Dental Neck Research Articles

Clinical Outcomes of Dental Implant Fractures: A Case Series and Analysis of Influencing Factors.

To observe and analyse patients with dental implant fracture and explore the factors influencing the fracture with the aim of providing reference for physicians' clinical work. The clinical data of 19 patients with dental implant fracture who visited the Department of Implantology of our hospital between 2007 and 2019 were retrospectively observed and analysed, and the fracture's influencing factors (e.g. the fracted implant site, implant diameter and connection mode, upper prosthetic method and fracture site) were analysed and investigated. The fractured implants comprised 12 Straumann implants (5 fractured at the smooth dental neck and 7 atop the central screws), 5 Bego implants (4 fractured at the smooth dental neck and 1 atop the central screw), 3 Lifecore implants fractured atop the central screws and 1 Anthogyr implant fractured atop the central screw. Of the 19 patients, 6 had anterior dental implant fracture, and 13 had posterior dental implant fracture (21 fractured implants in total). Maxillary anterior dental implant fracture was observed in 6 patients (8 implants), maxillary posterior implant fracture was observed in 3 patients (3 implants), and mandibular posterior dental implant fracture was observed in 10 patients (10 implants). A good implant system design, appropriate implant diameter and reasonable upper prosthetic method are key to maintaining long-term stability of a dental implant.

Cone beam computed tomography assessment of maxillary anterior teeth cervix dimensions in healthy adults for optimal anatomic healing abutments.

The abutments produced with circular symmetry failed to accurately replicate the natural teeth's cervical shapes. The purpose of this study was to measure cervical cross-sections of maxillary anterior teeth using cone beam computed tomography (CBCT) images to design anatomic healing abutments. CBCT data of 61 patients were analyzed using Ez3D Plus software. Measurements were taken at the cemento-enamel junction (CEJ) and 1 mm coronal to CEJ for maxillary central incisors, lateral incisors, and canines. Various parameters, including area, perimeter, and eight line segments in the distal (a), disto-palatal (b), palatal (c), mesio-palatal (d), mesial (e), mesio-labial (f), labial (g), and disto-labial (h) directions, were used to describe dental neck contours. The ratios (f/b and h/d) were analyzed, and differences based on sex and dental arch morphology were explored. Significant differences were found in area and perimeter between males and females, but not in f/b and h/d ratios. Differences in the f/b ratio were observed among dental arch morphologies for maxillary central incisors, lateral incisors, and canines. CBCT measurements of cervical cross-sections provide more accurate data for designing anatomic healing abutments. The fabrication of anatomical healing abutments needs to consider the influence of gender on cervical size and to explore the potential effect of arch shape on cervical morphology. The novel method provides detailed measurements for the description of dental cervical contours for patients with bilateral homonymous teeth missing. The measurements of this study could be utilized to design more accurate anatomic healing abutments to create desired morphology of peri-implant soft tissue.

Tooth discoloration induced by endodontic sealers and cervical limit: 1-year in vitro evaluation.

This laboratory study aimed to evaluate the influence of endodontic sealer and cervical limit of root filling on the discoloration of root canal treated teeth. Bovine incisors were randomly distributed into six experimental groups and control (n=21/group), according to the endodontic sealer used [AH Plus (AP); MTA Fillapex (MF) and Sealer Plus BC (SPB)] and the cervical limit of root filling [dental cervix (DC) or 2 mm in apical direction (2mm-AD)]. Tooth discoloration (ΔE) was evaluated by a digital spectrophotometer using the CIED2000 method. Color assessments were performed immediately before (baseline), 1 week, 1, 3, 6 months, and 1 year after obturation. Data were analyzed by ANOVA and Tukey's post-hoc tests (α=5%). Teeth filled with the three sealers showed perceptible tooth discoloration (ΔE≥2.7) in 1 week, maintaining similar values over time. There was a significant difference between MF and SPB sealers in the 2mm-AD groups. In addition, 2mm-AD groups promoted significantly lower discoloration than DC groups for AH (3 months) and SPB (1 and 3 months) sealer,s. Teeth filled with AP, MF, and SPB sealers displayed discoloration from 1 week to one year, with differences between MF and SPB sealers. A cervical limit of filling material at 2 mm from the dental cervix seems more advisable, promoting lower crown discoloration.

Tooth discoloration caused by endodontic treatment: A cross sectional study

Introduction: This cross-sectional study evaluated the influence of endodontic filling material, cervical limit of root filling, and tooth location on the color variation (ΔE00)from 1 to 60 months of follow-up. Materials and Methods: Color records were obtained from 70 participant’s who received 83 endodontic treatments. CIEL*a*b* color coordinates were measured on the homologous tooth, which was considered as baseline, and on endodontic treated teeth with a spectrophotometer. ΔE00 was calculated by the CIEDE2000 method at three conditions (condition 1: homologous tooth vs endodontically treated tooth after≤1 month; condition 2: homologous tooth vs endodontically treated tooth after >1–-12 months; condition 3: homologous tooth vs endodontically treated tooth after>12 months up to 5 years) for each variable. The zinc oxide and eugenol mineral trioxide aggregate or resin-based filling materials, dental cervix or ≥2 mm in the apical direction cervical limit of root filling and anterior or posterior tooth location were considered in the comparisons. Confidence intervals for the means (95% CI) were calculated,ΔE00 values and CIEL*a*b* individual color coordinates were compared for each pair of variables using the Student t test or Welch test (α = .05). Results: Greater ΔE00 values were generally observed in the condition 3 for cervical limit (ΔE00 = 10.7), use of zinc oxide and eugenol and mineral trioxide aggregate based filling materials (ΔE00 = 10.7), and anterior teeth (ΔE00 = 12.4). Only in the condition1, the ΔE00 values of the filling materials did not show statistical differences (P = .198). Conclusions: Higher ΔE00 values were yielded from zinc oxide and eugenol and mineral trioxide aggregate-based filling materials, anterior teeth, and dental cervix cervical limit of root filling. Clinical significance: Tooth discoloration yielded by endodontic materials and procedures is a challenge to clinical practice resulting in aesthetic problems and discomfort to both patient and professional, especially when it occurs in anterior teeth.

Salivary Redox Biomarkers in the Course of Caries and Periodontal Disease

Caries are a pathological process of extracorporeal nature, characterized by demineralization of inorganic substances as well as proteolysis triggered by acids produced by bacteria present in dental plaque, as a result of metabolism of sugars of both external and internal origin. Periodontal disease, on the other hand, is a multifactorial degenerative disease associated with inflammation, involving a group of tissues that surround the dental cervix and root of the tooth. It is believed that one of the mechanisms in the etiopathogenesis of caries and periodontitis are disorders of local and/or general oxidative stress (OS) parameters. Numerous clinical studies have confirmed the relationship between oxidative stress markers and oral diseases. In most analyzed studies, technical and biological variability was so high that none of the markers so far has proven suitable for routine clinical use. The aim of systematic reviews of the literature is to present the existing studies on OS parameters, mainly concerning the activity of antioxidant enzymes in saliva of patients with caries and periodontitis.

Tooth discoloration caused by endodontic treatment: A cross-sectional study.

This cross-sectional study evaluated the influence of endodontic filling material, cervical limit of root filling, and tooth location on the color variation (∆E00 ) from 1 to 60 months of follow-up. Color records were obtained from 70 participants who received 83 endodontic treatments. CIEL*a*b* color coordinates were measured on the homologous tooth, which was considered as baseline, and on endodontic treated teeth with a spectrophotometer. ∆E00 was calculated by the CIEDE2000 method at three conditions (condition 1: homologous tooth vs endodontically treated tooth after ≤1 month; condition 2: homologous tooth vs endodontically treated tooth after >1-12 months; condition 3: homologous tooth vs endodontically treated tooth after >12 months up to 5 years) for each variable. The zinc oxide and eugenol mineral trioxide aggregate or resin-based filling materials, dental cervix or ≥2 mm in the apical direction cervical limit of root filling and anterior or posterior tooth location were considered in the comparisons. Confidence intervals for the means (95% CI) were calculated, ∆E00 values and CIEL*a*b* individual color coordinates were compared for each pair of variables using the Student t test or Welch test (α = .05). Greater ∆E00 values were generally observed in the condition 3 for cervical limit (∆E00 = 10.7), use of zinc oxide and eugenol and mineral trioxide aggregate-based filling materials (∆E00 = 10.7), and anterior teeth (∆E00 = 12.4). Only in the condition 1, the ∆E00 values of the filling materials did not show statistical differences (P = .198). Higher ∆E00 values were yielded from zinc oxide and eugenol and mineral trioxide aggregate-based filling materials, anterior teeth, and dental cervix cervical limit of root filling. Tooth discoloration yielded by endodontic materials and procedures is a challenge to clinical practice resulting in aesthetic problems and discomfort to both patient and professional, especially when it occurs in anterior teeth.

Experimental Pulpitis Treated By Double-Pinhole Drainage

Objective: To search for a dental pulp preservative method in experimental pulpitis. Methods: 20 rabbits with experimental pulpitis were selected for this study; Teeth were randomly assigned to 2 groups (experimental and control groups) based on the final irrigation methods. In experimental group (double-pinhole drainage), the two pinholes were drilled in middle 1/3 dental cervix of buccal labial surface of tooth; the pinholes were inserted into infant transfusion needles then the two syringes were contacted with them, one for suck, another for irrigation. In control group, pinhole was sealed. Rabbits were executed in 1, 3, 5, 7 day. The inflammation in pulp chamber was assessed after 1, 3, 5, and 7 days. Results: At the 1, 5 day time intervals, control group reported more inflammation than experimental group (P < .05). There was no significant difference between two groups at the other time intervals (P > .05), and in all groups the inflammation decreased over time. Conclusion: Dental pulp can be preserved by double-pinhole drainage efficiently.

RESEARCH OF MAXILLARY IMPACTED CANINE IN ORTHODONTIC TREATMENT BASED ON NANOINDENTATION EXPERIMENTS

This study selected the maxillary labial impacted canine as the research object to build the model of periodontal ligament (PDL) and simulate the process of orthodontic treatment. This paper obtained stress–strain curve by calculating and analyzing the data of nanoindentation experiments. The parameters were identified through curve fittings by ABAQUS. The fitting results show that the third-order Ogden model is in good agreement with the experimental data which demonstrate that the third-order Ogden model is able to reflect the material properties of the PDL. In this paper, orthodontic process of the maxillary labial impacted canine was simulated. The results show that inside and outside surfaces of PDL all have stress variation, the stress on the root apex and dental cervix of PDL is relatively large, the maximum appears at dental cervix and the minimum appears close to tooth impedance center.

Effects of Silver Nanoparticles on the <i>In Vitro</i> Culture and Differentiation of Human Bone Marrow-Derived Mesenchymal Cells

The antibacterial properties of silver nanoparticles may be able to prevent inflammation around an implant when placed on the surface of the dental neck. The purpose of this study was to culture silver nanoparticles on human bone marrow stem cells in vitro to determine their effects on cell differentiation and to assess their biocompatibility. Silver nanoparticles were deposited on titanium foil implant surfaces using ion sputtering, and adult bone marrow mesenchymal stem cells were cultured on those surfaces to determine the effect of the silver nanoparticles on cell viability, suitability for subculture, proliferation and differentiation. The results indicated that the silver nanoparticles were biocompatible, allowing cell proliferation and differentiation of osteoblasts, but interfered with differentiation into chondrocytes and adipocytes.

インプラント30年のメッセージー過去・現在

This case is about a male patient of 55 years old, born in November 1924. At time of his first visit, he still had 20 teeth. Blade Vent Implants were placed to the free end missing in the lower right molar and the intermediate missing of the left molar. After 10 to 14 years due to the worsened prognosis, it became inevitable to remove them. To secure life-prolonging of the two anterior teeth of the mandible, Stabilizer Pin Implant was performed. Thereafter teeth difficult to conserve were extracted to be replaced by partial prosthesis, however due to the periodontal disease which is characteristic of aged patients and the dental neck caries, tooth extraction was inevitable. Since it came to a total loss of teeth both in maxilla and mandible, full denture was placed. While the maxilla was stable, there was a severe bone absorption in the mandible and as it was unstable, four Root Form Implants were placed to secure stability of the denture. Occlusion and aesthetic improved.

The Role of the Dentin Island in Root Bifurcation of the Human Molar

In the human molar, an area of calcification appears in the developmental process of tooth root bifurcation, independent of the tooth crown. This results in the formation of a dentin island, which subsequently fuses with the tooth crown dentin to form the root bifurcation. In the current study, I hypothesized that the role of the dentin island is to control the amount of dentin that is formed at the root bifurcation. The difference in the amount of dentin formed between the bifurcation side and the external- facing side of the root was investigated. The distance on the dentin surface from the dental neck to the root bifurcation midpoint, and the corresponding distance on the external mesial surface were measured. The distance on the bifurcation side was nearly twice as long as that on the external-facing side. The appearance of the dentin island is considered to supplement the formation of dentin in the bifurcation. It was possible to geometrically identify the position in the calcification point. This corresponded to the actual calcification point as determined from a tetracycline-labeling image.

Zahnwurzellänge und Zahnhalsdurchmesser als Indikatoren zur Geschlechtsbestimmung an menschlichen Zähnen

The length of the dental root and the diameter of the tooth neck are odontometric parameters which to date have rarely been used for the differentiation of the sexes. Teeth of 166 individuals from the early medieval burial ground of Eichstetten (south Germany) were available for examination. A correlation analysis was performed to show the possible dimensional interrelation of teeth which, however, applies only to the dental neck parameters. Using only diameters of the tooth neck and length of dental roots, it was possible to perform a new sex determination for 68 of the 166 individuals. It shows a good coincidence with a traditional sex determination. A traditional sex determination, performed in advance, as well as the archeological assignment of typical sex related grave goods were used for verification. For future sex determination based on teeth, examinations are recommended to be restricted to the six-year molar, the first upper premolar and, in particular, the canine. Also the dental neck diameter proved to be more useful than the crown diameter. Dental root lengths can be neglected. By comparing the results with those of a second Alamannic burial ground it could be established that discriminant analyses performed within the same population are highly congruent.

The Advantage of CO2-Treated Dental Necks, in Comparison with a Standard Method: Results of an in Vivo Study

Various methods are used for treatment of hypersensitive dental necks. They all aim to seal exposed dentinal tubules, which are open toward the oral cavity and transmit stimuli to the sensitive nerve endings of the tooth pulp. The main sealing materials are fluoride preparations, strontium chloride, and hydroxyapatite. However, these materials must be applied periodically to achieve permanent freedom from pain. Since the introduction of laser technology into dentistry, efforts have been made to treat dentine hypersensitivity with the laser. An in vitro study revealed that CO2 laser irradiation results in almost complete closure of the dentinal tubules in the dental neck region. In the present in vivo study, the efficacy of laser treatment was examined in 72 patients with dentine hypersensitivity and 72 control patients over a period of 12 weeks. When success was defined as complete freedom from pain, the success rate in the laser group was 94.5%; when marked pain relief was included in the definition of treatment success, 98.6% of the patients were treated successfully. Treatment of the control group with conventional dental neck fluoridation resulted in no marked improvement. Laser Doppler measurements of pulpal blood flow immediately before and after treatment revealed no effects of laser irradiation on pulpal blood flow. Dentine samples were obtained from the dental necks 6 weeks after laser treatment and examined with atomic absorption spectroscopy (AAS). Tin was present in the samples, which suggests that the combined laser treatment and fluoridation result in permanent integration of fluoride in the dentine surface.

光・加熱重合による臼歯部硬質レジンクラウン内面の形状変化

In order to clarify changes in the inner surface of posterior resin crowns in response to polymerization, changes in the contour of the inner surfaces of these crowns (1.0, 1.5 and 2.0 mm in thickness) under conditions of light polymerization or light and heat polymerization (heat polymerization) were determined by a three-dimensional measurement system, and changes with light polymerization were compared with those of heat polymerization. The results are summarized as follows:1. Under conditions of both light and heat polymerization, the inner surface shrank at all measurement sites and the amount of shrinkage with heat polymerization was greater than that with light polymerization.2. Under conditions of both light and heat polymerization, the amount of shrinkage was decreased in the region ranging from the occlusal surface to the dental neck, showing a claviform pattern. This tendency was marked under the light polymerization condition.3. Dimensional changes were observed, i.e., -16μm with light polymerization and -28μm with heat polymerizaiton, at a site 6 mm from the occlusal surface, -11μm with light polymerization and -30μm with heat polymerizaiton at a site 8 mm from the occlusal surface, and -8μm with light polymerization and -27μm with heat polymerization at the dental neck. There were significant differences in dimensional changes between light and heat polymerization at the site near the dental neck on the axial wall.4. When the thickness of the resin crown was 1.0, 1.5 or 2.0mm, the inner surface shrank at all of measurement sites. With the increase in thickness, the amount of constriction was increased.5. When the thickness of the resin crown was 1.0 or 1.5mm, the amount of shrinkage was decreased in the region ranging from the occlusal surface to the dental neck, showing a claviform pattern. When the thickness was 2.0mm, the amount of shrinkage was almost fixed. The ten-dency to form a claviform pattern with the 1.0mm-thick crown was greater than that with the 1.5 mm-thick crown.6. There were significant differences in all dimensional changes except height, at all measurement sites on the axial wall, between the 1.0mm-and 1.5 mm-thick crowns, and at all of measurement sites, except the occlusal surface, between the 1.0mm-and 2.0mm-thick crowns. There was a significant difference in the dimensional change of height between the 1.5mm-and 2.0mm-thick crowns.

上顎埋伏智歯の口蓋側切開抜去法

In view of the effects of impacted upper third molars upon occlusion and disarrangement of the dental arch, there recently has been an increasing tendency to remove these teeth.The author classified the surgical technique for the extraction of impacted third molars into buccal gum incision and palatal incision. This paper discusses the palatal technique, which is performed as follows: 1) An incision of 2-2. 5 cm is made parallel to the upper molars on the palatal side 5 mm away from their dental cervix, and another 1-1. 5 cm incision is made distal to the retromolar gum of 17 or 27. 2) The mucoperiosteal flap is peeled off and raised from the palatal side, while the surgeon notes the site of the foramen palatinum majus and its blood vessel bundles. 3) The bone surrounding the impacted tooth is cut off, and the tooth is removed. 4) The wound is sutured, with minimal drainage. Advantages of this technique are 1) easy access to the operative field with a good and broad view, 2) minimal bleeding, 3) minimal damage of the gingiva attachment and consequertly a short operation time. Its disadvantages are the risk of injuring a large palatal blood vessel and the inability to remove a buccally displaced impacted tooth.

上顎中切歯の歯髄腔形態のＸ線学的研究

The purpose of this study is to estimate the form of pulp cavities of upper central incisors using roentgenograms. Materials were fifty extracted upper central incisors. First, roentgenograms of these materials were taken from labio-lingual and mesio-distal directions. Then ten dentists read and traced the form of pulp cavities as shown by the roentgenograms, after which the percentage of readability was determined. Furthermore, the incisors were then cut in order to trace the actual form of pulp cavities and these tracings were compared with those made by the dentists as based on the roentgenograms. It was shown by this study that the tracings of pulp chamber at the dental cervix based on the roentgenograms taken from the labio-lingual direction and the tracings at the horn of pulp chamber based on the roentgenograms taken from the mesio-distal direction closely approximated the tracings of the cut materials. It was also found that readability of these points was 100% for all ten dentists. Based on these results, the two above mentioned points were designated as the datum points to be used when estimating the form of pulp cavities. Furthermore, the form of pulp cavities of the cut teeth was considered in order to determine the angle of the mesial and distal projection of the horn of pulp chamber against the datum plane of the dental cervix. In the above manner, a possible method of estimating the form of pulp cavities of upper central incisors using two roentgenograms was investigated.

Stress analysis of posterior bridge. Case of abutment teeth with reduced supporting tissues. Part I (Finite element method)

When the occlusal force was applied to the bridge on molar region, accompanied with a defect of the supporting tissue of abutment tooth, which ranged from 0 to 2/3 of the root length, possible change in the stress distribution occurring in the residual supporting tissue was analytically examined using two-dimensional finite element method. Furthermore, radicular tooth accompanied with various defects of the supporting tissue was simulated by a two-dimensional and a three-dimensional models and was analyzed using two-dimensional and three-dimensional finite elemnet methods.The following information was obtained:1. The stress of the mesial supporting tissue of the most anterior abutment tooth increased most with a larger defect of the supporting tissue of the abutment tooth.2. Additional abutment tooth was effective for the stress relief of the adjacent abutment tooth.3. When the defect of the supporting tissue of the most posterior abutment tooth exceeds 2/3of the root, no difference in stress distribution of the supporting tissue was found between intension bridging and free end bridging with extraction.4. Comparison of the analytical results of the two-dimensional and three-dimensional models revealed the approximation of stress values in the vicinity of root apex and largestress of the three-dimensional model in nearer approach to the dental neck.