Bilateral Mandibular Premolars Research Articles

Animal experiment on the accuracy of the Autonomous Dental Implant Robotic System

Objective: To evaluate the accuracy of the Autonomous Dental Implant Robotic System (ADIR) in vivo through animal experiments. Methods: Nine canine models with bilateral mandibular premolars loss were prepared. Two implants were placed in each side of canine's mandibular edentulous area. On each side, the two implants were completed by ADIR (robot group) and one experienced doctor using digital full-guided plate (guide template group) respectively. After the operation, the deviation between the actual implant position and the planned position was evaluated. The primary stability of the implant was measured, and the results of the robot group and the guide template group were statistically analyzed. Results: ADIR could successfully place implant for missing teeth in animals, and the coronal deviation, apical deviation and angular deviation [M(Q)] were 0.269 (0.152) mm, 0.254 (0.218) mm and 0.989° (0.517°) respectively, which were significantly lower than those of guide template group [the coronal deviation, apical deviation and angular deviation were 0.910 (0.872) mm, 1.179 (1.176) mm and 4.209°(5.208°) respectively] (P<0.05). Besides, there was no significant difference in the primary stability of the implant between the two groups (P>0.05). Conclusions: This study confirmed the accuracy of the ADIR in vivo, and laid a foundation for further clinical trials.

Root Reinforcement after Obturation with Calcium Silicate–based Sealer and Modified Gutta-percha Cone

IntroductionA root canal obturated with a calcium silicate–based sealer (bioceramic sealer [BCS]) and a modified gutta-percha cone (bioceramic cone [BCC]) might improve the fracture resistance of the root. The objective of this study was to evaluate root reinforcement of a bioceramic cone/sealer (TotalFill; FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) by investigating the fracture resistance, push-out bond strength, sealer penetration, and modulus of elasticity (MOE) in comparison with gutta-percha/AH Plus (Dentsply Maillefer, Tulsa, OK) (GP/AH). MethodsEighty-four roots from bilateral mandibular premolars were prepared. For fracture resistance, 40 teeth were randomly divided into 4 groups (n = 10 each): intact roots (negative control), prepared roots (positive control), and the roots obturated with either BCC/BCS or GP/AH. Root canals were obturated with the matched single-cone technique and vertically loaded with a spreaderlike tip until fracture. For push-out bond strength (n = 10 each), coronal, middle, and apical root slices of BCC/BCS and GP/AH were loaded with a cylindrical plunger, and failure modes were determined. Sealer penetration of BCC/BCS and GP/AH (n = 12 each) was evaluated for the maximum depth and the circumferential and total area of penetration at the coronal, middle, and apical levels using confocal laser scanning microscopy. The MOE was investigated according to ISO 4049:2000. ResultsThe fracture load of BCC/BCS, GP/AH, and the intact roots was not significantly different but significantly higher than the prepared, nonobturated roots. BCC/BCS provided a higher bond strength, maximum depth, and circumferential penetration at the apical root level as well as a greater sealer penetration area at all levels compared with GP/AH. The MOE of all materials was much lower than dentin. ConclusionsBCC/BCS and GP/AH bonded and reinforced the prepared roots; their fracture resistances were similar to the intact roots.

Novel bone substitute material in alveolar bone healing following tooth extraction: an experimental study in sheep.

Electrospun cotton wool-like nanocomposite (ECWN) is a novel synthetic bone substitute that incorporates amorphous calcium phosphate nanoparticles into a biodegradable synthetic copolymer poly(lactide-co-glycolide). The objectives of this study were to develop a tooth extraction socket model in sheep for bone graft research and to compare ECWN and bovine-derived xenograft (BX) in this model. Sixteen cross-bred female sheep were used. Bilateral mandibular premolars were extracted atraumatically. Second and third premolar sockets were filled (Latin-square allocation) with BX, ECWN or left unfilled. Resorbable collagen membranes were placed over BX and selected ECWN grafted sockets. Eight sheep per time period were sacrificed after 8 and 16weeks. Resin-embedded undemineralised sections were analysed for descriptive histology and histomorphometric analyses. At 8weeks, there were with no distinct differences in healing among the different sites. At 16weeks, osseous healing followed a fine trabecular pattern in ECWN sites. Non-grafted sites showed thick trabeculae separated by large areas of fibrovascular connective tissue. In BX grafted sites, xenograft particles were surrounded by newly formed bone or fibrovascular connective tissue. There were no statistically significant differences in bone formation across the four groups. However, ECWN sites had significantly less residual graft material than BX sites at 16weeks (P=0.048). This first description of a tooth extraction socket model in sheep supports the utility of this model for bone graft research. The results of this study suggested that the novel material ECWN did not impede bone ingrowth into sockets and showed evidence of material resorption.

Influence of low-intensity pulsed ultrasound on osteogenic tissue regeneration in a periodontal injury model: X-ray image alterations assessed by micro-computed tomography

ObjectiveThis study was conducted to evaluate, with micro-computed tomography, the influence of low-intensity pulsed ultrasound on wound-healing in periodontal tissues. MethodsPeriodontal disease with Class II furcation involvement was surgically produced at the bilateral mandibular premolars in 8 adult male beagle dogs. Twenty-four teeth were randomly assigned among 4 groups (G): G1, periodontal flap surgery; G2, periodontal flap surgery+low-intensity pulsed ultrasound (LIPUS); G3, guided tissue regeneration (GTR) surgery; G4, GTR surgery plus LIPUS. The affected area in the experimental group was exposed to LIPUS. At 6 and 8weeks, the X-ray images of regenerated teeth were referred to micro-CT scanning for 3-D measurement. ResultsBone volume (BV), bone surface (BS), and number of trabeculae (Tb) in G2 and G4 were higher than in G1 and G3 (p<0.05). BV, BS, and Tb.N of the GTR+LIPUS group were higher than in the GTR group. BV, BS, and Tb.N of the LIPUS group were higher than in the periodontal flap surgery group. ConclusionLIPUS irradiation increased the number, volume, and area of new alveolar bone trabeculae. LIPUS has the potential to promote the repair of periodontal tissue, and may work effectively if combined with GTR.

Evaluation of contiguous implants with cement-retained implant-abutment connections. A minipig study

Aim The presence of a microgap at the implant-abutment interface may permit bacterial contamination and lead to bone resorption, interfering with papillae formation. The present study evaluated adjacent implants with cement-retained abutments as an option to control such deleterious effects. Materials and methods Seven minipigs had their bilateral mandibular premolars previously extracted. After 8 weeks, four implants were installed in each hemi-mandible of each animal. The adjacent implants were randomly inserted on one side at the crestal bone level and on the other, 1.5 mm subcrestally. Immediately, a non-submerged healing and functional loading were provided with the abutments cementation and prostheses installation. Clinical examination and histomorphometry served to analyze the implant success. Results A total of 52 implants were evaluated at the end of the study. The subcrestal group achieved statistical better results when compared to the crestal group, clinically in papillae formation (1.97 x 1.57 mm) and histomorphometrically in crestal bone remodeling (1.17 x 1.63 mm), bone density (52.39 x 45.22%) and bone-implant contact (54.13 x 42.46%). Conclusion The subcrestal placement of cement-retained abutment implants showed better indexes of osseointegration and also improved papillae formation and crestal bone remodeling at the interimplant area after immediate loading, making them a promising option for the treatment of esthetic regions.

Novel hybrid drilling protocol: evaluation for the implant healing – thermal changes, crestal bone loss, and bone‐to‐implant contact

To evaluate a new hybrid drilling protocol, by the analysis of thermal changes in vitro, and their effects in the crestal bone loss and bone-to-implant contact in vivo. Temperature changes during simulated osteotomies with a hybrid drilling technique (biologic plus simplified) (test) versus an incremental drilling technique (control) were investigated. One hundred and twenty random osteotomies were performed (60 by group) in pig ribs up to 3.75-mm-diameter drill to a depth of 10 mm. Thermal changes and time were recorded by paired thermocouples. In a parallel experiment, bilateral mandibular premolars P2, P3, P4, and first molar M1 were extracted from six dogs. After 2-month healing, implant sites were randomly prepared using either of the drilling techniques. Forty eight implants of 3.75 mm diameter and 10 mm length were inserted. The dogs were euthanized at 30 and 90 days, and crestal bone loss (CBL) and bone-to-implant contact (BIC) were evaluated. The control group showed maximum temperatures of 35.3 °C ± 1.8 °C, ΔT of 10.4 °C, and a mean time of 100 s/procedure; meanwhile, the test group showed maximum temperatures of 36.7 °C ± 1.2 °C, ΔT of 8.1 °C, and a mean time of 240 s/procedure. After 30 days, CBL values for both groups (test: 1.168 ± 0.194 mm; control: 1.181 ± 0.113 mm) and BIC values (test: 43 ± 2.8%; control: 45 ± 1.3%) were similar, without significant differences (P > 0.05). After 90 days, CBL (test: 1.173 ± 0.187 mm; control: 1.205 ± 0.122 mm) and BIC (test: 64 ± 3.3%; control: 64 ± 2.4%) values were similar, without significant differences (P > 0.05). The BIC values were increased at 90 days in both groups compared with the 30-day period (P < 0.05). Within the limitations of this study, the new hybrid protocol for the preparation of the implant bed without irrigation, increase the temperature similarly to the incremental conventional protocol, and requires twice the time for the completion of the drilling procedure in vitro. Crestal bone loss and bone-to-implant contact in the hybrid drilling protocol are comparable with the conventional drilling protocol and do not affect the osseointegration process in vivo.

Bilateral Mandibular Premolars With Tooth Shape Deviation

Tooth shape deviations are a rare dental anomaly described in premolars and are characterized by simultaneous increased mesiodistal and decreased buccolingual dimension compared with other normal teeth. Man consulted the dentist with a complaint of misaligned teeth and requested orthodontic evaluation. After analysis of the plaster study models, it was noted that both mandibular first premolars presented a crown with an irregular shape (tooth shape deviation), larger mesiodistal measurement (11 mm), and discreetly smaller buccolingual measurement (8 mm) than the conventional premolars. Teeth are susceptible to developmental alterations, which may be primary or arise secondarily because of environmental influences. Along with alterations in size and shape, tooth shape deviation can also occur. These deviations alter the arch perimeter, leading to retention of the permanent canines and tooth crowding.

Bilateral mandibular premolars with tooth shape deviation: a rare dental anomaly

AbstractThe tooth shape deviations are rare dental anomaly described in premolars, characterized by to show simultaneously an increased mesio-distal dimension and decreased bucco-lingual dimension when compared with other normal teeth. The presence of such teeth with variation in size may be related to malocclusions, since there is a reduction in circumference of the dental arch. This report describes a rare case of bilateral tooth shape deviations in the two mandibular first premolars and discusses the prevalence of this condition and the eventual clinical consequences associated with this dental anomaly.

Effects of EMD in combination with bone swaging and calcium phosphate bone cement on periodontal regeneration in one‐wall intrabony defects in dogs

Although the application of EMD is a widely accepted periodontal-regenerative therapy, its effects on noncontained intrabony defects are unpredictable because of the lack of a space-making property. The combined use of EMD and autogenous bone grafts reportedly stimulates significant periodontal regeneration in intrabony defects. The aim of the present study was to evaluate the effects of EMD in combination with bone swaging (BS) and injectable calcium phosphate bone cement (CPC), which was placed into the spaces between the grafted swaged bone and the proximal host bone, on periodontal healing in one-wall intrabony defects in dogs. One-wall intrabony defects (3 mm wide and 5 mm deep) were surgically created on the mesial and distal sides of the bilateral mandibular premolars in four dogs. The 16 defects were assigned to one of the following treatments: EMD only, BS only, EMD with BS (EMD + BS), or EMD with BS and CPC (EMD + BS + CPC). The animals were killed 8 wk after surgery for histologic evaluation. The height of newly formed bone was significantly greater in the EMD + BS + CPC group (3.73 ± 0.30 mm) than in the BS-only (2.74 ± 0.33 mm; p < 0.05) and EMD + BS (2.88 ± 0.98 mm; p < 0.05) groups. The area of newly formed bone was significantly larger in the EMD + BS + CPC group (5.68 ± 1.66 mm(2)) than in the EMD-only (3.68 ± 0.33 mm(2); p < 0.05), BS-only (3.48 ± 1.26 mm(2); p < 0.05) and EMD + BS (3.38 ± 1.37 mm(2); p < 0.05) groups. The EMD-only (4.63 ± 0.42 mm), EMD + BS (4.67 ± 0.30 mm) and EMD + BS + CPC (4.78 ± 0.54 mm) groups showed significantly greater cementum formation than did the BS-only group (3.93 ± 0.56 mm; p < 0.05). These results indicate that treatment with EMD + BS + CPC promotes favorable periodontal healing in one-wall intrabony defects in dogs.

Influence of interimplant distances and placement depth on peri‐implant bone remodeling of adjacent and immediately loaded Morse cone connection implants: a histomorphometric study in dogs

The aim of this study was to histomorphometrically evaluate the influence of interimplant distances (ID) and implant placement depth on bone remodeling around contiguous Morse cone connection implants with 'platform-shifting' in a dog model. Bilateral mandibular premolars of six dogs were extracted, and after 12 weeks, each dog received 8 implants, four placed 1.5 mm subcrestally (SCL) on one side of the mandible and four placed equicrestally (ECL) on the other side, alternating the ID of 2 and 3 mm. The experimental groups were SCL with IDs of 2 mm (2 SCL) and 3 mm (3 SCL) and ECL with IDs of 2 mm (2 ECL) and 3 mm (3 ECL). Metallic crowns were immediately installed. After 8 weeks, the animals were euthanized and histomorphometric analyses were performed to compare bone remodeling in the groups. The SCL groups' indices of crestal bone resorption were significantly lower than those of ECL groups. In addition, the vertical bone resorption around the implants was also numerically inferior in the SCL groups, but without statistical significance. No differences were obtained between the different IDs. All the groups presented similar good levels of bone-to-implant contact and histological bone density. The subcrestal placement of contiguous Morse cone connection implants with 'platform shifting' was more efficient in preserving the interimplant crestal bone. The IDs of 2 and 3 mm did not affect the bone remodeling significantly under the present conditions.

Influence of Interimplant Distances and Placement Depth on Papilla Formation and Crestal Resorption: A Clinical and Radiographic Study in Dogs

Among the factors that contribute to the papilla formation and crestal bone preservation between contiguous implants, this animal study clinically and radiographically evaluated the interimplant distances (IDs) of 2 and 3 mm and the placement depths of Morse cone connection implants restored with platform switch. Bilateral mandibular premolars of 6 dogs were extracted, and after 12 weeks, the implants were placed. Four experimental groups were constituted: subcrestally with ID of 2 mm (2 SCL) and 3 mm (3 SCL) and crestally with ID of 2 mm (2 CL) and 3 mm (3 CL). Metallic crowns were immediately installed with a distance of 3 mm between the contact point and the bone crest. Eight weeks later, clinical measurements were performed to evaluate papilla formation, and radiographic images were taken to analyze the crestal bone remodeling. The subcrestal groups achieved better levels of papillae formation when compared with the crestal groups, with a significant difference between the 3 SCL and 3 CL groups (P = .026). Radiographically, the crestal bone preservation was also better in the subcrestal groups, with statistically significant differences between the 2SCL and 2CL groups (P = .002) and between the 3SCL and 3CL groups (P = .008). With the present conditions, it could be concluded that subcrestal implant placement had a positive impact on papilla formation and crestal bone preservation, which could favor the esthetic of anterior regions. However, the IDs of 2 and 3 mm did not show significantly different results.

Effect of biofunctionalized implant surface on osseointegration: a histomorphometric study in dogs

Among the different properties that influence bone apposition around implants, the chemical or biochemical composition of implant surface may interfere on its acceptance by the surrounding bone. The aim of this study was to investigate if a biofunctionalization of implant surface influences the bone apposition in a dog model and to compare it with other surfaces, such as a microstructured created by the grit-blasting/acid-etching process. Eight young adult male mongrel dogs had the bilateral mandibular premolars extracted and each one received 6 implants after 12 weeks, totaling 48 implants in the experiment. Four groups of implants were formed with the same microrough topography with or without some kind of biofunctionalization treatment. After histomorphometric analysis, it was observed that the modified microstructured surface with a 'low concentration of the bioactive peptide' provided a higher adjacent bone density (54.6%) when compared to the other groups (microstructured + HA coating = 46.0%, microstructured only = 45.3% and microstructured + 'high concentration of the bioactive peptide' = 40.7%), but this difference was not statistically significant. In conclusion, biofunctionalization of the implant surface might interfere in the bone apposition around implants, especially in terms of bone density. Different concentrations of bioactive peptide lead to different results.

Pulp revascularization of necrotic bilateral bicuspids using a modified novel technique to eliminate potential coronal discolouration: a case report

To present a case report in which the pulp of two bilateral mandibular premolars with dens evaginatus were revascularized using a modified novel technique to avoid undesired crown discolouration. Recently, regeneration of necrotic pulps has become an alternative conservative treatment option for young permanent teeth with immature roots and is a subject of great interest in the field of endodontics. This novel procedure exploits the full potential of the pulp for dentine deposition and produces a stronger mature root that is better able to withstand the forces than can result in fracture. However, the current protocol has potential clinical and biological complications. Amongst them, crown discolouration, development of resistant bacterial strains and allergic reaction to the intracanal medication. In the case presented, a modified technique to avoid undesired crown discolouration was applied sealing the dentinal tubules of the chamber, thus avoiding any contact between the tri-antibiotic paste and the dentinal walls. * Sealing the dentinal tubules of the chamber prevents the undesirable crown discolouration produced by tri-antibiotic medication whilst maintaining the revascularization potential of the pulp. * Further research is warranted to seek an alternative infection control protocol capable of preventing possible allergic reactions and development of resistant strains of bacteria, as well as a biological material capable of inducing angiogenesis and allow a more predictable scaffold and tissue regeneration.

Influence of Interimplant Distance on Papilla Formation and Bone Resorption: A Clinical-radiographic Study in Dogs

Implant esthetics has been the focus of attention for the past decade, and one vital issue is the effect of interimplant distance on interimplant papilla formation and crestal bone loss. The aim of this study was to evaluate the effect of 1, 2, and 3 mm of interimplant distance on papilla formation and crestal resorption in submerged and nonsubmerged Ankylos implants after prosthetic restoration. Bilateral mandibular premolars of 7 dogs were extracted, and after 12 weeks each dog received 8 implants. Implants were placed so that 3 interimplant distances were created at 1 mm (group 1), 2 mm (group 2), and 3 mm (group 3). The sides and the position of the groups were randomly selected. Twelve weeks after placement, the implants received metallic prostheses that allowed 5 mm of space between the prosthetic contact point (CP) and the crestal bone (CB). After 8 weeks, the distance between the CP and the papilla (CP-P) and the gingival height at the distal proximal aspect of the prosthesis (CP-DE) was clinically measured. Radiographic images were obtained to measure the distance of the CP to the CB within the interimplant surfaces (CP-IP) and adjacent to the edentulous surfaces (CP-ED). The clinical measurement of CP-P for submerged and nonsubmerged implants was 3.57+/-1.17 mm and 3.10+/-0.82 mm for group 1, 3.57+/-0.78 mm and 3.16+/- 0.87 mm for group 2, and 3.35+/- 0.55 mm and 3.07+/-0.93 mm for group 3. The CP-DE was 3.25+/-0.77 mm for submerged and 2.78+/- 0.64 mm for nonsubmerged implants. The CP-IP for the submerged and nonsubmerged implants was 6.91+/-0.95 mm and 7.68+/-2.73 mm for group 1, 7.46+/-1.43 mm and 5.87+/-1.71 mm for group 2, and 7.72+/-0.81 mm and 7.59+/-1.33 mm for group 3. The CP-ED was 6.77+/-1.33 mm for submerged implants and 6.03+/-1.58 mm for nonsubmerged implants. There were no statistical significant differences for any of the measured parameters. We conclude that when the distance from the CP to the CB was 5 mm, interimplant distances of 1 to 3 mm did not affect papilla formation or crestal resorption of submerged or nonsubmerged implants in the dog model.

抜歯創治癒への交感神経系の影響に関する研究 : 歯肉および抜歯窩内活性酸素動態の検討

The influence of the sympathetic nervous system activity on oxygen free radicals in tooth extraction wounds was studied in dogs. Cervical sympathetic trunks were stimulated continuously in seven healthy dogs by a portable pacemaker (group S). Postcervical ganglions were permanently blocked with pure ethanol in other seven dogs (group B). Bilateral gingival blood flow was measured in both groups by the hydrogen clearance method and the laser doppler method. Bilateral mandibular premolars and molars were extracted in all dogs of both groups. Activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and concentration of lipid peroxide (LPO) in gingivas and tooth extraction sockets of all dogs were measured on the fourth day after extraction. The results were as follows : 1. Gingival perfusion significantly decreased in group S and increased in group B in ipsilateral side compared with contralateral side without any remarkable cardiodynamic changes. 2. In group S, the average levels of SOD, GSH-Px activities and LPO concentration in ipsilateral gingivas seemed to be higher than those in contralateral gingivas. The level of CAT activity in ipsilateral gingivas seemed to be the same as that in contralateral gingivas. 3. The levels of SOD and CAT activities in ipsilateral extraction sockets seemed to be lower and the level of GSH-Px activity was significantly lower than those in contralateral extraction sockets in group S. Ipsilateral LPO concentration, however, seemed higher. 4. In group B, the level of ipsilateral gingival SOD activity seemed to be lower, moreover the levels of CAT, GSH-Px activities and LPO concentration were remarkably lower than those in contralateral gingivas. 5. The levels of SOD, CAT, GSH-Px activities and LPO concentration in ipsilateral extraction sockets showed no changes, the same as in contralateral side in group B. These results suggest that ischemia occurring by hyperactivity of sympathetic nervous system accelerates the production of oxygen free radicals in tooth extraction wounds. It seems that increase of perfusion by sympathetic nerve blocks suppresses those accelerations.