Regarding the relationship between the ISQ values and ALP or OC levels, although the ISQ values were weakly correlated with the bone markers (r = 0.226 for ALP level and r = 0.245 for OC level, P = 0.05), there were significant and positive correlations between the ISQ values and ALP or OC levels at all measurements from week 1 to week 12. These results are in harmony with the findings of a previous clinical study that investigated gene expression of bone markers in PICF. That pilot study showed that ALP gene expression was correlated with RFA at week 4 (r = 0.44, P = 0.03), and OC gene expression was correlated with RFA at week 2 (r = 0.5, P = 0.04). To our knowledge, correlations of the ISQ value with the bone markers which were detected at protein level in PICF are reported for the first time.

Vogel and Marcotte suggested that the correlation between mRNA and protein quantities is approximately 40%. As there are many mechanisms between transcription and translation, especially in human cell and protein stability, at the gene expression level, the transcription data is beneficial in making decisions about molecular candidates for future studies at the protein level. The colorimetric assay and ELISA techniques utilized in this study have many advantages, such as sensitivity, specificity, speed, and compatibility with standard clinical laboratory equipment. These techniques can be routinely applied in clinical situations. Although the high sensitivity and specificity of the quantitative, real-time, polymerase chain reaction are justified, the limitations of this technique are the sensitive nature of the work and the cost of the chemicals and equipment.

Within the limitations of this study and cautious interpretation due to small number of implants/patients, the ISQ values were weakly correlated with both ALP and OC molecules in PICF during the healing period. The results also show that osteocalcin may be used as a biological marker for monitoring implant healing at 6, 8, 10, and 12 weeks after implant placement. The ISQ values showed high stability of dental implants used over the healing period.