The all-on-four treatment concept: Systematic review

Effectiveness of zygomatic-implant fixed rehabilitation for the atrophic edentulous maxilla: protocol for a systematic review and network meta-analysis

BACKGROUND

Atrophic edentulous maxilla is a debilitating condition caused by the progressive and irreversible bone resorption following loss of teeth, that results in bone of inadequate volume and density. This makes conventional implant therapy extremely challenging without complex reconstructive procedures. Several techniques such as sinus augmentation, short implants, and tilted implants have been used for the rehabilitation of the atrophic maxilla. In recent years, zygomatic implants have emerged as a graftless rehabilitation technique. However, few studies compare zygomatic-implant fixed rehabilitation with other fixed rehabilitation techniques. The existing body of evidence on zygomatic implants is largely based on clinical and disease-oriented outcomes.

METHODS

A network meta-analysis (NMA) will be conducted in order to compare the effectiveness of zygomatic-implant fixed rehabilitation with the other rehabilitation techniques. Experimental and observational studies comparing different implant-assisted fixed rehabilitation in adults with atrophic maxilla will be included. The primary and secondary outcomes will be patient's satisfaction and quality of life respectively. Additional outcomes include the implant's survival/success, and biological and prosthetic complications. An electronic search will be performed through various databases for articles in English and French, without time limits. Risk of bias will be assessed using the Revised Cochrane Risk-of-Bias tool for randomized controlled trials, and ROBINS-I for non-randomized and observational studies. Two independent reviewers will screen the titles and abstracts and extract data. Any discrepancy between reviewers will be discussed and resolved through consensus or with the help of a third reviewer. Pairwise meta-analyses will be performed using a random effects model. I2, τ2, transitivity, subgroup/meta-regression analyses will assess and explain heterogeneity and distribution of effect modifiers. A network plot will be created to connect the different interventions directly and indirectly. Interventions will be ranked using the surface under cumulative ranking curve. Confidence in the results of the NMA will be assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE).

DISCUSSION

This study will be the first to assess the effectiveness of zygomatic-implant fixed rehabilitation for the atrophic maxilla using NMA. The evidence obtained will aid clinical decision-making and will advance the knowledge of the rehabilitation techniques for the atrophic maxilla.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42023353303.

Rehabilitation of Edentulous Arch Using All-on-Four Treatment Protocol: A Case Report

In edentulous arches, alveolar ridge atrophy after tooth extraction is a common problem that affects patient comfort and quality of life. Implant-supported fixed restorations are a well-proven treatment option for edentulism. The concepts of implant dentistry have developed over time to produce better aesthetics and functional results. To reduce cantilever length and enable prostheses with 12 teeth, the all-on-four technique entails inserting two anterior implants axially and distally orienting two posterior implants. Compared to conventional loading, immediate loading offers various benefits without compromising quality. An instantaneous fixed provisional allows patients immediate function and preserves their quality of life while also promoting a high degree of patient satisfaction in terms of aesthetics, phonetics, mastication, and psychological comfort.

Less Is More: A Case Report on All-on-4 Prosthesis

Severe alveolar ridge atrophy following tooth removal poses a common and worsening issue in edentulous jaws, affecting patient comfort and quality of life. The All-on-4 approach involves axially positioning two anterior implants and distally orienting two posterior implants, reducing cantilever length and enabling prostheses with 12 teeth. This less invasive option, utilizing distal tilting of implants at 30°, offers biomechanical advantages and has shown short-term success, though long-term research is limited. Immediate-loading treatments are gaining popularity for their high survival rates. Understanding the biomechanics of implant-supported prostheses is crucial for long-term success, emphasizing the importance of optimal occlusal schemes. Challenges such as bone defects and surgical complexity have led to the exploration of achieving full-arch fixed restorations with fewer implants, building upon Brånemark's early work with four implants. The All-on-4 concept, originating in 1999, proves to be a viable treatment option, providing excellent long-term results and improved load distribution in challenging clinical circumstances. This case report explores the successful rehabilitation of a jaw using the All-on-4 implant prosthesis concept, a technique strategically placing four implants in completely edentulous jaws to support a fixed, immediately loaded prosthesis.

Biomechanical effects of inclined implant shoulder design in all-on-four treatment concept: a three-dimensional finite element analysis

OBJECTIVES

The aim of the present study was to assess the biomechanical behaviour of using a posterior implant design with inclined shoulder designs in all-on-four treatment via three-dimensional finite element analysis.

METHODS

Implants with standard and inclined shoulder designs were modelled for posterior implants. Implants were positioned into the maxilla and mandible models according to the all-on-four concept. Compressive stresses in the peri-implant bone, the von Mises stresses in the different components of the prosthetic restoration, and movement of the prosthesis were obtained.

RESULTS

The compressive stresses of the models with inclined shoulder design resulted in 15-58 % decrease compared with standard shoulder design. The von Mises stresses in the posterior implants reduced 18-47 %, stresses in the implant body increased 38-78 %, stresses in the abutment screw reduced 20-65 %, stresses in the framework of prosthesis reduced 1-18 % and deformation of the prosthesis was reduced 6-37 % in the models of inclined shoulder design compared with models of standard shoulder design. The compressive and von Mises stresses were generally higher in the mandible models than in the maxilla models for standard and inclined shoulder designs.

CONCLUSIONS

All evaluated components of the simulated treatment except for posterior abutment bodies showed better biomechanical behaviour with inclined shoulder design. The clinical success of all-on-four treatment maybe enhanced by using posterior implants with an inclined shoulder design.

Treatment effect of implant-supported fixed complete dentures and implant overdentures on patient-reported outcomes: A systematic review and meta-analysis

OBJECTIVES

To analyze the effect of implant treatment in edentulous patients rehabilitated with implant-supported fixed complete dentures (IFCDs) or implant overdentures (IODs) on dental patient-reported outcomes (dPROs).

MATERIALS AND METHODS

In January 2022, Medline, Embase, CINAHL, Cochrane Library, PubMed Central, Web of Science, and ClinicalTrials.gov were screened for prospective clinical studies on completely edentulous patients treated with IFCDs and/or IODs, reporting pre-treatment and follow-up dPROs. Hedges' g effect sizes (ES) with corresponding 95% confidence intervals (CI) were calculated. Afterward, meta-analyses were conducted using random effect models.

RESULTS

A total number of 1608 records was initially identified. Of those, 28 studies reporting dPROs from 1457 patients were finally included. The applied dental patient-reported outcome measures (dPROMs) included several versions of the Oral Health Impact Profile (OHIP) or specific items assessing satisfaction with Visual Analogue Scales (VAS). The overall ES was large for rehabilitation with IFCDs (1.68 [CI: 1.15, 2.20]) and IODs (1.26 [CI: 0.99, 1.52]) with no significant difference (p = .165) between the two. Denture stability was the only factor rated significantly higher for IFCDs (ES difference: 2.37 [CI: 0.21, 4.54]; p = .032). Subgroup analyses revealed moderately higher ES for IODs on two implants relative to one implant (ES difference: 0.73 [CI: 0.34, 1.12]; p < .001).

CONCLUSIONS

There is a strong positive effect of implant treatment in edentulous patients, independent of the type of prosthetic rehabilitation. In patients seeking high stability, IFCDs may be preferable. In mandibular IODs on a single implant, there was a significantly positive effect of an additional implant on dPROs.

Does the Protrusion of Corticobasal Implants in the Maxillary Sinuses Affect Sinus Health? A Retrospective Study

AIM

The aim of this retrospective study is to investigate the effect of corticobasal implant penetration in the nasal and maxillary sinuses on sinus health and implant survival rate in cases of severely atrophid ridges.

MATERIALS AND METHODS

This retrospective study was conducted on thirty patients with 172 implants who underwent corticobasal implant treatment between 2014 and 2018. Implants were divided into two groups according to the penetration depths (Group A, <4 mm; Group B, 4 mm). Inclusion criteria for the study included: (A) patients with severe maxillary ridge resorption with an immediately loaded corticobasal implant-supported prosthesis that showed implant protrusion inside the maxillary sinus on cone-beam computed tomography (CBCT); and (B) patients with a preoperative and postoperative follow-up CBCT scan using the same standard technique and machine. (C) Patients without any history of sinusitis before implant insertion patients who fulfilled the inclusion criteria were recalled for follow-up. The presence of sinus complications was clinically assessed according to the clinical practice guidelines for adult sinusitis of the American Academy of Otolaryngology-Head and Neck Surgery and Radiologically using CBCT. Moreover, patient satisfaction was evaluated using yes-or-no questions. The result was statistically analyzed using Fisher's Exact test.

RESULTS

Despite the differences in implant penetration depths, no clinical signs of sinusitis were evident in any patient. One patient presented with transient epistaxis after the surgery, and 2 patients with nine implants revealed nonsignificant thickening of the sinus membrane radiologically (p = 0.055). All implants showed optimum bone-implant contact with a 100% survival rate. A significant relationship was reported between the thickness of the membrane and the patient's gender, hypertension, and smoking habits. (p = 0.001*, p = 0.002*, and p = 0.034*, respectively).

CONCLUSION

Penetration of corticobasal implants in the maxillary sinus did not compromise the health of the maxillary sinus or implant survival rate.

CLINICAL SIGNIFICANCE

Limited posterior maxillary bony support and maxillary sinus pneumatization present challenges in implant dentistry and increase the possibility of implant protrusion inside the maxillary and nasal cavities. Hence, studying the effect of this protrusion on the maxillary sinuses' health and implant survival is highly significant.

Distribution of implant failure caused by positioning in a certain part of Turkish society on CBCT

Purpose: The aim of this report was to evaluate the prevalence of implant failure rates due to implant positioning on Cone beam Computerized Tomography. Methods: Study sample (n= 333) consisted of CBCT(Cone-beam computerized tomography) scans of patients who were referred to the Department of Dentomaxillofacial Radiology, University of Health Sciences Turkey, Gülhane Faculty of Dentistry, Ankara, Turkey. Obtained data such as age, gender, number of implants and locations from CBCT images gathered and recorded. Results: The data consists of 333 patients and so the total data evaluated was 844. The implant survival rate of the patients between 20-40 years old (49.4%) was lower significantly than that of the patients ≥ 40 years old (P=0.001). In the R4 (right mandibular region), implant failure rate is 17.5% shows quite low rate compared to other regions. At the R1 (right maxillar region) (39%) and R2 (45%) the most common reason of failure was maxillary sinus perforation, the least common reason was palatinal bone perforation, respectively 4% and 1%. Conclusion: Preventing misinterpretations of clinicians is only possible by correct evaluation of incidental findings and better knowledge of head and neck anatomy.

Immediate Maxillary Full-Arch Rehabilitation of Periodontal Patients with Terminal Dentition Using Tilted Implants and Bone Augmentation: A 5-Year Retrospective Cohort Study

Background: All-on-four protocols with tilted implants in the maxilla are used to rehabilitate the terminal dentition of the severe generalized periodontitis patients. Data on long-term biological complications are scarce. Methods: Eighty-four axial and forty-six tilted immediate implants have been placed in the extraction sockets of 23 patients according to a four–six implants protocol combined with ridge augmentation. Within 72 h, a provisional prosthesis was cemented to the implants; after 6 months, a cemented ceramic–metallic prosthesis was delivered. The patients were followed for up to 5 years. Results: The 5-year survival rate of the straight and tilted implants was 100% and 97.8, and the prosthetic one was 100%. Marginal bone loss (MBL) of the straight implants was 0.42 ± 0.67 and 0.59 ±1.01 mm on the mesial and distal sides; for the tilted, it was 0.37 ± 0.68 and 0.34 ±0.62 mm, and the differences were not statistically significant. Implant position, smoking, keratinized mucosal width, and cantilever did not affect MBL. Peri-implant mucositis involved 29.4% and 22.2% of the straight and tilted implants, respectively; peri-implantitis involved 5.8% and 4.4% of the straight and tilted implants, respectively, without statistical significance. Conclusions: This immediate loading protocol’s 5-year survival and success rates were high. No difference between the straight and tilted implants was found regarding survival, success rates, and MBL.

Assessment of Preload Loss after Cyclic Loading in the OT Bridge System in an “All-on-Four” Rehabilitation Model in the Absence of One and Two Prosthesis Screws

The aim of this study was to evaluate the stability of prosthetic screws after applying cyclic loadings in an “all-on-four” rehabilitation model with the OT Bridge system. The model was tested both with and without anterior screws. Four implant analogues following the “all-on-four” concept were inserted in an edentulous mandibular resin model. An OT Bridge system with a Cr–Co prosthetic framework was fabricated. Depending on the presence or absence of one or two anterior screws on the implant analogues, three groups were created, i.e., Gr.1: three tightening screws, Gr.2: two tightening screws, Control Group: four tightening screws. Each single group underwent subsequent 400,000 cyclic loads, simulating approximately a year of chewing by using a dynamometer machine. This cycle was repeated five times for each group, and preload loss values were evaluated on each prosthetic screw after each cycle. All the data obtained were analyzed by one-way ANOVA and Student’s t-test. No statistically significant differences after intragroup analysis were found. A statistically significant difference within the Gr.1 between the screws in positions 33 and 36, equal to 15.2% (p-value = 0.0176), was found. The OT Bridge seems a useful system to maintain the retention of a prosthesis during mechanical stress conditions even in the absence of one screw in an “all-on-four” rehabilitation. This could represent a good solution to solve the esthetic problem of the screw buccal access hole for fixed solutions.

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.

A new mandibular deformation index predicts amount of bone deformation in edentulous patients treated with an implant-supported fixed prosthesis

PURPOSE

The present study was performed to examine the mandibular deformation during mouth opening in edentulous patients, treated with an implant-supported fixed prosthesis using strain gauges, and identify factors affecting deformation.

METHODS

Twenty patients with a fully edentulous mandible who received either 4 or ≥6 implants were included. The distal-most implants were placed mesial to the mental foramen (premolar region) in patients with 4 implants and distal to the mental foramen (molar region) in patients with ≥6 implants. Mandibular deformation during mouth opening was measured using strain gauges in two directions: anteroposterior direction and lateral direction between the distal-most implants on the left and right sides (arch width). The mandibular anatomy was evaluated using computed tomography.

RESULTS

Arch width reduction between the left and right implants during mouth opening ranged from 47.38 to 512.80 µm; the range of deformation was 0.12 to 15.14 µm in the anteroposterior direction. Furthermore, a significant positive correlation was noted between arch width reduction in the premolar region and the ratio between the symphyseal bone height and width (P = 0.0003, r = 0.72).

CONCLUSION

The reduction in arch width was higher in the molar region than in the premolar region during mouth opening. Moreover, the reduction could be high in the mandibular symphyseal bone because of its greater height and lesser width. The ratio between the symphyseal bone height and width is defined as the mandibular deformation index (MDI) and is used to predict the rate of mandibular bone deformation.

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.

Comparative Analysis of Stress and Deformation between One-Fenced and Three-Fenced Dental Implants Using Finite Element Analysis

Finite element analysis (FEA) has always been an important tool in studying the influences of stress and deformation due to various loads on implants to the surrounding jaws. This study assessed the influence of two different types of dental implant model on stress dissipation in adjoining jaws and on the implant itself by utilizing FEA. This analysis aimed to examine the effects of increasing the number of fences along the implant and to compare the resulting stress distribution and deformation with surrounding bones. When a vertical force of 100 N was applied, the largest displacements found in the three-fenced and single-fenced models were 1.7469 and 2.5267, respectively, showing a drop of 30.8623%. The maximum stress found in the three-fenced and one-fenced models was 13.518 and 22.365 MPa, respectively, showing a drop of 39.557%. Moreover, when an oblique force at 35° was applied, a significant increase in deformation and stress was observed. However, the three-fenced model still had less stress and deformation compared with the single-fenced model. The FEA results suggested that as the number of fences increases, the stress dissipation increases, whereas deformation decreases considerably.

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.

1-Year Evaluation of OT Bridge Abutments for Immediately Loaded Maxillary Fixed Restorations: A Multicenter Study

Objective  Preliminary data on survival and success rates of immediately loaded, maxillary, screw-retained, implant-supported, fixed restorations delivered on narrow and low-profile OT Equator abutments (OT Bridge, Rhein’83) were evaluated.

Materials and Methods  This retrospective study evaluated data collected from patients rehabilitated with OT Bridge prosthetic concept between November 2017 and February 2019 in six different centers. Outcome measures were implant and prosthetic survival rates, biological and technical complications, marginal bone loss (MBL), oral health impact profile (OHIP), bleeding on probing, and plaque index.

Results  A total of 76 implants were inserted in 14 patients. Patients were followed for a mean period of 15.8 months (range = 12–24). All the patients receive OT Equator (Rhein'83) as intermediate abutments. One year after loading, one implant failed (1.3%). None of the prosthesis failed. One prosthetic complication was experienced in one patient. Three out of 76 implants were connected to the prosthetic framework using only the Seeger system, without screw. Difference in OHIP values was statistically significant (71.9 ± 8.5; p = 0.000). One year after loading, MBL was 0.21 ± 0.11 mm and p- value was 0.000. One year after loading, 8.7% of the examined implant sites present positive bleeding on probing, while 6.4% of the implant sites presented plaque.

Conclusion  The OT Equator abutments (Rhein'83) showed successful results when used to support maxillary fixed dental prosthesis delivered on four to six implants. High implant and prosthetic survival rates, very low complications, high patient satisfaction, and good biological parameters, including only 0.2 mm of bone remodeling were experienced one year after function. Further studies are needed to confirm these preliminary results.

Immediate implant-prosthetic dental rehabilitation of patients with diabetes using four immediately loaded dental implants: a pilot study

Objectives

Type 2 diabetes mellitus (T2DM) involves endocrine changes that cause a persistent increase in blood glucose. Many disorders are associated with T2DM, including disorders that affect the oral cavity. Oral cavity disorders interfere with a patient’s capacity to follow a correct diet, which results in worsening systemic disease. Oral rehabilitation is necessary for patients with T2DM. Therefore, this prospective study was performed to evaluate the immediate dental rehabilitation capacity of patients with T2DM using four immediately loaded dental implants.

Methods

In this prospective study, four implants each were placed in four patients with T2DM and loaded within 24 hours. Demographic characteristics were assessed at baseline; systemic and oral health parameters were assessed at baseline and at 6 months after implant placement.

Results

The mean glycated hemoglobin (HbA1c) level was 7.05% (range, 6.8%–7.3%). The mean Implant Stability Quotient of the dental implants was 74.5 (range, 67–85). Postoperative evolution was favorable: only one implant exhibited inflammation of the prosthetic stump.

Conclusions

Immediate prosthetic rehabilitation using four maxillary dental implants was an effective treatment modality for patients with T2DM in this study. Larger studies are needed to confirm these findings.

A fixed reconstruction of fully edentulous patients with immediate function using an apically tapered implant design: a retrospective clinical study

Background

Immediate function has become an accepted treatment modality for fixed restorations in completely edentulous jaws. It is known that implant microtopography (surface) may enhance osseointegration, while implant macrotopography (macrodesign) plays an important role in primary stability in the patient requiring an immediate loading. The aim of this retrospective study was to evaluate the clinical and radiographic outcomes of the edentulous subjects treated with narrow and/or regular diameter, which placed and loaded immediately.

Methods

Forty-two consecutive patients received 171 implants, including regular and narrow diameter implants (NDIs). Each jaw, 19 mandibles and 24 maxillae, was treated with a fixed-full arch prosthesis according to the Straumann® Pro Arch concept. The majority (95%) of the restorations were supported by four implants, of which the posterior two implants were tilted. A provisional functional acrylic prosthesis was delivered on the day of surgery. All patients were followed up to 55 months. Cumulative survival rate was determined using Kaplan-Meier analysis. Radiological measurement of marginal bone level was performed.

Results

The overall follow-up time for survival rate was up to 55 months. Four implants (3 implants in maxilla, 1 implant in mandible) were lost, resulting in an overall cumulative implant survival rate of 97.7%. Implant survival rate in the axial and tilted implants was not statistically significant. The mean of interproximal marginal bone loss was 0.15 mm after 24 months. Good soft tissue health was observed in almost 99% of patients. The final prosthesis survival rate was 100%.

Conclusions

The results of this retrospective pilot study indicated that total edentulous patients requiring an immediate implant placement and loading can be successfully treated with this implant design. The improved mechanical properties of these implants might give a more conservative treatment option for the jaws showing a severe horizontal alveolar bone resorption.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40729-020-00271-1.

Periimplant Bone Resorption at the Level of Tilted Implants in SKY Fast & Fixed Restorations

Implant-prosthetic rehabilitation registers multiple variants, but their short- and long-term evolution has been a frequent concern. This study aimed to evaluate the peri-implant bone resorption at the level of the tilted implants in the SKY fast & fixed restorations, with reference to clinical and treatment parameters. An observational study was conducted on a convenience sample of patients with implant-prosthetic rehabilitation in one or both jaws, according to the SKY fast & fixed protocol (Bredent, Germany). Bone resorption was assessed on panoramic radiography. Other data were collected from the patient’s medical records. Thirty tilted implants were analyzed, 12 of which were in the maxilla and 18 in the mandible. After the follow-up period, both bone resorption (maximum 7 mm) and bone apposition (maximum 8 mm) were observed. There was a tendency for the resorption to be more pronounced in the mandible, in patients where tooth loss was due to periodontal disease, and when implants with length less than 16 mm were used. Resorption was statistically significantly lower when bone addition materials and membranes were used at the extraction socket, and when SKY fast & fixed rehabilitation was performed in both jaws. SKY fast & fixed implant-prosthetic technique, which involves applying a small number of implants, and a fixed prosthesis corresponding to a shortened dental arch, is a viable method of treatment that outcomes the need for complex and expensive surgical interventions, and proves to be beneficial in maintaining the optimal parameters of bone support.

How many implants are needed for mandibular full-arch rehabilitation?

Aim: To analyze the stress distribution at the peri-implant bone tissue of mandible in full-arch implant-supported rehabilitation using a different number of implants as support. Methods: Three-dimensional finite element models of full-arch prosthesis with 3, 4 and 5 implants and those respective mandibular bone, screws and structure were built. ANSYS Workbench software was used to analyze the maximum and minimum principal stresses (quantitative analysis) and modified von Mises stress (qualitative analysis) in peri-implant bone tissue after vertical and oblique forces (100N) applied to the structure at the cantilever site (region of the first molars). Results: The peak of tensile stress values were at the bone tissue around to the distal implant in all models. The model with 3 implants presented the maximum principal stress, in the surrounding bone tissue, higher (~14%) than the other models. The difference of maximum principal stress for model with 4 and 5 implants was not relevant (~1%). The first medial implant of the model with 5 implants presented the lower (17%) stress values in bone than model with 3 implants. It was also not different from model with 4 implants. Conclusion: Three regular implants might present a slight higher chance of failure than rehabilitations with four or five implants. The use of four implants showed to be an adequate alternative to the use of classical five implants.

A finite element analysis to study the stress distribution on distal implants in an all-on-four situation in atrophic maxilla as affected by the tilt of the implants and varying cantilever lengths

AIM

The aim of this work was to evaluate stress distribution on implants in All-on-Four situation with varying distal implant angulations (30°,40°,45°) and varying cantilever lengths (4 mm, 8 mm, 12 mm, 16 mm) in atrophic maxilla using finite element analysis.

SETTING AND DESIGN

A in vitro study, finite element analysis.

MATERIALS AND METHODOLOGY

Three-dimensional finite element model of an edentulous maxilla restored with a prosthesis supported by four implants was reconstructed to carry out the analysis. Three different configurations, corresponding to 3 tilt degrees of the distal implants (30°, 40°, and 45°) were subjected to 4 loading simulations.

STATISTICAL ANALYSIS USED

The results of the simulations obtained were evaluated in terms of Von Mises equivalent stress levels at the bone-implant interface.

RESULT

From a stress-level viewpoint, the 45° model was revealed to be the most critical for peri-implant bone. In all the loading simulations, the maximum stress values were always found at the neck of the distal implants. With increasing distal implant tilt, cantilever length reduces depending on the quality of bone. At 30° angulation of distal implant a maximum cantilever length of 16 mm may be given if the quality of bone is D3 but only 8 mm cantilever may be recommended if bone quality is D4. At 40° angulation, 16 mm in D3 bone and 0 mm in D4 bone whereas at 45° angulation, it reduces to 12 mm in D3 bone and no cantilever is recommended with D4 bone.

CONCLUSION

The 45° tilt induced higher stress values at the bone-implant interface, especially in the distal aspect, than the other 2 tilts analyzed. Stress values increased with increased cantilever length which was further influenced by the distal implant tilt and the quality of the bone.

Long-term follow-up of full-arch immediate implant-supported restorations in edentulous jaws: a clinical study

BACKGROUND

This study aims to show the long-time stability of straight and tilted implants loaded immediately with a provisional resin bridge followed by a definitive prosthodontic rehabilitation in edentulous jaws despite difficult hygiene conditions postoperatively.

RESULTS

This study included the participation of 23 patients and the restoration of 170 dental implants in 32 edentulous jaws. Patient data was analyzed from the start of treatment with a minimum follow-up period of 6 years in order to determine long-term implant success rates. However, the age of patients at time of surgery significantly affected the BOP to the detriment of younger patients (median 62 years old).

CONCLUSION

Although there was a higher risk of implant failure due to general disease, all the implants in this study survived successfully. As a replacement for a complete dental arch, the reduced number of implants in combination with the avoidance of augmentations reduces treatment costs. The immediate fixed prosthetic restoration of edentulous jaws thus represents a reliable therapeutic alternative to a two- to three-stage procedure. Optimized aftercare including professional teeth cleaning (PTC) (at least twice a year) can minimize the anamnestic effect of smoking, diabetes mellitus, and osteoporosis on BOP and possible bone loss.

To evaluate and compare the accuracy of definitive casts using various splinting methods on implant level impressions in All-on-Four treatment: An in vitro study

Aim:

The aim of this study is to evaluate and compare the accuracy of master casts obtained by different splinting techniques for implant level impressions in All-on-Four implant treatment protocol using a coordinate measuring machine.

Settings and Design:

The study design involves an in vitro study.

Materials and Methods:

In this in vitro study, a reference clear acrylic resin (AR) model comprising four regular platform implant 3.6 mm × 10.0 mm (Dentium Implant India Pvt. Ltd, Bengaluru, India) which was placed following the All-on-Four implant protocol is prepared. Impressions were categorized into three different groups: Group 1 – impression copings were nonsplinted; Group 2 – impression copings were splinted using AR sectioned 17 min after setting and rewelded with the same resin; and Group 3 – impression copings were splinted by titanium bar using an intraoral welder. A total of 33 (n = 11 in each group) impressions were made to evaluate three different splinting techniques. Impressions were poured with Type 4 dental stone. A coordinate measuring machine was used to record the x, y, and z co-ordinates and angular displacement. The measurements were compared with those obtained from the reference model.

Statistical Analysis Used:

One-way ANOVA test was used as a test of significance.

Results:

There was less linear and rotational displacement for the metal-splinted group (P < 0.001) In the x-axis, nonsplinted group showed a statistically significant difference in straight implants (2 and 3 implants) (P = 0.001) of All-on-Four treatment protocol.

Conclusion:

The splinting methods have a direct effect on the accuracy of definitive casts. The metal-splinted direct technique produced the most accurate casts followed by AR-splinted direct technique and nonsplinted direct technique.

Hybrid Polyetheretherketone (PEEK)-Acrylic Resin Prostheses and the All-on-4 Concept: A Full-Arch Implant-Supported Fixed Solution with 3 Years of Follow-Up

Background: The aim of this three-year prospective study was to examine the outcome of a solution for full-arch rehabilitation through a fixed implant-supported hybrid prosthesis (polyetheretherketone (PEEK)-acrylic resin) used in conjunction with the All-on-4 concept. Methods: Thirty-seven patients (29 females, 8 males), with an age range of 38 to 78 years (average: 59.8 years) were rehabilitated with 49 full-arch implant-supported prostheses (12 maxillary rehabilitations, 13 mandibular rehabilitations and 12 bimaxillary rehabilitations). The primary outcome measure was prosthetic survival. Secondary outcome measures were marginal bone loss, plaque and bleeding scores, veneer adhesion issues, biological complications, mechanical complications, and the patients’ subjective evaluation. Results: There were two patients (maxillary rehabilitations) lost to follow-up, while one patient withdrew (maxillary rehabilitation). One patient with bimaxillary rehabilitation fractured the mandibular PEEK framework, rendering a 98% prosthetic survival rate. Implant survival was 100%. Average (standard deviation) marginal bone loss at 3-years was 0.40 mm (0.73 mm). Veneer adhesion was the only technical complication (n = 8 patients), resolved for all patients. Nine patients (n = 11 prostheses) experienced mechanical complications (all resolved): fracture of acrylic resin crowns (n = 3 patients), prosthetic and abutment screw loosening (n = 4 patients and 3 patients, respectively), abutment wearing (n = 1 patient). One patient experienced a biological complication (peri-implant pathology), resolved through non-surgical therapy. A 90% satisfaction rate was registered for the patients’ subjective evaluation. Conclusions: Based on the results, the three-year outcome suggests the proposed rehabilitation solution as a legitimate treatment option, providing a potential shock-absorbing alternative that could benefit the implant biological outcome.

Treating severe periodontitis with staged load applied implant restoration: A case report

BACKGROUND

Because immediate implant surgery is not recommended for patients who have been diagnosed with periodontitis, researchers have treated these patients with a variety of methods, including combining orthodontic and periodontal surgeries as well as implantation. However, these treatments cost time and money for the patient. Although it has been reported that temporary implants released a severe gag reflex in 1 case, only a few studies have documented using temporary implants to treat patients diagnosed with severe periodontitis.

CASE SUMMARY

The patient was a 49-year-old female who was missing the majority of her teeth and had gingival atrophy and severe alveolar bone atrophy. After being diagnosed with severe periodontitis, the patient underwent staged load applied implant restoration therapy. The first load-bearing stage was carried out immediately by inserting temporary Osstem mini implants. Maxillary teeth were extracted by using the guided bone regeneration technique, and lateral maxillary sinus lifting was conducted on both sides. During the second load-bearing stage, temporary implants were removed, and permanent implants were placed. The resin bridge was segmented during the third load-bearing stage. During the fourth load-bearing stage, the permanent prosthesis was positioned in the patient’s mouth.

CONCLUSION

By conducting the load-bearing treatment in stages, the patient’s mouth contained restorations throughout the procedure, thus guaranteeing basic function and appearance.

Advantages and limitations of implant surgery with CAD/CAM surgical guides: A literature review

Background

The purpose of this study is to review the available literature associated with implant surgery using computer-aided design/computer-aided manufacturing (CAD/CAM) surgical guides and discuss the advantages and disadvantages of this advanced technique.

Material and Methods

An electronic literature search was conducted in the PubMed database for the relevant information on implant placement with CAD/CAM surgical guides. This review was constructed following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Articles were limited to those published within the past 10 years and in the English language. Only clinical studies were included. Inclusion criteria were: studies including 10 implants or more and studies presenting angular deviations in degrees and linear deviations in millimeter. Observational studies, reviews, animal studies, in vitro studies, case reports, simulation studies were excluded. Nine articles were included for qualitative synthesis.

Results

The initial search detected 61 articles, and after screening abstracts, a total of 15 articles were selected for full-text review. After the full-text analysis of the 15 articles, six articles were excluded as they did not meet inclusion criteria for study design, study population, and implant placement with data presentation for angular and linear deviations. Ultimately, nine articles providing angular and linear deviations between planned and actual placed implants were used in this review. Common problems that may be encountered by clinicians were listed, and recommendations were made on how to avoid those problems.

Conclusions

It has been suggested that although unrealistic expectations are often associated with implant placement with CAD/CAM surgical guides, there is no impeccable accuracy in the clinic. This review demonstrated that the practitioners should be aware of the angular and linear deviations up to 5 ° and 2.3 mm. Therefore, inexperienced dentists should obtain adequate training and be familiar with the basic steps with CAD/CAM surgical guides to avoid complications.

Key words:CAD/CAM, CBCT, implant, stereolithography, surgical guide.

Stress Distribution on the Prosthetic Screws in the All-on-4 Concept: A Three-Dimensional Finite Element Analysis

The all-on-4 concept, which is used to rehabilitate edentulous patients, can present with mechanical complications such as screw loosening and fracture. The purpose of this study was to evaluate the stress patterns induced in the prosthetic screws by the different prosthetic screw and abutment designs in the all-on-4 concept using finite element analysis. Von Mises stress values on 6 groups of each screw type, including short and narrow screw, short abutment; short and wide screw, short abutment; long and wide screw, short abutment; short and narrow screw, long abutment; short and wide screw, long abutment; and long and wide screw, long abutment, were compared under a cantilever loading of 200 N that was applied on the farther posterior to the position of the connection between the distal implant and the metal framework. Posterior prosthetic screws showed higher stress values than anterior prosthetic screws. The stress values in posterior prosthetic screws decreased as the length and diameter increased. In conclusion, the long and wide screw design offers advantages in stress distribution when compared with the short and narrow design.

Association between maxillary sinus pathology and odontogenic lesions in patients evaluated by cone beam computed tomography. A systematic review and meta-analysis

Background

A study is made of the association between maxillary sinus pathology and odontogenic lesions in patients evaluated with cone beam computed tomography.

Material and Methods

A literature search was made in five databases and OpenGrey. Methodological assessment was carried out using the Newcastle-Ottawa tool for observational studies. The random-effects model was used for the meta-analysis.

Results

Twenty-one studies were included in the qualitative review and 6 in the meta-analysis. Most presented moderate or low risk of bias. The periodontal disease showed to be associated with the thickening of the sinus membrane (TSM). Mucous retention cysts and opacities were reported in few studies. The presence of periapical lesions (PALs) was significantly associated to TSM (OR=2.43 (95%CI:1.71-3.46); I2=34.5%) and to odontogenic maxillary sinusitis (OMS) (OR=1.77 (95%CI: 1.20-2.61); I2=35.5%).

Conclusions

The presence of PALs increases the probability of TSM and OMS up to 2.4-fold and 1.7-fold respectively. The risk differences suggests that about 58 and 37 of out every 100 maxillary sinuses having antral teeth with PALs are associated with an increased risk TSM and OMS respectively. The meta-evidence obtained in this study was of moderate certainty, and although the magnitude of the observed associations may vary, their direction in favor sinus disorders appearance, would not change as a result.

Key words:Sinus pathology, Odontogenic Sinusitis, Sinus membrane thickening, CBCT, Periapical lesions, Periodontal disease

Effects of Different Positions and Angles of Implants in Maxillary Edentulous Jaw on Surrounding Bone Stress under Dynamic Loading: A Three-Dimensional Finite Element Analysis

PURPOSE

To evaluate the effects of different placements of mesial implants and different angles of distant implants in maxillary edentulous jaws on the stress on the implant and the surrounding bone tissue under dynamic loading.

MATERIALS AND METHODS

Cone beam computed tomography was used to acquire images of maxillary edentulous jaws. Using Mimics 17.0, Geomagic, and Unigraphics NX8.5 software, three-dimensional models were established: two mesial implants were placed vertically in the anterior region of the maxilla (bilateral central incisor, lateral incisor, and canine), and two distant implants were placed obliquely in the bilateral second premolar area at different inclined angles (15°, 30°, and 45°). The established models were designated I-IX. The models were subjected to dynamic load using Abaqus 6.12, with the working side posterior teeth loading of 150 N and simulation cycle of 0.875 s.

RESULTS

During the second to fourth phases of the mastication cycle, the stress was mainly concentrated on the neck of the distal implant. The stress of the distal implants was greater than that of mesial implants. Stress levels peaked in the third stage of the cycle. The stress of the distal cortical bone of distal implant of Model I reached the maximum of 183.437 MPa. The stress of the distal cortical bone and cancellous bone of distal implant of Model VIII represented the minima (62.989 MPa and 17.186 MPa, respectively).

CONCLUSIONS

Our models showed optimal stress reductions when the mesial implants were located in the canine region and the distal implants tilted 30°.

A clinical study on the 6-year outcomes of immediately loaded three implants for completely edentulous mandibles: "the all-on-3 concept"

The objective of the current study was to demonstrate the 6-year clinical and radiological treatment outcomes of the technique performed by immediately loading of three implants (single straight in the mid-line and two tilted distal implants) for the management of total edentulous mandibles and introduce a simple decision matrix for selection of the most appropriate protocol in cases with insufficient length of the interforaminal area. Re-assessments were performed over a total observation period of 6 years after surgery via measurement of bone resorption around implants, bleeding on probing, plaque accumulation, periodontal probing depth, bite force measurements and oral health impact profile. A total of 29 patients (45% women and 55% men) with a mean age of 65 ± 6 years enrolled in the study. 14 patients received an acryl-based bridge as definitive prosthetic restoration and 15 patients received a ceramic-based restoration. Both during the immediate loading phase and during the 6-year follow-up, there was no implantation loss. Regardless of the implant position, all implants showed continuous bone loss over the observation time. The bone loss around dental implants during observation period was only maximum 1.0 ± 1 mm and it remained well within the limits for 'success' according to the 2007 Pisa consensus (< 2 mm). The plaque index showed no significant fluctuations between the implant positions and the individual examination times. The approach described herein might help the surgeon by avoiding unnecessary loss of bone strength, selecting implant sites, and establishing the biomechanical advantage of increased A-P spread for immediate function.

Full Arch All-on-4 Fixed Implant-Supported Prostheses with 8.5 Years of Follow-Up: A Case Report

Typically, full arch reconstruction of edentulous ridges requires five to 10 dental implants; however, some patients demanding fixed implant-supported prostheses are not able to medically or economically afford complex bone grafts and/or a greater number of implants. These situations could pivot the treatment plan toward the All-on-4 protocol. Nevertheless, due to less implant support in this treatment option, mechanical and biological complications might arise. This article describes the treatment of a fully edentulous patient with two types of fixed implant-supported prostheses on four dental implants along with the following complications.