Biomechanics of implant-supported restorations / Biomecânica das restaurações implantossuportadas

The rehabilitation of patients with dental implant-supported restorations is an ideal treatment option in contemporary dentistry. The aim of this review was to compile and to demonstrate the mechanical response during loading condition, on the stress distributions of implant-supported prostheses. The findings show that the majority of stresses were concentrated in the cervical region of the implant/abutment interface and that they can be affected by several clinical parameters and loading conditions. Finally, the final prosthetic design should combine superior mechanical response, long-term survival rate and allow patient satisfaction. (AU)

A reabilitação de pacientes com restaurações implanto-suportadas é uma opção de tratamento ideal na odontologia contemporânea. O objetivo desta revisão foi compilar e demonstrar a resposta mecânica durante a aplicação de carga, na distribuição de tensão de próteses implanto-suportadas. Os achados mostram que a maioria das tensões se concentram na região cervical da interface implante/pilar e pode ser afetada por diversos parâmetros clínicos e condições de carregamento. Por fim, o desenho protético final deve combinar uma melhor resposta mecânica, taxa de sobrevida a longo prazo e permitir a satisfação do paciente. (AU)

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.

Stress Concentration of Hybrid Occlusal Splint-Mouthguard during a Simulated Maxillofacial Traumatic Impact: 3D-FEA.

Mouthguards (MG) are protective devices that can reduce the risks of facial trauma. However, many athletes do not use them. Additionally, MG wear with coincidental parafunctional activity has not been considered. The aim of this study was to evaluate the stress distribution as a consequence of a direct impact comparing a conventional MG with a novel hybrid appliance (HMG). Using computer-aided design (CAD) software, a human skull was modeled with the teeth inserted into their respective alveolus. The models were divided according to the MG type (conventional or hybrid). The geometries were exported to the computer-aided engineering (CAE) software and the materials were considered isotropic. Fixation was defined at the base of the maxilla. The load was applied using a hockey puck. The total deformation (mm) and the von Mises stress (MPa) results were obtained for the MGs (conventional and hybrid), upper teeth, lower teeth, and maxillary bone. Despite the presence of an MG, it is still possible to observe generated stress in all structures. However, the hybrid design was more efficient than the conventional design in reducing the displacement during the impact and consequently the stress on the upper teeth, lower teeth, and maxillary bone. Higher stress magnitude was more concentrated at the inner portion of the hybrid design than the conventional device. The HMG appliance decreased the stress concentration in the teeth and in the bone, limiting the areas susceptible to injuries to the regions directly impacted by the hockey puck. Although the novel HMG may mitigate injury, some stress will still result, and any possible injury should be evaluated by a dental professional.

A novel workflow for indirect cobalt-chromium restorations using additive manufacturing without digital design.

This preliminary investigation explored additive manufacturing to fabricate cobalt-chromium onlay restorations without the use of digital design. Extracted molars were prepared for four-surface onlays followed by the conventional approach for the fabrication of provisionals. The provisionals were digitized with an intraoral scanner, and stereolithography (STL) files were fabricated with additive manufacturing in cobalt-chromium, utilizing selective laser melting (SLM). Onlays were bonded to the corresponding tooth. Restorations were polished after cementation and assessed with photography, radiography, and a clinical post-cementation checklist. Cementation was unremarkable; marginal adaption and surface finish were generally acceptable. A simple, efficient, and inexpensive alternative workflow for the fabrication of indirect restorations without using the digital design is proposed.

In vitro assessment of a novel additive manufactured titanium implant abutment.

BACKGROUND: Dental implant temporization remains a clinical challenge. A novel abutment simplifying the procedure was developed, but conventional fabrication was costly and unpredictable. A workflow was developed to fabricate the novel abutment using additive manufacturing. This in vitro investigation assessed the additive manufactured (AM) novel abutments to conventionally manufactured (CM) abutments. MATERIAL AND METHODS: The AM abutments were fabricated in dental-grade titanium (Ti-6Al-4V) using Selective Laser Melting and were post-processed. The CM abutments were milled and subsequently laser welded manually. Pin strength of the abutments was assessed using a universal loading machine. Torque was measured by tightening the AM and CM abutments into dental implants within artificial bone. RESULTS: Average pin strength was 364.4 N for the AM abutments and 62.5 N for the CM abutments. Average torque was 49.9 Ncm for the AM abutments and 62.9 Ncm for the CM abutments. AM abutment's pin strength was higher than the CM abutments. CM abutments measured a higher torque than the AM abutments. CONCLUSIONS: Additive manufacturing with titanium using SLM provided an alternative fabrication pathway of a novel implant abutment. The AM approach was cost-effective, predictable, efficient and demonstrated pin strength and torque suitable for temporization procedures in implant dentistry. Key words:Abutment, dental implant, temporization, medical device, prototype design, additive manufacturing, 3D printing, titanium.

Biomechanical Behavior Evaluation of a Novel Hybrid Occlusal Splint-Mouthguard for Contact Sports: 3D-FEA.

BACKGROUND: Orofacial injuries are common occurrences during contact sports activities. However, there is an absence of data regarding the performance of hybrid occlusal splint mouthguards (HMG), especially during compressive loading. This study amid to evaluate the biomechanical effects of wearing a conventional custom mouthguard (MG) or the HMG on the teeth, bone, and the device itself. METHODS: To evaluate the total deformation and stress concentration, a skull model was selected and duplicated to receive two different designs of mouthguard device: one model received a MG with 4-mm thickness and the other received a novel HMG with the same thickness. Both models were subdivided into finite elements. The frictionless contacts were used, and a nonlinear analysis was performed simulating the compressive loading in occlusion. RESULTS: The results were presented in von-Mises stress maps (MPa) and total deformation (mm). A higher stress concentration in teeth was observed for the model with the conventional MG, while the HMG design displayed a promising mechanical response with lower stress magnitude. The HMG design displayed a higher magnitude of stress on its occlusal portion (7.05 MPa) than the MG design (6.19 MPa). CONCLUSION: The hybrid mouthguard (HMG) reduced (1) jaw displacement during chewing and (2) the generated stresses in maxillary and mandibular teeth.

Inclinometer: A new device for measuring intermolar torque and angle.

The torque of posterior teeth is of great importance in esthetics and occlusion. In the present article, we introduce a simple but useful device to measure intermolar torque. The device consists of two movable and adjustable arms that lie on the selected molar teeth bilaterally; the graduated plane at the body of the appliance then shows the intermolar torque. This device can measure intermolar torque easily and rapidly, with high validity and at a low cost.

Development of a novel dental shade determination application.

Determining the shade of dental materials is a challenging requirement for the restorative dentist. Improper shade selection is the second cause for laboratory remakes, resulting in inefficiency and additional cost, and unnecessary stress for the clinician and patient. The process of shade selection is somewhat subjective, with no consensus on the protocol. This research investigation aimed to develop a novel software application to provide an accurate, objective, and systematic approach to shade determination for teeth, soft tissues, and dental materials. An IOS software application was developed, termed Smile Shade, to facilitate a simple approach for dental shade determination. Smile Shade functions on a high-dynamic-range microcolor sensor with automatic temperature control and inter-device repeatability of <1.0 ∆E. The determination of shade is completed through the evaluation of color based on CMYK, RGB, and LAB, which are different techniques of storing colors. Further research is underway to compare this novel application to the traditional shade tab approach commonly practiced at most dental schools.

Preliminary Investigation of a Novel Mouthguard.

BACKGROUND: Mouthguards (MGs) remain an important piece of personal protection for athletes for the prevention of injury. Although MGs provide tremendous benefits, the design and fabrication process does not record the position of the mandible or the occlusion, which could lead to injury. This study compared a novel MG to over-the-counter (OTC) and custom MGs on a skull model. METHODS: The OTC MG was formed as per manufacturer's guidelines, the custom MG was laboratory fabricated, and the novel MG was fabricated through a proprietary process. Each group of the three MGs was assessed for vertical dimension change, occlusal contacts, and condylar displacement. RESULTS: Average number of occlusal contacts for the OTC, custom and novel MG were 2.4, 4.0, and 10, respectively. There was a significant difference between all values (P < 0.05). Average change in vertical dimension for the OTC, custom, and novel MG were 15.3 mm, 9.3 mm, and 8.0 mm, respectively. The novel MG value was significantly different (P < 0.05). The average distance of condylar displacement for the OTC, custom and novel MG were 1.9 mm, 1.3 mm and 0.6 mm, respectively. CONCLUSIONS: The novel MG was significantly different (P < 0.05). The data from this preliminary investigation suggests that the novel mouthguard had maximized occlusal contacts, minimized vertical dimension change and condylar displacement as compared to OTC and custom MGs.

A novel technique for the impression, model fabrication and provisionalization of pinlays.

Indirect non-metal restorations restore the function and esthetics of severely carious or broken teeth. This report explores a novel approach for the impression, model fabrication and provisionalization of a pin reinforced-onlay (pinlay) preparation. A dentoform molar was prepared for a pinlay indirect restoration. An impression, model and a provisional were fabricated with the employed pins and determined to be clinically acceptable. The pinlay may offer the patient and clinician another treatment option for oral rehabilitation.

3D printing of a novel dental implant abutment.

Implant-supported crowns remain an ideal treatment option for the replacement of a missing tooth. The provisionalization phase remains a critical step between surgery and final crown placement, guiding soft tissue healing and providing esthetics and function. Although there are several possible pathways for provisionalization, the options are time-consuming, technically difficult and expensive, resulting in confusion and frustration for the dentist and cost and time for the patient. A novel dental implant abutment has been developed that aims to resolve the shortcomings of current abutments and the provisionalization process. 3D printing or additive manufacturing, with plastic and metal, were employed as an alternative approach for production of the prototype abutment. Scanning, computer-aided design and 3D plastic and metal printing were employed. Abutments were fabricated in MED690 VeroDentPlus and Duraform 316L stainless steel, respectively. Prototypes were printed with a claimed accuracy of 16 µm (plastic) and 8 µm (metal). The prototypes were qualitatively assessed for functionality by implant threading and simulated provisionalization process in a laboratory setting. The plastic prototypes were not suitable due to threading issues and material weakness. Metal prototypes tolerated artificial tooth fabrication successfully but concerns with thread pitch and accuracy remained. 3D metal printing appears to be a suitable alternative to traditionally machined implant components; however, post-production processing seems to be required. Further research is warranted.

Preliminary study of a novel dental hand instrument for restorative procedures.

Background. There is no clear consensus on operative hand instrumentation. In general, there is one hand instrument that completes one task. Consequently, numerous instruments are required for the placement, shaping and carving of a restoration. This reduces clinical efficiency, increases cost and may generate frustration. Methods. A novel dental hand instrument has been developed. The instrument (GTI) can complete several tasks. The instrument was assessed in a laboratory setting with amalgam, composite and glass-ionomer restorations on dentoform teeth. Results. Results indicated that class II amalgam and composite restorations were significantly faster than conventional instrumentation (P<0.05). Differences in restoration quality were not statistically significant. Cost was significantly reduced as the GTI could perform the task of 9 conventional instruments. Conclusion. The GTI is an industry-translated, novel medical device that offers the clinician an alternative to standard instrumentation. Further investigations are required with increased samples sizes, clinical assessment and expanded utility.

Preliminary investigation of a novel endodontic obturator

Conventional endodontic treatment requires the removal of the pulp and dentin by shaping the inside of the tooth. The shaping occurs with the use of drills to a geometry that is directly related to a predetermined form of material that will obturate the tooth's interior.The aim of this study was to investigate a novel device that applies sonic energy during the obturation of the tooth's interior. Extracted human teeth underwent endodontic treatment. Half of the group were conventionally obturated and the other half were obturated with the novel device. Post-treatment radiographs were evaluated utilizing Schulich dental school endodontic marking criteria.No statistical significance (α = 0.05) was determined between each group. A higher incidence of filled space (60%) occurred with sonic obturation when compared to conventional obturation (33%). Micro-computer tomography (CT) images were obtained of one sample from each group to assess the three-dimensional obturation. The novel device facilitated easy handling and demonstrated potential for effective obturation. Further tests are required for device refinement, larger sample sizes and clinical validation to assess the attitude and practice of dental professionals towards using of advance Radiographic technique.

Digitizing the Facebow: A Clinician/Technician Communication Tool.

Communication between the clinician and the technician has been an ongoing problem in dentistry. To improve the issue, a dental software application has been developed--the Virtual Facebow App. It is an alternative to the traditional analog facebow, used to orient the maxillary cast in mounting. Comparison data of the two methods indicated that the digitized virtual facebow provided increased efficiency in mounting, increased accuracy in occlusion, and lower cost. Occlusal accuracy, lab time, and total time were statistically significant (P<.05). The virtual facebow provides a novel alternative for cast mounting and another tool for clinician-technician communication.

The use of pink porcelain to manage a malposed anterior implant: case report.

Pink porcelain was used in a custom zirconia abutment with a zirconia implant-supported anterior crown to compensate for a malposed anterior implant with horizontal bone deficiency and lack of keratinized tissue. This clinical procedure was able to reduce abutment height, mask the horizontal defect and create a symmetrical and esthetic effect.