Relationship between size of denture foundation area and resorption of alveolar ridge in the edentulous mandible.

summary The relationship between the size of the denture foundation area and the resorption of the alveolar ridge was investigated in 55 edentulous subjects. The denture foundation area was recorded using a modelling compound impression technique with border moulding. Both sides of each edentulous mandible were examined separately, making a total of 110 experimental sides in the study. On a stone cast made from each impression, the size of the superficial denture foundation area and of the projected denture foundation area on the tentative plane of occlusion of each anatomical zone were measured. The vertical height of the alveolar ridge at the lateral incisor and first molar region was also evaluated. The size of the superficial denture foundation area in the antero‐lingual and postero‐lingual zones showed no significant correlation with the degree of alveolar ridge resorption. The size of the projected denture foundation area on the tentative plane of occlusion in the anterior section showed negative significant correlation with the degree of alveolar ridge resorption. The size of the projected denture foundation area on the tentative plane of occlusion in the posterior section showed no significant correlation with the degree of alveolar ridge resorption.

AimTo evaluate the stress distribution and displacement of the denture base in a three dimensional finite element edentulous mandibular model with varied implant positions.Objectives1)To evaluate the stresses induced by implants placed in the anterior region of the edentulous mandible. 2)To evaluate the stresses induced by implants placed in the anterior and posterior region of the edentulous mandible. 3)To compare the stresses induced by implants placed in the anterior and posterior region of the edentulous mandible. 4)To evaluate the displacement of the denture base with implants placed in the anterior and posterior region of the edentulous mandible.5)To compare the displacement of the denture base with implants placed in the anterior and posterior region of the edentulous mandible.Materials and MethodsThe materials used were Nobel Biocare Mk III long implants 3.75×13mm and short 5.0×7.0 implants, with O-ball head attachment. ANSYS: Version 8.0 software was used to create a threedimensional model of an edentulous mandible and the two implants. Three models were prepared having different implant positions and locations. MODEL 1 Two long implants were placed interforaminally in lateral incisor region one on either side, MODEL 2 Four long implants placed were interforaminally in the central incisor and canine region two on either side and, MODEL 3 Two long implants were placed interforaminally in lateral incisor region one on either side and two short implants were placed in premolar region 3mm posterior to the mental foramen, one on either side. Two types of load were given ie. vertical load of 325N was applied in second premolar and first molar region and 10N load at 150 angulation was applied in the anterior incisors area. The models were loaded separately and stress pattern, amount of stresses and amount of displacement were analysed for each model.ResultsThe observations obtained from the ANSYS software were analysed and evaluated. Model 3 showed the least amount of stress and displacement as compared to the other models.ConclusionWhen the implants were spread across the arch both anteriorly and posteriorly, the stress induced in the bone and displacement of the denture base was seen to be less.

AimThe present study evaluated maximum principal stress, von Mises stress, and deformation on the mandible and surrounding structures during the insertion of an implant in various anatomical positions.Materials and MethodsFinite element models of straight two-piece implants of 4.5 mm × 11.5 mm were modeled using Ansys software, v. 16.0 (Ansys, Inc., Houston, TX, USA). The mandibular model was derived through cone-beam computed tomography of a cadaveric mandible using Mimics software (Materialise NV, Leuven, Belgium). An osteotomy was performed at the first molar region, second premolar region, lateral incisor region, central incisor region, canine region, and second molar region that had varying bone densities. Implant insertion was simulated with a variable load of 1 - 180 Newton, which was applied axially downward with a rotational velocity of 30 - 120 rpm. Maximum principal stresses, von Mises stress distribution at the implant insertion site, and maximum deformation on the entire mandible were recorded during the insertion of the implants.ResultsMaximum principal stress was highest in the crestal area of the right first molar region and least in the middle third of the central incisor region during implant insertion. Von Mises stress in the mandible was highest in the right first molar region and the least in the lateral incisor region during implant insertion. The extent deformation was recorded on the x-axis, y-axis, and z-axis of the mandible. Deformation on the x-axis was highest at the crestal region of the canine and least for the lateral incisor. On the y-axis, deformation was highest at the symphysis region during implant insertion at the first molar region and the least at the condylar area during implant placement in the canine area. On the z-axis, the deformation was highest at the condylar region during implant insertion at the first molar region, and the least was observed in the symphysis region during implant placement in the second molar region.ConclusionWhen overall stress was considered, there is a direct correlation between stress and quality of bone. The highest maximum principal stress and von Mises stress were recorded during the placement of implants in posterior regions of the mandible, which suggests that the presence of dense cortical bone results in higher stress values. The maximum deformation was observed at different regions of the mandible, away from the site of implant insertion. The resultant stress and deformation exerted on the bone during placement of implants at different sites in the mandible varies, which could be detrimental factors in the longevity of the implant.

Prosthetic rehabilitation of completely edentulous patients has been traditionally performed with complete dentures for many years. However, patient complaints are reported due to insufficient retention and high mobility of mandibular dentures. Therefore, in these patients, overdenture prostheses, which are usually made by placing at least two implants in the interforaminal region of the mandible, have become widespread. In these prostheses, bar, stud, magnetic, or ball and locator attachments are used. This study aimed to evaluate the stress on mandibles by an overdenture with locator attachments supported by two implants placed on three different bone types in three different regions. Finite element analysis (3D) was used to design a mandible and overdenture. Two implants and locator attachment systems were placed into the lateral incisor, canine, and premolar regions. In computer-generated mandible and overdenture models, a force of 100 N was loaded obliquely and vertically from the mandibular first molar teeth region; then, the values obtained from the forces were compared. Eighteen analyses were performed with two different loading options in nine different models. Von Mises, compressive, and tensile stress values were analyzed. As the bone type changed from D1 to D3, the stresses on the bone increased in direct proportion. However, with all three bone types, lower tensile values were found in cortical bone in an above-implant removable prosthesis supported by an implant in the lateral incisor region. Biomechanically, the lateral incisor and canine regions were more advantageous than the first premolar tooth region in prosthesis designs where two implants were used in all bone types.

The purpose of this study is to analyze, using CIELAB color system, the range ofgingival color variables in healthy gingiva of the maxillary incisor region.Results indicated:1. Color differences (dE) among the bilateral attached andmarginal gingiva of the incisor and lateral incisor regions were under 2.0. However, the attached and marginal gingiva of the canine regions were about 2.88 and2.45 respectively. The papillary gingiva was over 2.0 in each region.2. Compared to the incisor region, an increase in chromaticness and hue a*, b* with a decrease in lightness was observed in the attached, marginal, and papillary gingiva of the lateral incisor and canine region. The range in dE was from 2.28 to 3.36. In the attached and papillary gingiva, dE between the incisor and canine region was significantly bigger than the incisor and lateral incisor region.3.Decrease in chromaticness, lightness, and hue a*, b* was observed from the marginal to papillary gingiva, and dE was from 3.13 to 3.71 with a high being in theincisor region.4. Increase in chromaticness and hue a*, b* with a slight decreasein lightness was observed from the attached to marginal gingiva, and dE was from2.25 to 2.75.

Objective: Canalis sinuosus (CS) is a common anatomical variation in the anterior maxilla that originates from the infraorbital canal and carries the anterior superior alveolar nerve and vessels. This study aimed to examine the presence, frequency, and features of CS and its accessory canals (ACs) using cone beam computed tomography (CBCT) images. Methods: A total of 495 CBCT images were retrospectively analyzed in axial, sagittal, and coronal sections. Patient age and sex, presence or absence of CS, location as right, left, or bilateral if CS was present, and number of ACs were recorded. In addition, the end regions of the ACs were recorded as central incisor, central-lateral incisor, lateral incisor, lateral incisor-canine, and canine regions. All recorded data were statistically analyzed. Results: At least one CS was found in 54 (10.9%) of 495 CBCT images. CS(s) were bilateral in 26 (48.2%) cases and unilateral in 28 (51.8%; 25 on the left and 3 on the right side). The ACs of the CS predominantly terminated in the lateral incisor region (p =.025). The frequency of CS was not statistically different between males and females (p =.313). Conclusion: Accessory canals in the anterior maxilla are mostly associated with branches of the CS. In the current study, the prevalence of CS was 10.9%, and most of the CSs were opening in the lateral incisor region. Detection of accessory canals in the anterior maxilla and examination of this region with CBCT will prevent misdiagnoses and postoperative complications arising from damage to these structures.

56th Annual Meeting of the American Academy of Implant Dentistry and the World Congress of Oral Implantology 7 Abstracts, 2007

The aim of this study is to evaluate the stress distributions in the bone level, implant and prosthesis parts with three-dimensional (3D) finite element analysis (FEA) in treatment options obtained by using two implants in different positions and different diameters in the four missing maxillary incisors region. Four 3D FEA models were obtained simulating the human maxilla with anterior 4 missing teeth. It is an in vitro study evaluated only by performing FEA with a computer program. Model 1 (M1): 4.3mm diameter implant to 2 central incisors regions, Model 2 (M2): 4.3mm diameter implant to 2 lateral incisors regions, Model 3 (M3): 3.3mm diameter implant to 2 lateral incisors regions and Model 4 (M4): 4.3mm diameter implant to central incisor region, 3.3mm diameter to lateral incisor region. Titanium implants and titanium abutments were used. Four-unit monolithic zirconia cemented fixed partial prostheses were designed on them. An oblique force of 100N was applied to the cingulum of each tooth on the prosthesis at an angle of 45 degrees to the long axis. The data obtained by performing FEA on the stress values in the implants, prosthesis parts and bone were evaluated. Maximum and minimum principal stress in the bone tissue was observed most in model 3 and least in model 1. Von Mises values in the abutment, implant, screw and prosthesis were highest in model 3. According to the obtained stress values, it may be considered the best option to place a standard diameter implant where the central incisors are in the anterior region in order to reduce the stress on the bone. Treatment with a narrow-diameter implant with lateral incisors can be avoided.

Background:The thickness of the alveolar mucosa influences the probability of the occurrence of denture-induced irritations. Thick denture-supporting tissues offer relief from mucosal tenderness and ulcers; however, the uniformity of the thickness across the entire mandibular alveolar mucosa cannot be accurately determined in edentulous patients. This study aimed to assess the mucosal thickness of the denture-bearing area in the edentulous mandible.Methods:Twenty-seven edentulous patients underwent cone-beam computed tomography scanning, wherein the patients wore a record base to retract soft tissues away from the alveolar mucosa. The measured regions were the central incisor (IC), lateral incisor (IL), canine (Ca), first premolar (P1), second premolar (P2), first molar (M1), and second molar (M2) regions. The thickness was measured in the alveolar ridge crest (T), buccal (B1–B4), and lingual (L1–L4) alveolar ridge mucosa. The average thickness of the mucosa at buccal sides (B) and lingual sides (L) were also assessed.Results:The differences in the mucosal thickness between the left and right sides were not significant. In the Ca–M2 regions, T was the thickest, and L3 was the thinnest of all the measured points in the same regions. L was significantly less than B in posterior regions (P < 0.01). On the other hand, M2 at L4 was thinnest of all the measured regions from Ca to M2 (P < 0.01), and was thicker than IC, IL, P1, and P2 at B2.Conclusions:Since the mucosal thickness of denture-bearing area in the edentulous mandible is not uniform; the tissue surface of the denture base or custom tray should be selectively relieved, which may reduce the risk of denture-induced irritations.

The aim of this study was to introduce a novel soft tissue thickness measurement method using cone beam computed tomography (CBCT) and to compare the new method with ultrasonic device applications and transgingival probing measurements. Twenty-five participants (12 female, 13 male, age range, 25-51 years) were included the study. Soft tissue thickness in lateral incisor, canine, premolar, and molar regions were measured using transgingival probing (group T), ultrasonic device (group U), and CBCT scan measurements (group C). Differences and correlations between groups and agreement between measurement methods were evaluated. Soft tissue thickness was significantly lower in group U in premolar region, but was significantly higher in molar region compared with group C and group T (P < .05). There were significant positive correlations in lateral incisor and canine region, between group U and group C, in premolar region between group T and group C, and in molar region between group U and group C, and between group C and group T (P < .05). The highest agreement between measurement methods was evident between group T and group C. Soft tissue thickness values in maxilla may differ depending on the measurement method and location of the measurement. Ultrasonic device, transgingival probing, and CBCT measures may not necessarily correlate in all locations. The high agreement between CBCT measurements and transgingival probing may suggest the newly introduced method as a promising technique for soft tissue thickness evaluation. This study evaluated the relation between different soft tissue thickness measurement methods and demonstrated a novel method which can be used in any part of the mouth. The outcome also suggested that the measurement method and the location might affect the soft tissue thickness value obtained, and therefore might be important in clinical decision making.

A cross-sectional study into age changes of the human dental arch.

Bleeding in the floor of the mouth during implant surgery is attributed to arterial injuries in the sublingual space. This study aimed to assess the relative hemorrhage risk during implant surgery. We investigated the occurrence rate and diameter of submental and sublingual arteries with special reference to their relationship with the course patterns of these arteries using 26 human cadavers. Three types of arteries were distinguished: main duct (MD), mucoperiosteal branches (MB), and cortical branches (CB). The occurrence rate of MB and CB was significantly high at the central incisor region in the upper part of the mylohyoid muscle, whereas the diameter of the MB and CB was significantly smaller than the occurrence rate of MD at the incisor regions. The occurrence rate of MD in the submental artery was significantly higher at the lateral incisor, canine, and premolar regions in the lower parts, whereas the occurrence rate of MD was significantly lower at the second and third molars in the upper parts. The susceptibility of the submental artery to injury is suggested at the incisors, canine, premolars, and first molar regions during implant surgery.

Colorimetric distribution of human attached gingiva and alveolar mucosa

Orthodontic treatment for a patient with hypodontia involving the maxillary lateral incisors

BackgroundImplants have been widely used to restore missing teeth. Limited information on applied anatomy at the anterior maxilla compromises the clinical outcome for implant placement in this region. In the current study, Cone Beam Computerized Tomography (CBCT) was used to measure alveolar ridge and buccal undercut dimension at the anterior maxilla to help develop treatment planning for immediate implant placement.MethodsCBCT scans were screened to include 51 subjects with full dentition at right maxilla. Measurements were taken at the cross sectional views in the middle of the maxillary right central incisor, lateral incisor, and canine regions. Alveolar height was measured from the alveolar crest to floor of nasal fossa. Alveolar width was measured from the buccal to palatal cortical plate at the coronal, middle, and apical third of the distance from the alveolar crest to floor of the nasal fossa. Buccal undercut location was measured from where the buccal cortical plate started dipping to a line extending at the alveolar crest that was perpendicular to the long axis of the alveolar ridge. The buccal undercut depth was measured from the deepest point of the undercut at the buccal plate to a line tangent to the buccal plate paralleling the long axis of ridge.ResultsAlveolar width increased from coronal to apical direction for each tooth. Mean alveolar widths (mm) were: central incisor, 9.55; lateral incisor, 8.30; canine, 9.62. The lateral incisor had a significantly smaller alveolar width than the other anterior teeth. No significant difference in ridge height was noted among the teeth. Undercut locations from the alveolar crest (mm) were: central incisor, 5.84; lateral incisor, 3.59; canine, 5.11. Undercut depths (mm) were: central incisor, 0.76; lateral incisor, 0.87; canine, 0.73. The percentages of teeth with buccal undercuts were: central incisor, 41 %, lateral incisor, 77 %, and canine 33 %. Male demonstrate significant larger ridge width compared with females for all three teeth.ConclusionsAt anterior maxilla, the lateral incisor has the thinnest alveolar bone, and most frequently exhibits a buccal undercut which is the closest to alveolar ridge compared with other maxillary anterior teeth.