxilla published up to February 2024. Only studies with a minimum follow-up period of 12 months were selected for analysis. Meta-analysis was performed if at least two articles with similar characteristics were available.

RESULTS

Of the 288 articles initially considered, 5 were included in the analysis, involving 282 NDIs and 100 RDIs. At the 36-month follow-up, no statistically significant differences in ISR, which ranged 93.8-100% for NDIs and were 100% for RDIs, were observed between the two groups (relative risk, 0.989; 95% confidence interval, 0.839-1.165; p = 0.896). Similarly, MBL and PPD did not differ significantly between the two groups. Soft tissue dehiscence was the most common complication found in RDIs.

CONCLUSION

The results indicate that NDIs yield clinical outcomes similar to those of RDIs with bone augmentation in the anterior maxilla over a 36-month follow-up period.

CLINICAL RELEVANCE

Considering the similar clinical outcomes, the shortened treatment duration and more rapid esthetic improvement associated with NDIs may render them preferrable to RDIs with bone augmentation, particularly in this esthetic zone.

Clinical analysis of the tooth-implant papilla for two narrow-diameter titanium-zirconium implants in the anterior area: prospective controlled clinical study

BACKGROUND

Rehabilitation of the anterior area when the mesio-distal space is reduced is a challenge for the clinician, due to the patient's anatomical limitations and aesthetic requirements. Narrow Diameter Implants (NDI) are an option of treatment when the standard diameter implant is not possible, but the evidence is scarce. This prospective clinical study aims to analyze the formation of the tooth-implant papilla between the implant and the adjacent natural tooth in the maxillary lateral incisors and mandibular incisors.

METHODS

A total of 40 patients treated with NDI, of titanium-zirconium (Ti-Zr) alloy i.e., 2.9 mm Test Group (TG) and 3.3 mm Control Group (CG), were included. The mesiodistal distance between the adjacent natural teeth was used for implant selection, maintaining 1.5 mm between the fixation and the adjacent tooth. Clinical assessment was performed by a clinical examiner at 6 and 12 months after the final prosthesis. The primary variable was the Jemt Papillary Index. Also, implant survival rate (SR), complications, Implant Stability Quotient (ISQ), and patient-reported outcomes measures (PROMs) such as aesthetics, chewing, phonation, comfort, and self-esteem were analyzed.

RESULTS

A significant amount of papilla filling was observed concerning the baseline, with a trend towards more formation of the papilla in the TG, with a JPI score of 3. No significant differences were observed between the two groups regarding implant SR, clinical parameters, and complications. In terms of PROMs, a higher satisfaction in the TG was observed, with significant intergroup differences for aesthetics, comfort, self-esteem, and primary stability ISQ (TG: 59.05 (SD: 5.4) vs. CG: 51.55 (SD: 5.7)).

CONCLUSIONS

The 2.9 mm diameter Ti-Zr implants achieved a formation of papilla similar to 3.3 mm implants in the anterior region at 12 months of follow-up after the final prosthetic restoration. The use of Ti-Zr implants with a diameter of 2.9 mm to rehabilitate single teeth in areas of the anterior region, where the mesiodistal distance is limited, showed favorable clinical results and a high degree of satisfaction during 1 year of observation similar to 3.3 mm dental implants.

TRIAL REGISTRATION

This study was retrospectively registered in ClinicalTrials.gov with the number NCT05642520, dated 18/11/2022.

Clinical performance of additively manufactured subperiosteal implants: a systematic review

PURPOSE

The aim of this study was to assess implant survival and complications rate of modern subperiosteal implants (CAD designed and additively manufactured).

METHODS

A systematic review was conducted using three electronic databases; Medline (Pubmed), Cochrane library, and SCOPUS, following the PRISMA statement recommendations to answer the PICO question: "In patients with bone atrophy (P), do additively manufactured subperiosteal implants (I), compared to subperiosteal implants manufactured following traditional approaches (c), present satisfactory implant survival and complication rates (O)? The study was pre-registered in PROSPERO (CRD42023424211). Included articles quality was assessed using the "NIH quality assessment tools".

RESULTS

Thirteen articles were finally selected (5 cohort studies and 8 case series), including 227 patients (121 female / 106 male; weighted mean age 62.4 years) and 227 implants. After a weighted mean follow-up time of 21.4 months, 97.8% of implants were in function (5 failures reported), 58 implants (25.6%) presented partial exposure, 12 patients (5.3%) suffered soft tissue or persistent infection. Fracture of the interim prosthesis was reported in 8 of the155 patients (5.2%) in which the use of a provisional prosthesis was reported. A great heterogeneity was found in terms of study design and methodological aspects. For this reason, a quantitative analysis followed by meta-analysis was not possible.

CONCLUSIONS

Within the limitations of this study, modern additively manufactured subperiosteal implants presented a good survival in the short-time, but a noticeable number of soft-tissue related complications were reported. Further studies are needed to assess the clinical behavior in the medium- and long-term.

Biomechanical influence of narrow-diameter implants placed at the crestal and subcrestal level in the maxillary anterior region. A 3D finite element analysis

PURPOSE

To evaluate the tendency of movement, stress distribution, and microstrain of single-unit crowns in simulated cortical and trabecular bone, implants, and prosthetic components of narrow-diameter implants with different lengths placed at the crestal and subcrestal levels in the maxillary anterior region using 3D finite element analysis (FEA).

MATERIALS AND METHODS

Six 3D models were simulated using Invesalius 3.0, Rhinoceros 4.0, and SolidWorks software. Each model simulated the right anterior maxillary region including a Morse taper implant of Ø2.9 mm with different lengths (7, 10, and 13 mm) placed at the crestal and subcrestal level and supporting a cement-retained monolithic single crown in the area of tooth 12. The FEA was performed using ANSYS 19.2. The simulated applied force was 178 N at 0°, 30°, and 60°. The results were analyzed using maps of displacement, von Mises (vM) stress, maximum principal stress, and microstrain.

RESULTS

Models with implants at the subcrestal level showed greater displacement. vM stress increased in the implant and prosthetic components when implants were placed at the subcrestal level compared with the crestal level; the length of the implants had a low influence on the stress distribution. Higher stress and strain concentrations were observed in the cortical bone of the subcrestal placement, independent of implant length. Non-axial loading influenced the increased stress and strain in all the evaluated structures.

CONCLUSIONS

Narrow-diameter implants positioned at the crestal level showed a more favorable biomechanical behavior for simulated cortical bone, implants, and prosthetic components. Implant length had a smaller influence on stress or strain distribution than the other variables.

Clinical evaluation of 3.0-mm narrow-diameter implants: a retrospective study with up to 5 years of observation

PURPOSE

This study aimed to evaluate the clinical outcomes of a single type of narrow-diameter implant (NDI) by investigating its survival rate and peri-implant marginal bone loss (MBL). In addition, variables possibly related to implant survival and MBL were investigated to identify potential risk factors.

METHODS

The study was conducted as a retrospective study involving 49 patients who had received 3.0-mm diameter TSIII implants (Osstem Implant Co.) at Seoul National University Dental Hospital. In total, 64 implants were included, and dental records and radiographic data were collected from 2017 to 2022. Kaplan-Meier survival curves and a Cox proportional hazard model were used to estimate the implant survival rate and to investigate the effects of age, sex, jaw, implant location, implant length, the stage of surgery, guided bone regeneration, type of implant placement, and the surgeon's proficiency (resident or professor) on implant survival. The MBL of the NDIs was measured, and the factors influencing MBL were evaluated.

RESULTS

The mean observation period was 30.5 months (interquartile range, 26.75-45 months), and 6 out of 64 implants failed. The survival rate of the NDIs was 90.6%, and the multivariate Cox regression analysis showed that age was associated with implant failure (hazard ratio, 1.17; 95% confidence interval, 1.04-1.31, P=0.01). The mean MBL was 0.44±0.75 mm, and no factors showed statistically significant associations with greater MBL.

CONCLUSIONS

NDIs can be considered a primary alternative when standard-diameter implants are unsuitable. However, further studies are required to confirm their long-term stability.

Evaluation of the clinical safety and performance of a narrow diameter (2.9 mm) bone-level implant: a 1-year prospective single-arm multicenter study

PURPOSE

Narrow-diameter implants facilitate single-tooth restoration when interdental or inter-implant spaces and bone volume are inadequate for using standard diameter implants. This study reports the short-term data on the clinical safety and performance of a bone-level-tapered two-piece implant with a 2.9 mm diameter in the clinical practice setting. This study was retrospectively registered on March 1st, 2016 (NCT02699866).

METHODS

Implants were placed in partially healed extraction sockets of the central and lateral incisors in the mandible and lateral incisors in the maxilla for single-tooth replacement. The primary outcome was to assess implant survival at 12 months after placement. Secondary outcomes included implant success, pink esthetic score, marginal bone-level changes, and safety.

RESULTS

Twenty four males and 17 females with a mean age of 44.5 (± 18.3 standard deviation) received the implant. Three out of 41 implants were lost yielding a survival rate of 92.7% (95%-CI: 79.0%; 97.6%) at 1 year. One patient reported an ongoing foreign body sensation, pain, and/or dysesthesia at month 12. The average pink esthetic score at 6 months was 11.2 (95%-CI: 10.5; 11.9). The bone level was stable with a mean bone-level change of-0.3 mm (± 0.42 mm standard deviation) at 1 year after implantation. No serious adverse events or adverse device events were reported.

CONCLUSIONS

The use of a 2.9 mm diameter bone-level-tapered implant is a safe and reliable treatment option for narrow tooth gaps at the indicated locations. Overall performance and good survival rates support their use in cases, where wider implants are unsuitable.

Clinical outcomes of titanium-zirconium alloy narrow-diameter implants for single-crown restorations: a systematic review and meta-analysis

Evidence is limited on whether titanium-zirconium alloy, narrow-diameter implants (Ti-Zr NDIs) have promising clinical outcomes when used to support single crowns. The purpose of this systematic review and meta-analysis was to evaluate clinical evidence, including survival rates, success rates, and marginal bone loss (MBL) on Ti-Zr NDIs that support single crowns. An extensive search was performed in the databases of PubMed/MEDLINE, Scopus, Embase, and the Cochrane Library for studies published in English up to April 2022. Only peer-reviewed clinical studies with at least 10 patients and a follow-up time of at least 12 months were included. Risk of bias in each study was assessed and data extraction was carried out independently by two reviewers. The outcome variables were survival rates, success rates, and MBL. The search returned 779 results. Eight studies were identified for qualitative analysis and seven for quantitative synthesis. Overall, a total of 256 Ti-Zr NDIs were included. Cumulative implant survival rates and success rates were 97.5% (95% confidence interval (CI): 94.5% to 98.9%) and 97.2% (95% CI: 94.2% to 98.7%), respectively, over a maximum follow-up period of 36 months, with no difference between Ti-Zr NDIs and commercial pure titanium (cpTi) implants. Cumulative mean (SD) MBL was 0.44 (0.04) mm (95% CI: 0.36 to 0.52) after one year. Meta-analysis of MBL indicated a mean difference of 0.02 mm (95% CI: -0.23 to 0.10), with no differences between Ti-Zr NDIs and cpTi implants. Short-term results of Ti-Zr NDIs for single-crown restorations are quite promising, although the number of published studies and follow-up periods are insufficient to determine the real benefit for single crowns. Long-term, follow-up clinical studies are needed to verify the excellent clinical performance of Ti-Zr NDIs.

Same-Day Digital Dentistry Restorative Workflow for Single Immediate Provisionalization of Narrow-Diameter Implants: An Exploratory Prospective Study

This study evaluated the two-year clinical outcomes of 3.1 mm diameter dental implants, immediately provisionalized and later restored using same-day dentistry, in 10 patients receiving 11 narrow-diameter (3.1 mm) single implants. Each implant was placed and immediately restored with a provisional crown after placement. At least 2 months after placement, the implant was restored with a prefabricated titanium abutment and an all-ceramic crown using a same-day dentistry protocol. Clinical outcomes, including apical bone loss, probing depths, gingival index, and surgical and prosthetic complications, were documented. There was no implant failure over the course of two years. No surgical complications were reported. Two cases lost provisional crowns. One crown needed to be remade due to esthetic concern. The cumulative two-year survival rate of the implants was 100%. Implant bone loss after two years of functional loading was −0.56 ± 0.54 mm and −0.32 ± 0.68 mm for mesial and distal crestal bone, respectively. Two prosthetic complications included recementation of a crown and remaking of a crown. This exploratory study suggests that immediate provisionalization and a same-day restorative dentistry digital workflow protocol for narrow-diameter implants appear to be predictable clinical procedures with no reported surgical complications and minimal prosthetic complications.

Clinical and radiographic outcomes of maxillary lateral incisors rehabilitation using Morse taper connection extra-narrow implants at 12-month follow-up: A case report

Narrow-diameter implants (≤3.5 mm) have been proposed to address the challenge of implant placement in cases of insufficient bone quantity, thin alveolar crest, and small cervical diameter teeth replacement The aim of this study is to report one-year outcomes of extra-narrow implant rehabilitation of maxillary lateral incisors, due to agenesis, in a young adult that presented sites with reduced mesiodistal and buccolingual dimensions. A 26-year-old male patient in need of fixed-implant supported prostheses due to the absence of permanent maxillary lateral incisors and with limited space, was submitted to surgery to receive two 2.9 mm hybrid Morse taper connection implants with hydrophilic surfaces. Immediate loading was applied by means of insertion of provisional prostheses, which were replaced for all-ceramic prostheses 12 months after surgery. The 1 year follow-up showed clinical and radiographic success of extra-narrow implant rehabilitation. Also, both regions presented good evolution of peri-implant esthetics, as assesses using the pink esthetic score, with improvements at 4 months follow-up and reaching high scores 12 months after surgery. Although the prosthetic rehabilitation of maxillary lateral incisors is challenging due to limited space for the insertion of implants, the clinical case suggests that the use of extra-narrow Morse Taper implants with hybrid design and hydrophilic surface is a reliable alternative, presenting good outcomes regarding hard and soft tissue and it is a versatile solution or immediate loading procedure. Further studies are needed to confirm extra-narrow implant predictability.

Three interfaces of the dental implant system and their clinical effects on hard and soft tissues

Anatomically, the human tooth has structures both embedded within and forming part of the exterior surface of the human body. When a tooth is lost, it is often replaced by a dental implant, to facilitate the chewing of food and for esthetic purposes. For successful substitution of the lost tooth, hard tissue should be integrated into the implant surface. The microtopography and chemistry of the implant surface have been explored with the aim of enhancing osseointegration. Additionally, clinical implant success is dependent on ensuring that a barrier, comprising strong gingival attachment to an abutment, does not allow the infiltration of oral bacteria into the bone-integrated surface. Epithelial and connective tissue cells respond to the abutment surface, depending on its surface characteristics and the materials from which it is made. In particular, the biomechanics of the implant-abutment connection structure (i.e., the biomechanics of the interface between implant and abutment surfaces, and the screw mechanics of the implant-abutment assembly) are critical for both the soft tissue seal and hard tissue integration. Herein, we discuss the clinical importance of these three interfaces: bone-implant, gingiva-abutment, and implant-abutment.

A Novel Zirconia-Based Composite Presents an Aging Resistant Material for Narrow-Diameter Ceramic Implants

A novel ceria-stabilized zirconia-alumina-aluminate composite (Ce-TZP-comp) that is not prone to aging presents a potential alternative to yttrium-stabilized zirconia for ceramic oral implants. The objective of this study was to evaluate the long-term stability of a one-piece narrow-diameter implant made of Ce-TZP-comp. Implant prototypes with a narrow (3.4 mm) and regular (4.0 mm) diameter were embedded according to ISO 14801, and subgroups (n = 8) were subsequently exposed to dynamic loading (10⁷ cycles, 98N) and/or hydrothermal treatment (aging, 85 °C). Loading/aging was only applied as a combined protocol for the 4.0 mm diameter implants. One subgroup of each diameter remained untreated. One sample was cross-sectioned from each subgroup and evaluated with a scanning electron microscope for phase-transformation of the lattice. Finally, the remaining samples were loaded to fracture. A multivariate linear regression model was applied for statistical analyses (significance at p < 0.05). All samples withstood the different loading/aging protocols and no transformation propagation was observed. The narrow diameter implants showed the lowest fracture load after combined loading/aging (628 ± 56 N; p < 0.01), whereas all other subgroups exhibited no significantly reduced fracture resistance (between 762 ± 62 and 806 ± 73 N; p > 0.05). Therefore, fracture load values of Ce-TZP-comp implants suggest a reliable intraoral clinical application in the anterior jaw regions.