Indian Journal of Dental Research

: 2005  |  Volume : 16  |  Issue : 4  |  Page : 159--66

Correction of anterior open bite in a case of achondroplasia

S Karpagam1, K Rabin2, George Mathew2, Santhosh Koshy2,  
1 Department of Orthodontics, Christian Medical College, Vellore 632004, Tamilnadu, India
2 Department of Dental and Oral Surgery, Christian Medical College, Vellore 632004, Tamilnadu, India

Correspondence Address:
S Karpagam
Department of Orthodontics, Christian Medical College, Vellore 632004, Tamilnadu


Treatment planning for patients with skeletal deformities is often considered challenging. This article reports a female patient with achondroplasia who presented with severe maxillary retrognathism and vertical excess along with anterior open bite. The clinical and cephalometric findings of the patient are detailed here. The treatment plan consisted of modified anterior maxillary osteotomy for simultaneous vertical and sagittal augmentation along with orthodontic intervention. The course of surgical-orthodontic treatment and the results are presented. This treatment is to be followed by correction of vertical maxillary excess after completion of growth. This paper concludes that the dentoalveolar component of a skeletal deformity can be handled independent of the craniofacial management.

How to cite this article:
Karpagam S, Rabin K, Mathew G, Koshy S. Correction of anterior open bite in a case of achondroplasia.Indian J Dent Res 2005;16:159-66

How to cite this URL:
Karpagam S, Rabin K, Mathew G, Koshy S. Correction of anterior open bite in a case of achondroplasia. Indian J Dent Res [serial online] 2005 [cited 2023 Sep 30 ];16:159-66
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Treatment of dentofacial deformities in patients with achondroplasia can be complex and challenging. achondroplasia is a genetic disorder of cartilage and bone formation and is the most common cause of dwarfism [1],[2],[3],[4]. The characteristic craniofacial findings include short posterior cranial base, frontal bossing (due to compensatory overgrowth of cranial vault), collapsed midface and a deficient maxilla, commonly contributing to skeletal class III pattern of malocclusion and an elongated lower face [5],[6],[7],[8]. The hypoplasia of the maxilla can be attributed to the underdevelopment of the cranial base at the synchundroses [9]. Normal growth of the cranial base is essential for the forward translation of the nasomaxillary complex [10].

This article presents a case of a patient with achondroplasia exhibiting a unique combination of skeletal anterior openbite, vertical maxillary excess, severe maxillary retrusion and class I molar relation. The specific surgical strategy along with adjunctive orthodontics for correction of openbite and accompanying malocclusion is discussed. The treatment plan for correction of the vertical excess is also mentioned.


A 14-year-old female patient presented with the classic features of achondroplasia She had all the skeletal features of deficiencies secondary to achondroplasia along with apertognathia


The patient sought treatment for difficulty in closing the lips and loss of contact between the front teeth. She also wanted correction of her facial appearance. History revealed that she had mouth breathing habit (a possible consequence of reduced upper airway space). The patient had otherwise been in good health and had also received orthopaedic surgical correction for limb lengthening.


Along with the classical extraoral manifestations associated with achondroplasia like frontal bossing, collapsed midface and a concave profile, she also presented with incompetent lips, an interlabial gap of about 16 rmn. at rest and hyperactive mentalis. Lip closure was not possible for the patient without muscle strain. In profile, the mandible appeared normal and the chin was notprominent The nose was saddle�shaped [Figure 1]-A,B.

Frontufacial examination also revealed that her lower face appeared elongated in relation to the rest of the face. No gross facial assymetry was apparent. The upper lip was short.

Intraorally, she exhibited an anterior open bite of 5 mm, increased incisor exposure at rest, upto 7 mm. of gingival display upon smile, class I molar relationship, severely protruded upper anteriors, crowded lower anteriors, congenitally missing 22 with no residual space and midline shift of upper anterior teeth to the left by 3 nnm. Overjet was normal. Canine relationship was of class I on right side, class 11 on left side due to missing 22.

Occlusally, a good arch symmetry, good posterior occlusion and no transverse deformity were seen. Forward positioning of the tongue was evident, which probably occured secondary to the existence of anterior openbite. The patient had a tongue-thrust swallowing pattern. Her upper anterior teeth displayed mottling and intrinsic staining [Figure 2]A,B,O.


The pertinent cephalometric findings are summarised in [Table 1]. Skeletal analyses disclosed that maxilla was retrognathic with the SNA value of 73 �, distance of NA perpendicular to A of 9 mm.(mean 0-lmm.) and FH-NA value of 80 � (mean 88�). Mandible and chin position were normal with SNB of 78 � and facial angle of 88 '(mean 88�). AB - NPog measuring 5 '(mean 0') and ANB of - 5� indicated the presence of skeletal class III malocclusion. Facial axis angle of 84 � and FMA 37 revealed a vertical growth pattern

Upper anterior facial height (N -ANS) which measured 43 mm. was less compared to the mean of 50 mm.

Lower facial height (ANS - Me) and total facial height (N�Me) were above the normal range. Anterior palate was tipped up.

Upper 1-NF, Upper 6-NF Lower 1-MP and lower 6-MP were all increased suggestive of increased anterior and posterior maxillary and mandibular vertical excess. Upper and lower incisors were proclined as evidenced by increased values for upper 1 - NA, upper 1- SN, upper 1-A Po, lower 1-NB, lower 1-A Po, lower 1-MP and inter incisalangle. Upper pharyngeal width was reduced with a value of 5 mm. implying possible airway obstraction[11]. In summary, cephalometric appraisal disclosed that the patient possessed a retrognathic maxilla orthognafue mandible, anterior open bite, maxillary and manbibular dentoalveolar proclination, decreased upper anterior facial height, increased lower anterior facial height, anterior and posterior vertical maxillary excess and vertical growth pattern.


Dentally, the patient had a Class I malocclusion with severe upper anterior protrusion, lower anterior crowding and anterior openbite extending from 13 to 24. Skeletally, however, the patient had a Class III malocclusion with severe anterior maxillary retrusion[12],[13] (compensated by proclination of maxillary anteriors) and increased maxillary and mandibular vertical maxillary height.

Natural compensatory mechanisms like upper dentoalveolar protrusion served to camouflage the actual deformity and succeeded in preventing a severely collapsed profile and an anterior cross bite. The anterior palate was tipped upwards reducing the upper facial height and enhancing the lower facial height. Anterior open bite persisted inspite of the anterior maxillary vertical excess [14]. The posterior maxilla and occlusion remained relatively normal and unaffected.


The specific dental-orthodontic-orthognathic problems present in this patient are summarized as follows

Intrinsic staining of teeth due to enamel hypoplasia6 mm, anterior open bite.Vertical maxillary excess with gurmaysmile.Anterior maxillary base deficiency.Lip incompetence, mid facial soft tissue deficiencySeverely procumbent maxillary incisorsModerately proclined and crowded mandibular incisors.Increased lower facial height.Missing 22 and upper paidline, shift to left side.


Theimmediate treatment objectives were

To achieve closure of open bite To correct upper and lower anterior proclination and crowding.To maintain molar relationTo improve the profile.

The long teen (skeletal) treatment objectives were correction of anterior and posterior vertical maxillary excess, correction of gummy smile, reduction of the lower facial height and improvement in nose and midface profile. The long term objectives were to be met by future orthognathic, craniofacial and plastic surgeries. This was explained to the patient.


The dental treatment was initiated with elimination of stains due to localized enamel hypoplasia present on the upper central incisors. This procedure restored the normal appearance of enamel.

The specific treatment plan was designed to correct the openbite and the anterior maxilla was identified as the source of the deformity. The anterior maxillary surgery was modified to effect advancement of the anterior maxillary basal bone along with the vertical augmentation for open bite closure. A sequence of surgical and orthodontic management was formulated. This included initial orthodontic treatment for arch coordination followed by osteotomy of anterior maxilla

Presargical orthodontic procedtire

Presurgical orthodontics was designed to avoid mechanics which would correct the openbite per se, since extrusion of teeth was inappropriate in this case and posttreatment relapse is reportedly high. The goal of orthodontic treatment was restricted to correction of the lower anterior crowding and arch coordination to facilitate surgery. Measures to prevent further bite opening were undertaken.

We elected to proceed with comprehensive orthodontics in the lower arch commencing with extraction of lower premolars followed by alignment and retraction of anterior segment [Figure 3]A,B,C. Extractions of lower premolars were mandatory since lower anteriors exhibited crowding due to arch length discrepancy. Orthodontics in upper arch was limited to arch alignment only [Figure 4]. Extraction of upper left premolar 14 was contemplated but postponed until the time of the surgery. Since upper left lateral incisor 22 was missing and there was considerable midlines hift to the left, extraction of 24 was avoided.

Surgical technique

Mock surgery was done on models to simulate the position of the jaws after surgery. A splint was fabricated on these models.

Under general anaesthesia, vertical osteotomy cuts were made through maxillary alveolus between 22 and 24 and through the socket of 14 and extended upto the pyriform rim 6 rnm. above the nasal floor. The cuts were extended across the pyriformrim and connected to each other using osteotomes to separate the anterior maxillary segment from the palate. The anterior maxillary segment bearing 11,12,13,21,23 was retracted unilaterally into the space available from extraction of 14.The bony base of the maxillary segment was mobilized downwards and forwards dragging the nasal septum [Figure 7]. The entire segment was tied into the splint which was stabilized to the maxillary posterior teeth.

In summary, the anterior maxilla was repositioned with the anterior nasal spine rotated and advanced and the entire segment positioned inferiorly [15] to flatten the occlusal plane along with unilateral setback on the right side.

Post surgical orthodontic settling

After the surgical splint was removed, the postsurgical orthodontic treatment was commenced. Both arches were coordinated and any remaining space distal to the upper canines after maxillary surgery was closed. Patient was given upper and lower removable retainers.


Post treatment clinical evaluation and composite cephalometric superimposition tracing [Figure 8] illustrated the changes achieved.

Dental : A very acceptable occlusion was achieved. Upper and lower teeth were in good alignment, open bite closure was corrected and overbite and over jet were within normal limits [Figure 5] A,B,C. The inclination of upper anteriors had improved and lower anteriors were upright Class Imolar relation was maintained. Upper and lower midlines were coincident. 23 was positioned to serve as 22. Cephalometric changes revealed acceptable inclination of upper anteriors and satisfactory inclination of lower anteriors. Upper anteriors were allowed to remain a little proclined to compensate for the residual maxillary retrusion.

Eatraoral : The changes in profile were mild but positive [Figure 6]A,B.

Lengthening of nudfacial soft tissue component was appreciable. Lip competence had improved to some extent.

Skeletal: The post surgical cephalometric evaluation revealed the following changes:

SNA value showed a mild increase from 73�to74�.SNB decreased to 76 � as the mandible rotated in clockwise direction increasing the lower facial height.ANB increased from -5 � to -2 � and angle of convexity increased from -10 � to -9 � implying reduction in concavity of profile. Distance of point A from NA reduced from 9 mm. to 7 mm.There was considerable increase in upper anterior facial height as evidenced by increase in N - A N S from 43 mm to 52 mm Anterior maxillary height (NF to upper 1) increased from 33mmto 39 mmLower facial height (ANS-Me) remained constant at 81mrn, the increase in distance from ANS to Menton compensated by downward positioning of the AN S.Total anterior facial height (N-Me) increased from 124 mm. to 133 mm. attributable i n partto the vertical growth pattern.Superimposition demonstrated continued growth of face, mandible developing in a slightly more vertical direction than normal.Lengthening of midfacial soft tissue component was a very beneficial outcome of the treatment. There was a remarkable increase in the distance between N' to Sri from 42 mm. to 49 mm. Upper lip length was enhanced to 25 mm.


The patient displayed typical characteristics of achondroplasia like midfacial deficiency, concave profile and retrognathic maxilla. The additional significant features were the Class I molar relation, upper and lower anterior proclination, anterior open bite orthognathic mandible, maxillary and mandibular vertical excess. A Class III molar relation would have been ideal in this patient since she had a retrognathic maxilla. A Class I molar relation had probably existed due to a relatively normal growth of posterior maxilla. Class I molar limited the treatment options available and played a maj or role in determining the treatment plan in this patient

Dentally, this patient displayed severe upper anterior proclination and moderate lower proclination with crowding. Therefore, the treatment plan included extractions of premolars to correct the proclination. The orthodontic treatment plan was designed for extraction mechanics, with the understanding that surgical correction might be necessary in the future. Extraction of lower premolars was done during orthodontic treatment and extraction of 14 was done during surgery. Extraction of 24 was avoided since 22 was missing.

Extractions of the three premolars enabled correction of the arch length problems and the achievement of acceptable occlusion. Retraction of anterior teeth contributed to an appreciable improvement in the patient's soft-tissue profile on completion ofthe active treatment.

Open bite is generally considered difficult to treat and has a high incidence of relapse when it does not address the underlying cause of the deformity [16]. Surgical intervention is preferred over orthodontics for correction of apertognathia for a stable result Anterior segmental surgical procedures for correction of open bite have been reported to be very stable. The reason for the stability of these procedures has been found to be the non involvement of the muscles of mastication [16]. This patient required segmental surgery to correct the open bite and to retract and level the anterior maxilla which was tipped upwards.

Unilateral first premolar extraction was done during surgery followed by retraction of the anterior segment to the right side. This allowed correction of the upper midline shift and the upper left canine to be used as the lateral incisor. Along with unilateral setback, simultaneous anterior and downward rotation of the anterior maxillary segment was done. This allowed closure of the open bite and anterior maxillary base augmentation. Forward and inferior tipping of anterior maxilla also resulted in leveling the occlusal plane along with advancement of the anterior nasal spine and the adherent soft tissues.

No bone grafting was done around the down fractured segment. The splint held the anterior maxillary segment allowing a modified version of periosteal distraction. The surgical procedure can be considered as a type of immediate osteodistraction in 3 dimensions which produced a precise and stable result. This confirms that immediate distraction or stretch of periosteal tissues can also induce osteosynthesis. In this patient, osteosynthesis was required to increase the basal maxillary bone above the anterior maxillary alveolus. The distraction of the anterior maxillary segment could be preserved because the splint was anchored to the posterior maxillary segment which was stable and undisturbed by the surgery.

The results revealed that the ANB value was reduced from its pre surgical value. Decrease in proclination of two amount of torque. Open bite closure was achieved along with a reduction in the interlabial gap from 16 mm. to 12 mm.

The treatment resulted in an improved and satisfactory relationship of the anterior teeth.

The final occlusion was Class I with normal overbite, overjet and dental arch alignment. The resulting profile was mildly concave. Lengthening of the midfacial soft tissue component was a very significant and beneficial outcome of the treatment. Inferior positioning of the ANS and nasal septum had pulled the upper lip downwards resulting in improved lip closure. The lip incompetence persisted but the interlabial gap had reduced by 4 mm. Increase in anterior maxillary height and facial height emphasized the need for future surgeries for correction of excessive vertical dimensions. Posterior vertical maxillary excess was the other skeletal parameter which did not show any improvement with the present procedure and required further orthognathic surgical correction.

Prospective treatment plan

The subsequent surgeries to address the remaining skeletal deformities are to be done after completion of active growth. LeFort I maxillary superior impaction (followed by autorotation of mandible) was planned to be done in two years time, after cessation of any possible growth of the maxilla. It was discussed with the patient that further treatment would also include rhinoplasty lip lengthening and reduction genioplasty to improve the profile. [16],[17],[18]


The diagnostic findings and treatment planning in a patient with achondroplasia displaying craniofacial deformity, skeletal and dentualveolar malocclusion have been detailed and discussed in this article. It can be concluded that Achondroplastic patients with midfacial insufficiency and apertognathia can be treated in stages. In the first stage, the dental component of anterior open bite can be corrected and this can be followed by the treatment of the upper midface including the nasal complex in a second or later stages.


We wish to express our sincere appreciation to Mr. Santhosh Lal, our Technician for his help and co-operation.


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