PurposeContact and distance osteogenesis occur around all endosseous dental implants. However, the mechanisms underlying these processes have not been fully elucidated. We hypothesized that these processes occur independently of each other. To test this, we used titanium (Ti) tubes to physically separate contact and distance osteogenesis, thus allowing contact osteogenesis to be measured in the absence of possible triggers from distance osteogenesis.MethodsSandblasted and acid-etched (SLA) and modified SLA (modSLA) implants were used. Both types had been sandblasted with large grit and then etched with acid. The modSLA implants then underwent additional treatment to increase hydrophilicity. The implants were implanted into rabbit tibiae, and half were implanted within Ti tubes. The bone-to-implant contact (BIC) ratio was calculated for each implant. Immunohistochemical analyses of bone morphogenetic protein (BMP)-2 expression and new bone formation (Masson trichrome stain) were performed.ResultsThe implants outside of Ti tubes were associated with good bone formation along the implant surface. Implantation within a Ti tube significantly reduced the BIC ratio (P<0.001). Compared with the modSLA implants, the SLA implants were associated with significantly higher BIC ratios, regardless of the presence or absence of Ti tubes (P=0.043). In the absence of Ti tubes, the bone adjacent to the implant had areas of new bone formation that expressed BMP-2 at high levels.ConclusionsThis study disproved the null hypothesis and suggested that contact osteogenesis is initiated by signals from the old bone that undergoes distance osteogenesis after drilling. This signal may be BMP-2.

Light microscopy histomorphometry is a useful tool in dentistry to evaluate early biologic response at boneimplant interfaces. Using this analysis method, a quantitative study compared the bone response to two types of implant surface. Implants were inserted in the tibia of two New Zealand white rabbits. After sacrifice, the tibial bone blocks were sectioned and processed in the undemineralized state. Two histomorphometric quantities were measured: boneto-implant contact and bone area. Similar bone response was found for each implant surface. While this microscopy technique is limited to two dimensions, it was adequate for estimating bone response to implant surfaces.

Clinically, dental implants are an excellent treatment option for missing teeth. Implant surfaces have been modified in various ways in order to accelerate biologic bone responses around the implants, resulting in the decrease of patients' edentulous periods. Histomorphometry by light microscope is known to be the most reliable method to evaluate the early biologic response at the interface between the bone and the implant surface. The purpose of the study was to investigate the early bone response to several modified implant surfaces using histomorphometric analysis by light microscope. The tibiae of New Zealand white rabbits received the modified surfaced screw-shaped titanium implants; two implants in each tibia. The first experiment compared among the calcium phosphate coated, anodized, and sandblasted surfaces; the second between the calcium phosphate and hydroxyapatite coated surfaces; the third between fluoride-treated and anodized surfaces; the last among calcium phosphate coated/anodized (CPA), sandblasted/acid-etched (SA), and anodized surfaces. Commercially pure titanium surfaced implants served as control. The rabbits were sacrificed after 2 weeks of the implant insertion. The tibial bone blocks were sectioned and processed in the undemineralized states for the microscopic analyses. Two histomorphometric quantities were measured; bone-to-implant contact (BIC), which is defined as ratio of the bone length contacted with the implant surface over the total length of the surface, and bone area (BA), which is defined as ratio of the bone formed between the implant threads over the total area between the threads. The modified surfaces investigated in the study showed higher BIC and BA than the control (P < 0.05). The CPA surface suggested higher BA than the anodized surface (P < 0.05). There were no significant differences in the rest of comparisons among the modified surfaces. In conclusion, modified implant surfaces demonstrate the accelerated bone responses from the results of microscopic histomorphometry, compared to the commercially pure titanium surface. These microscopic analyses may be adequate tools to evaluate early bone responses to implant surfaces. However, such analyses have the limit of 2-dimensional measurement. This field requires an improved micro-analysis technique for 3-dimensional evaluation.