The effect of different extraction sites upon incisor retraction

Occlusal stress distribution in the human skull with permanent maxillary first molar extraction: A 3-dimensional finite element study

INTRODUCTION

The objective of this research was to analyze the effect of orthodontic treatment with maxillary permanent first molar extraction on the occlusal stress distribution and displacement in the human skull.

METHODS

A 3-dimensional finite element model was constructed on the basis of a computed tomography scan, and it was used as the pretreatment model. The software used for geometric modeling was Solid Works (Dassault Systèmes, Paris, France). For the extraction model, the maxillary permanent first molar was removed, followed by a repositioning of the anterior and posterior segments to create a space closure model. Stress distribution was evaluated under the simulation of 1000 N for occlusal forces and 400 N for masseter muscle force.

RESULTS

The highest von Mises stress was observed at the zygomatic process of the temporal bone across all 3 models (25 MPa), whereas stress at the pterygomaxillary suture area was almost 50% less. However, the stress in the pterygomaxillary suture area was lowest in the extraction model (18%) and space closure (30%). Stress in the zygomatic process of the frontal bone and frontal process of the maxilla increased from pretreatment to extraction model followed by space closure model.

CONCLUSIONS

The occlusal forces were transferred through maxillonasal, maxillozygomatic, and maxillopterygoid stress trajectories. The mesial displacement of the molars may weaken the role of maxillopterygoid stress trajectory while strengthening the role of maxillonasal stress trajectory.

Keys to Class II correction: A comparison of 2 extraction protocols

INTRODUCTION

The purpose of this study was to evaluate the effects of 2 extraction patterns on incisor and molar movements in patients with growing Class II Division 1.

METHODS

The sample included 54 patients 10-17 years of age treated by 2 private practice orthodontists using Tweed directional force mechanics, 4 premolar extractions, J-hook headgears, and Class II elastics or Saif springs. The sample was divided on the basis of having maxillary and mandibular first premolars (4/4) or maxillary first and mandibular second premolars (4/5) extracted. Each group included 27 patients. Treatment lasted 2.8 ± 0.60 years and 2.6 ± 0.54 years for the 4/4 and 4/5 groups, respectively. Pretreatment (T1) and posttreatment lateral cephalograms and dental casts were evaluated. Cranial base, mandibular, and maxillary superimpositions were performed to quantify tooth movements and displacements.

RESULTS

There were no statistically significant T1 between-group differences in crowding or in the SNA, SNB, ANB, and MPA angles. Analyses of covariance, controlling for statistically significant (P <0.05) differences in T1 mandibular incisor position, showed that mandibular first premolars extractions produced greater (1.6 mm) mandibular incisor retraction than second premolar extractions. The mandibular first molars were protracted significantly more (0.7 mm) after the second premolar than the first premolar extractions. Within-group changes of the MPA, between-group differences in the changes in MPA, and the amount of vertical eruption of the maxillary and mandibular molars were not significantly different between the 2 extraction patterns.

CONCLUSIONS

Extraction of mandibular second premolars enhances Class II molar correction, with greater mesial first molar movement and less distal incisor movement. Neither extraction pattern has an effect on the MPA or the vertical dimension (ie, there was no "wedge effect").

A clinical comparative study using anchorage from mini-implants and conventional anchorage methods to retract anterior teeth

Background:

Proclined teeth has been one of the main reasons for compromised esthetics. In a patient with proclined anteriors, retraction is done after 1^st premolar extraction. Absolute/maximum anchorage is required to achieve the best esthetics.

Objective:

We conducted this study with the aim of retracting the proclined maxillary anterior teeth and to check for efficient retraction, type of tooth movement during retraction, and amount of anchorage loss.

Methods:

Patients with proclined anterior teeth where therapeutic extraction of first premolars is required were included in the study, where anchorage was taken with mini-implants in one group, and in the second group, conventional anchorage method of 1^st and 2^nd molar banding with TPA was chosen. Each group consisted of 8 subjects. Lateral cephalogram was taken both preretraction and 4 months after starting retraction to compare anchor loss, rate of retraction, and type of tooth movement of retracted anteriors, in both groups.

Results:

The retraction in the implant group was more than in the conventional group and the difference was statistically significant (P < 0.05). Anchorage loss was seen to be greater in conventional group than in the implant group and was also significant statistically. The type of tooth movement of the anterior teeth on retraction was also compared, with the implant group showing predominantly controlled tipping and the conventional group showing uncontrolled tipping movement.

Treatment of bimaxillary protrusion using intra- and extra-alveolar miniscrews associated to self-ligating brackets system

INTRODUCTION

Moderate and severe bimaxillary protrusion impair the passive lip sealing and the facial and smile esthetics. The extraction of premolars can be avoided by the use of skeletal anchorage to retract both dental arches. This approach brings many advantages such as: prevents premolars extraction; simplifies orthodontic mechanics; there is no volume reduction of a premolar when smiling; control of overbite and gingival exposure. The utilization of this therapeutic approach, when associated with self-ligating brackets, can bring the possibility of spacing the appointments without damage to the treatment efficiency, and allows selection of the most appropriate torque prescriptions for each case. The intra-alveolar miniscrews are indicated for mild cases of bimaxillary protrusion, while extra-alveolar miniscrews may also be indicated for more severe cases.

OBJECTIVE

To report the treatment of three cases of mild, moderate and severe bimaxillary protrusion, in which intra- and extra-alveolar miniscrews were used, according to the retraction required.

CONCLUSION

The retraction of both upper and lower dental arches using orthodontic intra- and extra-alveolar miniscrews, associated with self-ligating brackets, is an excellent tool to correct mild to severe bimaxillary protrusion, thus reducing the need of premolar extraction and simplifying the orthodontic management.

Molar Incisor Hypomineralisation-To Extract or to Restore beyond the Optimal Age?

The management of compromised first permanent molars (FPMs) in children presents a clinical challenge to the dental team. Hypomineralised FPMs in molar incisor hypomineralisation (MIH) conditions could undergo post-eruptive breakdown, making them susceptible to caries, leading to their subsequent loss. The planned extraction of compromised FPMs is a valid alternative to complex restorative treatment. However, establishing the presence or absence of third permanent molars, amongst other considerations, is crucial to reaching a successful outcome. Clinicians should understand the importance of an orthodontic examination around the age of 8 years old with regard to establishing a differential therapeutic decision about the ideal timing of MIH-affected FPMs’ extraction in children. The aim of this article is to highlight that, with an interdisciplinary approach, a good outcome can be achieved following the extraction of poorly prognosed FPMs. The most cost-effective way of addressing MIH-affected FPMs is extraction, followed by orthodontic space closure when indicated. This obviates the need for the repeated restorative replacement and saves perfectly healthy premolars from being extracted for space creation in orthodontic treatment in several clinical scenarios.

Evaluation of the airway space changes after extraction of four second premolars and orthodontic space closure in adult female patients with bimaxillary protrusion - A retrospective study

Background & objectives

Previous studies have found that first premolar extractions during orthodontic treatment may alter the upper airway dimensions. The objective of this study is to investigate the effects of second premolar extraction during orthodontic treatment on the dimensions of the upper airway in a sample of female adults.

Methods

Twenty-nine female adult patients with ages between 18 and 30 years old and incisor bimaxillary protrusion were included in this study. They were treated with comprehensive orthodontic treatment which included the extraction of four second premolars. Pre and post cephalometric radiographs were analyzed using Dolphin imaging software for changes in tongue length and height, soft palate thickness and length, the superior, middle, and inferior airway space, and vertical airway length. Descriptive statistics were used to characterize measurements. Student’s paired t-test was preformed to compare the pre- and post-test mean values of the dimensions.

Results

A significant increase in the vertical airway length was observed after the extraction of the second premolars (p = 0.02). The soft palate length showed a tendency towards an increase that did not reach statistical significance (p = 0.053). No other significant changes in the airway soft tissue measurements were observed. The proclination and protrusion of the upper and lower incisors were significantly decreased compared to pre-treatment measurements.

Interpretation & conclusions.

Orthodontic treatment involving the extraction of all four second premolars in females with bimaxillary protrusion increases the vertical airway length, which is the amount of distance between base of the tongue and posterior nasal spine. No other significant alterations in the upper airway measurements were observed.

Three-dimensional analysis of the physiologic drift of adjacent teeth following maxillary first premolar extractions

We assessed the three-dimensional (3D) pattern of the physiologic drift of the remaining adjacent teeth after premolar extraction due to orthodontic reasons and the associated factors. Data were collected from 45 patients aged 17.04 ± 5.14 years who were scheduled to receive a fixed appliance after maxillary premolar extraction. Seventy-five drift models were obtained and digitalized via 3D scanning. The average physiologic drift duration was 81.66 ± 70.03 days. Angular and linear changes in the first molars, second premolars, and canines were measured using the 3D method. All the examined teeth had tipped and moved towards the extraction space, leading to space decreases. Posterior teeth primarily exhibited significant mesial tipping and displacement, without rotation or vertical changes. All canine variables changed, including distal inward rotation and extrusion. The physiologic drift tended to slow over time. Age had a limited negative effect on the mesial drift of posterior teeth, whereas crowding had a limited positive effect on canine drift. Thus, the mesial drift of molars after premolar extraction may lead to molar anchorage loss, particularly among younger patients. The pattern of the physiologic drift of maxillary canines can help relieve crowding and facilitate labially ectopic canine alignment, whereas canine drift is accelerated by more severe crowding.

The extraction of first, second or third permanent molar teeth and its effect on the dentofacial complex

The extraction of permanent molar teeth was first introduced in 1976 as a substitution for premolar extraction in cases with mild crowding. Since then, a number of studies have investigated the effect of permanent molar extraction on dentofacial harmony. Undertaking the procedure of molar extraction is most commonly recommended in response to factors such as: gross caries, large restorations and root-filled teeth, along with its application in the management of anterior open bite and reduction in crowding in facial regions. It has been indicated, however, that before undertaking the extraction of molar teeth it is important to investigate the potential influence of the procedure on other molars, with particular consideration of their eruption path. This is due to the doubt as to the effect of the exact molar teeth extraction and their consequences. In light of this, This review was undertaken to investigate and compare the effect of first, second and the third molar teeth extraction and their subsequent dentofacial complex changes.

Effect of incisor retraction on facial aesthetics

Incisor retraction may result in lip retraction, interlabial gap closure and increase of the nasolabial angle but a clear consensus on the effect of incisor retraction on facial aesthetics has not yet been achieved. Despite current evidence being weak, it seems to indicate that in a well-managed orthodontic case, with or without extractions, the soft-tissue and facial aesthetic changes are generally favourable or clinically insignificant.

Efficacy of the Nance appliance as an anchorage-reinforcement method

INTRODUCTION

The Nance appliance is widely considered to be an efficient method of anchorage reinforcement; however, much of the perceived advantage is based on clinical judgment. The aim of this study was to assess the amounts of anchorage loss and desired tooth movement associated with the Nance appliance.

METHODS

The mandibular arches of 7 beagle dogs were used. The first and third premolars were extracted. Reference miniscrews were placed at the first premolar sites as stable references to measure the amounts of anchorage loss and desired tooth movement. Four beagles were fitted with custom-made Nance appliances on the fourth premolars and orthodontic bands on the second premolars (Nance group). Three beagles were fitted with orthodontic bands on the second and fourth premolars with no anchorage reinforcement (control group). The second premolars were retracted over 15 weeks in both groups. The amounts of second premolar movement (desired tooth movement) and fourth premolar movement (anchorage loss) were recorded at 5, 10, and 15 weeks. The percentages of desired tooth movement and anchorage loss to the total space closure were calculated.

RESULTS

The mean desired tooth movement was significantly more in the Nance group than in the control group at 10 weeks (P <0.05) but was not significantly different at 5 and 15 weeks. The mean percentages of anchorage loss to the total space closure at 15 weeks were 45.7% in the control group and 28.8% in the Nance group. The Nance group had 16.9% less anchorage loss and 16.6% more desired tooth movement than did the control group at 15 weeks (P <0.05). Most of the anchorage loss (80%) in the Nance group occurred during the first 10 weeks.

CONCLUSIONS

The Nance appliance did not provide absolute anchorage, but there was significantly less anchorage loss with it than in the control group. The majority of anchorage loss occurred during the first 10 weeks in the Nance group.

Comparative evaluation of sagittal anchorage loss in lingual and labial appliances during space closure: A pilot study

Aim

The purpose of this investigation was to assess and compare the anchorage loss between labial and lingual appliance systems during space closure.

Materials and Methods

Twenty subjects were part of the study among which 10 subjects (mean age 21 ± 3.6 years) were treated using lingual appliance system (0.018” slot-STb™) and 10 subjects (mean age 19 ± 6.1 years) were treated using labial preadjusted edgewise appliance system (0.018” slot-MBT™). First premolar extractions were performed to enable retraction of anterior teeth. Lateral cephalometric radiographs were taken at two intervals, before starting space closure and after space closure that were connoted as T0 and T1 and were analyzed using the method described by Pancherz to measure anchorage loss. Intraclass correlation coefficient (ICC) was used to evaluate intraexaminer reliability of the measurements. Student’s t-test was performed to verify any statistical significant correlation between the labial and lingual appliance systems. Statistical differences were determined at the 95% confidence level (P < 0.05).

Results

The results showed that all ICC for lingual and labial group were ≥0.90 showing good repeatability of the measurements. Mean anchorage loss of 1.238 ± 0.17 mm in lingual appliance system and an anchorage loss of 2.06 ± 0.39 mm occurred with the labial appliance system. On the comparison between the two appliance systems, lingual appliance demonstrated a significantly lesser anchorage loss than did the labial appliance.

Interpretation and Conclusion

This prospective study concludes with the fact that lingual appliance provided better anchorage control than labial appliance during space closure. Use of lingual appliance could be considered in critical anchorage cases when compared with labial appliance.

Effects of first premolar extraction on airway dimensions in young adolescents: A retrospective cephalometric appraisal

OBJECTIVE

To evaluate the upper airway dimensions in adolescents treated for bimaxillary proclination with first premolar extraction.

MATERIALS AND METHODS

A retrospective cephalometric evaluation was carried out on the available pre and post orthodontic treatment records of 150 patients (12-18 years of age) who had bimaxillary proclination and were treated with fixed orthodontic therapy. Cephalometric landmarks for sagittal airway measurements and hyoid bone were identified; linear and angular measurements were obtained. Descriptive statistics using paired t-test was used to assess changes in pre and post treatment values and Pearson's correlation coefficient was calculated to evaluate the reliability of observations. The method error calculations were performed using the Dahlberg formula.

RESULTS

It was observed that the mean values of nasopharyngeal dimension and Total Airway Length (TAL) showed no statistically significant difference in pre and post treatment groups. All other airway and hyoid parameters showed statistically significant difference. Pearson's correlation coefficient showed statistically significant correlations in all the airway and hyoid parameters.

CONCLUSIONS

In the present study, the nasopharyngeal dimension and TAL were not found to be directly affected by the retraction of anterior teeth, This can be attributed to the fact that nasopharyngeal dimension and TAL are not under direct influence of tongue position. The other findings also indicated direct correlation of tongue position to oropharynx and hypopharynx. Consequently, we emphasize clinically relevant anatomic risk factors that should be given prime importance and serious consideration on the decision whether to extract or not in growing patients.

Treatment time, outcome, and anchorage loss comparisons of self-ligating and conventional brackets

OBJECTIVE

To compare the treatment time, outcome, and anchorage loss among orthodontic patients treated by self-ligating brackets (SLBs) and conventional brackets (CBs).

MATERIALS AND METHODS

A retrospective cohort study compared 34 patients (SLB group) treated by SmartClip brackets (3M Unitek, Monrovia, Calif) to 35 patients (CB group) treated by conventional preadjusted Victory series brackets (3M Unitek) and ligated by stainless steel wire ligatures. Pretreatment (T1) and posttreatment (T2) lateral cephalograms were traced and analyzed using Pancherz sagittal-occlusion analysis to obtain skeletal and dental changes in the maxilla and the mandible. The dental cast models were assessed by the Peer Assessment Rating (PAR) Index for the treatment outcomes.

RESULTS

The mean treatment time for SLBs (19.19 months) did not show a statistically significant difference from 21.25 months of CBs; the treatment time and pretreatment PAR scores were strongly correlated. There was no difference in anchorage loss between the SLB and CB groups. There were significant dental and skeletal changes among adolescent orthodontic patients regardless of the bracket used. The lingual inclination of the mandibular incisors in the CB group was 3.62° more than in the SLB group (P < .01).

CONCLUSIONS

The treatment time and anchorage loss are not influenced by the type of bracket used. There are significant dental and skeletal changes among adolescent orthodontic patients regardless of the bracket used. There is significantly greater lingual inclination of mandibular incisors in the CB group than in the SLB group.

Atypical orthodontic extraction pattern managed by differential en-masse retraction against a temporary skeletal anchorage device in the treatment of bimaxillary protrusion

This report introduces an innovative treatment approach of selecting atypical and unconventional teeth for orthodontic extraction without compromising the quality of treatment outcomes by using temporary skeletal anchorage devices in patients with bimaxillary protrusion. Both patients introduced in this report had solid Class I molar relationships with bimaxillary anterior protrusion without facial or dental midline asymmetry. Their chief concerns were significant facial convexity, which conventionally requires the extraction of all 4 first premolars. However, 3 second premolars and 1 first premolar were removed in the first patient, and 2 second premolars and 2 first premolars were removed in the second patient. All second premolars extracted had previously had root canal treatment and large prosthodontic restorations, which resulted in a compromised short lifespan of the teeth relative to the natural dentition. To manage these cases of asymmetric extraction space in a symmetric dental and skeletal environment, 2 mini-implants were placed in the posterior maxillary interradicular spaces, 1 on each side. Despite the unusual asymmetric extraction of teeth, superimposition of the pretreatment and posttreatment cephalometric tracings shows excellent treatment outcomes of facial convexity reduction by asymetric maximum retraction of the anterior teeth with no change in the molar relationships.

[Predictive factors of third molar eruption]

INTRODUCTION

We studied the prognosis of upper and lower third molar evolution.

PATIENTS AND METHODS

Seventy-eight patients were included after a clinical examination, dental casts, panoramic and lateral cephalometric radiographs on inclusion (T1) and two years after (T2). Five parameters were studied: retromolar space (RMS) between the third molar (M3) and the anterior ridge of the ramus; RMS/M3 crown diameter ratio, distances (PTV-M(1)) and (X(i)-Mi(2)); and third molar angle with occlusal plane.

RESULTS

They were noted at T1 and T2. The gain of retromolar space from T1 to T2 reached 1.2 to 2.2mm without extraction, 2 to 2.7mm with PM extraction, and 4.5 to 6.8mm with M1 extraction. The "RMS/M3 diameter" ratio increased in the maxilla from 0.6 to 0.8 and from 0.5 to 0.8 in the mandible (P=0.01) between T1 and T2. PTV-M1 increased significantly from 17.1 to 19.9mm (P<0.001), and Xi-M2i increased significantly from 18.5 to 22.4mm (P<0.001) between T1 and T2.

DISCUSSION

The extraction of premolars has little influence on the variation of the retromolar space; conversely first molar extraction increases that space. Prognosis techniques for the evolution of third molars are helpful when considering avulsion.

Comparison of anchorage capacity between implant and headgear during anterior segment retraction

Objective:

To compare the anchorage effects of the implants and the headgear for patients with anterior teeth retraction in terms of incisor retraction, anchorage loss, inclination of maxillary incisors, positional change of maxillary basal bone, and treatment duration.

Materials and Methods:

An electronic search for relative randomized controlled trials (RCTs) prospective and retrospective controlled trials was done through the Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, Embase, Medline, and CNKI, regardless of language of study. Study selection, methodological quality assessment, and data extraction were performed by two reviewers independently. Meta-analysis was performed when possible; otherwise descriptive assessment was done.

Results:

The search yielded 35 articles, of which eight met the inclusion criteria and were categorized into five groups according to types of intervention. For the midpalatal implant, the anchorage loss was much less than for the headgear group, with insignificant differences in terms of anterior teeth retraction, maxillary incisor inclination, positional change of basal bone, and treatment duration. For the mini-implant, greater anterior teeth retraction and less anchorage loss were demonstrated, with inconsistent results for the other measures. For the onplant, less anchorage loss was noted, with insignificant differences for the other measures.

Conclusions:

The skeletal anchorage of the midpalatal implant, mini-implant, and onplant offer better alternatives to headgear, with less anchorage loss and more anterior teeth retraction. There were inconsistent results from the included studies in terms of maxillary incisor inclination, positional change of maxillary basal bone, and treatment duration. More qualified RCTs are required to provide clear recommendations.

Compromised first permanent molars: an orthodontic perspective

The first permanent molar (FPM) is commonly subject to significant compromise which may arise due to caries or endodontic complication, or from developmental anomalies such as hypoplasia. Compromised teeth with questionable prognosis may result in short and long-term clinical dilemmas. This review article highlights the factors that require careful consideration when a compromised FPM is detected and the importance of timely FPM extraction. Several clinical cases are described in detail to discuss possible treatment options from the orthodontic perspective.

Extrações dentárias em Ortodontia: avaliação de elementos de diagnóstico

Algumas más oclusões exigem do ortodontista capacidade de diagnóstico para decidir pela melhor maneira de tratar o paciente. O objetivo dos autores deste artigo foi apresentar casos clínicos e discutir alguns elementos de diagnóstico utilizados na elaboração do plano de tratamento, auxiliando na decisão de extrair dentes. Foi dada ênfase em cada elemento de diagnóstico: aspectos relacionados à cooperação, discrepância de modelo, discrepância cefalométrica e perfil facial, idade esquelética (crescimento) e relações anteroposteriores, assimetrias dentárias, padrão facial e patologias. Sugere-se que a associação dos aspectos citados é importante para a decisão correta. Todavia, algumas vezes, uma característica, por si só, pode definir o plano de tratamento.

[Not Available]

Various factors participate to lower third molar eruption included premolar extractions. In Class II division 1 malocclusion, premolar extractions are sometimes decided to correct antero-posterior malocclusion. Alternative therapies without extractions exist such as DAC appliance. What is the influence on third molar eruption of extractions and non extractions in Class II division 1 malocclusion?

MATERIAL AND METHODS

We made a study with 60 subjects with Class II division 1 malocclusion: 30 were treated without extractions and 30 were treated with 4 extractions (included second lower premolars). We observed the evolution rate of third lower molars, the movement in the mandible and the modifications on lower arch.

RESULTS

Extractions of second lower premolars increase the possibilities of third lower molars eruption (that increase from 10% to 50%).

DISCUSSION

Like in others publications, extractions of second lower premolars, more than the first, may increase significantly the evolution rate of third molars. Nevertheless, inclusion risk is not reduced and is still important (50% in our study) with the probability that the treatment leads at the end to extractions of a quart of dental capital of the patients.

En Masse Retraction and Two-Step Retraction of Maxillary Anterior Teeth in Adult Class I Women

Objective: To compare the amount of anchorage loss of the maxillary posterior teeth and amount of retraction of the maxillary anterior teeth between en masse retraction and two-step retraction of the anterior teeth.

Materials and Methods: The sample consisted of 30 female adult patients with Class I malocclusion and lip protrusion who needed maximum posterior anchorage. The sample was subdivided into group 1 (n = 15, mean age = 21.4 years, en masse retraction) and group 2 (n = 15, mean age = 24.6 years, two-step retraction). Lateral cephalograms were taken before (T1) and after treatment (T2). Nine skeletal and 10 anchorage variables were measured, and independent t-test was used for statistical analysis.

Results: Although the amount of horizontal retraction of the maxillary anterior teeth was not different between the two groups, there was mild labial movement of the root apices of the upper incisors in group 2 at T2. There were no significant differences in the degree of anchorage loss of the maxillary posterior teeth between the two groups. Bodily and mesial movements of the upper molars occurred in both groups. Approximately 4 mm of the retraction of the upper incisal edges resulted from 1 mm of anchorage loss in the upper molars in both groups.

Conclusion: No significant differences existed in the degree of anchorage loss of the upper posterior teeth and the amount of retraction of the upper anterior teeth associated with en masse retraction and two-step retraction of the anterior teeth.

Running loop in unusual molar extraction treatment

Running loops have been used in mandibular second premolar extraction treatment instead of cherry or shoehorn closing loops in the Tweed technique. They can also be used when molar extraction patterns are unusual or if molars are missing or hopeless, or have extensive restorations. A running loop archwire is usually made of 0.018 x 0.025-in stainless steel, with a helical loop 5 mm mesial to the buccal tube. The effective tipback is usually about 20 degrees to 30 degrees to upright molars, and a slight toe-in is necessary to prevent mesiolingual rotation. As the extraction space closes, the distance between the running loop and the buccal tube is shortened. Then a helical loop can be moved mesially to maintain the distance and the force between them by simple archwire manipulation. Consequently, the extraction space can be closed with 1 running loop archwire after initial leveling.

Changes in mandibular third molar angle and position after unilateral mandibular first molar extraction

INTRODUCTION

Third molars often become impacted because of lack of space for their eruption. Because the third molars play an important role occlusally, premolars or second molars are sometimes extracted to create space. First molars are seldom extracted to create space, but they are occasionally extracted for other reasons, especially caries. The aim of this study was to investigate the spontaneous angular and positional changes in mandibular third molars when mandibular first molars are extracted.

METHODS

The sample consisted of panoramic radiographs of 107 patients (age, 18-40 years; mean, 25.69 years) who had unilateral mandibular first-molar extractions (because of caries) before age 16. Ramus relationship, impaction depth, and angulation of third molars on the extraction and nonextraction sides were assessed. A chi-square test was performed to compare the differences.

RESULTS

The prevalence of third molars at the anterior border of the mandibular ramus was significantly greater on the extraction side than on the nonextraction side (P < .001). Third molars were positioned more occlusally in the mandible on the nonextraction side than on the extraction side (P < .001). The prevalence of vertically angulated third molars was greater on the extraction side than on the nonextraction side (P < .001).

CONCLUSIONS

Mandibular first-molar extraction increases the space for mandibular third-molar eruption and helps the third molars move into better positions. But early extraction can lead to uncontrolled tipping of adjacent teeth into the extraction space. Only third-molar angle and position were evaluated in this study; problems such as dental asymmetry, premature contacts, and uncontrolled tipping should be assessed in the future.

Is orthodontic treatment without premolar extractions always non-extraction treatment?

While it is common in contemporary orthodontic and orthopaedic treatment to commence treatment for many growing patients during the mixed-dentition, the creation of anterior space, often involving the attempted distalization or holding-back of the upper and lower permanent molar teeth has been shown to commonly result in posterior space deficiencies. Although the extractions of permanent premolar teeth may have been avoided, the developing second and third permanent molars are often affected, so that third molar impaction results in many cases. This is not to say that orthodontic treatment carried-out without premolar extractions is not ideal in many cases, but on the available evidence, so-called absolute 'non-extraction' protocols should be questioned, so that both the dental profession and the public at large are not misled.

For four sixes

This article reviews the literature on orthodontic treatment involving extraction of first molars and highlights many of the clinical considerations when treating such cases. Case reports illustrate the potential problems and indicate some solutions.

An occlusal and cephalometric analysis of lower first and second premolar extraction effects

This study was designed to examine lateral cephalometric and arch dimensional changes that occur in the mandibular arch during orthodontic treatment involving the extractions of various premolars. Pretreatment and posttreatment records of 73 patients were chosen at random from completed cases in the practice of one experienced orthodontist. Eighteen involved the extraction of lower first premolars, and 55 involved the extraction of lower second premolars. Of these 55, 29 involved the extraction of upper first premolars and 26 involved the extraction of upper second premolars. In the lower first premolar group, however, all 18 involved the extraction of upper first premolars. Males and females were evenly represented in the 3 subgroups. Pretreatment factors that suggested a basis for the extraction choice in this group of patients were found to include incisal overjet, molar relationship, and underlying vertical facial pattern. A wide variety of arch dimensional changes was found with different lower premolar extraction patterns. There was evidence, however, of more intermolar arch width reduction after the extraction of lower second premolars than lower first premolars. Orthodontic treatment with the extraction of premolars did not consistently cause a retrusive effect on the incisors. In fact, instances of proclination of the incisors occurred within all of the extraction groups. A large amount of individual variation in incisor and molar changes accompanied treatment involving all lower premolar extraction patterns.

A longitudinal evaluation of extraction versus nonextraction treatment with special reference to the posttreatment irregularity of the lower incisors

A tendency exists in contemporary orthodontics to pursue a completely non-extraction philosophy. Moreover, it has been shown that the extraction versus non-extraction debate is still with us. Controversy exists as to which treatment decision will eventually lead to orthodontic stability. It is thus imperative to conduct investigations on long-term changes of the dentition in both treatment regimens. The present study serves as an example of such a longitudinal study. A random sample, inclusive of both extraction and non-extraction treatments, was examined with respect to long-term stability and an assessment was made as to whether one treatment option favors success over the other. It was concluded that the correct initial treatment choice will not only lead to correction of the malocclusion, but will also ensure clinically acceptable stability with no significant differences between extraction and non-extraction treatments.

Treatment strategies for lower third molars following orthodontic care

To examine the extent to which orthodontists consider it appropriate to refer post-orthodontic patients for lower third molar treatment. The subjects were 10 orthodontists from hospital, specialist practice and community setting. Participants were presented with 15 case histories of orthodontic patients (including full records) and asked to state whether they would have referred the case to an oral surgeon for management of their third molars. Data were analysed using multi-kappa measure. Two-hundred-and-sixty-two decisions of 300 (88%) were not to refer cases for third molar management. Little consensus was seen between orthodontists on which post-orthodontic cases referral (kappa = 0.14). Some clinicians referred cases much more frequently than others (Kruskall-Wallis = 46.84, P < 0.001) and some clinicians referred much more frequently (Kruskall-Wallis = 85.57, P < 0.001). This group of orthodontists did not refer post-orthodontic cases for third molar management and little consensus was observed regarding which cases did warrant removal.

Differential premolar extractions

The primary object of this research project was to establish the amount of incisor retraction to be expected during full fixed mechanotherapy and to generate regression models that could provide more accurate prediction of each of the three most popular combinations of symmetrical premolar extractions, where extraoral anchorage would not be used. Pretreatment and posttreatment records of 73 cases that had their four first premolars extracted (group 44), 74 cases with four second premolar extractions (group 55), and 59 cases with upper first and lower second premolar extractions (group 45) were selected. All these cases were treated by one orthodontist, who used the same edgewise technique throughout. The results indicate that, on average, maxillary retraction in relation to the facial plane (N Po) differed only slightly between group 55 (mean 4.2 +/- 2.4 mm) and group 44 (mean 4.7 +/- 2.3 mm), with relatively more retraction for group 45 (mean 6.6 +/- 2.5 mm; p < 0.05). In contrast, the mandibular incisors were retracted slightly more in group 44 than in the other two groups (p < 0.05). The regression models that were developed could be useful as an additional tool to assist the practitioner in the selection of which teeth to extract for a particular case.

A comparison of results of second molar and first premolar extraction treatment

The purpose of this study was to examine treatment results of maxillary and mandibular second molar extraction cases and compare them with treatment results of maxillary and mandibular first-premolar extraction cases. Records of 22 maxillary and mandibular second-molar extraction cases and 22 maxillary and mandibular first-premolar extraction cases were evaluated. For each case, pretreatment and posttreatment lateral cephalograms were traced and several cephalometric parameters were compared. From the pretreatment and posttreatment panoramic radiographs, angulations of the maxillary and mandibular third molars were evaluated. Average treatment time, in months, was recorded for both groups. The data obtained from each group were analyzed for statistical difference. The results showed that the two groups had fewer differences than indicated by advocates of second-molar extractions. Analysis of the cephalometric data demonstrated only a few statistical differences between the groups. The maxillary and mandibular incisors in the premolar group were retracted a significantly greater amount than in the second-molar group. The maxillary and mandibular first molars were protracted a greater amount in the premolar group than in the second-molar group. The lower lips in the premolar group were retracted a greater amount than in the second-molar group. The resulting facial profile after extraction of second-molars appears to be no different from that obtained after extraction of first premolars. The pantographic evaluation of the changes in third-molar angulation were not statistically different. In both groups, the maxillary third molars showed an improvement in third-molar angulation, while the mandibular third-molars showed an undesirable increase in angulation. The average treatment time for both groups was not statistically different.

Clinical experience with third molar orthodontics

An orthodontic uprighting technique for effective treatment of impacted third molars, exposed or unexposed, is described. When used with conventional fixed appliances, this technique presents a viable option to extraction or prediction of eruption. Several applications illustrate that, with proper intervention, this uprighting technique is simple and effective in positioning malposed third molars.

The effects of three methods of orthodontic appliance therapy on some commonly used cephalometric angular variables

This investigation was undertaken to study the effects of the Andresen activator functional appliance therapy, Begg therapy, and cervically directed extraoral forces upon several commonly used cephalometric angular variables, with particular reference to the relationship between the maxillary plane (palatal plane) and anterior cranial base as represented by SN line. The material consisted of 107 cases taken from the files of patients who had attended the Orthodontic Department, Eastman Dental Hospital, London. Ninety of the cases had received orthodontic treatment. For each case pretreatment, posttreatment, and postretention radiographs were traced and angular measurements made by means of a Lysta-Dent digitizer linked to an on-line computer. Descriptive statistics and one-sample and two-sample Student's t tests were performed. None of the treatment methods under investigation had a clinically significant effect upon the maxillary plane. An increase in the inclination of the mandibular plane was a feature of Begg and headgear therapies but not of Andresen therapy. Any increase observed was of a temporary nature. While no change in SNA occurred with Andresen therapy, Begg and headgear therapies produced a permanent reduction in the variable. A small reduction was also produced in SNB by Begg and headgear therapies. The behavior of SNB following Andresen therapy was not significantly different from that in the group of untreated subjects. Each appliance method produced a permanent reduction in ANB; however, a similar reduction was also demonstrated in the control group.

Second molar extractions: a review

In this exhaustive review, a number of parameters related to maxillary and mandibular second molar extractions are discussed. The parameters reviewed include the timing of extractions and the effect of extractions on third molar eruption, posterior interdigitation, and incisor imbrication. The advantages and limitations of this procedure are outlined. The available information strongly suggests that the extraction of second molars relieves crowding in the posterior part of the arch, causes faster eruption of third molars, and diminishes the number of unerupted and/or impacted third molars. Consideration of the decrease in the number of impacted third molars after second molar extraction should be balanced with the fact that the extracted teeth are usually sound and are unimpacted. In addition, the third molars that do erupt frequently are poorly angulated and/or in poor contact with the first molars. This will necessitate an additional "late" period of fixed-appliance therapy to bring these teeth into good occlusion.

Single arch extraction--upper first molars or what to do when nonextraction treatment fails

The logical goal of treatment must be to correct a malocclusion to the nearest possible approach in all respects to a normal condition as we understand it. When extraction within the upper arch only is the desired treatment plan, removal of two upper first molars will produce the closest approach to normalcy in terms of the dentition's function, its health, its influence on facial features, and its appearance. With the removal of upper first molars for treatment purposes, the result will be a dentition that has all the magnificent appearance of a dentition that never had any extractions at all. It will be a dentition that can have good functional movements at the end of treatment and on into the posttreatment period.

A radiographic evaluation of the response of previously avulsed teeth and partially avulsed teeth to orthodontic movement

Orthodontic movement, as documented in this study, can be accomplished successfully in the case of completely avulsed and partially avulsed teeth which have been reimplanted. These teeth respond to normal orthodontic forces and duration of treatment time by conventional orthodontic techniques and retention. Apical root resorption does occur more readily in these teeth before, during, and after orthodontic treatment. Six of the eighty-one involved teeth were lost because of complete root dissolution. The involved teeth which were reimplanted immediately without pulpal treatment and their integrity protected as living tissue were successfully treated orthodontically with no known losses as of this writing. It will be interesting to observe the tissue response of these avulsed teeth in the years ahead. How will time and circumstances deal with these teeth?

The effects on the lower third molar of the extraction of the lower second molar

A survey was carried out on 60 patients for whom lower second molar removal had been recommended at least 5 years previously, no other treatment being indicated in the lower arch. Of the 114 teeth recommended for removal, only 84 were extracted. Eighty four per cent of third molars erupted satisfactorily, where second molars had been extracted, while only 36 per cent of third molars erupted into good occlusion where the recommended extractions had not been carried out. In the extraction group, factors associated with a poor result were lack of third molar root formation at the time of removal of the second molar and space between the third molar crypt and the lamina dura of the second molar.