Incline and length of guiding elements in untreated naturally grown dentition

Abstract

The incline and length of guiding elements, i.e. marginal ridges and lingual surfaces of front teeth, marginal ridges and internal cusp slopes of premolars and molars, play an important role in dentistry. Since the so far reported values differ considerably, it was the purpose of the present investigation to replicate the measurements, including all the occlusal landmarks proposed and defined by previous investigators. The measurements were performed on 34 pairs of mounted casts from a selected group of untreated, naturally grown dentitions from adolescents of mean age 14 years. The upper casts were mounted with a face bow, the kinematic hinge axis and the left incisura infraorbitalis representing the posterior and anterior reference points. The lower pinned casts were mounted joint related. All measurements were carried out with a computer-aided, three-dimensional digitizer. The inclines were expressed as angles related to the axis-orbital-plane. Taking the proposed occlusal landmarks as a basis, the inclines of guiding elements were found to be in agreement with previously reported values, despite ethnic and racial differences of the various study-populations. The values, however, differed markedly when measurements based on individual, functional relevant landmarks were compared to measurements based on anatomical, easy identifiable or mathematically constructed landmarks. The successive decrease of the inclines of the guiding elements from the central incisors to the second molars could be confirmed, the molars displaying very flat inclines. Interestingly, 9% of the first molars and 21% of the second molars showed negative values, pointing to a functional arrangement characterized by a buccally oriented occlusal surface of those teeth. Combined with the finding that the length of the guiding elements of the anterior teeth was almost twice as long as that of the posterior teeth, the results corroborate the occlusal concept of an anterior-posterior sequence of the guiding elements, or a so-called sequential guidance with front-canine-dominance.

Geometrical effects of conventional and digital prosthodontic planning wax-ups on lateral occlusal contact number, contact area, and steepness

“…This observation accords with the cuspal morphology of the guiding teeth (1), as it is steeper closer to the fossae than at the cusp tips (14). This parabolic morphology was observed by Nishigawa et al in their evaluation of mandibular border movement of healthy dentition (12).…”

“…Similarly, Ekfeldt and Karlsson found that, after restoring worn dentition, the mandibular closing angle near the functional occlusal contact area became steeper (13). An earlier study of the occlusal steepness of posterior teeth in natural dentition found that steepness ranged from 6 to 47° (14). The present data show that the final steepness of evaluated casts, particularly pretreatment and conventional wax-up casts, is within this range.…”

“…3,[431][432][433][434][435][436][437][438]2017 Original Geometrical effects of conventional and digital prosthodontic planning wax-ups on lateral occlusal contact number, contact area, and steepness (1,11). Occlusal steepness is part of mandibular border movement and may affect the design of prostheses, the smoothness of gliding movement, and patient comfort (12)(13)(14). Complex prosthodontic treatment is associated with significant dental changes; therefore, several clinicians recommend use of a diagnostic wax-up (15,16), that is, simulated dental treatment on diagnostic casts.…”

Análise tridimensional pelo método de elementos finitos do comportamentto biomecânico do incisivo central superior hígido e restaurado com coroa cerâmica utilizando diferentes retentores intra-radiculares

“…O carregamento, ou seja, a aplicação estática de uma força resultante de 10 N no terço médio da superfície palatina, dividida na região das cristas marginais mesial e distal, sendo 5 N para cada região, baseado nos pontos de oclusão descritos por Kulmer (1999). Assim, a pressão foi posteriormente calculada e aplicada de forma perpendicular à face do elemento de acordo com os conceitos físicos de força normal (ou força de apoio) conforme ilustração da figura 4.17.…”

“…No entanto existem trabalhos em que esta linha de cimentação foi reproduzida por entender-se que o cimento resinoso é responsável pela cimentação entre pino intra-radicular no interior do conduto e união da coroa pura de porcelana ao núcleo e que se localiza em interfaces tanto entre o pino e a dentina como entre a coroa e o núcleo, áreas estas consideradas como susceptíveis a falhas. (LANZA et al, 2005;RIBEIRO, 2004 O carregamento, ou seja, a aplicação estática de uma força resultante de 10 N no terço médio da superfície palatina, dividida na região das cristas marginais mesial e distal, sendo 5 N para cada região foi aplicada, baseado nos pontos de oclusão descritos por Kulmer et al, 1999. Assim, a pressão foi posteriormente calculada e aplicada de forma perpendicular à face do elemento de acordo com os conceitos físicos de força normal (ou força de apoio).…”