The usefulness of cone-beam computed tomography gray values for alveolar bone linear measurements.

OBJECTIVES: To test a proof-of-concept that the accuracy and reliability of alveolar bone height measurements from orthodontic grade (large field-of-view [FOV], large voxel-size) cone-beam computed tomography (CBCT) images may be improved by using pixel gray values. MATERIALS AND METHODS: Twenty fresh cadaver pig heads underwent CBCT scans (17 × 23 cm FOV, 0.4-mm voxel size). Buccal alveolar bone heights of maxillary first molars were measured using the conventional vision-based (VB) and the proposed gray value-assisted (GVA) methods. The GVA methods entailed localization of landmarks through observation of gray value pattern changes across tissue boundaries followed by mathematical calculation of distances between landmark pixels. Interrater reliability and accuracy of CBCT measurements made by all methods were statistically analyzed by comparing with physical measurements (gold standards). RESULTS: The interrater reliability of CBCT measurements made by GVA methods was comparable to physical measurements but higher than those made by the VB method. The GVA (bend-down pattern) method yielded average measurements similar to physical measurements, while those obtained by the VB and the GVA (straight pattern) methods were significantly larger (repeated measures analysis of variance, P < .001). The GVA (bend-down pattern) method also produced significantly more measurements within one voxel size of physical measurements than did the VB and GVA (straight pattern) methods (Chi-square tests, P < .017). CONCLUSIONS: These data confirm a concept that local gray value change patterns may be used to improve the accuracy and reliability of alveolar bone height measurement from large FOV and large voxel-size CBCT images.

Comparison of cone-beam computed tomography with multislice computed tomography in detection of small osseous condylar defects.

INTRODUCTION: Previous studies have indicated that orthodontic-grade cone-beam computed tomography (CBCT) images are limited when displaying small defects at the mandibular condyles for diagnosis. In this study, we investigated whether this limitation was inherent to CBCT by comparing CBCT with multislice computed tomography (CT), and whether image segmentation and color mapping could overcome this limitation. METHODS: Nine fresh pig heads (18 condyles, 36 medial and lateral condylar regions) were used. Small osseous defects (diameter and depth, 1.5 mm) were created at the medial and lateral regions of the condyles shown by gutta percha markers. After the overlying soft tissues were restored, the pig heads underwent orthodontic-grade CBCT scans (0.4-mm voxel size; i-CAT; Imaging Sciences International, Hatfield, Pa) and medical-grade CT scans (0.625-mm voxel size; LightSpeed; GE, Little Chalfont, Buckinghamshire, United Kingdom). Subsequently, 2 calibrated and blinded raters diagnosed the defect numbers in each condylar region from CBCT and CT images using Dolphin 3D software (Patterson Supply, St Paul, Minn) without image segmentation, and then 1 week later with the proprietary image segmentation and color mapping tools of Dolphin 3D. Condylar polyvinyl siloxane impressions were collected and evaluated by the same raters to obtain physical diagnoses. Rediagnoses were made on randomly selected subsamples to assess reliability. Using the physical diagnoses as references, the accuracy of imaging diagnosis was assessed and statistically compared among the varied imaging and analysis methods. RESULTS: Image diagnoses of all imaging and analysis methods showed good or excellent intrarater and interrater reliability values, except for those of the segmented CBCT images, which were substantially lower. The numbers of overdiagnoses and underdiagnoses per condylar region were not significantly different among the varied imaging and analysis methods (Wilcoxon tests, P >0.05), but classification functions demonstrated substantially lower sensitivity and accuracy with CBCT than with CT. Logistic regression also showed that CT had a significantly higher probability (odds ratio, 2.4) than CBCT in reaching the correct diagnosis, whereas use of the image segmentation and color mapping tool proprietary to Dolphin 3D did not improve the diagnostic accuracy from CBCT images. CONCLUSIONS: Even at a lower voxel size than medical CT images, orthodontic-grade CBCT images of mandibular condyles may be inherently less reliable and less accurate for the diagnosis of small condylar defects.

Effect of long-term steam autoclaving on changes in torque delivery of spring- and friction-type torque wrenches.

STATEMENT OF PROBLEM: Two types of mechanical torque-limiting devices (MTLD) are available: friction-style and spring-style. Limited information is available regarding the accuracy of different types of MTLDs after sterilization. PURPOSE: The purpose of this in vitro study was to determine the accuracy of MTLDs after sterilization. MATERIAL AND METHODS: Three new friction-style and 3 new spring-style MTLDs (Astra Tech/Dentsply, Zimmer Dental, Biohorizons, Biomet 3i, Straumann [ITI] and Nobel Biocare; n=5 per manufacturer; 30 total) were selected to evaluate their accuracy in delivering the target torque values preset by their manufacturers before and after sterilization. Target torque measurements were made with a digital torque gauge (model DFS2-R-ND; Chatillon) 10 times for each device. All MTLDs were sterilized following the manufacturers' recommendations. The sterilization procedure was repeated 100 times, and the accuracy of all MTLDs was retested. Absolute torque differences were analyzed using a repeated measures analysis of variance with instrument as the repeated factor. MTLD type (friction or spring) and MTLD status (new or autoclaved) were the independent variables. Post hoc testing was done using the Tukey method for balanced data. RESULTS: No significant difference was found between the spring-style and friction-style MTLDs or within the spring-style and friction-style MTLDs before and after sterilization (P>.05). CONCLUSIONS: After 100 cycles of steam autoclaving, the accuracy of spring-style and friction-style MTLDs was similar. All MTLDs fell within ±10% of the target torque value before and after sterilization.

Anteroposterior Spread and Cantilever Length in Mandibular Metal-Resin Implant-Fixed Complete Dental Prostheses: A 7- to 9-Year Analysis.

PURPOSE: The purpose of this retrospective study was to investigate the relationship of specific prosthetic complications in patients with a maxillary complete removable dental prosthesis (CRDP) opposing a mandibular metal-resin implant-fixed complete dental prosthesis (MRIFCDP) with respect to anteroposterior (AP) spread and cantilever length. MATERIALS AND METHODS: Of the 46 patients contacted for this study, 23 patients responded. All patients had been treated with a maxillary CRDP and a mandibular MRIFCDP. They were reviewed for prosthetic complications, and the AP spread and cantilever length were evaluated. A polyvinyl siloxane impression was made of each MRIFCDP so that cantilever length and AP spread could be measured. The average recall time was 8.5 years. The mechanical complications noted were screw-related complications, including both the prosthetic and the abutment screw, consisting of loosening and/or fracture, and fracture of the metal framework. Three different individuals repeated each measurement three times. Inter- and intrarater reliability was evaluated with the intraclass correlation coefficient, and a linear regression analysis of age and average cantilever length to AP spread ratio was calculated. In addition, calculations using this ratio were divided into two groups (> 2.1 and ≤ 2.1) and examined with each variable individually. A logistic regression analysis was performed for a comparison between the two AP spread ratio groups by age, right cantilever length, left cantilever length, average cantilever length, posterior spread, and failures. RESULTS: None of the predictor values was significant for the linear regression analysis of age, cantilever length, and AP ratio on number of failures. There was no significance in complications between the groups that had an AP spread ratio > 2.1 and groups that had an AP spread ratio ≤ 2.1. CONCLUSIONS: There was no statistical significance in predicting whether a screw-related complication would occur in relation to age, cantilever length, or AP spread ratio. There was no increase or decrease in complications whether the AP spread ratio was greater than or less than or equal to 2.1. In mandibular MRIFCDPs opposing maxillary complete denture situations, screw-related complications may be less likely regardless of the patient's age, cantilever length, or AP spread ratio of the prosthesis.

Accuracy of mechanical torque-limiting devices for dental implants after clinical service.

STATEMENT OF PROBLEM: Limited information is available regarding the accuracy of mechanical torque-limiting devices (MTLDs) after their clinical use. PURPOSE: The purpose of this study was to determine the accuracy of 2 types of MTLDs (friction-style and spring-style) after clinical use. MATERIAL AND METHODS: Twenty-seven MTLDs in clinical service at The Ohio State University College of Dentistry were collected. Thirteen were friction-style and 14 were spring-style. A total of 6 different dental implant companies were represented (Astra Tech, Zimmer Dental, Biomet 3i, Straumann, Nobel Biocare, and Thommen Medical). All MTLDs had been in use for at least 6 months without being recalibrated, and all were tested to determine their accuracy in delivering target torque values. Statistical analysis used nonparametric tests to determine the accuracy of the MTLDs in delivering target torque values, and Bonferroni post hoc tests were used to assess pairwise comparisons. RESULTS: After clinical service, spring-style MTLDs were significantly more accurate than friction-style MTLDs (P<.05). CONCLUSIONS: Within the limitations of this study, it was concluded that after clinical service, spring-style MTLDs were more accurate than friction-style MTLDs. All MTLDs delivered torque values within 10% of the target torque value.

Temporary anchorage device utilization: comparison of usage in orthodontic programs and private practice.

AIM: There is limited data on how temporary anchorage devices (TADs) are currently used in orthodontics. The aim of this study was to survey two groups of orthodontic providers-graduate orthodontic residencies and private practitioners-about their use. METHODS: A 15-question survey was prepared and administered to all 61 accredited orthodontic residencies and an equal number of private orthodontic practitioners (all in the United States). A second survey was also included and provided to the residency programs. RESULTS: The response rate was 63.9% for private practitioners and 70.4% for orthodontic residency programs. The majority of the residency programs (82.9%) and practitioners (69.2%) reported placing TADs in their practices. TADs were placed in 6.0% of the patients treated by private practitioner and in 5.3% of patients treated in residency programs. A combination of topical and local anesthesia was the anesthetic of choice for 59.0% of private practitioners and 65.0% of orthodontic residency programs. A large majority of the private practitioners (79.0%) and orthodontic residency programs (61.9%) reported that the TADs were loaded immediately. The most frequently cited use for TADs was anterior en masse retraction. In total, 27.9% of the residency programs used miniplates, compared to 17.9% of the practitioners. CONCLUSION: Since 2005, a large number of US programs have incorporated TADs into their didactic/research curriculum and residency programs. Both mini-implants and miniplates may have a far-reaching impact on the clinical practice of orthodontics for decades to come. This survey detailed the trends and differences between practitioners and residencies in the TAD utilization experience and provided important information that is otherwise not available in the literature.

Prosthetic complications in mandibular metal-resin implant-fixed complete dental prostheses: a 5- to 9-year analysis.

PURPOSE: The purpose of this study was to investigate the prosthetic complications of patients with a maxillary complete removable dental prosthesis opposing a mandibular metal-resin implant fixed complete dental prosthesis. MATERIALS AND METHODS: This study is a retrospective analysis of an ongoing prospective study. Dental records from 46 patients treated with a maxillary complete removable dental prosthesis and a mandibular metal-resin implant-fixed complete dental prosthesis were reviewed for 15 different prosthetic complications. The average recall time was 7.9 years. The percentage of patients exhibiting each complication and corresponding 95% confidence intervals was calculated. Logistic regression analysis determined the effect of recall period, age, and gender on each of the following major complications: tooth fracture, complete denture relines, screw complications, and tooth replacement. The recall period was divided into 3 parts: < or = 2 years, 2 to 5 years, and more than 5 years. RESULTS AND CONCLUSION: Statistical significance was exhibited for complete denture relines, posterior tooth replacement, and screw complications. No abutment or framework fractures were recorded for any of the time intervals. The most common complications were prosthetic tooth fracture, tooth wear, maxillary hard relines, and screw complications. Patients were 1.06 times more likely to require a heat-processed hard reline with each year increase of age. After 2 to 5 years and > 5 years, patients were 3.7 times and 8.5 times more likely to require a hard reline than at < or = 2 years. Patients were 52.5 times more likely to need posterior tooth replacement at > 5 years than at < or = 2 years, and 7.7 times more likely to encounter a screw complication at > 5 years than at < or = 2 years.

Changes in mechanical properties of bone within the mandibular condyle with age.

The purpose of the study was to compare indentation modulus (IM) and hardness of condylar bone in young and adult dogs. In addition we desired to examine histologic sections for bone formation activity in the two groups. Mandibular condyles were obtained from adult (1- to 2-year-old) and young (approximately 5-m old) dogs. Two sections/condyle were obtained and one was processed for histomorphometry and the other for mechanical analyses. Indents were made on moist condylar trabecular bone to a depth of 500 nm at a loading rate of 10 nm/s using a custom-made hydration system to obtain IM and hardness. Histomorphometric analyses measured the bone volume/total volume (BV/TV%) and ratio of labeled to unlabeled bone within the condyle. Data were analyzed using a repeated-measures factorial analysis of variance and Tukey-Kramer method. Overall, the IM of the adult condyles (10.0+/-3.4 GPa, Mean+/-SD) were significantly (P<0.0001) higher than in young dogs (5.6+/-2.6 GPa). There was a greater bone mass in the young (60.2%) versus the adult condyles (42%). Also, significantly more labeled bone in the young (66.1%) condylar bone suggested higher bone forming activity than in adult condyles (27.5%). With age there is a change in mass and material properties in the trabecular bone of the mandibular condyle in dogs.

Bone remodeling in maxilla, mandible, and femur of young dogs.

Bone remodeling in the jaw is essential for metabolic needs, mechanical demands and for growth of the skeleton. Currently, there is no information on remodeling in the jaw of young dogs. Four approximately 5-month-old male dogs were given a pair of calcein bone labels. After killing, bone sections were obtained from the maxilla, mandible, and femur. The jaw specimens were obtained from regions associated with erupting permanent teeth. Undecalcified specimens were prepared for examination by histomorphometric methods to evaluate mineral apposition rate (microm/d), mineralizing surface/bone surface (%), and bone formation rate (BFR, %/yr) in the bone supporting erupting teeth and in the femurs. Only intracortical secondary osteonal remodeling units were measured. There were significant (P < 0.05) differences in the BFR for the three sites examined, with the highest BFR (72%/yr) being in the femur. The mandible had a BFR twofold greater than the maxilla (51%/yr vs. 25.5%/yr). The rate of turnover in the jaw and femur of young dogs is distinct from a similar comparison between the jaw and appendicular skeleton of adult ( approximately 1 yr old) dogs. Although BFR decreases with age in the femur, it remains elevated in the jaws.

Early soft tissue healing around one-stage dental implants: clinical and microbiologic parameters.

BACKGROUND: Despite the potential significance of early soft tissue healing to long-term outcomes, this aspect of one-stage dental implants has not been investigated. The purpose of this prospective study was to characterize clinical and microbiologic parameters of early soft tissue healing around dental implants placed following a one-stage protocol. METHODS: Twenty-one patients (11 females and 10 males, aged 18 to 78 years; two smokers) needing a single implant were included. Clinical parameters included probing depth, buccal flap thickness, papilla height, and bleeding on probing. Subgingival plaque samples were obtained pre- and postoperatively and analyzed using molecular techniques. RESULTS: The newly formed peri-implant sulcus probing depth remained fairly stable from 4 to 12 weeks (P > 0.05). There was no statistically significant association between flap thickness or papillary height and number of implant bleeding sites at 12 weeks (P > 0.05). Detection of known periodontal pathogens was rare. Fusobacterium nucleatum was present in 17 patients prior to surgery, and 71% of them became carriers of this bacterium at the implant site by the second postoperative week. The number of F. nucleatum-positive subjects around the implant was significantly lower than the number of F. nucleatum-positive subjects around teeth (P < 0.05). CONCLUSIONS: Peri-implant soft tissue clinical maturity may be established as early as 4 weeks following implant placement by a one-stage surgical protocol; neither preexisting flap thickness nor papillary height seemed to influence newly forming peri-implant sulcus depth or bleeding on probing prevalence. For the most part, the newly created peri-implant crevices were colonized by specific bacteria within 2 weeks.

Clinical color match of porcelain visual shade-matching systems.

BACKGROUND: Accuracy of the total color replication process has not been clinically evaluated for various porcelain visual shade-matching systems. PURPOSE: The purpose of this study was to evaluate the final color replication process of three porcelain visual shade-matching systems. Subjects' natural dentition was compared with laboratory-fabricated individualized porcelain shade tabs. MATERIALS AND METHODS: Shade matches of 10 subjects' incisors were obtained using three different porcelain visual shade-matching systems. Commercial laboratories fabricated one corresponding individualized porcelain shade tab for each incisor per visual shade-matching system selection. Color-match evaluations of the fabricated individualized porcelain shade tabs to the corresponding teeth were completed by prosthodontists' consensus and by subjects' self-evaluation using the US Public Health Service criteria. Statistical analysis was carried out on the combined evaluations with logistic regression and the Generalized Estimating Equation for repeated measures. RESULTS: The Vitapan 3D Master/Omega 900 system (Vident Inc., Brea, CA, USA) was significantly more likely than the Vita Lumin Vacuum/VMK 68 system (Vident Inc.) to obtain a clinically acceptable color match (odds ratio [OR]=6.31; 95% CI=1.24-32.07). The likelihood of obtaining a clinically acceptable color match through subjects' self-evaluation was found to be significantly higher compared with prosthodontists' consensus (OR=2.75; 95% CI=1.27-5.94). CONCLUSIONS: Within the limits of this preliminary study, significant differences in clinical acceptability were seen between the color matches of the fabricated individualized porcelain shade tabs from different systems and subjects' central incisors. Subjects' range of acceptability was much broader compared with that of the prosthodontists in assessing the color match of the fabricated porcelain shade tabs. CLINICAL SIGNIFICANCE: The use of certain porcelain visual shade-matching systems may result in a clinically acceptable color match of the final restoration more readily than the use of other systems. Color-match evaluation of final restorations should be accomplished through a consensus between prosthodontists and patients, given the difference in thresholds of acceptability.

Análise cefalométrica lateral de voluntários assintomáticos e pacientes sintomáticos com e sem deslocamento de disco da ATM bilateral / Lateral cephalometric analysis of asymptomatic volunteers and symptomatic patients with and without bilateral TMJ disc displacement

Poucos estudos têm sido realizados sobre a relação ortodôntica e as estruturas dentofaciais relativas à disfunção temporomandibular. Realizamos esta investigação para tentar determinar qualquer correlação de características ortodônticas e dentofaciais com deslocamento de disco da articulação temporomandibular (ATM) bilateral. Os pacientes sintomáticos e os voluntários assintomáticos (grupo de controle) foram examinados e padronizados em uma clínica especializada no tratamento de problemas ATM. Diferenças das características estruturais esqueletais foram determinadas entre três grupos de estudo: 1) voluntários assintomáticos sem deslocamento de disco da ATM, 2) pacientes sintomáticos sem deslocamento de disco da ATM e 3) pacientes sintomáticos com deslocamento de disco da ATM bilateral. Trinta e dois voluntários assintomáticos sem deslocamento de disco da ATM (25 mulheres, 7 homens) foram comparados com o mesmo número de pacientes sintomáticos sem deslocamento anterior de disco e pacientes sintomáticos com deslocamento de disco da ATM bilateral. Todos os participantes do estudo submeteram-se a um exame clínico padronizado, exame de ressonância magnética bilateral da ATM e análise de radiografia cefalométrica lateral. Os grupos foram formados de acordo com sexo, condição intracapsular da ATM, idade e classificação das maloclusões de Angle. Dezessete variáveis de radiografias cefalométricas laterais (dimensões maxilomandibulares, verticais e de base de crânio) foram avaliadas e comparadas entre os grupos de estudo. O ângulo SNB médio (interseção do plano sella-nasion e a linha nasion-ponto B - indicando retrognatismo mandibular relativo à base do crânio) do grupo de pacientes sintomáticos com deslocamento de disco foi significativamente menor do que o dos grupos dos voluntários assintomáticos e pacientes sintomáticos sem deslocamento de disco articular bilateral (p<0,05). As mulheres apresentaram medidas lineares de comprimento mandibular, altura facial inferior e altura facial anterior total menores do que os homens em todos os três grupos (p<0,05). O ângulo ANB médio (interseção dos planos ponto A-nasion e nasion-ponto B - indicando retrognatismo da mandíbula relativo à maxila) foi significativamente maior em mulheres do que em homens, em todos os grupos (p<0,05). Pacientes sintomáticos com deslocamento de disco bilateral apresentaram uma mandíbula retroposicionada, indicado por um ângulo SNB médio menor do que quando comparado com os voluntários...