Meta-analysis of single crowns supported by short (<10 mm) implants in the posterior region

Clinical outcomes of short dental implants supporting prostheses in the posterior region

Aim In clinically challenging scenarios with limited bone height and anatomical restrictions, the use of short implants have been proposed as a potential treatment strategy. The purpose of this retrospective study was to evaluate the clinical outcomes of short implants supporting prostheses in the posterior premolar region of the maxilla and mandible.Materials and methods A total of 30 patients requiring short 6 mm length implant placement in the posterior premolar region were included. Following a period of osseointegration, the implants were restored with either single crowns, fixed bridges or implant-supported removable overdentures. Implant and prosthetic survival with technical complications were recorded.Results In total, 45 implants were placed, with four failures reported before loading in two patients, resulting in a patient implant survival rate of 93.3% over the two-year follow-up. There was no statistically significant difference found between implant failure and arch placement. Prosthetic survival was 100% and minor technical complications recorded were low.Conclusion This study showed that short 6 mm implants could provide a viable treatment option, with high survival rates comparable with alternative bone augmentation procedures. Further research with longer observation periods would be required to validate these current findings.

Survival Rates of Short Dental Implants (≤6 mm) Used as an Alternative to Longer (>6 mm) Implants for the Rehabilitation of Posterior Partial Edentulism: A Systematic Review of RCTs

Short dental implants have been proposed as an alternative treatment option to bone regeneration procedures for the rehabilitation of resorbed alveolar ridges. The aim of this paper was to systematically review randomized controlled trials (RCTs) comparing short implants (≤6 mm) and longer implants (>6 mm) in atrophic alveolar ridges in terms of implant survival rates, peri-implant marginal bone loss (MBL), prevalence of peri-implantitis and technical complications. A thorough electronic search was performed until September 2023. RCTs with follow-up of at least 1-year post-loading comparing short implants with rough surfaces to longer implants in the posterior jaws of systemically and periodontally healthy, partially edentulous adults were considered. Studies with incomplete information on the number of patients, follow-up or definition of "short implants" were excluded. The revised Cochrane risk-of-bias tool for randomized trials was used for Risk of bias assessment. Fixed-effects meta-analysis of the selected studies was applied to compare the outcome variables. Random-effect meta-analysis was performed, on the basis of within-study comparisons. In total, 16 articles were selected for meta-analysis and incorporated 408 short implants and 475 longer implants inserted in 317 and 388 patients, respectively. The survival rates of longer implants in pristine or augmented bone were significantly increased compared to short implants (95%CI: 2-5%, p < 0.001). Standard-length implants displayed increased, although non-statistically significant MBL (95%CI: -0.17-0.04, p > 0.05), and prevalence of peri-implantitis (95%CI: 0-5%, p > 0.05). No statistically significant differences were observed between short and long implants in terms of technical complications (implant-level 95%CI: -4-6%, p > 0.05). Short implants represent a promising alternative treatment option for the rehabilitation of posterior jaws to avoid additional bone augmentation procedures. Nonetheless, they should be selected cautiously due to a potentially limited survival rate compared to longer implants. A major limitation of this study is the variability in the included studies regarding sample size, patient profile, type of bone, loading protocol, definition of peri-implantitis, among others. This study received no external funding. The study protocol was registered in PROSPERO (CRD42023485514).

Long-term clinical performance of short 6-mm implants supporting single crowns in the posterior region: A 10-year cohort study

INTRODUCTION

Long-term clinical success of non-splinted, posterior, and short implants still is unclear. This prospective cohort study reports the 10-year follow-up of 6-mm implants supporting single crowns in the posterior region, and patient-reported outcomes.

METHODS

Baseline sample comprised 20 patients treated with 46 screw-retained crowns supported by 6-mm implants with moderately rough implant surface. Participants were recalled for a 10-year clinical follow-up to assess survival rates, biologic and mechanic conditions, quality of life (OHIP-14), and treatment satisfaction. Data were collected with clinical-radiographic exams and analyzed using descriptive and inferential statistics.

RESULTS

Fourteen patients with 35 implant-crown units were examined after 127.6 ± 11.8 months. For the entire cohort period, 7/46 implants were lost (survival estimate: 77.7% at 133 months), and mechanic complications occurred in 14/46 units (survival estimate: 66.4% at 116 months). In the Cox models, "maximum occlusal force" had a significant effect for implant loss (p = 0.038) and for prosthetic screw loosening (p = 0.038); "arch" and "bruxism" were not significant. Peri-implant bone loss was 0.4 ± 0.6 mm at 10 years. For peri-implant bone level, "crown-to-implant ratio" (p < 0.001) and "time" (p = 0.001) were significant. Bone levels differed from baseline to 12, 48, and 120 months. Satisfaction VAS was 94.0 ± 7.9 mm and OHIP-14 was 2.3 ± 2.2.

CONCLUSION

Single screw-retained crowns supported by 6-mm implants have an acceptable long-term clinical performance, with stable peri-implant bone levels after 10 years of function.

A naïve comparison to assess the success of ultra-short implants

Introduction

Conventional implants are associated with ridge augmentation/sinus lift procedures in vertically insufficient ridges, which increase morbidity and healing time. Short implants provided some hope in this context. The present study considered the use of ultra-short implants in vertically insufficient posterior mandibular ridges and evaluated their success. Hence, study was done to evaluate the success of ultra-short implants in partially edentulous posterior mandible clinically and radiographically.

Materials and Methods

The study is a "Naïve direct comparison" of ultra-short implants to conventional implants for assessing their success in vertically insufficient posterior mandibular ridges. A total of 10 ultra-short implants were placed in a partially edentulous posterior mandibular ridge with at least 8-mm horizontal (at crest) and vertical dimensions. A delayed loading was done at three-month follow-up. Data acquisition was done at baseline (immediately after loading), 6-, 9-, 12-month intervals. Parameters assessed were marginal bone loss (MBL), probing pocket depth reduction (PPDR), modified plaque index (mPI), modified gingival index (mGI).

Results

All the placed 10 implants survived, and no failure was observed. "Independent sample t-test" and "paired sample t-test" was done for intergroup and intragroup analysis, respectively. Intergroup comparison between the ultra-short and conventional implants presented a statistically insignificant difference between all the parameters at all the follow-up visits (baseline, 6-, 9-, 12 months).

Conclusions

Within the limitations, it was thus concluded that ultra-short implants may be considered as a viable treatment option for vertically insufficient mandibular ridge. Further, long-term randomized controlled trials are required to establish the evidence.

Short implants compared to regular dental implants after bone augmentation in the atrophic posterior mandible: umbrella review and meta-analysis of success outcomes

PURPOSE

To assess the body of evidence of short versus regular implants after bone augmentation (BA) in the atrophic posterior mandible in the context of implant treatment success outcomes.

METHODS

Seven databases, two registries, and reference lists were searched for systematic reviews and meta-analysis (SR/MA), randomized controlled trials (RCTs) and longitudinal studies published in English, Spanish or German since 2012. Confidence in the SR/MA methodology was evaluated using AMSTAR-2 and the risk of bias of primary studies using Cochrane's RoB 2.0 and ROBINS-I. A random-effects meta-analysis and a meta-regression were performed for continuous and dichotomous outcomes. GRADE approach was used to assess the certainty of the evidence.

RESULTS

Eighteen SRs/MAs, most of them "critically low" and "low" confidence with substantial overlap, included 14 relevant RCTs with a high risk of bias. A cohort study with moderate risk of bias was added. Quantitative synthesis of 595 implants and 281 hemiarches/patients indicates that the use of short implants (< 10 mm) compared to regular implants and BA may reduce implant failure at 1-year follow-up, and marginal bone loss (MBL) at 3-, 5-, and 8-year follow-up; is likely to reduce the risk of biological complications at 1-, 3-, 5-, and 8-year follow-up; and may be the patient's preferred alternative. There is a correlation between bone height, MBL and biological complications.

CONCLUSIONS

The available evidence partially suggests that the use of short implants could decrease implant failure, MBL, and biological complications, and increase patient satisfaction. However, given the need for further RCTs and real-world evidence to fully evaluate short- and long-term outcomes, it would be prudent for clinicians to carefully consider the individual needs and circumstances of the patients before deciding whether to use short implants. Trial registration PROSPERO CRD42022333526.

Clinical performance of short and extrashort dental implants with wide diameter: A systematic review with meta-analysis

STATEMENT OF PROBLEM

Rehabilitation with wide-diameter reduced-length implants has become popular for patients with minimal vertical bone. However, a consensus on the benefits of this approach is lacking.

PURPOSE

The purpose of this systematic review with meta-analysis was to evaluate the influence of wide compared with regular diameter on the clinical performance of short (<10 mm) and extrashort (≤6 mm) dental implants used for rehabilitations with single crowns, fixed partial dentures, or both, in the posterior region.

MATERIAL AND METHODS

A search in 6 databases was conducted to select randomized controlled trials (RCTs) and nonrandomized controlled trials (N-RCTs). Five meta-analyses were performed, where the risk ratio (RR) was evaluated. The certainty of evidence was evaluated, and the risk of bias was determined from the Joanna Briggs Institute checklist.

RESULTS

Fourteen articles were included, 272 wide- and 478 regular-diameter implants. One study presented a low, 3 an unclear, and 11 a high risk of bias. Meta-analyses showed no statistical difference: implant survival, short dental implants in N-RCTs (up to 1 year - RR 1.01 [0.98; 1.03], 1 to 5 years - RR 1.01 [0.94; 1.08], more than 5 years - RR 1.01 [0.97; 1.06]), extrashort dental implants in N-RCTs (RR 1.04 [0.90; 1.20]), RCTs (RR 1.05 [0.88; 1.25]); implant success in N-RCTs (RR 1.01 [0.97; 1.05]); prosthesis success in N-RCTs (RR 1.01 [0.97; 1.05]).

CONCLUSIONS

Short and extrashort dental implants with a wide and regular diameter appear to be clinically appropriate options for implant-supported posterior restorations, with high survival, success, and prosthesis success rates.

Short and Ultra-Short Implants, in Association with Simultaneous Internal Sinus Lift in the Atrophic Posterior Maxilla: A Five-Year Retrospective Study

Recent short-term studies suggested the use of short and ultra-short implants in association with a modified osteotome sinus floor elevation (internal sinus lift) technique for the treatment of edentulous resorbed posterior maxilla. The aim of this retrospective study was to investigate this hypothesis in locking-taper implants with a mid-term follow-up of 5 years. Overall, 155 implants (32, 100, and 23 of, respectively, 5.0 mm, 6.0 mm, and 8.0 mm length) were positioned in the atrophic upper maxilla of 79 patients, and 151 implants were loaded with single crowns. Overall implant survival after 5 years was 94.84%. Implant survival for each length group was 93.75%, 94%, and 100% for 5.0, 6.0, and 8.0 mm length, respectively. Preoperative residual crestal bone height of 4.45 (1.3) mm increased to 9.25 (2.13) mm after implant placement and settled at 6.35 (1.73) mm after loading and at 5.25 (1.68) mm at follow-up. Elevation of the Schneiderian membrane was 4.8 (2.46) mm after implant placement, 3.06 (1.3) mm after loading, and 1.46 (1.06) mm at follow-up. Mean variations of peri-implant crestal bone loss and first bone-to-implant contact point were, respectively, -0.36 (1.3) mm and -0.62 (1.15) mm. It can be confirmed that internal sinus lift procedure revealed stable bone gain and negligible resorption at mid-term follow-up for atrophic upper crests with reduced height.

Simultaneous placement of short implants (≤ 8 mm) versus standard length implants (≥ 10 mm) after sinus floor elevation in atrophic posterior maxillae: a systematic review and meta-analysis

Purpose

The objective of this meta-analysis was to compare the clinical outcomes of using short implants (≤ 8 mm) inserted with osteotome sinus floor elevation (OSFE) and standard implants (≥ 10 mm) inserted with sinus floor elevation (SFE) in atrophic posterior maxillae with insufficient residual bone height (RBH).

Methods

An electronic search was performed on PubMed, EMBASE, and the Cochrane Library from 1994 to July 2022, in combination with a manual search of references in relevant articles. Randomized controlled trials (RCTs) that compared the clinical results between short and standard implant placement with SFE were included. The primary outcomes were implant survival rate and marginal bone loss (MBL); the secondary outcome was complication rate.

Results

Three RCTs were included, totaling 138 short and 156 standard implants. The results of the meta-analysis showed no significant differences between the short and standard implant groups in survival rate (RR = 1.02, 95% CI   0.96–1.08, p = 0.570), MBL (MD = − 0.13, 95% CI   − 0.32 to 0.07, p = 0.190) and complication rate (intra-surgical complication: RR = 1.14, 95% CI   0.46–2.83, p = 0.770; post-operative complication: RR = 1.34, 95% CI   0.71–2.55, p = 0.370).

Conclusions

Using short implants (≤ 8 mm) combined with OSFE might be an alternative to standard implants (≥ 10 mm) with SFE when the RBH of the posterior maxilla is insufficient. Based on a short-term clinical observation, short implants with OSFE show good results in terms of survival rate, MBL, and complication incidence.

Graphical Abstract

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.

Results at the 1-Year Follow-Up of a Prospective Cohort Study with Short, Zirconia Implants

The objective of this study was to clinically and radiologically evaluate the performance of a short (8 mm), 1-piece, zirconia implant after an observation period of 1 year in function. A total of 47 patients with 1 missing tooth in the position of a premolar or molar were recruited. Short (8 mm), 1-piece, zirconia implants were placed and loaded after a healing period of 2 to 4 months with monolithic crowns made of 3 different materials. Implants were followed up for one year and clinically and radiologically assessed. A total of 46 implants were placed. One was excluded since no primary stability was achieved at implant placement. At the 1-year follow-up, mean marginal bone loss 1 year after loading was 0.05 ± 0.47 mm. None of the implants showed marginal bone loss greater than 1 mm or clinical signs of peri-implantitis. A total of 2 implants were lost during the healing phase and another after loading, resulting in a survival rate of 93% after 1 year. All lost implants showed a sudden increased mobility with no previous signs of marginal bone loss or peri-implant infection. The short, 8 mm, zirconia implants showed stable marginal bone levels over the short observation period of 1 year. Although they revealed slightly lower survival rates, they can be suggested for the use in sites with reduced vertical bone. Scientific data are very limited, and long-term data are not yet available, and therefore, they are needed.

Survival of surface-modified short versus long implants in complete or partially edentulous patients with a follow-up of 1 year or more: a systematic review and meta-analysis

PURPOSE

Short implants are a potential alternative to long implants for use with bone augmentation in atrophic jaws. This meta-analysis investigated the survival rate and marginal bone level (MBL) of surface-modified short vs. long implants.

METHODS

Electronic and manual searches were performed for articles published between January 2010 and June 2021. Twenty-two randomized controlled trials (RCTs) comparing surface-modified short and long implants that reported the survival rate with at least 1 year of follow-up were selected. Two reviewers independently extracted the data, and the risk of bias and quality of evidence were evaluated. A quantitative meta-analysis was performed regarding survival rate and MBL.

RESULTS

The failure rates of surface-modified short and long implants differed significantly (risk ratio, 2.28; 95% confidence interval [CI], 1.46, 3.57; P<0.000). Long implants exhibited a higher survival rate than short implants (mean follow-up, 1-10 years). A significant difference was observed in mean MBL (mean difference=-0.43, 95% CI, -0.63, -0.23; P<0.000), favoring the short implants. Regarding the impact of surface treatment in short and long implants, for hydrophilic sandblasted acid-etched (P=0.020) and titanium oxide fluoride-modified (P=0.050) surfaces, the survival rate differed significantly between short and long implants. The MBL differences for novel nanostructured calcium-incorporated, hydrophilic sandblasted acid-etched, and dual acid-etched with nanometer-scale calcium phosphate crystal surfaces (P=0.050, P=0.020, and P<0.000, respectively) differed significantly for short vs. long implants.

CONCLUSIONS

Short surface-modified implants are a potential alternative to longer implants in atrophic ridges. Long fluoride-modified and hydrophilic sandblasted acid-etched implants have higher survival rates than short implants. Short implants with novel nanostructured calcium-incorporated titanium surfaces, hydrophilic sandblasted acid-etched surfaces, and dual acid-etched surfaces with nanometer-scale calcium phosphate crystals showed less marginal bone loss than longer implants. Due to high heterogeneity, the MBL results should be interpreted cautiously, and better-designed RCTs should be assessed in the future.

TRIAL REGISTRATION

International Prospective Register of Systematic Reviews (PROSPERO) Identifier: CRD42020160185.

Short and ultra-short (<6-mm) locking-taper implants supporting single crowns in posterior areas (part II): A 5-year retrospective study on periodontally healthy patients and patients with a history of periodontitis

Background

Short and ultra‐short implants implants supporting single crowns seem to demonstrate high percentages of survival and stable marginal bone levels at a mid‐term follow‐up. Nevertheless, insurgence of peri‐implant complications still represents a critical issue, especially for patients with history of periodontitis.

Purpose

The aim of this retrospective study was to evaluate implant survival, marginal bone loss and peri‐implant complications in 333 short and ultra‐short implants, placed in periodontally healthy patients and patients with a history of periodontitis.

Materials and Methods

Implants were placed in the maxillary and mandibular posterior regions of 142 patients with (PP) and without (NPP) a history of periodontitis. Clinical and radiographic examinations were performed at 5‐year recall appointments.

Results

Implants respectively placed in PP and NPP were: 35.68% and 42.50% in 8.0 mm‐length group, 33.33% and 36.67% in 6.0 mm‐length group, and 30.99% and 20.83% in 5.0 mm‐length group. Implant‐based survival after 5 years of follow‐up was 95.77% for PP and 96.67% for NPP (p = 0.77). Regarding crestal bone level variations, average crestal bone loss was statistically different (p = 0.04) among PP (0.74 mm) and NPP (0.61 mm). Implants presenting signs of mucositis were 6.86% in PP and 7.76% in NPP (p = 0.76). Setting the threshold for excessive bone loss at 1 mm after 60 months, peri‐implantitis prevalence was 7.84% in PP and 2.59% in NPP (p = 0.08). Overall implant success was 92.16% and 97.41%, respectively, for PP and NPP.

Conclusions

Under strict maintenance program, five‐year outcomes suggest that short and ultra‐short locking‐taper implants can be successfully restored with single crowns in the posterior jaws both in PP and NPP.

Survival rates of ultra-short (<6 mm) compared with short locking-taper implants supporting single crowns in posterior areas: A 5-year retrospective study

Background

Short and ultra‐short implants represent a predictable treatment, in terms of implant survival, with patients presenting insufficient available bone volumes. Moreover, single crown restorations represent a gold standard in terms of oral hygiene.

Purpose

The aim of this retrospective study was to evaluate implant survival, marginal bone loss, and peri‐implant complications in 333 locking‐taper short and ultra‐short implants.

Materials and Methods

Implants were placed in the maxillary and mandibular posterior regions of 142 patients. Clinical and radiographic examinations were performed at 5‐year recall appointments.

Results

All implants placed consisted of 8.0‐, 6.0‐, and 5.0‐mm length, 38.14%, 34.53%, and 27.33%, respectively. Three hundred thirty‐two implants (one early failure) were rehabilitated with single crowns in 141 patients. In 45.48% of the implants the crown‐to‐implant ratio was ≥2, with a mean value of 1.94. Overall implant‐based survival after 5 years of follow‐up was 96.10%: 96.85%, 95.65%, and 95.60% for 8.0‐, 6.0‐, and 5.0‐mm length implants, respectively (p = 0.82). Overall patient‐based survival was 91.55%. Regarding crestal bone level variations, average crestal bone loss and apical shift of the “first bone‐to‐implant contact point” position were 0.69 and 0.01 mm, respectively. Setting the threshold for excessive bone loss at 1 mm, during the time interval from loading to follow‐up, 28 implants experienced loss of supporting bone greater than 1 mm: 19 of them (67.85%) were surgically treated with a codified surgical regenerative protocol. After 60 months, a peri‐implantitis prevalence of 5.94% was reported, with an overall implant success of 94.06%: 95.93%, 92.73%, and 93.10% for 8.0‐, 6.0‐, and 5.0‐mm length implants, respectively (p = 0.55).

Conclusion

Long‐term outcomes suggest that short and ultra‐short locking‐taper implants can be successfully restored with single crowns in the posterior area of the maxilla and mandible.

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.

Influence of Dental Implant Diameter and Bone Quality on the Biomechanics of Single-Crown Restoration. A Finite Element Analysis

Background: Success of an implant-supported prosthesis is highly dependent on implant diameter and bone quality. The objective of this study is to assess these two variables under axial or 30° angulated loading. Methods: The study was conducted using finite element model simulations of dental implants with an unchanging length of 6.5 mm and varying diameters of Ø3.3; Ø3.5; Ø3.75; Ø4, Ø4.25 and Ø4.75 mm. The implants were placed in an axial position and a 2 mm high straight transepithelial (intermediate abutment) was used to perform a single tooth restoration. Four bone quality scenarios, Type IV, III, II or 0-I bone, were simulated from a simplified model of the mandible. A 200N load was applied both axially and at a 30° angle to the occlusal surface of the prosthesis, which was 11 mm above the implant platform, and the equivalent Von Mises stress in the bone was analyzed. Results: The maximum stress value was obtained for the Ø3.3 implant in Type IV bone (235 MPa), while the lowest value was obtained for the Ø4.75 implant and in Type 0-I bone (41 MPa). Regardless of the implant diameter, an improvement in bone quality produced a reduction in bone stress. The same effect was observed as the implant diameter was increased, being this effect even more pronounced. Conclusions: Implant diameter has an important effect on bone stress, with a reduction in stress as the implant diameter increases.

Clinical performance of short versus standard dental implants in vertically augmented bone: an overview of systematic reviews

OBJECTIVE

To answer the question: What do we know so far about the clinical performance of short implants (≤ 7 mm) when compared to standard length implants in vertically augmented bone, as well as which is the overall confidence of the systematic reviews (SRs) about this topic?

MATERIALS AND METHODS

An overview of SRs was conducted. The searches were performed in six electronic databases and grey literature. SRs about short (≤ 7 mm) versus standard dental implants performance in vertically augmented bone were included. The assessed outcomes were marginal bone loss (MBL), implant survival (IS), prosthetic (PC) and biological complications (BC), costs, surgical time, and patient satisfaction. AMSTAR 2 was used to evaluate the overall confidence of included SRs.

RESULTS

Thirteen SRs were included. Nine of twelve SRs reported a lower MBL for the short implant group. All the included SRs showed no difference in the IS between groups. A higher rate of BC was reported for standard-length implants in four out of five SRs. No differences regarding PC were reported in four of five SRs. Information related to patient preference, cost, and surgery time were underreported. The confidence evaluation of the SRs was stratified as low for five SRs and critically low for eight SRs.

CONCLUSIONS

In an overall low-to-very low confidence levels, short implants appear to perform better in the mid-term (up to 5 years) than standard dental implants associated with vertical bone augmentation regarding MBL and BC, but they have a similar performance regarding IS rates and PC. There is an imperative need to improve the methodological quality of SRs, and efforts should focus on conducting RCTs to broaden the knowledge on this topic.

CLINICAL RELEVANCE

Short implants could represent a viable, simpler, and less invasive treatment when available bone height is limited.

A within-subject comparison of short implants in the posterior region: retrospective study of up to 10 years

PURPOSE

This intra-patient retrospective study of up to 10 years evaluated the clinical success and risk factors of 6- and 8-mm long implants and their respective prostheses.

MATERIALS AND METHODS

The sample consisted of patients treated at a Military Polyclinic dental service, who received both 6- and 8-mm long tissue level implants in the posterior region of the same arch. Data were collected from the dental charts, clinical and radiographic exams, self-report of sleep bruxism, measurement of maximum occlusal force, and clinical crown-to-implant (C/I) ratio. Data were analyzed by descriptive and inferential statistics with univariate and hierarchical multivariate models, at the 0.05 significance level.

RESULTS

The 30 patients (27 women) had 85 implants and 83 prostheses. Two implants were lost before prosthesis installation (implant survival: 97.6%). Ten events of prosthetic complication (screw tightening loss) occurred in five patients (success rate: 87.9%) in a single moment. Only the variable C/I ratio had a significant effect for repairable prosthesis complication (P<.05).

CONCLUSION

The results suggest that 6- and 8-mm long implants have similar long-term clinical success for implants and prostheses.

Survival Rates of Splinted and Nonsplinted Prostheses Supported by Short Dental Implants (≤8.5 mm): A Systematic Review and Meta-Analysis

PURPOSE

To evaluate and compare the implant survival rates, marginal bone loss, and mechanical complications of prostheses supported by splinted and nonsplinted short implants (≤8.5 mm).

MATERIAL AND METHODS

Electronic database (MEDLINE, CENTRAL, Web of Science, and EMBASE) and manual searches up to May 2021 were conducted to identify studies comparing splinted and nonsplinted short implants (≤8.5 mm). The primary outcome was implant survival rate. Secondary outcomes were marginal bone loss and mechanical complications. The quality of included studies and risk-of-bias were assessed according to the Newcastle-Ottawa Scale. A random-effects model was used to analyze the data.

RESULTS

Twelve studies fulfilled the inclusion criteria and featured 1506 short implants (596 nonsplinted and 910 splinted) with a follow-up time ranging from 1 to 16 years. Quantitative analysis found no statistically significant differences between splinted and nonsplinted short implants (≤8.5 mm) for survival rate (RR = 0.98; 95% CI 0.96, 1.01; p = 0.26)) and marginal bone loss (SMD = -0.08; 95% CI - 0.23, 0.07; p = 0.28). Veneer chipping, abutment screw breakage, screw loosening, and loss of retention were reported in the selected studies as common complications. However, no statistically significant difference was found between splinted and nonsplinted short implants (RR = 0.56; 95% CI 0.20, 1.54; p = 0.26).

CONCLUSIONS

Within the limitations of the present meta-analysis, it might be concluded that splinted short implants (≤8.5 mm) do not present superior performance in survival rate, marginal bone maintenance and prevention of mechanical complications compared with single-unit prostheses.

Implant survival and risk factor analysis in regenerated bone: results from a 5-year retrospective study

Purpose

The aims of this study were to evaluate the 5-year cumulative survival rate (CSR) of implants placed with guided bone regeneration (GBR) compared to implants placed in native bone, and to identify factors contributing to implant failure in regenerated bone.

Methods

This retrospective cohort study included 240 patients who had implant placement either with a GBR procedure (regenerated bone group) or with pristine bone (native bone group). Data on demographic features (age, sex, smoking, and medical history), location of the implant, implant-specific features, and grafting procedures and materials were collected. The 5-year CSRs in both groups were estimated using Kaplan-Meier analysis. Risk factors for implant failure were analyzed with a Cox proportional hazards model.

Results

In total, 264 implants in the native bone group and 133 implants in the regenerated bone group were analyzed. The 5-year CSRs were 96.4% in the regenerated bone group and 97.5% in the native bone group, which was not a significant difference. The multivariable analysis confirmed that bone status was not an independent risk factor for implant failure. However, smoking significantly increased the failure rate (hazard ratio, 10.7; P=0.002).

Conclusions

The 5-year CSR of implants placed in regenerated bone using GBR was comparable to that of implants placed in native bone. Smoking significantly increased the risk of implant failure in both groups.

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.

Clinical evaluation of single 4-mm implants in the posterior mandible: A 3-year follow-up pilot study

STATEMENT OF PROBLEM

Extra-short implants in the posterior mandible can increase the functional surface area and reduce the risk of implant overload. However, reports of treatment using single extra-short implants in the posterior mandible with a midterm follow-up are lacking.

PURPOSE

The purpose of this prospective pilot study was to evaluate the clinical behavior of single extra-short 4-mm implants placed in the posterior mandible during a follow-up of 3 years from implant restoration.

MATERIAL AND METHODS

A total of 18 participants with a single extra-short 4-mm-long implant placed in the area of the mandibular first molars participated in this pilot study. The survival and success rates of implants, as well as biologic and prosthetic variables, were evaluated during a follow-up of 3 years from implant restoration.

RESULTS

The survival rate of the implants was 100%, with no implant or biologic complications recorded. One prosthetic complication (loosening of 1 screw) was observed.

CONCLUSIONS

Single extra-short (4 mm) implants in the posterior mandible showed favorable clinical behavior during the first 3-years of follow-up.

Biomechanical Evaluation of Stress Distribution in Subcrestal Placed Platform-switched Short Dental Implants in D4 Bone: In Vitro Finiteelement Model Study

The present study was carried out to assess stress distribution in the maxillary posterior bone region (D4 bone) with the help of a short platform switched subcrestal dental implants using the FEM model. Missing teeth surfaces related to the maxillary posterior region were stimulated. The bone model had a cancellous core of (0.5 mm) which represents D4 bone. A 7.5x4.6 mm screw type implant system with 3.5 platform switch abutment was selected. ANSYS WORKBENCH was used to model all the finite element structures. Force of 100 N was tested and adapted at an angle of 0º, 15º, 30º on the tooth model. Overall results from the current study showed that a high amount of stress was seen in cortical than in relation to cancellous bone. Stress values reduced from equicrestal to subcrestal (2 mm) placement of dental implants irrespective of angulation of load from 0o to 30o in both types of bone. However higher stress values were seen when force was applied in an oblique direction (30o) in comparison to a vertical load (0o). Least amount of stress was noticed when platform switched implants were placed 0.5 mm subcrestatlly irrespective of angulations of a load. Platform switched short subcrestal implants reduced the stress in the D4 cortical bone than in contrary equicrestal implant placement. This results in the preservation of marginal bone leading to implant success.

Survival of Short and Ultra-Short Locking-Taper Implants Supporting Single Crowns in the Posterior Mandible: A 3-Year Retrospective Study

The purpose of this retrospective study was to determine survival and peri-implant marginal bone loss of short and ultra-short implants placed in the posterior mandible. A total of 98 patients received 201 locking-taper implants between January 2014 and January 2015. Implants were placed with a 2-stage approach and restored with single crowns. Clinical and radiographic examinations were performed at 3-year recall appointments. At that time, the proportion of implant survival by length, and variations of crestal bone levels (mean crestal bone loss and mean apical shift of the "first bone-to-implant contact point" position) were assessed. Significance level was set at 0.05. The total number of implants examined 36 months after loading included: 71 implants, 8.0 mm in length; 82 implants, 6.0 mm in length; and 48 implants, 5.0 mm in length. Five implants failed. The overall proportion of survival was 97.51%, with 98.59% for the 8.0-mm implants, 97.56% for the 6.0-mm implants, and 95.83% for the 5.0-mm implants. No statistically significant differences were found among the groups regarding implant survival (P = .73), mean crestal bone loss (P = .31), or mean apical shift of the "first bone-to-implant contact point" position (P = .36). Single-crown short and ultra-short implants may offer predictable outcomes in the atrophic posterior mandibular regions, though further investigations with longer follow-up evaluations are necessary to validate our results.

CT-based dentulous mandibular alveolar ridge measurements as predictors of crown-to-implant ratio for short and extra short dental implants

The purpose was to predict the crown-to-implant ratio variation in the edentulous posterior mandibles rehabilitated with short dental implants. Hence, vertical and horizontal dimensions of dentulous posterior mandibles in a sample of 18- to 25-year-olds were measured, and correlations of these dimensions with sex and site were investigated. Mandibular computed tomography scans from 100 subjects were considered. Vertical and horizontal bone and tooth measurements were taken at the sites of the second premolar (PM), and the mesial and distal roots of the first and second molars (M1m, M1d, M2m and M2d, respectively). A hypothetical crown-to-implant ratio (C/I R) was calculated assuming the insertion of short and extra short implants (5, 6 or 7 mm), at 1.5 mm from the inferior alveolar canal, maintaining the position of the existing occlusal plane. All vertical bone dimensions decreased from the PM to the M2d. Width measurements increased from the mesial (PM) to the distal sites (M1m, M1d, M2m and M2d). Males had significantly greater vertical and horizontal measurements than females at all sites. The mean C/I R was higher than 2 for all sizes of implant. The C/I R was lower for the second molar than for the second premolar, while it was similar for the first molar and the second premolar. Males had a higher C/I R than females. Computed tomography can be used to study the anatomical features of alveolar bone, and to predict some clinical aspects of prosthetic rehabilitation with implants, such as the crown-to-implant ratio in conditions of serious bone atrophy.

Key factors influencing short implant success

AIM

This systematic article reviews the literature on the confounding parameters that affect short implant survival in order to establish specific surgical and prosthetic protocols that create an optimal biomechanical scenario and ensure implant longevity.

MATERIALS AND METHODS

The available literature was screened for randomized clinical trials and prospective cohort and retrospective studies, published up to February 20, 2020, on the prognosis of short-length implants placed in posterior jaws. Studies evaluating the 5-year clinical performance of short dental implants (5 mm or 6 mm) in fixed rehabilitations of partially edentulous posterior jaws were included.

RESULTS

Eleven studies were selected after assessment of inclusion and exclusion criteria, of which 8 were RCTs, 2 were prospective studies, and 1 was a retrospective study. After 5 years in function, 22 short (12 in maxilla and 10 in mandible) and 10 standard (2 in maxilla and 8 in mandible) implants were lost, resulting in high survival rates independent of implant length or location. More biological complications were found in standard implants especially those placed in augmented posterior mandibles (135 complications compared to 48 in short mandibular implants). Splinted prostheses were associated with less technical complications (15 out of 53 complications affecting short implants).

CONCLUSION

The findings of this review showed that, when used correctly, short implants achieve predictable and promising long-term outcomes, provided they are placed following a comprehensive surgical and prosthetic protocol, based on the different biomechanical parameters essential to optimize long-term prognosis.

CLINICAL SIGNIFICANCE

The use of short implants in clinical practice has considerably increased in a wide variety of cases, given that they offer several advantages for both patient and practitioner. Recent literature shows that, when specific criteria are respected, new generations of short implants present high, long-term survival rates. This review is designed to provide a thorough understanding of the surgical and prosthetic protocols that create an optimal biomechanical scenario for short implants and improve their prognosis.

Feasibility and needs for simultaneous or staged bone augmentation to place prosthetically guided dental implants after extraction or exfoliation of first molars due to severe periodontitis

BACKGROUND

The aim of this study was to retrospectively assess bone volumes, healed ridge topography and possibility to plan prosthetically guided implants (PGI) at least 6 months after extraction or exfoliation of first molars as a consequence of terminal periodontitis (EEFMP).

MATERIALS AND METHODS

45 subjects with stage III-IV periodontitis providing 74 extraction sites (maxillary = 51 and mandibular = 23) were included. The degree of residual periodontal support on each root was assessed by combining periodontal and radiographic data. Digital planning of PGI with 4.8/4.1 mm diameter, 8 mm long, root-form dental implant and need for bone augmentation (BA) were performed using CBCT with a radiographic stent. Possibility of standard implant placement (STANDARD) and need for simultaneous or staged BA were assessed.

RESULTS

Planning PGI placement was possible in all cases. For a 4.8 mm diameter implant, STANDARD was possible in 37.8% of the sites, 33.8% required BA at the time of implant placement, and 28.4% required staged BA before PGI. The use of 4.1 mm rather than 4.8 mm diameter implant allowed STANDARD in an additional 8.1% of cases that originally required simultaneous BA/osteotome sinus floor elevation (OSFE). The level of periodontal bone loss did not predict the complexity of implant placement, but significant differences were observed comparing maxillary with mandibular sites.

CONCLUSION

PGI planning at sites with first molar loss due to terminal periodontitis is possible but poses great challenge to rehabilitation, often requiring advanced augmentation procedures and sinus augmentation.

Short implants versus longer implants in the posterior alveolar region after an observation period of at least five years: A systematic review and meta-analysis

OBJECTIVES

This meta-analysis compared clinical outcomes, including survival rate, marginal bone loss (MBL), and technical and biological complications of short implants (<7 mm) and long implants (≥7 mm) placed in the posterior alveolar bone.

SOURCES

Electronic (via PubMed, EMBASE, Cochrane Library) and manual searches were performed for articles published prior to November 29, 2019.

STUDY SELECTION

The review protocol was registered with PROSPERO (CRD42019140718). Only randomized controlled trials (RCTs) comparing short implants and standard implants in the same study after an observation period of at least five years were included.

DATA

Nine RCTs were included in this study. The survival rates of short implants (<7 mm) ranged from 86.7 %-98.5 %, whereas the survival rates of longer implants (≥7 mm) were 95.1%-100% with follow-up ranging from 5 to 10 years. Dichotomous variables were compared using the Mantel-Haenszel (MH) method, and continuous variables were compared using the inverse variance (IV) method. The random effects model and the fixed effects model were used. Meta-analyses showed that short implants had a poorer survival rate than longer implants (P = 0.008). Short implants were associated with lower MBL than longer implants (P < 0.001). The biological complications of short implants were lower (P < 0.001) and the technical complications were higher, than those of long implants (P = 0.006).

CONCLUSIONS

The results indicate that although the survival rate of short implants in the maxilla may be lower than that of long implants, the survival rate of short implants in the mandible is similar to that of long implants, and short implants can result in a lower rate of biological complications. The conclusions should be interpreted with caution due to the limited numbers of participants and implants.

CLINICAL SIGNIFICANCE

When selecting the length of implants, surgeons should consider survival rate, the location of implant placement, their own clinical experience, and the incidence of complications.

Prosthetic Rehabilitation of the Posterior Atrophic Maxilla, Short (≤6 mm) or Long (≥10 mm) Dental Implants? A Systematic Review, Meta-analysis, and Trial Sequential Analysis: Naples Consensus Report Working Group A

PURPOSE

To compare the clinical and patient-reported outcomes of ≤6-mm implants with those of ≥10-mm implants placed after both lateral and transcrestal sinus floor elevation.

MATERIALS AND METHODS

Using PubMed (MEDLINE), EMBASE, and Cochrane, a literature search for randomized controlled trials was performed. All the outcome variables were evaluated through a quantitative meta-analysis, and the influence of other clinical covariates were determined with a metaregression. For the survival outcomes, trial sequential analysis (TSA) was performed to adjust results for type I and II errors and to analyze the power of the available evidence.

RESULTS

After full-text reading, 12 studies were included in the analyses. No statistically significant difference was found after 3 years between the 2 study groups (P = 0.36). Short implants displayed fewer biological complications (P = 0.05), less marginal bone loss (MBL) from implant placement (P < 0.01), and reduced surgical time and treatment cost. However, long implants showed a statistically significant smaller number of prosthetic complications (P = 0.03). TSA confirmed the results of the meta-analysis, revealing that additional studies are needed due to low statistical power of the available evidence.

CONCLUSION

The placement of short implants is a predictable option in treating patients with maxillary atrophy up to a 3-year follow-up. Studies with a longer observational period are needed to study the long-term performance of these implants.

Short implants (5-8 mm) vs long implants (≥10 mm) with augmentation in atrophic posterior jaws: A meta-analysis of randomised controlled trials

The aim of this systematic review was to compare the survival rate, marginal bone loss changes and complications between short implants (5-8 mm) and long implants (≥10 mm) with a bone-augmented procedure in the posterior jaw. An electronic search of the MEDLINE (PubMed), Embase and Cochrane Library databases through September 2018 was done to identify randomised controlled trials (RCT) assessing short implants and long implants with at least a 1-year follow-up period after loading. A quantitative meta-analysis was conducted on the survival rate, marginal bone loss changes and complications. Ten RCTs met the inclusion criteria. There were no significant differences in the survival rate (RR: 1.01; 95% CI: [0.99, 1.03]; P = .32) and complications (RR: 0.48; 95% CI: [0.20, 1.17]; P = .11) between the two groups. Compared with the long implant group, the short implant group had a lower marginal bone loss change, and the effect measure was significant (mean difference: -0.13; 95% CI: [-0.20, -0.06]; P < .05). This systematic review showed no difference between the survival rates and complications of short implants (5-8 mm) and long implants (≥10 mm). The marginal bone loss changes in short implants are lower than those in long implants.

Fifteen-Year Follow-up of Short Dental Implants in the Completely Edentulous Jaw: Submerged Versus Nonsubmerged Healing

PURPOSE

Short implants are a minimally invasive alternative in the management of alveolar bone atrophy. This study aimed to assess the influence of the surgical approach (1-stage vs 2-stage) on the 15-year survival and marginal bone loss of short implants in a fixed complete denture.

MATERIALS AND METHODS

A retrospective clinical study was conducted in a single private dental clinic that included short implants placed between January 2001 and December 2002.

RESULTS

Forty-one short implants supported 18 screw-retained complete dentures. The mean follow-up time was 15 ± 3 years. The surgical approach (1-stage vs 2-stage) did not significantly affect implant survival and marginal bone loss. The implant survival rate was 90.2%.

CONCLUSIONS

Short dental implants could be predictably indicated to support fixed complete dentures. The implants could be placed through a 1- or 2-stage surgery.

Descriptive retrospective study analyzing relevant factors related to dental implant failure

Background

The objective of this retrospective descriptive study was to analyze the characteristics of incident reports provided by dentists while using a specific brand of dental implants.

Material and Methods

The study was carried out in collaboration with Oxtein Iberia S.L.®, with the company providing access to the incident database in order to evaluate the characteristics of incidents from January 2014 to December 2017 (a total of 917 over four years). The data sheet recorded different variables during each of the stages of implant treatment, from initial implant placement to subsequent prosthetic rehabilitation. These variables included age, sex, systemic pathologies, smoking habits, bone quality, implant type, prosthesis type, and type of load applied, among others. SPSS Statistics was used to perform statistical analysis of the qualitative variables (univariate logistic regressions, χ2 test, Haberman's adjusted standardized residuals).

Results

The total study sample consisted of 44,415 implants shipped from Oxtein® warehouses on the dates indicated, of which 917 implants (2.1%) were flagged due to reports of lack of primary stability, failed osseointegration, or implant failure within one year of placement. When analyzing incident reports, it was observed that 61.6% of incidents occurred in male patients, compared to 38.4% in female patients. The average age of patients in the reported cases was 56.12 ± 12.15 years. A statistically significant correlation was discovered between incidents of implant failure and tobacco use, diabetes, heart disease, poor oral hygiene, previous infection, poor bone quality, and bruxism (p < 0.05). A (statistically significant) higher rate of incidents was also observed in tapered, internal connection, Grade IV titanium, narrow, and short implants.

Conclusions

Analysis of these implants reveals a higher rate of complication in short, tapered, internal connection and narrow-diameter implants. These data can help and encourage clinicians to use the utmost surgical precautions when placing these implants.

Key words:Pharmacovigilance, Dental implant, Dental implant failure.

A Retrospective Multicenter Study on Short Implants With a Laser-Microgrooved Collar (≤7.5 mm) in Posterior Edentulous Areas: Radiographic and Clinical Results up to 3 to 5 Years

PURPOSE

We aimed to retrospectively evaluate the radiographic and clinical results and the success rate of short implants with a laser-microgrooved collar (≤7.5 mm) placed in the posterior areas after up to 3 to 5 years of function and the possible influence of several variables-such as gender, periodontitis, smoking habit, location, implant stability at placement, and prosthetic fixation design-on implant marginal bone loss (MBL).

MATERIALS AND METHODS

A chart review was used for this multicenter study, which involved 5 private dental clinics. All patients had been treated with short dental implants with a laser-microgrooved collar from January 2012 to December 2015.

RESULTS

A total of 174 patients (99 male and 75 female patients; mean age, 51.6 ± 2.8 years) with 254 implants were evaluated. Seven short implants failed. The cumulative success rate was 97.2%, without a statistically significant difference between implants placed in the posterior maxilla and mandible. The mean MBL was 0.18 ± 0.7 mm at the mesial aspect and 0.19 ± 0.6 mm at the distal aspect. No statistical relationships were found between MBL and gender, periodontitis, smoking habit, location, implant stability at placement, and prosthetic fixation design.

CONCLUSIONS

At the end of the 3- to 5-year follow-up period, short implants with a laser-microgrooved collar (≤7.5 mm) in the posterior areas yielded a relatively high cumulative success rate. The laser-microgrooved collar implant maintained stable marginal bone levels. No investigated variable was statistically associated with MBL.

A Finite Element Analysis to Compare Stress Distribution on Extra-Short Implants with Two Different Internal Connections

Background: The goal of this study was to analyze the stress distribution on two types of extra-short dental implants with 5 mm of length: An internal hexagon (IH) and morse taper connection (MT). Methods: The three-dimensional model was composed of trabecular and cortical bone, a crown, an extra-short dental implant and their components. An axial load of 150 N was applied and another inclined 30° with the same magnitude. Results: Stress concentrations on the IH implant are observed in the region of the first threads for the screw. However, in the MT implant the highest stress occurs at the edges of the upper implant platform. Conclusions: In view of the results obtained in this study the two types of prosthetic fittings present a good stress distribution. The Morse taper connections presented better behavior than the internal in both loading configurations.

Mechanical fatigue behaviour of different lengths screw-retained restorations connected to two designs prosthetic connection level

The aim of this work is to compare the mechanical fatigue behaviour of different crown heights of single crown implant restorations made over two different internal hexagonal titanium dental implant connection levels. Two different groups of internal hexagonal connection were studied: (a) TL group (N = 26) included implants with a transmucosal connection (12.2 mm height and 4.8 mm width) and (b) BL group (N = 26) composed by implants at a bone level connection (10 mm height and 3.8 mm width). Two subgroups (N = 13) were established for each connection level according to crown heights (TL10 = 10 mm, TL15 = 15 mm, BL12 = 12 mm, BL17 = 17 mm). Dynamic load tests were carried out according to ISO Norm 14801. Failed samples and fracture surfaces were analysed with an optical and scanning electron microscope (SEM). The fatigue limit and the fatigue strength degradation (fatigue strength exponent) decreases with increasing crown height (5 mm) in both groups of internal hexagonal titanium dental implant connection levels. Consequently, the mechanical integrity of internal hexagonal dental implants varies with the height of the crown. An increase of 5 millimetres in the crown height appears to significantly decrease the fatigue life of both types of dental implants.

Is there an effect of crown-to-implant ratio on implant treatment outcomes? A systematic review

OBJECTIVES

High crown-to-implant ratios may lead to complications due to unfavorable occlusal forces, including nonaxial forces, on the bone surrounding the neck of the implant and within the connection of the crown and implant itself. The aim of this study was to perform a systematic review on the influence of crown-to-implant ratio of single-tooth, nonsplinted, implants on biological and technical complications.

MATERIALS AND METHODS

MEDLINE (1950-January 2018), EMBASE (1966-January 2018), and Cochrane Central Register of Controlled Trials database (1800-January 2018) were searched to identify eligible studies. Inclusion criteria were as follows: crown-to-implant ratio of single-tooth, nonsplinted, implant-supported restorations in the posterior maxilla or mandible and follow-up of at least 1 year. Main outcome measures were as follows: implant survival rate, marginal bone level changes, biological complications, and technical complications. Two reviewers independently assessed the articles. A meta-analysis was carried out for implant survival rate and peri-implant bone changes.

RESULTS

Of 154 primarily selected articles, eight studies fulfilled the inclusion criteria. Study groups presented a mean crown-to-implant ratio varying from 0.86 (with 10-mm implants) to 2.14 (with 6-mm implants). The meta-analysis showed an implant survival of more than 99% per year and mean peri-implant bone changes of <0.1 mm per year. Limited biological and technical complications were reported.

CONCLUSION

Data reviewed in the current manuscript on crown-to-implant ratio, ranging from 0.86 to 2.14, of single-tooth, nonsplinted, implants did not demonstrate a high occurrence of biological or technical complications.

Primary and Secondary Stability of Single Short Implants

PURPOSE

This prospective cohort study assessed the effect of bone quality on the primary and secondary stability of single short implants placed in the posterior region.

MATERIALS AND METHODS

A total of 39 short implants (4.1 × 6-mm long) were placed in the posterior region of the maxilla or mandible in 18 patients. Bone quality was classified into type I, II, III, or IV as assessed intrasurgically. Primary implant stability was measured with insertion torque, damping capacity (PTV values), and resonance frequency analysis (ISQ values). Secondary stability was measured by ISQ and PTV at abutment installation. Data were analyzed by using repeated-measures ANOVA and Tukey's test, Kruskall-Wallis test, and Spearman correlation tests.

RESULTS

Implants placed in bone type IV had significant lower insertion torque and ISQ values as well as higher PTV values than in bone types I to II (P < 0.05). The mean ISQ values were higher at abutment installation than at implant placement (P < 0.05), regardless the bone type. The assessment methods of implant stability showed a moderate correlation.

CONCLUSIONS

Bone quality influences both the primary and secondary stability of single short implants in the posterior region.

Meta-analysis of randomized clinical trials comparing clinical and patient-reported outcomes between extra-short (≤6 mm) and longer (≥10 mm) implants

AIM

To compare the clinical outcomes of ≤6 mm extra-short implants (test group) versus ≥10 mm long implants (control group), with and without bone augmentation procedures.

MATERIALS AND METHODS

A systemic literature search of randomized clinical trials was performed using the PubMed (MEDLINE) and EMBASE databases. A quantitative meta-analysis was conducted to compare all the outcome variables. Meta-regression analysis determined the effect of bone augmentation procedures and the influence of other clinical covariates on the results.

RESULTS

Eighteen studies comprising 1,612 implants (793 extra-short and 820 long implants) were selected for the meta-analysis. No statistically significant difference in the survival rate was observed at 1 and 3 years (p > 0.05). Extra-short implants displayed less marginal bone loss (MBL) from both implant placement time points (1 and 3 years) and prosthetic placement (1 year), as well as less biological complications, surgical time and treatment cost (p < 0.05). Contrarily, a statistically significant small number of prosthetic complications were reported with long implants (p < 0.05).

CONCLUSIONS

Placement of extra-short implants (≤6 mm) presented as an equivalent option in the treatment of patients with an atrophic posterior arch up to 3-year follow-up. However, the long-term effectiveness of extra-short dental implants remains to be further studied.

Long-term follow-up of single crowns supported by short, moderately rough implants-A prospective 10-year cohort study

OBJECTIVES

To evaluate prospectively the clinical and radiographic outcomes after ten years of short (6 mm) implants with a moderately rough surface supporting single crowns in the posterior region.

MATERIAL AND METHODS

Forty 6 mm modified sandblasted large-grit acid-etched (mod-SLA), soft tissue level implants were installed in the distal segments of 35 consecutive patients. After 6 weeks of healing, abutments were tightened, and single porcelain-fused-to-metal crowns were cemented. Implant survival, marginal bone loss, and clinical crown/implant ratio were evaluated at various time intervals up to 10 years after loading.

RESULTS

Two out of the 40 implants were lost before loading, one implant was lost after 7 years because of peri-implantitis. One patient with two implants died and was excluded from analysis. Two patients did not come at the 10-year follow-up and were considered as drop out (2 implants). The survival rate was 91.7% (n = 36). Thirty-three implants were available for marginal bone loss evaluation. A mean marginal bone loss after 10 years of function was 0.8 ± 0.7 mm. Between 5 and 10 years, the loss was 0.2 ± 0.4 mm. No technical complications were registered during the 10-year period. The clinical crown/implant ratio increased with time from 1.6 at the delivery of the prosthesis to 2.0 after 10 years of loading with no increase between 5 and 10 years.

CONCLUSION

Short (6 mm) implants with a moderately rough surface supporting single crowns in the posterior region and loaded after 6-7 weeks maintained full function for at least 10 years with low marginal bone resorption.

Short implants versus longer implants with maxillary sinus lift. A systematic review and meta-analysis

This study compared the survival rate of dental implants, amount of marginal bone loss, and rates of complications (biological and prosthetic) between short implants and long implants placed after maxillary sinus augmentation. This systematic review has been registered at PROSPERO under the number (CRD42017073929). Two reviewers searched the PubMed/MEDLINE, Embase, LILACS, and Cochrane Library databases. Eligibility criteria included randomized controlled trials, comparisons between short implants and long implants placed after maxillary sinus augmentation in the same study, and follow-up for >6 months. The Cochrane Collaboration's tool for assessing the risk of bias in randomized trials was used to assess the quality and risk of bias of the included studies. The search identified 1366 references. After applying the inclusion criteria, 11 trials including 420 patients who received 911 dental implants were considered eligible. No significant difference was observed in the survival rate [p = 0.86; risk ratio (RR): 1.08; 95% confidence interval (CI): 0.46-2.52] or in the amount of marginal bone loss (p = 0.08; RR: -0.05; 95%CI: -0.10 to 0.01). However, higher rates of biological complications for long implants associated with maxillary sinus augmentation were observed (p < 0.00001; RR: 0.21; 95%CI: 0.10-0.41), whereas a higher prosthetic complication rate for short implants was noted (p = 0.010; RR: 3.15; 95%CI: 1.32-7.51). Short implant placement is an effective alternative because of fewer biological complications and similar survival and marginal bone loss than long implant placement with maxillary sinus augmentation. However, the risk of mechanical complications associated with the prostheses fitted on short implants should be considered.

Evaluation of the Surrounding Ring of Two Different Extra-Short Implant Designs in Crestal Bone Maintanence: A Histologic Study in Dogs

The aim of this study was to compare the implant stability and bone resorption and formation of two different extra-short implant designs with different diameter rings placed in a dog´s maxilla. Thirty-six extra-short, 5 mm diameter × 4 mm length (Short DM^®, Bioner Sistemas Implantológicos, Barcelona, Spain), delayed implants were placed in each hemimaxilla of six dogs at the bone crest level. Eighteen implants of each design (wide and narrow ring) were installed. After 8 and 12 weeks of healing, histomorphometric analyses of the specimens were carried out to measure the crestal bone level values and the tissue thickness around the wide and narrow ring implant designs. In the microscopic analysis, less buccal bone resorption was observed in the narrow ring implants with a statistical significance (p < 0.001). For the peri-implant tissue thickness, the distance from the implant shoulder to the external portion of the epithelium was significantly higher for the implants installed with a wide ring with statistical significance (p < 0.001). Our findings suggest that the amount of peri-implant tissues (crestal bone loss) after remodeling over a period of 12 weeks was smaller in the narrow ring extra-short implant installed in the healed maxilla, compared with the wide ring extra-short implants.

Do short implants have similar survival rates compared to standard implants in posterior single crown?: A systematic review and meta-analysis

BACKGROUND

Short implants have been presented as an option for posterior rehabilitation in cases of poor bone height.

PURPOSE

To compare the survival rate of short implants and standard implants when used in posterior single crowns, in addition to reporting marginal bone loss, prosthetic failures, and surgical complications.

MATERIALS AND METHODS

Electronic search (PubMed, LILACS, Cochrane Library, Scopus, and Web of Science) and hand search were performed to identify all randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that evaluated both short and standard implants in posterior single crowns.

RESULTS

Out of 345 articles identified by both electronic and hand search, four studies were selected (one CCT and three RCTs). The meta-analysis for the survival rate showed that there was no significant difference between the short implants and the standard ones (P = 1.00; RR:1.00; CI:0.97-1.03) performed with three RCTs for a one-year follow-up. The mean marginal bone loss ranged from 0.1 mm to 0.54 mm. Only one study reported the presence of prosthetic failures and surgical complications.

CONCLUSIONS

The survival rate of short implants was similar to the standard ones in posterior single crowns, for the one-year follow-up period. They also presented low surgical complications, prosthetic failures and marginal bone loss, being a predictable treatment for single rehabilitation in posterior tooth loss.

Controversies in Implant Surgery

Dental implants are a mainstream treatment protocol to replace missing teeth. Patient and clinician demands have led to shorter length and narrower diameter implants, immediately placed implants into infected sites, and the use of implants in children. This article reviews some of the controversial topics in implant dentistry, and presents the evidence that supports and challenges these newer techniques. Because long-term studies are often not available, especially for implants in infected sites, mini implants, and implants in the growing patient, the field continues to evolve.

Dental Implants

Systematic reviews of literature over the period between 2008 and 2017 are discussed regarding clinical evidence for the factors affecting survival and failure of dental implants. The factors addressed include publication bias, tooth location, insertion torque, collar design, implant-abutment connection design, implant length, implant width, bone augmentation, platform switching, surface roughness, implant coatings, and the use of ceramic materials in the implant body and abutment.

Prosthetic Rehabilitation of the Partially Edentulous Atrophic Posterior Mandible with Short Implants (≤ 8 mm) Compared with the Sandwich Osteotomy and Delayed Placement of Standard Length Implants (> 8 mm): a Systematic Review

Objectives

Test the hypothesis of no difference in prosthetic rehabilitation of the partially edentulous atrophic posterior mandible with short implants (≤ 8 mm) compared with the sandwich osteotomy and delayed placement of standard lengths implants (> 8 mm).

Material and Methods

A MEDLINE (PubMed), Embase and Cochrane library search in combination with a hand-search was conducted by including studies published in English. No year of publication restriction was applied.

Results

Six randomized controlled trials characterized by low or moderate risk of bias fulfilled the inclusion criteria. There were no statistically significant differences (P > 0.05) in the survival rate of suprastructures and implants between the two treatment modalities after one year. Sandwich osteotomy and delayed implant placement demonstrated statistically significant higher long-term peri-implant marginal bone loss as well as biological and technical complications compared with short implants (P < 0.0001). Moreover, patients significantly favoured prosthetic rehabilitation with short implants (P < 0.0001).

Conclusions

Short implants and the sandwich osteotomy with delayed placement of standard length implants appear to result in predictable outcomes in terms of high survival rate of suprastructures and implants after prosthetic rehabilitation of the partially edentulous atrophic posterior mandible. However, further long-term randomized controlled trials assessing donor site morbidity, an economic perspective, professional and patient-related outcome measures with the two treatment modalities are needed before definite conclusions can be provided about the beneficial use of short implants for prosthetic rehabilitation of the partially edentulous atrophic posterior mandible compared with the sandwich osteotomy and delayed placement of standard length implants.

Clinical and Radiographic Evaluation of Short Implants Placed in the Posterior Mandible: A 1-Year Pilot Split-Mouth Study

In many cases, due to anatomical limitations, the placement of regular-length implants cannot be facilitated without the performance of advanced surgical procedures. However, these are associated with morbidity, prolonged treatment time, and costs. To overcome such disadvantages, short implants were introduced. The aim of this prospective pilot split-mouth study was to compare the clinical outcome between short implants (7 mm) and regular-length (≥10 mm) implants placed in the posterior mandible after 1 year of prosthetic delivery. Ten patients received 4 implants in the posterior mandible. Two short implants were placed in one side and 2 regular-length implants were placed contralaterally. These were restored by means of splinted screw-retained metal-ceramic crowns. Marginal bone loss (MBL) and soft-tissue parameters were compared. No implant failed. Both types of implants showed success rates of 90% and survival rates of 100%. From prosthetic delivery to 1 year post-loading a bone gain of +0.29 mm for short implants and +0.19 mm for regular-length implants was present without showing any statistically significant differences in MBL between the 2 implant types ( P > .05). Bleeding on probing, clinical attachment level, probing depth, and crown-to-implant ratio did not show any statistically significant differences between the 2 implant lengths ( P > .05). One case of chipping occurred in the regular-length implant group, leading to a prosthetic survival rate of 95%. Short implants showed a prosthetic survival rate of 100%. After 1 year, short implants showed comparable clinical outcomes to that of regular-length implants, making them a viable treatment option in the posterior mandible.

Short Dental Implants (≤7mm) Versus Longer Implants in Augmented Bone Area: A Meta-Analysis of Randomized Controlled Trials

Aim:

The aim of this systematic review was to compare the survival rate and the marginal bone loss between short implants (≤7 mm) placed in the atrophic area and longer implants placed in the augmented bone area of posterior regions of maxillaries.

Methods:

Electronic search using three databases was performed up to May 2017 to identify Randomized Controlled Trials (RCT) assessing short implants survival with a minimal follow-up of 12 months post-loading. For the meta-analysis, a Risk Difference (RD) with the 95% Confidence Interval (CI) was used to pool the results of implant failure rate for each treatment group. For the marginal bone changes, Mean Differences (MD) with 95% CI were calculated.

Results:

Seven randomized controlled trials met the inclusion criteria, being included in qualitative and quantitative analyses. The RD between the short implant group and the control group was -0.02 (95% CI: -0.04 to 0.00), I²=0 and Chi²=3.14, indicating a favorable survival rate for short implant, but with no statistical significance (p=0.09).

Discussion:

For marginal bone loss, the mean difference was -0,13 (95%CI: -0.22 to -0.05), favoring the test group with statistical significance (p=0.002). The studies showed more heterogeneity for bone loss compared to survival rate. Short and longer implants showed similar survival rates after one year of loading, however the marginal bone loss around short implants was lower than in longer implants sites.

Conclusion:

Placement of implants ≤7 mm of length was found to be a predictable alternative for the rehabilitation of atrophic posterior regions, avoiding all the disadvantages intrinsic to bone augmentation procedures.

Five-Year Survival of Short Single-Tooth Implants (6 mm): A Randomized Controlled Clinical Trial

The aim of the present study was to evaluate whether 6-mm dental implants in the posterior segments of either jaw perform equally well in terms of clinical and radiographic outcomes when compared with 10-mm implants after 5 y of loading. Patients with single-tooth gaps in the posterior area who were scheduled for implant therapy were randomly assigned to a group receiving either a 6- or 10-mm implant. After a healing period of 10 wk, implants were loaded with a screw-retained single crown and followed up at yearly intervals. Of 96 patients, 86 could be recalled after 5 y. The implant survival rates amounted to 91% (95% confidence interval: 0.836 to 0.998) for the 6-mm group and 100% for the 10-mm group ( P = 0.036). Median crown-to-implant (C/I) ratios were 1.75 (interquartile range [IQR], 1.50 to 1.90) for the 6-mm group and 1.04 (IQR, 0.95 to 1.15) for the 10-mm group, whereas the median marginal bone levels measured −0.29 mm (IQR, −0.92 to 0.23) for the 6-mm group and −0.15 mm (IQR: −0.93 – 0.41) for the 10-mm group after 5 y. The C/I ratio turned out to be statistically significant ( P < 0.001), whereas marginal bone levels showed no significant difference between the groups. The 6-mm implants exhibited significantly lower survival rates than the 10-mm implants over 5 y, whereas there was no difference between upper and lower jaws in terms of survival ( P = 0.58). Lost implants did not show any sign of marginal bone loss or peri-implant infection previous to loss of osseointegration. High C/I ratio and implant length had no significant effect on marginal bone level changes or technical and biological complications (German Clinical Trials Registry: DRKS00006290).