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The Effect of Cavity Design on Fracture Resistance and Failure Pattern in Monolithic Zirconia Partial Coverage Restorations - An In vitro Study

Harsha MS 1 , Praffulla M 2 , Babu MR 3 , Leneena G 4 , Krishna TS 5 , Divya G 6

Affiliations 

  • 1 General Practitioner, Consultant Endodontist, Guntur, Andhra Pradesh, India
  • 2 Senior Lecturer, Department of Conservative Dentistry and Endodontics, Drs Sudha and Nageswara Rao Siddhartha Institute of Dental Sciences, Vijayawada, Andhra Pradesh, India
  • 3 Professor and Head, Department of Conservative Dentistry and Endodontics, Drs Sudha and Nageswara Rao Siddhartha Institute of Dental Sciences, Vijayawada, Andhra Pradesh, India
  • 4 Lecturer, Department of Conservative Dentistry and Endodontics, Amist University, Kuala Lumpur, Wilayah Persekutuan Kuala Lumpur, Malaysia
  • 5 Senior Lecturer, Department of Conservative Dentistry and Endodontics, Mamata Dental College, Khammam, Telangana, India
  • 6 Senior Lecturer, Department of Pediatric and Preventive Dentistry, St. Joseph Dental College, Eluru, Andhra Pradesh, India
J Clin Diagn Res, 2017 May;11(5):ZC45-ZC48.
PMID: 28658906 DOI: 10.7860/JCDR/2017/25305.9856

Abstract

INTRODUCTION: Cavity preparations of posterior teeth have been frequently associated with decreased fracture strength of the teeth. Choosing the correct indirect restoration and the cavity design when restoring the posterior teeth i.e., premolars was difficult as it involves aesthetic, biomechanical and anatomical considerations.

AIM: To evaluate the fracture resistance and failure pattern of three different cavity designs restored with monolithic zirconia.

MATERIALS AND METHODS: Human maxillary premolars atraumatically extracted for orthodontic reasons were chosen. A total of 40 teeth were selected and divided into four groups (n=10). Group I-Sound teeth (control with no preparation). Group II-MOD Inlay, Group III-Partial Onlay, Group IV-Complete Onlay. Restorations were fabricated with monolithic partially sintered zirconia CAD (SAGEMAX- NexxZr). All the 30 samples were cemented using Multilink Automix (Ivoclar) and subjected to fracture resistance testing using Universal Testing Machine (UTM) (Instron) with a steel ball of 3.5 mm diameter at crosshead speed of 0.5 mm/minute. Stereomicroscope was used to evaluate the modes of failure of the fractured specimen. Fracture resistance was tested using parametric one way ANOVA test, unpaired t-test and Tukey test. Fracture patterns were assessed using non-parametric Chi-square test.

RESULTS: Group IV (Complete Onlay) presented highest fracture resistance and showed statistical significant difference. Group II (MOD Inlay) and Group III (Partial Onlay) showed significantly lower values than the Group I (Sound teeth). However, Groups I, II and III presented no significant difference from each other. Coming to the modes of failure, Group II (MOD Inlay) and Group III (Partial Onlay) presented mixed type of failures; Group IV (Complete Onlay) demonstrated 70% Type I failures.

CONCLUSION: Of the three cavity designs evaluated, Complete Onlay had shown a significant increase in the fracture resistance than the Sound teeth.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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