Interradicular Bone Research Articles

Bone response to orthodontic forces in diabetic Wistar rats

Patients with type 1 diabetes have shown decreased bone mineral density (BMD) values. The need for orthodontic treatment in diabetic patients is usually associated with occlusal problems and the occurrence of abnormalities in the development of the jaws. The aim of this study was to analyze bone response of insulin-treated and untreated diabetic rats after applying orthodontic forces. Wistar rats were divided into 3 groups: experimental orthodontics, experimental diabetes and orthodontics, and experimental diabetes treated with insulin and experimental orthodontics. Orthodontic forces were applied the first day of the seventh week. Forty-eight hours after placement, all the animals were killed, and the maxillae were excised and processed using routine histologic techniques. Bone activity in the periodontal cortex of the dental alveolus showed a significant decrease in bone formation and erosive areas in diabetic animals as compared with controls. A recovery of these parameters could be observed in the group with experimental diabetes treated with insulin and experimental orthodontics. Bone volume in the interradicular bone showed no significant differences among groups. People with diabetes should not receive orthodontic treatment until their metabolic status normalizes. Bone response to orthodontic forces in insulin-treated diabetic subjects does not differ significantly from that observed in healthy subjects.

Immediate Implantation in the Maxillary and Mandibular Molar Fresh Sockets: Technique and Results

Background and aims. The aim of this study was to evaluate the predictability of implantation at the time of maxillary and mandibular molar extraction. Materials and methods. Maxillary and mandibular molars were extracted with an atraumatic technique (root separation and careful extraction with a periotome) to preserve all remaining inter-radicular bone. Then, 115 tapered and straight implants were inserted in extraction sites. Inter-radicular bone was utilized to provide primary stability for the implants. Regenerative therapy including placement of bone substitute and resorbable membrane, was performed around all the implants. Results. Four out of 115 implants failed and were removed one month after insertion because of mobility and radiolucency around the implants. The 7-year cumulative survival rate (CSR) of implants was 96.5%. The maxillary and mandibular 7-year CSRs were 92.7% and 98.6%, respectively. Conclusion. The combination of atraumatic extraction of hopeless molars, immediate implant placement and concomitant regenerative therapy is a predictable surgical procedure, affording implant stability for restoration with a single crown.

Maxillary Sinus Augmentation by the Crestal Core Elevation Technique

The crestal core elevation (CCE) technique is reportedly a less invasive procedure than the lateral window elevation technique. We retrospectively evaluated long-term outcomes of CCE procedures over an 11-year time period. Core preparations were made after extractions of 57 upper molars in 45 patients. Extraction sites were drilled with a calibrated trephine bur to an estimated distance of 1 mm from the sinus membrane. The trephined interradicular bone and underlying sinus membrane were imploded into the sinus. The surgical crater and residual extraction socket were filled with deproteinized bovine bone mineral or freeze-dried bone allograft, stabilized, and protected with an absorbable collagen membrane and fully covered with coronally positioned flaps. Implants were placed 4 months later. Success was defined if ≥9 mm available bone height was available. Where the available bone height varied between 7 and 9 mm, implant placement was complemented using the bone-added osteotome sinus floor elevation technique; those sites were defined as a "partial success." The CCE technique was successful in 31 (68.9%) out of 45 sites, and partially successful in six (13.3%) out of 45 sites. Eight sites failed (17.8%). Surgical failures were caused by core detachment resulting in large tears of the sinus membrane. Implants placed in successful sites presented a 100% survival rate during the study duration. CCE implemented simultaneously with molar extractions provided therapeutic benefits and clinical limitations. The subsequent implant placement using CCE revealed an excellent survival rate in the study population evaluated.

Evidence that metyrapone in the presence of inflammation modulates cytokine mRNA expression

Objective Metyrapone (MT) has been used clinically to decrease glucocorticoid levels in human and animal studies. However, the potential effects of MT in the presence of inflammation are poorly understood. Thus, the aim of this study was to evaluate the effects of the administration of MT on the mRNA levels of pro-inflammatory cytokines in the presence of inflammation induced by the well-established model of ligature-induced periodontitis in rats. Material and methods Sixty animals were randomly assigned into three experimental groups of 20 rats each: G1-control; G2-periodontal disease (PD) induced by cotton ligature; G3-PD associated with 3 daily doses of MT (50 mg/kg/3 × 3 h). After 30 days, all animals were killed by decapitation. Blood samples were taken and the concentrations of corticosterone and catecholamines measured. Marginal tissues around ligated and non-ligated teeth were harvested and gene expression was assessed by quantitative polymerase chain reaction technique (qPCR). Moreover, the area of interradicular bone loss (ABL) was histometrically determined. Results Data analysis showed that: (i) ligature placement resulted in a significant ABL, as compared to non-ligated sites of G1 group; (ii) mRNA levels of all the pro-inflammatory factors assessed (INF-γ, TNF-α, IL-1β and IL-6) were increased in the PD group (G2) ( p < 0.05) when compared to G1; (iii) there were no significant differences in corticosterone and catecholamine plasmatic levels between the three groups; (iv) MT administration, in the presence of inflammation, induces an increased ABL and significantly increased mRNA levels of all pro-inflammatory cytokines analyzed ( p < 0.05). Conclusion Within the limits of this study, it can be concluded that MT in the presence of inflammation may modulate expression of pro-inflammatory cytokines, regardless of its effect on plasma corticosterone levels.

Therapy for Missing Lower Medial Incisor by Means of Reduced Diameter Implants

S ince Branemark first described the principle of osseointegration in the field of dentistry, dental implantology has become a rapidly evolving and innovative field. In 2004, the American Dental Association Council on Scientific Affairs cited dental implants as the ‘‘first generation of tissue engineering devices that will affect the dental profession.’’ Accordingly, a wide variety of implant materials, shapes, sizes, and surface treatments have been devised. Patients have become aware of the potential of dental implants; prostheses that function immediately are often desired. To meet this demand, implants of increasingly smaller diameter have been devised, and singlestage procedures with immediate functional loading have become available. Small-diameter implants (SDIs) are the preferred treatment modality in cases of limited anatomic geography. These implants range from 2.75–3.3 mm in width and from 8.0–15.0 mm in length. Specifically, SDIs are indicated for replacement of teeth with small cervical diameters and in cases of reduced interradicular bone. They also have been shown to be a viable alternative to bone augmentation when poor alveolar ridge width is encountered and in cases of restricted mesiodistal anatomy. Based on this in vivo and in vitro success, the mini dental implant (MDI) seems a logical successor. Smaller than their SDI counterparts, MDIs have diameters ranging from 1.8– 2.4 mm. MDIs were initially designed for temporary prosthetic stabilization during the healing phase of standard implants. Reproducible success in this indication has led to expanded use in orthodontic anchorage, for the temporary fixation of transplanted teeth, in periodontal therapy, and, more recently, for long-term fixed and removable prosthetics. Although the Sendax MDI (3M ESPE, OsseoSOURCE, St Paul, Minn) was the first MDI to gain approval from the U.S. Food and Drug Administration for long-term applications, several other MDI systems are available, including Hi Tec Implants (Hi Tec Implants, Herzlia, Israel) and Monorail MTI 1 Private dental practice, DEIMPERIO, LLC, Bratislava, Slovak Republic. 2 Department of Stomatology and Maxillofacial Surgery of the Faculty of Medicine, Comenius University and Oncologic Institute of St Elisabeth, Bratislava, Slovak Republic. 3 Private dental practice, DENTALNE CENTRUM, LLC, Trnava, Slovak Republic. 4 Private dental practice, Eurodent Medima, LLC, Martin, Slovak Republic. * Corresponding author, e-mail: richard.jurkovic@chello.sk DOI: 10.1563/AAID-JOI-D-09-00138 CASE LETTER

Modified Insertion Technique for Immediate Implant Placement into Fresh Extraction Socket in the First Maxillary Molar Sites: A 3-Year Prospective Study

Immediate implant placement after tooth extraction is a predictable solution in various clinical situations. The purpose of this study was to evaluate the predictability of a treatment, including the placement of implants, using a modified insertion technique at the time of maxillary molar extraction. Sixty-eight patients with a total of 68 teeth scheduled for tooth extraction and immediate implant placement into fresh sockets were included in the study. Implants were positioned just after teeth removal and, in case of necessity, a regenerative therapy was performed at the same time. After a 3-month period of healing, implants were restored with single crown fixed prostheses. All implants restored with single crowns were monitored for 36 months; only, 3 implants failed with a cumulative survival rate of 97.96%. The combination of atraumatic extraction of maxillary molars, sufficient residual inter-radicular bone, and the use of appropriate regenerative material at the time of implant insertion, represents a predictable long-term treatment.

Accurate pre-surgical determination for self-drilling miniscrew implant placement using surgical guides and cone-beam computed tomography

Miniscrew implants have proven to be effective in providing absolute orthodontic anchorage. However, as self-drilling miniscrew implants have become more popular, a problem has emerged, i.e. root contact, which can lead to perforation and other root injuries. To avoid possible root damage, a surgical guide was fabricated and cone-beam computed tomography (CBCT) was used to incorporate guide tubes drilled in accordance with the planned direction of the implants. Eighteen patients (5 males and 13 females; mean age 23.8 years; minimum 10.7, maximum 45.5) were included in the study. Forty-four self-drilling miniscrew implants (diameter 1.6, and length 8 mm) were placed in interradicular bone using a surgical guide procedure, the majority in the maxillary molar area. To determine the success rates, statistical analysis was undertaken using Fisher's exact probability test. CBCT images of post-surgical self-drilling miniscrew implant placement showed no root contact (0/44). However, based on CBCT evaluation, it was necessary to change the location or angle of 52.3 per cent (23/44) of the guide tubes prior to surgery in order to obtain optimal placement. If orthodontic force could be applied to the screw until completion of orthodontic treatment, screw anchorage was recorded as successful. The total success rate of all miniscrews was 90.9 per cent (40/44). Orthodontic self-drilling miniscrew implants must be inserted carefully, particularly in the case of blind placement, since even guide tubes made on casts frequently require repositioning to avoid the roots of the teeth. The use of surgical guides, fabricated using CBCT images, appears to be a promising technique for placement of orthodontic self-drilling miniscrew implants adjacent to the dental roots and maxillary sinuses.

The temporal expression and localization of extracellular matrix metalloproteinase inducer (EMMPRIN) during the development of perio-dontitis in an animal model

We previously demonstrated extracellular matrix metalloproteinase inducer (EMMPRIN) was associated with the matrix metalloproteinases production of human periodontitis. The aim of this study was to investigate the temporal expression and localization of EMMPRIN during ligature-induced periodontitis in rats. Periodontitis was induced in rats by placing a thread around the cervix of the first mandibular molar. Animals were killed 3, 7, 11, 15 or 21 d after ligation. Mandibles were processed for paraffin sections and stained with hematoxylin and eosin or picrosirius red. The distance from the amelocemental junction to the alveolar crest (ACJ-AC) and the area fraction (Area%) of collagen fibers were measured. EMMPRIN was examined by immunohistochemistry and quantified by positive cell counting. Correlation analyses were then performed. Histologically, alveolar bone was gradually destroyed from day 3 to 11 and then stabilized. Collagen fibers were slightly dissociated on day 3 and extensively broken on day 7. They were reconstructed from day 11 to 21. EMMPRIN was localized predominantly in infiltrating cells and adjacent fibroblasts in interdental gingiva. The number of EMMPRIN-positive cells increased on day 3, peaked on day 7 and then gradually subsided from day 11 to 21. Statistically, there was a moderate positive correlation regarding the ACJ-AC distance (r = 0.552, p < 0.01) and a strong negative correlation with the Area% of collagen fibers (r = -0.808, p < 0.01). In gingival epithelium, the immunoreactivity was extremely strong in basal layer cells and sulcular epithelial cells in health. It was greatly enhanced in the inflamed conditions on days 3 and 7. In the interradicular bone, EMMPRIN was localized in the osteoclasts on days 3 and 7, as well as in the osteoblasts from day 11 onwards. The expression and localization of EMMPRIN are temporally varied during the development of periodontitis. In addition, the inflammation-dependent expression of EMMPRIN might be involved in alveolar bone resorption and collagen breakdown.

Proper mesiodistal angles for microimplant placement assessed with 3-dimensional computed tomography images

To provide information about placement sites and angulations of microimplants between tooth roots, we analyzed 3-dimensional computed tomography images from 25 patients. The patients in the sample had good interdigitation, no restorations, and no arch length discrepancies in the posterior segments. Three-dimensional images of the maxillary and mandibular second premolars, first molars, and second molars were constructed. The distances and midpoints between the roots at 3 levels were calculated, and the angles between the lines connecting the midpoints and perpendicular lines to the occlusal plane at the contact points were also calculated. The midpoints between the roots were located distally to the contact point and from the cervical to the apical areas. The lines connecting these midpoints from the cervix to the apex of the roots in the mandibular arch had more distal inclination than in the maxillary arch. To minimize root contacts, microimplants need to be inclined distally about 10 degrees to 20 degrees and placed 0.5 to 2.7 mm distally to the contact point to minimize root contact according to sites and levels, except into palatal interradicular bone between the maxillary first and second molars.

Cyclophilin A (CypA) is associated with the inflammatory infiltration and alveolar bone destruction in an experimental periodontitis

Background and objective: CypA is able to regulate inflammatory responses and MMPs production via interaction with its cell surface receptor, EMMPRIN. This study aimed to address the possible association of CypA with pathological inflammation and destruction of periodontal tissues, and whether CypA–EMMPRIN interaction exists in periodontitis. Materials and methods: Experimental periodontitis was induced by ligation according to our previous method. Histological and radiographic examinations were performed. Western blot was used to detect CypA and EMMPRIN expressions in gingival tissues. Immunohistochemistry was applied for CypA, EMMPRIN, MMP-1, MMP-2, MMP-9, as well as cell markers of macrophage, lymphocyte and neutrophil. CypA expression, alveolar bone loss, and inflammatory infiltrations were quantified followed by correlation analyses. Results: Western blot revealed that CypA and EMMRPIN expressions were dramatically elevated in inflamed gingival tissues (ligature group) as compared to healthy gingival tissues (control group). The enhanced CypA and EMMPRIN expressions were highly consistent in cell localization on seriate sections. They were permanently co-localized in infiltrating macrophages and lymphocytes, as well as osteoclasts and osteoblasts in interradicular bone, but rarely expressed by infiltrating neutrophils. MMP-1, MMP-2, and MMP-9 expressions were also sharply increased in inflamed gingiva. MMP-2 and MMP-9 were mainly over-expressed by macrophages, while MMP-1 was over-produced by fibroblasts and infiltrating cells. The number of CypA-positive cells was strongly correlated with the ACJ–AC distance (r=0.839, p=0.000), the number of macrophages (r=0.972, p=0.000), and the number of lymphocytes (r=0.951, p=0.000). Conclusion: CypA is associated with the inflammatory infiltration and alveolar bone destruction of periodontitis. CypA–EMMPRIN interaction may exist in these pathological processes.

Estrogen Withdrawal Transiently Increased Bone Turnover Without Affecting the Bone Balance Along the Tooth Socket in Rats

Estrogen withdrawal causes marked bone loss in the appendicular skeleton but slightly affects mandibular cancellous bone; in contrast, little is known of its effects on alveolar wall turnover associated with tooth drift. In this study, we assessed short-term changes in alveolar wall turnover after an ovariectomy and compared it to other bone sites exhibiting different levels of turnover. Forty Sprague-Dawley rats were ovariectomized or sham operated. Right mandibles and femurs were processed without demineralization for bone histomorphometry in three different sites: the alveolar wall around the first molar buccal root, apical interradicular bone, and femoral metaphysis. Bone changes were assessed 14 and 28 days after the ovariectomy. Data were compared using non-parametric statistics. At 14 days, on the resorption side of the alveolar wall, resorption parameters were higher in the ovariectomized rats (P <0.01), whereas the formation was lower (P <0.05); on the formation side, the daily mineral apposition rate increased (P <0.01). The root resorption was higher in ovariectomized rats (P <0.05). In the periodontal ligament, the numbers of osteoclast precursors were significantly higher. At 28 days, the drift slowed down in both the sham and ovariectomized groups. The ovariectomy had no effect on interradicular bone turnover, whereas bone loss and numbers of osteoclasts were strongly increased in the femur as soon as 14 days after the ovariectomy. Estrogen withdrawal had transient repercussions on alveolar wall turnover. The different reactivities of the three envelopes studied suggest that a response to an ovariectomy in the short term is related to initial basal turnover.

Clinical outcome of narrow diameter implants inserted into allografts

Objective:Narrow diameter implants (NDI) (i.e. diameter <3.75 mm) are a potential solution for specific clinical situations, such as reduced interradicular bone, thin alveolar crest and replacement of teeth with small cervical diameter. NDI have been available in clinical practice since the 1990s, but only few studies have analyzed their clinical outcome and no study have investigated NDI inserted in fresh-frozen bone (FFB) grafts. Thus, a retrospective study on a series of NDI placed in homologue FFB was designed to evaluate their clinical outcome.Material and Methods:In the period between December 2003 and December 2006, 36 patients (22 females and 14 males, mean age 53 years) with FFB grafts were selected and 94 different NDI were inserted. The mean follow-up was 25 months. To evaluate the effect of several host-, surgery-, and implant-related factors, marginal bone loss (MBL) was considered an indicator of success rate (SCR). The Kaplan Meier algorithm and Cox regression were used.Results:Only 5 out of 94 implants were lost (i.e. survival rate - SVR 95.7%) and no differences were detected among the studied variables. On the contrary, the Cox regression showed that the graft site (i.e. maxilla) reduced MBL.Conclusions:NDI inserted in FFB have a high SVR and SCR similar to those reported in previous studies on regular and NDI inserted in non-grafted jaws. Homologue FFB is a valuable material in the insertion of NDI.

A radiographic evaluation of the availability of bone for placement of miniscrews.

Monocortical screws are increasingly being used to enhance orthodontic anchorage. The most frequently cited clinical complication is soft tissue irritation. It is thus clinically advantageous for these miniscrews to be placed in attached mucosa. The purpose of this study was to (1) determine radiographically the most coronal interradicular sites for placement of miniscrews in orthodontic patients and (2) determine if orthodontic alignment increases the number of sites with adequate interradicular bone for placement of these screws. Sixty panoramic radiographs (n = 30 pretreatment, n = 30 posttreatment) of orthodontic patients were obtained from an archival database after Institutional Review Board approval. Selection criteria included minimal radiographic distortion and complete eruption of permanent second molars. Interradicular sites were examined with a digital caliper for presence of three and four mm of bone. If three or four mm of bone existed, then a vertical measurement from the cementoenamel junction (CEJ) to first measurement was made. In addition, the magnification error inherent in panoramic radiographs was estimated. Ninety-five percent confidence intervals were calculated for the vertical distances from the CEJ to the horizontal bone location. Bone stock for placement of screws was found to exist primarily in the maxillary (mesial to first molars) and mandibular (mesial and distal to first molars) posterior regions. Typically, adequate bone was located more than halfway down the root length, which is likely to be covered by movable mucosa. Inability to place miniscrews in attached gingiva may necessitate design modifications to decrease soft tissue irritation.

The influence of thyroid hormones on periodontitis‐related bone loss and tooth‐supporting alveolar bone: a histological study in rats

Recent studies have pointed to potentially periodontal risk indicators, however no information is available on the impact of changes in thyroid hormone levels on the progression of periodontitis and on the quality of alveolar bone. Thus, the aim of the present study was to evaluate histologically, in rats, the influence of thyroid hormones on the rate of periodontal bone loss resulting from ligature placement and on the quality of tooth-supporting alveolar bone. Thirty-six male Wistar rats were randomly assigned to the following groups: healthy (control, n = 12), hypothyroidism (n = 12) and hyperthyroidism (n = 12). Once alterations were confirmed by total serum levels of triiodothyronine and thyroxine, ligatures were randomly placed around one of the first mandibular molars. Thirty days later, the animals were killed and specimens routinely processed for serial decalcified sections. The parameters assessed were periodontitis-related bone loss, quality of tooth-supporting alveolar bone and the number of cells positive for tartrate-resistant acid phosphatase (TRAP), a marker of bone resorption. At the ligated sites, intergroup analysis revealed that hypothyroidism significantly increased the bone loss resulting from ligature-induced periodontitis (p = 0.02) and the number of TRAP-positive cells on the linear surface of bone crest (p = 0.01). In addition, no significant differences were detected regarding the quality of the bone (p = 0.24) or the number of TRAP-positive cells in the area of the interradicular bone for ligated teeth among the groups (p = 0.17). It may be concluded that decreased serum levels of thyroid hormones may enhance periodontitis-related bone loss, as a function of an increased number of resorbing cells, whereas the tooth-supporting alveolar bone seems to be less sensitive to alterations in hormone levels.

Induction of osteopenia during experimental tooth movement in the rat: alveolar bone remodelling and the mechanostat theory

Increases in bone strains above a certain threshold have a positive effect on bone mass, whereas reductions in strain magnitude lead to bone loss and osteopenia; the term 'mechanostat' has been introduced to describe this tissue-level negative feedback mechanism. The mechanobiology of bone and particularly alveolar bone is poorly understood, and whether the mechanostat theory has any relevance to explaining the osseous changes that occur during orthodontic tooth movement remains unclear. To investigate the relationship further, an expansile force of 0.2 N was applied to the maxillary molars of 36, 6-week-old Wistar rats by helical coil springs. The animals were sacrificed at 1, 2, 4, and 8 days and the tissue response analyzed by histological, biochemical, and finite element (FE) methods. Differences between groups were determined by Student's t-test (two-tailed). The appliance produced an increase in the intermolar width averaging 0.5 mm after 8 days. Tetracycline uptake in the control rats suggested a rapid turnover of bone in both the interradicular domain and the bone-periodontal ligament interface. In the experimental group, however, incorporation of tetracycline into the interradicular domain was reduced and conventional histology revealed evidence of bone loss and osteopenia, in both the experimental and a group of sham-treated positive controls (with inactive, annealed springs). Serum alkaline phosphatase declined significantly in both experimental and sham-treated groups over the 8-day time course, indicating decreased bone formation. Serum acid phosphatase also declined, suggesting a concomitant decrease in bone resorption. Three-dimensional FE analysis of the stresses generated in the bone following occlusal (2 N) and orthodontic loading showed that the orthodontic force created a constant loading condition shielding some areas of bone from mechanical stress. Areas of low mechanical stimulation were coincident with sites of bone loss observed histologically, while bone mass was preserved in areas with higher levels of loading. These findings suggest that (1) the osteopenia resulted from stress shielding of the interradicular bone by the appliance, and a consequent reduction in occlusal loading below the critical threshold required for maintaining normal osseous architecture and (2) the mechanostat model can be employed to explain, at least in part, the response of the bone to orthodontic loading.

Evaluation of high-resolution cone beam computed tomography in the detection of simulated interradicular bone lesions

The purpose of this study is to assess the accuracy of limited-volume high-resolution cone beam CT (CBCT) in the detection of periodontal bone loss. 163 simulated periodontal lesions of different depths were created in dried human hemimandibles. Specimens were imaged using the intraoral paralleling technique and limited-volume CBCT (3DX Accuitomo; Morita Co. Ltd, Kyoto, Japan). Ten viewers examined the images. Data were analysed with receiver operating characteristics (ROC) analysis. ROC curves were generated and the areas under the maximum-likelihood curves (A(z)) were compared. Other statistical analyses were used to detect the normality of the distribution of the results. The results are reported as the individual viewer ROC curve areas for each of the two imaging modalities. In all experiments the A(z) area for CBCT (0.770-0.864) was larger than the A(z) area for periapical film (0.678-0.783); statistical tests showed a statistically significant difference between the two modalities. Results indicate that the CBCT technique has better accuracy and diagnostic value than periapical films in the detection of interradicular periodontal bone defects.

Sinus Floor Elevation From a Maxillary Molar Tooth Extraction Socket in a Patient With Chronic Inflammation

The compromised nature of the residual interradicular bone after extraction of periodontally hopeless maxillary molars often requires a sinus elevation procedure to ideally place the implants to accept future prosthesis. Maxillary sinus elevation surgery is a procedure used to increase the volume of bone mass so that dental implants can be placed. This article documents a sinus floor elevation technique through an extraction socket in a 65-year-old white male with chronic inflammation to increase the bone mass after the extraction of a periodontally involved maxillary molar tooth. Computerized tomography revealed an increased thickness of the sinus membrane, which was attributed to possible chronic sinus inflammation and periodontal inflammation. After consultation with the Department of Otolaryngology, it was diagnosed as chronic inflammation without any contraindication for sinus elevation surgery or implant placement. One month after the extraction, the sinus floor elevation surgery was performed through the extraction socket, and implants were placed 4 months later. An uneventful healing was noted after 6 months of osseointegration; two porcelain-fused-to-metal crowns were fabricated. Clinical follow-up took place every 3 months for 3 years, and successful healing was achieved. The patient was satisfied with the esthetic and functional results of the oral rehabilitation. Sinus floor elevation through an extraction socket without any residual bone, followed by dental implant placement, provided successful functional results and acceptable stability.

Bone density at interradicular sites: implications for orthodontic mini‐implant placement

Implant stability is primarily related to local bone density; Few studies have evaluated interradicular bone density related to mini-implant placement for orthodontic anchorage. Therefore, this study evaluated bone density differences between interradicular sites. Computed tomographic (CT) images were obtained from 14 males and 14 females (mean age 27 years, range 23-35 years). Bone density in Hounsfield units (HU) was measured at 13 interradicular sites and four bone levels. Bone densities in most areas were higher than 850 HU. Statistically significant differences in bone density were detected at different levels and sites. Bone densities in both maxilla and mandible significantly increased from the alveolar crest toward basal bone in posterior areas, while the opposite was observed in anterior areas. There were statistically significant differences in bone densities between the maxilla and mandible in posterior areas. Bone densities progressively increased from anterior to posterior areas in the mandible. The results suggest that mini-implants for orthodontic anchorage may be effective when placed in most areas with equivalent bone density up to 6 mm apical to the alveolar crest. Site selection should be adjusted according to bone density assessment.

Influence of Submandibulectomy on Alveolar Bone Loss in Rats

The incidence of dry mouth and its public health impact are increasing as the result of a progressively larger, medicated older population and because chronic diseases, like periodontitis, are prevalent pathologies among elderly patients. Periodontitis and continuous remodeling and rebuilding alveolar processes greatly affect the margin of the alveolar bone, and there is evidence indicating the role of submandibular glands in the regulation of immune/inflammatory reactions. The purpose of this study was to assess the effect of submandibular-sublingual complex ablation (Sx) on alveolar bone loss in rats submitted or not to ligature-induced experimental periodontal disease (EP). Wistar male rats were submitted to Sx or sham operations (day 0). Two weeks later, unilateral EP was induced on the right mandibular first molars for 7 days with the contralateral side serving as control. Bone loss at the level of the dental pieces was estimated by bone histomorphometry on mesio-distally oriented sections of the molars and by the determination on lingual and vestibular mandibular surfaces of the distances from the cemento-enamel junction to the alveolar crest. Sx and EP significantly increased lingual and vestibular alveolar bone loss. Molars with EP exhibited greater lingual loss in Sx animals compared to those with the sham operation. EP induced similar interradicular bone loss in sham and Sx rats. Sx has a deleterious effect on the periodontal tissues, particularly marginal alveolar bone, indicating the importance of the submandibular/sublingual glands in maintaining healthy periodontal conditions.

Effects of Hyperbaric Oxygen during Experimental Tooth Movement

To determine the effects of hyperbaric oxygen (HBO) on bone remodeling during orthodontic tooth movement. Twenty-four male, adult Sprague Dawley rats were randomly divided into two groups. HBO was administered in the first group, and the second group served as a control. The mandibular first molars were moved mesially by means of Ni-Ti closed coil springs in all groups. Results were evaluated histomorphometrically and the parameters of trabecular bone volume (BV/TV), trabecular bone number (Tr.N), and trabecular separation (Tr.Sep) were evaluated at the interradicular bone area of the mandibular first molars. Increases in BV/TV and Tr.N and decreases in Tr.Sep revealed the osteoblastic activity of HBO. HBO application caused an increase in bone apposition and osteoblastic activity or a decrease in osteoclastic activity. HBO enhanced the bone formation during experimental tooth movement. Therefore, the findings of this study support our hypothesis that osteoblastic activity might be modulated by changes in the environmental oxygen tension.