Basic Study of Fabricating Biomorphic Crowns

The purpose of this study is to compare among different designs of the occlusal surface of artificial crowns, trying to determine a guidance of fabricating artificial crowns with better mimesis of the original tooth crown in terms of morphology.

For occlusal surface design, each subject would be given 3 crowns using different fabricating guidance -- the FGP technique(FGP),the average setting technique(AVR) and conventional technique(CON), separately. Upon baseline visit, general tooth preparation procedures would be performed, including impression taking before and after treatment and tooth preparation. Sometimes photo taking is needed. On try-in visit, subjects would be ask to fill in questionaires(Likert's scale) and the adjusting time for each crown would be recorded. Moreover, t-scan would be used to assess the occlusal equilibrium. All in all, including adjusting visit for FGP, the subjects have to visit the clinic for 3 times which would take them 3-week time.

The Institutional Board(IRB) of the Stomatological Hospital of Fourth Military Medical University(FMMU) would be in supervision of the whole study and is responsible for the quality assurance plan, data check and source data verification.

Subject recruitment would done within those patients visit the department of prosthodontics of the Stomatological Hospital of FMMU and have an interest towards this study. One clinician would be appointed to enroll the subjects according to the standards. To avoid errors, all the examinations done in the study shall be accomplished by the same clinician and the crowns fabricated in the study shall be designed by the same technician. The clinician and the technician participated would receive adequate training before the study to ensure their performance. Every subject in the study should assign informed consents at the beginning of the study and establish case report forms(CRFs). During the study, if adverse events(such as crown chipping, crown dropping or iatrogenic gingivitis, etc) happen, subjects are required to contact the investigator within 24 hours; and the investigator should then report to the IRB within 24 hours. Following treatment or compensation would be done according to the clauses stated in the informed consent signed by the subjects.

The whole study needs subjects in total. During the study, subjects have their own right to quit the study at any time if they have discussed with the investigator in advance. These subjects then are deemed as "unavailable". If subjects don't contact the investigator and quit the study(the investigators can't contact them within the follow-up period), their records then are deemed as "missing".

All the information collected in the study would be protected and only be used within this study. The statistical analysis of this study would be processed with the aid of the department of statistics of FMMU.

Eligibility Criteria:
Inclusion Criteria:

* single crown restoration needed in posterior quadrants
* the antagonist of the abutment tooth is purely natural or received minimum restorations that does not change its morphology too much
* no orthodontic treatment history
* stable occlusion
* no parafunctional movements existed

Exclusion Criteria:

* sequential crown restorations needed
* the morphology of the antagonist of the abutment tooth has been largely changed by previous treatment
* no contact exists between the abutment tooth and its antagonist
* orthodontic treatment history
* unstable occlusion
* existed parafunctional movements
* participated in other clinical studies