Fabrication Of Dental Prostheses Research Articles

Prosthetic rehabilitation with an implant-supported fixed prosthesis using computer-aided design and computer-aided manufacturing dental technology for a patient with a mandibulectomy: A clinical report

The fabrication of dental prostheses with computer-aided design and computer-aided manufacturing shows acceptable marginal fits and favorable treatment outcomes. This clinical report describes the management of a patient who had undergone a mandibulectomy and received an implant-supported fixed prosthesis by using additive manufacturing for the framework and subtractive manufacturing for the monolithic zirconia restorations.

Restoration of Oral Function for Adult Edentulous Patients with Ectodermal Dysplasia: A Prospective Preliminary Clinical Study.

Therapy with zygomatic implants (ZIs) or conventional implants (CIs) has proven to be an effective method to restore oral function for systemically healthy patients. However, it is still a major challenge to fully restore oral function to edentulous adult patients with ectodermal dysplasia (ED). The aim of this study was to determine an effective treatment protocol for restoring oral function using ZIs and CIs to edentulous adult ED patients. Ten edentulous adult ED patients were treated in this study. The treatment protocol involved the following: (1) bone augmentation in the region of the anterior teeth; (2) placement of two ZIs and four CIs in the maxilla, and four CIs in the mandible; (3) fabrication of dental prosthesis; and (4) psychological and oral education. Following treatment of these patients, implant success rates, biological complications, patient satisfaction, and psychological changes were recorded. Although there was evidence of bone graft resorption in the maxilla, bone augmentation of the mandible was successful in all patients. Nine CIs in the maxilla failed and were removed. All ZIs were successful, and the CIs success rates were 77.50% in the maxilla and 100% in the mandible, with a mean of 88.75%. The mean peri-implant bone resorption for the CIs ranged from 1.3 ± 0.4 mm to 1.8 ± 0.6 mm, and four cases exhibited gingival hyperplasia in the maxilla and mandible. One hundred percent of the patients were satisfied with the restoration of their oral function, and >50% of the patients exhibited enhanced self-confidence and self-esteem. This study demonstrates that oral function can be restored in edentulous adult ED patients using a comprehensive and systematic treatment protocol involving psychological and oral education, bone augmentation, implant placement, and denture fabrication. Despite these positive outcomes, bone augmentation remains challenging in the anterior region of the maxilla for edentulous adult ED patients.

Intraoral Digital Impression Technique: A Review.

With the techniques of computer-aided design and computer-aided manufacturing (CAD/CAM) being applied in the field of prosthodontics, a concept of intraoral digital impressions was put forward in the early 1980s. It has drawn comprehensive attention from dentists and has been used for dental prosthesis fabrication in a number of cases. This new digital impression technique is expected to bring about absolute digitization to the mode of prosthodontics. A few published articles have indicated that dental prostheses fabricated from intraoral digital impressions have exhibited remarkable advantages over those from conventional impressions in several respects. The present review discusses intraoral digital impression techniques in terms of the following aspects: (1) categories and principles of intraoral digital impression devices currently available; (2) operating characteristics of the devices; and (3) comparison of the manipulation, accuracy, and repeatability between intraoral digital impression and conventional impression.

Intraoral scanning of hard and soft tissues for partial removable dental prosthesis fabrication

This article provides proof of concept for the use of intraoral scanning technology to record hard and soft tissue morphology for the fabrication of a cast partial removable dental prosthesis. An open source intraoral scanner was used to scan the hard and soft tissues to create a stereolithographic file that was subsequently imported into a computer-aided design software program for the digital/virtual design of a partial removable dental prosthesis framework. Computer-aided design and computer-aided manufacturing technology was then used to fabricate a resin framework that was trial placed to evaluate accuracy and for conventional investing and casting with a cobalt-chromium alloy. The cast framework and definitive prosthesis were judged to be clinically accurate in fit, stability, and retention.

CAD/CAM Zirconia for Dental Application

During the 20th century, both dental materials and dental technologies for the fabrication of dental prosthesis progressed remarkably. Owing to the increased demand of safety and aesthetics, 3 mol% yttria stabilized tetragonal zirconia polycrystalline has been recently introduced in prosthetic dentistry for the fabrication of crowns and fixed partial dentures, in combination with CAD/CAM technique. This greatly changed the conventional dental laboratory work which is labor-intensive and experience-dependent. This review mainly introduced the state of dental zirconia and the application of CAD/CAM technology in dentistry. Key words: Dental Zirconia; CAD/CAM Technique; Mechanical Properties; Transformation Toughing; Low Temperature Aging;

Effect of Heat Treatment Schedules and Glass Powder Particle Size on Glass Infiltration in Porous Alumina Preforms

Glass infiltrated alumina is one of the popular materials for fabrication of dental prostheses. Achieving complete and uniform glass infiltration is important to achieve desired properties in dental prostheses. This study examined the role of various factors on glass infiltration in sintered porous alumina preforms (porosity ~ 27%). Observations on infiltration in porous alumina samples at a heating rate of 3°C/min at 1100°C for 2 h showed residual glass on the surfaces of the samples indicating incomplete infiltration. Rapid heating of the samples to the peak infiltration temperature by introducing the samples into a preheated furnace resulted in complete infiltration of glass into the samples in <90 min. In addition to heating rate during infiltration, influence of soaking duration and the particle size of glass powder on glass infiltration were also examined.

Restoring anterior tooth aesthetics with a Non- Rigid connector – A modified approach (Case Report)

Aesthetic anterior tooth restoration is one of the greatest challenges for dentists in clinical practice. Patients expect contemporary dentistry to provide restorations that reproduce natural beauty while ensuring stability and functionality. The Fixed dental prosthesis fabrication requires equal consideration to be given to the retainer, pontic and connector design. The excessive flexing of the long-span fixed dental prosthesis, which varies with the cube of the length of span, can lead to material failure of prosthesis or to an unfavorable response. The size, shape, and position of the connector leads to the success of prostheses, as it prevent the distortion and fracture of the prosthesis. The conventional use of a non rigid connector aids in compensating for the difference in the resistance and retention form between the abutments. This paper describes a modified technique of restoring anterior aesthetics with non rigid connector.

The Application of Rapid Prototyping in Prosthodontics

Dentists have used rapid prototyping (RP) techniques in the fields of oral maxillofacial surgery simulation and implantology. With new research emerging for molding materials and the forming process of RP techniques, this method is becoming more attractive in dental prosthesis fabrication; however, few researchers have published material on the RP technology of prosthesis pattern fabrication. This article reviews and discusses the application of RP techniques for prosthodontics including: (1) fabrication of wax pattern for the dental prosthesis, (2) dental (facial) prosthesis mold (shell) fabrication, (3) dental metal prosthesis fabrication, and (4) zirconia prosthesis fabrication. Many people could benefit from this new technology through various forms of dental prosthesis production. Traditional prosthodontic practices could also be changed by RP techniques in the near future.

Current status, crisis and trends in Chinese dental technicians

Chinese dental technicians play a significant role in the globalised market of dental prosthesis fabrication, but this subject has not been investigated in detail. The demand for dental prostheses increases as individuals pay increasing attention to their oral health. Therefore, it is important to investigate the status of Chinese dental technicians. To evaluate the current status of Chinese dental technicians. Dental technicians' resumés, which reveal information regarding dental technician manpower, degrees, working age and salary, etc., were analysed and compared with those abroad. We also estimated the future demands of dental technician manpower, and discussed some potential solutions. There are fewer dental technicians in China than in other developed countries; they are also of a lower standard. Male technicians outnumber females. The education level of technicians is insufficient, and the education programme is still in its exploratory stage. The development of dental technician teams in China represents both an opportunity and a challenge. It is important to move forward from the current situation to yield long-term development. This article provides information on the Chinese dental technology industry, identifies the problems and offers solutions for its development.

Rapid prototyping and rapid manufacturing in medicine and dentistry

The fundamentals and latest developments of Rapid Prototyping (RP) and Rapid Manufacturing (RM) technologies and the application of most common biomaterials such as titanium and titanium alloy (Ti6Al4V) are discussed in this paper. The issues while fabricating pre-surgical models, scaffolds for cell growth and tissue engineering and concerning fabrication of medical implants and dental prostheses are addressed. Major resources related to RP/RM technology, biocompatible materials and RP/RM applications in medicine and dentistry are reviewed. A large number of papers published in leading journals are searched. Besides the titanium and titanium alloys which were established as bio-compatible materials over five decades ago, other biocompatible materials such as cobalt-chromium and PEEK have also been increasingly used in medical implants and dental prosthesis fabrication. For over a decade RP technologies such as Selective Laser Sintering (SLS) and Selective Laser Melting (SLM) along with the Fused Depositing Modelling (FDM) are predominantly employed in the fabrication of implants, prostheses and scaffolds. Recently Electron Beam Melting (EBM) has been successfully employed for fabrication of medical implants and dental prostheses with complex features. In dentistry crown restoration, the use of thin copings of Ti6Al4V made by the EBM process is an emerging trend. This review is based upon the findings published in highly cited papers during the last two decades. However the major breakthrough in the field of RP/RM for medical implants and dental prostheses took place in the last decade. The fabrication of medical implants and prostheses and biological models have three distinct characteristics: low volume, complex shapes and they are highly customised. These characteristics make them suitable to be made by RM technologies even on a commercial scale. Finally, current status and methodology and their limitations as well as future directions are discussed.

Application of rapid prototyping technology in dentistry

Rapid prototyping (RP) technologies are the most widely applied and known fabrication methods that are based on additive fabrication principles. RP represents a new set of manufacturing processes that can fabricate a representative three-dimensional (3D) physical model of any shape directly from a computer-aided design (CAD) model by using layer fabrication technique. As the result of the development in modern imaging, computerised 3D data processing and advanced engineering techniques, medical prostheses like dental prostheses can be accurately designed from CAD technique and the physical model of prostheses can be produced through RP, rapid tooling and computer-aided manufacturing technology. This paper discusses the application of RP technology in dentistry and methods of design and fabrication of dental prostheses by using RP technologies.

Relative position of the mylohyoid line on dentulous and edentulous mandibles

For the purpose of studying the relative position of the mylohyoid line, 156 Japanese mandibles (62 dentulous, 94 edentulous) were measured and comparisons made between specimens. Resorption of bone above the level of the mylohyoid line was recognized but no obvious changes were noted below the level of the mylohyoid line, except in rare cases. A straight pattern of the mylohyoid line was observed most frequently, with the segment of the mylohyoid line between the first and second molars being straight. The mean ratio between the total height of the mandible and the height of the mylohyoid line at the level of mesiolingual cusp of the lower first molar was 1:0.65 in males and 1:0.66 in females. These results will be useful in the fabrication of dental prostheses because the level of the occlusal plane can be estimated for edentulous patients using the proportional data for the the mylohyoid line's position.

Determination of bound and unbound water in dental alginate irreversible hydrocolloid by nuclear magnetic resonance spectroscopy

Objectives Alginate materials are considered unsuitable for precise fixed prosthetic rehabilitation due to their tendency to undergo spontaneous syneresis. Commercial alginate impression materials were investigated using Nuclear Magnetic Resonance (NMR) Spectroscopy to probe the relation between changes in the microscopic water environment and dimensional change to obtain a better understanding of spontaneous syneresis. Methods NMR was used to measure the spin-lattice relaxation times ( T 1) of 1H nuclei in water in alginate matrices to characterize changes in gel structure over time. These results were related to the dimensional stabilities of the alginate impression materials, their chemical compositions, and the Moisture Sorption Isotherms (MSI) obtained by incubation at fixed relative humidities. Results The rate of change of T 1 with time was found to be a better predictor of dimensional stability than MSI. The greatest dimensional stability for the alginate powders investigated was associated with a high filler:alginate ratio and a high Ca:Na ratio. Significance Nuclear magnetic resonance spectroscopy may used to measure changes in alginate impression materials under conditions where no dimensional change can be observed directly. Changes occurred rapidly even at 100% humidity, suggesting the dimensional stability of alginate impression materials is partially independent of the rate of dehydration. The results may open a way to formulate alginate impression materials more suitable for precise fabrication of dental prostheses.

Effect of cooling rate on Ti–Cu eutectoid alloy microstructure

Titanium alloys present a combination of properties that makes them suitable materials for various medical applications, and there is special interest in Ti–Cu alloys for the fabrication of dental prostheses. The addition of Cu to Ti lowers the melting point of the alloy, as well as leading to the development of desirable mechanical properties. In this study a eutectoid alloy was prepared and heat treated, then cooled at various cooling rates. The eutectoid structure (α + Ti 2Cu) was observed for all cooling rates used, and evidence of α′ martensite was found for cooling rate higher than 9 °C s –1. Lower cooling rates resulted in higher modulus values. This was attributed to the volume fraction of the α and Ti 2Cu phases. Higher cooling rates produced structures with lower modulus values and greater hardness, a result attributed mainly to the development of a martensitic structure.

Low temperature growth of thin film coatings for the surface modification of dental prostheses

In this work we present some results about the low temperature, plasma-assisted growth of silicon–oxygen amorphous thin film alloys (a-SiO x ) on different types of dental materials used for the fabrication of dental prostheses. The a-SiO x films were grown at substrate temperatures lower than 70 °C by a PECVD deposition system using silane (SiH 4) and nitrous oxide (N 2O) as precursor gases. The chemical bonding structure of the films was investigated by Fourier transform infra-red spectroscopy (FTIR), while the morphological characteristics of the dental materials were analyzed before and after the coating deposition by means of high-resolution mechanical profilometry. The surface energy of dental materials was estimated before and after the coating process by contact angle measurements, revealing that the coating produced a considerable change of surface energy in all the tested samples, evidenced by a contact angle reduction from more than 90° to less than 10°. Some tests were also performed to estimate the effect of the coating on the bacterial adhesion properties, revealing that the a-SiO x coatings show some effectiveness in reducing the bacterial adhesion on the dental materials surface.

Evaluation of four elastomeric interocclusal recording materials

Background: The fabrication of dental prosthesis requires the transfer of interocclusal records from patient's mouth to semiadjustable articulators using different kinds of recording media. Any inaccuracy in these interocclusal records leads to occlusal errors in the final prosthesis. This study was conducted to evaluate the dimensional changes occurring in the interocclusal recording material over a given period of time and the material's resistance to compression during the cast mounting on the articulator. Methods: In this in vitro study, the linear dimensional change and compressive resistance of four commercially available elastomeric interocclusal recording media was tested. Three were addition silicones and the fourth was a polyether material. Cylindrical samples of 10mm diameter of each material were prepared in three different thicknesses of 2, 4 and 6mm. Ten samples each of thickness of 2, 4 and 6mm for all four materials were prepared (total of 120 samples). The linear dimensional changes of the samples were evaluated after 24 hours of fabrication. The compressive resistance was measured when each of these was subjected to a constant compressive load of 25 Newtons. Results: The mean linear dimensional change in a horizontal plane was minimum for Kanibite Hard, an addition silicone. Ramitec showed the maximum linear dimensional change. The mean compression distance was least for Futar D Occlusion (an addition silicone) and maximum for Ramitec (a polyether). It was observed that the samples of thickness 2mm for all the materials underwent least compression. Conclusion: The compressive resistance of each elastomer was inversely proportional to the thickness of the sample. This implies that minimum thickness of the recording materials should be used for recording maxillomandibular relations without sacrificing the strength of the interocclusal record.

Perceptibility and acceptability of CIELAB color differences in computer-simulated teeth

Objectives To determine the perceptibility and acceptability of tooth color differences using computer-generated pairs of teeth with simulated gingival displayed on a calibrated color monitor using appropriate signal detection theory methodology (SDT). Methods Twelve dental professionals (four from each of the following groups: dentists, dental auxiliaries, and fixed prosthodontic technicians) and four dental patients served as subjects. Responses to tooth color differences (Δ E) were measured on each of the three principal axes of CIELAB color space ( L*, a*, and b*). As a control, responses to Δ E = 0 (the false alarm rate) were also measured in the same experimental session. Results No group differences among subjects were found. All gave 50% match or acceptance points that averaged about 1.0 Δ E units in the L* and a* directions, and 2.6 units in the b* direction. False alarm rates across all subjects averaged 27% (4–55%) and 28% (0.4–61%), respectively, for perceptibility and acceptability. A reanalysis of the data based on SDT, which takes subjects’ false alarm rates into account, gave somewhat larger color difference thresholds. Conclusions Color difference thresholds for our simulated teeth are generally in line with and extend results obtained with studies using “real” dental materials. No differences between thresholds for acceptability versus perceptibility were found. Furthermore, subjects often reported color differences when none existed, and this behavior needs to be factored into any determination of quality control standards for the fabrication of dental prostheses.

Flexural strength of pure Ti, Ni-Cr and Co-Cr alloys submitted to Nd:YAG laser or TIG welding

Welding of metals and alloys is important to Dentistry for fabrication of dental prostheses. Several methods of soldering metals and alloys are currently used. The purpose of this study was to assess, using the flexural strength testing, the efficacy of two processes Nd:YAG laser and TIG (tungsten inert gas) for welding of pure Ti, Co-Cr and Ni-Cr alloys. Sixty cylindrical specimens were prepared (20 of each material), bisected and welded using different techniques. Four groups were formed (n=15). I: Nd:YAG laser welding; II- Nd:YAG laser welding using a filling material; III- TIG welding and IV (control): no welding (intact specimens). The specimens were tested in flexural strength and the results were analyzed statistically by one-way ANOVA. There was significant differences (p<0.001) among the non-welded materials, the Co-Cr alloy being the most resistant to deflection. Comparing the welding processes, significant differences (p<0.001) where found between TIG and laser welding and also between laser alone and laser plus filling material. In conclusion, TIG welding yielded higher flexural strength means than Nd:YAG laser welding for the tested Ti, Co-Cr and Ni-Cr alloys.

Proper use of beryllium-containing alloys

To assist dentists in providing a safe and healthful workplace, the ADA Council on Scientific Affairs developed this advisory statement on the proper use of beryllium-containing alloys in the dental operatory and laboratory. Recommendations are made for reducing the potential risk of beryllium exposure for employees working in dental operatories or laboratories who fabricate or manipulate beryllium-containing alloys in dental prostheses. The Council recommends that practitioners adhere to the Ocupational Safety and Health Administration's recommendations for reducing beryllium exposure in the dental operatory and laboratory. These include the recommendation that--where possible--practitioners use alloys that do not contain beryllium in the fabrication of dental prostheses.

Prosthetic parameters among dental patients in Ile-Ife, Nigeria

The purpose of this study was to determine the Rest Vertical Dimension (RVD), Occlusal Vertical Dimension (OVD), Freeway Space (FWS) and their importance in the fabrication of dental prostheses. These prosthetic parameters were determined in 310 dentate patients attending the Dental Hospital of the Obafemi Awolowo University Teaching Hospitals' Complex Ile-Ife. The MMO was obtained by measuring inter-incisal distance. RVD and OVD were derived using Willis gauge. The FWS was taken as 'RVD minus OVD'. Of the 310 attendees, twenty-seven (8.7%) were denture wearers. There was no statistically significant difference between the genders with regards to the use of dentures (P = 0.17). The mean values (+/- standard deviation) for MMO was found to be 50.5 +/- 7.9 mm (range 18.0 to 70.0 mm). The RVD was 73.0 +/- 8.4 mm (range 50.0 to 94.0 mm) and OVD was 69.8 +/- 8.2 mm (range 47.0 t 92.0 mm). The mean FWS was 3.3 +/- 1.4 mm (range 1 to 9 mm). Following the loss of most of the posterior teeth or in a state of complete edentulism, the face profile appears squashed and the vertical dimensions are altered. To provide an efficient and functional prosthesis, the facial dimensions have to be restored to or near pre-edentulous state. The establishment of values for these facial dimensions in given population will assist in the provision of satisfactory prosthesis.