Resonance frequency analysis for evaluation of the connecting condition between fixed prostheses and their abutment teeth: An in vitro and finite element analysis study.

STATEMENT OF PROBLEM: Loss of retention is a clinical complication for fixed partial dentures (FPDs). However, a method sensitive enough to measure the early retention loss of FPDs is lacking. PURPOSE: The purpose of this in vitro and finite element analysis (FEA) study was to determine whether resonance frequency analysis (RFA) with a newly developed system can detect lack of FPD retention caused by cement loss. MATERIALS AND METHODS: Two evaluation methods were used: RFA of an in vitro model of a 3-unit FPD from the second premolar to the second molar and FEA by using a simplified model. The in vitro model was used to evaluate 4 connecting conditions: both crowns cemented, only the premolar crown cemented, only the molar crown cemented, and both crowns uncemented. Tapping stimulation (16 impulsive forces, 4 Hz) was directly applied to the buccal side of the second molar or the second premolar, and an attached 3D accelerometer sensor was used to record the resonance frequency (RF) of the tapped tooth. The amplitude, frequency, Q-value, and total area under the curve (AUC) of the RF values in the buccolingual direction were compared between connecting conditions. The FEA was done by using a simplified model of a 3-unit FPD with similar connecting conditions as the in vitro model study, and the RF amplitude and frequency of each tooth were calculated. Statistical evaluation included 1-way analysis of variance and the Tukey HSD test to compare the differences among each connecting condition under each parameter for measurement sites on the molar and the premolar, respectively (α=.05). RESULTS: For both the molar and premolar measurements in both the in vitro and FEA models, when the measurement site was on the uncemented tooth, the amplitude of RF-1 increased, the Q-value of RF-2 decreased, and the area under the curve increased (P<.05). CONCLUSIONS: The same 3 trends found between the measurement sites of the in vitro study and FEA indicated that RFA may be useful for detecting an FPD with loosening caused by cement loss, even partial cement loss.

Effectiveness of the socket shield technique in dental implant: A systematic review.

PURPOSE: Dental implant therapy is a common clinical treatment for missing teeth. However, the esthetic result is not as satisfactory as expected in some cases, especially in the anterior maxillary area. Poor esthetic results are caused by inadequate preparation of the hard and soft tissues in this area before treatment. The socket shield technique may be an alternative for a desirable esthetic outcome in dental implant treatments. STUDY SELECTION: In the present systematic review, PubMed-Medline, Google Scholar, and ScienceDirect were searched for clinical studies published from January 2000 to December 2018. RESULTS: Twenty studies were included, comprising one randomized controlled trial, two cohort studies, 14 clinical human case reports, and three retrospective case series. In total, 288 patients treated with the socket shield technique with immediate implant placement and follow-up between 3-60 months after placement were included. A quality assessment showed that 12 of the 20 included studies were of good quality. Twenty-six of the 274 (9.5%) cases developed complications or adverse effects related to the socket shield technique. Most studies reported implant survival without the complications (90.5%); most of the cases that were followed up for more than 12 months after implant placement achieved a good esthetic appearance. The failure rate was low without the complications, although there were some failures due to failed implant osseointegration, socket shield mobility and infection, socket shield exposure, socket shield migration, and apical root resorption. CONCLUSIONS: The socket shield technique can be used in dental implant treatment, but it remains difficult to predict the long-term success of this technique until high-quality evidence becomes available.

Osteogenic effect of low-intensity pulsed ultrasound and whole-body vibration on peri-implant bone. An experimental in vivo study.

OBJECTIVES: The aims of this study were (i) to compare the osteogenic impact of low-intensity pulsed ultrasound (LIPUS) and low-magnitude high-frequency (LMHF) loading achieved with whole-body vibration (WBV) on peri-implant bone healing and implant osseointegration in rat tibiae, and (ii) to examine their combined effect on these processes. MATERIAL AND METHODS: Titanium implants were inserted in the bilateral tibiae of 28 Wistar rats. Rats were randomly divided into four groups: LIPUS + WBV, LIPUS, WBV, and control. LIPUS was applied to the implant placement site for 20 min/day on 5 days/week (1.5 MHz and 30 mW/cm2 ). WBV was applied for 15 min/day on 5 days/week (50 Hz and 0.5 g). In the LIPUS + WBV group, both stimuli were applied under the same stimulation conditions as in the LIPUS and WBV groups. After 4 weeks of treatment, peri-implant bone healing and implant osseointegration were assessed using removal torque (RT) tests, micro-CT analyses of relative gray (RG) value, and histomorphometrical analyses of bone-to-implant contact (BIC) and peri-implant bone formation (BV/TV). RESULTS: The LIPUS + WBV group had significantly greater BIC than the WBV and control groups. Although there were no significant intergroup differences in RT, RG value, and BV/TV, these variables tended to be greater in the LIPUS + WBV group than the other groups. CONCLUSIONS: The combination of LIPUS and LMHF loading may promote osteogenic activity around the implant. However, further study of the stimulation conditions of LIPUS and LMHF loading is necessary to better understand the osteogenic effects and the relationship between the two stimuli.

Tightening and Loosening of the Abutment Screw Negatively Affects Implant Osseointegration in the Early Healing Stage in Rat Tibiae.

PURPOSE: To examine the effect of tightening and loosening the dental implant screw on implant osseointegration in an elderly rat model. MATERIALS AND METHODS: Titanium dental implants were inserted in the bilateral tibiae of 34 elderly Wistar rats (1 year and 3 months old). Rats were randomly divided into five groups: control (no loading); immediate loading (IL) (vertical load [3 Hz for 15 minutes/day] immediately after implantation); early loading (EL) (load started on postoperative day 7); five times abutment removal (R5) (tightening and loosening of the abutment screw once per day for 5 days each week); and two times abutment screw removal (R2) (tightening and loosening of the abutment screw once per day for 2 days each week). After 4 weeks, the rats were euthanized, and the bone structure surrounding the dental implants was evaluated using microcomputed tomography analysis. RESULTS: Osseointegration failed more frequently in the EL, R2, and R5 groups than in the control and IL groups (P = .06). The EL, R2, and R5 groups also tended to have lower relative gray values than the control and IL groups. CONCLUSION: Tightening and loosening the abutment screw might negatively affect dental implant osseointegration in the early healing stage in older adults.

Bactericidal activity and recovery effect of hydroxyl radicals generated by ultraviolet irradiation and silver ion application on an infected titanium surface.

This study investigated the bactericidal effect, the underlying mechanisms of treatment, and recovery of biocompatibility of the infected titanium surface using a combination treatment of silver ion application and ultraviolet-A (UV-A) light irradiation. Streptococcus mutans and Aggregatibacter actinomycetemcomitans were used in suspension and as a biofilm on a titanium surface to test for the bactericidal effect. The bactericidal effect of the combination treatment was significantly higher than that of silver ion application or UV-A light irradiation alone. The bactericidal effect of the combination treatment was attributable to hydroxyl radicals, which generated from the bacterial cell wall and whose yield increased with the silver concentration. To assess the biocompatibility, proliferation and calcification of MC3T3E1 cells were evaluated on the treated titanium surface. The treated titanium screws were implanted into rat tibias and the removal torques were measured 28 days post-surgery. The titanium surface that underwent the combination treatment exhibited recovery of biocompatibility by allowing cellular proliferation or calcification at levels observed in the non-infected titanium surfaces. The removal torque 28 days after surgery was also comparable to the control values. This approach is a novel treatment option for peri-implantitis.

Reduction of inflammation in a chronic periodontitis model in rats by TNF-α gene silencing with a topically applied siRNA-loaded calcium phosphate paste.

We developed a calcium phosphate-based paste containing siRNA against TNF-α and investigated its anti-inflammatory and bone-healing effects in vitro and in vivo in a rat periodontitis model. The bioactive spherical CaP/PEI/siRNA/SiO2 nanoparticles had a core diameter of 40-90 nm and a positive charge (+23 mV) that facilitated cellular uptake. The TNF- α gene silencing efficiency of the nanoparticles in J774.2 monocytes, gingival-derived cells, and bone marrow-derived cells was 12 ± 2%, 36 ± 8%, and 35 ± 22%, respectively. CaP/PEI/siRNA/SiO2 nanoparticles cancelled the suppression of alkaline phosphatase (ALP) activity in LPS-stimulated bone marrow-derived cells. In vivo, ALP mRNA was up-regulated, TNF-α mRNA was down-regulated, and the amount of released TNF-α was significantly reduced after topical application of the calcium phosphate-based paste containing siRNA-loaded nanoparticles. The number of TNF-α-positive cells in response to CaP/PEI/siRNA/SiO2 nanoparticle application was lower than that observed in the absence of siRNA. Elevated ALP activity and numerous TRAP-positive cells (osteoclasts) were observed in response to the application of all calcium phosphate pastes. These results demonstrate that local application of a paste consisting of siRNA-loaded calcium phosphate nanoparticles successfully induces TNF-α silencing in vitro and in vivo and removes the suppression of ALP activity stimulated by inflammation. STATEMENT OF SIGNIFICANCE: We developed a calcium phosphate-based paste containing nanoparticles loaded with siRNA against TNF-α. The nanoparticles had a core diameter of 40-90 nm and positive charge (+23 mV). The anti-inflammatory and osteoinductive effects of the paste were investigated in vitro and in vivo in a rat periodontitis model. In vitro, the TNF-α gene silencing efficiency of the nanoparticles in J774.2 monocytes, gingival-derived cells, and bone marrow-derived cells was 12 ± 2%, 36 ± 8%, and 35 ± 22%, respectively. The ALP activity of bone marrow-derived cells was recovered. In vivo, TNF-α mRNA was down-regulated and the amount of released TNF-α was significantly reduced, whereas the ALP mRNA was up-regulated. Elevated ALP activity and TRAP-positive cells were observed by immunohistochemistry.

Effect of mandibular position achieved using an oral appliance on genioglossus activity in healthy adults during sleep.

BACKGROUND: Oral appliances (OAs) are generally designed to displace the mandible anteriorly and downward, to increase the airway patency. The present study aimed to examine the relationship between genioglossus (GG) muscle activity and mandibular position, considering both anterior and vertical displacements during sleep. METHODS: Seven healthy male adults aged 29.4 ± 1.99 years were evaluated. Maxillary and mandibular OAs were fabricated from 2-mm-thick resin plates with pressure-welding. The activity of the left GG was recorded using two silver ball electrodes attached to the lingual edge of the mandibular OA. Respiratory status and right masseter muscle activity were measured by an airflow sensor and surface electrodes, respectively. Electroencephalography was used to determine the sleep status. Stage 2 (the second stage of sleep) was defined as the state of sleeping. Four test conditions with different mandibular positions (0 and 50% anterior protrusion) and bite openings (4 mm and 12 mm) were examined. RESULTS: GG activity in SL4A (4 mm bite opening, 50% protrusion during sleep) and SL12 (12 mm bite opening, 0% protrusion during sleep) were significantly higher than that in SL4 (4 mm bite opening, 0% protrusion during sleep). Respiratory volume did not significantly differ between all test conditions. CONCLUSION: GG activity is influenced not only by anterior protrusion of the mandible but also by vertical displacement during sleep. Thus, when determining the effectiveness of intraoral appliances in the treatment of obstructive sleep apnea, both protrusion and the size of the mandibular opening should be evaluated and taken into account.

The effect of low-magnitude high-frequency loading on peri-implant bone healing and implant osseointegration in Beagle dogs.

PURPOSE: Low-magnitude, high-frequency (LMHF) loading plays an important role in bone healing. The present study aimed to evaluate the effect of LMHF loading applied directly to titanium dental implants on peri-implant bone healing and implant osseointegration. METHODS: The mandibular premolars and molars were extracted from six male Beagle dogs. Three months post-extraction, each of the six dogs had three titanium implants (Aadva Standard Implant Narrow, Φ3.3×8mm) inserted into the mandibular premolar and molar area (three implants per side). In each animal, one side was randomly selected to undergo daily LMHF loading (treatment group), while the other side had no further intervention (control). The loading was applied directly to the implant abutment using an individual jig and a custom-made loading device (8µm, 100Hz). The implant stability quotient (ISQ) was tested every week. Three dogs were euthanized after 2 weeks, and three were euthanized after 8 weeks. Tissue samples were fixed and stained for micro-computed tomography (micro-CT) and histomorphometric analyses. Data were analyzed statistically, with significance set at p<0.05. RESULTS: The treatment group had significantly increased peri-implant bone volume relative to tissue volume in region of interest 2 (100-500µm) compared with the control group after 2 weeks of loading (p<0.05); however, there was no significant difference between groups after 8 weeks. The ISQ value and the micro-CT results did not differ between groups during the study period. CONCLUSIONS: LMHF loading positively influenced peri-implant bone healing in the early healing period.

Evaluation of implant screw loosening by resonance frequency analysis with triaxial piezoelectric pick-up: in vitro model and in vivo animal study.

OBJECTIVE: The aim of this study was to evaluate implant screw loosening using resonance frequency (RF) analysis with triaxial piezoelectric pick-up in vitro and in vivo. METHODS: For the in vitro experiment, a titanium implant was inserted into a mandibular model. The abutment screws were tightened to 10 N torque and loosened from 0 to 90° for RF measurement using 13 different screw conditions. In the in vivo experiment, three titanium implants were installed in each tibia of a New Zealand white rabbit, and the RF values were recorded after 8 weeks. For the RF analyses, a small 3D accelerometer was mounted rigidly onto the implant abutment, and impulsive vibration was directly applied to the abutment to vibrate the implant in a direction perpendicular to the tibia and implant (x-axis). The y-axis was defined as parallel to the tibia. The RF values of the x- and y-axis directions (RF-X and RF-Y) were used for evaluation. RESULTS: The RF values significantly decreased according to the degree of screw loosening (p < 0.05, ANOVA). In the in vitro model, RF-Y with x- and y-axis vibrations (RF-Yx and RF-Yy) significantly differed from the initial value at 10 and 15°, respectively (p < 0.05, Dunnett's test). In the in vivo experiment, the RF-Yy significantly differed from the initial value between 5 and 20° (p < 0.05). CONCLUSION: The results suggest that RF analysis with triaxial piezoelectric pick-up can be used to detect implant screw loosening. CLINICAL RELEVANCE: RF analysis with the triaxial piezoelectric pick-up can be used to detect screw loosening after mounting the superstructure.

Periodontal tactile sensation and occlusal loading condition of autotransplanted teeth: A retrospective pilot study.

PURPOSE: The objectives of this retrospective pilot study were: (1) to examine the occlusal properties (periodontal tactile sensation, occlusal force support ability, dynamic tooth mobility, occlusal force, contact area, preferred chewing side and main occluding area) of autotransplanted teeth with no clinical complications after transplantation (postoperative periods from 1 to 7 years). METHODS: Three groups were formed from 20 subjects (23 teeth in each group): autotransplanted teeth (ATP group), teeth contralateral to the recipient site (control group A), and teeth contralateral to the donor site (control group B). RESULTS: The tactile detection threshold of the ATP group was higher than both the control groups, and the individual occlusal force was significantly lower than control group A. The occlusal force ratio and the occlusal contact area ratio were significantly lower in the ATP group than in both control groups, while the mobility was similar in all groups. Eight out of 20 subjects chose the autotransplanted teeth side as the preferred chewing side. Especially when the recipient site was the first molar, the ATP of these subjects were included in the main occluding area. The pocket depth of the three groups was within the normal range. CONCLUSIONS: These results demonstrate that teeth autotransplantation can achieve a mastication efficiency and periodontal condition similar to normal teeth; however, without proper healing, the periodontal sensation of autotransplanted teeth may be inferior to that of normal teeth (<250).