Tilted implants and prototyping: a security option for improving the anchorage in atrophic maxilla

Rehabilitating atrophic maxilla poses many challenges. Reconstructive techniques that require sinus grafting are viable and acceptable; however, these techniques also are considered to be expensive, invasive, and time-consuming. Tilted implants anchored in distal areas using available bone have been reported as a less invasive and highly predictable treatment option. This article presents a case involving implant anchorage via tilted implants as an alternative technique to bone grafting procedures.

[Shape analysis of healthy gingival curve in maxillary anterior teeth in 120 Chinese youth]

OBJECTIVE

To establish the relationship of the gingival crest, the gingival curve characteristic point (inflection point, IP) and the contact points and to use it as reference to design the location of contact area in anterior teeth restoration to form the natural papillae.

METHODS

Two-dimensional gingival curve morphology analysis based on standardized digital images was done to measure the value of different points in the upper anterior teeth for 120 young Chinese.

RESULTS

In the maxillary anterior teeth, the average mesial papilla heights(MPH) of central incisors(CI), lateral incisors(LI), canines(CA) were (4.49 ± 0.86) mm, (3.64 ± 0.77) mm and (4.12 ± 0.92) mm; the average distal gingival papilla heights(DPH) were (4.09 ± 0.72) mm, (3.48 ± 0.83) mm and (4.13 ± 0.94) mm . The relationship of the gingival curve inflection points of maxillary anterior teeth with the gingival zenith and the contact points were determined in horizontal and vertical ways. In the CI, the mesial IP in X and Y axis were 0.61±0.10 and 0.26±0.07, in distal were 0.57±0.10 and 0.25±0.07. In the LI, the mesial IP in X and Y axis were 0.50±0.10 and 0.23±0.08, in distal were 0.56±0.11 and 0.26±0.08. In the CA, the mesial IP in X and Y axis were 0.52±0.09 and 0.23±0.07, the distal IP were 0.60±0.12 and 0.26±0.08.

CONCLUSION

The upper anterior teeth papillae shapes of the different teeth and gingival curves are determined with certain characteristics, and the gingival curve inflection points have some mathematical relationship with the gingival crest and the contact points.

Improving the digital workflow: direct transfer from patient to virtual articulator

When designing a custom-made dental restoration, using a digital workflow represents an important advance over mechanical tools such as facebows or mechanical articulators. When using virtual scanning procedures, there is a direct transfer from the patient to the articulator. This paper presents a novel methodology to design custom-made restorations. This new approach permits the transfer of all data directly from the patient to the virtual articulator, always taking into account the kinematics of the mandible. Rapid further developments can be expected in the near future.

Strategies for integrating new restorative materials with digital technology and sound restorative principles

Restorative dental materials have experienced a significant evolution over the past 40 years. The pace of change has especially accelerated in the past decade, while, concurrently, advances in implant technology and digital dentistry have paralleled this rapid growth. This article outlines the strengths and weaknesses of various popular ceramic restorative materials and how today's technology can be effectively utilized to fabricate these materials into exceptional restorations.

Digital protocol for reference-based guided surgery and immediate loading: a prospective clinical study

PURPOSE

To evaluate the performance of a computer-aided three-dimensional planning protocol in combination with previously inserted reference mini-implants and CAD/CAM technology to restore completely edentulous patients. The study evaluated implant and superstructure survival in a prospective clinical trial.

MATERIALS AND METHODS

The plan protocol called for treatment of 35 patients who were edentulous in either arch. Mini implants were used to establish a platform for computed tomography and fixation of the surgical template. The planning software based on three-dimensional simulation was used to plan ideal implant placement, digitally integrating the future prosthetic and anatomical situations to design the definitive superstructure.

RESULTS

A total of 35 patients, 20 with edentulous maxillae, 10 with edentulous mandibles, and 5 patients with edentulism in both arches were treated. All patients received definitive prostheses on the day of surgery. The majority of patients treated in maxilla underwent a sinus graft procedure to achieve sufficient bone to place implants. A total of 40 superstructures were inserted and immediately loaded. Of the 240 inserted implants, 229 (95.4%) survived, with 146 (93.6%) and 83 (98.8%) implants in the maxillary and mandibular arches, respectively. Of the 10 implants that failed in the maxilla, 9 occurred in patients with an augmented sinus. All definitive restorations demonstrated clinically acceptable fit.

CONCLUSIONS

When evaluating implant and superstructure survival, reference-based guided surgery seems to be a reliable treatment option for edentulous patients. The CAD/CAM superstructure, inserted and loaded immediately after guided implant insertion, demonstrated acceptable fit to the underlying implants.

Duplicating the form and function of posterior teeth with Class II resin-based composite

The most common material used to fill Class II restorations in posterior teeth is resin-based composite (RBC). Despite the popularity of RBC restorations, there are challenges to placing them properly. Improperly shaped restorations with sharp edges and corners will chip and fracture, resulting in premature failure. Properly placed RBC restorations will duplicate the embrasures, contact area, marginal ridge, and occlusal fossa of natural teeth. RBC restorations should mimic the smooth and rounded contours of the natural dentition to ensure longevity.

[Veneer computer aided design based on reverse engineering technology]

OBJECTIVE

To explore the computer aided design (CAD) method of veneer restoration, and to assess if the solution can help prosthesis meet morphology esthetics standard.

METHODS

A volunteer's upper right central incisor needed to be restored with veneer. Super hard stone models of patient's dentition (before and after tooth preparation) were scanned with the three-dimensional laser scanner. The veneer margin was designed as butt-to-butt type. The veneer was constructed using reverse engineering (RE) software.

RESULTS

The technique guideline of veneers CAD was explore based on RE software, and the veneers was smooth, continuous and symmetrical, which met esthetics construction needs.

CONCLUSIONS

It was a feasible method to reconstruct veneer restoration based on RE technology.

[Finite element analysis of tooth restored with one-piece of computer aided design and computer aided manufacturing zirconia post-core in three different radiuses]

OBJECTIVE

To compare the stress distribution of teeth restored with one-piece of computer aided design and computer aided manufacturing (CAD/CAM) zirconia post-cores in three different radiuses.

METHODS

Constructing the 2D finite element models of the standard maxillary central incisal restored by one-piece of CAD/CAM zirconia post-cores and all ceramic crowns, the radius of post was 1.5 mm, 2.0 mm and 2.5 mm respectively. Two tooth root types with or without the ferrule were constructed and there were 6 models in general. Group 1:100 N force loading to the restored teeth through the long axle of teeth and veritical the incisal edge. Group 2: 100 N inclined force loading beneath the incisal edge 2.0 mm by 45° cross the long axle of teeth in the palate side. The stress distribution characteristic of post-cores and teeth roots were analysed.

RESULTS

In veritical loading, the stress distribution of one-piece of CAD/CAM zirconia post-core with 2.0 mm radius was better distributed than the two others, The stress concentration of teeth roots locate at the root canal wall where the end of the post exists, which increased with the wider radius of the post-core. In 45° inclined loading, the maximum stress of the zirconia post-core and the teeth root was more than three times of which in vertical loading. In post-cores, the stress concentration was in the labia middle 1/3 of the post. In teeth roots, the stress concentration located at the lateral wall in the post end and the area of the apical foramen. The stress of the post-cores and teeth roots was decreasing in the teeth root with a 2.0 mm ferrule.

CONCLUSION

2.0 mm radicus of the one-piece of CAD/CAM zirconia post-core is a better choice in clinic. There should be a conical degree in the teeth roots preparing for one-piece of CAD/CAM zirconia post-core restoration. The force of protrusive movement has a greater influence on the post-core and teeth roots. The area of apical may be apt to break in overloading.

[Clinical case of cable-stayed bridge manufactured by means of CAD/CAM technology]

The paper describes modeling and manufacturing of cable-stayed bridge by means of CAD/CAM techniques (STL-modeling).

[Occlusion patterns of dental arches containing implant-supported restoration]

An experimental and clinical study was carried out on 76 patients with implant-supported restorations in the posterior zones of the lower jaw, divided in two groups (with no signs of bone resorption around the implants and with resorption signs) and one control group. The results of the study allowed optimizing the angulation of dental implants, providing an opportunity for individual positioning of dental implant in the mandible depending on the direction of functional load.

[Digital workflow with the Lava Chairside Oral Scanner C.O.S. and Lava technique]

This article describes the clinical procedure and functioning of the LAVA C.O.S scanner (3MEspe) in making digital impressions of patients. When used in combination with LAVA technology, fully ceramic tooth replacements can be produced in an entirely digital way. After scanning the prepared abutment teeth, the data is directly transmitted to the dental laboratory to enable the production of the ceramic structures, while, on the other hand, stereo lithography can be used to produce master models. The milled and sintered zirconium oxide caps are covered with system-specific baked ceramics on the model. Initial clinical results have confirmed the functionality of the system. C.O.S-(Chairside Oral Scanning) is a true innovation in reconstructive dental medicine.

A new concept for the integration of dynamic occlusion in the digital construction process

Major advances have been made in dental computer-assisted design and manufacturing (CAD/CAM) technology in recent years. New developments in intraoral optical scanning systems make it possible to rapidly obtain three-dimensional images and measurements of the jaw and entire quadrants, including the prepared teeth, neighboringteeth, and opposing dentition. In addition, the static relationship of the maxillary and mandibular teeth to one another can easily be determined by means of intraoral bite registrations or buccal scans. This information is the starting point for the implementation of digital occlusal surface design and surface reconstruction. Here, too, the knowledge-based concept of biogenerics has crystallized into a new method in which restoration proposals suitable for each individual case are automatically computed by the software. Consequently, the time required to manually edit the digital model has been significantly reduced or completely eliminated. In its current form, the digital workflow still lacks a strategy for integrating the dynamic occlusion into the restoration design with high precision and in atime-saving manner. The preliminary results of new digital concepts and approaches to solving this problem will be presented in this article.

Dimensional accuracy of pickup implant impression: an in vitro comparison of novel modular versus standard custom trays

PURPOSE

The purpose of this in vitro study was to compare the dimensional accuracy of the pickup impression technique using a modular individual tray (MIT) and using a standard individual tray (ST) for multiple internal-connection implants. The roles of both materials and geometric misfits were considered.

MATERIALS AND METHODS

First, because the MIT relies on the stiffness and elasticity of acrylic resin material, a preliminary investigation of the resin volume contraction during curing and polymerization was done. Then, two sets of specimens were tested to compare the accuracy of the MIT (test group) to that of the ST (control group). The linear and angular displacements of the transfer copings were measured and compared during three different stages of the impression procedure. Experimental measurements were performed with a computerized coordinate measuring machine.

RESULTS

The curing dynamic of the acrylic resin was strongly dependent on the physical properties of the acrylic material and the powder/liquid ratio. Specifically, an increase in the powder/liquid ratio accelerated resin polymerization (curing time decreases by 70%) and reduced the final volume contraction by 45%. However, the total shrinkage never exceeded the elastic limits of the material; hence, it did not affect the coping's stability. In the test group, linear errors were reduced by 55% and angular errors were reduced by 65%.

CONCLUSIONS

Linear and angular displacements of the transfer copings were significantly reduced with the MIT technique, which led to higher dimensional accuracy versus the ST group. The MIT approach, in combination with a thin and uniform amount of acrylic resin in the pickup impression technique, showed no significant permanent distortions in multiple misalignment internal-connection implants compared to the ST technique.

Effect of preparation depth differences on the marginal fit of zirconia crown copings: an in vitro study

If optical scanning is used for crown fabrication, variability in preparation depth may be a limitation. Therefore, this preliminary laboratory study evaluated marginal fit in relation to preparation depth. Three dies with different preparation depths between the vestibular and oral regions were fabricated. Ten zirconia copings were manufactured for each die, and marginal gaps were examined. Increasing differences in preparation depth influenced the size of the marginal gap between the vestibulo-oral and mesiodistal regions significantly (P < .001). This study shows primarily that differences in preparation depth resulted in decreasing marginal precision.

A finite element method approach for the mechanobiological modeling of the osseointegration of a dental implant

The aim of this paper is to introduce a new mathematical model using a mechanobiological approach describing the process of osseointegration at the bone-dental implant interface in terms of biological and mechanical factors and the implant surface. The model has been computationally implemented by using the finite element method. The results show the spatial-temporal patterns distribution at the bone-dental implant interface and demonstrate the ability of the model to reproduce features of the wound healing process such as blood clotting, osteogenic cell migration, granulation tissue formation, collagen-like matrix displacements and new osteoid formation. The model might be used as a methodological basis for designing a dental tool useful to predict the degree of osseointegration of dental implants and subsequent formulation of mathematical models associated with different types of bone injuries and different types of implantable devices.

[Digital inlaid design based on anatomical characteristics and preliminary implementation of its program]

OBJECTIVE

To explore the technical guideline of inlays computer aided design (CAD) for further development, to test the feasibility of processing for the design results of the technical guideline, and to assist co-operation with automatic inlay CAD software development.

METHODS

On the basis of point cloud data of right mandibular first molar of standard crown, we established the coordinate system,the landmarks and lines and the characteristic curves. A dental cast of right mandibular first molar MOD-inlay of an individual normal occlusion was scanned. The following objects were digitized: prepared tooth, neighbor teeth and intercuspal bite record. On the basis of parametric standard crown established in the research, using Surfacer 11.0, we achieved the reconstruction of MOD-inlay by extracting margin line, constructing tissue surface, constructing outer surface and occlusal grinding, then the design result was processed and try-in on the cast. We also developed automatic inlay CAD software based on the guideline of inlay CAD.

RESULTS

The guideline of inlay CAD was established, the design results were processed and an automatic inlay CAD software was developed on basis of Surfacer 11.0.

CONCLUSION

It is a feasible method to establish technical guideline of inlay based on reverse engineering technology and process its design result, and a automatic inlay CAD software could be developed based on the technical guideline.

[Research on computer-aided technology of surgical guide for dental implant]

The present paper was conducted to a systematic method of surgical guide for dental implant based on computer-aided technology through CT data and dental-cast data. By analyzing the patient's CT data, the implant region was planned using image processing techniques. For the specified implant region, the computer-aided method for the rational allocation of dental implant was addressed in a sense of anatomy. With biomechanical principles as well as aesthetical and functional requirements as preconditions, this method can make full use of bone quantity and quality to produce the optimum implantation axis. The transferring of implant planning to the patient was then realized by registration between CT models and dental-cast models. A case research explained the whole process of the surgical guide. The results validated the correctness and feasibility of this method, which has a great significance to enhance the quality and accuracy of implant surgery.

Design for functional occlusal surface of CAD/CAM crown using VR articulator

In this present study, we introduce an approach that utilizes the VR articulator to mimic lateral excursions and design a functional occlusal surface. We then take the resultant occlusal surface from this approach and compare it with a conventional method. As a result, we developed a novel CAD/CAM system which can render a functional occlusal surface, via a VR articulator. The marginal fit and occlusion in our CAD/CAM crown was sufficient to apply to the clinic.

[Clinical opportunities of 3D-modeling for implant treatment planning for the patients with full or partly adentia in difficult anatomo-topographic conditions]

The message is about dental rehabilitation in difficult anatomo-topographic conditions of full adentia and high-grade atrophy of alveolar processes. The more high quality level decision of this problem using the methods of 3D-computer modeling during the diagnostic examination and planning of dental implantation is proposed.

Achieving a precise color chart with common computer software for excellence in anterior composite restorations

Achieving similar features to those on natural teeth is a common problem with esthetic restorations. Color matching is a fundamental procedure required to perform a predictable composite resin restoration. It is no longer enough to measure these criteria with conventional shade guides, which provide the hue and chroma, but do not take into account other dimensions of the tooth such as value, intensives, opalescence and characterizations. The present article presents a simple and effective technique for color selection using a digital photograph of the tooth and an image-editing program such as Adobe Photoshop or Picture Project. The digital editing of the photograph with two simple steps described in this paper reveals the internal structures of the tooth easily. The modified photographs highlight the opalescence, white spots, shape of the internal mammelons and other features that are not visible at first glance. This procedure provides an accurate color chart with which the clinician can begin an esthetic restoration process.

A simple way to plan implant positioning: the "S-technique"

This study presents a technique for improving implant placements. As is widely known, a correct positioning is essential in restoration-driven implants, as well as in tilted implants in order to obtain satisfactory final functional and esthetic results. To this end, some authors have emphasized the importance of using a diagnostic and/or surgical guide to plan the exact implant position. In practice, one of the clinical problems faced is how to check the accuracy of the template prior to initiating the surgical phase. A simple method called the "S-Technique" is proposed in order to evaluate and to change, if necessary, the projected position of the implants by way of metal rods as radiopaque markers. This device is easy to produce and is cost-saving to the clinician and, therefore, to the patient. Furthermore, in specific patients, this method could also decrease the need for computerized tomography scans and/or radiographs, thus reducing health risks for the patient.