Sir John Walsh Research Institute Seminar Series

Wednesday 16 May 2012
Room 2.26 Walsh Building, 1:00 - 2:00 pm

Dr Michael Tholey

"The System Y-TZP and its Porcelain"

Dr Michael Tholey will address the importance of the firing of veneering porcelain on its mechanical and aesthetic properties, an area of huge importance to dentists and ceramicists worldwide.

Wednesday 30 May 2012
Room 2.26 Walsh Building, 1:00 - 2:00 pm

Dr Rohana Ahmad
Faculty of Dentistry
Universiti Teknologi MARA, Malaysia

"Mandibular bone remodeling in response to biomechanical loading from implant-related overdentures: A prospective clinical study."

The aim of this clinical study is to investigate how mandibular bone remodel when subjected to loading through implant-retained overdenture over a period of one and two years using cone beam computed tomography (CBCT). The CBCT enabled clear definition of the bone, mucosa and dentures from which bone remodeling patterns were analysed in a threedimensional manner using the medical imaging programs Mimics and 3-matics.

Twenty-four patients aged 52-79 initially consented to receive implants and overdentures, but four patients later refrained implants as they were satisfied with the new conventional dentures. Remodeling occurred predominantly on the denture bearing areas; occlusally in the molar region and more lingually in the premolar area. Remodeling occurs either by displacement of the entire thickness of cortical layer apically or by thinning of the surface layer. The extent of bone remodeling is highly variable between patients but for most of them, the depth of bone resorption and deposition is within -2 to +2 mm.

Remodeling was rapid during the first year with a mean decrease in volume of 3.6%. During the second year, the rate reduced to 2.8% per year. For patients without implant, the resorption rate was about half that of overdenture patients - 1.9% after the first year.

Both sides of mandible showed some degree of remodeling and it was independent of preferred chewing side, maximum bite force, and height of the mandibular residual body or corpus length. The gonial angle seems to be the major factor in influencing the rate of bone remodeling. Patients with low gonial angles had significantly more bone resorption compared to those with high gonial angles.

The mucosa also seems to play an important protective role in bone resorption. Where the mucosa thickness is more than 1.5 mm, there appear to be much less resorption.