Can the Macrogeometry of Dental Implants Influence Guided Bone Regeneration in Buccal Bone Defects? Histomorphometric and Biomechanical Analysis in Beagle Dogs.

Manuel Fernández-Domínguez,Nahum Samet,María Ramírez-Fernández,Elena Fuentes Numancia,Horia Barbu,José Calvo-Guirado,Victor Ortega-Asensio,Sergio Gehrke,Juan Aragoneses,Rafael Delgado-Ruiz

doi:10.3390/jcm8050618

Abstract

The aim of this experimental animal study was to assess guided bone regeneration (GBR) and implant stability (ISQ) around two dental implants with different macrogeometries. Forty eight dental implants were placed within six Beagle dogs. The implants were divided into two groups (n = 24 per group): G1 group implants presented semi-conical macrogeometry, a low apical self-tapping portion, and an external hexagonal connection (whereby the cervical portion was bigger than the implant body). G2 group implants presented parallel walls macrogeometry, a strong apical self-tapping portion, and an external hexagonal connection (with the cervical portion parallel to the implant body). Buccal (mouth-related) defects of 2 mm (c2 condition) and 5 mm (c3 condition) were created. For the control condition with no defect (c1), implants were installed at crestal bone level. Eight implants in each group were installed under each condition. The implant stability quotient (ISQ) was measured immediately after implant placement, and on the day of sacrifice (3 months after the implant placement). Histological and histomorphometric procedures and analysis were performed to assess all samples, measuring crestal bone loss (CBL) and bone-to-implant contact (BIC). The data obtained were compared with statistical significance set at p < 0.05. The ISQ results showed a similar evolution between the groups at the two evaluation times, although higher values were found in the G1 group under all conditions. Within the limitations of this animal study, it may be concluded that implant macrogeometry is an important factor influencing guided bone regeneration in buccal defects. Group G1 showed better buccal bone regeneration (CBL) and BIC % at 3 months follow up, also parallel collar design can stimulate bone regeneration more than divergent collar design implants. The apical portion of the implant, with a stronger self-tapping feature, may provide better initial stability, even in the presence of a bone defect in the buccal area.

Highlights

The quantity of peri-implant tissues resulting from remodeling over a 12-week period is influenced by several important factors: Placement in fresh extraction sockets or at healed sites; immediate or delayed placement following extraction or dental loss [1,2].Maxillary bone atrophy generally causes dehiscence at the moment of implant placement surgery
The present experimental animal study set out to assess the regenerative behavior of implants placed with buccal defects of 2 and 5 mm, comparing two different macrogeometries in relation to guided bone regeneration using a particle bone graft material
The clinical situations tested were selected because they are very common in the practice of implant dentistry, in which the use of guided bone regeneration (GBR) procedures involving bone graft materials plus membrane, is an adequate and commonly applied option [19,20]

Summary

Introduction

The quantity of peri-implant tissues resulting from remodeling over a 12-week period is influenced by several important factors: Placement in fresh extraction sockets or at healed sites; immediate or delayed placement following extraction or dental loss [1,2].Maxillary bone atrophy generally causes dehiscence at the moment of implant placement surgery. The potential for successful regeneration depends upon the dimensions of the dehiscence, and it is essential to consider this parameter in order to achieve adequate regeneration outcomes [3]. Most synthetic fillers available on the market are based on hydroxyapatite and tricalcium phosphate derivatives. These substitutes may vary in their chemical characteristics, i.e., elasticity, grain size, and texture. These materials have a lower regenerative capacity in comparison with autologous bone (which provides progenitor bone cells with a perfect scaffold for growth and regeneration), they do obtain adequate and predictable outcomes [2,4]

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Discussion

Conclusion