Efecto del ultrasonido de baja intensidad (USBI) sobre el movimiento dentario ortodóncico: estudio in vivo en ratas Sprague-Dawley / Effect of low intensity ultrasound (USBI) in the orthodontic dental movement: in vivo study in Sprague-Dawley rats

Este estudio se realizó con el propósito de analizar el efecto de la aplicación de ondas de USBI sobre la velocidad y distancia de movimiento dentario, y su efecto a nivel histológico en ratas Sprague-Dawley. Veintitrés ratas macho Sprague-Dawley fueron parte del experimento, las que fueron divididas aleatoriamente en tres grupos. Cinco ratas fueron utilizadas como control sin movimiento dentario ortodóncico (MDO), nueve ratas fueron sometidas a una aplicación de fuerza ortodóncica sin aplicación de USBI y nueve fueron sometidas a una aplicación de fuerza ortodóncica con USBI. Estas fuerzas ortodóncicas fueron realizadas entre el aspecto mesio vestibular del primer molar superior izquierdo y el incisivo central superior, traccionando el molar hacia mesial, aplicando una fuerza aproximada de 50 gramos durante 21 días, debido a problemas con la sedación estos dos últimos grupos quedaron compuestos de seis y ocho ratas respectivamente. En el grupo MDO sin USBI, se registró una reducción del espacio entre molares e incisivos de 2 mm. En el grupo MDO con USBI dicha reducción fue de 3.4 mm, siendo esta diferencia estadísticamente significativa. Histológicamente el grupo MDO c/USBI mostró un perímetro vascular y espacios medulares aumentados respecto de los otros grupos, no obstante, no se encontraron diferencias significativas en la cantidad de osteoclastos. Fue posible observar y demostrar cuantitativamente que el USBI es una forma de estimulación mecánica eficiente para la aceleración del MDO sobre un período experimental de 21 días, donde se observaron diferencias significativas entre el grupo control, el grupo MDO sin USBI y el grupo MDO con USBI en la magnitud del movimiento dentario. Se observó una mayor vascularidad en el grupo con USBI, expresando perímetros vasculares de mayor tamaño, esto pudo deberse al efecto estimulatorio del ultrasonido sobre la angiogénesis.

The objective of this study was to analyze the effect of USBI wave application on the speed and distance of dental movement, and its effect at histological level in SpragueDawley rats. In this study twenty-three male Sprague-Dawley rats were randomly divided into three groups. Five rats were used as control without orthodontic tooth movement (MDO), nine rats were subjected to an orthodontic force application without USBI application, and nine were subjected to an orthodontic force application with USBI. The orthodontic forces were performed between the vestibular mesio aspect of the first upper left molar and upper central incisor, pulling the molar mesially, applying an approximate force of 50 grams for 21 days. In light of sedation problems these last two groups were composed of six and eight rats respectively. In the MDO group without USBI, there was a reduction in the space between molars and incisors of 2 mm. In the MDO group with USBI this reduction was 3.4mm, this difference being statistically significant. Histologically, the MDO c / USBI group showed a vascular perimeter and enlarged spinal spaces with respect to the other groups, however, no significant differences were found in the amount of osteoclasts. It was possible to quantitatively demonstrate that USBI is a form of efficient mechanical stimulation for MDO acceleration over an experimental 21-day period, where significant differences were observed in tooth movement between the control group, the group without USBI and the group with USBI. A greater vascularity was observed in the group with USBI, expressing larger vascular perimeters, which could be due to the stimulatory effect of ultrasound on angiogenesis.

Anatomical relation of third molars and the retromolar canal.

The study was designed to assess, by direct anatomical observations and cone-beam computed tomography (CT), the prevalence of a retromolar canal and foramen in relation to the mandibular third molar in dry human mandibles. Dry mandibles from European skeletons (n=89) were observed directly and after cone-beam CT scanning (Newtom VGI evo). The following variables were assessed: the presence of a retromolar foramen and canal; the presence of a third molar, and orientation of the third molar. From the total of 89 mandibles selected, 73 showed a retromolar foramen (49 of which were bilateral). A retromolar canal was identified in 64 mandibles based on cone-beam CT assessment, with a total of 101 canals, including 74 that were bilateral. A total of 112 hemimandibles contained a third molar. Orientation of the third molar did not seem to indicate the presence of retromolar foramina or canals. A similar prevalence of retromolar canals was found for both vertically (41/79) and mesially (17/33) orientated third molars. A retromolar foramen and canal were present in most mandibles, with more than half being bilateral. We were unable to confirm a potential relation between the retromolar foramen and canal on the one hand, and the orientation of the third molar on the other.

Mandibular trabecular structures in alveolar ridge preservation using different grafting materials after tooth extraction / Estructura trabecular mandibular en preservación de reborde alveolar utilizando diferentes materiales de injerto después de la exodoncia

The aim was to describe the star volume analysis in ridge preservation using different grafting materials. Bilateral extraction of the first mandibular molars of sixteen male rabbits was performed, divided at random into four groups (n= 4 in each group) according to graft, using: blood clot (G1), xenograft (G2), pure phase beta-tricalcium phosphate (G3) and biphasic calcium phosphate (60 % HA / 40 % beta-TCP) (G4). Rabbits were euthanized at 4, 6, or 8 wk post-extraction; the trabecular bone structures was evaluated by star volume analysis. The Levene test was used to analyze variance, as was the independent sample t-test. A P-value of < 0.001 was used to establish a statistically significant. The star volume analysis of the mandibular trabecula shows that the marrow space star volume (V*m.space) was higher than the trabecular star volume (V*tr). At 6-week post-extraction, new trabecular bone was evident. At 8-week post-extraction V*tr increase in all groups and the V*m.space diminish, suggesting coarsening of the internal architecture. In G2, some trabecular bone was observed in the central region. In G3, most of the socket regions were occupied by newly formed and loose trabecular bone and in the G4, the sockets were almost entirely filled with trabecular bone. Star volume analysis is adequate to analysis of bone patterns formation using bone substitutes.

El objetivo de esta investigación fue describir el volumen estrella en preservación alveolar utilizando diferentes injertos óseos. La exodoncia bilateral del primer molar mandibular de 16 conejos machos fue realizada, dividiéndolos en 4 grupos (n= 4 en cada grupo) de acuerdo al injerto utilizado, siendo: coágulo sanguíneo (G1), xenoinjerto (G2), beta-tricalcio fosfato puro (G3) y fosfato de calcio bifásico (60 % HA / 40 % beta-TCP) (G4). Los conejos fueron sometidos a eutanasia a las 4, 6 u 8 semanas post exodoncia; el trabeculado óseo fue evaluado por medio del volumen estrella. La prueba de Levene fue utilizado para el análisis de varianza y luego la prueba t-test para muestras independientes. El valor de P menor a 0.001 fue establecido como significancia estadística. El análisis del volumen estrella del trabeculado mostró que el espacio medular de volumen estrella (V*m.space) fue mayor que trabeculado (V*tr). A 6 semanas post exodoncia, nuevo trabeculado óseo fue evidente. A las 8 semanas post exodoncia V*tr aumenta en todos los grupos y el V*m.space disminuye, sugiriendo un engrosamiento de la arquitectura interna. En el grupo G2, algún trabeculado óseo fue observado en la región central. En el G3, la mayoría del alveolo fue ocupado por nuevo hueso y perdió trabeculado óseo y en G4, el alveolo fue ocupado casi enteramente por hueso trabecular. El análisis de volumen estrella es adecuado para analizar el modelo de formación ósea utilizando sustitutos óseos.

Dento-alveolar measurements and histomorphometric parameters of maxillary and mandibular first molars, using micro-CT.

BACKGROUND: Micro-CT is a high-resolution, non-invasive, and non-destructive imaging technique, currently acknowledged as a gold standard modality for assessing quantitatively and objectively dental morphology and bone microarchitecture parameters. PURPOSE: The aim of this study was to analyze critical dental and periodontal measurements characterizing the mandibular (MandFM) and maxillary (MaxFM) first molar architecture, as well as the corresponding bony socket, using micro-CT. MATERIALS AND METHODS: Thirty-eight human dried skulls (22-76 years) were scanned to enable the virtual analysis of 61 first molars. Depending on the type of measurement, the parameters were recorded on two-dimensional sections or directly on three-dimensional models. Tooth morphology was described by four aspects (e.g., tooth width, trunk length, root length, and root span), while the socket architecture was assessed by buccal plate thicknesses and bone density measurements. RESULTS: Minimum, maximum, and mean distances as well as cortical and trabecular bone densities were recorded in MandFM and MaxFM. It is noteworthy that the buccal plate thickness was found to be less than 1 mm in more than 55% of cases in MaxFM, whereas only in 20.8% of cases in MandFM (and even 0% at two sites). A wide range of bone densities was observed and the comparison between MandFM and MaxFM did not show a significant difference. Furthermore, cortical densities were negatively correlated with aging, while trabecular densities were not influenced. CONCLUSIONS: Using micro-CT, three-dimensional aspects of the human first molar morphology and microstructural parameters of the surrounding bone were evaluated in the mandible and in the maxilla. These comprehensive measurements and their correlation with aging may be of great importance for the use of immediate implant placement in molar extraction sockets and thus the potential long-term success of this treatment modality.

A new procedure for processing extracted teeth for immediate grafting in post-extraction sockets. An experimental study in American Fox Hound dogs.

OBJECTIVES: To investigate freshly extracted dental particulate used to graft post-extraction sockets in dogs, comparing new bone formation at experimental and control sites. MATERIALS AND METHODS: Bilateral premolars P2, P3, P4 and first mandibular molars were extracted atraumatically from six American Fox Hound dogs. The teeth were ground immediately using a 'Smart Dentin Grinder'. The dentin particulate was sieved to ensure a grain size of 300-1200µm and immersed in an alcohol cleanser to dissolve organic debris and bacteria, followed by washing in sterile saline buffer solution. The animals were divided into two groups randomly: group 'A' (control) samples were left to heal without any extraction socket grafting procedure; group 'B' (experimental) sockets were filled with the autogenous dentin particulate graft. The rate of tissue healing and the quantity of bone formation were evaluated using histological and histomorphometric analyses at 60 and 90 days post-grafting. The type of bone generated was categorized as woven (immature bone) or lamellar bone (mature bone). RESULTS: Substantially more bone formation was found in Group B (experimental) than Group A (control) at 60 and 90 days (p<0.05). Less immature bone was identified in the dentin grafted group (25.7%) than the control group (55.9%) [corrected]. Similar differences were also observed at 90 days post grafting. CONCLUSION: Autogenous dentin particulate grafted immediately after extractions may be considered a useful biomaterial for socket preservation, protecting both buccal and lingual plates, generating large amounts of new woven bone formation after 60 days, and small amounts of lamellar bone after 90 days healing.

Evaluation of Bone Stability and Esthetic Results After Immediate Implant Placement Using a Novel Synthetic Bone Substitute in the Anterior Zone: Results After 12 Months.

The aim of this study was to assess bone and soft tissue changes after tooth extraction and immediate implant insertion in the anterior maxilla. A novel synthetic bone graft (VivOss, Straumann) was used to fill the gap between the implant surface and the alveolar bone. Implants with a reduced diameter compared to the size of the socket were used. A fixed or removable provisional restoration was provided immediately after implant placement. Cone beam computed tomography (CBCT) scans were taken to evaluate bone changes, showing minor variations after 12 months of follow-up. To evaluate soft tissue changes, clinical vertical measurements were performed. Based on the results obtained from 15 implants placed in 14 patients, it can be concluded that the use of an immediate implant in combination with a synthetic bone graft and immediate provisionalization seems to be a predictable treatment option with satisfactory esthetic results after 1 year.

Clinical and Histologic Evaluations of Immediately Placed SLA Dental Implants.

The goal of this investigation was to evaluate the bone-to-implant contact (BIC) of dental implants placed into fresh extraction sockets without pre-existing periapical pathology. When the extraction sites exhibited a gap distance of > 2 mm, autogenous bone harvested from surrounding surgical sites was grafted to fill that gap with no barrier membranes. All implants were clinically stable and successful at 6 months postoperative. The histologic examination demonstrated an average of 66.2% BIC for all five immediately placed dental implants. The results of this study provided sufficient histologic and histomorphometric knowledge to support immediate dental implant placement in carefully selected clinical scenarios.

Measurement properties of gingival biotype evaluation methods.

BACKGROUND: There are numerous methods to measure the dimensions of the gingival tissue, but few have compared the effectiveness of one method over another. OBJECTIVE: This study aimed to describe a new method and to estimate the validity of gingival biotype assessment with the aid of computed tomography scanning (CTS). MATERIALS AND METHODS: In each patient different methods of evaluation of the gingival thickness were used: transparency of periodontal probe, transgingival, photography, and a new method of CTS). Intrarater and interrater reliability considering the categorical classification of the gingival biotype were estimated with Cohen's kappa coefficient, intraclass correlation coefficient (ICC), and ANOVA (P < .05). The criterion validity of the CTS was determined using the transgingival method as the reference standard. Sensitivity and specificity values were computed along with theirs 95% CI. RESULTS: Twelve patients were subjected to assessment of their gingival thickness. The highest agreement was found between transgingival and CTS (86.1%). The comparison between the categorical classifications of CTS and the transgingival method (reference standard) showed high specificity (94.92%) and low sensitivity (53.85%) for definition of a thin biotype. CONCLUSION: The new method of CTS assessment to classify gingival tissue thickness can be considered reliable and clinically useful to diagnose thick biotype.

Morphological alterations in the position of the mandibular foramen in dentate and edentate mandibles.

The technique of inferior alveolar nerve (IAN) block must be based on precise anatomical knowledge regarding the correct position of the mandibular foramen (MF). The aim of the investigation reported here was to determine the anatomic and topographic localization of the MF according to mandibular ramus anatomic landmarks and to identify morphological alterations in the position of the MF and size and shape of the ramus in terms of the impact of tooth socket loss in the molar and premolar region. Seventy-three dry human adult mandibles were divided into two groups according to dental status. These were measured to determine the distances from the anterior and posterior ramus border (AB, PB) to the midpoint of the MF fossa, and from the mandibular notch (MN) and inferior ramus border (IB) to the MF entering point. A number of relevant ramus anatomic features were analyzed, such as ramus width (RW), height (RH), and thickness (RT). The MF was closer to the PB and IB in edentate mandibles (right/left mean PB-MF 10.66 ± 1.84/11.06 ± 2.05 mm; right/left mean IB-MF 21.77 ± 3.23/21.8 ± 2.27 mm) compared to dentate mandibles (right/left mean PB-MF 11.87 ± 2.08/12.04 ± 1.94 mm; right/left mean IB-MF 22.94 ± 3.09/22.74 ± 3.74 mm). Edentate mandibles demonstrated reduced RW (right/left mean RW 26.03 ± 3.53/26.49 ± 3.90 mm), significantly reduced (p = 0.03) right RH (right/left mean RH 43.56 ± 4.74/45.43 ± 4.86 mm), and significantly reduced (p < 0.05) RT in the area of the MF fossa depression (right/left mean RT 5.52 ± 1.21/5.21 ± 0.91 mm) compared to dentate mandibles (right/left mean RW 27.34 ± 3.84/27.48 ± 3.80 mm; right/left mean RH 46.33 ± 4.52/47.40 ± 4.20 mm; right/left mean RT 7.86 ± 1.98/8.10 ± 1.92 mm). Alterations in MF position and mandibular ramus anatomic features in edentate mandibles increase the potential risk of complications and failure of IAN block.

Evaluation of volumetric dimensional changes in posterior extraction sites with and without ARP using a novel imaging device.

BACKGROUND: Alveolar ridge volume loss may be minimized when postextraction sockets are filled by bone substitutes. PURPOSE: The aim of the study was to measure the effect of alveolar ridge preservation (ARP) in maintaining the external contour of the ridge after fresh socket grafting with or without particulate anorganic bovine bone mineral (BBM) and resorbable barrier covering. MATERIALS AND METHODS: In the present controlled study, patients subjected to single-tooth extraction were allocated to 2 groups: postextraction sockets grafted with bovine bone mineral (bbm), and naturally healing sockets (nat). Before and at 5 months following tooth extraction, plaster cast contours of the sockets were acquired by means of an optical scanner; the 2 contours of each patient underwent voxelization and fusion using a matrix elaborator. Outcome variables at 5 months (volumetric, surface, and linear changes) were measured in digital fused plaster casts with a dental scan software analyzing a volume of interest ranging from residual papilla to 10 mm toward the apical point. Intra- and inter-group pair-wise variables' comparisons were conducted. Level of significance was set at 0.05. RESULTS: Twenty-four sites were enrolled: 12 ARP and 12 naturally healed. Five-month percentage of volume loss of the bbm-group (21.7% ± 7.4%) was significantly lower (Ps < .0003) than that of the naturally healing group (38.8% ± 7.9%). When tooth position was investigated, volume loss in percentage registered a significantly better (P values ≤ .0485) behavior in molars (ΔV% = -19.1% ± 6.5% and ΔV% = -35.6% ± 7.6%, respectively, for bbm and nat) than that in premolars (ΔV% = -26.9% ± 7.2% and ΔV% = -45.1% ± 4.2%, respectively, for bbm and nat), in both the preserved and naturally healing groups. CONCLUSION: The dimensional loss in postextraction sockets grafted with anorganic bovine bone substitute and covered by a resorbable collagen barrier was lower than that of the naturally healing sites. However, ridge preservation was able to maintain almost 80% of the pristine bone.

Cutting-Edge Implant Rehabilitation Design and Management: A Tapered Abutment Approach.

Immediate implant placement can pose challenges surgically and, ultimately, restoratively. Yet immediate placement has become the standard when adequate bone is present to achieve primary stability and site infection is minimal. To avoid prosthetic complications and ensure the implant is encased in bone after healing, proper planning must consider that implant placement does not necessarily need to follow the trajectory of the root socket. As discussed in this article, maxillary anterior sites have potential issues related to the "triangle of bone" that are not encountered in molar sites and demand different approaches to ensure treatment success. Additionally, this article addresses decision-making on molar sites in regard to implant diameter, as well as the rationale for platform switching.

[Histomorphometric evaluation of ridge preservation after molar tooth extraction].

OBJECTIVE: To evaluate bone formation in human extraction sockets with absorbed surrounding walls augmented with Bio-Oss and Bio-Gide after a 6-month healing period by histologic and histomorphometric analyses. METHODS: Six fresh molar tooth extraction sockets in 6 patients who required periodontally compromised moral tooth extraction were included in this study. The six fresh extraction sockets were grafted with Bio-Oss particle covered with Bio-Gide. The 2.8 mm×6.0 mm cylindric bone specimens were taken from the graft sites with aid of stent 6 months after the surgery. Histologic and histomorphometric analyses were performed. RESULTS: The histological results showed Bio-Oss particles were easily distinguished from the newly formed bone, small amounts of new bone were formed among the Bio-Oss particles, large amounts of connective tissue were found. Intimate contact between the newly formed bone and the small part of Bio-Oss particles was present. All the biopsy cylinders measurement demonstrated a high inter-individual variability in the percentage of the bone, connective tissues and Bio-Oss particles. The new bone occupied 11.54% (0-28.40%) of the total area; the connective tissues were 53.42% (34.08%-74.59%) and the Bio-Oss particles were 35.04% (13.92%-50.87%). The percentage of the particles, which were in contact with bone tissues, amounted to 20.13% (0-48.50%). CONCLUSION: Sites grafted with Bio-Oss particles covered with Bio-Gide were comprised of connective tissues and small amounts of newly formed bone surrounding the graft particles.

[A study on effects of immediate bone grafting at mandibular first molar fresh extraction socket on maintaining alveolar bone height after space closure].

Objective: To investigate the effect of immediate bone grafting at mandibular first molar extraction socket on maintaining alveolar bone height after space closure. Methods: Thirty adult orthodontic patients who need to extract mandibular first molar, totally 38 target teeth, were included. The samples were divided into two groups randomly: graft group and non-graft group. All extraction space was closed orthodontically. Dental models of all patients were taken before extraction (T0), before space closure(T1) and after space closure (T2). The distance, time of the space closure and the velocity of tooth movement were recorded. Probing depth (PD) and clinical attachment level (CAL) at six sites (mesial buccal, buccal, mesial lingual, lingual, distal buccal and distal lingual) on adjacent teeth were measured before extraction (T0) and after space closure (T2). Cone-beam CT (CBCT) was taken at T0 and T2 to compare the changes of alveolar bone height at six sites on adjacent teeth using Invivo Dental 5.0 software. Results: The extraction space in both graft group and non-graft group was closed successfully. However, the space in graft group was closed more slowly than in non-graft group. In graft group, PD and CAL at the six sites on both the second molar and the second premolar did not change significantly after space closure, and CBCT showed that the alveolar bone height of the second premolar had no significant difference after treatment. In non-graft group, alveolar bone height decreased in both adjacent teeth and periodontal attachment loss was found after space closure. On average, alveolar bone height and periodontal attachment of the second premolar decreased (0.75±0.16) mm and (0.64±0.15) mm, respectively. Meanwhile, alveolar bone height and periodontal attachment of the second molar decreased (0.79±0.23) mm and (0.80±0.24) mm, respectively. Conclusions: Bone graft immediately after mandibular first molar extraction could delay alveolar bone resorption and preserve the periodontal attachment of the adjacent teeth during space closure. However, the procedure could slow down tooth movement.

Clinical and Histological changes after ridge preservation with two xenografts: preliminary results from a multicentre randomized controlled clinical trial.

OBJECTIVES: To evaluate and compare clinical and histological changes after ridge preservation procedures with those of spontaneous healing. MATERIALS AND METHODS: Ninety patients were enrolled in the present randomized controlled clinical trial and underwent single-tooth extraction in the premolar/molar areas. Thirty sites were grafted with collagenated cortico-cancellous (coll), 30 sites with cortical (cort) porcine bone and 30 sites underwent natural healing. Primary (vertical and horizontal bone changes after 3 months) and secondary outcomes (histomorphometric after 3 months) were evaluated at implant placement. RESULTS: The vertical bone changes at the grafted sockets were significantly (p < 0.0001) lower (0.30 mm for cort group and 0.57 mm for coll group) when compared to non-grafted sockets (2.10 mm for nat group). Moreover, the width reduction of the coll (0.93 mm) and cort (1.33 mm) groups was significantly lower (p < 0.0001) than the non-grafted group (3.60 mm). The analysis of subgroups attested that when premolar and molar sites were compared, the buccal bone loss appeared to be dependent both on tooth position and grafting material employed. CONCLUSION: The ridge preservation procedures had significantly better outcomes when compared to natural healing. The biomaterials did not differ for maintenance of bone width; even though, the bone height seemed to be better preserved with the cortical porcine bone.

Pressure Bearing Device Affects Extraction Socket Remodeling of Maxillary Anterior Tooth. A Prospective Clinical Trial.

BACKGROUND: Extraction socket remodeling and ridge preservation strategies have been extensively explored. PURPOSE: To evaluate the efficacy of applying a micro-titanium stent as a pressure bearing device on extraction socket remodeling of maxillary anterior tooth. MATERIALS AND METHODS: Twenty-four patients with a extraction socket of maxillary incisor were treated with spontaneous healing (control group) or by applying a micro-titanium stent as a facial pressure bearing device over the facial bone wall (test group). Two virtual models obtained from cone beam computed tomography data before extraction and 4 months after healing were 3-dimenionally superimposed. Facial bone wall resorption, extraction socket remodeling features and ridge width preservation rate were determined and compared between the groups. RESULTS: Thin facial bone wall resulted in marked resorption in both groups. The greatest palatal shifting distance of facial bone located at the coronal level in the control group, but middle level in the test group. Compared with the original extraction socket, 87.61 ± 5.88% ridge width was preserved in the test group and 55.09 ± 14.46% in the control group. CONCLUSIONS: Due to the facial pressure bearing property, the rigid micro-titanium stent might preserve the ridge width and alter the resorption features of extraction socket.

Chondral ossification centers next to dental primordia in the human mandible: A study of the prenatal development ranging between 68 to 270mm CRL.

The human mandible is said to arise from desmal ossification, which, however, is not true for the entire body of the mandible: Meckel's cartilage itself is prone to ossification, at least its anterior part in the canine and incisor region. Also, within the coronoid and in the condylar processes there are cartilaginous cores, which eventually undergo ossification. Furthermore, there are a number of additional single cartilaginous islets arising in fetuses of 95mm CRL and more. They are located predominantly within the bone at the buccal sides of the brims of the dental compartments, mostly in the gussets between the dental primordia. They become wedge-shaped or elongated with a diameter of around 150-500µm and were also found in older stages up to 225mm CRL, which was the oldest specimen used in this study. This report is intended to visualize these single cartilaginous islets histologically and in 3-D reconstructions in stereoscopic images. Although some singular cartilaginous tissue within the mandible may be remains of the decaying Meckel's cartilage, our 3-D reconstructions clearly show that the aforementioned cartilaginous islets are independent thereof, as can be derived from their separate locations within the mandibular bone. The reasons that lead to these cartilaginous formations have remained unknown so far.

Evaluation of mandibular anterior alveolus in different skeletal patterns.

BACKGROUND: The boundaries for orthodontic tooth movement are set by the bony support of the dentition. This study compares the mandibular anterior alveolar housing in individuals with low, average, and high mandibular plane angles before orthodontic treatment and measures alveolar bone loss and root resorption after orthodontic treatment. METHODS: Pretreatment cone-beam computed tomography (CBCT) images of 75 non-growing individuals, 25 in three groups: low-angle (sella-nasion to mandibular plane ≤28°), average-angle (30°-37°), and high-angle (≥39°), were analyzed. Buccolingual bone thickness was measured at the root apex, mid-root, and alveolar crest of the mandibular right central incisor. Pre- and posttreatment CBCT images of 11 low-angle, 20 average-angle, and 27 high-angle patients were compared to determine changes in the alveolus and mandibular incisor root after orthodontic treatment. RESULTS: The pretreatment anterior alveolar bone widths were significantly different, wider in low-angle than in average- and high-angle individuals (p value = 0.000). High-angle individuals also had greater posttreatment external root resorption, even though the bony housing changed minimally. CONCLUSIONS: Negative sequelae of orthodontic treatment are more frequently found in individuals with high mandibular plane angles and could be linked to their thin pre-existing alveolar housing.

The influence of altered functional loading and posterior bite-blocks on the periodontal ligament space and alveolar bone thickness in rats.

OBJECTIVES: Posterior bite-blocks are resin-based structures elevating the occlusion and creating intrusive force on the posterior teeth. Bite-blocks were applied to the molars of growing rats and a hard and soft diet was used to create altered functional masticatory forces. The aim of the present investigation was to study the effect of this appliance on the periodontal ligament space and alveolar bone thickness when combined with altered masticatory forces. MATERIAL AND METHODS: Fifty-two four-week-old rats were divided into two groups, hard and soft diet. Two weeks later, half of them received a bite-block appliance, creating four groups: control hard (CH), control soft (CS), bite-block hard (BH) and bite-block soft (BS). All were sacrificed at age of 10 weeks. Their heads were scanned by micro-CT and periodontal ligament space (PDL) width, cross-sectional alveolar socket surface and alveolar bone thickness were measured. Analysis of variance (ANOVA) was used to compare the groups. RESULTS: The PDL was 9.2% thinner in the CS group (p < 0.001) and 20.7% in the bite-block groups (p < 0.001) compared to the CH group. Within each of the four groups, the mesiodistal PDL space was larger than the palatobuccal. The alveolar bone was thinner by 5.8% (p = 0.018) in the CS group, 10.7% in the BH group (p < 0.001) and 16.7% in the BS group (p < 0.001) compared to the CH group. CONCLUSIONS: Young rats wearing posterior bite-blocks have narrower PDL space and thinner alveolar bone compared to controls. When fed a soft diet, the alveolar bone is even thinner but the PDL showed no difference.

Timing of single implant placement and long-term observation of marginal bone levels.

AIM: To assess the outcome of immediate or early placement of implants after tooth extraction supporting a single-tooth restoration with focus on the marginal bone level and its stability over time. MATERIAL AND METHODS: An electronic literature search without time restrictions was conducted of the Medline/PubMed database accompanied by a handsearch. Clinical human studies reporting on periimplant marginal bone level (BL) and/or changes in bone level (BLC) and with a follow-up period of at least 12 months were selected for the present review. RESULTS: The search strategy resulted in 816 articles and 115 relevant publications were included for full-text analysis. Only few randomised controlled trials exist comparing immediate or early implant placement with placement in healed bone (the conventional protocol). Summarising the results from prospective studies, it was found that the mean marginal bone loss around immediately or early placed implants from baseline (at implant placement or placement of restoration) to the latest followup visit (between 1 and 10 years) was less than 1.5 mm. CONCLUSION: The current literature indicates that immediate or early placement of single-tooth implants after tooth extraction may be a viable treatment with long-term survival rates and marginal bone level conditions matching those for implants placed conventionally in healed bone ridges.

Marginal and apical bone stability after staged sinus floor augmentation using bone condensing implants with variable-thread design: a two-dimensional analysis.

Studies on the vertical stability of augmented bone after sinus lifting differ substantially. In addition, long healing periods are usually advocated prior to implant installation. The purpose of this case series study was to evaluate the changes in bone height after sinus lifting with a bovine-derived xenograft and to evaluate the clinical outcome of bone condensing implants installed after a short healing period. Patients treated during the years 2010-2013 were re-examined using peri-apical radiographs to evaluate the changes in augmented bone height (BH) and marginal bone loss (BL). Fifty-seven of 70 eligible subjects (28 male and 29 female, mean age 56 years) attended for reassessment. Data were available for 53 sinus lifts and 105 implants installed after a mean healing period of 4.6±1.5 months. Implant survival was 99% after a mean time in function of 19±9 months. Baseline BH, BH at implant placement, and final BH were on average 3.87±1.74mm, 13.75±2.12mm, and 13.11±2.12mm, respectively (P<0.001). Mean BL was 0.51±0.65mm. Only limited resorption is to be expected after sinus lifting in the short term. A bone condensing implant can be used in the early healing phase with successful outcomes in terms of implant survival and bone adaptation.