Posterior Cantilever Research Articles

Prosthodontic criteria for maxillary immediate occlusal loading, surgical classifications of atrophic maxillae, and presentation of a new implant/anatomic classification system for immediate maxillary rehabilitation.

Immediate full-arch occlusal loading for patients with atrophic edentulous maxillae satisfies critical needs for this specific type of edentulous patient after placement of implants with high levels of primary implant stability. The needs include improved aesthetics, limited immediate improved function, and elimination of removable prostheses. Classification systems exist for edentulous maxillae but they do not include specifics regarding posterior implant placement. In conjunction with anterior implants, posterior implants improve Anterior/Posterior (A/P) spreads, decrease cantilevered segments (CLs), and likely will improve implant and prosthetic success rates. The purposes of this article include presenting a new classification system that outlines the different types of implants now available which will likely achieve the requisite primary stability for immediate fixed rehabilitation. This proposed classification system identifies a relationship between different implant options currently available and the remaining quantity of bone in the first and second maxillary molar zones. The available literature regarding current classification systems was reviewed. The benefits and limitations of each system were described. The parameters associated with Immediate Occlusal Loading (IOL) for full arch maxillary prostheses include: posterior cantilever lengths of full arch fixed prostheses; existing A/P spread considerations for full arch prostheses; and introduction of a new classification system for atrophic posterior maxillary edentulous ridges were identified. Currently, there are no available classification systems that outline specific implant options for posterior maxillae which will likely achieve the minimum primary stability needed for immediate rehabilitation. A new classification system was proposed where the rationale was to show clinicians that when a certain amount of bone remains in the posterior maxilla, there are specific implants designed to maximize primary stability. High implant primary stability is required for rehabilitation with immediate fixed implant-supported provisional prostheses. The proposed classification system assists clinicians in understanding what implant geometry is available and can be expected to achieve the requisite primary stability for immediate occlusal loading based on the available bone in the posterior maxillary molar zone. This article reviewed current classification systems for edentulous maxillary patients, as well as clinical parameters required for full arch, immediate occlusal loading. It also presented a new classification system to assist clinicians in selecting appropriate implants and surgical techniques for immediate fixed rehabilitation of patients with atrophic maxillae.

Initial damage and failure load of zirconia-ceramic and metal-ceramic posterior cantilever fixed partial dentures

ObjectivesThe aim of this study was to compare failure load and initial damage in monolithic, partially veneered, and completely veneered (translucent) zirconia cantilevered fixed partial dentures (CFPDs), as well as completely veneered metal-ceramic CFPDs under different support and loading configurations.Materials and methodsEight test groups with anatomically congruent CFPDs (n = 8/group) were fabricated, differing in CFPD material/support structure/loading direction (load applied via steel ball (Ø 6 mm) 3 mm from the distal end of the pontic for axial loading with a 2-point contact on the inner cusp ridges of the buccal and oral cusps and 1.3 mm below the oral cusp tip for 30° oblique loading): (1) monolithic zirconia/CoCr abutment teeth/axial, (2) monolithic zirconia/CoCr abutment teeth/oblique, (3) partially veneered zirconia/CoCr abutment teeth/axial, (4) partially veneered zirconia/CoCr abutment teeth/oblique, (5) completely veneered zirconia/CoCr abutment teeth/axial, (6) completely veneered CoCr/CoCr abutment teeth/axial (control group), (7) partially veneered zirconia/implants/axial, and (8) partially veneered zirconia/natural teeth/axial. Restorations were artificially aged before failure testing. Statistical analysis was conducted using one-way ANOVA and Tukey post hoc tests.ResultsMean failure loads ranged from 392 N (group 8) to 1181 N (group 1). Axially loaded monolithic zirconia CFPDs (group 1) and controls (group 6) showed significantly higher failure loads. Oblique loading significantly reduced failure loads for monolithic zirconia CFPDs (group 2). Initial damage was observed in all groups except monolithic zirconia groups, and fractography revealed design flaws (sharp edges at the occlusal boundary of the veneering window) in partially veneered zirconia CFPDs.ConclusionsMonolithic zirconia CFPDs might be a viable alternative to completely veneered CoCr CFPDs in terms of fracture load. However, oblique loading of monolithic zirconia CFPDs should be avoided in clinical scenarios. Design improvements are required for partially veneered zirconia CFPDs to enhance their load-bearing capacity.Clinical relevanceMonolithic zirconia may represent a viable all-ceramic alternative to the established metal-ceramic option for CFPD fabrication. However, in daily clinical practice, careful occlusal adjustment and regular monitoring should ensure that oblique loading of the cantilever is avoided.

Long-term survival and complications of Quad Zygoma Protocol with Anatomy-Guided Approach in severely atrophic maxilla: A retrospective follow-up analysis of up to 17 years.

The objective of the study was to provide long-term clinical outcomes and complications in the severely atrophic edentulous maxillae treated by means of the quad zygoma protocol (QZP) using the Anatomy-Guided Approach (AGA). This was a retrospective cohort study of all consecutive patients with severely atrophic edentulous maxilla and insufficient bone height and width in the anterior and posterior regions bilaterally, who underwent rehabilitation with the QZP between May 2006 and December 2021. All patients were followed for at least 1 year. All zygomatic implants (ZIs) were placed by the same surgeon. The primary endpoint of the study was the implant survival rate. Secondary endpoints were implant success rate, prosthesis success rate, complications, and Oral Health-Related Quality of Life using the OHIP-14 questionnaire. A total of 56 patients (men 16, women 40) with 224 ZIs (Nobel Biocare, n = 204; Straumann, n = 16; Southern Implant, n = 4) placement were included with a mean follow-up period 8.8 ± 3.9 years (range, 1.2-17.0). The survival (success) rate was 97.7%. Five ZIs in four patients failed. The mean time between implant placement and failure was 8.6 years (range, 0.5-13.3). All patients received immediate loading with acrylic prosthesis. The successful rates for the definitive prosthesis were 98.2%. Forty-two patients received posterior cantilever for rehabilitation of fixed definitive prosthesis. Local orofacial inflammation (35.7%) and Sinusitis (12.5%) were the most common complications, occurring at a mean follow-up of 10.0 (range, 4.2-14.9) and 10.3 (range, 4.3-16.2) years, respectively. In 48 patients, the mean score of the OHIP-14 questionnaire was 1.7 ± 2.6 with the follow-up period of 9.0 ± 4.1 years. The rehabilitation of severely atrophic edentulous maxilla using the QZP has shown a predictable and high survival rate in the long term. The implementation of an immediate loading protocol offers potential benefits in stabilizing ZIs with cross-arch stabilization. Moreover, the use of a posterior cantilever in reconstruction can effectively establish functional occlusion through well-distributed ZIs, eliminating the need for additional implant placement.

Topic: All-on-Four Concept Literature Review

In patients with total edentulism, dental implant treatment is a treatment model which has been accepted scientifically, and with long-term outcomes [1,2]. Dental implants with immediate function by making implant-supported fixed full-arch restorations are becoming the gold standard in dental implantology [3-5]. Normally in literature successful prostheses are made using [6-8] implants in the maxilla and 6 implants in the mandible and applying posterior cantilever extension where it is necessary, in these treatments, hygiene controls can be easily performed especially in full arch screw-retained fixed prostheses [7-9]. In some cases maxillary sinuses for maxilla restricts the implant placement in the posterior region. The posterior implant treatment is also difficult in patients with resorbed mandible with a mandibular nerve located at the top of the alveolar crest. The all-on-four implant concept has been developed to prevent these disadvantages presented by Malo for the first time in 2003 and the all-on-four concept that began to be used in atrophic full arch mandibular and in the maxilla in 2005. In this technique implants are positioned in the pre-maxillary region in the maxilla and in the inter-foraminal region in the mandible.Anterior implants are placed to the lateral incisor sites or canine/first premolar region, posterior implants are placed to the second premolar or first molar region [12-16].

Implant-Supported Fixed Partial Dentures with Posterior Cantilevers: In Vitro Study of Mechanical Behavior.

Rehabilitation with dental implants is not always possible due to the lack of bone quality or quantity, in many cases due to bone atrophy or the morbidity of regenerative treatments. We find ourselves in situations of performing dental prostheses with cantilevers in order to rehabilitate our patients, thus simplifying the treatment. The aim of this study was to analyze the mechanical behavior of four types of fixed partial dentures with posterior cantilevers on two dental implants (convergent collar and transmucosal internal connection) through an in vitro study (compressive loading and cyclic loading). This study comprised four groups (n = 76): in Group 1, the prosthesis was screwed directly to the implant platform (DS; n = 19); in Group 2, the prosthesis was screwed to the telescopic interface on the implant head (INS; n = 19); in Group 3, the prosthesis was cemented to the telescopic abutment (INC; n = 19); and in Group 4, the prosthesis was cemented to the abutment (DC; n = 19). The sets were subjected to a cyclic loading test (80 N load for 240,000 cycles) and compressive loading test (100 KN load at a displacement rate of 0.5 mm/min), applying the load until failure occurred to any of the components at the abutment-prosthesis-implant interface. Subsequently, an optical microscopy analysis was performed to obtain more data on what had occurred in each group. Results: Group 1 (direct screw-retained prosthesis, DS) obtained the highest mean strength value of 663.5 ± 196.0 N. The other three groups were very homogeneous: 428.4 ± 63.1 N for Group 2 (INS), 486.7 ± 67.8 N for Group 3 (INC), and 458.9 ± 38.9 N for Group 4 (DC). The mean strength was significantly dependent on the type of connection (p < 0.001), and this difference was similar for all of the test conditions (cyclic and compressive loading) (p = 0.689). Implant-borne prostheses with convergent collars and transmucosal internal connections with posterior cantilevers screwed directly to the implant connection are a good solution in cases where implant placement cannot avoid extensions.

Influence of retainer design and number of inlay boxes on the biomechanical behavior of zirconia cantilever resin bonded fixed dental prosthesis.

The development of dental adhesives with enhanced bond strength has assisted minimally invasive dentistry. The aim of this study was to evaluate the fracture load and stress distribution pattern of two retainer designs for posterior cantilever resin bonded fixed dental protheses (RBFDPs). Forty human mandibular molars were divided into two groups according to the retainer design; lingual coverage (LC) and occlusal coverage (OC) retainers. Each main group was then divided according to the number of inlay boxes (n = 10); one inlay and two inlay boxes. High translucency (3Y) zirconia was used to manufacture all restorations, and a dual-polymerizing adhesive resin cement was used for bonding. All specimens underwent 10,000 cycles of thermocycling (5-55°C), 240,000 cycles of dynamic loading (50 N, descending speed v = 30 mm/second, frequency = 1.6 Hz), and failure load test. Both one-way and two-way ANOVA tests were used to analyze the data. The four models included in the in-vitro study are part of the finite element analysis (FEA). When the restorations failed, maximal principal stress values on restorations, enamel, dentin, and luting resin were investigated. A statistically significant (p = 0.018) higher failure load was recorded for OC1 (627.00 ± 153.4 N) than the other groups; (548.0 ± 75.6 N, 521.20 ± 11.3 N, and 509.20 ± 14.9 N for LC1, LC2, and OC2, respectively). With regard to failure mode, one inlay box designs showed more favorable failure pattern than those of two inlay boxes. FEA showed higher stress magnitude transmitted to the tooth structure in models LC2 and OC2. Lingual coverage and occlusal coverage retainers are promising designs capable to withstand the normal occlusal force for cantilever RBFDP in premolar area. The use of two inlay boxes decreased the fracture load of the two retainer designs and increased the stress transmitted to the tooth and resulted in high incidence of catastrophic failure. Monolithic high translucent zirconia RBFDP could be considered as a viable treatment option to substitute missing posterior tooth, with improved esthetics and biocompatibility.

Evaluation of different designs for posterior cantilever zirconia inlay-retained fixed dental prostheses in missing tooth replacement: Stage one results with 18-month follow-up assessment

ObjectivesThis clinical study aimed to investigate the outcomes and survival rates of different variations of inlay-retained fixed dental prostheses (IR-FDPs) composed of monolithic zirconia ceramic. The IR-FDPs with a single-retainer design were used for replacing missing mandibular second premolars. The research evaluated the effectiveness and longevity of these prostheses in clinical settings. MethodsA total of 30 IR-FDPs (n = 30) were placed for 27 female patients who presented with missing mandibular second premolar teeth. For this study, the mandibular first molar was chosen as a retainer for the cantilever IR-FDPs and the study involved a random assignment of participants into three distinct groups, each comprising 10 individuals (n = 10). The criterion for the grouping was the retainer design: inlay ring (IR), lingual coverage (LC), and occlusal coverage (OC). The three groups included mesial inlay box with the same dimensions (3 mm height, 3 mm width and 2 mm depth). All IR-FDPs were manufactured using monolithic high translucent 3Y zirconia and the connector area to the cantilever pontic was adjusted to dimensions of 3 × 3 mm for all designs. The restorations were bonded using adhesive resin cement. The clinical and radiographic evaluations of the restorations were conducted for a duration of 18 months, following the modified FDI (World Dental Federation) criteria. ResultsThe restorations were observed in stage one for a period of 18 months. Only one restoration in group LC was debonded after 10 months and re-bonded. The clinical quality of all crowns and the patient's satisfaction were high. No adverse soft tissue reactions around the crowns were observed and only one abutment in group IR was endodontically treated after 12 months. ConclusionsZirconia cantilever IR-FDPs offer a viable short-term treatment option for replacing missing posterior teeth, providing esthetic and functional benefits while minimizing invasiveness. Over an 18-month observation period, these prostheses have demonstrated a remarkable survival rate of 100% and a success rate of 96.6%. These findings suggest the effectiveness and reliability of zirconia cantilever IR-FDPs as a short-term solution for replacing missing posterior teeth. Clinical significanceZirconia cantilever IR-FDPs could present a practical solution for addressing posterior tooth loss, especially in cases where implant placement is not recommended and conventional fixed dental prostheses entail excessive invasiveness.

Survival and debonding resistance of posterior cantilever resin-bonded fixed dental prostheses for moderately and severely worn dentition during thermomechanical loading.

The purpose of this study was to investigate the survival rate, the debonding resistance, and the failure modes of different occlusal veneer designs when used as a retainer for posterior cantilever, resin-bonded fixed dental prostheses (RBFDPs) at two tooth wear levels. Four test groups were assigned: two groups with occlusal-proximal preparation (PT1 and PT2 for grade 2 and 3 wear), and two groups for occlusal-proximal and lingual preparation (PLT1 and PLT2 for grade 2 and 3 wear) Monolithic zirconia ceramic (3Y-TZP) RBFDPs were luted with an adhesive bonding system (Panavia V5). The specimens underwent a chewing simulation for 1.200.000 cycles with a load of 5kg and thermocycling for 7500 cycles between 5°C and 55°C. The surviving restorations were debonded under quasi-static conditions. The results were analyzed with ANOVA. The specimens exhibited a 100 % survival rate after thermomechanical fatigue loading. The debonding resistance was statistically significant higher for group PLT1 than for group PT1 (P=0.004), and higher for group PT2 than group PT1 (P≤0.001). However, the debonding resistance showed no statistically significant difference between groups PT2 and PLT2 (P=0.343), and groups PLT1 and PLT2 (P=0.222). Groups PT1 and PT2 showed favorable failure modes in 62.5 % and 0.00 % of the specimens, respectively. While groups PLT1 and PLT2 presented 25 % favorable failure modes. Occlusal veneers showed promising results as a retainer for cantilever RBFDPs. The lingual extension might increase debonding resistance. Nevertheless, conservative designs with lingual and proximal bevels are to be recommended, irrespective of the level of tooth wear.

Mechanical response of different frameworks for maxillary all-on-four implant-supported fixed dental prosthesis: 3D finite element analysis.

This study's purpose is to assess the stress distribution in the peri-implant bone, implants, and prosthetic framework using two different posterior implant angles. All-on-four maxillary prostheses fabricated from feldspathic-ceramic-veneeredzirconia-reinforced lithium silicate (ZLS) and feldspathic-ceramic-veneeredcobalt-chromium (CoCr) were designed with17 or 30-degree-angled posterior implants. Posterior cantilever and frontal vertical loads were applied to all models. The distribution of maximum and minimum principal stresses (σmax and σmin) and von Mises stress (σVM) wasevaluated. Under posterior cantilever load, with an increase in posterior implant angle, σmax decreased by 4 and 7MPa in the cortical bone when ZLS and CoCr were used as a prosthetic framework, respectively. Regardless of the framework material, 17-degree-angled posterior implants showed the highest σVM (541.36MPa under posterior cantilever load; 110.79MPa under frontal vertical load) values. Regardless of the posterior implant angle, ZLS framework showed the highest σVM (91.59MPa under posterior cantilever load; 218.99MPa under frontal vertical load) values. Increasing implant angle from 17 to 30° caused a decrease in σmax values in the cortical bone. Designs with 30-degree posterior implant angles and ZLS framework material may be preferred in All-on-four implant-supported fixed complete dentures.

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.

Fracture behavior of cantilever fixed dental prostheses fabricated from different zirconia generations.

The aim of this study was to compare the fracture behavior of cantilever fixed dental prostheses (FDPs) fabricated from 3Y-TZP, 4Y-TZP, or 5Y-TZP zirconia. Posterior cantilever FDPs (three groups, each n = 16) were digitally designed and milled. After sintering, eight specimens/group were stored in demineralized water for 72 hours; eight specimens/group were subjected to accelerated aging using chewing simulation with thermal cycling (1,200,000 × 50 N; 2 × 3,000 × 5°C/55°C; H2O, 2 minutes/cycle) and finally stored in demineralized water for 24 hours. The cantilever FDPs were then statically loaded to failure to determine fracture load. Phase transformation towards the monoclinic phase was controlled with x-ray diffractometry. One failure was identified after accelerated aging in the 5Y-TZP group. Fracture load decreased with increasing yttria content and decreasing bending strength. Accelerated aging using chewing simulation with thermal cycling caused a significant decline in fracture load. All FDPs failed in the area of the prepared tooth and in proximity to the cantilever, where the largest bending moment occurred. The yttria content had no influence on the type of fracture. With increasing yttria content, the relation between deformation and fracture load decreased only slightly. On the surface of FDPs that had been subjected to chewing simulation, no phase transformation towards the monoclinic phase (eg, low temperature degradation) was detected. Within the limitations of a laboratory study, the data indicate that 3Y-, 4Y-, and 5Y-TZP may be employed as material for the fabrication of permanent posterior cantilever FDPs. However, more data are necessary to finally advocate the application of 5-Y-TZP. (Quintessence Int 2022;53:414-422; doi: 10.3290/j.qi.b2793243).

Determination of strain around distal implants as abutments for partial and fixed implant-supported prostheses with posterior cantilever.

This study aimed to compare strain around implants used as abutments for removable partial dentures with wrought wires and fixed partial dentures with ball attachments and fixed dentures with posterior cantilever. An edentulous mandibular model was constructed using epoxy resin with four parallel implants in the area between the two mental foramina. Four strain gauges were attached to the buccal, lingual, mesial, and distal aspects of each implant. One fixed prosthesis with cantilever and two removable partial dentures were considered as prosthetic treatments. A vertical 500-N force was applied with 10-N intervals. The maximum strain in the fixed prosthesis was higher than that of the partial removable denture; in the removable denture with a wrought wire arm, it was higher than that in the denture with a ball attachment (P < 0.001). The lowest rate of strain was recorded on the mesial aspect (P < 0.05). However, the highest rate of strain was recorded on the lingual and distal aspects of the removable denture with a wrought wire in the buccal aspect and the removable prosthesis with the ball attachment on the buccal and lingual aspects (P < 0.05). Finally, despite minor differences in the maximum strain rate in each implant position, the differences were not statistically significant (P > 0.05). Partial removable denture with a ball attachment decreased strain more than that by the removable portal denture with a wrought wire arm. The worst type of prosthesis in terms of the overall strain rate was the fixed prosthesis with cantilever.

Biomechanical variables affect peri-implant bone loss in implant-supported fixed complete dentures: A methodological and prospective study.

Implant-supported fixed complete dentures (IFCD) experience failures and complications related to biological and technical risk factors. This study investigated the effect of biomechanical variables of IFCD on 1-year peri-implant bone loss at the buccal, palatal/lingual, mesial, and distal implant sides. A new method was used to measure the geometric biomechanical variables of IFCD using cone beam computed tomography (CBCT). The study sample consisted of 246 external hexagon implants supporting 48 hybrid IFCD in 44 patients. CBCT images obtained immediately (T0) and 1 year (T1) after prosthesis installation were used to measure the support polygon area, clinical crown/implant (C/I) ratio (vertical lever), anteroposterior power and resistance arms, anterior and posterior cantilevers (horizontal levers), and peri-implant bone remodeling (T1-T0). Data were analyzed using multilevel multivariable models. The average total bone loss in the mandible and maxilla were 0.88 mm, with a loss of 0.62 mm in the mandible and 1.08 mm in the maxilla. The C/I ratio had a significant effect on bone loss on the mesial, distal, and palatal/lingual sides (P <.05). The anterior cantilever had a protective effect on the lingual side of the anterior implant. No effect on bone loss was found for the support polygon area, posterior cantilever, resistance arm, or power arm (P >.05). The results suggest that the C/I ratio and anterior cantilever in IFCD affect peri-implant bone loss according to the implant side and position in the arch.

Comparison of stresses in monoblock tilted implants and conventional angled multiunit abutment-implant connection systems in the all-on-four procedure

BackgroundThe All-on-four dental implant method is an implantology method designed to provide a comfortable prosthetic treatment option by avoiding advanced surgical procedures. This research aims to compare and evaluate the stress and tension values in conventional angled multiunit abutment-implant connection systems and monoblock dental implants used in the all-on-four procedure with finite element analysis.MethodsTwo master models were created by placing four implants connected to multiunit abutments (group A) in the interforaminal region of a completely edentulous mandible and four monoblock implants (group B) in the same region of another completely edentulous mandible. Group A implants were classified according to their diameter as follows: 3.5 mm (M1A), 4.0 mm (M2A), and 4.5 mm (M3A). Similarly, group B implants were classified as M1B, M2B, and M3B. In the six models rehabilitated with acrylic fixed prostheses, a 100 N force was applied to the anterior implant region, and a 250 N force was applied to the posterior cantilever in both axial and 30° oblique directions. Von Mises stresses were analyzed in the bone and implant regions of all models.ResultsM1A and M1B, M2A and M2B, and M3A and M3B were compared with each other under axial and oblique forces. The maximum Von Mises stresses in the bone around implants and the prosthesis screws, and the maximum and minimum principal stresses in the cortical and trabecular bone in group A models were significantly higher than those in group B models.ConclusionsIn monoblock implant systems under axial and oblique forces, higher stress is accumulated in the bone, prosthesis screw and implant compared to multiunit abutment-implant connection systems.

Evaluation of immediately loaded mandibular four vertical versus tilted posterior implants supporting fixed detachable restorations without versus with posterior cantilevers.

Distally inclining posterior implants may be technically challenging in certain situations. The presence of a posterior cantilever can also exert unfavorable forces on supporting implants. The aim of the present study was to evaluate and compare peri-implant soft and hard tissues around 4 mandibular interforaminal implants having tilted posterior implants with posterior cantilevers, versus vertical implants, 2 in the interforaminal region and 2 in the first molar regions, without posterior cantilevers. All implants supported full-arch fixed detachable restorations opposing complete dentures. A total of 80 implants were placed flapless in the mandibles of 20 edentulous participants. Four implants were placed for every participant, who were randomly assigned into 2 equal groups. Axial group implants were vertically aligned, with 2 implants in the interforaminal area and 2 in the molar area. Tilted group implants have 2 anterior axial and 2 posterior distally inclined implants. Interim screw-retained prostheses converted from pre-existing dentures were immediately fabricated and loaded on the same day of surgery. After awaiting period of 3months, all participants received fixed detachable metal acrylic resin definitive restorations. A follow-up protocol of 3, 6, and 12months was scheduled to assess the modified gingival index, modified plaque index, peri-implant probing depth, implant stability, and marginal bone level and bone density changes. No statistically significant differences (P > .05) were found in the modified gingival index, modified plaque index, peri-implant probing depth, implant stability, bone density, and marginal bone level between the axial and tilted implant groups after the 1-year follow-up period. Placing 4 flapless immediately loaded implants in mandibular edentulous patients that supported full-arch fixed restorations provided high implant and prosthodontic success rates whether posterior implants were tilted with posterior cantilevers or vertically aligned without posterior cantilevers. Pan African Clinical Trial Registry database, PACTR201907776166846. Registered 3 July 2019, www.pactr.org .

Digital Approach for the Rehabilitation of the Edentulous Maxilla with Pterygoid and Standard Implants: The Static and Dynamic Computer-Aided Protocols.

A full-arch rehabilitation of the edentulous upper jaw without grafting procedures exploits the residual alveolar or the basal bone, with the necessity of long implants placed with a particular orientation. The precision in planning and placing the fixtures is fundamental to avoid clinical problems and to allow an acceptable connection with the prosthesis. The computer-aided implantology resulted in more accuracy than the traditional one, with a high standard of correspondence between the virtual project and the real outcome. This paper reports about the two different digital protocols, static and dynamic, as support to implant-borne prosthetic rehabilitation of edentulous maxillae. Two pterygoid and two/four anterior standard implants were seated in both cases by two different operators, without flap raising, and immediately loaded. This approach avoided the posterior cantilever by-passing the maxillary sinus and was adequately planned and realized without any surgical or prosthetic error. The two digital flow-charts were described step by step, underlining each other’s advantages and drawbacks compared to a free-hand approach.

Combination of Implant-supported Fixed Prostheses and Removable Partial Denture in Edentulous Mandible Assisted by Digital Technologies: Two Case Report

In the fully edentulous mandible, the anterior part was restored by implant–supported fixed restoration as abutments for RPD, and the posterior part of the mandible was restored by distal extension conventional removable partial denture which can eliminate posterior cantilever. For doing this treatment, precise implant positioning was essential and CT-based guide implant template was very helpful to place implants in proper planned position. During prosthetic phase, prostheses design on virtual model can be converted to the try-in restoration by 3D printing for confirm vertical dimension, esthetics and phonetics.Properly used digital technology can help to reduce problems during comprehensive treatment like combination of implant-supported fixed prostheses and removable partial denture.

A Comparative Analysis on Two Types of Oral Implants, Bone-Level and Tissue-Level, with Different Cantilever Lengths of Fixed Prosthesis.

Depending on esthetic, anatomical, and functional aspects, in implant-prosthetic restoration of a completely edentulous jaw, the selection of implant type is highly important; however, bone- and tissue-level implants and their stress distribution in bone have not yet been comparatively investigated. Hence, finite element analysis was used to study the influence of cantilever length in a fixed prosthesis on stress distribution in peri-implant bone around these two types of oral implants. A 3D edentulous mandible was modeled. In simulations, a framework with four posterior cantilever lengths and two types of implants, bone-level and tissue-level, was considered. A compressive load was applied to the distal regions of the cantilevers, and the von-Mises stress of peri-implant bone was investigated. The independent t-test and the Pearson correlation coefficient analyzed the results (α = 0.05). Stresses in the cortical bone around the bone-level implants were greater than those in the tissue-level implants with the same cantilever length. In addition, by extending the cantilever length, the stress values in peri-implant bone increased. Therefore, when the cantilever was at its maximum length, the maximum stress was in cortical bone and around the bone-level distal implants. The results of the present study indicate that treatment with tissue-level implants is potentially more advantageous than with bone-level implants for implant-supported fixed prostheses.

Maxillary V-4: Four implant treatment for maxillary atrophy with dental implants fixed apically at the vomer-nasal crest, lateral pyriform rim, and zygoma for immediate function. Report on 44 patients followed from 1 to 3 years

Statement of problemThe V-4 implant placement technique is important for restoring patients with maxillary atrophy, but little has been documented on the outcomes of these treatments. PurposeThe purpose of this study was to evaluate the outcome of immediate function after 1 year when implants were placed without vertical bone augmentation in Cawood-Howell Classes IV-VI maxillary atrophy (Class C-D by the “all-on-four” site classification) with the nasal crest, lateral pyriform rim, and sometimes the zygoma for apical implant fixation. Material and methodsFunction of implants that had been immediately loaded were studied retrospectively after 1 year in 44 patients from 2 different clinics. For each patient studied, 2 angled implants were placed in the midline in the nasal crest/vomer area, and typically, 2 implants were engaged apically in the lateral pyriform rim bilaterally. All 4 of the implants used were angled toward the midline in a V formation, termed “V-4” implant placement. Insertion torque, anterior-posterior spread, implant diameter, implant length, and posterior cantilever were recorded. Implant survival and bone stability were assessed after 1 year. When the lateral pyriform was highly deficient (Class D), zygomatic implants were used posteriorly. ResultsA total of 179 implants were placed in 44 patients followed for 1 to 3 years. Six implants were lost, all in 1 patient. Anterior-posterior spread averaged 16 mm, with an average cantilever of 7.5 mm. Except for the lost implant sites, bone levels were stable throughout treatment for all patients. ConclusionsThe use of 4 implants angled toward the midline, including 2 implants placed into a V-shaped point at the nasal crest and 2 implants placed into an M-shaped point at the pyriform rim bilaterally, showed good stability after 1 year despite gross absence of bone mass as a result of severe maxillary atrophy. The V-4 placement pattern is important for patients with deficient bone mass between the sinus and nasal cavities. In Class D situations where lateral nasal rim bone mass is nearly absent, zygomatic implants can be used.

Clinical Evaluation of Immediate Loading of Electroeroded Screw‐Retained Titanium Fixed Prostheses Supported by Tilted Implant: A Multicenter Retrospective Study

Immediate occlusal loading of dental implants in the edentulous mandible has proven to be an effective, reliable, and predictable treatment protocol. However, there is limited long-term data available in the literature, when an electroeroded definitive cast-titanium fixed prosthesis is used for this treatment protocol. The aim of this study was to evaluate the clinical effectiveness of dental implants (Astra Tech Dental, Mölndal, Sweden) in the edentulous mandible immediately loaded with an electroeroded cast-titanium screw-retained fixed prosthesis. Forty-five patients received five implants each in the interforaminal area. All the implants were inserted with torque up to 40 Ncm and the distal implants were distally tilted approximately 20 to 30 degrees to minimize the length of posterior cantilevers. Implants were loaded within 48 hours of placement with an acrylic resin-titanium screw-retained prosthesis fabricated by electroerosion. Two of the 225 inserted implants failed after 3 and 16 months of healing, respectively, with a cumulative survival rate of 99.1% and a prosthetic survival rate of 97.8%. Immediate loading of tilted dental implants inserted in the edentulous mandible with a screw-retained titanium definitive prosthesis fabricated with electrical discharge machining provide reliable and predictable results.