Prenatal indices for mandibular retrognathia/micrognathia

Journal of Orofacial Orthopedics / Fortschritte der Kieferorthopädie - Micro- and retrognathia of mandibular origin may lead to life-threatening respiratory problems in connection with...     

Retrospective study of clinical complications during orthodontic treatment with either a removable mandibular acrylic splint Herbst or with a cantilever Herbst

Objective:To compare the clinical complications during treatment with either a removable mandibular acrylic splint (RMS) or with a cantilever (HC) Herbst appliance.Methods:Records from 159 Class II, division 1, consecutively treated patients with a Herbst appliance were examined. The sample was composed of 82 male and 77 female patients with a mean age of 11.8 years. The Herbst appliance was used for a mean of 12 months (standard deviation 2.15 months). Two main Herbst groups were analyzed: group RMS (n  =  125) and group HC (n  =  34). They were further subdivided according to the telescopic system used (Dentaurum type 1 or PMA) and fixation mode (splint with crowns or Grip Tite bands). Patients'' clinical records were assessed to identify clinical complications.Results:The incidence of complications during treatment was 85.3% for the HC group and 88.0% for the RMS group, with no statistically significant difference (Mann-Whitney test, P > .05). The fixation mode (crown or band) also did not show a statistically significant difference (P > .05). Regarding the telescopic system used, the Dentaurum group had 2.9 times more susceptibility to complications than the PMA group, regardless of the Herbst type.Conclusions:On average, approximately 2.5 complications per patient were reported. Most patients had a maximum of three complications during Herbst treatment. Herbst appliance type (RMS or HC) and fixation mode (crowns or Grip Tite bands) did not influence the number of complications. The PMA (without screws) telescopic system seemed to be more reliable (regarding the number of complications) than Dentaurum type 1, regardless of the appliance design (RMS or HC).     

正畸治疗中磨牙的拔除和保留（四十一）——减数磨牙替代常规减数前磨牙矫治的可行性研究

目的：探讨减数磨牙替代常规减数前磨牙矫治的可行性。方法：60例减数磨牙矫治病例再评价,按传统的设计认定42例可归于减数前磨牙模式,占70％。其中男12例,女30例;年龄15～40岁,平均26岁;安氏Ⅲ类18例、安氏Ⅱ类11例、安氏Ⅰ类13例。采用直丝弓矫治器矫治。矫治方法均采用颌间分段分次先Ⅲ类后Ⅱ类牵引进行矫治。结果：矫治期最短7个月,最长28个月,平均18个月。全部病例均获得理想的侧貌改变。前牙覆[牙合]覆盖正常,建立尖牙、磨牙的中性关系和良好的尖窝锁结关系。结论：设计减数磨牙矫治并保全28个牙齿的治疗理念对于解决牙弓后段存在的问题及避免减数前磨牙的弊端优势显著。     

Postretention relapse of mandibular anterior crowding in patients treated without mandibular premolar extraction.

Treatment stability is one of the most important objectives in orthodontics, but, despite decades of research, it is still agreed that the stability of aligned teeth is variable and largely unpredictable. This study aimed to evaluate the relapse of mandibular anterior crowding in patients treated without mandibular premolar extraction. The sample comprised 40 patients of both sexes with Class I or II malocclusions who received nonextraction treatment in the mandibular arch with edgewise mechanics. Lateral cephalograms and dental casts of each patient were obtained at pretreament, posttreatment, and 5 years postretention. Relapse of mandibular anterior crowding was assessed, and associations between this relapse and other clinical factors were also investigated. Mandibular anterior crowding was measured by the Little irregularity index, and the data were evaluated by the Mann-Whitney test. The mean relapse of mandibular anterior crowding was 1.95 mm (26.54%) over the long term. No clinical factor studied was predictive of crowding relapse in the long term.     

Comparison of treatment of mandibular retrognathia by functional regulators and activators

A tele-roentgenological longitudinal examination in 46 patients suffering from mandibular retrognathia analysed over a period of 2.35 years the development within the range of their facial skeleton. 24 patients had been treated by the regulator of function acc. to Fr?nkel, 20 patients by means of activators. Compared with the activator-treated group, the group treated by regulators of function offered an improved sagittal development of the lower jaw, an increased forward rotation of the lower jaw and a stable development of the lower region of incisors.     

The effect of mandibular first premolar extraction on third molar space

Change in molar space is compared in 48 mandibular first premolar extraction cases and 46 non-extraction cases over a five year period. Significantly greater increase in molar space is found in extraction cases. It is, to some extent, related to the initial degree of crowding.     

Herbst treatment with mandibular cast splints—revisited

Objective:The objective of this study was to reassess the dento-skeletal treatment effects and the amount of anchorage loss during reduced mandibular splint (RMS) Herbst treatment.Materials and Methods:One hundred consecutive Class II patients treated with a RMS-Herbst appliance were analyzed. The mean pretreatment age of the patients was 14.5 years, and the mean treatment time with the Herbst appliance was 8.1 months. Both before (T1) and after (T2) Herbst treatment a cephalometric measurement of lower incisor inclination, a sagittal occlusion analysis, and a dental cast analysis were performed. A comparison was performed with a historic Herbst control group treated with total mandibular cast splints (TMS).Results:During treatment the lower incisors proclined markedly (12.9° ± 4.6°). The amount of incisor proclination in the RMS group was, on average, 3.6° larger (P < .001) than in the TMS group. The lower incisor proclination increased from 11.9° (prepeak) to 14.3° (young adult). The level of professional experience of the practitioners performing the treatment did not influence the amount of incisor proclination significantly. The total available space in the lower arch increased by an average of 1.8 mm, and a space opened between the lower second premolars and lower permanent first molars in 62% of the present RMS-Herbst (average of 0.4 mm per side).Conclusions:Treatment with RMS-Herbst appliances leads to higher proclination of the lower incisors than does treatment with TMS-Herbst appliances; it also leads to an overall larger amount of anchorage loss.     

The mandibular first premolar as an abutment for distal-extension removable partial dentures: a modified clasp assembly design

Sound mandibular first premolars can be used as sole abutments for bilateral distal-extension removable partial dentures, if the denture is designed to minimise the torque applied to the abutment teeth. A simplified modification of the conventional torque-releasing clasp-assembly designs is suggested for these teeth. This modification entails a mesial rest on each abutment tooth connected to the distal proximal plate via a lingual bracing arm. A circumferential clasp arm is optional for buccal retention of the removable partial denture. As with conventional designs, the metal framework is designed to permit some rotational tissueward movement of the distal extension bases, yet not compromise the retention and stability of the prosthesis.     

减数下颌2个前磨牙矫治成人骨性反牙合的临床研究

目的评价采用减数下颌2个前磨牙矫治成人骨性反牙合病例的临床效果。方法选择18～30岁骨性反牙合临界病例18例,拔除下颌2个第一或第二前磨牙,分析治疗前后X线头颅侧位片各项指标的变化。结果所有病例在矫治结束后磨牙均变为完全Ⅲ类关系,尖牙为Ⅰ类关系,覆牙合覆盖正常。患者硬组织改变没有显著性(P≥0.05)。L1-MP角平均减小8.1°,U1-L1角平均增大7.7°,L1-NB角平均减小7.3°,L1-NB距平均减小4.8 mm,差异均有显著性(P<0.01)。软组织侧貌改善明显,Li-E距、Li-H距、Li-RL2距平均减小量分别为3.2、3.4和4.1 mm,差异均有显著性(P<0.01)。结论采用减数下颌2个前磨牙矫治成人骨性反牙合病例在临床上是一种较好的矫治方法,矫治后咬合关系良好,侧貌有向直面型发展的趋势。     

Effect of premolar extraction on mandibular third molar impaction in young adults

Objective:To test the null hypothesis that orthodontic therapy with or without premolar extraction does not result in any difference in third molar impaction.Materials and Methods:Two groups were formed: 22 patients in one group with first premolar extractions and 22 patients in the other group without extractions. All patients were nongrowing subjects who had normal gonial angles and were skeletal Class I at the beginning of treatment. The available space for third molars, inclination of second and third molars, and angle between the second and third molars were evaluated. Also, the correlation of measured parameters and type of orthodontic therapy with the eruption of third molars was evaluated.Results:Of the third molars, 81.8% were impacted in the nonextraction group and 63.6% were impacted in the extraction group. Impaction of mandibular third molars was significantly correlated to the pretreatment and posttreatment inclination of third molars and the angle between the second and third molars. In the extraction therapy group, the retromolar distance increased significantly with a mean of 1.30 ± 1.25 mm.Conclusions:When the inclination of the third molar is inconvenient, the tooth may remain impacted even if there is enough retromolar space.     

正畸治疗中下颌第一前磨牙拔除后下颌牙自然移动的临床研究

目的：观察不同类型错耠下颌第一前磨牙拔除后下颌牙的自然调整变化。方法：20例因正畸需要拔除下颌第一前磨牙的病例为研究对象,其中安氏I类错殆和安氏Ⅱ类错殆各10例。第一前磨牙拔除后6个月内下颌先不进行矫治,上颌行MBT矫治技术娇治。分别测量两组病例拔牙后30min、4个月时拔牙间隙近、远中方向最小径,比较分析两者拔牙间隙变化情况和Spee’s曲线曲度。结果：拔牙4个月后与拔牙后30min比较,两组拔牙间隙最小近远中径减小了1.35mm和1.26mm（P〈0.01）,Spee＇s曲线曲度也有显著性改变,分别减小了0.28—0.32mm,差异有统计学意义。结论：MBT技术治疗安氏I类和安氏Ⅱ类拥挤错殆,可以通过下颌第一前磨牙拔除后下颌牙白行调整,减小拔牙间隙,改善Spee＇s曲度。     

Long-term stability of Class I premolar extraction treatment.

This study evaluates Class I, 4-premolar-extraction patients who were treated with the edgewise appliance by 1 practitioner, according to the philosophy of Tweed, and who had been out of retention a minimum of 5 years. The sample includes 32 patients, who started treatment at an average age of 12.8 years and who were examined a mean of 15 years posttreatment (11.7 years postretention). Cephalometric and model analyses were conducted to evaluate treatment and posttreatment tooth movements. The results showed that irregularity, as measured by the irregularity index, decreased 5.3 mm during treatment and increased 0.7 mm (SD 1.1 mm) during the posttreatment period. Eighty percent of the patients had satisfactory (<3.5 mm) mandibular incisor alignment over 10 years postretention, and none was in the severe category (>6.5 mm). Mandibular intercanine width increased (1.7 mm) during treatment, whereas intermolar width decreased (-2.1 mm). Maxillary molar widths remained unchanged posttreatment, and mandibular intercanine width decreased 1.4 mm from immediately posttreatment to postretention. Arch lengths decreased during treatment because of molar protraction and incisor retraction. Mandibular arch length continued to decrease posttreatment (-1.4 mm) because of mesial molar movement rather than distal incisor movement. Satisfactory long-term results can be achieved for most Class I, 4-premolar-extraction patients for whom evidence-based treatment objectives-including minimal alteration of the mandibular arch form and the retraction and uprighting or maintenance of mandibular incisors in their original position-have been met.     

快速成型帽状夹板在下颌骨骨折中的应用

目的 寻求迅速、简便、有效的下颌骨骨折的固定方法。方法 真空成型牙列套的帽状夹板，利用其弹性来复位骨折片。结果 治疗骨折线位于牙列内的单发、多发下颌骨骨折11例，取得良好效果。此方法不影响进食，骨折端稳定。结论 快速成型帽状夹板在下颌骨骨折治疗中有较好固定效果。