4. Discussion
fracture, fractures, caries, tooth
CARIES
Modern restorative dentistry aims to preserve healthy dentition and replace missing tooth structures conservatively [Additionally, complete caries removal can also lead to the establishment of deep subgingival margins, which are often difficult to restore [Studies on the effect of DME on the periodontium indicate that it is well tolerated, both clinically and histologically [In the present study, a traditional hybrid composite was used for the DME, as it is known to reduce marginal gap formation. The use of other materials such as glass ionomers, resin-modified glass ionomers and smart dentin replacement (SDR) bulk-fill composites for DME have also provided acceptable results with regards to FR, marginal adaptation and microleakage [The comparison of IRs such as onlays, overlays/partial crowns and full crowns have been extensively studied in the literature, with the majority of these studies reporting them to have clinical efficacy in excess of 93% [The FR of posterior teeth was determined previously to be in the range of 1120–2500 N [Research on the effects of DME on FR among indirect CAD/CAM restorations have generally focused on teeth with inlays, onlays, overlays and endocrowns. Most of these studies reported that the use of DME did not significantly impact the FR of teeth [The type and site of fracture was visually evaluated. Failure type was classified based on the adaptation and modification from previous studies, as “restorable” for those with visible cracks and fracture lines on the zirconia crowns and “unrestorable” for those in which the fractures were seen below the CEJ [Under the limitations of this study, DME under normal depths (2 mm) rarely influenced the FR of teeth, except when the tooth structure was severely compromised, as in Group D. However, the load required to fracture the crowned teeth decreased as the extension of DME apical to the CEJ increased, thus rejecting the null hypothesis. Most of the samples failed unfavorably under maximum load. Nevertheless, more importantly, from a clinical point of view, the load required to fracture these samples far exceeded the maximum recorded biting force in posterior teeth, which is in the range of 800–1000 N [In spite of the perceived advantages in this study, it has some limitations; a. The ease in performing the DME, especially where the distance to the crown margins is greater than 2 mm, might not be established in clinical settings without STA violations. b. Natural teeth variances in strength and morphology when compared to the dyes used in some of the other studies could have an influence on the results. c. The fracture of the teeth/MZi crown assembly was evaluated visually in this study; a more detailed fractographic evaluation would have provided precise details regarding the initiation and causes of cracks. The future trends in research will change the ever-evolving material choices for direct restorations and the development of monolith crowns using newer CAD/CAM technologies, which will help establish an ideal restorative choice, esthetically and functionally.