Finite element analysis of three zygomatic implant techniques for the severely atrophic edentulous maxilla

Biomechanical evaluation of six zygomatic implants versus four zygomatic implants combined with dental implants in the treatment of different maxillary defects

BACKGROUND

This study aims to compare the biomechanics of six zygomatic implants (ZIs) and dental implants (DIs) combined with four ZIs with different maxilla defects.

METHODS

Three-dimensional constructs of the ZIs, DIs human skulls, and maxillary prostheses were created using SolidWorks Software (Version 2015, Dassault Systems SolidWorks Corporation, Waltham, MA, USA). Eight finite element models of the skull with four different alveolar defect types (0-4) were constructed. Type 0: No defect; Type 1: Bilateral posterior defects; Type 2: Right posterior defect; Type 3: Anterior and left posterior defects; Type 4: Bilateral posterior and anterior defects. In two models with the same defect type (for defect types 0-2), six ZIs or two DIs combined with four ZIs were inserted into the maxilla. Six ZIs were inserted in the maxilla models with defect types 3 and 4. Vertical (150 N) and masseteric (300 N) loads were simulated on the prosthesis. The maximum Von Mises stress in the implants/surrounding bone and bone deformation were evaluated.

RESULTS

The maximum Von Mises stresses in bone/implant were found highest in the defect type 2 model with four ZIs combined with two DIs. The lowest maximum Von Mises stress for bone was detected in the model with defect type 0 and with six ZIs.

CONCLUSION

Among the four types of defects, the posterior unilateral defect caused the highest stress value.

Assessment of different treatment alternatives for patients with total maxillectomy

PURPOSE

To assess the biomechanical advantages of combining zygoma and partial subperiosteal implants for maxillary reconstruction in severely atrophic maxillae, offering potential solutions to the challenges posed by traditional reconstruction methods.

MATERIAL AND METHODS

A finite element analysis used a craniofacial model simulating a totally resected maxilla. Four treatment scenarios (SCs) were evaluated: SC-1, the quad zygoma approach; SC-2, two zygoma implants (ZIs) and a one-piece subperiosteal implant (SI); SC-3, two ZI and a two-piece SI; and SC-4, four ZI and a one-piece SI. Stress distributions on bone, implants, abutments, and metal frameworks were compared under occlusal forces.

RESULTS

For the simulated bone regions under vertical and oblique forces, SC-4 values were higher than SC-1, while SC-2 and SC-3 values were comparable for pmax and pmin. In addition, SC-2 and SC-3 values were lower than those of SC-1 and SC-4. The most balanced von Mises stress values on the ZIsand were observed in SC-3 under vertical and oblique forces. Furthermore, lower von Mises stress values on the abutments were seen in SC-3 under oblique and vertical forces. Although the lower von Mises stress values on the metal frameworks at the lateral incisor and first premolar side were seen in SC-3, lower von Mises values were observed in SC-4 in the first molar region.

CONCLUSIONS

Overall, this study suggests that combining zygoma and partial subperiosteal implants may be a promising approach for reconstructing severely atrophic maxillae. These implants may offer improved biomechanical properties compared to ZIs alone.

How far can we go? A 20-year meta-analysis of dental implant survival rates

OBJECTIVE

This meta-analysis aims to investigate the long-term survival rates of dental implants over a 20-year period, providing a practical guide for clinicians while identifying potential areas for future research.

MATERIALS AND METHODS

Data were sourced from recent publications, focusing exclusively on screw-shaped titanium implants with a rough surface. Both retrospective and prospective studies were included to ensure an adequate sample size. A systematic electronic literature search was conducted in the databases: MEDLINE (PubMed), Cochrane, and Web of Science. The risk of bias for all studies was analyzed using a tool by Hoy et al. RESULTS: Three prospective studies (n = 237 implants) revealed a mean implant survival rate of 92% (95% CI: 82% to 97%), decreasing to 78% (95% CI: 74%-82%) after imputation (n = 422 implants). A total of five retrospective studies (n = 1440 implants) showed a survival rate of 88% (95% CI: 78%-94%). Implant failure causes were multifactorial.

CONCLUSION

This review consolidates 20-year dental implant survival data, reflecting a remarkable 4 out of 5 implants success rate. It emphasizes the need for long-term follow-up care, addressing multifactorial implant failure. Prioritizing quality standards is crucial to prevent overestimating treatment effectiveness due to potential statistical errors. While dental implantology boasts reliable therapies, there is still room for improvement, and additional high-quality studies are needed, particularly to evaluate implant success.

CLINICAL RELEVANCE

Never before have the implant survival over 20 years been systematically analyzed in a meta-analysis. Although a long-term survival can be expected, follow-up is essential and shouldn't end after insertion or even after 10 years.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Comparison of Two Types of Patient Specific Implants (PSI) and Quad Zygoma Implant (QZI) for Rehabilitation of Post-COVID Maxillary Mucormycosis Defect (PCMMD): Finite Element Analysis

Introduction

The residual post-COVID maxillary mucormycosis defect (PCMMD) were extensive, due to unilateral or bilateral maxillectomies. The Goal of rehabilitation of PCMMD is to deliver a prosthetically driven reconstruction. FEA was to evaluate the biomechanical response of PSI struts (PSI 1), PSI Screw retained (PSI 2) and QZI to masticatory load on virtual simulation to improve accuracy and enhance the design.

Aim

To validate and compare the Biomechanical benefit of the PSI struts, PSI Screw retained, QZI in a case of rehabilitation of post-COVID maxillary mucormycosis defect (PCMMD) by FEA study.

Methodology

The result of stress to masticatory load on virtual simulation for (1) Maximum and minimum stress (Von Mises stress); (2) the Displacement (in three positions) and (3) the Deformation (Plastic strain) was compared on virtual simulation for PSI 1 and PSI 2 and QZI.

Conclusion

The FEA and comparative evaluation of PSI 1, PSI 2 and QZI showed a good resistance to displacement. The stress and strain values are low and acceptable. In comparison QZI shows more stress in the anterior region.

Three-dimensional finite element analysis of zygomatic implants for rehabilitation of patients with a severely atrophic maxilla

STATEMENT OF PROBLEM

Stresses applied to zygomatic implants have been determined to be transferred mainly to the zygomatic bone; however, consensus regarding the stress distribution pattern in the bone surrounding zygomatic implants has not yet been reached.

PURPOSE

The purpose of this 3-dimensional (3D) finite element analysis (FEA) study was to visually compare the stress distribution pattern in 2 different zygomatic implant treatment modalities and evaluate the effect of masseter musculature involvement.

MATERIAL AND METHODS

A 3D FEA craniofacial model was constructed from the computed tomography (CT) data of a selected patient with a severely atrophic edentulous maxilla. Modeled zygomatic and conventional implants were inserted into the craniofacial model supporting a prosthesis superstructure. Two types of treatment were considered in the study: 2 zygomatic implants placed bilaterally or 2 zygomatic implants placed in conjunction with at least 2 conventional implants at the anterior maxilla. The models were loaded with a vertical force of 150 N, a lateral force of 50 N, and a distributed occlusal force of 300 N applied to the insertion area of the masseter muscle. The stresses on and deformations of the bones and implants were then observed and compared with and without the involvement of the musculature component.

RESULTS

The stresses were distributed efficiently along the vertical and horizontal facial buttresses, as in the dentate skull; however, a difference in distribution pattern was observed when the models were loaded without applying the muscle component. The maximum deformation of bones surrounding the implants occurred in the abutment connection of the conventional anterior implant in the model with an additional conventional anterior implant.

CONCLUSIONS

The FEA revealed the stresses were distributed efficiently along the vertical and horizontal facial buttresses, as in the dentate skull. However, the stresses in both models were concentrated in the zygomatic bone when incorporating the muscle component. Therefore, incorporating muscular force into FEA studies could affect the analysis result.

Stress Distribution Pattern in Zygomatic Implants Supporting Different Superstructure Materials

The aim of this study was to assess and compare the stress–strain pattern of zygomatic dental implants supporting different superstructures using 3D finite element analysis (FEA). A model of a tridimensional edentulous maxilla with four dental implants was designed using the computer-aided design (CAD) software. Two standard and two zygomatic implants were positioned to support the U-shaped bar superstructure. In the computer-aided engineering (CAE) software, different materials have been simulated for the superstructure: cobalt–chrome (CoCr) alloy, titanium alloy (Ti), zirconia (Zr), carbon-fiber polymers (CF) and polyetheretherketone (PEEK). An axial load of 500 N was applied in the posterior regions near the zygomatic implants. Considering the mechanical response of the bone tissue, all superstructure materials resulted in homogeneous strain and thus could reconstruct the edentulous maxilla. However, with the aim to reduce the stress in the zygomatic implants and prosthetic screws, stiffer materials, such Zr, CoCr and Ti, appeared to be a preferable option.

Survival of conventional dental implants in the edentulous atrophic maxilla in combination with zygomatic implants: a 20-year retrospective study

PURPOSE

Implant-supported prosthetic rehabilitation in the resorbed maxilla is a great challenge. The aim of this study was to determine the survival rate of conventional anterior implants placed in combination with zygomatic implants according to the Brånemark technique, and to identify risk factors for implant failure.

METHODS

We collected data retrospectively from 72 consecutive patients who received treatment from 1998 to 2018 at our center, according to Brånemark's original technique. Kaplan-Meier analysis was conducted to assess survival rate, and a survival regression model was used with the patient as the random factor, applying the Weibull distribution.

RESULTS

A total of 236 maxillary anterior implants were included, with a mean follow-up of 12.1 years. Kaplan-Meier analysis showed overall cumulative survival rates of 95.3% at 1 year, 94.8% at 2 years, 93.0% at 5 years, 90.5% at 10 years, 81.6% at 15 years, and 67.7% at 20 years. Survival regression showed an association between bruxism and implant failure as well as implants bearing an overdenture. Implants with length ≤ 10 mm had a significantly lower survival time. No significant association was found between the number of anterior implants and survival rate.

CONCLUSIONS

We found acceptable long-term anterior conventional implant survival. Significant risk factors for failure were bruxism, overdentures, and implants shorter than 10 mm.

Micromotion analysis of immediately loaded implants with Titanium and Cobalt-Chrome superstructures. 3D finite element analysis

Objective

The aim of this study was to evaluate the amount of micromotion of dental implants under immediate loading supported by Titanium (Ti) and Cobalt‐Chrome (Co‐Cr) superstructures.

Material and methods

A model of tridimensional half‐edentulous maxilla with three dental implants was made using the Finite Element Analysis (FEA). Two standard and one zygomatic implants were connected to a superstructure with an elliptic section of 6x 3 mm (mm). Two study models were established. Model A: Titanium (Ti) alloy superstructure; Model B: Cobalt‐Chrome (Co‐Cr) alloy superstructure. To simulate an immediate‐loading situation, a friction coefficient of 0.71 was applied between the implant and the bone surface. An axial load of 252.04 [N] was applied on standard and zygomatic implants.

Results

The Micromotion of dental implants was similar in both superstructure situations. The amount of micromotion was slightly higher in B1 and B3 models (Co‐Cr alloy‐superstructure) compared with A1 and A3 models (Titanium alloy superstructure). The micromotion values in two groups were greater than 150 μm in the incisive region (standard implant) and molar region (zygomatic). In general, the micromotion was higher on the implant that received the load with respect to the other implants. The greater difference was observed when the load was applied on the standard implant A1 (Model A1 = 189.12 μm) compared with standard implant B1(Model B1 = 263.25 μm).

Conclusions

Within the limits of present study, all implants on different load application points showed micromotion; in general, the amount of micromotion was slightly higher in the implants connected with Co‐Cr alloy superstructure.

Evaluation of Stress Distribution of Four Different Fixation Systems at High- and Low-Level Subcondylar Fractures on a Nonhomogenous Finite Element Model

PURPOSE

The aim of the present study was to provide insight into a suitable fixation system for subcondylar fractures located at different levels.

MATERIALS AND METHODS

High and low subcondylar fractures were simulated on a nonhomogenous mandibular model, and rhombic, trapezoid, and lambda plates and 2 miniplates were used for fixation. The stress in the bone and displacement of the fracture site were measured using finite element analysis.

RESULTS

For both high and low subcondylar fractures, the lowest von Mises stress was measured in the rhombic plate system. For high subcondylar fractures, the highest tension in the cortical bone was measured in the trapezoid plate system, and the highest compression was measured in the rhombic plate system. For low subcondylar fractures, the highest tension in the bone was measured in the rhombic system and the highest compression was measured in the trapezoid system. In both high and low subcondylar fracture models, the least displacement amount was measured in the 2-plate system.

CONCLUSIONS

The results of the present study have shown that the rhombic plate system might be the proper choice for high subcondylar fractures and the 2-plate system might provide better results for low subcondylar fractures.

Stress Analysis of Zygomatic Implants on the Augmented Maxillary Sinus: Is It Necessary to Graft?

PURPOSE

Zygomatic implants are becoming an ideal therapy with advanced implant-supported prosthetic treatment for the posterior atrophic maxilla. The purpose of this study is to examine the quantity and distribution of stress, which was caused by zygomatic implants placed using intrasinus method with or without augmentation to the atrophic posterior maxilla.

MATERIALS & METHODS

In this study, 3-dimensional atrophic edentulous maxilla models with and without sinus augmentation are designed with computer-aided programs. Stress analysis was carried out on the created computer models for maxillary alveolar cortical bone, for cortical bone in the zygomaticomaxillary suture, and for zygomatic spongy bone at the apex of the zygomatic implant and for metal substructure of Von Misses stress data.

RESULTS

Having augmented the maxillary sinus with graft, it was observed that after the loading especially in the posterior region, the tensile and compressive stresses on the alveolar crest was distributed more homogeneously and the stress generated on the cortical bone was reduced through the graft.

CONCLUSION

Although zygomatic implants are graftless solutions for athrophic maxilla, sinus augmentation will be useful for bearing stress around the implants.

Stresses generated by two zygomatic implant placement techniques associated with conventional inclined anterior implants

Purpose

To make a comparative evaluation, by means of the finite element method, of the stress generated on supporting tissues and prosthetic system components, using zygomatic implants with the exteriorized and extramaxillary techniques, and different placement positions, associated either with inclined anterior implants, or those without inclination.

Materials and methods

Eight (8) tridimensional models were created to represent the clinical situations being researched, using the dataset of scanned images of an edentulous model. The implants and prosthetic components were photographed on millimeter paper and inserted into Rhinoceros 3D modeling computer software. From the measurements made on the image, the virtual models were made. The application force was distributed on the occlusal surface of the working side of the left maxillary first molar, first and second premolars, and incisal regions of the central incisor, simulating the occlusal load during mastication, in a total of 150 N.

Results

The extramaxillary technique presented considerable variation in increased tension on the prosthesis screws and bone tissue. In the exteriorized technique, the highest tension values occurred in the region of the ridge, and the lowest, on the zygomatic process; the absence of cantilever reduced the stress on bone tissue in almost all regions.

Conclusion

The exteriorized technique was shown to be more favorable to the distribution of stresses on the micro-unit screws and bone tissue, with the model with zygomatic implant placed in the region of the first molar and inclined anterior implant presenting the best results.

•

The extramaxillary technique showed considerable variation in stress increase.

•

In the exteriorized technique, the highest stress occurred in the alveolar ridge region.

•

The alveolar bone support for zygomatic implants reduced the internal stress generated by the vertical force.

Zygoma Quad Compared With 2 Zygomatic Implants: A Systematic Review and Meta-analysis

PURPOSE

The aim of this study was to systematically review and compare the survival rates (SRs) of oral rehabilitations performed with 2 zygomatic implants (ZIs) combined with regular implants (RIs) versus 4 ZI.

MATERIAL AND METHODS

An electronic search was performed in several databases for articles published in English between 2007 and 2015. Articles reporting human studies were included in this systematic review.

RESULTS

The search yielded to a total of 417 studies, of which 6 were included in this study. ZIs SR weighted mean was 98.0% with a 95% confidence interval (CI) of 96.7% to 99.8%. For the control group (2 ZIs + 2 RIs) and the test group (4 ZIs), the implant SR was 98.6% and 97.4%, respectively, with a 95% CI. No statistically significant differences in terms of SRs were obtained between both groups P = 0.286.

CONCLUSIONS

The data analysis showed favorable results for treatment with 4 ZIs. The results showed no statistical differences in using 1 or another treatment, in terms of survival and failure rates. The reduction on treatment time and morbidity related to regenerative approaches may be its main advantage. In conclusion, the zygoma quad seems to be the treatment of choice for the rehabilitation of the severely atrophic maxilla.

Treatment of severe atrophic maxilla with zygomatic implants: a case series

Treatment of severe maxillary atrophy with implants has achieved important successes in recent years. The limit of implant insertion is related to inadequate bone quantity (i.e. height and width). Alveolar bone grafting, sinus lifting and major grafting via Le Fort I osteotomy have used in the past to restore bone volume prior of implant insertion. However successes do not always occur and a second stage surgery is necessary in most cases. Immediate loading cannot be performed in all grafted bone. In recent years a new treatment approach has been proposed by using zygomatic implants. This new technique can provide a better stability to the prosthesis and less morbidity for patient. Here a cases series of eighteen patients rehabilitated with zygomatic together with standard implants and immediate loading is reported.

Evaluation of satisfaction of individuals rehabilitated with zygomatic implants as regards anesthetic and sedative procedure: A prospective cohort study

PURPOSE

To evaluate the satisfaction of individuals with atrophic maxilla, rehabilitated with fixed dental prostheses, anchored on zygomatic implants, with variables being the anesthetic procedure: general anesthesia, or local with sedation.

MATERIALS AND METHODS

By means of the clinical record charts from the Training Course in Advanced Hospital Surgeries for Implant Dentists conducted at the Campinas-SP unit of the São Leopoldo Mandic School of Dentistry, 30 individuals were randomly selected. They had zygomatic implant placement surgeries performed, and were rehabilitated with fixed implant supported complete dentures, between the years 2005 and 2011. One group of 15 individuals underwent surgery in hospital, under general anesthesia. The other 15 were treated in the post-graduation clinic at the School of Dentistry, under local anesthesia and sedation.

RESULTS

From the emotional point of view, the Wilcoxon test revealed that irrespective of the anesthesia procedure used, at the beginning of treatment, the emotional condition of individuals differed from that verified after conclusion of the treatment (p < 0.0001).

CONCLUSION

There was no difference between the two groups as regards the anesthetic procedure. General satisfaction was high; there was emotional improvement after conclusion of the treatment, thus improving the quality of life.

Maxillary "All-On-Four" treatment using zygomatic implants. A mechanical analysis

OBJECTIVE

Zygomatic implants may be used for dental rehabilitation in atrophic maxillae. The aim of this study was to establish experimentally the areas of stress distribution using 2 kinds of "All-On-Four" maxillary procedures.

STUDY DESIGN

The best position to insert the implants was selected using polyurethane craniomaxillary models and surgical guides were made. Group 1 was designed with two posterior zygomatic implants and two conventional anterior implants, and group 2 with two posterior zygomatic implants and two anterior zygomatic implants. A titanium bar was built to link the 4 implants in both groups. Photoelastic replicas of these models were made and the implants were inserted using the surgical guides. An Instrom 4411 testing machine was used to perform a unilateral compressive loading at the level of the right first molar until 2mm of displacement was obtained.

RESULTS

Group 1 showed a high strain concentration in the right lateral orbital region at the level of the apex of the zygomatic implant. Less strain was noticed at the apical levels of the conventional implants in the anterior sector and of the contralateral zygomatic implant. Group 2 showed high strains in the lateral inferior orbital area. The load was low in the alveolar bone sector.

DISCUSSION

Zygomatic bone and paranasal structures are loaded at high levels when zygomatic implants are used to stabilize a full maxillary prosthodontic rehabilitation on 4 implants. The use of 4 zygomatic implants loads the alveolar bone to a lower extent and seems better suited from a mechanical point of view than the use of 2 zygomatic implants.

CAD based design sensitivity analysis and shape optimization of scaffolds for bio-root regeneration in swine

Tooth root supports dental crown and bears occlusal force. While proper root shape and size render the force being evenly delivered and dispersed into jawbone. Yet it remains unclear what shape and size of a biological tooth root (bio-root), which is mostly determined by the scaffold geometric design, is suitable for stress distributing and mastication performing. Therefore, this study hypothesized scaffold fabricated in proper shape and size is better for regeneration of tooth root with approving biomechanical functional features. In this study, we optimized shape and size of scaffolds for bio-root regeneration using computer aided design (CAD) modeling and finite element analysis (FEA). Statical structural analysis showed the total deformation (TD) and equivalent von-mises stress (EQV) of the restored tooth model mainly concentrated on the scaffold and the post, in accordance with the condition in a natural post restored tooth. Design sensitivity analysis showed increasing the height and upper diameter of the scaffold can tremendously reduce the TD and EQV of the model, while increasing the bottom diameter of scaffold can, to some extent, reduce the EQV in post. However, increase on post height had little influence on the whole model, only slightly increased the native EQV stress in post. Through response surface based optimization, we successfully screened out the optimal shape of the scaffold used in tissue engineering of tooth root. The optimal scaffold adopted a slightly tapered shape with the upper diameter of 4.9 mm, bottom diameter of 3.4 mm; the length of the optimized scaffold shape was 9.4 mm. While the analysis also suggested a height of about 9 mm for a metal post with a diameter of 1.4 mm suitable for crown restoration in bio-root regeneration. In order to validate the physiological function of the shape optimized scaffold in vivo, we transplanted the shape optimized treated dentin matrix (TDM) scaffold, seeding with dental stem cells, into alveolar bone of swine and further installed porcelain crown. Results showed that tooth root has not only been successfully regenerated histologically but also performed masticatory function and maintained stable for three months after crown restoration. Our results suggested that TDM scaffold with 9.4 mm in length and 4.9 mm/3.4 mm in upper/bottom diameter is a suitable biological scaffold for tooth root regeneration. These results also provided a recommendable design protocol for fabricating other scaffolds in tooth root reconstruction.

Stress distribution in bone simulation model with pre-angled implants

The aim of this study was evaluate the biomechanical behaviour of prostheses screwed into conventional (0° angulation) and pre-angled experimental (8, 12 and 20°) external hexagon implants (13 × 4 mm) by photoelastic analysis. Eight casts were made in photoelastic resin. Casts were divided into groups of single crowns or three combined elements. Each unit was positioned in a circular polariscope. By using a universal testing machine, 100 N loads were applied in the axial and oblique (45°) directions to fixed points on the occlusal surfaces of the crowns. Generated stresses were recorded photographically and analysed qualitatively in a graphics program. In single-element prostheses, the number of high-stress fringes increased with increasing implant angle. However, in three-element prostheses, there was no difference in the stress distribution with implant angle, except for the 12° implant that had a higher degree of stress. For the other groups pre-angulation of the implant increases the concentration and intensity of stresses for single prosthesis and has similar stress distribution in three-element fixed prostheses.

Oral Rehabilitation of Adult Edentulous Siblings Severely Lacking Alveolar Bone Due to Ectodermal Dysplasia: A Report of 2 Clinical Cases and a Literature Review

The oral conditions of adult edentulous patients with ectodermal dysplasia (ED) often lead to decreased physical and psychological health, and the negative effects can become as extreme as social and psychological isolation. However, restoring oral function of adult edentulous patients with ED using zygomatic implants (ZIs) or conventional implants (CIs) remains challenging for dentists because of the severe atrophy of these patients' alveolar ridges. This report describes 2 cases of adult edentulous siblings with ED; they exhibited severe alveolar bone atrophy and were treated with ZIs and CIs as bases to augment the bone in their anterior jaws. For these patients, bone augmentation was completed with an autogenous fibular graft. Although there was mild evidence of bone graft resorption in the maxilla, the bone augmentation procedures were successful in the 2 patients. Effective osseointegration of the implants was obtained. After placement, the functional and esthetic results of the oral rehabilitation were acceptable. More importantly, restoration of the patients' oral function enhanced their self-confidence and self-esteem. Therefore, restoring oral function in adult patients with ED and edentulous jaws using ZIs and CIs as the bases for bone augmentation is an effective approach.

Finite element analysis of stability and functional stress with implant-supported maxillary obturator prostheses

STATEMENT OF PROBLEM

Maxillary resections jeopardize the stability and functional stress generated by implanted-supported prostheses.

PURPOSE

The purpose of this study was to evaluate the stability and functional stress caused by implanted-supported obturator prostheses in simulated maxillary resections of an edentulous maxilla corresponding to Okay Classes Ib, II, and III, with no surgical reconstruction.

MATERIAL AND METHODS

Implants were positioned in the residual maxilla, and bar-clip retention systems were designed for each experimental model. The 3-dimensional models of the maxillary resection and corresponding implanted-supported obturator prosthesis, constructed from a computed tomography scan, were used to develop a finite element mesh. Loads were simultaneously applied to the occlusal (80 N) and anterior (35 N) platforms corresponding to the prosthetic teeth. Qualitative analysis was based on the scale of maximum principal stress; values obtained by means of quantitative analysis were expressed in MPa.

RESULTS

The implant-supported obturator prostheses tended to rotate toward the surgical resection, the region with no osseous support. Tensile and compressive stresses in the gingival mucosa and in the cortical bone increased as the osseous support and the numbers of implants and clips diminished.

CONCLUSIONS

All evaluated bar-clip retention systems displayed a tendency toward dislodgment of the obturator prosthesis, increasing as the osseous resection area amplified. The osseous tensile and compressive stresses resulting from the bar-clip retention system for Okay Classes Ib, II, and III maxillectomy may not be favorable to the survival rate of implants.