Effect of rapid maxillary expansion on halitosis


The objective of this study was to evaluate the effect of rapid maxillary expansion (RME) on halitosis.


Thirty children (11-15 years old) were randomly divided into RME and control groups. The RME group consisted of 15 children treated with hyrax appliances, and the control group included 15 children without treatment. Halitosis was evaluated with the halimeter and the organoleptic method. Plaque index and gingival index scores were recorded. Acoustic rhinometry was used to measure the nasal volume. Measurements were obtained at 2 times: before RME, and after retention at 4 months. The Wilcoxon signed rank test and the paired t test were used for intragroup comparisons, and the Mann-Whitney U test and the Student t test were used for intergroup comparisons.


Halitosis (halimeter and organoleptic values) decreased significantly in the RME group ( P <0.001). Insignificant changes of halitosis were observed in the control group. Intragroup and intergroup comparisons showed no statistically significant differences for the plaque index. Gingival index values were significantly decreased with RME ( P ≤0.05). Nasal cavity volume increased significantly in the RME group ( P <0.01).


RME was shown to lower halitosis values. RME could be a treatment option for patients with maxillary transverse deficiency and halitosis.


  • Oral malodor was significantly lower in RME patients than in controls.

  • Nasal cavity volume was increased by RME.

  • Negative correlation was found between nasal cavity volume and oral malodor.

  • Plaque index did not change after RME, but gingival index scores were decreased.

Halitosis is used to describe a bad or an unpleasant odor in the mouth. It is a condition that causes patients to feel insecure and embarrassed, thus reducing their quality of life.

When halitosis is examined, volatile sulfur compounds (VSCs) are found to be the responsible for the odor. VSCs are formed by the proteolysis of sulfur-containing amino acids such as cysteine, cystine, methionine, and proteins by bacteria in saliva and gingival fluid, and on the tongue and other parts of the oral cavity.

There are certain conditions for the formation of VSCs. Acidic or basic pH value of the saliva, decreased saliva amount and flow rate, gingivitis, periodontitis accompanied by an increase of gram-negative anaerobic bacteria, a diet supporting bacteria reproduction and metabolism, low oxygen, and pharyngeal infections are some conditions leading to halitosis.

Transverse maxillary deficiency, accompanied by a high palatal vault, is a symptom of a skeletally developed syndrome that causes some rhinologic disorders and has certain undesirable effects on the dentofacial pattern. Some features of this problem are a decrease in nasal permeability resulting from nasal stenosis, elevation of the nasal floor, bilateral dental maxillary crossbite, mouth breathing, and, because of enlargement of the nasal turbinates, a decrease in nasal airway size.

Treatment for transverse maxillary constriction involves the use of rapid maxillary expansion (RME). It promotes the separation of the maxillary bones in a pyramidal shape in which maximum expansion is near the incisors, just below the nasal valves. This treatment expands the external walls of the nasal cavity to increase its capacity. This can result in improvement of the patient’s ability to breathe through the nose. Gray found that RME could replace oral breathing over to nasal breathing in 80% of patients. Considering this information, we planned this study with the idea that changes in the nasal cavity obtained by RME treatment in patients with maxillary constriction might facilitate nasal breathing and decrease oral malodor.

The effects of orthodontic treatment on oral malodor have been evaluated in several studies. Some researchers have found that brackets, ligatures, and other attachments used for orthodontic treatment cause plaque accumulation as well as periodontal inflammation, hyperemia, hyperplasia, and oral malodor because of their retentive properties. In contrast, some studies have reported that periodontal tissues are not affected by orthodontic treatment, and even plaque indexes might be lower as a result of increased oral hygiene motivation. Although several studies have evaluated the relationship between oral malodor and removable appliances and fixed orthodontic treatment, the effects of RME, an orthopedic treatment, have not been documented. Thus, this prospective randomized clinical study was performed to investigate the effect of RME on halitosis.

Material and methods

This study protocol was approved both by the Ethics Committee for Clinical Research of Kirikkale University (14/03-2015) and the Medicine and Medical Devices Agency of Turkey (2015-AC-CE-114). The Coordinatorship of Scientific Research Projects of Kirikkale University financially supported this study (grant number 2015/09).

Thirty subjects with ages between 11 and 15 years were randomly selected. They were divided into 2 groups: the RME group (7 girls, 8 boys; mean age, 12.6 ± 1.17 years) and the control group (10 girls, 5 boys; mean age, 13.06 ± 1.22 years). The inclusion criteria were maxillary constriction, deep palatal vault, bilateral crossbite, and presence of first premolars and first molars. Patients were excluded if they had congenital or developmental deformities or systemic disorders, thumb sucking, tongue thrust, periodontal problems, or were using antibiotics or mouthwash, or were receiving orthodontic treatment. Orthodontic treatment of the control group subjects started after this study. We received informed consent from all patients. The block randomization method was used for selection of the patients. Details of the allocated groups were written on colored cards placed in sequentially numbered, opaque, sealed envelopes.

All subjects received oral hygiene instructions to maintain their usual oral hygiene procedures at every appointment. Halitosis and organoleptic measurements, acoustic rhinometry results, and plaque and gingival index records were obtained before treatment (T0) and after retention of RME (T1).

Hyrax appliances consisting of an expansion screw and stainless steel extensions (Dentaurum, Pforzheim, Germany) were used to expand the maxilla. The screw was positioned parallel to the occlusal plane and as close as possible to the palate. The appliance was cemented to the first premolars and first molars with glass ionomer cement (3M Unitek, Monrovia, Calif). The screw was activated 0.5 mm per day until the midpalatal suture was opened. The opening of the midpalatal suture was determined with an occlusal radiograph and midline diastema of the maxilla. Then it was activated 0.25 mm per day until the palatal cusps of the maxillary molars were in contact with the buccal cusps of the mandibular first molars. RME appliances were used as retainers without debanding for 4 months.

The amount of VSCs representing halitosis was measured with a halimeter device (Interscan, Chatsworth, Calif) at T0 and T1. Halitosis scores were divided into 4 categories and classified as normal (0-100 ppb), weak (101-150 ppb), strong (151-300 ppb), or very strong (≥301 ppb).

The patients were asked to breathe through their noses for 3 minutes before sampling. Then they were instructed to place the disposable straw at the posterior dorsum of the tongue and not to touch the oral mucosa or the tongue. They were told to keep their lips 1.5 cm apart during the measurements. Measurements were repeated 3 times at 3-minute intervals. The mean value was calculated in parts per billion for each patient.

Another method for the evaluation of oral malodor was the organoleptic method with scores in 5 categories: 0, no malodor; 1, slight malodor; 2, clearly noticeable malodor; 3, moderate malodor; 4, strong malodor; and 5, very strong oral malodor. The organoleptic measurements of breath were taken at a distance of 10 cm from the oral cavity and scored.

All subjects were requested to avoid eating onions, garlic, and spices for 2 days before the halitosis measurements. They were instructed to brush their teeth after dinner on the evening before the measurements and to refrain from eating, drinking, toothbrushing, mouthwashing, and gum chewing before the appointment the next morning. All measurements were made in the morning before breakfast. No antibiotics were used for 2 months before the measurements. In addition, the measurements from the girls were taken when they were not menstruating. The assessments were made by the same examiner (T.S.E.) throughout the study. The examiner avoided tea, coffee, orange juice, fragrances, and cosmetics before the organoleptic evaluation.

The measurements were carried out using an acoustic rhinometry device (SRE 2000, Rhinoscan 2.5; RhinoMetrics, Lynge, Denmark), which produces an acoustic signal in the form of discrete impulses, according to the criteria determined and recommended by the Standardization Committee on Acoustic Rhinometry guidelines.

The room where the acoustical rhinometry measurements were taken was silent, with an approximate temperature of 22°C and humidity of 50% to 60%. The subjects were seated in a stable position during the measurement, facing up, with glasses removed to prevent pressure on the nose and possible change of nose shape. Before each measurement, the system was calibrated. The most suitable nose adapter was chosen, and gel was applied to the tip of the nose adapter to prevent sound wave loss. It was set at an angle of 45° so as not to disturb the nostril anatomy. Measurements were carried out after cleaning the subject’s nose and without using decongestant to ensure standardization.

The nasal volume was computed separately for each nostril as the volume of the nasal cross-section 5 cm from the nasal inlet. The total volume of the nasal cavity was calculated by summing the volumes of each nostril (total nasal volume = volume right + volume left).

Plaque index and gingival index values were measured at 6 sites (mesiobuccal, distobuccal, midbuccal, mesiolingual, midlingual, distolingual) for all teeth with a Williams probe. Periodontal measurements were calculated as the sum of the mean scores of each examined tooth divided by the number of evaluated teeth.

Scores for the plaque index were defined as follows: 0, no plaque in the gingival area; 1, a film of plaque adhering to the free gingival margin and adjacent area of the tooth that could be recognized only by running a probe across the tooth surface; 2, moderate accumulation of soft deposits in the gingival pocket and on the gingival margin and adjacent tooth surface that could be seen by the naked eye; and 3, abundance of soft matter in the gingival pocket and on the gingival margin and adjacent tooth surface.

Scores for the gingival index were defined as follows: 0, normal gingiva; 1, mild inflammation, slight change in color, slight edema, and no bleeding on palpation; 2, moderate inflammation, redness, edema, glazing, and bleeding on probing; and 3, severe inflammation, marked redness and edema, ulceration, and tendency to spontaneous bleed.

Statistical analysis

The power analysis showed that for a power of 0.80, with an α error of 0.05 (effect size 1.1), 15 patients were required for each group.

Statistical analysis was performed with SPSS software (version 20.0; IBM, Armonk, NY). The distribution of variables was evaluated by the Shapiro-Wilk test. The Wilcoxon signed rank test and the paired t test were performed for intragroup comparisons. The Mann-Whitney U test and the Student t test were used for intergroup comparisons. The Spearman rank order correlation was applied to measure the association between halitosis and nasal cavity volume. P values equal to or less than 0.05 were considered statistically significant.


The changes in mean intercanine and intermolar width were 2.33 ± 1.54 mm and 6.33 ± 1.54 mm, respectively (T0-T1).

The mean and median values of halitosis, periodontal scores, and nasal cavity measurements are given in Tables I through III .

Table I
Comparison of halimeter and organoleptic values of groups and changes between T0 and T1
Halimeter T0 T1 T1-T0 P
Mean ± SD
RME group 128 ± 85.44 17.6 ± 12.49 −110.86 ± 82.10 <0.001 [CR] b
Control group 89.56 ± 26.22 82.43 ± 30.05 −7.12 ± 14.96 0.076b
Between groups Z = –1.72c Z = –4.53 c Z = –4.68 c
Organoleptic Median (minimum-maximum)
RME group 3 (2-3) 1 (0-2) −2 (–3-[–1]) <0.001 a
Control group 1 (1-3) 2 (1-3) 0 (0-1) 0.056a
Between groups Z = –3.66 c Z = –4.53 c Z = –4.98 c
a , Wilcoxon signed rank test; b , paired t test; c , Mann-Whitney U test.

Significant at P ≤0.001.

Table II
Comparison of total nasal volume of groups and changes between T0 and T1
Nasal total volume T0 T1 T1-T0 P
Median (minimum-maximum)
RME group 7.36 (4.81-9.33) 10.69 (7.99-15.07) 3.31 (0.04-6.30) 0.001†a
Control group 9.26 (5.55-13.65) 9.27 (5.53-14.02) 0.06 (–0.59-0.89) 0.267a
Between groups Z = –2.64†b Z = –1.93b Z = –4.41†b
a , Wilcoxon signed rank test; b , Mann-Whitney U test.
Significance: * P ≤0.01; † P ≤0.001.

For the halimeter measurements (T0-T1), the intragroup evaluation showed that, in the RME group, the measurements decreased significantly ( P <0.001); however, there were no statistically significant differences in the control group. Intergroup analysis showed significant differences ( P <0.001) ( Table I ).

Dec 8, 2018 | Posted by in Orthodontics | Comments Off on Effect of rapid maxillary expansion on halitosis
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