Impact of Different Etching Strategies on Margin Integrity of Conservative Composite Restorations in Demineralized Enamel

Class-I and Class-II Restorations with the Application of a Flowable Composite as an Intermediate Layer-A Narrative Review of Clinical Trials

The objective of this review is to investigate the effect of an additional layer of flowable composite for cavity lining on the clinical outcome of direct posterior composite restorations. The PICO question (patient, intervention, comparison, and outcome) was stated as follows: Does the additional application of a flowable composite as a cavity liner improve the clinical outcome of Class-I and Class-II restorations? The electronic databases MEDLINE, Web of Science, LILAS, and BBO were assessed for identifying relevant clinical studies. After removal of duplicate records, 309 records could be identified and, after a screening of the title and abstract, 20 articles were selected for full-text analysis. Finally, six studies met the eligibility criteria and were included in this review for further investigation. Four of the included studies have a follow-up period of two years, while the other two studies had an observation period of three and seven years, respectively. No significant differences in annual failure rates were observed between restorations with and without a flowable composite liner. Consequently, the additional usage of flowable composites as a cavity liner seems to have no effect on the clinical longevity of direct composite restorations in Class-I and Class-II cavities. Therefore, the application of a flowable composite is a possible option in everyday dental clinical practice.

Effect of different techniques on removal of residual resin cement and marginal roughness of porcelain laminate veneers

STATEMENT OF PROBLEM

A consensus regarding how to effectively remove residual resin cement and polish the restoration margin during the cementation of porcelain laminate veneers (PLVs) is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of different cleaning and polishing techniques on the removal of residual resin cement and margin surface roughness of PLVs.

MATERIAL AND METHODS

PLVs were bonded to prepared buccal surfaces of extracted human premolars. All specimens were randomly divided by using a random number table into 8 groups (n=6): curette (C); brush (B); curette + polisher (CP); curette + rotary instrument (CR); curette + rotary instrument + polisher (CRP); brush + polisher (BP); brush + rotary instrument (BR); brush + rotary instrument + polisher (BRP). The relative amount of residual cement along the PLV margins were observed with a stereomicroscope and evaluated with a software program of Image J. The surface roughness and 3-dimensional (3D) morphology of the restoration margins were evaluated with a 3D topography scanner. Scanning electron microscopy (SEM) was used to detect the microscopic morphological characteristics of the restoration margins. Statistical analysis was performed by 2-way analysis of variance (α=.05).

RESULTS

Different techniques were associated with significantly different efficiencies in terms of removing residual cement and the surface roughness at the restoration margins (P<.001). The lowest relative amount of residual cement, as well as the lowest surface roughness, was detected in the BRP group (P<.001). SEM observation indicated that the BRP technique also maintained the integrity of the cement layer.

CONCLUSIONS

The removal of excess cement before polymerization using a brush, followed by sequential polishing with high-speed rotary instruments and low-speed polishers represents an effective technique in the removal of residual cement and smoothing the restoration margin without impairing the integrity of the bonded interface.

Influence of Cavity Lining on the 3-Year Clinical Outcome of Posterior Composite Restorations: A Randomized Controlled Clinical Trial

The purpose of this randomized, split-mouth-designed controlled and single-blinded clinical study was to evaluate the 3-year clinical performance of Class I and Class II resin composite restorations placed with or without cavity lining with a flowable composite. Fifty patients with treatment needs in two premolars or molars were included. One of the teeth was restored using the nanohybrid composite (Grandio®SO, control group), in the test group a high viscosity flowable composite was additionally applied as a first layer. In both groups, the same self-etch adhesive system was applied. Clinical evaluation after 3 years was carried out using the modified USPHS/Ryge criteria. At the 3-year follow-up the recall rate was 92%. Four restorations failed in the test group (8.7%), three due to the loss of vitality and one after fracture. The control group exhibited a cumulative success rate of 100%, while the test group achieved a success rate of 91.3%. This led to significant differences in the annual failure rate (AFR) between the two groups, with rates of 0% and 2.9% (p < 0.05; Mann-Whitney U-test). After 3 years the cumulative survival rate including all restorations was 95.7%. Statistical analysis revealed significant differences for the parameters: tooth vitality, marginal discoloration, success rate, and AFR. The other parameters exhibited no significant differences. Consequently, the nanohybrid composite demonstrated excellent performance over a 3-year period, whereas the utilization of a flowable composite for the cavity lining did not appear to exert a beneficial influence on clinical outcomes.

Relation between internal adaptation and degree of conversion of short-fiber reinforced resin composites applied in bulk or layered technique in deep MOD cavities

OBJECTIVE

The purpose was to evaluate the degree of conversion (DC), internal adaptation (IA) and closed porosity (CP) of short-fiber reinforced resin composites (SFRC) associated with layered or bulk restorative procedures in deep MOD cavities.

METHODS

Eighty third molars with standardized MOD cavities (5-mm-depth, 2.5-mm-width) were randomly divided into four groups and restored as follows: 1) bulk SFRC; 2) layered SFRC; 3) flowable bulk-fill resin-based composites (RBC); 4) layered conventional RBC. After one-month wet storage the samples were subjected to micro-computed tomography measurements and scanning electron microscopy to assess the IA and CP. Micro-Raman spectroscopy was used to determine the DC in different depths. Data were subjected to ANOVA and Tukey's post-hoc test, multivariate analysis and partial eta-squared statistics (p < 0.05). Pearson correlation coefficient was determined to assess the relationship among the parameters of interest.

RESULTS

Gap/total interface volume ratio ranged between 0.22-0.47%. RBCs applied in bulk revealed significantly lower gap volume (p < 0.001) and CP (p < 0.05). Each group showed complete detachment on the pulpal and partial on the lateral walls, except for group3. While the highest DC% was achieved by the conventional RBC (87.2%), followed by the flowable bulk-fill (81.2%), SFRC provided the best bottom to top DC ratio (bulk: 96.4%, layered: 98.7%). The effect of factors studied (RBC type, filling technique) on IA and DC was significant (p < 0.001).

SIGNIFICANCE

Bulk placement of RBCs exhibited lower interfacial gap volume and achieved satisfactory DC without significant correlation between these parameters. Incremental insertion of SFRC had no advantage over bulk placement in terms of IA and DC.

What causes failure of fixed orthodontic retention? - systematic review and meta-analysis of clinical studies

BACKGROUND

Orthodontic retention aims to maintain optimal teeth positions after active treatment. The stability is affected by numerous factors, including patients' individual features, thus retention should be adjusted in the most optimal way. Bonding a retainer makes retention less dependent on patient's compliance.

QUESTIONS ARISE

What wire or fiber splint type provides the best treatment stability? What materials should be used to bond the wire or fiber splint? Should be the bonding procedure be direct or indirect? The aim of the study is to assess and synthesize available controlled trials investigating failures of fixed retainers.

METHODS

Literature searches of free text and MeSH terms were performed in Scopus, Web of Science, Embase and PubMed Central in order to find studies, referring to failures of fixed retention (12th February 2021). The keywords were: ("orthodontic retainers AND failure AND wire"). The framework of this systematic review according to PICO was: Population: orthodontic patients; Intervention: fixed orthodontic retainer bonding; Comparison: Different protocols of fixed orthodontic retention applied; Outcomes: failure rate, survival rate. Three different specific scales from the Cochrane Collaboration Handbook were used, according to each study type. Additionally, a meta-analysis was conducted to compare the effectiveness of retention using fiber reinforced composite and multistranded steel wire.

RESULTS

The search identified 177 potential articles: 114 from PubMed, 41 from Scopus, 20 from Web of Science and 2 from Embase. After excluding studies inconsistent with selection criteria, 21 studies were included and subjected to qualitative analysis. The main outcome investigated was failure rate. This systematic review has some potential limitations due to the heterogeneity of design between included studies.

CONCLUSIONS

No retainer is proved to guarantee a perfect stability of dental alignment. The retainer should be bonded to all adherent teeth, preferably with additional use of bonding resin. No wire or fiber splint present superior characteristics concerning failure rate. Fiber reinforced composite retention is more sensitive to operator skills, and with imperfect bonding technique, failure rate is much higher. During the first 6 months after bonding retainer the patient should be under frequent control. The study protocol was registered in PROSPERO database with the number CRD42021233406.