Arthur Rodriguez Gonzalez Cortes

Mandibular Tori Are Associated With Mechanical Stress and Mandibular Shape

PURPOSE The influence of mechanical stimulation on the formation of torus mandibularis (TM) is still poorly understood. We sought to understand the etiology of TMs by investigating the role of parafunctional activity and mandibular morphology on the formation of TMs. MATERIALS AND METHODS We designed a case-control study for patients attending the dental clinic of the present study (University of São Paulo School of Dentistry, São Paulo, SP, Brazil). Patients presenting with TMs were defined as cases, and those without TMs were defined as controls. Finite element analysis (FEA) was used in 3-dimensional mandibular models to examine the stress distribution in the mandibles with and without TMs. In addition, the associations of mandibular arch shape, mandibular cortical index, and parafunctional activity with the presence of T were assessed using odds ratio analysis. RESULTS A total of 10 patients with TMs and 37 without TMs were selected (22 men and 25 women, mean age 54.3 ± 8.4 years). FEA showed a stress concentration in the region in which TMs form during simulation of parafunctional activity. The radiographic assessment showed that those with TMs were more likely to have a square-shaped mandible with sharp angles (P = .001) and a normal mandibular cortex (P = .03). The subjects without TMs had a round-shaped mandible with obtuse angles and an eroded mandibular cortex. CONCLUSIONS Parafunctional activity could be causing the formation of TMs by concentrating mechanical stress in the region in which TMs usually form. Thus, mandibular geometries that favor stress concentration, such as square-shaped mandibles, will be associated with a greater prevalence of TMs.

Assessment of osteoporotic alterations in achondroplastic patients: a case series

Achondroplasia (ACH) is the most common form of human dwarfism and has been associated with biochemical alterations of the bone tissue, also observed in cases of osteoporosis. The present case series aimed at assessing low bone density, diagnosed with spinal bone mineral density (BMD) analysis and with panoramic radiograph measurements, in ACH patients. Spinal BMD was measured by means of dual-energy X-ray absorptiometry at the lumbar region (L1–L4). On dental panoramic radiographs of the patients, the mandibular cortical width was measured separately on the right and left sides. The Klemetti Index was also assigned as appropriate for evaluating the cortical area below the mandibular foramen. Additional parameters such as patient age, gender, body mass index, and number of teeth were also recorded. BMD results showed that 5/11 cases presented with skeletal osteopenia/osteoporosis diagnoses. Additionally, mandibular cortical erosion was detected in panoramic radiographs in 8/11 cases. The BMD and panoramic radiographic alterations found in this study suggest that the diagnosis of low bone density may have a special clinical relevance in cases of bone tissue disorders, such as achondroplasia.

Assessment of Panoramic Radiomorphometric Indices of the Mandible in a Brazilian Population

The aim of this study was to evaluate radiomorphometric indices in dental panoramic radiographs in order to identify possible interrelationships between these indices and the sex and age of the patients analyzed. The study included 1287 digital panoramic radiographic images of patients that were grouped into five age groups (1 = age 17–20; 2 = age 21–35; 3 = age 36–55; 4 = age 56–69; 5 = over age 70). Two indices—cortical width at the gonion (GI) and below the mental foramen (MI)—were measured bilaterally in all panoramic radiographs. Statistical analysis was performed with Kruskal-Wallis and Mann-Whitney tests (alpha = 0.05). Results for the indices measurements showed significant differences among patient age groups of both sexes, considering that groups 4 and 5 presented lower values for the cortical width of both indices. The present paper supports the role of sex- and age-related changes in mandibular radiomorphometric indices in identifying skeletal osteopenia.

Effect of Cone-Beam Computed Tomography Field of View and Acquisition Frame on the Detection of Chemically Simulated Peri-Implant Bone Loss In Vitro

BACKGROUND The aim of this study is to determine the influence of field of view (FOV) and number of acquisition projection images (frames) on the detection of chemically simulated peri-implant defects by cone-beam computed tomography (CBCT) using an in vitro bovine rib bone model. METHODS Eighty implants were placed in bovine ribs in which small and large bone defects were created using 70% perchloric acid. CBCT images were acquired at three acquisition protocols: protocol 1 (FOV 4 × 4 cm, 0.08-mm voxel size, 1,009 frames [high fidelity]; protocol 2 (same as protocol 1 except 512 frames [standard]); and protocol 3 (FOV 14 × 5 cm, 0.25-mm voxel size; high fidelity). Two oral and maxillofacial radiologists (OMRs) and two oral and maxillofacial surgeons (OMSs) rated the presence or absence of bone defects on a five-point scale. κ and area under the curve (AUC) were calculated and compared using analysis of variance with post hoc Tukey test at P ≤ 0.05. RESULTS Intra- and interobserver agreement for OMRs ranged from moderate to good and from slight to moderate for OMSs. For the detection of small lesions, protocol 1 (AUC 0.813 ± 0.045) provided higher detection rates than protocol 2 (AUC 0.703 ± 0.02) and protocol 3 (AUC 0.773 ± 0.55) [F(2,9) = 1.6377]. For larger defects, the trends were similar, with protocol 1 (AUC 0.852 ± 0.108) providing higher detection rates than protocol 2 (AUC 0.730 ± 0.045) and protocol 3 (AUC 0.783 ± 0.058) [F(2,9) = 1.9576]. CONCLUSION Within the limits of this study, optimal detection of chemically simulated pericircumferential implant crestal bone defects is achieved at the least radiation detriment using the smallest FOV, the highest number of acquisition frames, and the smallest voxel.

Two-Dimensional Magnesium Phosphate Nanosheets Form Highly Thixotropic Gels That Up-Regulate Bone Formation

Hydrogels composed of two-dimensional (2D) nanomaterials have become an important alternative to replace traditional inorganic scaffolds for tissue engineering. Here, we describe a novel nanocrystalline material with 2D morphology that was synthesized by tuning the crystallization of the sodium-magnesium-phosphate system. We discovered that the sodium ion can regulate the precipitation of magnesium phosphate by interacting with the crystals surface causing a preferential crystal growth that results in 2D morphology. The 2D nanomaterial gave rise to a physical hydrogel that presented extreme thixotropy, injectability, biocompatibility, bioresorption, and long-term stability. The nanocrystalline material was characterized in vitro and in vivo and we discovered that it presented unique biological properties. Magnesium phosphate nanosheets accelerated bone healing and osseointegration by enhancing collagen formation, osteoblasts differentiation, and osteoclasts proliferation through up-regulation of COL1A1, RunX2, ALP, OCN, and OPN. In summary, the 2D magnesium phosphate nanosheets could bring a paradigm shift in the field of minimally invasive orthopedic and craniofacial interventions because it is the only material available that can be injected through high gauge needles into bone defects in order to accelerate bone healing and osseointegration.

Influence of pulse sequence parameters at 1.5 T and 3.0 T on MRI artefacts produced by metal–ceramic restorations

OBJECTIVES Susceptibility artefacts from dental materials may compromise MRI diagnosis. However, little is known regarding MRI artefacts of dental material samples with the clinical shapes used in dentistry. The present phantom study aims to clarify how pulse sequences and sequence parameters affect MRI artefacts caused by metal-ceramic restorations. METHODS A phantom consisting of nickel-chromium metal-ceramic restorations (i.e. dental crowns and fixed bridges) and cylindrical reference specimens immersed in agar gel was imaged in 1.5 and 3.0 T MRI scanners. Gradient echo (GRE), spin echo (SE) and ultrashort echo time (UTE) pulse sequences were used. The artefact area in each image was automatically calculated from the pixel values within a region of interest. Mean values for similar pulse sequences differing in one parameter at a time were compared. A comparison between mean artefact area at 1.5 and 3.0 T, and from GRE and SE was also carried out. In addition, a parametric correlation between echo time (TE) and artefact area was performed. RESULTS A significant correlation was found between TE and artefact area in GRE images. Higher receiver bandwidth significantly reduced artefact area in SE images. UTE images yielded the smallest artefact area at 1.5 T. In addition, a significant difference in mean artefact area was found between images at 1.5 and 3.0 T field strengths (p = 0.028) and between images from GRE and SE pulse sequences (p = 0.005). CONCLUSIONS It is possible to compensate the effect of higher field strength on MRI artefacts by setting optimized pulse sequences for scanning patients with metal-ceramic restorations.

Nontraumatic bone expansion for immediate dental implant placement: an analysis of 21 cases.

Ridge bone resorption is a common event that occurs in tooth loss areas and that can happen in different degrees. The harvesting of autogenous bone can significantly increase treatment time and costs, and poses some risks, including postoperative pain, or possibly nerve or arterial injury. The aim of this article is to demonstrate and analyze the use of bone expansion in order to circumvent problems related to bone harvesting. This is done with screws, followed by immediate implant placement. Twenty-one cases are used to define management solutions for this type of technique to enable the later implant rehabilitation of sites affected by poor bone width.

Correction of buccal dehiscence at the time of implant placement without barrier membranes: a retrospective cone beam computed tomographic study.

PURPOSE To assess the clinical and tomographic findings of a grafting approach without barrier membranes to treat peri-implant buccal bone dehiscences at the time of implant placement. MATERIALS AND METHODS This retrospective study was conducted on all patients who needed implant placement with buccal bone grafting and were treated consecutively between March 2007 and June 2010. Two different implant systems were used (PSI, Globtek; XiVE Plus, Dentsply/Friadent). All sites had thick soft tissue (> 2 mm). All bone dehiscences were completely grafted with biphasic calcium phosphate and covered only by a soft tissue flap. Cone beam computed tomographic images were used to assess vertical buccal bone loss by measuring the distance between the implant platform and the first buccal bone contact with the implant body. Statistical analysis (Mann-Whitney test) was carried out to compare the outcomes from the two different implant systems analyzed. RESULTS Forty-one subjects (18 men, 23 women; mean age 57.3 ± 10.4 years) were selected and received 60 implants (52 delayed and 8 immediate placement). Mean follow-up was 26 months (range, 18 to 39 months). All 8 immediate implants and 33 of the 52 delayed implants presented buccal bone loss from 0 to 0.5 mm. Only two delayed sites presented buccal bone loss over 2 mm. No significant differences were seen between the implant systems. The study implant cumulative success rate was 100% (mean follow-up, 26 months). CONCLUSION Predictable outcomes can be obtained by grafting buccal bone dehiscence areas without barrier membranes in sites with a minimum soft tissue thickness greater than 2 mm.

Cone beam computed tomographic evaluation of a maxillary alveolar ridge reconstruction with iliac crest graft and implants.

The present article discusses an atrophic maxilla reconstruction with iliac crest bone block and particulate grafts and dental implants. Onlay block grafts were used to restore bone volume of the anterior maxilla, whereas bilateral sinus floor augmentation was performed using a particulate graft. Ten months after the grafting surgery, 9 dental implants were placed to rehabilitate the case. Results of a 7-year follow-up were obtained clinically and by cone beam computed tomographic images.

Evaluation of a Maxillary Sinus Floor Augmentation in the Presence of a Large Antral Pseudocyst

Abstract Sinus floor augmentation has been established as a predictable technique to overcome maxillary bone loss. Antral cystic lesions may lead to intrasurgical complications and should be accurately diagnosed. However, antral pseudocysts have recently been described not to be contraindicated for sinus-grafting procedures. The current article sought to report clinical, cone beam computed tomographic, and histologic results of a maxillary sinus floor augmentation, performed with piezoelectric surgery, in the presence of a large antral pseudocyst. Success of graft maturation was confirmed with histologic analysis, which also indicated the absence of inflammatory infiltration in the tissue evaluated. On the basis of our findings, it is possible to perform a predictable treatment based on sinus floor augmentation in the presence of antral pseudocysts. Graft maturation can also be achieved 6 months after sinus-lifting surgeries.