Background The purpose of this in vitro study was to evaluate the effect of the percentages of preserved enamel on ceramic laminate veneers’ (CLVs) shear bond strength (SBS). Methods Seventy extracted human maxillary central incisors were scanned and reconstructed into three-dimensional models. The extracted teeth were then embedded and randomly divided into seven groups (n = 10 per group). Based on digital analyses of the three-dimensional models, guided tooth preparation and bonding procedures were performed individually to form seven different percentages (100%, 80%, 60% 50%, 40%, 20% and 0%) of remaining enamel thickness on the bonding surface. Finally, the SBS test was performed, and the data were statistically analysed by one-way ANOVA with LSD post hoc test (α = 0.05). Results The complete enamel surface exhibited the highest SBS (19.93 ± 4.55 MPa), followed by 80% enamel (19.03 ± 3.66 MPa), 60% enamel (18.44 ± 3.65 MPa), 50% enamel (18.18 ± 3.41 MPa), 40% enamel (17.83 ± 3.01 MPa) and 20% enamel (11.32 ± 3.42 MPa) group. The lowest SBS (9.63 ± 3.46 MPa) was detected in 0% enamel group. No significant difference was observed among the 40–100% enamel groups, while the 20% or 0% enamel group demonstrated a significantly lower mean SBS than the 40% enamel group (p < 0.05). Conclusion The SBS value of CLVs bonded to 100% enamel on the finishing surfaces (nearly 20 MPa) was twice that which bonded to 0% enamel (nearly 10 MPa). Bonding to 100% enamel is the most reliable treatment. When dentin exposure is inevitable, enamel should be preserved as much as possible to maintain good bonding. In addition, 40% of preserved enamel on the bonding surface was the minimal acceptable value to fulfil the requirements of good bonding strength.
To describe a digital workflow for creating a provisional restoration by using an extracted tooth rapidly, finally fixing the provisional restoration in the targeted position precisely and preserving the natural emergence profile from the time of provisional restoration to final restoration. Clinical considerations:The use of extracted tooth as an immediate provisional restoration is an effective method for preserving the shape of the emergence profile. However, the existing methods for creating a provisional restoration by using natural tooth are time-consuming and there is no reliable method to precisely attach tooth to temporary abutment. This case demonstrates a new method for using patient's natural tooth as an immediate provisional restoration under a sequence of guides, which significantly reduces the chair-side time and inconvenience for clinicians and patients. Immediate provisional restoration contributes to preserving the soft tissue architecture after post-extraction implant placement, especially when using the patient's tooth as a provisional restoration. Digital technology can help to improve the chair-side clinical efficiency of dentist.Clinical significance: Maintaining the natural soft tissue architecture is a huge challenge in dental implantology. Use of the extracted tooth as a provisional restoration is likely to achieve an optimal outcome. And digital technology is helpful to the efficiency and accuracy of treatment.
Using composite resin restoration of full‐coverage crowns to obtain a completely symmetrical esthetic restoration of individual central incisors remains difficult. Freehand direct composite resin restoration is challenging even for highly skilled dentists. This clinical report describes a digital protocol for achieving symmetrical restoration of two central incisors using a custom‐designed, two‐in‐one template.
Background Using a rotary instrument or ultrasonic instrument for tooth preparation is a basic operation in the dental clinic that can produce a significant number of droplets and aerosols. The dental droplet and aerosol can lead to the transfer of harmful germs. The goal of this study was to analyze the properties of microbiological aerosol created by droplets and aerosol generated by three common tooth-preparation instruments. Methods Streptococcus mutans UA159 was used as the biological tracer to visualize the droplets and aerosols. The passive sampling method was used to map the three-dimensional spatial distribution and the six-stage Andersen microbial sampler (AMS) was used as the active sampling method to catch aerosol particles at a specific time. Results The aerosol concentration is related to instruments, three-dimensional spatial distribution, and dissipation time. Most aerosols were generated by air turbines. More microorganisms are concentrated at the 1.5 m plane. The majority of the post dental procedure contamination was detected within the 0–10-min period and it decreased rapidly within 30 min. Conclusion This study is conducive to the proposal and improvement of relevant infection control measures in dental procedures and provides a basis for the assessment of measures, reducing the risk of nosocomial infection.
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