Standards of Teeth Preparation for Anterior Reszin Bonded All- Ceramic crowns in Private Dental Practice in South India

Sangeetha Shankar¹, Dr. Revathy Gounder²

¹BDS Student, Saveetha Dental College 162, Poonamallee High Road, Vellapanchavadi Road, Chennai - 600077

²Senior Lecturer, Dept. of Prosthodontics, Saveetha Dental College 162, Poonamallee High Road,

llapanchavadi Road, Chennai-600077

*Corresponding Author E-mail: sangeetha14151@gmail.com

ABSTRACT:

Title: A study on standards of teeth preparations for anterior resin bonded all-ceramic crowns in private dental practice in India. Aim: To analyse the standards of teeth preparations for anterior resin bonded all-ceramic crowns in private dental practice in India. Objective: To evaluate the standards of teeth preparations for anterior resin bonded all-ceramic crowns in private dental practice in India. Background: Tooth preparation is one of the important aspects of restorative dentistry because it establishes the foundation for whatever restoration is being placed⁵. Unfortunately, training in dental schools relative to tooth preparation is too often oriented to the dimensions of rotary instruments rather than tooth morphology⁶. Understanding of tooth morphology is essential for developing preparations that will permit the restorations placed upon them to be functionally durable, provide optimal esthetics, and be biologically compatible with the periodontal tissues. The most important aspect of tooth preparation is retention of the crown and esthetics⁷. these two are governed by finish line. Hence a proper, specific finish line has to be chosen for different types of crowns. Reason: A dentist must be aware of different types of finish lines and the most preferred ones for each type of restorative material used. This is important because the occlusal forces vary in different regions of the oral cavity ,for eg: the mastication load is more on the posteriors than on the anteriors. Hence preparing a suitable finish line for a specific restorative material can increase the retention of the restorative material and therefore this research was being conducted.

KEYWORDS: Supragingival margin, Subgingival margin, restoration.

INTRODUCTION:

All-ceramic dental crowns are restorations whose full thickness is made entirely of a glass-like substance, such as porcelain¹. They were used more than 10,000 years ago during the Stone Age. In 1723, Pierre Fauchard described the enameling of metal denture bases². De Chemant, a French dentist, introduced the first porcelain denture tooth in 1789. The first ceramic crown was introduced in 1903 by Dr. Charles Land³. The most defining and important feature of these crowns is that they have high esthetic value as they are made from a translucent material which is attractive to look at and blends in well with the rest of the teeth.

Now a days ceramic crowns are produced using computer technology, e.g. CAD/CAM technology which is based upon 3D design. There are two types of ceramic crown-Zirconia and E-Max. A zirconia crown is a popular type of all-ceramic crown which is worn to improve the appearance of a tooth which has become stained or disfigured over the years⁴. They are durable, easy to wear and long lasting. The E-Max crown is a type of all-ceramic crown which is preferred for its longer lasting, aesthetic qualities.

BACKGROUND:

Tooth preparation is one of the important aspects of restorative dentistry because it establishes the foundation for whatever restoration is being placed⁵. Unfortunately, training in dental schools relative to tooth preparation is too often oriented to the dimensions of rotary instruments rather than tooth morphology⁶. Understanding of tooth morphology is essential for developing preparations that will permit the restorations placed upon them to be functionally durable, provide optimal esthetics, and be biologically compatible with the periodontal tissues. The most important aspect of tooth preparation is retention of the crown and esthetics⁷. these two are governed by finish line. Hence a proper, specific finish line has to be chosen for different types of crowns.

Overall, the preparation should be as conservative as possible with retention of some enamel⁸. The overall amount of tooth reduction is 2.0 mm. Occlusal clearence should be a minimum of 1 millimeter in centric relation and lateral excursions⁹. A taper of 6º to 10º MUST ALSO BE OBTAINED on the prepared tooth.

The preferred finish line for all ceramic crowns is radial shoulder¹⁰. It is established when all the axial walls ( buccal, lingual and proximal) are prepared using a flat end tapered bur. And a uniform finish line has to be obtained.

A dentist must be aware of different types of finish lines and the most preferred ones for each type of restorative material used. This is important because the occlusal forces vary in different regions of the oral cavity, for eg: the mastication load is more on the posteriors than on the anteriors. Hence preparing a suitable finish line for a specific restorative material can increase the retention of the restorative material. And moreover any marginal discrepancies disrupt smooth tooth surfaces and hence render the site vulnerable to plaque accumulation while micro-leakage at the margin which allows the passage of ions, molecules, fluids or bacteria between the prepared tooth and the restorative material. Hence this research was being conducted.

METHODOLOGY:

100 laboratory casts with tooth preparations for all ceramic crowns for anterior teeth obtained from different general dental practitioners in Chennai were analyzed with an inclusion criteria of fixed partial denture casts for anteriors for all ceramic crowns and excluding complete and removable partial denture dental casts.

The following were analyzed using the casts:

1. The positions of tooth preparation margin in relation to the gingival margin on the buccal and lingual aspects.:

supragingival margin

Subgingival margin

Level with gingival margin

No clear margin

2. The total amount of tooth reduction in the buccolingual and mesiodistal planes:

>3 mm

1-2mm

<1mm

3. The amount of incisal reduction:

>3 mm

1-2mm

<1mm

4. The type of finish line:

radial Shoulder

Chamfer

knife edge

No clear margin

5. Axial convergence angle between opposing walls of prepared tooth.

< 6º axial convergence

6º and 10º axial convergence

> 10º axial convergence

6. Finish line depth:

< 0.5 mm depth

0.5 and 1.5 mm depth

> 1.5 mm

7. Uniformity of finish line:

present

absent

RESULTS:

Question

Option A

Option B

Option C

Option D

1)The positions of tooth preparation margin in relation to the gingival margin on the buccal and lingual aspects

Supragingival

(35)

Sub gingival

(2)

Level with gingival margin

(2)

No clear margin

(11)

2)The total amount of tooth reduction in the buccolingual and mesiodistal planes

>3mm

(10)

1-2mm

(38)

<1mm

(2)

3)Incisal reduction

>3mm

(19)

1-2mm

(30)

<1mm

(1)

4)Type of finish line

Radial shoulder

(30)

Chamfer

(3)

Knife edge

(2)

No clear Margin

(15)

5)Axial convergence angle between opposing walls of prepared tooth

<6degree axial convergence

(18)

6degree and 10 degree convergence

(28)

>10degree axial convergence

(2)

6)Finish line depth

<0.5mm depth

(12)

0.5mm and 1.5mm depth

(38)

>1.5 mm depth

7)Uniformity of finish line

Present

(48)

Absent

(2)

DISCUSSION:

Tooth preparation is one of the important aspects of restorative dentistry because it establishes the foundation for whatever restoration is being placed. Unfortunately, training in dental schools relative to tooth preparation is too often oriented to the dimensions of rotary instruments rather than tooth morphology. Understanding of tooth morphology is essential for developing preparations that will permit the restorations placed upon them to be functionally durable, provide optimal esthetics, and be biologically compatible with the periodontal tissues. The most important aspect of tooth preparation is retention of the crown and esthetics. these two are governed by finish line. Hence a proper, specific finish line has to be chosen for different types of crowns.

Finish line position can be placed supragingivally on sound tooth tissue, but in reality this is often not possible. Sometimes aesthetics dictates a margin to be placed subgingivally and in these situations it should extend by 0.5-1 mm, but certainly not more than half the depth of the gingival sulcus, to ensure the epithelial attachment is not compromised. According to several authors like Ziad Nawaf AL-DWAIRI, Ahmad Saleh AL-HIYASAT and Haitham ABOUD, the placement of tooth margins subgingivally is critical because of the possibility of microleakage if the margins are placed either on dentin or cementum¹¹.

The overall amount of tooth reduction is 2.0 mm. Occlusal clearence should be a minimum of 1 millimeter in centric relation and lateral excursions. A taper of 6º to 10º MUST ALSO be obtained on the prepared tooth.Overall, the preparation should be as conservative as possible with retention of some enamel.

From several journals, it has been reported that the preferred finish line for all ceramic crowns is radial shoulder. It is established when all the axial walls (buccal, lingual and proximal) are prepared using a flat end tapered bur. And a uniform finish line has to be obtained for retention purposes.

From the above analysis, it was found that 35% of the dentists preferred a supra gingival margin for the tooth preparation whereas 11% had no clear margin. Almost 10% of the dentists made a reduction of >3mm in buccolingual and media distal planes. Majority preferred radial shoulder finish line over other types but a handful of them had no clear type of finish line being prepared with a depth in the range of 0.5mm to 1.5mm. An axial convergence of 6 - 10 degree was prepared by 28% of the dentists.

CONCLUSION:

This study showed that preparations for RBCs of the Indian clinicians' work investigated varied widely. Most of the clinicians follow proper tooth preparation principles while a handful of clinicians followed no specific principles. It is a dentist's duty to provide best treatment to the patients , hence proper tooth preparation principles must be followed to ensure effective treatment in terms of esthetics and retention.

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11. Ziad Nawaf AL-DWAIRI, Ahmad Saleh AL-HIYASAT, and Haitham ABOUD. Standards of teeth preparations for anterior resin bonded all-ceramic crowns in private dental practice in Jordan. J Appl Oral Sci. 2011 Jul-Aug; 19(4): 370–377.

Received on 07.08.2016 Modified on 30.11.2016

Research J. Pharm. and Tech 2020; 13(3):1127-1130.

DOI: 10.5958/0974-360X.2020.00207.3