Does two-dimensional vs. three-dimensional surgical simulation produce better surgical outcomes among patients with class III facial asymmetry?

The aim of this study was to compare the outcomes of traditional two-dimensional planning (2DP) and three-dimensional surgical simulation (3DS) in the surgical correction of skeletal class III with facial asymmetry. This retrospective cohort study included 37 consecutive adult Taiwanese patients. Preoperative and postoperative three-dimensional cephalometric measurements were obtained from cone beam computed tomography scans. The outcome variables were the differences in preoperative and postoperative linear and angular measurements and the differences between the two groups after surgery. When the surgical result was compared between the 2DP and 3DS groups, significant differences were found for four cephalometric variables: the distance from gonion on the non-deviated side to the midsagittal plane (MSP), mid-gonion to the MSP, upper first molar on the non-deviated side to the Frankfort horizontal plane, and the yaw angle. In the 3DS group, mandibular symmetry was achieved because the centre between the bilateral gonions was improved, and because there was no significant difference in the horizontal gonion (Go to the MSP) between the deviated and non-deviated sides after surgery. 3DS provides all the necessary information for planned surgical movements for the correction of facial asymmetry; it should be considered during surgical planning to improve surgical outcomes, particularly the achievement of bilateral mandibular contour symmetry.     

Pre-cementation procedures’ effect on dental zirconias with different yttria content

ObjectveSeveral pre-cementation procedures have been advocated to enhance adhesion between zirconia and resin-based cement. There is, however, limited documentation on how these pre-treatments affect the strength of zirconia crowns as most tests are performed on discs or bars.The aim was to assess the effect of pre-cementation procedures on fracture mode, fracture strength and cement retention on zirconia.MethodsTwo dental zirconia materials with different yttria content were assessed (<4 and>5 mol%). Both discs (n = 45) and crown-shaped specimens (n = 30) of the two materials were pretreated with either air-abrasion or hot-etching with KHF₂ and compared with untreated controls with regards to surface roughness, crystallography, wettability, cement adhesion and fracture strength.Results and SignificanceAir-abrasion improves adhesion and strength of zirconia with moderate yttria content (<4 mol%). Acid etching with heated KHF₂ showed the best effect on strength and cement retention on zirconia with higher yttria content (>5 mol%). Application of KHF₂ was, however, complicated on crown-shaped specimens. Pre-treatment and cementation protocols should be optimized for different dental zirconias to improve both strength and retention.     

Control of lower incisor inclination with a completely customized lingual appliance for dentoalveolar compensation of class III malocclusion

Objective

Bracket slots and orthodontic archwires offering high dimensional precision are needed for fully customized lingual appliances. We aimed to investigate whether high-precision appliances of this type enable dentoalveolar compensation of class III malocclusion so that lower incisor inclination at the end of treatment will closely match the anticipated situation as defined in a pretreatment setup.

Materials and methods

This retrospective study included a total of 34 consecutive patients who had worn a fully customized lingual appliance to achieve dentoalveolar compensation for class III malocclusion by intermaxillary elastics, or proximal enamel reduction, or extraction of teeth in one or both jaws. Casts fabricated at different points in time were three-dimensionally scanned to analyze how precisely the lower incisor inclinations envisioned in the setup were implemented in clinical practice.

Results

Aside from minor deviations of ±3.75°, the lower incisor inclinations were clinically implemented as planned even in patients with major sagittal discrepancies.

Conclusion

Treatment goals predefined in a setup of dentoalveolar compensation for class III malocclusion can be very precisely achieved via a customized lingual appliance. Correct planning can prevent undesirable lingual tipping of the lower incisors. This finding should not encourage a more liberal use of dentoalveolar compensation, but it should heighten clinicians’ awareness of how essential it is to sufficiently consider the individual anatomy of the dentoalveolar complex during treatment planning.     

Is skeletal stability after bimaxillary surgery for skeletal class III deformity related to surgical occlusal contact?

A stable occlusion at the time of surgery is considered important for post-surgical stability after orthognathic surgery. The aim of this study was to determine whether skeletal stability after bimaxillary surgery using a surgery-first approach for skeletal class III deformity is related to the surgical occlusal contact or surgical change. Forty-two adult patients with a skeletal class III deformity corrected by Le Fort I osteotomy and bilateral sagittal split osteotomy with a surgery-first approach were studied. Dental models were set and used to measure the surgical occlusal contact, including contact distribution, contact number, and contact area. Cone beam computed tomography was used to measure the surgical change (amount and rotation) and post-surgical skeletal stability. The relationship between skeletal stability and surgical occlusal contact or surgical change was evaluated. No relationship was found between maxillary or mandibular stability and surgical occlusal contact. However, a significant relationship was found between maxillary and mandibular stability and the amount and rotation of surgical change. The results suggest that in the surgical-orthodontic correction of skeletal class III deformity with a surgery-first approach, the post-surgical skeletal stability is not related to the surgical occlusal contact but is related to the surgical change.     

Bimaxillary ‘rotation advancement’ procedures in patients with obstructive sleep apnea: a 3-dimensional airway analysis of morphological changes

The aim of this retrospective three dimensional (3D) computed tomographic analysis was to investigate the morphological airway changes in 17 obstructive sleep apnea (OSA) patients following bimaxillary rotation advancement procedures. Morphological changes of the nasal cavity and naso-, oro- and hypopharynx were analysed separately, as were the total airway changes using nine parameters of airway size and four of shape. The Wilcoxon test was used to compare airway changes and the intraclass correlation coefficient to qualify inter-observer reliability. Following bimaxillary advancement and anti-clockwise maxillary rotation, the total airway volume and the lateral dimension of the cross-sectional airway increased significantly. The total length of the airway became shorter (p < 0.05). Remarkable changes were seen in the oropharynx: the length, volume, cross-sectional area (CSA), antero-posterior and medio-lateral distance changed (p < 0.05). This combined with a significant 3D change in the shape of the airway from round to elliptical. The average cross-sectional oropharyngeal area was nearly doubled, the minimal CSA increased 40%, and the hyoid bone was located more anterior and superior. Inter-examiner reliabilities were high (0.89). 3D airway analysis aids the understanding of postoperative pathophysiological changes in OSA patients. The airway became shorter, more voluminous, medio-laterally wider, and more compact and elliptical.     

Light-curing units used in dentistry: factors associated with heat development—potential risk for patients

Objectives

To investigate how heat development in the pulp chamber and coronal surface of natural teeth with and without cusps subjected to irradiance using light-emitting diode (LED)–light-curing units (LCUs) is associated with (i) irradiance, (ii) time, (iii) distance, and (iv) radiant exposure.

Materials and methods

Three different LED-LCUs were used. Their irradiance was measured with a calibrated spectrometer (BlueLight Analytics Inc., Halifax, Canada). An experimental rig was constructed to control the thermal environment of the teeth. The LED-LCU tip position was accurately controlled by a gantry system. Tooth surface temperature was measured by thermography (ThermaCAM S65 HS, FLIR Systems, Wilsonville, USA) and pulp chamber temperature with a thermocouple. LED-LCU tip distance and irradiation times tested were 0, 2, and 4 mm and 10, 20, and 30 s, respectively. Ethical permission was not required for the use of extracted teeth.

Results

Maximum surface and pulp chamber temperatures were recorded in tooth without cusps (58.1 °C  ± 0.9 °C and 43.1 °C ± 0.9 °C, respectively). Radiant exposure explained the largest amount of variance in temperature, being more affected by time than irradiance.

Conclusions

At all combinations of variables tested, repeated measurements produced consistent results indicating the reliability of the method used. Increased exposure time seems to be the factor most likely to cause tissue damage.

Clinical relevance

Risk of superficial tissue damage at irradiances >1200 mW/cm² is evident. There is a risk of pulp damage when only thin dentin is left at higher irradiances (>1200 mW/cm²). Clinicians should be aware of LED-LCU settings and possible high temperature generated.

     

Discrimination or discretion? Exploring dentists' views on treating patients with hepatitis C

BACKGROUND: People with hepatitis C (over 259 000 Australians) experience stigma and discrimination, whether perceived or actual, in health care settings. They are less likely to access health care, presenting a major barrier to preventive care and treatment. This study aims to identify factors contributing to such discrimination, barriers to optimal care and strategies to overcome these. METHODS: A purposive sample of 25 Victorian dentists took part in semi-structured interviews to investigate their experiences and attitudes in providing care to people with hepatitis C. Interviews were taped, transcribed and coded for thematic analysis. RESULTS: All dentists interviewed were aware of Standard Precautions. However, there were some who changed practices when seeing a client with hepatitis C, suggesting that they lack confidence in Standard Precautions. When prompted, these dentists were concerned that patients may perceive these actions as discriminatory. All participants, including a small minority who expressed negative views about injecting drug users, felt a professional obligation to treat all patients. CONCLUSIONS: Most dentists have appropriate attitudes regarding patients with blood-borne viruses. However, it is important for dentists to understand how their actions may be interpreted by those who feel sensitive about their status. Dentists need to feel genuinely confident about Standard Precautions and have a realistic view of the infection risk posed by patients with blood-borne viruses.     

Are occlusal features associated with different temporomandibular disorder diagnoses in bruxers?

Aims:

The present study was designed to test the hypothesis that dental occlusion may have a role in mediating the effects of bruxism in temporomandibular disorders (TMD) patients. It aimed to answer the clinical research question: in a population of TMD patients with clinically diagnosed clenching-type bruxism, are the different TMD diagnoses associated with different occlusal features?

Materials and methods:

A total of 294 TMD patients (73% females, mean age 38·3±9·2 years) who were positive for a clinical diagnosis of clenching-type bruxism underwent an assessment in accordance with the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) axis I, as well as a recording of nine occlusal features. Statistical analyses were performed to test the null hypotheses that: (1) no differences existed between the patients with or without the various occlusal features as for the prevalence of the various single and combined RDC/TMD group diagnoses (single variable analysis), and (2) having any specific occlusal feature makes no difference in distinguishing within the RDC/TMD diagnoses (multiple variable analysis).

Results:

The distribution of the different combination of RDC/TMD axis I diagnoses was significantly different in patients with laterotrusive interferences with respect to those without such interferences (chi-square?=?15·209; P?=?0·033) as well as in patients with a slide from retruded contact position (RCP) to maximum intercuspation (MI) >2 mm with respect to those without such slide (chi-square?=?4·029; P?=?0·012) and in those with or without molar class asymmetry (chi-square?=?17·438; P?=?0·015). Multinomial regression analysis showed that the model including the various occlusal features account for 20·4% of the variance for RDC/TMD diagnoses (Nagelkerke R²?=?0·204) and allowed the rejection of the null hypothesis that having such specific occlusal features makes no difference in distinguishing within the RDC/TMD diagnoses.

Conclusions:

Within the limitations of this study, it can be suggested that in a population of patients with TMD and clinically-diagnosed clenching-type bruxism, the patterns of TMD diagnoses may be influenced, at least in part, by the presence of some features of dental occlusion, namely, slide RCP-MI, laterotrusive interferences, and molar asymmetry.     

Changes in soft-tissue profiles after treatment of class II/1 patients with bite-jumping appliances

We performed this study to describe changes in the soft-tissue profile after orthodontic treatment with Tränkmann’s bite-jumping appliances. A total of 69 patients thus treated were compared to a control group of 36 age-matched patients based on cephalograms. Statistical analysis included mean values, standard deviations, t-tests, and Pearson’s correlation testing. Highly significant (p<0.001) changes in total profile angle (N’-Ns-Pog’) were observed over the course of treatment. Furthermore, a mildly significant (p<0.05) correlation with SNA angles was noted. Changes in the soft-tissue profile angle (N’-Sn-Pog’) were moderately significant (p<0.001). The profile angles of the upper lip (Sn-SS-Ls) and lower lip (Pog’-Sm-Li) did not reveal significant changes. We observed highly significant (p<0.001) findings in the esthetic line (NsPog’) advancement relative to the Ls and Li landmarks and in increases in lower-face height. Midface heights remained unchanged. Our results indicate that treatment with bite-jumping appliances results in increased facial convexity, advancement of the esthetic line, and increased lower-face height. The cumulative effects of growth and treatment do not, however, appear pronounced enough to result in a preference for or against treatment with a bite-jumping appliance.     

Soft and hard tissue changes in skeletal Class III patients treated with double-jaw orthognathic surgery—maxillary advancement and mandibular setback

The soft tissues of the facial profile may change after skeletal movement in orthognathic surgery. The aim of this study was to evaluate and compare the differences and correlation between hard and soft tissues after double-jaw surgery in skeletal Class III subjects. Radiographs from the following time points were assessed using Dolphin Imaging software: preoperative (T0), 2–4 months postoperative (T1), and 6–12 months postoperative (T2). Eleven hard and soft tissue points of the facial profile were evaluated. The Student's t-test was used to assess the significance of differences between the time intervals; Pearson's correlation coefficient was used to assess the significance of correlation existing between these points; significance was set at P < 0.05. In the sample of 58 subjects, the correlation between hard and soft tissues in the mandible was greater than in the maxilla. Similarly, the correlations only between hard tissues and only between soft tissues presented a greater correlation in the mandible. The results are similar to those found in studies on single-jaw surgery for both the maxilla and the mandible. The influence of movements in hard tissues was restricted to the soft tissues of the same jaw, although there were exceptions.     

Evaluation of relapse after orthodontic therapy combined with orthognathic surgery in the treatment of skeletal class III

Introduction

Multidisciplinary treatment of skeletal malocclusion by orthognathic surgery in addition to orthodontics is a routine strategy believed to offer good functional and esthetic outcomes. Postoperative relapse is, however, a problem. The present study was conducted to analyze the stability of outcomes achieved by surgical treatment of skeletal class III patients in terms of the rate and extent of relapses.

Patients and methods

A total of 30 patients who had undergone orthodontic treatment combined with orthognathic surgery were included. The primary inclusion criterion was a skeletal class III treated by mandibular setback (Obwegeser/Dal Pont) surgery alone or combined with maxillary advancement (Le Fort I) surgery. Analysis was based on one preoperative and two postoperative cephalograms per patient.

Results

We observed relapse (defined, in accordance with Proffit, as changes >2 mm or 2°) at a rate of 24% after bimaxillary procedures, compared to a lower rate of 21% after mandibular setback procedures only. The relapse rate was 21% among patients who had undergone upper-jaw surgery versus 27% among those who had undergone lower-jaw surgery, which was statistically significant.

Conclusion

The majority of patients exhibited stable treatment outcomes. Maxillary advancement procedures were found to be less susceptible to relapse—resulting in more stable outcomes—and mandibular setback distances correlated positively with the degree of the relapse. No statistically significant differences were observed between the procedures conducted in both jaws versus in the lower jaw only, or in the extent of upper-jaw repositioning.     

Prevotella nigrescens and Porphyromonas gingivalis are associated with signs of carotid atherosclerosis in subjects with and without periodontitis

Yakob M, Söder B, Meurman JH, Jogestrand T, Nowak J, Söder P.‐Ö. Prevotella nigrescens and Porphyromonas gingivalis are associated with signs of carotid atherosclerosis in subjects with and without periodontitis. J Periodont Res 2011; 46: 749–755. ©2011 John Wiley & Sons A/S Background and Objective: Oral microorganisms may be involved in the development of cardiovascular diseases, and Porphyromonas gingivalis is one of the periodontal microorganisms that has been found in carotid atheroma. The aim of this work was to study subgingival microorganisms and early carotid lesions in subjects with and without periodontitis. Material and Methods: Eighty‐eight subjects with periodontitis and 40 subjects without periodontitis underwent dental examinations in 2003. The presence of the periodontal microorganisms Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens and Tannerella forsythia was analyzed from subgingival plaque using PCR amplification. The common carotid artery was scanned using ultrasound and the calculated intima‐media area (cIMA) was measured. The association between periodontitis, the cIMA value and the presence of periodontal microorganisms, together with several confounders, was studied in a multiple logistic regression model. Results: Smoking [odds ratio (OR) = 5.64; p = 0.001), level of education (OR = 5.02; p < 0.05) and the presence of P. gingivalis (OR = 6.50; p < 0.05) were associated with periodontitis. Explanatory factors for the increased cIMA were periodontitis (OR = 4.22; p < 0.05), hypertension (OR = 4.81; p < 0.05), high body mass index (OR = 5.78; p < 0.01), male gender (OR = 3.30; p < 0.05) and poor socioeconomic status (OR = 4.34; p < 0.05). P. nigrescens (OR 4.08; p < 0.05) and P. gingivalis (OR 7.63; p < 0.01) also appeared as explanatory variables associated with increased cIMA values. Conclusion: This cross‐sectional study showed that P. nigrescens and P. gingivalis were significantly associated with increased cIMA values.     

Zygomatic mini-implant for Class II correction in growing patients

Objective

The correction of some Angle Class II malocclusions requires distalization of the upper first molars via an induced orthopedic effect. In the present study, we tested the potential of using a mini-implant to achieve a modified zygomatic anchorage system for Class II correction.

Materials and methods

Our study comprised 10 treated and 10 control Class II growing female subjects aged 10–12 years. Orthodontic mini-implants were placed in the zygomatic buttress to act as anchorage for the distalization. The follow-up period was 6 months; treatment changes were assessed by cone beam CT scans.

Results

Compared to the control group, the treatment group showed significant retrusion of point A, anti-clockwise rotation of the maxillary plane, and a mean molar distalization of 2.92?±?0.69 mm with no extrusion, no tipping or buccal rolling. There was significant upper incisor intrusion (1.89?±?0.84 mm) with no changes in incisor inclination. No change in the mandibular plane angle was detected.

Conclusion

Use of this technique allowed Class II correction with concomitant reduction in the visible gingiva in the treated subjects without the adverse effects experienced with other appliances.