Mesiodistal Distance Research Articles

Incidence and effect of an extra root on the crown morphometry of the maxillary second molars among Malaysian Mongoloids.

This study aimed to investigate whether the presence of two palatal roots on permanent maxillary second molars (MSMs) can affect the crown size and crown's buccolingual and mesiodistal diameters. A retrospective study was conducted using 592 CBCT scans to investigate 1120 MSMs of Mongoloid Malaysians. 3D models were created to assess the four-rooted MSMs and other related teeth carefully. Crown size and crown's buccolingual and mesiodistal diameters were measured for the four-rooted MSM, the adjacent maxillary first molar (MFM), and their antimeres to investigate the effect of the presence of an extra root on the size and morphological features of the crown of these associated teeth. Only six out of the 1120 MSMs displayed four roots (0.53%). The incidence was 0.67% (2/298) for the Malay males and 0.4% (1/247) for the Malay females, with the Malay male having a bilateral occurrence of four-rooted MSM. The incidence was 0.34% (1/294) for the Chinese males, while 0.71% (2/281) was detected in Chinese females. Interestingly, the four-rooted MSMs showed a wider mesiodistal distance than their three-rooted antimeres in three out of four cases. The presence of two palatal roots may also increase the crown's buccolingual diameter. The presence of anatomical variations and the dramatic change in crown measurements can be good indicators of the presence of extra roots, including in some of their related neighbours. This might help dentists to take precautionary measures when performing tooth extractions and endodontic therapy.

Accuracy of the infrazygomatic orthodontic bone screws digital planning and surgical guided positioning: A observational study

Objectives: The objective of the study was to evaluate the accuracy of surgical guidance for the insertion of infrazygomatic (IFZ) miniscrews by means of a cone beam computed tomography (CBCT) evaluation. Material and Methods: Nine patients (five men and four women, from 14.8 to 41.4 years of age) were recruited for the study. Rhinoceros software was used to digitally plan the infrazygomatic miniscrew insertion with the INFRABSTEER method (INFRA-zygomatic and Buccal Shelf method), superimposing intraoral scans and a CBCT obtained at T0. No orthodontic movement was performed, and six months later a second CBCT was done (T1). Rhinoceros software was used to superimpose T0 and T1 files. Mesio-distal, bucco-palatal, and vertical linear discrepancy in cap and tip and an angular discrepancy between the mini-screws was measured. To check the repeatability of the measurements, the intraclass coefficient (ICC) was calculated. The significance level considered is P < 0.05. The ICCs are all >0.85 and significantly different from 0 (P < 0.05), indicating excellent repeatability of measurements. Results: The lowest mean linear distance was found to be the mesio-distal distance at the tip with 0.23 ± 0.241 mm. All linear distances produced an average distance of less than 0.5 mm, except for the bucco-palatal distance measured at the tip. The smallest angular measurement was obtained from the intersection of the axes of the miniscrews in the mesio-distal plane (1.58° ± 1.458°). Conclusion: The combination of a digitally planned and a template-guided surgical positioning procedure allows excellent control of infrazygomatic miniscrews insertion.

Clinical analysis of the tooth-implant papilla for two narrow-diameter titanium-zirconium implants in the anterior area: prospective controlled clinical study

BackgroundRehabilitation of the anterior area when the mesio-distal space is reduced is a challenge for the clinician, due to the patient’s anatomical limitations and aesthetic requirements. Narrow Diameter Implants (NDI) are an option of treatment when the standard diameter implant is not possible, but the evidence is scarce. This prospective clinical study aims to analyze the formation of the tooth-implant papilla between the implant and the adjacent natural tooth in the maxillary lateral incisors and mandibular incisors.MethodsA total of 40 patients treated with NDI, of titanium-zirconium (Ti-Zr) alloy i.e., 2.9 mm Test Group (TG) and 3.3 mm Control Group (CG), were included. The mesiodistal distance between the adjacent natural teeth was used for implant selection, maintaining 1.5 mm between the fixation and the adjacent tooth. Clinical assessment was performed by a clinical examiner at 6 and 12 months after the final prosthesis. The primary variable was the Jemt Papillary Index. Also, implant survival rate (SR), complications, Implant Stability Quotient (ISQ), and patient-reported outcomes measures (PROMs) such as aesthetics, chewing, phonation, comfort, and self-esteem were analyzed.ResultsA significant amount of papilla filling was observed concerning the baseline, with a trend towards more formation of the papilla in the TG, with a JPI score of 3. No significant differences were observed between the two groups regarding implant SR, clinical parameters, and complications. In terms of PROMs, a higher satisfaction in the TG was observed, with significant intergroup differences for aesthetics, comfort, self-esteem, and primary stability ISQ (TG: 59.05 (SD: 5.4) vs. CG: 51.55 (SD: 5.7)).ConclusionsThe 2.9 mm diameter Ti-Zr implants achieved a formation of papilla similar to 3.3 mm implants in the anterior region at 12 months of follow-up after the final prosthetic restoration. The use of Ti-Zr implants with a diameter of 2.9 mm to rehabilitate single teeth in areas of the anterior region, where the mesiodistal distance is limited, showed favorable clinical results and a high degree of satisfaction during 1 year of observation similar to 3.3 mm dental implants.Trial registrationThis study was retrospectively registered in ClinicalTrials.gov with the number NCT05642520, dated 18/11/2022.

Vascular Delay Soft Tissue Technique in Oral/Maxillary Bone Reconstructive Surgery: A Technical Note.

The present study describes a new presurgical soft tissue technique in oral/maxillary bone reconstructive surgery for reducing the risk of soft tissue dehiscence and its related complications. Ten consecutive patients with Cawood and Howell type V atrophy were scheduled for CAD/CAM titanium mesh bone reconstructive surgery after applying the vascular delay technique 21 days before regenerative surgery. The surgical and healing complications were clinically assessed at nine time points, ranging from the time of bone regenerative surgery to 9 months after surgery. Surgical complications included flap damage and neurologic and vascular complications. Healing complications were subdivided into four classes. These classes comprised Class I: small membrane exposure (≤ 3 mm) without purulent exudate; Class II: large membrane exposure (> 3 mm) without purulent exudate; Class III: membrane exposure with purulent exudate; and Class IV: abscess formation without membrane. The study sample included seven men and three women (mean age: 48.2 ± 3.5 years) with seven mandibular cases and three maxillary cases. The defect length ranged from three to six teeth, with a mean mesiodistal distance of 29.9 ± 8.5 mm and a mean volume augmentation of 2.03 ± 0.9 cm3. There were no surgical complications. One patient presented a Class I healing complication that did not affect the regeneration outcome. The vascular delay technique appears to reduce the risk of soft tissue dehiscence and exposure in bone regenerative surgery, though randomized studies involving larger samples and longer follow-up periods are needed in order to draw firm conclusions.

Comparison of the morphology of the primary first molars and the forms of stainless steel crowns used in clinical practice.

This study aimed to assess the difference in the mesiodistal (MD) and buccolingual (BL) dimensions of primary first molars between Taiwanese boys and girls using a three-dimensional (3D) scanner (Microscribe G2 digitizer), record the coordinates in the 3D systems of Graph-R Project and reconstruct 3D images for subsequent analysis. We also determined whether the differences in these parameters between primary first molars and stainless steel crowns (SSC, 3M ESPE, No. 2-7) could be used as a reference for selecting a suitably-sized SSC and performing adjustments during restoration. The results indicated a statistically significant difference in the mesiodistal distance of lower primary first molar crowns between boys (7.75 ± 0.38 mm) and girls (7.41 ± 0.41 mm) (p < 0.05) but no differences in the mesiodistal distance of upper primary first molars between the two sexes. The mean mesiodistal distances of the upper and lower primary first molars of boys were close to SSC size 4 and 3, respectively, while those of girls were close to size 3 in both arches. Overall, the buccolingual distance between the first maxillary and mandibular molars of Taiwanese children was greater than the buccolingual distance between the 3M ESPE SSC. Reducing the buccolingual length of the abutment teeth might quickly help achieve a better fit, reduce chair time, and minimize patient discomfort. In addition, trimming the mesial and distal metal margins of SSCs might help reduce microleakage from the crown margins and improve its retention and survival rate. In conclusion, the 3D scanning and analysis method used in this study can serve as a reference for fabricating SSC to achieve better crown adaptation and improve dental procedures.

Suggested mesiodistal distance for multiple implant placement based on the natural tooth crown dimension with digital design.

The purpose of this investigation was to identify a mesiodistal algorithm for multiple posterior implant placement based upon an ideal prosthetically restoration design. One hundred one cases of posterior free-end edentulous arches were selected for digital crown designs and measurements. Cone bean computed tomogram and digital fabricated crown were applied. DICOM files were exported to a viewer software (BlueSkyPlan4) to generate digital crown and measurement. The mesiodistal space between roots of adjacent teeth and center of the potential implant horizontally, from both cross-section and coronal plane were measured. Comparisons were performed using t-tests. No significant difference was found in the distances of the maxillary and mandibular posterior implants to adjacent natural teeth (p > 0.05). For interdental/implant distances, premolars are around 4.2 mm and molars are 5.4 mm, correspondently. The second premolar interimplant distance is around 7-7.4 mm. The distance of interimplant of the first molar is about 8-8.5 mm. For the maxillary second molar, the interimplant distance is 9.26 ± 0.29 mm and the mandibular second molar interimplant distance is 9.58 ± 0.19 mm, which is significantly different. No difference was found between the two different measurement methods. A mesiodistal algorithm of 4-4.6 (implant to adjacent canine tooth), 7-7.4, 8-8.5, and 9-9.5 mm was recommended for interimplant/tooth distance from first premolar to second molar when placing implants with or without case-specific prosthetic planning prior to surgery.

Mesiodistal Measurements for Dental Implant Planning: A Prospective Clinical Study of Linear Measurements on Cone-Beam Computed Tomography Images in Comparison with Caliper-Based Measurements on Plaster Casts.

Althouh cone beam computed tomography (CBCT) is popular for dental implant planning, the horizontal mesiodistal space of the edentulous ridge is still conventionally measured with a handheld sliding caliper in the oral cavity or on a plaster cast. For clinical application in implant planning, our aim was to evaluate the accuracy of CBCT horizontal mesiodistal linear measurements in comparison with conventionally obtained direct measurements on plaster casts. Postoperative CBCT acquisitions and plaster casts of 27 patients with adjacent posterior mandibular implants were analyzed in a prospective clinical study. On CBCT images, two observers assessed the inter-implant distances on axial and sagittal views. On plaster casts, the inter-implant distances were measured with a digital caliper. CBCT measurements on axial and sagittal views were, on average, 0.2 mm larger than measurements on plaster casts. Correlation was perfect between measurements of the same inter-implant distance performed by the observers on CBCT images and on plaster casts. When compared with conventionally obtained direct measurements on plaster casts, CBCT views slightly overestimated (mean 0.2 mm) the horizontal mesiodistal measurements between two implants as reference points. CBCT imaging is sufficiently accurate to evaluate mesiodistal distances on axial and sagittal views for dental implant planning in clinical practice.

DIMENSIONAL ACCURACY OF DIGITAL IMPRESSION AND DOUBLE IMPRESSION MOLDING MODELS IN THE MANUFACTURING OF BRIDGE DENTAL

Dimensional accuracy of the impression model is very important in determining the success of denture treatment. The choice of printing technique is a factor that has a big influence on the printout. Digital impression and double impression techniques have good dimensional stability and provide accurate print details on the working model. The purpose of this study was to determine the level of dimensional accuracy of the digital impression and double impression models in the manufacture of bridge dentures. The research materials used were polyvinyl siloxanes elastomeric impression materials, stone gypsum type IV and aquades. The tools used are the master model, physiological printing spoon, glass stirrer, lekron, bowl spatula, calipers and 3D laser scanner. This research method used a laboratory experimental study design, and the master model was imprinted on the simulation of two abutments using digital impression and double impression techniques. The results showed that the digital impression technique showed a significant difference measured from the mesiodistal distance with the smallest value -0.004, the largest 0.011, the average difference 0.0369, at the occlusogingival distance the smallest value -0.003, the largest 0.009, the average difference 0.0375 , and the smallest value of interbutment distance is -0.001 and the largest is 0.000, and the average difference is -0.00031. The double impression technique showed a significant difference measured from the mesiodistal distance, the smallest value was -0.004, the largest was 0.011, the average difference was 0.00663, at the occlusogingival distance the smallest value was -0.014, the largest was 0.003, the average difference was 0.00300, and the interabutment distance was the smallest -0.001, the largest 0.003, and the average difference 0.00044. The conclusion of this study is that the digital impression technique is more accurate than the double impression technique in making denture bridges.

Aesthetics with Single Implants in the Anterior Sector: What Experts Claim

The objective of this article is to review the keys for the correct placement of implants in the anterior sector of the maxilla in order to achieve long-term implant success and, since it is an anterior sector, correct aesthetics.&#x0D; There should be a distance of at least 1.5 mm between the tooth and the implant, and ideally, the minimum vestibular thickness of bone of the implant should be 2 mm. Between implants the mesio-distal distance should be 3 mm and regarding the apico-coronal we should have at least 3 mm from the margin of the implant to the future restoration.&#x0D; The case must be planned carefully and we have to decide: when to place the implant, the provisional restoration, the type of implant, requirement of a graft, etc.

Permanent Maxillary Odontometrics for Sex Estimation Based on a 3-Dimensional Digital Method.

BackgroundIn the field of forensic medicine, sex estimation is a critical step in personal identification. Teeth are the hardest tissue and have high temperature resistance and corrosion resistance. In cases such as an airplane crash or the corpse of an unknown person, teeth often play a crucial role in identification. This study applied 3-dimensional technology to obtain odontometrics of permanent maxillary teeth and to examine the sexual dimorphism, finding suitable discriminant indicators to construct appropriate equations for sex estimation.Material/MethodsA total of 204 participants (104 men and 100 women) from the Han population in Kashgar were included. Plaster models of their maxillary dentition were obtained to scan and measure through an accepted and commonly used 3-dimensional digital method. Descriptive statistics, t tests, and discriminant analyses were statistically analyzed using IBM SPSS 23.0 software.ResultsThis study showed high intra- and interexaminer reliability (intraclass correlation coefficient >0.950). There were statistically significant sex-related differences (P<0.05), with male values generally being higher for buccolingual distance, mesiodistal distance, intercanine distance, crown area, crown module, crown index, and maxillary canine index. Compared with other measurements, mesiodistal distance and crown area indicator exhibited distinct sexual dimorphism. In addition, several appropriate equations were constructed through different discriminant analyses that could be used to estimate sex in our specific population.ConclusionsThree-dimensional digital technology offers a promising method for odontometry. Combining mesiodistal distance and buccolingual distance of particular teeth or using maxillary canine index in discriminant functions are acceptable auxiliary tools for sex estimation in the forensic field.

Accuracy of Three-Dimensional (3D) Printed Dental Digital Models Generated with Three Types of Resin Polymers by Extra-Oral Optical Scanning.

Digital impression devices are used alternatively to conventional impression techniques and materials. The aim of this study was to evaluate the precision of extraoral digitalization of three types of photosensitive resin polymers used for 3D printing with the aid of a digital extraoral optical scanner. The alignment of the scans was performed by a standard best-fit alignment. Trueness and precision were used to evaluate the models. The trueness was evaluated by using bias as a measure and the standard deviation was used to evaluate the precision. After assessing the normality of the distributions, an independent Kruskal–Wallis test was used to compare the trueness and precision across the material groups. The Mann–Whitney test was used as a post-hoc test for significant differences. The result of the analysis showed significant differences (U = 66, z = −2.337, p = 0.019) in trueness of mesiodistal distances. Upon visual inspection of the models, defects were noticed on two out of nine of the models printed with a photosensitive polymer. The defects were presented as cavities caused by air bubbles and were also reflected in the scans. Mean precision did not vary too much between these three photosensitive polymer resins, therefore, the selection of 3D printing materials should be based on the trueness and the required precision of the clinical purpose of the model.

Need for lateral bone augmentation at two narrow-diameter implants: A prospective, controlled, clinical study.

To detect the potential influence of implant diameter and anatomic factors on the need for bone augmentation procedures (BAPs) when replacing congenitally missing lateral incisors (MLIs). Patients with congenitally missing MLIs with a mesio-distal distance between the canine and the central incisor of 5.9-6.3mm received a Ø2.9mm implant while Ø3.3mm implants were placed when the distance was 6.4-7.1mm. The following linear measurements were recorded using a calliper: width of the alveolar process (WAP), width of the bony alveolar ridge (WAR) and thickness of the facial bone after implant osteotomy (TFB). Guided bone regeneration was performed in case of fenestration- or dehiscence-type defects or a thin TFB (<1.7mm). Fifty Ø2.9mm and 50 Ø3.3mm were included in 100 patients. WAP and WAR did not differ between the groups (p>.05). TFB was statistically significant larger in the Ø2.9 group (1.75±0.59mm) compared to the Ø3.3 group (1.5±0.63mm) (p=.041). Fenestration-type defects (p=.005) and a thin facial bone wall (p=.045) was observed more frequently in the Ø3.3 compared to the Ø2.9 group. Correspondingly, BAP was indicated more frequently in the Ø3.3 compared to the Ø2.9 group (p=.017). WAP, MD and WAR were statistically significant correlated to the need for BAP (p<.001). As independent variable, only WAR influenced the probability of BAP (p<.001). The use of 2.9 diameter implants was correlated to a reduced frequency of BAP compared to 3.3mm implants, without reaching a statistically significant difference. Measurement of the WAP provides the clinician useful information to predict BAP.

Accuracy of half-way mucosa-supported implant guides for edentulous jaws: a retrospective study with a median follow-up of 2 years.

ObjectiveTo assess the accuracy of half-way digital mucosa-supported implant guides (HDMIGs) for edentulous jaws.MethodsNinety-five consecutive patients (859 implants) with edentulous jaws who underwent implant placement using an HDMIG from July 2012 to June 2018 were retrospectively identified. The primary endpoint was implant-related complications (nerve injury and unexpected perforation), and the secondary endpoints were the faciolingual distance, mesiodistal distance, buccolingual angle, and mesiodistal angle. Follow-ups occurred at 1 month, 2 months, and then every 2 months following implant placement.ResultsTwenty-seven (28.4%) patients met the exclusion criteria, leaving 68 eligible patients (636 implants) for the final analysis. The median follow-up was 24 months (range, 18–27 months). No patients developed nerve injury, revision, or unexpected perforation. At the final follow-up, the mean faciolingual distance was 0.65 ± 0.16 mm, the mean mesiodistal distance was 1.16 ± 0.61 mm, the mean buccolingual angle was 4.04° ± 2.26°, and the mean mesiodistal angle was 3.75° ± 2.56°. In the comparison of the first month after surgery and the last follow-up, no significant differences were detected in any of the four measured variables.ConclusionUse of an HDMIG may be a convenient and safe method to ensure correct implantation.

Repeatability of Freehand Implantations Supported with Universal Plastic Sleeves—In Vitro Study

Repeatability and precision are major factors which have an influence on final implant treatment results. The aim of this study was to evaluate the repeatability of freehand implant procedures assisted with special plastic sleeves which are placed on the drill to guarantee the proper mesiodistal distance from the landmark’s surface. Patient data required for implant treatment, including images of mandibles from CBCT scans and virtual models of soft tissues and teeth, were used to prepare complete virtual models of patient clinical conditions. The models were saved as STL files and 3D printed in five copies. Drilling procedures were done at positions 37, 46 and 47. Each model was scanned with pins in the osteotomies and compared using digital aligning of the models’ surfaces. The average deviation was −1.38 ± 1.4 mm. Average deviations on guide pins placed at position 37 were −0.46 ± 0.59 mm, at position 46 were −1.46 ± 0.88 mm (landmark’s surface of both: distal tooth’s surface), and at position 47 were the highest: −2.69 ± 1.62 mm (landmark’s surface: surface of plastic sleeve). The following conclusion was drawn: Using universal plastic sleeves could improve implant procedure precision especially in the case of partially edentulous patients.

Effect of ceramic material type on the fracture load of inlay-retained and full-coverage fixed dental prostheses

Objective Ceramic inlay-retained fixed partial denture (IRFPD) is a conservative prosthetic option but the mechanical durability of new high strength zirconia reinforced glass ceramic FPDs is not investigated. The purpose of this study was to compare fracture load of 3-unit ceramic FPDs. Materials and methods Extracted premolars and molars (N = 64) were used to create three test groups (IRFPDs) and one control group (full coverage FPD) (n = 8). The teeth were embedded in PMMA resin with a mesiodistal distance of 6 mm. Premolars had a distal and molars had a mesial inlay preparation (width: 3 mm; height: 4 mm) in the test groups. IRFPDs were made from a zirconia reinforced lithium silicate (VS) or a monolithic zirconia. Zirconia IRFPDs received 2 types of surface treatments: sandblasting (Zr-IRFPD) or internal coating with feldspathic porcelain (ZrC-IRFPD). Control group was made from monolithic zirconia with the same connector size and zirconia surfaces were sandblasted (Zr-FPD). All restorations were cemented using a resin luting cement. After 5000 thermo-cycles, fracture load values (N) were determined with a universal testing machine at a crosshead speed of 0.75 mm/min. Data were analyzed using 1-way ANOVA and Tukey`s post hoc test (p ˂ .05). Result Fracture load (mean ± SD) of Zr-FPDs, Zr-IRFPDs and ZrC-IRFPDs were 672 ± 183, 672 ± 123 and 638 ± 59, respectively, being not statistically different (p > .05). VS-IRFPD exhibited statically lower values (391 ± 136). The predominant mode of failure was fracture at the connector area in all groups. Conclusion The fracture load of 3-unit IRFPD was significantly affected by types of ceramics but the retainer design and surface treatment in Zr groups did not show a significant effect.

Computed tomographic features of desmoplastic ameloblastoma of the jaw

Objective To retrospectively analyze the clinical and CT imaging features of desmoplastic ameloblastomas (DA) in comparison with other types of ameloblastomas. Methods Patients diagnosed with ameloblastoma histopathologically in Peking University School and Hospital of Stomatology from July 2000 to August 2017 were reviewed to analyze the constituent ratios and characteristics of DA. CT imaging features of DA (28 cases) were investigated in comparison with consecutive cases of solid/multicystic and unicystic ameloblastomas. The following imaging perspectives were analyzed: the border, internal structure, three-dimensional shape, tooth, the periodontium, the cortex and the expansion of the tumors. CT values were measured in the region of interest for quantitative analysis. Results Among the 1 269 cases of ameloblastomas, 50 (3.9%) were DA, which showed predilections for males (74.0%). The average age of DA was about 43.9 years old, which was higher than the other two types. The anterior incisorcanine region (62.0%) and premolar region (30.0%) were most frequently affected. The incidence rate of DA in mandibule was 56.0% (28/50), which was slightly higher than that of maxilla (44.0%). The DA characteristically showed scallop border and honeycomblike or soapbubble internal structure with bone formation on CT. The mean ratios of height to mesiodistal and buccal-lingual to mesio-distal distances were 0.76 and 0.63, which were higher than the other two types. According to the degree of internal bone formation, three subtypes of DA could be observed: densely ossifying type (I), honeycomb/soap bubble type (II) and sparsely ossifying type (III). The means and standard deviations of CT values of DA were significantly higher than those of the other two types, which were (488.8±164.0) HU (type I), (171.7±102.8) HU (type II), (42.1±8.8) HU (type III). Conclusion CT is helpful for diagnosis of DA, which shows as solid tumor with varying degrees of internal ossification.

Comparison of Dimensional Accuracy of Cast Obtained from Polyvinyl Siloxane Impression with Different Putty-Wash Techniques and Spacer Thickness - In Vitro Study

Introduction: Dimensional accuracy of cast obtained after making impressions is crucial factor for the quality of fixed prosthodontic treatment. The impression technique with different thickness of putty wash material is critical factor affecting this accuracy. There is much discussion in the dental literature concerning the effect of this impression technique on the accuracy of cast restorations.&#x0D; Materials and methods: This in-vitro study was carried out in 60 impression made from master model with Polyvinyl siloxane impressions material using single step putty- wash technique and two step putty-wash technique with varying spacer thickness (0.5mm, 1mm, 1.5 mm). It was further divided into four groups. Group I: Single step putty-wash impression technique, Group II: Two step putty-wash impression technique with 0.5mm spacer, Group III: Two step putty-wash impression technique with 1mm spacer, Group IV: Two step putty-wash impression technique with 1.5mm spacer. Each group consists of 15 impressions. Casts were poured using type IV dental stone after 1 hour. After 24 hour the die of each cast was scanned using CAD/CAM digital scanner and measured mesiodistally, facio-lingually, height (cervico-occlusally), interabutment or interdie distances. The data were recorded and statically analyzed.&#x0D; Results: The highest mean values of mesio-distal, bucco-lingual, cervico-occlusal distances were shown by Group I, whereas the inter-die distance showed equal mean value in Group I, II and III. With the increase in the spacer thickness, the mean value also increases in mesio-distal distance. The mean measurement of bucco-lingual dimension was highest when spacer thickness was 0.5mm and it declined with the increase in spacer thickness. The spacer thickness had no effect on cervico-occlusal and inter-die dimensions.&#x0D; Conclusions: Within the limitations of the study, accuracy of cast obtained from single step putty-wash technique was more accurate than two step putty-wash technique. In two step putty-wash technique, 1.5 mm thickness of spacer showed more accurate cast in comparison to 0.5mm and 1mm.

Need-to-knows about Digital Implant Surgery

Nowadays computer-guided "flapless" surgery for implant placement using templates is gaining popularity among clinicians and patients. The advantages of this surgical protocol are its minimally invasive nature, accuracy of implant placement, predictability, less post-surgical discomfort and reduced time required for definitive rehabilitation. Aim of this study is to describe the digital implant protocol, thanks to which is now possible to do a mini-invasive static guided implant surgery. This is possible thanks to a procedure named surface mapping based on the matching between numerous points on the surface of patient's dental casts and the corresponding anatomical surface points in the CBCT data. With some critical points and needing an adequate learning curve, this protocol allows to select the ideal implant position in depth, inclination and mesio-distal distance between natural teeth and or other implants enabling a very safe and predictable rehabilitation compared with conventional surgery. It represents a good tool for the best compromise between anatomy, function and aesthetic, able to guarantee better results in all clinical situations.

Effects of anterior tooth crown inclination on occlusal relationship—A study in three-dimensional reconstruction

ObjectiveThis study aims to analyze the relationship between the central incisor crown inclination and occlusal relationship via three-dimensional study. MethodsTen Chinese volunteers with normal occlusion were selected from physical examination of college students. Lateral cephalograms and CT scans were taken, and the CT data were imported into Simplant pro 11.04 to reconstruct three-dimensional model. In the three-dimensional model, every tooth was separated independently. The upper and lower central incisors were moved labial inclination(up) or lingual inclination(down) and then the upper and lower tooth were aligned based on the central incisor’s position according to the principles of Andrew’s six keys. Four groups were set up with different changes of central incisors. The upper and the lower arch were aligned again based on the moved central incisors. After every motion, the mesio-distal distances of upper and lower canines and first molars were recorded. All data were analyzed using t-test via SPSS19.0, and the significance level was set at 5%. ResultsThe results showed that the mesio-distal distances of occlusal relationship were different from normal occlusal relations, when either upper incisor crown inclination or lower incisor crown inclination was changed, and both upper and lower incisor crown inclination were moved in same or opposite direction. According to the statistical analysis, there was no significant difference when the changes of U1-L1 were no more than 10° (P > 0.05). But there was statistically significant difference (P < 0.05) when changes of U1-L1 were more than 20°. ConclusionsThe incisor crown inclination has influence on the establishment of occlusal relationships. The bigger difference upper and lower incisor crown inclination has, the more deviations from the normal occlusal relationship exist.

Mastication in goats shows achewing side preference

Developmental instability theory suggests that variation in some body parts in part can reflect the ability to buffer development from key environmental and genetic perturbations. Support for this approach comes mainly from assessment of fluctuating asymmetry, or deviations from symmetry of body features that are symmetric at the population level. In order to study dental asymmetry in domestic goats, we sampled 22 adult goat skulls. Bucco-palatine and mesio-distal distances (width and length) of the second molar on each side for each skull, on their occlusal aspect, were measured and compared using standard lineal methods. There was evidence of directional asymmetry, that is, unilateral mastication habits, being the left teeth of the arch slightly but systematically longer than the right. This directional change supported a right chewing side preference in the sample. It is important to highlight that the sample comes from non-pathological specimens. Therefore, it does depict the sample population of animals used in general. The observed asymmetries was not associated with any other cranio-facial abnormalities.