The goal of this prospective, observational clinical cohort study is to study the effect of the preoperative condition of the tooth on the outcome of partial removal of carious tissue in mature teeth in adults. The main questions the study aims to answer are:

• Do preoperative symptoms affect the outcome?
• Does the depth of the carious lesion affect the outcome?

One hundred participants will be recruited. Patients who meet the eligibility criteria will be asked to give their informed consent to participate in the study. Partial carious tissue removal will be performed regardless of participation in the study because selective carious tissue removal is the standard treatment of choice for a vital tooth with a deep carious lesion according to the Finnish national treatment guidelines. Participants will be asked to fill in a questionnaire regarding symptoms 7 days post-treatment. The teeth will then be followed up for 12-24 months.

The null hypothesis is that there is no difference in the success between i) deep and extremely deep carious lesions and ii) initial and mild pulpitis.

Inclusion Criteria:

• the patient is communicating in the Finnish or English language
• a deep primary or secondary carious lesion in 1st or 2nd premolar or molar on occlusal or proximal surface, extending to the deepest quarter of dentine assessed from the radiograph
• asymptomatic or symptoms not more severe than reversible pulpitis (mild pulpitis according to the new pulpitis classification proposal)
• pulp responding to the electric pulp testing and cold testing
• the periodontal stage of the tooth should be I or II.

In case the patient has several teeth fulfilling the inclusion criteria, the one with the deepest lesion and/or most severe symptoms is chosen to the study.

Exclusion Criteria:

• general medical condition which makes the patient more susceptible to odontogenic infection complications
• pregnancy, breastfeeding
• mental retardation, memory disorder
• the carious lesion is extending to more than three surfaces or to both proximal surfaces
• the tooth has previous other filling(s): i) extending deeper than to the outer third of dentine; or ii) the filling is larger than Class I or II; or iii) Class II filling is not restricted to enamel; or iv) the filling has secondary/residual caries
• the tooth is not restorable
• periapical changes in the periapical radiograph
• sensitivity to percussion; swelling; sinus tract; increased mobility; resorption
• furcal lesion more severe than Class I
• ongoing orthodontic treatment
• declining to sign the written consent.

The first 100 consecutive patients that have entered the dental clinics involved, fulfilling the inclusion criteria, have given their informed consent, and have responded to the questionnaire after 7 days post-treatment, will be recruited.