Factors that influence the accuracy of intraoral scanning of total edentulous arches rehabilitated with multiple implants: A systematic review.

STATEMENT OF PROBLEM: The direct digitalization of completely edentulous arches rehabilitated with multiple implants still represents a limitation regarding obtaining accurate images for prosthetic purposes. PURPOSE: The purpose of this systematic review was to present the factors that may influence the accuracy of intraoral scanning of completely edentulous arches. MATERIAL AND METHODS: This review was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria and registered with International Prospective Register of Systematic Reviews (PROSPERO) (CRD42020171021). Three examiners performed an electronic search in the Medline/PubMed, Cochrane Library, Scopus, and Web of Science databases for articles published up to January 2021. RESULTS: The electronic search resulted in 11 498 studies. After removing duplicates, 11 347 studies remained. Twelve studies were selected (10 in vitro and 2 in vivo) according to the eligibility criteria. Several factors were found to influence the performance of intraoral scanners (Carestream Dental and TRIOS, 3Shape presented the best results), the intraoral scanning technique (Promoting physical paths that join the digitization bodies can increase the accuracy of transferring the position of the implants), environmental conditions (temperature: 20 °C to 21 °C, air pressure: 750 to 760 ±5 mmHg, air humidity: 45%, angle and distance between the implants: up to 15 degrees and 16 to 22 mm, and the material of the scan body: PEEK more accurate). CONCLUSIONS: The accuracy of the intraoral scanning of completely edentulous arches is affected by factors such as the type of intraoral scanner, scanning technique, environmental conditions, angle and distance between implants, and material of the scan bodies.

Additively manufactured scan body for transferring a virtual 3-dimensional representation to a digital articulator for completely edentulous patients.

A technique is described for obtaining a virtual 3-dimensional representation of completely edentulous patients with the virtual definitive casts mounted on the virtual articulator. An additively manufactured intraoral scan body was developed to record the definitive maxillary and mandibular casts and gothic arch interocclusal registration. The intraoral scan body guided the integration of the digital definitive casts and facial scans to obtain the virtual 3-dimensional patient's representation and facilitated the transfer of the definitive casts to the virtual articulator.

3D Virtual Patient Representation for Guiding a Maxillary Overdenture Fabrication: A Dental Technique.

This report describes a technique to obtain a 3D virtual representation of a maxillary edentulous patient guided by an additively manufactured intraoral scan body. The intraoral scan body incorporated a custom tray and occlusion rim which facilitated the acquiring of a digital definitive cast, maxillary occlusion rim position, interocclusal registration, and guided the integration of the facial scans. The technique simplified the design and manufacturing of the maxillary overdenture.

Denture scanning technique for computer-guided implant-supported restoration treatment of edentulous patients.

The traditional protocol for guided surgery in a completely edentulous patient is time-consuming, requiring the fabrication of a radiographic guide and a dual cone beam computed tomography (CBCT) scan. Using intraoral scanners to scan the edentulous ridge and the existing denture has been advocated to simplify the process. This technique offers a versatile, precise, and predictable method for the digital planning workflow in edentulous patients for either a fixed or removable restoration. In addition, this approach can help improve the quality of the guide produced by reducing CBCT artifacts associated with the existing denture, as well as capture the soft-tissue contour to further improve the fit of the surgical guide.

Influence of implant position on the accuracy of intraoral scanning in fully edentulous arches: A systematic review.

STATEMENT OF PROBLEM: Parallel dental implants improve prosthesis longevity and facilitate the impression making steps when compared with angled implants. The effect of implant angulation on the accuracy of casts generated by using intraoral scanners has not been fully investigated. PURPOSE: The present systematic review addressed following the patient, intervention, control, and outcome (PICO) question: Does implant position affect the intraoral scanning accuracy of arches that will receive complete-arch implant-supported fixed dental prostheses? MATERIAL AND METHODS: A bibliographic search was performed in the Medline-PubMed, Scopus, Web of Science, and Cochrane Library databases by using specific descriptors for studies published until July 2020. All studies evaluated the intraoral scanning accuracy of arches rehabilitated with multiple implants through implant linear and/or angular deviation. RESULTS: Eight in vitro studies that met the eligibility criteria were evaluated. Five publications showed lower linear and angular displacements for the digital scans compared with the conventional technique. Two studies showed that the digital scan presented higher angular and linear distortions than the conventional technique. Only 1 study did not find differences between the 2 recording methods. CONCLUSIONS: Digital scanning is reliable. However, caution is needed concerning its indication, especially in patients where the angles between implants are greater than 15 degrees. The association of the implant angulation with the clinical factors needs to be further investigated. The absence of clinical evidence and methodological heterogeneity limited the results of this study.

Prevalence of horizontal alveolar changes in edentulous patients: a retrospective tomographic study.

Horizontal bone loss after tooth extraction is a common finding that demands bone reconstruction in various cases. The aim of this study was to assess the horizontal alveolar status in partially and completely edentulous patients using cone-beam computed tomography (CBCT). In total, 1516 CBCT scans of 1404 adult patients were analyzed. Assessment of the images was performed in accordance with the previously published horizontal alveolar change (HAC) classification, which categorizes horizontal bone defects into four classes: HAC 1, HAC 2, HAC 3 and HAC 4 (from the least severe to the most severe condition). Analysis of 1048 scans from partially edentulous patients presented a distribution of 63.55%, 22.14%, 13.36% and 0.95% in HAC 1, HAC 2, HAC 3 and HAC 4, respectively. Analysis of 468 scans from completely edentulous patient images presented a distribution of 19.87%, 28.63%, 41.67% and 9.83% in HAC 1, HAC 2, HAC 3 and HAC 4, respectively. Based on these results, as in HAC 4, no cancellous bone was found between the cortical buccal and lingual/palatal bone plates, it seems reasonable to state that the absence of cancellous bone is higher in completely edentulous patients than in partially edentulous patients. Therefore, the absence of cancellous bone seems to be higher in completely edentulous than in partially edentulous patients.

Prevalence of horizontal alveolar changes in edentulous patients: a retrospective tomographic study

Abstract Horizontal bone loss after tooth extraction is a common finding that demands bone reconstruction in various cases. The aim of this study was to assess the horizontal alveolar status in partially and completely edentulous patients using cone-beam computed tomography (CBCT). In total, 1516 CBCT scans of 1404 adult patients were analyzed. Assessment of the images was performed in accordance with the previously published horizontal alveolar change (HAC) classification, which categorizes horizontal bone defects into four classes: HAC 1, HAC 2, HAC 3 and HAC 4 (from the least severe to the most severe condition). Analysis of 1048 scans from partially edentulous patients presented a distribution of 63.55%, 22.14%, 13.36% and 0.95% in HAC 1, HAC 2, HAC 3 and HAC 4, respectively. Analysis of 468 scans from completely edentulous patient images presented a distribution of 19.87%, 28.63%, 41.67% and 9.83% in HAC 1, HAC 2, HAC 3 and HAC 4, respectively. Based on these results, as in HAC 4, no cancellous bone was found between the cortical buccal and lingual/palatal bone plates, it seems reasonable to state that the absence of cancellous bone is higher in completely edentulous patients than in partially edentulous patients. Therefore, the absence of cancellous bone seems to be higher in completely edentulous than in partially edentulous patients.

Segmentation Methods for Micro CT Images: A Comparative Study Using Human Bone Samples.

X-ray microtomography (microCT) is a nondestructive technique used to assess bone morphometry. For an accurate analysis, it is necessary to segment the bone tissue from the background images, avoiding under- or overestimation of the real bone volume. Thus, segmentation methods for microCT can influence the accuracy of bone morphometry analysis. The purpose of this study was to compare two different image segmentation methods available on microCT software (subjective and objective) regarding to the human bone morphometric analysis. Sixteen samples containing a fixation screws covered by 0.5-1mm of bone were scanned using the SkyScan 1173 scanner. Three examiners segmented the microCT images subjectively and recorded the threshold values. Subsequently, an objective segmentation was also done. The 3D analysis was performed for both images using the values​ previously determined in CTAn software. Five bone morphometric parameters were calculated (BV/TV, Tb.Th, Tb.N, Tb.Sp, Conn.Den) and used as dependent variables. ANOVA showed no significant differences between the methods concerning BV/TV (p=0.424), Tb.N (p=0.672), Tb.Th (p=0.183), Tb.Sp (p=0.973) and Conn.Den (p=0.204). Intra- and interobserver agreement ranged from satisfactory to excellent (0.55-1 and 0.546-0.991, respectively). Therefore, results obtained with subjective threshorlding were similar to those obtained with objective segmentation. Since objective segmentation does not have human input and it is a truly objective method, it should be the first choice in microCT studies that concern homogeneity and high resolution human bone sample.

Segmentation methods for micro ct images: a comparative study using human bone samples

Abstract X-ray microtomography (microCT) is a nondestructive technique used to assess bone morphometry. For an accurate analysis, it is necessary to segment the bone tissue from the background images, avoiding under- or overestimation of the real bone volume. Thus, segmentation methods for microCT can influence the accuracy of bone morphometry analysis. The purpose of this study was to compare two different image segmentation methods available on microCT software (subjective and objective) regarding to the human bone morphometric analysis. Sixteen samples containing a fixation screws covered by 0.5-1mm of bone were scanned using the SkyScan 1173 scanner. Three examiners segmented the microCT images subjectively and recorded the threshold values. Subsequently, an objective segmentation was also done. The 3D analysis was performed for both images using the values​ previously determined in CTAn software. Five bone morphometric parameters were calculated (BV/TV, Tb.Th, Tb.N, Tb.Sp, Conn.Den) and used as dependent variables. ANOVA showed no significant differences between the methods concerning BV/TV (p=0.424), Tb.N (p=0.672), Tb.Th (p=0.183), Tb.Sp (p=0.973) and Conn.Den (p=0.204). Intra- and interobserver agreement ranged from satisfactory to excellent (0.55-1 and 0.546-0.991, respectively). Therefore, results obtained with subjective threshorlding were similar to those obtained with objective segmentation. Since objective segmentation does not have human input and it is a truly objective method, it should be the first choice in microCT studies that concern homogeneity and high resolution human bone sample.

Resumo A microtomografia computadorizada (microTC) é uma modalidade de imagem não destrutiva utilizada para avaliar a morfometria óssea. Para análise acurada, faz-se necessário segmentar o tecido ósseo do fundo (background) da imagem, evitando assim, sub ou sobre estimação do volume ósseo real. Desta forma, fica evidente que os métodos de segmentação em análise de microTC podem influenciar a precisão dos cálculos da morfometria óssea. A realização do presente estudo teve como objetivo comparar o desempenho de dois diferentes métodos de segmentação de imagem de microTC, subjetivo e objetivo, através da avaliação dos resultados das análises morfométricas obtidas de ossos humanos. Dezesseis amostras contendo parafusos de fixação cobertos por 0,5- 1 mm de osso humano foram escaneados usando o microtomógrafo SkyScan1173. Três examinadores realizaram a segmentação das imagens de forma subjetiva (visualmente) obtendo seus respectivos valores de threshold. Em seguida, a segmentação objetiva (automática) foi realizada. As análises tridimensionais foram obtidas utilizando os valores determinados por ambos os métodos no software CTAn. Cinco parâmetros morfométricos do osso foram calculados (BV / TV, Tb.Th, Tb.N, Tb.Sp, Conn.Den) e usados ​​como variáveis ​​dependentes. O teste ANOVA não mostrou diferenças estatisticamente significantes entre os métodos comparados: BV / TV (p=0,424), Tb.N (p=0,672), Tb.Th (p=0,183), Tb.Sp (p=0 973) e Conn.den (p=0,204). A concordância intra e interobservardores variou entre satisfatória e excelente (0,55-1 e 0,546-0,991, respectivamente). Portanto, os resultados obtidos com a segmentação subjetiva foram semelhantes aos obtidos com a automática. Entretanto, a segmentação automática dispensa intervenção humana, sendo um método verdadeiramente objetivo e deve ser a primeira escolha em estudos microTC que objetivam avaliar a morfometria óssea humana.

Stability and Crestal Bone Behavior Following Simultaneous Placement of Multiple Dental Implants (Two or More) with the Bone Splitting Technique: A Clinical and Radiographic Evaluation.

PURPOSE: The present study aimed to measure the implant stability quotient (ISQ) values at three different time points after surgical procedures and crestal bone behavior in multiple implants (two or more) installed simultaneously with the bone splitting technique. MATERIALS AND METHODS: For this study, 45 patients with different edentulous areas in the maxilla were selected, and a total of 114 dental implants were installed. Implant stability was measured by resonance frequency analysis immediately following implant placement to assess immediate stability (time 1) and stability at 90 days (time 2), and 150 days (time 3). Crestal bone height was measured in peri-apical radiographs at 90 and 150 days after implantation in relation to each implant shoulder, given that the implants were installed at the level of the crestal bone. RESULTS: Six implants were not osseointegrated. Overall, the means and standard deviations of the ISQ values were 60.3 ± 4.94 (95% confidence interval [CI], 44-69) at baseline, 66.6 ± 5.28 (95% CI, 49-75) at 90 days, and 72.1 ± 4.28 (95% CI, 59-79) at 150 days (p < 0.0001). The mean marginal bone loss of the implants was 1.11 ± 0.61 mm on the mesial side and 1.17 ± 0.61 mm on the distal side at time 2, and 1.73 ± 0.68 mm on the mesial side and 1.79 ± 0.70 mm on the distal side at time 3. A strong positive correlation between implant stability and bone loss was detected (p < 0.0001). CONCLUSIONS: Within the limits of this study, the bone splitting technique with simultaneous implant installation exhibited a good success rate with respect to the osseointegration index but requires attention with respect to crestal bone behavior.

Analysis of the blood supply to the post-fracture edentulous mandible: study by colour Doppler sonography.

PURPOSE: This study assessed the arterial blood supply to the mandible of edentulous patients treated for mandibular fractures using colour Doppler ultrasound. METHODS: The blood supply of edentulous patients surgically treated for mandibular fractures (group A) and edentulous fracture-free individuals (group B) was assessed. Only the fractured sides were evaluated in the first group (N = 17), whereas each side was evaluated in the second group (N = 20). The arterial flow of six sites was assessed. The systolic-peak maximum velocity (SPV), final diastolic velocity (FDV), resistive index (RI), pulsatility index (PI), acceleration and flow direction of each artery were obtained. Additionally, the presence of local vascular obstructive factors was evaluated. The differences between groups were analysed using the Kruskal-Wallis test, which was complemented by the Mann-Whitney test, for correlations between the degree of alveolar atrophy and the study factors (p < 0.050). RESULTS: There was a significant decrease in the flow of certain arteries, especially the submental (SPV, p = 0.007, PI, p = 0.022, and acceleration, p = 0.015), in the fracture group. The facial artery in both groups showed lower values related to local obstructive factors (SPV, p = 0.001, FDV, p = 0.040, and PI, p = 0.030). The submental artery flow was higher (SPV, p = 0.006, and FDV, p = 0.009) in non-atrophic individuals. CONCLUSIONS: There was a decreased flow mainly in the submental artery, but there were no cases of major vascular injury in edentulous patients treated for mandibular fractures.

Retained third molars removal in a severely resorbed edentulous mandible. A case report.

The presence of asymptomatic third molars can represent a potential problem in the mandible when these teeth are retained and the patient has lost all normally erupted teeth. Once the mandibular first and second molars are removed, the mandibular body becomes weaker with time, increasing the complexity, morbidity and incidence of complication in the surgical procedure to remove the retained third molar. This paper reports a case where the mandibular third molars retained in a severely resorbed mandible were removed in a 54-year-old female patient. The treatment plan was based on the safe surgical removal of the teeth and prosthetic rehabilitation with an implant-supported milled bar overdenture and a bone-mucous-supported complete denture in the mandibular and maxillary arch, respectively. If the removal of a retained third molar is indicated in a severely resorbed edentulous mandible, the treatment plan must involve not only preventive measures in order to avoid mandible fracture during or after tooth removal, but also alternatives that allow an adequate mandibular rehabilitation.

Experimental model of distraction osteogenesis in edentulous rats.

UNLABELLED: Distraction osteogenesis (DO) is a surgical technique producing bone lengthening by distraction of the fracture callus. Although a large number of experimental studies on the events associated with DO of craniofacial skeleton have been reported, the few employing rat mandibular bone DO used complicated designs and produced a small volume of newly formed bone. Thus, this study aims to present an original experimental model of mandibular DO in edentulous rats that produces a sufficient quantity and quality of intramembranous bone. Eight male Wistar rats, weighing 75 g, underwent extraction of lower molars. With rats weighing 350 g, right mandibular osteotomy was performed and the distraction device was placed. The distraction device was custom made using micro-implants, expansion screws, and acrylic resin. STUDY PROTOCOL: latency: 6 days, distraction: » turn (0.175 mm) once a day during 6 d, consolidation: 28 d after distraction phase, sacrifice. DO-treated and contralateral hemimandibles were dissected and compared macroscopically and using radiographic studies. Histological sections were obtained and stained with H&E. A distraction gap filled with newly formed and mature bone tissue was obtained. This model of mandibular DO proved useful to obtain adequate quantity and quality of bone to study bone regeneration.

Tomographic distortion in toothless patients.

The main aim of this work is to compare the measurements of paraxial slices of the standard Denta-Scan technique and a new technique (Occlusal technique) in toothless patients. On a more specific level, our goal is to assess the effect of a change in the reference plane of computer axial tomography (CAT), for which the Denta-Scan system is usually employed, by transferring the palate plane to the prosthetic plane, which goes from the center of the external auditory canal to the anterior nasal spine. For the experiment, 15 maxillaries were used from toothless skulls belonging to adult patients who had lost their teeth prior to their death. For each one, a wax rim was made in reference to the Occlusal Plane (Camper's Prosthetic Plane) and a 10 mmx 3.3 mm reference implant was placed. Two tomography scans were made of each skull; one using the conventional technique, and the other using Camper's Prosthetic Plane. The tomograph used was of the helicoid type (Phillips MX8000), with 1.3 mm slices every 0.6 mm. To perform the comparative measurements between the two techniques, a VIS Caliper (Poland), was employed, and the data recorded in a table with the reference of each sample and technique. This was repeated with all 15 skulls. The results obtained were evaluated with the measurement of the reference implant for each technique. It was found that the standard technique (Horizontal Plane) showed 19.20% magnification, as opposed to the technique under examination (Camper's Occlusal Plane), which showed 16.5% magnification. The study showed distortions in each measurement as regards the real measurements of the reference implants. These distortions were less significant in the case of the Occlusal Plane technique than in the Horizontal Technique; however neither of them fully matched the measurements of the reference implant.

Electrognathographic evaluations of rehabilitated edentulous patients.

This study investigated, through computerized electrognathographic evaluations (K6-I Diagnostic System, Myotronics-Noromed Inc., Tukwila, USA), the mandibular movement pattern of 16 patients rehabilitated with complete dentures presenting no symptoms of stomatognathic functional alterations. The patients were instructed to wear an intra-oral appliance for occlusal plane coverage over their usual superior denture and were then rehabilitated with new dentures preserving a free-way space of 3 mm. After sixty days, the occlusal vertical dimension was increased and the modified inferior dentures were used for another 60 days. The obtained results were submitted to the Tukey Test and to the Friedman test, depending on which variable was under consideration, both at a significance level of 5%. The data revealed a significant decrease in free-way space when the first and the last evaluations were compared. No significant differences were found during opening and closing. It was concluded that the presence of a free-way space at the end of the treatment confirms the importance of its existence for maintaining the balance of the masticatory system, assuming the occurrence of a postural repositioning.

Diagnostic agreement of conventional and inverted scanned panoramic radiographs in the detection of the mandibular canal and the mental foramen.

The aim of this study was to evaluate the diagnostic agreement of conventional panoramic radiographs and their inverted scanned images in the detection of the mandibular canal and mental foramen. A total of 77 panoramic radiographs obtained from the files of totally edentulous patients were used. Digitization was done by means of a scanner with brightness and contrast adjustment, as well as image inversion. The extension of mandibular canal was divided into anterior, middle, and posterior regions, and the presence of a radiopaque line that characterized the mandibular canal was classified according to a 5-point confidence scale. The mental foramen was classified in 4 types: continuous, separated, diffuse, and unidentified. Both conventional and inverted scanned panoramic radiographs were evaluated by 3 calibrated implantologists at 2 distinct moments with a minimum interval of 10 days between them. Intraexaminer agreement was evaluated by Kappa statistics by point and by 95% confidence interval. Because the intraexaminer level of agreement was low, interexaminer agreements could not be carried out. The results showed a substantial (in 2 situations), moderate (in 16 situations), and fair (in 18 situations) intraexaminer agreement for mandibular canal and a substantial (in 1 situation), fair (in 1 situation), and moderate (in 10 situations) intraeaminer agreement for mental foramen. There were no statistically significant differences in most instances. In conclusion, the diagnostic agreement of conventional and inverted scanned panoramic radiographs for detection of mandibular canal and mental foramen was low.

[Diagnosis for osseointegrated implants]. / Diagnostico en implantes osteointegrados.

It is discussed the importance of the diagnostic, prognostic and treatment design procedures in the oral rehabilitation where osseointegrated implants are used, doing a detail of the sequence to follow during this important treatment stage.

[Panoramic radiograph in edentulous and partially edentulous patients]. / La radiografia panoramica en pacientes edentulos y parcialmente edentulos.

A group of two hundred patients from the School of Dentistry, UCV were study using panoramic RX, in order to determined the incidence of impacted roots, impacted teeth, radiographic feature (radiolucent and radiopaque) and foreign body. From the 200 patient 118 (59%) were edentulous and 82 (415) partially edentulous, from of clinically point of view; 40 (20%) were male and 160 (80%) female. From the total sample only 77 (38.5%) showed radiographic feature meanwhile 123 (61.5%) had not any present. Only the patients with radiographic feature were considered and the result according the age were the following: 18 patients 20-40 years old (23.4%); 41 patients 41-60 years old (53.2%) and 18 patients 61-80 years old (23.4%). The higher numbers of feature were observed in the range of age 41-60 years old. In relation to the form there was a predominance of diffuse form (53.3%). However, the size was greater of 5 mm. (43.3%). On the other hand, the higher numbers of feature were observed in the area 456 in the mandible (50%). This findings are in agreement with the result found by Jones & et al (1985) (J. Prosthet Dent 53:535-539). This values are in the same range 20-60% founded in other countries. No significant difference were founded between the partially or totally edentulous patients. This work suggest the important of the panoramic RX as a diagnostic aid before a prosthetic treatment.