Effect of implant size and shape on implant success rates: a literature review

Studies on the performance of selective laser melting porous dental implant by finite element model simulation, fatigue testing and in vivo experiments

Biomaterials have been widely used for stomatological reconstructive surgery in recent years. Many studies have demonstrated that the porous structure of an implant promotes bone ingrowth and its stiffness can be controlled via the design of the porosity. Although some researchers have paid attention to investigating the porous structure for dental implants, the biomechanical properties and osseointegration have not been well studied. In this study, finite element analysis and experiments have been used to evaluate the biomechanical performance and osseointegration of dental implants with porous/solid structures fabricated by selective laser melting using commercially pure titanium (CP-Ti, Grade 2). The implants were tested and the fracture surfaces were observed by scanning electron microscope to investigate the failure mechanisms. To reduce bone resorption, the porosity of dental implant was designed to optimize its stiffness. Finally, animal experiments revealed that bone tissue ingrowth was seen into the porous structure. It is believed that the porous dental implants have great potential in future applications.

A review of nanostructured surfaces and materials for dental implants: surface coating, patterning and functionalization for improved performance

The emerging field of nanostructured implants has enormous scope in the areas of medical science and dental implants. Surface nanofeatures provide significant potential solutions to medical problems by the introduction of better biomaterials, improved implant design, and surface engineering techniques such as coating, patterning, functionalization and molecular grafting at the nanoscale. This review is of an interdisciplinary nature, addressing the history and development of dental implants and the emerging area of nanotechnology in dental implants. After a brief introduction to nanotechnology in dental implants and the main classes of dental implants, an overview of different types of nanomaterials (i.e. metals, metal oxides, ceramics, polymers and hydrides) used in dental implant together with their unique properties, the influence of elemental compositions, and surface morphologies and possible applications are presented from a chemical point of view. In the core of this review, the dental implant materials, physical and chemical fabrication techniques and the role of nanotechnology in achieving ideal dental implants have been discussed. Finally, the critical parameters in dental implant design and available data on the current dental implant surfaces that use nanotopography in clinical dentistry have been discussed.

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.

Three-year Outcomes of a Randomized Controlled Trial Comparing a 4.5-mm-Wide to a 3.75-mm-Wide Titanium Implant for Bone Conduction Hearing

OBJECTIVE

To compare 3-year implant stability, survival, and tolerability of a 4.5-mm-wide (test) and a 3.75-mm-wide (control) percutaneous titanium implant for bone-conduction hearing, loaded with the sound processor after 3 weeks.

METHODS

Sixty implants were allocated in a 2:1 ratio (test-control) in 57 adult patients included in this prospective randomized controlled clinical trial. Follow-up visits were performed at 7, 14, 21, and 28 days; 6 and 12 weeks; 6 months; and at 1, 2, and 3 years after implantation. During these visits, the implant stability quotient (ISQ) was measured by means of resonance frequency analysis (RFA). The peri-abutment soft tissue status was assessed according to the Holgers classification. Skin height around the abutment was evaluated.

RESULTS

The mean area-under-the-curve (AUC) of ISQ-low was statistically significantly higher for the test implant (65.7 versus 61.4, p = 0.0002). Both implants showed high survival rates (97.4% versus 95.0%, p = 0.6374). Adverse soft tissue reactions were observed sporadically, with no significant inter-group differences. Skin thickening was seen in the majority of the patients, but no correlation with adverse soft tissue reactions or implant type was observed.

CONCLUSION

The 4.5-mm-wide implant provides significantly higher ISQ values during the first 3 years after surgery compared with the previous generation 3.75-mm-wide implant. Both implants showed high survival rates and good tolerability. These long-term results indicate that the wider implant, loaded with a sound processor at 3 weeks, is a safe and well-performing option for hearing rehabilitation in specific types of hearing loss.

Clinical outcomes of ultrashort sloping shoulder implant design: A survival analysis

BACKGROUND

Short implants are preferred in cases of limited bone height. Length and design of implant credits to stability and implant success, shorter implants tend to survive for longer time duration.

PURPOSE

Retrospective cohort study was conducted with an aim to assess the clinical outcome and cumulative survival rate of sloping shoulder implants over a period of 8 years.

MATERIALS AND METHODS

Data was collected from all patients attending private clinics in Dubai, UAE. Subjects received ultrashort sloping shoulder (Bicon) implant. Implants of 6 mm and less than 6 mm length were included in the study. Subject's information like age, gender, systemic condition, habits, and radiographs were collected. Implant variables that is number of implants placed, location of placement, loading type, bone type, bone condition, and graft type were collected. Data was analyzed using multivariate cox regression model to evaluate the correlation between implant variables and to identify the implant variables associated with failure. Kaplan-Meier method was adopted to assess the survival pattern of implants.

RESULTS

Cumulative survival rate was 97% with average follow up of 28 months. Statistically significant differences were seen with implant length, arch type, bone type, and bone condition with P value <.001.

CONCLUSION

Short implants with sloping shoulder design and plateau-type roots have superior survival rates when compared with regular implants. The bone condition was also witnessed to be statistically significantly superior.

Evaluation of bone stimulation by different designs of microthreaded implants in enhancing osseointegration: An in vivo animal study supported by a numerical analysis

BACKGROUND

An optimal shape of the thread design of the implants is required for equal distribution of stresses to the surrounding bone matrix and for stimulation and promotion of bone remodeling.

PURPOSE

The study was construed with the aim of histomorphometric evaluation of bone stimulation generated by different microthread designed implants in enhancing osseointegration, and to assess the pattern of stress dissipation through a two-dimensional finite element analysis.

MATERIALS AND METHODS

Computer Aided Designing of two type of microthreads, one V-shaped and the other Power-shaped microthreaded dental implants with only microthreads all along body of the implant from the neck to the apex was made and 30 implant prototypes were milled. Two-dimensional finite elemental analysis (FEA) was carried out to assess the pattern of stress distribution in the bone around these implant designs and for In vivo study 24 implant prototypes were placed in rabbits tibia and femur, out of which 12 were with V-shaped microthreads and the other 12 were with Power-shaped microthreads. Histomorphometric analysis was carried out of the sections obtained from the enbloc specimen retrieved from the sacrificed rabbits.

RESULTS

FEA showed less stress around the V-shaped microthreaded implant model when compared to Power-shaped microthreaded implant model. Hitomorphometry showed statistical significance difference in new bone volume (BV) and Total BV for V-shaped microthreaded prototype implant.

CONCLUSIONS

V-shaped microthreaded dental implant design can be preferred over Power-shaped microthreaded dental implant for proper stress distribution and for promoting osseointegration.

Long-term Retrospective Study based on Implant Success Rate in Patients with Risk Factor: 15-year Follow-up

AIM

The purpose of this retrospective study is to assess implant success rates with various risk factors.

MATERIALS AND METHODS

Two hundred patients with a total of 650 implants were selected. Risk factors, such as smoking, antidepressants, bruxism, diabetes, and bone augmentation procedures were considered, and patients were followed up for a period of 8 to 15 years.

RESULTS

Of 650 implants placed, the success rate was 88%, i.e., a total of 572 implants were successful. A total of 78 implants were considered failure; and out of 78, twenty implants were surgically removed.

CONCLUSION

Based on this study's results, it is concluded that risk factors, such as smoking, bruxism, diabetes, and bone augmentation play an important role in success rate of dental implants.

CLINICAL SIGNIFICANCE

Several factors, such as bruxism, diabetes, and supporting bone can play an important role in dental implant success.

Study to assess the relationship between insertion torque value and implant stability quotient and its influence on timing of functional implant loading

Purpose:

One of the crucial requirements for the success of implants is to achieve good stability. Two well-accepted quantitative methods to assess implant stability, the insertion torque value (ITV), and resonance frequency analysis (RFA) can be a valuable adjunct to radiological and clinical examination. This study was conducted to assess the relationship between ITVs and implant stability quotient (ISQ) and its influence on timing of functional implant loading, as well as to determine the effect of some of the factors on the stability of implants.

Materials and Methods:

Forty implants were inserted in 37 patients in the posterior mandibular region according to conventional protocol and allowed to heal by placing a healing abutment at the time of placement. For each implant, ITV was measured at the time of the implant placement by manual torque wrench (Nobel Biocare), and the ISQ value was measured by using resonance frequency analyzer (Osstell-ISQ; Integration Diagnostics) at the baseline levels, 3^rd week, 7^th week, 11^th week, and 15^th week interval.

Results:

The correlation between ITV and ISQ was found to be moderately positive and significant (r = 0.399) (P = 0.000). The correlation of ITV value at baseline and ISQ values recorded at the subsequent weeks was also found to be statistically significant at week 3 (r = 0.376) (P = 0.000) and week 7 (r = 0.327) (P = 0.000).

Conclusion:

It can be concluded from this study that there is a positive and statistically significant correlation between the ITV and ISQ values.

Short dental implants as compared to maxillary sinus augmentation procedure for the rehabilitation of edentulous posterior maxilla: Three-year results of a randomized clinical study

BACKGROUND

Several treatment options exist for the implant-supported rehabilitation of edentulous posterior maxilla.

PURPOSE

To compare maxillary sinus floor augmentation associated to standard length implants, with direct placement of implants of reduced length in the available residual bone.

MATERIALS AND METHODS

Patients with edentulous posterior maxilla and a residual height of 4-7 mm were randomly allocated to the test (short implants [SIs], 6.5 to 8.5mm long) or the control (sinus augmentation [SA] and implants ≥10mm long) group. Anorganic bovine bone was the grafting material for the control group. In both groups pure platelet-rich plasma was used to bioactivate implant surface prior to insertion. Implant and prosthesis survival, clinical variables, radiographic bone level change, quality of life, and patient satisfaction were assessed.

RESULTS

Twenty-five patients were treated in the control group (58 standard length implants) and 27 in the test group (42 SIs). After 3 years of follow-up no implant failure and biological or mechanical complications were recorded. Marginal bone loss, soft tissue, and oral hygiene parameters were similar in the 2 groups at both 1 and 3 years' follow-up. Postoperative pain, swelling and other symptoms and daily activities were better in the SIs group than in the SA group, while patients' satisfaction after 1 year was similar.

CONCLUSIONS

In spite of comparable medium-term clinical and radiographic outcomes, when the residual ridge height is sufficient for a safe placement, SIs may be preferred due to simplified protocol, less invasiveness, shorter treatment time, and reduced postoperative discomfort as compared to SA.

Mechanical properties and microstructures of dental cast Ti-6Nb-4Cu, Ti-18Nb-2Cu, and Ti-24Nb-1Cu alloys

The mechanical properties -tensile strength, yield strength, elongation after fracture, and Vickers hardness- and alloy phases of the dental cast alloys Ti-6%Nb-4%Cu, Ti-18%Nb-2%Cu, and Ti-24%Nb-1%Cu were investigated. Ti-6%Nb-4%Cu consisted of a single α-phase, while Ti-18%Nb-2%Cu and Ti-24%Nb-1%Cu consisted of α- and β-phases. The tensile strengths, yield strengths, and hardnesses of these alloys were higher than those of Ti-5%Cu and Ti-30%Nb; however, their breaking elongations were smaller. These differences in the mechanical properties are attributable to solid-solution strengthening or to precipitation strengthening by the dual-phase (α+β) structure. Thus, Ti-Nb-Cu alloys are suitable for use in high-strength dental prostheses, such as implantretained superstructures and narrow-diameter implants.

Is the shortened dental arch still a satisfactory option?

Aims Dental practitioners may hold the view that missing posterior teeth should be replaced to ensure a healthy masticatory system and satisfactory oral function. However, the shortened dental arch (SDA) concept is still in use, but after 35 years is it acceptable? This review searches the literature for the evidence and opinions regarding the suitability of the SDA as a current treatment modality.Methods Medline and PubMed databases were searched for relevant terms, all the abstracts were assessed and articles selected according to the pre-set exclusion and inclusion criteria.Results The search yielded 1,895 articles and after the assessment of the abstracts and application of the exclusion and inclusion criteria, 44 articles were selected for this review. These included 11 cohort studies, two longitudinal studies, two animal studies, three cross sectional studies, eight clinical studies and 18 case control studies. There appears to be a trend over the past three decades for more papers to be opposed to the SDA concept.Conclusion Evidence that the SDA causes pathology is lacking. Clinicians, healthcare authorities and patients have shown favourable attitudes towards the SDA and this continues, although there is an increase in studies opposing the concept and some are dissatisfied with this option. The concept remains viable particularly for the medically compromised patient or where restorations are considered unsuitable but further more specific studies are warranted.

Osseointegration of standard and mini dental implants: a histomorphometric comparison

Background

Mini dental implants (MDIs) are becoming increasingly popular for rehabilitation of edentulous patients because of their several advantages. However, there is a lack of evidence on the osseointegration potential of the MDIs. The objective of the study was to histomorphometrically evaluate and compare bone apposition on the surface of MDIs and standard implants in a rabbit model.

Methods

Nine New Zealand white rabbits were used for the study to meet statistical criteria for adequate power. Total 18 3M^™ESPE^™ MDIs and 18 standard implants (Ankylos^® Friadent, Dentsply) were inserted randomly into the tibia of rabbits (four implants per rabbit); animals were sacrificed after a 6-week healing period. The specimens were retrieved en bloc and preserved in 10% formaldehyde solution. Specimens were prepared for embedding in a light cure acrylic resin (Technovit 9100). The most central sagittal histological sections (30–40 μm thick) were obtained using a Leica SP 1600 saw microtome. After staining, the Leica DM2000 microscope was used, the images were captured using Olympus DP72 camera and associated software. Bone implant contact (BIC) was measured using Infinity Analyze software.

Results

All implants were osseointegrated. Histologic measures show mineralized bone matrix in intimate contact with the implant surface in both groups. The median BIC was 58.5 % (IQR 8.0) in the MDI group and 57.0 % (IQR 5.5) in the control group (P > 0.05; Mann-Whitney test). There were no statistical differences in osseointegration at 6 weeks between MDIs and standard implants in rabbit tibias.

Conclusions

Based on these results, it is concluded that osseointegration of MDIs is similar to that of standard implants.

Short dental implants in the posterior maxilla: a review of the literature

The purpose of this study was to perform a literature review of short implants in the posterior maxilla and to assess the influence of different factors on implant success rate. A comprehensive search was conducted to retrieve articles published from 2004 to 2015 using short dental implants with lengths less than 10 mm in the posterior maxilla with at least one year of follow-up. Twenty-four of 253 papers were selected, reviewed, and produced the following results. (1) The initial survival rate of short implants in the posterior maxilla was not related to implant width, surface, or design; however, the cumulative success rate of rough-surface short implants was higher than that of machined-surface implants especially in performance of edentulous dental implants of length <7 mm. (2) While bone augmentation can be used for rehabilitation of the atrophic posterior maxilla, short dental implants may be an alternative approach with fewer biological complications. (3) The increased crown-to-implant (C/I) ratio and occlusal table (OT) values in short dental implants with favorable occlusal loading do not seem to cause peri-implant bone loss. Higher C/I ratio does not produce any negative influence on implant success. (4) Some approaches that decrease the stress in posterior short implants use an implant designed to increase bone-implant contact surface area, providing the patient with a mutually protected or canine guidance occlusion and splinting implants together with no cantilever load. The survival rate of short implants in the posterior edentulous maxilla is high, and applying short implants under strict clinical protocols seems to be a safe and predictable technique.

Removal techniques for failed implants

The use of dental implants is an accepted and predictable way of replacing missing or lost teeth. However, implants can and will fail and there are a variety of reasons why this occurs, which the practitioner should understand. In some instances failed implants may require removal and, therefore, practitioners should be aware of techniques that can be used to remove failed implants to potentially enable future rehabilitation of an edentulous region.

Survival of Brånemark System Mk III implants and analysis of risk factors associated with implant failure

The purpose of this study was to retrospectively investigate the outcomes of Brånemark System Mk III TiUnite/Groovy implants placed in patients at Kobe University Hospital. Various risk factors for implant failure, including mechanical coupling, were investigated by univariate and multivariate analysis. The predictive variables investigated included age, sex, smoking habit, general health, history of radiation therapy, application of a dentomaxillary prosthesis, type of prosthesis, use of alveolar bone augmentation, site of implant insertion, mechanical coupling between implants, and the length and diameter of the implants. Of the 907 implants investigated, only 23 were unsuccessful; the overall survival rate was 96.7%. Increased age, radiation therapy, application of a removable prosthesis or dentomaxillary prosthesis, lack of mechanical coupling between implants, and shorter implants (≤8.5mm) were significant risk factors for implant failure according to univariate analysis (P<0.05). Multivariate analysis identified a significant association (P<0.05) between dental implant failure and a lack of mechanical coupling between implants (odds ratio 6.88) and shorter implants (≤8.5mm) (odds ratio 3.43). The findings of this study demonstrated multivariate relationships between various risk factors and dental implant failure.

Stability, Survival, and Tolerability of an Auditory Osseointegrated Implant for Bone Conduction Hearing: Long-Term Follow-Up of a Randomized Controlled Trial

OBJECTIVE

To compare implant stability, survival, and soft tissue reactions for a novel (test) and previous generation (control) percutaneous auditory osseointegrated implant for bone conduction hearing at long-term follow-up of 5 years.

STUDY DESIGN

Single follow-up visit of a previously completed multicenter, randomized, controlled trial.

PATIENTS

Fifty-seven of the 77 participants of a completed randomized controlled trial on a new auditory osseointegrated implant underwent a single follow-up visit 5 years after implantation, which comprised implant stability measurements and collection of Holgers scores. Additionally, implant survival was recorded for all 77 patients from the original trial.

RESULTS

The test implant showed significantly higher implant stability quotient (ISQ) values compared with the control implant throughout the 5-year follow-up. Mean area under the curve of ISQ high from baseline to 5 years was 71.6 (standard deviation [SD] ±2.0) and 66.7 (SD ±3.4) for the test and control implant, respectively (p < 0.0001). For both implants, the mean ISQ value recorded at 5 years was higher compared with implantation (test group +2.03 [SD ±2.55, within group p < 0.0001] and control group +2.25 [SD ±4.95, within group p = 0.12]). No difference was noticed in increase from baseline between groups (p = 0.64). Furthermore, evaluation of soft tissue reactions continued to show superiority of the test implant. At the 5-year follow-up visit, one patient (2.5%) presented with a Holgers grade 2 in the test group, compared with four patients (23.5%) in the control group (p = 0.048); no patient presented with more severe soft tissue reactions. Excluding explantations, the survival rate was 95.8% for the test group and 95.0% for the control group. The corresponding rates including explantations were 93.9 and 90.0%.

CONCLUSION

The test implant showed superiority in terms of higher mean ISQ values and less adverse soft tissue reactions, both at the single 5-year follow-up visit and during the complete follow-up. In addition, both implants showed an equally high implant survival.

Effect of length, diameter, intraoral location on implant stability

OBJECTIVES

To quantitatively compare stability of dental implants with varying lengths, diameters, and intraoral locations.

STUDY DESIGN

Retrospectively, 200 consecutive NobelReplace Tapered Groovy implants of varying lengths and diameters were evaluated via implant stability quotient readings at placement (T1) and follow-up (T2). Data were analyzed by analysis of variance and simple linear regression tests.

RESULTS

Intraoral location was statistically significant at T1 and T2. Although implant diameter was not statistically significant, implant length resulted in T1 (P = .08) and T2 (P = .09), which may have a clinically relevant effect on implant stability. An overall implant survival rate of 98% was achieved. Gender and age did not seem to affect implant stability quotient values at placement, follow-up, or implant survival.

CONCLUSIONS

Intraoral location is an important factor in implant stability, with implants placed in the mandible being more stable than implants placed in the maxilla both at T1 and T2. Length may have a clinically relevant effect on implant stability.

FEA model analysis of the effects of the stress distribution of saddle-type implants on the alveolar bone and the structural/physical stability of implants

BACKGROUND

As dental implants receive masticatory stress, the distribution of stress is very important to peri-implant bone homeostasis and implant survival. In this report, we created a saddle-type implant and analyzed its stability and ability to distribute stress to the surrounding bone.

METHODS

The implants were designed as a saddle-type implant (SI) that wrapped around the alveolar bone, and the sizes of the saddles were 2.5, 3.5, 4.5, and 5.5 mm. The X and Y displacement were compared to clarify the effects of the saddle structures. The control group consisted of dental implants without the saddle design (CI). Using finite element modeling (FEM), the stress distribution around the dental implants was analyzed.

RESULTS

With saddle-type implants, saddles longer than 4.5 mm were more effective for stress distribution than CI. Regarding lateral displacement, a SI of 2.5 mm was effective for stress distribution compared to lateral displacement. ASI that was 5.6 mm in length was more effective for stress distribution than a CI that was 10 mm in length.

CONCLUSIONS

The saddle-type implant could have a bone-gaining effect. Because it has stress-distributing effects, it might protect the newly formed bone under the implant.

Impact of implant diameter and length on stress distribution in osseointegrated implants: A 3D FEA study

Aims and Objectives:

Dimension of dental implant is an important parameter which has a considerable impact on the biomechanical load transfer characters and its prognosis. Excessive stress in the bone–implant interface may result in the failure of the implant. The aim of this study was to evaluate the impact of implant diameter and length on neighboring tissues around the implant. The results of the study will help in developing a scientific methodology to select appropriate implant diameter and length.

Materials and Methods:

In this study, tapered implants of different diameter and length were numerically analyzed using bone–implant models developed from computed tomography generated images of mandible with osseointegrated implants. The impact of various diameters on stress distribution was examined using implants with a length of 13 mm and diameters of 3.5 mm, 4.3 mm and 5.0 mm. Implants with a diameter of 4.3 mm and lengths of 10 mm, 13 mm, 16 mm was developed to examine the impact of various implant length. All materials were assumed to be linearly elastic and isotropic. Masticatory load was applied in a natural direction, oblique to the occlusal plane. The Statistical Package for the Social Sciences software package was used for statistical analysis.

Results:

Maximum von Mises stresses were located around the implant neck. It was demonstrated that there was statistically significant decrease in von Mises stress as the implant diameter increased.

Conclusion:

Within the limitations of this study there was statistically significant decrease in von Mises stress as the implant diameter increased.

Analysis of the Factors Affecting Surgical Success of Implants Placed in Iranian Warfare Victims

OBJECTIVE

The aim was to evaluate the survival time and success rates of dental implants in warfare victims and factors that affect implant success.

SUBJECTS AND METHODS

This retrospective study involved 250 Iranian warfare victims who received dental implants from 2003 to 2013. Patients' demographic characteristics, as well as the brand, diameter, length, location and failure rate of the implants were retrieved from patients' dental records and radiographs. The associations between these data and the survival rate were analyzed. Statistical analysis was carried out with χ2 and log-rank tests.

RESULTS

Overall, out of the 1,533 dental implants, 61 (4%) failed. The maxillary canine area had the highest failure rate [9 of 132 implants (6.8%)], while the mandibular incisor region had the least number of failures [3 of 147 implants (2.0%)] and the longest survival time (approximately 3,182 days). Maxillary canine areas had the shortest survival (about 2,996 days). The longest survival time was observed in implants with 11 mm length (3,179.72 ± 30.139 days) and 3.75-4 mm diameter (3,131.161 ± 35.96 days), and the shortest survival was found in implants with 11.5 mm length (2,317.79 ± 18.71 days) and 6.5 mm diameter (2,241.45 ± 182.21 days). Moreover, implants with 10 mm length (10.7%) and 5.5-6 mm diameter (22.2%) had the highest failure rate; however, the least failure rate occurred when the implants were 11.5 mm in length (1.9%) and 3-3.5 mm in diameter (3.1%).

CONCLUSIONS

The brand, length and diameter of implants affected the survival time, failure rate and time to failure. The location of the implant was not statistically significant regarding the mentioned factors, although it has clinical significance.

A meta-analysis on the effect of implant characteristics on the survival of the wide-diameter implant

The purposes of the study are to study the implant survival of the wide-diameter implant and to analyze if the length, the implant surface, or the placement location has any effect on its survival. Electronic databases were searched from inception to Dec 2014. Studies included in the review had implants placed in areas of adequate bone width and had clear inclusion and exclusion criteria for patient selection. Immediately placed and immediately loaded implants were excluded. A meta-analysis was done using the “random effects” model on the included studies. And, a meta-regression was used to evaluate the effects of location, length, and surface on the implant survival. Of the six studies selected, three evaluated surface-treated implants and three machined implants. The overall pooled survival rate of the wide implant is 96.3 %. The meta-regression showed that when using a wide implant, neither its surface nor its length nor its position in the maxilla or mandible adversely affected its survival (P > 0.05). This meta-analysis concluded that the location, length, and surface of the wide-diameter implant did not affect its survival and therefore suggested that when the conditions of the implant site corresponded to the inclusion criteria of our meta-analysis, choosing a wide-diameter implant in the posterior mandible or maxilla, where implant length may be limited by the nerve or the sinus, the use of a short implant regardless of its surface would not affect its survival.

Loading of osseointegrated implants for bone conduction hearing at 3 weeks: 3-year stability, survival, and tolerability

The objective of this study was to ascertain the long-term safety of loading osseointegrated implants for bone conduction hearing 3 weeks post-surgery. Thirty consecutive adult patients were implanted with the Baha BI300 (Cochlear Bone Anchored Solutions) in our tertiary referral center. Implants were loaded with the sound processor 3 weeks post-surgery. Follow-up examinations were performed at 10 days; 3, 4, 6, 8, and 12 weeks; 6 months; and 1, 2, and 3 years after implant surgery. At each follow-up visit, implant stability quotient (ISQ) values were recorded by means of resonance frequency analysis, and soft tissue status was evaluated according to Holgers’ classification. ISQ trends, implant survival, and soft tissue reactions were compared to a population of 52 patients with the same type of implants loaded from 6 weeks post-surgery as part of another study. Subjective benefit was measured by means of the Glasgow Benefit Inventory (GBI). After an initial dip in ISQ at 10 days after implantation, a gradually increasing trend in ISQ was found until 6 months in both populations, after which ISQ values remained above baseline values. Implant survival was 97 % in the study population and 96 % in the comparison population. Clinically relevant soft tissue reactions were found in 0.9 % (study population) and 1.7 % (comparison population) of all visits. Patients reported subjective benefit; the mean GBI score was 22.8. In conclusion, loading these implants at 3 weeks post-surgery is safe based on the current study, as long-term results show high ISQ values and good implant survival and tolerability.

A SIMPLE AND EFFICIENT METHODOLOGY TO IMPROVE DESIGN PROPOSALS OF DENTAL IMPLANTS — A DESIGN CASE STUDY

Objective: To propose a methodology based on virtual simulation to assist in the design proposals of dental implants. Methods: The finite element method (FEM) was used to analyze the biomechanical dental implant system behavior, determining von Mises stress distribution induced by functional loads, varying parameter as load direction and geometric characteristic of the implant (taper, length, abutment angulation, thread pitch and width pitch). A final design was obtained by considering the parameters that showed improved performance. The estimated lifetime of the final design was calculated by reproducing in a virtual way the experimental fatigue test required by the ISO:14801 standards. Results: For all the studied cases, the maximum stresses were obtained in the connecting screw under oblique loads (OLs). The estimated lifetime for this critical part is at least 5 × 106 cycles, which meets the requirement of the ISO:14801. In bone tissue, the largest stresses were concentrated in cortical bone, in the zone surrounding the implant, in good agreement with previous reports. Conclusions: A dental implant design was obtained and validated through a simple and efficient methodology based on the application of numerical methods and computer simulations.

Long-term Short Implants Performance: Systematic Review and Meta-Analysis of the Essential Assessment Parameters

<p>Lack of standard criteria in the outcome assessment makes it difficult to draw conclusions on the clinical performance of short implants and, under these circumstances, determine the reasons for implant failure. This study evaluated, through a systematic review of the literature and meta-analysis, the essential parameters required to assess the long-term clinical performance of short and extra-short implants. Electronic databases (Pubmed-MEDLINE, Cochrane Library Database, Embase, and Lilacs) were searched by two independent reviewers, without language limitation, to identify eligible papers. References from the selected articles were also reviewed. The review included clinical trials involving short dental implants placed in humans, published between January 2000 and March 2014, which described the parameters applied for outcome's measurements and provided data on survival rates. Thirteen methodologically acceptable studies were selected and 24 parameters were identified. The most frequent parameters assessed were the marginal bone loss and the cumulative implant survival rate, followed by implant failure rate and biological complications such as bleeding on probing and probing pocket depths. Only cumulative implant survival rate data allows meta-analysis revealing a positive effect size (from 0.052 (fixed) to 0.042 (random)), which means that short implant appears to be a successful treatment option. Mechanical complications and crown-to-implant (C/I) ratio measurement were also commonly described, however, considering the available evidence; no strong conclusions could be drawn since different methods were used to assess each parameter. By means of this literature review, a standard evaluation scheme is proposed, being helpful to regiment further investigations and comparisons on future studies.</p>

Clinical evaluation of implant survival based on size and site of placement: A retrospective study of immediate implants at single rooted teeth sites

Objectives

This retrospective clinical study sought to evaluate the survival of immediate implants placed at maxillary and mandibular single-rooted tooth extraction sites and to determine the relationship among implant size, placement site, and implant survival.

Methods

Between January 2010 and June 2011, 85 patients (33 males, 52 females; mean age: 45 years) underwent immediate implant placement after extraction of single-rooted teeth. All implants were restored between 12 and 14 weeks after implant placement. The implant survival and its relationship with implant size and implantation site were evaluated by odds ratios (ORs).

Results

Implants were placed at the following sites: upper central incisor (UCI, n = 35), upper lateral incisor (ULI, n = 27), upper second premolar (U2ndP, n = 36), lower incisor (LI, n = 53), and lower premolar (LP, n = 22). Implants of the following sizes were used: 5 × 10 mm (n = 24), 5 × 8 mm (n = 21), 4.3 × 10 mm (n = 77), 4.3 × 8 mm (n = 36), 3.5 × 10 mm (n = 12), and 3.5 × 8 mm (n = 3). After a mean follow-up time of 47 months, the overall implant survival rate was 96%. Survival rate was highest at the LI site (98.1%) and lowest at the ULI site (92.6%). All of the 5-mm implants survived (100%), as did most of the 4.3 × 10 mm implants (96.1%). Implants of 4.3 × 8 mm and 3.5 × 10 mm were the least successful (91.7%). Mandibular implants had a better survival rate (97.3%) than maxillary implants (94.9%). There was no significant OR of increased survival for any particular implant size or site.

Conclusions

Immediate implant placement in fresh extraction sockets can give predictable clinical outcomes, regardless of the implant size and site of placement.

Radiographic Evaluation of Crestal Bone Loss Around Dental Implants in Maxilla and Mandible: One Year Prospective Clinical Study

PURPOSE

The aim of the study was to analyze the amount of maxillary and mandibular crestal bone loss around Bredent Sky Blue type of implants of different dimensions one year after implantation.

MATERIALS AND METHODS

36 implants of diameter 3.5 x 10 mm were inserted in the maxilla and 12 in the mandible. 52 implants of diameter 4.0 x 8 mm were inserted in the maxilla, and 61 in the mandible (two-stage implant surgery).

RESULTS

No statistically significant differences were found between the right and left side of the maxilla and between the right and left side of the mandible at the implant sites regarding distal and mesial bone losses as shown by analysis of variance (ANOVA).

CONCLUSION

Statistically significant differences were found between anterior maxilla, posterior maxilla and anterior mandible and posterior mandible at implant sites regarding distal and mesial bone losses as shown by analysis of variance (ANOVA).

Comparing the influence of crestal cortical bone and sinus floor cortical bone in posterior maxilla bi-cortical dental implantation: a three-dimensional finite element analysis

OBJECTIVE

This study aimed to compare the influence of alveolar ridge cortical bone and sinus floor cortical bone in sinus areabi-cortical dental implantation by means of 3D finite element analysis.

MATERIALS AND METHODS

Three-dimensional finite element (FE) models in a posterior maxillary region with sinus membrane and the same height of alveolar ridge of 10 mm were generated according to the anatomical data of the sinus area. They were either with fixed thickness of crestal cortical bone and variable thickness of sinus floor cortical bone or vice versa. Ten models were assumed to be under immediate loading or conventional loading. The standard implant model based on the Nobel Biocare implant system was created via computer-aided design software. All materials were assumed to be isotropic and linearly elastic. An inclined force of 129 N was applied.

RESULTS

Von Mises stress mainly concentrated on the surface of crestal cortical bone around the implant neck. For all the models, both the axial and buccolingual resonance frequencies of conventional loading were higher than those of immediate loading; however, the difference is less than 5%.

CONCLUSION

The results showed that bi-cortical implant in sinus area increased the stability of the implant, especially for immediately loading implantation. The thickness of both crestal cortical bone and sinus floor cortical bone influenced implant micromotion and stress distribution; however, crestal cortical bone may be more important than sinus floor cortical bone.

Impact of Bone Quality and Implant Type on the Primary Stability: An Experimental Study Using Bovine Bone

The purpose of this in vitro study was to compare the primary stability and removal torque of bone level and tissue level implants in different bone qualities. Twenty tissue level and bone level implants (3.3 × 10 mm and 4.1 × 10 mm) were used for assessing the stability in type II and type IV bone. Forty bovine rib blocks were used in this study. The primary stability of the implant was measured by the resonance frequency using an Osstel device. The removal torque values (RTV) of the implants was assessed using a digital torque gauge instrument. The implant stability quotient (ISQ) values and the RTV showed a marginally higher stability with bone level implants as compared to tissue level implants. However, these differences were not statistically significant in both type of bone used (P &gt; 0.05). On the other hand, compared to type IV, type II bone showed significant differences in the ISQ (P &lt; 0.01) and RTV (P &lt; 0.001) of bone level and tissue level implants. The study concluded that bone quality is an important factor in establishing primary stability than the implant dimension. Bone level and tissue level implants of same dimensions can be selected based on the esthetic demands since they showed similar mechanical properties.

Stability, survival, and tolerability of a 4.5-mm-wide bone-anchored hearing implant: 6-month data from a randomized controlled clinical trial

The objective of this study was to compare the stability, survival, and tolerability of 2 percutaneous osseointegrated titanium implants for bone conduction hearing: a 4.5-mm diameter implant (test) and a 3.75-mm diameter implant (control). Fifty-seven adult patients were included in this randomized controlled clinical trial. Sixty implants were allocated in a 2:1 (test–control) ratio. Follow-up visits were scheduled at 7, 14, 21, and 28 days; 6 and 12 weeks; and 6 months. At every visit, implant stability quotient (ISQ) values were recorded by means of resonance frequency analysis (RFA) and skin reactions were evaluated according to the Holgers classification. Implants were loaded with the bone conduction device at 3 weeks. Hearing-related quality of life was evaluated using the Abbreviated Profile of Hearing Aid Benefit (APHAB), the Glasgow Benefit Inventory (GBI), and the Glasgow Health Status Inventory (GHSI). ISQ values were statistically significantly higher for the test implant compared to the control implant. No implants were lost and soft tissue reactions were comparable for both implants. Positive results were reported in the hearing-related quality of life questionnaires. These 6-month results indicate that both implants and their corresponding hearing devices are safe options for hearing rehabilitation in patients with the appropriate indications. Loading at 3 weeks did not affect the stability of either implant.

Association between implant apex and sinus floor in posterior maxilla dental implantation: A three-dimensional finite element analysis

The aim of the present study was to evaluate the effect of the association between the implant apex and the sinus floor in posterior maxilla dental implantation by means of three-dimensional (3D) finite element (FE) analysis. Ten 3D FE models of a posterior maxillary region with a sinus membrane and different heights of alveolar ridge with different thicknesses of sinus floor cortical bone were constructed according to anatomical data of the sinus area. Six models were constructed with the same thickness of crestal cortical bone and a 1-mm thick sinus floor cortical bone, but differing heights of alveolar ridge (between 10 and 14 mm). The four models of the second group were similar (11-mm-high alveolar ridge and 1-mm-thick crestal cortical bone) but with a changing thickness of sinus floor cortical bone (between 0.5 and 2.0 mm). The standard implant model based on the Nobel Biocare^® implant system was created by computer-aided design (CAD) software and assembled into the models. The materials were assumed to be isotropic and linearly elastic. An inclined force of 129 N was applied. The maximum von Mises stress, stress distribution, implant displacement and resonance frequencies were calculated using CAD software. The von Mises stress was concentrated on the surface of the crestal cortical bone around the implant neck with the exception of that for the bicortical implantation. For immediate loading, when the implant apex broke into or through the sinus cortical bone, the maximum displacements of the implant, particularly at the implant apex, were smaller than those in the other groups. With increasing depth of the implant apex in the sinus floor cortical bone, the maximum displacements decreased and the implant axial resonance frequencies presented a linear upward tendency, but buccolingual resonance frequencies were hardly affected. This FE study on the association between implant apex and sinus floor showed that having the implant apex in contact with, piercing or breaking through the sinus floor cortical bone benefited the implant stability, particularly for immediate loading.

Short implants: are they a viable option in implant dentistry?

Short-length implants (<10 mm) can be used effectively in atrophic maxillae or mandibles even with crown/implant ratios that previously would have been considered excessive. Short implants can support either single or multiple units and can be used for fixed prostheses or overdentures. The use of short-length implants may avoid the need for complicated bone augmentation procedures, thus allowing patients who were either unwilling or unable for financial or medical reasons to undergo these advanced grafting techniques to be adequately treated.

Stress Distribution Around Single Short Dental Implants: A Finite Element Study

Bone height restrictions are more common in the posterior regions of the mandible, because of either bone resorption resulting from tooth loss or even anatomic limitations, such as the position of the inferior alveolar nerve. In situations where adequate bone height is not available in the posterior mandible region, smaller lengths of implants may have to be used but it has been reported that the use of long implants (length ≥10 mm) is a positive factor in osseointegration and authors have reported failures with short implants. Hence knowledge about the stress generated on the bone with different lengths of implants needs scientific evaluation. The purpose of this study was to compare and evaluate the influence of different lengths of implants on stress upon bone in mandibular posterior area. A 3 D finite element model was made of the posterior mandible using the details from a CT scan, using computer software (ANSYS 12). Four simulated implants with lengths 6 mm, 8 mm, 10 mm and 13 mm were placed in the centre of the bone. A static vertical force of 250 N and a static horizontal force of 100 N were applied. The stress generated in the cortical and cancellous bone around the implant were recorded and evaluated with the help of ANSYS. In this study, Von Mises stress on a 6 mm implant under a static vertical load of 250 N appeared to be almost in the same range of 8 and 10 mm implant which were more as compared to 13 mm implant. Von Mises stress on a 6mm implant under a static horizontal load of 100 N appeared to be less when compared to 8, 10 and 13 mm implants. From the results obtained it may be inferred that under static horizontal loading conditions, shorter implants receive lesser load and thus may tend to transfer more stresses to the surrounding bone. While under static vertical loading the shorter implants bear more loads and comparatively transmit lesser load to the surrounding bone.

Implant diameter and length influence on survival: interim results during the first 2 years of function of implants by a single manufacturer

OBJECTIVES

The aim of the present study was to evaluate the influence of implant length and diameter on implant survival.

METHODS

A retrospective cohort of 787 consecutive patients from 2 private practices between the years 2008 and 2011 had been evaluated. Patient demographics, site and implant characteristics, and time of follow-up were recorded from the medical files.

RESULTS

Overall, 3043 implants were investigated. Overall survival rate was 98.7% with 39 implant failures recorded. Survival rates for narrow- (<3.75 mm), regular- (3.75-5 mm), and wide- (>5 mm) diameter implants were 98.2%, 98.7%, and 98.5%, respectively (P = 0.89). Survival rates of short (<10 mm) and regular (10 mm and above) implants were 97% and 98.7%, respectively (P = 0.22).

CONCLUSIONS

Implant length and diameter were not found to be significant factors affecting implant survival during the first 2 years of function in the present investigation of this specific implant system by a single manufacturer. Further long-term follow-up studies are warranted because 2-years are only interim short-term results when dealing with dental implants.

Current trends in dental implants

Tooth loss is very a very common problem; therefore, the use of dental implants is also a common practice. Although research on dental implant designs, materials and techniques has increased in the past few years and is expected to expand in the future, there is still a lot of work involved in the use of better biomaterials, implant design, surface modification and functionalization of surfaces to improve the long-term outcomes of the treatment. This paper provides a brief history and evolution of dental implants. It also describes the types of implants that have been developed, and the parameters that are presently used in the design of dental implants. Finally, it describes the trends that are employed to improve dental implant surfaces, and current technologies used for the analysis and design of the implants.

Biomechanical analysis and comparison of 12 dental implant systems using 3D finite element study

Finite element analysis plays an important role in dental implant design. The objective of this study was to show the effect of the overall geometry of dental implants on their biomechanics after implantation. In this study, 12 dental implants, with the same length, diameter and screw design, were simulated from different implant systems. Numerical model of right mandibular incisor bone segment was generated from CT data. The von-Mises stress distributions and the total deformation distributions under vertical/lateral load were compared for each implant by scores ranking method. The implants with cylindrical shapes had highest scores. Results indicated that cylindrical shape represented better geometry over taper implant. This study is helpful in choosing the optimal dental implant for clinical application and also contributes to individual implant design. Our study could also provide reference for choice and modification of dental implant in any other insertion sites and bone qualities.

Osseointegration of short titan implants: A pilot study in pigs

Reduced vertical bone level in the implantation area is often considered one of the limiting factors before implant insertion. Inserting implants of reduced length might be useful in order to avoid vertical bone augmentation prior to implantation. To the present day, no official guidelines exist as to the optimal length for these implants. It is nevertheless well known that the stability of an implant depends primarily on its osseointegration, which could otherwise be influenced by modifying implant surface texture. The aim of our study was to evaluate osseointegration in correlation with implant length and surface texture. Three different variations of titan implants (n=5) were compared: two types, each with an acid-etched and ceramic blasted surface, were inserted in the upper jaw of adult female minipigs at different lengths (tioLogic ST Shorty, 5mm length; tioLogic ST, 9mm length) and were compared to a control group (tioLogic ST, 9mm length, ceramic blasted surface). Eight weeks after unloaded healing, bone tissue specimens containing the implants were processed, stained with Masson-Goldner-trichrome and analyzed histologically. Regardless of implant length and surface texture, new bone formation with no signs of inflammation could be detected in the area of the threads. Implants with a modified surface showed no statistically significant difference in bone-implant-contact (BIC) (tioLogic ST Shorty, 56.5%; tioLogic(©)ST; 77.2%), but a statistically significant difference could be found, when the 9mm implants were compared to the control group (BIC 48.9%). Surface modification could positively influence osseointegration as well as contribute to overcoming the adverse effects of length reduction.