Maxillary Sinus Augmentation with Autologous and Heterologous Bone Graft: A Clinical and Radiographic Report of Immediate and Delayed Implant Placement

Purpose

The aim of this study was to evaluate cumulative survival rate of implants placed on augmented maxillary sinus using a mixture of autologous bone harvested from the maxillary tuberosity and bovine-derived HA and to assess the height of the grafted material through radiographic evaluation.

Methods

Thirty-five patients were treated with maxillary sinus augmentation and 93 implant fixtures were installed. The height of the augmented sinus and the gain of bone volume were measured by Cone Beam CT Scan and intraoral radiographs immediately after augmentation and up to 48 months subsequently. Changes in the height of the sinus graft material were calculated radiographically.

Results

The cumulative survival rate was 98.92 % in all 93 implants. Additionally, normal healing process without any complication was observed in all patients. The original sinus height was a mean of 4.52 mm (range 2.0–6.4 mm) and the augmented sinus height was a mean of 14.1 mm (range 12.0–16.5 mm) after the surgery. The bone volume gain was a mean 9.613 mm (range 7–13 mm).

Conclusions

Within the limitations of this study, it would appear from the clinical and radiographic results that the sinus lift procedure with autologous bone graft harvested from the maxillary tuberosity combined with deproteinized bovine bone allows for a predictable outcome regarding the amount of bone formation in sinus floor augmentation and the immediate placement of implants, when possible, is recommended.     

Clinical Evaluation of Use of Platelet Rich Plasma in Bone Healing

Background

Tooth extraction is performed for a wide variety of reasons as we know. Several techniques aiming at enhancing the regeneration process in the extraction socket have been adopted such as filling the socket with autogenous bone grafts or bone substitutes. We know platelets play a central role in hemostasis and healing processes but relative contradictory effect of platelet in bone regenerating capacity have been published in different in vitro and in vivo studies.

Method

To explore this we used platelet-rich plasma (PRP) (autogenous) alone in empty extraction socket of bilateral impacted mandibular third molars. For that we selected five patients having bilateral impacted teeth. Out of two sockets one was used as intervention by filling with PRP and the other was allowed to heal without PRP. All patients were followed for clinical and radiological evaluation by using digital OPG view after 1 week, 1, 2 and 4 months period.

Result and conclusion

PRP enhanced the osteogenic response in initial bone healing at 1 month duration but there was no added benefit in late bone healing at 4 months period compared in both intervention and control groups. However PRP significantly improved the soft tissue healing in PRP treated sites compared to control group.     

Comparison of Efficacy of Mandible and Iliac Bone as Autogenous Bone Graft for Orbital Floor Reconstruction

Objective

This study evaluated and compared the efficacy of mandible and iliac bone as autogenous bone graft for correction of orbital floor fractures.

Patients and Methods

Twenty patients who suffered orbital floor fractures took part in the study. The subjects enrolled in the study sustained both isolated orbital floor fracture and orbital floor fracture associated with fracture of zygomatico-maxillary complex. Each inferior orbital wall was reconstructed using either a mandible bone graft or an iliac graft. Mandibular symphysis was opted as a donor site for graft harvest from mandible and anterior iliac crest for the iliac group. CT scans were taken before the operation. Inclusion criteria consisted of at least 2 months postsurgical follow-up, pre- and post-surgical photographic documentation, and complete medical records regarding inpatient and outpatient data. To describe the distribution of complications and facilitate statistical analysis, we categorized our findings into diplopia, enophthalmos, and restriction of ocular movements before and after treatment. We also considered the time required for the harvest of the grafts and the donor site complications. A comparative study was carried out using Chi square test and student t test. We considered P value <0.05 to be statistically significant.

Results

Ten iliac crest grafts and ten mandible bone grafts were placed. The mean age of the patients was 33.1 years. 80 % of the patients were males. The most common complication of orbital floor fracture was diplopia, followed by enophthalmos and restriction of ocular movements. The post operative results were compared after 2 months of the surgery. In iliac crest group, diplopia got corrected in six out of seven patients (85 %), enophthalmos in four out of five patients (80 %) and restricted ocular movement showed 100 % correction. While in mandible group, diplopia and ocular movement showed 100 % correction and enophthalmos got corrected in five out of six patients (83 %). No statistically significant differences were found between the two groups on comparing these variables. On the other hand the mean time required for the harvest of iliac graft and mandible graft was 30.2 ± 3.52 min and 16.8 ± 1.75 min respectively. The difference was statistically significant.

Conclusion

There is no difference in the ability of mandible and anterior iliac crest bone grafts to correct post-traumatic diplopia, enophthalmos and restricted ocular movements. But the time and ease of harvest of the graft from mandible was comparatively less and easy especially when the treating doctor was an oral and maxillofacial surgeon. Secondly the post-operative morbidity was low and the quality and contour of the bone graft was very adaptable for the reconstruction of the orbital floor.     

The Need for Lateral Piriform Rim Augmentation in Patients with Unilateral Cleft Lip/Palate During Alveolar Cleft Bone Grafting

Background

Alveolar bone grafting in unilateral cleft lip/palate (CLP) patients can improve nasal symmetry and facial esthetic. In some cases lateral piriform hypoplasia cannot be compensated by soft tissue thickness of the face, necessitating onlay bone grafting. This study was designed to estimate the proportion of patients among unilateral CLP patients requiring this procedure.

Materials and Methods

In a retrospective study, unilateral CLP patients with severe paranasal deficiency, who were managed by paranasal augmentation with cortico-cancellous bone graft during the alveolar cleft bone grafting, were included.

Results

From 85 unilateral CLP patients treated from 2005 to 2011 in the Oral and Maxillofacial Surgery Department, Mashhad University of Medical Sciences, fourteen patients were treated with lateral piriform augmentation technique. Mean age of the patients at the time of operation was 16 ± 4.8 years. Follow-up period was 2–6 years.

Conclusion

Concomitant alveolar bone grafting and lateral piriform augmentation is needed at least in 16.5 % of unilateral CLP patients.     

A prospective study on the effectiveness of newly developed autogenous tooth bone graft material for sinus bone graft procedure

PURPOSE

The purpose of this prospective study was to evaluate the effectiveness of newly developed autogenous tooth bone graft material (AutoBT)application for sinus bone graft procedure.

MATERIALS AND METHODS

The patients with less than 5.0 mm of residual bone height in maxillary posterior area were enrolled. For the sinus bone graft procedure, Bio-Oss was grafted in control group and AutoBT powder was grafted in experimental group. Clinical and radiographic examination were done for the comparison of grafted materials in sinus cavity between groups. At 4 months after sinus bone graft procedure, biopsy specimens were analyzed by microcomputed tomography and histomorphometric examination for the evaluation of healing state of bone graft site.

RESULTS

In CT evaluation, there was no difference in bone density, bone height and sinus membrane thickness between groups. In microCT analysis, there was no difference in total bone volume, new bone volume, bone mineral density of new bone between groups. There was significant difference trabecular thickness (0.07 µm in Bio-Oss group Vs. 0.08 µm in AutoBT group) (P=.006). In histomorphometric analysis, there was no difference in new bone formation, residual graft material, bone marrow space between groups. There was significant difference osteoid thickness (8.35 µm in Bio-Oss group Vs. 13.12 µm in AutoBT group) (P=.025).

CONCLUSION

AutoBT could be considered a viable alternative to the autogenous bone or other bone graft materials in sinus bone graft procedure.     

Evaluation of Three-Dimensional Volumetric Changes After Sinus Floor Augmentation with Mineralized Cortical Bone Allograft

Aim

The aim of this retrospective study was to quantify three-dimensional (3D) volumetric bone changes over a two-year period in maxillary sinuses augmented with a mineralized cortical bone allograft material (MCBA) material.

Patients and Methods

Eleven patients (6 males and 5 females) with mean of age of 51.6 (range: 46–61) years were treated to increase the vertical dimension of the alveolar crest by maxillary sinus floor augmentation procedure. Study data were collected from patient records and by analyzing preoperative radiographs and cone beam computed tomography (CBCT) scans taken within the first two weeks after maxillary sinus lift (T0), immediately before implant placement four months after grafting (T1), and after one year of implant loading (T2). All DICOM-formatted images were rendered into volumetric images using software that automatically calculated the volume of the grafted material in cubic centimeters.

Results

Mean graft volume was 16.24 ± 1.54 cm³ at T0, 14.48 ± 1.48 cm³ at T1 and 13.06 ± 1.39 cm³ at T2. Mean volume retraction resulted in 1.76 ± 0.34 cm³ ΔV1 (T0–T1) and 1.42 ± 0.4 cm³ ΔV2 (T1–T2) and was 10.83 % of the initial total volume at (T0–T1) and 9.8 % of the total volume (T1–T2).

Conclusion

The present retrospective investigation demonstrated a 20.63 % decrease in graft volume. Volumetric 3D assessment of CBCT scans with the selected software appeared to be a promising approach to quantifying long-term changes in the grafted area.     

Microcomputed tomography analysis of particular autogenous bone graft in sinus augmentation at 5 months: differences on bone mineral density and 3D trabecular structure

Objectives

This study investigated the effects of gender on the three-dimensional (3D) bone mineral density (BMD) and micromorphology of the trabeculae of matured autogenous bone grafts after sinus floor augmentation, and compared them to those of adjacent native bone.

Materials and methods

Ten bone biopsy samples were removed from the implant placement areas of patients who had received second-stage sinus floor augmentation, and analyzed by microcomputed tomography. BMD phantoms with two calcium hydroxyapatite densities (0.25 and 0.75 g/cm³) were used to determine the BMD of the grafted and native bone samples. The 3D structural parameters of the trabeculae, including percentage of bone volume (bone volume/tissue volume, BV/TV), trabecular thickness (Tb.Th), trabecular number, trabecular separation, trabecular pattern factor (Tb.Pf), and structure model index, were analyzed between males and females and between grafted bone and native bone.

Results

No significant gender-specific differences in BMD and 3D trabecular structure of either native or grafted bone were found (P?>?0.05). Compared to the adjacent native bone, the autogenous grafted bone exhibited lower BV/TV and Tb.Th as well as a higher Tb.Pf (P?<?0.05). Additionally, there was a weak positive correlation between the Tb.Th values of grafted and native bone (R ²?=?0.58).

Conclusions

In the maxillary sinus, autogenous grafted bone exhibited lower BV/TV, Tb.Th, and trabecular connectivity than the adjacent native bone. No significant gender-specific differences were found for either the BMD or 3D trabecular structure of grafted bone.

Clinical relevance

After bone remodeling, autogenous grafted bone revealed different 3D trabecular structure as compared to native bone.     

Role of Platelet Rich Fibrin and Platelet Rich Plasma in Wound Healing of Extracted Third Molar Sockets: A Comparative Study

Aims and objectives

This prospective study was done to evaluate and compare the utility and effectiveness of platelet rich fibrin (PRF) with that of platelet rich plasma (PRP) on soft tissue healing and bone tissue healing of extracted third molar sockets.

Materials and methods

This study included split mouths of 20 patients who underwent bilateral extraction of impacted third molars. During the same appointment, following which PRF and PRP were prepared from patients’ autologous blood and placed in right and left extracted sockets, respectively. The data for soft tissue healing were recorded at end of 1 week, using healing index of Landry et al. and the data for bone tissue healing were recorded at the end of 4 months using digitalized orthopantomogram images on Adobe Photoshop CS; which was then compared between the two sites of the same patient.

Results

The mean values of soft tissue healing collected at 1 week post-operative, for PRF group were significantly higher as compared to PRP group. And the mean values of bone density collected at the end of fourth month post-operative, for PRF group were also significantly higher as compared to PRP group. Both tests showed p value of 0.00.

Conclusion

PRF is significantly better in promoting soft tissue healing and also faster regeneration of bone after third molar extraction, in comparison with PRP. This could be attributed to simpler preparation protocols of PRF over PRP and the ability of PRF to release growth factors in a controlled way.     

Horizontal and Vertical Reconstruction of the Severely Resorbed Maxillary Jaw Using Subantral Augmentation and a Novel Tenting Technique with Bone from the Lateral Buccal Wall

Aim

The aim of this study was to evaluate the effect of using the lateral wall bone in sinus lifting two-dimensional reconstruction on bone augmentation.

Patients and Methods

Ten patients affected by class V or VI maxillary atrophy with less than 3 mm of residual horizontal ridge were selected. Using a piezo-ultrasonic surgery tip bony lateral wall was cut. To expose native bone to the bone graft, multiple perforations, made through the cortical plate of the recipient site with a round bur. Once the bony buccal wall was adjusted it was fixed away from the ridge with two 1.5 x 13 mm bone fixation screws. Deficiencies created between the bony buccal wall and the ridge was filled with a mineralized cortical bone. A pericardium membrane was then placed on the graft. A biopsy for histologic evaluation was made.

Results

The data analysis in bone volume changes reported significant differences between the anterior and posterior locations before and after grafting (p < 0.05). The biopsy shows mature cancellous bone with predominantly lamellar structure.

Conclusion

The use of the lateral wall bone in sinus lift surgery showed significant increase in bone volume.     

Cortical Tibial Bone Graft for Nasal Augmentation

Background

This study sought to determine the efficacy of cortical tibial bone graft for nasal augmentation. Nine cases of augmentation rhinoplasty with cortical tibial bone graft are presented.

Methods

This prospective study evaluated the postoperative results of nine patients who underwent augmentation rhinoplasty using cortical tibial bone graft. There were six males and three females aged between 21 and 36 years (mean age 29). All the nine cases were treated through closed rhinoplasty incisions.

Results

Nine patients were operated on and the average follow up was 18 months. The results were favorable. The aesthetic results were gratifying; with good nasal projection in every case without any significant postoperative effects or complications requiring surgery were noted during the follow up.

Conclusion

The findings of this study support the use of cortical tibial bone graft for nasal augmentation although further studies with more sample size are required.     

Anterior alveolar dimensions among different classifications of sagittal jaw relationship in Saudi subjects

Sound orthodontic movement of anterior teeth is delineated by the biological dimensions of the anterior alveolus.

Objective

To establish and compare the anterior alveolar dimensions among normal and abnormal sagittal maxillomandibular relationships in a Saudi sample.

Materials and methods

The lateral cephalometric radiographs of 81 Saudi subjects (42 males and 39 females) were used to determine the anteroposterior and vertical dimensions of the anterior alveolus in Class I (N = 30), Class II (N = 24), and Class III (N = 27) cases. The anterior alveolar dimensions were then compared among males and females belonging to the same sagittal classification and between the different sagittal classifications of the same gender.

Results

Significant differences (P < 0.05) in the anterior alveolar dimensions between males and females were demonstrated for the same sagittal jaw classification. Also, significant differences (P < 0.05) were detected between the anterior alveolar dimensions among the different sagittal maxillomandibular classifications of the same gender.

Conclusion

Both the gender and the sagittal maxillomandibular relationship can affect the anteroposterior and vertical dimensions of the anterior alveolus.     

Assessment of Osstell? and Periotest? systems in measuring dental implant stability (in vitro study)

Objectives

The objectives of this in vitro study were to investigate the sensitivity and reliability of the Osstell™ systems (Resonance Frequency Analysis – RFA) compared to the Periotest® system in implant bone simulated conditions. Three conditions were simulated: (1) the direct fixture-bone contact and fibrous tissue fixture contact, (2) The different levels of horizontal bone loss, and (3) The hardening implant–bone interface.

Materials and methods

Forty-nine dental implant fixtures were placed in the center of acrylic cubes. In Part I seven fixtures were placed in direct contact with acrylic and another seven were placed in contact with polyvinyl siloxane impression material as soft interface. Part II: four sets of 0, 2, 4 and 6 mm horizontally exposed fixture samples were made (seven fixtures in each set). Part III: seven fixtures were placed in contact with a thin mix of autopolymerizing resin. The stability of these fixtures was measured using Osstell™ and Periotest® systems.

Results

The mean Periotest® value(PTV) and Osstell™ measurements showed a significant difference between the direct contact and soft interface (P < 0.001). These values also showed statistically significant difference between the different levels of horizontally exposed fixture groups (P < 0.001). The level of horizontal fixture exposure was strongly correlated with the PTVS (r = 0.967) and strongly negatively correlated with Implant Stability Quotient (r = −0.946). A strong correlation was found between the Osstell™ readings and the change in the stiffness of the autopolymerizing resin fixture interface group (r = 0.986).

Conclusions

Both Osstell™ and Periotest® systems proved to be sensitive in measuring dental implant stability in hard and in soft interfaces. Osstell™ also proved to be sensitive in detecting changes in the fixture interface stiffness. Osstell™ system proved to be more reliable compared to Periotest® system in measuring dental implant stability in hard and in soft interfaces.     

Effect of platelet rich plasma on bone regeneration in maxillary sinus augmentation (randomized clinical trial)

This study evaluates bone quality in sinus augmented with autogenous bone with or without platelet rich plasma (PRP) mix. 15 partially edentulous patients requiring maxillary sinus floor augmentation, followed by implant insertion were studied. In Group I, 5 patients underwent maxillary sinus lifting with autogenous bone augmentation and implant insertion at 6 months post grafting. In Group II, 10 patients underwent maxillary sinus lifting with autogenous bone augmentation mixed with PRP prepared from the patient's own blood with implant insertion at 4 or 6 months post grafting (n = 5 for each implantation time). A core biopsy was taken at the time of implant placement for histological and histomorphometric evaluation. Immediately and 3 months after implantation, Group I showed the statistically significant highest mean bone density (p = 0.046 and 0.022, respectively). At 6 months post-implantation, Group II showed the statistically significant highest mean bone density (p = 0.041). Histomorphometric analysis showed that Group I had the statistically significant highest mean value (39.5 ± 7.4; p = 0.003). Enrichment with PRP did not significantly improve bone density or morphometric value at 3 months post grafting. PRP enriched bone grafts were associated with superior bone density at 6 months post grafting.     

A Prospective Study Involving the Use of Platelet Rich Plasma in Enhancing the Uptake of Bone Grafts in the Oral and Maxillofacial Region

Abstract

Platelet-rich plasma (PRP) is an autologous product that contains highly concentrated number of platelets in a small volume of plasma, derived from whole blood by gradient density centrifugation. It has been speculated that local growth factors in human platelets (insulin-like growth factor, IGF; transforming growth factor, TGF-β; platelet derived growth factor, PDGF) would enhance healing of grafts and also counteract resorption. The aim of this study was to evaluate efficacy of PRP on early healing after autogenous bone grafting. Of the twenty patients selected ten were treated with autogenous bone graft and PRP (PRP group) and other ten with autogenous bone graft alone (non-PRP group). PRP group consisted of two benign tumor of mandible, one post surgical defect, two unilateral alveolar cleft, one bilateral alveolar cleft with skeletal class III malocclusion, one maxillary hypoplasia, one oronasal fistula, one recurrent tumor of mandible, one multiple impacted mandibular teeth. Non-PRP group consisted of seven benign tumor of jaw, one keratocyst odontogenic tumor, one orbital blow out fracture, one residual traumatic defect. Biopsies were taken in the native bone, PRP treated grafted bone, grafted bone without PRP at 3 months to assess the maturity of bone. Radiographic imaging was performed by panoramic radiography at 3 and 6 months to evaluate bone opacity of grafted bone on comparison with native bone and computerized tomography at 6 months to evaluate grafted bone morphologically and to measure bone density in Hounsfield units. Microscopic results showed that significantly more matured bone was formed at PRP treated sites as that of native bone and immature bone in controls after 3 months of healing. Bone opacity of PRP treated bone grafts was close to that of native bone than that of non-PRP treated bone grafts on panoramic radiograph at 3 and 6 months. There was graft loss in three cases and graft resorption in one case of non-PRP treated bone grafts at 6 months. In PRP group the compact bone was clearly differentiated from cancellous bone as in native bone and thick in five cases, thin in five cases. In non-PRP group the compact bone was thin as a whole. Comparing native bone group and PRP group the CT value of PRP treated bone graft was more or less close to native bone group and comparing native bone group and non-PRP group CT value was low in non-PRP treated bone graft. Whereas when comparing PRP and non-PRP group CT value was higher in PRP group. Autologous PRP was a safe, biocompatible, effective, source for growth factors and carries no risk of transmissible diseases. It enhances and accelerates bone regeneration of autogenous bone grafts.     

The short-term skeleto-dental effects of a new spring for the intrusion of maxillary posterior teeth in open bite patients

Background

The technology surrounding temporary skeletal anchorage devices has improved in leaps and bounds. However, no specific auxiliary exists for the intrusion of molars in conjunction with these devices and currently clinicians are forced to make do with available force delivery materials. A new intrusion auxiliary, the Sydney Intrusion Spring (SIS), was designed to facilitate intrusion without frequent need for reactivation or tissue irritation.

Methods

The subjects consisted of 16 adolescent patients (12 females and 4 males) with an average age of 13.1 years (range 12.2 to 14.3 years). All patients were in the permanent dentition with an anterior open bite of ≥2 mm. Four self-drilling miniscrews were placed into the posterior maxillary buccal alveolar bone. The intrusion appliance consisted of a bonded acrylic appliance and the SIS, activated to produce an initial intrusive force of 500 g. Cone beam computed tomograms were taken after miniscrew placement and at the end of active intrusion. Rendered lateral cephalograms were produced and measurements were taken and compared.

Results

All study objectives were achieved in 4.91 months (range 2.5 to 7.75 months). The mean molar intrusion was 2.9 ± 0.8 mm (P < .001), resulting in over bite increase of 3.0 ± 1.5 mm (P < .001). The intrusion led to a 2.6° ± 1.3° (P < .001) clockwise occlusal plane rotation and a 1.2° ± 1.3° (P < .01) counter-clockwise rotation of the mandible. Dental measurements showed a significant uprighting and elongation of the incisors. There was no significant extrusion of the lower molars.

Conclusion

The SIS is an effective appliance for the intrusion of maxillary posterior teeth, in conjunction with miniscrews.     

Comparative,Histological and Histomorphometric Analysis of Three Anorganic Bovine Xenogenous Bone Substitutes: Bio-Oss,Bone-Fill and Gen-Ox Anorganic

Introduction

Anorganic bovine xenogenous grafts show the best performance as bone substitutes in implantodontics. Bio-Oss is the world’s most widely used and investigated anorganic bone substitute. This article compares two anorganic bovine bone substitutes (Bone-Fill and Gen-Ox anorganic) with Bio-Oss.

Materials and Methods

Eight New Zealand rabbits were implanted with 4 titanium cylinders randomly filled with Bio-Oss, Bone-Fill, Gen-Ox anorganic or a blood clot. Four animals were sacrificed after 8 weeks; 12 weeks later, the remaining four were sacrificed. The contents of the cylinders were removed, cut and stained with HE before they were evaluated with an optical microscope. The samples were submitted to histomorphometry for analysis.

Results

The bone formation with Bio-Oss at 8 weeks was 8.43 mm²; at 12 weeks, it was 9.32 mm². The bone formation with Bone-Fill at 8 weeks was 7.24 mm²; at 12 weeks, it was 9.01 mm². The bone formation with Gen-Ox anorganic at 8 weeks was 2.78 mm²; at 12 weeks, it was 3.02 mm². The bone formation with the blood clot at 8 weeks was 0.65 mm²; at 12 weeks, it was 0.63 mm².

Conclusion

Following this model, Bone-Fill was comparable to Bio-Oss and superior to Gen-Ox and blood clot.     

The effect of orthodontic bands or tubes upon periodontal status during the initial phase of orthodontic treatment

Introduction

Orthodontic bands cause periodontal inflammation. In theory, the use of a buccal tube (bond) instead of a band should prevent or minimize periodontal changes because the bonds are positioned away from the gingival margins.

Objective

The primary aim of this study was to investigate the periodontal status of orthodontic bands compared with bonds in the first three months of orthodontic treatment.

Materials and methods

Twenty-four orthodontic patients (mean age = 12.6 years) were enrolled in this Randomized Controlled Trial (RCT). Using the cross-mouth technique, bands and bonds were used in opposite quadrants. Periodontal parameters including the presence or absence of Bleeding On Probing (BOP) and Probing Depths (PDs) were taken at the start and three months into treatment.

Results

Bands caused a statistically significant change in the Bleeding On Probing (BOP) (P = 0.001 and 0.021) and bonds displayed a statistically insignificant change in the Bleeding On Probing (BOP) (P = 0.125 and 1.00) for the upper and lower arch. The difference in Probing Depths (PDs) between bands and bonds was also statistically significant (P = 0.001).

Conclusion

Molar bands are associated with greater periodontal inflammation compared with molar bonds in the first three months of fixed orthodontic treatment.     

Orthognathic model surgery by using of a passive Robot Arm

Purpose

The possibility of using a passive Robot Arm (3D method) in model surgery and comparing with manual technique model surgery.

Patients and methods

Seventeen patients undergoing orthognathic surgery gave consent for this study. Model surgery was performed by using a manual technique and using the Robot Arm. The model surgery that was performed by using the manual technique named group A and the one performed by the Robot Arm named group B. Patients’ maxillary casts were measured before and after model surgery, and results were compared with those for the original treatment plan in the horizontal (X-axis), vertical (Y-axis), and transverse (Z-axis) planes.

Results

Statistical analysis using Mann–Whitney U test for X- and Y-axis and independent sample t test for Z-axis have shown significant differences between both groups in X-axis (P = .026) and Y-axis (P = .021) but not in Z-axis (P = .762).

Conclusions

Model surgery performed with a Robot Arm is more accurate in all dimensions X, Y, and Z than the manual model surgery.     

Fracture resistance of porcelain veneered zirconia crowns with exposed lingual zirconia for anterior teeth after thermal cycling: An in vitro study

Statement of problem

In some clinical conditions minimally invasive complete crown tooth preparations are indicated. This is especially true when gross removal of tooth structure would weaken the remaining tooth or violate the vitality of the dental pulp.

Objective

The purpose of this study was to investigate the influence of (1) exposed lingual zirconia with veneered zirconia crowns, and (2) reduced lingual thickness of monolithic lithium disilicate crowns on the fracture resistance of the crowns after cyclic loading. Metal-ceramic crowns with exposed lingual metal served as controls.

Materials and methods

Twenty-four maxillary central incisor crowns were fabricated in identical shape on metal testing dies in 3 groups: metal-ceramic crowns (MC, n = 8), veneered zirconia crowns (VZ, n = 8), and monolithic lithium disilicate crowns (MO, n = 8). A conservative preparation design with 0.75 mm lingual clearance was used for each crown system. All crowns were cemented to their corresponding crown preparations with self-adhesive resin cement (Multilink Automix). The crowns were subjected to 1000 cycles of thermal cycling, then cyclic loading of 111 N by means of a stainless steel ball, and 50,000 cycles of loading were applied for the fatigue test. Fatigue loading was followed by a continuously increasing compressive load, at a crosshead speed of 1 mm/min until failure. The compressive load (N) required to cause failure was recorded. Means were calculated and analyzed with one-way ANOVA and the Tukey HSD test (α = .05).

Results

There was a significant difference between MO vs. MC (P = .0001), MO vs. VZ (P = .0001), and VZ vs. MC (P = .012).

Conclusions

There was a significant difference in the mean fracture resistance of MC, VZ, and MO crowns in this in vitro study. The MC group recorded the highest mean fracture strength.     

Bond strength of self-adhesive resin cements to tooth structure

Objectives

The aim of this study was to evaluate the strength of the bond between newly introduced self-adhesive resin cements and tooth structures (i.e., enamel and dentin).

Methods

Three self-adhesive cements (SmartCem2, RelyX Unicem, seT SDI) were tested. Cylindrical-shaped cement specimens (diameter, 3 mm; height, 3 mm) were bonded to enamel and dentin. Test specimens were incubated at 37 °C for 24 h. The shear bond strength (SBS) was tested in a Zwick Roll testing machine. Results were analyzed by one-way ANOVA and t-test. Statistically significant differences were defined at the α = 0.05 level. Bond failures were categorized as adhesive, cohesive, or mixed.

Results

The SBS values ranged from 3.76 to 6.81 MPa for cements bonded to enamel and from 4.48 to 5.94 MPa for cements bonded to dentin (p > 0.05 between surfaces). There were no statistically significant differences between the SBS values to enamel versus dentin for any given cement type. All cements exhibited adhesive failure at the resin/tooth interface.

Conclusions

Regardless of their clinical simplicity, the self-adhesive resin cements examined in this study exhibit limited bond performance to tooth structures; therefore, these cements must be used with caution.