Tilted Implants for the Rehabilitation of Edentulous Jaws: A Systematic Review

Evaluation of Biomechanical Effects of Mandible Arch Types in All-on-4 and All-on-5 Dental Implant Design: A 3D Finite Element Analysis

This study evaluates the biomechanical effects of different implant configurations in various mandibular arch types using finite element analysis (FEA). Stress distribution and deformation patterns were analyzed under different loading conditions in square, U-shaped, and V-shaped arches. The results indicate that increasing the number of implants generally reduces cortical bone stress, particularly in U and V arches, while implant-level stress tends to increase. Under molar loading, cortical bone stress in the square arch decreased by 16.9% (from 90.61 MPa to 75.27 MPa) with the All-on-5 system, while implant stress in the V arch dropped by 46.26% (from 142.35 MPa to 76.5 MPa). Additionally, the cantilever effect in All-on-4 configurations resulted in higher stress on the prosthesis and implants, particularly in V arches. While the All-on-5 system provided better load distribution, the study highlights the importance of optimizing implant positioning based on mandibular anatomy. Despite limitations such as the use of static forces and standardized arch types, these findings offer valuable insights into the biomechanical performance of full-arch implant rehabilitations, supporting future clinical applications and research.

An in vitro assessment of the accuracy of guided tilted and axial implant placement in the edentulous mandible

PURPOSE

To assess the precision of implant placement when comparing tilted orientations to axial orientations, utilizing a fully guided surgical protocol in an edentulous mandibular model.

MATERIALS AND METHODS

Fourteen rubber-coated mandibular models were scanned with fiducial markers using a commercial benchtop surface scanner, followed by cone beam computed tomography for implant planning through a dual-scan protocol. The models were randomly divided into control and experimental groups. In the control group, each model was planned for four axially oriented implants. Conversely, the experimental models were planned for two axially oriented implants near the lateral incisors and two posteriorly tilted implants at a 30-degree angle. A mucosal-supported, pin-retained surgical guide was designed and 3D-printed, facilitating the fully guided implant placement. All implants received scan bodies and were rescanned for evaluation of the trueness between the planned and the actual implant location using the implant planning software. Mixed model ANOVA was used to detect differences between groups with regards to angular deviation, offset at base, and offset at tip.

RESULTS

A total of 56 implants were placed across all models. Fourteen posterior implants in each group served as control and experimental conditions, while the remaining 28 anterior implants acted as secondary control. No significant differences were observed between the experimental and control groups in terms of angular deviation (p = 0.7001), offset at base (p = 0.6409), or offset at tip (p = 0.6931). Analysis comparing anterior implant deviations between groups and anterior to posterior implant deviations within the control arches also was not significant. However, secondary analysis revealed a significant difference between anterior and posterior implants within the experimental group for offset at base (p = 0.0087) and offset at tip (p = 0.0288).

CONCLUSIONS

Despite the limitations inherent to a benchtop study, the findings suggest that there are no statistically significant 3D deviations at the base or apex, nor in angular deviations, when comparing tilted and axial implant placements using a digital workflow and fully guided protocols in an edentulous model.

Finite Element Analysis of Functionally Loaded Subperiosteal Implants Evaluated on a Realistic Model Reproducing Severe Atrophic Jaws

Implant-supported prosthetic rehabilitation for patients with severely atrophic jaws is challenging due to complex anatomical considerations and the limitations of conventional augmentation techniques. This study explores the potential of subperiosteal (juxta-osseous) implants as an alternative solution, using finite element analysis (FEA) to evaluate mechanical performance. Realistic jaw models, developed from radiographic data, are utilized to simulate various implant configurations and load scenarios. Results indicate that different screw placements, implant designs, and structural modifications can significantly influence stress distribution and biomechanical behavior. Upper and lower jaw models were assessed under multiple load conditions to determine optimal configurations. Findings suggest that strategic adjustments, such as adding posterior screws or altering implant connections, can enhance load distribution and reduce stress concentration, particularly in critical areas. Tensile loads in critical bone areas near cortical fixing screws exceeded 50 MPa under anterior loading, while configurations with larger load distributions reduced stress on both implant and bone. The study provides evidence-based insights into optimizing subperiosteal implant design to improve stability, longevity, and patient outcomes.

Comparison of stress distribution around all-on-four implants of different angulations and zygoma implants: a 7-model finite element analysis

BACKGROUND

In recent years, zygomatic implants and the all-on-four treatment concept have been increasingly preferred for rehabilitation of atrophic maxillae. However, debate continues regarding the optimal configuration and angulation of the implants. The aim of this study was to analyze the biomechanical stress in implants and peri-implant bone in an edentulous maxilla with zygomatic implants and the all-on-four concept, using multiple implant configurations.

METHODS

A total of 7 models consisting different combinations of 4-tilted dental implants and zygomatic implants were included in the study. In each model, a total of 200 N perpendicular to the posterior teeth and 50 N with 45° to the lateral tooth were applied. A finite element analysis was performed for determination of stress distribution on implants and peri-implant bone for each model.

RESULTS

Higher stress values were observed in both cortical and trabecular bone around the 45°-tilted posterior implants in all-on-four models when compared to zygomatic implants. In cortical bone, the highest stress was established in an all-on-four model including 45°-tilted posterior implant with 4,346 megapascal (MPa), while the lowest stress was determined in the model including anterior dental implant combined with zygomatic implants with 0.817 MPa. In trabecular bone, the highest stress was determined in an all-on-four model including 30°-tilted posterior implant with 0.872 MPa while the lowest stress was observed in quad-zygoma model with 0.119 MPa. Regarding von Mises values, the highest stress among anterior implants was observed in an all-on-four model including 17° buccally tilted anterior implant with 38.141 MPa, while the lowest was in the including anterior dental implant combined with zygomatic implants with 20,446 MPa. Among posterior implants, the highest von Mises value was observed in the all-on-four model including 30°-tilted posterior implant with 97.002 MPa and the lowest stress was in quad zygoma model with 35.802 MPa.

CONCLUSIONS

Within the limits of the present study, the use of zygoma implants may provide benefit in decreasing biomechanical stress around both dental and zygoma implants. Regarding the all-on-four concept, a 17° buccal angulation of anterior implants may not cause a significant stress increase while tilting the posterior implant from 30° to 45° may cause an increase in the stress around these implants.

Analysis of ultra-short implants with different angulations: a retrospective case-control study with 2 to 9 years of follow-up

OBJECTIVES

Does the angulation of ultrashort implants influence the stability of the peri-implant bone? The present study aimed to evaluate the effectiveness of non-axial ultrashort implants after 2 to 9 years of follow-up in resorbed alveolar ridges.

MATERIALS AND METHODS

All partially edentulous patients with ultrashort implants (< 6 mm) used in the posterior region of an atrophic mandible or maxilla, to support partial dentures in conjunction with standard implants, were included in this study. Peri-implant bone loss, success and survival rates, crestal bone levels, crown-to-implant ratio and implant angulation were measured for each implant. Implants were divided into two groups: straight implants with angulation < 17° (control group) and tilted implants with angulation > 17° (test group). Statistical analysis was used to find any significant differences between the two study groups and to investigate significant linear correlations among all the variables (p = 0.05).

RESULTS

A total of 42 ultrashort implants with a mean of 4 years of follow-up were included: 20 ultrashort axially loaded implants and 22 tilted implants. Mean crestal bone levels from baseline loading to maximum follow-up did not reveal statistical differences in regard to PBL; mean success and survival rates were 100% in all groups.

CONCLUSIONS

PBL, success and survival rates of axial ultrashort implants and tilted ultrashort implants are comparable to those of conventional implants.

CLINICAL RELEVANCE

This retrospective study revealed that ultrashort implants, even when placed with an angulation > 17°, can safely be used to support partial fixed prostheses. Further prospective clinical studies with larger samples and prospective design are needed to confirm these findings.

On the fatigue life of dental implants: Numerical and experimental investigation on configuration effect

Dental implants have seen widespread and successful use in recent years. Given their long-term application and the critical role of geometry in determining fracture and fatigue characteristics, fatigue assessments are of utmost importance for implant systems. In this study, nine dental implant system samples were subjected to testing in accordance with ISO 14801 standards. The tests included static evaluations to assess ultimate loads and fatigue tests conducted under loads of 270 N and 230 N at a frequency of 15 Hz, aimed at identifying fatigue failure locations and fatigue life. Fatigue life predictions and related calculations were carried out using Fe-safe software. The initial model featured a 22° angle for both the fixture and abutment. Subsequently, variations in abutment angles at 21° and 23° were considered while keeping the fixture angle at 22°. In the next phase, the fixture and abutment angles were set as identical, at 21° and 23°. The results unveiled that when the angles of the abutment and fixture matched, stress values decreased, and fatigue life increased. Conversely, models featuring abutment angles of 21° and 23°, with a 22° angle for the fixture, led to a 49.1 % increase in stress and a 36.9 % decrease in fatigue life compared to the primary model. Notably, in the case of the implant with a 23° angle for both abutment and fixture, the fatigue life reached its highest value at 10 million cycles. Conversely, the worst-case scenario was observed in the implant with a 21° abutment angle and a 23° fixture angle, with a fatigue life of 5.49 million cycles.

Implant survival rate and marginal bone loss with the all-on-4 immediate-loading strategy: A clinical retrospective study with 1 to 4 years of follow-up

STATEMENT OF PROBLEM

Assessing peri-implant marginal bone loss (MBL) and its risk factors with cone beam computed tomography (CBCT) may clarify the risk factors for the all-on-4 (5 or 6) strategy and further improve its survival rate.

PURPOSE

The purpose of this retrospective clinical study was to evaluate the implant survival rate, MBL, and associated risk factors of all-on-4 (5 or 6) prostheses after 1 to 4 years of follow-up with CBCT.

MATERIAL AND METHODS

A total of 56 participants rehabilitated with 325 implants by using the all-on-4 (5 or 6) concept between October 2015 and December 2019 were included. Outcome measures were cumulative implant survival (life-table analysis) and MBL. Four CBCT scans, a scan immediately after surgery (T0), a scan 1 year after surgery (T1), a scan 2 years after surgery (T2), and a scan 3 to 4 years after treatment (T3), were obtained to evaluate the MBL. The Pearson correlation coefficient analysis and linear mixed models were performed to assess the potential risk factors for MBL (α=.05).

RESULTS

The implant survival rate was 99.38%, and the prosthesis survival rate was 100%. The reductions in the vertical buccal bone height (△VBBH) were 0.74 ±0.10 mm (T0-T1), 0.37 ±0.12 mm (T1-T2), and 0.15 ±0.14 mm (T2-T3). Except for T2-T3, the △VBBH showed a significant difference at T0-T1 and T1-T2 (P≤.05). The alterations in vertical mesial bone height (VMBH), vertical distal bone height (VDBH), and vertical lingual bone height (VLBH) were similar to the trend observed in VBBH. The △VBBH (T0-T3) was negatively correlated with the horizontal buccal bone thickness (HBBT) (T0) (r=-.394, P<.001). Linear mixed models revealed that factors such as smoking (P=.001), mandible implant site (P<.001), immediate implant (P=.026), tilted implant (P<.001), female sex (P=.003), systemic disease (P=.025), and bruxism (P=.022) negatively affected MBL. The cantilever length (CL) also had a negative effect on MBL around the implants at the distal extension (P<.001).

CONCLUSIONS

The high implant and prosthesis survival rates and low MBL confirmed the predictability of the all-on-4 (5 or 6) concept. Smoking, mandible implant site, systemic disease, bruxism, female sex, immediate implant, tilted implant, and CL were identified as potential risk factors for MBL.

Functional and aesthetic rehabilitation using 'all on 4' treatment protocol with intraoral welding

With the increasing life expectancy and improved quality of life, the conventional prosthodontic removable treatment modalities are being replaced with implant retained fixed prostheses. A full-arch conventional rehabilitation of edentulous ridges requires six to ten dental implants. However, some patients demand fixed implant-supported prostheses inspite of medical conditions and economic concerns. Also in completely edentulous cases, the insufficient bone morphology directs the treatment plan towards alternatives such as cantilever prostheses, short implants or ridge augmentation procedures. These clinical conditions have brought in a quantum shift in treatment planning towards the 'all on 4 protocol' providing immediately loaded fixed prosthesis supported by 4 implants thereby providing optimum and immediate restoration of function and esthetics.

Treatment alternatives for the rehabilitation of the posterior edentulous maxilla

Rehabilitation of the edentulous maxilla with implant-supported fixed dental prostheses can represent a significant clinical challenge due to limited bone availability and surgical access, among other factors. This review addresses several treatment options to replace missing teeth in posterior maxillary segments, namely the placement of standard implants in conjunction with maxillary sinus floor augmentation, short implants, tilted implants, and distal cantilever extensions. Pertinent technical information and a concise summary of relevant evidence on the reported outcomes of these different therapeutic approaches are presented, along with a set of clinical guidelines to facilitate decision-making processes and optimize the outcomes of therapy.

Comparison between Two Design Concepts of Four Implants Placement Used to Support Telescopic Mandibular Overdenture: A Prospective Study of Implant Marginal Bone Height Changes

AIM

The aim of this present study was to compare two placement designs of four implants used to support a telescopic mandibular overdenture regarding the marginal bone height changes.

MATERIALS AND METHODS

Each patient received four implants. Two anterior implants were installed vertically in the canine area. Patients were randomized into two groups according to the direction of posterior implants installed in the premolar area. Group I: where the implants were installed vertically parallel to the anterior implants and group II: where the implants were installed 30^º distally. The implants were delayed loaded with a telescopic mandibular overdenture. The implant's marginal bone changes were evaluated after 6 and 12 months of overdenture insertion.

RESULTS

Mean marginal bone loss of anterior implants showed a statistically significant difference between both groups. The vertically parallel posterior implants in group I showed statistically significant higher marginal bone loss than posterior implants in group II after follow-up periods. The 30^º distally tilted posterior implants maintained the implant marginal bone after 12 months of overdenture insertion.

CONCLUSION

Rehabilitation of the edentulous mandible with telescopic overdenture supported by four parallel implants is a promising successful treatment option.

CLINICAL SIGNIFICANCE

Tilting the posterior implants will improve the anteroposterior spread that in turn increases the support and the survival rate of the implants. Also, using this technique gives us an opportunity to use fewer implants.

Clinical outcomes of full-arch immediate fixed prostheses supported by two axial and two tilted implants: A retrospective cohort study with 12-15 years of follow-up

PURPOSE

To retrospectively assess clinical and radiographic outcomes of immediately loaded full-arch fixed prostheses supported by axial and tilted implants up to 15 years of function.

MATERIALS AND METHODS

Patients with one completely edentulous arch received an immediate full-arch fixed prosthesis supported by two anterior axial and two posterior tilted implants. Definitive prosthesis consisting of a CAD-CAM titanium framework and acrylic teeth was delivered 6 months later. Patients were regularly followed to assess clinical parameters and marginal bone level (MBL) change. Multilevel regression analysis was performed to investigate factors affecting implant failure and MBL.

RESULTS

Six hundred ninety-two implants were placed in 72 maxillae and 101 mandibles. Seven maxillary implants (5 axial and 2 tilted) in 6 patients and 12 mandibular implants (6 axial and 6 tilted) in 5 patients failed. 15-year cumulative implant survival was 97.51% and 96.91% in maxilla and mandible, respectively (p = .64). After 10 years, the difference in MBL between axial and tilted implants was not significant in the maxilla (p = .47, 65 patients), while it was in the mandible (p < .001, 80 patients). Significant higher bone loss was reported in the mandible at both 5- and 10-year follow-up (p < .001 and p = .004, respectively). Mixed-effect multilevel linear regression evidenced a correlation between arch and bone loss at 5- and 10-year follow-up, while no correlation was found with age, gender, smoking, diabetes, and history of periodontal disease.

CONCLUSION

This long-term study suggests that the present technique can be considered a viable treatment modality for the immediate rehabilitation of both maxilla and mandible.

Volumetric Evaluations of Full-Arch Implant Supported Restorations and Their Role on Patients’ Quality of Life: A Mixed-Model Analysis

Introduction

Full-arch, implant-supported hybrid restorations, employing tilted implants, can offer an efficient way of treating edentulous patients. Several factors, such as the timing of implant placement and the inclination of the fixture, can have a detrimental effect on their stability. This retrospective study is aimed at discerning the role played by those factors.

Materials and Methods

Patients treated with full-arch, implant supported restorations were selected for this study; cone-beam computed tomography (CBCT) images, taken 3 months and 3 years after delivery of the final restoration, as well as peri-implant values, were obtained and compared; bone loss was measured on four sites for each implant and then averaged. These patients were recalled, and the OHIP-5 questionnaire was administered.

Results

21 patients, with a mean age of 53 years, were included in the present analysis. 108 implants were placed, and 25 Toronto prostheses were delivered. According to a mixed-model analysis, tilted implants (0.51, p < 0.001) had a higher rate of bone loss, while implants placed in a healed ridge suffered less bone loss than immediate implants (-0.21, p < 0.001). Patient-level variables have a significant effect on this variable, as implants coming from the same subject share a similar risk of bone loss. The mean response to the self-administered OHIP-5 questionnaire was 1.53 ± 0.29; other variables did not have a statistically significant effect on this outcome. Discussion/Conclusions. The results of the present study show that Toronto bridges prostheses are an efficient procedure for treating edentulous patients, as their oral-related quality of life is reported as satisfactory even 7 years after delivery of the restoration. Tilted and immediate implants are more at risk of bone loss. Implants coming from the same subject share a similar risk of bone loss.

Evaluation of Viability and Cell Proliferation in Bone and Gingival on Dental Implant Fixtures with Active Sandblasted and Sandblasted Surfaces by the Cytotoxicity Test Method

In recent years, the technology of dental implants has advanced a lot and this has become one of the main reasons for dentists to refer to implants immediately after tooth extraction. Evaluation of cell survival in implantology studies to determine cell sensitivity determines the outcome of treatment. This study aimed to investigate the bone integration properties as well as the cytotoxicity between the implant surface and the jaw bone. In this study, cytotoxicity test was used to evaluate the toxicity and viability of sandblasted large grit acid etched, and sandblasted large grit acid etched active surfaces in 3A brand dental implants with G292 osteoblastic cells and human gingival fibroblasts cells are discussed. This operation was performed using a laboratory incubator of the German company MEMMERT for 24 hours, by neubauer lam cells counting for one hundred thousand cultured cells in each test at a temperature of 37 °C, a pressure of 1 atmosphere and 90% humidity. Based on the scanning electron microscopy images and the cytotoxicity test results, it can be seen that the bone graft of the implant, with the sandblasted large grit acid etched active surface treatment, is much better and also one week faster than the implant with the sandblasted large grit acid etched one. However, the viability of the implant with the sandblasted large grit acid etched active surface treatment for both G292 osteoblastic cells and human gingival fibroblasts cells samples was equal to 98.4% and 97.3%, respectively, and is lower than the sandblasted large grit acid etched surface treatment. The results show that the viability of the sandblasted large grit acid etched implant is about 1.5 to 2% higher than the sandblasted large grit acid etched active one, but the surface integrity of sandblasted large grit acid etched active is better than sandblasted large grit acid etched in all samples, and the treatment process is reduced by one week.

Rehabilitation of the Completely Edentulous Mandible by All-on-Four Treatment Concept: A Retrospective Cohort Study with Up to 10 Years Follow-Up

(1) Background and Objectives. Currently, there are no definitive long-term data about clinically significant difference in the failure of prosthesis and implant or marginal bone loss related to the rehabilitation of the completely edentulous mandible by all-on-four treatment concept. The main aim of present investigation was to report the long-term outcomes (10-years follow-up) of complete-arch mandibular rehabilitations based on the all-on-four concept. (2) Materials and Methods. Patients in need of extractions of teeth due to the occurrence of caries and/or severe periodontal disease and patients presented with edentulous mandibles were enrolled to the study. A total of 96 participants (mean follow-up period after intervention of 3185.2 days) were enrolled in the study. Participants were evaluated at the first visit, 10 days after intervention and every year after the intervention. Implant and prosthesis survival, bone loss and both local biological and mechanical complications were evaluated during the follow-up period. (3) Results. An implants’ survival rate of 97.9% was observed at the end of the follow-up period. Biological complications were reported in 19.8% of patients, whereas mechanical complications were reported in 27.1% of cases. The average marginal bone level at baseline was −0.03 mm. A significant marginal bone loss was observed after 10-years follow-up (2.5 mm). Binary logistic regression analysis showed significant association between smoke and both marginal bone loss and local biological complications. Lastly, a significant association was observed between bruxism and mechanical complications. (4) Conclusions. The high implant and prosthesis survival rate and the moderate incidence of biological and mechanical complications observed in present investigation can be associated to several factors such as high implant primary stability, prosthetic design, and control of the occlusal forces.

Effect of Schneiderian Membrane Thickening on the Maxillary Sinus Augmentation and Implantation Outcomes: A Systematic Review

Background

Schneiderian membrane thickness may influence the final clinical outcome of sinus augmentation and dental implantation. Mucosal thickening has been regarded as a contributing factor for post-treatment complications. This study aimed to systematically review the available literature on the association between mucosal thickening and potential complications related to sinus augmentation and implant placement.

Methods

An electronic search was carried out in MEDLINE, Embase, and Web of Science by two independent reviewers. It was complemented by manual search of the reference lists of all relevant studies. The studies reporting on sinus augmentation and dental implantation in cases with preoperative mucosal thickening were considered eligible for this study.

Results

The initial search yielded 1032 articles. Five hundred and sixty-four records were screened by title and abstract, and 57 studies succeeded the inclusion criteria for full-text evaluation. Finally, 10 records remained for data extraction. The included studies assessed sinus augmentation and implantation procedures in 765 patients, 324 (42.3%) of them showed mucosal thickening. Increased membrane thickness did not significantly elevate the frequency of sinus augmentation complications. In addition, the overall implant survival rate was 99.03%.

Conclusions

Within the limitations of the present study, the presence of mucosal thickening might not be a risk factor for sinus augmentation and implant survival rate.

Oral health-related quality of life and satisfaction in edentulous patients rehabilitated with implant-supported full dentures all-on-four concept: a systematic review

OBJECTIVE

Address oral health-related quality of life (OHRQoL) and patient satisfaction rehabilitated by the all-on-four concept as the primary outcome.

MATERIAL AND METHODS

A search was performed in the PubMed/MEDLINE, Web of Science, and Cochrane databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis criteria (PRISMA). The PICO question was used to address the following specific question: "What is the level of oral health-related quality of life and satisfaction in edentulous patients and with atrophic jaws who received dental implants for full-arch implant-supported restorations following the all-on-four in the mandible or maxilla?"

RESULTS

Eleven studies including 693 patients aged 55 to 71 years were selected. The shortest follow-up period was 3 months and the longest, 7 years. Regarding the OHRQoL assessment method and patient satisfaction, the oral health impact profile (OHIP) and the visual analog scale (VAS) were the most used.

CONCLUSION

OHRQoL and satisfaction in patients whose rehabilitation was based on the all-on-four concept were high. However, the current evidence is still limited by the quality of the available studies, making long-term randomized studies necessary to establish the real effectiveness of this surgical-prosthetic approach.

CLINICAL RELEVANCE

Carefully analyze the aspects related to satisfaction and oral health-related quality of life of rehabilitated patients with implant-supported total prostheses made according to the all-on-four concept, aiming to achieve success through procedures with greater predictability and less complexity, as these are directly associated with recovery oral health of edentulous individuals with less morbidity and minimized costs.

Survival rates of axial and tilted implants in the rehabilitation of edentulous jaws using the All-on-four™ concept: A systematic review

Aim:

The aim of this review was to evaluate the survival rate of axial and tilted implants in rehabilitation of edentulous jaws using all on four concept.

Setting and Design:

Systematic Review.

Materials and Methods:

A literature review was performed in MEDLINE, PubMed Central (PMC), Google scholar, Embase, Cochrane Central Register of Controlled Trials. Hand searches were conducted of the bibliographic of related journals and systematic reviews. A total of 380 articles were obtained from the intial screening process. Of these articles, 25 articles fulfilled the inclusion criteria. The authors performed evaluation of articles independently as well as data extraction and quality assessment.

Statistical Analysis Used:

Qualitative analysis.

Results:

The major prosthetic complication was the fracture of the acrylic prosthesis. The mean cumulative survival rate of implants (72-132 months) were 94% to 98%. The prosthesis survival rate (12 months) was between 99% to 100%. The averaged bone loss was 1.3 ±0.4 mm (12-60 months). No Significant difference was found between survival rates of axial and tilted implants nor between maxilla and mandible.

Conclusion:

All on four concept can be employed successfully in the edentulous patients with resorbed ridges while improving their quality of life and reducing morbidity. However,randomized clinical trials with large sampling size and long term follow up should be incorporated.

Investigation of the Effect of Abutment Angle Tolerance on the Stress Created in the Fixture and Screw in Dental Implants Using Finite Element Analysis

Today, an artificial tooth root called a dental implant is used to replace lost tooth function. Treatment with dental implants is considered an effective and safe method. However, in some cases, the use of dental implants had some failures. The success of dental implants is influenced by several biomechanical factors such as loading type, used material properties, shape and geometry of implants, quality and quantity of bone around implants, surgical method, lack of rapid and proper implant surface's integration with the jaw bone, etc. The main purpose of functional design is to investigate and control the stress distribution on dental implants to optimize their performance. Finite element analysis allows researchers to predict the stress distribution in the bone implant without the risk and cost of implant placement. In this study, the stresses created in the 3A.P.H.5 dental implant's titanium fixture and screw due to the change in abutment angles tolerance have been investigated. The results show that although the fixture and the screw's load and conditions are the same in different cases, the change of the abutment angle and the change in the stress amount also made a difference in the location of maximum stress. The 21-degree abutment puts the fixture in a more critical condition and increases the chance of early plasticization compared to other states. The results also showed that increasing the abutment angle to 24 degrees reduces the stress in the screw, but decreasing the angle to 21 degrees leads to increased screw stress and brings it closer to the fracture.

Clinical performance of narrow-diameter titanium-zirconium implants in immediately loaded fixed full-arch prostheses: a 2-year clinical study

Objectives

The aim of this study was to evaluate the outcomes of immediate fixed full-arch prostheses supported by axial or tilted narrow-diameter Ti-Zr implants (3.3 mm) (Roxolid®, Institut Straumann® AG, Basel, Switzerland) (NDIs) in combination with standard-diameter implants up to 2 years’ follow-up.

Materials and methods

The study was conducted at Kocaeli University Faculty of Dentistry from 2016 to 2018. 37 jaws of 28 patients with an average age of 52 years were rehabilitated with fixed full-arch prostheses supported by 179 implants. Cumulative survival rate (CSR), implant success, marginal bone loss (MBL), and prosthetic survival rate as well as complications were analyzed.

Results

Total CSR of 99.4% and 98.5% for all and narrow implants respectively have been observed at 2 years’ follow-up. No prosthesis failures were observed, yielding a cumulative prosthetic survival rate of 100%. The NDIs achieved 0.63 mm MBL at 1 year and 1.02 mm at 2 years. The mean MBL at 1 year was 0.51 mm (mandible 0.63 mm/maxilla 0.41 mm) and 0.73 mm (mandible 0.90 mm/maxilla 0.43 mm) at 2 years. Both implant angulation and loading protocol did not influence the MBL.

Conclusions

The combination of narrow-diameter implants with standard-diameter implants in immediate fixed full-arch rehabilitation has a good prognosis to become a new standard of care for severely atrophic jaws.

Clinical relevance

The use of narrow-diameter implants in fixed full-arch rehabilitations in atrophic ridges would be a successful and predictable treatment approach.

Oral Health-Related Quality of Life and Full-Arch Immediate Loading Rehabilitation: An Evaluation of Preoperative, Intermediate, and Posttreatment Assessments of Patients Using a Modification of the OHIP Questionnaire

The aim of this study was to assess oral health-related quality of life (OHRQoL) of patients before, during, and after completion of implant-supported full-arch immediate loading rehabilitation according to the Columbus Bridge Protocol. Twenty-five patients with compromised dentition were rehabilitated according to the Columbus Bridge Protocol and were assessed for OHRQoL using 4 questionnaires specifically designed for this study and inspired by the Oral Health Impact Profile questionnaire. Patients assessed themselves before surgery, during the healing period (1 week and 2 months after surgery), and after definitive prosthodontic treatment (4 months after surgery). The questionnaires specifically investigated patients' pain, comfort, home oral hygiene habits, satisfaction related to esthetics, masticatory ability, phonetics and general satisfaction with the treatment. Patients reported an improvement of OHRQoL after full-arch immediate-loading rehabilitation. A statistically significant improvement in esthetics and chewing ability was found. After 4 months 92% of the patients did not feel tense about their smile, 96% did not indicate problems relating to other people or smiling, and 92% did not have difficulty eating some foods. Phonetics were a critical issue, especially in the intermediate phase of healing. One week after surgery, the percentage of patients who were very satisfied with phonetics slightly decreased from 48% to 36%. The assessment of patients' OHRQoL related to full-arch immediate-loading implant therapy exhibited a significant improvement in quality of life. The questionnaires herein presented could be an effective tool to evaluate patients' reaction to oral rehabilitation.

Fixed full-arch maxillary prostheses supported by four versus six implants with a titanium CAD/CAM milled framework: 3-year multicentre RCT

OBJECTIVES

This RCT compares marginal bone level (MBL) change and the clinical parameters after a 3-year function in maxillary implant-supported fixed complete dentures (FCDs) treated with four-implants (4-I) or six-implants (6-I).

MATERIAL AND METHOD

Three centres treated 56 patients with 280 implants allocated to the 4-I or 6-I group. Radiographic and clinical examinations were performed. The primary outcome was to investigate MBL change between the groups.

RESULTS

Implant survival rates were 100% and 99% in the 4-I and 6-I groups, respectively. Considering the clustering effects, the MBL change was not significantly different between the groups over the 3-year follow-up. The MBL in the 4-I group was 0.30 ± 0.50 mm at baseline, 0.24 ± 0.31 mm at 1 year and 0.24 ± 0.38 mm at 3 years. In the 6-I group, MBL was 0.14 ± 0.32 mm at baseline, 0.16 ± 0.35 mm at 1 year and 0.12 ± 0.26 mm at 3 years. There was a statistically significant difference between the groups at BL and 3Y. No significant differences between the groups were reported for clinical parameters at each time point as well as in between the visits. The technical and biological complications rates were 1.6% and 6.0%, respectively. Prosthetic complications affected 25 FCDs (47.2%).

CONCLUSION

Marginal bone level change revealed a stable condition in the 3-year period in the two groups. Few technical and biological complications occurred apart from the chipping/fracture of the prosthetic teeth. Four-implant is a feasible solution if the rehabilitation is oriented towards the most cost-effective treatment and towards avoiding bone augmentation procedures. Clinicians have to consider the potential required visits for prosthetic maintenance.

The effect of the design of a mandibular implant-supported zirconia prosthesis on stress distribution

STATEMENT OF PROBLEM

Prosthetic complications have been frequently reported in implant-supported complete-arch prosthesis. Prosthetic restorations designed with an all-on-four treatment concept and fabricated from zirconia ceramic may be used to overcome these problems.

PURPOSE

The purpose of this biomechanical study was to evaluate the effects of cantilever length and inclination of implant on the stress distribution in bone tissue, implant, and a monolithic zirconia ceramic-lithium disilicate glass-ceramic superstructure for all-on-four prosthesis.

MATERIAL AND METHODS

All-on-four mandibular prosthesis fabricated from a zirconia and lithium disilicate glass-ceramic (LDGC) superstructure was designed with cantilever lengths of either 5 mm or 9 mm and posterior implants with a distal tilt of either 15 or 30 degrees. Stresses were evaluated with a simulated application of a static load of 600 N.

RESULTS

Increasing implant inclination from 15 to 30 degrees led to a decrease in maximum principal stress (MaxPS) values of approximately 4 to 7 MPa in cortical bone around all implants except the right anterior implant in the designs with short cantilevers and an increase in MaxPS values (approximately 3 to 19 MPa) in the same places in the designs with the long cantilevers. Increasing cantilever length from 5 to 9 mm resulted in an increase in minimum principal stress (MinPS) values of approximately 3 to 13 MPa in the cortical bone surrounding all posterior implants. In the designs with the long cantilever, MaxPS values increased approximately 3 to 4 MPa in spongy bone adjacent to the right posterior implant. An increase in cantilever length also led to higher vMS values at the first and second implant grooves in the right posterior implant in the design with the 15-degree implant tilt. An increase in implant inclination in the design with the short cantilever resulted in lower vMS values at the apex and all grooves of the left posterior implant, whereas in the design with the long cantilever, an increase in implant inclination resulted in lower stress values in the first and second grooves of the same implant. An increase in implant inclination led to in an increase in vMS values in the core structure.

CONCLUSIONS

In zirconia ceramic restorations by using an all-on-four design with an LDGC superstructure, short cantilevers may be preferable because they result in a more favorable distribution of stress than long cantilevers. An increase in implant angulation from 15 to 30 degrees decreased MaxPS values in cortical bone.

Biomechanical effect of implant design on four implants supporting mandibular full-arch fixed dentures: In vitro test and finite element analysis

BACKGROUND/PURPOSE

Impact of the implant shape on the biomechanical performance of all-on-four treatment of dental implant is still unclear. This study evaluated the all-on-four treatment with four osseointegrated implants in terms of the biomechanical effects of implant design and loading position on the implant and surrounding bone by using both in vitro strain gauge tests and three-dimensional (3D) finite element (FE) analyses.

METHODS

Both in vitro and 3D FE models were constructed with placing NobelSpeedy and NobelActive implants as well as a titanium framework in an edentulous jawbone based on the concept of all-on-four treatment. Three types of loads were applied: at the central incisor area (loading position 1) and at the molar regions with (loading position 2) and without (loading position 3) the denture cantilever. For the in vitro tests, the principal bone strains were recorded by rosette strain gauges and statistically evaluated using Wilcoxon's rank-sum test. The 3D FE simulations analyzed the peak von-Mises stresses in the implant and surrounding cortical bone.

RESULTS

The peak stress and strain in the surrounding bone were typically 36-62% (3D FE analysis) and 47-57% (in vitro test) (p < 0.001)higher for loading position 3 than for loading positions 1 and 2. Between those two implant designs, the bone strains and bone stresses did not differ significantly.

CONCLUSION

For all-on-four treatment with four osseointegrated dental implants, altering the implant design does not appear to affect the biomechanical performance of the entire treatment, especially in terms of the stresses and strains in the surrounding bone.

Are There Alternatives to Invasive Site Development for Dental Implants? Part II

Despite improvements in bone preservation following tooth extraction, edentulous sites are often deficient in bone volume for conventional dental implant therapy. Missing bone volume is often recaptured by surgery and grafting. This article discusses noninvasive alternatives to bone grafting. Part I of this topic discussed the use of short and narrow diameter implants. Part II discusses three additional alternatives: the use of tilted implants, the use of four or fewer tilted and axially-loaded implants to support a full-arch fixed-dental-prosthesis (FAFDP), and the use of zygomatic implants to restore the severely-atrophic edentulous maxillae lacking adequate bone for conventional treatment.

Implant supported cantilevered fixed dental rehabilitations in partially edentulous patients: Systematic review of the literature. Part I

OBJECTIVES

To investigate in which clinical situations a cantilever fixed implant supported restorations can be a treatment alternative and which complications are reported.

MATERIALS AND METHODS

Two operators screened the literature (MEDLINE, EMBASE) and performed a hand search on the main journals dealing with implantology and prosthetics until 31 December 2017. Only articles that considered cantilever implant fixed restorations with at least 10 patients and with a mean follow-up of at least 5 year were selected. The outcome variables were survival of implants and prosthesis, mechanical, technical and biological complications, marginal bone loss. The review was performed according to the PRISMA statements. Risk of bias assessment was evaluated. Failure and complication rates were analysed using random effect Poisson regression models to obtain summary estimate of 5- and 10-year survival and complication rates.

RESULTS

A total of nine papers were selected for partially edentulous patients and reported high survival rate of the prosthesis. The estimated survival rate for 5-10 years was calculated to be 98.4% for the implants and 99.2% for the rehabilitations. Mechanical, technical and biological complications were reported with a cumulative 5-10 years complication rate of 28.66% and 26.57% for the patients and for the prosthesis, respectively. Two papers for single implant supporting 2-unit cantilever were not sufficient to draw conclusions.

CONCLUSIONS

There is evidence that cantilever can be successful treatment in partially edentulous patients. In two adjacent edentulous sites, data are not yet sufficient.

Implant rehabilitation of the edentulous jaws: Does tilting of posterior implants at an angle greater than 45° affect bone resorption and implant success?: A retrospective study

PURPOSE

This study aimed to (1) investigate the success of posterior implants tilted >45° when 4 immediately loaded implants were used to support full-arch prostheses, eliminating any distal cantilever and (2) examine the effect on marginal bone loss (MBL) of different combinations of anterior multi-unit abutment (MUA) angles and posterior implant tilting angles.

MATERIALS AND METHODS

Records of patients rehabilitated according to the Columbus Bridge Protocol were analyzed. Peri-implant bone levels (PBLs) and MBL were measured for each implant. The influence of posterior implant tilting angle on PBL, MBL, and implant and prosthetic success rate was investigated. The impact on the same endpoints of different anterior MUA angles, and different combinations of anterior MUA and tilted posterior implant angles was also examined.

RESULTS

Records of 41 patients were analyzed, for a total of 46 complete rehabilitations, and 142 implants (52 anterior, 63 posterior tilted ≤45° [group 1], and 27 posterior tilted >45° [group 2]). No implants were lost during the follow-up (25.9 months), and no prosthetic complications were reported. Success rate for posterior implants was 100% in group 1 and 96.3% in group 2. Mean MBL differed significantly between the 2 groups (0.45 mm in group 1, 0.66 in group 2 [P = .04]), but not when the analysis was limited to implants in the same jaw. Implant tilting angle did not correlate with MBL and the MUA angle had no effect on bone resorption around posterior implants, neither in the sample as a whole nor in individual patients.

CONCLUSIONS

Posterior implants tilted >45° to eliminate distal cantilever may be as safe as those tilted less in severely atrophic jaws rehabilitated with immediately loaded, full-arch prostheses supported on 4 implants. Further prospective studies on larger samples of patients and implants and with longer follow-up are needed to confirm these findings.

Dental Implants

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

Immediate implant and rehabilitation based on All-on-4 concept in patients with generalized aggressive periodontitis: A medium-term prospective study

BACKGROUND

Aggressive periodontitis renders a great challenge to the conventional implant due to the risks of infection and ongoing marginal bone loss (MBL). A study about full-arch immediate implant and restoration in patients with advanced generalized aggressive periodontitis (GAP) was not read, even though the All-on-4 concept has been proven to be predictable for edentulous patients.

PURPOSE

This prospective study aimed to evaluate the feasibility and medium-term outcomes of immediate implant and rehabilitation based on the All-on-4 concept in patients with advanced GAP via clinical and radiographic analyses.

MATERIALS AND METHODS

Seventeen patients (mean age 39.4 years) with advanced GAP received immediate postextraction implant and rehabilitation based on the All-on-4 concept between January 2009 and January 2014. Eighty implants were inserted into 20 arches (7 maxillae and 13 mandibles). The average follow-up duration was 5 years (range 2-7). Complications, probing depth, and plaque, bleeding, and gingiva indices were evaluated. MBL was measured based on the panoramic radiographs taken immediately after surgery and annually thereafter.

RESULTS

The cumulative survival rate (CSR) of the implants was 98.75% (79/80) after an average of 5 years. One tilted implant failed due to peri-implantitis. The average peri-implant MBL was 0.8 ± 0.4 and 1.2 ± 0.3 mm after 1 and 7 years, respectively. The CSR was 100% (20/20) for definite prostheses, while 85% (17/20) for provisional prostheses. The average probing depth, and plaque, bleeding, and gingiva indices at the last recall visit were 3.0 ± 0.5, 1.2 ± 0.4, 0.5 ± 0.5, and 0.4 ± 0.4 mm, respectively. Patient showed high satisfaction to the overall effects.

CONCLUSIONS

Based on this study, the All-on-4 concept provided predictable outcomes in patients with GAP in 2- to 7-year follow-ups, and averted the severe bone defect area of aggressive periodontitis.

Primary stability of implants placed at different angulations in artificial bone

INTRODUCTION

The aim of this study was to evaluate the primary stability (PS) of titanium implants with a progressive thread design and more thread stability in the apical threads placed in artificial bone materials.

MATERIALS AND METHODS

A total of 120 implants were placed in commercially available polyurethane composite bone blocks. The angulations that were chosen to place the implants in bone types II and IV were 0, 10, and 20 degrees, respectively. The implant dimensions were 11 mm in length and 3.5 mm in diameter. Two clinicians placed all implants, and an independent examiner evaluated the PS using the Osstell (ISQ) and Periotest devices. The χ test was used to evaluate the statistical differences between the PS at different angulations.

RESULTS

This study showed that there was a statistically significant difference (P = 0.02) of the PS values, when measured using the Periotest values, among all 3 angulations in both bone qualities. Tilted implants with 10 degrees, angulation had a better stability than conventionally placed implants.

CONCLUSIONS

The PS of dental implants is higher for implants placed in type II when compared with type IV artificial bone. A higher stability was found for implants placed with 10-degree angulations.

The all-on-four concept may be a viable treatment option for edentulous rehabilitation

Data sourcesMedline, the Cochrane Library, Google and hand-searches of systematic reviews and bibliographies from related journals in English and German up to August 2012.Study selectionThree reviewers independently searched for clinical trials that assessed the success rates of placing two anterior and two posterior tilted dental implants in humans either in the maxilla or mandible according to the all-on-four treatment concept. Inclusion limited studies with a minimum follow-up period of one year.Data extraction and synthesisThe primary outcome measure was the failure rate of implants. The secondary outcomes were prosthesis failure and marginal bone loss/bone level changes assessed through radiological examination. Failure rate was used to calculate standard deviations (SDs) of implants, whereas the mean success rate was used for dental implants and prostheses. Evaluation and quality assessment of articles and data extraction were performed by three independent reviewers. These reviewers estimated risk of bias by assessing the trial quality using a criteria form focused on the trial design, specification of inclusion/exclusion criteria, performance of surgery, outcome measure provided, radiographic examination of marginal bone level change as well as its evaluation and completeness of follow-up. Outcome measures were based on weighted means using a variance components analysis.ResultsThirteen studies, including 4,804 dental implants (2,000 maxilla and 2,804 mandible) placed in 1,201 jaws met the inclusion criteria. Nine were prospective trials, three retrospective studies and one longitudinal trial. All studies except one were considered to be at high risk of bias. Seventy-four (37 axially, 37 tilted) dental implants failed, with most failures (74%) within the first 12 months. Fifty-seven out of 1,201 prostheses failed but were repairable. The major prosthetic complication was the fracture of the all-acrylic prostheses. At 36 months the mean cumulative survival rates for implants and prostheses were 99.0 ± 1.0% (SD) and 99.9 ± 0.3% (SD), respectively with an average bone loss of 1.3 ± 0.4 mm (SD). There were no statistically significant differences in the clinical outcomes between maxillary versus mandibular arches and axially versus tilted placed implants.ConclusionsThe available evidence shows a promising short-term prognosis for the all-on-four treatment concept. However the evidence is limited by the quality of the available studies and the paucity of clinical trials of greater than five years.

Long-term Evaluation of Peri-implant Bone Level after Reconstruction of Severely Atrophic Edentulous Maxilla via Vertical and Horizontal Guided Bone Regeneration in Combination with Sinus Augmentation: A Case Series with 1 to 15 Years of Loading

BACKGROUND

To the best of the authors' knowledge, there is very limited clinical data on the outcomes of simultaneous guided bone regeneration (GBR) for horizontal and/or vertical bone gain for the reconstruction of severely atrophic edentulous maxilla. Therefore, the purpose of the clinical series presented herein was to clinically evaluate long-term horizontal and vertical bone gain, as well as implant survival rate after reconstruction of severely atrophic edentulous maxillary ridges.

MATERIAL AND METHODS

Sixteen patients (mean age: 64.6 ± 14.6 years of age) were consecutively treated for vertical and/or horizontal bone augmentation via GBR in combination with bilateral sinus augmentation utilizing a mixture of autologous and anorganic bovine bone. Implant survival, bone gain, intraoperative/postoperative complications and peri-implant bone loss were calculated up to the last follow-up exam.

RESULTS

Overall, 122 dental implants were placed into augmented sites and have been followed from 12 to 180 months (mean: 76.5 months). Implant survival was 100% (satisfactory survival rate of 97.5%). Mean bone gain was 5.6 mm (max: 9 mm; min: 3 mm) While vertical bone gain was 5.1 ± 1.8 mm; horizontal bone gain was 7.0 ± 1.5 mm. No intraoperative/postoperative complications were noted. Mean peri-implant bone loss values were consistent within the standards for implant success (1.4 ± 1.0 mm). At patient-level, only one patient who had three implants presented with severe peri-implant bone loss.

CONCLUSION

Complete reconstruction of an atrophied maxilla can be successfully achieved by means of guided bone regeneration for horizontal and/or vertical bone gain including bilateral sinus augmentation using a mixture of anorganic bovine bone and autologous bone.

Reconstruction of the severely atrophic edentulous maxillae with calvarial bone grafts

OBJECTIVES

Treatment of the severely atrophic maxilla with dental implants is challenging due to the insufficient horizontal and vertical bone volume and centripetal resorption pattern of the maxilla. Bone-augmentation procedures are often necessary prior to implant placement. The objective of this study was to assess the suitability of using calvarial bone grafts to enable implant placement in severely atrophic maxillae.

MATERIAL AND METHODS

Seventeen patients with severe atrophic edentulous maxillae were reconstructed with autogenous calvarial bone grafts. After a 4-month healing period, the patients received a total of 134 dental implants, which were left to heal in submerged positions for 3 months before prosthetic rehabilitation was performed. Patients were followed clinically and radiographically for an average observation period of 53.94 months.

RESULTS

At the intraoral recipient sites, two infections developed, causing partial loss of the respective bone grafts. Implant placement, however, was possible at all sites. No donor-site complications occurred. Two of 134 implants were lost in two patients prior to prosthetic loading. The implant survival rate was 98.51%. The implant success rate was 87.6%, and a mean marginal bone loss of 0.62 mm (SD 0.77 mm) was documented.

CONCLUSIONS

Patients with severe bone atrophy of the edentulous maxilla can be successfully reconstructed with calvarial bone grafts and dental implants and show a stable clinical and radiographic situation after a mean observation period of 53 months.

Prevalence of Peri-Implant Mucositis and Peri-Implantitis in Patients Treated with a Combination of Axial and Tilted Implants Supporting a Complete Fixed Denture

Objectives. The aim of this retrospective study was to assess the incidence and prevalence of peri-implant mucositis and peri-implantitis in patients with a fixed full-arch prosthesis supported by two axial and two tilted implants. Materials and Methods. Sixty-nine patients were included in the study. Each patient received a fixed full-arch prosthesis supported by two mesial axial and two distal tilted implants to rehabilitate the upper arch, the lower arch, or both. Three hundred thirty-six implants for 84 restorations were delivered. Patients were scheduled for follow-up visits every 6 months in the first 2 years and yearly after. At each follow-up visit peri-implant mucositis and peri-implantitis were diagnosed if present. Results. The overall follow-up range was from 12 to 130 months (mean 63,2 months). Three patients presented peri-implantitis. The prevalence of peri-implant mucositis ranged between 0 and 7,14% of patients (5,06% of implants) while the prevalence of peri-implantitis varied from 0 to 4,55% of patients (3,81% of implants). Conclusions. The prevalence and incidence of peri-implant mucositis and peri-implantitis are lower than most of the studies in literature. Therefore this kind of rehabilitation could be considered a feasible option, on the condition of adopting a systematic hygienic protocol.

Simplified procedure for the immediate loading of a complete fixed prosthesis supported by four implants in the maxillary jaw: a 2-year prospective study

PURPOSE

The aim of this study was to verify the reliability of a system for the fixed retention of complete maxillary prostheses supported by four implants with a follow-up of 2 years.

MATERIAL AND METHODS

Patients were treated between September 2009 and December 2010 with four Straumann Bone Level SLActive implants supporting a complete prosthesis (CPs). The two distal implants were positioned mesially to the maxillary sinus and with a mesio-distal inclination ≤ 30° in order to reduce the distal prosthesis cantilever. An immediate loading surgical protocol was used. The CPs were planned to be fixed to multibase abutments to test their retention for a fixed rehabilitation. Clinical and radiographic parameters as probing pocket depth (PPD), bleeding score (mBI), plaque index (PI), and marginal bone loss (MBL) were assessed at a 1- and 2-year follow-up visits. Moreover, any biological and prosthodontic maintenance events were recorded. Clinical and radiographic parameters changes were analyzed.

RESULTS

Twenty-one patients treated with a total of 84 implants completed the 2-year examination period. Four patients were lost to follow up. No technical complication was recorded. Also, no implant, reconstruction, or abutment failures were observed. Therefore, an implant and prosthetic survival rate of 100% were achieved after 2 years. The mean periodontal parameter scores after 2 years of function were 2.6 mm for PPD (SD 0.8 mm), 0.3 for mBI (SD 0.5 mm), and 1.2 for PI (SD 0.4 mm) indexes, respectively. In addition, the mean MBL score measured at the 2-year follow-up visit was -0.34 mm (SD of -0.45 mm). Furthermore, no peri-implant soft tissue inflammation or peri-implant infection was observed.

CONCLUSIONS

It has been shown that immediate loading of four implants positioned anteriorly to the maxillary sinus could be a reliable treatment procedure to support fixed complete restorations.

Angulated implants: an alternative to bone augmentation and sinus lift procedure: systematic review

Rehabilitation of completely edentulous patients with implant becomes challenging due to reduced amount of bone available and pneumatisation of maxillary sinus or both. To successfully treat such patients, prior to implant placement, patient has to undergo invasive procedures like sinus lift and/or bone augmentation which is not possible many time due to many reasons. This article focuses on an alternative treatment procedure in which two posterior implants are placed at an angle and two anterior implants are placed axially thereby eliminating the need for sinus lift or bone augmentation procedures. This article broadly discusses this "All on Four" concept in all aspects, its effects on bone, prosthesis survival, forces acting etc along with various related studies.

Modified protocol of the intraoral welding technique for immediate implant-supported rehabilitation of the edentulous maxilla

PURPOSE

The aim of this study was to report the outcomes of a treatment option of immediate loading with intraoral welding on only 4 implants for the restoration of patients with maxillary edentulism.

MATERIALS AND METHODS

Seventeen consecutive patients were rehabilitated with 2 parallel and 2 tilted implants in the maxilla. Immediately after implant placement, angulated abutments were screwed on the implants to create better parallelism among the implants; thereafter, a titanium bar was intraorally welded to the welding pins to create a superstructure that rigidly splinted the implants. A fixed full-arch durable prosthesis was delivered on the same day of the surgery. The patients were followed for 26.5 months on average.

RESULTS

During the follow-up time, 2 implants were lost giving an implant survival rate of 97%. Nonetheless, all the prostheses remained in function and the prosthetic success was 100%.

CONCLUSIONS

The rehabilitation of the edentulous maxilla with an immediately loaded full-arch prosthesis, obtained through intraoral welding on only 4 implants, is a functionally and esthetically successful treatment.

All-on-4® Treatment Concept for the Rehabilitation of the Completely Edentulous Mandible: A 7-Year Clinical and 5-Year Radiographic Retrospective Case Series with Risk Assessment for Implant Failure and Marginal Bone Level

BACKGROUND

Studies are needed to evaluate long-term outcomes of the All-on-4® treatment concept (Nobel Biocare AB) for rehabilitation of edentulous mandibles by assessing marginal bone levels and risk indicators for implant failure.

PURPOSE

To evaluate 7-year clinical outcomes and 5-year radiographic outcomes of the All-on-4 treatment concept.

MATERIALS AND METHODS

This retrospective case series included patients admitted for implant rehabilitations in the mandible, who were followed for 7 years clinically and 5 years radiographically. Primary outcome measures were cumulative prosthetic and implant survival using patient as the unit of analysis (Kaplan-Meier product limit estimator). Secondary outcome measure was marginal bone level (MBL) at 5 years. Variables associated with implant failure were analyzed using the Cox proportional hazards regression model to calculate hazard ratios (HRs) with 95% confidence intervals (CIs). Binary logistic regression was used to compute odds ratio (OR) with 95% CIs for variables associated with MBL ≥2.8 mm at 5 years.

RESULTS

A total of 324 patients (194 women, 130 men, average age = 58.9 years) were rehabilitated with 1,296 implants supporting 324 full-arch fixed immediately loaded mandibular prostheses. Sixty-four patients (19.8%) were lost to follow-up. Prosthetic survival was 323/324 (99.7%), and 14 patients lost 18 implants, with an estimated cumulative survival rate of 95.4% at 7 years. Variables associated with implant failure were smoking (HR = 5.28; 95% CI: 1.33, 20.91]) and the learning curve effect (0.69 < HR < 0.33 for more experienced levels). Mean MBL at 5 years was 1.81 mm (95% CI: 1.70, 1.92), and smoking was associated with MBL ≥2.8 mm (OR = 2.4; 95% CI: 1.02, 5.62).

CONCLUSIONS

The high implant and prosthetic survival rates and excellent MBL outcome confirm the predictability and safety of the All-on-4 treatment concept over a longer term than previously reported.

Ongoing Crestal Bone Loss around Implants Subjected to Computer-Guided Flapless Surgery and Immediate Loading Using the All-on-4® Concept

BACKGROUND

The All-on-4(®) concept is widely applied for full-arch rehabilitations, using two tilted and two axially loaded implants in order to overcome anatomical constraints.

PURPOSE

The aim of this study was to assess the survival and individual success of implants immediately loaded with an All-on-4 full-arch screw-retained prosthetic bridge in fully edentulous mandibles or maxillae over up to 3 years.

MATERIALS AND METHODS

In total, 20 patients with atrophic jaws (9 maxillae, 11 mandibles) were treated with computer-guided flapless surgery and immediately provided with a provisional bridge. The final prosthesis was delivered after 6 months. In total, 80 TiUnite(™) Brånemark implants were placed. Radiographs were taken after surgery and 1 and 3 years later.

RESULTS

A 3-year survival rate of 100% was seen for all implants, both in lower and in upper jaw. None of the temporary or definite prostheses were lost over the follow-up period of 3 years. After 1 year, the mean bone loss was 1.13 mm (SD 0.94; range -0.1 to 3.8), and after 3 years, it was 1.61 mm (SD 1.40; range 0 to 5). The mean bone loss between the 1-year and 3-year follow-ups was 0.48 mm (SD 0.66; range -1.2 to 3.6). This difference was statistically significant (p < .001), indicative of ongoing bone loss. Twenty-six percent of the implants had bone loss above 1.5 mm after 1 year, but after 3 years, 30% of the implants had already lost more than 1.9 mm.

CONCLUSION

The implant and prosthetic survival was 100%, and patients benefited from the All-on-4 treatment. However, unacceptable ongoing bone loss was seen in 49.2% of the patients; this may be a warning sign for future problems and needs clinical attention. Overloading and surgery-related aspects need to be investigated as potential explanations.

Maxillary sinus lateral wall thickness and morphologic patterns in the atrophic posterior maxilla

BACKGROUND

The aim of the present study is to examine the sinus lateral wall thickness (LWT) of atrophic posterior maxilla (<10 mm) of patients with complete and partial edentulism and determine the influence of residual ridge height (RH), sex, and age on maxillary LWT.

METHODS

Four hundred fourteen measures were taken from 140 consecutive patients that met the inclusion criteria. On the selected sagittal section, a built-in digital caliper recorded in millimeters the RH and LWT (a perpendicular line at 3, 5, 7, 10, 13, and 15 mm from the lowest point of the sinus floor). Edentulous spans were further classified as complete edentulous atrophic maxilla (CEM) and partial edentulous atrophic maxilla (PEM). The mixed linear model was used to test the effects of sex, type of edentulism, edentulous span, and RH on the measurement of the LWT of the sinus.

RESULTS

Mean LWT for PEM was 1.71 ± 0.12 mm, and for CEM, 1.57 ± 0.07 mm (P = 0.01). The mixed model yielded significant effect of edentulous span (P = 0.048) and interactions among type of edentulism and edentulous span (P <0.001) and edentulous span by RH (P <0.01). Age and RH were positively associated with LWT; however, they did not interact with RH, sex, or type of edentulism. RH has been shown to correlate with edentulous span (P <0.001) and type of edentulism (P = 0.01). The longer the edentulous span, the thinner the LWT. Similarly, RH was larger for PEM (6.85 ± 0.34 mm) than CEM (5.69 ± 0.26 mm).

CONCLUSIONS

The maxillary sinus lateral wall tends to increase in thickness from the second premolar to the second molar and from 5 mm up to 15 mm. In addition, RH, presence of teeth adjacent to the edentulous atrophic ridge, and age were shown to influence maxillary sinus LWT.