Performance of CAD/CAM Milled and 3D-printed Full-arch Implant-supported Provisionals Restorations

BACKGROUND

Since the discovery of osseointegration by Professor Branemark, dental implants have been introduced into clinical practice and are currently one of the most demanded treatments, being considered the first choice for the rehabilitation of patients with partial or total edentulism. Of all of them, the rehabilitation of the completely edentulous patient is one of the greatest challenges for the professional, since it requires meticulous planning to restore the patient's function and improve esthetics.

In this regard, the introduction of CAD/CAM technology has been a major breakthrough since it allows, as its name suggests, computer assistance in the design and fabrication phase. Its inclusion in the design phase facilitates this process and communication between the clinician and the laboratory with the design file, which could be re-fabricated if there are any complications. P or its use at the manufacturing stage decreases the influence of the laboratory technician's skill and allows the use of new materials. To date, these new materials have been manufactured by milling from a solid disk, the most commonly used materials being polymethylmethacrylate (PMMA) and polyoxymethylene (POM).

In recent years, the industry has focused its efforts on manufacturing by additive technology, by 3D printing, which has different advantages compared to subtractive technology or milling; such as, for example, the greater use of the material or the reduced limitations when manufacturing geometries where milling cannot reach. Gradually, new materials for 3D printing are appearing, with more applications, being already possible the fabrication of models, removable prostheses, gingival masks, unloading splints, and long-lasting temporary prostheses, or surgical guides. Recently, a new material has appeared, whose properties could be comparable to those of the materials used today as temporaries, mainly polymethylmethacrylate (PMMA), which is made by milling from solid blocks.

JUSTIFICATION

The emergence of new biocompatible 3D printing materials- indicated even for definitive restorations, with mechanical properties similar to the materials currently used as temporary materials- raises the use of this fabrication technique for long-lasting temporary materials.

HYPOTHESIS

Null hypothesis (H0): There are no differences in the mechanical behavior and optical properties of the materials used as provisional material in full-arch restorations on implants manufactured by CAD/CAM technology by machining or 3D printing.

Alternative hypothesis (H1): There are differences in the mechanical behavior and optical properties of the materials used as provisional materials in full-arch restorations on implants fabricated by CAD/CAM technology through machining or 3D printing.

OBJECTIVES

General Objective:

To compare the mechanical behavior and optical properties of the materials used as provisional material in full-arch restorations on implants manufactured by CAD/CAM technology, by machining or 3D printing.

Specific Objectives:

• To analyze the mechanical behavior and the absence of complications, fracture of the structure, material jumping or wear, loosening or debonding of the materials used as provisional material in full-arch restorations on implants manufactured by CAD/CAM technology, by machining or 3D printing.
• To analyze the optical properties, initial color, and degradation of the materials used as provisional material in full-arch restorations on implants manufactured by CAD/CAM technology, by machining or 3D printing.

MATERIAL AND METHODS

The research protocol was reviewed and approved by the Hospital Clínico San Carlos ethics committee, which served the Faculty of Dentistry of the Complutense University of Madrid (22/170- EC_P).

Study design:

Prospective parallel-group randomized controlled clinical study following CONSORT guidelines.

Reference and study population:

The study population will consist of patients seen at the Advanced Implant Prosthetics Clinic of the Complutense University of Madrid, of both sexes, over 18 years of age, edentulous upper, lower, or both jaws, whose treatment plan is at least a full-arch implant-supported fixed restoration (at least from right first molar to left first molar) and who meet all the inclusion criteria but none of the exclusion criteria.

Once the informed consent has been read and explained, and any possible doubts regarding the treatment and the study have been resolved, patients must give their written informed consent to participate in the study prior to any study-related procedure.

Data collection and information sources:

The data required for this study will be collected by a single investigator, using a case report form (CRF) for all patients from whom we obtain informed consent is obtained. First name initials will be used to code and track information for each patient. Also, will be coded numerically for each interim as the subject of study during the conduct of the study.

The patient will not know what temporary material the temporary restoration is made of.

• Demographic data: Subject demographics, including age, sex, and smoking habit, will be documented at the screening visit. Smoking habits will be classified in:

• Non-smoker.
• Smoker:

• Mild: 5 or fewer cigarettes a day or one cigar a day.
• Moderate: 6 to 15 cigarettes per day.
• Severe: more than 16 cigarettes per day on average or more than one cigar per day (note: exclusion criteria).
• Electronic cigarette consumer.
• General health status and dental history: General health status and dental history will be obtained at the screening visit. The investigator will assess relevant medical history and current medical conditions, based on available information, and classify the patient according to the ASA physical status classification system (18). Information may be obtained from the subject's general practitioner or from oral communication with the subject.

General health subjects' will be classified into:

• ASA I: Normal healthy patient (no acute or chronic diseases), healthy, non-smoker, no or minimal alcohol consumption. BMI and normal percentile for age.
• ASA II: Patient with mild systemic disease (only without substantial functional limitations), including current smokers, social alcohol drinkers, pregnant and/or patients with obesity, well-controlled DM/HTA, and mild pulmonary disease.
• ASA III: A patient with severe systemic disease (note: exclusion criteria). o ASA IV: A patient with a severe systemic illness that poses a constant threat to life (note: exclusion criteria).
• ASA V: A dying patient who is not expected to survive surgery (note: exclusion criteria).

Dental history:

• Indicate reasons for dental losses or extractions of the jaw to be rehabilitated.
• Indicate the presence of severe bruxing or clenching habits (note: exclusion criteria).

Diagnostic imaging: A panoramic radiograph should be available at the screening visit to evaluate anatomical structures and dentition. E n case it is available, it will be used for treatment planning. The panoramic radiograph may be taken during the screening visit or be available from an earlier date within 6 months.

STATISTICAL ANALYSIS

The variables will be recorded in a Microsoft Excel spreadsheet and analyzed by professional statisticians using specific software (IBM SPSS Statistics, v25 for Windows; IBM Corp.). The statistical analysis will include tests to determine whether the distribution of the data complies with normality principles (Shapiro- Wilk test) and then perform the inferential analysis. For the analysis of the optical behavior, a t-student for related samples will be used, and for the analysis of the mechanical behavior data, a repeated measures analysis of variance (ANOVA) will be used. Once it has been checked in an a priori test whether there are statistically significant differences, if they appear, a posteriori test (Tuckey test) will be performed to determine between which groups they occur.

STUDY LIMITATIONS

One of the study's main limitations is the recruitment of patients since completely edentulous patients are increasingly less prevalent in our society. In addition, they must be in good health and have good bone availability, which makes them susceptible to inclusion in the study. On the other hand, planning for this type of patient is laborious and often requires previous treatments (such as extractions or basic periodontal treatment) that lengthen the treatment time.

CHRONOGRAM / WORK PLAN

• January 2022 - February 2022: Study design, obtain ethics committee approval.
• March 2022 -April 2025: Patient treatment and data collection.
• April 2025 - July 2025: Data analysis and statistical study.
• September 2025 - December 2025: Report writing and possible manuscripts for publication in indexed journals.

PROTOCOL AMENDMENTS

Protocol changes will be kept to a minimum. Only those changes that are deemed essential to the successful completion of the protocol will be considered.

PUBLICATION RIGHTS

Analysis of data will be conducted by Data Management. The final manuscript will be prepared by the principal investigator in conjunction with sub-investigators and submitted for publication. Additionally, the results of the study will be entered on clinicaltrials.gov.

If it's decided on the future sharing of the IPD the following data will be shared and available:

• Participant's data that underlie the results reported in this article, after deidentification (text, tables, figures).
• The data and protocols may be only available to investigators and researchers who provide a methodologically sound proposal for individual participant data meta-analysis.

Inclusion criteria

• Males and females at least 18 years of age.
• Healthy patients; ASA I or ASA II.
• Maxillary, mandibular, or both maxillary edentulous patients whose prosthetic treatment plan is a full-arch implant-supported fixed prosthesis.
• Patients must have voluntarily signed informed consent, be willing and able to attend scheduled follow-up visits, and agree to have coded data collected and analyzed.

Exclusion criteria

• Any contraindications for oral surgical procedures.
• Smokers classified as "heavy smokers" above 10 cigarettes per day (or more than 1 cigar per day) or smokers of chewing tobacco.
• Subjects with drug or alcohol abuse.
• Severe bruxing habits.
• Conditions or circumstances that, in the opinion of the investigator, would preclude completion of participation in the study or interfere with the analysis of the study results.