Biomechanical performance of mini-implants as mandibular overdenture retainers: in vitro and in silico study

Author(s)

Guilherme Almeida Borges

• Document type: Master's Dissertation
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2020-02-19

Examining board members

Marcelo Ferraz Mesquita; Eduardo Piza Pellizzer; Vanessa Cavalli

• Advisor: Marcelo Ferraz Mesquita

Abstract

Dental implants for the rehabilitation with mandibular overdenture (MO) is a well- defined treatment for edentulous patients, regarding the restoration of aesthetics and function. Although MO rehabilitation is effective and recommended throughout the clinician; limitations based on costs, multiple surgical phases, morbidity and anatomical features may hamper an optimal scenario from the patient perspective. Therefore, the use of immediate (ILP) as well as early (ELP) loading protocol might be an alternative for the patients’ long waiting time for the final prostheses. Similarly, another possibility it would be to reduce the minimum protocol of two implants for only one; or even to switch the standard implant diameter (SDI) for a mini- implant design. For this purpose, two studies were designs: at first, [1] a systematic review to evaluate whether (ILP)/ (ELP) loading protocols achieve comparable long-term clinical outcomes when compared with a conventional loading protocol (CLP) in edentulous patients rehabilitated with MO. The results showed that the ILP/ELP demonstrated similar success and survival rates (P>.05) compared with those of the CLP. Similarly, no difference between/among groups was found for marginal bone loss (P>.05). With regard to probing depth, lower values (P<.05) were associated with conventional loading at 36 months of follow-up compared with the immediate/early loading protocols. When plaque index was considered, lower indices (P<.05) were assessed for the CLP compared with the ILP/ELP. Implant stability quotient presented favorable values (P<.05) for the conventional loading protocol at only 3 months, since, at subsequent follow-up periods, values similar to those of the ILP were achieved (P>.05). ILP showed the same bleeding (P>.05) on probing than the conventional loading protocol. The second study, [2] it was an experimental study (in vitro and in silico) to assess and compare the biomechanical behavior of MO retained by either one or two implants, using SDI or dental mini-implants. MO with 2 SDI showed the lowest posterior and total shear stress even for the groups retained by 1 and 2 mini-implants. In addition, peri-implant shear stress was similar (P> 0,05) for both SDI and mini-implants, irrespective of the implant number. Irrespective of the loading area (molar or incisor), the groups with one or two mini-implants showed the lowest values of von Misses stress in the implant (P< 0,05). Under incisor loading, the group with one mini-implant presented greatest stress for the housing compared with the other groups. The attachment was the most overloaded structure with high values under incisor loading, especially for the groups with two implants. In conclusion, ILP/ELP for MO is presented as a well? established treatment and worthy of consideration in clinical practice. Moreover, regardless of the implant number, MI is a promising rehabilitation method with similar peri-implant shear stress and low von Misses stress to the implant compared to SDI for implant-retained MO. (AU)

• FAPESP's process: 18/03136-4 - Mandibular overdentures retained by one or two implants: comparison between mini implants and conventional implants with different types of connection - photoelastic and finite element analysis
• Grantee: Guilherme Almeida Borges
• Support Opportunities: Scholarships in Brazil - Master