Metal-ceramic bridges from commercial dental laboratories: alloy composition, cost and quality of fit

Dental practice in the UK in 2015/2016. Part 3: aspects of indirect restorations and fixed prosthodontics

Objective

This paper reports data which helps identify changes and trends in the provision of indirect fixed prostheses in general dental practice in the UK. To determine by means of an anonymous, self-report questionnaire, the current trend in the provision of fixed prosthodontic treatments, with a special emphasis on the choice of treatment modalities, techniques and materials.

Methods

The data presented were extracted from the data obtained from a validated,121-question questionnaire distributed at random to general dental practitioners in the UK attending postgraduate meetings in 2015/2016, with a wide distribution of locations.

Results

A response rate exceeding 66% was achieved. Amalgam and light-cured composite were the preferred material for core build-up of vital teeth for around 62% of the respondents. Dentine pins were still being used by 66% of the respondents. The vast majority of respondents (92%) used a post and core to restore root-treated teeth. Fibre posts were the most commonly used (63%) type of preformed post among the respondents. Using the opposing and adjacent teeth as a reference to control tooth structure reduction during vital tooth preparation was the most common method, used by 42% of the respondents. Addition-cured silicone impression materials were the most frequently used impression material (78%). The surveyed practitioners were equally split between precious and non-precious metals as the substructure for indirect restorations. Glass-ionomer luting cements (47%) and resin-based cements (52%) were the most commonly used to cement porcelain fused to metal and zirconia indirect restorations, respectively. Laboratory made aesthetic veneers were prescribed by half of the respondents, while a third of them preferred direct resin composite as a veneer material.

Conclusion

Within the limitations of the study, it was concluded that there has been an increase in the use of adhesive bonding and metal-free restorations. Amalgam and dentine pinscontinued to be used, contrary to international trends. Studies of the type reported are considered important in investigating trends and developments in dentistry.

The knowledge, attitude and practice of fixed prosthodontics: A survey among Qassim dental practitioners

Aim:

The aim of this study was to evaluate the knowledge, attitude and fixed prosthodontics practice guidelines amongst dental practitioners of Qassim in Saudi Arabia.

Materials and Methods:

A descriptive cross-sectional study was done amongst the Dental Practitioners of Qassim Province, Saudi Arabia in 2018. A total of 290 dentists were selected randomly (from public and private dental clinics and dental schools). A survey was conducted through printed and online questionnaire composed of 19 open and multiple-choice questions. Data from the completed questionnaires were analysed using the SPSS Statistical Software Package (version 25). All statistical analyses were carried out at a significance level of P < 0.05. Results were analysed and compared using the Chi-square test and frequency test.

Results:

This study showed that 227 (78.3%) of the participants assessed abutment tooth radiographically, also most of them fabricated study cast before starting crown and bridge procedures 37.2% (108). The vitality test for restored abutments was always done by 132 (45.5%) respondents, and 111 (38.3%) of them used poly vinyl siloxane for making final impression, which provides the level of quality of final impression. A total of 117 (40.3%) of them always used retraction cord before making final impression. Both written prescriptions and verbal instructions were used by 209 (72.1%) of the practitioners for communication with the lab. The study revealed that there were no significant differences between males and females in answering questions 11, 13 and 17.

Conclusion:

The dental practitioners (DPs) of Qassim displayed an acceptable level of knowledge and a level of awareness of fixed prosthodontics practicing. However, to further enhance the proficiency, efforts should be made to encourage the practitioners to be aware of the advances in fixed prosthodontics practice through state-of-the-art continuous education programmes.

Clinical Significance:

As fixed prosthodontic restorative procedures are widely practiced for dental rehabilitation in Saudi Arabia, it was very important to measure and evaluate the knowledge of DPs about the details of basic steps in the field of fixed prosthodontics and the way of practicing this important branch of dentistry.

Assessment of crown and bridge work quality among Sudanese dental practitioners

PURPOSE

The aim of the present study is to investigate the quality of crown and bridge work among dentists in Khartoum state by mean of a questionnaire.

MATERIALS AND METHODS

Questionnaire was distributed to all dentists (about 230) who work in private clinics and primary health centers in Khartoum state. A total of 152 usable questionnaires were collected, giving a response rate 66.09%.

RESULTS

High-speed hand pieces were the instrument of choice (80.54%) and according to number of spray ports single port was found to be the most common type (80.43%). Alginate was the material of choice as a final impression material (68.24%) followed by condensation-cured silicone (24.32%). Impression trays used by dentists were metal tray 23.53%, rigid plastic tray 12.5% and both 63.97%. Results in concern of the use of the retracting cord indicated that 53.69% never use it. Results also indicated that 36.05% never used temporary crown and bridge. Traditional glass ionomer cements and zinc phosphate cements (56%) were equally selected as best choice for final luting cement of crown and bridge work. Both verbal and written prescriptions (81.73%) were the most common used way of communication between dentists and dental technicians.

CONCLUSION

It is concluded that the majority of the surveyed dentists mainly used alginate as a final impression material for crown and bridge work. It was also observed, the absence of application of retraction cord and temporary restoration in their practice for crown and bridge work.

Materials for chairside CAD/CAM-produced restorations

BACKGROUND

and Overview. Although the use of computer-aided design/computer-aided manufacturing (CAD/CAM) seems to be a recent addition to the dental restorative armamentarium, this concept was first investigated more than 35 years ago. CEREC (Sirona Dental Systems GmbH, Bensheim, Germany) was the first and is the only available chairside system, and it has more than 20 years of use in the dental office. The initial concept had three tenets: esthetic ceramic reconstruction, a single patient visit and minimal tooth reduction (inlays and onlays instead of crowns). The author reviews the materials used for CAD/CAM-fabricated restorations. The structure, properties and clinical success of the materials for full-contour chairside restorations, as well as laboratory-based high-strength all-ceramic restorations are presented.

RESULTS

CAD/CAM restorations have demonstrated clinical success owing to a combination of improvements in materials with advances in CAD/CAM systems. Full-contour ceramic restorations fabricated chair-side may reinforce the tooth, providing good long-term clinical success. High-strength milled restorations allow for the use of all-ceramic restorations for multiple-unit posterior and anterior bridges.

CLINICAL IMPLICATIONS

Examination of the structure, properties and clinical results of CAD/CAM materials supports their use in routine dental practice.

The effect of investment material and ceramming regime on the surface roughness of two castable glass-ceramic materials

OBJECTIVE

To assess the surface roughness (R(a)) of two castable glass-ceramic materials, cast using four different investment materials and employing different ceramming regimes.

METHODS

Forty discs, each 12 mm diameter and 2 mm thick were produced from two castable glass-ceramic materials, one a glass ionomer derivative based on 1.5SiO(2)-1Al(2)O(3)-0.53P(2)O(5)-1CaO-0.67CaF(2) (LG112), the other a fluorcanasite material based on 0.60SiO(2)-0.05K(2)O-0.10Na(2)O-0.15CaO-0.10CaF(2) (SG3). The discs were made using four dental investments, two gypsum-bonded (Whip-Mix Cristobalite (WMC), Degussa California (DC)) and two phosphate-bonded (Fujivest Super (FS), Techceram Glass (TG)). A Ni-Cr metal/ceramic alloy (Wiron 99) was also used as a control. Each investment was used to produce 10 discs for each glass-ceramic material, five left in the as-cast, glass state, the other five cerammed. Ceramming was carried out either within the investment mold or after de-vesting from the investment mold. The discs had their surface roughness values measured using a stylus, surface contact measuring instrument.

RESULTS

For the Ni-Cr alloy the phosphate-bonded investments produced discs significantly smoother than those produced by the two gypsum-bonded investments (p<0.05). The FS investment produced the smoothest discs (p<0.05), but there was no significant difference between the discs produced by the two gypsum-bonded investments (p>0.05). For the SG3 material no significant differences were seen between the as-cast glass and cerammed discs (p>0.05), with the WMC investment producing the smoothest discs (p<0.05), and the TG investment the roughest (p<0.05). The LG112 material showed a significant difference between glass and cerammed discs for the gypsum-bonded investments (p<0.05) but not when using phosphate-bonded investments (p>0.05). With LG112 the WMC investment produced smoother discs than the DC and TG investments (p<0.05). The DC investment produced rougher discs than the two phosphate-bonded investments (p<0.05).

SIGNIFICANCE

The selection of investment material can have a significant effect on the as-cast surface finish of castable glass-ceramic materials. A gypsum-bonded investment material gave smoother surface finishes compared to phosphate-bonded investments. The ceramming process significantly increases surface roughness.

Crowns and extra-coronal restorations: materials selection

Materials selection is the second in the series on crowns and other extra-coronal restorations. Some of us are less than inspired by dental materials science. Nevertheless, many of the things that concern us clinically with crowns and their alternatives are based on material properties. We worry about the strength of the restoration, how well it fits and its aesthetics. We also worry about wear, occlusal control and biocompatibility. Not least of our concerns are dental laboratory charges, which inevitably have to be passed on to the patient.

Accuracy of wax, autopolymerized, and light-polymerized resin pattern materials

PURPOSE

The marginal fit of MOD inlay and full-crown patterns fabricated from wax, autopolymerized acrylic resin, and two light-polymerized, diacrylate resin pattern materials was compared on standardized dies.

MATERIALS AND METHODS

Four pattern materials were studied-two light-polymerized, diacrylate resin materials (Palavit G LC and Triad VLC Burnout Paste), an inlay wax, and an autopolymerized resin (Duralay). Patterns were fabricated using incremental and bulk techniques on stone dies made from addition silicone impressions of American Dental Association MOD and full-crown master dies. Gaps were measured with a measuring microscope in four marginal areas on the master dies at 1 and 24 hours after fabrication.

RESULTS

For the MOD inlay patterns, marginal gaps ranged from 7 to 23 microns, and the light-polymerized, diacrylate resins and autopolymerized acrylic resin material had statistically smaller gaps than the inlay wax. For the full-crown patterns, marginal gaps ranged from 10 to 23 microns, with the exception of the autopolymerized acrylic resin prepared by the bulk technique (40 to 46 microns). With the incremental technique, the light-polymerized, diacrylate resins and inlay wax had statistically smaller gaps than the autopolymerized acrylic resin material. Overall, the incremental technique produced equal or smaller marginal gaps than the bulk technique for full-crown patterns. Generally, the patterns measured at 1 hour had smaller marginal gaps than at 24 hours.

CONCLUSIONS

When measured on intra- and extracoronal master dies, the light-polymerized, diacrylate resins had equal or better marginal fit, compared with wax or autopolymerized acrylic resin, and were less affected by placement technique and storage. The marginal gaps of all four pattern materials ranged from 7 to 46 microns and are within the range of clinical acceptability.