To our knowledge, the effect of Vit C on dental implant osseointegration in rat living bone tissue undergoing GBR was examined for the first time in this study. On the other hand, few molecular dynamics simulations, animal experimental studies or cell culture studies have shown that Vit C improves osseointegration and has positive effects on bone tissue. In this sense, clinical observation studies are also available. We reviewed these research designs when calculating the dose of Vit C to be administered to the rats in our study. For example, we noted that the synthesis of collagen type I, osteonectin and osteocalcin levels increased with 200 μg/ml of Vit C, in an in-vitro study
16. Although various factors such as gender, age, smoking, pregnancy and breastfeeding can change the amount of Vit C required, it can be said that the amount to be taken daily is roughly 75-105 mg/day
17. Moreover, studies suggest that single oral doses higher than 200 mg are characterized by relatively low bioavailability, suggesting that such high doses should rather be divided into several subdoses
18. Taking this pharmacokinetic information into account, we administered 5 mg of Vit C, which we calculated as an adult human equivalent dose, to rats, since no other rat studies were available.
The experience of the physician and the quality of the implant are often not sufficient for perfect osseointegration. Nastri et al.19 stated that for perfect osseointegration, the immunological status of the host and its nutritional content and balance should be taken into account. It is noteworthy that the effects of daily nutrients, including vitamins and minerals, may be more than expected, and more studies are being conducted in this area. Because of its direct effects on bone metabolism, vitamin D has been the most researched vitamin in studies. It is known that vitamin D deficiency slows down implant osseointegration and increases the risk of graft infection20. Liu et al. reported that vitamin D supplementation has increased the fixation of titanium implants in the case of chronic renal failure, which has negative effects on bone metabolism 21. In another experimental study, the effect of vitamin supplementation was measured by using immediate implants instead of extracted premolar teeth of dogs. It was remarkable that vitamin D supplementation in these dogs without vitamin D deficiencies reduced crestal bone loss and increased osseointegration22. In one of the above-mentioned studies, Vit C supplementation in addition to vitamin D, increased the success of dental implant surgery in patients with vitamin D deficiency19. However, although the literature evaluating the effects of Vit C on bone tissue has been reached, there are very few studies that have observed its effects on dental implants and osseointegration. A study of Vit C on the gene level showed that Vit C improves trabecular bone formation by influencing the bone matrix gene expression of osteoblasts 23. In a study comparing the data of the fifth lumbar vertebra and femur in ovarectomized rats, it was found that Vit C increased bone density 24. Malmir et al. conducted a meta-analysis on clinical researches 11. They stated that higher dietary Vit C intake resulted in a lower risk of hip fracture and osteoporosis, as well as a higher bone mineral density in the femoral neck and lumbar spine. Vit C contributes to the normal function of bones and teeth by enhancing osteoblastogenesis and inhibiting osteoclastogenesis through Wnt/β-catenin signaling. In this study, it has been shown for the first time that Vit C improves bone regeneration and teeth health25. Thereafter, the European Food Safety Authority's opinion of Vit C was shaped by its contribution to the normal function of bones and teeth. All these findings and opinions of the authorities support our results that a positive effect was observed at the 5 mg/kg dose of Vit C. There is no definite indication for the use of Vit C in wound healing. However, supplementation with Vit C for 10 days after extraction of premolar teeth has been shown to improve wound healing26. In a cell culture study by Li et al., it was stated that gelatins doubly modified with Vit C and β-glycerophosphate salt can be scaffolds for versatile bone tissue engineering27. With its effectiveness in both bone tissue and non-bone tissue, Vit C seems to be essential for osseointegration following dental implant surgery to be at the desired level. These effects were confirmed by a randomized controlled trial, in which 128 patients with chronic periodontitis were treated with Vit C after dental implant surgery with bone grafts or GBR like in our study. It was observed that the wound healing of the patients who took vitamin C supplements for 14 days after the surgery were better than the patients who did not. Another conclusion of the same study is that vitamin C supplementation provides a more significant improvement especially in patients with chronic periodontitis who underwent implant surgery15. The most recent systematic review that was published in 2022 stated that Vit C accelerated bone healing without causing any side effects28. This review also supports the more remarkable result of our study, that with an application dose above the plateau (10 mg), the osseointegration values remained almost the same as those of the control group without causing any advers effects in the reverse torque.
Reverse torque analysis is used in in vivo and in vitro research to assess osseointegration. The reverse torque analysis method cannot be used clinically. Reverse torqueing of the implant in the bone tissue into which it is placed provides a biomechanical measurement of the force required to break the bone-implant connection. It is an objective method for evaluating bone-implant attachment. Reverse torque analysis is a method that allows the evaluation of the interaction of all bone tissue around the titanium implant with the implant surface. A very thin section is required for histological analysis. In our study, reverse torque test was used to evaluate the effect of different postoperative vitamin C doses on osseointegration according to the literature. Although numerical differences were detected between the groups, no statistical difference was detected29.
Research on the role of Vit C supplementation in patients with dental implants continues with interest. It is not difficult to predict that Vit C, which is essential for the maturation of collagen and the normal function of bone tissue, is a virgin area in dentistry studies and will be examined as much as vitamin D in the future. Based on the limited results of this study, the difference in ossointegration levels in the experimental groups at the numerical level, although not statistically, is promising in terms of the Vit C and bone tissue regeneration relationship. Further studies are needed to examine the relationship between osseointegration and Vit C.
Acknowledgement
The authors wish to thanks Implance Dental Implant System, AGS Medical Corporation, Istanbul, Turkiye for providing the titanium implants.
Competing interests: The authors declerate there is no competing interests. The authors do not have any financial interests, either directly or indirectly, in the products or information listed in the paper.