Early implant placement in ridge preserved extraction sockets: A pre-clinical in vivo study.

OBJECTIVES: The aim was to analyse the outcomes of early implant placement after 6 and 12 weeks of healing in ridge preserved sites in a canine model. MATERIALS AND METHODS: Implants were placed in second maxillary incisors sites in 9 dogs 6 weeks after grafting of the sockets with 90% deproteinized bovine bone mineral in 10% collagen matrix (DBBMC) and closure with resorbable type I/III porcine collagen matrix (PCM). The implants were randomly assigned to 6 (T6) and 12 (T12) weeks of healing. RESULTS: The percentage of bone-to-implant contact (%BIC), old bone, new bone and residual DBBMC was similar between T6 and T12. In relation to the implant shoulder (IS), the original bone crest (IS-ROB) was more apical on the buccal than the palatal side. The regenerated bone crest (IS-C) and IS-ROB were similar between groups. However, the distance from IS to first bone-to implant contact (IS-fBIC) was significantly less in T12 compared with T6 (p = .022; Wilcoxon signed-rank test). The bucco-palatal ridge dimensions between T6 and T12 were similar. CONCLUSIONS: This study confirms that implants can successfully be placed early in ridge preserved maxillary second incisor sites and are osseointegrated by 6 weeks. There were significantly lower IS-fBIC values at 12 weeks than at 6 weeks on the buccal aspect. The original buccal bone crest underwent greater corono-apical resorption than the palatal crest. The %BIC, relative proportions of mineralized tissues and dimensions of the alveolar ridge demonstrated stability between 6 and 12 weeks of healing.

Primary stability and healing outcomes of apically tapered and straight implants placed into fresh extraction sockets. A pre-clinical in vivo study.

OBJECTIVES: To compare the stability of apically tapered and straight (non-tapered cylindrical) implants at the time of immediate placement and to histologically evaluate the healing outcomes after 6 weeks. MATERIALS AND METHODS: The second maxillary incisors were extracted bilaterally in nine dogs. After randomization, apically tapered and straight implants with a 3.3 mm shoulder diameter were inserted into the extraction sockets. The implant stability quotient (ISQ) of the implants was recorded after placement. Peri-implant defects on the buccal aspect were filled with deproteinized bovine bone mineral and covered with resorbable type I/III porcine collagen matrix. After 6 weeks of healing, sections were prepared for histological and morphometric analysis. RESULTS: All implant sites healed uneventfully. The apically tapered implants had significantly higher ISQ values compared to straight implants at placement (p = .009). The histomorphometric outcomes 6 weeks following implant placement in both experimental groups were similar, except in the apico-palatal region. Apically tapered implants demonstrated significantly less percentage bone-to-implant contact (p = .035) in the apico-palatal region. At both implant types, substantial corono-apical resorption of the buccal bone wall was noted in the coronal 2 mm of the implant. CONCLUSION: Apically tapered implants had significantly higher ISQ values at immediate placement compared to straight implants. The healing outcomes and remodelling of the buccal bone wall were similar for both implant designs. In the apico-palatal region, there was less %BIC at the implant surface at apically tapered implants compared to straight implants.

The influence of deproteinised bovine bone mineral on dimensional changes in the maxillary second incisor socket.

OBJECTIVES: To investigate the dimensional changes following the extraction of maxillary second incisors and to evaluate the influence of deproteinised bovine bone mineral on the healing outcomes. MATERIALS AND METHODS: The second maxillary incisors in nine dogs were extracted bilaterally in a minimally traumatic manner. Deproteinised bovine bone mineral with collagen (DBBMC) and a collagen matrix (CM) was placed in one socket with the contralateral socket left to heal naturally. After 3 months of healing, the dogs were sacrificed and the pre-maxilla resected. Cone beam computerised tomography scans (CBCTs) were obtained and the specimens prepared for histological preparation and analysis. Surface scans of study models taken pre- and post-extraction were digitally subtracted to analyse volumetric changes. RESULTS: All dogs healed uneventfully without any complications. No inflammation was seen, and DBBMC was well integrated into a network of mineralised tissues, bone marrow and connective tissue. The horizontal width of the buccal crest was found to be significantly greater in grafted sockets, but the vertical height to be similar. No significant difference was seen in regard to volumetric changes in sockets over 3 months post-extraction. CONCLUSION: Maxillary second incisor sockets of dogs grafted with DBBMC post-extraction had significantly greater horizontal width at the ridge crest compared with ungrafted sockets. Volumetric analysis revealed no significant difference between grafted and non-grafted sockets, suggesting possible soft tissue thickening post-extraction to counteract osseous resorption.

Healing of Bio-Oss® grafted marginal gaps at implants placed into fresh extraction sockets of incisor teeth in dogs: a study on the effect of submerged vs. non-submerged healing.

OBJECTIVES: To evaluate the effect of submerged vs. non-submerged (NS) protocols in healing outcomes of grafted marginal defects of immediate implants. MATERIALS AND METHODS: The second maxillary incisors were extracted bilaterally in six greyhound dogs. Bone level reduced diameter implants were installed into the extraction sockets leaving orofacial gaps of 2 mm wide. Defects were filled with Bio-Oss(®) and covered with Bio-Gide(®). On the one side, the flap was advanced to fully submerge the implant, and on the other, the flap was sutured to allow NS healing. After 3 months of healing, the dogs were sacrificed and block biopsies were obtained to perform histological and morphometric analysis. RESULTS: All implants were clinically healthy and well integrated into bone. In the majority of the specimens, the original bone in the coronal 2-3 mm of the buccal crest had completely resorbed and was replaced by a regenerated bone wall consisting of Bio-Oss(®) particles surrounded by newly formed bone. Horizontal and vertical resorption of the buccal bone resulted in ≥1 mm exposure of the implant surface in one-third of implants. Minor differences existed in some aspects of hard tissue healing between submerged and NS. CONCLUSION: There was very little difference in healing outcomes as well as modelling of the facial bone wall between the submerged and NS protocols in relation to immediate implant placement in this dog model.

Fibrous dysplasia of mandibular bone in a dog.

A nine-year-old, male German shepherd dog was presented with a firm, discrete mass lingual to the interdental space of the mandibular left third and fourth premolars. The lesion was excised and diagnosed as fibrous dysplasia of bone based on histopathologic examination. Fibrous dysplasia of bone is a rare, non-aggressive, radiolucent, non-neoplastic lesion considered developmental in origin. Usually observed as a solitary lesion, it has been reported in animals and man in the polyostotic form. The disease process causes deformity of bone which may lead to loss of bone strength. Clinical signs are secondary to site specific problems associated with expansile bone lesions. Oral examination performed 18-months postoperatively indicated no signs of recurrence.