Evaluation of hydroxylapatite particles in repair of alveolar clefts in dogs

Biocerâmica de fosfato de cálcio nanoestruturada micro-macroporosa em grânulos de absorção rápida no preenchimento de defeito crítico em rádio de coelhos (Oryctolagus cuniculus)

RESUMO O objetivo do presente trabalho foi avaliar, por radiografia, histologia e densitometria óssea, o efeito da HA/βTCP em grânulos de absorção rápida em defeito ósseo crítico em rádio de coelhos. Foram utilizados 35 coelhos machos, da raça Nova Zelândia, e realizou-se um defeito crítico nos rádios direito e esquerdo. Os animais foram distribuídos em GI, enxerto autólogo e GII, HA/βTCP em grânulos de absorção rápida. Avaliações radiográficas foram feitas antes da cirurgia, após, aos oito, 15, 30, 45 e 60 dias e avaliações histológicas e de densitometria. Verificou-se diferença significativa ao se comparar a densidade mineral óssea obtida ao longo do tempo de estudo. Observou-se formação de rede vascular entre os poros da biocerâmica desde o primeiro tempo de avaliação, (oito dias). Foram observados tecido ósseo primário e trabéculas em tecido ósseo preexistente a partir de 30 dias da implantação. Aos 60 dias, constatou-se presença de matriz óssea em segmentos ósseos preexistentes, caracterizando a formação óssea centrípeta. A biocerâmica HA/βTCP nanoestruturada micro-macroporosa em grânulos de absorção rápida não causa alterações microscópicas indicativas de rejeição, permite a invasão e a multiplicação celular, bem como propicia a regeneração óssea, constituindo um implante apropriado para preenchimento de falhas ósseas críticas.

In Vivo Behavior of Zirconia—Hydroxyapatite (ZH) Ceramic Implants in Dogs: A Clinical, Radiographic, and Histological Study

The main goal of this study is to evaluate potential applications of two zirconia—hydroxyapatite composites, Z4H6 and Z6H4, as bone substitutes. Composite plugs were implanted into the distal femoral metaphysis and also onto the longissimus dorsi of 18 adult mixed-breed dogs in order to assess in vivo biocompatibility by immediate clinical and radiographic evaluation 30, 90, and 120 days after implantation. Radiographic examination revealed radiolucency on the defect site. However, a progressive increase in bone density was observed over time, reaching a radiopacity similar to that of bone 120 days after implantation. Histological study revealed that a thin layer of fibroblasts was observed at the implant—bone interface in addition to osteoblastic activity 30 days after implantation, whereas bone neoformation around the implants was detected for the subsequent implantation times (90 and 120 days). Otherwise, the histological evaluation of the implant—muscle interface showed the presence of an initially thick fibrous tissue layer 30 days after implantation, which decreased with longer investigation times (90 and 120 days). The numbers of plasmocytes, lymphocytes, and macrophages gradually reduced as a function implantation time, being completely absent 120 days after implantation with a resulting complete osteointegration process. The zirconia phase content did not affect the bioactive behavior of the implants investigated and did not induce bone formation when implanted into muscle either.

Osteointegração da hidroxiapatita sintética no processo alveolar da mandíbula de cães: aspectos clínicos e radiográficos

Avaliou-se o efeito da hidroxiapatita sintética na regeneração do osso alveolar e o efeito no tecido vivo de cães. Em dois grupos de 14 cães adultos hígidos, pesando entre 10 e 15kg, foram criados defeitos de 6 x 5mm na superfície vestibular do processo alveolar mandibular direito até atingir a raiz do quarto pré-molar. Em um grupo (tratado), o defeito foi preenchido com hidroxiapatita sintética; o grupo sem tratamento foi usado como controle. Efetuaram-se avaliações clínicas diárias durante uma semana, avaliações radiográficas após a cirurgia e aos oito, 21, 42, 60, 90 e 120 dias do pós-operatório. Vinte e quatro cães apresentaram inflamação, sendo a recuperação no grupo tratado mais lenta. Todos os animais tiveram sangramento com a hidroxiapatita. No grupo-controle houve aumento crescente da radiopacidade dos defeitos, no entanto, aos 120 dias do pós-operatório, os defeitos ainda eram visíveis. No grupo tratado, inicialmente a radiopacidade foi maior que a do osso normal, com diminuição gradual até se tornar semelhante à do osso vizinho, 60 dias após a cirurgia. A hidroxiapatita T290800-1 acelerou o preenchimento do defeito provocado no processo alveolar e acarretou inflamação e hemorragia gengival, o que, no entanto, não contra-indicou o seu uso.

Retrospective analysis of secondary alveolar cleft grafts using iliac of chin bone

The osseous closure of alveolar clefts is an integral component of a comprehensive rehabilitation of patients with cleft lip and palate and has assumed an essential position in the reconstruction of cleft deformity. Our study consists of 35 patients aged between 7 and 11 years who received secondary bone grafting of their cleft alveolus over a 30 month period from July 1999 to December 2003. There were 22 (62.9%) males and 13 (37.1%) females. In 25 cases, bone graft was harvested from the iliac crest and in 10 others, from the mandibular symphysis. A total number of 41 osteoplasties was performed in the 35 patients. Twenty osteoplasties maintained an alveolar height up to 75% and approximately that number showed resorption varying between 50% and 75%. There was no case of complete resorption of graft. There were no serious periodontal pockets found. In all cases, the wound healed well, and there was no complication. Our experience demonstrates that secondary alveolar bone grafting is an efficacious method of rehabilitating patients with alveolar clefts.

Reconstruction of an alveolar cleft for orthodontic tooth movement

Bone grafting to repair an alveolar cleft has long been an integral part of the treatment of persons with unilateral and bilateral clefts of the lip and alveolus. The presence of the cleft places a limitation on the orthodontist who would like to move teeth in the area of the cleft. Various grafting materials have been placed in alveolar clefts in an attempt to solve this problem. The case to be presented is a patient with a Class II, Division 2, malocclusion with a left unilateral alveolar cleft and a repaired cleft lip. Ten months after initiating orthodontic treatment, a free gingival graft procedure was performed because of insufficient vestibular depth and the narrow width of the keratinized attached gingiva at the left maxillary lateral and central incisor region. Two months after periodontal surgery, a mix of decalcified freeze-dried bone allograft and a granular bioactive glass graft material (1:1) were applied subperiostally on the buccal aspect of the edentulous cleft region. Six months later, the teeth adjacent to the grafted alveolar cleft were orthodontically moved into the edentulous area. The treatment results indicated that orthodontic, periodontal, and surgical interventions resulted in a successful closure of the alveolar cleft as well as improved periodontal conditions of the teeth adjacent to the cleft area. From the orthodontic point of view, tooth movement can be achieved successfully into a bone graft made of freeze-dried bone and bioactive glass.

Prospective evaluation of morbidity associated with iliac crest harvest for alveolar cleft grafting

PURPOSE

This study prospectively evaluated the morbidity associated with iliac crest bone harvest when performed for alveolar cleft grafting.

PATIENTS AND METHODS

Twenty-two consecutive patients who underwent an alveolar cleft graft with iliac crest bone harvest were evaluated. The estimated blood loss, length of hip incision, and volume of bone that was harvested were recorded. The duration of time until postoperative ambulation and the length of hospitalization were measured.

RESULTS

All patients tolerated the iliac harvest without major complication, and the volume of bone was sufficient in all but one case. Postoperatively, ambulation occurred at an average of 3 hours 18 minutes. Twenty-one patients were discharged the day after surgery; one patient had the surgery performed as an outpatient.

CONCLUSIONS

Harvesting cancellous bone from the iliac crest does not result in delayed ambulation or prolonged hospitalization. The morbidity that has been reported to occur with iliac crest bone harvest was not consistent with the results of this study.

Effect of calcium phosphate ceramic particle insertion on tooth eruption

The effects of calcium phosphate ceramic implants on tooth eruption were investigated radiographically and histologically in 20 3-month-old dogs. Four kinds of ceramic particles were used: dense and porous hydroxyapatite particles, and dense and porous tricalcium phosphate particles. These particles were implanted in the sockets after deciduous tooth extraction. The four types of calcium phosphate ceramic particles produced similar radiographic and histologic findings. There was no delay of tooth eruption, no dysplasia, and no resorption of dental hard tissue.

A comparative investigation on autologous mandibular and iliac crest bone grafts. An experimental study in sheep

Nine Friesian sheep (age 1.5-2 years) were used to evaluate the quality of bone repair in artificial cleft-like maxillary defects repaired with autologous bone grafts of embryologically different origin. After bilateral extraction of the upper first deciduous molar the tooth socket was enlarged resulting in an open connection between the oral and nasal cavities. In the same session a graft, obtained from the iliac crest, was implanted in one of the two bilateral maxillary defects and on the opposite side a graft, obtained from the mandible, was inserted. During the experiment, serial radiographs were taken. After six months the sheep were sacrificed and the bone of the grafted areas was submitted to histological and histomorphometric investigation. Comparing both areas, it appeared that the quality of bone remodelling and alveolar reconstruction was independent of the origin of the grafts.

The diagnostic value of subtraction radiography in the assessment of granular hydroxylapatite implants

Although histologic analysis of osseous changes around hydroxylapatite (HA) implants can be highly accurate, it is of limited use in human beings. Digital subtraction radiography may provide a noninvasive alternative. Ten patients with bony lesions were operated on and nine of the iatrogenic defects were filled with granulated HA. In one patient, the defect was left unfilled for reference. Customized film holders provided standardized radiography. Follow-up images after 4 to 6 months were subtracted from immediately obtained postoperative images, and changes around the implants were noted. From ten pairs of radiographs, eight could be successfully subtracted, whereas two pairs required corrective image transformation before subtraction. Although no bone loss was observed in any of the patients, the implants did not appear to enhance physiologic bone regeneration either. Hence, subtraction radiography holds the potential of clinical utility for the follow-up of HA implants. However, technical improvements are necessary to yield quantitative data.

Nonporous hydroxylapatite in the repair of alveolar clefts in a primate model: clinical and histologic findings

Twelve adult Rhesus monkeys with surgically created alveolar clefts (ACs) underwent repair that used nonporous hydroxylapatite (NPHA) granules on one side and autogenous particulate bone in the contralateral defect. Clinical and radiographic evaluations at 1, 2, 3, 6, and 12 months postoperatively disclosed some displacement of granules initially, but this stabilized by 2 months. Three of 12 sites repaired with NPHA and four of 12 sites repaired with bone dehisced; however, all of these healed by 2 months. No untoward inflammatory or resorptive changes were observed beyond 3 months. The repaired alveolar processes were similar in bulk and contour in sites grafted with NPHA and with bone. Histologically, giant cells were noted at 3 months, but the number decreased at 6 months and remained at that level up to 12 months. The NPHA granules were embedded in mature fibrous connective tissue with osseous ingrowth evident in eight of the 12 defects. It was concluded that NPHA granules are an acceptable implant material for repair of residual alveolar clefts in which erupting teeth and orthodontic movements are not factors.

Radiographic and histological analysis of tooth eruption through calcium phosphate ceramics in the cat

The effect of implanting calcium phosphate ceramics (CPC) into metabolically active sites within kitten mandibles during permanent premolar tooth eruption was examined. Forty kittens, 3-4 months of age were used: the deciduous second and third mandibular premolars were extracted and their sockets implanted with autologous blood clot, autogenous cancellous marrow, and the calcium phosphate ceramics, non-porous beta-tricalcium phosphate or porous hydroxylapatite. Animals were killed at 1, 2, 3, 4 and 5 months after implantation and undermineralized sagittal sections were evaluated by light microscopy. Eighty percent of hydroxylapatite implanted mandibles showed delay in tooth eruption concurrent with distortion in crown development, and a dense cellular fibro-proliferative response within the follicle of unerupted teeth. This response occurred in only one specimen with tricalcium phosphate, whereas normal eruptive patterns and crown development were routinely noted. Both the tricalcium phosphate and hydroxylapatite were integrated into the surrounding alveolar bone without evidence of an inflammatory response. Thus hydroxylapatite initiated a dense cellular fibrous network within the dental follicle preventing formation of an eruptive pathway, delaying tooth eruption and causing crown deformation. This was rarely seen with tricalcium phosphate, and may be due to the resorbability of tricalcium phosphate when compared to hydroxylapatite. Hydroxylapatite should therefore be used with caution for implanting into areas containing unerupted teeth with a metabolically active dental follicle.