Retrospective study of patients with amelogenesis imperfecta treated with different bonded restoration techniques.

OBJECTIVE: The aim of this retrospective study was to evaluate clinical success and satisfaction of patients with amelogenesis imperfecta treated with three different types of bonded restorations at a university clinic. MATERIALS AND METHODS: One hundred fifty-four restorations in 15 subjects with mean age of 17.3 years (SD 8.2) were evaluated after treatment with three different types of bonded restorations: all ceramic enamel-dentin bonded restorations, prefabricated composite veneers, and direct composite resin restorations. A modified version of the Californian Dental Association system for quality evaluation of dental care and a questionnaire assessing patient satisfaction were used for classification. The restorations were evaluated with respect to patient satisfaction, esthetics, technical, and biological complications. RESULTS: Mean observation period for the restorations was 42.5 months (SD 35.6). All restorations were in place at the time of the examination. Surface and color calibration showed a success of 95% for the ceramic enamel-dentin bonded restorations, 44% for the direct composite resin restorations, and 0% for the prefabricated composite veneers. The same pattern was evident for anatomy and marginal integrity. The subjects reported a high degree of satisfaction with both the esthetics and function of their restorations. CONCLUSION: The results indicated that all ceramic restorations demonstrated the best results for patients with amelogenesis imperfecta.

Antibacterial Properties of Nanoparticles in Dental Restorative Materials. A Systematic Review and Meta-Analysis.

Background and Objectives: Nanotechnology has become a significant area of research focused mainly on increasing the antibacterial and mechanical properties of dental materials. The aim of the present systematic review and meta-analysis was to examine and quantitatively analyze the current evidence for the addition of different nanoparticles into dental restorative materials, to determine whether their incorporation increases the antibacterial/antimicrobial properties of the materials. Materials and Methods: A literature search was performed in the Pubmed, Scopus, and Embase databases, up to December 2018, following PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guidelines for systematic reviews and meta-analyses. Results: A total of 624 papers were identified in the initial search. After screening the texts and applying inclusion criteria, only 11 of these were selected for quantitative analysis. The incorporation of nanoparticles led to a significant increase (p-value <0.01) in the antibacterial capacity of all the dental materials synthesized in comparison with control materials. Conclusions: The incorporation of nanoparticles into dental restorative materials was a favorable option; the antibacterial activity of nanoparticle-modified dental materials was significantly higher compared with the original unmodified materials, TiO2 nanoparticles providing the greatest benefits. However, the high heterogeneity among the articles reviewed points to the need for further research and the application of standardized research protocols.

Effect of zirconia surface treatment, resin cement and aging on the load-bearing capacity under fatigue of thin simplified full-contour Y-TZP restorations.

This study investigated the effect of zirconia surface treatment (air-abrasion with aluminum oxide or tribochemical silica coating) and aging on the fatigue behavior of thin monolithic Y-TZP (yttria-stabilized tetragonal zirconia polycrystal) restorations cemented with 2 types of resin cements, containing or not containing MDP, to a dentin-like substrate. Y-TZP ceramic (Zenostar T, diameter (Ø) 10 mm, 0.7 mm thick) and dentin-like discs (Ø 10 mm, 2.8 mm thick) were assigned into eight groups according to three factors: 'zirconia surface treatment' (aluminum oxide particles air-abrasion 'AO'; or tribochemical silica coating via silica-coated aluminum trioxide particles air-abrasion + silanization 'SC'); 'MDP-containing resin cement' (with: Panavia F2.0, 'MDP'; or without: Multilink Automix, 'nMDP'); and 'aging' (baseline; or aged - 'AG':12,000 thermal cycles + 60 days water storage). Y-TZP intaglio surface was conditioned and dentin-like substrate was etched with hydrofluoric acid prior to bonding. Aging was performed in half of the specimens before the fatigue testing (Staircase, 20 Hz; 250,000 cycles). Fractographic and topographic characteristics were analyzed by stereomicroscope and SEM. Prior to aging, no significant difference was found between the two surface treatments, irrespective to the cement. Samples bonded with resin cement containing MDP had a significant reduction in their fatigue failure load when Y-TZP was air-abraded with aluminum oxide particles and subjected to aging (MDP-AO = 2050.71A; MDP-AO/AG = 1756.67B). Other studied conditions were not affected by aging. Topographic images revealed a rougher surface for aluminum oxide air-abrasion. Fractography supports all failures as a radial crack starting at the Y-TZP intaglio surface. Bonded thin simplified Y-TZP restorations had a high load-bearing capacity, regardless of the studied factors. The MDP-containing resin cement applied on aluminum oxide air-abraded zirconia surface was not enough to maintain the fatigue performance after aging, while higher stability to aging was achieved by treating with the tribochemical silica coating method. When using MDP-free resin cement, the surface treatment and the aging did not impact the fatigue performance.

Quantifying machining outputs of pristine human teeth relevant to dental preparation procedures.

Minimally-assisted tooth repair (MaTR) systems are envisioned to be capable of substituting for the skill of a dentist. If successfully developed, MaTR systems could enable lower-skilled dental technicians to provide dental care at a fraction of the overall medical cost. This paper explores a key initial step towards the development of such systems by quantifying the machining responses of pristine human teeth relevant to dental preparation procedures. The working hypothesis of the study is that such findings will enable the benchmarking of key process planning and control metrics relevant for the future development of MaTR systems. To this end, pristine human cadaver teeth were cut using a computer-controlled motion platform and dental hand-piece. Relevant cutting responses, such as cutting forces, in-process rotational speed of the dental bur, teeth morphology, and bur wear were captured. The trends in cutting forces show the potential for implementing region-specific process parameters for cutting the enamel and dentin regions of the tooth. A feed-per-tooth value of 0.1 µm at rotational speeds of 8 krpm and 50 krpm is seen to cut both the enamel and dentin regions at cutting forces lower than patient discomfort thresholds identified in literature. Cutting force signals were also successfully mapped against the CT-scan data of the tooth. This mapping indicates a clear identification of the enamel/dentin regions, and a transition region that is dependent on cutting parameters, tooth/tool geometry and tool pose. The trends in the in-process rotational speed of the dental bur indicate that stalling of the dental bur occurs at feed per tooth values greater than 0.25 µm. The evidence of stalling can be detected by both a drop in the cutting force signal and by surface morphology changes on the cut surface of the tooth. MaTR systems should be designed to avoid bur stalling regions by either operating at feed per tooth values ≤ 0.25 µm or by the use of dental spindles with higher torque capacity. Lastly, the type of fit present on the shank of the bur is seen to result in differences in the cutting force signals and wear of the cutting edges (flutes) of the dental bur. In general, a right-angle (RA) fit on the shank of the dental bur results in a larger tool runout leading to uneven loads on the flutes and increased tool wear. The friction grip (FG) fit avoids these problems and may be more suited for MaTR systems.

The effect of abrading and cutting instruments on machinability of dental ceramics.

The aim was to investigate the effect of machining instruments on machinability of dental ceramics. Four dental ceramics, including two zirconia ceramics were machined by three types (SiC, diamond vitrified, and diamond sintered) of wheels with a hand-piece engine and two types (diamond and carbide) of burs with a high-speed air turbine. The machining conditions used were abrading speeds of 10,000 and 15,000 r.p.m. with abrading force of 100 gf for the hand-piece engine, and a pressure of 200 kPa and a cutting force of 80 gf for the air-turbine hand-piece. The machinability efficiency was evaluated by volume losses after machining the ceramics. A high-abrading speed had high-abrading efficiency (high-volume loss) compared to low-abrading speed in all abrading instruments used. The diamond vitrified wheels demonstrated higher volume loss for two zirconia ceramics than those of SiC and diamond sintered wheels. When the high-speed air-turbine instruments were used, the diamond points showed higher volume losses compared to the carbide burs for one ceramic and two zirconia ceramics with high-mechanical properties. The results of this study indicated that the machinability of dental ceramics depends on the mechanical and physical properties of dental ceramics and machining instruments. The abrading wheels show autogenous action of abrasive grains, in which ground abrasive grains drop out from the binder during abrasion, then the binder follow to wear out, subsequently new abrasive grains come out onto the instrument surface (autogenous action) and increase the grinding amount (volume loss) of grinding materials.

Comparative Study on the Cutting Effectiveness and Heat Generation of Rotary Instruments Versus Piezoelectric Surgery Tips Using Scanning Electron Microscopy and Thermal Analysis.

PURPOSE: The search for optimizing rehabilitation results with the use of osseointegrated implants has led oral surgeons to look for other technologies that can provide better predictability for treatments; however, effectiveness must be considered as well. This study aimed to compare temperature variation during preparation of implant surgical beds using conventional rotary implant burs versus ultrasonic tips and to study perforation effectiveness by analyzing the functional wear of both systems and the influence of such wear on the overheating of cortical bone. MATERIALS AND METHODS: This evaluation was made using thermocouples placed in fresh bovine cortical bone (femur) and connected to a data collector so that the recorded temperatures could provide the thermal behavior of both systems after repeated use of the burs and piezoelectric tips, to compare the wear and the loss of cutting efficiency. Scanning electron microscopy (SEM) was used to compare the topography of both systems' perforations. Biostatistics assays were performed comparing both techniques as well. RESULTS: The collected data and images showed that the wear of the burs and tips did not significantly influence the temperature variation, and the greatest variation occurred in the piezoelectric system for preparations of 13-mm depth. The SEM images show a different surface topography between both systems. While the burs cut the bone, showing a smooth surface, the piezoelectric tips condense the bone and present a rough surface. CONCLUSION: The use of either rotatory burs or piezoelectric tips generates a temperature that does not affect the tissue healing. Burs create a smooth surface, and piezoelectric tips show a more rough and condensed bone surface. The wear of both systems does not have a relevant increase in temperature after the preparation of 30 surgical beds.

Glass-ionomer Cements in Restorative Dentistry: A Critical Appraisal.

Glass-ionomer cements (GICs) are mainstream restorative materials that are bioactive and have a wide range of uses, such as lining, bonding, sealing, luting or restoring a tooth. Although the major characteristics of GICs for the wider applications in dentistry are adhesion to tooth structure, fluoride releasing capacity and tooth-colored restorations, the sensitivity to moisture, inherent opacity, long-term wear and strength are not as adequate as desired. They have undergone remarkable changes in their composition, such as the addition of metallic ions or resin components to their composition, which contributed to improve their physical properties and diversified their use as a restorative material of great clinical applicability. The light-cured polymer reinforced materials appear to have substantial benefits, while retaining the advantages of fluoride release and adhesion. Further research should be directed towards improving the properties, such as strength and esthetics without altering its inherent qualities, such as adhesion and fluoride releasing capabilities.

Is mechanical retention for adhesive core build-up needed to restore a vital tooth with a monolithic zirconium crown? - An in vitro study.

PURPOSE: To show the influence of retentive cavity, cavity wall preparation and different luting techniques on the fracture resistance of severely damaged teeth restored with adhesive core build-ups and monolithic zirconium crowns. METHODS: Extracted molars were prepared with 2 mm ferrule height and divided into eleven groups (n = 8/group). In nine groups a retentive occlusal cavity with a width and depth of 1 or 2 mm was prepared. Two control groups without a retentive cavity were made. Zirconium crowns were manufactured. 48 copings were cemented with glass-ionomer cement (Ketac Cem), the others (n = 40) with adhesive resin cement (Panavia F 2.0). Artificial ageing was carried out in the following way: n = 88, thermocycling (10,000 cycles, 6° C/60° C), n = 80 chewing simulation (1,200,000 cycles, 64 N). The samples were tested for load at first damage and fracture load with non-axial force. For statistical analysis ANCOVA with post hoc, Bonferroni-adjusted t-test were used ( p ≤ 0.05). RESULTS: No differences between the tested cements were detected. Influence of the cavity wall thickness was significant ( p = 0.001). Mostly, the samples with wall thickness of 2 mm showed better results. Both control groups (no cavity) showed results comparable to study groups with cavity. CONCLUSIONS: Retentive cavity is most likely not mandatory. However, if prepared, the cavity wall thickness is of higher importance than cavity depth. Glass-ionomer and adhesive resin cement are comparable for use with zirconia crowns.

Influence of repair procedure on composite-to-composite microtensile bond strength.

PURPOSE: To investigate the effect of different repair procedures and storage time on microtensile bond strength (µTBS) of a resin composite to an older one from a simulated previous restoration. METHODS: Composite disks were made by layering 2 mm-thick increments of a nanohybrid composite (Grandio) shade A1 in a Teflon mold (4 x 8 mm). Afterwards, they were light-cured and stored (37 degrees C/7 days) in a saline solution. Specimens were randomly divided into groups according to the surface treatment applied: (1) Composite surface was roughened with a bur (Cimara) and Solobond Plus adhesive was applied; (2) Sandblasting with 27 µm aluminum oxide particles (KaVo Rondoflex), and adhesive application; (3) Air-abrasion with 30 µm alumina particles coated with silica (CoJet Sand), silane (Monobond-S) and adhesive application; (4) Negative control group with only adhesive application. Afterwards, Grandio composite (shade A3.5) was packed incrementally on the treated surface obtaining another disk (4 x 8 mm). Repaired blocks were stored (24 hours or 6 months) and afterwards µTBS test was performed and failure mode was evaluated. Also, beams obtained from 8 mm-high composite blocks without any surface treatment were immediately submitted to µTBS test to determine Grandio composite cohesive bond strength (positive control group). Data were analyzed using ANOVA and Tukey's test (P < 0.05). RESULTS: The repair procedure affected µTBS values (P < 0.001) while neither storage time nor interactions did (P > 0.05). All repair procedures achieved bond strength values higher than the negative control group but they did not reach the composite's cohesive bond strength. The overall conclusion was that an increased superficial roughness by means of a bur, silica coating or alumina sandblasting improved µTBS of the repaired composite and bond strength remained stable after 6 months.

[Currently Recommended Restorative Materials in Modern Conservative Dentistry]. / Aktualnie zalecane materialy odtwórcze w nowoczesnej stomatologii zachowawczej.

Conservative treatment which restores the function, aesthetics and protects remaining tooth structure, and what is the most important, the viability of the tooth pulp, is still needed. Dental fillings replace specialized tissues of the tooth that have been lost due to caries or injury. Any decision concerning the use of a particular restorative material should be individualized and based on the competence regarding the composition, properties and characteristics of the specific restorative material. This requires continuous updating of knowledge about available dental materials as well as education of patients who, according to actual models of dental care, should be active partners in the therapeutic process. The selection of restorative materials is often related to financial abilities of the patients, and more generally to the economic model of organized health care in a particular country. Nowadays, amalgam is increasingly dislodged by adhesive materials which permit to save more tooth structure and allow to preserve natural teeth for a longer time. In the nearest future we can expect further development of minimally invasive techniques and improvements of restorative materials, especially their mechanical properties like strength and wear resistance as well as biocompatibility. The article presents restorative materials used in modern dentistry.

Effect of Diamond Bur Grit Size on Composite Repair.

PURPOSE: This study investigated the effect of diamond bur grit size on the repair bond strength of fresh and aged resin composites. MATERIALS AND METHODS: Blocks of microhybrid composite (Opallis, FGM) were stored in distilled water at 37°C for 24 h (fresh composite) or subjected to 5000 thermal cycles (aged composite). The surfaces were roughened using diamond-coated, flame-shaped carbide burs with medium grit (#3168), fine grit (#3168F), or extra-fine grit (#3168FF). The control group underwent no surface treatment. Surface roughness, water contact angle, and surface topography by scanning electron microscopy (SEM) were evaluated (n = 3). Samples were restored with resin composite and sectioned into beam-shaped specimens, which were subjected to microtensile bond testing. Failure modes were classified using a stereomicroscope. Data were statistically analyzed using the Student- Newman-Keuls test and two-way ANOVA, with significance set at p < 0.05. RESULTS: Higher surface roughness was observed for groups treated with the medium- and fine-grit burs; aged composites were rougher than fresh composites. The water contact angle formed on the aged composite was lower than that on the fresh composite. The highest repair bond strength was observed for the fine-grit bur group, and the lowest was recorded for control. Interfacial failures were more predominant. SEM images showed that the surfaces treated with fine- and extra-fine-grit burs had a more irregular topography. CONCLUSION: Surface roughening of fresh or aged resin composites with diamond burs improved retention of the repair material. Fine-grit burs generally performed better than medium- and extra-fine-grit burs.

Matrixing for MID success.

The proper use of matrices can lead to successful, stable dental restorations. Their importance is further advanced in MID restorations. The 3 Cs of contour, contact, and control properly exercised with correct placement of matrices can enhance the long-term success of any restoration. Matrices create healthy gingival contours, mimic natural tooth contours, and also create good healthy contacts. All of these benefits can be achieved while controlling the flow of bonding products from the gums and keeping sulcular fluids from contaminating the bonding surfaces.

Discrimination of tooth layers and dental restorative materials using cutting sounds.

Dental restoration begins with removing carries and affected tissues with air-turbine rotary cutting handpieces, and later restoring the lost tissues with appropriate restorative materials to retain the functionality. Most restoration materials eventually fail as they age and need to be replaced. One of the difficulties in replacing failing restorations is discerning the boundary of restorative materials, which causes inadvertent removal of healthy tooth layers. Developing an objective and sensor-based method is a promising approach to monitor dental restorative operations and to prevent excessive tooth losses. This paper has analyzed cutting sounds of an air-turbine handpiece to discriminate between tooth layers and two commonly used restorative materials, amalgam and composite. Support vector machines were employed for classification, and the averaged short-time Fourier transform coefficients were selected as the features. The classifier performance was evaluated from different aspects such as the number of features, feature scaling methods, classification schemes, and utilized kernels. The total classification accuracies were 89% and 92% for cases included composite and amalgam materials, respectively. The obtained results indicated the feasibility and effectiveness of the proposed method.