Optimal number of implants for complete-arch implant-supported prostheses with a follow-up of at least 5 years: A systematic review and meta-analysis

A Finite Element Analysis to Study the Stress Distribution on Distal Implants in All-on-Six Treatment Concepts as Affected Tilted and Short Implant

The number of implants and their respective configurations for implant-supported treatment modalities have been studied for 4 implant-supported prostheses; however, it is not yet clear whether the use of tilting or short implants in rehabilitation would result in substantially improved bone/implant/prosthesis biomechanics in all-on-six concepts. This study compared the biomechanical behavior of tilted long implants and axially short implants to support fixed prostheses in an atrophic maxilla with all-on-six treatment concepts. Three different implant configurations were planned, and six models were obtained with posterior maxilla D3 and D4 bone densities in this study. Implants proper for the all-on-four concept were placed in all models. In models 1 and 2, the short implant was placed; in models 3 and 4, 30°, the mesial-angled implant was placed; and in models 5 and 6, 45°, the mesial-angled implant was placed to the molar region. In the models created, 200 N vertical and 150 N oblique (45° angled buccopalatal direction) forces were implemented to the bilateral tooth regions 4-5-6 on the rigid titanium-supported fixed hybrid prosthesis made on these models. When the stress values in the models were investigated, the oblique forces had higher stress values than the vertical forces did. When the stresses created by oblique forces were assessed, the highest values were observed in the models created with short implants, and the lowest stress values were observed in the models made with 30° angle to mesial. When bone densities were assessed, more stress values were noted in models with D4 bone density. It has been shown that mesial tilted long implants placed in the posterior molar region, in addition to all four implant treatment concepts, create less stress against undesirable oblique forces compared with short implants.

Rehabilitation with dental prostheses and its influence on brain activity: A systematic review

STATEMENT OF PROBLEM

The consequences of edentulism depend on its complexity and are far-reaching, but limited evidence regarding its association with neurologic health is available.

PURPOSE

The purpose of this systematic review was to establish the relationship between oral prosthetic rehabilitation and the regional increase in brain activity.

MATERIAL AND METHODS

This systematic review was registered in the International Prospective Register of Systematic Reviews (CRD42021262247), and the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guideline was followed. Randomized clinical trials, prospective studies comparing the brain activity of patients rehabilitated with and without the use of dental prostheses, and studies that analyzed the human brain by using noninvasive techniques were used as inclusion criteria. The risk of bias in each study was assessed by using the Risk Of Bias In Non-randomized Studies-of Interventions (ROBINS-I).

RESULTS

The search was carried out in the PubMed/MEDLINE, Embase, Cochrane Library, and https://clinicaltrials.gov databases up to June 2021. After a search conducted by 2 reviewers, 8 articles were included in the review. A regional increase in blood flow and regional cerebral activity during dental prosthesis use was identified in the studies.

CONCLUSIONS

A positive association was found between the different types of prosthetic rehabilitation and brain function. Prostheses may preserve and restore neurological health.

Outcomes that may affect implant and prosthesis survival and complications in maxillary fixed prosthesis supported by four or six implants: A systematic review and meta-analysis

Objective

To investigate whether the clinical and radiographical outcomes are affected when four or six implants support the maxillary fixed complete denture (FCD).

Materials and methods

This study was registered on PROSPERO (CRD42021226432) and followed the PRISMA guidelines. The focused PICO question was, "For an edentulous maxillary patient rehabilitated with an implant-supported fixed prosthesis, do the clinical and radiographical outcomes differ when four or six implants support the prosthesis ". A thorough search of the relevant studies was designed and performed electronically. The survival rate of implant and prosthesis, marginal bone loss, and complications (mechanical and biological) were the primary outcomes, whereas implant distribution and using the surgical guide, follow-up, and framework material were evaluated as secondary outcomes.

Results

Out of 1099 articles initially retrieved, 53 clearly stated the outcomes of interest and were included in this study. There were no significant differences in implant and prosthesis survival, technical/mechanical complications, and biological complications between the 4-implant group (4-IG) and the 6-implant group (6-IG). However, marginal bone loss (MBL) was significantly higher in the 4-IG (p < 0.01). The surgical guide and follow-up period did not significantly affect implant/prosthesis survival. Additionally, using the CAD/CAM milled framework and anteroposterior implant distribution were associated with significantly higher implant survival in the 6-IG (p < 0.01).

Conclusion

The findings of this study indicated that having a greater number of implants, as seen in the 6-implant group, can lead to a decrease in technical and biological complications and reduce marginal bone loss. It is worth noting that factors such as using CAD/CAM frameworks and the anteroposterior distribution of implants were recognized as important in improving implant survival rates when more implants are present.

A Modified Ridge-Splitting Technique to Restore a Completely Edentulous Maxillary Arch With a Cement-Retained Implant Prosthesis

The present report describes a technique in which the maxillary bone was molded to the desired location using a series of instruments for ridge-splitting procedures. This technique aims to improve bone quality all around the implants at both the crest and apex locations. In some clinical scenarios, insufficient horizontal bone with less than 3 mm prevents implant placement. Thus, ridge splitting is a treatment of choice, and this technique creates bone expansion to form a better receptor site for endosteal implants. A case report is presented involving a completely edentulous 52-year-old male patient presented to the clinic with a horizontal bone defect. The patient complained of having difficulty eating and wants to improve his smile. In this clinical case, a modified ridge-splitting technique was employed, differing from the conventional procedure that uses mallets, chisels, or osteotomes. A lancet and spatula were used for precise ridge splitting, followed by the placement of four endosseous tapered implants-two on each side (Dentis USA, La Palma, USA). Each implant had a diameter of 3.7 mm and a length of 10 mm. These implants were clinically placed in a single visit, with a torque of 30 N/cm² applied to ensure secure fixation. To accommodate the patient's unique maxillary bone anatomy, 25-degree angulated abutments were chosen for the four implants, ensuring a common path of insertion, and optimal angulation for long-term stability and aesthetics. Subsequently, a cemented provisional dental prosthesis restoration was fitted, and the patient reported satisfaction with both function and aesthetics. After a period of five months of osseointegration, the stability of the implants was assessed using a resonance frequency analyzer, yielding positive results. The average resonance frequency values for the maxillary left (canine and premolar) were ISQ 68 and ISQ 71, respectively, while for the maxillary right (lateral incisor and premolar), the values were ISQ 69 and ISQ 73. These readings indicate satisfactory implant stability following the osseointegration process. The postoperative cone-beam computed tomography (CBCT) showed gain to the bone width besides better function and good results concerning the esthetics. This report describes a modified ridge-splitting technique with a predictable and satisfactory outcome that fulfilled the patient's demands. The presented approach overcomes the disadvantages of two-staged implant placement bone grafting procedures and is also a more affordable option for the patient. CBCT evaluation confirmed bone gain with minimal morbidity after the procedure.

Study on Overdenture of Immediate Implant Placement and Function

OBJECTIVE

This study aims to investigate the bone remodelling and resorption in immediate implantation and restoration of clinical implant-supported overdentures.

MATERIALS AND METHODS

Six adult domestic dogs were divided into 2 groups: In the experimental group, 6 implants were immediately placed in each mandible, the distal end implants were inclined distal to the long axis of the tooth at an angle of 30 degrees, and restored immediately. As the control group, the animals underwent immediate implant placement with single denture restoration, respectively, nontilting and tilting at 30 degrees in the long axis of the tooth. The osseointegration index (OI) and rate of bone ingrowth fraction were measured, and the peri-implant bone remodelling was observed. The marginal bone loss was measured in the slices of bone-implant and analyzed.

RESULTS

New bone regenerated and had remodelled in each group. The experimental group had no statistically significant differences, when compared with other groups, except the tilted implant control group, in terms of the OI and bone ingrowth fraction.

CONCLUSION

Obvious bone absorption did not statistically significantly occur in implant-supported overdenture of immediate implant placement and function with satisfactory new bone and OI.

Prevention of peri-implant disease in edentulous patients with fixed implant rehabilitations

OBJECTIVES

To provide an overview about the current approaches to prevent peri-implant diseases in edentulous patients with complete-arch implant-supported prostheses, and to review the clinical applications of the latest digital technologies for implant prosthodontics.

METHODS

A review of the guidelines to prevent peri-implant diseases in patient's receiving complete-arch implant-supported prostheses including facially driven treatment planning procedures using either conventional or digital methods, computer-aided implant planning procedures, and prosthodontic design variables including the optimal number and distribution of dental implants, implant to abutment connection type, implant or abutment level design, screw- or cement-retained alternatives, prostheses contours, and material selection is provided. Furthermore, an outline of the current therapeutic management approaches to address peri-implant diseases is reviewed.

CONCLUSIONS

Clinicians should understand and know different planning and design-related variables that can affect biological and mechanical complication rates of complete-arch implant-supported prostheses. Maintenance protocols are fundamental for minimizing biological and mechanical complications.

Limited marginal bone loss in implant-supported fixed full-arch rehabilitations after 5 years of follow-up

PURPOSE

The aim of the present study was to evaluate the 5-year results in terms of marginal bone level (MBL) around implants supporting fixed full-arch metal-ceramic restorations in a series of cases of patients who had lost their teeth in that dental arch because of severe periodontal disease.

MATERIAL AND METHODS

A retrospective cohort study was designed to evaluate the 5-year MBL results of OsseoSpeed™ Astra Tech TX implants with internal tapered conical connection. Age, gender, bone substratum, smoking habits, history of periodontitis, and prosthetic features were recorded. Mixed linear model was used to determine the influence of the different variables on MBL.

RESULTS

In this series, a total of 160 implants placed in 19 patients were evaluated. No implant failure was reported during the 5 years of follow-up. Only 14 (8.75%) implants had more than 2 mm of MBL. Abutment height, F(3,142) = 6.917, p < .001, and implant diameter, F(1,141) = 15.059, p < .001, were determined to be statistically associated with MBL. No other effect was significant. Pairwise comparisons showed that MBL was larger for abutment height = 1 (MBL = -0.987, SE = 0.186) compared with the remaining heights [-0.335 (0.171), -0.169 (0.192) and -0.247 (0.267), 2, 4 and 6 mm, respectively]. MBL was larger for narrow (-0.510, SE = 0.169) than for wide implants (-0.364, SE = 0.190).

CONCLUSION

The current study demonstrates that the vast majority of internal conical connection implants supporting fixed full-arch metal-ceramic restorations do not suffer from relevant MBL after 5 years in function. Particularly, those implants with transmucosal abutments longer than 2 mm show less than 0.5 mm from the implant shoulder to the marginal bone.

Biomechanical analysis of stress around the tilted implants with different cantilever lengths in all-on-4 concept

Background

Many clinical studies have reported the high success rate of the All-on-4 concept. In the present study, we aimed to compare the stress distribution with different tilted distal implants and cantilever lengths in an All-on-4 system using the two-dimensional photoelastic method and to establish the All-on-4 implant photoelastic model by computer-aided design (CAD) and rapid prototyping (RP). 

Methods

The data of the human edentulous mandible were acquired by computed tomography (CT). Three human edentulous mandible All-on-4 implant models with different distally inclined implant holes were fabricated using Mimic, Geomagic Studio software, and a light solidifying fast shaping machine. Then the final photoelastic models were established through the traditional method. Each of the three models had four NobelSpeedy Replace implants between the interforaminal regions. The two posterior implants were placed 0, 15, and 45 degrees distally before the mental foramen. The four implants were splinted by wrought cobalt-chromium alloy frameworks. Each of the three photoelastic models was submitted to a 150 N vertical load at five points on the framework: the central fossa of the mandibular first molar, and 0 mm, 5 mm, 10 mm, and 15 mm of the cantilever length. The stress produced in the models was photographed with a digital camera, and the highest value of the stressed fringe pattern was recorded.

Results

The All-on-4 implant photoelastic model established by CAD and RP was highly controllable and easy to modify. The position and inclination of implants were accurate, and the frameworks could be passively emplaced. The stress values were higher around a single tilted implant compared with the distal implant in All-on-4 with the same inclination. The 0-degree distal implant and 45-degree distal implant demonstrated the highest and lowest stress when loading at the central fossa of the mandibular first molar, respectively. With the same inclination of distal implant, the peri-implant bone stress increased as the length of cantilever increased.

Conclusion

The method of establishing the All-on-4 implant photoelastic model by CAD and RP was highly controllable, convenient, fast, and accurate. The tilted implants splinted in the fully fixed prosthesis with reduced cantilever lengths did not increase the stress level compared with the vertical distal implants.And this illustrated that the influence of cantilever on stress distribution was greater than the influence of implant inlination.

Digitally prefabricated versus conventionally fabricated implant-supported full-arch provisional prosthesis: a retrospective cohort study

Background

To evaluate and compare the clinical outcomes of digitally prefabricated and conventionally fabricated implant-supported full-arch provisional prostheses.

Methods

In this retrospective study, a total of 39 patients (22 males and 17 females) who underwent implant-supported full-arch rehabilitation using the All-on-4 concept with an immediate loading protocol were included: 20 patients treated with digitally prefabricated provisional prostheses were assigned into Group A, and 19 patients treated with conventionally fabricated provisional prostheses were assigned into Group B. Implant/provisional prosthesis survival rates and complications were reviewed. Marginal bone loss (MBL) was investigated by CBCT. Surgical time, restorative time, and total operative time were analyzed. Postoperative pain and swelling were evaluated with the visual analog scale (VAS). The oral health impact profile (OHIP) questionnaire was administered before and after surgery.

Results

The implant/provisional prosthesis survival rate was 100%, and complications appeared with low frequency in both groups, while the mean MBL was 0.30 ± 0.29 mm in Group A and 0.31 ± 0.41 mm in Group B after 3~ 6 months (P > 0.05). The average restorative time in Group A (116.16 ± 16.61 min) was significantly shorter than that in Group B (242.11 ± 30.14 min) (P < 0.05). Patients in Group A showed lower pain/swelling VAS scores after surgery than Group B (P < 0.05). Low OHIP scores with high satisfaction with the overall effects were shown in both groups.

Conclusion

Prefabricated prostheses reduced the prosthetic time and postoperative discomfort in patients whose immediate rehabilitation was based on the All-on-4 concept. This prefabrication technology may be a predictable alternative to improve the short-term clinical outcome of implant-supported full-arch provisional rehabilitation.

The use of three implants to support a fixed prosthesis in the management of the edentulous mandible: a systematic review

BACKGROUND

Dental implants have been widely utilised as a treatment modality for prosthetic rehabilitation. The aim of this study was to evaluate the implant and prosthetic survival rate, changes in marginal bone level, and patient satisfaction outcomes with the use of three implants to support a fixed prosthesis in the edentulous mandible.

METHODS

A comprehensive electronic search was performed in the MEDLINE, Embase and Cochrane databases to retrieve studies that met the selection criteria. Sixteen articles were selected which consisted of two randomised controlled trials, eight prospective cohort studies, five retrospective studies and one case series.

RESULTS

A total of 2055 implants were placed in 685 patients with a mean age of 62.2 years. The mean cumulative implant survival rate was 96.2% over a mean follow-up period of 3.35 years. Mean marginal bone loss recorded was 1.25 mm and high patient satisfaction rates were reported across the studies.

CONCLUSION

The use of three implants to support a fixed prosthesis appears to be a successful approach to restoring the edentulous mandible in the short-to-medium term. Further longitudinal comparative studies are required to support longer-term success, and to guide minimum implant dimension requirements for the technique.

Mandibular full-arch fixed prostheses supported by three-dental-implants: A protocol of an overview of reviews

INTRODUCTION

To minimize trauma and cost of treatment, oral health practitioners have successfully rehabilitated full arches by supporting the prostheses on four implants. However, there is no consensus whether less than four implants supporting full mandibular arches would provide similar clinical outcomes to other well-established all-on-four alternative.

OBJECTIVE

To identify, summarize, appraise, and compare the clinical outcomes evidence of three-implant fixed full-arch prostheses in completely edentulous mandibular patients.

MATERIALS AND METHODS

This overview of systematic reviews (OoSRs) will include secondary synthesis studies (i.e., systematic reviews with or without a meta-analysis). A three-step search strategy will be conducted in MEDLINE (Ovid), EMBASE (Ovid), Cochrane Database of Systematic Reviews, Scopus, Web of Science (WoS Core Collection), and Google Scholar. Grey literature and a manual search in 12 specialized journals will also be conducted. Three independent reviewers will screen all retrieved articles for eligibility, extract data and assess the methodological quality of the included studies. The results will be presented as tables or narrative synthesis. The studies will be evaluated for risk of bias by ROBIS and methodology quality by the AMSTAR-2 tool. If new primary studies are identified, a meta-analysis will be conducted. Certainty of the evidence will be assessed to answer the following focused research question: In edentulous mandibular patients, what are the implant and prostheses clinical outcomes of three-implant fixed full-arch prostheses compared to other all-on-x solutions?

DISCUSSION

There are some systematic reviews about the use of fixed complete dental prostheses supported by three implants; however, their clinical outcomes related to the other all-on-four plus solutions are conflicting. So, an overview on this topic is required to provide recommendations.

REVIEW REGISTRATION NUMBER

International prospective register of systematic reviews (PROSPERO) ID#: CRD42021262175. National Institute for Health Research (NIHR) and Centre for Reviews and Dissemination, University of York, York, United Kingdom.

Radiographic Evaluation of Prosthodontic Patients

This article focuses on radiographic imaging with regard to planning, treating, and maintaining partially and completely edentulous prosthodontic patients with dental implants. Cone-beam computed tomography (CBCT) is the preferred imaging method for pretreatment dental implant treatment planning. Radiographic guides containing radiopaque materials and/or fiducial markers transfer both the proposed prosthesis design and desired implant location for appropriate radiographic evaluation. The three-dimensional CBCT analysis provides information on the adjacent relevant anatomy, bone volume of the edentulous sites, and restorative space assessment.

Clinical Behavior and Complications of Mandibular Full-Arch Fixed Dental Prostheses Supported by Three Dental Implants. A Systematic Review and Meta-Analysis

This systematic review and meta-analysis set out to assess the clinical behavior of mandibular implant-supported fixed complete dental prostheses (ISFCDP) on three dental implants by analyzing implant and prosthetic survival rates, marginal bone loss, biological/technical complications, and patient-reported outcomes. The review was conducted according to PRISMA guidelines. Electronic searches were conducted in the Medline (PubMed), Web of Science, and Cochrane databases, complimented by a manual search in specialist journals for relevant articles published up to February 2021. The Newcastle-Ottawa Quality Assessment Scale tool was used to assess the quality of evidence in the studies reviewed. The study included 13 articles with 728 patients treated with 2184 implants. A mean implant survival rate of 95.9% (95% CI: 94.6-97.3%) and a prosthetic survival rate of 97.0% (95% CI: 95.7-98.3%) were obtained over 1-6-year follow-up periods. Mandibular implant-supported fixed complete dental prostheses on three dental implants would appear to be a viable option for restoring the edentulous mandible in comparison with mandibular ISFCDP on more than three implants. Further comparative studies are needed, with adequate protocols, as well as sufficient sample sizes and follow-up periods to confirm these findings.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

This comprehensive review of the 2019 restorative dental literature is offered to inform busy dentists regarding remarkable publications and noteworthy progress made in the profession. Developed by the Scientific Investigation Committee of the American Academy of Restorative Dentistry, each author brings discipline-specific expertise to 1 of 8 sections of the report: (1) prosthodontics; (2) periodontics, alveolar bone, and peri-implant tissues; (3) implant dentistry; (4) dental materials and therapeutics; (5) occlusion and temporomandibular disorders; (6) sleep-related breathing disorders; (7) oral medicine and oral and maxillofacial surgery; and (8) dental caries and cariology. The report targets important information likely to influence day-to-day dental treatment decisions. Each review is not intended to stand alone but to update interested readers so that they may visit source material when greater detail is desired. As the profession moves toward evidence-based clinical decision-making, an incredible volume of potentially valuable dental literature continues to increase. It is the intention of this review and its authors to provide assistance in negotiating the extensive dental literature published in 2019. It is our hope that readers find this work useful in the clinical management of dental patients.

[Clinical analysis of the short-term and long-term results of the implant-supported Trefoil dental rehabilitation in Russia]

THE AIM OF THE STUDY

Was to presents the first clinical medium-term (18 months) results of implant-supported rehabilitation using this method in Russia, with the special attention paid to the assessment of the patient's quality of life on the GOHAI scale.

MATERIALS AND METHODS

The authors performed a clinical and paraclinical examination of 29 patients (20 women and 9 men). The age of the patients ranged from 47 to 88 (average value - 65.45±9.7). We performed a retrospective analysis of all patients operated from June 2017 till March 2019. The patients filled in GOHAI questionnaires about their state of health and quality of life (before treatment and 6 weeks post-surgery). Patients with one or more anterior teeth present as well as fully edentulous mandibles were included in the study. The antagonist teeth could be presented as complete dentures, natural teeth, or implant-supported fixed restorations. All patients received three Trefoil implants (Nobel Biocare AB) inserted with a torque of at least 35 Ncm. The Trefoil bar (Nobel Biocare AB) was used as the framework of the Trefoil bioengineering structure. Statistical processing of the results was performed using the SPSS 23 software. The t-test for dependent samples was used to compare the results of GOHAI surveys before and after the operation and the following statistical hypotheses were suggested: H0 - the results of the GOHAI survey before the operation do not differ from the results of the GOHAI survey after the operation; H1 - GOHAI pre-op survey results are different from GOHAI post-op survey results. A comparison was made between the GOHAI results before and after surgery in male and female patients using the t-test for independent samples.

RESULTS

29 patients included in this (20 females and 9 males) with the mean age of 65 (range:47-88). The average time of operation (surgical operation, prosthetic stage including dental lab work) the Trefoil technique was 6.18 ± 0.87 hours. With the presence of teeth in the mandible, the operation took longer by an average of 45 minutes. Patients were followed for 15±6 months. No chipping of artificial teeth or fractures of the veneering was observed. The survival rate of restorations was 100%. The implant survival rate was 98.85%. The results of the GOHAI survey after surgery show a significant difference from the results of the pre-op survey. If we analyze the average values for the sample, it can be argued that the average result for the GOHAI survey before the operation (29.86) is significantly lower than the average one for the GOHAI survey after the operation (54.93).

CONCLUSION

Preliminary medium-term results of the Trefoil concept for implant-supported rehabilitation of the mandible indicate high patient satisfaction results after 6-18 months of follow-up. It requires a further comprehensive study to obtain data with more patients and over a longer follow-up period.