In the present study, a higher prevalence of deep pockets was confirmed in the TiUnite implants placed in the patients prescribed with antihypertensive medications. Furthermore, a high prevalence of peri-implantitis was also observed at the implant level in the patients taking antihypertensive medications.
Based on the concept of periodontal medicine, periodontal disease might be a risk indicator for several systemic conditions, such as diabetes mellitus and coronary heart disease (CHD) . In previous epidemiological studies, associations between CHD and periodontal diseases have been described . In contrast, reports mentioning the relationship between CHD and peri-implant diseases are limited. Researchers have failed to demonstrate that systemic disorder-related factors (i.e., smoking and high blood pressure) are definitive risk factors for developing peri-implantitis [17, 18]. However, it is also true that the proportion of patients with peri-implantitis with diabetes mellitus and hypertension is high . Because no definitive opinion on the relationship between peri-implant inflammation and hypertension exists, the present study findings are quite valuable.
In the present study, the mean age of the participants was 66.1 years, and the mean age of the AH group patients was 66.7 years, which indicates the accordance of patients’ age in relation to the presence of hypertension and use of dental implants. The AH group used various antihypertensive medication combinations, and several patients took multiple medications, which reflects the current medical situation among Japanese patients with hypertension. The average follow-up duration was approximately 7 years. Because 5 or more years of observation are needed to assess the stability of tissue around dental implants , the average follow-up duration of the present study was long enough. The proportions of the patients with peri-implantitis were 17.1% and 14.3% at the patient and implant levels, respectively. Although the proportions were relatively small compared with those in previous reports, considering the narrow inclusion criteria (excluding smokers and patients with periodontal disease), the proportions were not very small.
For the probing pocket depth, a significant difference was observed between the AH and H groups. This result indicates possible medication-induced gingival hyperplasia in patients with hypertension, which is known to be a side effect of calcium channel blocking agents . It is known that the symptoms begin with cation flux inhibition, which leads to decreased cellular folate uptake, changes in matrix metalloproteinase metabolism, and failure to activate collagenase. Decreased availability of activated collagenase results in decreased degradation of accumulated connective tissue. To date, no reports of hyperplasia in peri-implant tissue are available; however, the results of the present study suggest some correlations. There are several differences between periodontal and peri-implant tissues, such as the presence of the periodontal ligament, orientation of collagen fibers, and properties of exudate. Considering these differences, further assessment regarding hyperplasia in peri-implant tissue is needed. Furthermore, other antihypertensive medications, such as angiotensin receptor blockers and thiazide diuretics, were also included in this study. Assessment of the influence of these medications on peri-implant tissue is needed.
There was no significant difference in bleeding on probing and modified plaque index parameters between the two groups. However, both values tended to be larger in the AH group. Hence, it was suggested that the hygiene around the implant was poor and there was inflammatory response compared to the H group.
Although there was a significant difference in the probing pocket depth, the marginal bone loss in relation to the radiographic parameter was quite small in both groups. This could be attributable to the influence of both antihypertensive medications and the surface characteristics of TiUnite implants. Generally, antihypertensive medications are known to affect bone metabolism. Recent animal studies involving antihypertensive medications and implants have shown that the bone implant contact percentage and peri-implant bone tissue volume of rats are significantly increased by propranolol, a non-selective beta-blocker . In a study of spontaneously hypertensive rats, it was observed that the expression of bone resorption markers was decreased, and that the cortical levels of TRAP+ cells were increased in the group taking calcium channel blockers . In clinical studies of humans, favorable results were observed in the group taking calcium channel blockers based on the findings of dental cone beam computed tomography, which was used to evaluate the maxillary bone density of patients with hypertension who were administered with chronic antihypertensive medications . In a cohort study on the survival rate of dental implants with antihypertensive therapy, it was concluded that the implant survival rate in antihypertensive medication users was higher than that in non-users . On the other hand, survival rate was not examined in this study. Our results were exhibited increasing of probing depth and peri-implantitis prevalence in AH group, which means the implant success rate has worsened. Thus, it was suspected that the implant success rate stays low during maintenance period even if not causing implant loss under the antihypertensive medications. However, no articles in this area have been reported, and future research is needed.
The results of multivariate analysis in our study revealed that the antihypertensive medication affects the development of peri-implantitis. We found that the adjusted data for multivariate analysis were higher than the crude data in history of antihypertensive medications. In terms of eliminating confounding factors, this finding suggests that the medications might be a risk factor for the outcome of peri-implantitis. In the future, we need to be careful hearing history of antihypertensive medications in order to achieve implant maintenance successfully.
One of the limitations of the present study was the small sample size. Only nonsmoker patients without periodontal and systemic diseases other than hypertension were included in this study, and the strict inclusion criteria decreased the sample size. In the future, a prospective observational study with a large sample size on individual medications and statistical adjustment of covariates should be conducted.