Accuracy of 3-dimensional printing of dental casts: A proposal for quality standardization.

STATEMENT OF PROBLEM: A digital workflow in fixed prosthodontics may use a 3D printer to obtain a cast for porcelain application. Standards exist that define the accuracy of traditional casts, but the accuracy requirements of 3D-printed casts have not been defined. PURPOSE: The purpose of this retrospective study was to investigate how the accuracy of 3D-printed casts affected prosthesis fit and whether they correctly reproduced interproximal contacts. MATERIAL AND METHODS: Copings with different die spacings were used to test different 3D-printed casts of the same dental arch. The accuracy of the 3D casts was assessed by imaging and comparing the resulting standard tessellation language (STL) files with the original through a matching software program. Accuracy scores were then correlated with a score measuring how well the copings fit the casts. The first data set was obtained from a patient receiving restoration of the 4 maxillary incisors. The teeth were prepared, the dental arch was imaged intraorally, and 10 resin casts were printed with four 3D printers. Two sets of 4 zirconia test copings were prepared, and 3 clinicians assessed their fit on each cast. A further set of casts was created from a second patient requiring prosthetic restoration for 5 adjacent teeth to assess whether undersizing affected the best fit of the copings on their dies. RESULTS: The clinical scores and accuracy scores did not correlate. The results suggested that printed dies showing a certain degree of undersizing might provide a better fit than those showing better correspondence to the actual anatomic structure. The oversized dies were the worst. Only 7 of 17 casts being assessed were deemed suitable for veneering of the copings. The undersized casts tested clinically better than casts printed by using the same printer under standard settings. CONCLUSIONS: This retrospective study indicated that 3D-printed casts that do not allow copings to fit appropriately usually show mean excess oversizing. Axially undersizing the printed dies on casts might allow a better fit of copings to be veneered.

Distribution of Trabecular Bone Density in the Maxilla and Mandible.

INTRODUCTION: Implant osseointegration is strongly influenced by the bone quality at the implant insertion site. The present work aims to create distribution diagrams showing the average bone density at each position within the jaws. MATERIALS AND METHODS: Data were retrospectively collected from 4 oral surgeons who sought bone-density measurements during implant placement using a torque-measuring implant micromotor. Statistical analyses were performed to investigate whether bone density correlated with the patients' sex and age and whether the bone-density values at different positions within each arch correlated to each other. RESULTS: Records of 2408 patients and 6060 bone-density readings were retrieved, and density distribution diagrams were created. Density values showed a significant variation within subjects. Within the same jaw, density between adjacent positions showed significant differences. Density at a given position correlated significantly with that at the other positions in most cases. Bone density was significantly lower in women than in men; no significant correlation was found between bone density and the patient age. CONCLUSIONS: Bone density of patients displays significant interindividual variation, thus meaningful assessment must be conducted on a patient-by-patient basis.

The insertion torque-depth curve integral as a measure of implant primary stability: An in vitro study on polyurethane foam blocks.

STATEMENT OF PROBLEM: Recent research has shown that dynamic parameters correlate with insertion energy-that is, the total work needed to place an implant into its site-might convey more reliable information concerning immediate implant primary stability at insertion than the commonly used insertion torque (IT), the reverse torque (RT), or the implant stability quotient (ISQ). Yet knowledge on these dynamic parameters is still limited. PURPOSE: The purpose of this in vitro study was to evaluate whether an energy-related parameter, the torque-depth curve integral (I), could be a reliable measure of primary stability. This was done by assessing if (I) measurement was operator-independent, by investigating its correlation with other known primary stability parameters (IT, RT, or ISQ) by quantifying the (I) average error and correlating (I), IT, RT, and ISQ variations with bone density. MATERIAL AND METHODS: Five operators placed 200 implants in polyurethane foam blocks of different densities using a micromotor that calculated the (I) during implant placement. Primary implant stability was assessed by measuring the ISQ, IT, and RT. ANOVA tests were used to evaluate whether measurements were operator independent (P>.05 in all cases). A correlation analysis was performed between (I) and IT, ISQ, and RT. The (I) average error was calculated and compared with that of the other parameters by ANOVA. (I)-density, IT-density, ISQ-density, and RT-density plots were drawn, and their slopes were compared by ANCOVA. RESULTS: The (I) measurements were operator independent and correlated with IT, ISQ, and RT. The average error of these parameters was not significantly different (P>.05 in all cases). The (I)-density, IT-density, ISQ-density, and RT-density curves were linear in the 0.16 to 0.49 g/cm³ range, with the (I)-density curves having a significantly greater slope than those regarding the other parameters (P≤.001 in all cases). CONCLUSIONS: The torque-depth curve integral (I) provides a reliable assessment of primary stability and shows a greater sensitivity to density variations than other known primary stability parameters.

Horizontal-guided Bone Regeneration using a Titanium Mesh and an Equine Bone Graft.

AIM: The present work describes a horizontal ridge augmentation in which a titanium mesh was preshaped by adapting it to a stereolithographic model of the patient's jaw that was fabricated from CT scans. BACKGROUND: Guided bone regeneration (GBR) involves covering the augmentation site with a long-lasting barrier to protect it from the invasion of surrounding soft tissues. Among barriers, titanium meshes may provide a successful outcome, but the intraoperatory time needed to shape them is a disadvantage. CASE DESCRIPTION: The 54-year-old patient, missing the right mandibular second bicuspid, first molar, and second molar, had her atrophic ridge augmented with a 30:70 mixture of autogenous bone and equine, enzyme-deantigenic collagen-preserved bone substitute. Two conical implants were inserted concomitantly in the second bicuspid and first molar positions, and the site was protected with the preshaped mesh. Four months later, the titanium mesh was retrieved, a bone sample was collected, and histological and histomorphometric analyses were performed. Provisional and definitive prostheses were then delivered, and follow-up controls were performed for up to 24 months. CONCLUSION: Preshaping the mesh on a model of the patient's mandible shortened the surgical time and enabled faster mesh placement. Two years after surgery, the implants were perfectly functional, and the bone width was stable over time as shown by radiographic controls. Histological analysis of the bone sample showed the heterologous biomaterial to be biocompatible and undergoing advanced remodeling and replacement with newly formed bone. CLINICAL SIGNIFICANCE: Preshaping a titanium mesh over a stereolithographic model of the patient's jaw allowed for a significant reduction of the intraoperative time and may be therefore, advisable in routine practice.

Horizontal GBR with anorganic equine bone combined with a customized titanium mesh.

This case report describes the fixed rehabilitation of the lower left arch in a patient following an horizontal GBR procedure by means of a customized titanium mesh and a new slow resorption bone substitute of equine origin.

Indications for implant-supported rehabilitation of the posterior atrophic maxilla: A multidisciplinary consensus among experts in the field utilising the modified Delphi method.

PURPOSE: To establish consensus-driven guidelines that could support the clinical decision-making process for implant-supported rehabilitation of the posterior atrophic maxilla and ultimately improve long-term treatment outcomes and patient satisfaction. MATERIALS AND METHODS: A total of 33 participants were enrolled (18 active members of the Italian Academy of Osseointegration and 15 international experts). Based on the available evidence, the development group discussed and proposed an initial list of 20 statements, which were later evalu-ated by all participants. After the forms were completed, the responses were sent for blinded ana-lysis. In most cases, when a consensus was not reached, the statements were rephrased and sent to the participants for another round of evaluation. Three rounds were planned. RESULTS: After the first round of voting, participants came close to reaching a consensus on six statements, but no consensus was achieved for the other fourteen. Following this, nineteen statements were rephrased and sent to participants again for the second round of voting, after which a consensus was reached for six statements and almost reached for three statements, but no consensus was achieved for the other ten. All 13 statements upon which no consensus was reached were rephrased and included in the third round. After this round, a consensus was achieved for an additional nine statements and almost achieved for three statements, but no consensus was reached for the remaining statement. CONCLUSION: This Delphi consensus highlights the importance of accurate preoperative planning, taking into consideration the maxillomandibular relationship to meet the functional and aesthetic requirements of the final restoration. Emphasis is placed on the role played by the sinus bony walls and floor in providing essential elements for bone formation, and on evaluation of bucco-palatal sinus width for choosing between lateral and transcrestal sinus floor elevation. Tilted and trans-sinus implants are considered viable options, whereas caution is advised when placing pterygoid implants. Zygomatic implants are seen as a potential option in specific cases, such as for completely edentulous elderly or oncological patients, for whom conventional alternatives are unsuitable.

A bone density-measuring micromotor distinguishes different cortical/cancellous combinations in vitro: a study using polyurethane foam blocks.

PURPOSE: In the clinical setting, assessing bone quality and quantity at the implant site is the basis to select implant characteristics and the insertion protocol to be applied. However, a quantitative method to classify bone quality and quantity is still lacking. A recently introduced implant placement micromotor that provides site-specific, operator-independent cancellous bone density measurements may be useful for this purpose, but it remains unknown whether this device can detect the presence of a cortical bone layer and measure its thickness and density. MATERIALS AND METHODS: Thus, an in vitro experiment was performed on six double-layer polyurethane foam blocks mimicking the jaw bone with different cortical thickness/cancellous density combinations. The densities were measured using the micromotor, either removing the cortical layer or leaving it intact, with and without irrigation. RESULTS: The results collected in each condition were compared by means of non-parametric statistical tests. Independent of irrigation, the micromotor detected the cortical layer when it was left intact and accurately estimated its thickness. The micromotor did not discriminate each block from the other ones when they were considered separately, but it did when they were grouped into four or three classes. CONCLUSION: The present study suggested that the micromotor may represent a valid device to quantitatively assess bone quality and density. If the micromotor can quantitatively distinguish different cortical/cancellous bone combinations in humans, it may be a helpful tool to define finely-tuned, patient-tailored preparations of the implant seat, making teeth rehabilitation in challenging clinical conditions more predictable.

A comparison between anorganic bone and collagen-preserving bone xenografts for alveolar ridge preservation: systematic review and future perspectives.

After tooth extraction, dimensional changes affect the alveolar socket, leading to loss in alveolar bone height and width. Histological modifications also occur, with initial formation of a blood clot that is replaced with granulation tissue and subsequently with a provisional connective tissue matrix. Spontaneous healing ends with socket filling with woven bone, which is gradually replaced with lamellar bone and bone marrow. Adequate alveolar ridge dimensions and bone quality are required to assure optimal stability and osseointegration following dental implant placement. When a tooth is extracted, alveolar ridge preservation (ARP) procedures are an effective method to prevent collapse of the post-extraction socket. Heterologous bone is widely chosen by clinicians for ARP, and anorganic bone xenografts (ABXs) made bioinert by heat treatment represents the most used biomaterial in clinical applications. Collagen-preserving bone xenografts (CBXs) made of porcine or equine bone are fabricated by less invasive chemical or enzymatic treatments to remove xenogenic antigens, and these are also effective in preserving post-extraction sites. Clinical differences between anorganic bone substitutes and collagen-preserving materials are not well documented in the literature but understanding these differences could clarify how processing protocols influence biomaterial behavior in situ. This systematic review of the literature compares the dimensional changes and histological features of ABXs versus CBXs in ridge preservation procedures to promote awareness of different bone xenograft efficacies in stimulating the healing of post-extraction sockets.

Sinus lift with autologous bone alone or in addition to equine bone: an immunohistochemical study in man.

PURPOSE: The aim of the present study was to perform a comparative histological and immunohistochemical evaluation of microvessel density, vascular endothelial growth factor, and nitric oxide synthase (NOS) expression in sinus augmentation using autologous bone alone or in combination with equine bone. MATERIALS AND METHODS: Sixteen patients underwent sinus augmentation with autologous bone and a 50:50 mixture of autologous and equine bone. Control cores were harvested from preexisting nonaugmented bone under the sinus floor. The specimens were processed for immunohistochemistry. RESULTS: The greatest values of microvessel density were found in the sites grafted with autologous bone with significant differences between control versus autologous group (P < 0.01) and control versus autologous + equine group (P < 0.01). The higher and lower intensities of vascular endothelial growth factor and NOS3 expression were prevalent in the sites grafted with autologous bone with significant differences with the controls (P < 0.05). No significant differences (P > 0.05) were found in the NOS1 expression among the groups. CONCLUSION: The results obtained showed that the mixture of autologous and equine bone was biocompatible, and its use was associated with new blood vessels ingrowth during healing, which has been found to be extremely important for bone formation.

A retrospective preliminary histomorphometric and clinical investigation on sinus augmentation using enzyme-deantigenic, collagen-preserving equine bone granules and plasma rich in growth factors.

BACKGROUND: Enzyme-deantigenic equine bone (EDEB) is a substitute of autogenous bone. Mixing it with plasma rich in growth factors (PRGF) seems a viable option to achieve enhanced bone formation in alveolar bone augmentation surgeries. This retrospective study aims to first report the histomorphometric and clinical outcomes achieved when using the EDEB/PRGF mixture for performing sinus augmentation procedures followed by delayed implant placement. MATERIALS AND METHODS: Records of 11 patients who underwent 14 sinus augmentation surgeries using EDEB/PRGF followed by delayed implant placement were retrospectively collected and analyzed to assess histomorphometric data concerning newly formed bone (NFB) and residual biomaterial (RB) recorded at implant placement, marginal bone loss (MBL) values of implants placed in the augmented sinuses, and implant and prosthetic success and survival rates. RESULTS: At 5.6 ± 1.1 months after grafting, NFB and RB were 34.0 ± 9.1% and 11.3 ± 2.2% respectively, and no histologic signs of inflammation or immune reaction were observed in any of the 34 bone biopsies being collected. Further, 86.5 ± 4.3 months after implant placement, MBL was 0.40 ± 0.07 mm. No implant or prosthesis failed, and the implant success and survival rates were 100% CONCLUSIONS: Within the limitations of the present study, grafting EDEB/PRGF for lateral sinus augmentation and delayed implant placement seems to be safe. Compared to published data concerning EDEB alone, results of the present study do not suggest that the EDEB/PRGF combination may provide a histomorphometric or medium-/long-term clinical advantage.

Cortical Thickness, Bone Density, and the Insertion Torque/Depth Integral: A Study Using Polyurethane Foam Blocks.

PURPOSE: Bone density and implant primary stability parameters have been introduced that are based on calculating (1) the average of the instantaneous torque needed to keep the rotation speed of a bone density probe constant while it descends into bone or (2) the integral of the instantaneous torque-depth curve at implant insertion (I), a quantity that is equal to the insertion energy multiplied by a constant. This study aimed to determine how these two quantities are affected by the presence and thickness of a cortical bone layer. MATERIALS AND METHODS: An instantaneous torque-measuring micromotor was used to measure the density of six double-layer polyurethane foam blocks mimicking different cortical/cancellous bone combinations. Twenty measurements per block were collected, averaged, and compared. The insertion torque and the integral (I) of the instantaneous torque-depth curve at implant insertion were recorded when 20 3.75 × 12-mm cylindrical implants were inserted in each of nine blocks, including three single-layer blocks simulating the absence of a cortical layer, under three final cortical (countersink) preparations: 4.0, 3.7, and 3.5 mm. The relationship between the insertion torque, the integral of the instantaneous torque-depth curve at implant insertion (I), cortical thickness, and the final diameter preparation were investigated with regression and best-fit slope analyses. RESULTS: Bone density measurements showed that the average of the instantaneous torque at probing allowed differentiation of five of six different bone classes (hard-hard, hard-normal, hard-soft, normal-normal, normal-soft, soft-soft); the post hoc analysis of variance (ANOVA) comparisons were all statistically significant except for the hard-soft-normal-soft pair. The insertion torque and the integral (I) of the instantaneous torque-depth curve at implant insertion increased proportionally with cortical bone thickness (Pearson's r > 0.96 in all cases). CONCLUSION: When the final preparation varied from 3.7 mm to 3.5 mm, the insertion torque-thickness plot slope did not change significantly, while that of the instantaneous torquedepth curve integral (I)-thickness plot did change, suggesting that the torque-depth curve at implant insertion integral (I) may detect the increase in implant stability consequent to slight anatomical changes or changes in the site preparation protocol better than the insertion torque when measuring the cortical bone layer stress while undergoing insertion. These findings concerning bone density and primary stability should be investigated further using different experimental settings. If confirmed, they might generate improvements in the predictability of implant and prosthetic rehabilitation outcomes.

Stability of Dental Implants and Thickness of Cortical Bone: Clinical Research and Future Perspectives. A Systematic Review.

Dental surgery implantation has become increasingly important among procedures that aim to rehabilitate edentulous patients to restore esthetics and the mastication ability. The optimal stability of dental implants is correlated primarily to the quality and quantity of bone. This systematic literature review describes clinical research focusing on the correlation between cortical bone thickness and primary/secondary stability of dental fixtures. To predict successful outcome of prosthetic treatment, quantification of bone density at the osteotomy site is, in general, taken into account, with little attention being paid to assessment of the thickness of cortical bone. Nevertheless, local variations in bone structure (including cortical thickness) could explain differences in clinical practice with regard to implantation success, marginal bone resorption or anchorage loss. Current knowledge is preliminarily detailed, while tentatively identifying which inconclusive or unexplored aspects merit further investigation.

Implant Diameter, Length, and the Insertion Torque/Depth Integral: A Study Using Polyurethane Foam Blocks.

The amount of energy necessary to place an implant in its seat, described as the integral of the torque-depth curve at insertion (I), has been validated as a reliable measure of primary stability. This study aimed to investigate whether (I) may detect the variations in primary stability caused by changes in the implant length or diameter better than the insertion torque (IT). Cylindric implants featuring a double-etched, sandblasted surface with different diameters or lengths were placed into monolithic polyurethane foam blocks with different densities that mimicked human bone. (I)-, (I)*-, IT-, IT*-diameter and -length plots ((I)* and IT* were the derived values corrected for undersizing) were drawn and the relation between (I), (I)*, IT, and IT* and the fixture diameter or length was investigated with correlation analysis. (I)* and IT* correlated better than (I) and IT with the fixture diameter; (I), (I)*, IT, and IT* correlated equally well with the fixture length. In all cases, the slopes of the lines best fitting the experimental data were greater for (I) or (I)* than IT or IT*, respectively. (I) or (I)* were better detectors than IT or IT* of the changes in primary stability that can be achieved by increasing the fixture diameter or length.

Implant and Prosthetic Success Following Peri-implant Guided Bone Regeneration in the Esthetic Zone Using an Equine Cortical Bone Membrane and an Equine Enzyme-Treated Bone Graft: A Retrospective Study with 9-year Follow-Up.

PURPOSE: A barrier membrane consisting of an equine-derived, demineralized cortical bone sheet has been made available, yet evidence of its effectiveness is currently only anecdotal. This study aimed to obtain preliminary evidence concerning the medium-term prosthetic and implant success rates that may be achieved when such a membrane is used in combination with an equine, enzyme-treated bone graft, concomitantly to implant placement in the esthetic zone. MATERIALS AND METHODS: Records of patients who had one or two implants placed in the anterior sectors of the two arches and had peri-implant bone regeneration carried out using the equine-derived membrane and equine-derived collagen-preserving bone granules were retrospectively collected. Peri-implant marginal bone loss (MBL) was used to assess implant survival. When available, histologic data concerning the equine membrane and cone beam computed tomography (CBCT) scans were analyzed as well. RESULTS: Records of 32 patients (ages 36 to 73 years), corresponding to 44 implants placed, were retrieved and analyzed. The mean follow-up was 113.9 ± 10.2 months. Two implants failed. The implant success rate was 90.9%. Twelve membrane samples could be retrieved and analyzed, showing the membrane was still occlusive at 4.2 ± 1.1 months and only beginning to undergo remodeling. Twelve CBCT scans showed that 65.1 ± 9.8 months after surgery, a newly formed cortical layer could be observed in the zone that had undergone grafting. CONCLUSION: The equine cortical bone membrane and the enzyme-treated bone graft used in this case series achieved a medium-term implant and prosthetic success rate that was not dissimilar to that of other resorbable membranes and grafts for peri-implant guided bone regeneration augmentation. Preliminary medium-term histologic and CBCT data suggest that the membrane may be occlusive for a period of at least 4 months and may contribute to preserve the ridge thickness over time.

Chemical, Clinical and Histomorphometric Comparison between Equine Bone Manufactured through Enzymatic Antigen-Elimination and Bovine Bone Made Non-Antigenic Using a High-Temperature Process in Post-Extractive Socket Grafting. A Comparative Retrospective Clinical Study.

Enzyme-deantigenic equine bone (EDEB) and anorganic bovine bone (ABB) are two xenografts made non-antigenic through different processing methods. This study aimed to characterize them for the presence of native bone collagen and other proteins and to compare their histomorphometric outcome when they were used to graft post-extractive sockets. The records of 46 patients treated with EDEB (n = 22) or ABB (n = 24) and followed-up for at least four months after delayed implant placement, were retrospectively collected. Samples of EDEB and ABB were analyzed using Attenuated Total Reflection Fourier Transform Infrared and Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis for the presence of collagen and other proteins. For histomorphometric analysis on bone specimens, newly formed bone and residual biomaterial percentages were calculated. Results of the present study show that EDEB contains type I bone collagen in its native conformation, while no proteins were detected in ABB. Grafting EDEB resulted in a significantly greater quantity of newly formed bone and less residual biomaterial. Our findings suggest that the manufacturing process can greatly affect the graft behavior and a process preserving collagen in its native form may favor bone tissue regeneration.

Bone Density and Implant Primary Stability. A Study on Equine Bone Blocks.

Previous results on synthetic blocks mimicking bone indicate that bone density can be measured by the friction encountered by a rotating probe while it descends into bone, and that primary implant stability may be measured through the integral (I) of the torque-depth curve at implant insertion. This study aims to repeat those tests on collagen-preserving equine bone blocks as they better reproduce the mechanical properties of natural bone. Fifteen cancellous equine blocks had their density measured using a measuring probe. This was compared to their known physical density through linear regression analysis. Implant placement was carried out into six cancellous equine blocks and primary stability was measured using (I), as well as the insertion torque (IT), the implant stability quotient (ISQ), and the reverse torque (RT). The relation between (I), (IT), (ISQ), and (RT) was investigated by correlation analysis. Bone density measured using the probe correlated significantly with actual density, both with (r = 0.764) and without irrigation (r = 0.977). (I) correlated significantly with IT and RT under all irrigation conditions, and with ISQ only without irrigation (r = 0.886). The results suggest that the probe provides actual bone density measurements. They also indicate that (I) measures primary implant stability and is more sensitive to density variations than IT, RT, and ISQ. Results are consistent with those obtained on synthetic blocks but suggest that equine bone blocks may better reproduce the mechanical properties of human cancellous alveolar bone. This should be the subject of additional studies.

A Preshaped Titanium Mesh for Guided Bone Regeneration with an Equine-Derived Bone Graft in a Posterior Mandibular Bone Defect: A Case Report.

One of the most often used bone augmentation techniques is the guided bone regeneration procedure. The authors report the case of a 75-year-old man with an atrophic right posterior mandible who underwent bone augmentation through guided bone regeneration with a preshaped titanium mesh adapted on a stereolithographic model of the patient's jaw. The graft volume was simulated with a light-curing resin. The actual site was grafted with a mixture of autogenous and equine-derived bone. Five months later, the mesh was retrieved, three cylindrical implants were positioned, and a bone biopsy was collected for histomorphometric analysis. A provisional prosthesis was delivered three and a half months later. Definitive rehabilitation was accomplished after one additional month. The graft allowed for effective bone formation (newly formed bone, residual biomaterial, and medullar spaces were, respectively, 39%, 10%, and 51% of the core volume). The patient has functioned successfully throughout six and a half years of follow-up. Using the preshaped titanium mesh in association with the enzyme-treated equine bone substitute provided effective bone regeneration.

Correlation between Implant Geometry, Bone Density, and the Insertion Torque/Depth Integral: A Study on Bovine Ribs.

During insertion of dental implants, measurement of dynamic parameters such as the torque-depth curve integral or insertion energy might convey more information about primary stability than traditional static parameters such as the insertion or removal torque. However, the relationship between these dynamic parameters, bone density, and implant geometry is not well understood. The aim of this investigation was to compare static and dynamic implant stability measurements concerning three different implant designs when implants were inserted into bovine bone ribs and dynamic parameters were collected using an instantaneous torque measuring implant motor. Standard implant osteotomies were created in segments of bovine ribs. After measuring the bone density using the implant motor, 10 cylindrical, 10 hybrid tapered-cylindrical, and 10 modified cylindrical implants were placed, and their primary stability was assessed by measuring the torque⁻depth curve integral, along with insertion and removal torque. The relationship between these quantities, bone density, and implant geometry was investigated by means of regression and covariance analysis. The regression lines describing the relationship between the torque⁻depth integral and bone density differed significantly from those describing the relationship between insertion torque, removal torque, and bone density for all three designs. The torque⁻depth curve integral provides different information about immediate primary stability than insertion and removal torque and in certain clinical conditions might be more reliable than these static parameters for assessing implant primary stability. Further research should be carried out to investigate the findings of the present study.

Evaluation of Peri-implant Bone Stress on D1 Bone Using a Computerized Torque-Measuring Implant Motor: A Study on Photoelastic Resin Blocks.

PURPOSE: Recently, a torque-measuring micromotor that calculates the integral (I) of torque-depth curve at implant insertion was developed. This device was used to investigate the correlation between (I) and mechanical stress in photoelastic resin blocks with the density of D1 bone. MATERIALS AND METHODS: Using the micromotor, 40 implants (3.75 × 12 mm) were placed in 40 D1 blocks that had been prepared in four different ways. Four groups of 10 blocks each were prepared according to tunnel length (12 or 14 mm) and debris removal (yes or no). After insertion, peri-implant mechanical stress and its correlation with (I) were assessed by photoelastic and linear regression analysis, respectively. Analysis of variance (ANOVA) and Kruskal-Wallis tests investigated differences in mechanical stress patterns and dynamic parameters among the groups. RESULTS: (I) significantly correlated with mechanical stress in D1 resin under all conditions, except for 12-mm implant sites still containing debris. The correlation was significant concerning the whole dataset (r = 0.979) and separately for the coronal (r = 0.940), middle (r = 0.964), and apical (r = 0.948) portions of the implants. Peak torque did not correlate significantly with peri-implant mechanical stress. Longer implant sites and debris removal were significantly associated with lower peri-implant mechanical stress. CONCLUSION: (I) provides a reliable measure of mechanical stress in D1 bone during implant placement. Preparation of longer osteotomies and routine removal of all debris might reduce peri-implant bone stress significantly.

Sinus augmentation and concomitant implant placement in low bone-density sites. A retrospective study on an undersized drilling protocol and primary stability.

BACKGROUND: Recently, a torque-measuring micromotor has been shown to provide a reliable, quantitative intraoperative evaluation of bone density and implant primary stability. This may be particularly useful for determining bone quality of residual bone and consequently the most appropriate site preparation in the posterior maxilla, where bone often is of low density and quality. PURPOSE: This work aimed to assess the medium-term success of implants placed during 1-stage sinus augmentations using an undersized drilling protocol. In case of low bone density, the relationship between residual bone height (RBH) and primary stability was also investigated. MATERIALS AND METHODS: Clinical records of patients who underwent sinus augmentation and concomitant implant placement following a 12.5% undersized drilling protocol were retrospectively analyzed. In all patients, bone density measured intraoperatively was ≤ 0.45 g/cm3 . A minimum of 60 months of follow-up was required for inclusion. RESULTS: Records of 106 patients who received 253 implants were reviewed. No significant difference in the implant success rate was found for patients who had less than 4 mm of RBH and those who had more. CONCLUSIONS: Underpreparation of the implant-placement sites enabled achievement of successful implant-supported rehabilitation of the posterior maxilla even when both RBH and bone density were low.