Implications Of Non-Metallic Prosthetic Approaches In The Formative Aspects Of Dental Medicine

Abstract

Introduction. Contemporary dentistry is governed by special aesthetic demands based on avant-garde techniques and technologies in conjunction with the type of biomaterials used, all these aspects tailored to the particularities of each clinical case, with the ultimate goal of conferring the individuality of each prosthetic restoration. The purpose of this study is to establish the performance criteria in the formative implementation of non-metallic prosthetic theoretical dental medicine, current therapeutical trajectories, the therapeutic decision materializing in a synthesis of an analysis of local, loco-regional and general factors. Material and method. Analysis of prosthetic rehabilitation possibilities through non-metallic materials and quantification of the impact of training in dental medicine. Results and discussions. The achievement of the aesthetic and functional desires in the nonmetallic prostheses is in full agreement with the specific prosthetic rehabilitation of each clinical case, the importance of knowledge and transposition in the current practice has a decisive role in the formative aspects of dental medicine. Occlusal rehabilitation is a mandatory stage for an optimally established fixed prosthetic therapy and clinically-technologically adapted to each clinical case. Zirconia frameworks can be produced according to two different CAD/CAM techniques. In soft machining technique, CAD/CAM systems shape pre-sintered blocks, which involves machining enlarged frameworks in a so-called green state. Conclusions . Non-metallic prosthesis is materialized in a complex approach that brings together both aesthetic, biomechanical and biological aspects, with a spectacular evolution currently in full agreement with the types of biomaterials and technologies, with the permanent face-to-face approach of analogy to digital.

Keywords: CAD/CAM techniqueszirconia

Introduction

Prosthetic treatments have traditionally sought to restore lost function (mastication, phonation,

swallowing), while offering aesthetics that meet the criteria of attraction. The requirement for optimal

aesthetics is conditioned by both social pressure and dental care. Just a few decades ago, some types of

dental restorations, such as fenestra crowns or partial envelope crowns, have been described as aesthetic

and, to some extent, the requirement for these restorations remains high. However, at present, the term

"aesthetic restorations" refers to ceramic restorations, and in particular to non-metallic ceramic restorations

(Aboushelib, Feilzer, Jager, & Kleverlaan, 2008; Bonfante et al., 2009; Cehreli, Kokat, & Akca, 2009).

Towards the end of the last century, a dentist and dental industry have a climate of non-acceptance of metal

alloys in the oral cavity, and given the growing demand for aesthetic treatments, these factors have led to

the development of new re-growth total ceramic prosthetic. For this reason, recent studies have focused on

ceramics, seeking restorations to provide optimal aesthetics as long as replacement of ceramic restorations

with whole ceramic restorations have similar mechanical strength. Zirconia is a restorative material that

exhibits aesthetic properties and satisfactory functionality. Despite manufacturers' efforts to improve its

translucency, zirconium transmission does not yet equal that of lithium disilicate. More research is needed

to enhance the translucency of the material so it can be used as aesthetic material for crowns made entirely

of zirconium (Coelho, Bonfante, Silva, Rekow, & Thompson, 2009; Donovan, 2009; Huang, Thompson,

Rekow, & Soboyejo, 2008). Contemporary dentistry is governed by special aesthetic demands based on

avant-garde techniques and technologies in conjunction with the type of biomaterials used, all these aspects

tailored to the particularities of each clinical case, with the ultimate goal of conferring the individuality of

each prosthetic restoration.

Problem Statement

Choosing the most powerful material that meets the minimal aesthetic need of the patient simply

acquires meaning. Knowing the excellent adaptation, versatile performance and widespread popularity of

new generation ceramics, such as lithium disilicate, when the use of monolithic zirconium is most

desirable?

Hinged monolithic zirconia crowns (without stratified porcelain) have the potential to last longer than others

such as porcelain-fused-to-metal (PFM), as there is no decorative porcelain to delaminate, chip or fracture.

Layer porcelain can be added to the brim of zirconium to enhance aesthetics, but the poor adherence of

overlapping or pressed layers is an area of clinical failure during the fabrication of the veneer (as is the case

with the traditional MFP crown) (Kim, Kim, Myoung, Pines, & Zhang, 2008a; Kim, Kim, Janal, & Zhang,

2008b; Kohorst, Dittmer, Borchers, & Stiesch-Scholz, 2008). The zirconia advances have made the material

becomes less opaque and has a more aesthetic appearance than in previous years times. This material cannot

be as aesthetic as a high quality PFM restoration made by a skilled ceramist but improvements in aesthetics

with zirconia (such as opacity and shades) have enabled zirconium restorations to become an acceptable

clinical option in all cases, but also in the most aesthetically difficult situations (Larsson Vult von Steyern

Sunzel, &, Nilner, 2006; Marchack, Futatsuki, Marchack, & White, 2008). With patients with

parafunctional habits for whom there is a doubtful occlusal scheme or signs of occlusal overload may

indicate zirconia crowns with total contours, especially when moderate aesthetics are acceptable.

Research Questions

The first question that governs this study is represented by :What are the criteria underlying the

choice of non-metallic prostheses? Followed by two other key questions, to what extent the formative

impact of these prosthetic methods will lead to a performing dental medical practice, namely to what extent

can we consider the other types of standard therapies on the verge of extinction

Purpose of the Study

The purpose of this study is to establish the performance criteria in the formative implementation of

non-metallic prosthetic theoretical dental medicine, current therapeutical trajectories, the therapeutic

decision materializing in a synthesis of an analysis of local, loco-regional and general factors.

Research Methods

Analysis of prosthetic rehabilitation possibilities through non-metallic materials and quantification

of the impact of training in dental medicine. The algorithm of the therapeutic decision anchored in the

register of non-metallic rehabilitations is based on a thorough clinical and paraclinical analysis of the local,

clinical, biological and odonto-periodontal mucous bony indices, in the context of the assessment of the

static and dynamic occlusion, as well as of the particularities of the mandible – cranial relationships. All

these elements are correlated with the principles that govern the current esthetic, linking the facial shape,

the type of smile and the tooth morphology. In view of optimizing the didactic process and in an attempt to

familiarize oneself with the theoretical and practical knowledge of modern methods of functional and

esthetic rehabilitation materialized in full ceramic prostheses or ceramic prostheses on zirconium support, a 10 questions questionnaire was elaborated, focused on the maneuvers that arise the student’s interest, as

well as on the teaching and implementation method used.

Findings

The achievement of the aesthetic and functional desires in the nonmetallic prostheses is in full

agreement with the specific prosthetic rehabilitation of each clinical case, the importance of knowledge and

transposition in the current practice has a decisive role in the formative aspects of dental medicine. Occlusal

rehabilitation is a mandatory stage for an optimally established fixed prosthetic therapy and clinically-

technologically adapted to each clinical case.In the questionnaires addressed to the students of the five and

six years of the faculties of dentistry, over 70% consider particularly the importance of knowledge of

rehabilitation methods and techniques through non-metallic restorations, to classical restorations,

prompting them to know very well the techniques that practice the actual dental practice, offering added

aesthetics and functionality that meet the exigencies of today's society. One significant advantage of full-

contour monolithic zirconia restoration is that the preparation can be more conservative than other all-

ceramic or even metal-ceramic restorations, with a preparation design similar to that of a full cast gold

crown. The amount of space required will vary slightly depending on the detail of occlusal morphology

expected in the outcome. The recommendation of specialists for the configuration of the zirconia

framework is modifying it by thickening the marginal area. All the recent results indicate that choosing the

zirconia framework in detriment to the classic metallic alloys is the right choice for modern dental practices.

Zirconia frameworks can be produced according to two different CAD/CAM techniques. In soft machining

technique, CAD/CAM systems shape pre-sintered blocks, which involves machining enlarged frameworks

in a so-called green state. The enlarged pre-sintered zirconia frameworks are then sintered in a sintering

furnace to their full strength that is accompanied by shrinkage of the milled framework by 25% to the

desired dimensions. An eloquent clinical case, illustrated in Figure 01 , is the rehabilitation of the frontal

area of a 25-year-old patient with carious odon lesions at levels 12,11, 21, 22, in a first stage the wax-up of

the future prosthetic rehabilitation was carried out, followed by demock -up, and defend the final

rehabilitation of the patient. In the framework of non-metallic rehabilitation, a high degree of difficulty

rests with the rehabilitation at the one-sided level, regarding the integration of the future prosthetic

restoration at the level of morphology and color integration.

See Full Size >

Figure 02 offers a clear image of the requirements for restoring a single incisor.Aesthetic

expectations of patients are usually very high and the end result is entirely dependent on the dental

technician. It is usually necessary for the technician to spend some time with the patient at different stages

during the crown making and it is not unusual when the crown is restored if the aesthetic lens is not fulfilled.

This factor prolongs the duration of treatment and the patient needs to be aware of this from the beginning.

The dentist must understand the technical difficulties and the talent needed to fit a unique crown into a

natural underlying tooth as well as the high costs. In addition to preparing dental tissue for the crown, the

dentist should facilitate the opportunity of meeting the dental technician with the patient once or more times

if necessary. The appointment between the patient and the technician must be at the same time as the

patient's appointment. This eliminates any insignificant discussion between the three parties.

See Full Size >

Another important factor for success in these cases is the provisory crown. A very good temporary

crown will immediately satisfy the aesthetic, functional and biological needs of the patient and the dentist.

Once this has become accomplished, time becomes a friend and not an enemy and can be used by the dentist

and technician to ensure all aspects of the final restoration - good things take time. To use the provisional

crown to its full potential, the dentist must ensure that this is the best option in the situation. Failure to do

so will be detrimental to treatment and will increase patient anxiety, reduce dental confidence and limit the

time available for treatment. Of this the dentist should be able to create a provisional crown with good

shape, functionality and colour and be qualified to use materials to allow this.

Another case of grafting as non-metallic prostheses, illustrated in Figure 03 , is representative of lateral

anodontia . Thus, a representative clinical case is the use of whole ceramic restorations at the level of the

canines and they will be transformed laterally through ceramic restorations.

See Full Size >

The effort to replace metal in high - strength ceramic metal - ceramic restorations began at the end

of the 20th century and have not yet reached a conclusion. Currently, zirconia is the main objective of

research and clinical trials. The main features that favour its use as a biomaterial are chemical and

dimensional stability, mechanical strength, hardness, and a modulus of elasticity of the same order as

stainless steel. Zirconium oxide is f began in 1960. From the beginning, its promising in vitro properties

attracted the attention of dental scientists, and in the last decade it has gained increasing importance.

The properties that favor its use in dentistry are biocompatibility, low thermal conductivity, corrosion

resistance and high fidelity due to its crystalline microstructure. However, being opaque, it needs to be

covered with better ceramic translucency, to improve aesthetics. When the function of both ceramic and

metal - ceramic restorations are evaluated over normal time, there are two concepts that are often considered

synonymous: success and survival.

Surviving a restoration means that it performs its function in the oral cavity even if it has suffered some

additional damage. Success can be defined as a restoration in which it maintains the qualities of the surface

maintained intact, the anatomical shape and function, as well as the optimal aesthetics. In fixed zirconium

dentures, despite the high fracture resistance of the material, plaque can be fractured during mastication

and this is a frequent problem. This complication generates some uncertainty as to the long-term

performance of the material in dental restorations. Factors that reduce the resistance of plated ceramic-

zirconium restorations and thus increase the risk of fracture are:

• Residual stress due to differences in thermal expansion coefficient (CTE) between zirconium and plated

ceramics • Poor elasticity of the platted ceramics, driving to the engagement of the materials and a low

micromechanic concentration

• faulty fabrication (Griffith defects).

In this way, a greater number of mechanical failures arise for:a traditional manual layering of ceramics in

place of thermally pressed ceramics,fixed partial prosthesis instead of one-piece prostheses, pre-fabricated

restoration. The current literature attends the idea that a zirconium infrastructure should adequately support

the ceramic facade.

Conclusion

1.Non-metallic prosthesis is materialized in a complex approach that brings together both aesthetic,

biomechanical and biological aspects, with a spectacular evolution currently in full agreement with the

types of biomaterials and technologies, with the permanent face-to-face approach of analogy to digital,

having profound implications at the formative level.

2.Contemporary non-metallic aesthetic restorations represents an avant-garde field that brings

together the current evolutionary trends of dental medicine in terms of new techniques and technologies in

conjunction with the type of biomaterials used, all these aspects adapted to the particularities of each clinical

case, with the ultimate goal of conferring individuality.

3.Non-metallic prosthetic restorations offer optimal aesthetics and functionality.

4.They are in full agreement with modern fingerprinting techniques, as well as CAD-CAM

technologies.

References

1. Aboushelib, M. N.Feilzer, A. J.Jager, N.Kleverlaan, C. J. (2008). Prestresses in bilayered all-ceramic Biomed Mater Res B Appl Biomater. , 87, 139-145, restorations. J
2. Bonfante, E. A.da Silva, N. R.Coelho, P. G.Bayardo-Gonzalez, D. E.Thompson, V. P.Bonfante, G. (2009). Effect of framework design on crown J Oral Sci, . https://www.academia.edu/37310100/, 117, 194-199, failure. Eur
3. Cehreli, M. C.Kokat, A. M.Akca, K. (2009). CAD/CAM zirconia glass-infiltrated alumina/zirconia all-ceramic crowns: 2-year results of a randomized controlled clinical trial. J Appl Oral Sci, .. http://dx.doi.org/. , 17, 49-55, vs. slip-cast
4. Coelho, P. G.Bonfante, E. A.Silva, N. R.Rekow, E. D.Thompson, V. P. (2009). Laboratory simulation of Y-TZP all-ceramic crown clinical Dent Res. , 88, 382-386, failures. J
5. Donovan, T. E. (2009). Porcelain-fused-to-metal (PFM) Esthet Restor Dent, 21, 4-6. https://doi.org/10 x. , 1111(j.1708-8240.2008.00222), alternatives. J
6. Huang, M.Thompson, V. P.Rekow, E. D.Soboyejo, W. O. (2008). Modeling of water absorption induced cracks in resin-based composite supported ceramic layer Biomed Mater Res B Appl Biomater, . https: doi.org/, 84, 124-130, structures. J
7. Kim, J. H.Kim, J. W.Myoung, S. W.Pines, M.Zhang, Y. (2008a). Damage maps for layered ceramics under simulated Dent Res. , 87, 671-675, mastication. J
8. Kim, J. W.Kim, J. H.Janal, M. N.Zhang, Y. (2008b). Damage maps of veneered zirconia under simulatedmastication J Dent Res. , 87, 1127-1132
9. Kohorst, P.Dittmer, M. P.Borchers, L.Stiesch-Scholz, M. (2008). Influence of cyclic fatigue in water on the load-bearing capacity of dental bridges made of Biomater 4: reconstructions. A randomized, prospective clinical trial.. Swed Dent J. , 30(45-53), zirconia. Acta
10. Larsson , C.Vult von Steyern , P.Sunzel , B.Nilner , K. (2006). All-ceramic two- to five-unit implantsupported. , https://www.ncbi.nlm.nih.gov/pubmed/16878679
11. Marchack B, W.Futatsuki , Y.Marchack C, B.White S, N. (2008). Customization of milled zirconia copings for all-ceramic crowns: a clinical Prosthet Dent. , 99(169-173), report. J