The second molar dilemma in orthodontics: to bond or not to bond?

OBJECTIVES: To compare orthodontic treatment (OT) outcome in adolescents undergoing nonextraction fixed OT with or without bonding of second molars using the score of the American Board of Orthodontics Cast Radiograph Evaluation (C-R-Eval). MATERIALS AND METHODS: This study included healthy adolescents with skeletal Class I or mild Class II/Class III malocclusion, normal or deep overbite (OB), and mild-to-moderate dental crowding (<5 mm) who underwent nonextraction fixed OT with ("bonded" group) or without ("not-bonded" group) bonding of second molars. Patient treatment records, pre- and posttreatment digital models, lateral cephalograms, and orthopantomograms were assessed. The evaluated outcomes included leveling of the curve of Spee (COS), OB, control of incisor mandibular plane angle (IMPA), number of emergency visits (related to poking wires and/or bracket failure of the terminal molar tubes), treatment duration, and C-R-Eval. Treatment variables were compared across time points and among groups. RESULTS: The sample included 30 patients (mean age 16.07 ± 1.80 years) in the bonded group and 32 patients (mean age 15.69 ± 1.86 years) in the not-bonded group. The mean overall C-R-Eval score was significantly higher (P < .001) in the not-bonded group (25.25 ± 3.98) than in the bonded group (17.70 ± 2.97). There were no significant differences in mean changes of COS, OB, IMPA, or treatment duration among groups. The mean number of emergency visits was significantly higher in the bonded (3.3 ± 0.6) than the not-bonded group (1.9 ± 0.4) (P < .001). CONCLUSIONS: Bonding of second molars enhances the outcome of nonextraction fixed OT as demonstrated by the C-R-Eval without increasing treatment duration, irrespective of more emergency visits.

Artificial intelligence for treatment planning and soft tissue outcome prediction of orthognathic treatment: A systematic review.

BACKGROUND: The accuracy of artificial intelligence (AI) in treatment planning and outcome prediction in orthognathic treatment (OGT) has not been systematically reviewed. OBJECTIVES: To determine the accuracy of AI in treatment planning and soft tissue outcome prediction in OGT. DESIGN: Systematic review. DATA SOURCES: Unrestricted search of indexed databases and reference lists of included studies. DATA SELECTION: Clinical studies that addressed the focused question 'Is AI useful for treatment planning and soft tissue outcome prediction in OGT?' were included. DATA EXTRACTION: Study screening, selection and data extraction were performed independently by two authors. The risk of bias (RoB) was assessed using the Cochrane Collaboration's RoB and ROBINS-I tools for randomised and non-randomised clinical studies, respectively. DATA SYNTHESIS: Eight clinical studies (seven retrospective cohort studies and one randomised controlled study) were included. Four studies assessed the role of AI for treatment decision making; and four studies assessed the accuracy of AI in soft tissue outcome prediction after OGT. In four studies, the level of agreement between AI and non-AI decision making was found to be clinically acceptable (at least 90%). In four studies, it was shown that AI can be used for soft tissue outcome prediction after OGT; however, predictions were not clinically acceptable for the lip and chin areas. All studies had a low to moderate RoB. LIMITATIONS: Due to high methodological inconsistencies among the included studies, it was not possible to conduct a meta-analysis and reporting biases assessment. CONCLUSION: AI can be a useful aid to traditional treatment planning by facilitating clinical treatment decision making and providing a visualisation tool for soft tissue outcome prediction in OGT. REGISTRATION: PROSPERO CRD42022366864.

Correction: Santucci et al. Assessment of Posterior Dentoalveolar Expansion with Invisalign in Adult Patients. Int. J. Environ. Res. Public Health 2023, 20, 4318.

There was an error in the original publication [...].

Assessment of Posterior Dentoalveolar Expansion with Invisalign in Adult Patients.

PURPOSE: The primary aim was to evaluate dentoalveolar expansion with Invisalign clear aligners comparing linear measurements in ClinCheck vs. cone beam computed tomography (CBCT). This would enable an assessment of to what extent expansion gained from Invisalign clear aligners was due to buccal tipping and/or bodily translation of the posterior teeth. The study also evaluated the predictive value of Invisalign ClinCheck® (Align Technology, San Jose, CA, USA) to final outcomes. METHODS: The orthodontic records of thirty-two (32) subjects comprised the sample to conduct this study. Linear values of the upper arch width were measured for premolars and molars at two different points (occlusal and gingival) utilized for ClinCheck® measurements and three different points for CBCT measurements before (T0 and after treatment (T1). Paired T-tests at a significance level of 0.05 were used for analyses. RESULTS: Expansion was found to be possible with Invisalign clear aligners. However, more expansion was measured at the cusp tips compared to gingival margins (p < 0.0001), indicating more tipping was occurring than bodily translation. ClinCheck® also showed a significant overestimation of the amount of expansion capable, with nearly 70% expression in the first premolar area, and the expression decreased as one moved posteriorly with only 35% expressed at the first molar area (p < 0.0001). CONCLUSIONS: Dentoalveolar expansion with Invisalign is achieved through buccal tipping of posterior teeth and bodily translation; and there is a significant overestimation of the amount of expansion achieved between ClinCheck® and clinical results.

Temporomandibular Disorders: Implications in Restorative Dentistry and Orthodontics.

Over the past several decades, the science of restorative/reconstructive dentistry and orthodontics has evolved tremendously, following sound principles passed down from robust literature and scientific rationale. These principles have been solid and instrumental in enhancing dentistry, from a single tooth restoration to complex full-mouth rehabilitations. However, it must be noted that some of the principles and philosophies followed over these decades have been questioned based on the advances in science, technology, and evidence-based medicine. The scenario became complex when clinicians were faced with the question of guidance for optimum joint and muscle health as related to restorative dentistry and orthodontics.

Mini-implant assisted posterior intrusion: A quantification of anterior bite closure in nongrowing subjects.

INTRODUCTION: This study aimed to identify the vertical radiographic changes in nongrowing patients after treatment of anterior open bites (AOBs) using mini-implant assisted intrusion and to provide a predictive model to quantify the achievable intrusion. METHODS: This retrospective radiographic study evaluated the dentoskeletal changes in adults using orthodontic mini-implants in 53 treated patients with AOB. Radiographs before and after posterior intrusion were utilized to evaluate the associated changes. Conventional cephalometric analyses provided data for assessment. A paired t test was used to identify significant changes. A regression model (best subsets selection algorithm) was generated to quantify the relationship between mini-implant-assisted intrusion and the resultant change in overbite. A matched, untreated control sample was used for comparison. RESULTS: One hundred percent of AOBs were corrected using mini-implant-assisted intrusion of the maxillary molars. The overbite increased by an average of 3.6 mm. The average amount of maxillary first molar intrusion was 2.67 mm. The mandibular first molar moved an average of 1.93 mm closer to the palatal plane because of an average clockwise mandibular rotation of 0.78°. The occlusal plane steepened by an average of 3.95°. If all other inputs are held constant, 1 mm of intrusion of the maxillary first molar results in a 0.86 mm increase in overbite. CONCLUSIONS: Mini-implant-assisted intrusion successfully treated AOB in adults with significant dentoalveolar but no significant skeletal changes. An average of 2.67 mm of intrusion of the maxillary first molars is achievable with this method showing that 1 mm of intrusion of the maxillary first molar increased overbite by 0.86 mm. Longer periods of intrusion resulted in greater amounts of bite closure.

Sugar-free chewing gum versus conventional analgesic drugs for pain relief with fixed orthodontic appliances. A systematic review and meta-analysis.

OBJECTIVE: To compare the effect of chewing sugar-free gum towards alleviating self-reported orthodontic treatment (OT) pain compared with conventional analgesic drugs (CADs). SEARCH SOURCES: An unrestricted search of indexed databases and manual searching was performed up to September 2021. DATA SELECTION: Randomised controlled trials (RCTs) comparing the impact of chewing gum and CADs on relieving self-reported orthodontic pain were included. DATA EXTRACTION: Data screening, extraction and risk of bias (RoB) assessment were performed by two authors. Meta-analyses were performed using a random-effects model. The quality of available evidence was assessed using the Grades of Recommendation, Assessment, Development and Evaluation approach. RESULTS: Nine RCTs were included. Eight RCTs used the Visual Analogue Scale for self-reported pain assessment, while one RCT used the Numeric Rating Scale. Five RCTs had a high RoB and four RCTs had a moderate RoB. Power analysis for sample size estimation was performed in six RCTs. Separate meta-analyses were performed by pooling quantitative data from five RCTs that compared self-reported orthodontic pain between chewing gum and ibuprofen groups for the following timepoints: baseline; immediately; 2 hours; 6 hours; bedtime; 24 hours; 2 days; 3 days; 5 days; and 7 days after the placement of orthodontic appliances. None of the timepoints individually indicated a difference in self-reported pain scores between chewing sugar-free gum and ibuprofen groups. The overall level of evidence was very low. CONCLUSION: Chewing sugar-free gum is a potentially useful alternative to CADs towards pain alleviation during fixed OT.

Comparison of shear bond strength of orthodontic brackets bonded to human teeth with and without fluorotic enamel: A systematic review and meta-analysis of experimental in vitro studies.

The aim of this systematic review was to compare the shear bond strength (SBS) of orthodontic brackets bonded to human teeth with and without enamel fluorosis (EF) using conventional bonding interventions/techniques. An unrestricted search of indexed databases was performed with the following eligibility criteria: (a) human fluorotic teeth (experimental-group); (b) human teeth without fluorosis (control-group); (c) studies using phosphoric acid (PA) etching without air abrasion (AA), PA etching combined with AA, and application of self-etching primer (SEP) alone as bonding interventions/techniques and (d) measuring SBS in megapascals (MPa). Data screening, selection and extraction were performed by two reviewers. The risk of bias (rob) was assessed using the JBI Critical appraisal tool for Quasi-Experimental Studies. Meta-analyses were performed using a random effects model. The quality of available evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation approach. Ten in vitro studies were included. Subgroup analyses were performed for each intervention type. The SBS was significantly lower in fluorotic teeth when PA was used without AA (mean difference = 3.26 MPa, confidence interval: [1.00, 5.52]); and there were no significant differences for the PA combined with AA and SEP interventions. All studies had a low rob. The overall level of evidence was at best low. The SBS is lower in teeth with EF when traditional PA is used. No significant differences were found in SBS between teeth with and without EF when PA is used with AA or when SEP is used alone.

Association between nonextraction clear aligner therapy and alveolar bone dehiscences and fenestrations in adults with mild-to-moderate crowding.

INTRODUCTION: This study aimed to assess the association between nonextraction clear aligner therapy (CAT) and the presence of alveolar bone dehiscences (ABDs) and fenestrations (ABFs) in adults with mild-to-moderate crowding. METHODS: Cone-beam computed tomography images from 29 adults were obtained before and immediately after nonextraction CAT. Total root lengths were evaluated in axial and cross-sectional slices. Linear measurement for dehiscence (LM-D) was defined as the distance between the alveolar crest to the cementoenamel junction of each root (critical point set at 2 mm). Linear measurement for fenestration (LM-F) was recorded when the defect involved only the apical one-third of a root (critical point set at 2.2 mm). Counts of ABDs/ABFs and magnitudes of LM-Ds/LM-Fs were recorded before and immediately after nonextraction CAT at buccal and lingual root surfaces. Binary logistic regression analyses and repeated measures analyses of variance were performed. RESULTS: Counts of ABDs/ABFs and magnitudes of LM-Ds/LM-Fs increased at most jaw locations and root surfaces. Nonextraction CAT was associated with an increased presence of ABDs and ABFs. Nonextraction CAT was associated with a higher magnitude of LM-Ds but not LM-Fs. CONCLUSIONS: Immediate posttreatment cone-beam computed tomography scans showed that nonextraction CAT is associated with increased ABDs and ABFs in adults with mild-to-moderate crowding.

Effectiveness of Curcumin in Reducing Self-Rated Pain-Levels in the Orofacial Region: A Systematic Review of Randomized-Controlled Trials.

The aim was to systematically review randomized controlled trials (RCTs) that assessed the effectiveness of curcumin in reducing self-rated pain levels in the orofacial region (OFR). The addressed focused question was "Is curcumin effective in reducing self-rated pain levels in the OFR?". Indexed databases (PubMed (National Library of Medicine), Scopus, EMBASE, MEDLINE (OVID), and Web of Science) were searched up to and including February 2022 using different keywords. The inclusion criteria were (a) original studies (RCTs) in indexed databases; and (b) studies assessing the role of curcumin in the management of pain in the OFR. The risk of bias was assessed using the Cochrane risk of bias tool. The pattern of the present systematic review was customized to primarily summarize the pertinent information. Nineteen RCTs were included. Results from 79% of the studies reported that curcumin exhibits analgesic properties and is effective in reducing self-rated pain associated with the OFR. Three studies had a low risk of bias, while nine and seven studies had a moderate and high risk of bias, respectively. Curcumin can be used as an alternative to conventional therapies in alleviating pain in the OFR. However, due to the limitations and risk of bias in the aforementioned studies, more high-quality RCTs are needed.

Influence of low-level-laser therapy on the stability of orthodontic mini-screw implants. A systematic review and meta-analysis.

BACKGROUND: The influence of low-level-laser therapy (LLLT) on the stability of orthodontic mini-screw implants (MSIs) has not been systematically reviewed. OBJECTIVES: The aim was to assess the influence of LLLT on the stability of orthodontic MSIs. METHODS: An unrestricted search of indexed databases was performed. SELECTION CRITERIA: Randomized controlled clinical trials (RCTs) investigating the influence of LLLT on orthodontic MSI stability. DATA COLLECTION AND ANALYSIS: Two authors independently performed study retrieval and selection, and data extraction. The risk of bias (RoB) of individual studies was assessed using the Cochrane RoB Tool for RCTs. Meta-analyses were performed separately for RCTs using periotest and resonance frequency analysis (RFA) to measure MSI stability; and a random effects model was applied. Subgroup analyses were performed based on the time-points of MSI stability evaluation. The quality of available evidence was evaluated using the Grades of Recommendation, Assessment, Development, and Evaluation approach. RESULTS: Initially, 1332 articles were screened. Six RCTs with a split-mouth design were included. The periotest was used in 4 RCTs and 2 RCTs used RFA to measure MSI stability. All RCTs had a low RoB. Subgroup analyses based on periotest indicated that MSIs treated with LLLT had significantly higher stability than untreated MSIs at 21 and 30 days [weighted mean difference (MD) = -2.76, confidence interval (CI): [-4.17, -1.36], P-value = 0.0001) and at 60 days (weighted MD = -3.47, CI: [-4.58, -2.36], P < 0.00001); and the level of certainty was high. Subgroup analyses based on RFA showed higher stability of MSIs treated with than without LLLT at 56 and 60 days (standardized MD = 0.82, CI: [0.32, 1.32], P = 0.001), and at 70 and 90 days (standardized MD = 0.86, CI: [0.36, 1.36], P = 0.0007); and the level of certainty was moderate. LIMITATIONS: Due to limited number of relevant studies, it was not possible to perform sensitivity analysis, subgroup analyses for patient and intervention-related characteristics, and reporting biases assessment. CONCLUSIONS: The role of LLLT on the secondary stability of MSIs placed in patients undergoing OT remains debatable. CLINICAL TRIAL REGISTRATION: PROSPERO (CRD42021230291).

Changes in Airway Dimensions Following Non-extraction Clear Aligner Therapy in Adult Patients with Mild-to-moderate Crowding.

AIM AND OBJECTIVE: This retrospective study aimed to assess changes in airway dimensions with non-extraction clear-aligner-therapy (NE-CAT) in adult patients with mild-to-moderate crowding. MATERIALS AND METHODS: Cone-beam computed tomographic images were evaluated for 24 adults (16 females and 8 males) with mild-to-moderate crowding, and Class I or mild skeletal Class II malocclusion before and after NE-CAT. Cross-sectional and volumetric airway measurements were performed at the level of the nasal cavity, upper pharyngeal airway space (UAS), and lower pharyngeal airway space (LAS). The Frankfort-mandibular plane angle (FMA), point A-nasion-point B (ANB) angle, and intermolar width were measured. A paired t-test was used to assess changes in airway measurements. Linear regression analyses were performed to identify predictors of the pharyngeal airway volume change at the levels of the UAS and LAS. RESULTS: There was a significant decrease (p = 0.004) in UAS mean volume (486.63± 752.73 mm3), LAS mean volume (p = 0.006), and cross-sectional airway area (p = 0.022) (1536.92± 2512.02 mm3 and 34.66± 69.35 mm2, respectively) with NE-CAT. The mean airway volume of the nasal cavity, mean cross-sectional airway areas of the nasal cavity and UAS, and mean minimum cross-sectional pharyngeal airway area did not change significantly with NE-CAT. Changes in pharyngeal airway volume were not significantly associated with patients' age, gender, treatment duration, pretreatment ANB angle, and changes in FMA and maxillary first intermolar width with NE-CAT. CONCLUSION: Significant changes in the pharyngeal airway dimensions of the UAS and LAS with NE-CAT in adult patients with mild-to-moderate crowding were identified. CLINICAL SIGNIFICANCE: The results of the present study show that NE-CAT is not associated with an improvement in airway dimensions in adults with mild to moderate crowding.

Patients' and parents' expectations of orthodontic treatment in university settings.

INTRODUCTION: The primary aim was to compare patients' and parents' orthodontic treatment expectations at the Eastman Institute for Oral Health, University of Rochester, Rochester, NY (UR) in the United States. Secondary aims were to assess the association between sociodemographic factors and UR participants' expectations; and compare participants' expectations between UR, Academic Centre for Dentistry Amsterdam (ACTA) and King's College Dental Hospital, London, United Kingdom (KC) (previously published data). METHODS: One hundred and forty participants [70 patients and one of their parents (n = 70)] completed a validated questionnaire (10 questions) to measure orthodontic treatment expectations before screening at the Orthodontic Department at UR. Various sociodemographic factors were assessed. The paired t test (for continuous responses) and the Fisher exact test (for categorical responses) were used to compare UR patients' and parents' responses. Two-sample t test and the Fisher exact test were used to compare participants' responses among sociodemographic groups. One-way analysis of variance followed by the Tukey test, and the Fisher exact test were used to compare participants' responses between UR, and ACTA and KC (data collected from previous publications). A multiplicity correction was performed to control the false discovery rate. RESULTS: Patients at UR expected less check-up and diagnosis, and less discussion about treatment at the initial visit, more dietary restrictions, and less improvement in smile esthetics and social confidence with orthodontic treatment than parents. Participants' responses differed by sociodemographic factors at UR and between UR, ACTA, and KC. CONCLUSIONS: Expectations of orthodontic treatment differ between patients and their parents, are associated with sociodemographic factors, and vary among United States and European University centers.

Influence of thyroxine supplementation on orthodontically induced tooth movement and/or inflammatory root resorption: A systematic review.

The role of thyroxine administration on orthodontically induced tooth movement and/or inflammatory root resorption remains unclear. The aim was to assess the influence of thyroxine administration on orthodontically induced tooth movement and/or inflammatory root resorption. The study protocol was registered in PROSPERO (CRD42020164151). An electronic search of indexed databases was conducted without time or language restrictions up to and including May 2020. The following eligibility criteria were imposed: (a) original prospective controlled clinical studies and/or experimental studies on animal models; (b) subjects undergoing orthodontic therapy with fixed appliances; (c) presence of a control group [orthodontic tooth movement without thyroxine administration]; and (d) intervention: orthodontic tooth movement with thyroxine administration. Review articles, commentaries, letters to the editor, case reports/series, studies with no control group, cross-sectional studies, retrospective studies and studies where thyroxine was administered along with other interventions such as calcitonin and prostaglandins were excluded. Quality of available evidence and risk of bias within studies were assessed. Any disagreements were resolved via consensus discussions. Based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, 8 animal studies were included. Four studies reported that thyroxine administration increases the rate of orthodontic tooth movement; 3 studies did not show a significant difference. Three studies showed that thyroxine administration decreases orthodontically induced inflammatory root resorption; 2 studies found no significant difference. The risk of bias among studies was high. In conclusion, the influence of thyroxine administration on orthodontic tooth movement and/or orthodontically induced inflammatory root resorption in animal models remains unclear.

Interdisciplinary Management of a Class III Anterior Open Bite Malocclusion in a Patient With Cerebral Palsy.

Dentofacial disharmony in patients with cerebral palsy (CP) can lead to low self-esteem and functional limitations. However, medical and behavioral challenges in patients with developmental disorders often prevent dental practitioners from offering the necessary treatment. This report describes the clinical interdisciplinary management of a 20-year-old man with CP, including orthodontic, periodontal, and orthognathic surgery therapy. The patient presented with the chief complaint of having difficulty chewing, was wheelchair dependent, had poor orofacial muscle control, and exhibited a Class III malocclusion with a skeletal anterior open bite. The lower midline was shifted 3 mm to the right, there was severe maxillary spacing, and the patient had gingival overgrowth. A combined orthodontic, periodontal, and orthognathic surgery treatment approach was chosen to meet the patient's interdisciplinary needs. Because of his physical limitations, it was necessary to avoid complicated and prolonged orthodontic treatment mechanics. Interdisciplinary therapy improved the patient's oral function, periodontal health, and facial esthetics and led to a good occlusion, which remained stable 1 year after treatment. Regardless of the treatment challenges, combined orthodontic and surgical therapy in the present patient with CP led to favorable treatment results and improved the patient's self-esteem, confidence in social interactions, and speaking and chewing abilities.

Long-term 3-dimensional stability of mandibular advancement surgery.

PURPOSE: To evaluate 3-dimensional changes in the position of the condyles, rami, and chin from 1 to 3 years after mandibular advancement surgery. MATERIALS AND METHODS: This prospective observational study used pre- and postoperative cone-beam computed tomograms of 27 subjects with skeletal Class II jaw relation and normal or deep overbite. An automatic technique of cranial base superimposition was used to assess positional and bone remodeling changes that were visually displayed and quantified using 3-dimensional color maps. Analysis of covariance with presence of genioplasty, age at time of surgery, and gender as explanatory variables was used to estimate and test adjusted mean changes for each region of interest. RESULTS: The chin rotated downward and backward 1 to 3 years after surgery. Changes of at least 2 mm were observed in 17% of cases. Mandibular condyles presented with displacements or bone remodeling of at least 2 mm on the anterior surface (21% of cases on the left side and 13% on the right), superior surface (8% on right and left sides), and lateral poles (17% on left side and 4% on right). Posterior borders of the rami exhibited symmetric lateral or rotational displacements in 4% of cases. CONCLUSION: In the hierarchy of surgical stability, mandibular advancement surgery is considered one of the most stable surgical procedures. However, 1 to 3 years after surgery, approximately 20% of patients had 2- to 4-mm changes in horizontal and vertical chin positions or changes in condylar position and adaptive bone remodeling.

Three-dimensional quantification of mandibular asymmetry through cone-beam computerized tomography.

OBJECTIVE: The aim of this study was to determine if 3-dimensional (3D) shape analysis precisely diagnoses right and left differences in asymmetry patients. STUDY DESIGN: Cone-beam computerized tomography (CT) data were acquired before treatment from 20 patients with mandibular asymmetry. 3D shape analysis was used to localize and quantify the extent of virtually simulated asymmetry. Two approaches were used: 1) mirroring on the midsagittal plane determined from landmarks; and 2) mirroring on an arbitrary plane and then registering on the cranial base of the original image. The validation presented in this study used simulated data and was applied to 3 clinical cases. RESULTS: For mirroring on the midsagittal plane, there was a >99% probability that the difference between measured and simulated asymmetry was <0.5 mm. For mirroring with cranial base registration, there was a >84% probability of differences <0.5 mm. CONCLUSIONS: Mandibular asymmetry can be precisely quantified with both mirroring methods. Cranial base registration has the potential to be used for patients with trauma situations or when key landmarks are unreliable or absent.

Prediction of lip response to four first premolar extractions in white female adolescents and adults.

OBJECTIVE: To develop models for predicting changes in lip position of Class I extraction patients. MATERIALS AND METHODS: Pretreatment and posttreatment lateral cephalograms of 46 white female adults and 109 white female adolescents were examined. Mean pretreatment ages for the adolescent and adult groups were 12.2 +/- 1.2 years and 23.0 +/- 8.5 years, respectively. Subjects were treated with conventional edgewise mechanics. Multivariate prediction models were derived from a randomly selected sample of 119 subjects and validated on the remaining 36 subjects. RESULTS: Adolescents demonstrated significant vertical and horizontal skeletal growth and treatment changes, while adults showed only small increases in anterior face height. While significant retraction of the upper and lower incisors occurred in both groups, the amounts were greater in adults than in adolescents. Ratios for horizontal hard tissue to soft tissue movements ranged from 1.4:1 to 1.1:1 and 1.3:1 to 1:1 for the upper (Ls) and lower (Li) lips, respectively. There were moderate relationships between horizontal lip and underlying hard tissue movements (correlations ranged from .57 to .78 for Ls and from .58 to .86 for Li). Multiple regressions to predict lip movements showed moderately strong relationships for the upper lip (R = .79 to .81) and strong relationships for the lower lip (R = .89 to .90). Two to three variables were necessary to predict vertical lip movements (R = .82 to .87). The validation sample showed no systematic biases and similar levels of accuracy. CONCLUSIONS: Upper and lower lip retraction in four first premolar extraction cases can be predicted with moderately high levels of accuracy in white female adolescents and adults.

Masticatory exercise as an adjunctive treatment for hyperdivergent patients.

OBJECTIVE: This retrospective study was designed to evaluate the morphologic effects of masticatory muscle exercise as an adjunctive therapy for hyperdivergent patients treated with fixed orthodontic appliances. MATERIALS AND METHODS: Three samples of 50 subjects were selected, including one sample treated with orthodontics combined with exercise, one sample treated with orthodontics only, and an untreated control sample. Subjects were matched on the basis of age, sex, mandibular plane angle (MPA), treatment duration, and treatment rendered. Patients in the treated exercise sample were instructed to clench their teeth together as hard as possible for 15 seconds and to repeat this process at least four times for a total of one minute; this one-minute exercise was to be performed as often as possible throughout the day. Morphologic data was derived from pre- and posttreatment lateral cephalograms. RESULTS: Exercise with orthodontics produced significant (P < .05) increases in overbite compared to orthodontics alone. However, changes in vertical facial morphology were not significantly different between the two treated samples. Relative to untreated controls, both treated samples showed significantly greater increases in the MPA (S-N to Go-Me), Y-axis, and the lower to total facial height ratio; the treated samples also showed significantly less true forward mandibular rotation than the untreated controls. CONCLUSION: Short-term clenching exercises performed daily are insufficient as an adjunct to traditional orthodontic treatment for correcting or controlling the vertical dimension.