Objectives: Titanium implants with mean arithmetic roughnesses (Ra) of 1–2µm are associated with improved osseointegration and clinical outcome. However, the procedures used for producing a roughened surface usually change other parameters, such as spatial characteristic skewness and kurtosis, and sub-micrometre and nanoscale roughness. Studies are needed to explore the effect of different surface characteristics on osseointegration and clarify the relationship between Ra and osseointegration. This study aimed to investigate how titanium surfaces with different micrometer-scale roughnesses influenced proliferation, migration and differentiation of osteoblasts in vitro. Methods: Titanium replicas with surface roughnesses (Ra) of approximately 0µm, 1µm, 2µm and 4µm were produced. The surfaces have no significant sub-micrometre or nanoscale roughness and have similar skewness and kurtosis. MG-63 osteoblasts were cultured on the surfaces for up to 5 days and their behavior was investigated using time-lapse microscopy. The speed of cell migration was quantified using specialised software. Gene and protein expression were determined for alkaline phosphatase (ALP), osteocalcin and vascular-endothelial growth factor (VEGF). Results: Cell migration speeds were significantly lower on surfaces with Ra of about 4µm compared to those with lower Ra levels, with no differences between those with Ra in the range 0–2µm. Cell proliferation decreased gradually with increasing Ra. Gene expression of ALP, osteocalcin and VEGF was greater for the 1-µm and 2-µm Ra surfaces than the 0-µm and 4-µm surfaces. These findings were similar for protein expression. ALP and osteocalcin content in the conditioned media were significantly higher for cells grown on the 2-µm Ra surface compared to the 0-µm and 4-µm surfaces. The production of VEGF by cells on the 1-µm and 2-µm surfaces was significantly higher than that of the 0-µm surface. Cells grown on the 2-µm surface produced significantly more VEGF than those on the 4-µm surface. Conclusion: Surfaces with lower and higher roughnesses in this study seem to be suboptimal for osteoblasts. We suggest that decreased cell migration on surfaces with Ra 4µm might be associated with decreased osteoblast differentiation, probably through inhibition of cell-to-cell contact.

Laboratory tests have limited value for assessing the safety and effectiveness of new therapies in people. Tests must also be conducted on animals that resemble humans, both biologically and developmentally. We generally acknowledge that certain animals may be caught and sold, kept in captivity, or eaten, but using animals to meet human needs is as an area of huge controversy. This chapter gives a broad perspective on the ethical basis for animal experiments, drawing from the modern “common sense” view and several longstanding philosophical theories. Moral status is considered, alongside integrity, autonomy and dignity of animals, and their ability to reason, to form memories, and to experience pleasure or pain. Smaller animals, such as mice, rats and rabbits are essential for proving a basic principle or concept. Larger animals, such as goats, pigs, sheep, dogs and monkeys, are used more sparingly, not least because of the costs involved in their care; they are necessary because of their greater similarity to humans and thus are more relevant to advancing clinical practice. However, conflicts of interest tend to be larger with animals that are more similar to humans. Primate and dogs tend to evoke our compassion more strongly than rodents or animals we commonly eat. The authors provoke thought on this subject through examples in which the interests of humans are weighed up with those of animals in studies of cosmetics, childhood leukemia and dental defects.

The alveolar ridge is the bony tissue that surrounds a fully erupted tooth. Its structure may be compromised after extraction of the tooth, but it can be preserved by use of bone substitutes, dental implants and buccal overbuilding with soft tissue grafts. Ridge preservation techniques must be developed in animals before clinical trials in patients can be conducted, and various processes, such as wound healing, can be explored that are not feasible to study in people. Dogs are most commonly used because of their similar tooth types,  root structures and fast remodeling time. Several preclinical studies are described in this chapter – mostly using the dog mandible – that compare different experimental conditions, biomaterials, grafts and implants after extraction of teeth. These provide information on the timing and sequence of extraction and grafting procedures, and timepoints for assessing tissue shrinkage and resorption of alveolar bone. Other studies address osseous resorption of flaps, the lack of a periodontal ligament, buccal overbuilding, alveolar plate resorption and inflammatory reactions. Jaw casts, morphometry, histology and high-resolution imaging are used as valid endpoints relating to the alveolar process and socket walls, and the cellular content and mineralization of tissues. The protocols outlined in this chapter will contribute to the accuracy with which preclinical studies predict responses in people.