Clinical Behavior of Short Dental Implants: Systematic Review and Meta-Analysis

A comparative analysis of particulate bovine bone substitutes for oral regeneration: a narrative review

PURPOSE

Particulate bovine bone substitutes (BS) are commonly used in oral regeneration. However, more literature is needed focusing on comparative analyses among various particulate bovine BS. This study evaluates pre-clinical and clinical data of different particulate bovine BS in oral regeneration.

METHODS

A narrative review was conducted by screening the PubMed database Included in the review were pre-clinical and clinical studies until 2024 comparing a minimum of two distinct particulate bovine BS. In addition to examining general data concerning manufacturing and treatment processes, biological safety, physical and chemical characteristics, and graft resorption, particular emphasis was placed on assessing pre-clinical and clinical data related to ridge preservation, sinus floor elevation, peri-implant defects, and various forms of alveolar ridge augmentation utilizing particulate bovine BS.

RESULTS

Various treatment temperatures ranging from 300 to 1,250 °C and the employment of chemical cleaning steps were identified for the manufacturing process of particulate bovine BS deemed to possess biosecurity. A notable heterogeneity was observed in the physical and chemical characteristics of particulate bovine BS, with minimal or negligible graft resorption. Variations were evident in particle and pore sizes and the porosity of particulate bovine BS. Pre-clinical assessments noted a marginal inclination towards favorable outcomes for particulate bovine BS subjected to higher treatment temperatures. However, clinical data are insufficient. No distinctions were observed regarding ridge preservation, while slight advantages were noted for high-temperature treated particulate bovine BS in sinus floor elevation.

CONCLUSIONS

Subtle variances in both pre-clinical and clinical outcomes were observed in across various particulate bovine BS. Due to inadequate data, numerous considerations related to diverse particulate bovine BS, including peri-implant defects, must be more conclusive. Additional clinical studies are imperative to address these knowledge gaps effectively.

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 analysis of different fixed dental restorations on short implants: a finite element study

OBJECTIVES

Although the use of short implants is becoming more common for patients with atrophic alveolar ridges, their use is still quite limited. This is due to the lack of data of long-term survival compared to standard-length implants. The aim of this study was to determine the load in the bone and implant system with different superstructures.

METHODS

Three kinds of prosthetic restorations were created on short implants based on CT-Data. Two short implants with different macro-geometries were used. The implants were inserted in idealised posterior lower mandibular segments and afterwards restored with a crown, a double splinted crown, and a bridge.

RESULTS

The analysis was performed under load of 300 N either divided between a mesial and distal point or as a point load on the pontic/mesial crown. The different design of the implant systems had a noticeable influence on the stress in the cortical bone, in the implant system, and the displacement of the superstructure as well.

CONCLUSIONS

Compared with implants of standard length, higher stresses were observed, which can lead early failure of the implant during the healing period or a late cervical bone resorption. Precise indications are essential for short implants to avoid the failure of short implants.

6 mm short versus 11 mm long inter-foraminal implants in the full-arch rehabilitation of edentulous non-atrophic mandibles: 5-year results from a multicenter randomized controlled trial

OBJECTIVE

The aim of this multicenter parallel-group randomized controlled trial is to compare, in the same clinical scenario, 6 mm short with 11 mm long implants for the rehabilitation of completely edentulous non-atrophic mandibles.

MATERIALS AND METHODS

Thirty patients in three study centers received a fixed full-arch mandibular rehabilitation supported by five inter-foraminal implants, with no need for bone augmentation procedures. Patients were randomly allocated (1:1 ratio), at the time of surgery, to test (6 mm implants) or control group (11 mm implants). After 3 months, a screw-retained full-arch prosthesis was positioned (baseline). Peri-implant marginal bone level change (MBLc, primary outcome) together with implant and prosthesis survival rate, and biological/technical complications (secondary outcomes) were evaluated up to 5 years.

RESULTS

Twenty seven patients were controlled at 5 years (3 drop-outs). No implant or prosthesis loss occurred. No significant intergroup difference for biological/technical complications (p > .05, Fisher's exact test) and no significant intragroup and intergroup difference in the MBLc values were registered (test -0.03 ± 0.17 mm and control -0.13 ± 0.32 mm at 5-years; p > .025, one-sided Mann-Whitney U-test).

CONCLUSIONS

When used in comparable anatomic, surgical, and prosthetic conditions, no difference in the clinical and radiographic outcomes between 6-mm and 11-mm implants was observed at 5 years of follow-up. Short implants showed to be a reliable option for the rehabilitation of completely edentulous non-atrophic mandibles. There is growing clinical evidence supporting the use of short implants, even in the case of non-atrophic sites.

Single-crown restorations in premolar-molar regions: short (≤ 6.5) vs longer implants: retrospective cohort study

Purpose

To compare the survival, changes in marginal bone level and prosthetic complications rate of short (≤ 6.5 mm) and longer implants (≥ 7.5) supporting a single-crown restoration in the maxillary/mandibular premolar or molar region.

Methods

This cohort study was conducted following the STROBE statement recommendations for observational studies. Clinical outcomes of 88 short implants in 78 patients and 88 long implants in 88 patients were examined. All the implants had been placed by the same surgeon and restored following the same prosthetic concept; using a transepithelial abutment (intermediate abutment) and a screw retained restoration.

Results

All the implants were in function after the follow-up period since insertion (median: 31 months; range 11 to 84 for SiG vs median: 35 months; range: 6–117 for CG; p = 0.139). No statistical differences (p = 0.342) were observed related to prosthetic complications (screw loosening 2/88 vs 5/88 CG, ceramic chipping 1/88 vs 0/88, temporary crown resin chipping 1/88 vs 0/88 for SiG and CG, respectively) or related to marginal bone level (Mesial or Distal MBL ≥ 2 mm in 1/88 implants for SiG vs 3/88 for CG; p = 0.312).

Conclusions

Within the limitations of this study, no survival differences have been observed between short implants and longer implants in single-crown restorations in posterior maxilla/mandible.

Short versus Longer Implants in Sites without the Need for Bone Augmentation: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

OBJECTIVES

The present systematic review and meta-analysis aims to analyse the clinical performance of short compared to longer implants inserted in sites without the need for bone augmentation.

METHODS

The protocol of the present PRISMA-driven meta-analysis was registered on PROSPERO (CRD42021264781). Electronic and manual searches were performed up to January 2022. All Randomized Controlled Trials (RCTs) comparing short (≤6 mm) to longer (≥8.5 mm) implants placed in non-atrophic and non-augmented sites were included. The quality of the included studies was assessed using the Cochrane risk of bias tool for randomized clinical trials (RoB 2) and the quality of evidence was determined with the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. A meta-analysis was performed on implant survival rate, marginal bone level change (MBLc), and technical and biological complications at the available follow-up time points. The power of the meta-analytic findings was determined by trial sequential analysis (TSA).

RESULTS

From 1485 initial records, 13 articles were finally included. No significant difference was found in the survival rate between short and long implant at any follow-up (moderate quality of evidence). Significantly more bone loss for long implants at 1 and 5 years from implant placement and more technical complications with short implants at 10 years were found. No other significant inter-group differences in terms of MBLc and biological complications were detected.

CONCLUSIONS

Moderate evidence exists suggesting that short implants perform as well as longer ones in the rehabilitation of edentulous sites without the need for bone augmentation. Further long-term, well-designed RCTs, however, are still needed to provide specific evidence-based clinical recommendations for an extended use of short implants in non-atrophic sites.

Effect of a digital guide on the positional accuracy of intermaxillary fixation screw implantation in orthognathic surgery

BACKGROUND

Intermaxillary fixation screw (IMFS) implantation is a common procedure in orthognathic surgery (OGS) performed to the temporary maxillary-mandibular fixation and stable bite relationships. The study aims to assess the accuracy of IMFS implantation with a digital guide to reduce the occurrence of root damage.

METHODS

This prospective study involved 40 patients undergoing OGS at the Affiliated Hospital of Qingdao University from August 2017 to May 2021. The patients were randomly divided into two groups according to whether the IMFS implantation was with or without digital guide (20 patients in the experimental group and 20 controls). The digital guides used in the experimental group were designed according to a virtual implantation plan and printed using stereolithography. In the control group, IMFSs were directly implanted by a surgeon based on clinical experience. Postoperatively, cone-beam computed tomography was performed to compare root proximity of IMFSs between the two groups and verify the accuracy of IMFS placement.

RESULTS

In the experimental group, there was no case of root damage, the incidence of the periodontal ligament (PDL) injured was 22.1%, and 77.9% IMFSs were placed without contacting adjacent anatomic structures. In the control group, the incidence of root damage had been up to 20.8%, 31.7% IMFSs injured the PDL, and only 47.5% IMFSs were placed between the roots (P < 0.001).

CONCLUSION

IMFSs can be placed more accurately with surgical guides, reducing the incidence of root and PDL damages.

Experimental validation of a micro-CT finite element model of a human cadaveric mandible rehabilitated with short-implant-supported partial dentures

PURPOSE

This study aimed to address the predictive value of a micro-computed tomography (μCT)-based finite element (μFE) model of a human cadaveric edentulous posterior mandible, rehabilitated by short dental implants. Hereby, three different prosthetic/implant configurations of fixed partial dentures ("Sp"-3 splinted crowns on 3 implants, "Br" - Bridge: 3 splinted crowns on 2 implants, and "Si"- 3 single crowns) were analysed by comparing the computational predictions of the global stiffness with experimental data.

METHODS

Experimental displacement of the bone/implant/prosthesis system was measured under axial and oblique loads of 100 N using an optical deformation system (GOM Aramis) and the overall movement of the testing machine (Zwick Z030). Together with the measured machine force, an "Aramis" (optical markers) and "Zwick" (test machine) stiffness were calculated. FE models were created based on μCT-scans of the cadaveric mandible sample (n = 1) before and after implantation and using stl-files of the crowns. The same load tests and boundary conditions were simulated on the models and the μFE-results were compared to experimental data using linear regression analysis.

RESULTS

The regression line through a plot of pooled stiffness values (N/mm) for the optical displacement recording (true local displacement) and the test machine (machine compliance included) had a slope of 0.57 and a correlation coefficient R² of 0.82. The average pooled correlation of global stiffness between the experiment and FE-analysis (FEA) showed a R² of 0.80, but the FEA-stiffness was 7.2 times higher. The factor was highly dependent on the test configuration. Sp-configuration showed the largest stiffness followed by Br-configuration (17% difference in experiment and 21% in FEA).

CONCLUSIONS

The current study showed good qualitative agreement between the experimental and predicted global stiffness of different short implant configurations. It could be deduced that 1:1 splinting of the short implants by the crowns is most favorable for the stiffness of the implant/prosthesis system. However, in the clinical context, the absolute in silico readings must be interpreted cautiously, as the FEA showed a considerable overestimation of the values.

Posterior jaws rehabilitation with < 7mm-short implants. A review

INTRODUCTION

The results with shorter and shorter implants have been revolutionizing the implantology scenario and are worthy of being well-analyzed and understood. This review aims to add further knowledge about the last 10-years observation period on < 7mm-short implants in the posterior atrophic jaws, better defining the indication of their use.

METHODS

From a Medline database research, systematic reviews, controlled and no- controlled trials (CT, n-CT) with ≥ 3years-follow-ups on <7 mm / ≥ 5mm-short implants (group A), and clinical studies with ≥ 1year-follow-up on 4mm-short implants (group B) were considered. The outcomes, in terms of implant survival rate (SR), marginal bone loss (MBL), and complications were analyzed according to the duration of follow-ups, implant site (maxilla and mandible), type of prosthesis (single crown or splinted units), vertically impaired or normal sites.

RESULTS

Thirty-four trials (28 for group A and six for group B) were selected. Group A: a mean follow up of 5,8 (3-10) years came out; pre-and post-loading SR range was 94.4- 100% and 89.6-100%, respectively; the range of MBL was 0.12-1.49; 50% of CT found less statistically significant surgical complications in comparison with standard implants (ST) in reconstructed sites, while major prosthetic problems were recorded with short -implants (SH) in 37.5% of CT; in no atrophied sites, a mean SR range of 86.7-100 % vs. 88-100 % and a total bone loss of 2 vs.1.6 for SH vs.ST emerged. Group B: the overall mean follow-up period was 2,3 years, and the pre-and post- SR ranges were 93-100 % and 87.5-100 %, respectively. The MBL range was 0.02- 0.63 mm. All RCT reported significantly fewer surgical complications with SH than with ST in reconstructed mandibles within one year. No prosthetic complications were reported for up to 5 years using no pontics or cantilevers fixed bridges.

CONCLUSIONS

Similar or even better results for SH than ST in terms of post-loading SR and MBL came out for < 7mm/ ≥ 5mm-short implants in atrophic bone regardless of the prosthetic solutions, with less surgical complications but a few more prosthetic problems; the good results up to 5 years for 4mm-short implants in mandibles are associated with splinted and no-risk prosthetic solutions.

The Anatomical Conditions of the Alveolar Process of the Anterior Maxilla in Terms of Immediate Implantation-Radiological Retrospective Case Series Study

The feasibility and the level of difficulty of immediate flapless implantation depend largely on the residual alveolar bone. The purpose of the study was to determine how often immediate flapless implantation in the anterior maxilla is feasible and assess the difficulty level using cone-beam computed tomography (CBCT) scans. A radiological retrospective case series study was conducted. In total, 1200 CBCT scans from 300 consecutive patients were analyzed with dedicated planning software. Immediate flapless implants were possible in 78.33% of cases. Drilling direction was either through the apex or the palatal slope. Bimodal was conducted in 9% of the cases; only through the apex in 13.08% of the cases and in 56.25% only in the slope. In 21.67%, immediate flapless implants were excluded. The feasibility and degree of difficulty differed statistically to the disadvantage of the lateral incisors compared to the central incisors. Drilling direction caused that BASE classification reflects the difficulty level of immediate implantation. CBCT is a helpful diagnostic tool for assessing the feasibility of immediate flapless implants due to the residual bone shape and volume. BASE classification helps to determine a challenge level that may also facilitate communication and result in comparison. The alveolar bone condition allows for immediate flapless implants in most cases in the aesthetic region of the maxilla, but they should be performed by an experienced specialist with regard to the bone and soft tissue quality.

Short (6 mm) and Regular Dental Implants in the Posterior Maxilla-7-Years Follow-up Study

Short 6 mm dental implants are considered as an alternative to the maxillary sinus elevation and bone augmentation procedure where there is a reduced alveolar ridge height. The aim of this study was to compare the implant survival rate between short dental implants (6 mm) and regular length implants (11-13 mm) when placed in combination with bone grafting and loaded with a single non splinted crown, seven years after placing the implant. It was conducted as a controlled clinical study of 30 patients with partial edentulism in the posterior maxilla. The protocol included radiological and clinical evaluation of the C/I ratio (length of the superstructure divided by the length of the implant crestal part), marginal bone level (MBL), ultrasonography measurement of soft tissue surrounding implant (STT), patient-reported outcomes, and biological and technical complications. A total number of 28 implants (93%) remained integrated during follow-up period. MBL of 0.50 and 0.52 mm was observed for short implants and regular implants, respectively. MBL was checked for correlation with STT, and a negative correlation was found between MBL: STT. Our study has demonstrated a significantly lower implant survival rate for short implants compared to regular implants (87% compared to 100%). Despite the loss of several implants, good clinical results were achieved in the remaining implants in both groups. It is, therefore, worth considering short implants as an alternative to regular implants with a sinus lift surgery.

Survival Rate of 1008 Short Dental Implants with 21 Months of Average Follow-Up: A Retrospective Study

This retrospective study evaluated the survival rate of short, sandblasted acid-etched surfaced implants with 6 and 8 mm lengths with at least 120 days of follow-up. Data concerning patient, implant and surgery characteristics were retrieved from clinical records. Sandblasted and acid-etched (SLA)-surfaced tissue-level 6 mm (TL6) or 8 mm (TL8) implants or bone-level tapered 8 mm (BLT8) implants were used. Absolute and relative frequency distributions were calculated for qualitative variables and mean values and standard deviations for quantitative variables. A Cox regression model was performed to verify whether type, length and/or width influence the implant survival. The cumulative implant survival rate was assessed by time-to-event analyses (Kaplan–Meier estimator). In all, 513 patients with a mean age of 58.00 ± 12.44 years received 1008 dental implants with a mean follow-up of 21.57 ± 10.77 months. Most implants (78.17%) presented a 4.1 mm diameter, and the most frequent indication was a partially edentulous arch (44.15%). The most frequent locations were the posterior mandible (53.97%) and the posterior maxilla (31.55%). No significant differences were found in survival rates between groups of type, length and width of implant with the cumulative rate being 97.7% ± 0.5%. Within the limitations of this study, the evaluated short implants are a predictable option with high survival rates during the follow-up without statistical differences between the appraised types, lengths and widths.