Mini-Implants, Mega Solutions: A Case Series

Influence of dental implant/mini-implant design on stress distribution in overdentures: a systematic review

PURPOSE

Critically evaluate the existing literature and answer the question, "Does the dental implant/mini-implant design influence the stress distribution in prosthetic overdentures according to finite element analysis?".

METHODS

This systematic review was registered in the Open Science Framework (osf.io/2bquj) and followed the PRISMA protocols. The custom search strategy was applied to 4 databases. In vitro experimental studies that evaluated the influence of dental implant/mini-implant design on stress distribution in overdentures by FEM, without time and language restrictions, were included. The selection process was carried out in two stages by two reviewers independently. Risk of bias analysis was performed by a checklist of important parameters.

RESULTS

Sixty articles were evaluated by their title and abstract, four were selected for full reading, three were relevant, and nine were included by additional search. The 12 studies have a low risk of bias. The meta-analysis could not be performed due to the heterogeneity of the data (implant type, design variation, load intensity, and direction).

CONCLUSION

It can be inferred from the evaluated literature that design modifications influence the stress distribution, but as the FEM presents limitations inherent to the in vitro study, clinical trials are necessary to infer the effectiveness of the modifications. It should be noted that there is no consensus on which is the best thread design and that implants with a very narrow diameter are subject to the highest stress concentration.

Effect of Splinting on Orthodontic Mini-Implant Tipping and Bone Histomorphometric Parameters: An In Vivo Animal Model Study

This study aimed to address the stability of orthodontic mini-implants submitted to an immediate orthodontic functional load, in splinted or unsplinted conditions, further characterizing the histomorphometric parameters of the neighboring bone tissue, in an in vivo experimental model. Mini-implants (1.4 × 6.0 mm) were placed in the proximal tibia of New Zealand White rabbits and immediately loaded with a 150 g force. Tissue healing was characterized within 8 weeks. Microtomography was used to assess the mini-implants' tipping and bone histomorphometric indexes. Loaded implants were evaluated in splinted and unsplinted conditions, with data being compared to that of unloaded mini-implants with the Kruskal-Wallis nonparametric test, followed by Dunn's multiple comparison tests. The splinting of mini-implants submitted to immediate orthodontic loading significantly reduced the tipping to levels similar to those of unloaded mini-implants. Immediate loading further increased the histomorphometric indexes associated with bone formation at the peri-implant region, in both splinted and unsplinted conditions, with no significant differences between the tension and compression regions. Accordingly, within this experimental setting, splinting was found to lessen tipping and mini-implants' displacement, without affecting the increased bone formation at the peri-implant region, induced by a functional orthodontic load.

Dental mini-implant designs to support overdentures: Development, biomechanical evaluation, and 3D digital image correlation

STATEMENT OF PROBLEM

Custom mini-implants are needed for edentulous patients with extensive mandibular deficiencies where endosteal placement is not possible. However, the best design for these mini-implants is unclear.

PURPOSE

The purpose of this in vitro study was to develop 2 dental mini-implant designs to support mandibular overdentures and evaluate the effect of their geometries on primary stability and stress distribution.

MATERIAL AND METHODS

Two mini-implant designs were developed with changes in the shape, size, and arrangement of threads and chamfers. The experimental mini-implants were made of Grade V titanium alloy (Ti-6Al-4V), (Ø2.0×10 mm) and submitted to a nanoscale surface treatment. Thirty mini-implants (n=10) were placed into fresh swine bones: experimental-threaded, experimental-helical, and a commercially available product model (Intra-Lock System) as the control. The biomechanical evaluations of the experimental mini-implants were compared with those of the control in terms of primary stability, through insertion torque (IT), and with the pullout test. The analysis of stress distribution was performed by using the method of 3D digital image correlation under 250-N axial load and 100-N oblique (30-degree angled model) load. The data were analyzed by ANOVA and the Tukey HSD test (α=.05).

RESULTS

The IT and pullout test presented a statistically significant difference for all mini-implants (P<.05), with higher IT for the experimental-threaded and maximum pullout force for the control, followed by threaded (P=.001) and helical (P=.001). Regarding the 3D digital image correlation, a lower incidence of stress was found in the cervical third for all mini-implants. No statistically significant differences were found between the designs evaluated (P>.05).

CONCLUSIONS

Comparing the experimental mini-implants with the commercially available control, the experimental-threaded model presented greater primary stability, and all mini-implants showed less stress in the cervical third.

Three-Dimensional Radiographic Outcome of Free-Handed Flaplessly Placed Mini Dental Implants in Edentulous Maxillae after 2-Years Function

Background: Free-handed, flaplessly placed mini dental implants (MDIs) are a valuable, more affordable and minimally invasive treatment to support overdentures in fully edentulous jaws, especially for medically compromised patients. However, critical 3D radiographic evaluation is lacking. This multicenter prospective case series assessed clinical outcome and carried out 3D- cone-beam computerized tomography (CBCT) analysis of free-handed flaplessly placed one-piece maxillary MDIs by an experienced maxillofacial surgeon. Methods: Thirty-one patients suffering from an ill-fitting maxillary denture relating to compromised bone volume (as confirmed on CBCT), with a dentate mandible, were selected. They received 5–6 MDIs free-hand flaplessly placed and mentally guided with preoperative CBCT. Final connection and attachment activation took place six months later. After two years each implant was individually assessed with CBCT for perforations on eight sites. Implant survival, prosthetic failure, clinical stability and sinus/nasal complaints were registered after three years. Results: 32/185 (17.3%) MDIs failed during the provisional loading with non-activated attachments; 17 replacements in 10 patients were performed. Of the 170 actively loaded 170 MDIs, 82.3% survived and 27/31 prostheses (87%) were fully functional. In total 98/170 MDIs showed no perforation. Based on 1360 CBCT observations, 231 perforations (16.9%) were registered. Of most perforations 37 (25%) were observed at the apical tip and 37 were positioned (21%) into the sinus/nasal cavity, although without clinical complaints. Conclusions: Given the compromised population, the minimally invasive procedure and the low treatment cost involved, a failure rate of 17% is substantial, however clinically acceptable given the critical bone condition. However, even in experienced surgical hands, freehanded and flapless placement yield a high risk for implant perforation, although this did not necessarily lead to complications.

Endangered Pinzgauer cattle subtype Jochberger Hummel are genetically distinct

Autochthonous cattle breeds are an important part of cultural heritage and reservoir of genetic diversity. Usually, such breeds have been selected over centuries and reflect adaptation to a specific local environment and human demands. However, owing to low effective population size in conjunction with increased inbreeding and genetic drift, many of these lineages are threatened with extinction. The Jochberger Hummel ('Jochberger Bumblebee') is such an endangered subtype of the Pinzgauer cattle originating from a single polled female calf. To evaluate the suspected uniqueness of this subtype and to assess whether it should be kept separate or managed together with the Pinzgauer cattle as one population, I examined the genetic diversity in a set of 844 cattle (Angus, Charolais, Holstein, Jochberger Hummel, Pinzgauer, Uckermaerker and Tux-Zillertaler) using principal component and biogeographical ancestry analysis. The analysis showed that the Jochberger Hummel is still a distinct subtype of Pinzgauer cattle with less than 5% admixture and a low inbreeding coefficient.

Comparison of patient satisfaction with mini-implant versus standard diameter implant overdentures: a systematic review and meta-analysis of randomized controlled trials

Mini-implants have certain advantages over standard size implants which are being tested in various randomized controlled trials. This systematic review and meta-analysis aims to compare conventional implant overdentures to mini-implant-retained overdentures as regards to patient satisfaction. Electronic databases were searched for eligible studies data required were extracted. The extracted data were analyzed using non-Cochrane mode in RevMan 5.0 software. The heterogeneity between the studies was assessed using Forest plot, I² statistics, and chi-square test with a statistical P value of less than 0.10 to indicate statistical significance. Random-effect models were used in case of moderate heterogeneity. Four studies were included for the review and two for meta-analysis. Two studies in 177 patients comparing quality of life with mini or standard diameter implants showed a pooled result of −4.76 [−6.48, −3.04] favoring the use of mini-implants. The results for other outcomes were incomputable due to inadequate studies. GRADE approach was used for quality of life, and the strength of evidence was observed to be “low”. Mini-implant-supported overdentures had better patient satisfaction levels compared to standard diameter implant overdenture. There is definite lack of evidence to support the use of mini-implants for overdentures.