An interventional study of Hydrofluoric Acid-Etched Lithium Disilicate Ceramic Dental Crowns and Atmospheric-Pressure Plasma-Treated Lithium Disilicate Ceramic Dental Crowns in Prosthodontics, Dental Adhesives/Restorations Performance and Crowned Posterior Teeth, sponsored by University of Ljubljana, Faculty of Medicine. Recruiting at 1 site in Slovenia. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-15.
Sponsored by University of Ljubljana, Faculty of Medicine · Not applicable, Interventional, and Treatment
In this randomized, controlled, double-blind clinical trial, we will follow adult participants who receive partial or full dental crowns made of lithium disilicate ceramic (LDC). Before the crowns are permanently attached to teeth, those in the control group will be etched with hydrofluoric acid (HF) according to the standard laboratory protocol, while those in the intervention group will undergo an innovative surface treatment with atmospheric-pressure nonthermal plasma (APP).
The goal of this study is to determine whether the innovative APP pretreatment of LDC crowns can result in outcomes comparable to or better than those achieved with the standard HF treatment, including:
Participants will be asked to attend scheduled follow-up visits 1 week and 1, 3, 6, and 12 months after the crowns are cemented. At each visit:
Lithium disilicate ceramic (LDC) is widely used for partial- and full-coverage fixed dental restorations because of its favorable mechanical and optical properties. The long-term clinical performance of these restorations depends on several factors, including appropriate surface treatment before their permanent attachment to teeth.
Hydrofluoric acid (HF) etching is an established method for conditioning glass-ceramic dental restorations before adhesive cementation. The treatment modifies the ceramic surface by selectively removing the glassy phase, which enables micromechanical retention of the resin cement. Despite its established clinical and laboratory use, HF is a highly corrosive and toxic substance and requires careful handling to avoid injuries and environmental damage.
According to preclinical studies, surface treatment with atmospheric-pressure nonthermal plasma (APP) may represent an alternative to conventional HF etching. APP treatment can modify surface properties of LDC, including surface elemental composition, roughness and wettability, and thus improve the resin-ceramic bond. However, clinical evidence regarding the long-term performance of LDC restorations treated with APP is limited.
The present clinical trial will evaluate whether the innovative APP treatment of LDC restorations before cementation results in clinical outcomes comparable or superior to those achieved with conventional HF etching of these restorations. Particular emphasis will be placed on participants' self-reported oral health-related quality of life and the clinical performance and survival of the restorations.
Participants will be randomized to receive either conventionally or experimentally treated crowns. In both groups, full- and partial-coverage crowns will be designed digitally on three-dimensional models obtained through intraoral scanning and then milled from presintered monochromatic blocks of lithium disilicate ceramic (e.max CAD, Ivoclar Vivadent). For the etching of ceramic in the control group, a commercially available etchant gel containing 9,5 % HF will be used (IPS Ceramic Etching-gel, Ivoclar Vivadent). The crowns will be rinsed and ultrasonically cleaned after the etching. In the experimental group, the crowns will be treated with APP in atmospheric conditions for several minutes using a commercially available plasma pen (kINPen IND, Neoplas control GmbH) and argon as source gas. Application of a silane-coupling agent will follow the surface treatment in both groups. Within two hours after the treatment, the crowns will be attached to participants' teeth following the standard clinical protocol using a composite resin cement (Variolink Esthetic DC for partial-coverage crowns and Multilink Automix for full-coverage crowns, Ivoclar Vivadent) and a compatible dentin adhesive system.
Participants will attend scheduled follow-up visits according to the follow-up plan. Clinical examination for complications associated with the prosthetic restorations will follow the study protocol, whereas the oral health-related quality of life will be evaluated using the Oral Health Impact Profile (OHIP) questionnaire, containing 49 multiple-choice questions regarding the participants' oral health in the last week.
If it turns out that APP treatment provides clinical outcomes comparable to or superior to conventional HF etching, it could represent an alternative approach for conditioning LDC restorations before adhesive cementation and may become part of a new standard cementation protocol.
University of Ljubljana, Faculty of Medicine is the lead sponsor of 18 studies on the registry; 3 are open to participants now.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants receive partial- or full-coverage lithium disilicate ceramic (LDC) crowns that undergo atmospheric-pressure nonthermal plasma (APP) surface treatment before their permanent attachment to teeth (adhesive cementation). The APP treatment is performed in a dental laboratory up to two hours before cementation using a pencil-type plasma torch under atmospheric conditions with argon as the source gas. Immediately after the treatment, a silane-coupling agent is applied onto the intaglio surface of crowns in the same manner as provided by the established clinical protocol. The APP-treated LDC crowns are then cemented on teeth according to the standard clinical protocol using composite resin cement, making the plasma treatment the only difference from the study's control arm (HF-treated crowns). The participants are blinded to the type of crown pretreatment and comply to the same follow-up visit schedule as in the control arm.
Device: Atmospheric-Pressure Plasma-Treated Lithium Disilicate Ceramic Dental Crowns
Participants receive partial- or full-coverage lithium disilicate ceramic crowns (LDC) that are etched with hydrofluoric acid (HF) before their permanent attachment to teeth (adhesive cementation). The HF etching is performed in a dental laboratory up to two hours before cementation using a commercially available ceramic etching gel (9.5% HF, 20 seconds). After rinsing off the acid, the crowns undergo a 5-minute ultrasonic bath to get cleaned of any acid residues. The crowns are then dried with compressed air and a silane-coupling agent is applied onto the intaglio surface in the same manner as provided by the established clinical protocol. The HF-etched LDC crowns are then cemented on teeth according to the standard clinical protocol using composite resin cement, making the HF etching the only difference from the study's control. The participants are blinded to the type of crown pretreatment and comply to the same follow-up visit schedule.
Device: Hydrofluoric Acid-Etched Lithium Disilicate Ceramic Dental Crowns
* Full-coverage single dental crowns or partial-coverage dental crowns, covering the entire occlusal surface (onlays, overlays), * fabricated from lithium disilicate ceramic using computer-assisted milling, * used to restore posterior teeth (premolars and molars) with vital dental pulp, * etched with hydrofluoric acid and silanized before adhesive cementation, as part of the conventional clinical protocol.
Also known as: HF-etched LDC crowns, HF-etched LDC restorations, HF-treated LDC crowns, HF-pretreated LDC crowns, acid-etched dental crowns, crowns made of dental silicate ceramics, HF-treated crowns made of lithium-disilicate glass ceramic, HF-etched ceramic onlays, HF-etched ceramic overlays
* Full-coverage single dental crowns or partial-coverage dental crowns, covering the entire occlusal surface (onlays, overlays), * fabricated from lithium disilicate ceramic using computer-assisted milling, * used to restore posterior teeth (premolars and molars) with vital dental pulp, * treated with atmospheric-pressure gaseous plasma and silanized before adhesive cementation
Also known as: APP-treated LDC crowns, APP-treated LDC restorations, plasma-treated LDC crowns, NTAP-treated LDC crowns, nonthermal atmospheric-pressure plasma-treated LDC crowns, atmospheric plasma-treated LDC crowns, APP-treated crowns made of lithium-disilicate glass ceramic, APP-treated ceramic onlays, APP-treated ceramic overlays, plasma-treated ceramic onlays
Change from Baseline in Oral Health-Related Quality of Life (OHIP Score)
Oral health-related quality of life (OHRQoL) will be assessed using the Oral Health Impact Profile (OHIP-49), a validated 49-item questionnaire designed to measure the impact of oral health conditions on an individual's well-being and daily functioning. Participants will report the frequency of oral health-related problems experienced during the previous 7 days. Responses are scored using a Likert-type scale, with higher scores indicating a greater negative impact of oral health on quality of life. OHIP-49 scores will be calculated at each assessment, and changes in score from baseline will be determined at each follow-up time point. The primary outcome will be the change in OHIP-49 score from baseline to each follow-up assessment after crown cementation. Changes in OHIP-49 scores over time will be compared between the intervention group (APP-treated crowns) and the control group (HF-etched crowns).
Time frame: The OHIP questionnaire will be completed by each participant before prosthodontic rehabilitation, at the time of enrollment, and at each scheduled follow-up visit: 1 week and 1, 3, 6, and 12 months after crown cementation.
Clinical Success of Partial- and Full-Coverage Dental Crowns Made of Lithium Disilicate Ceramic
The presence or absence of material, technical, or biological complications associated with the cemented lithium disilicate ceramic (LDC) dental crowns will be recorded at each scheduled follow-up visit. Clinical examinations will be performed according to a standardized study protocol to identify any potential complications. Clinical success will be defined as the absence of material, technical, or biological complications associated with the crown. The cumulative probability of clinical success over the follow-up period will be estimated using Kaplan-Meier analysis. Clinical success will be compared between the intervention group (APP-treated crowns) and the control group (HF-etched crowns).
Time frame: Presence or absence of material, technical and biological complications associated with the cemented LDC dental crowns will be recorded at each scheduled follow-up visit: 1 week and 1, 3, 6, and 12 months after crown cementation.
Clinical Survival of Partial- and Full-Coverage Dental Crowns Made of Lithium Disilicate Ceramic
The presence or absence of the cemented LDC crowns in situ will be recorded at each scheduled follow-up visit. Clinical survival will be defined as the crown remaining in situ and in function, without a serious complication that would require removal or replacement of the crown. The cumulative probability of clinical survival over the follow-up period will be estimated using Kaplan-Meier analysis. Clinical survival will be compared between the intervention group (APP-treated crowns) and the control group (HF-etched crowns).
Time frame: The presence or absence of the cemented LDC dental crowns in situ will be assessed at each scheduled follow-up visit: 1 week and 1, 3, 6, and 12 months after crown cementation.
Incidence of Complications Associated with Partial- and Full-Coverage Dental Crowns Made of Lithium Disilicate Ceramic
The general incidence of complications related to golden standard treated (HF-etched) LDC crowns will be assessed during the follow-up period to provide new scientific evidence on the incidence of complications associated with single tooth LDC restorations. The incidence of complications will be defined as the appearance of new material, technical, or biological complications among the HF-etched LDC crowns during the 12-month follow-up period or between two different follow-up time points.
Time frame: The presence or absence of any material, technical, and biological complications will be recorded at each scheduled follow-up visit: at 1 week, and 1, 3, 6, and 12 months after crown cementation.
Plan to share: No
Start is estimated for Sep 2026; primary completion for Sep 2029, 36 months later.
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University of Ljubljana, Faculty of Medicine