Guided tooth preparation for a pediatric zirconia crown

A comparison of the mechanical proprieties of different types of primary tooth restorations: an in vitro study

OBJECTIVE

To compare the different restoration types of primary teeth to determine which type is appropriate for extensive caries of primary molars and incisors based on mechanical properties.

MATERIALS AND METHODS

A total of 160 primary teeth were evaluated in this study, including 80 incisors and 80 molars. Each category was divided into four groups: the control group, composite resin group, pre-veneered stainless steel crown (stainless steel crown) group, and zirconia crown group. Compressive strength test and fatigue strength test were performed.

RESULTS

The compressive strength and fatigue strength of the composite resin group were significantly decreased compared with the control group (P < 0.05). The prefabricated crown groups showed increased fatigue and compressive strength compared with the control group, and the zirconia crown group was higher than that of the pre-veneered stainless steel crown group (P < 0.05). The zirconia crown group was less than the stainless steel crown group (P < 0.05) in the compressive strength but more than the stainless steel crown group (P < 0.05) in the fatigue strength.

CONCLUSIONS

The compressive strength and fatigue strength of crown restoration were superior to that of the composite resin filling. The fatigue strength of the zirconia crown also performed better than the pre-veneered stainless steel crown and the stainless steel crown. The compressive strength of the zirconia crown was less than that of the stainless steel crown.

CLINICAL RELEVANCE

The zirconia crown is a new restoration method for primary teeth that may be commonly applied in clinical practice.

Use of Restorative Full Crowns Made with Zirconia in Children: A Systematic Review

Aim and objective

The purpose of this systematic review is to analyze the suitability of the zirconia crowns for restoration of damaged primary teeth in children.

Background

This systematic review has been conducted in line with the preferred reporting items for systematic reviews (which is also called as PRISMA) guidelines. A search for the relevant articles of zirconia crowns in deciduous teeth has been made in electronic database of PubMed and a study design (meta-analysis), i.e., PICOS framework. The words used in the search are “zirconia crowns” and “primary molars,” “zirconia crowns” and “primary incisors,” “zirconia crowns” and “children,” “zirconia crowns” and “primary teeth.”

Review results

The database search showed 44 studies of which 20 articles were excluded as they were irrelevant, duplicates, and data were not available. In the present systematic review, the remaining 24 articles were included.

Conclusion

Zirconia crowns have been proved with better results than other crowns in terms of gingival and periodontal health, esthetics, and crown fractures. However, the quantity of tooth preparation and the wear of antagonist tooth are reported to be more in case of zirconia crowns. Future randomized control studies should be carried out in primary teeth due to less number of randomized studies on this topic.

Clinical significance

Zirconia crowns are now widely used in dentistry and there is an increase in the number of studies, so a systematic review evaluating and comparing results is warranted.

How to cite this article

Ajayakumar LP, Chowdhary N, Reddy VR, et al. Use of Restorative Full Crowns Made with Zirconia in Children: A Systematic Review. Int J Clin Pediatr Dent 2020;13(5):551–558.

[Evaluation of the effect of using ultrasonic instruments to improve the shoulder of the preparations]

OBJECTIVE

To provide the basis for the clinical development of ultrasonic shoulder preparation by comparing the roughness and three-dimensional topography of shoulder surface between ultrasonic instruments and conventional rotary instruments, to make preliminary suggestions for clinical use of ultrasonic instruments.

METHODS

(1) Four areas of buccal and palatal surfaces of six extracted human premolars were prepared with different grit size of rotary instruments. Polyether was used to take impression of the shoulder area, 3-D topography measurement laser microscope (3-D TMLM) was used to scan the impressions and compare the shoulder surface roughness of the four areas. (2) Six extracted human premolars were prepared, mesial half of the shoulder was finished with traditional rotary instruments and distal half with ultrasonic instruments. Polyether was used to take impression of the shoulder area, 3-D TMLM was used to scan the impressions and compare the shoulder surface roughness and 3-D topography, and the shoulder surface morphology was observed by surgical microscope (×25 magnification). (3) Twenty extracted human maxillary symmetrical homonymous anterior teeth were poured into die stone using artificial gingiva, ultrasonic instruments group and rotary instruments group were divided randomly. After preparing the teeth and taking the shoulder impression with polyether in dental simulate on the training system, the surface roughness of the shoulder impression in mesial, middle and distal areas was scanned and compared. The data were analyzed using SPSS 25.0 software package.

RESULTS

(1) There was no significant difference in Ra and Rz values between the abutment shoulder and impression shoulder in different areas. (2) The surface roughness of the shoulder impression prepared by ultrasonic instruments [Ra:(6.59±2.33) μm, Rz:(34.69±7.29) μm] was significantly smaller than that of the rotary instruments [Ra:(21.79±4.89) μm, Rz:(91.69±14.82) μm] (P < 0.05). The morphology of the shoulder prepared by ultrasonic instruments was clear and continuous under microscope observation. (3) The surface roughness of each area of the shoulder prepared by ultrasonic instruments was significantly lower than that of the rotary instruments (P < 0.001); there was no significant difference of the surface roughness (Ra) in each area of the shoulder impression after ultrasonic instrument preparation, while the shoulder impression roughness in the mesial and distal areas was significantly higher than that in the middle area (P < 0.001) after rotary instrument preparation.

CONCLUSION

Compared with the rotary instruments, the ultrasonic instruments can obtain a smoother shoulder surface, especially can significantly improve the shoulder preparation effect near the proximal surface.

Computer-aided Design and Manufacturing Crown on Primary Molars: An Innovative Case Report

Aim

Crowns are applicable on primary teeth with extensive caries, cervical decalcification, developmental defects, interproximal caries extending beyond line angles, and following pulpotomy or pulpectomy.

Background

Until now, prefabricated crowns, i.e., stainless-steel crowns (SSCs), pre-veneered SSC, and all ceramic/porcelain/zirconia crowns have been available in a range of sizes to match the first and the second primary molar teeth.

Case description

This case report illustrates a clinical use of computer-aided design and manufacturing technology (CAD/CAM) for the fabrication of a crown for a decayed primary molar using a study model as a reference. The material used was a hybrid ceramic CAD/CAM block.

Conclusion

This approach has the advantage of the customization of the abutment tooth in contrast to the previously mentioned prefabricated options.

How to cite this article

Mourouzis P, Arhakis A, et al. Computer-aided Design and Manufacturing Crown on Primary Molars: An Innovative Case Report. Int J Clin Pediatr Dent 2019;12(1):76-79.

Virtual diagnostics and guided tooth preparation for the minimally invasive rehabilitation of a patient with extensive tooth wear: A validation of a digital workflow

The recent evolution of digital technologies in dentistry has enabled virtual 3D diagnostic analysis of a dentition before treatment, allowing for virtual, minimally invasive treatment planning. In this report, an extensively worn dentition was 3D virtual analyzed at an increased vertical dimension of occlusion. Virtual waxing (exocad DentalCAD; Exocad) and subsequent analysis of the need for minimally invasive preparations were performed. Areas of each tooth without adequate clearance for the minimal thickness of a definitive restoration (set at 1.5 mm in the software), including the amount of tooth substance to be removed (GOM Inspect; GOM), were visualized in color. A preparation guide was virtually designed according to this diagnostic plan (3-matic; Materialise) and 3D printed (Connex3 Objet260; Stratasys) from resin (VeroMagenta RGD851; Stratasys). The teeth were minimally prepared using the guide, and the amount of preparation was validated by superimposing the scan of the prepared model on the initial scan and comparing it with the diagnostic plan.