Dental Implant Patients Grouped by the Brinkman Index: Their Attitude toward Smoking, Nicotine Dependence, and Knowledge of Peri-Implantitis

Purpose: This study investigated the attitude of patients, grouped by the Brinkman index, towards smoking by using the Kano Test for Social Nicotine Dependence (KTSND) and their knowledge of peri-implantitis. Methods: The participants were 3093 new patients who visited the Tokyo Medical and Dental University Hospital from January 2012 to December 2013 for an oral implant. The methodology included a questionnaire about sex, age, smoking status, daily average number of cigarettes, years of smoking, knowledge of peri-implantitis, and the KTSND. The patients were grouped according to their smoking status by calculating their Brinkman index (over 200 or not): current smokers with the possibility of nicotine dependence (BI(+)CS), current smokers with no possibility of nicotine dependence (BI(-)CS), ex-smokers (ES), and non-smokers (NS). The Brinkman index is obtained by multiplying one’s daily average number of cigarettes by the number of years they have been smoking. Results: Data were collected from 2182 respondents (response rate = 71%). The KTSND scores of BI(+)CS (16.89 ± 4.26) were significantly higher than the scores of ES (11.99 ± 4.52) and NS (11.53 ± 5.01). In current smokers, there were no significant differences between BI(+)CS and BI(-)CS. The patients replied “I don’t know” about peri-implantitis most often in all groups;however, there were no significant differences between the groups. Discussion: BI(+)CS were more dependent on nicotine in social situations than the other groups were. In Japan, a Brinkman index over 200 is required for a nicotine-dependence management fee to be instituted for health insurance treatment. This is a major concern for young smokers, who may be excluded from treatment because their years of smoking are substantially less. Results revealed that there were no significant differences between BI(+)CS and BI(-)CS. Therefore, it was suggested that the Brinkman index did not sufficiently group the participants.

Combination of simvastatin and hydroxyapatite fiber induces bone augmentation

This study evaluated the capability of hydroxyapatite fiber (HAF) as a carrier and the bone formation by blending simvastatin. The mixture of HAF and simvastatin (0.15, 0.45, 0.75 mg) was placed in 1 ml of tris-buffer and the release of simvastatin from HAF was calculated per 24 hours for 10 days. Bilateral 5 mm-diameter and 3 mm-hight Teflon chambers were fixed on calvaria of adult Japanese white rabbits and filled with 40 mg HAF which containing simvastatin (0, 0.15, 0.45, 0.75 mg). The animals were sacrificed at 4 and 8 weeks and calculated radiologically by Micro-CT. After dyeing by toluidine blue the samples were analyzed histologically. In all of the study groups approximately 25% of simvastatin was released until 10 days. The new bone volume ratio measured by Micro-CT of 4 and 8 weeks group was (22.4%, 21.3%, 41.6%, 26.3%) and (20.2%, 11.7%, 42.1%, 31.2%) in different doses respectively. The 0.45 mg group showed significantly higher new bone volume ratio than 0 mg group and 0.15 mg group. The histological measurement and observations also supported these results. In conclusion, the HAF could be used as a carrier for simvastatin. Combinations of HAF and simvastatin have the potentiality to stimulate new bone formation and approximately 0.45 mg simvastatin in 40 mg HAF is the optimal dose in rabbit chamber model.

Three-Dimensional Finite Elemental Analysis of Bone Stress near an Implant Placed at the Border between Mandible and Fibular Graft in Mandibular Reconstruction

Purpose: The aim of the present study was to use finite elemental analysis (FEA) to evaluate bone stress near an implant placed at the border between the mandible and fibular graft in mandibular reconstruction. Materials and Methods: A fibular model (FM) and transplantation model (TM) were constructed for FEA. In TM, mandible was on the mesial side and the fibular graft was on the distal side. The implant was positioned at the center of both bone models. In TM, it was placed on the border between the mandible and fibular graft. A 10-mm implant was used in the monocortical model and a 15-mm implant was used in the bicortical model. The loading force was set at 100 N, the angle was set at 90°, and the loading position was set as center, mesial, or distal on the upper surface of the prosthesis. Von Mises equivalent stress values of the bone near the implant collar and apex at the middle line between buccal and lingual side were measured. Results: In all models, stress values were significantly lower with center loading than with distal loading and mesial loading. In center loading, the stress values were significantly lower in the bicortical model than in the monocortical model. There were no significant differences in stress values between FM and TM in all conditions. Conclusions: Bone stress was least with the center loading position, which was further decreased by bicortical fixation. There was no increase in mechanical stress associated with placing an implant at the border between the mandible and the fibular graft.

Effects of low intensity pulsed ultrasound stimulation on bone regeneration in rat parietal bone defect model

Purpose: Low intensity pulsed ultrasound stimulation (LIPUS) has been clinically applied to promote bone fracture healing in the orthopedic field. Thus, it is likely that LIPUS also stimulates bone regeneration in bone defects in the cranial-maxillofacial area. However, this has not been clearly proved. Furthermore, optimal time point and period of the application after the surgery has not been reported. The purpose of the present study was to evaluate the effect of LIPUS on bone regeneration in the rat parietal bone defects especially focusing on time and period of the application. Materials and Methods: Eighteen Wistar rats (14 weeks old) were divided into 6 groups: 5 experimental groups and a control group. Bone defect of 5 mm diameter was prepared on each side of the parietal bone and customized gelatin membranes were placed over the bone defects. LIPUS (160 mW/cm2, 15 min/day) was applied to the defect area with an active transducer externally in the experimental groups according to the schedules of the applications: Group 1 (day 6 - 12), group 2 (day 13 - 19), group 3 (day 20 - 26), group 4 (day 6 - 19) and group 5 (day 6 - 26). All the animals were sacrificed at 28 days. The defects were analyzed with micro CT and then histologically. Results: In Group 1, new bone formation was significantly promoted and the newly-formed bone was thick and matured compared to the one of the control group. In other experimental groups there were tendencies of stimulation of new bone formation;however, they were not statistically significant. Discussion and Conclusion: The present study demonstrated that amount of new bone formation in the bone defect depended on the time and period of LIPUS application. It has been suggested that application of LIPUS at an early healing period, the second week after the surgery, effectively accelerated new bone formation.

Long-term morphological evaluation of porous poly-DL-lactic acid for soft tissue augmentation

Soft tissues are important for aesthetic considerations in implant therapy. The purpose of this study was to investigate soft tissue augmentation by using porous poly-DL-lactic acid (PDLLA)shaped as a tablet, with a diameter of5.0 mmand a height of2.0 mm. Porous PDLLA was implanted between the periosteal and epithelial tissues in 25 rats that were sacrificed at 1, 2, 4, 12, and 24 weeks. The average height of the PDLLA scaffolds at approximately 24 weeks was 1.85 ±0.08 mm, and the molecular weight decreased with time. Sinusoidal capillaries at 1 week, connective tissues at 4 weeks, and necrotic tissues at 24 weeks were observed more than other periods. At 24 weeks, the connective tissue surviving in the pores was confirmed to contain blood vessels;therefore, blood vessels are considered to be critical for the survival of soft tissue in scaffold pores. In this study, PDLLA was found to be useful for soft tissue augmentation in the long term. Although the molecular weight of PDLLA decreased with time, the height of the PDLLA scaffolds was preserved. The connective tissue surviving in the pores of the scaffolds at 24 weeks were associated with blood vessels. Further studies are necessary to investigate the optimal scaffold shape and surface characteristics to improve the penetration of blood vessels.