[The influence of occlusal interferences on pulp vitality threshold in permanent dentition]

Examination of pulp vitality is a valuable aid in diagnosis and treatment and thus has been in use for a long time. Numerous factors influencing the pain threshold have been found including occlusal interferences. The effect of EOI (Experimental Occlusal Interferences) has been described, while the effect of primary occlusal interference awaits further investigation. The aim of this work was to evaluate the influence of malocclusion (primary occlusal interference) on pulp vitality. At first, the pattern of bite forces in normal occlusion was established. For this purpose, 20 individuals were examined. The following results were found: (a) Bite forces on the right and left side are symmetrical; (b) Total bite forces are distributed as follows: (I) upper half arch: medial incisor 6.3%, lateral incisor 2.9%, canine 3.6%, first premolar 10.4%, second premolar 11.7%, first molar 29.4%, second molar 23.8%; (II) lower half arch: medial incisor 4.1%, lateral incisor 4%, canine 4.8%, first premolar 9%, second premolar 15.1%, first molar 27.3%, second molar 29.7% (Fig. 4). Next, 83 patients with unilateral malocclusion were subjected to clinical examination (orthodontic diagnosis) and measurement of bite forces (with T-Scan system). A computer program was used to establish bite forces (in %) for each tooth. 576 teeth were divided into 9 groups in accordance with the orthodontic diagnosis as follows: class II tendency (n = 126), cross-bite (n = 50), rotated (n = 30), scissors bite (n = 23), class III tendency (n = 19), class II (n = 16), open bite (n = 15), class III (n = 9), normal occlusion (n = 288). Each tooth in malocclusion was assigned a contralateral "control" tooth (Fig. 5). Bite forces acting on teeth in malocclusion were compared with control teeth using Student's t-test (Fig. 6). There is no difference between bite forces of teeth in normal occlusion and malocclusion on the opposite side of dental arches in the same patient, the only exceptions being open and cross-bite. Bite force values obtained in a group with normal occlusion and those reported by Blamphin, Kochańska and Gidzińska-Głódkowska formed parallel lines (Fig. 7). Pulp vitality threshold was measured at the buccal and occlusal side in all teeth of the group of 83 patients. Measurements were performed using Ez-Test (Satelec). The results are summarized in Table I.

1. Bite forces are symmetrical on the right and left side and differ for each tooth. 2. There is no difference between bite forces of teeth in normal occlusion and malocclusion on the opposite side of dental arches in the same patient except for open and cross-bites. 3. Bite forces in patients with unilateral malocclusion are slightly lower than in patients with normal occlusion. 4. There is no difference between pulp vitality in normal occlusion and malocclusion on the opposite side of dental arches in the same patient. 5. Pulp vitality threshold is higher at the buccal than occlusal side. 6. Pulp vitality threshold decreases with age and differs with gender.