Analysis of the influence of implant shape on primary stability using the correlation of multiple methods

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.

Influence of Implant Macro-Design, -Length, and -Diameter on Primary Implant Stability Depending on Different Bone Qualities Using Standard Drilling Protocols-An In Vitro Analysis

(1) Background: Primary implant stability is vital for successful implant therapy. This study explores the influence of implant shape, length, and diameter on primary stability in different bone qualities. (2) Methods: Three implant systems (two parallel-walled and one tapered) with various lengths and diameters were inserted into polyurethane foam blocks of different densities (35, 25, 15, and 10 PCF) using standard drilling protocols. Primary stability was assessed through insertion torque (IT) and resonance frequency analysis (RFA). Optimal ranges were defined for IT (25 to 50 Ncm) and RFA (ISQ 60 to 80). A comparison of implant groups was conducted to determine adherence to the optimal ranges. (3) Results: Implant macro-design, -length, and -diameter and bone block density significantly influenced IT and RFA. Optimal IT was observed in 8/40 and 9/40 groups for the parallel-walled implants, while the tapered implant achieved optimal IT in 13/40 groups (within a 25-50 Ncm range). Implant diameter strongly impacted primary stability, with sufficient stability achieved in only one-third of cases despite the tapered implant's superiority. (4) Conclusions: The findings highlight the need to adapt the drilling protocol based on diverse bone qualities in clinical practice. Further investigations should explore the impact of these adapted protocols on implant outcomes.

Comparison of mechanical stability of mini-screws with resorbable blasting media and micro-arc oxidation surface treatments under orthodontic forces: An in vitro biomechanical study

INTRODUCTION

The aim of this study was to compare the primary stability of mini-screws with different surface treatments such as resorbable blasting media (RBM) and micro-arc oxidation (MAO) under in vitro orthodontic forces.

MATERIAL AND METHODS

Thirty-six self-drilling TiAl6V4-ELI grade 23 titanium alloy 1.6×8mm mini-screws were inserted into polyurethane foam blocks and divided into three groups according to surface properties: machine surface (MS), RBM-treated, and MAO-treated. An orthodontic force of 150g was applied to the mini-screws using NiTi coils. Maximum insertion torque (MIT) and maximum removal torque (MRT) were measured with a digital torque screwdriver during insertion and removal. For each mini-screw, stability measurements were made with the Periotest M device at day 0 and weeks 1, 2, 4, 8, and 12.

RESULTS

Significant differences in MIT were observed between all groups in pairwise comparisons (P<0.001) with the highest value in the MAO-treated group and the lowest in the MS group. The mean MRT values differed in all three groups (P=0.001). In pairwise comparisons of MRT, only the difference between MS group and RBM-treated group was significant. The highest value was observed in the RBM-treated group, while the lowest value was observed in the MS group. Periotest values were significantly higher in the MAO-treated group than the RBM-treated group at weeks 8 and 12. A positive significant correlation was found between MIT and MRT in all groups. No significant correlation was found between MIT, MRT and Periotest values in all groups.

CONCLUSION

RBM-treated group was significantly higher than the MS group in MIT and MRT values. According to Periotest values, RBM-treated group was found to be significantly more stable than the MAO-treated group at weeks 8 and 12. Therefore, RBM surface treatment was found to be more favourable than other surfaces to increase success rate in clinical applications.

Dental implant failure rates with low insertion torque with a nonsubmerged surgical approach: A retrospective clinical study

BACKGROUND

It is currently unclear if a low insertion torque (IT) should prompt a clinician to submerge the dental implant at time of placement.

PURPOSE

This study aimed to analyze implant failure rates and marginal bone loss (MBL) as a function of IT and surgical approach.

MATERIALS AND METHODS

A total of 197 patients who had received 295 Mozo Grau (MG) implants were included in this study. The healing of submerged or nonsubmerged implants was evaluated in regular IT (≥20-25 Ncm) or low IT (<20-25 Ncm) cases. Implant failure and MBL were evaluated before prosthesis placement and at 6 and 12 months after functional loading with generalized estimating equations.

RESULTS

The overall 12-month implant failure rate was 4.8% (95% confidence interval [CI]: 2.7%-8.2%). When successful at 12 months, dental implants placed with low IT and nonsubmerging had the same MBL as implants dental implants placed with other approaches (mean difference = -0.02 mm; 95% CI -0.05 to 0.02). Low IT combined with nonsubmerging of the dental implant was associated with a 30-fold increased odds for dental implant failure (95% CI: 3.8-236.6).

CONCLUSION

low IT and nonsubmerged healing was associated with a high failure rate.

An experimental study on the effects of the cortical thickness and bone density on initial mechanical anchorage of different Straumann® implant designs

Background

The aim of the current study was to comparatively assess the primary stability of different Straumann® implant designs (BLX, Straumann Tapered Effect, Bone Level Tapered, and Standard Plus) via resonance frequency analysis by using an implant insertion model in freshly slaughtered bovine ribs with and without cortical bone. Tapered Effect (4.1 × 10 mm), Bone Level Tapered (4.1 × 10 mm), Standard Plus (4.1 × 10 mm), and BLX (4.0 × 10 mm) implants were inserted into the distal epiphysis on the longitudinal axis of the freshly slaughtered bovine ribs. As a control, implants with the same sizes were inserted into the proximal diaphysis. The stability of the implants was examined with resonance frequency analysis.

Results

BLX and Tapered Effect implants showed higher implant stability quotient values in both study and control groups. All implant systems showed a significant decrease of mechanical anchorage in the study group. BLX and Bone Level Tapered designs had a significantly lower loss of mechanical anchorage in the lack of cortical bone.

Conclusion

Both Tapered Effect and BLX designs could ensure sufficient initial stability; however, BLX implants could be an appropriate option in the lack of cortical bone and poor bone quality at the implant recipient site.

Clinical relevance

BLX is a novel implant system, which could be especially beneficial in the presence of spongious bone type at posterior maxillae.

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.

Effect of bone quality and quantity on the primary stability of dental implants in a simulated bicortical placement

OBJECTIVES

Conventional dental implants inserted in the molar region of the maxilla will reach into the sinus maxillaris when alveolar ridge height is limited. When surgery is performed without prior augmentation of the sinus floor, primary stability of the implant is important for successful osseointegration. This study aimed at identifying the impact of bone quality and quantity at the implantation site on primary implant stability of a simulated bicortical placement.

MATERIALS AND METHODS

In our in vitro measurements, bone mineral density, total bone thickness and overall cortical bone thickness were assessed by micro-computed tomography (μCT) of pig scapulae, which resembled well the bicortical situation found in human patients. Dental implants were inserted, and micromotion between bone and implant was measured while loading the implant with an axial torque.

RESULTS

The main findings were that primary implant stability did not depend on total bone thickness but tended to increase with either increasing bone mineral density or overall cortical bone thickness.

CLINICAL RELEVANCE

Limited bone height in the maxilla is a major problem when planning dental implants. To overcome this problem, several approaches, e.g. external or internal sinus floor elevation, have been established. When planning the insertion of a dental implant an important aspect is the primary stability which can be expected. With other factors, the dimensions of the cortical bone might be relevant in this context. It would, therefore, be helpful to define the minimum thickness of cortical bone required to achieve sufficient primary stability, thus avoiding additional surgical intervention.

Immediate non-submerged implants with laser-microtextured collar placed in the inter-radicular septum of mandibular molar extraction sockets associated to GBR: Results at 3-year

Background

The aim of the present study was to radiographically evaluate the vertical socket walls changes, and the peri-implant marginal bone remodelling, and clinicallly the soft tissues conditions around the non-submerged single implants placed into the inter radicular septum of mandibular molar sockets, associated with a collagen membrane, after 3 years of loading.

Material and Methods

Thirty patients underwent to placement of a non-submerged implants with a laser-microtextured collar into the inter radicular septum of mandibular molar fresh extraction sockets. A collagen membrane and the mucoperiosteal flap were adapted around the neck of the implants, leaving the laser-microtextured collar to heal in a transmucosal fashion.

Results

At the end of the follow-up period, no statistical differences were found for each radiographic measurements used for the examination of extraction sockets vertical bone changes. Compared to implants placement, at the end of the 3-year follow-up, the vertical radiographic mesial and distal peri-implant marginal bone levels showed a statistically significant gain of 0.9 (SD 0.5), and 1.0 mm (SD 0.6), respectively (P=0.037).

Conclusions

In mandibular fresh extraction sockets, the method of GBR around transmucosal implants with laser-microtextured surface placed into the interadicular septum may be used successfully to counteract the ridge remodelling.

Key words:Non-submerged implants, GBR, laser-microtextured collar.

Rationale for a reverse tapered body shift implant for immediate placement

Immediate implant placement holds considerable value, yet primary implant stability is often a critical factor. The aim of this study was to evaluate the stability, volumetric viability, and buccal gap size of reverse tapered body shift (RTBS) implants after immediate placement. Peak insertion torque measurements of two RTBS designs (apical 40% vs. apical 50%), relative to conventionally tapered implants, were assessed in simulated extraction sockets prepared in synthetic bone blocks. Additionally, the proximity of the RTBS implants to neighbouring teeth and anatomical structures, and the buccal gap distance were evaluated in human cadavers. The mean (± standard deviation) insertion torque was 12.00±1.40N•cm for the conventionally tapered implants (n=50), 35.36±2.74N•cm (n=50) for RTBS-1, and 48.20±2.90N•cm (n=50) for RTBS-2; the difference between designs was statistically significant (P<0.01). In total, 40 RTBS implants (20 per design) were placed in six cadaveric premaxillae. Only one locus was inappropriate for both RTBS implant designs, due to the proximity of neighbouring teeth. The average buccal gap for both implant designs was 2.8mm (P=0.104). The improved primary stability and increased buccal gap size with RTBS implants may enhance the feasibility of immediate placement. The study findings should be further validated in clinical trials.

Comparison of histomorphometry and microradiography of different implant designs to assess primary implant stability

OBJECTIVES

To contribute toward optimizing the long-term stability of dental implants. Our working hypothesis was that the degrees of immediate implant-bone contact, and hence of primary stability, would demonstrably differ between implant systems due to their different external geometries and thread designs (macro-design). This demonstration was provided in a bovine model (ex vivo) by employing and comparing histomorphometry and microradiography as evaluation methods.

MATERIALS AND METHODS

A total of 120 implants, representing six different implant thread designs, were inserted following the recommended surgical protocol in ribs of freshly slaughtered cattle. Twenty specimens of implants with surrounding bone were prepared per system and were divided into two equally sized groups of 60 specimens for analysis by either histomorphometry or micro-computed tomography. Data were analyzed by Mann-Whitney U test (P ≤ .05).

RESULTS

One of the implant systems, featuring a slight tapered external geometry and a progressive thread design, consistently revealed the most favorable bone-implant contacts in both histomorphometric and microradiographic evaluations. Overall, consistently higher values of bone-implant contact were obtained with the microradiographic than the histomorphometric approach, and this difference reached statistical significance in three of the six implant systems tested.

CONCLUSIONS

Progressive threads offering a bone-condensing effect can significantly help to maximize implant-bone contact percentages. Compared to histomorphometry, microradiography is likewise a suitable method to evaluate bone-implant contact, offering the additional benefits of being noninvasive and less time consuming.

Effect of implant design on the initial biomechanical stability of two self-tapping dental implants

BACKGROUND

This study evaluated the effect of two self-tapping implants on implant stability in immediate implantation.

METHODS

Two types of self-tapping implants, straight flute (STF) and spiral flute (SPF) designs, were studied. Two synthetic bone blocks with varying densities (0.32 g/cm³ and 0.16 g/cm³) were chosen to simulate the bone quality of the anterior maxilla. Insertion torque values were measured by a torque testing machine during implant insertion. Four biomechanical tests were performed: resonance frequency analysis was conducted using the Osstell device, and the strengths of screw push-in, lateral bending, and pull-out were evaluated using an MTS machine. The strength for each design feature was obtained by averaging the results of 10 trials. In total, 40 specimens were tested for each bone density. Statistical difference was determined by one-way analysis of variance followed by Bonferroni post hoc multiple tests between groups.

FINDINGS

The STF and SPF groups exhibited similar insertion torque values (p = 0.525 in low-density bone, and p = 0.99 in high-density bone). A significant difference (p < 0.001) was observed in the push-in test between the two groups when low-density bone was tested. The SPF group exhibited a significantly higher lateral bending force (p = 0.001) and a higher stiffness (p < 0.001) than the STF group in high-density bone. The SPF design attained higher (p < 0.001) ISQ numbers than the STF design, but all numbers were below 60.

INTERPRETATION

Implant stability can be influenced by the apical fixture design of self-tapping implants in immediate implantation.

Influence of an Alternative Implant Design and Surgical Protocol on Primary Stability

The purpose of thisin vitrostudy was to evaluate the influence of a new proposal of implant design and surgical protocol on primary stability in different bone densities. Four groups were tested (n=9): G1 - tapered, cone morse, Ø 4.3 mm x 10 mm in length (Alvim CM); G2 - experimental tapered; G3 - cylindrical, cone morse, Ø 4.0 mm x 11 mm in length (Titamax CM) and G4 - experimental cylindrical. The experimental implants were obtained from a design change in the respective commercial models. The insertion was performed in polyurethane (PU) blocks 0.24 g/cm3(20 pcf) and 0.64 g/cm3(40 pcf), according to different surgical protocols. The primary stability was measured by means of insertion torque (IT) and pullout test. Data were analyzed by ANOVA, Tukey's test (α=0.05) and Pearson's correlation. For IT and pullout, conventional and experimental implants showed no difference between them when inserted in the 20 pcf PU (p>0.05). In the 40 pcf PU, the modified implants exhibited greater IT (p<0.05) and lower pullout (p<0.05) compared to the respective conventional models. The implant design tested associated with the surgical protocol, positively influenced primary stability in higher density bones.

Correlation between Implant Geometry, Bone Density, and the Insertion Torque/Depth Integral: A Study on Bovine Ribs

During insertion of dental implants, measurement of dynamic parameters such as the torque-depth curve integral or insertion energy might convey more information about primary stability than traditional static parameters such as the insertion or removal torque. However, the relationship between these dynamic parameters, bone density, and implant geometry is not well understood. The aim of this investigation was to compare static and dynamic implant stability measurements concerning three different implant designs when implants were inserted into bovine bone ribs and dynamic parameters were collected using an instantaneous torque measuring implant motor. Standard implant osteotomies were created in segments of bovine ribs. After measuring the bone density using the implant motor, 10 cylindrical, 10 hybrid tapered-cylindrical, and 10 modified cylindrical implants were placed, and their primary stability was assessed by measuring the torque–depth curve integral, along with insertion and removal torque. The relationship between these quantities, bone density, and implant geometry was investigated by means of regression and covariance analysis. The regression lines describing the relationship between the torque–depth integral and bone density differed significantly from those describing the relationship between insertion torque, removal torque, and bone density for all three designs. The torque–depth curve integral provides different information about immediate primary stability than insertion and removal torque and in certain clinical conditions might be more reliable than these static parameters for assessing implant primary stability. Further research should be carried out to investigate the findings of the present study.

[Factors affecting osteointegration and the use of early functional load to reduce the duration of treatment in dental implantation]

The article presents literature data on the impact of the surface and shape of dental implants and early functional load with aesthetic and functional rehabilitation on osteointegration and stability of implants at various implantation terms.

The functional loading of implants increases their stability: A retrospective clinical study

PURPOSE

To assess the difference in the evolution of implant stability values, determined by resonance frequency analysis (RFA), between two groups of implants subjected to two different loading protocols: immediate and delayed.

MATERIALS AND METHODS

A retrospective clinical study was conducted, including a total of 93 implants placed in 38 patients. All implants corresponded to one of two models of the Klockner Implant System (Essential Cone and Vega) and were divided into two groups according to the loading protocol adopted: delayed loading in group A (>10 weeks) and immediate loading in group B (<48 hours). Implant stability was measured four times throughout the study period with a Penguin RFA device: implant placement (T0), definitive loading (T1), 6 months after loading (T2), and 12 months after loading (T3).

RESULTS

Implant stability quotient (ISQ) values showed a statistically significant increase in both groups after loading. In group A, the greatest increase in stability occurred between T1 and T2, whereas in group B, the greatest increase occurred between T0 and T1, coinciding in both cases with the period in which the implants were subjected to prosthetic loading.

CONCLUSIONS

The functional loading of implants increases their stability, as measured in ISQ values by RFA. Increases in ISQ values are greater during the months immediately following loading, which shows that immediate or early loading protocols are not only possible but can also be beneficial.

One-stage laser-microtextured implants immediately placed in the inter-radicular septum of molar fresh extraction sockets associated with GBR technique. A case series study

Background

The outcome of one-stage trans-mucosal immediate implants with simultaneous guided bone regeneration (GBR) technique has become highly predictable. Furthermore, when this approach is performed to place one-stage implants into the inter-radicular septum of fresh extraction sockets in the molar region, the risk of incorrect emergence profile and off-angle loading is reduced. The aim of the present study was to clinically evaluate the horizontal hard and soft tissue changes, and radiographically the vertical socket walls remodeling, and the early peri-implant marginal bone loss (EMBL) following the placement of immediate one-stage implants in the inter-radicular septum of molar fresh extraction sockets, associated with a collagen membrane.

Material and Methods

Twenty patients were selected to receive a one-stage implant with laser-microtextured collar surface into the inter-radicular septum of a fresh molar extraction sockets, associated with a simultaneous placement of a collagen membrane. Intraoral radiographs and model casts were used for the evaluation. Correlation between the amount of the keratinized tissue thickness (KTT) with EMBL was also analyzed.

Results

After 4 months, the vertical radiographic mesial and distal EMBL around implants was of 0.06 ±0.01 mm and 0.04±0.02 mm, respectively, with no statistically significant difference between T0 and T1 (P >0.05). No statistical differences were found also for each radiographic measure used for the examination of implant sites vertical bone changes (p >0.05). Clinically, horizontal changes of the bucco-lingual central width were found statistically significant (p<0.05), whereas no statistical differences were found for bucco-lingual mesial and distal width changes (p >0.05). In addition, no statistically significant correlation between EMBL and the amount of KTT was found (P >0.05).

Conclusions

Results suggest that the immediate placement of one-stage laser-microtextured implants could provide advantages in preserving the extraction socket's hard and soft tissue remodeling, and the peri-implant marginal bone level before the prosthetic loading. Key words:One-stage implant, laser-microtextured collar surface, GBR, collagen membrane.

Stability of tapered and parallel-walled dental implants: A systematic review and meta-analysis

BACKGROUND

Clinical trials have suggested that dental implants with a tapered configuration have improved stability at placement, allowing immediate placement and/or loading. The aim of this systematic review and meta-analysis was to evaluate the implant stability of tapered dental implants compared to standard parallel-walled dental implants.

MATERIALS AND METHODS

Applying the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement, randomized controlled trials (RCTs) were searched for in electronic databases and complemented by hand searching. The risk of bias was assessed using the Cochrane Collaboration's Risk of Bias tool and data were analyzed using statistical software.

RESULTS

A total of 1199 studies were identified, of which, five trials were included with 336 dental implants in 303 participants. Overall meta-analysis showed that tapered dental implants had higher implant stability values than parallel-walled dental implants at insertion and 8 weeks but the difference was not statistically significant. Tapered dental implants had significantly less marginal bone loss compared to parallel-walled dental implants. No significant differences in implant failure rate were found between tapered and parallel-walled dental implants.

CONCLUSIONS

There is limited evidence to demonstrate the effectiveness of tapered dental implants in achieving greater implant stability compared to parallel-walled dental implants. Superior short-term results in maintaining peri-implant marginal bone with tapered dental implants are possible. Further properly designed RCTs are required to endorse the supposed advantages of tapered dental implants in immediate loading protocol and other complex clinical scenarios.

Sinus augmentation and concomitant implant placement in low bone-density sites. A retrospective study on an undersized drilling protocol and primary stability

BACKGROUND

Recently, a torque-measuring micromotor has been shown to provide a reliable, quantitative intraoperative evaluation of bone density and implant primary stability. This may be particularly useful for determining bone quality of residual bone and consequently the most appropriate site preparation in the posterior maxilla, where bone often is of low density and quality.

PURPOSE

This work aimed to assess the medium-term success of implants placed during 1-stage sinus augmentations using an undersized drilling protocol. In case of low bone density, the relationship between residual bone height (RBH) and primary stability was also investigated.

MATERIALS AND METHODS

Clinical records of patients who underwent sinus augmentation and concomitant implant placement following a 12.5% undersized drilling protocol were retrospectively analyzed. In all patients, bone density measured intraoperatively was ≤ 0.45 g/cm³ . A minimum of 60 months of follow-up was required for inclusion.

RESULTS

Records of 106 patients who received 253 implants were reviewed. No significant difference in the implant success rate was found for patients who had less than 4 mm of RBH and those who had more.

CONCLUSIONS

Underpreparation of the implant-placement sites enabled achievement of successful implant-supported rehabilitation of the posterior maxilla even when both RBH and bone density were low.

Increasing the Stability of Dental Implants: the Concept of Osseodensification

One of the most important factors that affect osseointegration is the primary stability of the implant. Dental implants inserted at the posterior region of the maxilla exhibit the lowest success rates as the low density bone in this area often jeopardize rigid fixation of the implant. Many surgical techniques have been developed to increase the primary stability of an implant placed in low density bone, such as bicortical fixation of the implant, undersized preparation of the implant bed and bone condensation by the use of osteotomes. A new promising technique, named osseodensification, has been recently developed that creates an autograft layer of condensed bone at the periphery of the implant bed by the aid of specially designed burs rotating in a clockwise and anti-clockwise direction. The purpose of this review is to emphasize that implant primary stability is strongly influenced by the surgical technique, to quote and briefly analyse the various surgical procedures laying weight to osseodensification procedure.

In Vitro Evaluation of the Primary Stability of Short and Conventional Implants

The objective of this study was to evaluate the primary stability of short and conventional dental implants with different platform types at different site densities in vitro. One hundred twenty implants were placed in polyurethane blocks that simulate different bone densities (bone types I and IV). The implants were divided into 10 groups, with 12 implants each according to the type of prosthetic connections (external hexagon, EH; morse taper, MT) and size of the implants (conventional: 4 × 10 mm; short: 5 × 5, 5.5 × 5, 5 × 6, and 5.5 × 6 mm). Insertion torque and resonance frequency analyses were performed to evaluate the primary stability. The Kruskal-Wallis test complemented by Dunn's test and the Mann-Whitney test were used for statistical analysis. These tests were applied at the confidence level of 95% (P < .05). The implants installed in blocks with density type IV exhibited reduced insertion torque compared with implants placed in blocks with density type I. Short implants with EH exhibited increased insertion torque compared with short implants with MT in blocks with bone density type I. In general, implants installed in blocks with density type I exhibited greater primary stability. The short implants with EH with a 5.5-mm diameter and the short implants with MT with a 5-mm diameter exhibited reduced primary stability. No differences between short and conventional implants were noted. Short implants have primary stability and insertion torque at least equivalent to conventional implants irrespective of the platform type and density of the site.