Table 4 Prognostic factors for the occurrence of IORN (n = 204)

Dental status before starting radiotherapy

Absent

0.110

Present

0.107

Carious

0.026

Significant

Deeply carious destroyed

0.202

Loose

0.104

Root remainders

0.595

Devital

0.287

Roots – filled completely

0.949

Roots – filled incompletely

0.789

Apical periodontitis

0.888

Cysts

0.392

Retained

0.1620

Conservative treatment possible

0.430

No conservative treatment possible

0.179

Filled

0.751

Not sufficiently filled teeth

0.549

Teeth with not sufficient crowns

0.968

Item

Chronic periodontitis with less to moderate attatchment loss

0.418

Localized

General

Chronic periodontitis with severe attatchment loss

0.210

Localized

General

Dental treatment before radiotherapy

Endodontic treatment

0.379

Removal of root remainders

0.636

Tooth extraction

0.291

Conserving treatment

0.603

Cystectomy

0.936

Healthy teeth remaining after dental rehabilitation

0.158

Demographic and oncological data

Age

0.106

Karnofsky performance status

0.625

T-stage

0.222

N-stage

0.040

Significant

Total dose

0.005

Significant

BED2

0.040

Significant

Daily fraction

0.036

Significant

Multivariate analysis

Carious teeth

0.0089

Significant

N-stage

0.1256

Total dose

0.3524

BED 2

0.4182

Daily fraction

0.5596