Effect of 2 Different Drilling Speeds on the Osseointegration of Implants Placed With Flapless Guided Surgery: A Study in Rabbits.

OBJECTIVE: The aim of this study was to evaluate the influence of the drilling speed on bone healing and the osseointegration of implants placed with a guided flapless surgical technique in rabbit tibias. METHODS: For the evaluation of bone healing, a total of 30 perforations (defects) were made in both tibias of 15 rabbits using 2 different drilling speeds (1500 rpm-control group; 50 rpm-test group). The regeneration of bone tissue in the surgical sites was evaluated at 0, 7, and 14 days. For the evaluation of implant osseointegration, another 15 rabbits underwent drilling in both tibias for implant placement. Thirty implants (3.75 × 10 mm) were placed to evaluate osseointegration at 4, 8, and 12 weeks after surgery. RESULTS: Both groups showed a progressive healing of the defect, which involved the complete closure of the perforation. The osseointegration occurred in all groups with no statistically significant differences in the assessment of the osseointegration between the groups. CONCLUSION: In the experimental models used, the drilling speed does not prejudice the pattern of bone healing and osseointegration of implants placed with guided flapless surgery.

Clinical similarities and histological diversity comparing fresh frozen onlay bone blocks allografts and autografts in human maxillary reconstruction.

BACKGROUND: In the absence of autologous bone for harvesting, fresh-frozen bone allografts turned into an alternative for bone reconstruction procedures. PURPOSE: The purpose of this study was to make a histological analysis of fresh-frozen onlay bone allografts (ALs), compared with autografts, in patients who needed maxillary reconstruction prior to dental implants placement. MATERIALS AND METHODS: Twelve patients with bone deficiencies (width inferior to 4 mm) in the sites where the implants were planned were enrolled in the study. From these, six were elected to be treated with autogenous (AT) bone grafts and six with fresh-frozen bone AL. This last group included the patients who had absence of a convenient amount of bone in donor sites. Each patient received from one to six graft blocks, totalling to 12 ATs and 17 ALs. Seven months after grafting procedures, biopsies of the grafts were made using 2-mm internal diameter trephine burs, and processed for histological analysis. One biopsy was retrieved from each patient. RESULTS: Clinically, all grafts were found to be firm in consistency and well-incorporated to the receptor bed. Histological analysis showed a large amount of necrotic bone surrounded by few spots of new-formed bone in the AL group, suggesting low rate of graft remodeling. In the AT group, an advanced stage of bone remodeling was seen. CONCLUSIONS: Human fresh-frozen bone block AL showed clinical compatibility for grafting procedures, although associated to slow remodeling process. Further studies are needed to define, at long term, the remodeling process chronology the clinical longitudinal results for fresh-frozen bone AL.

Avaliação da influência da velocidade de perfuração na reabsorção óssea ao redor de implantes osseointegrados instalados por meio de cirurgia guiada sem retalho: estudo clínico, radiográfico e histológico / Effect of drilling speed on bone remodelling around implants installed with flapless guided surgery. Clinical radiographic and histologic study

O objetivo deste estudo realizado em humanos e animais foi avaliar clínica, radiográfica e histologicamente a influência da velocidade de perfuração no tecido ósseo peri-implantar em implantes instalados com cirurgia guiada sem retalho. No estudo em animais, 30 implantes foram instalados em ambas as tíbias de 15 coelhos com diferentes velocidades de perfuração (Controle ­ 1500 r.p.m e Teste ­ 50 r.p.m.) para avaliação histológica de BIC e BA nos períodos de 4, 8 e 12 semanas. Na segunda parte do estudo, foram realizadas 30 perfurações ósseas nas tíbias de 15 coelhos. A distribuição dos grupos foi de acordo com a velocidade de perfuração utilizada na primeira parte do estudo para avaliação histológica nos períodos de 0, 7 e 14 dias. No estudo em humanos, 64 implantes foram instalados com cirurgia guiada sem retalho em 16 mandíbulas edêntulas. Em cada paciente foram instalados 2 implantes utilizando as duas velocidades de perfuração do estudo em coelhos. A avaliação clínica e radiográfica foi realizada durante 1, 3, 6 e 12 meses. No estudo em coelhos, os 2 grupos mostraram regeneração óssea progressiva na região do defeito sem mostrar diferença estatística. Na avaliação do contato osso-implante e área óssea entre as espiras, não foram observadas diferenças significantes entre os grupos. No estudo clínico foi observado um índice de sucesso de 90% após um ano em função. O nível ósseo médio durante o período experimental foi de 0,83 mm. Treze em 16 próteses pré-fabricadas não apresentaram adaptação confirmada por radiografias periapicais digitais. Três implantes de cada grupo foram perdidos durante o período de avaliação de 3 meses. Um dos implantes perdidos foi avaliado mediante histologia e apresentou necrose na região apical. Não foi observada diferença significante entre os grupos com relação ao IP, SS e à avaliação da estabilidade dos implantes. Na avaliação por subtração radiográfica foi observada diferença estatisticamente significante nos valores médios de tons de cinza relacionados ao ganho ósseo e na área média relacionada ao ganho e à perda óssea entre os grupos experimentais (p<0.05). Dentro das limitações deste estudo, podemos concluir que a velocidade de perfuração não influenciou o padrão de regeneração óssea na região do defeito e também não afetou o padrão de osseointegração em implantes instalados em coelhos. Clinicamente, não foi observada a influência da velocidade de perfuração no nível ósseo. Entretanto, a velocidade de perfuração de 50 r.p.m. apresentou maior mineralização no tecido ósseo peri-implantar durante o período experimental

The aim of this study was to evaluate clinical, histologic and radiographically the effect of drilling speed on bone tissue around implants installed with flapless guided surgery. Thirty implants were installed in the tibial metaphysis of 15 rabbits with 2 different drilling speed (Control ­ 1500 r.p.m and Test ­ 50 r.p.m.). BIC and BA were assessed during 4, 8 and 12 weeks after implant placement. Then, 30 bone defects were performed in the tibial metaphysis of 15 rabbits with the same drilling speed groups. The histologic evaluation was performed at 0, 7 and 14 days. In the clinical study, 64 implants were installed in 16 edentulous mandibles with flapless guided surgery. Two implants per patient were instaled wtih the same protocol and distribution of drilling speed groups of the animal study and they were clinical and radiographically evaluated during 1, 3, 6 and 12 months. In rabbits, both groups showed progressive bone repair around the defect without statistical differences. No differences between groups were showed in terms of bone implant-contact and bone area. The clinical evaluation showed 90% of implant survival during the experimental period. Mean bone level after 12 months of function was 0.83 mm. A radiographically misfit was observed in 13 of 16 patients between abutment and pre-fabricated prostheses. Three implants of both experimental groups were lost during 3 months evaluation. One implant was assessed histologically and showed apical necrotic bone. No statistical difference between groups were showed at PI, BoP and implant stability. Statistically difference (p<0.05) was showed between groups at mean gray level of bone gain and mean area of bone gain and bone loss evaluation. Within the limitations of this study, it can be concluded that the drilling speed do not have effect on bone repair and it did not present alterations on the osseointegration pattern. Clinically, it did not show influence at bone level around implants installed with flapless guided surgery. However, low drill speed induced increase of mineralizated periimplant bone tissue during the experimental study

Efeito da dieta com deficiência de magnésio sobre a manutenção da osseointegração de implantes de titânio: análise radiográfica, densitométrica e de torque reverso / Effect of magnesium deficiency on diet on the maintenance of the osseointegration on titanium implants: radiographic, densitometric and removal torque study

A deficiência de magnésio (Mg) na dieta pode ser considerada um fator de risco para o desenvolvimento de osteoporose. A diminuição de Mg na dieta está relacionada à perda de massa óssea em humanos; e em animais, estudos têm demonstrado osteopenia, crescimento ósseo anormal e fragilidade esqueletal. Este estudo avaliou a influência da deficiência de Mg na dieta em ratos jovens e adultos sobre o torque de remoção de implantes e sobre a densidade óssea e radiográfica ao redor de implantes osseointegrados instalados na tíbia dos ratos. Noventa ratos Holtzman foram separados em 2 grupos (n=45; 180 gr - animais jovens/ n=45; 360 gr - animais adultos); cada animal recebeu um implante em cada metáfise tibial. Após a osseointegração dos implantes (60 dias), os dois grupos de animais foram sub-divididos em três grupos: grupo Controle (CTRL, n=15), grupo de deficiência de Mg de 75% (Mg1; n=15) e grupo de deficiência de Mg de 90% (Mg2; n=15). Após 150 dias da instalação dos implantes, todos os animais foram sacrificados. Foram coletadas amostras de sangue e urina, realizada a densitometria óssea das vértebras lombares (L2, L3 e L4) e do fêmur, realizada a densidade óssea radiográfica e mensuração da espessura da cortical óssea, além do teste biomecânico de torque de remoção dos implantes. A análise densitométrica (vértebras lombares e fêmur) e os valores da concentração plasmática e urinária de Mg confirmaram o comprometimento sistêmico dos animais, mostrando valores menores de densidade óssea para os grupos Mg1 e Mg2. A análise da densidade radiográfica demonstrou alterações no osso cortical e medular dos grupos Mg1 e Mg2. A análise da espessura da cortical óssea demonstrou alterações na espessura do osso cortical, apresentando valores menores nos grupos Mg1 e Mg2. A análise do torque de remoção dos implantes nos animais jovens mostrou diminuição dos valores de torque com diferença significante para os grupos Mg1 e Mg2 (P <0.05) com relação ao grupo controle. Nos animais adultos, os valores de torque de remoção nos grupos Mg1 e Mg2 também foram menores, mas não foram significantes. De acordo com este estudo, observou-se que a deficiência de Mg na dieta causa influência negativa nas características biomecânicas do tecido ósseo ao redor de implantes osseointegrados

Low dietary magnesium (Mg) may be a risk factor for osteoporosis. Mg intake has been associated with bone mass loss in humans. Mg deficiency in animal models has showed osteopenia, impaired bone growth and skeletal fragility. This study evaluated the influence of magnesium deficiency on diet in young and adult rats on the removal torque of osseointegrated titanium implants. Ninety male Holtzman rats (n=45; 180 gr - young rats / n=45; 360 gr - adult rats) were divided in two groups and received a titanium implant in the tibia metaphysis. After the healing period of 60 days, the animals were randomly divided in three sub-groups: control group (CTRL, n=15 animals), 75% magnesium deficiency group (Mg1, n=15 animals) and 90% magnesium deficiency group (Mg2, n=15 animals). The dietary magnesium deficiency was induced in two groups (Mg1 and Mg2) for 90 days. After 150 days postimplant placement, all animals were sacrificed and collected samples of blood and urine. Densitometry of femur and lumbar vertebrae was performed by dual-energy x-ray absorptiometry (DXA), bone density was measured by digital radiographs at 6 points on sides of the implant and was performed the measurement of the thickness of the cortical bone. All implants were subjected to removal torque. Densitometric analysis (femur and lumbar vertebrae) and serum and urinary magnesium concentration confirmed a systemic impairment of the animals, showing lower bone mineral density for Mg1 and Mg2 in young and adult rats. The analysis of radiographic bone density revealed a negative impact of the Mg deficiency in the cancellous and cortical bone. Analysis of the thickness of cortical bone showed alterations on cortical bone in Mg1 and Mg2 groups. Analysis of the removal torque of the implants in young rats showed a decrease of the removal torque for the Mg1 and Mg2 groups (P <0.05) with a statistical difference in relation to the CTRL group. Analysis of the removal torque of the implants in adult rats showed a decrease of the removal torque for the Mg1 and Mg2 groups but without statistical difference in relation to the CTRL group. According to this study, magnesium deficiency on diet was observed to have a negative influence on the biomechanical characteristics of bone tissue around osseointegrated implants