Aim of study: is to asses biological and esthetical success of ceramic onlay restorations while preparing the teeth using shoulder finish line preparation versus butt joint with bevel preparation.

Methods:

Patients with need to posterior onlay restoration (premolars and molars) will be allocated into two groups either conventional (shoulder finish line) or conservative group (butt joint with bevel), after tooth preparation impression, restoration fabrication, try in, cementation and restoration will be evaluated two weeks post cementation then follow up will be held every two months for 1 year.

• Research objective: The aim of this study is to asses biological and esthetical success of ceramic onlay restorations while preparing the teeth using shoulder finish line preparation versus butt joint with bevel preparation.

• Research Procedure:

  • Visit 1: Preoperative records, face-to-face adherence reminder session, clinical, radiographic examination, intraoral photographs and primary impression (alginate impression*) for diagnostic cast construction.
  • Visit 2: Tooth preparation according to its group either shoulder, or butt joint with bevel preparation, secondary impression using addition silicone rubber base material two step two viscosities technique and temporary restoration.
  • Visit 3: evaluation of e-max press onlay ceramic restoration on the cast then evaluation intra-oral on the prepared tooth and permanent cementation of the final restoration using adhesive resin cement.
  • Visit 4: Every 2 months post operatively follow-up visit for one year.
  • PICOTS P: Population: Patients requiring posterior onlays. I: Intervention: butt joint finish line with bevel preparation for ceramic onlay.

C: comparator: shoulder finish line preparation for ceramic onlay.

O: Outcome:

Primary: Postoperative sensitivity Secondary: Marginal discoloration Tertiary: Secondary Caries T: Time: 1 year. S: Study design: Randomized controlled clinical trial.

• Research question For patients requiring posterior onlays, does the use of conservative preparation offer better biological response and esthetics when compared to conventional onlay preparation?

• Participant timeline:

• The patient will be treated in visits designated as follows:

  • Visit 1: Preoperative records, face-to-face adherence reminder session, clinical, radiographic examination, intraoral photographs and primary impression (alginate impression) for diagnostic cast construction.
  • Visit 2: Tooth preparation according to its group either shoulder, or butt joint with bevel preparation, secondary impression using addition silicone rubber base material two step two viscosities technique and temporary restoration.
  • Visit 3: evaluation of e-max press onlay ceramic restoration on the cast then evaluation intra-oral on the prepared tooth and permanent cementation of the final restoration using adhesive resin cement.
  • Visit 4: Every 2 months post operatively follow-up visit for one year.

• Allocation

Randomization:

- Simple randomization will be done using computerized random number generator

Allocation:

• Sequence generation
• A dental colleague will allocate the participant patients into two groups with 1:1 allocation ratio by using computerized Sequence generation
• Blinding
• Double blinding (trial participants and outcome assessor)
• Two dental colleague assessors who are blinded about the aim of the study and participant's allocation will be responsible for assessing the outcomes of this study.

Data collection methods:

• Primary 1ry: Postoperative sensitivity will be assessed by asking patients according to modified USPHS criteria and given a score (Alpha, Bravo)
• Secondary 2ry outcome: Marginal discoloration will be assessed according to modified USPHS criteria and given a score (Alpha, Bravo B1, Bravo B2, Charlie).
• Tertiary 3ry outcome: Secondary Caries will be assessed by visual and given a score (Alpha, Bravo).

Plans to promote participant retention & complete follow-up:

• The main investigator will record telephone numbers and address of the patients included in the study. All patients will be given a phone call before the next appointment. Many efforts will be done to promote participant retention such as, sending SMS greetings in the feasts, any celebration and in his/ her birthday.
• Data management
• The main investigator will enter patient data electronically. Patient files are to be stored in Numerical order in a secured place.
• Statistical methods
• Qualitative data will be presented as frequencies and percentages. Chi-square test or Fisher's Exact test when applicable will be used for comparisons related to qualitative variables. Friedman's test will be used to study the changes by time within each group. Dunn's test will be used for pair-wise comparisons when Friedman's test is significant.
• The significance level will be set at P ≤ 0.05. Statistical analysis will be performed with IBM® SPSS® Statistics Version 20 for Windows (SPSS, Inc., an IBM Company).

D) Data monitoring

• Monitoring

• The main supervisor is responsible of data monitoring if harms arise, interim analysis will be done.

• Harms

• The main investigator will record, document and treat any adverse effect like pain or even failure.

• Expected risk to the human subjects:

  1. Possibility of restoration dislodgment (the patient should keep the restoration and contact the researcher as soon as possible as the restoration will be assessed for cementation or replacement).
  2. Possibility of restoration fracture (the patient should keep the fractured part and contact the researcher as soon as possible as a new restoration will be placed).
  3. In case failure of the onlay restoration the tooth will be assessed for the new required restorative modality.

• Consent

• Researcher will discuss the trial with all patients. Patients will then be able to have an informed discussion with the researcher. Researcher will obtain written consent from patients willing to participate in the trial.

Inclusion Criteria:

• 1-From 18-70 years old, be able to read and sign the informed consent document.30 2- Have no active periodontal or pulpal diseases, have teeth with good restorations.

  3- Psychologically and physically able to withstand conventional dental procedures 4- Patients with teeth problems indicated for posterior onlay (molars or premolars).

  1. Decayed teeth
  2. Teeth restored with large filling restorations 5- Able to return for follow-up examinations and evaluation

Exclusion Criteria:

1. Patient less than 18 or more than 70 years
2. Patient with active resistant periodontal diseases
3. Patients with poor oral hygiene, high caries risk and uncooperative patients
4. Pregnant women
5. Patients in the growth stage with partially erupted teeth
6. Psychiatric problems or unrealistic expectations
7. Lack of opposing dentition in the area of interest. 8- the presence of a removable or fixed orthodontic appliance, signs of bruxism or clenching, the absence of more than one unit in the posterior region.

the outcome results

double blinded