Treatment of Resorbed Mandibles with Titanium Plate and Immediate Implant-Supported Prosthesis - Case Series.

Severely resorbed mandibles with only cortical bone remaining can fracture during or after implant placement. This case series presents a technique to reduce the risk or the consequences of mandibular fracture. Seven patients with only cortical mandibular bone remaining were treated with the fixation of a titanium plate in the frontal surface previously to implant placement, during the same surgical procedure. Immediate complete-arch implant supported prosthesis were installed. Patient's systemic and local conditions that could influence implant survival were registered previously to surgery and during the follow up period. Biological and biomechanical complications were recorded. The condition of peri-implant tissues was evaluated. The follow-ups ranged from 12 to 84 months. Twenty-nine implants were placed and no implant failure or other biological complication was observed. The peri-implant tissue evaluation demonstrated most implants was surrounded by keratinized tissue (89.5%). No marginal recession (implant platform cervical to gingival margin) was observed. Probing depth was normal, ranging from 0 to 3 mm. Low scores of plaque index or bleeding on probing were recorded. Biomechanical complications evolved loosening of 4 prosthetic screws and 1 fractured. The use of a titanium plate for the fixation of severely resorbed mandibles with only cortical bone remaining was a safe treatment procedure, avoiding biological and major biomechanical complications in the treatment with immediate complete-arch implant-supported prosthesis.

Treatment of resorbed mandibles with titanium plate and immediate implant-supported prosthesis - case series

Abstract Severely resorbed mandibles with only cortical bone remaining can fracture during or after implant placement. This case series presents a technique to reduce the risk or the consequences of mandibular fracture. Seven patients with only cortical mandibular bone remaining were treated with the fixation of a titanium plate in the frontal surface previously to implant placement, during the same surgical procedure. Immediate complete-arch implant supported prosthesis were installed. Patient's systemic and local conditions that could influence implant survival were registered previously to surgery and during the follow up period. Biological and biomechanical complications were recorded. The condition of peri-implant tissues was evaluated. The follow-ups ranged from 12 to 84 months. Twenty-nine implants were placed and no implant failure or other biological complication was observed. The peri-implant tissue evaluation demonstrated most implants was surrounded by keratinized tissue (89.5%). No marginal recession (implant platform cervical to gingival margin) was observed. Probing depth was normal, ranging from 0 to 3 mm. Low scores of plaque index or bleeding on probing were recorded. Biomechanical complications evolved loosening of 4 prosthetic screws and 1 fractured. The use of a titanium plate for the fixation of severely resorbed mandibles with only cortical bone remaining was a safe treatment procedure, avoiding biological and major biomechanical complications in the treatment with immediate complete-arch implant-supported prosthesis.

Resumo Mandíbulas severamente reabsorvidas com apenas osso cortical remanescente podem fraturar durante ou após a colocação de implantes. O presente relato de casos apresenta uma técnica para reduzir o risco ou as consequências da fratura mandibular. Pacientes com apenas osso cortical remanescente foram tratados com a fixação de placa de titânio na superfície frontal, previamente a colocação dos implantes, no mesmo procedimento cirúrgico. Próteses totais implanto-suportadas foram instaladas com carga imediata. Condições locais e sistêmicas dos pacientes que poderiam influenciar a sobrevivência dos implantes foram registradas previamente a cirurgia e durante o período de acompanhamento. Complicações biológicas e biomecânicas foram registradas. A condição dos tecidos peri-implante foi avaliada. Sete pacientes completaram o período de acompanhamento, variando entre 12 e 84 meses. Vinte e nove implantes foram colocados e nenhuma falha ou complicação biológica foi observada. A avaliação do tecido peri-implante demonstrou que a maioria dos implantes possuía tecido queratinizado (89,5%). Nenhuma recessão marginal (plataforma do implante cervical à margem gengival) foi observada. Profundidade de sondagem mostrou-se normal, variando entre 0 e 3 mm. Baixos escores de índice de placa ou sangramento à sondagem foram observados. Complicações biomecânicas envolveram perda de 4 e 1 fratura de parafusos protéticos. O uso da placa de titânio para fixação de mandíbulas severamente reabsorvidas com apenas osso cortical remanescente pode ser considerado tratamento seguro, evitando alterações biológicas e maiores complicações biomecânicas no tratamento com próteses totais imediatas implanto-suportadas.

The Influence of Post System Design and Material on the Biomechanical Behavior of Teeth with Little Remaining Coronal Structure.

PURPOSE: To evaluate the influence of different post systems on the biomechanical behavior of teeth with a severe loss of remaining coronal structure. MATERIALS AND METHODS: Fifty standardized bovine teeth (n = 10 per group) were restored with: cast post-and-core (CPC), prefabricated metallic post (PFM), parallel glass-fiber post (P-FP), conical glass-fiber post (C-FP), or composite core (no post, CC). The survival rate during thermomechanical challenging (TC), the fracture strength (FS), and failure patterns (FP) were evaluated. Finite element models evaluated the stress distribution after the application of 100 N. RESULTS: All specimens survived TC. Similar FS was observed among post-containing groups. Groups P-FP and CC presented 100% repairable fractures. The von Mises analysis showed the maximum stresses into the root canal in groups restored with metallic posts. Glass-fiber posts and CC presented the maximum stresses at the load contact point. Glass-fiber groups showed lower stresses in the analysis of maximal contact pressure; CPC led to the highest values of contact pressure. The modified von Mises (mvM) stress in dentin did not show differences among groups. Moreover, mvM values did not reach the dentin fracture limit for any group. CONCLUSIONS: The type of intracanal post had a relevant influence on the biomechanical behavior of teeth with little remaining coronal structure.

Characterization of Residual Stresses in Veneering Ceramics for Prostheses with Zirconia Framework.

The aim of this study was to evaluate the influence of the coefficient of thermal expansion (CTE or α) and glass transition temperature (Tg) of three veneering ceramics used with zirconia frameworks of full-arch fixed prostheses. The generation of residual stresses and linear contraction after the simulation of the cooling process and mechanical loading were measured. The analysis was based on the finite element method in three-dimensional model of a maxillary full-arch fixed prosthesis with zirconia framework (e.max ZirCAD) and veneer by felsdpathic ceramics (GEC - IPS e.max Ceram, GVM - Vita VM9 and GLC - Lava Ceram). The linear contraction simulation was performed by cooling the structures from the Tg of each veneer ceramic at room temperature (25°C). A loading of 100 N on the occlusal region of the first molar was performed. The magnitude of the maximum principal stress (smax) and linear contraction were evaluated. The levels of CTE mismatch between veneering ceramics and framework showed no relevant influence on smax and linear contraction. The Tg values of the veneer ceramic showed to be directly proportional to amount of smax and linear contraction. The GEC presented the highest values of smax and linear contraction. The GVM and GLC did not present significant differences between them. In conclusion, GVM was similar to GLC, while GEC presented differences in relation to other veneer ceramics in terms of residual stress and linear contraction.

Rehabilitation of a Severely Resorbed Posterior Mandible with 4-mm Extra-Short Implants and Guided Bone Regeneration: Case Report with 3-year Follow-up.

Alveolar bone resorption has been a major challenge for implant placement in regions limited by anatomical structures. New alternatives have been introduced with the inclusion of extra-short implants in dentistry. The association of guided bone regeneration (GBR) with the use of extra-short implants might be a viable alternative for regions with limited bone height. This case report aimed to present the rehabilitation of a patient with severe mandibular bone resorption in the posterior region. The association of GBR with the use of extra-short implants was a viable alternative after a 3-year follow-up.

Implant Inclination and Horizontal Misfit in Metallic Bar Framework of Overdentures: Analysis By 3D-FEA Method.

The aim of this study was to evaluate by three-dimensional finite element analysis (3D-FEA) the biomechanics involved in bar-framework system for overdentures. The studied factors were latero-lateral angulation in the right implant (-10, -5, 0, 5 and 10 degrees), and different bar cross-sections (circular, Hader and oval) presenting horizontal misfits (50 or 150 µm) on the opposite implant. Positive angulation (5 and 10 degrees) for implant inclination to mesial position, negative angulation (-5 and -10 degrees) for distal position, and zero degree for parallel implants. The von Mises stresses evaluated the bar, screw and the implant; maximum principal, minimum principal and shear stress analyses evaluated the peri-implant bone tissue. Parallel implants provide lower stress in alveolar bone tissue; mesial inclined bars showed the most negative effect on prosthetic structures and implants. In conclusion, bar cross-section showed no influence on stress distribution for peri-implant bone tissue, and circular bar provided better behavior to the prosthetic system. Higher stress concentration is provided to all system as the misfit increases.

Biomechanical behavior of teeth without remaining coronal structure restored with different post designs and materials.

The aim of this study was to access the biomechanical behavior of teeth without remaining coronal structure when restored with posts of different materials and configurations. Fifty bovine teeth (n=10 per group) with standard dimensions were restored as follows: cast post and core (CPC), prefabricated metallic post (PFM), parallel glass-fiber post (P-FP), conical glass-fiber post (C-FP) or composite core (no post, CC). The survival rate during thermomechanical challenging (TC), the fracture strength (FS), and failure pattern (FP) were evaluated. Finite element models were realized to evaluate the stress distribution with a 100N load. All post-containing teeth survived TC, while CC had 30% of failures. CPC and C-FP had the higher fracture strength, but a high number of irreparable fractures (60%), such as PFM (70%). Von Mises analysis has shown the maximum stresses into the canal in groups restored with metallic posts, while glass-fiber posts and CC presented the maximum stresses at load contact point in the crown. CPC led to higher modified von Mises (mvM) stress in the cervical third of dentin. However, mvM values did not reach the dentin fracture limit for any group. Analysis of maximal contact pressure has shown better stress distribution along with the dentin interface in post-containing groups, especially for CPC.