Assessment of the correlation between supracrestal gingival tissue dimensions and other periodontal phenotypes components via the digital registration method: a cross­sectional study in a Chinese population.

BACKGROUND: Supracrestal gingival tissue dimensions (SGTDs) has been considered to be an essential element of periodontal phenotype (PP) components. This study aimed to explore the relationship between SGTDs and other PP components by digital superposition method that integrated cone beam computed tomography (CBCT) with intraoral scanning. METHODS: This cross-sectional study was conducted at the Stomatology Hospital of Fujian Medical University. Participants were recruited based on the inclusion and exclusion criteria. The data obtained from the digital scanner (TRIOS 3, 3Shape, Denmark) and CBCT images were imported into the TRIOS software (Implant Studio, 3Shape, Denmark) for computing relevant parameters. The significant level was set at 0.05. RESULTS: A total of 83 participants with 498 maxillary anterior teeth were finally included. The mean values of supracrestal gingival height (SGH) and the distance from the cementoenamel junction (CEJ) to the crest of the alveolar ridge (CEJ-ABC) on the buccal site were significantly higher than palatal SGH (SGH-p) and palatal CEJ-ABC (CEJ-ABC-p). Men exhibited taller CEJ-ABC and SGH-p than women. Additionally, tooth type was significantly associated with the SGH, SGH-p and CEJ-ABC-p. Taller SGH was associated with wider crown, smaller papilla height (PH), flatter gingival margin, thicker bone thickness (BT) and gingival thickness (GT) at CEJ, the alveolar bone crest (ABC), and 2 mm apical to the ABC. Smaller SGH-p displayed thicker BT and GT at CEJ, the ABC, and 2 and 4 mm apical to the ABC. Higher CEJ-ABC showed lower interproximal bone height, smaller PH, flatter gingival margin, thinner GT and BT at CEJ, and 2 mm apical to the ABC. Smaller CEJ-ABC-p displayed thicker BT at CEJ and 2 and 4 mm apical to the ABC. On the buccal, thicker GT was correlated with thicker BT at 2 and 4 mm below the ABC. CONCLUSION: SGTDs exhibited a correlation with other PP components, especially crown shape, gingival margin and interdental PH. The relationship between SGTDs and gingival and bone phenotypes depended on the apico-coronal level evaluated. TRIAL REGISTRATION: This study was approved by the Biomedical Research Ethics Committee of Stomatology Hospital of Fujian Medical University (approval no. 2023-24).

Dental trauma: assessment and acute management of fractures.

Acute dental trauma is unscheduled and presents infrequently to the majority of practitioners. Therefore, a consistent, logical and systematic process for examination, prioritisation and management is imperative for all sustained injuries to have an optimal outcome. Fractures are a frequent sequela to dental trauma and can involve any aspect of the tooth structure or supporting alveolar bone. While some minor crown fractures may initially seem inconsequential, they may be a subtle indication to a more serious underlying root fracture. Concomitant injuries and injuries that have been initially missed are generally associated with poorer outcomes. The time sensitive management of traumatic dental injuries aims to preserve pulpal and periodontal health where possible. The follow up period for tooth or alveolar fractures are important to allow for early intervention if pathology develops.

Compatibility of digital and analog methods in assessment of gingival zeniths.

OBJECTIVE: The compatibility of digital and analog methods assessing the positions of gingival zenith (GZ) points has not been evaluated before. Therefore, the aim of this study was to investigate the accuracy of a digital scanner and a three-dimensional (3D) measuring tool in specifying positions of GZs by comparing it to the conventional method, an analog plaster cast and a caliper. MATERIALS AND METHODS: Both analog and digital impressions were obtained from 32 individuals. Following measurements were conducted in the anterior maxillary region from canine to canine on both the plaster casts and 3D images: (1) The distance from GZ to the corresponding vertical midline in each tooth (GZVM), (2) The distance from GZ of lateral incisor to the corresponding tangent that connects GZs of central incisor and canine (GZLI). RESULTS: The intraclass correlation coefficients (ICC) of GZVM in each tooth varied between 0.366 and 0.755, demonstrating moderate to good compatibility between the two methods. The ICC of analog and digital GZLI for the right and left lateral incisors was 0.788 and 0.395, respectively. CONCLUSION: The digital and analog methods used in this study are compatible in determining the positions of GZs. Therefore, within the limitations of the present study, the choice of method can be based on the available equipment, time, comfort, and personal preference of the researcher. CLINICAL SIGNIFICANCE: Both digital and analog methods have the capability of determining the positions of GZs in compatible way.

Computed tomography assessment of hypodontia and crown size in hemifacial microsomia.

OBJECTIVE: Our aims were to assess the prevalence of hypodontia in unilateral hemifacial microsomia (HFM), and to compare tooth (crown) size between affected and unaffected sides. DESIGN: In a retrospective cross-sectional study of South Australians, computed tomography (CT) scans were used to assess hypodontia and crown size (mesiodistal length, buccolingual width and crown height). The inclusion criteria were the absence of other congenital anomalies and the availability of CT scans. The exclusion criteria were the lack of extraction history or reproducible landmarks for morphometric assessment. The final sample comprised 41 participants in both dentitions, including 32 children and 9 adults (median age 13.9 years, range 0.4 - 47.6 years; 19 males and 22 females). Hypodontia was assessed in all participants, and the permanent crown size in 30 (73.2%) participants. Linear mixed-effects models were performed to determine if crown size was significantly different between the two sides, controlling for sex, HFM severity, and tooth and jaw type. RESULTS: Hypodontia occurred in none of the participants in the primary dentition, but in 6/30 (20%) participants in the permanent dentition (3/30 each on the affected and unaffected sides). There was no significant difference in the mean crown dimensions between the two sides, but the crown size was larger in males (p < 0.05), except for mesiodistal length, and became progressively smaller with increased HFM severity (p < 0.05). CONCLUSIONS: Hypodontia spared the primary dentition but featured prominently in the permanent dentition. The permanent crown dimensions were unaltered between the two sides.

Assessment of gingival thickness in the maxillary anterior region using different techniques.

OBJECTIVES: Gingival phenotype is closely related to treatment success and aesthetic results in the maxillary anterior region. Several methods were proposed to measure the dimensions of the gingival tissue. This study aimed to evaluate the gingival thickness using clinical and radiographic techniques and to explore the association between gingival thickness and gingival phenotypes classified by color-coded phenotype probes. MATERIALS AND METHODS: The gingival thickness of 86 periodontally healthy maxillary anterior teeth was assessed using transgingival probing (TGP) and cone-beam computed tomography (CBCT). The gingival phenotype was classified as thin, medium, thick, or very thick by transparency of the color-coded probes through the gingival sulcus. The labial alveolar bone thickness was measured on CBCT images. The keratinized tissue width (KTW) was recorded. RESULTS: Good to excellent agreement was found between TGP and CBCT regarding the thickness of the gingiva (p<0.001). There was a very high correlation between the phenotypes determined by color-coded probes and the gingival thickness measured by TGP (r=0.953, p<0.001). KTW was significantly higher in thick and very thick phenotype groups compared with thin phenotype group. CONCLUSION: Cone-beam computed tomography images and the probe transparency method with color-coded probes are reliable for identifying the gingival phenotype in the maxillary anterior region, based on comparisons to direct transgingival probing. CLINICAL RELEVANCE: The assessment of the gingival phenotype is essential, especially in the aesthetic zone, to obtain predictable and favorable clinical outcomes in various dental procedures. The newly introduced color-coded probes comprise a non-invasive and reliable method for this.

Central incisors shape and proportions prevalence in Argentinian university students: by visual assessment and a new standardized method.

The aim of this study was to analyze the dimensions of the clinical crown of upper central incisors and the prevalence of tooth shapes by two different protocols. Assessment was performed on each of the 111 dental stone type V maxillae models of students of dentistry from Buenos Aires University [93 females and 18 males, mean age 23.70 (± 2.26) years] The mesial and distal-vestibular angles were defined on each right upper incisor, and the following segments were defined: AB (zenith - incisal edge), CD, EF, GH (apical, middle, and incisal thirds - vestibule - mesial and vestibule-distal angles) and their lengths were determined with a precision caliper. Then, the CD/AB, EF/AB and mean CD-EF/AB ratios were calculated. Shapes were assessed by four independent observers, three of whom evaluated digital images of the models, while the fourth had no access to the images, and determined the shapes using an algorithm developed from the dimensions of the studied segments. Rates and confidence intervals were determined, and Fleiss' Kappa was calculated to assess the agreement among the evaluators who worked with the images and among all of them. Average incisor length was 10 mm, and widths at CD and EF were 7.35 mm (0.65) and 8.27 mm (0.58), respectively. Regarding shapes, 51.58% (47.90-55.20) of the incisors were identified as square, 18.02% (14.50-21.90) as ovoid and 30.41% (30.00-30.90) as triangular. Fleiss' Kappa agreement was 0.71 (0.62-0.80). The application of the proposed algorithm provided a considerable level of agreement among the observers. Regarding tooth size, both the average segment length and the proportions were similar to those reported by various authors.

El objetivo de este trabajo fue analizar las dimensiones de las coronas clínicas de incisivos centrales superiores, y la prevalencia de cada una de las formas dentarias según diferentes formas de determinación. Se utilizaron modelos de yeso tipo V de 111 estudiantes (93 mujeres y 18 varones) con una media de edad de 23,70 (± 2,26) años. Se definieron los ángulos vestíbulo - mesial y distal para los incisivos centrales superiores derechos (1.1), se definieron los siguientes segmentos: AB (cenit - borde incisal), CD, EF, GH (tercios apical, medio e incisal - ángulos vestíbulo - mesial y vestíbulo- distal) y se determinaron sus longitudes con un calibre de precisión. Se calcularon las proporciones CD/AB, EF/AB y media CDEF/ AB. Las formas de las piezas dentarias fueron identificadas por cuatro observadores independientes, tres lo hicieron mediante la evaluación de imágenes digitales de los modelos confeccionados. El cuarto observador, sin acceso a las imágenes, asignó a cada pieza una de las formas determinadas mediante la aplicación de un algoritmo elaborado ad-hoc. Se obtuvieron tasas e intervalos de confianza y se calculó Kappa de Fleiss para valorar la concordancia entre evaluadores. La longitud promedio fue de 10 mm y el ancho en los segmentos CD y EF fueron de 7.35 mm (0.65) y 8.27 mm (0.58) respectivamente. En cuanto a formas el 51,58% (47.90-55.20) de los incisivos estudiados fueron identificados como cuadrados, el 18.02% (14.50-21.90) como ovoides y el 30,41% (30.00-30.90) triangulares. La concordancia de Kappa de Fleiss fue de 0.71 (0.62-0.80). La aplicación del algoritmo propuesto alcanzó un nivel de concordancia considerable entre los evaluadores. En cuanto al tamaño dentario, tanto la longitud promedio de los segmentos estudiados como las proporciones halladas son similares a las reportadas por diversos autores.

Treatment of Teeth with an Insufficient Clinical Crown. Part 2: Treatment Cost and Time and Patient Outcomes.

This study involves a group of 168 teeth in 126 patients treated with crown lengthening and tooth reconstruction (experimental group), and a group of 75 teeth from 62 patients that were judged irrational to treat, extracted, and replaced (control group). In the control group, 13 teeth in 12 patients were not replaced; 37 were replaced with an implant-supported crown, 14 with a tooth-supported partial denture, 2 with a Maryland partial denture; and 9 patients requested a removable prosthesis. In the experimental group, 44 teeth in 37 patients received a conservative restoration (24 direct and 20 indirect), while 124 teeth in 94 patients received a full crown. All 168 teeth were surgically treated with minimally invasive crown lengthening. Endodontic treatment and orthodontic extrusion were applied when necessary. Treatment resulted in healthy periodontal and dental/implant conditions at the 1-year follow-up in both groups. Function and esthetics were described from satisfactory to extremely satisfactory by patients of both groups, with the exception of three patients in the control group who received a mobile prosthesis restoration and reported some difficulties in chewing. When comparing treatment cost and duration of the reconstructed teeth (experimental group) to the treatment cost and duration of extracted and replaced teeth (control group), the difference is significantly in favor of the preservation of natural teeth, both monetarily and in terms treatment time. Saving a tooth with a compromised crown is more favorable for the patient than extraction and replacement. This conservative approach is advisable to clinicians whenever the clinical conditions enable treatment.

Open and closed surgical exposure of palatally displaced canines: a cost-minimization analysis of a multicentre, randomized controlled trial.

OBJECTIVE: To evaluate the costs of open and closed surgical exposure and subsequent orthodontic treatment for the correction of palatally displaced canines (PDCs). TRIAL DESIGN: A multicentre, two-arm parallel group randomized controlled trial. METHODS: One hundred twenty adolescents between 9 and 16 years of age, from three orthodontic specialist centres, were randomized to one of the two surgical exposure interventions. The randomization was conducted according to a two-arm parallel group 1:1 allocation ratio, using computerized lists with block randomization. In both the surgical techniques, whole mucoperiosteal flaps were raised, and bone covering the PDCs was removed. In the open technique, glass ionomer was built up on the PDC crown - reaching above the mucosa through a hole punched in the flap - to allow the canine to erupt autonomously. After eruption, the canine was orthodontically moved above the mucosa. In the closed technique, an eyelet was bonded onto the PDC, the flap was repositioned and the canine was orthodontically moved beyond the mucosa. The trial ended when the PDC was successfully aligned in the dental arch.Cost analysis was performed including costs for surgery, orthodontic treatment, emergency visits, and material, as well as costs for transports and time spent in connection with every appointment. BLINDING: Patients and caregivers could not be blinded due to obvious limitations of the clinical setting, while outcome assessors and data analysts were blinded. RESULTS: A cost-minimization analysis was performed since both exposure groups succeeded equally well in terms of treatment effects. The two different surgical exposures and following orthodontic treatments did not differ significantly in terms of costs. GENERALIZABILITY AND LIMITATIONS: Costs are estimated in the Swedish setting, which needs to be considered if applying the results in other settings. Calculations of total cost do not include finishing, debonding, retention, and follow-up. CONCLUSION: There is no significant difference in costs between closed and open surgical exposure with following orthodontic treatments in PDCs. TRIAL REGISTRATION: ClinicalTrials.gov, ID: NCT02186548.

Three-dimensional assessment of root migration and rotation patterns after coronectomy: bone-embedded roots versus soft tissue-covered roots.

In this study, a three-dimensional evaluation was performed to explore differences between bone-embedded and soft tissue-covered roots after mandibular third molar (M3M) coronectomy. Patients were recruited according to the results of cone-beam computed tomography, 6 months after coronectomy. Completely bone-embedded M3Ms were assigned to group B, while completely soft tissue-covered M3Ms were assigned to group S. Data were recorded using digital software. A total of 213 M3Ms in 181 patients were investigated, of which 170 were assigned to the two study groups. Age was the primary factor influencing root migration (P<0.001). The smaller the degree of angulation of the M3M, the more likely was the root complex to rotate distally (r=-0.37, P<0.001). The depth of the impacted M3M contributed to the regeneration of new bone (P≤0.008). The length of the root complex (odds ratio 0.82, P=0.048) and distance from the root to the alveolar crest (odds ratio 1.23, P=0.026) were two critical factors influencing whether the root complex was bone-embedded. Ensuring that the length of the root complex is <7.6mm and the distance between the root and alveolar crest is ≥5mm were both found to be critical to the remaining root being completely bone-embedded and thus preventing eruption and the need for secondary surgery.

A systematic review of the complications of high-risk third molar removal and coronectomy: development of a decision tree model and preliminary health economic analysis to assist in treatment planning.

Coronectomy is an alternative surgical technique for the management of high-risk third molars. It involves the removal of the crown of a tooth and the deliberate retention of the roots, thereby avoiding injury to the inferior alveolar nerve (IAN). Previous studies have suggested that it reduces the risk of nerve injury when compared with surgical extraction. The purpose of this study was to systematically review the incidence of complications following coronectomy such as IAN injury, pain, dry socket, infection, root migration, and need for re-operation. A comparative cost analysis of coronectomy and surgical extraction was done based on the results of the review. This provides an insight into the economic implications of the two procedures. A search through the MEDLINE database via Ovid, PubMed, Scopus, EMBASE via Ovid, and Web of Science, was carried out to extract randomised and non-randomised controlled trials. Four studies fulfilled the inclusion criteria. A meta-analysis was conducted to measure the overall effect of each outcome. The pooled odds ratio (OR) for IAN injury was 0.16 (95% CI 0.01 to 0.39). Coronectomy reduced this risk by 84%. Dry socket may occur less frequently following coronectomy whereas infection did not show a higher incidence with either intervention. Root migration was found to occur in 13%-85% of cases and the average incidence of re-operation was 2.2%. The ratio of the average costs was 1.12 favouring coronectomy if cone-beam computed tomography (CBCT) was not done prior to the procedure. If a scan was taken routinely for coronectomy, the cost ratio marginally favoured extraction. Coronectomy reduced the risk of nerve injury in high-risk third molars. Definitive conclusions, however, cannot be made for outcomes such as the need for re-operation, which may alter the cost ratio of coronectomy:extraction, as higher quality studies with longer follow-up are needed.

An accurate and efficient method for occlusal tooth wear assessment using 3D digital dental models.

Tooth or material wear in a dentition is a common finding that requires timely diagnosis for management and prevention of further loss or associated esthetic or functional impairment. Various qualitative and quantitative methods have been suggested to measure tooth or material wear, but they present with limitations, such as imprecision, subjectivity, or high complexity. Here we developed and assessed an efficient 3D superimposition method to accurately measure occlusal tooth wear on 3D digital dental models. For this purpose, teeth on plaster casts were manually grinded on their occlusal surfaces to simulate various degrees of tooth wear. The casts were scanned using a surface scanner. Grinded tooth crowns (T1) were segmented and compared to the original crowns (T0) using five 3D surface superimposition techniques and a gold standard technique (GS). GS measurements were obtained by using intact adjacent structures as superimposition references. The technique of choice (complete crown with 30% estimated overlap of meshes) showed the best reproducibility (maximum difference < 0.050 mm3) and excellent agreement with the GS technique (median difference: 0.032 mm3). The suggested 3D superimposition method offers a highly efficient and accurate tool for tooth wear assessment, which could be applicable to clinical conditions.

Assessment of gingival phenotype through periodontal and crown characteristics: a cluster analysis.

OBJECTIVE: To evaluate gingival phenotypes in 100 subjects (n = 100), with regard to maxillary central incisors and surrounding periodontium in an observational diagnostic study. MATERIALS AND METHODS: Individuals were grouped based on: Probing depth (PD); keratinized mucosa (KM); Ratio Height/Width Crown (CH/CW), papilla area (PA), gingival thickness (GT) and Gingival Volume (GV). ANOVA and chi-square tests were performed with a significance level of 5%. Results: PD (p=0.860) and CH/CW (p=0.086) were not statistically significant. Cluster analysis identified three groups: Cluster I (n = 32) had the lowest values: KM (4.54mm), GT (0.83mm), PA (15.64mm²) and GV (3.80mm³); Cluster II (n = 43) presented KM (8.02mm); GT (1.40mm); GV (11.18mm³) and PA (14.10mm²); Cluster III (n = 19) exhibited an average KM of 5.57mm, GT (1.14mm), PA (20.08mm²) and GV (6.48mm³). RESULTS: Cluster I was characterized as a thin phenotype; cluster II as thick, and cluster III, as an intermediate. Significant associations were found when transparency on probing was compared among clusters (p less than 0.05) and gingival exposure when smiling (p less than 0.05). CONCLUSION: Thin phenotype was found in 34.04% of the sample (cluster I), thick phenotype in 45.75% (cluster II) and intermediate phenotype in 20.21% (Cluster III)..

Radiographic assessment of the relationship between root canal treatment quality, coronal restoration quality, and periapical status.

OBJECTIVE: The aim of this cross-sectional study was to assess the prevalence of apical periodontitis in root canal treated teeth in Turkish subpopulation and to evaluate the effects of both coronal restoration quality and root canal treatment (RCT) quality on apical periodontitis. MATERIALS AND METHODS: Panoramic images of individuals who applied to our department for different diagnostic reasons were randomly and retrospectively scanned. Total RCT number, RCT quality, type of coronal restoration, restoration quality, periapical status, and total number of teeth were recorded. The criteria used for coronal restorations quality and RCT quality were defined by De Moor et al. and slightly modified by Gunduz et al. Periapical status was assessed by the periapical index developed by Orstavik et al. Pearson's Chi-square test was used for statistical analysis, and the intraobserver agreements were assessed by Kappa coefficients. Values of P < 0.05 were accepted to be meaningful. RESULTS: The total examined teeth number was 6064, of which had 541 (8.9%) RCT. The prevelance of apical periodontitis was 40.5%. The number of adequate RCT was 178 (32.9%), and 138 (77.5%) of them were healthy. The number of adequate coronal restoration was 334, and 62.3% of them were healthy. For the cases that have adequate coronal restorations, there was statistically significant relationship between adequate RCT and periapical status (P < 0.001). CONCLUSION: The prevelance of apical periodontitis was 40.5% and there was statistically significant relationship between adequate RCT and periapical status.

Volumetric assessment of the dental crown for sex estimation by means of cone-beam computed tomography.

Sex estimation has a vital role in the solution of forensic cases when the identification of a large number of victims is needed. Considering the sexual dimorphism of the human teeth, the objective of this study was to estimate human sex by means of cone beam computed tomography (CBCT)-based volumetric assessment of the dental crown. A total of 78 CBCT images of the upper central incisors, upper and lower canines, and lower lateral incisors were equally selected from a Brazilian population aged between 8 and 36 years old. The dental crowns were subjected to image-based volumetric assessment by manual segmentation using the 3D slicer software, and the outcomes were compared by the Mann-Whitney test, unpaired t-test, Pearson correlation test, conditional backward stepwise logistic regression and intraclass correlation coefficient (α=0.05). The volumetric accuracy of the upper central incisor, upper canine and lower canine for sex estimation were 64.1%, 74.4% and 79.5%, respectively. The combined analysis of the upper and lower canines allowed an average accuracy of 83.7%. In conclusion, the combined volumetric analysis of the crown of the upper and lower canines can be applied for sex estimation in the studied population.

Plain radiographs for the assessment of coronectomy: not always a case of black or white.

In recent years, coronectomy of impacted lower third molar teeth has become an increasingly popular alternative to removal. Traditionally, orthopantomograms of mandibular third molars have been used to indicate features that show that the tooth is in close proximity to, or in an intimate relation with, the inferior dental nerve. Some authors advocate coronectomy as opposed to surgical removal to reduce the risk of damage to the nerve. In our Trust during the last two years, there has been a noticeable increase in the prescription of coronectomy for the management of pericoronitis associated with mandibular third molars. The purpose of this study therefore was to examine the differences among clinicians in their assessment of the need for coronectomy using plain-view radiographs. An online survey was completed by 25 clinicians with different levels of experience from six units across the UK and Republic of Ireland. We found a wide variation in the number of coronectomies prescribed (intraclass correlation 2.67), and when prescribed, a lack of agreement about the radiographic feature that had influenced the decision. These judgments are not straightforward. They are, to some extent, subjective, and in certain cases may benefit from a team-led approach.

Three-Dimensional Assessment of Crown Size and Eruption Space for Developing Third Molars: Data Collection Techniques Based on Cone-Beam Computed Tomography (CBCT).

Third molar development and eruption are two related areas of major interest in dental research into the etiology of "wisdom tooth" impaction. Third molars are not only an excellent model for studying dental development but also of fundamental clinical importance because they are very frequently impacted. Because the third molar is located in the distal-most region of the oral cavity, clinical access is relatively challenging. With the increasingly widespread use of cone-beam computed tomography (CBCT) in dentistry, studies and measurements of the third molar and its eruption area have become considerably easier to do. Here we present a novel CBCT-based measurement methodology we developed for our recent investigations that we hope will also be useful for the broader dental research community.

First systematic assessment of dental growth and development in an archaic hominin (genus, Homo) from East Asia.

Several human dental traits typical of modern humans appear to be associated with the prolonged period of development that is a key human attribute. Understanding when, and in which early hominins, these dental traits first appeared is thus of strong interest. Using x-ray multiresolution synchrotron phase-contrast microtomography, we quantify dental growth and development in an archaic Homo juvenile from the Xujiayao site in northern China dating to 161,000-224,000 years or 104,000-125,000 years before present. Despite the archaic morphology of Xujiayao hominins, most aspects of dental development of this juvenile fall within modern human ranges (e.g., prolonged crown formation time and delayed first molar eruption). For its estimated age-at-death (6.5 years), its state of dental development is comparable to that of equivalently aged modern children. These findings suggest that several facets of modern human dental growth and development evolved in East Asia before the appearance of fully modern human morphology.

In Vitro Assessment of Retention and Resistance Failure Loads of Teeth Restored with a Complete Coverage Restoration and Different Core Materials.

PURPOSE: To investigate in vitro the retention and the resistance form, as well as the failure modes of maxillary premolars restored with cast metal crowns and different core materials. MATERIALS AND METHODS: Sixty human extracted maxillary premolars were selected according to their size and were embedded in PMMA resin blocks. After removing a part of their clinical crowns, the teeth were randomly divided into 3 groups of 20 teeth and were either left unrestored, or they were restored with amalgam or composite resin. All teeth were prepared for a cast metal complete coverage restoration. The restorations were cemented on the prepared teeth with a resin-modified glass ionomer luting agent (GC Fuji Plus). All specimens were subjected to static loading at 1 mm/min by a universal testing machine, until failure. Half the specimens of each group were subjected to tensile loading along the long axis of the teeth. The other half were subjected to compressive loading at a 30° angle. Failure loads and failure modes for each tooth were recorded. The statistical analysis included descriptive statistics, one-way ANOVA, and Tukey's HSD test. RESULTS: One-way ANOVA revealed statistically significant differences among the 3 tested groups (p < 0.05) for both tests. The group of teeth with no core material presented the highest failure loads for both the tensile and the compressive loading tests, with mean loads of 381.02 Ν and 741.21 Ν, respectively. Mean tensile and compressive failure loads for the amalgam group were 277.34 Ν and 584.75 Ν, while the composite resin group presented the lowest tensile and compressive failure values, which were 250.77 Ν and 465.78 Ν, respectively. The compression loading test resulted in the same failure mode for all specimens, which included unfavorable fracture of the teeth in combination with detachment of the cast metal complete coverage restorations. The tensile loading test resulted in different failure modes between the groups that used a core material and the group with no core material. CONCLUSIONS: Teeth that lost more than half of their coronal structure presented better retention and resistance form if no core material was used, provided that a minimum of 2-mm axial wall height was present at the missing part. Teeth that have lost more than half of their coronal structure and were restored with amalgam core presented better retention and resistance form than those restored with composite resin. Catastrophic fractures, extending to the root, were associated with compression forces but not with tensile forces.

The Middle Pleistocene (MIS 12) human dental remains from Fontana Ranuccio (Latium) and Visogliano (Friuli-Venezia Giulia), Italy. A comparative high resolution endostructural assessment.

The penecontemporaneous Middle Pleistocene sites of Fontana Ranuccio (Latium) and Visogliano (Friuli-Venezia Giulia), set c. 450 km apart in central and northeastern Italy, respectively, have yielded some among the oldest human fossil remains testifying to a peopling phase of the Italian Peninsula broadly during the glacial MIS 12, a stage associated with one among the harshest climatic conditions in the Northern hemisphere during the entire Quaternary period. Together with the large samples from Atapuerca Sima de los Huesos, Spain, and Caune de l'Arago at Tautavel, France, the remains from Fontana Ranuccio and Visogliano are among the few mid-Middle Pleistocene dental assemblages from Western Europe available for investigating the presence of an early Neanderthal signature in their inner structure. We applied two- three-dimensional techniques of virtual imaging and geometric morphometrics to the high-resolution X-ray microtomography record of the dental remains from these two Italian sites and compared the results to the evidence from a selected number of Pleistocene and extant human specimens/samples from Europe and North Africa. Depending on their preservation quality and on the degree of occlusal wear, we comparatively assessed: (i) the crown enamel and radicular dentine thickness topographic variation of a uniquely represented lower incisor; (ii) the lateral crown tissue proportions of premolars and molars; (iii) the enamel-dentine junction, and (iv) the pulp cavity morphology of all available specimens. Our analyses reveal in both samples a Neanderthal-like inner structural signal, for some aspects also resembling the condition shown by the contemporary assemblage from Atapuerca SH, and clearly distinct from the recent human figures. This study provides additional evidence indicating that an overall Neanderthal morphological dental template was preconfigured in Western Europe at least 430 to 450 ka ago.