The effect of low-level laser irradiation on hyperglycemia-induced inflammation in human gingival fibroblasts.

Hyperglycemia-induced inflammation can greatly increase the risk of periodontal disease in people with diabetes. Low-level laser irradiation (LLLI) has been used for wound healing and anti-inflammation in many cases, and LLLI is known to inhibit the lipopolysaccharide (LPS)-stimulated inflammatory response. However, the therapeutic effect of LLLI in diabetes patients with periodontitis remains unknown. In this study, we cultured human gingival fibroblasts (HGFs) in high-glucose medium (35 mM) to mimic a hyperglycemic environment, and then measured the anti-inflammatory effect of LLLI by assessing the expression of pro-inflammatory genes including tumor necrosis factor-α (TNF-α), interleukin (IL)-1ß, IL-6, and IL-8 by quantitative real-time polymerase chain reaction. The results demonstrated no significant inflammatory response in HGFs cultured in mannitol medium and in those treated only with LLLI. However, HGFs cultured only in high-glucose medium showed significantly higher expression of pro-inflammatory cytokine than in those treated together with LLLI. We then observed that LLLI reduced the expression of pro-inflammatory cytokines in HGFs cultured in high-glucose medium by modulating cAMP signaling. We also investigated whether antioxidant (vitamin C) treatment reduced the inflammatory effect of oxidative stress in HGFs cultured in high-glucose medium but found no additive effect upon co-treatment with LLLI, suggesting that LLLI may activate cAMP signaling, but not reactive oxygen species (ROS) signaling, to reduce the high glucose-induced inflammation. In conclusion, LLLI may have an anti-inflammatory effect on HGFs in a high glucose environment and may benefit the treatment of periodontal disease in diabetes patients.

The influence of dental experience on a dental implant navigation system.

BACKGROUND: This study evaluated the operating performance of an implant navigation system used by dental students and dentists of prosthodontic background with varying levels of experience. A surgical navigation system and optical tracking system were used, and dentists' accuracies were evaluated in terms of differences between the positions of actually drilled holes and those of the holes planned using software before surgeries. METHODS: The study participants were 5 dental students or dentists who had studied in the same university and hospital but had different experience levels regarding implants. All participants were trained in operating the AqNavi system in the beginning of the study. Subsequently, using 5 pairs of dental models, each participant drilled 5 implant holes at 6 partially edentulous positions (11, 17, 26, 31, 36, and 47). In total, each participant conducted 30 drilling tests. RESULTS: In total, 150 tests among 5 dentists at 6 tooth positions (11, 17, 26, 31, 36, and 47) were conducted. Although a comparison of the tests revealed significant differences in the longitudinal error (P < .0001) and angular error (P = .0011), no significant difference was observed in the total error among the dentists. CONCLUSIONS: A relatively long operating time was associated with relatively little implant experience. Through the dental navigation system, dental students can be introduced to dental implant surgery earlier than what was possible in the past. The results demonstrated that the operational accuracy of the dental implant navigation system is not restricted by participants' implant experience levels. The implant navigation system assists the dentist in the ability to accurately insert the dental implant into the correct position without being affected by his/her own experience of implant surgery.

Anti-inflammatory effects of low-level laser therapy on human periodontal ligament cells: in vitro study.

Periodontal disease is a chronic inflammatory disease that is commonly treated with surgical and nonsurgical techniques. However, both approaches have limitations. Low-level laser therapy (LLLT) has been widely applied in reducing inflammatory reactions, and research indicates that LLLT induces an anti-inflammatory effect that may enhance periodontal disease therapy. The purpose of this study was to investigate the anti-inflammatory effect of LLLT on human periodontal ligament cells (hPDLCs) in an inflammatory environment and aimed to determine the possible mechanism of action. Cells were cultured and treated with or without lipopolysaccharide (LPS) from Porphryromonas gingivalis or Escherichia coli, followed by irradiation with a gallium-aluminum-arsenide (GaAlAs) laser (660 nm) at an energy density of 8 J/cm2. Quantitative real-time polymerase chain reactions were used to assess the expression of pro-inflammatory genes, including tumor necrosis factor-α (TNF-α), interleukin (IL)-1ß, IL-6, and IL-8. The dual-luciferase reporter assay was used to examine nuclear factor-κB (NF-κB) transcriptional activity. An enzyme-linked immunosorbent assay was used to monitor the concentration of intracellular cyclic adenosine monophosphate (cAMP). Both LPS treatments significantly induced the mRNA expression of pro-inflammatory cytokines. However, LLLT inhibited the LPS-induced pro-inflammatory cytokine expression and elevated intracellular levels of cAMP. The LLLT inhibitory effect may function by downregulating NF-κB transcriptional activity and by increasing the intracellular levels of cAMP. LLLT might inhibit LPS-induced inflammation in hPDLCs through cAMP/NF-κB regulation. These results should be further studied to improve periodontal therapy.

Fracture resistance of monolithic zirconia crowns with different occlusal thicknesses in implant prostheses.

STATEMENT OF PROBLEM: The use of monolithic zirconia crowns in implant prostheses is increasing, especially when the interdental space is insufficient. However, fractures have been reported in clinical practice. PURPOSE: The purpose of this study was to determine the minimal thickness of a complete zirconia crown used for an implant prosthesis in the posterior dental region. MATERIAL AND METHODS: Fifty complete zirconia crowns were produced using a computer-aided design/computer-aided manufacturing technique. In each group, 5 crowns of varying thicknesses (0.4, 0.5, 0.6, 0.7, and 0.8 mm) were subjected to cycles of vertical and 10-degree oblique compressive loading at 5 Hz and 300 N in a servohydraulic testing machine. Five finite element models comprising 5 different occlusal thicknesses (0.4, 0.5, 0.6, 0.7, and 0.8 mm) were simulated at 2 loading angles (0 and 10 degrees) and 3 loading forces (300, 500, and 800 N). Data were statistically analyzed, and fracture patterns were observed with a scanning electron microscope. RESULTS: Cyclic loading tests revealed that the fracture resistance of the specimens was positively associated with prosthesis thickness (P<.01). Low von Mises stress values were obtained for prostheses with a minimal thickness of 0.7 mm under varying loading directions and forces. CONCLUSIONS: Zirconia prostheses with a minimal thickness of 0.7 mm had a high fracture resistance and the lowest stress values. Therefore, dentists and laboratory technicians should carefully choose the optimum thickness of zirconia prostheses.

Impact of removable dentures on oral health-related quality of life among elderly adults in Taiwan.

BACKGROUND: Although the use of removable dentures can improve oral function and esthetics for elderly people, compared to those who do not wear removable dentures, those wearing removable dentures could have worse oral health related-quality of life (OHRQoL). Additional information is required to assess which factors related to denture wearing influence the OHRQoL of elderly individuals. The purpose of this study is to evaluate the association between denture wearing and OHRQoL in a sample of elderly individuals in Taiwan. METHODS: The study population included 277 elderly people wearing removable dentures (mean age = 76.0 years). Using face-to-face interviews, we collected data on the participants' socio-demographic characteristics, dental care service usage (regular dental checkups, treatment during toothache, dental visits in the last year), and factors related to denture wearing (perceived oral pain, perceived loose denture, perceived oral ulcer, perceived halitosis, perceived dry mouth, and perceived total denture satisfaction scores). OHRQoL was measured using the Taiwanese version of the Geriatric Oral Health Assessment Index (GOHAI-T). The location and number of remaining natural teeth and the type of denture were also recorded. Hierarchical multiple regression analysis was performed using GOHAI-T scores as the dependent variable. RESULTS: All the predictors together accounted for 50% of the variance in GOHAI-T scores. Further, education level, number of natural teeth, denture status, perceived loose denture, perceived oral ulcer, and perceived total denture satisfaction scores had statistically significant influences on OHRQoL. When compared with other variables, factors related to denture wearing, especially perceived total denture satisfaction scores, had the greatest impact on GOHAI-T scores. CONCLUSIONS: Of the factors analyzed in this study, denture satisfaction was the strongest predictor of OHRQoL. This suggests that denture satisfaction is useful for assessing the effect of denture treatment on the OHRQoL of elderly individuals wearing removable dentures.

Masticatory factors as predictors of oral health-related quality of life among elderly people in Kaohsiung City, Taiwan.

OBJECTIVE: This study aimed to evaluate which masticatory factor is the best predictor of oral health-related quality of life (OHRQoL) in elderly Taiwanese individuals aged 65 years and older. METHODS: Subjects were 332 community-dwelling, independently living elderly adults (mean age, 76.0 ± 0.4 years) in Kaohsiung City, Taiwan. Information concerning age, gender, and socioeconomic status was collected via face-to-face interview questionnaires; the number of food groups rated 'easy to chew' was determined by using food intake questionnaires; and OHRQoL data were obtained by using the Taiwanese version of the Geriatric Oral Health Assessment Index (GOHAI-T). The number of natural teeth, functional tooth units, and posterior occlusal contacts according to Eichner Index was assessed by dental examination. Multiple regression analysis was conducted to determine the best masticatory factor that could serve as a predictor of GOHAI scores. RESULTS: The number of food groups rated 'easy to chew' was found to be the only masticatory factor affecting GOHAI-T scores, after adjustment for age, gender, socioeconomic status, and other masticatory variables. As compared to subjects who listed less food groups as 'easy to chew,' subjects who rated more food groups as 'easy to chew' were less likely to have low GOHAI-T scores. CONCLUSIONS: Of the masticatory predictors analyzed in this study, perceived masticatory ability, as measured using a food intake questionnaire, could be the best masticatory predictor of OHRQoL in the elderly.

Impact of oral health behaviours and oral habits on the number of remaining teeth in older Taiwanese dentate adults.

PURPOSE: To evaluate the impact of oral health behaviours and oral habits on the number of remaining teeth in older Taiwanese dentate adults. SUBJECTS AND METHODS: Subjects comprised dentate patients (mean age, 60.0 ± 9.9 years) in Taiwan. Information on demographic data, oral health behaviours, oral habits and self-perceived health status was collected via self-administered questionnaires and dentition status was assessed by oral examination. Multiple logistic regression analyses were used to determine variables correlated with the low dentition group (subjects with less than 20 natural teeth or 8 functional tooth units). RESULTS: The analysis showed that the low dentition group was more likely to be older and to exhibit low educational levels, less frequent use of dental floss, more common smoking habits, poor self-perceived dental health and to be exbetel- nut chewers. In addition, the low dentition group was less likely to be current betel-nut chewers. CONCLUSIONS: These results underscore the importance of the use of dental floss and confirm the adverse effects of smoking on dental health. Hence, the dental profession should continue to encourage proper oral health behaviours and oral habits.

Rural-urban disparities in Oral Health-related Quality of Life for middle-aged and older adults with diabetes in Taiwan.

Background: Public health faces a significant challenge in reducing rural-urban disparities in diabetes. Since dietary control is part of the medical regimen for diabetes management, how diabetic patients perceive the impact of oral health on their quality of life is critical. The present study aimed to compare the Oral Health-related Quality of Life (OHRQoL) between rural and urban diabetic patients. Methods: The study design was cross-sectional. The study sample included 831 self-reported diabetic patients, extracted from the first wave of the new-cohort Taiwan Longitudinal Study on Aging survey (NC_TLSA) that comprised a nationally representative sample of community-dwelling adults aged 50 and above in Taiwan. The composite score generated from the Oral Health Impact Profile-7 (OHIP-7), which has seven questions, was used to construct two OHRQoL measures, the severity of perceived poor OHRQoL and the prevalence of poor OHRQoL. These two OHRQoL measures were treated as dichotomous variables. Multivariate logistic regression models were applied for analysis. Results: Rural diabetic patients had a higher likelihood of experiencing the severity of perceived poor OHRQoL than those in urban areas (OR = 2.40, 95% CI: 1.30-4.40). Although rural diabetic patients also had a higher prevalence of poor OHRQoL than urban diabetic patients, the difference was not significant (OR = 1.47, 95% CI: 0.95-2.28). Social determinants, such as education, are essential factors attributed to both OHRQoL measures. Conclusion: Overall, rural diabetes community-dwelling patients had a poorer OHRQoL than those in urban areas. Given a bidirectional relationship between oral health and diabetes, improving oral health in rural areas may be a critical avenue to improve the quality of diabetes care in rural areas.

Rural-urban disparities in the incidence and treatment intensity of periodontal disease among patients with diabetes.

Background: Diabetes threatens population health, especially in rural areas. Diabetes and periodontal diseases have a bidirectional relationship. A persistence of rural-urban disparities in diabetes may indicate a rural-urban difference in periodontal disease among patients with diabetes; however, the evidence is lacking. This retrospective study aimed to investigate rural-urban discrepancies in the incidence and treatment intensity of periodontal disease among patients who were newly diagnosed with type 2 diabetes in the year 2010. Methods: The present study was a retrospective cohort design, with two study samples: patients with type 2 diabetes and those who were further diagnosed with periodontal disease. The data sources included the 2010 Diabetes Mellitus Health Database at the patient level, the National Geographic Information Standardization Platform and the Department of Statistics, Ministry of Health and Welfare in Taiwan at the township level. Two dependent variables were a time-to-event outcome for periodontal disease among patients with type 2 diabetes and the treatment intensity measured for patients who were further diagnosed with periodontal disease. The key independent variables are two dummy variables, representing rural and suburban areas, with urban areas as the reference group. The Cox and Poisson regression models were applied for analyses. Results: Of 68,365 qualified patients, 49% of them had periodontal disease within 10 years after patients were diagnosed with diabetes. Compared to urban patients with diabetes, rural (HR = 0.83, 95% CI: 0.75-0.91) and suburban patients (HR = 0.86, 95% CI: 0.83-0.89) had a lower incidence of periodontal disease. Among 33,612 patients with periodontal disease, rural patients received less treatment intensity of dental care (Rural: RR = 0.87, 95% CI: 0.83, 0.92; suburban: RR = 0.93, 95% CI: 0.92, 0.95) than urban patients. Conclusion: Given the underutilization of dental care among rural patients with diabetes, a low incidence of periodontal disease indicates potentially undiagnosed periodontal disease, and low treatment intensity signals potentially unmet dental needs. Our findings provide a potential explanation for the persistence of rural-urban disparities in poor diabetes outcomes. Policy interventions to enhance the likelihood of identifying periodontal disease at the early stage for proper treatment would ease the burden of diabetes care and narrow rural-urban discrepancies in diabetes outcomes.

Biomechanical analysis of alveolar bone stress around implants with different thread designs and pitches in the mandibular molar area.

Threaded implants have been shown to play an important role in increasing mechanical osseointegration. The aim of this study was to determine bone stress distribution when using different types of implant thread pitches and designs. Five 3D finite element models were constructed to simulate bone stresses induced in implant bodies with two types of thread form: triangular ("Tri" prefix) and trapezoidal ("Trap" prefix). The former had thread pitches of 0.8, 1.2, and 1.6 mm, while the latter had thread pitches of 1.2 and 1.6 mm. A biting load of 143 N was applied vertically and obliquely to the occlusal central fossa of the crown. The main effects of each level of the three factors investigated (loading type, pitch, and thread form) in terms of the stress value were computed for all models. Results indicated that the loading type was the main factor of influence on the peak compressive stress of the alveolar bone. Optimal thread pitch was 1.2 mm for a triangular-thread implant, and a trapezoidal-threaded implant with thread pitch of 1.6 mm had the lowest stress value among trapezoidal-threaded implants. This study concluded that each thread form has its unique optimal thread pitch with regard to lower concentration of bone stress. Clinically, this study suggests that in biomechanical consideration, thread pitch exceeding 0.8 mm is more appropriate for a screwed implant. For clinical cases that require greater bone-implant interface, trapezoidal-threaded implants with thread pitch of 1.6 mm provide greater primary stability and lower concentration of bone stress under different loading directions.

Effects of denture maintenance on satisfaction levels of Taiwanese elderly using removable partial dentures: a pilot study.

OBJECTIVE: The aim of this study was to evaluate the correlation between patient satisfaction with removable partial dentures and denture maintenance by patients, including regular application of denture adhesives and cleansers. BACKGROUND: The success of removable partial dentures depends on patient satisfaction with dentures and their regular denture maintenance. MATERIALS AND METHODS: Demographic information, the Oral Impacts on Daily Performance (OIDP) indicator and details of denture maintenance (including the use of denture cleansers and adhesives) were collected from 193 (41.5% men and 58.5% women) participants by using questionnaires. A dentist performed oral examinations to evaluate denture function according to the OIDP items photographically and recorded the number of remaining teeth and Kennedy's classification. RESULTS: Most participants were satisfied with their removable partial dentures and tended to have higher satisfaction levels than the dentist's estimation. Further, those using denture adhesives and cleansers had higher satisfaction levels than those not using such denture maintenance. CONCLUSIONS: Appropriate education regarding denture use is important because regular denture maintenance by patients affects their degree of satisfaction with dentures, as well as the dentist's skill and the patient's oral condition. Dentists could use this information to predict the potential success of dentures.

Evaluation of a self-assessed screening test for masticatory ability of Taiwanese older adults.

OBJECTIVES: The aim of this study was to evaluate a screening test based on a food intake questionnaire to discriminate the masticatory ability of Taiwanese older adults with 20 and more natural teeth and at least 8 functional tooth units (FTUs) from the masticatory ability of those with fewer than 20 natural teeth and 8 FTUs. MATERIALS AND METHODS: The subjects were 2244 patients (mean age, 60.4±10.0 years) recruited from 23 counties and cities in Taiwan. Information about their demographic data, dentition, and masticatory ability was collected. Masticatory ability was measured for 23 food groups comprising 35 common Taiwanese foods, and receiver operation characteristic curve analysis was performed. RESULTS: The results showed that the final questionnaire included 14 food groups and a subject choosing 'difficult to eat' responses for 4 and more of these food groups had the same masticatory ability as individuals with fewer than 20 natural teeth and 8 FTUs. CONCLUSION: In conclusion, foods that are the most difficult to eat are not necessarily good discriminatory indicators. Hence, the 14-food group questionnaire can be considered the best screening test for masticatory ability of Taiwanese older adults in terms of the presence of 20 and more natural teeth and at least 8 FTUs.

Correlation between the change of gonial region and skeletal relapse after intraoral vertical ramus osteotomy for correction of mandibular prognathism.

BACKGROUND: The gonial region is coincided with harmonious face and masticatory function. The aims of the present study were to assess changes in the gonial region in patients who had mandibular setback surgery by intraoral vertical ramus osteotomy (IVRO) and to investigate the contributing factors in relation to skeletal relapse. METHODS: Twenty-one patients with mandibular prognathism were corrected by IVRO. Three cephalometric radiographs were collected from preoperative orthodontic treatment (T1), immediately after surgery (T2), and at 2-year postoperative follow-up (T3). Relapse was defined as forward movement of menton (Me) after the 2-year follow-up. Three angular (SN-Go angle, mandibular plane angle, and gonial angle) and 2 linear (horizontal-Me and vertical-Me) measurements were compared after immediate operation and at the 2-year follow-up. Spearman rank correlation and Student t tests were used for statistical analysis. RESULTS: The mean setback of the Me was 12.7 mm, and the mean relapse was 1.5 mm. The magnitude of setback was not significant for relapse. There were weak correlations between relapse and factors concerned with the gonial region (SN-Go angle, mandibular plane angle, and gonial angle). CONCLUSIONS: Surgical correction of mandibular prognathism using IVRO can lead to an increase in the angle changes of gonial region but not correlate to skeletal relapse in long-term follow-up.

Assessment of the related factors of blood loss and blood ingredients among patients under hypotensive anesthesia in orthognathic surgery.

OBJECTIVE: The objective of the study was to understand the factors associated with presurgical and postsurgical blood loss and blood ingredients among patients in the treatment of mandibular prognathism by intraoral vertical ramus osteotomy combined genioplasty. METHODS: Preoperative and postoperative values of blood loss and blood ingredients were collected from 30 mandibular prognathic patients who underwent orthognathic surgery. The linear regression models and correlation coefficients were used to identify factors with respect to patients' blood loss level and 3 types of blood ingredients (ie, red blood cells, hemoglobin, and hematocrit). RESULTS: The mean blood loss and operation time were 179.2 mL and 311.7 minutes, respectively. No blood transfusion was received by our patients. After adjusting for potential factors, the regression models showed that no significant factor was found to be associated with blood loss and reduce blood ingredients. Moreover, female patients were found to be more likely to have a low level of presurgical blood ingredients (ß = -0.293 to -3.551; P < 0.05), whereas female sex (ß = -1.606 to -4.008; P < 0.001), a high blood loss level (ß = -0.003 to -0.009; P < 0.05), and long operation time (ß = -0.005 to -0.018; P < 0.05) were associated with a low level of postsurgical blood ingredients (ie, hemoglobin and hematocrit). CONCLUSIONS: No significant factor was associated with blood loss and reduced blood ingredients among patients in orthognathic surgery with hypotenstive anesthesia. Improvements in anesthesia provided surgeons with more time to promote hemostasis during surgery. Hypotensive anesthesia was a well-accepted method to reduce blood loss during orthognathic surgery.

Changes in the transverse dimensions by vertical ramus osteotomy after mandibular prognathism correction.

OBJECTIVE: A harmonious face displays not only a good lateral profile but also a pleasant frontal appearance. The purpose of the current study was to evaluate the changes in the transverse dimensions by vertical ramus osteotomy (VRO) in the treatment of mandibular prognathism correction. METHODS: Twenty patients who underwent mandibular prognathism correction by VRO were included. Lateral and frontal cephalometric radiographs were obtained at the following stages: preoperative (T1), immediately after the surgery (T2), and completion of orthodontic treatment (T3). Three linear measurements (menton, intercondylion, and intergonial distances) and the ramus angle were compared from T1 to T3. RESULTS: A final mean menton setback of 12.2 mm and upward movement of 0.3 mm were noted. The intercondylion and intergonial distances significantly increased by 5.1 and 7.1 mm, respectively. Without significant difference, ramus angles decreased 1.7 degrees in the right side and 0.1 degrees in the left side. CONCLUSION: The surgical correction of mandibular prognathism using VRO led to an increase in the transverse dimensions.

The perception of pain following interdental microimplant treatment for skeletal anchorage: a retrospective study.

During orthodontic therapy, patients frequently complain about pain and discomfort, especially during insertion of fixed appliances. Skeletal anchorage using an interdental microimplant is a new concept in orthodontic treatment. The purpose of this study was to investigate differences and changes in the level of pain among patients in relation to orthodontic microimplant treatments. Forty microimplants were applied to the maxilla as skeletal anchors in the orthodontic treatment. The visual analog scale (VAS) was used to evaluate the patients' perception of pain during this new modality treatment. The premolar extraction VAS core was used as a baseline for the complete orthodontic procedure. The mean VAS score was 35.8 mm at 24 h after premolar extraction. The mean VAS score for insertion and removal of the microimplant 24 h after the operation was 12.3 and 7.8 mm, respectively. Three months after removal of the skeletal anchors, the VAS score had decreased to 3.2 mm and was the same as with the traditional orthodontic treatment. By using the repeated-measure general linear model (GLM), we found that the score 1 day after microimplant placement was significantly less than that 1 day after first premolar extraction or that 1 day after fixed appliance insertion. This result indicates that interdental microimplant did not generate any greater pain than other orthodontic procedures. Therefore, patients were willing to adopt the new orthodontic treatment.

FEM analysis of the mandibular first premolar with different post diameters.

Several reports have pointed out that endodontically treated teeth can lack strength, and that the teeth can be reinforced using posts. However, it has not been clear how to select posts that meet the needs of most clinical situations, particularly in terms of the post diameter, which has a major influence on the occurrence of root fracture. The purpose of this study was to analyze the stress distributions of posts of various diameters during masticatory loads using a finite element method. A 3-dimensional (3D) finite element model of a lower first premolar was developed. We used the image software Geomagic Studio (3D Digital 2002; Geomagic, Research Triangle Park, NC, USA) to reduce the post diameter by 6 ratios to a root diameter of 20, 30, 40, 50, 60, and 80% and then individually implemented them into the root of a tooth. A chewing static force of 100 N was applied as a 45° diagonal load on the buccal cusp tip, and the σ(von Mises) and σ(max) stresses were calculated. Analysis of the σ(von Mises) values revealed that the stresses were concentrated in the middle 1/3 of both the post and the root surface for all models, as were the σ(max) values. The results also indicated that when the diameter of the post was 50% of that of the root, the stress distributions of the post and the root surface were most favorable. In conclusion, the clinical implications of the results will need to be further studied and discussed.

The stability of intraoral vertical ramus osteotomy and factors related to skeletal relapse.

BACKGROUND: Intraoral vertical ramus osteotomy (IVRO) and sagittal split ramus osteotomy (SSRO) have been advocated as two major procedures for the correction of mandibular prognathism. However, only a few reports with at least a 2-year follow-up period describe the long-term stability especially of the IVRO method. This study aimed to identify factors contributing to skeletal relapse after a 2-year postoperative follow-up period. METHODS: A set of three standardized lateral cephalograms were obtained from each subject, taken preoperatively (T1), immediately postoperatively (T2), and 2 years postoperatively (T3). Relapse was defined as forward movement of the menton (Me) after a 2-year follow-up period. Two angular measurements (SNB and SN-occlusal plane angle) and five linear measurements (horizontal Me, vertical Me, overbite, anterior facial height, and mandibular length) were compared immediately after the operation and at the 2-year follow-up visit. RESULTS: The mean setback of the menton was 12.8 mm, and the mean relapse was 1.3 mm (10.2% = 1.3/12.8). The magnitude of the setback was not significantly accounted for in the relapse. There were weak correlations between the relapse and the concerned factors, namely, overbite, anterior facial height, mandibular length SNB, and SN-occlusal plane angle). CONCLUSION: The current study confirmed the stability of IVRO in the treatment of mandibular prognathism.

Horizontal pull-out strength of orthodontic infrazygomatic mini-implant: an in vitro study.

PURPOSE: New modified mini-implants have recently come into use for reinforcing skeletal anchorage in orthodontic application. The aim of this study was to investigate the influence of the design of a mini-implant on its mechanical strength. MATERIALS AND METHODS: We measured the insertion torques and horizontal pull-out strengths of 3 brands of infrazygomatic mini-implants (AbsoAnchor, Bioray, and Lomas; 2 mm for all). Five implants of each brand were manually driven 6 mm into the artificial bone. Significant differences in various parameters among the brands were investigated with the Kruskal-Wallis test. RESULTS: There was no significant relationship between insertion torque and horizontal pull-out strength. The Bioray mini-implants had significantly greater horizontal pull-out strength than the AbsoAnchor mini-implants. CONCLUSIONS: The design of the mini-implant can influence its insertion torque and horizontal pull-out strength. In our findings, the horizontal pull-out strength of all mini-implants placed in the infrazygomatic crest was significantly greater than the orthodontic force applied.

Emergence angles of the cementoenamel junction in natural maxillary anterior teeth.

STATEMENT OF THE PROBLEM: Fabrication of normal crown contour to maintain gingival health is difficult in the absence of emergence angle data. PURPOSE: The aim of this study was to measure the geometric values of the emergence angles on the cementoenamel junction (CEJ) for natural maxillary anterior teeth. MATERIAL AND METHODS: This study collected 148 natural permanent maxillary anterior teeth (74 central incisors, 59 lateral incisors, and 15 canines) with intact cervixes for this study. The teeth were scanned with a three-dimensional (3D) scanner to construct 3D models. This study measured the emergence angles of the cervical CEJ on the zenith of labial, palatal, mesial, and distal, for each tooth. RESULTS: Measurements made on 148 maxillary anterior teeth showed the emergence angle to be within a narrow range from 11.30° to 15.26°, irrespective of the tooth location. There were no statistically significant differences between any two groups (p > 0.05). CONCLUSIONS: On the basis of measurements taken from natural teeth, we conclude that the emergence angles of the CEJ in natural maxillary anterior teeth should be 15° from the root surface. CLINICAL SIGNIFICANCE: The information presented in this article may be useful in helping to create dental restorations with optional emergence angles over the CEJ in natural maxillary anterior teeth. Prior to the treatment the dentist should consider not only the fit of the crown, but also the emergence angles and contours of the soft tissues surrounding the involved teeth.