Full-arch Implant-supported Prosthesis Research Articles

Research progress on accuracy of intraoral digital impressions for implant-supported full-arch prostheses.

With the rapid development of implant techniques and digital technology, digital impressions have become a commonly used impression method in implant restoration. At present, the accuracy of intraoral digital impressions directly applied to implant-supported full-arch prostheses remains inadequate, which is due to the high accuracy requirement of full-arch implant impressions, while there are still technical challenges in intraoral digital impressions about recognition and stitching. In this regard, scholars have proposed a variety of scanning strategies to improve the accuracy of intraoral scan, including mucosal modifications, auxiliary devices and novel scan bodies. At the same time photogrammetry, as a new digital impression technique, has been developing steadily and exhibits promising accuracy. This article reviews the research progress on the accuracy of edentulous full-arch implant impressions and techniques which can improve the accuracy of intraoral digital impressions, to provide reference for clinical application.

A modified technique for simplifying full-arch screw-retained implant rehabilitation with rapid digital conversion: a case report.

In this case report, a novel technique is described for an efficient, simple, and effective digital approach to immediate provisionalization of the implant-supported full-arch prosthesis. Today's patient population is increasingly educated about treatment options and expects efficient, esthetic, and comfortable results. This novel technique delivers on these aims while eliminating the many challenges posed by previously described digital and analog techniques to the immediate provisionalization of the implant- supported full-arch prosthesis. This technique requires minimal chair time and cost to the provider and reduces patient discomfort and complication risk. Combining the best features of analog and digital methods to conversion of the implant-supported full-arch, this novel method presents a promising new protocol for this popular procedure.

Fiber-Reinforced Composites for Full-Arch Implant-Supported Rehabilitations: An In Vitro Study.

Background: Fiber-reinforced composites (FRCs) have been proposed as an alternative to traditional metal alloys for the realization of frameworks in full-arch implant-supported prostheses. The aim of the present in vitro study was to evaluate the deflection under load of seven prostheses endowed with frameworks made of different materials, including different types of fiber-reinforced composites (FRCs). Methods: A master cast with four implant analogues in correspondence with the two lateral incisors and the two first molars was used to create full-arch fixed prostheses with the same shape and different materials. Prostheses were made of the following different materials (framework+veneering material): gold alloy+resin (Au+R), titanium+resin (Ti+R), FRC with multidirectional carbon fibers+resin (ICFRC+AR), FRC with unidirectional carbon fibers+composite (UCFRC+C), FRC with glass fibers+resin (GFRC+AR), FRC with glass fibers+composite (GFRC+C), and resin (R, fully acrylic prosthesis). Flexural tests were conducted using a Zwick/Roell Z 0.5 machine, and the deflection of the lower surface of the prosthesis was measured in order to obtain load/deflection graphs. Results: Greater rigidity and less deflection were recorded for UCFRC+C and GFRC+C, followed by Ti+R and Au+R. The greatest deformations were observed for resin alone, ICFRC+R, and GFRC+R. The results were slightly different in the incisal region, probably due to the greater amount of veneering material in this area. Conclusions: When used to realize full-arch frameworks, Au and Ti allow for predictable mechanical behavior with gradual deformations with increasing load. UCFRC also demonstrated good outcomes and less deflection than ICFRCs when loaded. The GFRC full-arch framework may be a valid alternative, although it showed greater deflections. Further studies are needed in order to evaluate how different prosthesis designs and material thicknesses might affect the outcomes.

Does intra-oral scan improve the impression accuracy of full-arch implant-supported prostheses: A systematic review and meta-analysis.

The present study aimed to systematically review the studies comparing the accuracy of intraoral scan (IOS) and conventional implant impressions (CI) in completely edentulous patients. Electronic searches were performed in PubMed, Embase and Cochrane CENTRAL up to December 1, 2023. Clinical studies and in vitro studies reporting the accuracy of digital full arch impressions were included. The primary outcome is the 3-dimensional deviations between the study reference models. A risk of bias assessment was performed for clinical studies. A stratified meta-analysis and a single-armed meta-analysis were conducted. A total of 49 studies were included, with 8 clinical studies and 41 in vitro studies. For comparison between IOS and conventional impressions, studies were categorized into two groups based on the different measurement methods employed: RMS and CMM. In studies using RMS, the result favored the IOS in the unparalleled situation with the mean difference of -99.29 μm (95% CI: [-141.38, -57.19], I2 = 81%), while the result was opposite with the mean difference of 13.62 μm (95% CI: [10.97, 16.28], I2 = 26%) when implants were paralleled. For different brands of IOS, the accuracy ranged from 76.11 μm (95% CI: [42.36, 109.86]) to 158.63 μm (95% CI: [-14.68, 331.93]). Accuracy of intraoral scan is clinically acceptable in edentulous arches, especially for unparalleled implants. More clinical studies are needed to verify the present finding.

The All-on-4 Concept Using Polyetheretherketone (PEEK)-Acrylic Resin Prostheses: Follow-Up Results of the Development Group at 5 Years and the Routine Group at One Year.

It is necessary to investigate the application of polymer materials in implant dentistry. The aim of this study was to examine the outcome of full-arch polyetheretherketone (PEEK)-acrylic resin implant-supported prostheses. Seventy-six patients were rehabilitated consecutively with 100 full-arch implant-supported prostheses of PEEK-acrylic resin (a development group (DG): 37 patients with 5 years of follow-up; a routine group (RG): 39 patients with 1 year of follow-up). The primary outcome measure was prosthetic survival. Secondary outcome measures were implant survival, marginal bone loss, biological complications, prosthetic complications, veneer adhesion, plaque levels, bleeding levels, and a patient subjective evaluation (including the Oral Health Impact Profile for the RG). In both groups, prosthetic (DG: 93.6%; RG: 100%) and implant survival (DG: 98.9%; RG: 99.5%) were high, and marginal bone loss was low (DG: 0.54 mm; RG: 0.28 mm). The veneer adhesion rate was 28.6% of prostheses in DG (RG = 0%). Mechanical complications occurred in 49% and 11.8% of prostheses in DG and RG, respectively. Biological complications, plaque, and bleeding levels were low in both groups. The subjective patient evaluation was excellent in both groups (8.6 < DG < 8.8; 9.3 < RG < 9.5; OHIP = 1.38). Within the limitations of this study, PEEK can be considered a viable prosthetic alternative.

A follow-up study of the severe occlusal surface wear of implant-supported full-arch prostheses

Objective: To evaluate the severe occlusal surface wear of implant-supported full-arch prostheses, and to explore the risk factors affecting the severe occlusal surface wear of implant-supported full-arch prostheses. Methods: Five hundred and thirty-five patients who received implant-supported fixed complete dental prostheses or implant-overdentures and completed at least one follow-up 3 months after the delivery of definitive prostheses were enrolled from October 1994 to October 2021 in this retrospective cohort study. The information on demographics, implants, definitive prostheses, and related outcomes was collected. Cox proportional hazard regression model was adopted to analyze the risk factors of the severe wear of occlusal surfaces in implant-supported full-arch prostheses. Univariate analysis was performed on the factors that may affect the severe wear of occlusal surfaces, and the parameters of P<0.10 in univariate analysis were included in multivariate analysis to explore the risk factors affecting the severe wear of occlusal surfaces in implant-supported full-arch prostheses. Results: Severe wear of the posterior occlusal surfaces was detected in 114 prostheses with a duration of 61.4 (33.3, 89.4) months. 13 cases occurred≤2 years after the delivery of definitive prostheses, 44 cases>2 years and≤5 years, 44 cases>5 years and≤10 years, and the other 13 cases>10 years. There was no significant difference in the average time of severe occlusal surface wear between implant-supported fixed complete dental prostheses and implant-overdentures in the maxilla (Z=-1.03, P=0.303). However, in the mandible, it was 48.2 (31.2, 80.2) and 79.2 (51.3, 119.1) months respectively, which was statistically significant (Z=-2.93, P=0.003). Cox proportional hazard regression model showed opposed fixed dentition, bruxism, and posterior resin occlusal surfaces were risk factors (P<0.05) affecting the severe wear of the occlusal surfaces. Conclusions: Severe occlusal surface wear was clinically common with the prolonged application of implant-supported full-arch prostheses. Prostheses opposed to fixed dentition, in patients with bruxism, and made of posterior resin materials were at higher risk of severe occlusal surface wear on the posterior artificial teeth. Regular follow-up, patients' behavior guidance, and clinicians' appropriate intervention were necessary to manage this complication.

Clinical performance of full-arch implant-supported fixed restorations made of monolithic zirconia luted to a titanium bar: A retrospective study with a mean follow-up of 16 months

ObjectivesThis retrospective case series aimed to evaluate the short-term clinical advantages and limitations of full-arch implant-supported restorations made of monolithic zirconia suprastructures passively luted to titanium bar infrastructures and to report the rate of complications within a minimum of 1-year follow-up. Materials and methodsThis study included 31 patients (19 men and 12 women) requiring full-arch implant-supported prostheses in the upper or lower jaw. The patients were treated using an entirely digital approach from implant planning and guided implant placement to prosthetic construction planning, design, and fabrication. Full-arch implant-supported monolithic zirconia suprastructures luted to prism-shaped titanium bars were used in all the cases. All the restorations were evaluated for biological and technical complications during fixed control appointments. ResultsNo implant failures or serviceable prosthetic complications were reported, and the prosthetic survival rate was 100%, with a follow-up duration ranging from 12 months to 20 months. In two cases, a fracture line was observed in the zirconia suprastructures, although it did not require any intervention. ConclusionsAfter a 16-month mean follow-up period, the monolithic zirconia implant-supported full-arch fixed dental prostheses demonstrated no biological or technical complications. Further clinical studies with long-term results are required to confirm these reported outcomes. Clinical significanceCAD-/CAM-milled monolithic zirconia structures passively luted to titanium bar infrastructures are a viable treatment option for full-arch restorations over implants, demonstrating 100% survival and success rates in the present study. The outcomes of this short-term retrospective study indicated high success in function, aesthetics, phonetics, and the ability to maintain flawless hygiene. However, the long-term results of restorations produced using the proposed technique should be considered before recommending this approach for routine clinical use.

All-On-Four Concept Literature Review

The All-on-4 concept is a dental implant technique that provides a solution for patients who have lost or are about to lose all of their teeth in one or both jaws. This concept was developed to simplify the implant process and make it more accessible for individuals with extensive tooth loss. In the review performed in Pubmed and Cochrane Library between 2005 and 2023, Full arch implant-supported prosthesis, 4-implant full arc, osseointegration, inclined implant, total edentulism and different combinations in which some of these keywords were used together were chosen. 100 of the articles achieved from the review were evaluated with respect to the subject we examined. The inclusion criteria for articles were as follows: 1-Articles were related to the all-on-four concept. 2-Abstracts were obtained when the full texts could not be obtained. The All-on-4 concept in dental implantology offers several advantages, making it a popular and effective solution for patients with extensive tooth loss. The All-on-4 concept allows for the immediate loading of prostheses onto the implants shortly after surgery. Compared to traditional implant approaches, All-on-4 reduces treatment time significantly. The concept utilizes tilted posterior implants, which take advantage of available bone and reduce the necessity for bone grafting in areas with insufficient bone volume. All-on-4 may be more cost-effective than traditional implant-supported restorations due to the reduced number of implants and the associated surgical procedures. The concept aims to provide a fixed, full-arch prosthesis that closely resembles natural teeth. Numerous studies have reported high success rates for the All-on-4 concept, with the majority of patients experiencing successful osseointegration and long-term stability of the implants. All-on-4 often results in a more comfortable experience for patients, with fewer surgical interventions and reduced healing periods. The tilted posterior implants increase the contact between bone and implant, enhancing stability and support for the prosthesis.

Autonomous robotic surgery for zygomatic implant placement and immediately loaded implant-supported full-arch prosthesis: a preliminary research

ObjectivesA patient with extensive atrophy of the alveolar ridge in the posterior portion of the maxilla was selected to complete an experimental and clinical case of the robotic zygomatic implant to investigate the viability of an implant robotic system in clinical use.MethodsThe preoperative digital information was collected, and the implantation position and personalized optimization marks needed for robot surgery were designed in advance in a repair-oriented way. The resin models and marks of the patient’s maxilla and mandible are all printed in 3D. Custom-made special precision drills and handpiece holders for robotic zygomatic implants were used to perform model experiments and compare the accuracy of the robotic zygomatic implant group (implant length = 52.5 mm, n = 10) with the alveolar implant group (implant length = 18 mm, n = 20). Based on the results of extraoral experiments, a clinical case of robotic surgery for zygomatic implant placement and immediate loading of implant-supported full arch prosthesis was carried out.ResultsIn the model experiment, the zygomatic implant group reported an entry point error of 0.78 ± 0.34 mm, an exit point error of 0.80 ± 0.25 mm, and an angle error of 1.33 ± 0.41degrees. In comparison, the alveolar implant group (control group) reported an entry point error of 0.81 ± 0.24 mm, an exit point error of 0.86 ± 0.32 mm, and an angle error of 1.71 ± 0.71 degrees. There was no significant difference between the two groups (p > 0.05). In clinical cases, the average entry point error of two zygomatic implants is 0.83 mm, the average exit point error is 1.10 mm and the angle error is 1.46 degrees.ConclusionsThe preoperative planning and surgical procedures developed in this study provide enough accuracy for robotic zygomatic implant surgery, and the overall deviation is small, which is not affected by the lateral wall deviation of maxillary sinus.

Accuracy of Conventional and Digital Impressions for Full-Arch Implant-Supported Prostheses: An In Vitro Study.

Both conventional and digital impressions aim to record the spatial position of implants in the dental arches. However, there is still a lack of data to justify the use of intraoral scanning over conventional impressions for full-arch implant-supported prostheses. The objective of the in vitro study was to compare the trueness and precision of conventional and digital impressions obtained with four intra-oral scanners: Trios 4 from 3Shape®, Primescan from Dentsply Sirona®, CS3600 from Carestream® and i500 from Medit®. This study focused on the impression of an edentulous maxilla in which five implants were placed for implant-supported complete prosthesis. The digital models were superimposed on a digital reference model using dimensional control and metrology software. Angular and distance deviations from the digital reference model were calculated to assess trueness. Dispersion of the values around their mean for each impression was also calculated for precision. The mean distance deviation in absolute value and the direction of the distance deviation were smaller for conventional impressions (p-value < 0.001). The I-500 had the best results regarding angular measurements, followed by Trios 4 and CS3600 (p < 0.001). The conventional and I-500 digital impressions showed the lowest dispersion of values around the mean (p-value < 0.001). Within the limitations of our study, our results revealed that the conventional impression was more accurate than the digital impression, but further clinical studies are needed to confirm these findings.

Plaque accumulation on the fitting surface of full-arch implant-supported fixed prostheses with contact or noncontact pontics: A split mouth randomized controlled trial.

To explore the differences in plaque accumulation on the fitting surface of full-arch implant-supported fixed prostheses with contact or noncontact pontics. Nineteen patients (20 prostheses, 7 in the maxilla, and 13 in the mandible) intending to undergo full-arch implant-supported immediate function prostheses were recruited. During immediate restoration and using the midline as the boundary, one side was restored as a pontic and mucosa noncontact type (the test group), and the opposite side was restored as a pontic and mucosa contact type (the control group). In a follow-up 6 months after the surgery, the cleanliness of the fitting surface of the immediate prosthesis was evaluated by plaque staining and debris index determination. Patient satisfaction was investigated by questionnaire. Twenty prostheses from 19 patients included in the randomized controlled trial were followed up. Among the 20 prostheses, the percentage of area covered with plaque was significantly lower in the test group compared with that in the control group (31.5 ± 15.8% vs. 43.7 ± 15.3%; p < 0.001). The debris index in the test group was lower than that in the control group, although the difference was not statistically significant (2.77 ± 0.73 vs. 3.15 ± 0.90; p > 0.05). In the patient satisfaction survey, most of the patients were satisfied with most aspects of the prostheses, however, nearly half of the patients were not satisfied with the cleaning. The pontic and mucosa noncontact prosthetic design reduces plaque accumulation on the fitting surface, which is beneficial for maintaining oral cleanliness. However, the majority of study samples were mandible and conclusions may not be fully applicable to maxilla. www.chictr.org.cn (ChiCTR1900028576). The noncontact design in full-arch implant-supported fixed prostheses may be an effective measure of improving oral hygiene promotion. There is need for more research that can further improve oral hygiene of patients with full-arch implant-supported prostheses.

Retrospective Cohort Evaluation of Full-Arch Zirconia Implant-Supported Fixed Prostheses.

Objective: To determine the median event-free survival and relative complication rates of monolithic and minimally layered full-arch zirconia prostheses, as well as to identify risk factors for prosthesis complications. Materials and Methods: In this retrospective cohort study, a total of 129 subjects (173 prostheses) were included in the chart review and 56 subjects (75 prostheses) participated in a clinical follow-up visit. All subjects had either single- or dual-arch monolithic or minimally layered zirconia implant-supported prostheses. Data related to patient, implant, and prosthesis factors were extracted from charts. The subgroup that presented for a clinical visit were asked to complete a satisfaction questionnaire. For this subgroup, the following clinical measures were assessed: routine intraoral examination, number of occluding units, cantilever length on each side of the prosthesis (right and left), prosthesis height, occlusal scheme, and oral hygiene methods. Periapical radiographs were obtained when the last radiographs of the patient were taken more than 12 months prior. Results: The follow-up period ranged from 12 months to 7.1 years (mean: 1.9 years). Observed complications included implant loss, peri-implantitis, mucositis, purulence, sinus tract formation, oroantral communication, implant fracture, titanium base debonding, ceramic chipping, prosthetic screw fracture or loosening, damage to opposing teeth, and clicking sounds. There was an insufficient number of complications to evaluate the effect of covariates on the risk of specific complications, such as titanium base debonding (eight events), ceramic chipping (nine events), and peri-implantitis (eight events). The unadjusted event-free median survival time was 5.8 years. The proportion of all prostheses with at least one complication was 30%. There were no observed prosthesis losses during the follow-up period. Conclusion: Monolithic and minimally layered zirconia full-arch implant-supported prostheses demonstrate an acceptable median event-free survival time. Event-free survival times were increased and the number of complications was reduced in prostheses with five to eight implants and conventional (as opposed to zygomatic) implants. There was a reduced hazard of complications with a regular recall regimen. Patient satisfaction with these prostheses was high.

Three-Dimensional FEA Analysis of the Stress Distribution on Titanium and Graphene Frameworks Supported by 3 or 6-Implant Models

Titanium is the main component of dental implants. It is also routinely used as a framework material for implant-supported full-arch prostheses due to its low density, biocompatibility, and other mechanical properties. Remarkable mechanical properties such as lesser mass density and higher young's modulus of graphene have gained popularity among scientists, improving the properties of biomedical implants. Thus, our study aimed to compare the outcome through the von Mises stresses generated on All-on-6 and All-on-3 implant models, as well as on the framework, and evaluate the effect of stress patterns on the crestal bone around implants in the mandible. FEA (Finite Element Analysis) study was carried out using edentulous mandible models. Four 3D FEA models with 3 and 6 implants were used (Model 1: Titanium bar-supported 6 straight implants; Model 2: Graphene bar-supported 6 straight implants; Model 3: Titanium bar-supported 3 implants with 30 degrees-tilted; Model 4: Graphene bar-supported 3 implants with 30 degrees-tilted) in order to simulate endosseous implant designs. The implant measuring 4.2 mm in diameter and 11.5 mm in length were used. The most distal implants in the 3-implant models were placed with angulation of 30 degrees; in 6 implants, they were vertically placed. All the models were analyzed for vertical and oblique axis with a single force magnitude of 100 N. In all four implant models and under loading conditions, the peak stress points were always on the neck of the most distal implant. von Mises stresses were within the normal stress range. In a conventional six-straight implant model supported by a titanium framework, the cortical stress in the region of implants was 25.27 MPa, whereas, in the graphene framework, it was 12.18 MPa. Under vertical load, there was a significant difference in the cortical stress around the tilted implants (30 degrees) in the 3-implant system of titanium and graphene frameworks, respectively, 70.31 MPa and 21.27 MPa. The graphene framework demonstrated better results than the titanium framework for the conventional six-implant system under vertical load, achieving stress of 30.09 MPa and 76.60 MPa, respectively. In the case of the 3-implant system, a significant difference in the bar stress was observed between graphene and titanium, respectively, 256.32 MPa and 180.1 MPa of bar stress. Within the limitation of this study, the peri-implant stresses were decreased using graphene framework models. Hence, it was possible to conclude that the best load-bearing capacity results were found in the graphene framework group compared to the titanium framework for All-on-6 and All-on-3 implant models, even though both materials are reliable options used as framework materials in implant-supported full-arch prostheses.

Full-mouth rehabilitation of upper and lower jaws with computer-guided flapless surgery and immediate loading of implants inserted and mastication analysis

ABSTRACT Although a number of approaches to implant-supported restoration of severely atrophic maxillae and mandibles have been developed, most of these treatments are expensive and protracted. An exception is the concept, which uses only guided implant surgeries and immediate loading with a hybrid, screw-retained provisional prosthesis delivered on implant placement, followed by a definitive hybrid prosthesis later. The present article describes full-arch rehabilitations using implant-supported prostheses and analyzes the functional efficacy of the treatment done by mastication analysis. This innovative technique allows for full-arch implant-supported prosthesis without the need for any bone grafting procedures even in atrophic situations and immediate function. In this technique, four or six or more implants are placed in the jaws, immediately loaded with temporalization, and put into function.

Mechanical behavior of implant-supported full-arch prostheses in different locations in the maxilla: 3D-FEA and strain gauge analysis

Mechanical behavior of implant-supported full-arch prostheses in different locations in the maxilla: 3D-FEA and strain gauge analysis

Accuracy of the Different Materials Used to Fabricate a Verification Jig of Implant-Supported Fixed Complete Dental Prostheses: An In Vitro Study

Introduction The passive fit of a full arch implant-supported prosthesis is one of the elements influencing implant success. Achieving the passive fit of a prosthesis requires verification of the master cast before the fabrication of the framework. A verification jig is a common way to verify the implant master cast and ensure the accuracy of the implant impression and produced cast. Different materials can be used to fabricate verification jigs, and each material exhibits different dimensional changes. In this study, we compared the accuracies of verification jig materials by 3D assessment. Materials and methods A type IV stone cast with four implant analogs was constructed and used as a control. Verification jigs were constructed from five different materials, and test casts were made from these jigs and poured using low expansion stone (type IV), resulting in five groups (n=5). All test casts and the control cast were scanned using a lab scanner. The scans of test casts were superimposed on that of the control cast for 3D accuracy assessment. The distortion of the implant analogs was recorded using Geomagic Design X and GeomagicControlX software (3D Systems, Rock Hill, South Carolina, USA). Statistical differences in the 3D accuracies between the five groups were analyzed using the Kruskal-Wallis test. Result The photopolymerizable resin group had a mean value of 23.16 (± 0.88) µm; the composite group had a mean value of 46.72 (± 2.122) µm; the GC pattern group had a mean of 23.51 (± 0.736) µm; the type III stone group had a mean of 19.84 (± 1.017) µm; the type IV stone group had a mean of 18.72 (± 0.819) µm. The Kruskal-Wallis test indicated that there were statistically significant differences between groups 2 (composite), 4 (type III stone), and 5 (type IV stone). Conclusion The most accurate cast was produced by type IV stone, followed by type III stone, photopolymerizable resin, GC pattern, and composite in order of decreasing accuracy. Within the limitations of the study, a material with low distortion and high accuracy is recommended when fabricating verification jigs of implant-supported complete dental prostheses.

Evaluation of Stress and Fatigue on Different Implant Lengths in the Rehabilitation of Atrophic Mandibles with Full-Arch Fixed Prosthesis Using Finite Element Method.

This research aimed to evaluate the stress and fatigue generated in short implants compared to regular implants in rehabilitation with fixed full-arch implant-supported prostheses in atrophic mandibles using the finite element method (FEM). Four models were constructed with different implants lengths: 4, 6, 8, and 10 mm. A 100-N oblique load was applied to evaluate the stress on the bone, implant, and prosthetic components. Similar behavior was observed for all groups, except for 4 mm, which showed more discrepant values. During the fatigue test, all the groups exhibited infinite lives except G4. Based on the similarity of all the models, it is suggested that all short implants investigated are seemingly viable alternatives for the rehabilitation of atrophic mandibles. However, the 6-mm-long and 8-mm-long implants evinced more favorable mechanical behavior than the 4-mm-long type.

Occlusal considerations for full-arch implant-supported prostheses: A guideline

Full-arch implant prostheses of various types and materials have become a popular treatment modality for edentulous arches. Studies have found that the prevalence of prosthetic complication is higher than biological complication with these restorations. Occlusion may be one of the contributing factors for prosthetic complications in full-arch implant supported prostheses. However, available literature regarding the occlusal scheme of full-arch implant prostheses is often insufficient or unclear. Often the articles do not give details regarding the material type or the opposing dentition. The occlusal scheme should not only provide the patient with function and comfort, but also minimize the risk of various prosthetic complications. Metal-acrylic and all-ceramic are popular material options for full-arch implant supported prostheses. The proposed guideline will suggest occlusal considerations based on material type (metal-acrylic or all-ceramic) as well as the opposing dentition (natural or prosthetic dentition) in order to minimize prosthetic complications. Five possible scenarios are presented: 1) Metal-Acrylic vs. Metal-Acrylic 2) Metal-Acrylic vs. Natural Dentition 3) All-Ceramic (Zirconia) vs. All-Ceramic (Zirconia) 4) All-Ceramic (Zirconia) vs. Metal-Acrylic 5) All-Ceramic vs. Natural Dentition. The guidelines are based on compilation of available occlusal concepts from natural teeth and implant prosthetics.

Prosthesis-Implant Arch Area Ratio (PIAAR) - A New Geometric Paradigm, Replacing the Current 'A-P Spread' of a Cantilever in Full-Arch Implant Prosthesis: A Proof-of-Concept Experiment.

The anterior-posterior spread concept is relied upon to understand the bioengineering aspects of cantilevers in fixed complete denture prostheses. This concept is not evidence-based. With no other category existing in contemporary implant dentistry, this conventional anterior-posterior spread concept may have limited more precise and accurate biomechanical analysis. This paper aims to validate a scientific rationale for utilizing this new prosthesis-implant arch area ratio instead of the preexisting anterior-posterior spread concept. Utilizing the preexisting mathematical principle of "Heron's formula," enabling the calculation of the area of a triangle with three known lengths and no angular information, a new prosthesis-implant arch area ratio is introduced through algebraic derivation. Geometrically, three different sections of prosthetic cantilevers are defined as: (1) anterior cantilever; (2) lateral cantilever; (3) posterior cantilever. The prosthesis-implant arch area ratio is defined as the prosthesis arch area (anterior, lateral, or posterior cantilever) divided by the sum of the platform arch area and the selected prosthesis arch area. As a proof-of-concept experiment, fifteen different laboratory cast arches (n = 15) were chosen; theorized four implant platforms were referenced from the conventional anterior-posterior spread ration of 1:1.5, followed by calculating platform arch area and prosthesis arch area using Heron's formula. Then, three different horizontal arch width ratios (1:1, 1.25:1, and 1.5:1) under the constant linear height ratio of anterior-posterior spread (1:1.5) were drawn to assign different experimental groups of prosthesis arch area on each patient scenario, followed by cantilever comparison combining all ratio values (n = 45). One-way ANOVA and Tukey's post hoc multiple comparison tests were used for statistical analysis. One-way ANOVA revealed statistical differences of all prosthesis-implant arch area ratios on each cantilever group; anterior cantilever, F(2, 42) = 8.326, p = 0.0009; lateral cantilever F(2, 42) = 43.92, p < 0.0001; posterior cantilever, F(2, 42) = 26.66, p < 0.0001, as well as cantilever's comparison, F(2, 132) = 240.8, p < 0.0001. Tukey's post hoc test showed a statistically significant ascending trend of prosthesis-implant arch area ratio as the horizontal width ratio increases. Interestingly, the posterior cantilever had the greatest prosthesis-implant arch area ratio. Compared to the preexisting anterior-posterior spread concept, a new prosthesis-implant arch area ratio seemed to be a more categorized, geometric, and perceptive modality of assessing the prosthetic cantilever in a full-arch implant-supported prosthesis, allowing a more systematic indexing of different full-arch implant clinical scenarios with greater specificity and consistency.

In Vitro Accuracy of Digital and Conventional Impressions for Full-Arch Implant-Supported Prostheses.

The aim of this study was to evaluate the accuracy of full-arch digital impressions when compared to conventional impressions, when performed on the abutment or implant level. Methods: One resin cast with six implants and another cast with six abutments were scanned with Primescan v5.1 (PS51), Primescan v5.2 (PS52), Trios 3 (T3), and Trios 4 (T4). Additionally, conventional impressions (A) were made, poured in gypsum, and digitized using a lab scanner (IScan D104i). A coordinate machine (Atos, GOM, Braunschweig, Germany) was used to generate the reference scan of both casts. For all scans, the position of the implants was calculated and matched with the reference scan. Angular and coronal measurements per implant were considered for trueness and precision. Results: For the implant-level model, PS52 performed significantly better in terms of trueness and precision compared to all other impressions, except for the angular trueness of A (p = 0.072) and the coronal trueness of PS51 (p = 1.000). For the abutment-level model, PS52 also performed significantly better than all other impressions, except for the coronal trueness and precision of A (p = 1.000). Conclusions: Digital impressions for full-arch implant supported prostheses can be as accurate as conventional impressions, depending on the intra-oral scanner and software. Overall, abutment level impressions were more accurate compared to implant level impressions.