Ceramic Inlay Bonded Interfaces in Minimally Invasive Preparations: Damage and Contributing Mechanisms in Sliding Contact

SUMMARY Background: In the preparation of inlay cavities, a choice must be made between conventional standard and minimally invasive preparation designs; in the long run, this choice can affect the integrity of the bonded interface. Purpose: To evaluate the effect of minimally invasive cavity preparation designs on the extent and contributing mechanisms of damage to ceramic inlay bonded interfaces. Methods and Materials: Tooth blocks with 90°, 120° and 75° marginal angles were prepared, representing tooth cavities with conventional standard and minimally invasive preparations with large divergence and convergence angles and bonded to monolithic ceramic (IPS e.max CAD). Vickers indentations were placed at various distances from the bonded interface. The indentation morphology and crack length were observed. Reciprocating wear tests were performed on the bonded interface with a 20-newton (N) vertical load. The wear depth and wear-scar morphology were characterized after increments of cyclic sliding contact. Results: The 120° group exhibited longer indentation cracks in the ceramic, whereas the 75° group showed larger indentations in the enamel when compared to the 90° group (p<0.001). Consistent with the weaker edge crack resistance, the 120° group experienced the greatest wear (p=0.008), and the wear depth in the enamel of the 75° group exceeded that of the 90° group (p<0.001) in the early stage (5×102 cycles). However, no significant difference in the wear depth (p>0.147) and morphology were found at the later wear stage among the three groups. Conclusion: Within the limitations of this study, minimally invasive preparations with 120° and 75° marginal angles can result in early sever damage at the ceramic inlay bonded interface but show comparable wear behaviors to the conventional 90° group at the later stage.

Influence of Preparation Design and Restorative Material on Fatigue and Fracture Strength of Restored Maxillary Premolars

SUMMARY Statement of Problem: Extensive carious lesions and/or large preexisting restorations possibly contribute to crack formation, ultimately resulting in a fracture that may lead to the loss of a tooth cusp. Hence, preparation design strategy in conjunction with the restorative material selected could be influential in the occurrence of a cuspal fracture. Purpose: The purpose of this in vitro study was to evaluate the fatigue behavior and fracture strength of maxillary premolars restored with direct composite and indirect ceramic inlays and overlays, with different preparation depths in the presence or absence of cuspal coverage, and analyze their failure types. Methods and Materials: Sound maxillary premolars (N=90; n=10) were divided into nine groups: group C: control; group DCI3: direct composite inlay 3 mm; group DCI5: direct composite inlay 5 mm; group ICI3: indirect ceramic inlay 3 mm; group ICI5: indirect ceramic inlay 5 mm; group DCO3: direct composite overlay 3 mm; group DCO5: direct composite overlay 5 mm; group ICO3: indirect ceramic overlay 3 mm; group ICO5: indirect ceramic overlay 5 mm. In indirect ceramic, lithium disilicate restoration groups, immediate dentin sealing was applied. After restoration, all specimens were tested in fatigue (1,200,000 cycles, 50 N, 1.7 Hz). Samples were critically appraised, and the specimens without failure were subjected to a load to failure test. Failure types were classified and the data analyzed. Results: Zero failures were observed in the fatigue testing. The following mean load to failure strengths (N) were recorded: group ICO5: 858 N; group DCI3: 829 N; group ICO3: 816 N; group C: 804 N; group ICI3: 681 N; group DCO5: 635 N; group DCI5: 528 N; group DCO3: 507 N; group ICI5: 482 N. Zero interaction was found between design-depth-material (p=0.468). However, significant interactions were found for the design-depth (p=0.012) and design-material (p=0.006). Within restorations at preparation depth of 3 mm, direct composite overlays obtained a significantly lower fracture strength in comparison to indirect ceramic onlays (p=0.013) and direct composite inlays (p=0.028). In restorations at depth 5 mm, significantly higher fracture load values were observed in indirect ceramic overlays compared with the inlays (p=0.018). Indirect ceramic overlays on 3 mm were significantly stronger than the deep inlays in ceramic (p=0.002) and tended to be stronger than the deep direct composite inlays. Severe, nonreparable fractures were observed with preparation depth of 5 mm within ceramic groups. Conclusions: The preparation depth significantly affected the fracture strength of tooth when restored with either composite or ceramic materials. Upon deep cavity preparations, cuspal coverage proved to be beneficial when a glass ceramic was used as the restorative material. Upon shallow cavity preparations, a minimally invasive approach regarding preparation design used in conjunction with a direct composite material was favorable.

Survival rate of ceramic inlay and onlay restorations in posterior tooth with one-surface or multi-surface after 10 years observation: A systematic review and meta-analysis

Object: This study aimed to evaluate the survival rate of ceramic inlay and onlay restorations in posterior tooth with one -surface or multi-surface after 10-year observation. Methods: PubMed, Web of Science, Cochrane library, Embase, and Wanfang databases were searched for articles published up to July 31, 2016. Randomized controlled trial and non-randomized trial were collected and patients with posterior tooth defect were included. Publication bias and sensitivity analysis were also assessed. Results: 5 studies with 6720 cases were included in this meta-analysis. The results indicated that the survival rate of ceramic inlay and onlay restoration with two-surface was significantly higher than one-surface (10 years) (HR=2.11, 95%CI:1.33-3.36,P=0.002), and three-surface was higher than three-surface(HR=2.50, 95%CI:1.36-4.59,P=0.003). Conclusions: Survival rate (for 10 years) of ceramic inlays and onlays were reported, the current meta-analysis shows that the increase of surfaces increase the survival rate of inlay and onlay restorations.

Comparison of strength characteristics of direct and indirect dental restorations under uniaxial compression

An urgent task in modern restorative therapeutic dentistry is to make a decision in each specific clinical case, which is justified not only from the esthetic and medical, but also from the economic, as well as the biomechanical and ergonomic points of view. According to many authors, the key to the successful restorative treatment of hard tissue defects of any genesis is to understand the etiological causes and conditions of their occurrence, as well as to assess the size of the defect and the level of material and technical base of modern dentistry.Long-term results of esthetic restoration of teeth using the direct method with various composite materials indicated the admission of multiple errors and complications, such as inconsistency in the color and transparency of the filling; violation of the marginal adherence; and the appearance of marginal staining along the border of the composite material with the tooth tissues, both during and in various terms after treatment.In contrast to the direct method of restoration, the ceramic inlay is made indirectly. This allows reducing polymerization shrinkage, which in turn improves marginal adherence and reduces the frequency of caries recurrence.

Postless Approach for the Restoration of Nonvital Posterior Teeth: Clinical Guidelines

This article describes a case of a 42-year-old male patient who presented with a chief complaint of pain, bleeding, and disability to maintain good oral hygiene in the interproximal zones between the first and second maxillary molar. A comprehensive examination revealed a composite resin restoration in the maxillary first molar. In the interproximal zones, plaque accumulation was also detected. Radiographic examination showed a bone loss in the proximal zone. The endodontic filling was rated as good. Options of treatment were discussed. The decision of ceramic inlay was retained. The patient was satisfied thanks to a well-planned approach. The purpose of this paper is to present a simplified clinical protocol for the restoration of non-vital teeth using ceramic inlay onaly.

Effect of Two Antibacterial Luting Protocols with and without Immediate-Dentin-Bonding on Microtensile Bond Strength of Glass Ceramic to Bur-Cut Cavity Floor Dentin

SummaryBackground/Aim: The aim of this study was to evaluate the bond strength of glass ceramic inlay system using 2 antibacterial adhesive luting protocols with 2 cementation techniques to bur-cut dentin.Material and Methods: Class I inlay cavities with 6-degree occlusal divergence and size of 6-, 3- and 2-mm in length, width and depth, were prepared on extracted human molars, randomly assigned to 2 main groups; each to 1 cementation technique, with or without immediate-dentin-bonding (IDB or NIDB) further divided into 3 subgroups; 2 to 2 antibacterial luting protocols, traditional (T) and experimental (E); and 1 to a control (C) group. In group IDBT, IDB-E and IDB-C dentin bonding was applied immediately after cavity preparation. In group NIDB-T, NIDB-E and NIDB-C dentin bonding was applied just before cementation of the restorations. The cavities in IDB-T and NIDB-T were treated with 2% chlorhexidine-digluconate (CHX) prior to dentin bonding application. The cavities in IDB-E and NIDB-E were treated only with dentin bonding system containing MDPB (12-methacryloyloxydodecylpyridinium bromide) active monomer featuring antibacterial effect. IDB-C and NIDB-C served as control. Dual-cure adhesive resin cement was used for the cementation of lithium disilicate-based ceramic inlay restorations. Fourteen test specimens per group were prepared for microtensile testing and consecutively subjected to tensile load at a crosshead speed of 1 mm/min. The mode of failure was observed under SEM and evaluated for each group. The Kruskal-Wallis test was used to investigate the statistical difference between groups (α=0.05).Results: The microtensile load was 5.96 MPa (median: 5.99 MPa) for IDB-T, 7.23 MPa (median: 7.55 MPa) for IDB-E, 6.68 MPa (median: 6.56 MPa) for IDB-C, 7.24 MPa (median: 7.20 MPa) for NIDB-T, 6.98 MPa (median: 6.30 MPa) for NIDB-E, and 7.02 MPa (median: 6.99 MPa) for NIDB-C, with no statistical difference between the groups (p>0.05). SEM monitoring for mode of failure revealed either cohesive (within resin cement) or adhesive-cohesive (mostly within resin cement along with partially involved areas between resin cement and ceramic restoration) character.Conclusions: Within the limitations of the current study, none of the tested antibacterial luting protocols with either cementation technique was found to be superior in terms of bond strength.